ambient CO2 with high N, high CO2 with low N, high CO2 with high N. These results agree with previous data. New findings are: (1) with elevated CO2 a new equilibrium in transpiration is established in which leaf area increases offset decreases? in stomatal conductance; (2) the addition of nitrogen increases transpiration without any indication of a new equilibrium contrasted with the effects of added nitrogen. Results were expressed as totals for the catchment or spatially distributed across the catchment. For the total catchment, water yield increased in the order: high CO2 with low N, high CO2 with high N, ambient CO2 with low N, ambient CO2 with high N. LAI increased from 3.3 to 5.7 in the order: ambient CO2 with low N,pA^7337^As experimental elevation of CO2 in short-term experiments may produce organic matter with decomposition characteri Key features of the model are (1) an ability to scale hydrological processes at the catchment scale in three dimensions, a nd (2) a means to integrate multiple factors/stresses on plant growth. The effects of CO2 on catchment hydrology (water yield or soil moisture content) and forest growth (expressed as leaf area index, LAI) were modelled for a 2-year period, and A^3153^A spatially explicit hydroecological landscape model of water, carbon and energy balances (Topog-IRM) is described. The landscape is envisaged as a catchment forested with a single stratum comprising Eucalyptus maculata trees. The model was used to simulate the direct effects of a 2X elevation in atmospheric carbon dioxide at two levels of nitrogen on catchment water yield, soil moisture status and tree growth, Experimental results used to parameterise the model are detailed. s on greenhouse effect gas emissions.al differences in gas exchange and response to environmental stress in dioecious {iS150^4^Hatton,TJ^Walker,J^Dawes,WR^Dunin,FX^1992^1^Simulations of hydroecological responses to elevated CO2 at the catchment scale^182^40^4-5^679-696^^^^^^^^^^3154nental fossil fuel burning and land clearing combined. The rate of sequestration is predicted to continue to increase until 2050 AD and beyond if atmospheric CO2 concentration and temperature continue to increase. However, there remains considerable experimental uncertainty about the correct parameterisation of the model. The findings have implications for policieanel on Climate Change (IPCC) is applied. The standard parameterisation of the model suggests that the changing CO2 concentration and temperature regime since 1750 AD has been causing continuous net sequestration of carbon into Australian live vegetation and soils. The present modelled rate of net sequestration is of a similar magnitude to CO2 emissions from contion from the literature is used to parameterise CQUESTA. A standard set of parameters is adopted for exploratory purposes. Historical information is used to describe the average CO2 concentration and temperature over the southern hemisphere from 1750 AD to the present. From the present to 2050 AD the 'business-as-usual' scenario described by the Intergovernmental Pralian terrestrial carbon budget - integration using a simple-model^182^40^4-5^527-543^^^^^^^^^^3152ospheric environment^A^3151^A simple continentally aggregated model of the Australian terrestrial carbon budget (CQUESTA) integrates information on CO2 and temperature effects and is applied to evaluating whether vegetation is absorbing anthropogenic CO2. Informati148^4^Field,CB^Chapin,FS^Matson,PA^Mooney,HA^1992^1^Responses of terrestrial ecosystems to the changing atmosphere - a resource-based approach^27^23^^201-235^149^1^Gifford,RM^1992^1^Implications of the globally increasing atmospheric CO2 concentration and temperature for the Aust"creased respiration, delayed senescence, and allocation of the additional carbon to roots and rhizomes. The complex intera#ction of these diverse responses suggests that the rising atmospheric CO2 may have a significant impact on ecosystem processes.ssess%this was accompanied by decreased biomass in the C4 component of the community. Elevated CO2 reduced water loss, increased& water potential and delayed senescence in all three species. Many factors contributed to CO2 stimulated carbon accumulati!on in the plant community dominated by the C3 sedge, Scirpus olneyi, including: sustained high photosynthetic capacity, de(otosynthetic capacity, reduced dark respiration, increased numbers of shoots, roots and rhizomes, reduced nitrogen concent)ration of all tissues, increased nitrogen fixation and increased ecosystem carbon accumulation. In a mixed community of th$e sedge and C4 grass species, Spartina patens and Distichlis spicata, biomass of the C3 component increased over 100% and + the C4 grass, Spartina patens, and a mixed community of these two species and the C4 grass, Distichlis spicata. Treatment, began in the spring of 1987 and will continue through the 1994 growing season. During the first 4 years of exposure, elev'ated CO2 had the following effects on mono-specific stands of the C3 sedge, Scirpus olneyi: increased quantum yield and ph40^4-5^579-595^^^^^^^^^^3149 R^1993^1^Gender-specific physiology, carbon isotope discrimination, and habitat distribution/A^3148^Open top chambers are being used in a long-term project to determine the effects of elevated CO2 on ecosystem proce*sses on a Chesapeake Bay wetland. Three communities are studied: mono-specific stands of the C3 sedge, Scirpus olneyi, andl as affecting the nutrient value of grain such as rice.y and clonal foraging of Calamagrostis canadensis in response to ^3147t heterogeneity^12^81^^769-776^^34^^^^^^^^^^^^^^^^^^^^^^^^-147^1^Drake,BG^1992^1^A field-study of the effects of elevated CO2 on ecosystem processes in a Chesapeake Bay wetland^182^4ed CO2, irrespective of availability of nitrogen in the soil. In natural ecosystems, the lower nitrogen to carbon ratio of5 the litter may alter rates of nutrient cycling. For farmers, the rising CO2 concentrations could cause reductions in grai0n nitrogen, and therefore protein content. This could have important implications for baking quality of hard wheats as wel7 concentrations are used to evaluate nutrient status of crop and forest species and to manage fertiliser programs, they wi8ll need reassessing as the atmospheric CO2 concentration rises. Another consequence of the altered nutrient requirement at3 high CO2 is that the nitrogen concentrations of foliage, roots and grain are consistently lower in plants grown at elevat:n through the photoreductive cycle is increased and photorespiration is suppressed. This change in metabolism appears to a;lter the foliar nutrient concentration required to promote maximum productivity (critical concentration). Higher phosphoru6s concentrations are needed at elevated CO2, whereas the nitrogen requirement is reduced by CO2 enrichment. Since critical=naged ecosystems because photosynthetic rates will be higher. The greatest absolute increase in productivity will occur wh>en nitrogen and phosphorus availability in the soil is high. Low nitrogen does not preclude a growth response to high CO2,? whereas some C3 species fail to respond to high CO2 when phosphorus is low, possibly because insufficient phosphorus is a9vailable to maintain maximum photosynthetic activity at high CO2. C3 plants response to high CO2 because the flux of carbo=2286^3^Yeates,G W^Newton,P C D^Ross,D J^1999^1^Response of soil nematode fauna to naturally elevated CO2 levels influenced1146^1^Conroy,JP^1992^1^Influence of elevated atmospheric CO2 concentrations on plant nutrition^182^40^4-5^445-456^^^^^^^^^eat shock proteins, our results showed little relationship between plant nitrogen status and the ability of a plant to tolerate an acute increase in temperature.ns of QTLs affecting the correlated traits DFF, LLF, LL35 and NN suggest that thes@ore susceptible to a heat shock than ambient-CO2-grown plants, because the reduced N concentrations of high-CO2 grown plan=ts could result in the reduced synthesis of heat shock proteins and reduced thermotolerance. Although we did not examine hBand nutrient treatments, all had some significant effects on plant performance, but plants from both CO2 treatments responCded similarly to heat shocks. We also found, as expected, that plants grown under high CO2 had dramatically decreased tiss?ue N concentrations relative to plants grown under ambient conditions. We predicted that high- CO2-grown plants would be mEas plants of all species in either the vegetative or reproductive phase of growth were exposed to a 4-h heat shock in whicFh the temperature was raised an additional 14-23-degrees-C (depending on plant age). Total biomass and reproductive biomasAs were examined to determine the effect of CO2, nutrient and heat shock treatments on plant performance. Heat shock, CO2, Hntly affected by a heat shock than plants grown at ambient CO2 levels. Plants of a C3 annual (Abutilon theophrasti), a C3 Iannual crop (Sinapis alba) and a C4 annual (Amaranthus retroflexus) were grown from seed in growth chambers under either 4D00 or 700 cm3 m-3 CO2, and were fertilized with either a high or low nutrient regime. Young seedlings of S. alba, as well Kpatterns. Changes in mean air temperatures that might be induced by rising levels of CO2 and other greenhouse gases could Lalso be accompanied by increased variability in daily temperatures such that acute increases in air temperature may be morGe likely than at present. Consequently, we investigated whether plants grown in a CO2 enriched atmosphere would be differeN43^4^Coleman,JS^Rochefort,L^Bazzaz,FA^Woodward,FI^1991^1^Atmospheric CO2, plant nitrogen status and the susceptibility of plants to an acute increase in temperature^9^14^7^667-674^^^^^Sep^^^^^2947JA^2946^Elevated levels of CO2 in the atmosphere are expected to affect plant performance and may alter global temperature Q high-CO2 internal environment. In aquatic autotrophs, the CO2 concentrating mechanisms acclimate to the external CO2, beiRng suppressed at high-CO2. It is unclear, whether a doubling in atmospheric CO2 will be sufficient to cause a de-adaptive trend in the rubisco kinetics of future C3 plants, producing higher catalytic activities.29451^no, cameron lib. QC 879.7 I62Uonses. Over geological time, aquatic autotrophs and terrestrial C4 and CAM plants have genetically adapted to a decline inV the external CO2/O2 ratio, by the development of mechanisms to concentrate CO2 internally; thus circumventing O2 inhibitiPon of rubisco. Here rubisco affinity for CO2 is less, but its catalytic activity is greater, a situation compatible with aXd with reduced net photosynthesis, possibly causing feedback inhibition of the RuBP/P(i)-regeneration capacities, or chlorYoplast disruption. As exemplified by field-grown soybeans and salt marsh species, a reduction in net photosynthesis and ruTbisco activity is not inevitable under CO2 enrichment. Strong sinks or rapid translocation may avoid such acclimation resp[that is ultimately mediated by a decline in rubisco activity, though the RuBP/P(i)-regeneration capacities of the plant ma\y play a role. The decline is due to decreased rubisco protein, activation state, and/or specific activity, and it maintaiWns the rubisco fixation and RuBP/P(i)-regeneration capacities in balance. Carbohydrate accumulation is sometimes associate^ morphologically, physiologically or biochemically. So, CO2 exerts secondary effects in growth regulation, probably at the_ molecular level, that are not predictable from its primary biochemical role in carboxylation. After an initial increase wZith CO2 enrichment, net photosynthesis often declines. This is a common acclimation phenomenon, less so in field studies, a plants, rubisco has a low catalytic activity, operates below its K(m) (CO2), and is inhibited by O2. Consequently, increabses in the CO2/O2 ratio stimulate C3 photosynthesis and inhibit photorespiration. CO2 enrichment usually enhances the prod]uctivity of C3 plants, but the effect is marginal in C4 species. It also causes acclimation in various ways: anatomically.d289^7^Shaver,GR^Billings,WD^Chapin,FS^Giblin,AE^Nadelhoffer,KJ^Oechel,WC^Rastetter,EB^1992^1^Global change and the carbon balance of arctic ecosystems^14^42^6^433-441^^^^^Junfsurements of C-13/C-12 in shells of foraminiferas support the hypothesis that these CO2 changes are caused by changes in the ocean's biological pump, i.e. the flux of detrital organic carbon from the surface to the deep ocean, which affects thehthe oil-embargo in 1973. - Of special interest regarding the understanding of the carbon cycle and its role in controllingi the climate of the Earth are the observations in polar ice cores covering the past 160.000 years, corresponding to one aned a half glaciation cycles. They show variations of atmospheric CO2, CH4, and N2O parallel to the climatic variations. Meakere, of natural and nuclear weapon produced C-14 in the ocean and in the biota and of other natural or anthropogenic tracelrs. - Based essentially on such information, models for the CO2 uptake by the carbon system have been developed which are gcapable of reproducing the result of the drop in the rate of increase of CO2 emissions from 4.5% to 2% per year following nA^3412^For the estimate of the distribution in the carbon system of the CO2 emitted into the atmosphere due to human activoities, the exchange of carbon between atmosphere and ocean, and between atmosphere and biosphere needs to be considered. Ijnformation on this spreading of excess CO2 can be obtained from measurements of a.o. CO2, C-13/C-12, C-14/C in the atmosphqf the current zones. Despite these uncertainties, the direction of these models indicates future developments and could be used for policy purposes.^^^288^1^Oeschger,H^1992^1^Atmospheric co2 - global change and regulation mechanisms^203^96^3^252-257^^^^^Mar^^^^^3413t addressed. Examples are drawn from different impact studies on large-scale vegetation patterns, forest dynamics and agricuultural systems. General conclusions of these studies are that vegetation and agricultural zones will shift on global, conptinental and regional scales, but that large uncertainties still exist in the timing, actual response and rate of change ow2^3^Garbutt,K^Williams,WE^Bazzaz,FA^1990^1^Analysis of the differential response of 5 annuals to elevated CO2 during growth^11^71^3^1185-1194^^^^^Junmic Press^San Diego, CA^^Y^^1974^^^^^^^^^^^^^^^^^^^^^^^^3^5^Grulke,NE^Riechers,GH^Oechel,WC^Hjelm,U^Jaeger,C^1990^1^Carbon balance in tussock tundra under ambient and elevated atzA^3410^The changing composition of the atmosphere could lead to significant changes in regional and continental climate. T{he methodology to develop consistent climate-change scenarios and to link them to different impact-models is discussed. Ressults of both static and dynamic models are presented and the advantages and disadvantages of the different approaches aree three separate factors that could complicate this simple test.black spruce seedlings to elevated CO{-2} under varied wa~287^1^Leemans,R^1992^1^Modeling ecological and agricultural impacts of global change on a global scale^202^51^8-9^709-724^^^^^Aug-Sep^^^^^3411indicator of global warming and as a reliable test for identifying its onset. Hence, as the effective CO2 content of the atmosphere has already risen by nearly 50% above its pre-industrial level (Michaels, 1990; Houghton et al., 1990), studies |of drought trends of the past century might even now provide evidence for the reality of global warming. However, there arhile Rind et al. (1990) have demonstrated that CO2-induced global warming, if it occurs as projected, could raise the frequency of severe drought in the USA from 5 to 50% by the year 2050. If drought is truly this responsive to changes in precipitation and potential evapotranspiration, and there is little reason to believe it is not, it could serve as a sensitive A^3167^An analysis of elevated CO2 effects (2-4 times ambient) on dark respiration rate and carbon content was undertaken for a wide range of plant species, using both published reports and new data. On average, leaf respiration per unit leaf area was slightly higher for plants grown at high CO2 (16%), whereas a small decrease was found when respiration was express been postulated to result from minor changes in the atmospheric supply of moisture (precipitation) and major changes in the atmospheric demand for moisture (potential evapotranspiration), as a result of increased surface temperatures. Waggoner (1989), for example, has shown how a 10% drop in precipitation can lead to a 46% increase in the frequency of drought; w286^2^Idso,SB^Balling,RC^1992^1^United-states drought trends of the past century^107^60^3-4^279-284^^^^^31 Aug^^^^^3409moA^3408^One of the primary concerns about potential global change is that the steadily rising CO2 content of earth's atmosphere may lead to significant increases in the severity and frequency of drought, especially in the agricultural heartland of the USA (Manabe et al., 1981; Gleick, 1987; Manabe and Wetherald, 1986, 1987, McCabe et al., 1990). This consequence haSIGMA-CO2 was found necessary to maintain a maximal growth rate of 0.7 doublings/day. We also found that the increased productivity more than offsets the cost of adding the CO2.285^4^Carpenter,SR^Fisher,SG^Grimm,NB^Kitchell,JF^1992^1^Global change and fresh-water ecosystems^27^23^^119-139^ionship between inorganic carbon availability and algal production. Our results suggest that through additions of CO2 gas we were able to maintain sufficient dissolved carbon to stabilize outdoor algal cultures. Increases in the rate of addition of CO2 increased levels of dissolved CO2, total dissolved inorganic carbon (SIGMA-CO2), and decreased pH in the growth medium. This translated into improved buffering capacity of the culture medium and higher growth rate. A minimum of 2.4 mM 284^3^Olaizola,M^Duerr,EO^Freeman,DW^1991^1^Effect of co2 enhancement in an outdoor algal production system using tetraselmis^187^3^4^363-366^^^^^Dec^^^^^3406sts^Advances in ecological research^Academic Press^London^2-55^^1994^^19^^^^^^^^^^^^^A^3405^One of the objectives of microalgal culture is to provide reliable production technology for important live aquaculture feed organisms. Presented here are the results of experiments designed to provide a better understanding of the relatlish them. The kinetics of the stimulation indicate that the rate of photosynthesis is affected by two blue-light- dependent components with different time courses of induction and decay. The faster component seemed to be at least partially suppressed at red-light irradiances which were not saturating for photosynthesis. Lowering the pH of the medium had the same effects as an increase of the carbon concentration to levels of approx. 10 mM. This indicates that Ectocarpus takes up free CO2 only and not bicarbonate, although additional physiological mechanisms may enhance the availability of CO2.A^3369^Geochemical models that deduce latitudinal source/sink relationships of atmospheric CO2 suggest that, in tropical regions, there is almost zero net exchange of CO2 between the atmosphere and the terrestrial biosphere. The implication is  both the troughs and the peaks of the rhythm and before and after blue-light pulses. Only at very low carbon concentrations was a clear deviation found from these lines for photosynthesis at the rhythm maxima (red and blue light), which indicated that the strong carbon limitation specifically affected photosynthesis at the peak phases of the rhythm. Very high inorganic carbon concentrations (20 mM) in the medium diminished the responses to blue light, although they did not fully aboo under very low red-light irradiances after a period of adaptation, provided that the inorganic-carbon concentration was not in excess. Double-reciprocal plots of light-saturated photosynthetic rates versus the concentration of total inorganic carbon (up to 10 mM total inorganic carbon) were linear and had a common constant for half-saturation (3.6 mM at pH 8) atffected photosynthesis, the effects of inorganic carbon on photosynthetic light saturation curves were studied under different irradiation conditions. The circadian rhythm of photosynthesis was apparent only at irradiances which were not limiting for photosynthesis. The same was found for blue- light-stimulated photosynthesis, although stimulation was observed als266^2^Polglase,PJ^Wang,YP^1992^1^Potential co2-enhanced carbon storage by the terrestrial biosphere^182^40^4-5^641-656^^^^A^3403^Photosynthesis of Ectocarpus siliculosus (Dillwyn) Lyngb. under continuous saturating red irradiation follows a circadian rhythm. Blue-light pulses rapidly stimulate photosynthesis with high effectiveness in the troughs of this rhythm but the effectiveness of such pulses is much lower at its peaks. In an attempt to understand how blue light and the rhythm a402^Holsinger,K S^1993^3^The evolutionary dynamics of fragmented plant populations^Biotic interactions and global change^283^3^Schmid,R^Forster,R^Dring,MJ^1992^1^Circadian-rhythm and fast responses to blue-light of photosynthesis in ectocarpus (phaeophyta, ectocarpales) .2. Light and co2 dependence of photosynthesis^6^187^1^60-66^^^^^Apr^^^^^340490, however, suggest a relative growth enhancement for the CO2-enriched trees of the order of five to seven, which is clearly impossible on the basis of the direct growth measurements. It is shown that this discrepancy is due to a problem inherent in the act of enclosing a leaf in a leaf chamber, but that its effects can be removed by means of a simple correction procedure.essrees supplied with an extra 300 cm3 of CO2 m-3 of air is approximately 2.8 times greater than that of similar trees growing in ambient air. Net CO2 exchange measurements made on individual leaves over three 24 h periods in May, June and July 19282^1^Idso,SB^1992^1^Net photosynthesis - corrections required of leaf chamber measurements^107^58^1-2^35-42^^^^^Mar^^^^^3A^3401^Direct measurements of trunk and branch volumes and fine-root biomass confirm that the growth rate of sour orange tonditions. Chemical names used: 3-chloro-4-(2'-nitro-3'-chlorophenyl)-pyrrole (pyrrolnitrin); N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide (captan); methyl 1-(butylcarbamoyl)-2-benzimidazolecarbamate) (benomyl); 3-(3,5-dichlorophenyl)-N-(1-methylethyl)-2,4-dioxo-1- imidazolidinecarboxamide (Rovral, iprodione).ostharvest quality of black raspberries at both storage temperatures by reducing gray mold development. The combination of standard fungicide or pyrrolnitrin, high CO2, and low temperature resulted in more than 2 weeks of storage with less than 5% disease on black raspberries; however, discoloration limited marketability after almost- equal-to 8 days under these cd fungicide treatment (captan + benomyl or iprodione) or a distilled water control applied 1 day before first harvest. Black raspberries were stored at 18 or 0 +/- 1C in air or 20% CO2. Red raspberries were stored at the same temperatures in air only. Pyrrolnitrin-treated berries often had less gray mold (Botrytis cinerea Pers. ex Fr.) in storage than the control but more than berries treated with the standard fungicides. Storage in a modified atmosphere of 20% CO2 greatly improved pA^3399^The effects of preharvest applications of pyrrolnitrin (a biologically derived fungicide) on postharvest longevity of 'Bristol' black raspberry (Rubus occidentalis L.) and 'Heritage' red raspberry [R. idaeus L. var. strigosus (Michx.) Maxim] were evaluated at two storage temperatures. Preharvest fungicide treatments were 200 mg pyrrolnitrin/liter, a standaritical CO2, the only parameter determined from the dynamic extraction rate data, increases with temperature and pressure.281^5^Goulart,BL^Hammer,PE^Evensen,KB^Janisiewicz,W^Takeda,F^1992^1^Pyrrolnitrin, captan + benomyl, and high co2 enhance raspberry shelf-life at 0C or 18C^154^117^2^265-270^^^^^Mar^^^^^3400158^1^Rawson,HM^1992^1^Plant-responses to temperature under conditions of elevated CO2^182^40^4-5^473-490^^^^^^^^^^3170^^A^3169^A literature survey of the interactive effects of CO2 enrichment and temperature on plant development and growth, itndicated that the responses cannot be interpreted within a simple framework. For example, although plant development is gefluenced by both intraparticle diffusion in the water-soaked beans and external mass transfer. A mathematical model based on a linear-driving-force approximation of mass transfer and partitioning of caffeine between the water and the supercritical CO2 describes the time-dependent process. The partition coefficient for caffeine distributed between water and supercrow extraction apparatus. Decaffeination rates were determined as a function of CO2 flow rate, temperature and pressure by continuously monitoring the caffeine in the effluent with aflame ionization detector. Soaking the raw beans in water prior to decaffeination enhanced the rate of extraction, which increased markedly with water content. Using CO2 saturated with water also increased the rate of extraction. The rate of decaffeination increased with pressure and temperature and was in280^4^Peker,H^Srinivasan,MP^Smith,JM^McCoy,BJ^1992^1^Caffeine extraction rates from coffee beans with supercritical carbon-dioxide^201^38^5^761-770^^^^^May^^^^^339825^^2032^^^^^^^^^^^^^^^^^^^^^^^^^^^^^Bliss,L C^Heal,O W^Moore,J JA^3397^The extraction of caffeine from whole coffee beans with supercritical carbon dioxide was studied in a continuous-fl(commercial classification: 'Select' and 'No. 1') was enhanced for this period compared with the same period the previous year when no supplemental carbon dioxide was provided. Generally the planting scheme of two parallel rows gave the best overall results.131^1^Peterson,RB^1991^1^Effects of O2 and CO2 concentrations on quantum yields of photosystem-I and photosystem-II in tobacco leaf tissue^8^97^4^1388-1394^^^^^Dec^^^^^3117^^^^^^^^A^3116^The interactive effects of irradiance and O2 and CO2 levels on the quantum yields of photosystems I and II have beeth of the plants compared to plants grown in ambient light conditions. Marketable yield per plant was increased significantly by 79% (P< 0.05) for the crop period from 1 January to 24 March 1988 when a PPFD of 50-mu-mol s-1 m-2 was added to ambient light conditions. Carbon dioxide enrichment increased yield by 113% when a PPFD of 50-mu-mol s-1 m-2 was added to ambient light during the crop period of 1 January to 24 March, 1989. The number of flowers per plant in the superior classes ality of RosaXhybrida cultivar 'Royalty' was investigated. Three planting schemes (two, three, and four parallel rows) and three light treatments (ambient light and ambient light Plus supplemental lighting with either 50 or 100-mu-mol s-1 m-2 PPFD (high pressure sodium lamps) were studied. Generally, supplementary PPFD enhanced the vegetative and reproductive grow279^2^Menard,C^Dansereau,B^1992^1^Influence of photosynthetic photon flux-density and planting scheme on growth and development of cultivar royalty roses^165^50^3^197-207^^^^^May^^^^^3396A^3395^The influence of photosynthetic photon flux density (PPFD) and planting scheme on growth, development, yield and qu latitudes the median values are 71 tCha-1 (n=401) and 66 tCha-1 (n=170), respectively. Preliminary projections are that if these practices were implemented on 0.6 to 1.2 x 10(9) ha of available land over a 50-yr period, approximately 50 to 100 GtC could be sequestered.es. Results indicate that the most promising management practices are reforestation in the temperate and tropical latitudes, afforestation in the temperate regions, and agroforestry and natural reforestation in the tropics. Across all practices, the median of the mean C storage values for the boreal latitudes is 16 tCha-1 (n=46) while in the temperate and tropicalCO2. The question is how much C can be sequestered by forest and agroforest management practices. To address the question, a global database of information was compiled to assess quantitatively the potential of forestry practices to sequester C. The database presently has information for 94 forested nations that represent the boreal, temperate and tropical latitudlowering of rosa L and kalanchoe- blossfeldiana V poelln^165^51^1-2^145-153^^^^^Jul^^^^^3324412^^2221^^^^^^^^^^^^^^^^^^^^A^3323^The effects of increasing the CO2 concentration from 350 to 700-mu-l l-1 on growth and flowering of Rosa L. and Kaltrunk and branch volume, and 190% more trunk, branch and fruit rind volume than the ambient-treatment trees.ross- sectional area. They also reveal a sustained beneficial impact of atmospheric CO2 enrichment. After 3 full years of differential CO2 exposure, the CO2-enriched trees had nearly 100% more branches, 75% more leaves, approximately 160% more aves per tree, and the total trunk plus branch volume per tree can all be adequately inferred from measurements of trunk co air enriched with an extra 300 cm3 of CO2 m-3 of air. Inventories of all aboveground plant parts conducted at the conclusions of the second and third years of the study reveal that the total number of branches per tree, the total number of leopen-top enclosures for 3.5 years. For the last 3 years of this period, half of the trees have been continuously exposed tions for 3 full years^107^60^1-2^145-151^^^^^15 Aug^^^^^3322ater requirements of C{-3} plants grown at glacial to presentA^3321^Sour orange trees have been grown from the seedling stage out- of-doors at Pheonix, Arizona in clear-plastic-wall, 240^2^Idso,SB^Kimball,BA^1992^1^Aboveground inventory of sour orange trees exposed to different atmospheric co2 concentrattion.Fitter,A H^Fitter,R S R^Harris,I T B^Williamson,M H^1995^1^Relationships between first flowering date and temperatur239^1^Idso,SB^1992^1^Shrubland expansion in the american southwest^50^22^1^85-86^^^^^Sep air) or in shake flasks. The stimulation of root growth via CO2 enrichment reduced the time required for biomass accumulaet hairy root tissue was also cultured aeroponically in nutrient mists. Beet hairy root cultured in nutrients mists enriched with 1.0 % CO2 showed a 15 % increase in biomass over a 7-day period vs tissue cultured in nutrient mists (with ambient regulated to protect sensitive metabolic sites from salt toxicity. Salt-tolerant species exclude most of the salt from the transpiration stream, but the salt flux from a highly saline soil is still considerable. To maintain internal ion concenatrations within physiologically acceptable levels, the salt influx to leaves must match the capacities of leaves for salt 25^^^^^^^^^^3143L^Vitt,DH^and K.P. Timoney^1989^1^Patterns of community structure and morphology of bryophytes and lichenA^3142^This review explores effects of elevated CO2 concentrations on growth in relation to water use and salt balance of halophytic and non-halophytic species. Under saline conditions, the uptake and distribution of sodium and chloride must behetic machinery and the rest of the plant; and (3) changing the response of stomata to CO2 and humidity to increase water-use efficiency even further than is currently predicted.76144^2^Ball,MC^Munns,R^1992^1^Plant-responses to salinity under elevated atmospheric concentrations of CO2^182^40^4-5^515-5 lants may not be genetically adapted to optimise their growth and performance at elevated CO2 and that consideration shoul d be given to exploring avenues for manipulating plants for more optimal responses. Targets for improvement of growth at elevated CO2 include (1) altering source-sink relations; (2) improving the redistribution of nitrogen between the photosyntotential gains are greatly ameliorated by a redistribution of plant resources. This primarily occurs via a reduction in the leaf area ratio which offsets increases in the net assimilation rate. In addition, there may be an overcommitment of nit rogen in key photosynthetic components such as Rubisco and the thylakoid electron transport system. It is concluded that pt. These include increases in the efficiencies for light, nitrogen and water utilisation, particularly at elevated temperatures, resulting from the improvement which will occur in the performance of the primary carboxylating enzyme, Rubisco. Ho wever, while growth experiments at elevated CO2 indicate that C3 plants show stimulation of dry matter accumulation, the p CO2 must be capable of generating such realised environmental niche responses for species.s at some localities in northe143^1^Badger,M^1992^1^Manipulating agricultural plants for a future high CO2 environment^182^40^4-5^421-429^^^^^^^^^^3141A^3140^This paper discusses the potential ways in which C3 plant performance may benefit from a future high-CO2 environmen where t is temperature and letters are parameters. The probability of occurrence is shown to be a skewed function of mean annual temperature. Any process-models of climate change for vegetation incorporating temperature changes due to elevateds in southern New South Wales, Australia. Seven environmental variables or factors are considered: mean annual temperature, mean annual rainfall, mean monthly solar radiation, topographic position, rainfall seasonality, lithology, and soil nutrient status. The temperature response is modelled with a beta-function, log y = a + alpha log (t - a) + delta log (b - t),odels are to be tested for predictive success by reference to naturally occurring communities and temperature gradients. An example of a statistical method for quantifying the realised environmental niche respone of a species to temperature is provided. It is based on generalised linear modelling (GLM) of presence/absence data on Eucalyptus fastigata for 8377 siteinuum concept. Confusion exists between the different approaches over the shape of response curves to temperature. Distinc tions need to be made between responses due to growth (physiological response), potential fitness (fundamental niche) and observed performance (realised niche). These types of response should be quantified and related to each other if process-m"ure responses for plants. Physiologists often assume a skewed non-monotonic curve with a tail towards low temperatures, fo#rest modellers using FORET type models, a symmetric curve, and community ecologists a skewed response with a tail towards high temperatures. These assumptions are reviewed in relation to niche theory, and recent propositions concerning the cont%A^3138^No simple natural gradients in CO2 concentration exist for testing predictions about changes in plant communities i&n response to elevated CO2. However indirect effects of CO2 via temperature increases can be tested by reference to natura!l analogues. Physiologists, vegetation modellers of climate change and community ecologists assume very different temperat(142^1^Austin,MP^1992^1^Modeling the environmental niche of plants - implications for plant community response to elevated CO2 levels^182^40^4-5^615-630^^^^^^^^^^3139* the reliability of these models in conditions where Rubisco has a flux-control coefficient approach unity (i.e. "limits" +photosynthesis), but also indicates that these models are less useful in conditions where control is shared between Rubisco and other components of the photosynthetic apparatus...-saturating irradiance and CO2 are suppressed in decreased- activity transformants before the steady-state rate of photosyn.thesis is affected. This provides direct evidence that these oscillations reveal the presence of "excess" Rubisco. (vi) Co)mparison of the flux-control coefficients of Rubisco with mechanistic models of photosynthesis provides direct support for0l coefficient of stomata for photosynthesis was calculated from the flux- control coefficient of Rubisco and the internal 1CO2 concentration, by applying the connectivity theorem. Control by the stomata varies between zero and about 0.25. It is ,increased by increased irradiance, decreased CO2 or decreased vapour-pressure deficit. (v) Photosynthetic oscillations in 3hat Rubisco still exerts marginal control in these conditions because decreased Rubisco leads to increased thylakoid energ/isation and high-energy dependent dissipation of light energy, and lower light-harvesting efficiency. (iv) The flux-contro5e available capacity is being used. Control increases as utilisation rises to 80%, and approaches unity (i.e. strict limit6ation) when more than 80% of the available capacity is being used. (iii) In low light, plants with reduced Rubisco have ve2ry high energy-dependent quenching of chlorophyll fluorescence (qE) and a decreased apparent quantum yield. It is argued t8r) or low light (310 mumol m-2 s-1) and was also decreased at high vapour- pressure deficit (17 mbar). No control was exer9ted in 5% CO2. (ii) The flux-control coefficients of Rubisco were compared with the fractional demand placed on the calcul4ated available Rubisco capacity. Only a marginal control on photosynthetic flux is exerted by Rubisco until over 50% of th;ntent versus assimilation rate. The flux-control coefficient had a value of 0.8 or more in high irradiance, (1050 mumol m-72 s-1), low-vapour pressure deficit (4 mbar) and ambient CO2 (350-mu-bar). Control was marginal in enhanced CO2 (450-mu-ba=estigate the contribution of Rubsico to the control of photosynthesis at different irradiance, CO2 concentrations and vapo>ur-pressure deficits. Assimilation rates, transpiration, the internal CO2 concentration and chlorophyll fluorescence were :measured in each plant. (i) The flux-control coefficient of Rubisco was estimated from the slope of the plot of Rubisco co@A^3136^Transgenic tobacco (Nicotiana tabacum L.) plants transformed with 'antisense' rbcS to produce a series of plants wiin the atmosphere 9. Here we use the Rothamsted model for the turnover of organic matter in soil 3 to calculate the amountDA^3126^ONE effect of global warming will be to accelerate the decomposition of soil organic matter, thereby releasing CO2 Eto the atmosphere, which will further enhance the warming trend 1- 7. Such a feedback mechanism could be quantitatively imAportant, because CO2 is thought to be responsible for approximately 55% of the increase in radiative forcing arising from acting as a second electron-accepting assimilatory process in addition to CO2 fixation.vegetation types in Alaska^10^11^^H136^3^Jenkinson,DS^Adams,DE^Wild,A^1991^1^Model estimates of CO2 emissions from soil in response to global warming^36^351^6324^304-306^^^^^23 May^^^^^3127Jht-intensity curve. No stimulation Of O2 evolution was otherwise observed after feeding KCl or NH4Cl. The data indicate thFat nitrate assimilation uses photosynthetically generated reductant and stimulates the rate of noncyclic electron flow by Lvum L. cv Lincoln) in a CO2-saturating atmosphere was enhanced when KNO3 (1-2.5 millimolar) had been previously supplied tMhrough the transpiration stream. The extra O2 evolution observed after feeding KNO3 increased with the light intensity, beIing maximal at near saturating photon flux densities and resulting in no changes in the initial slope of the O2 versus lig of safe strategies to minimize the negative impacts and maximize the benefits of these changes.s accumulation in Eriopho135^3^Delatorre,A^Delgado,B^Lara,C^1991^1^Nitrate-dependent O2 evolution in intact leaves^8^96^3^898-901^^^^^Jul^^^^^3125KA^3124^Evolution Of O2 by illuminated intact detached leaves from barley (Hordeum vulgare L. cv Athos) and pea (Pisum satiRt in interior western Canada. Increases in annual temperature of 3 to 7-degrees-C are projected for Alberta under a 2 x COS2 scenario by 2030-2050 A.D. Such an unprecedented rate of change has many short- and long-term implications for forest maNnagement and for industries. As the boreal forest is highly sensitive to climatic changes, foresters need to develop a setU134^2^Singh,T^Wheaton,EE^1991^1^Boreal forest sensitivity to global warming - implications for forest management in western interior canada^66^67^4^342-348^^^^^Aug^^^^^3123QA^3122^Unmitigated global warming due to the enhanced greenhouse effect could have significant impacts on the boreal foresXowth to readjust the sink-source balance. In the final part of the review, I argue that similar changes of Rubisco and, possibly, other proteins are probably also involved during acclimation to high CO2.Znt, involving decreases in amounts of key photosynthetic enzymes, including Rubisco. This decreases the rate of photosynthWesis, and potentially would allow resources (e.g. amino acids) to be remobilized from the leaves and reinvested in sink gr\mportant in the short-term regulation of partitioning to sucrose and starch, but that its contribution to 'sink' regulatioYn has not yet been conclusively demonstrated. Indirect or 'adaptive' regulation of photosynthesis is probably more importa^'sink' regulation of photosynthesis. Accumulating carbohydrate could lead to a direct inhibition of photosynthesis, involv[ing mechanical damage by large starch grains or Pi-limitation due to inhibition of sucrose synthesis. I argue that Pi is i`to an inadequate demand for carbohydrate in the remainder of the plant. Differences in the long-term response to CO2 may bae explained by differences in the sink-source status of plants. depending upon the species, the developmental stage, and t]he developmental conditions. In the third part of the review, I consider the biochemical mechanisms which are involved in cs sensitively), and that photosynthesis will be stimulated by 25- 75% when the CO2 concentration is doubled from 35 to 70 dPa. This is in good agreement with the published responses. In the next part of the review, I discuss the evidence that mo_st plants undergo a gradual inhibition of photosynthesis during acclimation to enhanced CO2. I argue that this is related fe demand on partial processes like carboxylation, light harvesting and electron transport, the Calvin cycle, and end-produgct synthesis; and (2) the extent to which these various processes actually control the rate of photosynthesis. I conclude bthat control is usually shared between Rubisco (which responds sensitively to CO2) and other components (which respond lesiA^3120^In the first part of this review, I discuss how we can predict the direct short-term effect of enhanced CO2 on photeosynthetic rate in C3 terrestrial plants. To do this, I consider: (1) to what extent enhanced CO2 Will stimulate or relievted plants was found for both salinity and water stress. the sensitivity of tundra ecosystems to climate change^76^72^^8l133^1^Stitt,M^1991^1^Rising CO2 levels and their potential significance for carbon flow in photosynthetic cells^9^14^8^741-762^^^^^Oct^^^^^3121nly, in journalned only 5% of the total increase in solutes in salinity- acclimated and 10 to 20% in water-stress-acclimated plants. This oacclimation was interpreted in light of the higher protein content per unit leaf area and the enhanced ribulose bisphosphajte carboxylase activity. At saturating CO2 Partial pressure, the declined inhibition in CO2 assimilation of stress-acclimaqn acclimated than in nonacclimated plants, resulting in turgor maintenance even at -0.9 megapascal. In nonacclimated plantrs, turgor pressure reached zero at approximately -0.5 megapascal. The accumulation of Cl- and Na+ in the salinity-acclimatmed plants fully accounted for the decrease in leaf osmotic potential. The rise in concentration of organic solutes compristonship, were increased in plants acclimated to salinity of -0.3 and -0.6 megapascal but not in nonacclimated plants. In plpants acclimated to water stress, this change in slopes was not significant. Leaf osmotic potential was reduced much more iv nonacclimated plants. The decrease of CO2 assimilation in salinity-exposed plants was significantly less in acclimated asw compared with nonacclimated plants. Such a difference was not found under water stress at ambient CO2 partial pressure. Tshe slopes of net CO2 assimilation versus intercellular CO2 partial pressure, for the initial linear portion of this relatiyA^3118^Cotton (Gossypium hirsutum L. cv Acala SJ2) plants were exposed to three levels of osmotic or matric potentials. Thze first was obtained by salt and the latter by withholding irrigation water. Plants were acclimated to the two stress typeus by reducing the rate of stress development by a factor of 4 to 7. CO2 assimilation was then determined on acclimated andrescence was unaffected by CO2 concentration.d food quality influences feeding behavior, assimilation efficiency and grow}132^2^Plaut,Z^Federman,E^1991^1^Acclimation of CO2 assimilation in cotton leaves to water- stress and salinity^8^97^2^515-522^^^^^Oct^^^^^3119 on photosystem II arising from a build-up in the thylakoid proton gradient during electron transport to O2. Covariation between quantum yields of photosystems I and II was not affected by concentrations of either O2 or CO2. The dependence of q{uantum yield of electron transport to CO2 measured by gas exchange upon photosystem II quantum yield as determined by fluotion is suspected to mediate such positive effects of O2 through increases in the availability of CO2 and recycling of orthophosphate. Conversely, at low intercellular CO2 concentrations, 41.2% O2 was associated with lower photosystem II quantu~m yield compared with that observed at 20.5% O2. Inhibitory effects of 41.2% O2 may occur in response to negative feedbacksorbance change at 830 nanometers, the absorption band of P700+. Normal (i.e. 20.5%, v/v) levels of O2 generally enhanced photosystem II quantum yield relative to that measured under 1.6% O2 as the irradiance approached saturation. Photorespiran studied under steady-state conditions at 25-degrees-C in leaf tissue of tobacco (Nicotiana tabacum). Assessment of radiant energy utilization in photosystem II was based on changes in chlorophyll fluorescence yield excited by a weak measuring beam of modulated red light. Independent estimates of photosystem I quantum yield were based on the light-dark in vivo abons above ambient. Increasing CO2 concentration had no effect on the carbohydrate concentration in the grain at maturity.130^1^Wittwer,SH^1990^1^Implications of the greenhouse-effect on crop productivity^170^25^12^1560-1567^^^^^Decon. At maturity, increasing CO2 concentration resulted in an increase in total non-structural carbohydrate (TNC) concentration in leaf blades, leaf sheaths and culms. Carbohydrates that were stored in vegetative plant parts before heading made a smaller contribution to grain dry weight at CO2 concentrations below 330 mu-mol mol-1 than for treatments at concentrati-1 CO2. Similarly, photosynthesis also increased with CO2 concentrations up to 500 mu-mol mol-1 and then reached a plateau at higher concentrations. The ratio of starch to sucrose concentration was positively correlated with the CO2 concentrati0, 250, 330, 500, 660, and 900 mu-mol CO2 mol-1 air. In leaf blades, the priority between the partitioning of carbon into storage carbohydrates or into export changed with development stage and CO2 concentration. During vegetative growth, leaf sucrose and starch concentrations increased with increasing CO2 concentration but tended to level off above 500 mu-mol molcentration sometime during the next century. The objective of this investigation was to determine the long-term effects of different CO2 concentrations on carbohydrate status and partitioning in rice (Oryza sativa L. cv. IR-30). Rice plants were grown season-long in outdoor, naturally sunlit, environmentally controlled growth chambers with CO2 concentrations of 16129^4^Rowlandbamford,AJ^Allen,LH^Baker,JT^Boote,KJ^1990^1^Carbon-dioxide effects on carbohydrate status and partitioning in rice^78^41^233^1601-1608^^^^^Dec^^^^^3114A^3113^The atmospheric carbon dioxide (CO2) concentration has been rising and is predicted to reach double the present concement by CO2 enrichment was 2.3. Two genotypes showed significant genotype x CO2 interaction. The consequences of these results for tomato breeding are discussed.108^4^Couteaux,MM^Mousseau,M^Celerier,ML^Bottner,P^1991^1^Increased atmospheric CO2 and litter quality - decomposition of sweet chestnut leaf litter with animal food webs of different complexities^15^61^1^54-64^^^^^May^^^^^3073notypes were found for average plant fresh and dry weights and for relative growth rates. The average overall growth enhanex can be calculated. Our preliminary results give promise of extending the record of stomatal density response back at least 10,000 years. indicates CO2 levels markedly different from pre-industrial levels, provides one means for eliciting long-term plant responses to changing CO2 regimes. We have prepared cuticles from Quaternary leaf fossils, from which stomatal density and indxperimental exposure of plants to elevated CO2 regimes in controlled environment chambers can only indicate immediate, phenotypic, short-term responses. The investigation of fossil leaves of extant species growing under the different atmospheric conditions of the last glacial and deglacial transition, when evidence from an Antarctic ice core (Barnola et al., 1987)A^3070^Continued increases in the global atmospheric CO2 concentration have been predicted from current and projected rates of fossil fuel burning. Understanding the response of stomatal density as an important ecophysiological parameter controlling the productivity of vegetation is essential if the role of plants in the global carbon budget are to be predicted. E107^5^Beerling,DJ^Chaloner,WG^Huntley,B^Pearson,A^Tooley,MJ^1991^1^Tracking stomatal densities through a glacial cycle - their significance for predicting the response of plants to changing atmospheric CO2 concentrations^175^1^5^136-142^^^^^Sep^^^^^3071re roses the number of flower buds was significantly increased under diurnally changing CO2 concentration or when the CO2 level was constant at 600 ppm compared with a constant 900 ppm. Time to flowering was decreased by constant CO2 at 900 ppm as compared with the other treatments.atural daylength and irradiance. The tallest plants and greatest increment in height for Ficus occurred with plants grown under constant CO2 concentration at 600 ppm and also with increasing CO2 concentration. In both experiments the dry weight per pot was lowest when plants were grown under a constant CO2 concentration at 900 ppm. In both experiments with miniatuo 1500 ppm and one decreasing from 1500 to 600 ppm, each in four steps of 300 ppm during the day-time. In all treatments 900 ppm CO2 was maintained during the night when supplementary light was used, except in the treatment with constant 600 ppm where 600 ppm was also continued throughout the night. Plant growth was monitored under both decreasing and increasing nent^174^66^5^569-574^^^^^Sep^^^^^30691^The sensitivity of phenological events to changes in nutrient availability for sevA^3068^Plants of Ficus benjamina and miniature rose (Rosa hybrida cv. Red Minimo) were grown under four CO2 treatments. Two had constant CO2 levels (600 and 900 ppm) and the other two had diurnal changes in CO2 levels, one increasing from 600 tearch is for integrated studies on plant and soil processes.hotosynthesis in arctic plants^31^5^^158-163^^1166106^1^Andersson,NE^1991^1^The influence of constant and diurnally changing CO2 concentrations on plant-growth and developm dynamics of these plant-soil interactions and the future status of soils in different life zones as sources or sinks of carbon is poorly understood. More data are also needed on the distribution of waterlogged forest soils in the boreal zone and responses to warming, which include the production of methane as well as CO2. The primary recommendation for future resre more predictable in well-drained grassland and forest soils than in waterlogged soils of the tundra and boreal region. Over longer periods of time, however, plant species and soil types will alter in response to new temperature and moisture regimes above- and belowground interacting with the effects of carbon enrichment and changes in nutrient availability. Thement regulating SOM dynamics is not a direct function of macroclimatic conditions. Grasslands contain a greater proportion of highly stabilized SOM than coniferous forests, distributed over greater depth in the soil profile, which is less susceptible to changes in mineralization rates. It is concluded that short-term responses of soil processes to climate change ae change, carbon mineralization rates from arctic and sub-arctic soils could be very rapid under warmer and drier conditions because of low stabilization of soil organic matter (SOM) and enhanced microbial responses to small changes in soil moisture and temperature. Predicting the response of these systems to climate change is complicated where the edaphic environ an increase in grasslands. These scenarios also indicate a northerly shift in agricultural regions, bringing virgin soils under cultivation. The direct effects of man on tundra,boreal forest, and temperate grassland ecosystems are likely to result in less carbon mobilization from soils and vegetation than from tropical forests. However, as a consequence of climat105^1^Anderson,JM^1991^1^The effects of climate change on decomposition processes in grassland and coniferous forests^56^1^3^326-347^^^^^Aug^^^^^3067e^2^62^^196-198^^1178A^3066^Current models of climate change predict a reduction of area covered by northern coniferous forests and tundra, andson spider mite damage of the 990 and 280-mu-mol mol-1 treatments reduced yields. These data confirm not only that rising CO2 should increase plant growth, but also that plant growth was probably seriously limited by atmospheric [CO2] in preindustrial revolution times back to the previous global glaciation.e percentage of total plant mass in leaf trifoliolates decreased with increasing [CO2] whereas the percentage in structural components (petioles and stems) increased. At final harvest the respective [CO2] treatments resulted in 38, 53, 62, 100, 120, and 92% seed yield with respect to the 330-mu-mol mol-1 treatment. Total dry weight responses were similar. Late seamu-mol (CO2) mol-1 (air). Total dry matter growth rates during the linear phase of vegetative growth were 5.0, 8.4, 10.9, 12.5, 18.2, and 20.7 g m-2 d-1 for the above respective [CO2]. Samples taken from 24 to 94 d after planting showed that thture expected CO2 levels and to increase confidence in [CO2] response curves by imposing a wide range of [CO2] treatments. Soybean was grown in outdoor, sunlit, controlled- environment chambers at CO2 levels of 160, 220, 280, 330, 660, and 990-A^3064^Rising atmospheric carbon dioxide concentration [CO2] is expected to cause increases in crop growth and yield. The objective of this study was to investigate effects of subambient, as well as superambient, [CO2] on soybean [Glycine max (L.) Merr.] dry matter production and allocation for two reasons: to assess response of plants to prehistoric as well as fu104^4^Allen,LH^Bisbal,EC^Boote,KJ^Jones,PH^1991^1^Soybean dry-matter allocation under subambient and superambient levels of carbon-dioxide^48^83^5^875-883^^^^^Sep-Oct^^^^^3065 treatments, while tuber yields of Russet Burbank and Norland were increased 18 and 9%, respectively. The results show a pattern of greater plant growth from CO2 enrichment under lower PPF and a short photoperiod.total plant dry weight by 39 and 34%, respectively, under a 12-h photoperiod at 400-mu-mol m-2 s-1; 27 and 19% under 12 h at 800-mu-mol m-2 s-1; 9 and 9% under 24 h at 400-mu-mol m-2 s-1. It decreased dry weights by 9 and 9% under 24 h at 800-mu-mol m-2 s-1. Tuber yield of Denali showed the greatest increase (21%) in response to increased CO2 across all irradianceher at 350 or 100-mu-mol mol-1 and applied in combination with 12- or 24-h photoperiods at 400 or 800-mu-mol m-2 s-1 photosynthetic photon flux. Air temperatures and relative humidity were held constant at 16-degrees-C and 70%, respectively, and plants were harvested 90 d after planting. When averaged across all cultivars, CO2 enrichment increased tuber yield and A^3062^Carbon dioxide concentration can exert a strong influence on plant growth, but this influence can vary depending on irradiance. To study this, potato plants (Solanum tuberosum L.) cultivars 'Norland'. 'Russet Burbank', and 'Denali' were grown in controlled-environment rooms at different levels of CO2 and irradiance. Carbon dioxide levels were maintained eittor that induces the CCM, although secondary regulation must also be involved.love Lowland, Devon Island, N.W.T., Canada^103^3^Wheeler,RM^Tibbitts,TW^Fitzpatrick,AH^1991^1^Carbon-dioxide effects on potato growth under different photoperiods and irradiance^164^31^5^1209-1213^^^^^Sep-Oct^^^^^3063 activities. Other known mutants of the CCM show patterns of PGPase and glycolate DH activity after transfer to limiting CO2 which are different from WT and cia-5 but which are consistent with changes in activity being initiated by the same facells is double that seen in CO2-enriched cells. Unlike WT, the high-CO2-requiring mutant, cia-5, does not respond to limiting CO2 conditions: it does not induce any known aspects of the CCM and it does not show changes in PGPase or glycolate DHoxygenase. PGPase in cell extracts shows a transient increase in activity that reaches a maximum 3 to 5 hours after transfer and then declines to the original level within 48 hours. The decline in PGPase activity begins at about the time that physiological evidence indicates the CCM is approaching maximal activity. Glycolate DH activity in 24 hour air-adapted WT c. Adaptation to air levels of CO2 by Chlamydomonas involves induction of a CO2-concentrating mechanism (CCM) which increases the internal inorganic carbon concentration and suppresses oxygenase activity of ribulose-1,5-bisphosphate carboxylase/A^3060^The activity of two photorespiratory enzymes, phosphoglycolate phosphatase (PGPase) and glycolate dehydrogenase (glycolate DH), changes when CO2-enriched wild-type (WT) Chlamydomonas reinhardtii cells are transferred to air levels of CO2102^2^Marek,LF^Spalding,MH^1991^1^Changes in photorespiratory enzyme-activity in response to limiting CO2 in Chlamydomonas reinhardtii^8^97^1^420-425^^^^^Sep^^^^^3061ant's photosynthetic response to atmospheric CO2 enrichment is inversely proportional to its degree of CO2-induced stomatal closure. in stomatal conductance^173^31^4^381-383^^^^^Oct^^^^^3059ing, sexual selection, and the evolution of dioecy in plants^16A^3058^Simultaneous measurements of net photosynthesis and stomatal conductance of leaves of sour orange trees growing in normal and CO2-enriched air, together with similar data for cotton, cotton, soybeans and water hyacinth, suggest that a pl by a distinct reduction of leaf area growth and by chlorotic discolorations. in plants^32^250^^923-930^^1218101^1^Idso,SB^1991^1^A general relationship between CO2-induced increases in net photosynthesis and concomitant reductionsith 1% CO2 already after a few days. Equal reactions were observed with radish, var. sativus. With tomatoes strong injuries of the leaves causing leaf death were observed after 7 days with 1% CO2 and after 5 days with 2% CO2. Bush beans reactedk using 2% CO2 and after 2-3 days using 3% CO2. The warm-season species tested reacted more sensitive. Cucumbers tolerated 1% CO2 for 2-3 weeks, using 2% CO2 wilting and driving injuries occurred already after 1 day table 2). In case of disturbances of the water status of the plants by transplanting, top dressing or sharp decrease of air humidity cucumber wilted w photosynthesis is limited by the rate of RuBP regeneration. in biologically active ultraviolet radiation reaching the gr93^2^Sasek,TW^Strain,BR^1991^1^Effects of CO2 enrichment on the growth and morphology of a native and an introduced honeysuckle vine^5^78^1^69-75^^^^^Jan^^^^^3044s per square meter per second increased the activation state of rubisco but had little effect on the K(cat). These results support modelled simulations of the rubisco response to light and CO2, where rubisco is assumed to be down-regulated when state of rubisco was dependent on C(i). Otherwise, RuBP pool sizes increases as C(i) was reduced. ATP pools in C. album tended to increase as C(i) was reduced. In P. vulgaris, decreasing C(i) at a subsaturating light intensity of 190 micromole C(i) was elevated above 120 microbars at 550 micromoles per square meter per second and above 300 microbars at 1750 micromoles per square meter per second. The pool size of RuBP was independent of C(i) only under conditions when the activation 550, and 150 micromoles per square meter per second) and at intercellular CO2 partial pressures (C(i)) between the CO2 com pensation point and 500 microbars. Above a C(i) of 120 microbars, the activation state of rubisco was light dependent. At light intensities of 550 and 1750 micromoles per square meter per second, it was also dependent on C(i), decreasing as theBP regeneration limited photosynthesis, but not when rubisco capacity limited photosynthesis. Measured observations closel y matched modeled simulations. The activation state of rubisco was measured at three light intensities in C. album (1750,  square meter per second in C. album and below 200 micromoles per square meter per second in P. vulgaris). Modeled simulat ions indicated that the initial slope of the CO2 response of photosynthesis exhibited light dependency when the rate of Ru ADP were studied in the C3 annuals Chenopodium album and Phaseolus vulgaris at 25-degrees-C. The initial slope of the photosynthetic CO2 response curve was dependent on light intensity at reduced light levels only (less than 450 micromoles pert-intensity and CO2 in the C3 annuals Chenopodium album L and Phaseolus vulgaris L^8^94^4^1735-1742^^^^^Dec^^^^^3042n^75A^3041^The light and CO2 response of (a) photosynthesis, (b) the activation state and total catalytic efficiency (K(cata)) of ribulose-1,5-bisphosphate carboxylase (rubisco), and (c) the pool sizes of ribulose 1,5-bisphosphate, (RuBP), ATP, and, the activity of rubisco is downregulated to balance the limitation in the rate of RuBP regeneration. Comparisons with published data demonstrate a general consistency between modelled predictions and measured results.92^3^Sage,RF^Sharkey,TD^Seemann,JR^1990^1^Regulation of ribulose-1,5-bisphosphate carboxylase activity in response to lighion are down-regulated in order that the rate of RuBP regeneration matches the rate of RuBP consumption by rubisco. Similarly, at subsaturating light intensity or elevated CO2, when electron transport or Pi regeneration may limit photosynthesisre regulated to balance the capacity of limiting processes. Thus, at CO2 partial pressures below ambient, when a limitation on photosynthesis by the capacity of rubisco is postulated, the activities of electron transport and phosphate regeneratA^3039^A model of the regulation of the activity of ribulose-1,5-bis- phosphate carboxylase, electron transport, and the rate of orthophosphate regeneration by starch and sucrose synthesis in response to changes in light intensity and partial pressures of CO2 and O2 is presented. The key assumption behind the model is that nonlimiting processes of photosynthesis a!91^1^Sage,RF^1990^1^A model describing the regulation of ribulose-1,5-bisphosphate carboxylase, electron-transport, and triose phosphate use in response to light-intensity and CO2 in C3 plants^8^94^4^1728-1734^^^^^Dec^^^^^3040#of all species was increased by elevated CO2. In the case of Scirpus (C3), this increase was caused by increased net photo$synthesis, for Spartina patens (C4) photosynthesis was not increased, but transpiration was reduced. The water potential of the shoot was less negative under conditions of CO2 enrichment, in particular at increased salinity (250 mM NaCl).&ent, no such increase was found in the C4 grass species. High salinity reduced growth of the C3 species tested, but this r'elative growth reduction was not prevented by elevated CO2 concentration. The growth increase at elevated CO2 of Scirpus m"aritimus and Puccinellia maritima is greater under aerated than under anaerobic solution conditions. Water-use efficiency ) anglica C.E. Hubbard and Spartina patens (Ait.) Muhl. were grown at ambient (340 p.p.m. CO2) and elevated (580 p.p.m. CO2*) atmospheric CO2 concentration, at low (10 mM NaCl) and high salinity (250 mM NaCl) under aerated and anaerobic condition%s in the culture solution. The relative growth rate of both the C3 grass species was enhanced with atmospheric CO2 enrichm,90^7^Rozema,J^Dorel,F^Janissen,R^Lenssen,G^Broekman,R^Arp,W^Drake,BG^1991^1^Effect of elevated atmospheric CO2 on growth, photosynthesis and water relations of salt-marsh grass species^159^39^1-2^45-55^^^^^Feb^^^^^3038(A^3037^The C3 grass species Scirpus maritimus L. and Puccinellia maritima (Huds.) Parl., and the C4 grass species Spartina/nthesis; however, during pod fill potential increased significantly with increasing CO2 concentration, as elevated CO2 dec0reased water use rates, lowering soil water stress. Alleviation of water stress during critical reproductive phases was strongly suggested.2resistance, except near the end of the sampling period when a sudden increase in resistance was observed under low CO2 owi3ng to low soil water availability. Midday xylem potential for well-watered plants was greater than values for stressed pla.nts and was unaffected by CO2 treatment. Under low moisture conditions, elevated CO2 had no effect on xylem potential at a5d pod fill, plants grown under CO2 enrichment exhibited greater leaf area. Nevertheless, water use per plant either remain6ed constant (stressed plants at anthesis) or else declined (well- watered plants at pod fill; both moisture levels during 1pod fill) in response to CO2 enrichment. At pod fill, leaves of CO2-enriched plants generally displayed a higher stomatal 8 treatments started to decrease under well-watered conditions during anthesis and by early pod formation under water-stres9sed conditions. During reproductive growth, normal and stressed plants at 349-mu-l-l-1 (ambient level) received irrigation4 water 29 and 12 times, respectively, compared with 21 and 9 times, respectively, at 946-mu-l-l-1 CO2. At both anthesis an69^35^1^13-25^^^^^Mar^^^^^3036c and alpine vegetations: similarities, differences, and susceptibility to disturbance^14^2grees- C at least once during the 10 years simulated, which would be lethal to most prickly pear cacti, was reduced from 49 to 18% by the general warming expected to accompany an approximate doubling of the atmospheric CO2 concentration.:89^4^Prior,SA^Rogers,HH^Sionit,N^Patterson,RP^1991^1^Effects of elevated atmospheric CO2 on water relations of soya bean^1And Northwest where the PAR index lowered EPI. The predicted annual dry weight productivity for O. ficus-indica was 12.8 MgB ha-1 yr-1 under current conditions, and 16.3 Mg ha-1 yr-1 under those associated with 650-mu-L L-1 CO2. Both productiviti=es are relatively high compared with other agronomic plants. The percentage of sites where temperatures fall below - 15-deD of maximal net CO2 uptake during a 24-h period for the prevailing plant water status). For closely spaced plants that leaEd to a high productivity per unit ground area, EPI averaged about 0.10, except in desert regions where the water index low@ered EPI, in the far North or South and at high elevations where the temperature index lowered EPI, and in the Northeast aG O. ficus-indica was directly measured, and low temperature limitations on productivity were considered. The dry weight gaHin of O. ficus-indica during 6 mo in an environmental growth chamber was 23% greater at 650 compared with 350-mu-L L-1 CO2C and increased as the duration of the wet period increased, in agreement with predictions of the water index (the fractionJty can be predicted. This investigation calculated the water index the temperature index, and the PAR index, whose productK equals EPI, for 169 sites distributed approximately uniformly across the contiguous USA for present climatic conditions aFs well as for those associated with an elevated CO2 concentration of 650-mu-L L-1. The effect of elevated CO2 on growth ofMA^3033^Opuntia ficus-indica (L.) Mill., a prickly pear cactus cultivated worldwide for its fruits and stem segments, can hNave an annual dry weight productivity exceeding that of many crops. Using a recently introduced environmental productivityI index (EPI), the influences of water status, temperature, and photosynthetically active radiation (PAR) on its productivions^14^41^2^96-104^^^^^Feban Veldhuizen,RM^and C.E. Teutsch^1983^1^Artificial regeneration of trees and tall shrubs in exQ88^2^Nobel,PS^Decortazar,VG^1991^1^Growth and predicted productivity of Opuntia ficus-indica for current and elevated carbon-dioxide^48^83^1^224-230^^^^^Jan-Feb^^^^^3034Shyll synthesis is not disturbed, and growth and biomass accumulation intensify in plants under conditions of elevated CO2 concentration. black spruce/feather moss sites in interior Alaska^53^1987^^84-88^^1342O87^5^Mooney,HA^Drake,BG^Luxmoore,RJ^Oechel,WC^Pitelka,LF^1991^1^Predicting ecosystem responses to elevated CO2 concentratiVclined. The excess of amino acids (alanine and aspartic acid) is evacuated from the metabolic pool into vacuoles, with theR result that a normal metabolic pool of amino acids is preserved. A state of homeostasis is preserved, protein and chloropXmosphere. Intensification of nitrogen metabolism occurred mainly due to increase of NR activity. Activity of GS and GO incYreased to a lesser extent. Significant changes were detected in the rates of synthesis of separate amino acids. Thus, formUation of alanine and aspartic acid increased by 84 and 40%, respectively, but the rates of glycine and serine synthesis de[ of nitrogen metabolism in leaves of mustard plants in the vegetative phase of growth are higher under conditions of elevaWted atmospheric CO2 concentration than in leaves of plants that developed under conditions of normal CO2 content in the atnd nitrogen-metabolism of mustard plants^168^37^5^687-692^^^^^Sep-Oct^^^^^3031ce, Picea glauca, seed^72^97^^104-106^^1350^A^3030^We investigated the effect of prolonged (8- to 10-day) influence of elevated atmospheric CO2 content (0.14%) on theZ photosynthetic rate and nitrogen metabolism in mustard plants (Brassica juncea L.). The photosynthetic rate and intensity`io; thus shoot and wholeplant growth were decreased to a much greater extent than total-P uptake which resulted in elevated P concentrations in the tissue. Therefore, P-utilization efficiency was markedly reduced by N stress.\86^4^Maevskaya,SN^Andreeva,TF^Voevudskaya,SY^Cherkanova,NN^1990^1^Effect of elevated CO2 concentration on photosynthesis acrowth as total-N uptake and plant growth were decreased to the same extent by P stress resulting in unaltered tissue N condcentrations. In contrast, decreased total P-uptake by N-stressed plants was associated with a restriction in root growth a_s P-uptake efficiency of the roots was unaltered. This response was coupled with an increased root-to-shoot dry weight ratfent and vice versa. Nutrient-stress treatments lowered the relative seed yield response to atmospheric CO2 enrichment. Decgreased total-N uptake by P- stressed plants was associated with both decreased root growth and N-uptake efficiency of the broots. Nitrogen-utilization efficiency was also decreased by P-stress. This response was associated with decreased plant giies at 27 days after transplanting (DAT) and seed yield at maturity (98 DAT). Atmospheric CO2 enrichment increased growth jand N- and P-utilization efficiencies at 27 DAT and seed yield in all nutritional treatments and did not affect N- and P-ueptake efficiencies at 27 DAT. Parameter responses to nutrient stress at 27 DAT were not altered by atmospheric CO2 enrichmlnd utilization efficiencies in dry matter production (gdw2/mg nutrient). Nutritional treatments were imposed in aerial envmironments containing either 350 or 700-mu-L/L atmospheric CO2 to determine whether the nutrient interactions were modifiedh when growth rates were altered. Nutrient-stress treatments decreased growth and N- and P-uptake and utilization efficienc13^11^1419-1433^^^^^^^^^^3029,P^McPeters,RD^Herman,JR^1991^1^Total ozone trends deduced from Nimbus 7 TOMS data^65^18^^10pA^3028^Nonnodulated soybean plants (Glycine max. [L.] Merr. 'Lee') were supplied with nutrient solutions containing growthk limiting concentrations of N or P to examine effects on N- and P-uptake efficiencies (mg nutrient accumulated/gdw root) ar the rise in C(a) but the effect of temperature on WUE was unclear. It is concluded that, whthin limits, under high C(a), C4 crop plants expand their photosynthetic capacity in an environment of high temperature.n85^3^Israel,DW^Rufty,TW^Cure,JD^1990^1^Nitrogen and phosphorus nutritional interactions in a CO2 enriched environment^166^ully in C4 crop plants. With the rise of C(a), the E in C4 crop plants decreased more than in C3 crop plants and it was corqrelated with the decrease in stomatal conductance to CO2 transfer. The water use efficiency (WUE) of leaves increased withwfor rates of CO2 exchange (CER) and transpiration (E) of leaves at 23, 28 and 33-degrees-C in terms of C(a) (0-500-mu-mol xmol-1). The responses of CER to C(a) were slightly lower in plants grown in high C(a) than those in normal C(a) and were ltargely influenced by temperature. The promotive effect of elevating C(a) on CER was larger at higher temperatures, especiazA^3026^The effects of elevated CO2 in the atmosphere and the accompanied temperature rise predicted for the future on gas {exchanges of two summer C3 (rice, soybean) and two C4 (Japanese millet, finger millet) crop plants were examined. Plants wvere grown in artificially illuminated growth cabinets under 350 and 500-mu-mol mol-1 ambient CO2 (C(a)) and were measured }84^2^Imai,K^Okamotosato,M^1991^1^Effects of temperature on CO2 dependence of gas exchanges in C3 and C4 crop plants^160^60^1^139-145^^^^^Mar^^^^^3027 not linear with increasing CO2 concentrations. In well-watered plants, biomass production and storage root yield increased at elevated CO2, and these were greater as compared to water-stressed plants grown at the same CO2 concentration.25375^yestion of 438 and 666-mu-mol mol-1 than in plants grown at 364-mu-mol mol-1. The 364-mu-mol mol-1 CO2 grown plants had to be rewatered 2d earlier than the high CO2-grown plants in response to water stress. For plants grown under water stress, the~ yield of storage roots and root:shoot ratio were greater at high CO2 than at 364-mu-mol mol-1; the increase, however, was] 'Georgia Jet') on biomass production and plant-water relationships in an enriched CO2 atmosphere. Plants were grown in pots containing sandy loam soil (Typic Paleudult) at two concentrations of elevated CO2 and two water regimes in open-top field chambers. During the first 12 d of water stress, leaf xylem potentials were higher in plants grown in a CO2 concentra83^6^Bhattacharya,NC^Hileman,DR^Ghosh,PP^Musser,RL^Bhattacharya,S^Biswas,PK^1990^1^Interaction of enriched CO2 and water-stress on the physiology of and biomass production in sweet-potato grown in open-top chambers^9^13^9^933-940^^^^^Dec^^^^^30A^3024^The objective of this study was to investigate the effects of water stress in sweet potato (Ipomoea batatas L. [Lamon with long term exposure to elevated CO2. This experiment suggests that: (1) a global rise in CO2 may have significant effects on photosynthesis and productivity in a wide variety of tropical species, and (2) increases in productivity and photosynthesis may be related to physiological adaptation(s) to increased CO2. were noted for the C4 grass, Paspallum conjugatum. Increases in the apparent quantum efficiency (AQE) for all C3 species suggest that elevated CO2 may increase photosynthetic rate relative to ambient CO2 over a wide range of light conditions. The response of CO2 assimilation to internal C(i) suggested a reduction in either the RuBP and/or Pi regeneration limitatiignificant increases in total plant dry weight were also noted for 4 out of the 5 C3 species tested and in one CAM species, Aechmea magdalenae at high CO2. In contrast, no significant increases in either photosynthesis or total plant dry weightincreases in photosynthesis and greater water use efficiency (WUE) for all species possessing C3 metabolism, when compared to the ambient condition. No desensitization of photosynthesis to increased CO2 was observed during the 3 month period. Sposure to elevated carbon-dioxide^2^86^3^383-389^^^^^^^^^^3023centrations and whole plant senescence^11^64^^1311-1314^^13A^3022^Seedlings of nine tropical species varying in growth and carbon metabolism were exposed to twice the current atmospheric level of CO2 for a 3 month period on Barro Colorado Island, Panama. A doubling of the CO2 concentration resulted in hinochloa under low-N. These experiments show that for these species nitrogen was more important than light or elevated pCO2 in determining the extent of competitive interactions in mixed culture.82^4^Ziska,LH^Hogan,KP^Smith,AP^Drake,BG^1991^1^Growth and photosynthetic response of 9 tropical species with long-term exeatments but this was insufficient to offset a marked decline in shoot growth with increasing proportion of C3 plants in mixed cultures. The unexpected stimulation of growth of C4 plants by elevated CO2 was correlated with more negative delta- C-13 values of C4 root biomass, suggesting a partial failure of the CO2 concentrating mechanism of C4 photosynthesis in Ec. Root growth of the C3 plants was generally stimulated by elevated CO2, but was only occasionally sensitive to the presence of C4 plants in mixed culture. However, growth of the C4 plants was often sensitive to the presence of C3 plants in mixed culture. In mixed cultures, elevated CO2 plants stimulated growth of C4 plants at high PPFD, high-N and in all low-N trbut C4 plants had overtaken them by the time of the second harvest. Elevated atmospheric CO2 (640-mu-bar) stimulated shoot growth of Triticum in 15 of 16 treatment combinations and the stimulation was greatest in plants provided with low NO3BARt biomass. In air (320-mu-bar CO2) at high PPFD and with high root zone-N, the shoot biomass of C3 and C4 components at the first harvest (28 days) was in proportion to the sowing ratio. However, by the second harvest (36 days) the C4 component predominated in both mixtures. Under the same conditions, but with low PPFD, C3 plants predominated at the first harvest 640-mu-bar), two photosynthetic photon flux densities (PPFDs) (daily maximum 2000 and 500-mu-mol m-2 s-1) and two levels of nitrogen nutrition (12 mM and 2 mM NO3BAR). Growth of shoots of both components in mixed culture was measured by physical separation, and the proportions of root biomass due to each component were calculated from delta-C-13 value of total rooA^3020^Wheat (Triticum aestivum L.), a C3 species, and Japanese millet (Echinochloa frumentacea Link), a C4 species, were grown in pots in monoculture and mixed culture (2 C3:1 C4 and 1 C3:2 C4) at two ambient partial pressures of CO2 (320 and cum aestivum (C3) and Echinochloa frumentacea (C4) during growth in mixed culture under different CO2, N-nutrition and irradiance treatments, with emphasis on belowground responses estimated using the delta-C-13 value of root biomass^92^18^2^137-152^^^^^^^^^^3021ts into the soil as well as the subsequent microbial turnover of root-derived carbon are reviewed. We discuss possible consequences of an increased CO2 level in the atmosphere on these processes.81^2^Wong,SC^Osmond,CB^1991^1^Elevated atmospheric partial-pressure of CO2 and plant-growth .3. Interactions between Triti input of organic carbon into the soil due to the expected increase in primary production. Whether this will lead to accumulation of greater amounts of organic carbon in soil depends on the flow of carbon through the plant into the soil and its subsequent transformation in the soil by microorganisms. In this paper the major controls of carbon translocation via rooA^3018^The flow of carbon from photosynthesizing tissues of higher plants, through the roots and into the soil is one of the key processes in terrestrial ecosystems. An increased level of CO2 in the atmosphere will likely result in an increased80^4^Vanveen,JA^Liljeroth,E^Lekkerkerk,LJA^Vandegeijn,SC^1991^1^Carbon fluxes in plant-soil systems at elevated atmospheric CO2 levels^56^1^2^175-181^^^^^May^^^^^3019mation of photosynthesis was reversible. Reductions in photosynthetic capacity as root growth was progressively restricted suggest sink-limited feedback inhibition as a possible mechanism for regulating net photosynthesis of plants grown in elevated CO2.owth was restricted suggesting that ribulose-1,5- bisphosphate carboxylase/oxygenase activity may be responsive to plant source-sink balance rather than to CO2 concentration as a single factor. When root-restricted plants were transplanted into large pots, carboxylation efficiency and ribulose-1, 5-bisphosphate regeneration capacity increased indicating that accliwas found to be primarily an accumulation of leaf starch. Reduced photosynthetic capacity of plants grown at elevated levels Of CO2 was clearly associated with inadequate rooting volume. Reductions in net photosynthesis were not associated with decreased stomatal conductance. Reduced carboxylation efficiency in response to CO2 enrichment occurred only when root gromass and leaf area of plants grown in 270 and 350 microbars Of CO2 were not significantly different. Plants grown in small pots in 650 microbars Of CO2 produced greater total biomass than plants grown in 350 microbars, but the dry weight gain ted from small pots into large pots after 20 days. Reduction of root biomass resulting from growth in small pots was accompanied by decreased shoot biomass and leaf area. When root growth was less restricted, plants exposed to higher CO2 partial pressures produced more shoot and root biomass than plants exposed to lower levels of CO2. In small pots, whole plant biA^3016^Interactive effects of root restriction and atmospheric CO2 enrichment on plant growth, photosynthetic capacity, and carbohydrate partitioning were studied in cotton seedlings (Gossypium hirsutum L.) grown for 28 days in three atmospheric CO2 partial pressures (270, 350, and 650 microbars) and two pot sizes (0.38 and 1.75 liters). Some plants were transplan79^2^Thomas,RB^Strain,BR^1991^1^Root restriction as a factor in photosynthetic acclimation of cotton seedlings grown in elevated carbon-dioxide^8^96^2^627-634^^^^^Jun^^^^^3017t from the above considerations of the effects of natural leaf temperature regimes and prevailing lapse conditions on CO2 uptake potential. A(P) with altitude when predicted leaf temperatures and moist lapse conditions were simulated. There was a significant (almost-equal-to 10%) increase in A(P) with altitude when leaf temperature was held constant at 30-degrees- C (regardless of altitude) under moist lapse conditions. Future studies evaluating the effects of elevation on photosynthesis could benefite of 0.003-degrees-C m-1 resulted in less than a 4% decrease in A(P) over the same altitude range. When natural leaf temperatures (predicted from heat balance analyses) were simulated, A(P) was significantly greater (almost-equal-to 20%) than when leaf temperatures were considered equal to air temperature for all lapse conditions. There was virtually no change inncentration, and (4) the diffusion coefficient for CO2 in air. When a dry lapse rate (0.01-degrees-C m-1) in air temperature was simulated, significant declines (up to 14%) in A(P) were predicted from sea level to 4km altitude. A moist lapse ra3-136^^^^^Jan^^^^^3015a,L^1989^1^Sex expression and sex ratios in intra- and interspecific hybrid families of Salix L^67^A^3014^A simulation of the quantitative influence of altitude on photosynthetic CO2 uptake capability (A(P)) included the effects of predicted changes (1) in air temperature (lapse rate) and (2) leaf temperature, (3) ambient pressure and CO2 coway and acclimation of respiration rates to different climates are poorly understood, but may substantially affect the reliability of model estimates of plant respiration.78^2^Smith,WK^Donahue,RA^1991^1^Simulated influence of altitude on photosynthetic CO2 uptake potential in plants^9^14^1^13ation may decline under CO2 enrichment, but the mechanism, independence from changes in protein content, and acclimation are unknown. Response of respiration to temperature can be modelled as a Q10 relationship, if corrections for bias arising from daily and annual temperature amplitude are applied. Occurrence and control of the cyanide- resistant respiratory pathurnover, water stress, and atmospheric pollutants. For a wide variety of plant tissues, maintenance respiration, corrected for temperature, appears to be linearly related to Kjeldahl nitrogen content of live tissue. Total and maintenance respirm carbon flux will change as the balance between photosynthesis and respiration changes. Partitioning respiration into the functional components of construction, maintenance, and ion uptake will aid the estimation of plant respiration for ecosystems. Maintenance respiration is the component most sensitive to changes in temperature, CO2, protein concentration and tort elicited a large transient engagement of the alternative oxidase when present uninhibited.ns pallida and Impatiens ca77^1^Ryan,MG^1991^1^Effects of climate change on plant respiration^56^1^2^157-167^^^^^May^^^^^3013A^3012^Plant respiration is a large, environmentally sensitive component of the ecosystem carbon balance, and net ecosyster in the presence of the uncoupler carbonyl-cyanide m-chlorophenyl hydrazone. The activity of cytochrome c oxidase of callus tissue homogenates was also inhibited by CO2/bicarbonate. The results suggested that high carbon dioxide levels (mainly free CO2) Partially inhibited the cytochrome pathway (apparently at the oxidase level), and this block in electron transption did not occur in animal tissues such as rat diaphragm and isolated hepatocytes, and was inhibited by salicylhydroxamic acid in carnation callus cells and E. canadensis leaves. This suggested that the alternative oxidase was engaged during the stimulation in plant tissues. The cytochrome pathway was severely inhibited by CO2/bicarbonate either in the absence ooncentration of gaseous CO2 in the solution. These stimulatory responses lasted several minutes and then decreased, but additional bicarbonate or gaseous CO2 again stimulated respiration, suggesting a reversible effect. Carbonic anhydrase in the solution increased the stimulatory effect of potassium bicarbonate. The CO2/bicarbonate dependent stimulation of respira photomixotrophic and heterotrophic carnation (Dianthus caryophyllus L.) callus, of Elodea canadensis (Michx) leaves, and of other plant tissues. This phenomenon occurred at pH values lower than 7.2 to 7.8, and the stimulation depended on the chaping the response of a plant to CO2.^1989^1^Ecophysiology of exotic and native shrubs in southern Wisconsin. I. Relatio76^4^Palet,A^Ribascarbo,M^Argiles,JM^Azconbieto,J^1991^1^Short-term effects of carbon-dioxide on carnation callus cell respiration^8^96^2^467-472^^^^^Jun^^^^^3011A^3010^The addition of potassium bicarbonate to the electrode cuvette immediately stimulated the rate of dark O2 uptake of increase in carbon assimilation per unit leaf area. Although the compensation between photosynthesis and leaf area reduced the potential growth response to CO2, the reduction in leaf area ratio was associated with a significant increase in water-use efficiency. This unexpected result demonstrated the importance of feedbacks and interactions between resources in sal mineral nutrients and in unfertilized plants, although the fertilized plants grew 10-fold larger. The increase in dry weight resulting from elevated CO2 occurred only in root systems. Although leaves were produced continuously during the experiment, leaf area was slightly reduced in elevated CO2, and the whole-plant growth response was wholly attributable to anof mineral nutrients (unfertilized or weekly additions of complete nutrient solution), and three harvests (6, 12, and 24 weeks). Plant growth rate, water use, foliar gas exchange, component dry weights, and nutrient contents were measured. Both hypotheses were rejected. Whole-plant dry weight increased similarly with CO2 enrichment in plants provided with additiones were tested in an experiment in which yellow-poplar plants were grown from seed for 24 weeks in controlled- environment chambers. The experimental design comprised three atmospheric CO2 concentrations (371, 493, and 787 cm3 m-3), two levels tion and nutrient requirements of the species, it was predicted that (1) CO2 enrichment would enhance growth of yellow-poplar seedlings both through accelerated leaf area production and through higher rates of carbon assimilation per unit leaf s that terpenes may have been one of several important leaf characteristics limiting consumption of the low nutrient hostsinteractive in that nutrient limitation slightly reduced the C/N balance among the high-CO2 plants. Leaf volatile terpene concentration increased only in the nutrient limited plants and did not follow the overall increase in leaf C/N ratio. Grato reduce leaf nitrogen concentration and water content. Carbon dioxide enrichment and soil nutrient limitation both acted to increase the balance of leaf storage carbohydrate versus nitrogen (C/N). The two treatment effects were significantly tly controlled by changes in carbon allocation to shoot mass alone. Growth under CO2 enrichment increased the starch concentrations of leaves grown under both nutrient regimes, while increased CO2 and low nutrient availability acted in concert  tation completely constrained the response to elevated CO2. Root biomass was unaffected by any treatment. Plant root/shoot ratios declined under carbon dioxide enrichment but increased under low nutrient availability, thus the ratio was apparen A^2996^Artemisia tridentata seedlings were grown under carbon dioxide concentrations of 350 and 650-mu-l l-1 and two levels of soil nutrition. In the high nutrient treatment, increasing CO2 led to a doubling of shoot mass, whereas nutrient limite change.ild,AE^Cody,WJ^1980^2^Vascular plants of continental Northwest Territories, Canada^National Museums of Canada^O69^2^Johnson,RH^Lincoln,DE^1991^1^Sagebrush carbon allocation patterns and grasshopper nutrition - the influence of CO2 enrichment and soil mineral limitation^2^87^1^127-134^^^^^^^^^^29976Ȅ/o/\\i/c?Έ3g`Fz(67^3^Idso,SB^Kimball,BA^Allen,SG^1991^1^Net photosynthesis of sour orange trees maintained in atmospheres of ambient and e-increases in primary production, in spite of greater nitrogen limitation, and (2) led to greater storage of carbon in plan*t residues and soil organic matter. The increased carbon storage was not great enough to keep pace with the present rate o/tments in the responses of soil, plants, animals and microbes. Elevated temperature extended the growing season but depres,sed photosynthesis in the summer, with little net effect on annual primary production. Doubling CO2 (1) caused persistent 1was driven with observed weather and with combinations of elevated atmospheric CO2, elevated temperature, and either incre.ased or decreased precipitation. Precipitation and CO2 level accounted for most of the variation among climate change trea3s seasonal dynamics of shoots, roots, soil water, mycorrhizal fungi, saprophytic microbes, soil fauna, inorganic nitrogen,0 plant residues and soil organic matter. Forty-year simulations were made for several climate change scenarios. The model n-model for the effects of climate change on temperate grassland ecosystems^81^53^3-4^205-246^^^^^Apr^^^^^2991$hرyvd2A^2990^We studied the responses of temperate grasslands to climate change using a grassland ecosystem model which simulate7phenylmethyl)-1H-purin-6-amine (BA); 1H-indole-3-butyric acid (IBA); alpha-naphthaleneacetic acid (NAA); thidiazuron (TDZ).al Academy of Sciences (USA), Washington^D.C^^N^^1585S^d&Ɔ>Y÷3!DppRrph466^10^Hunt,HW^Trlica,MJ^Redente,EF^Moore,JC^Detling,JK^Kittel,TGF^Walter,DE^Fowler,MC^Klein,DA^Elliott,ET^1991^1^Simulatio:f 20,000 ppm CO2 and a photosynthetic photon flux density (PPFD) of 150 to 200-mu-mol.s-1.m-2. Subcultured nodal cuttings ;continued to elongate and produce leaves under elevated CO2 and light levels, and some formed roots. Subculture of microcu6ttings under CO2 enrichment could be the basis for a rapid system of micropropagation for cacao. Chemical names used: N- (a-cacao^154^116^3^585-589^^^^^May^^^^^2989ltraviolet radiation^IN J.G. Titus, ed. Effects of changes in stratospheric ozo>A^2988^Axillary shoots of cacao (Theobroma cacao L.), induced in vitro with cytokinins (BA or TDZ), elongated and produced? leaves only in the presence of cotyledons and/or roots. Detached axillary shoots, which do not grow in vitro under conven@tional tissue culture protocols, rooted with auxin and developed normally in vivo. Detached axillary shoots from cotyledon9ary nodes and single-node cuttings from mature plants were induced to elongate and produce normal leaves in the presence oBemoval did not reduce shoot weights or reproductive weights of plants in either CO2 treatment relative to control plants. CHowever, plants from both CO2 treatments experienced reductions in root weights with leaf area removal, indicating that plDants compensated for lost above-ground tissues, and maintained comparable levels of reproductive output and seed viability, at the expense of root growth.N^^1591UpPRp#(Т EC/5}7[u9V{W 笈l<65^3^Figueira,A^Whipkey,A^Janick,J^1991^1^Increased co2 and light promote invitro shoot growth and development of theobromGallocated 10% of their carbon resources to reproduction whereas ambient CO2-grown plants allocated over 20%. Effects of siAmulated herbivory on plant performance were much less dramatic than those induced by enriched CO2 atmospheres. Leaf area rIgnificantly greater shoot weights, leaf areas, and root weights, yet had significantly lower reproductive weights (i.e. stJalks + spikes + seeds) and produced fewer seeds, than plants grown in ambient CO2 environments. Relative biomass allocatioFn patterns further illustrated differences in plant responses to enriched CO2 atmospheres: enriched CO2-grown plants only Lae) was grown in either near ambient (380 ppm) or enriched (700 ppm) CO2 atmospheres, and then after 4 weeks, plants experMienced either 1) no defoliation; 2) every fourth leaf removed by cutting; or 3) every other leaf removed by cutting. PlantNs were harvested at week 13 (9 weeks after simulated herbivory treatments). Vegetative and reproductive weights were compaHred, and seeds were counted, weighed, and germinated to assess viability. Plants grown in enriched CO2 environments had sin response to simulated herbivory and elevated CO2 environments^2^87^1^37-42^^^^^^^^^^2987IN B.R. Strain and J.D. Cure, eQA^2986^We tested the prediction that plants grown in elevated CO2 environments are better able to compensate for biomass lKost to herbivory than plants grown in ambient CO2 environments. The herbaceous perennial Plantago lanceolata (PlantaginaceSm 195- 735-mu-mol mol-1 was also examined using individual leaves, attached to the plant, in an environmentally controlledT cuvette. Here the stomata of leaves which had been fumigated with SO2 + NO2 behaved in a similar manner to the non-fumigated leaves, both showing closure in elevated CO2 concentrations.mps*BхHzoycQaHovSβCqBދDO64^3^Fajer,ED^Bowers,MD^Bazzaz,FA^1991^1^Performance and allocation patterns of the perennial herb, Plantago lanceolata, iWed responses strongly implicated impaired physiology of the guard cells rather than mechanical changes in the epidermis thXat might, for example, result from damage to the cuticle. Stomatal closure was considerably slower in polluted leaves compYared with the controls. This decline in responsiveness to ABA was observed using leaves excised from well-watered plants aRnd in the absence of any externally visible injury. The ability of stomata to respond to a range of CO2 concentrations fro[er loss was then examined after terminating the pollutant treatment. Observations of diurnal changes in stomatal resistanc\e of well- watered plants, using a viscous flow porometer, failed to indicate any major alterations which could be attribu]ted to prior exposure to SO2 + NO2. By contrast, when an ABA solution (10(-1) mol m-3) was applied to detached leaves, theV stomata of polluted plants were less responsive than plants previously exposed to control air. The dynamics of the observ_63^3^Atkinson,CJ^Wookey,PA^Mansfield,TA^1991^1^Atmospheric-pollution and the sensitivity of stomata on barley leaves to abscisic-acid and carbon-dioxide^84^117^4^535-541^^^^^Apr^^^^^2985evaluation of methods and initial results^IN J.H. McBeathaA^2984^Spring barley (Hordeum vulgare L. cv. Klaxon) plants were exposed to mixtures of SO2 + NO2 (at concentrations of 24b-35 nl l-1 of each gas, depending upon fumigation system), or to charcoal-filtered, or unfiltered ambient air during the pZeriod in which the second, and subsequent, leaves were emerging. The ability of individual detached leaves to regulate watd62^3^Woodward,FI^Thompson,GB^McKee,IF^1991^1^The effects of elevated concentrations of carbon-dioxide on individual plants, populations, communities and ecosystems^52^67^^23-38^^^^^Jun3:6:MqdkT3Eھ:-n :_bPو%ifmation severity. Foliar K decreased while deformation increased. In another study, foliage of half the plants of one genotgype received foliar applications of 7 millimolar KH2PO4. Untreated foliage showed significantly greater deformation than threated foliage. Reduced foliar K concentration may cause CO2- enhanced foliar deformation. Reduced K may occur following decreased nutrient uptake resulting from reduced root mass due to the change in partitioning from root to fruit.6`F?LTjth CO2 enrichment exhibited nonepinastic foliar deformation similar to nutrient deficiency symptoms. Foliar deformation vakried among genotypes, increased throughout the season, and became most severe at elevated CO2. Foliar deformation was posiltively related to fruit yield. Foliage from the lower canopy was sampled throughout the growing season and analysed for stearch, K, P, Ca, Mg, Fe, and Mn concentrations. Foliar K and Mn concentrations were the only elements correlated with defornA^2981^Yield increases observed among eight genotypes of tomato (Lycopersicon esculentum Mill.) grown at ambient CO2 (abouot 350) or 1000 microliters per liter CO2 were not due to carbon exchange rate increases. Yield varied among genotypes whilie carbon exchange rate did not. Yield increases were due to a change in partitioning from root to fruit. Tomatoes grown wico protein in the leaf.The measurement of viability^IN Roberts, E.H., ed. Viability of seeds. Chapman and Hall^London^^N^r61^5^Tripp,KE^Peet,MM^Pharr,DM^Willits,DH^Nelson,PV^1991^1^CO2-enhanced yield and foliar deformation among tomato genotypes in elevated CO2 environments^8^96^3^713-719^^^^^Jul^^^^^2982;>rFɱr~GŠ L'ڪ(d܈#lC9Ď@Ƹte (CA-1-P). However, the inhibitor did not seem to be involved in the acclimation response. The degree of carbamylation ofu the rubisco enzyme was unchanged by the CO2 growth regime, except at 900-mu-mol mol-1 where it was reduced by 24%. The acpclimation of rice to different atmospheric CO2 conditions involved the modulation of both the activity and amount of rubiswein, and by 60% on a leaf area basis. For leaves in the dark, the total rubisco activity (CO2/Mg2+- activated) was reduceds by more than 60%. This indicates that rice accumulated an inhibitor in the dark, probably 2- carboxyarabinitol 1-phosphatyr the CO2 concentration range 160 to 900-mu- mol mol-1. When expressed on a leaf area basis, rubisco activity decreased byv 66%. This was accompanied by a 32% decrease in the amount of rubisco protein as a fraction of the total soluble leaf prot{sed significantly with increasing CO2. Although leaf dry weight and leaf area index increased, the overall response was no|t statistically significant. Leaf nitrogen content dropped slightly with elevated CO2, but the response was not statisticaxlly significant. The specific activity of ribulose bisphosphate carboxylase/oxygenase (rubisco) declined significantly ove~mospheric CO2 concentrations in outdoor, computer-controlled, environment chambers under natural solar radiation. The CO2 concentrations were maintained at 160, 250, 330, 500, 660 and 900-mu-mol mol-1 air. Photosynthesis increased with increasizng growth CO2 concentrations up to 500-mu-mol mol-1, but levelled off at higher CO2 values. Specific leaf area also increa60^4^Rowlandbamford,AJ^Baker,JT^Allen,LH^Bowes,G^1991^1^Acclimation of rice to changing atmospheric carbon-dioxide concentration^9^14^6^577-583^^^^^Aug^^^^^2980&Qnm&Dx\E"Jʎ\+-lr*\~\++O <n<]\ :}A^2979^The effects were studied of season-long (75 and 88 d) exposure of rice (Oryza sativa L. cv. IR-30) to a range of atunction for polyamines. The ability of increased CO2 to protect soybeans from O3 damage, however, does not appear to involve polyamine accumulation.`U Un in control wheat plants. N-use efficiency by wheat was increased by CO2 enrichment. From a practical point of view, the study indicates that critical total-N and NO3-N concentrations used to diagnose the N status of wheat will need to be reassessed as global CO2 levels increase. Elevated CO2 may also reduce the protein content of grain and thus the baking qualitand maize increased with increasing N supply. CO2-enriched wheat plants accumulated more N than the controls but the proportional increase in N content was not as great as that in dry matter, with the result that concentrations of total-N and nitrate-N were lower in all organs of enriched plants, including ears. Nitrate reductase activity was lower in enriched thaspective of N supply. Enriched wheat plants had a lower Leaf Area Ratio but higher Net Assimilation Rate and Relative Growth Rate than control plants. There was no effect of CO2 enrichment on specific leaf weight. The enriched plants had lower shoot to root dry matter ratios than thecontrols at 6 mol m-3 N and higher. Shoot to root dry matter ratios of both wheat 500 cm3 m-3) on N supplies ranging from deficient (0.5 mol m-3) to more than adequate for maximum growth (25 mol m-3). Wheat responded to both CO2 enrichment and N supply; maize responded only to N supply. CO2-enriched wheat produced about twice the dry matter of control plants at all levels of N supply. Tiller and ear numbers were increased by CO2 enrichment irreA^2971^Atmospheric CO2 levels are increasing, but little is known about how this will affect tissue concentrations and the partitioning of agriculturally important nutrients such as nitrogen (N) within crop plants. To investigate this, a glasshouse experiment was conducted in which wheat, a C3 species, and maize, a C4 species, were grown for 8 weeks at high CO2 (155^2^Hall,DO^Scurlock,JMO^1991^1^Climate change and productivity of natural grasslands^52^67^^49-55^^^^^Junannotinum L. a56^2^Hocking,PJ^Meyer,CP^1991^1^Effects of CO2 enrichment and nitrogen stress on growth, and partitioning of dry-matter and nitrogen in wheat and maize^92^18^4^339-356^^^^^^^^^^29722>侑Q6yP@؞QU{ikJW=ch concentration and deformation severity. Foliar C exchange rates in the lower canopy were not affected by severity of deformation. Data from these experiments do not support the hypothesis that excess foliar starch is responsible for foliar deformation at elevated CO2.Fbtxݓײ͍!DFj|H-v{ mH0]hr=5AZ*-TϰKҷ lNg#=QZuring Jan.-June 1987 and 1988. In both years, CO2-enrichment increased foliar deformation and foliar starch, but during the season, foliar starch levels decreased while deformation increased. 'Laura' had more deformation, while 'Michigan-Ohio' had higher foliar starch concentration. During an entire season, there was no significant relationship between foliar star54^4^Tripp,KE^Peet,MM^Willits,DH^Pharr,DM^1991^1^CO2-enhanced foliar deformation of tomato-relationship to foliar starch concentration^154^116^5^876-880^^^^^Sep^^^^^29699A^2968^Two cultivars of greenhouse tomato (Lycopersicon esculentum Mill.) were grown with ambient or 1000-mu-l CO2/liter dd. Results support the contention that increasing atmospheric CO2 partial pressures will enhance productivity and N-fixing activity of N-fixing tree seedlings, but that the magnitude of early seedling response to CO2 will depend greatly on plant and soil nutrient status.age nodule weight, total nodule weight per plant, and the amount of leaf nitrogen provided by N-fixation (as indicated by leaf delta-N-15). While CO2 enrichment reduced the N concentration of some plant tissues, whole plant N accretion increasecreased 50% by CO2 enrichment but there was little indication that photosynthate translocation from leaves to roots or that plant N (fixed by Rhizobium) was altered by elevated CO2. In seedlings supplied with soil N, elevated CO2 increased averwithout available soil N, a condition in which seedlings initially experienced severe N deficiency because bacterial N-fixation was the sole source of N. Biomass of leaves, stems, and roots increased significantly with CO2 enrichment (by 32%, 15% and 26%, respectively) provided seedlings were supplied with N fertilizer. Leaf biomass of N-deficient seedlings was inl pressures of 350 and 650-mu-bar (current ambient and a predicted partial pressure of the mid-21st century) and with plus N or minus N nutrient solutions to control soil N status. Of particular interest was seedling response to CO2 when grown lated with N-fixing Rhizobium bacteria and grown in growth chambers for 71 days to investigate interactive effects of atmospheric CO2 and plant N status on early seedling growth, nodulation, and N accretion. Seedlings were grown with CO2 partiairicidia sepium (jacq) walp) exposed to elevated atmospheric carbon-dioxide^2^88^3^415-421^^^^^^^^^^296727-55^^1688A^2966^Seeds of Gliricidia sepium (Jacq.) Walp., a tree native to seasonal tropical forests of Central America, were inocufruiting period stimulated canopy CER, decreased chlorophyll and leaf protein loss, and enhanced fruit set and consequent fruit production.1627-1637^^169253^5^Thomas,RB^Richter,DD^Ye,H^Heine,PR^Strain,BR^1991^1^Nitrogen dynamics and growth of seedlings of an n-fixing tree (Gl41-251^^^^^Nov^^^^^2965^Temperature observations in high arctic plants in relation to microclimate in the vegetation of PA^2964^Short-term carbon dioxide (CO2) enrichment (1000-mu-l l-1 for 10 days), starting 2 weeks after initial bloom, enhanced the leaf CO2 exchange rate (CER) in rockwool-cultured strawberry (Fragaria x ananassa). CO2 enrichment throughout the t effects of the atmospheric CO2 level on net CO2 uptake. In summary, simulations based on EPI indicate that O. ficus-indica may presently be advantageously cultivated over a substantial fraction of the earth's surface, such regions increasing markedly with a future doubling in atmospheric CO2 levels.me^United States Environmental Protection Agency^^N^^169652^2^Sung,FJM^Chen,JJ^1991^1^Gas-exchange rate and yield response of strawberry to carbon- dioxide enrichment^165^48^3-4^2es increased by 43 and 5%, respectively, for the global warming accompanying the elevated CO2. Productivity of O. ficus-indica was at least 15 tonnes dry weight hectare-1 year-1, comparable to that of many agronomic crops, for 20 sites with temperatures always above -10-degrees-C in the contiguous United States and for 12 such sites worldwide under current climatic conditions; such sites increased by 85 and 117%, respectively, under the elevated CO2 condition, mainly because of direcity index (EPI), was used to predict the productivity of O. ficus-indica under current climatic conditions and under those accompanying a possible increase in the atmospheric CO2 level to 650-mu-mol mol-1. Sites with temperatures always above -10- degrees-C and hence suitable for prickly-pear cultivation numbered 37 in the United States and 110 worldwide; such sitsynthetic photon flux density (PPFD). Each of these environmental factors was represented by an index with a maximum value of unity when that factor was not limiting net CO2 uptake over a 24-h period. The water index, the temperature index, and the PPFD index were determined for 87 sites in the contiguous United States using data from 189 weather stations and for 148 sites worldwide using data from 1464 weather stations. The product of these three indices, the environmental productived atmospheric CO2 levels^9^14^7^637-646^^^^^Sep^^^^^2963ts^E.R. Lemon, ed. CO2 and plants. The response of plants to risA^2962^The productivity of the prickly-pear cactus Opuntia ficus- indica, which is cultivated worldwide for its fruits and stem segments, was predicted based on the responses of its net CO2 uptake to soil water status, air temperature and photociated with elevated CO2 concentration, ameliorated the response to the greenhouse climate. Grain yields for the greenhouse climates as compared to current conditions increased, or decreased only slightly, except when the greenhouse climate was assumed to result in severely decreased rainfall.^Reynolds,JF^Shaver,GR^Svoboda,J51^1^Nobel,PS^1991^1^Environmental productivity indexes and productivity for Opuntia ficus-indica under current and elevaties of crop performance under alternate conditions. One such study, presented here, was a yield assessment for rainfed maize under possible "greenhouse" climates where temperature and atmospheric CO2 concentration were increased. An increase in temperature combined with decreased rainfall lowered grain yield, although the increase in crop water use efficiency asso gas exchange to the soil water budget were developed from experimental studies. The model was used to interpret a range of field experiments using observed daily values of temperature, solar radiation, and rainfall or irrigation, where water deficits of varying durations developed at different stages of growth. The relative simplicity of the model and its robustness in simulating maize yields under a range of water-availability conditions allows the model to be readily used for studechanistic model in which temperature regulates crop development and intercepted solar radiation is used to calculate crop biomass accumulation. A soil water budget was incorporated into the model by accounting for inputs from rainfall and irrigation, and water use by soil evaporation and crop transpiration. The response functions of leaf area development and crop3^6^1052-1059^^^^^Nov-Dec^^^^^2961^Effects of global change on the carbon balance of arctic plants and ecosystems^Arctic A^2960^The availability of water imposes one of the major limits on rainfed maize (Zea mays L.) productivity. This analysis was undertaken in an attempt to quantify the effects of limited water on maize growth and yield by extending a simple, mfor which there are few data (e.g. rice). Field studies on the effects of elevated CO2 in combination with temperature, water and nutrition are essential; they should be related to the development and improvement of mechanistic crop models, and designed to test their predictions.ffries,RL^Reynolds,JF^Shaver,GR^Svoboda,J50^2^Muchow,RC^Sinclair,TR^1991^1^Water deficit effects on maize yields modeled under current and greenhouse climates^48^8ater-use efficiency in all plants. The increased productivity of crops with CO2 enrichment is also related to the greater S42^1^Bowes,G^1991^1^Growth at elevated CO2 - photosynthetic responses mediated through rubisco^9^14^8^795-806^^^^^Oct^^^^^A^2944^The global uptake of CO2 in photosynthesis is about 120 gigatons (Gt) of carbon per year. Virtually all passes through one enzyme, ribulose bisphosphate carboxylase/oxygenase (rubisco). which initiates both the photosynthetic carbon redu`ction, and photorespiratory carbon oxidation, cycles. Both CO2 and O2 are substrates; CO2 also activates the enzyme. In C3ces measured in the enzyme activities between the two CO2 concentrations. The results suggest that the photosynthetic capacity did not change and that there were no characteristic adaptations to long-term growth (up to 20 weeks) at elevated C02 concentrations. The maintenance of Rubisco and CA activities with prolonged exposure to C02-enriched atmospheres is proposed as the reason for long-term yield increases in roses when grown in enriched environments.!2뺏7-6,p; o) and carbonic anhydrase (CA) of greenhouse roses were studied. Plants of Rosa X hybrida 'Red Success' were grown for 2 y ears at ambient and 900-mu-l CO2/liter during winter and spring with 75-mu-mol.m-2.s-1 photosynthetically active radiation supplemental lighting for 2 years. Measurements of initial and Mg+2-Co2-activated activities of Rubisco and CA were made during shoot development and at different positions within the plant canopy. Generally, there were no significant differen41^2^Beeson,RC^Graham,MED^1991^1^CO2 enrichment of greenhouse roses affects neither rubisco nor carbonic-anhydrase activities^154^116^6^1040-1045^^^^^Nov^^^^^2943^^^^^^^^^^^^^^/%OķX8{{}0_53+ඊ9\@oKKnt-w A^2942^The effect of prolonged CO2 enrichment on the activities of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubiscs and solubilisation of lignocarbohydrate were highest when wheat grown at ambient CO2 concentrations (350 ppm) was used as C-source. Growth of S. viridosporus and solubilisation were reduced when the plant material was derived from wheat grown at 645 PPM CO2. The results suggest that modifications in plant structure occur when wheat is grown under conditions of elevated atmospheric CO2 which make it more resistant to microbial digestion.H-:̗W9tn#WCD:/fql}P ^^^2939arion,G M^Henry,G H R^Molgaard,P^Oechel,W C^Jones,M H^Vourlitis,G L^1993^5^Open-top devices for manipulating field40^1^Ball,AS^1991^1^Degradation by Streptomyces viridosporus t7a of plant-material grown under elevated CO2 conditions^163^84^2^139-142^^^^^15 Nov^^^^^2941ld Regions, 28 Sept.-1 Oct. 1993. U.S. Army Cold Regions Research and Engineering LaboraA^2940^The biodegradability of plant material derived from wheat grown under different concentrations of atmospheric CO2 was investigated using the lignocarbohydrate solubilising actinomycete, Streptomyces viridosporus. Growth of S. viridosporu the root/shoot ratio increased when root growth was not restricted and decreased in plants grown in small pots. The data presented in this paper suggest that plants growing in the field will maintain a high photosynthetic capacity as the atmospheric CO2 level continues to rise.<^xrvZGh ܖ(nL}U]v+!A):P>iOkF- reduction or an increase in this capacity. Pot volume also determined the effect of elevated CO2 on the root/shoot ratio:d that the reduction of photosynthetic capacity in elevated CO2 was most pronounced when the increased supply of carbohydrates was combined with small sink size. The volume of pots in which plants were grown affected the sink size by restricting root growth. While plants grown in small pots had a reduced photosynthetic capacity, plants grown in the field showed no!38^4^Yelle,S^Beeson,RC^Trudel,MJ^Gosselin,A^1990^1^Duration of CO2 enrichment influences growth, yield, and gas- exchange of 2 tomato species^154^115^1^52-57^^^^^Janer different weather and soil moisture conditions^2^88^^317-324^^1811^^^^^^^^^# capacity is often reduced after long-term exposure to elevated CO2. This reduction appears to be brought about by end product inhibition, resulting from an imbalance in the supply and demand of carbohydrates. A review of the literature reveale%37^2^Wallick,K^Zinnen,TM^1990^1^Basil chlorosis - a physiological disorder in CO2-enriched atmospheres^162^74^2^171-173^^^^^Feb^do not possess\^AXW Wg gk<>'^)eJuą/pоxoQ  f֒CH*lanata^161^164^3^168-173^^^^^Apr85^1^Intraspecific variation in the response to CO{-2} enrichment in seeds and seedlings (36^3^Titus,JE^Feldman,RS^Grise,D^1990^1^Submersed macrophyte growth at low ph .1. CO2 enrichment effects with fertile sediment^2^84^3^307-313^2 -(o #` ^9S9*䃴0 gIxVAN8 :0X51r vV 8BdmZV&Bsס*34^2^Sasek,TW^Strain,BR^1990^1^Implications of atmospheric CO2 enrichment and climatic-change for the geographical-distribution of 2 introduced vines in the USA^50^16^1^31-51^^^^^Feb^^`Y L RhZfQ$%l]ym޶@ڂX*.sť.&35^2^Stuhlfauth,T^Fock,HP^1990^1^Effect of whole season CO2 enrichment on the cultivation of a medicinal plant, digitalis--32^2^Radoglou,KM^Jarvis,PG^1990^1^Effects of CO2 enrichment on 4 poplar clones .2. Leaf surface- properties^52^65^6^627-632^^^^^Junn the xylem of the trunk of Larix and Picea trees--a comparison of xylem flow, porometer and cuvette measurement/33^3^Rey,P^Eymery,F^Peltier,G^1990^1^Effects of CO2-enrichment and of aminoacetonitrile on growth and photosynthesis of photoautotrophic calli of Nicotiana plumbaginifolia^8^93^2^549-554^^^^^Jun<+z<#X>\ʙ 3'rs,mIn_Sֱ-580^^^^^Aug,C L^Neilson,R E^Talbot,H^Jarvis,P G^1985^1^Stomatal conductance and photosynthesis in a mature Scots pine fo231^2^Radoglou,KM^Jarvis,PG^1990^1^Effects of CO2 enrichment on 4 poplar clones .1. Growth and leaf anatomy^52^65^6^617-626^^^^^Junssess)PPFiM9cM; , &lYz[Vvv9{7E)3 l-/PlVC-$Y~1IvpP\rlJ4 of these models required to incorporate directional migration of species are described. To predict establishment success 5of species, we suggest that a more fundamental understanding is needed of how establishment ability under different conditFions relates to seed and seedling attributes and how this may be affected by elevated CO2. Finally, we examine whether pla7ce long distance dispersal events will be critically important in determining migration rates. We examine the JABOWA-deriv8ed gap replacement models and vital attributes/FATE models and ask: what do we need to know about dispersal and establishm3ent to make improved projections of vegetation dynamics under climate change using these models? The minimal modifications:A^3157^The distribution of many plant species will change with global climate change, depending on their ability to disper;se into, and establish in, new communities. Past migrations of species under climate change have been an order of magnitud6e slower than the rate of predicted climate change for the next century. The limited evidence available suggests that chan=tes that are both important in population regulation and responsive to global change. This analysis shows that elevated CO>2 is not likely to have a major influence on probability of insect outbreak, except possibly in systems in which nitrogen-based defensive compounds are produced by plants in response to herbivory. Systems that will have high potential to outbre@ being reached during the simulated period; (3) the spatial distribution of soil moisture changes, presenting a new resourAce base for spatial changes to species composition and growth rates. The major hydroecological responses to elevated CO2 aIre seen as increased maximum upper canopy leaf area, increased litter inputs, especially at times of drought (hence changelobal atmospheric change^182^40^4-5^565-577^^^^^^^^^^3156nthesis in seedlings of three conifers^49^29^^71-78^^1833^^^^^^^DA^3155^There are many possible ways in which changes in the global atmosphere could influence the outbreak potential of heͨH%ڣ$Dnry mass allocation of seedlings of alnus-rubra bong^84^116^1^55-66^^^^^Sepic CO{-2} concentration on growth, photosynthes13^4^Barr,AG^King,KM^Thurtell,GW^Graham,MED^1990^1^Humidity and soil-water influence the transpiration response of maize to CO2 enrichment^146^70^4^941-948^^^^^Oct> J5}(l,aļe߷#3<7S7!/9a̩n;?#|o>Z>11^5^Allen,LH^Valle,RR^Mishoe,JW^Jones,JW^Jones,PH^1990^1^Soybean leaf gas-exchange responses to CO2 enrichment^156^49^^192-198^in intact willow leaves^6^166^^380-388^^1906^^^^^^^^^^^^^^^^^^^^^^^^o@M/E}%Kpy&<-4NC12^2^Arnone,JA^Gordon,JC^1990^1^Effect of nodulation, nitrogen-fixation and CO2 enrichment on the physiology, growth and dtates to elevated CO2^155^20^9^1479-1484^^^^^Sep^1^Effects of CO{-2} enrichment and carbohydrate content on the dark resp10^3^Acock,B^Acock,MC^Pasternak,D^1990^1^Interactions of CO2 enrichment and temperature on carbohydrate production and accumulation in muskmelon leaves^154^115^4^525-529^^^^^JulϘP:! SYCDT:k\"R[gsrʕ2W5sJjujy`Nn~'}Wɽ+ changed from 18 to a 24 h day-1 the diurnal rhythm disappeared. Transpiration followed the same diurnal rhythm as that for photosynthesis. The water-use efficiency was enhanced by raising the CO2 concentration. A decrease in the CO2 concentration from 700 to 350-mu-mol mol-1 after six days at high CO2 first significantly decreased the photosynthesis, but three damu-mol mol-1). Net photosynthesis increased to a maximum after 5-6 and 6-7 h of light at 12 and 18 h day-1 photoperiods, r espectively, followed by a decrease towards the end of the photoperiod. At a photoperiod of 18 h day-1 similar diurnal curves were found at 350 and 700-mu-mol mol-1 CO2, and at 40 and 120-mu-mol m-2 s-1 PPFD. Five days after the photoperiod wasod, co2 concentration and light level^200^42^2^100-105^^^^^Jun^^^^^3388carbon, and water relations of a xylem-tapping mis#A^3387^The diurnal net photosynthesis of Ficus benjamina L., cultivar Cleo, was studied at different daylengths (12, 18 and 24 h day- 1), photosynthetic photon flux densities (40 and 120-mu-mol m-2 s-1 PPFD) and CO2 concentrations (350 and 700-% climate change. Selection of papers has been made to facilitate rapid introduction to most of the important issues and findings in an area. Over 600 articles, reports, and books are discussed.œ7Ϙnteractions among carbon, nutrient and hydrological cycles; and 5) an excess of carbon production over consumption in seveCificant amount of CO2 emissions from fossil-fuel combustion; 2) probable, human-caused imbalances in C exchanges among vegAetation, soils, and the atmosphere; 3) enhanced C storage in vegetation in response to excess atmospheric CO2; 4) strong iBta, observations, and model simulations that demonstrate: 1) the existence of natural CO2 sinks that could mitigate a signFsis of current research on the carbon cycle, CO2 sinks and associated processes and fluxes, and critical research needs toD assess the potential role of forest and land-use management in carbon sequestration. The papers in this volume present daE CO2 presented in this special issue and its companion hard-bound volume of Water, Air, & Soil Pollution, provide a syntheIA^3381^Natural CO2 sinks in terrestrial and marine environments are important components of the global carbon cycle, yet tGhe sign and magnitudes of key fluxes among them are unknown. The results of the Palmas Del Mar Workshop - Natural Sinks of439-453^^^^^Aug^^^^^3382}i Ѥ":QHmH"~XK-Hj?_/$zL*NfZ;.dryland rice areas and could make it possible to slightly expand them.s for monitoring vegetation^102^8^^127-150^^2098^^^J272^2^Downing,JP^Cataldo,DA^1992^1^Natural sinks of co2 - technical synthesis from the palmas-del- mar workshop^94^64^1-2^Kures. The expected increase in water-use efficiency due to enhanced CO2 might decrease the water deficit vulnerability of O varies with each model. Predictions of changes in rainfall vary widely between models. Global warming should in principleM allow a northward expansion of rice-growing areas and a lengthening of the growing season now constrained by low temperatNdoubling in atmospheric carbon dioxide (CO2) concentration. The regional seasonality and extent of the rise in temperatureRons correlate well with the observed values. Predictions of monthly rainfall correlate poorly. Virtually all models agree Pthat significant increases in temperature (from 1 to 7-degrees-C) will occur in the region including Thailand following a Qmatic conditions in Thailand are compared to predictions from four general circulation models (GCMs). Temperature predictiUA^3379^In Thailand, the world's largest rice exporter, rice constitutes a major export on which the economy of the whole cSountry depends. Climate change could affect rice growth and development and thus jeopardize Thailand's wealth. Current cli^347-366^^^^^Aug^^^^^3380ƛ&‘кZ9 jB D 3-day eggs > first instar. The four species exhibited a trend of tolerance of C pomonella > E. postvittana = P. oct\tolerance to this CA was similar for E. postvittana, C. pomonella, P. octo, and C. obliquana i.e., fifth instar > third in_levating the treatment temperature enhanced controlled atmosphere (CA) efficacy more than did increasing the CO2 concentra]tion. Thus at 20-degrees-C, a 0.4% O2/5.0% CO2 CA gave the most rapid kill of the mixtures tested. The order of lifestage ^s reviewed and additional data are presented. For both E. postvittana and C pomonella, reducing the O2 concentration and ebA^3377^Work on the mortality responses of four lepidopteran pests of apples in New Zealand-Epiphyas postvittana (Walker), `Cydia pomonella (L.), Planotortrix octo Dugdale, and Ctenopseustis obliquana (Walker)-to low O2/moderate CO2 atmospheres ist disinfestation of new-zealand apples^199^20^2^217-222^^^^^^^^^^3378Zt<"Hwp b)6|2pYd(4,Fated before making a general recommendation.xide concentration on respiration of growing and mature soybean leaves^9^18^^c270^3^Whiting,DC^Vandenheuvel,J^Foster,SP^1992^1^Potential of low oxygen moderate carbon-dioxide atmospheres for postharvedrs and preventing over-ripening, further work is needed on other cultivars, and lower O2 concentrations should be investighsed O2 concentration in absence of high CO2 showed some benefit in 'July Red'. No deleterious effect of CO2 concentrationsf even as high as 20% could be detected. Thus, even though high CO2 in CA conditions showed promise for controlling disordegng ripening, the best results being mostly obtained with 20% CO2. O2 levels assayed did not show clear effects, but decreaked water loss and ripening, increasing fruit softening markedly. Conversely, high CO2 delayed fruit ripening in CA storagei, keeping the fruit firmer, and preventing the development of woolliness, internal browning and reddish discoloration durijbsence of elevated CO2 levels but did not affect internal browning and increased reddish discoloration; further, it enhancn. The fruit was evaluated following cold storage, 31 days after harvest, and after four and eight days under 'shelf conditlions'(ripening at 15-18-degrees-C). Warming of the fruit at 20-degrees-C before cold storage prevented woolliness in the amcontrolled atmosphere (CA) conditions at 0-degrees-C. Combinations of 0, 10, 15 and 20% CO2 with 8 and 16% O2 were assayedep^^^^^3376k,L G^Watkinson,A R^Norton,L R^Ashenden,T W^1995^1^Plant populations and global environmental change: the efferA^3375^A storage experiment was aimed at preventing low temperature storage disorders in nectarine fruits, of cvs July Redo and Autumn Grand. Fruit was either cooled immediately after harvest or kept at 20-degrees-C for 48 h, before transfer to p269^4^Retamales,J^Cooper,T^Streif,J^Kania,JC^1992^1^Preventing cold-storage disorders in nectarines^174^67^5^619-626^^^^^Su Finally, building on the previous example by using two different models, this study illustrates that results can be strongly model dependent and encourages extreme caution in their interpretation. ͵S +`0& `ӲKapF 0$ N tstudy, the analysis of the results shows how, in a greenhouse warmed world, St Paul, MN, might look like North Platte, NE.xered in future studies of this kind. The paper also provides explanations regarding the movement of ecotones, defined as tvhe transition zones between different vegetation assemblages. Taking the North American forest/prairie boundary as a case w are likely major factors in determining the ecosystem response to greenhouse warming. Consequently, they should be consid{tput of an atmospheric general circulation model (GCM). Within this context, the paper demonstrates through the examples iyt analyses that both potential stomatal response to CO2 and the possible range of changes in atmospheric relative humidity~y (predator or parasitoid) control of the dormant phase of herbivorous insects may be very important in preventing or allo|bal changes that increase environmental stress on host plants are most likely to favour sap-feeding insects. Critical enem R163^4^Allen,LH^Drake,BG^Rogers,HH^Shinn,JH^1992^1^Field techniques for exposure of plants and ecosystems to elevated co-2 teraction are discernible in different combinations of factors. All three factors at the upper level appreciably induced activity of phosphoenolpyruvate carboxylase (PEPCase) in cotton leaves.^^^^^^^^^^^^^^^^^^^8 ])~5rsTd X zlogically based water budget and an explicit treatment of ecological dynamics. In principle, EXE could be forced by the ounts the results of numerical simulations performed with the Energy, water and momentum exchange, and Ecological dynamics (EXE) model at a local scale over periods of 400-800 (simulation) years. EXE constitutes a first attempt to couple a physiotions of the interactions between climate, plant physiology and ecology are badly needed. In this spirit, this paper preseanges in the ambient concentration of CO2. This may have important consequences for agriculture and natural resource exploitation. A formal recognition of atmosphere/biosphere interrelationships is crucial but insufficient. Systematic investigaeric chemistry. In particular, it partially controls the carbon cycle. In turn, vegetation is influenced by climate and chA^3373^Vegetation plays a significant role in determining the local and regional hydrology of ice-free continental surfaces and the dynamics of the atmosphere above it. Vegetation also influences the global climate directly by affecting atmosphas not significantly affected. In both data sets direction of responses was variable. A sensitivity analysis of carbon budsed on a leaf weight basis (14%). For the few data on root respiration, no significant change due to high CO2 could be detected. Carbon content of leaves and stem showed a small increase (1.2 and 1.7% respectively), whereas C-content of roots wfactors in the growth-response of plants to elevated CO2^182^40^4-5^501-513^^^^^^^^^^3168L@HpϷ uV$b؇$0*Elevated CO2 might not increase survival of C3 Plants under dry conditions, if temperatures are too high for them.em.pre157^4^Poorter,H^Gifford,RM^Kriedemann,PE^Wong,SC^1992^1^A quantitative-analysis of dark respiration and carbon content as 82^40^4-5^717-735^^^^^^^^^^3374il㖊m1#e!Pt};|;|H+7; ܑcɜw!`iCpjS` Z"Sig?gets under elevated CO2 identified changes in respiration rate, and to a lesser extent carbon content, as important factors affecting the growth response to elevated CO2 in quite a number of cases. Any comprehensive analysis of growth responseseginning of the study, Poa pratensis (Kentucky bluegrass), the dominant C3 species, had the highest frequency of 43.3%, bundrical plastic chambers were placed on the prairie to maintain two levels of CO2 (ambient or twice ambient) during two growing seasons in 1989 and 1990. Frequency of species was determined on 25 July 1989 and on 5 and 10 October 1990. At the bwater regime, the reverse occurred (frequencies: 3.6 % and 11.0 % for high and low CO2, respectively). The frequency of mat decreased with time. However, at the end of the experiment and under the high soil-water level, there were more P. pratensis plants in the elevated CO2 treatment (frequency: 13.5%) than in the ambient CO2 treatment (1.0%). Under the low soil f the climate becomes drier, A. scoparius will flourish more than S. nutans or A. gerardii, and P. pratensis may die out. d of the study, Indian grass grown with high water had the highest frequency of all species on the prairie (frequency at the end of the study in October, 1990, of 44.4% and 47.4% for the high and low CO2 levels, respectively). Unlike Indian grass, little bluestem grew better under low water conditions than under high water conditions. These results suggest that, ibetween 1989 and 1990. Under both soil moisture levels, the frequencies of S. nutans and A. scoparius increased. At the enjor C4 plants, Andropogon gerardii (big bluestem), A. scoparius (little bluestem) and Sorghastrum nutans (Indian grass) was not affected by CO2. However, water did affect their frequency. Under low water, the frequency of A. gerardii decreased f deforestation, would result in much higher predicted concentrations and rates of increase of atmospheric CO2 and, as a cic CO2 concentrations. Predictions which take account of the combined effects of deforestation, the return of carbon previously stored through the CO2 'fertilisation effect' and the loss of a large proportion of the 'missing sink' as a result oe effects have not been considered in the IPCC (Intergovernmental Panel on Climate Change) projections of future atmospherredicting future CO2 concentrations. If tropical rainforest destruction continues then much of the CO2 stored as a result of the CO2 'fertilisation effect' will be rereleased to the atmosphere and much of the 'missing sink' will disappear. Theself be playing an important role in enhanced carbon storage by tropical rainforests. This has important implications for pte the possibility that a significant net CO2 uptake (> 1 Pg C yr- 1), a CO2 'fertilisation effect', may be occurring in tropical rainforests, effectively accounting for much of the 'missing sink'. This sink may currently balance much of the CO2 added to the atmosphere from deforestation and biomass burning. Interestingly, CO2 released from biomass burning may itsprobable rates of carbon sequestration for the major ecosystem complexes and global 3-D tracer transport model runs indicaA^3371^The biosphere plays an important role in determining the sources, sinks, levels and rates of change of atmospheric CO2 concentrations. Significant uncertainties remain in estimates of the fluxes of CO2 from biomass burning and deforestation, and uptake and storage of CO2 by the biosphere arising from increased atmospheric CO2 concentrations. Calculation of 267^2^Taylor,JA^Lloyd,J^1992^1^Sources and sinks of atmospheric co2^182^40^4-5^407-418^^^^^^^^^^3372have underestimated tropical NPP by a factor of about 2, then it is unlikely that CO2-ECS could have negated the 1.5- 3.0 Gt of carbon that are estimated to have been emitted by tropical deforestation in 1990.ween plants and microbes?^2^103^^4^^^^^^33702^^^^^^^^^^^^^^^^^^^^^^^^rtainties in this (and other) models; total CO2-ECS is particularly sensitive to changes in NPP. Unless published surveys ere in 1990 was 1.1 Gt. When more appropriate values of beta were used (derived from a theoretical response of vegetation to increasing temperature and CO2), CO2-ECS was 1.3 Gt, of which tropical biomes accounted for 0.7 Gt. There are many uncery production (NPP) and atmospheric CO2 concentration. Using beta = 0.3 as a reference state, CO2-ECS by the global biosphthat CO2-enhanced carbon storage (CO2-ECS) by tropical biomes is negating the output of CO2 from deforestation. We describe here a 10-biome model for CO2-ECS, in which carbon accumulation in living vegetation is coupled to the Rothamsted soil carbon model. A biotic growth factor (beta) was used to describe the relationship between literature estimates of net primae experiments with other GCMs.s of an increased frequency and severity of floods in most regions. However, we discuss various important sources of uncertainty in the results presented, and indicate the need for rainfall intensity results to be examined in enhanced greenhousriod of such events decreases markedly. If realistic, the findings have potentially serious practical implications in terman CO2 treatments.988^1^Variation in leaf dissection and leaf energy budgets among populations of {iAchillea} from an altd for four selected regions of interest. In all regions the frequency of high rainfall events increases, and the return pe feed back inhibition. Carbohydrate partitioning within the plant organs were predominantly governed by N supply levels th starch glucose, fructose, and sucrose and in tuber starch concentrations. Photosynthetic reduction at low N supply showed a significant correlation with leaf starch concentration at both CO2 levels indicating that the inhibition is a result ofls, after seven weeks of reduction in NO3 supply. In leaves lowest NO3 treatment increased starch and sucrose and in rootsas not affected by N deficiency at both CO2 levels. Low NO3 had a lesser effect on photosynthesis than on leaf area growth; photosynthetic rates of mature leaves at both CO2 levels were lowered by about 30 % as compared to the respective contros-1 per mu-l intercellular CO2 l-1) was reduced by both low N supply and CO2 enrichment. Intercellular CO2 concentration w uptake of plants at all N supply levels. Water use efficiency, photosynthesis and stomatal conductance were increased by high CO2 only at 1.0 and 6.0 mM supply and reduced at the lowest N level. Photosynthetic efficiency (mu-Mol CO2 fixed m-2 f N-nutritional regimes (0.1, 1.0 or 6.0 mM nitrate supply). Carbon dioxide enrichment significantly increased total waterr gongylodes L) .1. Water-use, gas-exchange, and carbohydrate partitioning^172^57^3^138-145^^^^^May-Jun^^^^^3328 S^YurtseA^3327^Six weeks old kohlrabi plants (Brassica oleracea var, gongylodes [L.] cv. Express Forcer) were grown in growth chambers for three weeks at two levels of CO2 concentration (300-mu-l CO2 l-1-low or 900-mu-l CO2 l-1-high) and three levels o243^2^Sritharan,R^Lenz,F^1992^1^Effects of carbon-dioxide enrichment and nitrogen supply on kohlrabi (brassica-oleracea vad complexities in understanding mineral availability and plant mineral nutrition.ber traps": some considerations^113^28^^69-242^^2202^^^^^^^^^^^^^^^^^^^^^^^^c evaluations of the effects of climate change on plant growth will be challenged to contend with the large uncertainty an organic matter deposition in the soil. On the other hand, increased temperature and altered rainfall patterns may result in increased losses of soil minerals. Even the direction in the net change in available soil minerals is unclear. RealistiA^3325^The limiting factor concept has often been used to describe plant growth responses to altered availability of resoufree-living organisms and symbiotic systems, and improve soil properties for mineral availability as a result of increasedls. Consequently, it is very difficult to predict the plant growth response to climate change because of the large uncertainty about mineral availability. On the one hand, increased CO2 concentrations should stimulate nitrogen fixation by both e response to increased CO2 concentration, for example, requires an increase in plant uptake of the total amount of mineraously limiting. Further, in considering the limitation in plant growth to mineral nutrition it is important to consider both the solution concentration and the total amount of the individual minerals available to the plant. Sustaining a positivneral availability on plant growth. It is proposed that these resources for plant growth may be better viewed as simultanerces. However, even preliminary experiments, where atmospheric CO2 concentrations and solution mineral concentrations were varied, demonstrated that a more complex concept was required to interpret the potential effects of climate change and mi0/20- degrees-C) and the 23/14-degrees-C treatments gave the shortest and tallest plants, respectively.^^^^^^^^^^^^^^^^^^242^1^Sinclair,TR^1992^1^Mineral-nutrition and plant-growth response to climate change^78^43^253^1141-1146^^^^^Aug^^^^^332ith the 23/14-degrees-C treatment compared with the effects of the other temperature treatments. A constant temperature (2icant interactions between CO2 and temperature were found. Plant dry weight and fresh weight of flowers in Kalanchoe were generally enhanced by CO2 enrichment. The effects of CO2 on dry weight, plant height and flower stem length were greater wer than with the other temperature treatments. The results were the same for Rosa cultivars 'Frisco' and 'Kiss'. No signiflength and diameter of the rose shoot, while the number of days until flowering was not affected. With the 17/26-degrees-C treatment, rose shoots were 3-4 cm shorter, and with the 23/14- degrees-C treatment flowering occurred about 2 days earlirease in the CO2 concentration resulted in enhanced total dry weight, stem: leaf fresh weight ratio, flower fresh weight, rees-C day/night, and 20/20-degrees-C with 2 h at 14- degrees-C in the morning) were studied in 16 growth chambers. An incanchoe blossfeldiana at four different day/night temperature combinations (20/20-degrees-C, 23/14-degrees-C and 17/26- deg241^2^Mortensen,LM^Moe,R^1992^1^Effects of co2 enrichment and different day night temperature combinations on growth and fet ecosystem CO2 flux can be accurately tracked with this system. Field measurements indicate net ecosystem CO2 loss under temperatures, or net ecosystem CO2 flux. Chamber effects are generally small, and the experimental design allows separatio n and interpretation of treatment effects despite any unavoidable chamber effects. Both diurnal and seasonal patterns of n of ambient values. Comparison to unenclosed tundra indicates minimal chamber effects on depth of thaw, air, leaf, or soil mbers average within 1-degrees-C of ambient or target temperatures over a 24-h period and carbon dioxide concentration con trol rivals that of laboratory-based, control- environment systems. Photon flux density within the chambers is within 93% olved in tracking a naturally fluctuating environment, the CO2LT system performs very well. Temperatures in individual cha (150-200-mu-l l-1) to more than 900-mu-l l-1. Air temperature can be fixed, set to track ambient, or can track ambient tem perature with a specified offset allowing studies of the interaction of CO2 and temperature. Despite the complications inv concentration and temperature. Carbon dioxide can be maintained in each chamber at concentrations from well below ambient measure the instantaneous ecosystem-level CO2 exchange rates within each of the plots under the treatments imposed. This is a computer-controlled, closed, null-balance greenhouse system consisting of 12 chambers with individual control of CO2 u ecosystem-level manipulation of atmospheric CO2 concentration and temperature for intact plots of tussock tundra, and to 228^6^Oechel,WC^Riechers,G^Lawrence,WT^Prudhomme,TJ^Grulke,N^Hastings,SJ^1992^1^Co2lt an automated, null-balance system for studying the effects of elevated co2 and global climate change on unmanaged ecosystems^43^6^1^86-100^^^^^^^^^^3301itrog A^3300^An automated, CO2-controlled, long-term greenhouse system ('CO2LT') has been developed to provide replicated in sit to consider leaf age in assessing response to elevated CO2.  K y the developmental characteristics of the leaf. Further, both biochemical and structural modifications appear to be invol ved in this response. Because of the very different responses of young versus old leaves, future studies should be careful is at low CO2 was limited by CO2 regardless of developmental environment, whereas photosynthesis at high CO2 was limited b ed no photosynthetic depression. Leaves developed at low CO2 and switched to high CO2 exhibited increases in specific leaf  weight and leaf thickness. The increase in leaf thickness was proportional to length of time spent at high CO2. High CO2 depressed the rate at which stomata developed but did not affect final stomatal density. Results suggest that photosynthes "227^3^Kelly,DW^Hicklenton,PR^Reekie,EG^1991^1^Photosynthetic response of geranium to elevated co2 as affected by leaf age r in Sungro. Differences between hybrids and their response to water stress is discussed in relation to control of RuBP regeneration.asses: an evaluation with {+13}C labeling^2^105^^151-159^^2320^^^^^^^^^^^^^^^^^^^^^^^^ CO2. Similarly, leaves developed at low CO2 switched to high CO2 for various lengths of time, and returned to low CO2 show enhancement. Middle-aged leaves exhibited a temporary depression followed by permanent enhancement. Leaves developed at hi gh CO2 and switched to low CO2 did not exhibit any photosynthetic depression relative to plants grown continuously at low es grown at 350-mu-L.L-1 CO2 were switched to 1000-mu-L.L-1 CO2. Leaves switched later in development exhibited permanent ged leaves; very young leaves exhibited little enhancement, and net photosynthesis in the oldest leaves was depressed by e levated CO2. Temporary increases in net photosynthesis (relative to leaves developed at high CO2) resulted when young leav d by leaf age and by leaf position was determined. Elevated CO2 enhanced photosynthesis to the greatest extent in middle-aand time of co2 exposure^188^69^11^2482-2488^^^^^Nov^^^^^3299es among temperate, subarctic, and arctic species grown unde !A^3298^Geranium plants were grown from seed in chambers maintained at 350 or 1000-mu-L.L-1 CO2. Photopsynthesis as affecte t of RuBP from approximately 130 to 40 micromoles per square meter in SH-3622 and from 80 to 40 micromoles per square mete & photosynthesis; neither was decreased stomatal conductance (or stomatal "patchiness"). Reduction of photosynthesis per un $it leaf area from 25 to 5 micromoles CO2 per square meter per second in both hybrids was caused by a decrease in the amoun %d Rubisco protein, and Rubisco activity and activation state were small and were not sufficient to explain the decrease in )3622 had more, smaller cells per unit area and 60% more RuBP per unit leaf area than that of Sungro-380. Water stress deve 'loping over 4 days decreased the assimilation of both hybrids similarly. Changes in the amounts of chlorophyll, soluble an (tivity of Rubisco and its activation state did not differ significantly between hybrids. However, unstressed leaves of SH- , ribulose-1,5- bisphosphate (RuBP) were determined to assess the factors regulating the differences in assimilation of the * hybrids at high and low water potentials. The amounts of chlorophyll, soluble protein, Rubisco protein and the initial ac +total soluble and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) protein, and in Rubisco activity and amount of /ht and elevated CO2; the carboxylation efficiency was also larger. Growth at large photon flux increased assimilation rate -s of both hybrids. The changes in leaf composition, including cell numbers and sizes, chlorophyll content, and amounts of .mature leaves of SH-3622 under well-watered conditions was approximately 30% greater than that of Sungro-380 in bright lig 2A^3296^The effect of short-term water stress on photosynthesis of two sunflower hybrids (Helianthus annuus L. cv Sungro-38 00 and cv SH-3622), differing in productivity under field conditions, was measured. The rate of CO2 assimilation of young, ^98^2^516-524^^^^^Feb^^^^^3297'6^ܐF+F9Ft >^ܐ$F^㋏$"؎&^ܐF discussed.ja,E^Kapiainen,K^Niemel,P^Tuomi,J^1983^1^Plant availability hypothesis and other epxlanations of herbivore cy 3226^3^Gimenez,C^Mitchell,VJ^Lawlor,DW^1992^1^Regulation of photosynthetic rate of 2 sunflower hybrids under water-stress^8 4a, thus enhancing photosynthesis and growth. The relevance of the results to removal of atmospheric CO2 by marine algae is 8ng H+. Photosynthesis of the alga was found to be enhanced in the seawater of elevated dissolved inorganic carbon (DIC, CO 62 + HC O3- + CO3-). It is concluded that the increased pH in the light resulted in the increase of DIC in the culture medi 7 the photosynthetic conversion of HCO3- to OH- and CO2 proceeded much faster than the dissociation of hydrated CO2 releasi ;elis, were cultured using aeration with high CO2. It was found that the higher the CO2 concentration, the faster the growt 9h of the thalli. Aeration with elevated CO2 lowered pH in dark, but raised pH remarkably in light with the thalli, because :A^3294^Leafy thalli of the red alga Porphyra yezoensis Ueda, initiated from conchospores released from free-living conchoc >225^6^Gao,K^Aruga,Y^Asada,K^Ishihara,T^Akano,T^Kiyohara,M^1991^1^Enhanced growth of the red alga porphyra-yezoensis ueda in high co2 concentrations^187^3^4^355-362^^^^^Dec^^^^^3295>t\FI^㋇FFLN؎&L xport in the light phase of the diurnal cycle as plants adjust to enriched CO2 and a more rapid growth rate."  Antrol. In the developing sink leaf, high rates of export in the light occurred as the leaf approached full expansion. The ?results indicate that a specific acclimation process occurs in source leaves which increases the capacity for assimilate e @ximately 7 days, assimilate export in the light began to increase and by 12 days reached rates 3 to 5 times that of the co Devident in the two leaf types. Net CO2 exchange rate (CER) immediately increased and remained elevated in high CO2. Initia Blly, the additional assimilate at high CO2 levels in the light and was utilized in the subsequent dark period. After appro Cfor 12 days after transfer from a control (350-mu-l l-1) to a high (700-mu-l l-1) CO2 environment. Similar responses were Goccur over time when plants are exposed to enriched atmospheric CO2. We examined assimilate relations of source (primary u Enifoliolate) and developing sink (second mainstem trifoliolate) leaves of soybean [Glycine max (L.) Merr. cv. Lee] plants FA^3292^Evidence from previous studies suggested that adjustments in assimilate formation and partitioning in leaves might J224^3^Cure,JD^Rufty,TW^Israel,DW^1991^1^Assimilate relations in source and sink leaves during acclimation to a co2-enriched atmosphere^37^83^4^687-695^^^^^Dec^^^^^3293^^^^^^^^^^^^^؎F&FL 9F@!F搛"rFFto respond to elevated levels of atmospheric CO2.^ʐ>L tFF؎&^F M seasons, the photosynthetic capacity has actually increased by 31%. An increase in photosynthetic capacity has been obser Kved in other species growing in the field, which suggests that photosynthesis of certain field grown plants will continue L, it was shown that, for a wild C3 species growing in its natural environment and exposed to elevated CO2 for four growing PA^3290^While a short-term exposure to elevated atmospheric CO2 induces a large increase in photosynthesis in many plants, Nlong-term growth in elevated CO2 often results in a smaller increase due to reduced photosynthetic capacity. In this study^9^14^9^1003-1006^^^^^Dec^^^^^3291t >L t[FH^㋇vvp$r$؎&F environment.L^Ericson,L^1987^1^Dynamics of tundra and taiga populations of herbaceous plants in relation to the Tihomiro Q223^2^Arp,WJ^Drake,BG^1991^1^Increased photosynthetic capacity of scirpus-olneyi after 4 years of exposure to elevated co2 R two cultivars suggest that lines of rice could be identified that would maximize reproductive output in a future high CO2 Vrences in reproductive characteristics were also observed between cultivars at an elevated CO2 environment with a signific Tant increase in harvest index for IR-36 but not for Fujiyama-5. Changes in carbon allocation in reproduction between these Upproximately the same in both cultivars, although differences in allocation patterns were noted in root/shoot ratio. Diffe Ytosynthetic response at 5% CO2 and the response of CO2 assimilation (A) to internal CO2 (C(i)) suggest a reallocation of b Wiochemical resources from RuBP carboxylation to RuBP regeneration. Increases in total plant biomass at elevated CO2 were a dA^3288^Two rice (Oryza sativa L.) cultivars of contrasting morphologies, IR-36 and Fujiyama-5, were exposed to ambient (36 \222^2^Ziska,LH^Teramura,AH^1992^1^Intraspecific variation in the response of rice (oryza-sativa) to increased co2 - photosynthetic, biomass and reproductive characteristics^37^84^2^269-276^^^^^Feb^^^^^3289w ݆f^ҐF!9F>@ ularge and small subunit transcripts.v >t |^Fx$>F" >uE>x$t _th subunit polypeptides. We have found that this decrease in synthesis of large and small subunits results from specific a ]nd coordinated down-regulation of translation of both subunits possibly resulting, at least in part, from modification of ^ells that had been transferred from elevated CO2 to limiting CO2 exhibit transient declines of label incorporation into bo borganic carbon. A correlation between limiting inorganic carbon-induced induction of the CO2-concentrating mechanism and d `ecreased synthesis of the large and small subunits of ribulose 1,5-bisphosphate carboxylase/oxygenase has been observed. C Xh cultivars and photosynthetic enhancement was still evident after 3 months of exposure to a high CO2 environment. The pho e0-mu-l l-1) and ambient plus 300-mu-l l-1 CO2 from time of emergence until ca 50% grain fill at the Duke University Phytot cron, Durham, North Carolina. Exposure to increased CO2 resulted in about a 50% increase in the photosynthetic rate for bot a enables the cell to photosynthesize efficiently with little oxygen inhibition, even in conditions of limiting external in hA^3286^In conditions of limiting external inorganic carbon, the unicellular alga Chlamydomonas reinhardtii induces a mecha fnism to actively transport and accumulate inorganic carbon within the cell. A high internal inorganic carbon concentration1414^^^^^Apr^^^^^3287!6! 6@  " D Fi^㋇FFmass development, but is favoured by elevated CO2 levels even more than the leaves.hapin,FS,III^1996^1^Siberian CO{-2} ef l221^3^Winder,TL^Anderson,JC^Spalding,MH^1992^1^Translational regulation of the large and small subunits of ribulose bispho isphate carboxylase oxygenase during induction of the co2-concentrating mechanism in chlamydomonas-reinhardtii^8^98^4^1409- jation somewhat higher than in air (500 ppm). while higher CO2 pressure restrains growth. Root growth reflects the leaf bio oa CO2 deficit. Decrease in growth rate during the summer can be avoided through CO2 addition in July when CO2 availability m is low and epiphytes are thriving. Growth of J. bulbosus in the laboratory is stimulated by CO2 addition up to a concentr nA^3284^The unusual growth pattern exhibited by Juncus bulbosus L. in a slightly acidic Swedish brown-water lake is due to r220^1^Svedang,MU^1992^1^Carbon-dioxide as a factor regulating the growth dynamics of juncus-bulbosus^159^42^3^231-240^^^^^Apr^^^^^3285ge at Barrow, Alaska^56^5^^846-855^^2378^^^^^^^^^^^^^^^^^^^^^^^^$?Qlnd biodegradation of this very complex compound.F####$$$"#( uinhibited both growth and chlorophyll synthesis. Release of lignin into the nutrient medium was observed in several experi vments, especially in slow-growing cultures supplemented with sucrose. Only a few successive passages of suspensions that p sroduced lignin could be cultured before cell death. The cultures releasing lignin may be unique for studies on synthesis a twith low (0.5%) sucrose or without any carbohydrate source, suggesting photomixotrophism. A high concentration of kinetin yved on a medium containing 2% sucrose and a low level of organic nitrogen (0.25 mM arginine and 0.5 mM glutamine) suppleme nted with 2,4-D (0.5-mu-M) and kinetin (2.5-mu-M). The same medium with 4% sucrose gave the best growth response, but a ne x chlorophyllous embryo callus in an elevated CO2 (2%) atmosphere. A continuous chlorophyllous suspension culture was achie |A^3282^The effect of different concentrations of sucrose (0-4%) and of two growth regulators (0-50-mu-M 2,4-D and 0-25-mu- zM kinetin) was tested on growth and chlorophyll content of suspension cultures of Picea abies (L.) Karst. originating from^37^84^3^374-379^^^^^Mar^^^^^3283: ? b        ants that experienced long-term low humidity.sodium and potassium on mineral balance in captive meadow voles ({iMicrotus }219^3^Simola,LK^Lemmetyinen,J^Santanen,A^1992^1^Lignin release and photomixotrophism in suspension-cultures of picea-abies ~curred only in the plants grown in low humidity. These results may be related to enhanced dehydration resistance of the pl n both high and low humidities were caused by CO2 enrichment. Elevated water content (kg m-2 leaf area) caused by CO2 enri chment, higher water content at a given water potential, and notably lower rate in desiccation from detached leaves all oc s-C and CO2 concentrations of 350 or 650-mu-mol mol-1. Elevated leaf water potentials of the water-stressed plants grown imidity, and carbon-dioxide^4^139^5^600-604^^^^^Mar^^^^^3281ent mineralization and fungal spore composition of fecal pelle A^3280^Well watered and water-stressed Abutilon theophrastic, were grown with relative humidity of 45% or 85% at 30-degree 218^2^Luo,YH^Strain,BR^1992^1^Leaf water status in velvetleaf under long-term interactions of water-stress, atmospheric hu both treatments define a single relationship between fine-root biomass and trunk cross-sectional area. The data also show the CO2-enriched trees to have approximately 2.3 times more fine-root biomass in this soil layer than the trees grown in a 12 months, we have determined the fine-root biomass in the top 0.4 m of the soil profile beneath the trees. Results from sures with clear plastic walls for 3.5 years. For the last 3 years of this period, half of the trees have been continuousl y exposed to air enriched with CO2 to 300-mu-mol mol-1 above the ambient concentration. At 2-month intervals over the last A^3278^Sour orange trees have been grown from the seedling stage out- of-doors at Phoenix, Arizona, USA, in open-top enclo 217^2^Idso,SB^Kimball,BA^1992^1^Seasonal fine-root biomass development of sour orange trees grown in atmospheres of ambient and elevated co2 concentration^9^15^3^337-341^^^^^Apr^^^^^3279^^^^^^^^^^^^^^^^^^^^^^^^7!;!?!E!first 36 d of growth.^!c!i!n!r!v!!!!!!! re conditions was approximately 25% greater in leaves of plants grown in high CO2, despite the reduction in leaf conductan ce. Greater assimilation rate was one factor allowing plants grown in high CO2 to incorporate 30% more biomass during the ly slightly less than that of leaves grown in 35Pa CO2, net photosynthesis measured at the growth CO2, light and temperatu n plants grown at high CO2, Stomatal conductance of leaves of plants grown and measured at 65 Pa CO2 was approximately 32% lower than that of plants grown and measured at 35 Pa. Because photosynthetic capacity of leaves grown in high CO2 was on the only difference between CO2 treatments being a slight reduction in the slope of the line relating Vc(max) to leaf N i Rubisco activity (Vc(max)), estimated from A versus C(i) response curves measured at 29-degrees-C, was almost-equal-to 10% lower in leaves from plants grown in high CO2. The relationship between key model parameters and total leaf N was linear, gh CO2 plants, the photosynthetic characteristics of leaves in both treatments were similar, although the maximum rate of egression techniques, but in order to achieve reasonable fits, it was necessary to include a phosphate limitation resultin g from inadequate triose phosphate utilization. Despite the accumulation of large amounts of starch (> 50 g m-2) in the hi ted model of C3 leaf photosynthesis was parameterized for leaves from both CO2 treatments using non-linear least squares r282^^^^^Apr^^^^^3277^Predicting the response of populations to environmental change^11^76^^926-941^^2406^^^^^^^^^^^^^^^^^ A^3276^Cotton plants were grown in CO2-controlled growth chambers in atmospheres of either 35 or 65 Pa CO2. A widely accep 216^4^Harley,PC^Thomas,RB^Reynolds,JF^Strain,BR^1992^1^Modeling photosynthesis of cotton grown in elevated co2^9^15^3^271- ty. However, the biomass increase made up for this reduction in such a way that the total nitrogen pool per tree remained unchanged.rnicus}^2^59^^167-177^^2408^^^^^^^^^^^^^^^^^^^^^^^^!!""["}"" dioxide enrichment significantly reduced the nitrogen concentration in all organs, irrespective of the nutrient availabili biomass was very different: on the unfertilized soil, only the root biomass was increased, leading to an increase in the root: shoot ratio. Contrastingly, on fertilized soil only stem biomass and diameter but not height were increased. Carbon tly increased total biomass by about 20%, both on fertilized and on unfertilized forest soil. However, the partitioning of eedlings (Castanea sativa Mill), grown in pots outdoors throughout the vegetative season. Fertilization had a pronounced e ffect on dry weight accumulation, tree height, leaf area, and plant nitrogen content. Carbon dioxide enrichment significan g levels of mineral nutrition on dry weight, nitrogen accumulation and partitioning were examined in 2-year-old chestnut s on soil nutrient availability in sweet chestnut (castanea-sativa mill)^186^49^2^83-90^^^^^^^^^^3275 {iMicrotus californi A^3274^The effect of 2 levels of atmospheric carbon dioxide (ambient, ie 350 ppm, and double, ie 700 ppm) and 2 contrastin ontent in air which seem to be necessary to avoid potential photoinhibition and premature water exhaustion from gelled med 215^3^Elkohen,A^Rouhier,H^Mousseau,M^1992^1^Changes in dry-weight and nitrogen partitioning induced by elevated co2 dependia.^^^^^^^^^^^^^^^^^^^^^^6J6H6d6b6 6 =t^&G 6 6 jl=tt ent is achievable through careful increments of light quanta, balanced with increments of humidified air flow and/or CO2 c dry weight as those from a conventional culture tube treatment. This study shows that it is possible to favour photoautotr ophic growth when elevated PPFD, enhanced air-exchange and hydroponic medium flow are provided concurrently. This enhancem ton flux density (PPFD) and hydroponic irrigation. After 15 days of treatment, plantlets gained more than 3 times as much AGEHS monitors and controls several parameters relevant to plant growth. Shootlets of Chrysanthemum, x morifolium Ramat. cv. Envy were treated with flow of air or CO2-enriched air under controlled relative humidity, elevated photosynthetic pho iological requirements for photoautotrophic growth in vitro and alleviation of the needs for ex vitro acclimatization. The A^3272^An aseptic gas exchange and hydroponic system (AGEHS) has been developed in an attempt for characterization of physof photosynthesis invitro^37^84^3^409-416^^^^^Mar^^^^^3273FVFVFVFVp$r$FV¡$$FȉV 214^2^Dube,SL^Vidaver,W^1992^1^Photosynthetic competence of plantlets grown-invitro - an automated-system for measurement heses suggesting that root/shoot partitioning is controlled by some aspect of plant C/N balance.؎&F9 } and shoots were not affected by CO2 treatment. This phenomenon was consistent with the hypothesis that root/shoot partiti oning is related to the daily rate of starch accumulation by leaves during the photoperiod, but is inconsistent with hypot rate at which leaves accumulated starch over the course of the light period and the partitioning of biomass between roots ion, photosynthetic rate, water use efficiency, nitrogen per unit leaf area, and starch and soluble sugar levels in leaves increased with increasing atmospheric CO2 concentration, whereas specific leaf area and nitrogen concentration of leaves significantly decreased. Despite substantial changes in radish growth, resource acquisition and resource partitioning, the ntrations (200 ppm, 330 ppm and 600 ppm) with a stable hydroponic 150-mu- mol l-1 nitrate supply. Radish biomass accumulat gated in order to examine several hypotheses about the mechanisms that govern dry matter partitioning between shoots and r oots. Wild radish plants (Raphanus sativus x raphanistrum) were grown for 25 d under three different atmospheric CO2 conce A^3270^The effects of CO2 enrichment on plant growth, carbon and nitrogen acquisition and resource allocation were investi 213^3^Chu,CC^Coleman,JS^Mooney,HA^1992^1^Controls of biomass partitioning between roots and shoots - atmospheric co2 enrichment and the acquisition and allocation of carbon and nitrogen in wild radish^2^89^4^580-587^^^^^Apr^^^^^3271P`ported..ssessFPHJ=tt FP =tt  latively low cost. A preliminary assessment of the chambers has been made and concentrations can be maintained at +/- 6% f or a target atmosphere of 680 cm3 m-3 CO2 under normal operating conditions. Other chamber environmental conditions are re0A^3268^An inexpensive, potentially mobile field exposure system is described which may be easily constructed by a small wo 212^3^Ashenden,TW^Baxter,R^Rafarel,CR^1992^1^An inexpensive system for exposing plants in the field to elevated concentrations of co2^9^15^3^365-372^^^^^Apr^^^^^3269. 0 >zt >|u6|6zHz|>$t >$u a result of enhanced CO2 may be eliminated or reduced if UV-B radiation continues to increase.6H higher concentration of these compounds than IR-36 in all environments, and the production of these compounds in Fujiyama -5 was stimulated by UV-B fluence. Results from this study suggest that in rice alterations in growth or photosynthesis as ons with increased UV-B radiation appeared to be related to leaf production of UV-B- absorbing compounds. Fujiyama-5 had a of photosystem II as estimated from the ratio of variable to maximum chlorophyll fluorescence. Little change in RuBP rege neration and photochemistry was evident in cultivar Fujiyama-5, however. The degree of sensitivity of photochemical reacti ficiency. Changes in the RuBP regeneration limitation in IR-36 were consistent with damage to the photochemical efficiency tion to photosynthesis with increased UV- B radiation was the capacity for regeneration of ribulose bisphosphate (RuBP), w hereas for Fujiyama-5 the primary photosynthetic decrease appeared to be related to a decline in apparent carboxylation ef response of CO2 uptake to internal CO2 concentration at light saturation suggested that, for IR-36, the predominant limita n, CO2 enhancement effects on respiration, photosynthesis, and biomass were eliminated in IR-36 and significantly reduced in Fujiyama-5. UV-B radiation simulated a 25% depletion in stratospheric ozone at Durham, North Carolina. Analysis of the nd yield for both curtivars. However, in plants exposed to simultaneous increases in CO2 and ultraviolet-B (UV-B) radiatio (660 microbars) from germination through reproduction in unshaded greenhouses at the Duke University Phytotron. Growth at elevated CO2 resulted in significant decreases in nighttime respiration and increases in photosynthesis, total biomass, a A^3266^Two cultivars of rice (Oryza sativa L.) IR-36 and Fujiyama-5 were grown at ambient (360 microbars) and elevated CO2 211^2^Ziska,LH^Teramura,AH^1992^1^Co2 enhancement of growth and photosynthesis in rice (oryza- sativa) - modification by increased ultraviolet-b radiation^8^99^2^473-481^^^^^Jun^^^^^3267^s8F\^؎&FF\^on levels of organization.ɚKv8F$$؎&FF$$؎&F\^ of the growth form, 2) our understanding about the clonal biology and population ecology of this growth form is still evol ving and 3) the modular construction of this growth form may result in variable responses at the ramet, clone and populati cult to anticipate because: 1) caespitose graminoids consist of both C3 and C4 species which will complicate the response se proximity requires further evaluation but may center on intra-plant competitive interactions. The response of this larg e sub-group of clonal plants to climate change will significantly impact community structure and function because of their diversity and dominance in numerous biomes. The impact of climate change on the caespitose graminoid growth form is diffi ue conferred by a clonal architecture composed of an assemblage of autonomous physiological individuals growing within clo nd longevity of individual ramets. Restricted resource allocation among ramet sequences within clones is primarily caused by the disintegration of vascular connections among ramet sequences following death of the seminal ramet. The survival val t generations comprising the physiological individual is determined by demographic variables influencing the recruitment a trated that physiological integration in the caespitose graminoid Schizachyrium scoparium is restricted to individual rame t sequences consisting of three connected ramet generations as opposed to all ramets within the clone. This number of rame low level of continuous resource allocation between parental and juvenile ramets. Isotopic and severing experiments demons A^3264^Caespitose graminoids are characterized by the compact spatial arrangement of ramets within clones and the absence of rhizomes or stolons. Resource allocation is principally acropetal with established ramets supporting juvenile ramets du ring early development. However, after juvenile ramet maturation a responsive resource transfer system is maintained by a sis with reference to climate change^15^63^3^357-365^^^^^Apr^^^^^3265secific recommendation of the creation of a tropical research center.,N R^Hodkinson,I D^1995^1^Climatic severity and the r 210^2^Welker,JM^Briske,DD^1992^1^Clonal biology of the temperate, caespitose, graminoid schizachyrium-scoparium - a synthe development and application of equipment for field measurements in several representative natural ecosystems and makes sp draws heavily on studies from artificial environments and conditions in an attempt to summarize knowledge of global envir onmental change on forests and other non-agricultural ecosystems. Finally the paper concludes that there is a need for the of larger scale field studies in natural vegetation. This paper lists and summarizes the best field studies available but s. A few field microcosm studies have been completed and a system for the free air release of CO2 has been applied in cott on fields. Unfortunately, the requirement of large amounts of CO2 and financial restrictions have precluded the initiation op chambers are being used in several autecological field studies in an attempt to obtain more realistic field environment nd growth chambers. Several lines of evidence indicate that controlled environment studies using plants growing in pots in duce experimental artifacts that reduce confidence in the use of results for prediction of future global responses. Open t field conditions. Most measurements have been conducted in the synthetic environments of totally controlled greenhouses a mptions are valid and how natural systems might respond under future scenarios of CO2 increase and possible climate change s. Few measurements of the effects of CO2 and global climate change have been made on "natural" ecosystems under realistic ironmental conditions. There is also evidence that CO2 acts as a plant fertilizer. It is of interest to know if these assu45-60^^^^^Aug^^^^^3263t,K R^1991^1^Loess ecosystems of northern Alaska: regional gradient and toposequence at Prudhoe Bay A^3262^It is generally assumed that healthy, natural ecosystems have the potential to sequester carbon under favorable env 209^2^Strain,BR^Thomas,RB^1992^1^Field-measurements of co2 enhancement and climate change in natural vegetation^94^64^1-2^d zones, with an increase in the areal extent of tropical forests and a shift of the boreal forest zone into the region cu^ture. Plants of both species grown under an elevated temperature regime had substantially decreased reproductive allocatio have led to the reduced biomass accumulation of high CO2 grown plants that we observed during the last 30 d of growth. Pla nts of both species grown in elevated CO2 exhibited reduced tissue-specific rates of nitrogen absorption, increased plant photosynthetic rate per unit of conductance, and increased initial allocation of biomass to roots, irrespective of temperaf an effect on tillering is not known.c JU| imarily due to the fact that CO2 concentration did not influence tiller (branch) numbers. In the absence of an effect on t iller numbers, any possible weight increment was restricted to the c. 2.5 leaves of each tiller. The reason for the lack o onditions and was accompanied by substantial reductions of whole-plant nitrogen content and leaf photosynthesis. This may per unit leaf area early in the experiment apparently compensated for reduced leaf area. For Amaranthus at 38-degrees, pea k leaf area production was not affected by CO2 treatment, but the rate of net leaf area loss hastened under elevated CO2 c duced peak leaf areas under elevated CO2 in comparison to ambient CO2 grown plants, but increased rates of photosynthesis tosynthesis, whereas nitrogen retention was unaffected in Abutilon. Thus, at 28-degrees, final biomass of Abutilon was not stimulated in a high CO2 environment whereas the final biomass of Amaranthus was. At 38-degrees, Abutilon had slightly re apparently enhanced the ability of Amaranthus to retain nitrogen at this temperature, which may have helped to enhance pho ecies, which led to an initial stimulation of biomass accumulation at the higher CO2 level. However, in elevated CO2 at 28 -degrees, the rate of net leaf area loss for Abutilon increased while that of Amaranthus decreased. Furthermore, high CO2 t whole- plant nitrogen retention. At 28-degrees-C, elevated CO2 stimulated the initial production of leaf area in both sp  but not at 38-degrees, and had no significant effects on final biomass at either temperature. These results are interpret ed in light of the interactive effects of CO2 and temperature on the rates of net leaf area production and loss, and on ne es but was depressed at 38-degrees. For Abutilon, elevated CO2 increased initial plant relative growth rates at 28-degrees ation, and resource acquisition (i.e., photosynthesis and nitrogen uptake), and the strength and direction of these effect s were often dependent on plant species. For example, final biomass of Amaranthus was enhanced by elevated CO2 at 28-degre levated CO2 and temperature treatments had significant independent and interactive effects on plant growth, resource alloc  were made on individuals of Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) grown in environments with atmosphe ric CO2 levels of 400 or 700-muL/L and with light/dark temperatures of 28-degrees/22-degrees or 38-degrees/31-degrees-C. E allocation of two annual plants that were supplied with a single pulse of nutrients. Physiological and growth measurementsls^11^73^4^1244-1259^^^^^Aug^^^^^32431988^1^Respiratory burst after freezing and thawing of soil: experiments with soil b A^3242^We examined how CO2 concentrations and temperature interacted to affect growth, resource acquisition, and resource 199^2^Coleman,JS^Bazzaz,FA^1992^1^Effects of co2 and temperature on growth and resource use of cooccurring C3 and C4 annua hotosynthetic adjustment to elevated carbon dioxide concentration was evident only in Q. robur. All species examined had lower rates of dark respiration per unit of mass when grown and measured at elevated carbon dioxide concentration. manipul plants grown and measured at elevated carbon dioxide concentration only at measurement temperatures above 33- degrees-C. P " and measured at 700 cm3 m-3 carbon dioxide did not differ from that of plants grown and measured at 350 cm3 m-3 in Malus domestica, Quercus prinus and Quercus robur at any measurement time. In Acer saccharinum, lower conductances occurred for !le- plant carbon dioxide efflux rates in darkness were also determined. The stomatal conductance of leaves of plants grown %rbon dioxide to examine how aspects of their gas exchange would be altered by growth at elevated carbon dioxide concentrat #ion. Leaf conductances to water vapour and net carbon dioxide exchange rates were determined periodically near midday. Who $A^3240^Seedlings of temperate deciduous tree species were grown outdoors at ambient and at an elevated concentration of ca of foraging by these root systems, as indicated by the horizontal spread of roots, may be increased.iannikova,OV^1993^1^ )198^1^Bunce,JA^1992^1^Stomatal conductance, photosynthesis and respiration of temperate deciduous tree seedlings grown outdoors at an elevated concentration of carbon-dioxide^9^15^5^541-549^^^^^Jun^^^^^3241y 'reatments. Thus, under elevated CO2 the intensity of foraging S. vulgaris root systems might be unchanged while the extent ,terns and root length similar to those grown under ambient CO2 with a high water supply. 3. Overall, water had a more pron *ounced impact on the growth rate of S. vulgaris roots than did CO2. The density of rooting remained unchanged across all t +ged through larger volumes of soil. Under elevated CO2 and a low water supply, root systems had branching and foraging pat / atmospheric CO2 concentration and a high or a low supply of water. 2. CO2 and water had a significant impact on the way t -hat S. vulgaris root systems filled the soil matrix. Elevated CO2 resulted in more branched, longer root systems that fora .structively monitor the development of roots in situ at both an elevated (700-mu-mol mol-1) and ambient (350-mu-mol mol-1) 2A^3238^1. The impact of elevated CO2 and drought on the architecture and development of root systems of Senecio vulgaris w 0as examined and implications for water and nutrient uptake discussed. Plants were grown in miniature rhizotrons to non- de drought^43^6^3^324-333^^^^^^^^^^3239ͷͷͷͷͷͷͷͳͷͷͷͷͷͷͷͷͷͷͷͷͷͷͷͷ]cV]`uD rures also rise.,R A^Massman,W J^Musselman,R C^Mosier,A R^1996^1^Diffusional flux of CO{-2} through snow: spatial and temp 3197^2^Berntson,GM^Woodward,FI^1992^1^The root-system architecture and development of senecio- vulgaris in elevated co2 and 4y to be beneficial to rice growth and yield, potentially large negative effects on rice yield are possible if air temperat 8egrees-C temperature treatment. Across this temperature range, the number of panicles plant-1 nearly doubled while the num 6ber of seeds panicle-1 declined sharply. These results indicate that while future increases in atmospheric [CO2] are likel 7ment, grain yield decreased from 10.4 to 1.0 Mg ha-1 with increasing temperature from 28/21/25-degrees-C to the 37/30/34-d ;t a [CO2] of 330-mu-mol mol-1 and temperature regime of 28/21/25- degrees-C. Carbon dioxide enrichment at 28/21/25-degrees 9-C increased both biomass accumulation and tillering and increased grain yield by 60%. In the 660-mu-mol mol-1 [CO2] treat :y bulb air temperature/paddy water temperature) and [CO2] of 660-mu-mol CO2 mol-1 air. An ambient chamber was maintained a > IR-30). Rice plants were grown season-long in outdoor, naturally sunlit, controlled-environment, plant growth chambers in < temperature regimes ranging from 25/18/21-degrees-C to 37/30/34-degrees-C (daytime dry bulb air temperature/night-time dr =rtant food crops. This study was conducted to determine the effects of [CO2] and temperature on rice (Oryza sativa L., cv. AA^3236^The continuing increase in atmospheric carbon dioxide concentration ([CO2]) and projections of possible future incr ?eases in global air temperatures have stimulated interest in the effects of these climate variables on agriculturally impol^^^^^3237essors may play an important role in mediating effects on plant growth.991^1^Biogeochemical diversity along a riverside topo B196^3^Baker,JT^Allen,LH^Boote,KJ^1992^1^Temperature effects on rice at elevated co2 concentration^78^43^252^959-964^^^^^Ju Cmulation in the same experiment, suggesting that responses of developmental processes to elevated CO2 and interacting fact G leaf area was slightly increased at 38-degrees relative to 28-degrees, and elevated CO2 levels resulted in increased leaf E area at 28-degrees but decreased leaf area at 38-degrees. The effects on leaf area closely parallel rates of biomass accu F at 38-degrees. Branch leaf area displayed a similar response to CO2, but was greater at 38- degrees. Overall, whole-plant Jole-plant leaf area. In Amaranthus, leaf initiation rate increased with temperature, and was increased by elevated CO2 at H28-degrees. Individual leaf area was greatest at 28-degrees, and was increased by elevated CO2 at 28-degrees but decreased I initiation rates. Elevated CO2 concentration increased leaf initiation rate at 28-degrees, resulting in an increase in wh Mwhole-plant leaf area and the number of main stem nodes. In Abutilon, leaf initiation rate was highest at 38- degrees, but K area of individual leaves was greatest at 28- degrees. Total leaf area was greatly reduced at 18-degrees due to slow leaf Lmined by the production of nodes on the main stem (the plastochron index), and through shifts in the relationship between Powth was analyzed in terms of the leaf initiation rate, leaf expansion, individual leaf area, and, in Amaranthus, producti Non of branch leaves. Temperature and CO2 influenced leaf area production through effects on the rate of development, deter Oconcentrations of carbon dioxide (400 and 700-mu-L/L). The production of whole-plant leaf area during the first 30 d of gr SA^3234^We studied leaf area production in two annual plant species, Abutilon theophrasti and Amaranthus retroflexus, under Q three day/night temperature regimes (18-degrees/14-degrees, 28- degrees/22-degrees, and 38-degrees/31-degrees-C) and two t-species^11^73^4^1260-1269^^^^^Aug^^^^^3235t Par 15,/4$t D T$" ]a c exposed to elevated CO2 remains unresolved. density and season on the population rate of change in the meadow vole^15^78 T195^4^Ackerly,DD^Coleman,JS^Morse,SR^Bazzaz,FA^1992^1^Co2 and temperature effects on leaf-area production in 2 annual plan Uase in other metabolic processes. Whether these reductions are beneficial or detrimental to the long-term growth of plants Ywth respiration was largely offset by a greater dry mass for leaves grown at elevated CO2 concentrations. Although reducti Wons in the respiratory loss of carbon could be beneficial, respiration is unlikely to decrease without a concomitant decre Xpiration were dominated by a lower rate of maintenance respiration, while the contribution of a lower specific rate of gro \eaf growth simulation model indicated that total respiration would be reduced by 21 to 26 % for a leaf exposed to + 150 or Z + 300 cm3 m-3 CO2 throughout its 50-d lifespan compared with one grown at ambient CO2 conditions. Reductions in total resdthe site were differentiated most of the significant correlations were with soil microbial carbon; they were positive in t [135 mg CO2 g-1 d-1 for leaves from the ambient treatment. Incorporating these growth and maintenance coefficients into a l `enance respiration, SRR was a linear function of SGR. Ambient-grown leaves had a growth respiration coefficient of 704 mg aCO2 g-1 dry mass compared with 572 and 570 mg CO2 g-1 for leaves grown at the two higher CO2 concentrations. Leaves from t ^he elevated CO2 treatments had an average maintenance respiration coefficient of 88 mg CO2 g-1 dry mass d-1 compared with _tes were correlated with reduced leaf nitrogen concentrations. As described by the two-component model of growth and maint dce of a CO2 effect on individual leaf expansion or specific growth rate (SGR), increasing the CO2 concentration to ambient b + 150 or + 300 cm3 m-3 decreased SRR by 28 to 45 % compared with ambient- grown controls. These lower leaf respiration ra cs of yellow-poplar (Liriodendron tulipifera L.) after 3 vr of CO2 enrichment in open-top field chambers. Despite the absena L exposed to long-term carbon-dioxide enrichment in the field^84^121^4^515-523^^^^^Aug^^^^^3233etween woody plants and eA^3232^Specific respiration rate (SRR) was mathematically partitioned into its growth and maintenance components for leave f194^3^Wullschleger,SD^Norby,RJ^Gunderson,CA^1992^1^Growth and maintenance respiration in leaves of liriodendron- tulipiferly, but are, as yet, unpredictable.of winter grazing by reindeer on vegetation^15^40^^337-343^^2629^^^^^^^^^^^^^^^^^^^^^^^^^^3231s opposed to N. Sweden for V. Uliginosum. We also postulate that the differences in the spring and autumn cliamt i However, response to elevated CO2 vanes among species. Thus, shifts in composition within plant communities are also like mreased drought frequency may increase plant stress and thereby increase the frequency of insect outbreaks and disease. Pre kdictions of species responses are complicated by direct effects of increased CO2, such as increased water-use. efficiency. lrange. Insect pests and microbial pathogens should respond to climatic warming faster than long-lived trees. Predicted inc p rates much lower than Pleistocene observations. Thus migration response is likely to lag far behind rates of climatic cha nnge, potentially threatening narrowly distributed species whose predicted future ranges do not overlap with their current oy. A simulation model that predicts the migration response of trees through modem fragmented landscapes predicts migration ss northward range shifts in response to climate change vary from 100 km to over 500 km. Historical evidence of species ran qge movements following the Pleistocene indicate that tree species typically migrated at rates of 10 km to 40 km per centur re changes will be greater at high latitudes. Mid-continental regions will experience lower rainfall. Predictions of specie tbled atmospheric CO2 predict that mean temperatures will increase between 1.5 and 4.5-degrees-C globally; these temperatur uCO2 levels could double the pre-industrial level of 280 ppm by the year 2100, perphaps much earlier. Climate models of dou j193^1^Schwartz,MW^1992^1^Potential effects of global climate change on the biodiversity of plants^66^68^4^462-471^^^^^Aug^ vA^3230^Climatologists have observed a consistent increase in atmospheric CO2 over the past 30 years. It is predicted that -565^^^^^Junsrainfall conditions (Haglund  s4< (#-1981). Tillering or vegetaive reproduction y192^2^Ryle,GJA^Stanley,J^1992^1^Effect of elevated co2 on stomatal size and distribution in perennial ryegrass^52^69^6^563ses could be enormous.le displacement #F\  PC=^P#of C4 #d\  PCP# }ts were an increase in root length (110%) and root dry weight (143%). Root diameter, stele diameter, cortex width, root/sh {oot and root weight ratios all increased; root numbers did not increase. The long-term implications for belowground proces |ion demonstrate substantial effects on root system architecture, micromorphology and physiology. The most pronounced effec5^6^749-752^^^^^Aug^^^^^32281987^1^Small rodents with social and trophic interactions in a seasonally varying environment ~A^3227^Plant root response to atmospheric CO2 enrichment can be great. Results from this controlled environment investigat 191^4^Rogers,HH^Peterson,CM^McCrimmon,JN^Cure,JD^1992^1^Response of plant-roots to elevated atmospheric carbon-dioxide^9^1 O2 treatment was found to alleviate the afternoon depression in A observed in ambient CO2. A temperature optimum shift or/and a larger carbohydrate sink capacity through altered root/shoot ratio are proposed in explanation.g 20 cm in depth, ar tween temperature and light intensity, there was evidence that temperature rather than light determined M. Further, high C on average twice as large in high compared to ambient CO2. This response (called M = A in high CO2/A in ambient CO2) coul d not be explained by changes in canopy conductance for CO2 diffusion (GC). In spite of interaction and strong coupling be ver the entire range of temperature and light conditions (which were strongly coupled and increased simultaneously), A was the day, was examined in full-cover vegetative Lolium perenne canopies after 17 days of regrowth. The stands were grown at ambient (358 +/- 50-mu-mol mol-1) and increased (626 +/- 50-mu-mol mol- 1) CO2 concentration in sunlit growth chambers. O A^3225^The relative increase with elevated CO2 of canopy CO2 uptake rate (A), derived from continuous measurements during 190^3^Nijs,I^Impens,I^Vanhecke,P^1992^1^Diurnal changes in the response of canopy photosynthetic rate to elevated co2 in a coupled temperature-light environment^91^32^2^121-130^^^^^May^^^^^3226*2" without warmer and or wetter condding to a change in forest tree growth.,**2" ofecosystem microclimate, though the presence of spores, se nt species, which may be related to their developmental strategies, are largely ignored. Much experimental effort is neede d to parameterize all the physiological processes which are susceptible to change with an increase in atmospheric CO2, lea n leaf area development. The paper emphasizes large areas of ignorance: the reasons for the different responses of differe increase in root investment in elevated CO2 is related to a poor mineral status. The mineral content of trees grown in el evated CO2 is generally lowered compared to controls. No general rule has yet been found for the effect of increased CO2 o ts are still controversial. Biomass partitioning in elevated CO2 is clearly related to the mineral supply of the trees: An ncreased photosynthetic rate, as predicted by leaf models. In longer experiments this increase is reduced after a few week s or months by mechanisms that remain to be found. Elevated CO2 seems to decrease the dark respiration rate, but the resul mental approaches are described, as well as the principal results already obtained. Short-term experiments have shown an i A^3223^CO2 enrichment of the atmosphere is now well documented and its effect on the growth of world forests is being ques tioned by the scientific community. The direct effects of increased CO2 on tree species are reviewed: the different experi43^253^1121-1130^^^^^Aug^^^^^3224d some of the original species such as the moss, Chorisodontium.  atment.lringer,J R^Dawson,T E^1992^1^Water uptake by plants: perspectives from stable isotope composition^9^15^^1073-1082 189^2^Mousseau,M^Saugier,B^1992^1^The direct effect of increased co2 on gas-exchange and growth of forest tree species^78^ dry weight, which was greatest under the high water, ambient CO2 treatment. The shoot: root ratio did not change with tre cant effect on root dry weight in the 0-40 cm depth. In the 0-10 cm depth, doubled CO2 reduced dry weight and length of ro ots of plants grown under the high water level by 47 and 31 %, respectively. Warm-season, C4 grasses had the highest shoot re determined. Shoot growth also was measured to determine shoot: root ratios. The CO2 and water treatments had no signifi ). Sixteen cylindrical plastic chambers were placed on the prairie to maintain two levels of CO2 (ambient or twice ambient ). At the end of two seasons' exposure to the different treatments, dry weight and length of roots in the 0-40 cm depth we airie kept at a high water level (73 cm of water in a 200 cm soil profile) and a low water level (66 cm of water in 200 cm A^3221^The atmospheric concentration of carbon dioxide (CO2) is increasing and knowing how this will affect native vegetat ion is important. The objective of this study was to determine the effect of elevated CO2 on root growth in a tallgrass prer elevated carbon-dioxide^173^32^3^193-201^^^^^Jul^^^^^32221990). These disturbances may have cascading effects on nutrophic, as indicated by the changes in titratable acidity, delta-C-13 values and (CO2)-C-14 fixation. results from a Taraw 188^7^Mo,G^Nie,D^Kirkham,MB^He,H^Ballou,LK^Caldwell,FW^Kanemasu,ET^1992^1^Root and shoot weight in a tallgrass prairie und decreased. CO2 enrichment did not increase ion uptake or growth. The nutrition of plantlets in culture was mainly heterotr supplemented with sugar. Ammonium uptake was also affected by light. However, the rates of ammonium and nitrate uptake we re sluggish. The fresh weight of plantlets increased with the presence of sugar in the media but the relative growth rate itrate. Uptake of nitrate was relatively low and increased with increase in light intensity or when the culture medium wasuptake of dendrobium plantlets^174^67^5^601-611^^^^^Sep^^^^^3220 Holocene hydrologic change along boreal treeline reveale A^3219^The effects of light intensity, sugar and CO2 concentrations on nitrate and ammonium uptake, growth and photosynthe tic activity of dendrobium plantlets grown on agar medium were studied. There was a preferential uptake of ammonium over n 187^4^Lim,LY^Hew,YC^Wong,SC^Hew,CS^1992^1^Effects of light-intensity, sugar and co-2 concentrations on growth and mineral ons among components, and it emphasizes the urgent need for whole-system experimental approaches in global-change research.otope measurements^36^380^^515-517^^2677^^^^^^^^^^^^^^^^^^^^^^^^es by denuding the areas of vegetation and compacting s s study points at the inadequacy of scaling-up from physiological baselines to ecosystems without accounting for interacti h accumulation in the tops of canopies, increased fine-root production, and a doubling of CO2 evolution from the soil. Sti mulated rhizosphere activity was accompanied by increased loss of soil carbon and increased mineral nutrient leaching. Thi avior were detected between ambient and elevated CO2 treatments. Major responses under elevated CO2 included massive starc tropical plant communities treated with CO2-enriched atmospheres. Despite vigorous growth, no significant differences in stand biomass (of both the understory and overstory), leaf area index, nitrogen or water consumption, or leaf stomatal beh A^3217^Carbon, nutrient, and water balance as well as key plant and soil processes were simultaneously monitored for humid 186^2^Korner,C^Arnone,JA^1992^1^Responses to elevated carbon-dioxide in artificial tropical ecosystems^32^257^5077^1672-1675^^^^^18 Sep^^^^^3218^^^^^^^^^^^^^^^^^^^^^olonization of Antarctic habitats as has been reported for other polar regionts that changing CO2 environments may not improve the fitness of certain genotypes over others.tundra where vehicles remo ynthesize or activate the appropriate enzyme systems. Moreover, although plant genotype significantly affected plant growt h, reproduction, and chemistry, we never observed significant genotype-by-CO2 interactions for these factors, which sugges er for increased secondary metabolism; instead, hormonal and/or direct physical cues (such as light) may be essential to s similar, or lower, concentrations of carbon-based allelochemicals than plants grown in ambient (350-mu-L.L-1) CO2 conditio ns. We suggest that augmented substrate concentrations (i.e., excess carbohydrates) are a necessary but insufficient trigg onditions. However, in contrast to the C/N balance hypothesis, plants grown in elevated (700-mu-L.L-1) CO2 conditions had (2) quantified aucubin, catalpol, and verbascoside contents of replicate plants of six genotypes. Plants grown under low- nutrient conditions do have higher concentrations of carbon- based allelochemicals than plants grown under high-nutrient c ent CO2 and nutrient environments and then (1) measured the total allocation to shoots, roots, and reproductive parts and sed allelochemicals in plantago - a test of the carbon nutrient balance hypothesis^16^140^4^707-723^^^^^Oct^^^^^3216blish A^3215^In a test of the carbon/nutrient (C/N) balance hypothesis, we grew the perennial herb Plantago lanceolata in differGC4-4}{++}re incipient communities are established (Matthews and Whittaker 1987, Chapin et al. 1994, Smith 1994a). In ou 185^3^Fajer,ED^Bowers,MD^Bazzaz,FA^1992^1^The effect of nutrients and enriched co2 environments on production of carbon-ba al foliar concentrations currently used to define nutritional status and fertilizer management may need to be reassessed as the atmospheric CO2 concentration rises.4^^^^^^^^^^^^^^^^^^^^^^^^ site (Komarkova 1983, 1984), and the surrounding hab lower at elevated CO2 concentration partly because of the higher specific leaf weight. These results indicate that critic greater at high CO2 concentration at all fertilizer addition rates, but nitrogen uptake was either lower or unchanged at high CO2 concentration except at the highest nitrogen fertilizer rate. The shoot to root ratio was increased by CO2 enrich ment, primarily because the specific leaf weight was greater. The nitrogen and phosphorus concentration in the foliage was growth. At high CO2, growth reached a maximum at between 80 and 160 mg nitrogen kg-1 soil. Total uptake of phosphorus was wever, at 660-mu-mol CO2 mol-1, growth only began to plateau at a phosphorus addition rate of 920 mg kg-1 soil. At 340-mu- mol CO2 mol-1 and high phosphorus availability, increasing nitrogen from 40 to 160 mg kg-1 soil had little effect on plant owth was stimulated by addition of phosphorus up to 76 mg kg-1 soil. Further additions of phosphorus had little effect. Ho CO2 mol-1. The absolute response was largest when both nitrogen and phosphorus availability was high but the relative incr ease in dry weight was greatest at low phosphorus availability. At 340-mu-mol CO2 mol-1 and high nitrogen availability, gr ected by CO2 concentration. At 660-mu-mol CO2 mol-1, seedling dry weight was up to five times greater than at 340- mu-mol dlings at either 340 or 660-mu-mol CO2 mol-1 for 6 weeks. Graded increments of phosphorus and nitrogen fertilizers were ad ded to a soil deficient in these nutrients to establish if the growth response to increasing nutrient availability was aff A^3213^The response of Eucalyptus grandis seedlings to elevated atmospheric CO2 concentrations was examined by growing see 184^3^Conroy,JP^Milham,PJ^Barlow,EWR^1992^1^Effect of nitrogen and phosphorus availability on the growth- response of eucalyptus-grandis to high co2^9^15^7^843-847^^^^^Sep^^^^^3214etely attributable to warmer temperatures, because dilute solutsynthetic process as a result of acclimation to elevated CO2.tion of water may have been just as important as the warmer , experimental as well as simulatory evidence suggests that doubling CO2 concentration in the air may improve carbon assim ilation and compensate partially for the negative effects of water stress even if we assume a down-regulation of the photo refore, in productivity. On the other hand, the increase in air temperature may result in more respiratory losses. However own. Plant production is more closely related to the integral of photosynthesis over time and total foliage area than to t he instantaneous rates of the photosynthetic process. Water deficits result in a decrease in foliage area biomass and, the eds to be clearly identified. Similarly, the effects of extended exposure to elevated CO2 under arid conditions are not kn oinhibition, which might otherwise result in significant losses in plant production under stress conditions. In the longer term though, a negative acclimation of photosynthesis appears to occur in many species, an explanation for which still ne s to indicate that under conditions of high irradiance, plants growing at elevated CO2 may develop protection towards phot increase in CO2 in the atmosphere may diminish the importance of stomatal limitation for carbon assimilation, inhibit phot orespiration, stimulate carbon partitioning to soluble sugars and increase water-use efficiency. Some recent evidence seem are superimposed, a decline in photosynthetic capacity may be observed. In the short term, under drought conditions, the take under water deficit, the photosynthetic machinery being highly resistant to dehydration. However, when other stresses s now well established that in most species and under most circumstances stomata are the main limiting factor to carbon up er a high CO2 concentration in the atmosphere can compensate for the decrease in carbon gain in water-stressed plants. The processes which determine dry matter production and the ways they are affected by soil water deficits are discussed. It i its and high light stress are likely to occur in conjunction with elevated atmospheric CO2. This raises the question wheth183^2^Chaves,MM^Pereira,JS^1992^1^Water-stress, co2 and climate change^78^43^253^1131-1139^^^^^Aug^^^^^3212pen meadow in A^3211^Climatic change may bring about increased aridity to large areas of Europe. Higher temperatures, larger water deficactions between CO2 and O3 are discussed. wetter conditions which will be expressed by longer annual growth segments and vated CO2. Moreover, there were indications that cumulative changes in source:sink relations in O3-exposed plants may limi t plant response to CO2-enrichment to an even greater extent in the long-term. The future ecological significance of inter wgative correlation between chlorophyll level and growth was observed. The chlorophyllous cultures grew slowly in a medium mbient air.his for caribou trail ms and control recolonization and ecosystem recovery. To achieve our objective, we w least in part) the detrimental effects of phytotoxic concentrations of O3, whilst conversely, O3 reduced the impact of ele N, S, Mg and Ca. Interactions between the gases were complex, and often subtle. In general, elevated CO2 counteracted (at enhanced uptake of these nutrients from the growth medium. However, there was no affect of O3 on tissue concentrations of s of O3 injury, and effects on carbon assimilation were reflected in reduced growth, with shoot growth maintained at the e xpense of the root. In addition, O3 increased the P and K concentration in shoot and root (+hypocotyl) tissue, indicating atal closure, with the result that WUE(i) declined. All plants exposed to 'polluted' air developed typical visible symptom in elevated CO2, indicating that total uptake of these nutrients was not affected by CO2, and there was an increase in th e C:N ratio in root (+ hypocotyl) tissue. In contrast, O3 depressed A(sat), (almost-equal-to 26 %) and induced slight stom sted in leaf area expansion. Tissue concentrations of N, S, P, Mg and Ca were lower (particularly in the root + hypocotyl) oot growth or leaf area. Moreover, a decline in SLA and LAR in CO2-enriched plants suggested that less dry matter was inve arbon fixed in elevated CO2 stimulated growth of the root (+ hypocotyl) by 43 %, but there was no significant effect on sh composition were assessed at a final whole-plant harvest after 27 d. In 'non-polluted air' CO2 enrichment resulted in a p rogressive stimulation in A(sat), whilst there was a decline in g(s) which decreased E (i.e. improved WUE(i)). The extra cled CO2 was slightly more (36.9 mumol m-2 s-1) than that of plants grown with ambient CO2 (31.7 mumol m-2 s-1). This obser sults are consistent with previous findings, which showed that the photosynthetic rate of C4 plants on rangeland was not a ugmented when the CO2 concentration was increased. Under the low-water treatment, photosynthesis of plants grown with doub g chambers with the different CO2 and water treatments, but late in the season, differences occurred among chambers, possi bly because of the amount of tall grasses that shaded the radiometers. Under the high-water treatment, canopy photosynthes is of plants grown with doubled and ambient CO2 averaged 41.8 mumol m-2 s-1 and 44.5 mumol m-2 s-1, respectively. These re he chambered plots averaged 2.7-degrees-C warmer than outside. Early in the season, net radiation was usually similar amon ean concentrations varied from 710.8 to 720.1 cm3 CO2 m-3. For chambers with ambient CO2, the chamber-to-chamber variation  was minor, with mean values ranging from 350.8 to 356.0 cm3 CO2 m- 3. Daytime air temperatures at 100 cm aboveground in t 6 chambers on 49 sunny days during the season. The target value for high- CO2 chambers was 720 cm3 CO2 m-3; the measured m ilty clay loam) was kept at a high water (field capacity) or a low water level (no water added). Carbon dioxide concentrat ion, air temperature, net radiation, canopy photosynthetic rate, and canopy evapotranspiration rate were measured in the 1 d on the prairie to maintain two levels of CO2 (ambient and twice ambient) over a full growing season in 1990. The soil (s  of prairie (rangeland) plants growing under natural field conditions. The dominant plants were warm-season grasses with t he C4 type of photosynthesis. Sixteen closed-top, cylindrical, plastic chambers (1.5 m in diameter; 1.8 m tall) were place agricultural plants. The objective of this study was to determine the effect of elevated CO2 on canopy photosynthetic rate doubled carbon-dioxide in closed-top chambers^107^61^3-4^205-217^^^^^Oct^^^^^3189rctic soils^137^11^^163-172^^2826^^^^^^ A^3188^It is important to know how the increasing atmospheric concentration of carbon dioxide (CO2) will affect growth of 169^5^Nie,D^He,H^Mo,G^Kirkham,MB^Kanemasu,ET^1992^1^Canopy photosynthesis and evapotranspiration of rangeland plants under , E. vaginatum may shift from being a nutrient-limited to a carbon-limited system and, consequently, increased season length and elevated CO2 concentrations may play an important role in controlling E. vaginatum productivity.<5.JjD΁|wY apidly because the plant becomes limited by carbon uptake. Thus, if nitrogen availabilities more than double in the future aginatum to climate change is linearly (and almost exclusively) dependent on our ability to predict the effects of climate  change on nitrogen cycling. At nitrogen availabilities > 2 x current availabilities, the relationship flattens out very r nitrogen availabilities. Therefore, at low- to-moderate increases in nitrogen availability, the predicted response of E. v  in nitrogen alone. In essence, the model predicts that climate change will have substantial effects on E. vaginatum only indirectly through changes in nitrogen availability. Simulated peak biomass responds linearly up to a doubling of current nt changes in climate and nitrogen availability, the model predicts a slight decline in peak biomass compared to increases importance in productivity. The model predicts that a simultaneous increase in the direct effects of temperature, season l ength, and CO2, with no change in nitrogen availability, will result in a slight decrease in peak biomass. A simulated lon g-term doubling of nitrogen availability results in an almost-equal-to 70% increase in peak biomass, whereas with concurre 680 muL/L). Similarly, a wide range of nitrogen availabilities (from 9 to 18 g.m 2.vr-1) was also examined because of its "n E. vaginatum photosynthesis. The effect of a 50-yr period of climate change on peak biomass (overwintering biomass plus #seasonal production) in E. vaginatum was explored. We use climate change here to refer to linear increases over a 50-yr pe riod in temperature (from 8-degrees to 13-degrees-C), season length (from 100 to 120 d), and atmospheric CO2 (from 340 to ! on the growth responses of E. vaginatum to temperature and shading, and (2) the effects of elevated CO2 and temperature o &imate change. Our simulation model utilizes a mechanistic framework and includes the effects of light, temperature, season ' length, nitrogen availability, and CO2 concentration on E. vaginatum growth dynamics. The model was parameterized based o $n a series of published studies of the growth responses of E. vaginatum to nutrients and validated using (1) field studies %d physiology, we chose this species as a test case to model the potential long-term response of arctic plants to global cl *A^3186^It appears that polar regions of the Ear-th will bear the brunt of global temperature increases. Because of the eco (logical importance of the sedge Eriophorum vaginatum in the arctic and the large amount ot data available on its growth an3-340^^^^^Nov^^^^^3187JZJRBZJZJZJZJRJZJZJZJZJZJZJZJRJB9nductance to elevated carbon-dioxide in field-grown cotton^183^11^2-3^227-231^nnial plants from low and high altitudes in +168^2^Leadley,PW^Reynolds,JF^1992^1^Long-term response of an arctic sedge to climate change - a simulation study^56^2^4^32 ,167^6^Hileman,DR^Bhattacharya,NC^Ghosh,PP^Biswas,PK^Lewin,KF^Hendrey,GR^1992^1^Responses of photosynthesis and stomatal cohe field and provide evidence for a new mechanism by which elevated atmospheric CO2 could influence seasonal carbon gain.166^1^Hendrey,GR^1992^1^Global greenhouse studies - need for a new approach to ecosystem manipulation^183^11^2-3^61-74^Y> /C(i) above 400 mubar on day 68. These results indicate the potential for direct CO2 fertilization of P. grandidentata in t 3eight, suggesting a delay in senescence with long-term exposure to high CO2. High CO2 grown plants also maintained photosy 1nthetic sensitivity to increasing C(i) throughout the exposure period, while ambient CO2 grown plants were insensitive to 2. In contrast, plants grown at elevated CO2 showed no late- season decline in photosynthetic capacity or changes in leaf w 6similation rates. Specific leaf nitrogen (mg N . (cm2 leaf area)-1) did not change during this period, although leaf carbo 4n content and leaf weight (mg . cm-2) both increased. In ambient grown plants stomatal conductance also declined at day 68 5slope of the net CO2 assimilation versus intercellular CO2 Partial pressure relationship and to decreased CO2 saturated as 92. In ambient grown plants, light saturated assimilation rates increased from day 28 to day 45 and then declined at day 68 7 (15 September). This late-season decline, typical of senescing Populus leaves, was due both to a decrease in the initial 8nts. Photosynthetic light and CO2 response characteristics were measured 28, 45, and 68 days after exposure to elevated CO A^3182^Rising atmospheric carbon dioxide concentrations may have important consequences for forest ecosystems. We studied ?165^2^Curtis,PS^Teeri,JA^1992^1^Seasonal responses of leaf gas-exchange to elevated carbon- dioxide in populus-grandidenta Centration Of CO2. These patterns do not support either the feedback-inhibition or the nutrient-stress hypothesis of photosynthetic adjustment to elevated concentrations of CO2.lication^^^^^^^^^^^^^^^^^^^^^^^^^^Merritt,J F\:V5[F22/!ED>I_#-2RFH Bation, with net rates of CO2 exchange the next day equal to those of leaves of plants grown from seed at the elevated conc Fes-C, was not greater at a photon flux density of 1.0 than at 0.5 mmol M- 2 s-1 and was not greater with limiting nutrient Ds. Furthermore, in soybean, negative photosynthetic adjustment could be induced by a single night at elevated CO2 concentr Eer all treatments. Negative photosynthetic adjustment to elevated CO2 concentration was not greater at 20 than at 25-degre Ire then measured at both 350 and 700 mul l-1 CO2. Plants grown at the elevated CO2 concentration had net rates of leaf CO2 G exchange which were reduced by 33% in sugar beet and 23% in soybean when measured at 350 mul l-1 CO2 and when averaged ov H or the sixth leaf of sugar beet had finished expanding. Net rates Of CO2 exchange of the most recently expanded leaves we Lar beet (Beta vulgaris L. cv. Mono Hye-4) were grown from seed at 350 and 700 mul l-1 CO2, at 20 and 25-degrees-C, at a ph Joton flux density of 0.5 and 1.0 mmol m-2 s-1 and with three nutrient regimes until the third trifoliolate leaf of soybean Kcentration is due to (1) feedback inhibition or (2) nutrient stress. Soybean [Glycine max (L.) Merr. cv. Williams] and sug OA^3180^The short-term stimulation of the net rate of carbon dioxide exchange of leaves by elevated concentrations of CO2 u Psually observed in C3 plants sometimes does not persist. Experiments were conducted to test whether the patterns of respon Mse to the environment during growth were consistent with the hypotheses that photosynthetic adjustment to elevated CO2 conn of carbon-dioxide^37^86^1^173-179^^^^^Sep^^^^^3181TYA8QHW2AQC: MH<3B&6E)I+LRSE[Q]?8B;0V(9UJ6JT)RV6VP(4`2;*CQQS%,9;EW,4and other trace gases^183^11^2-3^85-119^ponses of the Norwegian alpine {iBetula nana} community to nitrogen fertilization Q164^1^Bunce,JA^1992^1^Light, temperature and nutrients as factors in photosynthetic adjustment to an elevated concentratio c C-14 in SDP, GMP, and malate, but decrease of it in sucrose, alanine, glycine, and serine. Very perceptible effects of inv Ved temperature increased accumulation of the label in PGA, sucrose, and malate, but lowered it in GMP, alanine, glycine, ax Tnd serine. Growing plants at enhanced CO2 concentration led to acceleration of photosynthesis and increase of the share of Uperature increase by itself and in any combination with other factors at the upper level suppressed photosynthesis. Elevat Yynthesis and stimulated incorporation of C-14 into phosphoglyceric acid (PGA), sugar diphosphate (SDP), fructose monophosp Whate (FMP), and malate, but suppressed incorporation of C-14 into sucrose, glucose monophosphate (GMP), and glycerate. Tem Xon metabolism in the cotton (Gossypium hirsutum L.) leaf Increase of light intensity during cultivation accelerated photos \A^3177^We used the method of mathematical experiment planning (a 2(3) scheme) to study the influence of environmental fact Zors separately or in combination on the photosynthetic rate and distribution of C-14 among products of photosynthetic carbhotosynthetic metabolism of carbon in cotton leaves^168^39^2^140-144^^^^^Mar-Apr^^^^^3178H])OB*'$D&_;MLW7]- M?1-R[XEX#O/phenomenon.I^1997^1^Growth, herbivory and disease in relation to gender in {iSalix viminalis} L^2^111^^61-68^^2874^^^^^^^ ]162^5^Abdullaev,AA^Dzhumaev,BB^Abdurakhmanova,ZN^Kaler,VL^Magmedov,IM^1992^1^Integral effect of environmental-factors on p ^ respiration are affected by CO2 enrichment and as such should provide useful information for the future modeling of this b bvely. The maintenance coefficient was similarly reduced from a control rate of 114 mg CO2.g-1 d-1 to below 65 mg CO2.g-1.dd `-1 for leaves exposed to CO2 enrichment. Our results quantitatively describe the magnitude by which growth and maintenance_ d1^4^Curtis,PS^Balduman,LM^Drake,BG^Whigham,DF^1990^1^Elevated atmospheric CO2 effects on belowground processes in C3 and Ca4 estuarine marsh communities^11^71^5^2001-2006^^^^^Octctngton, DC USA^257-288^^^^^^^^^^^^^^^^^^^^^^^^^^H@T@\gs that had been planted directly into the ground within open-top chambers and exposed to ambient, ambient + 150 muL.L-1, X gnnials. It has vet to be determined, however, whether these reductions reflect changes in maintenance respiration alone orZ e whether CO2 might affect growth respiration as well. This possibility was examined in white oak (Quercus alba L.) seedlinV pauciflora. Growth indices for E. camaldulensis and E. cypellocarpa species, and especially E. camaldulensis, generally eR jvated CO2 in all species on either N treatment. Moreover, high N increased NAR under either CO2 treatment in all species. hThere was a positive N X CO2 interaction on NAR in E. camaldulensis and E. cypellocarpa, but not in E. pulverulenta and E.Q lreased in E. camaldulensis and E. cypellocarpa, but decreased in E. pulverulenta and E. pauciflora. Whole plant NUE showedM i no consistent response to elevated CO2 when plants were supplied high N. Net assimilation rate (NAR) was increased by eleO nlar order. A distinction can be made between N and CO2 effects on growth processes as follows. When trees were grown on loJ kw N, elevated CO2 increased nitrogen-use efficiency (NUE) at both leaf and whole plant levels. On high N, leaf NUE was incG p species throughout the study period. In E. camaldulensis and E. cypellocarpa, plant mass was doubled by high N at 33 Pa CE qO2, compared with a three to four- fold increase at 66 Pa to reach 34 g by final harvest. In E. pulverulenta and E. paucifF mlora, slower growth resulted in about 50% less mass at a given age, but relative increases due to CO2 and N were of a simi1 s (33 Pa) and CO2-enriched (66 Pa) greenhouses. Analysis of growth response to treatments (2 X 2 factorial) was based on de, tstructive harvest of plants sampled on four occasions over 84 days for E. camaldulensis and E. cypellocarpa, and 100 days . ofor E. pulverulenta and E. pauciflora. A positive CO2 X N interaction on plant dry mass and leaf area was expressed in all) vast, E. pauciflora and E. pulverulenta become smaller trees, and show a more limited distribution. Seedlings were establis+ rhed in pots (5 L) of a loamy soil and supplied with nutrient solution containing either 1.2 or 6.0 mM NO3- in both ambient' uellocarpa were taken as examples of fast-growing species with a wide distribution, that develop into large trees. By contr$40^4-5^457-472^^^^^^^^^^3174B^Boer,G J^Cubasch,U^Meleshko,V P^1992^3^Climate modelling, climate prediction and model vali zA^3173^Four eucalypt species were selected to represent two ecologically disparate groups which would be expected to contrT wast in seedling vigour and in the nature of growth responses to CO2 X nitrogen supply. Eucalyptus camaldulensis and E. cypPely related birch species differ in their habitat preferences and successional status.s.nstitute, Inc.^Cary, NJ^^N^846^^ x160^3^Wong,SC^Kriedemann,PE^Farquhar,GD^1992^1^CO2 X nitrogen interaction on seedling growth of 4 species of eucalypt^182^ {in comparison to unrelated species of the same ecosystem that had been studied by others, despite the fact that these clos cies. (iv) The presence and identity of a neighbor did not influence the magnitude or pattern of response to CO2 in birche }s of a given community. Our results suggest that congeneric species might be more similar in their response to global CO2  ~ation, shoot architecture, and leaf nitrogen content were affected differently by CO2 concentrations for the different spe . The most shade-intolerant, fast-growing species (grey birch; Betula populifolia Marsh.) took greater advantage of the elM evated CO2 resource than the more shade-tolerant, later successional species (e.g., yellow birch). (iii) Patterns of allocO pecies were significantly stimulated by enriched CO2 Conditions, but the magnitude of response was different among species: es. We found the following: (i) yellow birch (Betula alleghaniensis Britton) was the only species whose survival differed < among CO2 treatments. Survival was slightly increased by elevated CO2. (ii) All growth parameters considered in all four s. 159^2^Rochefort,L^Bazzaz,FA^1992^1^Growth-response to elevated CO2 in seedlings of 4 cooccurring birch species^155^22^11^1/583-1587^^^^^Nov^^^^^3172^^-0SR5IEF'(H2V$%"D=@B%O9-A"O*.:V)MC M0?(8QC&'8>O!I.08<2EU>13@2A"V5&*%*2A)(=2E1;)4(Q2E8<(KDSYC# environmental variables.DK9`.(N/^(KJ]DX;7533WO=2-89)XU#3&^. MG8!&QX>H,/>>;0G44T8O.@]TH_FFQV>QL"E04`1^32+(%0(46`-)<>)+< 297^3^Dufrene,E^Pontailler,JY^Saugier,B^1993^1^A branch bag technique for simultaneous co2 enrichment and assimilation measurements on beech (fagus-sylvatica L)^9^16^9^1131-1138^^^^^Dec^^^^^3429@_,PQY`KAU, M*P:5P'#F\-E""$CRKLVTJ-FTDFVVT"X"D5J A^3428^A cheap CO2 enrichment system was designed to perform continuous gas exchange measurements of branches of mature Eu ropean beech trees (Fagus sylvatica L.). Branches were grown at ambient (350 cm(3) m(-3)) and elevated CO2 (700 cm(3) m(-3 )) during the whole 1992 leafy period. Leaks resulting from airtightness defaults in the system appeared to be low enough  to measure accurately net CO2 assimilation and transpiration rates during the day. However, the CO2 exchange rates during  the night (respiration) were too low to allow accurate measurements. Elevated CO2 had a great effect on the net assimilati on rate of branches via its influence on both the C-3 photosynthetic pathway and the shade-tolerance of beech frees (85% iq ncrease). The A/C-a curves showed no acclimation effect to high CO2, both control and enriched branches increasing their nm et assimilation in the same way. The decrease of net assimilation rates in mature leaves was similar for both control and c enriched branches. The pattern of daily transpiration rates remained the same for both control and enriched branches, henc^e we can assume that there was no visible CO2 effect on stomata.\8N M";JUEIN%KEB@K^[JO-'15$)?L-;3M=LJ6PEP!`<@W(&0Q'EOBJI` 298^3^Eamus,D^Berryman,CA^Duff,GA^1993^1^Assimilation, stomatal conductance, specific leaf-area and chlorophyll responses Uto elevated co2 of maranthes corymbosa, a tropical monsoon rain-forest species^92^20^6^741-755^^^^^^^^^^3431/'_"-?Q1Q`Z_<P A^3430^Seeds of Maranthes corymbosa Blume, a monsoon rain forest species of northern Australia, were sown under ambient orE elevated CO2 concentrations in tropical Australia. Seedlings were grown under conditions of photon flux density, temperat= ure and atmospheric vapour pressure deficit which followed ambient variations as closely as possible. Specific leaf area, 8 chlorophyll, stomatal density, stomatal conductance and assimilation responses to photon flux density were measured after 5 30 weeks growth. Gas exchange characteristics were divided into morning and afternoon data sets and analysed separately. S+ tomatal density decreased and leaf area:dry weight ratio decreased in response to elevated CO2. In contrast there was no e) ffect of elevated CO2 upon chlorophyll (total or ratio of a:b). Apparent quantum yield and rates of light saturated assimi! lation (A(max)) increased in response to elevated CO2. There was a significant decline in apparent quantum yield for both  treatments between morning and afternoon. Stomatal conductance (g(s)) declined in response to elevated CO2. There was no s ignificant difference in g(s) between morning and afternoon for ambient grown trees, but g(s) declined significantly betwe en morning and afternoon for elevated CO2 grown trees. Instantaneous transpiration efficiency (ITE) was higher for elevate d CO2 grown trees compared with control trees. There was a significant increase in ITE between morning and afternoon data  for ambient grown trees; in contrast a significant decline in ITE was observed for elevated CO2 grown trees between mornin g anf afternoon data sets. The slope of the regression between assimilation rate and stomatal conductance increased for pl ants grown under elevated CO2. These data are discussed and compared with the responses of plants adapting to different photon flux densities.YC7FMYB<6\QXK9V MA^" A^3432^Open-Top Chambers (OTCs) are commonly used to evaluate the effect of CO2, O3, and other trace gases on vegetation.  A study was conducted to develop and test a new technique for measuring forced air flow and net CO2 flux from OTCs. Experi ments were performed with a 4.5-m diam. OTC that had a sealed floor and a specialized air delivery system. Air flow throug h the chamber was computed with the Bernoulli equation using measurements of the pressure differential between the air del ivery ducts and the chamber interior. An independent measurement of air flow was made simultaneously to calibrate and veri fy the accuracy of the Bernoulli relationship. The CO2 flux density was calculated as the product of chamber air flow and  the difference in CO2 concentration between the air entering and exhausting from the OTC (C(in) - C(out)). Accuracy of the system was evaluated by releasing CO2 within the OTC at known rates to emulate respiration from the field surface. Data w ere collected with OTCs at ambient and elevated CO2 (almost-equal-to 700 mumol mol-1). Results showed that the Bernoulli e quation, with a flow coefficient of 0.7, accurately measured air flow in the OTC to within +/- 5% regardless of flow rate  and air duct geometry. Experiments in ambient OTCs showed that CO2 flux density (mumol m-2 s-1), computed from 2-min avera ges of air flow and C(in) - C(out), was typically within +/- 10% of actual flux, provided that the exit air velocity at th e top of the OTC was greater than 0.6 m s-1. Obtaining the same level of accuracy in CO2- enriched OTCs, however, required a critical exit velocity near 1.2 m s-1 to minimize the incursion of ambient air and prevent contamination of the exit ga s sample. When flux data were integrated over time to estimate daily CO2 flux (mumol m-2 d- 1), actual and measured values agreed to within +/- 2% for both ambient and CO2-enriched chambers, suggesting that accurate measurements of daily net C exchange are possible with this technique.(#S$#=`I0JT""BM"1`V4#Y M?<0\/<#_`"FAS09Q1;(^7M]X)KN7O.OE_4015,USKXKY-1&DAC'V99 300^3^Masle,J^Hudson,GS^Badger,MR^1993^1^Effects of ambient co2 concentration on growth and nitrogen use in tobacco (nicot iana-tabacum) plants transformed with an antisense gene to the small-subunit of ribulose-1,5- bisphosphate carboxylase oxygenase^8^103^4^1075-1088^^^^^Dec^^^^^3435'@^+C#A+M&7*2EF9S M`X!K[31B@>:RG>9JB6GF#1)+4@.#VD@D/R;/7&&HE)1O$UO9)M+T"A*8%LH/ A^3434^Growth of the R1 progeny of a tobacco plant (Nicotiana tabacum) transformed with an antisense gene to the small sub| unit of ribulose-1,5-carboxylase/oxygenase (Rubisco) was analyzed under 330 and 930 mubar of CO2, at an irradiance of 1000y mumol quanta m-2 s-1. Rubisco activity was reduced to 30 to 50% and 13 to 18% of that in the wild type when one and two cs opies of the antisense gene, respectively, were present in the genome, whereas null plants and wild-type plants had similao r phenotypes. At 330 mubar of CO2 all antisense plants were smaller than the wild type. There was no indication that Rubisa co is present in excess in the wild type with respect to growth under high light. Raising ambient CO2 pressure to 930 muba] r caused plants with one copy of the DNA transferred from plasmid to plant genome to achieve the same size as the wild typT e at 330 mubar, but plants with two copies remained smaller. Differences in final size were due mostly to early differenceP s in relative rate of leaf area expansion (m2 m-2 d-1) or of biomass accumulation (g g-1 d-1): within less than 2 weeks afL ter germination relative growth rates reached a steady-state value similar for all plants. Plants with greater carboxylati? on rates were characterized by a higher ratio of leaf carbon to leaf area, and at later stages, they were characterized al; so by a relatively greater allocation of structural and nonstructural carbon to roots versus leaves. However, these change+ s per se did not appear to be causing the long-term insensitivity of relative growth rates to variations in carboxylation - rate. Nor was this insensitivity due to feedback inhibition of photosynthesis in leaves grown at high partial pressure of  CO2 in the air (p(a)) or with high Rubisco activity, even when the amount of starch approached 40% of leaf dry weight. We  propose that other intrinsic rate-limiting processes that are independent of carbohydrate supply were involved. Under plen tiful nitrogen supply, reduction in the amount of nitrogen invested in Rubisco was more than compensated for by an increas e in leaf nitrate. Nitrogen content of organic matter, excluding Rubisco, was unaffected by the antisense gene. In contras t, it was systematically lower at elevated p(a) than at normal p(a). Combined with the positive effects of p(a) on growth, this resulted in the single-dose antisense plants growing as fast at 930 mubar of CO2 as the wild-type plants at 330 mubar of CO2 but at a lower organic nitrogen cost.ƥ 301^5^Owensby,CE^Coyne,PI^Ham,JM^Auen,LM^Knapp,AK^1993^1^Biomass production in a tallgrass prairie ecosystem exposed to ambient and elevated co2^56^3^4^644-653^^^^^Nov^^^^^3437s A^3436^Responses to elevated CO2 have not been measured for natural grassland ecosystems. Global carbon budgets will likel} y be affected by changes in biomass production and allocation in the major terrestrial ecosystems. Whether ecosystems sequz ester or release excess carbon to the atmosphere will partly determine the extent and rate that atmospheric CO2 concentratj ion rises. Elevated CO2 also may change plant community species composition and water status. We determined above- and bell owground biomass production, plant community species composition, and measured and modeled water status of a tallgrass prae irie ecosystem in Kansas exposed to ambient and twice-ambient CO2 concentrations in open-top chambers during the entire grb owing season from 1989 through 1991. Dominant species were Andropogon gerardii, A. scoparius, and Sorghastrum nutans (C-4 X metabolism) and Poa pratensis (C-3). Aboveground biomass and leaf area were estimated by periodic sampling throughout the T growing season in 1989 and 1990. In 1991, peak biomass and leaf area were estimated by an early August harvest. Relative rV oot production among treatments was estimated using root ingrowth bags which remained in place throughout the growing seas on. Latent heat flux was simulated with and without water stress. Botanical composition was estimated annually. Compared t o ambient CO2 levels, elevated CO2 increased production of C-4 grass species, but not of C-3 grass species. Species compos ition of C-4 grasses did not change, but Poa pratensis (C-3) declined, and C-3 forbs increased in the stand with elevated  CO2 compared to ambient. Open-top chambers appeared to reduce latent heat flux and increase water-use efficiency similar t o the elevated CO2 treatment when water stress was not severe, but under severe water stress, the chamber effect on water- use efficiency was limited. In natural ecosystems with periodic moisture stress, increased water-use efficiency under elevated CO2 apparently would have a greater impact on productivity irrespective of photosynthetic pathway. 302^3^Pettersson,R^McDonald,AJS^Stadenberg,I^1993^1^Response of small birch plants (betula-pendula roth) to elevated co2 and nitrogen supply^9^16^9^1115-1121^^^^^Dec^^^^^3439 A^3438^Small birch plants were grown for up to 80 d in a climate chamber at varied relative addition rates of nitrogen in  culture solution, and at ambient (350 mu mol mol(-1)) or elevated (700 mu mol mol(-1)) concentrations of CO2. The relative addition rate of nitrogen controlled relative growth rate accurately and independently of CO2 concentration at sub- optim um levels. During free access to nutrients, relative growth rate was higher at elevated CO2. Higher values of relative gro wth rate and net assimilation rate were associated with higher values of plant N-concentration. At all N-supply rates, elevated CO2 resulted in higher values of net assimilation rate, whereas leaf weight ratio was independent of CO2. Specific l  A^3072^Two-year-old chestnut trees were grown for two yr under ambient (350 ppm) and enriched (700 ppm) CO2 concentrations  , in two naturally lit growth chambers. The doubling of CO2 resulted in a dilution of the nitrogen concentration in the le  af litter, with C:N ratios of 40 and 75 for the ambient and enriched CO2 concentrations, respectively. The litter was ster + ilized and inoculated with microflora and animal groups of increasing complexity (microflora + Protozoa; + nematodes; + Co , llembola; + Isopoda) and incubated over 24 wk. Every two wk, the CO2 release was measured and the litter was leached with 9 demineralized H2O. The following analyses were performed on the leachates: pH, total nitrogen, dissolved and particulate c ; arbon, inorganic nitrogen (NH4+ and NO3-), phosphate, and biological counts (Protozoa, nematodes and Rotifera). The initia A l decomposition stages (the first 12 wk) were dominated by the litter quality factor: CO2 release and nitrogen losses in l C eachates were higher and carbon losses lower in water leaching from the litter with low C:N ratio. Towards the late stages N , when carbon mineralization decreased in the control litter, the animal effect emerged in litter with a high C:N ratio. T P wo groups appeared: (1) In the microflora + Protozoa units, carbon mineralization was reduced by 60% compared with the con ` trol litter. (2) In the diversified food web combinations, it became progressively higher with increasing complexity of th b e animal community and was enhanced by 30% compared with the control litter. This unexpected fundamental difference was ex l plained by a change in the composition and activity of the microflora. Litter bleaching, respiration, C and N leaching and m  acidification rose with increasing animal complexity of the systems. Biological and chemical reasons explaining the invas y ion by white-rot fungi and its activity only in the material with a high C:N ratio are discussed. During the 24 wk. nitrog {en and phosphorus mineralization was very low, indicating a high incorporation of the nutrient in the soil biomass.n mine 109^2^Eamus,D^Murray,M^1991^1^Photosynthetic and stomatal conductance responses of norway spruce and beech to ozone, acid mist and frost - a conceptual-model^35^72^1^23-44^^^^^^^^^^3075s enhanced by 30% compared with the control litter. This A^3074^Two-year-old beech and Norway spruce seedlings were exposed to a combination of ozone and acid mist treatments in o pen-top chambers in Scotland during the months of July through to September 1988. Replicate pairs of chambers received cha rcoal- filtered air (control), ozone-enriched air (140 nl ozone litre- 1) or 140 nl ozone litre-1 plus a synthetic acid mi st (pH 2.5) composed of ammonium nitrate and sulphuric acid. Field measurements of assimilation and stomatal conductance w ere made during August. In addition, measurements of assimilation and conductance were made during September in the labora tory. Light response curves of assimilation and conductance were determined using a GENSTAT non-rectangular hyperbolic mod el. During February 1988/9 the Norway spruce were subject to a four day warming period at 12-degrees-C and the light respo nse of assimilation determined. The same plants were then subject to a 3-h night-time frost of -10-degrees-C. The followin g day the time-course of the recovery of assimilation was determined. It was found that ozone fumigation did not influence  the light response of assimilation of beech trees in the field, although stomatal conductance was reduced in the ozone-fu migated trees. The rate of light-saturated assimilation of Norway spruce was increased by ozone fumigation when measured i n the field. Measurements of assimilation of Norway spruce made during the winter showed that prior to rewarming there was ! no difference in the rate of light-saturated assimilation for control and ozone-fumigated trees. However, the ozone plus "acid mist- treated trees exhibited a significantly higher rate. The 4-day period of warming to 12-degrees-C increased the #rate of light-saturated assimilation in all treatments but only the ozone plus acid mist-treated trees showed a significan $t increase. Following a 3-h frost to -10-degrees-C the control trees exhibited a reduction in the rate of light-saturated %assimilation (A(max)) to 80% of the pre-frost value. In comparison, following the frost, the ozone-fumigated trees showed &an A(max) of 74% of the pre-frost value. The ozone plus acid mist-treated trees showed an A(max) of 64% of the pre- frost 'trees. The time taken for A(max) to attain 50% of the pre-frost value increased from 30 min (control) to 85 min for ozone- (fumigated trees to 190 min (ozone plus acid mist). These results are discussed in relation to the impact of mild, short- t )erm frosts, which are known to occur with greater frequency than extreme, more catastrophic frost events. A simple concept *ual framework is proposed to explain the variable results obtained in the literature with respect to the impact of ozone upon tree physiology.g signal at g = 2.0007 is attributed to a rapidly tumbling CO2- radical. An axial CO2- radical is s 8110^4^Hunt,R^Hand,DW^Hannah,MA^Neal,AM^1991^1^Response to CO2 enrichment in 27 herbaceous species^43^5^3^410-421^^^^^^^^^^ -A^3076^CO2-enrichment experiments were performed on 25 British native species of widely differing ecology. Two crops, one  .C3 (sunflower) and one C4 (maize), were also included. The background regime involved full-light, glasshouse conditions, n| /on-limiting supplies of water and mineral nutrients and a daytime mean temperature of 18-degrees-C. Four CO2 treatments wex 0re maintained at nominal concentrations of 350, 500, 650 or 800 v.p.m. over a 56-day period. Hyperbolic functions were fitk 1ted to yield vs CO2 concentration. The functions were then used to generate predictions of Q540/350 (the quotient of preseh 2nt yield under the CO2 regime predicted for the year 2050) and Q700/350 (the quotient of present yield predicted for a douT 3bling of ambient CO2 concentration). Values of Q540/350 for whole-plant dry weight ranged from below 1.01 to 1.49, the uppV 4er values being at least similar in magnitude to those already observed in C3 crops. The mean value of whole-plant Q700/35O 50 for 11 species of near-competitive strategy was 1.43. Four species of stress-tolerant or ruderal strategy had a mean Q70P 60/350 of only 1.05. High CO2 responsiveness was common only within the competitive strategy and its close relations. The fG 7itted Q540/350 for species of the pure strategy was 1.38. In the centre of the strategic range the fitted value was 1.12, Cand at the far extreme, the value for species of ruderal or stress-tolerant strategy was only 1.03.f beech trees in the f=3077ugh stomatal conductance was reduced in the ozone-fumigated trees. The rate of light-saturated assimilation of Norway: :111^2^Idso,SB^Kimball,BA^1991^1^Effects of 2 and a half years of atmospheric CO2 enrichment on the root density distributi%on of 3-year-old sour orange trees^107^55^3-4^345-349^^^^^Jun^^^^^3079of light-saturated assimilation for control and oz! sly supplied with a CO2 enriched atmosphere consisting of an extra 300 cm3 CO2 m-3 of air. Extensive soil coring of the tr ?ees' root zones conducted in July 1990 indicated that two and a half years of growth under these conditions produced a fin @e root biomass enhancement of 175% in the CO2 enriched trees. This growth enhancement is of the same order of magnitude asE our previously reported results for net photosynthesis and trunk and branch volumes for these trees. min (control) to 85? B112^4^Laforge,F^Lussier,C^Desjardins,Y^Gosselin,A^1991^1^Effect of light-intensity and CO2 enrichment during invitro rooti' Mng on subsequent growth of plantlets of strawberry, raspberry and asparagus in acclimatization^165^47^3-4^259-269^^^^^Jul^$ DA^3080^Growth of plantlets of asparagus (Asparagus officinalis L.), raspberry (Rubus idaeus L.) and strawberry (Fragaria X E ananassa Duch.), treated during the in vitro rooting stage under three photosynthetic photon flux densities (PPFD) (80, 1 F25 and 250- mu-mol s-1 m-2) (17.5, 26.9 and 53.8 W m-2 (PAR), respectively) and three CO2 enrichment levels (CDE) (330, 16 G50 and 3000-mu- mol mol-1), was monitored during the acclimatization stage. For the three species, generic differences wer He observed in the plant response to treatments. A significant residual growth enhancement was caused by CDE. High PPFD in Z Ivitro increased the dry weight of strawberry and fresh weight of asparagus in acclimatization. Raspberry leaf dry weight wU Jas increased by 262% in acclimatization after in vitro treatment with high CDE. This enhanced the performance of micropropA Kagated plantlets in acclimatization and reduced by 2 weeks the acclimatization period with raspberry. Our results suggest B Lthat in vitro leaves may be a source of nutritional reserves for leaves initiated ex vitro, but do not exclude a morphogen2etic effect of CO2 during the in vitro rooting stage.weights were compared, and seeds were counted, weighed, and germinat.^^^^3081ability. Plants grown in enriched CO2 environments had significantly greater shoot weights, leaf areas, and root  O113^5^Novero,R^Smith,DH^Moore,FD^Shanahan,JF^Dandria,R^1991^1^Field-grown tomato response to carbonated water application^ 48^83^5^911-916^^^^^Sep-Oct^^^^^3083 biomass allocation patterns further illustrated differences in plant responses to en QA^3082^Direct release of CO2 gas to achieve a cost-effective method of atmospheric CO2 enrichment has not been proven feas Rible under field conditions. We hypothesized that greater efficiency of application would occur by applying CO2 via carbon Sated water and that application would also result in beneficial modifications of the soil environment. Our objectives wereK T to evaluate crop, soil, and atmospheric CO2 responses to application of carbonated water under pressure through a drip irC Urigation system. Studies were conducted under mulched and unmulched conditions in 1988 using tomato (Lycopersicon esculent Vum Mill.). In 1989, carbonated water was applied at approximately 2-, 4-, and 6-d intervals to determine the effect of irr9 Wigation frequency. In 1988, a positive yield response of 9% was obtained in the presence of mulch. No response was observe Xd in open beds. Fruit yields were increased at all three irrigation frequencies in 1989, with increases in fresh-market an Yd total fruit yields averaging 16.4 and 15.9%, respectively. Atmospheric enrichment was observed during carbonated water a Zpplication, but residual enrichment between irrigations was difficult to detect. Significant increase in soil-air CO2 from [ carbonated water application was noted throughout the intervals between successive irrigation events. Carbonated water ap \plication also decreased soil pH for periods of up to 5 d after irrigation and increased apparent uptake of P, K, Ca, Mg,  ]Zn, Fe, Mn, Cu, and B. Based on the limited duration of enrichment relative to the entire growing season for any of the cag ^rbonated water treatments, the yield responses observed could not be attributed solely to atmospheric enrichment. Thus, wei _ conclude that yield increases resulted from the combined effects of limited atmospheric CO2 enrichment and soil environment modifications leading to improved nutrient uptake.es in isotopic distribution patterns for diamonds of ultrabasic and a114^5^Agren,GI^McMurtrie,RE^Parton,WJ^Pastor,J^Shugart,HH^1991^1^State-of-the-art of models of production decomposition linkages in conifer and grassland ecosystems^56^1^2^118-138^^^^^May^^^^^3085lues of the early generation vary widely, where cA^3084^We review the state-of-the-art of models of forests and grasslands that could be used to predict the impact of a fu dture climate change arising from increased atmospheric carbon dioxide concentration. Four levels of resolution are recogni ezed: physiologically based models, population models, ecosystem models, and regional or global models. At the physiologica | fl level a number of important processes can be described in great detail, but these models often treat inadequately intera y gctions with nutrient cycles, which operate on longer time scales. Population and ecosystem models can, on the other hand,  hencapsulate relationships between the plants and the soil system, but at the expense of requiring more ad hoc formulations i of processes. At the regional and global scale we have so far only steady-state models, which cannot be used to predict t _ jransients caused by climate change. However, our conclusion is that, in spite of the gaps in knowledge, there are several [ kmodels based on dominant processes that are well enough understood for the predictions of those models to be taken serious~ly.FECTS OF CO2 ENRICHMENT AND NITROGEN STRESS ON GROWTH, AND PARTITIONING OF DRY-MATTER AND NITROGEN IN WHEAT AND MAIZE S115^1^Amthor,JS^1991^1^Respiration in a future, higher-CO2 world^9^14^1^13-20^^^^^Jan^^^^^3087 AUSTRALIA. ID CARBON-DIOXI N nA^3086^Apart from its impact on global warming, the annually increasing atmospheric [CO2] is of interest to plant scientis A ots primarily because of its direct influence on photosynthesis and photorespiration in C3 species. But in addition, 'dark' @ p respiration, another major component of the carbon budget of higher plants, may be affected by a change in [CO2] independ 0 qent of an increase in temperature. Literature pertaining to an impact of [CO2] on respiration rate is reviewed. With an in . rcrease in [CO2], respiration rate is increased in some cases, but decreased in others. The effects of [CO2] on respiration - s rate may be direct or indirect. Mechanisms responsible for various observations are proposed. These proposed mechanisms r ) telate to changes in: (1) levels of nonstructural carbohydrates, (2) growth rate and structural phytomass accumulation, (3)  u composition of phytomass, (4) direct chemical interactions between CO2 and respiratory enzymes, (5) direct chemical inter  vactions between CO2 and other cellular components, (6) dark CO2 fixation rate, and (7) ethylene biosynthesis rate. Because w a range of (possibly interactive) effects exist, and present knowledge is limited, the impact of future [CO2] on respirat xion rate cannot be predicted. Theoretical considerations and types of experiments that can lead to an increase in the understanding of this issue are outlined.hat concentrations of total-N and nitrate-N were lower in all organs of enriched pla z116^1^Brown,KR^1991^1^Carbon-dioxide enrichment accelerates the decline in nutrient status and relative growth-rate of Populus tremuloides Michx seedlings^13^8^2^161-173^^^^^Mar^^^^^3089udy indicates that critical total-N and NO3-N concentrati |A^3088^Changes in growth dynamics and mineral nutrient concentrations were measured in Populus tremuloides Michx., trembli }ng aspen, grown for 100 days following germination in atmospheres containing 350 or 750-mu-l l-1 CO2. Seedlings were ferti ~lized with nitrogen (N) at concentrations of 15.5 mM (high-N), 1.55 mM (medium-N), or 0.155 mM (low-N). Initially, relativ e growth rates were enhanced by CO2 enrichment in each N regime, but the effects did not persist. In plants grown in high- N or medium-N, foliar concentrations of Ca and Mg decreased in response to CO2 enrichment. During the 100-day study, whole -plant concentrations of N and P decreased in all treatments. The decreases in mineral nutrient concentrations over time w ere accelerated in CO2-enriched plants and accompanied the disappearance of the CO2-induced growth enhancement. It is conc luded that the depression of relative growth rates often associated with long-term CO2 enrichment of plants may result from decreases in plant nutrient status.ed with 7.5, 6.2 and 6.4 mg/g dry wt, respectively, for control plants grown at the 117^3^Caporn,SJM^Mansfield,TA^Hand,DW^1991^1^Low temperature-enhanced inhibition of photosynthesis by oxides of nitrogen in lettuce (Lactuca sativa L)^84^118^2^309-313^^^^^Jun^^^^^3091the three growth stages. Critical concentrations of NO3-N  A^3090^The response of photosynthetic gas exchange to oxides of nitrogen (NO(x)) was studied in leaves of lettuce (Lactucap sativa L.) at different temperatures. Exposure to high concentrations (e.g. 1.3-mu-mol NO(x) mol-1), similar to those oftq en found in commercial glasshouses, caused a rapid inhibition of the net assimilation of CO2. This appeared to be by a dird ect effect on photosynthesis rather than by a change in the stomatal conductance. In ambient CO2 (345-mu-mol mol-1), the pf ercentage inhibition at 10 and 5-degrees-C was approximately 3 x and 5 x, respectively, that measured at 20- degrees-C. Th is effect of temperature also occurred when measured in CO2 enriched air (1050-mu-mol mol-1), which would normally accompa ny NO(x) in a glasshouse. The extent of photosynthetic inhibition caused by NO(x) was, however, always less in high than i n low CO2. The results suggest that when burning fuel to raise the CO2 concentration and heat the glasshouse air, growers should avoid generating high concentrations of NO(x) in conditions of low temperature.ominal concentrations of 350, 500, 118^3^Elkohen,A^Pontailler,JY^Mousseau,M^1991^1^Effect of doubling of atmospheric CO2 concentration on dark respiration in aerial parts of young chestnut trees (Castanea sativa mill)^176^312^9^477-481^^^^^25 Apr^^^^^3093r the year 2050) and Q A^3092^Two-year-old sweet chestnut seedlings were grown in constantly ventilated tunnels at ambient (350 vpm) or double (7 00 vpm) CO2 concentration during a full growing season. End-of-night dark respiration of aerial parts was measured in each CO2 concentration throughout the growing season. Dark respiration rate of enriched plants showed a net decrease as compar ed to control plants during the first half of the growing season. This difference decreased with time and became negligibl e in the fall. Atmospheric CO2 concentration acted instantaneously on the respiration rate: when doubled, it decreased con trol plant respiration and when decreased, it enhanced CO2 enriched plant respiration. The explanation of these findings r emains hypothetical. It is concluded that the rise in carbon dioxide level of the atmosphere will affect the carbon balanc e of young trees not only through an increase in net photosynthesis during the day, but also at night by reducing respirat ory losses.& TECHNOL, DEPT BIOCHEM & APPL MOLEC BIOL, POB 88, MANCHESTER M60 1QD, LANCS, ENGLAND. ID ACETATE CATABOLISM; 119^3^Idso,SB^Kimball,BA^Allen,SG^1991^1^CO2 enrichment of sour orange trees - 2.5 years into a long- term experiment^9^14 ^3^351-353^^^^^Apr^^^^^3095d an acetoclastic culture for the methanogenic stage. In continuous culture, A. kivui ferment A^3094^Eight sour orange trees have been grown from seedling stage in the field at Phoenix, Arizona, U.S.A., in four ident z ically-vented, open-top, clear-plastic-wall chambers for close to 2.5 years. Half of the chambers have been maintained at w ambient atmospheric CO2 concentrations over this period, while half of them have been maintained at 300 ppm (300-mu-mol CO x 2 per mol air) above ambient. Initially, the trees in each treatment were essentially identical; but in less than 2 years, h the trunks of the CO2-enriched trees had become twice as large as their ambient-treatment counterparts. After 2 full year g s of growth, the enriched trees had 79% more leaves, 56% more primary branches with 172% more volume, 70% more secondary b V ranches with 190% more volume, and 240% more tertiary branches with 855% more volume. In addition, the CO2-enriched trees R also had fourth-, fifth- and sixth-order branches, while the ambient- treatment trees had no branches above third order. T D otal trunk plus branch volume of the CO2-enriched trees was 2.79 times that of the ambient-treatment trees after 2 full ye @ars of growth.ated negative feedbacks related to cloud characteristics may be a moderate increase in nighttime minimum t 5 120^3^Jiao,J^Tsujita,MJ^Grodzinski,B^1991^1^Influence of temperature on net CO2 exchange in roses^146^71^1^235-243^^^^^Jan 1^^^^^3097educe low temperature stresses on biological and mechanical systems, significantly amplify many of the positive ( A^3096^The effect of temperature on net CO2 exchange of source and sink tissues of the flowering shoots and of whole plant & s was examined using single-stemmed Samantha roses. At all stages of shoot development, the optimal temperature range for  whole-plant carbon (C) gain at saturating irradiance and ambient CO2 level was between 20-degrees and 25-degrees-C, narrow  er than the temperature range for optimal leaf net photosynthesis. Dark respiration increased more dramatically than photoX synthesis with temperatures between 15 and 35-degrees-C. At 25-degrees-C, C loss due to respiration from the flower bud atU colour bud stage accounted for 45% of the C loss of the flowering shoot. At low irradiance levels (e.g. 200-mu-mol m-2 s-H 1) whole-plant net photosynthesis was greater at 16-degrees than at 22-degrees-C because of a greater reduction in respiraF tion. Lowering the night temperature from 27 to 17- degrees-C also increased daily C gain due to a reduction in the C lost, at night. Whole-plant net photosynthesis of plants grown and measured at enriched (1000 +/- 100-mu-L L-1) CO2 was greater. than that of plants grown and measured at ambient (350 +/- 50-mu-L L-1) level at temperatures between 15-degrees and 35-d egrees-C. Furthermore, the optimal temperatures for whole- plant net photosynthesis in CO2 enrichment was higher than at ambient CO2 level.HIGH CO2 LEVELS - NO EVIDENCE FOR EITHER PHENOMENON IN 3-YEAR STUDY OF SOUR ORANGE TREES SO PLANT PHYSI 121^4^Kozai,T^Iwabuchi,K^Watanabe,K^Watanabe,I^1991^1^Photoautotrophic and photomixotrophic growth of strawberry plantlets invitro and changes in nutrient composition of the medium^177^25^2^107-115^^^^^May^^^^^3099antium L.) trees maintained i A^3098^Explants excised from strawberry (Fragaria x ananassa Duch.) plantlets were cultured in vitro for 21 days on half-s trength MS (Murashige & Skoog 1962) basal liquid medium with 20 g l-1 sucrose and without sugar in the vessels capped with gas permeable microporous polypropylene film. The experiments were conducted under CO2 nonenriched (350-450-mu-mol mol-1 in the culture room) and CO2 enriched (2,000-mu-mol mol-1 during the photoperiod in the culture room) conditions with a PP F (photosynthetic photon flux) of 200-mu-mol m-2 s-1. The CO2 concentration in the vessels decreased to approximately 200- mu- mol mol-1 during the photoperiod on day 21 under CO2 nonenriched conditions. The fresh and dry weight, net photosynthe tic rate (NPR) per plantlet, NPR per g leaf fresh weight, NPR per g leaf dry weight, the number of unfolded leaves, and io n uptake of PO4(3-), NO3-, Ca2+, Mg2+ and K+ on day 21 were the greatest under photoautotrophic (no sugar in the medium) a nd CO2 enriched conditions. The residual percent of PO4(3-) was 3% on day 21 under photoautotrophic and CO2 enriched condi tions.n on cyclic AMP synthesis was studied in glia-free, low-density, monolayer cultures of chick retinal photoreceptors 122^2^Paffen,BGP^Roelofs,JGM^1991^1^Impact of carbon-dioxide and ammonium on the growth of submerged Sphagnum cuspidatum^1 59^40^1^61-71^^^^^Apr^^^^^3101lar concentration of cyclic AMP and stimulated the conversion of [H-3]adenine to [H-3]cycli A^3100^In a culture experiment, the influence of carbon dioxide and ammonium on the growth of Sphagnum cuspidatum Hoffin. was studied. During a 12-week period, S. cuspidatum was grown in a solution with various concentrations of carbon dioxide and ammonium. The culture experiment clearly demonstrated that the biomass and the length of S. cuspidatum only increased strongly when the carbon dioxide concentration of the water was high. Further it is shown that ammonium enrichment without CO2 enrichment does not lead to an increase in biomass of S. cuspidatum.photoreceptor-enriched cultures. BP 615-621 PG 7 123^3^Baker,JT^Allen,LH^Boote,KJ^1990^1^Growth and yield responses of rice to carbon-dioxide concentration^178^115^^313-32 0^^^^^Dec^^^^^3103SO2 RECOVERY FROM FLUE-GAS BY PRESSURE SWING ADSORPTION SO INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH A^3102^Rice plants (Oryza sativa L., cv. IR30) were grown in paddy culture in outdoor, naturally sunlit, controlled-enviro nment, plant growth chambers at Gainesville, Florida, USA, in 1987. The rice plants were exposed throughout the season to subambient (160 and 250), ambient (330) or superambient (500, 660, 900 mu-mol CO2/mol air) CO2 concentrations. Total shoot biomass, root biomass, tillering, and final grain yield increased with increasing CO2 concentration, the greatest increas e occurring between the 160 and 500 mu-mol CO2/mol air treatments. Early in the growing season, root:shoot biomass ratio i ncreased with increasing CO2 concentration; although the ratio decreased during the growing season, net assimilation rate increased with increasing CO2 concentration and decreased during the growing season. Differences in biomass and lamina are a among CO2 treatments were largely due to corresponding differences in tillering response. The number of panicles/plant w as almost entirely responsible for differences in final grain yield among CO2 treatments. Doubling the CO2 concentration f  rom 330 to 660 mu-mol CO2/mol air resulted in a 32% increase in grain yield. These results suggest that important changes { in the growth and yield of rice may be expected in the future as the CO2 concentration of the earth's atmosphere continues q to rise. indicate that the results of the present work can be further improved by using these polymeric sorbents. BP 198 p 124^3^Fajer,ED^Bowers,MD^Bazzaz,FA^1991^1^The effects of enriched CO2 atmospheres on the buckeye butterfly, Junonia coenia k^11^72^2^751-754^^^^^AprT OF LIGHT-INTENSITY AND CO2 ENRICHMENT DURING INVITRO ROOTING ON SUBSEQUENT GROWTH OF PLANTLETS g 125^1^Jansen,DM^1990^1^Potential rice yields in future weather conditions in different parts of asia^179^38^4^661-680^^^^^ [Dec^^^^^3106ORT, DEPT PHYTOL, QUEBEC CITY G1K 7P4, QUEBEC, CANADA. DE ASPARAGUS-OFFICINALIS; FRAGARIAXANANASSA; LIGHT; MI Z A^3105^Future climate change is expected to vary between regions, with possible different effects on crop growth. Various S sites in Asia were selected to represent major rice growing environments. Historic weather data of these sites were adapte O d to possible changes in temperature and in CO2 level, to mimic climate change. Potential rice yields at present, and for I the years 2020 and 2100 were calculated with a crop growth simulation model. Simulated yields rose in low and middle tempe H rature change scenarios, but decreased in the high temperature scenario. Effects were stronger in the year 2100, when also = regional differences became clear: more than elsewhere, yields were affected by high temperatures between 10 and 35-degre < es-N. Water use efficiency decreased in the high temperature scenario irrespective of CO2 scenario, and increased otherwis 5e.e of micropropagated plantlets in acclimatization and reduced by 2 weeks the acclimatization period with raspberry. Ou 1 126^3^Jiao,J^Tsujita,MJ^Grodzinski,B^1991^1^Influence of radiation and CO2 enrichment on whole plant net CO2 exchange in r oses^146^71^1^245-252^^^^^Jan^^^^^31088tro rooting stage. BP 259-269 PG 11 JI Sci. Hortic. PY 1991 PD JUL VL 47 IS 3-4 G # A^3107^At three stages of flowering shoot development, varying the irradiance and CO2 levels had a similar effect on the w  hole- plant net CO2 exchange rate (NCER) of Samantha rose plants. At 22-degrees-C, the NCER was saturated at 1000-mu-mol m  -2 s-1 photosynthetically active radiation (PAR). The duration of the light period was also important in determining daily carbon (C) gain. When roses were exposed to a constant daily radiant energy dose of 17.6-mu-mol m-2 provided either as a 12-h irradiation interval at 410-mu-mol m-2 s-1 PAR or 24 h of irradiation at 204-mu-mol m-2 s-1 PAR, the plants exposed t o 24 h of continuous irradiation at the lower photon flux density retained 80% more C. Under saturating irradiance, the ne t photosynthetic rate at an enriched (1000-mu-L L-1) CO2 level was almost double that at ambient (350-mu-L L-1) CO2. Howev er, plants grown at ambient and enriched CO2 levels had similar whole-plant NCERs when compared at the same assay CO2 leve l. Under CO2 enrichment the flower stem was longer and thicker but the flower bud size at harvest was not significantly different to that of roses grown at the ambient CO2 level.bjects studied. Superimposed on this increase were short-term non 127^5^Kurooka,H^Fukunaga,S^Yuda,E^Nakagawa,S^Horiuchi,S^1990^1^Effect of carbon-dioxide enrichment on vine growth and berry quality of kyoho grapes^180^59^3^463-470^^^^^Dec^^^^^3110nential models. Triglyceride FSR of the subjects over the firs A^3109^Although ambient temperature is kept adequate, grape cultivation under covered facilities during winter months in J apan gives rise to low yields of poor quality berries because of low light intensities. This investigation was conducted i n leaf chamber, using Vitis labruscana Bailey cv. Kyoho, to determine the influence of leaf age, light intensity, and CO2 concentrations on photosynthesis. The effects of CO2 enrichment on vine growth and fruit quality were also investigated in growth chambers. 1. The rate of photosynthesis per unit leaf area (Pn) between May 28 and September 19 rapidly increased ~ with leaf growth, reaching a maximum of 18.9 mg CO2/dm2/hr, 37 days after the unfolding of a leaf. Pn then gradually decre| ased with leaf age. In young leaves, higher CO2 concentrations and stronger light intensities resulted in a significant inj crease in Pn. Older leaves exhibited a similar enhancement of Pn upon exposure to high light intensity. Pn was saturated ai t 828 ppm CO2. 2. Administration of 1,000 to 1,100 ppm CO2 to vines for an 8 hr/day at a late stage of berry development u ntil harvest had no effect on berry size but resulted in an increase in sugar and anthocyanin contents but a decrease in o rganic acid content. Dry weight of newly developed roots doubled as a result of CO2 enrichment. 3. Application of CO2 unde r a long-day photoperiod at an early stage of berry development to a week before veraison markedly promoted shoot elongati on. Furthermore, CO2 enrichment gave a 36% increase in both berry and cluster weights and also a higher sugar-acid ratio at harvest.O2 production in grain at 17% water content (table I and fig 6). This led to oxygen consumption within a few d 128^2^Lindhout,P^Pet,G^1990^1^Effects of CO2 enrichment on young plant-growth of 96 genotypes of tomato (Lycopersicon esculentum)^181^51^2^191-196^^^^^Dec^^^^^3112s 1-2). The adsorption-desorption effect was quantitatively assessed. This per A^3111^The early growth of 96 genotypes of tomato was studied at 320 ppm CO2 and at 750 ppm CO2 in separate climate rooms. Plants were harvested at 40 and 55 days after sowing. Fresh and dry weights were determined. Large differences between ge  244^6^Beerling,DJ^Chaloner,WG^Huntley,B^Pearson,JA^Tooley,MJ^Woodward,FI^1992^1^Variations in the stomatal density of sali  x-herbacea L under the changing atmospheric co2 concentrations of late-glacial and postglacial time^190^336^1277^215-224^^ ^^^29 May^^^^^3330 Assuming a population of a short-lived perennial (or annual?) with a short-lived seed bank and high  A^3329^The rapidly rising CO2 concentration of the past 200 years has been shown to be accompanied by a fall in stomatal d % ensity in the leaves of temperate trees. The present study attempts to investigate the relationship of atmospheric CO2 cha & nge and stomatal density in the arctic-alpine shrub, Salix herbacea, over the longer time span of 11 500 years offered by ( fossil leaves from post-glacial deposits. Comparisons of fossil material from Scotland and Norway are made with leaves fro / m living populations growing in Austria, Greenland and Scotland. The Austrian material, from an altitudinal gradient betwe 2 en 2000 and 2670 m above sea level, gives added comparison of contemporary differences of CO2 partial pressure with altitu < de. The results of our investigation indicate, rather surprisingly, that the rising CO2 concentration of the past 11 500 y > ears has been accompanied by an increase in the stomatal density of S. herbacea in contrast to the shorter-term observatio N ns on the herbarium material of temperate trees. The most likely explanation appears to centre on the temperatures and wat P er availability of the early post-glacial environment overriding the effect of the lower CO2 regime. However, the scale of a  the time interval involved may also be significant. Natural selection over the 11 500 year period concerned may have favo c ured a different response to what is, in effect, an acclimatory response observed in trees within the period of rapid CO2 irise of the past 200 years.ime.ease.lsoft.com [209.119.1.41]) by mx2.osu.edu (PMDF V5.2-29 #34303) with ESMTP id <0F7 j 245^2^Grimm,AG^Fuhrer,J^1992^1^The response of spring wheat (triticum-aestivum L) to ozone at higher elevations .1. Measur lement of ozone and carbon-dioxide fluxes in open-top field chambers^84^121^2^201-210^^^^^Jun^^^^^333299 15:31:52 -0500 D z A^3331^The flux of O3 was determined in open-top chambers (OTC) used to investigate its effect on spring wheat (Triticum a | estivum L., cv. Albis) in 1989 and 1990. The experimental site was located at 900 m above sea level at Zimmerwald, near Be rn (Switzerland). The aims were to evaluate the use of OTCs for O3 flux measurements under field conditions, to assess the  role of stomata in controlling the O3 fluxes, and to establish a quantitative relationship between radiation-weighted O3 concentrations and O3 flux. Measurements were carried out from full expansion of flag leaves until the onset of senescence . Ozone flux was determined by mass balance using the concentrations of O3 measured at the inlet and outlet of the OTC. Th e CO2 exchange rate was corrected for soil-borne CO2 and used as a reference. Measurements of temperature, photosynthetica lly active radiation (PAR), saturated water vapour pressure deficit (SVPD), and boundary layer conductance were used to de scribe the microclimate inside OTCs. In the warmer microclimate in 1989, the plant canopy was characterized by a smaller l eaf area index (LAI) than in 1990, while the fluxes of O3 and CO2 during daytime were generally larger in 1989. The diurna l patterns of fluxes of O3 and CO2 in OTCs supplied with unfiltered air were similar. It is estimated that O3 absorption v ia the stomata contributed 50-70 % of its total flux. Identical relationships between leaf conductance for O3 measured by porometry and leaf conductance calculated from O3 flux were found in both years, but measured leaf conductance during dayt !ime was generally smaller in 1990 than in 1989. The results indicate that stomatal conductance largely controlled O3 flux, " and that the canopy structure has an influence on the overall conductance of the canopy. Different linear functions were #obtained for the relationship between radiation-weighted O3 concentration and O3 flux, using data from OTCs supplied with $either charcoal-filtered air, unfiltered air or unfiltered air enriched with O3 (two levels). These relationships form the basis for the calculation of mean O3 fluxes which can be used as an exposure index in the exposure-response analysis.v 246^1^Grodzinski,B^1992^1^Plant nutrition and growth-regulation by co2 enrichment^14^42^7^517-525^^^^^Jul-Aug '247^2^Idso,SB^Kimball,BA^1992^1^Effects of atmospheric co2 enrichment on photosynthesis, respiration, and growth of sour o range trees^8^99^1^341-343^^^^^May^^^^^3335arperspective )A^3334^Numerous net photosynthetic and dark respiratory measurements were made over a period of 4 years on leaves of 24 so *ur orange (Citrus aurantium) trees; 8 of them growing in ambient air at a mean CO2 concentration of 400 microliters per li +ter, and 16 growing in air enriched with CO2 to concentrations approaching 1000 microliters per liter. Over this CO2 conce ,ntration range, net photosynthesis increased linearly with CO2 by more than 200%, whereas dark respiration decreased linea -rly to only 20% of its initial value. These results, together with those of a comprehensive fine-root biomass determinatio .n and two independent above-ground trunk and branch volume inventories, suggest that a doubling of the air's current mean CO2 concentration of 360 microliters per liter would enhance the growth of the trees by a factor of 3.8.sland Sound, CT/Ns 0248^4^Kozai,T^Kushihashi,S^Kubota,C^Fujiwara,K^1992^1^Effect of the difference between photoperiod and dark period temperaq 1tures, and photosynthetic photon flux-density on the shoot length and growth of potato plantlets invitro^180^61^1^93-98^^^e^^Jun^^^^^3337v 609:02 PM 17 02 1999 -0600John Madsena 3A^3336^Potato plantlets (Solanum tuberosum L. cv. Benimaru) under CO2 enriched and photoautotrophic culture conditions werW 4e subjected to three different photo-/dark period temperature combinations (25-degrees/15-degrees-C, 200/20-degrees-C and T 515-degrees/25- degrees-C) and two levels of photosynthetic photon flux densities (74 and 147-mu-mol.m-2.sec-1). The shoot L 6length of the plantlets under the same photosytnthetic photon flux density (PPF) was reduced with decreasing the differencH 7e between photoperiod and dark period temperatures (it is named DIF, photoperiod temperature minus dark period temperature8 8). No marked differences in the fresh and dry weights per plantlet were observed among the three DIF treatments in each PP: 9F treatment. The higher PPF led to a decrease in the shoot length, an increase in the fresh weight, dry weight and leaf ar. :ea per plantlet in each DIF treatment. It is suggested that shoot length of plantlets in vitro under CO2 enriched and phot0 ;oautotrophic culture conditions can be controlled without reducing the weight increments and leaf area per plantlet by reg&ulating the difference between photoperiod and dark period temperatures.1999 -0500Martin Mitchell" =249^3^Nederhoff,EM^Dekoning,ANM^Rijsdijk,AA^1992^1^Leaf deformation and fruit production of glasshouse grown tomato (lycopersicon-esculentum mill) as affected by co-2 plant-density and pruning^174^67^3^411-420^^^^^May^^^^^3339USGS # ?A^3338^During summer, glasshouse grown tomato plants (Lycopersicon esculentum Mill.) often demonstrate leaf deformation, r @educed leaf area (short leaves) and low Specific Leaf Area (SLA), sometimes accompanied by higher dry matter content of le Aaves and stems and higher leaf starch content. This so-called "Short Leaves Syndrome" (SLS), which decreases the productio Bn capacity, was investigated with emphasis on the effects of CO2 concentration. As a working hypothesis it was postulated  Cthat SLS is indirectly caused by an oversupply of assimilates relative to the sink capacity. An experiment was conducted b Detween 10 May and 31 July 1990 in 12 glasshouse compartments. The sink/source ratio was varied by maintaining two levels o Ef CO2, multifactorially combined with two plant densities and three pruning treatments. CO2 enrichment and wider planting  Fenhanced SLS and decreased leaf area and SLA of upper leaves. Leaf pruning and fruit pruning, however, did not give clear  Geffects on vegetative characteristics, although the impact on the sink/source ratio was of the same order of magnitude. As H a mechanism for these effects, we suggest that SLS is caused by calcium deficiency in the apex, a condition more severe w Ihen much phloem sap (with low calcium content) is available, i.e. when the sink/source ratio is lower. Stronger effects of J CO2 and plant density than of pruning on the incidence of SLS, may be due to local effects of sink/source relationships o Kr to involvement of other processes, like transpiration. In crops with little SLS-symptoms, CO2 enrichment increased the w Leight of fruits grown during the treatment period by 31%, whereas in crops with severe SLS, CO2 enrichment aggravated SLS  Mand had no significant effect on fruit production. CO2 enrichment in summer is beneficial if SLS is prevented, which can be achieved by maintaining a higher plant density or, in an early crop, an extra shoot on the plants in spring and summer. O250^2^Rastetter,EB^Shaver,GR^1992^1^A model of multiple-element limitation for acclimating vegetation^11^73^4^1157-1174^^^^^Aug^^^^^3341ntervals to determine the effect of irrigation frequency. In 1988, a positive yield response of 9% was obt QA^3340^In this paper we present a simple model of multiple-element limitation of plant production and biomass accumulation R. The primary aim of this model is to develop a theoretical framework for examining multiple-element limitation vs. single} S-element limitation and for examining the relationship between short- term and long-term responses to changes in element ay Tvailability. In the model we assume that there is an "optimal" ratio of mineral elements in vegetation biomass, and that tr Uhe vegetation continually adjusts its relative element uptake capacities to compensate for shifts away from this optimum. m VWe examine the responses of this model to changes in element availability in the plant environment, where "availability" ic Ws defined either as fixed concentrations of non-depletable elements or as fixed replenishment rates of depletable elements X. The model results suggest that the nature of the controls on element availability has a major impact on whether single-  Yor multiple-element limitation prevails, even when plants can acclimate so as to maintain an "optimal" nutritional balance Z. Single-element limitation occurs when the replenishment rate of an essential element to the available pool is limited an [d sustainable plant uptake of that element equals the replenishment rate. Furthermore, when single- element limitation pre \vails, there is little or no correlation between short-term responses to a change in element availability and long-term, e ]quilibrium responses. In general, previous experimental studies and models of plant growth in response to changes in relat ^ive availability of multiple, essential elements have either not specified how those resources are controlled, or have exa _mined only one type of control. Our results help to explain the diversity of results of past studies of multiple-element l `imitation, suggest some improvements in experimental design for future studies, and have important implications for the extrapolation of the results of controlled experiments to field situations.th CO2-enriched solution (pH0 6.0) resulted in f b251^3^Watanabe,Y^Ohmura,N^Saiki,H^1992^1^Isolation and determination of cultural-characteristics of microalgae which funct ions under co2 enriched atmosphere^191^33^5-8^545-552^^^^^May-Aug^^^^^3343New Opportunity for Ecology Education dA^3342^A fresh-water microalgae, which functions under CO2 enriched atmosphere conditions, was isolated and its cultural c eharacteristics were investigated. The HA-1 strain, identified as genus Chlorella, was newly isolated from a paddy field by f an enrichment culture using reproduced stack gases from a thermal power plant with a concentration of CO2 and O2 of 15 % gand 2 % respectively. It showed maximum growth at 10 % CO2 enriched air flowing condition, and showed a good growth rate i hn a broad range of physically controllable conditions, including CO2 enriched air flow rate, temperature and pH value. The results indicated the feasibility of the HA-1 strain for mass cultivation using stack gases.:54 AM 11 02 1999 -0700 252^1^Goudriaan,J^1992^1^Where goes the carbon-dioxide - the role of vegetation^192^23^243^597^^^^^May k253^4^Doi,M^Oda,H^Ogasawara,N^Asahira,T^1992^1^Effects of co2 enrichment on the growth and development of invitro cultured plantlets^180^60^4^963-970^^^^^Mar^^^^^3346U3  mA^3345^Plantlets of Caladium bicolor (C3 plant), Saccharum officinarum (C4 plant), and Phalaenopsis hybrid (CAM plant) at nthe preparation stage for acclimatization (the final stage of in vitro culture) were cultured on the medium containing 2% osucrose. The culture vessels were kept under continuous, 16 hr, or 8 hr lighting conditions; half of the vessels were vent pilated continuously with 0.8 +/- 0.4% CO2 enriched atmosphere; while the remainder was exposed to ambient atmosphere. The  qgrowth of plantlets was promoted with an increase in daylength under both ambient and CO2 enriched atmospheres. When the p rlantlets were supplied with adequate CO2, dry matter production increased under all daylength treatments except Caladium c sultured under continuous lighting. This promotive effect of CO2 enrichment was especially noticeable in root growth. In Ca tladium and Phalaenopsis, the leaf chlorophyll content of plantlets cultured under CO2 enriched atmosphere was less than th uat of leaves from plantlets grown in ambient atmosphere. Although the chlorophyll was less concentrated in leaves of plant vlets growing under the CO2 enriched treatment, the rate of CO2 uptake of these plantlets measured at the midpoint of the l wight period was higher than that of leaves exposed to ambient atmosphere. Increasing the O2 concentration in culture vesse xls to 37% also promoted the growth of Caladium and Dendrobium phalaenopsis (CAM plant) under CO2 enriched condition. Becau* yse of the development of photoautotrophy, the Caladium plantlets exposed to enriched CO2 atmosphere and cultured on sugar-,free medium using ceramic wool plug system responded with vigorous growth when transplanted into pots.PIENZA, DIPARTMENTO7 {254^4^Easterling,WE^Rosenberg,NJ^Lemon,KM^McKenney,MS^1992^1^Simulations of crop responses to climate change - effects wit9 h present technology and currently available adjustments (the smart farmer scenario)^107^59^1-2^75-102^^^^^15 Apr^^^^^3348E }A^3347^If climate changes, farmers will have to adapt to a new set of climate constraints. In this paper we examine the efG ~ficacy of strategies for dealing with climate change that are currently available to farmers and that are inexpensive to u[ se; we refer to this group of strategies as 'adjustments'. Adjustment schemes of various kinds were identified for us by a] gricultural experts in the Missouri-Iowa-Nebraska-Kansas (MINK) states. These can involve changes in land use, changes in s variety and crop selection, changes in planting and harvesting practices, and changes in fertility and pest management. Usu ing the erosion productivity impact calculator (EPIC) model on a small set of representative farms, we tested adjustments  of these kinds. The simulations show that earlier planting, longer- season cultivars and the use of furrow diking for mois ture conservation would offset some of the yield losses induced by climate change in warm-season crops. Longer-season vari eties of wheat (a cool-season crop) and shorter-season varieties of the perennials wheatgrass and alfalfa were also effect ive. The adjustments to climate change diminished yield losses in all crops but irrigated wheat. Despite the positive effe cts of adjustments, however, yields of all dryland warm-season crops remained lower than control levels. The adjustments a lso increased demand for irrigation water. Carbon dioxide enrichment had the same incremental effect on crop yields with o r without adjustments (see the fourth paper in this issue), except in the case of alfalfa and sorghum, where a CO2- adjust ment interaction was found. We conclude that currently available techniques would partially offset the yield reductions caused by a 1930s-like climate, but that in most crops the yield reductions would still be substantial.nt, in particular atsed salinity (250 mM NaCl). BP 45-55 PG 11 JI Aquat. Bot. PY 1991 PD FEB VL 39 IS 1-2 GA FC985 RP ROZEMA J J9 AQUAT BOT E 255^3^Grobbelaar,N^Chou,WM^Huang,TC^1992^1^Effect of co2, o2, dcmu, fccp, and dl-glyceraldehyde on the nitrogenase activity of synechococcus rf-1^193^33^2^167-174^^^^^Apr^^^^^3350STRUCTION RESPIRATION; MAINTENANCE RESPIRATION; NITROGEN; PLANT  A^3349^Elevated atmospheric CO2 concentrations drastically inhibit nitrogenase activity of the unicellular Synechococcus R F-1 but stimulate photosynthetic CO2 assimilation. The inhibitory effect on nitrogenase activity is stronger in the light  than in the dark. During three hours, 1% CO2 in air can reduce nitrogenase activity in the light by about 50% compared to  that in unenriched air. The inhibitory effect of elevated CO2 concentrations on nitrogenase activity persists for many hou rs after the organism has been returned to air not enriched with CO2. The nitrogenase activity of heterocystous cyanobacte ria, generally, does not appear to be affected by 5% CO2 in the air. DCMU strongly enhanced nitrogenase activity and inhib ited the assimilation of CO2 by Synechococcus RF-1 in the light, and elevated atmospheric O2 concentrations reduced the ni trogenase activity, especially in the dark. DL-glyceraldehyde at a concentration of 19.4 mM strongly inhibited nitrogenase" activity, dark respiration, and photosynthesis. FCCP had no effect on dark respiration but depressed nitrogenase activity$ and photosynthesis of Synechococcus RF-1. The inhibitory effect of FCCP on nitrogenase activity was stronger in the dark 4than in the light.climation of respiration rates to different climates are poorly understood, but may substantially affec6 256^2^Hollander,B^Krug,H^1992^1^Effects of high co2-concentrations on vegetable species .2. Growth, co2-gas-exchange and s<tomata resistance^172^57^1^32-43^^^^^Jan-Feb^^^^^3352TASSIC AND SODIC ALTERATION ACCOMPANYING GOLD MINERALIZATION IN THE > A^3351^In the climatic conditions tested the growth of young cucumber plants (3-7 leaf stage) was slightly promoted as welF l by day as by continuous enrichment with 5000-mu-l/l CO2 compared to the control (400-mu-l/l CO2). A definite effect of eH nrichment during the night was not evident. The analysis of the growth components and gas exchange measurements revealed, O that CO2 enrichment during the day as well as during day and night increased net assimilation rate and dark respiration diQ stinctly. Enrichment during the night showed no effect on net assimilation rate and increased dark respiration only slight\ ly. The specific leaf area was strongly reduced by the high CO2 concentration, but leaf weight ratio was rarely changed. B^ y these morphogenetic effects growth promotion by an increased net assimilation rate was diminished. Continuous CO2 enrichk ment to cucumber plants with CO2 concentrations greater- than-or-equal-to 1000-mu-l/l decreased stomata resistance. This em ffect increased with higher CO2 concentrations and longer treatments. The stomata remained open even at night and at low a{ ir humidity. Also with CO2 enrichment up to 5000-mu-l/l during the day or during the night only the stomata remained wider} open than in the control plants. The reaction of stomata to high CO2-concentrations is reversible. The regeneration proce eds all the faster as lower the proceeding concentration and shorter the exposition. The actions of high CO2- concentrations on stomata movement of cucumbers were confirmed with other species.teration episodes are considered to be part of the 257^1^Smith,RB^1992^1^Controlled-atmosphere storage of redcoat strawberry fruit^154^117^2^260-264^^^^^Mar^^^^^3354the cru A^3353^Strawberries (Fragaria x ananassa Duch.) cv. Redcoat were stored at several temperatures and for various intervals  in controlled atmospheres (CA) containing 0% to 18% CO2 and 15% to 21% O2. Bioyield point forces recorded on the CA-stored fresh fruit indicated that the addition of CO2 to the storage environment enhanced fruit firmness. Fruit kept under 15% C O2 for 18 hours was 48% firmer than untreated samples were initially. Response to increasing CO2 concentrations was linear . There was no response to changing O2 concentrations. Maximum enhancement of firmness was achieved at a fruit temperature of 0C; there was essentially no enhancement at 21C. In some instances, there was a moderate firmness enhancement as time  in storage increased. Carbon dioxide acted to reduce the quantity of fruit lost due to rot. Fruit that was soft and bruised after harvest became drier and firmer in a CO2-enriched environment.ZENES; AROMATIC COMPOUNDS ID SULFATE-REDUCING BACTE 258^2^Vanhinsberg,N^Horton,RF^1992^1^Ethylene metabolism in pulvini of phaseolus-vulgaris L^194^188^1^51-55^^^^^Feb^^^^^33 A^3355^The ability of leaf blade, pulvinar and petiolar tissue from primary leaves of Phaseolus vulgaris to release ethyle ne when incubated in a 1 mM solution of the ethylene-biosynthesis precursor, 1-aminocyclopropane-1-carboxylic acid, was de termined over a 6h period. Ethylene release was measured under CO2-enriched and CO2-depleted conditions in the light and d ark. In contrast to blade and petiolar tissue, the pulvini released more ethylene in the light than in the dark when held in sealed flanks. The amount of the gas released is largely independent of external levels of carbon dioxide.roquinone as56 donor. The strain grew in sulfide-reduced mineral medium supplemented with 7 vitamins. The DNA base ratio was 59% G + 259^3^Wilson,JW^Hand,DW^Hannah,MA^1992^1^Light interception and photosynthetic efficiency in some glasshouse crops^78^43^248^363-373^^^^^Mar^^^^^3358ogallol-grown cells showed different kinetics of hydroxyhydroquinone and pyrogallol degradatio A^3357^Productivity of glasshouse crops is strongly limited by light receipt, and efficient interception and use of light  in photosynthesis is correspondingly important. Mature row crop canopies of cucumber and tomato intercepted about 76% of t he light incident on their upper surfaces; about 18% was lost through gaps between the rows. Light transmitted through the entire depth of the canopy was reflected back by white plastic on the ground, so that the lower surface of the canopy rec eived approximately 13% of the light incident on the upper surface. The light flux incident on the sides of these canopies! (c. 2 m tall and 6 m x 16 m in area) amounted to some 20-30% of that incident on the upper surface. About 32% of daylight# falling on the glasshouse (c. 9 m x 18 m in area) was intercepted by the glasshouse structure and glazing; of the 68% ent3 ering the house, some fell on headlands occupying 35% of the glasshouse area. The loss of light to headlands, and the gain5 from canopy side-lighting, would be relatively smaller for larger glasshouses. At near-ambient CO2 concentrations, net phK otosynthetic rates of the cucumber canopy were comparable to those of closed canopies of other glasshouse and field crops M which have maximum light conversion efficiencies of 5-8-mu-g CO2 J-1 at 50-200 W m-2 incident light flux density. EfficienY cy decreases only slightly with stronger light. Glasshouse crops with CO2 enrichment to 1200 vpm achieve conversion effici[ encies of 7-10-mu-g CO2 J-1. Efficiencies of utilization of intercepted light, on an energy basis, reach 6-10% in various l field and glasshouse crops with near-ambient CO2, and reached an exceptional 11% for the cucumber canopy. Glasshouse cropsn with CO2 enrichment achieve maximum efficiency of light energy utilization between 12% and 13%.out significant decomposi| 260^2^Chalabi,Z^Fernandez,JE^1992^1^Spatiotemporal responses of a glasshouse to gaseous enrichment^195^51^2^139-151^^^^^Fe~bction. However, by reaction with NO, PtCl3(CO)- in the CuCl-CuCl2-HCl system evolves CO2 and N2O rapidly. The presence  261^1^Mortensen,LM^1992^1^Effects of ozone concentration on growth of tomato at various light, air humidity and carbon-dioxide levels^165^49^1-2^17-24^^^^^Jan^^^^^3361the observed behavior of the system, the results of kinetic studies may be e A^3360^The effect of ozone (O3) Concentration on the growth of Lycopersicon esculentum was studied at different photosynth etic photon flux densities (PPFD), relative air humidities (RH) and carbon dioxide (CO2) concentrations. Increasing the O3 concentration from < 10 to 85 nl l-1 for 6 h per day reduced the shoot dry weight 35% at 70% RH and 62% at 90% RH. Increa sing the PPFD from 100 to 350-mu-mol m-2 s-1 significantly reduced the effect of O3 in one of two experiments. The most pr onounced interaction between RH, PPFD and O3 was found on plant height. High O3 levels generally decreased plant height at low PPFD and had no, or a stimulating, effect at high PPFD. Raising the RH from 70 to 90% significantly increased the neg ative effect of O3 on height. Increasing the O3 concentration from < 10 to 65 nl l-1 significantly decreased plant height at low CO2 concentration (300-340-mu-l l-1), but small effects were found at high CO2 concentration (700-800-mu-l l-1).NN 262^3^Suzuki,T^Ohtaguchi,K^Koide,K^1991^1^Effects of gas-flow rate of co2-enriched air, high co2 concentration, and anaerobic atmosphere on the growth of blue- green-alga anacystis-nidulans^196^24^6^797-798^^^^^Dec Precision laboratory isotopi 263^3^Wullschleger,SD^Norby,RJ^Hendrix,DL^1992^1^Carbon exchange-rates, chlorophyll content, and carbohydrate status of 2 forest tree species exposed to carbon-dioxide enrichment^13^10^1^21-31^^^^^Jan^^^^^3364s was 9 to 16% in 50O3 and 8 to 11 A^3363^Seedlings of yellow-poplar (Liriodendron tulipifera L.) and white oak (Quercus alba L.) were exposed continuously t o one of three CO2 concentrations in open-top chambers under field conditions and evaluated after 24 weeks with respect to carbon exchange rates (CER), chlorophyll (Chl) content, and diurnal carbohydrate status. Increasing the CO2 concentration from ambient to +150 or +300-mu-l l-1 stimulated CER of yellow- poplar and white oak seedlings by 60 and over 35%, respec tively, compared to ambient-grown seedlings. The increases in CER were not associated with a significant change in stomata l conductance and occurred despite a reduction in the amounts of Chl and accessory pigments in the leaves of plants grown  in CO2-enriched air. Total Chl contents of yellow-poplar and white oak seedlings grown at +300-mu-l l-1 were reduced by 27 and over 55%, respectively, compared with ambient-grown seedlings. Yellow-poplar and white oak seedlings grown at +300-mu -l l-1 contained 72 and 67% more morning starch, respectively, than did ambient-grown plants. In contrast, yellow-poplar a nd white oak seedlings grown at +300-mu-l l-1 contained 17 and 27% less evening sucrose, respectively, than did plants gro" wn at ambient CO2 concentration. Diurnal starch accumulation and the subsequent depletion of sucrose contributed to a pron$ ounced increase in the starch/sucrose ratio of plants grown in CO2-enriched air. All seedlings exhibited a substantial red/ uction in dark respiration as CO2 concentration increased, but the significance of this increase to the carbohydrate statu1s and carbon economy of plants grown in CO2-enriched air remains unclear.alyst prereduced and used in CO hydrogenation at@ 264^6^Briones,GL^Varoquaux,P^Chambroy,Y^Bouquant,J^Bureau,G^Pascat,B^1992^1^Storage of common mushroom under controlled atBmospheres^197^27^5^493-505^^^^^Oct^^^^^3366u enrichment occurs on the topmost layer of catalysts. BP 335-344 PG 10 JI CatD A^3365^The effect of controlled atmosphere (CA) on the shelf-life of the common mushroom (Agaricus bisporus) was assessed N using six parameters correlated with its commerical qualities. Low CO2 concentrations (up to 2.5%) reduced brown discolourP ation compared to the control in air. Higher CO2 concentrations enhanced both internal and external browning. Low O2 conce] ntrations reduced growth of micro-organisms, including pseudomonads. Respiration rate, when the mushrooms are placed again_ in normal air, is proportional to CO2 concentration during storage suggesting that CO2 exhibits a phytotoxic effect on mup shrooms. A lower mannitol content was noted in mushrooms stored under CA than those stored in air (control). Mushrooms stor red in a 5% CO2 atmosphere for 7 days did not break their veil but their texture was very soft and spongy. Texture losses tdecreased when CO2 concentrations increased.pected increase in primary production. Whether this will lead to accumulation} 265^5^Gordon,HB^Whetton,PH^Pittock,AB^Fowler,AM^Haylock,MR^1992^1^Simulated changes in daily rainfall intensity due to the enhanced greenhouse-effect - implications for extreme rainfall events^198^8^2^83-102^^^^^Dec^^^^^3368ots into the soil a A^3367^In this study we present rainfall results from equilibrium 1 x - and 2 x CO2 experiments with the CSIRO 4-level gen eral circulation model. The 1 X CO2 results are discussed in relation to observed climate. Discussion of the 2 x CO2 resul ts focuses upon changes in convective and non-convective rainfall as simulated in the model, and the consequences these ch anges have for simulated daily rainfall intensity and the frequency of heavy rainfall events. In doing this analysis, we r ecognize the significant shortcomings of GCM simulations of precipitation processes. However, because of the potential sig nificance of any changes in heavy rainfall events as a result of the enhanced greenhouse effect, we believe a first examin ation of relevant GCM rainfall results is warranted. Generally, the model results show a marked increase in rainfall origi nating from penetrative convection and, in the mid- latitudes, a decline in large-scale (non-convective) rainfall. It is a rgued that these changes in rainfall type are a consequence of the increased moisture holding capacity of the warmer atmos phere simulated for 2 x CO2 conditions. Related to changes in rainfall type, rainfall intensity (rain per rain day) increa ses in the model for most regions of the globe. Increases extend even to regions where total rainfall decreases. Indeed, t he greater intensity of daily rainfall is a much clearer response of the model to increased greenhouse gases than the changes in total rainfall. We also find a decrease in the number of rainy days in the middle latitudes of both the Northern and Southern Hemispheres. To further elucidate these results daily rainfall frequency distributions are examined globally anA^3442^Two-year-old Sitka spruce (Picea sitchensis (Bong.) Carr.) plants from four clones were grown in naturally lit growth chambers for 6 months at either ambient (350 ppm) or ambient + 250 ppm (600 ppm) CO2 concentration. Plants were grown in large boxes filled with peat, in a system that allowed the roots of individual plants to be harvested easily at the end of the growing season. Half of the boxes were kept well watered and half were allowed to dry out slowly over the summer. Plants growing in elevated CO2 showed a 6.9% increase in mean relative growth rate compared to controls in the drought treatment and a 9.8% increase compared to controls in the well-watered treatment, though there was considerable variation in response among the different clones and water treatments. Rates of net CO2 assimilation were higher and stomatal conductanc es were lower in plants grown in elevated CO2 than in ambient CO2 in both the well-watered and drought treatments. Both of  these factors contributed to the doubling of instantaneous water use efficiency. The partitioning of biomass to roots was unaffected by elevated CO2, but the ratio of needle mass/stems + branches mass decreased. Together with reduced stomatal conductance, this probably caused the observed increases in xylem pressure potentials with elevated CO2.CELLS; GONADOTROP! 305^2^Tremmel,DC^Patterson,DT^1993^1^Responses of soybean and 5 weeds to co2 enrichment under 2 temperature regimes^146^73,^4^1249-1260^^^^^Oct^^^^^3445TS; CA-2+ AB The patch-clamp technique has been used to measure changes in membrane capacita.A^3444^Rising atmospheric CO2 levels could affect plant growth both directly, through effects on physiology, and indirectl:y, through the effects of possible CO2-induced temperature increases. In this study we examined the interacting effects of< CO2 enrichment and temperature on the growth and allocation of soybean and five weeds. individual plants of soybean [GlycNine max (L.) Merr. 'Braxton'] , johnsongrass [Sorghum halepense (L.) Pers. quackgrass [Elytrigia repens (L.) Nevski] , redOroot pigweed (Amaranthus retroflexus L.), sicklepod (Cassia obtusifolia L.). and velvetleaf (Abutilon theophrasti Medic.) \were grown in growth chambers in all combinations of two temperatures (avg. day/night of 26/19-degrees-C and 30/23- degree^s-C) and two CO2 concentrations (350 and 700 ppm) for 35 d. Leaf area and plant biomass were greater at higher temperaturels, regardless of CO2 level, in all species except quackgrass. Quackgrass (C3) produced its greatest leaf area and biomass nat elevated CO2, whereas johnsongrass (C4) showed little response. Redroot pigweed (C4) and the C3 dicotyledenous species y(soybean, sicklepod, velvetleaf) produced their greatest biomass at high CO2, though effects on leaf area were less consis{tent or absent. In general, when significant CO2 by temperature interactions were found, CO2 responses were smallest at higher temperatures. These differential responses to elevated CO2 concentrations may cause changes in the relative importance of competitive pressure from these weeds.306^3^Tschaplinski,TJ^Norby,RJ^Wullschleger,SD^1993^1^Responses of loblolly-pine seedlings to elevated co2 and fluctuating water-supply^13^13^3^283-296^^^^^Oct^^^^^3447A^3446^Osmotic adjustment of loblolly pine (Pinus taeda L.) seedlings to fluctuating water supply in elevated CO2 was investigated. Seedlings were grown in controlled-environment chambers in either 350 or 700 mul l-1 CO2 with weekly watering fo r four months, after which they were either watered weekly (well- watered treatment) or every two weeks (water-stress trea!tment) for 59 days. Osmotic adjustment was assessed by pressure-volume analysis of shoots and by analysis of soluble carbo"hydrates and free amino acids in roots during the last drying cycle. In well-watered seedlings, elevated CO2 increased the# concentration of soluble sugars in roots by 68%. Water stress reduced the soluble sugar concentration in roots of seedlin$g growing in ambient CO2 to 26% of that in roots of well-watered seedlings. Elevated CO2 mitigated the water stress-induce%d decrease in the concentration of soluble sugars in roots. However, this was probably due, in part, to carbohydrate loadi&ng during the first four months when all seedlings were grown in the presence of a high water supply, rather than to osmot'ic adjustment to water stress. Water stress caused a doubling in the concentration of free primary amino acids in roots, w(hereas elevated CO2 reduced primary amino acid and nitrogen concentrations to 32 and 74%, respectively, of those in roots )of seedlings grown in ambient CO2. There was no indication of large-scale osmotic adjustment to water stress or that elevated CO2 enhanced osmotic adjustment in loblolly pine.p/y!8@GM+307^2^Williams,TG^Colman,B^1993^1^Identification of distinct internal and external isozymes of carbonic-anhydrase in chlorella-saccharophila^8^103^3^943-948^^^^^Nov^^^^^3449-A^3448^External carbonic anhydrase (CA) was detected in whole cells of alkaline-grown Chlorella saccharophila but was supp.ressed by growth at acid pH or growth on elevated levels of CO2. Internal CA activity was measured potentiometrically as a /n increase in activity in cell extracts over that of intact cells. Cells grown under all conditions had equal levels of in,0ternal CA activity. Two isozymes were identified after electrophoretic separation of soluble proteins on cellulose acetate.1 plates. The fast isozyme was found in cells grown under all conditions, whereas the slow isozyme was found only in cells 32grown at alkaline pH. Western blot analysis following sodium dodecyl sulfate-polyacrylamide gel electrophoresis using anti53bodies produced against the periplasmic form of CA from Chlamydomonas reinhardtii revealed a single band at 39 kD, which dA4id not change in intensity between growth conditions and was associated only with proteins eluted from the fast band. The C5slow isozyme was inactivated by incubation of cell extract at 30 degrees C and by incubation in 10 mM dithiothreitol, wherN6eas the internal form was unaffected. These results indicate that external and internal forms of CA differ in structure anPd their activities respond differently to environmental conditions.2244>9I9O9_9g9n9t9{99X8308^1^Muller,J^1993^1^Dry-matter production, co2 exchange, carbohydrate and nitrogen- content of winter-wheat at elevated Yco2 concentration and drought stress^161^171^4^217-235^^^^^Nov^^^^^3451dc:A^3450^Methods of mathematical modelling and simulation are being used to an increasing degree in estimating the effects oe;f rising atmospheric CO2 concentration and changing climatic conditions on agricultural ecosystems. In this context, detaipitrogen content was studied in two winter wheat varieties from shooting to milk ripeness. Elevated CO2 concentration leads? to a compensation of drought stress and at optimal water supply to an increase of vegetative dry matter and of yield to t@he fourfold value. This effects were caused by enhanced growth of secondary tillers which were reduced in plants cultivateAd at atmospheric CO2 concentration. Analogous effects in the development of ear organs were influenced additionally by comBpetitive interactions between the developing organs. The content and the mass of ethanol soluble carbohydrates in leaves aCnd stems were increased after the CO2 treatment and exhausted more completely during the grain filling period after droughDt stress. Plants cultivated from shooting to milk ripeness at elevated CO2 concentration showed a reduced response of net photosynthesis rate to increasing CO2 concentration by comparison with untreated plants.F309^3^Ahmed,FE^Hall,AE^Madore,MA^1993^1^Interactive effects of high-temperature and elevated carbon- dioxide concentration on cowpea [vigna-unguiculata (L) walp]^9^16^7^835-842^^^^^Sep^^^^^3453VVVWvWX]_h_m_z___HA^3452^Limitations in carbohydrate supplies have been implicated as a factor responsible for reproductive failure under heIat stress. Heat stress affects two stages of reproductive development in cowpea [Vigna unguiculata (L.) Walp.], and genotyJpes are available with tolerance and sensitivity to heat during these different stages. The objectives of this study were Kto determine the responses of these cowpea lines to ambient and elevated [CO2], under heat stress and optimal temperature,L and test whether differences in carbohydrate supplies due to genotypes, CO2 enrichment and heat stress are associated witMh differences in sensitivity to heat during reproductive development. Plants were grown in reach-in growth chambers and suNbjected to day/night temperatures of either 33/20 or 33/30- degrees-C, and [CO2] levels of either 350 or 700 mumol mol-1. OUnder intermediate night temperature (33/20-degrees-C), all lines set substantial numbers of pods. Under high night temperPature (33/30-degrees-C) with either ambient or elevated [CO2], one heat-sensitive line produced no flowers and the other sQet no pods, whereas the heat-tolerant line abundantly set pods. High night temperature reduced the overall carbohydrate coRntent of the plants, especially peduncle sugars, and caused decreases in photosynthetic rates. The high pod set of the heaSt-tolerant line, under high night temperature, was associated with higher levels of sugars in peduncles compared with the Theat-sensitive lines. The heat-tolerant line accumulated substantial shoot biomass, exhibited less accumulation of starch Uin leaves, and possibly had less down- regulation of photosynthesis in response to CO2 enrichment and heat stress than theV heat-sensitive lines. Elevated [CO2] resulted in higher overall carbohydrate levels in heat- sensitive lines (starch in lWeaves, stems and peduncles), but it did not increase their heat tolerance with respect to flower production or pod set. He'Xat-induced damage to floral buds and anthers in the sensitive lines was associated with low sugars levels in peduncles, in)Ydicating that heat had greater effects on assimilate demand than on leaf assimilate supply. The heat- tolerant line was th0Ze most responsive genotype to elevated [CO2] with respect to pod production under either high or intermediate temperatures2.{vv5w{{{{{{{{{| | ||&|[|u|||^}~~"(-6<\310^1^Carmi,A^1993^1^Effects of shading and co2 enrichment on photosynthesis and yield of winter grown tomatoes in subtrop>ical regions^79^28^3^455-463^^^^^^^^^^3455dK^A^3454^The effects of exposing winter-grown tomato (Lycopersicon esculentum L.) to various sunlight irradiances and CO2 coM_ncentrations, on dark respiration (R(D)), night respiration (R(N)), net photosynthetic-rate (P(N)), dry matter production R`(DMP), yield earliness and yield amount were studied. Plants were grown in greenhouses under controlled temperatures and eTaxposed to: full (FS) or half (HS) sunlight irradiance in combinafion with atmospheric (A) or enriched (E) concentrations o]bf 300-330 or 1400-1500 g(CO2) m-3, respectively. The P(N) of intact leaves at noontime reached 10.7, 15.2, 5.9 and 9.6 mum^col(CO2) m-2 s-1 in treatments of FSA, FSE, HSA and HSE, respectively. The irradiances on the upper leaf surface during thedd P(N) measurements ranged between 160-190 and 450-550 mumol m-2 s-1 in the HS and FS treatments, respectively. R(D) of leafeves which were kept in darkness following the P(N) measurement arrived at efflux of 2.6, 2.5, 1.4 and 1.4 mumol(CO2) m-2 spf-1 While their R(N) (between 20:00 and 24:00) reached values of 0.9, 1.3, 0.8 and 0.8 mumol(CO2) m-2 s-1 in treatments of rgFSA, FSE, HSA and HSE, respectively. Elevating the CO2 concentration from 300 to 1500 g m-3 increased P(N) by 16, 28, 30 a~hnd 46% under an irradiance of 160 mumol m-2 s-1, and 19, 34, 59 and 44% under irradiance of 320 mumol m-2 s-1 in the FSA, iFSE, HSA and HSE treatments, respectively. Increasing the measurement irradiance from 160 to 320 mumol m-2 s-1 enhanced P(jN) by 69, 78, 23 and 49% in an atmosphere of 300 g m-3 CO2, and by 73, 84, 49 and 47% in an atmosphere of 1500 g m-3 CO2, kin the FSA, FSE, HSA and HSE treatments, respectively. DMP was strongly influenced by the different environmental conditiolns and the total dry matter accumulation in the shoot per plant during 145 d reached 580, 347, 398 and 235 g in the FSA, FmSE, HSA and 14SE treatments, respectively. CO2 enrichment promoted early yield under both full and partial sunlight irradinance. The HSE treatment led to earlier yield harvesting than the FSA and HSA treatments. The yield of the seven first trusoses reached 6.8, 4.6, 5.7 and 3.2 kg per plant in the FSA, FSE, HSA and HSE treatments, respectively. Some increase in frupit fresh matter and diameter of fruits was detected in the CO2-enriched treatments as compared to the non-enriched ones. Tqhus the combination of moderate shading and CO2 enrichment might provide a more productive option for winter-grown tomatoers in regions of subtropical climate, even in the winter, than the conventional management of aerated greenhouses without CO2 enrichment which are exposed to full sunlight.t311^3^Elkohen,A^Venet,L^Mousseau,M^1993^1^Growth and photosynthesis of 2 deciduous forest species at elevated carbon-dioxide^43^7^4^480-486^^^^^Aug^^^^^3457vA^3456^1. Two-year-old sweet chestnut (Castanea sativa) and beech (Fagus sylvatica) seedlings were grown in large pots of wforest soil, at ambient (+/-350 mul l-1) and double (700 mul l-1) atmospheric CO2 Concentration in constantly ventilated.mxini- green-houses during an entire growing season. 2. CO2 enrichment caused very different changes in these two temperate ydeciduous species. A 20% dry weight enhancement was obtained for sweet chestnut, and a 60% enhancement in beech. This greazter effect of elevated CO2 in beech was the result of a significant increase of net photosynthesis of the seedlings occurr{ing during the whole season. However, in sweet chestnut, this increase in photosynthesis lasted only a few weeks and then "|an acclimation process took place. 3. No effect of increased CO2 could be found on sweet chestnut leaf area or leaf number$}, while a significant effect was found with beech, in which total leaf area per plant increased, owing to a greater number:~ of growth flushes, of progressively larger leaves. 4. The partitioning of the biomass increase due to elevated CO2 was ve<ry different in the two species. All additional dry matter was allocated to the roots in sweet chestnut, while it was partJitioned equally amongst all organs of the beech seedling. 5. The reactions to elevated CO2 of different tree species is diKscussed in relation to their specific growth strategy.dR312^3^Griffin,KL^Thomas,RB^Strain,BR^1993^1^Effects of nitrogen supply and elevated carbon-dioxide on construction cost inT leaves of pinus-taeda (L) seedlings^2^95^4^575-580^^^^^Oct^^^^^3459aA^3458^Seedlings of loblolly pine (Pinus taeda L.) were grown under varying conditions of soil nitrogen and atmospheric cadrbon dioxide availability to investigate the interactive effects of these resources on the energetic requirements for leafk growth. Increasing the ambient CO2 partial pressure from 35 to 65 Pa increased seedling growth only when soil nitrogen wams high. Biomass increased by 55% and photosynthesis increased by 13% after 100 days of CO2 enrichment. Leaves from seedlinvgs grown in high soil nitrogen were 7.0% more expensive on a g glucose g-1 dry mass basis to produce than those grown in lxow nitrogen, while elevated CO2 decreased leaf cost by 3.5%. Nitrogen and CO2 availability had an interactive effect on leaf construction cost expressed on an area basis, reflecting source-sink interactions. When both resources were abundant, leaf construction cost on an area basis was relatively high (81.8 +/- 3.0 g glucose m-2) compared to leaves from high nitrogen, low CO2 seedlings (56.3 +/- 3.0 g glucose m-2) and low nitrogen, low CO2 seedlings (67.1 +/- 2.7 g glucose m-2). Leaf construction cost appears to respond to alterations in the utilization of photoassimilates mediated by resource availability.!0PSTYz pH$)=ELSXan313^3^Gunderson,CA^Norby,RJ^Wullschleger,SD^1993^1^Foliar gas-exchange responses of 2 deciduous hardwoods during 3 years of growth in elevated co2 - no loss of photosynthetic enhancement^9^16^7^797-807^^^^^Sep^^^^^3461tA^3460^Responses of photosynthesis and stomatal conductance were monitored throughout a 3-year field exposure of Liriodendron tulipifera (yellow-poplar) and Quercus alba (white oak) to elevated concentrations of atmospheric CO2. Exposure to atmospheres enriched with +150 and +300 mumol mol-1 CO2 increased net photosynthesis by 12-144% over the course of the study. Net photosynthesis was consistently higher at +300 than at +150 mumol mol-1 CO2. The effect Of CO2 enrichment on stomatal conductance was limited, but instantaneous leaf-level water use efficiency increased significantly. No decrease in the responsiveness of photosynthesis to CO2 enrichment over time was detected, and the responses were consistent throughout the canopy and across successive growth flushes and seasons. The relationships between internal CO2 concentration and photosynthesis (e.g. photosynthetic capacity and carboxylation efficiency) were not altered by growth at elevated concentrations of CO2. No alteration in the timing of leaf senescence or abscission was detected, suggesting that the seasonal duration of effective gas-exchange was unaffected by CO2 treatment. These results are consistent with data previously reported for these species in controlled-environment studies, and suggest that leaf-level photosynthesis does not down-regulate in these species as a result of acclimation to CO2 enrichment in the field. This sustained enhancement of photosynthesis provides the opportunity for increased growth and carbon storage by trees as the atmospheric concentration of CO2 rises, but many additional factors interact in determining whole-plant and forest responses to global change.314^2^Kostkarick,R^Manning,WJ^1993^1^Radish (raphanus-sativus L) - a model for studying plant- responses to air-pollutants and other environmental stresses^35^82^2^107-138^^^^^^^^^^3463 A^3462^The use of Raphanus sativus L. as a model crop for studies on plant response to environmental stresses is reviewed  with emphasis on the effects of different atmospheric pollutants (O3, SO2, NO2, acidic precipitation) and their combinations. Responses to temperature, light supply, water stress, and atmospheric CO2 are also studied and discussed. In addition, the references reviewed are evaluated in terms of their experimental protocols on growth conditions and recommendations f%or optimal ranges of environmental and cultural variables, i.e. light, temperature, nutrient supply are given. Its distinc't pattern of biomass partitioning, the small dimensions along with short and easy culture make radish an excellent experim/ental plant. The fleshy below-ground storage organ, formed by the hypocotyl and upper radicle, acts as the major sink duri1ng vegetative development. Abundant assimilate supply due to elevated levels of CO2 along with high irradiation frequently7 promote hypocotyl growth more than shoot growth, whereas under conditions of stress shoot growth is maintained at the exp9ense of the hypocotyl. This makes the hypocotyl:shoot ratio of radish a very sensitive and suitable indicator for various @environmental stresses. Potential weaknesses and short- comings of radish in its role as a model crop, particularly the hiBgh variability of injury and growth responses, are discussed along with possible solutions. Future research needs are deriDved from the summarized results presented and from some disparities among findings within the literature reviewed.E315^3^Luxmoore,RJ^Wullschleger,SD^Hanson,PJ^1993^1^Forest responses to co2 enrichment and climate warming^94^70^1-4^309-32O3^^^^^Oct^^^^^3465@4 Plain Text CJOJQJ R   M +QA^3464^Two of the major uncertainties in forecasting future terrestrial sources and SinkS Of CO2 are the CO2-enhanced growSth response of forests and soil warming effects on net CO2 efflux from forests. Carbon dioxide enrichment of tree seedling[s over time periods less than 1 yr has generally resulted in enhanced rates of photosynthesis, decreased respiration, and ]increased growth, with minor increases in leaf area and small changes in C allocation. Exposure of woody species to elevat_ed CO2 over several years has shown that high rates of photosynthesis may be sustained, but net C accumulation may not necgessarily increase if CO2 release from soil respiration increases. The impact of the 25% rise in atmospheric CO2 with indusitrialization has been examined in tree ring chronologies from a range of species and locations. In contrast to the seedlintg tree results, there is no convincing evidence for CO2-enhanced stem growth of mature trees during the last several decadves. However, if mature trees show a preferential root growth response to CO2 enrichment, the gain in root mass for an oak-xhickory forest in eastern Tennessee is estimated to be only 9% over the last 40 years. Root data bases are inadequate for detecting such an effect. A very small shift in ecosystem nutrients from soil to vegetation could support CO2-enhanced growth. Climate warming and the accompanying increase in mean soil temperature could have a greater effect than CO2 enrichment on terrestrial sources and sinks Of CO2. Soil respiration and N mineralization have been shown to increase with soil temperature. If plant growth increases with increased N availability, and more C is fixed in growth than is released by soil respiration, then a negative feedback on climate warming will occur. If warming results in a net increase in CO2 efflux from forests, then a positive feedback will follow. A 2 to 4-degrees-C increase in soil temperature could increase CO2 efflux from soil by 15 to 32% in eastern deciduous forests. Quantifying C budget responses of forests to future global change scenarios will be speculative until mature tree responses to CO2 enrichment and the effects of temperature on terrestrial sources and sinks of CO2 can be determined.IXdv{(.FNX`fn316^6^McGuire,AD^Joyce,LA^Kicklighter,DW^Melillo,JM^Esser,G^Vorosmarty,CJ^1993^1^Productivity response of climax temperate forests to elevated- temperature and carbon-dioxide - a north-american comparison between 2 global-models^50^24^4^287-310^^^^^Aug^^^^^3467&3pt LY!zA^3466^We assess the appropriateness of using regression- and process- based approaches for predicting biogeochemical responses of ecosystems to global change. We applied a regression-based model, the Osnabruck Model (OBM), and a process-based model, the Terrestrial Ecosystem Model (TEM), to the historical range of temperate forests in North America in a factorial experiment with three levels of temperature (+0-degrees-C, +2-degrees-C, and +5-degrees-C) and two levels Of CO2 (350 ppmv and 700 ppmv) at a spatial resolution of 0.5-degrees latitude by 0.5-degrees longitude. For contemporary climate (+0-degrees-C, 3 50 ppmv), OBM and TEM estimate the total net primary productivity (NPP) for temperate forests in North America to be 2.250 and 2.602 x 10(15) g C . yr-1, respectively. Although the continental predictions for contemporary climate are similar, the responses of NPP to altered changes qualitatively differ; at +0-degrees-C and 700 PPMV CO2, OBM and TEM predict median increases in NPP of 12.5% and 2.5%, respectively. The response of NPP to elevated temperature agrees most betwee n the models in northern areas of moist temperate forest, but disagrees in southern areas and in regions of dry temperate forest. In all regions, the response to CO2 is qualitatively different between the models. These differences occur, in part, because TEM includes known feedbacks between temperature and ecosystem processes that affect N availability, photosynthesis, respiration, and soil moisture. Also, it may not be appropriate to extrapolate regression-based models for climatic *conditions that are not now experienced by ecosystems. The results of this study suggest that the process-based approach i,s able to progress beyond the limitations of the regression-based approach for predicting biogeochemical responses to glob7al change.D9317^5^Miglietta,F^Raschi,A^Bettarini,I^Resti,R^Selvi,F^1993^1^Natural co2 springs in italy - a resource for examining longD- term response of vegetation to rising atmospheric co2 concentrations^9^16^7^873-878^^^^^Sep^^^^^3469Times NFA^3468^It is estimated that more than 100 geothermal CO2 springs exist in central-western Italy. Eight springs were selectRed in which the atmospheric CO2 concentrations were consistently observed to be above the current atmospheric average of 3S54 mumol mol-1. CO2 concentration measurements at some of the springs are reported. The springs are described, and their meajor topographic and vegetational features are reported. Preliminary observations made on natural vegetation growing aroungd the gas vents are then illustrated. An azonal pattern of vegetation distribution occurs around every CO2 spring regardlekss of soil type and phytoclimatic areas. This is composed of pioneer populations of a Northern Eurasiatic species (Agrostims canina L.) which is often associated with Scirpus lacustris L. The potential of these sites for studying the long-term rzesponse of vegetation to rising atmospheric CO2 concentrations is discussed.ss Normal.dot{318^4^Miglietta,F^Raschi,A^Resti,R^Badiani,M^1993^1^Growth and onto-morphogenesis of soybean (glycine-max merril) in an open, naturally co2-enriched environment^9^16^8^909-918^^^^^Nov^^^^^3471A^3470^Springs emitting carbon dioxide are frequent in Central Italy and provide a way of testing the response of plants to CO2 enrichment under natural conditions. Results of a CO2 enrichment experiment on soybean at a CO2 spring (Solfatara) are presented. The experimental site is characterized by significant anomalies in atmospheric CO2 concentration produced by a large number of vents emitting almost pure CO2 (93%) plus small amounts of hydrogen sulphide, methane, nitrogen and oxygen. Within the gas vent area, plants were grown at three sub-areas whose mean CO2 concentrations during daytime were 350, 652 and 2370 mumol mol-1, respectively. Weekly harvests were made to measure biomass growth, leaf area and ontogenetic development. Biomass growth rate and seed yield were enhanced by elevated CO2. In particular, onto-morphogenetic development was affected by elevated CO2 with high levels of CO2 increasing the total number of main stem leaf nodes and the area of the main stem trifoliolate leaves. Biochemical analysis of plant tissue suggested that there was no effect of the small amounts of H2S on the response to CO2 enrichment. Non-protein sulphydryl compounds did not accumulate in leaf tissues and the overall capacity of leaf extracts to oxidize exogenously added NADH was not decreased. The limitations and advantages of experimenting with crop plants at elevated CO2 in the open and in the proximity of carbon dioxide springs are discussed.319^4^Morse,SR^Wayne,P^Miao,SL^Bazzaz,FA^1993^1^Elevated co2 and drought alter tissue water relations of birch (betula-populifolia marsh) seedlings^2^95^4^599-602^^^^^Oct^^^^^3473A^3472^The effect of increasing atmospheric CO2 concentrations on tissue water relations was examined in Betula populifolia, a common pioneer tree species of the northeastern U.S. deciduous forests. Components of tissue water relations were estimated from pressure volume curves of tree seedlings grown in either ambient (350 mul l-1) or elevated CO2 (700 mul l-1), and both mesic and xeric water regimes. Both CO2 and water treatment had significant effects on osmotic potential at full hydration, apoplasmic fractions, and tissue elastic moduli. Under xeric conditions and ambient CO2 concentrations, plants showed a decrease in osmotic potentials of 0.15 MPa and an increase in tissue elastic moduli at full hydration of 1.5 MPa. The decrease in elasticity may enable plants to improve the soil- plant water potential gradient given a small change in  water content, while lower osmotic potentials shift the zero turgor loss point to lower water potentials. Under elevated CO2, Plants in xeric conditions had osmotic potentials 0.2 MPa lower than mesic plants and decreased elastic moduli at full hydration. The increase in tissue elasticity at elevated CO2 enabled the xeric plants to maintain positive turgor pressures at lower water potentials and tissue water contents. Surprisingly, the elevated CO2 plants under mesic conditions had t"he most inelastic tissues. We propose that this inelasticity may enable plants to generate a favorable water potential gra$dient from the soil to the plant despite the low stomatal conductances observed under elevated CO2 conditions./320^1^Overdieck,D^1993^1^Effects of atmospheric co2 enrichment on co2 exchange-rates of beech stands in small model-ecosys1tems^94^70^1-4^259-277^^^^^Oct^^^^^3475՜.+,D hp Ddling dry weight decreased with high UV treatment but was unaffected by CO2 enrichment. High UV treatment also shifted bioFmass partitioning in favor of leaf production. Both CO2 and UV treatments decreased the dark respiration rate and light coTmpensation point. High UV light inhibited photosynthesis at 350 but not at 750 mumol mol-1 CO2 due to a UV induced increasVA^3474^CO2 enrichment experiments were performed during two vegetation periods on young beech stands in four closed mini-g`reenhouses. The houses were climatized according to the outside microclimate (+/- 0,5-degrees-C, +/- 15 % rel. air humiditby, wind speed approximately to outside in the range of 0.5 - 2.5 m s-1, max. 17 % PAR reduction). The model ecosystems - cjonsisting of 36 young beech (2.5 yr-old) in a soil block of 0.38 m3 and an air volume of 0.64 m3 - were exposed to CO2 conlcentrations of the unchanged ambient air (350 +/- 34 ppmv, control) and of 700 ppmv (698 +/- 10 ppmv). Plant growth parameyters were measured non distructively and at the end of the 1st season samples were taken for weighing the phytomass. CO2 g{as exchange of the stands taken as a whole were continuously measured with two entire mini-greenhouses and, in addition, a compact mini-cuvette system (CMS 400, Walz) was used for measuring dark respiration and CO2 net assimilation rates of sin gle leaves in both stands. Under the influence of the additional CO2 supply stem diameter (2 cm above the first lateral ro ots) was increased by 13.5 %, stem height by 27.4 %, and the number of leaves/tree by 33 % at the end of the 2nd season. T he number of buds was not significantly different and the effect on mean area per leaf was insignificant. Leaf area index  was by 1.4 units greater. All dry weights of the main organs were increased after the 1st season: leaf 60 %, stem 34 %, bud 54 %. Roots < 2 mm phi weighed 1.5-fold more and roots > 2 mm phi 1.7-fold more under elevated CO2. CO2 gas exchange of two systems was measured. Whole system CO2 losses during night as well as photosynthetic CO2 gains during days were greater at 700 ppmv than in the control system. However, if one balances CO2 gains with CO2 losses over a period of five days in August both model-ecosystems taken as a whole were sinks for CO2. During this selected time period of 5 days at the peak of the season the beech stand at 350 ppmv was the greater sink. At 350 ppmv CO2 (control) the average leaf respiration for 20-degrees- C amounted to 0.31 +/- 0.18 and at 700 ppmv to 0.57 +/- 0.42 mumol CO2 m-2 s-1 (n = 35/40, t = 3.48, alpha < 0.05), and correlated positively with leaf temperature. At light saturation the mean net assimilation rate was 4.48 mumol m-2 (leaf area) s-1 in the control and 6.21 mumol m-2 s-1 at the high CO2 concentration corresponding with an enhancement factor of 1.39 for the selected time period. Results from the whole stand and from single leaf measurements are compared by means of mathematical modelling procedures in order to quantify CO2 enrichment effects on beech model ecosystems.321^1^Owensby,CE^1993^1^Potential impacts of elevated co2 and aboveground and belowground litter quality of a tallgrass prairie^94^70^1-4^413-424^^^^^Oct^^^^^3477A^3476^Increased atmospheric CO2 will likely impact the productivity of arid and semiarid ecosystems through increased C, N, and water use efficiencies at the individual plant level. Tallgrass prairie has had increased above- and belowground biomass production under elevated CO2, primarily due to increased water use efficiency. There is an apparent decreased N requirement to sustain increased productivity in CO2-enriched tallgrass prairie, and C:N ratios of plant litter above and bel"ow ground have increased. The tallgrass prairie ecosystem level response to elevated CO2 on the C cycle could potentially #increase C storage. Reduced litter quality associated with elevated CO2 in tallgrass prairie has the potential to reduce d0 ecomposition rates, and ruminant digestion rate of plant biomass apparently has been lowered. Reduced intake by ruminants 2!would shunt more of the plant biomass directly into the detrital food chain, thereby slowing decomposition further. The poBtential impact is for increased C to be retained as soil organic matter in the tallgrass prairie.D#322^3^Owensby,CE^Coyne,PI^Auen,LM^1993^1^Nitrogen and phosphorus dynamics of a tallgrass prairie ecosystem exposed to elevQated carbon-dioxide^9^16^7^843-850^^^^^Sep^^^^^3479S%A^3478^A tallgrass prairie ecosystem was exposed to ambient and twice- ambient CO2 ConCentrations in open-top chambers andd& compared to unchambered ambient CO2 during the entire growing season from 1989 through 1991. Dominant species were Andropf'ogon gerardii (C4), A. scoparius (C4), Sorghastrum nutans (C4) and Poa pratensis (C3). Nitrogen and phosphorus concentratix(ons in A. gerardii, P. pratensis and dicotyledonous herbs above ground biomass were estimated by periodic sampling throughz)out the growing season in 1989 and 1990. In 1991, N and P concentrations in peak biomass were estimated by an early August* harvest. N and P concentrations in root production as a function of treatment were estimated using root ingrowth bags tha+t remained in place throughout the growing season. Total N and P in above- and belowground biomass were calculated as prod,ucts of concentration and peak biomass by species groups. N concentration in A. gerardii and dicotyledonous herb abovegrou-nd biomass was lower and total N higher in elevated CO2 plots than in ambient CO2 PlOts. N concentration in P. pratensis a.boveground biomass was lower in elevated CO2 plots than in ambient, but total N did not differ among treatments in 2 out o/f 3 years. In 1990, N concentration in root ingrowth bag biomass was lower and total N greater in elevated CO2 than in amb0ient CO2 plots. Root ingrowth bag biomass N concentration did not differ among treatments in 1991, but total N was greater1 in elevated CO2 plots than in ambient CO2 Plots. P concentration was lower under elevated CO2 compared to ambient in 19892, but did not differ substantially among treatments in 1990 or 1991. In all years, total P in aboveground A. gerardii and 3root ingrowth bag biomass was greater under elevated CO2 than ambient. P concentration and total P in P. pratensis was similar among treatments.5323^2^Penuelas,J^Matamala,R^1993^1^Variations in the mineral-composition of herbarium plant- species collected during the last 3 centuries^78^44^266^1523-1525^^^^^Sep^^^^^3481m qqRqTqssftltttuuu"uvv7A^3480^Mineral content (dry weight basis) was determined for herbarium specimens of 12 C3 plants (trees, shrubs and herbs)8 collected during the last 250 years in N.E. Spain. Present values of Al, Ca, Cu, Sr, Fe, P, Mg, Mn, K, Na, S, and Zn were9 always lower than in any other period of the last three centuries. Only one C4 plant was analysed. It presented a similar: pattern to the C3 plants. These results are in accordance with experimental results that have shown that the mineral cont;ent of plants grown in elevated CO2 is generally lowered. Increased atmospheric CO2 and other anthropogenic environmental changes are suggested as possible causes of the changes in mineral content. Q[ft=324^4^Smernoff,DT^Gale,J^Macler,BA^Reuveni,J^1993^1^Inhibition of photosynthesis in duckweed by elevated co2 concentration$ is rapid and is not offset by a temperature- induced increase in metabolic-rate^79^28^1^17-28^^^^^^^^^^3483p¼̼&?A^3482^The rates of net photosynthesis (P(N)), respiration and growth of Lemna gibba L. were measured as functions of time1@ across ranges of temperature, irradiance and carbon dioxide concentrations. P(N) on an area basis increased with temperat3Aure up to 30-degrees-C but decreased dramatically with a few hours of exposure to elevated CO2, when reported on a dry mas8Bs basis. Reductions in the apparent quantum efficiency, photosynthetic capacity and the affinity of ribulose- 1,5-bisphosp:Chate carboxylase/oxygenase for CO2 were observed for plants grown at elevated CO2. Starch concentration was not significanFDtly affected by elevated CO2. Although elevated temperature increased metabolic activity, it only partially alleviated theHE inhibition of P(N). L. gibba exhibits a characteristic C3-type response to elevated CO2 and the methodology described is Wuseful for further elucidating the mechanism of photosynthetic acclimation to elevated CO2.jXG325^6^Smith,TM^Cramer,WP^Dixon,RK^Leemans,R^Neilson,RP^Solomon,AM^1993^1^The global terrestrial carbon-cycle^94^70^1-4^19-Z37^^^^^Oct^^^^^3485 @ Q       BL lqsv/3hIA^3484^There is great uncertainty with regard to the future role of the terrestrial biosphere in the global carbon cycle. kJThe uncertainty arises from both an inadequate understanding of current pools and fluxes as well as the potential effects |Kof rising atmospheric concentrations of CO2 on natural ecosystems. Despite these limitations, a number of studies have est~Limated current and future patterns of terrestrial carbon storage. Future estimates focus on the effects of a climate changMe associated with a doubled atmospheric concentration of CO2. Available models for examining the dynamics of terrestrial cNarbon storage and the potential role of forest management and landuse practices on carbon conservation and sequestration are discussed.IIIYJcJ KK3K;KvK~KKKKK#L2LRLaLLLMMQQRRP326^3^Tissue,DT^Thomas,RB^Strain,BR^1993^1^Long-term effects of elevated co2 and nutrients on photosynthesis and rubisco in loblolly-pine seedlings^9^16^7^859-865^^^^^Sep^^^^^3487ZZZZZZL]R]j]s]t]}]]]]]RA^3486^The effects of long-term CO2 enhancement and varying nutrient availability on photosynthesis and ribulose-1,5-bisphSosphate carboxylase/oxygenase (rubisco) were studied on loblolly pine (Pinus taeda L.) seedlings grown in two atmospheric TCO2 partial pressures (35 and 65 Pa) and three nutrient treatments (low N, low P, and high N and P). Measurements taken inU late autumn (November) after 2 years Of CO2 enrichment and nutrient addition showed that photosynthetic rates were higherV for plants grown at elevated CO2 only when they received supplemental N. Total rubisco activity and rubisco content decreWased at elevated CO2, but there was an increase in activation state. At elevated CO2, proportionately less N was found in Xrubisco and more N was found in the light reaction components. These results demonstrate acclimation of photosynthetic proYcesses to elevated CO2 through reallocation of N. Loblolly pine grown in nutrient conditions similar to native soils (low ZN availability) had lower needle N and chlorophyll content, lower total rubisco activity and content, and lower photosynth[etic rates than plants grown at high N and P. This suggests that the magnitude of the photosynthetic response to a future, high-CO2 environment will be dependent on soil fertility in the system.]327^2^Vloedbeld,M^Leemans,R^1993^1^Quantifying feedback processes in the response of the terrestrial carbon-cycle to global change - the modeling approach of image-2^94^70^1-4^615-628^^^^^Oct^^^^^3489$_A^3488^The terrestrial biosphere component of the Integrated Model to Assess the Greenhouse Effect (IMAGE 2) uses changes &`in land cover to compute dynamically the C fluxes between the terrestrial biosphere and the atmosphere. The model explores5a the potential impact of feedback processes incorporated in the model, which are the enhancement of plant growth (CO2 fert7bilization) and a more efficient use of water under increased CO2 concentrations in the atmosphere; the temperature responsDce of photosynthesis and respiration of plants; the temperature and soil water response of decomposition processes; and theFd climate-induced changes in vegetation and agricultural patterns with the consequent changes in land cover. In this paper Xewe discuss the implementation and operation of the different feedback processes in the IMAGE 2 model. Results are shown foZfr each process separately as well as the combined processes. The aim of this paper is to quantify the importance of these cgfeedback processes geographically. The main results are that vegetation shifts due to climatic change and increased water ehuse efficiency, CO2 fertilization decreases net C emissions, while changed decomposition rates strongly increase C emissiorins to the atmosphere. Changes in the global balance between photosynthesis and respiration make little net difference. Wittjh the IPPC business-as-usual scenario the terrestrial biosphere continues to emit C into the atmosphere. This behavior is zgoverned by changes in land-use, caused by a multitude of anthropogenic processes.|l328^2^Bowler,JM^Press,MC^1993^1^Growth-responses of 2 contrasting upland grass species to elevated co2 and nitrogen concentration^84^124^3^515-522^^^^^Jul^^^^^3491nA^3490^Growth parameters of Agrostis capillaris L. and Nardus stricta L. were measured in relation to ambient and elevatedo concentrations of CO2 (340 and 550 mul CO2 l-1, respectively) and at low and high concentrations of nitrogen (0.8 and 3 mpm NH4NO3, respectively). After 60 d of growth A. capillaris had attained approx. four times the total dry weight of N. strqicta in all treatments, which was attributed to the greater leaf area ratio of the former. A. capillaris grown at the low rnitrogen concentration attained 30% of the total dry weight of plants grown at high nitrogen. Over the 60 d period, destrusctive harvests (seven in total) showed the growth of N. stricta to be less sensitive than that of A. capillaris to the contcentration of nitrogen, but in both species growth analysis showed the lower total dry weight at low nitrogen to be attribuutable to lower unit leaf rate. There was a differential response of both species to elevated concentrations of CO2 which vwas nitrogen dependent. A. capillaris grown at elevated CO2 attained a greater total dry weight than at ambient CO2 and thwis response was proportionately greater at low nitrogen (78% increase) than at high nitrogen (58% increase). In contrast, xin N. stricta there was no effect of CO2 concentration on the total dry weight at low nitrogen whilst at high nitrogen playnts grown at elevated CO2 had a greater total dry weight after 48 d of growth. Calculation of the allometric coefficient (zK) relating root growth to shoot growth indicated that the effect of the lower nitrogen concentration was to increase partitioning to the roots while the higher CO2 concentration did not alter partitioning.|329^1^Crush,JR^1993^1^Hydrogen evolution from root-nodules of trifolium-repens and medicago-sativa plants grown under elevated atmospheric co2^167^36^2^177-183^^^^^^^^^^3493~A^3492^Nitrogenase activity and hydrogen (H-2) evolution from nodules of Trifolium repens L. and Medicago sativa L. were m easured on plants grown under 700 or 350 mul/l atmospheric CO2 and day/night temperatures of 18/13-degrees-C or 28/23-degrees-C. Assays were done after 39, 47, and 54 days' exposure to the treatments. In Trifolium, nitrogenase activity/plant wa1s stimulated by elevated CO2 and higher temperatures but in Medicago only temperature had an effect. Hydrogen emission/pla3nt was greater in Trifolium plants grown at 700 mul/l CO2 than in plants at 350 mul/l CO2, but in Medicago, H-2 emission r=ates did not respond to elevated CO2. Elevated CO2 reduced nodule relative efficiency (RE) in 39-day-old Trifolium plants ?growing at 18/13-degrees-C, but not under other conditions. It is concluded that predicted future CO2 concentration will lJead to a greater contribution from legume nitrogen (N) fixation to global H-2 sources. The magnitude of the increase will Lbe influenced by the legume species involved and temperature.[330^4^Diaz,S^Grime,JP^Harris,J^McPherson,E^1993^1^Evidence of a feedback mechanism limiting plant-response to elevated car]bon-dioxide^36^364^6438^616-617^^^^^12 Aug^^^^^3495gA^3494^IN short-term experiments under productive laboratory conditions, native herbaceous plants differ widely in their piotential to achieve higher yields at elevated concentrations of atmospheric carbon dioxide1-8. The most responsive speciesp appear to be large fast-growing perennials of recently disturbed fertile soils7,8. These types of plants are currently inrcreasing in abundance9 but it is not known whether this is an effect of rising carbon dioxide or is due to other factors. ~Doubts concerning the potential of natural vegetation for sustained response to rising carbon dioxide have arisen from experiments on infertile soils, where the stimulus to growth was curtailed by mineral nutrient limitations2,3,10. Here we present evidence that mineral nutrient constraints on the fertilizer effect of elevated carbon dioxide can also occur on fertile soil and in the earliest stages of secondary succession. Our data indicate that there may be a feedback mechanism in which elevated carbon dioxide causes an increase in substrate release into the rhizosphere by non-mycorrhizal plants, leading to mineral nutrient sequestration by the expanded microflora and a consequent nutritional limitation on plant growth.331^2^Idso,SB^Kimball,BA^1993^1^Tree growth in carbon-dioxide enriched air and its implications for global carbon cycling and maximum levels of atmospheric co2^137^7^3^537-555^^^^^Sep^^^^^3497A^3496^In the longest carbon dioxide enrichment experiment ever conducted, well-watered and adequately fertilized sour orange tree seedlings were planted directly into the ground at Phoenix, Arizona, in July 1987 and continuously exposed, from mid-November of that year, to either ambient air or air enriched, with an extra 300 ppmv of CO2 in clear-plastic-wall open-top enclosures. Only 18 months later, the CO2-enriched trees had grown 2.8 times larger than the ambient-treated trees; and they have maintained that productivity differential to the present day. This tremendous growth advantage is due to two major factors: a CO2-induced increase in daytime net photosynthesis and a CO2-induced reduction in nighttime dark respiration. Measurements of these physiological processes in another experiment have shown three Australlian tree species to respond similarly; while an independent study of the atmosphere's seasonal CO2 cycle suggests that all earth's trees, in the mean, probably share this same response. A brief review of the plant science literature outlines how such a large growth response to atmospheric CO2 enrichment might possibly be maintained in light of resource limitations existing in nature. Finally, it is noted that a CO2 ''fertilization effect'' of this magnitude should substantially slow the rate at which anthropogenic carbon dioxide would otherwise accumulate in the atmosphere, possibly putting an acceptable upper limit on the level to which the CO2 content of the air may ultimately rise. 332^1^Johnsen,KH^1993^1^Growth and ecophysiological responses of black spruce seedlings to elevated co2 under varied water* and nutrient additions^155^23^6^1033-1042^^^^^Jun^^^^^3499,A^3498^Two controlled-environment studies examined growth and ecophysiological responses of black spruce (Picea mariana (M<ill.) B.S.P.) seedlings to elevated CO2 under varied water and nutrient additions. Growth analyses were conducted followed> by measurements of gas exchange, xylem pressure potential and foliar N concentrations. Growth under elevated CO2 (700 ppmI) increased final seedling dry weights by 20-48% compared with seedling growth under ambient CO2 (350 ppm). Percent increaKses in seedling dry weight were greater under drought versus well- watered conditions and higher versus lower nutrient addWitions. Seedlings grown under elevated CO2 displayed higher water use efficiency than seedlings grown under ambient CO2. TZhis was apparent based upon instantaneous gas exchange as well as xylem potential pressure measurements. Elevated CO2-indunced stimulation of relative growth rate was greatest shortly after seedling emergence and decreased with increased seedlinpg size. Acclimation of net photosynthesis was observed and was reversible. Analyses using allometric principles indicate n|et photosynthetic acclimation resulted from: (i) growth-induced nutrient dilution; (ii) a decrease in foliar N levels not ~owing to dilution; and (iii) a decrease in net photosynthetic activity. 333^4^Kubo,Y^Tsuji,H^Inaba,A^Nakamura,R^1993^1^Effects of elevated co2 concentrations on the ripening in banana fruit by exogenous C2h4^180^62^2^451-455^^^^^Sep^^^^^3501OPQRSTUVWXYZ[\]^_`A^3500^Green bananas were treated with 0 to 60% CO2 and 1 to 100 PPM C2H4 to study their interaction on the ripening process. 1. The CO2 treatment did not block completely the initiation of ripening of banana by exogenous C2H4. When the concentration of applied C2H4 was kept constant and the CO2 concentration high, the appearance of the yellow pigment in the peel was delayed. 2. The combination of various concentrations of CO2 and C2H4 on the respiratory climacterics in green banana, monitored with an automated microcomputer system, revealed that the onset of the climacteric rise of bananas under any CO2 concentration combined with 1 PPM C2H4 commenced simultaneously with fruits which were kept under air and 1 PPM C2H4. However, the progress of the climacteric rise was slower and the peaks were lower at high CO2 concentration than they were at low CO2 concentrations. With 60% CO2 and 100 PPM C2H4, the fruit color remained green until the end of the gas treatment, in spite of the slow respiratory rise and ripening of the flesh. Our results suggest that the elevated CO2 concentration has no effect on the initiation-time of banana ripening induced.by exogenous C2H4 but lowers the progress rate of ripening.e!334^6^Lawlor,DW^Mitchell,RAC^Franklin,J^Mitchell,VJ^Driscoll,SP^Delgado,E^1993^1^Facility for studying the effects of elevated carbon-dioxide concentration and increased temperature on crops^9^16^5^603-608^^^^^Jun^^^^^3503A^3502^The requirements for the experimental study of the effects of global climate change conditions on plants are outlined. A semi-controlled plant growth facility is described which allows the study of elevated CO2 and temperature, and their interaction on the growth of plants under radiation and temperature conditions similar to the field. During an experiment# on winter wheat (cv. Mercia), which ran from December 1990 through to August 1991, the facility maintained mean daytime C%O2 concentrations of 363 and 692 cm3 m-3 for targets of 350 and 700 cm3 m-3 respectively. Temperatures were set to follow 6outside ambient or outside ambient +4-degrees-C, and hourly means were within 0.5-degrees-C of the target for 92% of the t8ime for target temperatures greater than 6-degrees- C. Total photosynthetically active radiation incident on the crop (solDar radiation supplemented by artifical light with natural photoperiod) was 2% greater than the total measured outside overF the same period.FMicrosoft Word Document MSWordDocWord.Document.89qP335^12^Lawton,JH^Naeem,S^Woodfin,RM^Brown,VK^Gange,A^Godfray,HJC^Heads,PA^Lawler,S^Magda,D^Thomas,CD^Thompson,LJ^Young,S^1R993^1^The ecotron - a controlled environmental facility for the investigation of population and ecosystem processes^190^34g1^1296^181-194^^^^^29 Jul^^^^^3505iA^3504^This paper reports on aspects of the design and philosophy of the Ecotron, an integrated series of 16 controlled enrvironmental chambers at the NERC Centre for Population Biology. The Ecotron serves as an experimental means for analysing tpopulation and community dynamics and ecosystem processes under controlled physical conditions. Within the chambers, terrestrial experimental communities are assembled into foodwebs of desired complexity from a pool of species selected for their preadaptations to the physical conditions of the Ecotron. These species include decomposers (earthworms, snails, microarthropods and microbes), primary producers (16 species of plants), primary consumers (four species of herbivorous arthropods), and secondary consumers (four species of parasitoids). The design of the Ecotron is unique in several aspects with respect to its blend of biology and technology. It supports small, dynamic communities of up to 30 plant and metazoan species, thereby making it among the more biologically complex controlled environmental systems currently in use. Its architecture permits replication and variation of spatial scale in experimental design. Its artificial climate simulates natural environmental conditions within chambers allowing experimental control over light, water, temperature, humidity, and in the near future CO2 and uv-B radiation. Sensors monitor both macro- and micro-environmental conditions of a number of physical factors within the chambers. Preliminary experiments show the Ecotron to be an excellent facility for long-term population and community-level experiments. We discuss the results of one of these early experiments and briefly consider ongoing and future experiments.336^5^Mitchell,RAC^Mitchell,VJ^Driscoll,SP^Franklin,J^Lawlor,DW^1993^1^Effects of increased co2 concentration and temperature on growth and yield of winter-wheat at 2 levels of nitrogen application^9^16^5^521-529^^^^^Jun^^^^^3507A^3506^Winter wheat (Triticum aestivum L., cv. Mercia) was grown in chambers under light and temperature conditions similar to the UK field environment for the 1990/1991 growing season at two levels each of atmospheric CO2 concentration (seasonal means: 361 and 692 mumol mol-1), temperature (tracking ambient and ambient +4-degrees-C) and nitrogen application (equivalent to 87 and 489 kg ha-1 total N applied). Total dry matter productivity through the season, the maximum number of shoots and final ear number were stimulated by CO2 enrichment at both levels of the temperature and N treatments. At high N, there was a CO2-induced stimulation of grain yield (+15%) similar to that for total crop dry mass (+12%), and there was no significant interaction with temperature. This contrasts with other studies, where positive interactions between the effe cts of increases in temperature and CO2 have been found. Temperature had a direct, negative effect on yield at both levels" of the N and CO2 treatments. This could be explained by the temperature-dependent shortening of the phenological stages, 4and therefore, the time available for accumulating resources for grain formation. At high N, there was also a reduction in6 grain set at ambient +4-degrees-C temperature, but the overall negative effect of warmer temperature was greater on the nBumber of grains (-37%) than on yield (-18%), due to a compensating increase in average grain mass. At low N, despite increDasing total crop dry mass and the number of ears, elevated CO2 did not increase grain yield and caused a significant decreSase under ambient temperature conditions. This can be explained in terms of a stimulation of early vegetative growth by COU2 enrichment leading to a reduction in the amount of N available later for the formation and filling of grain.,c337^2^Retuerto,R^Woodward,FI^1993^1^The influences of increased co2 and water-supply on growth, biomass allocation and wateer-use efficiency of sinapis-alba L grown under different wind speeds^2^94^3^415-427^^^^^Jun^^^^^3509mA^3508^We examined how independent and interactive effects of CO2 concentrations, water supply and wind speed affect growtoh rates, biomass partitioning, water use efficiency, diffusive conductance and stomatal density of plants. To test the prediction that wind stress will be ameliorated by increased CO2 and/or by unrestricted water supply we grew Sinapis alba L. plants in controlled chambers under combinations of two levels of CO2 (350 ppmv, 700 ppmv), two water regimes and two wind speeds (0.3 ms-1, 3.7 ms-1). We harvested at ten different dates over a period of 60 days. A growth analysis was carried out to evaluate treatment effects on plant responses. Plants grown both in increased CO2 and in low wind conditions had significantly greater stem length, leaf area and dry weights of plant parts. Water supply significantly affected stem diameter, root weight and leaf area. CO2 enrichment significantly increased the rate of biomass accumulation and the relative ratio of biomass increase to leaf area expansion. High wind speed significantly reduced plant growth rates and the rate of leaf area expansion was reduced more than the rate of biomass accumulation. Regression analysis showed significant CO2 effects on the proportion of leaf and stem dry weight to total dry weight. A marked plant-age effect was dependent on water supply, wind speed and CO2 concentration. A reduced water supply significantly decreased the stomatal conductance, and water use efficiency significantly increased with a limited water supply, low wind and increased CO2. We found significant CO2 x wind effects for water diffusion resistance, adaxial number of stomata and water use efficiencies and significant wind x water effect for water use efficiency. In conclusion, wind stress was ameliorated by growing in unrestricted water but not by growing in increased CO2.er mite damage of the 990 and 280-mu-mol mol-1 treatments reduced yields. These data confi338^3^Reuveni,J^Gale,J^Mayer,AM^1993^1^Reduction of respiration by high ambient co2 and the resulting error in measurements of respiration made with o2 electrodes^52^72^2^129-131^^^^^Augglaciation. BP 875-883 PG 9 JI Agron. J. PY 1991 PD SEP-O339^2^Stewart,JD^Hoddinott,J^1993^1^Photosynthetic acclimation to elevated atmospheric carbon- dioxide and uv irradiation in pinus-banksiana^37^88^3^493-500^^^^^Jul^^^^^3512CATIONS SN 1051-0761 C1 EXETER UNIV, DEPT BIOL SCI, EXETER EX4 4PS, ENA^3511^Pinus banksiana seedlings were grown for 9 months in enclosures in greenhouses at CO2 concentrations of 350 or 750 mumol mol-1 with either low (0.005 to 0.3 W M-2) or high (0.25 to 0.90 W M- 2) ultraviolet-B (UV-B) irradiances. Total see A^3513^Elevated atmospheric carbon dioxide partial pressures have been shown to have variable direct and indirect effects on plant respiration rates. In this study, growth, leaf respiration, and leaf nitrogen and carbohydrate partitioning were measured in Gossypium hirsutum L. grown in 35 and 65Pa CO2 for 30 d. Growth and maintenance coefficients of leaf respirati on were estimated using gas exchange techniques both at night and during the day. Elevated CO2 stimulated biomass producti on (107%) and net photosynthetic rates (35-50%). Total day-time respiration (R(d)) was not significantly affected by growt h CO2 partial pressure. However, night respiration (R(n)) of leaves grown in 65 Pa CO2 Was significantly greater than that , of plants grown in 35 Pa CO2. Correlation of R(d) and R(n) with leaf expansion rates indicated that plants in both CO2 tr . eatments had equivalent growth respiration coefficients but maintenance respiration was significantly greater in elevated 6 CO2. Increased maintenance coefficients in elevated CO2 appeared to be related to increased starch accumulation rather tha 8n to changes in leaf nitrogen.h is less susceptible to changes in mineralization rates. It is concluded that short-term r C 341^3^Thompson,GB^Brown,JKM^Woodward,FI^1993^1^The effects of host carbon-dioxide, nitrogen and water-supply on the infect Eion of wheat by powdery mildew and aphids^9^16^6^687-694^^^^^Aug^^^^^3516ant species and soil types will alter in respons UA^3515^In two experiments, winter wheat (Triticum aestivum cv. Cerco) was grown in 350 (ambient) and 700 mumol mol-1 (elev Wated) atmospheric CO2 concentrations. In the first experiment, plants were grown at five levels of nitrogen fertilization, c and in the second experiment, plants were grown at three levels of water supply. All plants were infected with powdery mi eldew, caused by the fungus Erysiphe graminis. Plants grown in elevated atmospheric CO2 concentrations had significantly re oduced % shoot nitrogen contents and significantly increased % shoot water contents. At elevated atmospheric CO2 concentrat qions, where plant nitrogen content was significantly reduced, the severity of mildew infection was significantly reduced, |and where host water content was significantly increased, the severity of mildew infection was significantly increased. In ~ a moderate water supply treatment, the plants grown in elevated atmospheric CO2 concentrations had significantly reduced nitrogen contents (9.9%) and significantly increased water content (4%), the amount of mildew infection was unchanged. The severity of mildew infection appeared to be more sensitive to host water content than to host nitrogen content.500 ppm a 342^2^Ueda,Y^Bai,JH^1993^1^Effect of short-term exposure of elevated co2 on flesh firmness and ester production of strawbe rry^180^62^2^457-464^^^^^Sep^^^^^3518 light was used, except in the treatment with constant 600 ppm where 600 ppm was als A^3517^Strawberry fruits (Fragaria X ananasa cv. Hokowase) were treated with 20% CO2 for 12 to 48 hr at 1-degrees-C and th en stored at the same temperature for an additional 24 to 48 hr; subsequently they were transferred to 20-degrees-C and he ld for 8 hours. 1. Berries exposed to CO2, including those stored for 8 hr at 20-degrees-C were firmer than the control be rries exposed to air. 2. The CO2 treatment had a little effect on the evolution of methyl acetate and methyl butyrate, the  predominant volatiles. However, the evolution of ethyl acetate and ethyl butyrate, the minor volatiles, was increased sha rply by the CO2 treatment. These changes in the concentration of volatiles gave the berries an unnatural aroma. 3. In berr  ies given the same CO2 treatment for 24 hr but stored longer period at 1-degrees-C, the abnormal aroma formation persisted for at least 5 days. MJ TI TRACKING STOMATAL DENSITIES THROUGH A GLACIAL CYCLE - THEIR SIGNIFICANCE FOR PREDICTING THE R "343^4^Volin,JC^Tjoelker,MG^Oleksyn,J^Reich,PB^1993^1^Light environment alters response to ozone stress in seedlings of ace r-saccharum marsh and hybrid populus L .2. Diagnostic gas-exchange and leaf chemistry^84^124^4^637-646^^^^^Aug^^^^^3520UR!$A^3519^Diagnostic gas exchange measurements and foliar chemical assays were conducted on hybrid poplar (Populus tristis Fi!%sch. x P. balsamifera L. cv. Tristis) and sugar maple (Acer saccharum Marsh.) seedlings grown under contrasting light and !&ozone treatments. Seedlings were grown in low irradiance (c. 2.5 mol m-2 d-1) and six-fold greater irradiance (c. 16.6 mol!' m-2 d-1) in combination with low (< 10 nl l-1) and elevated (99-115 nl l-1) ozone. Analysis of light response curves show!((ed ozone- induced reductions in photosynthetic capacity and quantum yield for unshaded poplar and shaded sugar maple, but !*)not the contrasting light treatments. Photosynthesis at saturating CO2 concentrations was decreased in the elevated ozone !;*treatment in both the unshaded and shaded poplar and in shaded sugar maple. Poplar had significant reductions in chlorophy!<+ll concentration due to ozone exposure in both unshaded and shaded treatments. Older leaves of unshaded poplar plants had !F,significantly greater reductions in chlorophyll levels due to ozone than older leaves of shaded plants. In maple, only sha!H-de-grown leaves had significant decreases in chlorophyll concentration due to ozone exposure. The diagnostic gas exchange !T.measurements in conjunction with chlorophyll measurements indicate that in hybrid poplar, unshaded leaves may be more sens!U/itive to ozone than shade leaves, while in sugar maple, shade leaves are more sensitive to ozone. For hybrid poplar a decr!h0ease in photosynthetic capacity, quantum yield and chlorophyll concentration in the unshaded, moderately high light enviro!j1nment due to elevated ozone is consistent with prior studies. The results indicating that sugar maple seedlings may be mor!w2e detrimentally affected by elevated ozone in the lower light environment may have serious implications for this and other!y shade-adapted species with respect to their performance in an understorey environment. RESPONSES; THERMOTOLERANCE; ENRIC!4344^6^Zak,DR^Pregitzer,KS^Curtis,PS^Teeri,JA^Fogel,R^Randlett,DL^1993^1^Elevated atmospheric co2 and feedback between carb!on and nitrogen cycles^206^151^1^105-117^^^^^Apr^^^^^3522d by rising levels of CO2 and other greenhouse gases could also !6A^3521^We tested a conceptual model describing the influence of elevated atmospheric CO2 on plant production, soil microor!7ganisms, and the cycling of C and N in the plant-soil system. Our model is based on the observation that in nutrient- poor!8 soils. plants (C3) grown in an elevated CO2 atmosphere often increase production and allocation to belowground structures!9. We predicted that greater belowground C inputs at elevated CO, should elicit an increase in soil microbial biomass and i!:ncreased rates of organic matter turnover and nitrogen availability. We measured photosynthesis, biomass production, and C!; allocation of Populus grandidentata Michx. grown in nutrient-poor soil for one field season at ambient and twice-ambient !<(i.e., elevated) atmospheric CO2 concentrations. Plants were grown in a sandy subsurface soil i) at ambient CO2 with no op!=en top chamber, ii) at ambient CO2 in an open top chamber, and iii) at twice-ambient CO2 in an open top chamber. Plants we!>re fertilized with 4.5 g N m 2 over a 47 d period midway through the growing season. Following 152 d of growth, we quantif!?ied microbial biomass and the availabilities of C and N in rhizosphere and bulk soil. We tested for a significant CO2 effe!@ct on plant growth and soil C and N dynamics by comparing the means of the chambered ambient and chambered elevated CO2 tr!Aeatments. Rates of photosynthesis in plants grown at elevated CO2 were significantly greater than those measured under amb!Bient conditions. The number of roots, root length, and root length increment were also substantially greater at elevated C!CO2. Total and belowground biomass were significantly greater at elevated CO2. Under N-limited conditions, plants allocated!D 50-70% of their biomass to roots. Labile C in the rhizosphere of elevated-grown plants was significantly greater than tha"Et measured in the ambient treatments; there were no significant differences between labile C pools in the bulk soil of amb"Fient and elevated-grown plants. Microbial biomass C was significantly greater in the rhizosphere and bulk soil of plants g" Grown at elevated CO2 compared to that in the ambient treatment. Moreover, a short-term laboratory assay of N mineralizatio"Hn indicated that N availability was significantly greater in the bulk soil of the elevated-grown plants. Our results sugge"Ist that elevated atmospheric CO2 concentrations can have a positive feedback effect on soil C and N dynamics producing gre"Jater N availability. Experiments conducted for longer periods of time will be necessary to test the potential for negative" feedback due to altered leaf litter chemistry.ns, respectively. The litter was sterilized and inoculated with microflor""L345^2^Ziska,LH^Bunce,JA^1993^1^The influence of elevated co2 and temperature on seed- germination and emergence from soil^"/207^34^2^147-157^^^^^Aug^^^^^3524measured and the litter was leached with demineralized H2O. The following analyses were"1NA^3523^Seed of six crop species, alfalfa, Medicago sativa L. cv. 'Arc', soybean, Glycine max L. (Merrill) cv. 'Williams', "9Omaize, Zea mays L. cv. SS 885, pea, Pisum sativum L. cv. 'Maestro', sunflower, Helianthus annuus L. cv. 'Mammoth', and pum":Ppkin Cucurbita pepo L. cv. 'Big Max' and four weedy species, Amaranthus hypochondriacus L., Amaranthus hybridus L., Chenop"BQodium album L. and Abutilon theophrasti, were grown at two different CO2 concentrations of 350 mul l-1 (ambient) and 700 m"DRul l-1 (elevated) in controlled-environment chambers to determine the effect of elevated CO2 on germination and emergence."FS Doubling the CO2 concentration resulted in an increase in the rate and final percentage of germination, for M. sativa, A."LT hybridus and C album. In a separate field experiment (silt-loam soil), elevated CO2 resulted in a significant increase in"NU the total number of weed seedlings present 3 weeks after tilling. In a second set of experiments using controlled-environ"cVment chambers, the interaction between increased temperature and CO2 was examined in seven of the species used previously."fW No significant interaction was observed between CO2 and temperature on the germination response. Overall, this investigat"sXion suggests that as CO2 increases, differential changes in germination and/or emergence between crops and weeds could occ"uur.s. BP 54-64 PG 11 JI Oikos PY 1991 PD MAY VL 61 IS 1 GA FR485 J9 OIKOS ER PT J AU EAMUS, D MURRAY, M TI PHOTOSYNTHETI"~Z346^2^Arnone,JA^Korner,C^1993^1^Influence of elevated co2 on canopy development and red - far- red ratios in 2-storied sta"nds of ricinus-communis^2^94^4^510-515^^^^^Jul^^^^^3526QB, MIDLOTHIAN, SCOTLAND. ID ABIES L KARST; CO2 ASSIMILATION; PINU"\A^3525^Vertical structure of plant stands and canopies may change under conditions of elevated CO2 due to differential res"]ponses of overstory and understory plants or plant parts. In the long term, seedling recruitment, competition, and thus po"^pulation or community structure may be affected. Aside from the possible differential direct effects of elevated CO2 on ph"_otosynthesis and growth, both the quantity and quality of the light below the overstory canopy could be indirectly affecte"`d by CO2- induced changes in overstory leaf area index (LAI) and/or changes in overstory leaf quality. In order to explore"a such possible interactions, we compared canopy leaf area development, canopy light extinction and the quality of light be"bneath overstory leaves of two-storied monospecific stands of Ricinus communis exposed to ambient (340 mul-1) and elevated "c(610 mul-1) CO2. Plants in each stand were grown in a common soil as closed ''artificial ecosystems'' with a ground area o"df 6.7 m2. LAI of overstory plants in all ecosystems more than doubled during the experiment but was not different between "eCO2 treatments at the end. As a consequence, extinction of photosynthetically active radiation (PAR) was also not altered."f However, under elevated CO2 the red to far-red ratio (R: FR) measured beneath overstory leaves was 10% lower than in ecos"gystems treated with ambient CO2. This reduction was associated with increased thickness of palisade layers of overstory le"haves and appears to be a plausible explanation for the specific enhancement of stem elongation of understory plants (witho"iut a corresponding biomass response) under elevated CO2. Col enrichment led to increased biomass of overstory plants (main"jly stem biomass) but had no effect on understory biomass. The results of this study raise the possibility of an important "kindirect effect of elevated CO2 at the stand-level. We suggest that, under elevated CO2, reductions in the R:FR ratio bene"ath overstory canopies may affect understory plant development independently of the effects of PAR extinction.owed an A(m"m347^3^Bernstson,GM^McConnaughay,KDM^Bazzaz,FA^1993^1^Elevated co2 alters deployment of roots in small growth containers^2^"94^4^558-564^^^^^Jul^^^^^3528 of the pre-frost value increased from 30 min (control) to 85 min for ozone-fumigated trees "oA^3527^Previously we examined how limited rooting space and nutrient supply influenced plant growth under elevated atmosph"peric CO2 concentrations (McConnaughay et al. 1993). We demonstrated that plant growth enhancement under elevated CO2 was i#qnfluenced more by the concentration of nutrients added to growth containers than to either the total nutrient content per # rpot or amount or the dimensions of available rooting space. To gain insight into how elevated CO2 atmospheres affect how p#slants utilize available belowground space when rooting space and nutrient supply are limited we measured the deployment of#t roots within pots through time. Contrary to aboveground responses, patterns of below-ground deployment were most strongly#!u influenced by elevated CO2 in pots of different volume and shape. Further, elevated CO2 conditions interacted differently##v with limited belowground space for the two species we studied, Abutilon theophrasti, a C3 dicot with a deep taproot, and #+wSetaria faberii, a C4 monocot with a shallow fibrous root system. For Setaria, elevated CO2 increased the size of the larg#-xest region of low root density at the pot surface in larger rooting volumes independent of nutrient content, thereby decre#6yasing their efficiency of deployment. For Abutilon, plants responded to elevated CO2 concentrations by equalizing the patt#8zern of deployment in all the pots. Nutrient concentration, and not pot size or shape, greatly influenced the density of ro#A{ot growth. Root densities for Abutilon and Setaria were similar to those observed in field conditions, for annual dicots a#Bnd monocots respectively, suggesting that studies using pots may successfully mimic natural conditions.nt CO2 environment#P}348^3^Berryman,CA^Eamus,D^Duff,GA^1993^1^The influence of co2 enrichment on growth, nutrient content and biomass allocatio#Rn of maranthes-corymbosa^182^41^2^195-209^^^^^^^^^^3530es to reproduction whereas ambient CO2-grown plants allocated over#aA^3529^Seedlings of Maranthes corymbosa Blume, an evergreen tree of tropical Australia and Indonesia were grown for 32 wee#cks under conditions of ambient and elevated (700 mumol CO2 mol-1) CO2 in tropical northern Australia. Seedlings were expos#jed to ambient temperature, vapour pressure deficit and photon flux density fluctuations. Rates of germination and percenta#lge germination were not affected by elevated CO2.Total plant biomass, height growth, total plant leaf area, numbers of lea#tves and branches and specific leaf weight were significantly increased by elevated CO2. Root:shoot ratio and foliar P, K, #vMg, Mn and Ca levels were unaffected but foliar nitrogen levels were decreased by elevated CO2, Nutrient-use-efficiency wa#s unaffected for phosphorus, magnesium, manganese, calcium and potassium but nitrogen-use-efficiency increased in response# to elevated CO2.AL-NUTRITION; USE EFFICIENCY; NUTRIENT CONCENTRATION; PLANT-GROWTH; NITRATE; YIELD; WATER; PHOTOSYNTHESI#349^1^Bowes,G^1993^1^Facing the inevitable - plants and increasing atmospheric co(2)^208^44^^309-332^e concentrations and#350^6^Britz,SJ^Krizek,DT^Lee,DR^Harris,WG^Hungerford,WE^Bailey,WA^1993^1^Soybean growth under microwave-powered lamps, hig#h-irradiance- discharge lamps, or solar-radiation at ambient or elevated co2^8^102^1^141^^^^^Mayeks at high CO2 (1500 cm3#351^3^Grulke,NE^Hom,JL^Roberts,SW^1993^1^Physiological adjustment of 2 full-sib families of ponderosa pine to elevated co2#^13^12^4^391-401^^^^^Jun^^^^^3534ze responded only to N supply. CO2-enriched wheat produced about twice the dry matter o#A^3533^Seeds from two full-sib families of ponderosa pine (Pinus ponderosa) with known differences in growth rates were ge#rminated and grown in an ambient (350 mul l-1) or elevated (700 mul l-1) CO2 concentration. Gas exchange at both ambient a#nd elevated CO2 concentrations was measured 1, 6,39, and 112 days after the seed coat was shed. Initial stimulation of CO2# exchange rate (CER) by elevated CO2 was large (> 100%). On Day 1, CER of seedlings grown in elevated CO2 and measured at #ambient CO2 was significantly lower than the CER of seedlings grown and measured at ambient CO2, indicating physiological #adjustment of the seedlings exposed to elevated CO2. Physiological acclimation to elevated CO2 was complete by Day 39 when# there was no significant difference in CER between seedlings grown and measured at ambient CO2 and seedlings grown and me#asured at elevated CO2. After 4 months, the light response of seedlings in the two treatments was determined at both ambie#nt and elevated CO2. Light compensation point, CER at light saturation, and apparent quantum efficiency of seedlings grown# and measured at ambient CO2 were not significantly different from those of seedlings grown and measured at elevated CO2. #With a short-term increase in CO2, CER at light saturation (5.16 +/- 0.52 versus 3.13 +/- 0.30 mumol CO2 m-2 s- 1 ) and ap#parent quantum efficiency (0.082 +/- 0.011 versus 0.045 +/- 0.003 mumol CO2 mumol-1 quanta) were significantly increased. #Leaf C/N ratio was significantly increased in the elevated CO2 treatment. There were few significant differences between f#amilies for any response to elevated CO2. Under the experimental conditions, high growth rate was not correlated with a gr$eater response to elevated CO2.antially decreased critical concentrations of NO3-N and total-N in stem bases and leaves. $352^4^Heagle,AS^Miller,JE^Sherrill,DE^Rawlings,JO^1993^1^Effects of ozone and carbon-dioxide mixtures on 2 clones of white$ clover^84^123^4^751-762^^^^^Apr^^^^^3536 with 7.5, 6.2 and 6.4 mg/g dry wt, respectively, for control plants grown at th$A^3535^The effects of mixtures of ozone and carbon dioxide on growth and physiology of an O3-sensitive (NC-S) and an O3-re$sistant (NC-R) clone of white clover (Trifolium repens L.) were determined. The experiment was performed in a greenhouse w$ ith O3 treatments of 5 and 82 nl l-1 (ppb) for 6 h d-1 and CO2 treatments of 380 (ambient), 490,600, and 710 mul l-1 (ppm)$" for 24 h d-1. Enrichment with CO2 decreased foliar gas exchange (measured as stomatal resistance) of NC-R more than that $/of NC- S whereas O3 decreased gas exchange of NC-S more than that of NC-R. Ozone caused extensive foliar injury of NC-S bu$1t caused only slight injury of NC-R. CO2 enrichment suppressed O3- induced foliar injury of NC-S as measured after 4 wk of$: exposure, but this effect diminished after 8 wk of exposure. CO2 enrichment decreased the relative chlorophyll content (m$<ug of chlorophyll mg-1 of leaf tissue sampled) but not the total chlorophyll (total chlorophyll in the leaves sampled). Th$Gere were no O3 x CO2 interactions for foliar chlorophyll. High concentrations of CO2 caused reddening of new leaves near t$Ihe end of the 8 wk exposure period. CO2 enrichment decreased foliar concentrations of N, P, K, S, Cu, B, and Fe, increased$S foliar concentrations of Mn, but did not affect Zn, Ca, or Mg. Ozone exposure did not modify the CO2 effects on foliar nu$Ttrient concentration. Ozone decreased growth of NC-S but not NC-R while CO2 enrichment stimulated growth of both clones. The highest CO2 concentration appeared to decrease the effects of O3 on growth of NC-S. However, except for a transitory effect on foliar injury, there was no evidence that CO2, at concentrations less than the highest used in this study, will pr$votect white clover from the effects of tropospheric O3. being at least similar in magnitude to those already observed in $x353^2^Kimball,BA^Mauney,JR^1993^1^Response of cotton to varying co2, irrigation, and nitrogen - yield and growth^48^85^3^7$06-712^^^^^May-Jun^^^^^3538mean Q700/350 of only 1.05. High CO2 responsiveness was common only within the competitive str$A^3537^The CO2 concentration of the atmosphere is increasing and is expected to double sometime near the middle of the next century. To determine the effects of such a CO2 increase on cotton (Gossypium hirsutum L.) growth and productivity, a series of experiments from 1983 through 1987 were conducted with open-top CO2-enriched field chambers at ample as well as limiting levels of water and N at Phoenix, AZ. Comparisons with open-field plots showed that there was a significant chamber effect, amounting to a 30% average increase in growth inside, but under dry conditions in 1985, the situation was reverse$d. No significant effects of CO2 on harvest index, root-shoot ratio, or lint percentage were found, so the primary effect $of elevated CO2 was to produce plants that were larger. Comparing the results of 500 and 650 mumol mol-1 CO2 treatments, t$he increments of growth from ambient (about 350 mumol mol-1) to 500 mumol mol-1 were not significantly different from incr$ements from 500 to 650 mumol mol-1. No statistically significant interactions were detected between CO2 level and either i$rrigation or nitrogen level, even when these variables were sufficiently low enough to limit growth. However, under well-m$aintained water stress conditions, the growth response to CO2 tended to be somewhat larger than under normal irrigation le$vels. Averaging over all the data available from these experiments, seed cotton yield (lint plus seed) and above- ground b$iomass were increased by 60 and 63%, respectively, by CO2 enrichment to 650 mumol mol-1.5287. ID ATMOSPHERIC CO2 ENRICHME%354^4^Krapp,A^Hofmann,B^Schafer,C^Stitt,M^1993^1^Regulation of the expression of rbcs and other photosynthetic genes by ca%rbohydrates - a mechanism for the sink regulation of photosynthesis^209^3^6^817-828^^^^^Jun^^^^^3540nd summer mean maximu%A^3539^These experiments were carried out to investigate whether accumulation of carbohydrate leads to decreased expressio%n of genes involved in photosynthesis. Addition of glucose to autotrophic cell suspension cultures of Chenopodium led to a%% large and reversible decrease of the steady state transcript levels of rbcS, cab and atp-delta within 5 h, but did not de%&crease 18S rRNA or transcript for two glycolytic enzymes. Run-on transcription in isolated nuclei showed that transcriptio%4n rate had been decreased. [S-35]Methionine feeding showed that de novo synthesis of Rubisco was inhibited. Decreased rbcS%6 transcript was also found after feeding glucose to detached leaves, and in transgenic plants expressing invertase in the %Eapoplast to inhibit phloem transport, and in leaves on intact tobacco and potato plants which were cold- girdled to decrea%Gse export. The decrease of rbcS transcript level occurred within 12 h of cold-girdling. Comparison of carbohydrate content%U and rbcS transcript level indicated that carbohydrate content per se is not the direct signal for regulation of gene expr%Wession. Feeding of transported analogues indicates that metabolism rather than transport of the sugars is required. Over-e%ixpression of rbcS was found in low CO2, again indicating metabolic control of expression. ft is proposed that photosynthet%kic gene expression is inhibited by metabolic factors related to high carbohydrate content, and that this represents a basi%c mechanism for the 'sink regulation' of photosynthesis.ancement is of the same order of magnitude as our previously repo%355^2^Luo,YQ^Nobel,PS^1993^1^Growth-characteristics of newly initiated cladodes of opuntia- ficus-indica as affected by sh%ading, drought and elevated co2^37^87^4^467-474^^^^^Apr^^^^^3542T J AU IDSO, SB KIMBALL, BA TI DOWNWARD REGULATION OF PHO%A^3541^Biomass accumulation and area expansion of newly initiated cladodes of Opuntia ficus-indica were studied to help un%derstand the high productivity of this Crassulacena acid metabolism species. In a glasshouse, both dry weight and area inc%reased more and more rapidly for about 30 days and then increased linearly with time up to 63 days. The relative growth ra%te averaged 0.12 day-1, comparable to values for productive C3 and C, plants. New cladodes initiated on basal cladodes wit%h 2-fold higher initial dry weight grew twice as fast. Drought reduced biomass accumulation and area expansion of new clad%odes by 62 and 52%, respectively. A 70% reduction in irradiation decreased biomass accumulation of new cladodes by 17% and% their thickness by 11%. In a growth chamber containing 720 mumol CO2 (mol air)-1, biomass of newly initiated cladodes was% 7% higher, area was 8% less, specific mass was 16% higher and less carbohydrate was translocated from basal cladodes than% for 360 mumol CO2 mol-1. The large capacity for storage of carbohydrate and water in basal cladodes of O. ficus-indica ap%parently buffered environmental stresses, thereby reducing their effects on growth of daughter cladodes. 30322. DE CYCLIC%356^3^McConnaughay,KDM^Berntson,GM^Bazzaz,FA^1993^1^Limitations to co2-induced growth enhancement in pot studies^2^94^4^55%0-557^^^^^Jul^^^^^3544NT; OUTER SEGMENT; MOUSE RETINA; GMP; LIGHT; DARK; CONDUCTANCE; INDUCTION AB The effect of membrane%A^3543^Recently, it has been suggested that small pots may reduce or eliminate plant responses to enriched CO2, atmosphere%s due to root restriction. While smaller pot volumes provide less physical space available for root growth, they also prov%ide less nutrients. Reduced nutrient availability alone may reduce growth enhancement under elevated CO2. To investigate t%he relative importance of limited physical rooting space separate from and in conjunction with soil nutrients, we grew pla&nts at ambient and double-ambient CO2 levels in growth containers of varied volume, shape, nutrient concentration, and tot&al nutrient content. Two species (Abutilon theophrasti, a C3 dicot with a deep tap root and Setaria faberii, a C4 monocot &with a shallow diffuse root system) were selected for their contrasting physiology and root architecture. Shoot demography&( was determined weekly and biomass was determined after eight and ten weeks of growth. Increasing total nutrients, either &*by increasing nutrient concentration or by increasing pot size, increased plant growth. Further, increasing pot size while&8 maintaining equal total nutrients per pot resulted in increased total biomass for both species. CO2-induced growth and re&:productive yield enhancements were greatest in pots with high nutrient concentrations, regardless of total nutrient conten&Et or pot size, and were also mediated by the shape of the pot. CO2-induced growth and reproductive yield enhancements were&F unaffected by pot size (growth) or were greater in small pots (reproductive yield), regardless of total nutrient content,&V contrary to predictions based on earlier studies. These results suggest that several aspects of growth conditions within &Xpots may influence the CO2 responses of plants; pot size, pot shape, the concentration and total amount of nutrient additi&cons to pots may lead to over- or underestimates of the CO2 responses of real-world plants.he enrichment ratio are also il&e357^6^Melillo,JM^McGuire,AD^Kicklighter,DW^Moore,B^Vorosmarty,CJ^Schloss,AL^1993^1^Global climate-change and terrestrial n&qet primary production^36^363^6426^234-240^^^^^20 May^^^^^3546rption stream contains 7% SO2. Further improvement can be o&tA^3545^A process-based model was used to estimate global patterns of net primary production and soil nitrogen cycling for &{contemporary climate conditions and current atmospheric CO2 concentration. Over half of the global annual net primary prod&}uction was estimated to occur in the tropics, with most of the production attributable to tropical evergreen forest. The e&ffects of CO2 doubling and associated climate changes were also explored. The responses in tropical and dry temperate ecos&ystems were dominated by CO2, but those in northern and moist temperate ecosystems reflected the effects of temperature on& nitrogen availability.ECT OF LIGHT-INTENSITY AND CO2 ENRICHMENT DURING INVITRO ROOTING ON SUBSEQUENT GROWTH OF PLANTLETS&358^5^Nakadai,T^Koizumi,H^Usami,Y^Satoh,M^Oikawa,T^1993^1^Examination of the method for measuring soil respiration in cult&ivated land - effect of carbon-dioxide concentration on soil respiration^143^8^1^65-71^^^^^Apr^^^^^3548ANANASSA; LIGHT; M&A^3547^An acceleration of soil respiration with decreasing CO2 concentration was suggested in the field measurements. The &result supports that obtained in laboratory experiments in our previous study. The CO2 concentrations in a chamber of the &alkali absorption method (the AA-method) were about 150-250 parts/10(6) lower than that in the atmosphere (about 350 parts&/ 10(6)), while those observed in the open-flow IRGA method (the OF-method) were nearly equal to the soil surface CO2 leve&ls. The AA-method at such low CO2 levels in the chamber appears to overestimate the soil respiration. Our results showed t&hat the rates obtained by the AA-method were about twice as large as those by the OF-method in field and laboratory measur&ements. This finding has important consequences with respect to the validity of the existing data obtained by the AA-metho&d and the estimation of changes in the terrestrial carbon flow with elevated CO2 concentrations.period with raspberry. O&359^4^Nicolas,ME^Munns,R^Samarakoon,AB^Gifford,RM^1993^1^Elevated co2 improves the growth of wheat under salinity^92^20^3^&349-360^^^^^^^^^^3550CO2 during the in vitro rooting stage. BP 259-269 PG 11 JI Sci. Hortic. PY 1991 PD JUL VL 47 IS 3-4 &382^4^Polley,HW^Johnson,HB^Mayeux,HS^Malone,SR^1993^1^Physiology and growth of wheat across a subambient carbon- dioxide g&radient^52^71^4^347-356^^^^^AprIO MASS-SPECTROMETRY SO BIOLOGICAL MASS SPECTROMETRY SN 1052-9306 C1 UNIV BRITISH COLUMBIA&383^1^Possingham,HP^1993^1^Impact of elevated atmospheric co2 on biodiversity - mechanistic population-dynamic perspective&^182^41^1^11-21^^^^^^^^^^3592de (TG) synthesis was measured over 48 h in four healthy males from the incorporation rate o&iochemically not only to interspecific differences in host chemistry, but also to resource-mediated, intraspecific changes' in host chemistry. Such responses are likely to be important for the dynamics of plant-insect interactions as they occur 'A^3549^Wheat plants (Triticum aestivum cv. Matong and T. durum cv. Modoc) were grown at ambient and elevated CO2 (350 cm3 ')m-3 above ambient) in soil with or without 150 mol m-3 NaCl for 6 weeks. The increase in dry matter, leaf area and tilleri'+ng under high CO2 was relatively greater under saline than non- saline conditions for both cultivars. Tillering was the pr'3imary component of growth affected by both salinity and high CO2. Salinity greatly reduced tillering and high CO2 partly r'5eversed the effects of salinity. High CO2 increased dry matter accumulation of the salt-sensitive Modoc to a greater exten'Dt (+ 104%) than that of the more salt-tolerant Matong (+ 73 %) in the salt treatment. Transpiration rates were greatly red'Euced by salinity for both cultivars. Under high CO2, increased leaf areas compensated for reduced transpiration rates per 'Z unit leaf area (i.e. greater stomatal closure), and total transpiration was little affected by CO2 level within each treat'\ ment. The more salt-tolerant Matong showed greater stomatal closure and higher transpiration efficiencies than the salt-se'k nsitive Modoc under salinity. High CO2 reduced transpiration rate (per unit dry weight) by 40 to 50%, but did not signific'm antly change the rate of sodium accumulation (per unit dry weight), indicating that salt uptake was largely independent of' water uptake, and that high CO2 did not increase growth by reducing the salt load. Our results suggest that high CO2 incr'eased growth by stimulating the development of tiller buds that would otherwise have been inhibited.nditions, a trial on '360^3^Nie,GY^Long,SP^Webber,A^1993^1^The effect of nitrogen supply on down-regulation of photosynthesis in spring wheat gr'own in an elevated co2 concentration^8^102^1^138^^^^^Mayage); - hermetic storage; - initial purge with gas mixture, 50% C'361^3^Rogers,HH^Prior,SA^Runion,GB^1993^1^Effects of elevated atmospheric co2 on soybean and sorghum root-growth^8^102^1^1'73^^^^^Mayae. Weekly sampling over a 3-month storage period permitted determination of the lethal effects on insects, CO'362^2^Samuelson,LJ^Seiler,JR^1993^1^Interactive role of elevated co2, nutrient limitations, and water-stress in the growth'-responses of red spruce seedlings^49^39^2^348-358^^^^^May^^^^^3554compensated for by microfloral respiration which is th'A^3553^Red spruce (Picea rubens Sarg.) seedlings were grown from seed for 5 mo in ambient (362 ppm) or elevated (711 ppm) 'CO2 to determine the potential effect of an increase in global CO2 concentration on seedling growth and establishment. CO2' exposure treatments were crossed with two levels of soil fertility and water stress treatments to determine if seedling d'ry weight, size, and fixed growth responses to elevated CO2 depended on nutrient and water supply. Seedling dry weight and& size responses to elevated CO2 at 5 mo did not depend on nutrient and water supply. Seedlings grown in both soil fertilit(y treatments and water stress treatments responded similarly to CO2 treatment. Water stress and CO2 treatments did have an(  interactive influence on the fixed growth potential of the terminal leader. Leaf weight, leaf area, and height of the ter(minal leader of water-stressed seedlings were greater in seedlings exposed to elevated CO2 during budset than seedlings ex(posed to ambient CO2. Total new fixed growth (lateral plus terminal) and total terminal fixed growth (leaf plus stem) were(! greater in seedlings that formed shoot primordia in elevated CO2 than in ambient CO2. Red spruce seedlings grown in eleva(2ted CO2 for 5 mo had greater stem diameter, height, branching density, leaf weight, root weight, stem weight, total weight(4 , and mean relative growth rate (RGR) from 3 to 5 mo than seedlings grown in ambient CO2. Red spruce seedling responses to(?! elevated CO2 suggest that seedling establishment in natural environments may be enhanced when ambient CO2 concentrations (Arise even if water and nutrient availabilities are limited.thousand; dioritic and anorthositic rocks: 5.5 to 7.6 parts p(S#363^2^Silvola,J^Ahlholm,U^1993^1^Effects of co2 concentration and nutrient status on growth, growth rhythm and biomass par(Utitioning in a willow, salix- phylicifolia^15^67^2^227-234^^^^^Jun^^^^^3556 in unaltered plutonic rocks of equivalent com(`%A^3555^Cuttings of the willow Salix phylicifolia were grown in pots containing moist organic-rich soil for four months in (b&closed chambers at 4 CO2 concentrations (300). 500, 700, 1000 ppm) and 4 nutrient levels (fertilization of 0, 100, 500, 10(k'00 kg ha-1 monthly). The plants received natural light, but the average temperature was 3-6-degrees-C higher than out of d(m(oors. Both CO2 concentration and fertilization affected biomass production. the average increase caused by CO2 enhancement(z) being approx. 100%. Nutrient level had a considerable effect on the increased biomass production achieved by CO2 enhancem(|*ent, since the increase was minimal at lower nutrient levels. At the same time the effect of fertilization was dependent o(+n the CO2 concentration, the production increase caused by fertilization being much less at 300 ppm than at the other CO2 (,concentrations. CO2 concentration and fertilization had the opposite effects on biomass partitioning, a higher nutrient le(-vel increasing the proportion of the biomass located in the stems and a higher CO2 concentration that in the roots. Both f(.ertilization and CO2 concentration affected the growth rhythm, a high CO2/nutrient ratio leading to a shorter growing seas(on and a low ratio to a longer one.osition appear to have occurred during granulite facies metamorphism, implying limited(0364^2^Ziska,LH^Bunce,JA^1993^1^Inhibition of whole-plant respiration by elevated co2 as modified by growth temperature^37^(87^4^459-466^^^^^Apr^^^^^3558A model involving an association between mantle-derived mafic magma and O-18- enriched crust(2A^3557^Plants of alfalfa (Medicago sativa) and orchard grass (Dactylus glomerata) were grown in controlled environment cha(3mbers at two CO2 concentrations (350 and 700 mumol mol-1) and 4 constant day/night growth temperatures of 15, 20, 25 and 3(40-degrees-C for 50-90 days to determine changes in growth and whole plant CO2 efflux (dark respiration). To facilitate com(5parisons with other studies, respiration data were expressed on the basis of leaf area, dry weight and protein. Growth at (6elevated CO2 increased total plant biomass at all temperatures relative to ambient CO2, but the relative enhancement decli) 7ned (P less- than-or-equal-to 0.05) as temperature increased. Whole plant respiration (R(d)) at elevated CO2 declined at 1)85 and 20- degrees-C in D. glomerata on an area, weight or protein basis and in M. sativa on a weight or protein basis when)9 compared to ambient CO2. Separation of R(d) into respiration required for growth (R(g)) and maintenance (R(m)) showed a s):ignificant effect of elevated CO2 on both components. R(m) was reduced in both species but only at lower temperatures (15-)(;degrees-C in M. sativa and 15 and 20-degrees-C in D. glomerata). The effect on R(m) could not be accounted for by protein )*perennial species used in the present study, the data suggest that both R(g) and R(m) can be reduced by anticipated increa)??ses in atmospheric CO2; however, CO2 inhibition of total plant respiration may decline as a function of increasing tempera)Ature.e section). Consideration of these data in the context of delta- temperature relations suggests that 1) surface wat)SA365^2^Beerling,DJ^Chaloner,WG^1993^1^The impact of atmospheric co2 and temperature-change on stomatal density - observatio)Uns from quercus-robur lammas leaves^52^71^3^231-235^^^^^Marom the highest, 2) the increasing delta-O-18 values also refle)`C366^3^Bottomley,PA^Rogers,HH^Prior,SA^1993^1^Nmr imaging of root water distribution in intact vicia-faba L plants in eleva)bted atmospheric co2^9^16^3^335-338^^^^^Apr^^^^^3561peratures, and 3) the significant variation in delta-O-18 from oldest )oEA^3560^The effect of elevated atmospheric CO2 on water distribution in the intact roots of Vicia faba L. bean seedlings gr)qFown in natural soil was studied noninvasively with proton (H-1) nuclear magnetic resonance (NMR) imaging. Exposure of 24-d)wG-old plants to atmospheric Co2-enriched air at 650 cm3 m-3 produced significant increases in water imaged in upper roots, )xHhypogeal cotyledons and lower stems in response to a short-term drying- stress cycle. Above ground, drying produced neglig)Iible stem shrinkage and stomatal resistance was unchanged. In contrast, the same drying cycle caused significant depletion)J of water imaged in the same upper root structures in control plants subject to ambient CO2 (350 m3 m-3), and stem shrinka)Kge and increased stomatal resistance. The results suggest that inhibition of transpiration caused by elevated CO2 does not)L necessarily result in attenuation of water transport from lower root structures. Inhibition of water loss from upper root)Ms and lower stem in elevated CO2 environments may be a mitigating factor in assessing deleterious effects of greenhouse ch)anges on crops during periods of dry climate.ARK BASIN, SOUTHWEST PACIFIC SO GEOCHIMICA ET COSMOCHIMICA ACTA SN 0016-7037)O367^1^Bunce,JA^1993^1^Effects of doubled atmospheric carbon-dioxide concentration on the responses of assimilation and con)ductance to humidity^9^16^2^189-197^^^^^Mar^^^^^3563TASMANIA, HOBART, TAS 7001, AUSTRALIA. ID OCEAN-RIDGE BASALT; CARBON-)QA^3562^Experiments were performed to determine if growth at elevated partial pressure of CO2 altered the sensitivity of le)Raf water vapour conductance and rate of CO2 assimilation to the leaf-to- air difference in the partial pressure of water v)Sapour (DELTAw). Comparisons were made between plants grown and measured at 350 and 700 muPa Pa-1 partial pressures of CO2 )Tfor amaranth, soybean and sunflower grown in controlled environment chambers, soybean grown outdoors in pots, and orchard )Ugrass grown in field plots. In amaranth, soybean and orchard grass, both the absolute and the relative sensitivity of cond*Vuctance to DELTAw at the leaf surface were less in plants grown and measured at the elevated CO2. In sunflower, there was *Wno change in the sensitivity of conductance to DELTAw for the two CO2 partial pressures. Tests in soybeans and amaranth sh*Xowed that the change in sensitivity resulted from elevated CO2 during the measurement of the DELTAw response. Assimilation*Y rate of CO2 was not altered by DELTAw in amaranth, which has C4 metabolism. In sunflower, the assimilation rate of plants*(Z grown and measured at elevated CO2 was insensitive to DELTAw, consistent with the response of assimilation rate to interc**[ellular CO2 partial pressure in the prevailing range. In soybean, the sensitivity of assimilation rate to DELTAw was not d*,\ifferent between CO2 treatments, in contrast to what would be expected from the response of assimilation rate to intercell*:ular CO2 partial pressure.n and partial melting. It appears that the Woodlark Basin basalts have at least three differen*<^368^3^Coleman,JS^McConnaughay,KDM^Bazzaz,FA^1993^1^Elevated co2 and plant nitrogen-use - is reduced tissue nitrogen concen*>tration size-dependent^2^93^2^195-200^^^^^Mar^^^^^3565a PY 1991 PD AUG VL 55 IS 8 GA GC439 RP MUENOW DW J9 GEOCHIM COSMOC*F`A^3564^Plants often respond to elevated atmospheric CO2 levels with reduced tissue nitrogen concentrations relative to amb*Haient CO2- grown plants when comparisons are made at a common time. Another common response to enriched CO2 atmospheres is *Jban acceleration in plant growth rates. Because plant nitrogen concentrations are often highest in seedlings and subsequent*Tcly decrease during growth, comparisons between ambient and elevated CO2-grown plants made at a common time may not demonst*Vdrate CO2-induced reductions in plant nitrogen concentration per se. Rather, this comparison may be highlighting difference*des in nitrogen concentration between bigger, more developed plants and smaller, less developed plants. In this study, we di*ffrectly examined whether elevated CO2 environments reduce plant nitrogen concentrations independent of changes in plant gro*tgwth rates. We grew two annual plant species, Abutilon theophrasti (C3 photosynthetic pathway) and Amaranthus retroflexus (*vhC, photosynthetic pathway), from seed in glass-sided growth chambers with atmospheric CO2 levels of 350 mumol . mol-1 or 7*i00 mumol . mol- 1 and with high or low fertilizer applications. Individual plants were harvested every 2 days starting 3 d*jays after germination to determine plant biomass and nitrogen concentration. We found: 1. High CO2-grown plants had reduce*kd nitrogen concentrations and increased biomass relative to ambient CO2-grown plants when compared at a common time; 2. Ti*lssue nitrogen concentrations did not vary as a function of CO2 level when plants were compared at a common size; and 3. Th*me rate of biomass accumulation per rate of increase in plant nitrogen was unaffected by CO2 availability, but was altered *nby nutrient availability. These results indicate that a CO2- induced reduction in plant nitrogen concentration may not be *odue to physiological changes in plant nitrogen use efficiency, but is probably a size-dependent phenomenon resulting from *accelerated plant growth.hat yield increases resulted from the combined effects of limited atmospheric CO2 enrichment and*q369^1^Conroy,JP^1993^1^Influence of elevated atmospheric co2 concentrations on plant nutrition (vol 40, pg 445, 1992)^182^*41^1^143^N J ER PT J AU PLONSKY, IM DUNINABARKOVSKAYA, AY CHAILAKHYAN, LM TI EFFECT OF CO2 ON CELL-CELL JUNCTION CONDUCT*s370^2^Garcia,JM^Streif,J^1993^1^Quality and storage potential of pear .1. Influence of ca- storage and ulo-storage conditi*ons^172^58^1^36-41^^^^^Jan-Feb^^^^^3568MISS PROBLEMS, MOSCOW V-71, USSR. AN BELOZERSKII MOLEC BIOL & BIOORGAN CHEM LAB, M*uA^3567^In a CA experiment the storage potential of different pear cultivars was investigated, especially the behaviour of *vthe fruits against elevated CO2 concentrations and/or ultra low oxygen (ULO).The following CA combinations were tested: < *w1 % CO2 + 3 % O2; 3 % CO2 + 3 % O2; < 1 % CO2 + 1 % O2; 3 % CO2 + 1 % O2, and refrigerated storage at - 1-degrees-C 'Packh*xam's Triumph' showed the best storage potential of all tested cultivars followed by 'Conference' and 'Doyenne' du Comice. *yThe keepability of 'General Leclerc' was only slightly improved by CA conditions compared with cold stored pears. CA stora*zge of 'Alexander Lucas' and 'Bristol Cross' didn't show an obvious advantage because of high CO2 damages. Therefore, CO2 c*{oncentrations in CA storage of these two cultivars should be < 1 %. 'Conference' and 'General Leclerc' tolerate up to 2 % +|CO2, 'Doyenne du Comice' and 'Packham's Triumph' up to 3 % CO2. ULO conditions amplified the CO2 damages in the CO2 sensit+ive cultivars, but improved the keepability of 'Doyenne du Comice' and 'Packham's Triumph'.Ca greater-than-or-equal-to 9.+~371^2^Graybill,DA^Idso,SB^1993^1^Detecting the aerial fertilization effect of atmospheric co2 enrichment in tree-ring chro+nologies^137^7^1^81-95^^^^^Mar^^^^^3570periments CO2 was still capable of uncoupling the cells. We conclude that the eff+A^3569^The growth-promoting effects of the historical increase in the air's CO2 content are not yet evident in tree-ring r+ecords where yearly biomass additions are apportioned among all plant parts. When almost all new biomass goes into cambial+ enlargement, however, a growth increase of 60% or more is observed over the past two centuries. As a result, calibration +#of tree-ring records of this nature with instrumental climate records may not be feasible because of such growth changes. +%However, climate signals prior to about the mid-19th century may yet be discovered by calibrating such tree-ring series wi+0th independently derived proxy climate records for those times.ar junction conductance in isolated pairs of mouse hepatoc+2372^5^Gross,U^Gilles,F^Bender,L^Berghofer,P^Neumann,KH^1993^1^The influence of sucrose and an elevated co2 concentration o+Bn photosynthesis of photoautotrophic peanut (arachis-hypogaea L) cell-cultures^177^33^2^143-150^^^^^May^^^^^3572he extern+DA^3571^Using photoautotrophic cells of Arachis hypogaea (L.) growing at ambient CO2, it was shown that exogenous sucrose s+Rupplied to the liquid medium reduced (CO2)-C-14 fixation (supplied as NaH (CO3)-C-14) . This was mostly due to a reduced l+Tabelling in P-esters, and to a lesser extent, in the serine/glycine moiety. However, radioactivity in the neutral sugar fr+Vaction was increased upon supplement of exogenous sucrose. The reduced labelling of P-esters and serine/glycine agrees wit+dh a lower concentration and specific activity of Rubisco in the sucrose supplied treatments as compared to the control. Fo+fllowing a transfer into a sugar free nutrient medium the concentration and activity of Rubisco is increased. The concentra+ytion of PEPCase was not influenced by sucrose application, although its specific activity was increased. At elevated CO2 c+{oncentration (2.34% v/v) the Rubisco concentration and specific activity was at the same level as in the control (0.03% V/+V CO2). However, the concentration and the specific activity of PEPCase was increased and dry weight increase was about 8-+9-fold higher than at ambient CO2.AGONE, R FIERRO, G INVERSI, M LOJACONO, M MORETTI, G TI COPPER COBALT HYDROXYSALTS AND +373^2^Hao,YY^Brackett,RE^1993^1^Influence of modified atmosphere on growth of vegetable spoilage bacteria in media^210^56^+3^223-228^^^^^Mar^^^^^3574ITA CATALIT SISTEMI OSSIDI, I-00185 ROME, ITALY. DE COPPER-COBALT OXYSALT; MIXED OXIDE PRECURSO+A^3573^Six gas mixtures (CO2/O2/N2: 0/5/95, 0/10/90, 5/10/85, 5/20/75, 10/5/85, and 10/20/70) and air were used to investi+gate the effect of modified atmosphere (MA) on growth of four vegetable spoilage bacteria. In addition, we determined the +ability of the MA which most inhibited spoilage bacteria to reduce spoilage in bell peppers inoculated with the respective+ bacteria. In general, MA did not significantly affect growth of the bacteria tested. Growth of Erwinia, Pseudomonas, Xant+homonas, and Pepper # 15 (a pectinolytic Pseudomonas) at 10 and 20-degrees-C was not significantly affected regardless of +gas mixtures. At 5-degrees-C, growth of Erwinia, Xanthomonas, and Pepper # 15 was slightly reduced by some gas mixtures (C+O2/O2/N2: 0/5/95, 0/10/90, and 10/5/85; 10/5/85; 0/5/95 and 10/5/85, respectively). Modified atmosphere containing 10% CO2+, 5% O2, and 85% N2 did not reduce the ability of bacteria tested to grow at elevated concentrations of sodium chloride. I+n addition, this MA composition did not change the percentage of bell peppers spoiled by test bacteria inoculated. However+, overall visual quality was enhanced by MA.weaker at increasing cobalt loading. The observed decrease in volume of the )374^3^Havstrom,M^Callaghan,TV^Jonasson,S^1993^1^Differential growth-responses of cassiope-tetragona, an arctic dwarf-shrub,, to environmental perturbations among 3 contrasting high sites and sub-arctic sites^15^66^3^389-402^^^^^Apr^^^^^3576d by, A^3575^Three populations of Cassiope tetragona (Ericaceae) were subjected to in situ environmental perturbations simulatin, g predictions of global warming. The populations were selected to represent different parts of the range of the species, o,ne growing in a high arctic coastal heath at Ny-Alesund (Svalbard, northern part of the species' range), one at a subarcti,c fellfield at 1150 m a.s.l. at Abisko, Swedish Lapland, and one in a subarctic tree-line heath at 450 m a.s.l. at Abisko,,' southern part of the species' range. The manipulations included nutrient addition, shading and two levels of temperature ,)enhancement using passive greenhouses. The micrometeorological effects of the shading treatment was similar to that of a m,3ountain birch canopy and the temperature enhancement treatments had the desired effect to increase the average air tempera,5ture by 2-4-degrees-C. Greenhouses which had a gap between the soil and the greenhouse plastic were particularly successfu,Cl in creating the desired climatic perturbation without causing extreme maximum temperatures or other unwanted side-effect,Fs. The environmental manipulations caused strikingly different responses in the vegetative growth pattern of main shoots o,^f C. tetragona among the three populations: at the subarctic tree-line heath, nutrient addition caused a substantial incre,`ase in growth, whereas it was the temperature enhancement treatments that caused increases, although smaller, at the subar,octic fellfield and the high arctic heath sites. At the high arctic site, we also found growth reduced in response to shadi,qng, but at the subarctic sites, and particularly at the tree-line heath site, shading caused a marked etiolation of the sh,oots. Hence, different factors seem to produce very different responses in the vegetative growth of C. tetragona in differ,ent parts of its geographical range. We conclude that competition for nutrients and light are the main limiting factors fo,r the growth of Cassiope tetragona near the lower distributional limit (LODIL) of the species, but that temperature is the, main limiting factor in the northern parts of its range, and at high altitudes in the southern parts of its range. We als,o suggest that the direct effect of predicted future climatic warming on the growth of Cassiope tetragona will increase to,wards the north, whereas a possible indirect effect of increasing nutrient availability following a temperature increase w,ill be the main effect in the southern and lower parts of its range. These responses could, however, be modified by shadin,g from other species responding to environmental change by increased growth.ith CO2 enrichment of aquatic habitats from r,375^3^Idso,SB^Kimball,BA^Hendrix,DL^1993^1^Air-temperature modifies the size-enhancing effects of atmospheric co2 enrichme,nt on sour orange tree leaves^173^33^2^293-299^^^^^Apr^^^^^3578s based on laboratory data and on theoretical consideratio,A^3577^Every other month for a period of 2 years, leaf area and dry weight measurements were made on the foliage of sour o,range trees growing in ambient air and in air enriched with an extra 300 mul/l CO2. Leaf starch content measurements were $made at approximate 2-month intervals for a period of 1 year. The data demonstrated that all three plant parameters were s$ignificantly increased by atmospheric CO2 enrichment, except in the coldest portion of the year. A plot of the ratio of CO$2-enriched leaf dry weight to ambient-treatment leaf dry weight against the mean air temperature of the preceding month re$vealed this relationship with temperature to be linear. The relationship shows atmospheric CO2 enrichment to have a neglig$ible effect on leaf dry weight at a mean air temperature of approximately 5- degrees-C. At a mean air temperature of 35-de$grees-C, however, it shows individual CO2-enriched leaves of our experiment to weigh 40% more than their ambient-treatment, counterparts. This phenomenon helps to explain the vastly different effects of atmospheric CO2 enrichment that have been ,reported for a number of diverse ecosystems.ate, propionate, butyrate, or a mixture of aliphatic fatty acids (C4 through - 376^2^Jalil,A^Carlson,RM^1993^1^Potassium uptake by marianna plum under limited oxygen and elevated carbon-dioxide levels - in the root atmosphere^166^16^4^723-737^^^^^^^^^^3580ids such as formate, propionate, butyrate, caproate, valerate, pyruv-A^3579^Potassium (K) uptake rates were determined for Marianna 2624 rootstocks with 'French' prune scions using th nutrien-t solution depletion technique. The nutrient solutions were bubbled with factorial combinations of nitrogen (N2), oxygen (-)O2), and carbon dioxide (CO2) to create treatment root atmospheres with O2 ranging from 0.01 to 0.10 m3/m3 and CO2 ranging-+ from 0 to 0.05 m3/m3. The K+ uptake rate was more susceptible to 02 deprivation than to elevated CO2 in the root atmosphe-5re. Decreasing 02 levels from 0.10 M3/M3 decreased K+ uptake in a hyperbolic fashion to no net uptake at 0.01 M3/M3 02. In-7creasing root atmosphere CO2 from 0 to 0.05 M3/M3 had a small depressing effect on net K+ influx from 60 muM K+ solutions -Cat 0.10 and 0.05 M3/M3 02, but no effect when 02 was 0.025 or 0.01 M3/M3. Elevating CO2 decreased Km for the net K+ influx-E rate at 0.10 and 0.05 M3/M3 02. Increased pH buffering from higher HCO3 concentration at the plasma membrane surface was -Nsuggested to explain the CO2 effect on Km.scussed. BP 2302-2307 PG 6 JI Appl. Environ. Microbiol. PY 1991 PD AUG VL 57 IS-P377^4^Kimball,BA^Mauney,JR^Nakayama,FS^Idso,SB^1993^1^Effects of elevated co2 and climate variables on plants^211^48^1^9-1-Y4^^^^^Jan-FebMOSPHERIC CARBON-DIOXIDE CONCENTRATION SO PLANT CELL AND ENVIRONMENT SN 0140-7791 C1 UNIV FLORIDA, DEPT AGRO-[378^1^Krauchi,N^1993^1^Potential impacts of a climate change on forest ecosystems^212^23^1^28-50^^^^^Apr^^^^^3583AINESVIL-fA^3582^Review of literature indicates that many uncertainties and assumptions exist in predicting the impacts of a climate-h change on forest ecosystems. However, current knowledge is sufficient to encourage any measures that are combating climat-se change, that is to reduce first and foremost the release of harmful substances to the atmosphere, lithosphere and biosph-uere. a range of atmospheric CO2 concentrations in outdoor, computer-controlled, environment chambers under natural solar -379^7^Lucas,WJ^Olesinski,A^Hull,RJ^Haudenshield,JS^Deom,CM^Beachy,RN^Wolf,S^1993^1^Influence of the tobacco mosaic-virus 3-0-kda movement protein on carbon metabolism and photosynthate partitioning in transgenic tobacco plants^6^190^1^88-96^^^^^-May^^^^^3585antly with increasing CO2. Although leaf dry weight and leaf area index increased, the overall response was n-A^3584^Transgenic tobacco (Nicotiana tabacum L.) plants expressing the 30-kDa movement protein of tobacco mosaic virus (TM-V-MP) were employed to investigate the influence of a localized change in mesophyll-bundle sheath plasmodesmal size exclus-ion limit on photosynthetic performance and on carbon metabolism and allocation. Under conditions of saturating irradiance-, tobacco plants expressing the TMV-MP were found to have higher photosynthetic CO2-response curves compared with vector c-ontrol plants. However, this difference was significant only in the presence of elevated CO2 levels. Photosynthetic measur-ements made in the greenhouse, under endogenous growth conditions, revealed that there was little difference between TMV-M-P- expressing and control tobacco plants. However, analysis of carbon metabolites within source leaves where a TMV-MP-indu-ced increase in plasmodesmal size exclusion limit had recently taken place established that the levels of sucrose, glucose-, fructose and starch were considerably elevated above those present in equivalent control leaves. Although expression of -the TMV-MP did not alter total plant biomass, it reduced carbon allocation to the lower region of the stem and roots. This- difference in biomass distribution was clearly evident in the lower root-to-shoot ratios for the TMV-MP transgenic plants-. Microinjection (dye-coupling) studies established that the TMV- MP-associated reduction in photosynthate delivery (alloc-ation) to the roots was not due to a direct effect on root cortical plasmodesmata. Rather, this change appeared to result .from an alteration in phloem transport from young source leaves in which the TMV-MP had yet to exert its influence over pl.asmodesmal size exclusion limits. These results are discussed in terms of the rate-limiting steps involved in sucrose move.ment into the phloem.ntial increase in phosphorus loading from urban sources (approximately 1940-70), and decreased phosp.380^4^Nie,D^He,H^Kirkham,MB^Kanemasu,ET^1992^1^Photosynthesis of a C3 grass and a C4 grass under elevated co2^79^26^2^189-.'198^^^^^^^^^^3587storical dynamics and cycling of major nutrients. The temporal pattern of organic carbon production clos.)A^3586^The net photosynthetic rate (P(N)), intercellular CO2 concentration (C(i)), transpiration rate (E), stomatal resist.9ance (r(s)), and water potential (PSI(W)) of a C3 grass (Kentucky bluegrass, Poa pratensis L.) and a C4 grass (big blueste.;m, Andropogon gerardii Vitman) growing in the spring in a tallgrass prairie under two levels of CO2 (ambient and twice amb.Fient) were compared. Elevated CO2 (HC) increased P(N) of Kentucky bluegrass (C3) by 47.0 % but did not affect P(N) of big .Hbluestem (C4). HC increased C(i) of both grasses by about the same amount (is-approximately-equal-to cm3 m-3), but reduced.S E (and parallelly increased r(s)) of big bluestem more than those of Kentucky bluegrass. HC increased PSI(W) of both gras.Uses by about 30 %. Kentucky bluegrass had a lower PSI(W) than big bluestem, but HC increased PSI(W) of Kentucky bluegrass .ato values more similar to those of big bluestem under ambient CO2 (LC). Hence a high PSI(W), resulting from HC, was necess.cary for a high P(N).VEY, DIV WATER RESOURCES, MS 408, LAKEWOOD, CO 80225. WOODS HOLE OCEANOG INST, DEPT BIOL, WOODS HOLE,.e381^4^Polle,A^Pfirrmann,T^Chakrabarti,S^Rennenberg,H^1993^1^The effects of enhanced ozone and enhanced carbon-dioxide conc.nentrations on biomass, pigments and antioxidative enzymes in spruce needles (picea-abies L)^9^16^3^311-316^^^^^Apr^^^^^358.pA^3588^During one growing period, 5-year-old spruce trees (Picea abies L., Karst.) were exposed in environmental chambers .{to elevated concentrations of carbon dioxide (750 cm3 m-3) and ozone (0.08 cm3 m-3) as single variables or in combination..} Control concentrations of the gases were 350 cm 3 m-3 CO2 and 0.02 cm3 m-3 ozone. To investigate whether an elevated CO2 .concentration can prevent adverse ozone effects by reducing oxidative stress, the activities of the protective enzymes sup.eroxide dismutase, catalase and peroxidase were determined. Furthermore, shoot biomass, pigment and protein contents of tw.o needle age classes were investigated. Ozone caused pigment reduction and visible injury in the previous year's needles a.nd growth reduction in the current year's shoots. In the presence of elevated concentrations of ozone and CO2, growth redu.ction in the current year's shoots was prevented, but emergence of visible damage in the previous year's needles was only .delayed and pigment reduction was still found. Elevated concentrations of ozone or CO2 as single variables caused a signif.icant reduction in the activities of superoxide dismutase and catalase in the current year's needles. Minimum activities o.f superoxide dismutase and catalase and decreased peroxidase activities were found in both needle age classes from spruce .trees grown at enhanced concentrations of both CO2 and ozone. These results suggest a reduced tolerance to oxidative stres.s in spruce trees under conditions of elevated concentrations of both CO2 and ozone.equately quantify the processes contr.9 and N transport and transformation within these environments. BP 1815-1825 PG 11 JI Geochim. Cosmochim. Acta PY 1991 P.A^3591^Biodiversity is characteristically defined on three levels: genetic diversity, species diversity and ecosystem dive.rsity. In this paper I consider the impact of elevated CO2 and associated climate change on the biodiversity of terrestria.l systems at the species level. I attempt to understand the impact of a rapidly changing physical environment mechanistica.lly. The direct impact of elevated CO2 is emphasised. A changing physical environment will cause behavioural and physiolog.ical responses in organisms that will affect population dynamics and interspecific relationships. In the short term, extin/ctions will occur via the direct interaction of species with their changing environment. Species exposed to new diseases, /and species dependent on mutualists or keystone species that become extinct or change geographical range, may become extin/  ct rapidly through interactions with other species. I hypothesise that the effect of environmental change on competitive i/ nteractions will play a minor role in causing declines in biodiversity. Existing literature on the impact of climate chang/ e on terrestrial ecosystems emphasises the way in which ecosystems and species should track suitable climates across the l/! andscape. Here I argue that each species will be affected in one, or a combination, of the following ways: range change to/) track shifting climate zones, tolerating the environmental change, microevolutionary change, and extinction.tored Prod. /+384^2^Woodrow,L^Grodzinski,B^1993^1^Ethylene exchange in lycopersicon-esculentum mill - leaves during short-term and long-/3term exposures to co2^78^44^259^471-480^^^^^Feb^^^^^3594YME PATTERN AND INTRACELLULAR LOCATION SO PLANTA SN 0032-0935 C1 /5A^3593^The effects of long-term and transient exposure to elevated CO2 concentrations on photosynthetic gas exchange and e/Athylene release by tomato leaves were investigated. The net CO2 assimilation rate was enhanced when leaf tissue grown at a/Cmbient (35 Pa CO2) levels was assayed at 100 Pa CO2. Leaf tissue grown at high (130 Pa) CO2 exhibited a lower net CO2 assi/Tmilation rate at high CO2 levels than leaf tissue grown at ambient (35 Pa) CO2. This decrease in CO2 exchange rate in resp/Uonse to growth at high CO2 is typical Of C3 species. Rates of endogenous and 1-aminocyclopropane-1-carboxylic acid (ACC)- /hStimulated ethylene release from leaf tissue were enhanced by exposure to elevated CO2 levels whether the leaf tissue had /jbeen grown at ambient or enriched CO2 levels, The data demonstrate that CO2 enhanced C2H4 release from leaf tissue in resp/xonse to both short-term perturbations in CO2 concentration and long-term growth and development under high CO2. Prolonged /zgrowth at elevated CO2 concentrations induced a higher endogenous rate of C2H4 release relative to that of leaf tissue gro/~wn at lower CO2 levels. Leaf tissue from all leaf positions of plants grown at high CO2 consistently evolved more C2H4 tha/n corresponding tissue from ambient-grown plants when assayed under standardized conditions. Endogenous (ACC) tissue conte/nts and rates of ACC-stimulated ethylene release were also higher at all leaf positions in CO2-enriched tissue. Thus the h/igher rates appeared to be due to both higher endogenous precursor (ACC) levels in the tissue and greater ACC to C2H4 conv/ersion capacity. Growth at elevated CO2 levels resulted in a persistent increase in the rate of endogenous C2H4 release in/ leaf tissue. The capacity for increased ethylene release in response to CO2 did not decline after prolonged growth at hig/h CO2.STRAIN, BR TI ROOT RESTRICTION AS A FACTOR IN PHOTOSYNTHETIC ACCLIMATION OF COTTON SEEDLINGS GROWN IN ELEVATED CARB/ 385^2^Adamse,P^Britz,SJ^1992^1^Amelioration of uv-b damage under high irradiance .1. Role of photosynthesis^63^56^5^645-65/0^^^^^Nov^^^^^3596NRICHMENT; INHIBITION; TEMPERATURE; CARBOXYLASE; EXCHANGE; SOYBEANS AB Interactive effects of root rest/"A^3595^Sensitivity to ultraviolet-B radiation (UV-B, 280-315 nm) is generally reduced when background irradiance is high. /#We tested the involvement of photosynthesis in the amelioration of UV-B damage by treating plants at high PAR (photosynthe/$tically- active radiation. 400-700 nm; 1000 mumol m-2 s-1) with supplemental UV-B at double ambient levels of biologically/%- effective radiation (18 kJ m-2 d-1) and either ''ambient'' (450 mumol mol-1) or short term elevated (750 mumol mol-1) CO/&2 levels. Responses to UV-B were assessed by photosynthetic gas exchange, leaf expansion and production of UV-absorbing co/'mpounds (presumptive flavonoids) in cultivars of cucumber (Cucumis sativus L.) previously demonstrated to be relatively se/(nsitive (cv. Poinsett) and insensitive (cv. Ashley) to UV-B. Except for marginal leaf interveinal chlorosis observed in Po/)insett, both cultivars responded similarly. UV-B had little direct effect on leaf photosynthesis, but it did cause reducti0*ons in leaf area and corresponding increases in leaf dry matter per area. Increased CO2 stimulated plant growth, counterac0+ting the effect of UV-B on leaf growth and indicating an important role for photosynthesis. In contrast, the accumulation 0of UV-absorbing flavonoid compounds was enhanced by UV-B exposure but was not affected by CO2 enrichment.vity may be resp0/-386^5^Arp,WJ^Drake,BG^Pockman,WT^Curtis,PS^Whigham,DF^1993^1^Interactions between C-3 and C-4 salt-marsh plant-species dur01ing 4 years of exposure to elevated atmospheric co2^24^104^^133-143^^^^^Jan^^^^^3598n capacity increased indicating that 0D/A^3597^Elevated atmospheric CO2 is known to stimulate photosynthesis and growth of plants with the C3 pathway but less of 0F0plants with the C4 pathway. An increase in the CO2 concentration can therefore be expected to change the competitive inter0O1actions between C3 and C4 species. The effect of long term exposure to elevated CO2 (ambient CO2 concentration + 340 mumol0R2 CO2 mol-1) on a salt marsh vegetation with both C3 and C4 species was investigated. Elevated CO2 increased the biomass of0Z3 the C3 sedge Scirpus olneyi growing in a pure stand, while the biomass of the C4 grass Spartina patens in a monospecific 0[4community was not affected. In the mixed C3/C4 community the C3 sedge showed a very large relative increase in biomass in 0h5elevated CO2 while the biomass of the C4 species declined. The C4 grass Spartina patens dominated the higher areas of the 0j6salt marsh, while the C3 sedge Scirpus olneyi was most abundant at the lower elevations, and the mixed community occupied 0z7intermediate elevations. Scirpus growth may have been restricted by drought and salt stress at the higher elevations, whil0|8e Spartina growth at the lower elevations may be affected by the higher frequency of flooding. Elevated CO2 may affect the09 species distribution in the salt marsh if it allows Scirpus to grow at higher elevations where it in turn may affect the 0growth of Spartina.out the growing season and analysed for starch, K, P, Ca, Mg, Fe, and Mn concentrations. Foliar K and 0;387^2^Baker,JT^Allen,LH^1993^1^Contrasting crop species responses to co2 and temperature - rice, soybean and citrus^24^1040^^239-260^^^^^Jan^^^^^3600the plants of one genotype received foliar applications of 7 millimolar KH2PO4. Untreated folia0=A^3599^The continuing increase in atmospheric carbon dioxide concentration ([CO2]) and projections of possible future incr0>eases in global air temperatures have stimulated interest in the effects of these climate variables on plants and, in part0?icular, on agriculturally important food crops. Mounting evidence from many different experiments suggests that the magnit0@ude and even direction of crop responses to [CO2] and temperature is almost certain to be species dependent and very likel0Ay, within a species, to be cultivar dependent. Over the last decade, [CO2] and temperature experiments have been conducted0B on several crop species in the outdoor, naturally- sunlit, environmentally controlled, plant growth chambers by USDA-ARS 0Cand the University of Florida, at Gainesville, Florida, USA. The objectives for this paper are to summarize some of the ma0Djor findings of these experiments and further to compare and contrast species responses to [CO2] and temperature for three0E diverse crop species: rice (Oryza sativa, L.). soybean (Glycine max, L.) and citrus (various species). Citrus had the low0Fest growth and photosynthetic rates but under [CO2] enrichment displayed the greatest percentage increases over ambient [C0GO2] control treatments. In all three species the direct effect of [CO2] enrichment was always an increase in photosyntheti0Hc rate. In soybean, photosynthetic rate depended on current [CO2] regardless of the long-term [CO2] history of the crop. I1In rice, photosynthetic rate measured at a common [CO2], decreased with increasing long-term [CO2] growth treatment due to 1Ja corresponding decline in RuBP carboxylase content and activity. Rice specific respiration decreased from subambient to a1Kmbient and superambient [CO2] due to a decrease in plant tissue nitrogen content and a decline in specific maintenance res1Lpiration rate. In all three species, crop water use decreased with [CO2] enrichment but increased with increases in temper1Mature. For both rice and soybean, [CO2] enrichment increased growth and grain yield. Rice grain yields declined by roughly1 10% per each 1-degrees-C rise in day/night temperature above 28/21-degrees-C.GENASE; OXIDATION; LACTATE; ALANINE; INJURY11388^1^Dahlman,RC^1993^1^Co2 and plants - revisited^24^104^^339-355^^^^^Jan^^^^^3602lucose metabolism that makes the sever13PA^3601^The decade-long USA research program on the direct effects of CO2 enrichment on vegetation has achieved important m1>Qilestones and has produced a number of interesting and exciting findings. Research beginning in 1980 focused on field expe1@Rriments to determine whether phenomena observed in the laboratory indeed occurred in natural environments. The answer is y1OSes. Data obtained from numerous field studies show mixed response of crop and native species to CO2 enrichment however. Ne1QTarly all experiments demonstrate that plants exhibit positive gain when grown at elevated CO2; although the magnitude vari1^Ues greatly. Most crop responses range from 30 to 50 % increase in yield. Results from long-term experiments with woody spe1`Vcies and ecosystems are even more variable. Huge growth responses (100 to nearly 300 % increase relative to controls) are 1sWreported from several tree experiments and the salt-marsh ecosystem experiment. Other results from experiments with woody 1uXspecies and the tundra ecosystem suggest little no effect of CO2 on physiology, growth or productivity. Numerous studies o1Yf the physiology of the CO2 effect are continuing in attempts to understand controlling mechanisms and to explain the vari1Zable growth responses. Particular emphasis needs to be given to physiological measures of interactions involving the CO2 e1[ffect and other environmental influences, and to the wide-ranging observations of photosynthesis acclimation to CO2. Prosp1ects for future research are identified.t of pyruvate directed to oxidation, thereby reducing the conversion of pyruvate 1]389^2^Debevec,EM^Maclean,SF^1993^1^Design of greenhouses for the manipulation of temperature in tundra plant-communities^110^25^1^56-62^^^^^Feb^^^^^3604dichloroacetate treatment, no unique effect of dichloroacetate on glucose or protein kinetic1_A^3603^Passive greenhouses can be used to elevate the temperature of natural communities, but they also introduce other ef1`fects. We tested the effects of potential greenhouse materials-clear polyethylene plastic film, polyester fabric, and rigi1ad fiberglass panels-on light transmission, photosynthesis of Salix planifolia, elevation of air and soil temperature, and 1bthaw depth. Plastic had the greatest light transmittance and caused the least depression of photosynthesis (- 5%). Greenho1cuses covered with plastic elevated daily maximum and daily mean air temperatures by an average of 7.8 and 2.0- degrees-C a1dnd depressed daily minimum temperature by 1.1- degrees-C compared with the control. Plastic is impervious to gases and may1e alter CO2 concentration and humidity within greenhouses. Fiberglass had lower transmittance, especially of short waveleng1fth radiation. Fabric had the lowest light transmission and reduced photosynthesis by 10%, but it has the advantage of perm1geability to CO2 and water vapor. Greenhouses covered with fabric, alone, produced only a small effect (daily mean temperat1hure elevated 0.4-degrees-C above controls). A mixed greenhouse design (plastic and fabric) raised daily mean temperatures 1iby 0.9-degrees-C and may minimize adverse effects on gas diffusion. Because of the effect of the materials on amount and s1jpectral distribution of radiation and on photosynthesis, the appropriate treatment control for any greenhouse design is an1k open plot shaded with the same material. Soil temperature at 10 cm depth was elevated in all greenhouses, but no effect o1n depth of thaw was detected.ive strains. Catabolism of benzyl alcohol by phototrophic bacteria has not been previously 1m390^3^Denhertog,J^Stulen,I^Lambers,H^1993^1^Assimilation, respiration and allocation of carbon in plantago major as affect1ed by atmospheric co2 levels - a case-study^24^104^^369-378^^^^^Jan^^^^^3606thoxybenzoate). However, catabolism of vanil1oA^3605^The response of Plantago major ssp. pleiosperma plants, grown on nutrient solution in a climate chamber, to a doubl/ping of the ambient atmospheric CO2 concentration was investigated. Total dry matter production was increased by 30 % after/q 3 weeks of exposure, due to a transient stimulation of the relative growth rate (RGR) during the first 10 days. Thereafte0rr RGR returned to the level of control plants. Photosynthesis, expressed per unit leaf area, was stimulated during the fir2sst two weeks of the experiment, thereafter it dropped and nearly reached the level of the control plants. Root respiration2 t was not affected by increased atmospheric CO2 levels, whereas shoot, dark respiration was stimulated throughout the exper2uimental period. Dry matter allocation over leaves stems and roots was not affected by the CO2 level. SLA was reduced by 102!v%, which can partly be explained by an increased dry matter content of the leaves. Both in the early and later stages of t2#whe experiment, shoot respiration accounted for a larger part of the carbon budget in plants grown at elevated atmospheric 2:xCO2. Shifts in the total carbon budget were mainly due to the effects on shoot respiration. Leaf growth accounted for near2<ly 50 % of the C budget at all stages of the experiment and in both treatments.) were studied in isolated perfused rat li2Nz391^2^Idso,SB^Kimball,BA^1993^1^Effects of atmospheric co2 enrichment on net photosynthesis and dark respiration rates of 2Q3 australian tree species^4^141^2^166-171^^^^^Feb^^^^^3608pH 7.4), which was recycled through the liver for 2 hr. Individ2i|A^3607^Net photosynthesis and dark respiration rates of leaves of three Australian tree species exposed to a range of atmo2k}spheric CO2 concentrations were measured throughout the summer of 1991. For all three species - the Australian bottle tree2{~ (Brachychiton populneum (Schott.) R. Br.) and two eucalyptus (Eucalyptus microtheca F. Muell. and E. polyanthemus Schauer2}) - dark respiration dropped by approximately 50 % for a 360 to 720 muL/L doubling of the air's CO2 concentration, while n2et photosynthesis rose by a factor of two. These results were not significantly different from results obtained previously2 for the common sour orange tree (Citrus aurantium L.). Additionally, the perfusate concentration of oleate in the free f2392^3^Johnson,HB^Polley,HW^Mayeux,HS^1993^1^Increasing co2 and plant-plant interactions - effects on natural vegetation^242^104^^157-170^^^^^Jan^^^^^3610genously supplied fatty acid. The net secretion rate of VLDL lipids and protein was stimula2A^3609^Plant species and functional groups of species show marked differences in photosynthesis and growth in relation to 2rising atmospheric CO2 concentrations through the range of the 30 % increase of the recent past and the 100 % increase sin2ce the last glaciation. A large shift was found in the compositional mix of 26 species of C3's and 17 species of C4's grow2n from a native soil seed bank in a competitive mode along a CO2 gradient that approximated the CO2 increase of the past 1250 years and before. The biomass of C3's increased from near zero to 50 % of the total while that of the C4's was reduced 225 % as CO2 levels approached current ambient. The proposition that acclimation to rising CO2 will largely negate the fert2ilization effect of higher CO2 levels on C3's is not supported. No signs of photosynthetic acclimation were evident for Av2ena sativa, Prosopis glandulosa, and Schizachyrium scoparium plants grown in subambient CO2. The effects of changing CO2 l2evels on vegetation since the last glaciation are thought to have been at least as great, if not greater, than those which2 should be expected for a doubling of current CO2 levels. Atmospheric CO2 concentrations below 200 ppm are thought to have2 been instrumental in the rise of the C4 grasslands of North America and other extensive C4 grasslands and savannas of the2 world. Dramatic invasion of these areas by woody C3 species are accompanying the historical increase in atmospheric CO2 c2oncentration now in progress. that of oleate or DHA. Furthermore, utilization of endogenous fatty acids for TG synthesis 2393^4^Kaji,H^Ueno,M^Ikebe,T^Osajima,Y^1993^1^Effects of low o-2 and elevated co2 concentrations on the quality of matsutak3 e [tricholoma-matsutake (s ito et imai) sing] during storage^213^57^3^363-366^^^^^Mar^^^^^3612n of EPA provide substantia3 A^3611^Matsutake [Tricholoma matsutake (S. ITO et IMAI) SING.] was stored under conditions of low O2 and elevated CO2 conc3 entrations. The storage conditions were as follows: with an O2 concentration of 2.5+/-0.5%, the CO2 concentrations were 5%3", 10%, 15%, and 20%, and relative humidity (RH) was about 100%; with an O2 concentration of 2.0+/-0.5%, the CO2 concentrat31ions were 0%, 5%, 10%, and 15%, and RH was about 100%; the storage temperature was 1.0+/-0.1-degrees-C. The fruit was also33 stored in air and under 100% N2 as controls. Quality factors such as 'neto' (slimy microbial flora which develop on the m3Doist surface of the fruiting body), weight loss, whiteness, firmness, and off-odor were measured. The development of neto 3Fand browning (loss of whiteness) of the inner stipe were suppressed for more than 14 days, except with storage under 100% 3VN2. Storage in air and under 0% or a high concentration (> 10%) of CO2 caused an early development of off-odor, compared t3Xo storage under 5% and 10% CO2. In air, the development of mold was observed after 14 days. Under a low O2 concentration a3knd 5% to 10% CO2, the quality factors of matsutake were most retained, and the fruit was still acceptable after 14 days of3m storage. A weight decrease of the fruit was recognized as the CO2 concentration was increased.3y394^4^Kimball,BA^Mauney,JR^Nakayama,FS^Idso,SB^1993^1^Effects of increasing atmospheric co2 on vegetation^24^104^^65-75^^^3{^^Jan^^^^^36143A^3613^The increasing atmospheric CO2 concentration probably will have significant direct effects on vegetation whether pr3edicted changes in climate occur or not. Averaging over many prior greenhouse and growth chamber studies, plant growth and3 yield have typically increased more than 30%, with a doubling of CO2 concentration. Such a doubling also causes stomatal 3conductance to decrease about 37 which typically increases leaf temperatures more than 1-degrees-C, and which may decrease3 evapotranspiration, although increases in leaf area counteract the latter effect. Interactions between CO2 and climate va3riables also appear important. In one study the growth increase from near-doubled CO2 ranged from minus 60% at 12- degrees3-C to 0% at 19-degrees-C to plus 130% at 34-degrees-C, suggesting that if the climate warms, the average growth response t3o doubled CO2 could be consistently higher than the 30% mentioned above. Even when growing in nutrient-poor soil, the grow3th response to elevated CO2 has been large, in contrast to nutrient solution studies which showed little response. Several3 studies have suggested that under water-stress, the CO2 growth stimulation is as large or larger than under wellwatered c3onditions. Therefore, the direct CO2 effect will compensate somewhat, if not completely, for a hotter drier climate. And i3f any climate change is small, then plant growth and crop yields will probably be significantly higher in the future high-3CO2 world.3395^2^Krupa,SV^Kickert,RN^1993^1^The greenhouse-effect - the impacts of carbon-dioxide (co2), ultraviolet-b (uv-b) radiati3on and ozone (o3) on vegetation (crops)^24^104^^223-238^^^^^Jan^^^^^3616s/0 000p199993A^3615^Man's influence on the 'greenhouse effect,' the heating of the atmosphere due to increasing concentrations of tropo3spheric trace gases, is of much international concern. Among the climatic variables, elevated levels of carbon dioxide (CO32), ultraviolet-B (UV-B) radiation and ozone (O3) are known to have a direct effect on vegetation. Our current knowledge o3f these effects is mainly based on studies involving single stress mode. Thus, the joint effects of CO2, UV-B and O3 on ve4getation are poorly understood. Nevertheless, based on the literature analysis of plant response to individual stress fact4ors, it can be concluded that sorghum, pea, bean, potato, oat, lettuce, cucumber, rice and tomato are among the crop speci4es potentially sensitive to the joint effects of the aforementioned three variables. Similar information for tree species 4 is essentially lacking. At least with some climatic variables such as O3, present modeling efforts of cause-effect relatio4"nships have proven to be controversial. While at a regional geographic scale ambient CO2 concentrations appear to be relat4)ively homogeneous, ambient concentrations of O3 exhibit significant temporal and spatial variability. Because of the prote4+ctive action of O3 against UV-B, similar but inverse temporal and spatial variability is expected in the surface levels of4: UV-B. Thus, future experimental designs should consider these exposure dynamics and modeling cause-effect relationships s4<hould be directed to stochastic processes.4K396^1^Lambers,H^1993^1^Rising co2, secondary plant-metabolism, plant-herbivore interactions and litter decomposition - the4Moretical considerations^24^104^^263-271^^^^^Jan^^^^^36184ZA^3617^A brief account is given of the ecological significance of quantitatively important secondary plant compounds, main4\ly those of a phenolic nature, in herbivory and decomposition. Phenolic compounds accumulate to a greater extent in slow- 4hgrowing species than in fast-growing ones, particularly when soil conditions (nutrients, water) restrict growth. Two hypot4jheses to explain the increased concentration of phenolics when soil conditions are unfavorable are presented. The first hy4vpothesis (the 'carbon supply model of secondary plant metabolism') considers the increased levels of non-structural carboh4xydrates as the major trigger. The second hypothesis (the 'amino acid diversion model of secondary plant metabolism') state4s that increased accumulation of phenolics stems from a decreased use of a common precursor (phenylalanine or tyrosine) fo4r protein synthesis. Current experimental evidence, though still fairly limited, supports the second hypothesis, but furth4er testing is required before the first model can be rejected. So far, there is very little evidence for a direct effect o4f atmospheric CO2 on the concentration of secondary compounds in higher plants. However, there are likely to be indirect e4ffects, due to a stronger limitation by the nitrogen supply in plants whose growth has been promoted by atmospheric CO2. I4t is concluded that it is very likely that phenolic compounds accumulate to a greater extent in plants exposed to elevated4 CO2, due to a greater limitation of nutrients, rather than as a direct effect of elevated CO2.o@oMoo4397^2^Leadley,PW^Drake,BG^1993^1^Open top chambers for exposing plant canopies to elevated co2 concentration and for measu4ring net gas-exchange^24^104^^3-15^^^^^Jan^^^^^36204A^3619^Open top chamber design and function are reviewed. All of the chambers described maintain CO2 concentrations measur4ed at a central location within +/- 30 ppm of a desired target when averaged over the growing season, but the spatial and 4temporal range within any chamber may be closer to 100 ppm. Compared with unchambered companion plots, open top chambers m4odify the microenvironment in the following ways: temperatures are increased up to 3-degrees-C depending on the chamber de4sign and location of the measurement; light intensity is typically diminished by as much as 20%; wind velocity is lower an4d constant; and relative humidity is higher. The chamber environment may significantly alter plant growth when compared wi4th unchambered controls, but the chamber effect on growth has not been clearly attributed to a single or even a few enviro4nmental factors. A method for modifying an open top chamber for tracking gas exchange between natural vegetation and the a4mbient air is described. This modification consists of the addition of a top with exit chimney to reduce dilution of chamb5er CO2 by external ambient air, is quickly made and permits estimation of the effects of elevated CO2 and water vapor exch5ange. The relatively simple design and construction of open top chambers make them the most likely method to be used in th5e near future for long-term elevated CO2 exposure of small trees, crops and grassland ecosystems. Improvements in the basi5c geometry to improve control of temperature, reduce the variation of CO2 concentrations, and increase the turbulence and 5wind speed in the canopy boundary layer are desirable objectives. Similarly, modifications for measuring water vapor and c5*arbon dioxide gas exchange will extend the usefulness of open top chambers to include non-destructive monitoring of the re5,sponses of ecosystems to rising atmospheric CO2.5?398^4^Lenssen,GM^Lamers,J^Stroetenga,M^Rozema,J^1993^1^Interactive effects of atmospheric co2 enrichment, salinity and flo5Aoding on growth of C-3 (elymus-athericus) and C-4 (spartina- anglica) salt-marsh species^24^104^^379-388^^^^^Jan^^^^^36225OA^3621^The growth response of Dutch salt marsh species (C3 and C4) to atmospheric CO2 enrichment was investigated. Tillers5Q of the C3 species Elymus athericus were grown in combinations of 380 and 720 mul l-1 CO2 and low (0) and high (300 mM NaC5]l) soil salinity. CO2 enrichment increased dry matter production and leaf area development while both parameters were redu5^ced at high salinity. The relative growth response to CO2 enrichment was higher under saline conditions. Growth increase a5gt elevated CO2 was higher after 34 than 71 days. A lower response to CO2 enrichment after 71 days was associated with a de5icreased specific leaf area (SLA). In two other experiments the effect of CO2 (380 and 720 mul l-1) on growth of the C4 spe5ucies Spartina anglica was studied. In the first experiment total plant dry weight was reduced by 20% at elevated CO2. SLA 5walso decreased at high CO2. The effect of elevated CO2 was also studied in combination with soil salinity (50 and 400 mM N5aCl) and flooding. Again plant weight was reduced (10%) at elevated CO2, except under the combined treatment high salinity5/non- flooded. But these effects were not significant. High salinity reduced total plant weight while flooding had no effe5ct. Causes of the salinity-dependent effect of CO2 enrichment on growth and consequences of elevated CO2 for competition b5etween C3 and C4 species are discussed.Xciqx~ٳQt5399^1^Lincoln,DE^1993^1^The influence of plant carbon-dioxide and nutrient supply on susceptibility to insect herbivores^254^104^^273-280^^^^^Jan^^^^^36245A^3623^The carbon/nutrient ratio of plants has been hypothesized to be a significant regulator of plant susceptibility of 5leaf-eating insects. As rising atmospheric carbon dioxide stimulates photosynthesis, host plant carbon supply is increased5 and the accompanying higher levels of carbohydrates, especially starch, apparently 'dilute' the protein content of the le5af. When host plant nitrogen supply is limited, plant responses include increased carbohydrate accumulation, reduced leaf 5protein content, but also increased carbon-based defensive chemicals. No change, however, has been observed in the concent5ration of leaf defensive allelochemicals with elevated carbon dioxide during host plant growth. Insect responses to carbon5-fertilized leaves include increased consumption with little change in growth, or alternatively, little change in consumpt5ion with decreased growth, as well as enhanced leaf digestibility, reduced nitrogen use efficiency, and reduced fecundity.5 The effects of plant carbon and nutrient supply on herbivores appear to result, at least in part, from independent proces5ses affecting secondary metabolism.js-O\ 5400^3^Lindroth,RL^Jung,SM^Feuker,AM^1993^1^Detoxication activity in the gypsy-moth - effects of host co2 and no3-availabil5ity^112^19^2^357-367^^^^^Feb^^^^^36266A^3625^We investigated the effects of host species and resource (carbon dioxide, nitrate) availability on activity of deto3xication enzymes in the gypsy moth, Lymantria dispar. Larvae were fed foliage from quaking aspen or sugar maple grown unde#r ambient or elevated atmospheric CO2, with low or high soil NO3- availability. Enzyme solutions were prepared from larval6 midguts and assayed for activity of cytochrome P-450 monooxygenase, esterase, glutathione transferase, and carbonyl reduc6tase enzymes. Activity of each enzyme system was influenced by larval host species, CO2 or NO3- availability, or an intera6ction of factors. Activity of all but glutathione transferases was highest in larvae reared on aspen. Elevated atmospheric6% CO2 promoted all but transferase activity in larvae reared on aspen, but had little if any impact on enzyme activities of6' larvae reared on maple. High NO3- availability enhanced activity of most enzyme systems in gypsy moths fed high CO2 folia62ge, but the effect was less consistent for insects fed ambient CO2 foliage. This research shows that gypsy moths respond b64401^3^Lindroth,RL^Kinney,KK^Platz,CL^1993^1^Responses of deciduous trees to elevated atmospheric co2 - productivity, phyto6Bchemistry, and insect performance^11^74^3^763-777^^^^^Apr^^^^^36286DA^3627^Although rising levels of atmospheric carbon dioxide are expected to directly affect forest ecosystems, little is k6Qnown of how specific ecological interactions will be modified. This research evaluated the effects of enriched CO2 on the 6Sproductivity and phytochemistry of forest trees and performance of associated insects. Our experimental system consisted o6_f three tree species (quaking aspen [Populus tremuloides], red oak [Quercus rubra], sugar maple [Acer saccharum]) that spa6an a range from fast to slow growing, and two species of leaf- feeding insects (gypsy moth [Lymantria dispar] and forest te6p nt caterpillar [Malacosoma disstria]). Carbon-nutrient balance theory provided a framework for tests of three hypotheses; 6r in response to enriched CO2: (1) relative increases in tree growth rates will be greatest for aspen and least for maple, (6 2) relative decreases in protein and increases in carbon-based compounds will be greatest for aspen and least for maple, a6 nd (3) relative reductions in performance will be greatest for insects fed aspen and least for insects fed maple. We grew 6 1- yr-old seedlings for 60 d under ambient (385 +/- 5 muL/L) or elevated (642 +/- 2 muL/L) CO2 regimes at the University o6f Wisconsin Biotron. After 50 d, we conducted feeding trials with penultimate-instar gypsy moth and forest tent caterpilla6rs. After 60 d, a second set of trees was harvested and partitioned into root, stem, and leaf tissues. We subsequently ana6lyzed leaf material for a variety of compounds known to affect performance of insect herbivores. In terms of actual dry-ma6tter production, aspen responded the most to enriched CO2 atmospheres whereas maple responded the least. Proportional grow6th increases (relative to ambient plants), however, were highest for oak and least for maple. Effects of elevated CO2 on b6iomass allocation patterns differed among the three species; root-to-shoot ratios increased in aspen, decreased in oak, an6d did not change in maple. Enriched CO2 altered concentrations of primary and secondary metabolites in leaves, but the mag6nitude and direction of effects were species-specific. Aspen showed the largest change in storage carbon compounds (starch6), whereas maple experienced the largest change in defensive carbon compounds (condensed and hydrolyzable tannins). Consum6ption rates of insects fed high-CO2 aspen increased dramatically, but growth rates declined. The two species of insects di6ffered in response to oak and maple grown under enriched CO2. Gypsy moths grew better on high-CO2 Oak, whereas forest tent6 caterpillars were unaffected; tent caterpillars tended to grow less on high-CO2 maple, whereas gypsy moths were unaffecte6d. Changes in insect performance parameters were related to changes in foliar chemistry. Responses of plants and insects a6greed with some, but not all, of the predictions of carbon-nutrient balance theory. This study illustrates that tree produ7ctivity and chemistry, and the performance of associated insects, will change under CO2 atmospheres predicted for the next7  century. Changes in higher level ecological processes, such as community structure and nutrient cycling, are also implica7ted.%%%%%%%%%'&&&&%'l',,,,,,,,,,,,,'-7402^3^Long,SP^Baker,NR^Raines,CA^1993^1^Analyzing the responses of photosynthetic co2 assimilation to long-term elevation 7(of atmospheric co2 concentration^24^104^^33-45^^^^^Jan^^^^^3630@@%@*@3@B@M@P@Q@V@p@@AA7*!A^3629^Understanding how photosynthetic capacity acclimatises when plants are grown in an atmosphere of rising CO2 concent77"rations will be vital to the development of mechanistic models of the response of plant productivity to global environment79#al change. A limitation to the study of acclimatisation is the small amount of material that may be destructively harveste7F$d from long-term studies of the effects of elevation of CO2 concentration. Technological developments in the measurement o7H%f gas exchange, fluorescence and absorption spectroscopy, coupled with theoretical developments in the interpretation of m7S&easured values now allow detailed analyses of limitations to photosynthesis in vivo. The use of leaf chambers with Ulbrich7U't integrating spheres allows separation of change in the maximum efficiency of energy transduction in the assimilation of 7a(CO2 from changes in tissue absorptance. Analysis of the response of CO2 assimilation to intercellular CO2 concentration al7c)lows quantitative determination of the limitation imposed by stomata, carboxylation efficiency, and the rate of regenerati7m*on of ribulose 1:5 bisphosphate. Chlorophyll fluorescence provides a rapid method for detecting photoinhibition in heterog7o+eneously illuminated leaves within canopies in the field. Modulated fluorescence and absorption spectroscopy allow paralle7}l measurements of the efficiency of light utilisation in electron transport through photosystems I and II in situ.7-403^1^Lurie,S^1993^1^Modified atmosphere storage of peaches and nectarines to reduce storage disorders^214^16^1^57-65^^^^^7Feb^^^^^3632ion6;6j6!08:31 AM 29 01 17/A^3631^Low density polyethylene or polyolefin films were used to seal pack various varieties of peaches and nectarines. Lo70w density polyethylene film of 40 micron thickness was beneficial in extending storage life of these fruits and decreasing71 internal flesh breakdown and reddening, while polyolefin film was ineffective. Six fruits per pack generated a higher CO272 and lower O2 modified atmosphere than two or four fruits per pack and gave better quality fruit after storage. The improv7ement of fruit quality was correlated with elevated CO2 levels rather than with decreased O2 levels.1?RGw60574404^3^Madsen,TV^Sandjensen,K^Beer,S^1993^1^Comparison of photosynthetic performance and carboxylation capacity in a range 7of aquatic macrophytes of different growth forms^159^44^4^373-384^^^^^Feb^^^^^36340:16 AM 30 01 1999 -0500CO2MAP76A^3633^Photosynthesis, carbon extraction capacity and ribulose-1,5- biphosphate carboxylase/oxygenase (RUBISCO) activity w77ere determined for 35 species of submerged aquatic macrophytes differing with respect to taxonomy, growth form and habitat78. Photosynthetic rates per unit of chlorophyll and dry weight at ambient CO2 concentrations (about 15 muM) as well as carb79on extraction capacity increased among plant groups in the order: isoetids, amphibious species, elodeids with no apparent 7:HCO3- use, elodeids with HCO3- use, marine angiosperms and marine macroalgae. Photosynthetic rates at elevated CO2 concent7;rations (300-350 muM) showed the same pattern but smaller differences among the groups. Only for some of the marine macroa8ume ratio. The opposite pattern was found among species with low carbon extraction capacity. The low chlorophyll content a8?nd high chlorophyll specific photosynthesis of species with high carbon transport capability (i.e. particularly the marine8@ algae), suggest that running costs associated with inorganic carbon assimilation are reduced when a CO2 concentrating sys8!tem operates.Dby|610:33 AM 01 02 1999 -0500CURTIS Peter80B405^2^McMurtrie,RE^Wang,YP^1993^1^Mathematical-models of the photosynthetic response of tree stands to rising co2 concentr82ations and temperatures^9^16^1^1-13^^^^^Jan^^^^^3636 -0500CO2MAP8?DA^3635^Two published models of canopy photosynthesis, MAESTRO and BIOMASS, are simulated to examine the response of tree s8AEtands to increasing ambient concentrations of carbon dioxide (C(a)) and temperatures. The models employ the same equations8ZF to described leaf gas exchange, but differ considerably in the level of detail employed to represent canopy structure and8\G radiation environment. Daily rates of canopy photosynthesis simulated by the two models agree to within 10% across a rang8nHe of CO2 concentrations and temperatures. A doubling of C(a) leads to modest increases of simulated daily canopy photosynt8pIhesis at low temperatures (10% increase at 10-degrees- C), but larger increases at higher temperatures (60% increase at 308|J-degrees-C). The temperature and CO2 dependencies of canopy photosynthesis are interpreted in terms of simulated contribut8~Kions by quantum-saturated and non-saturated foliage. Simulations are presented for periods ranging from a diurnal cycle to8L several years. Annual canopy photosynthesis simulated by BIOMASS for trees experiencing no water stress is linearly relat8Med to simulated annual absorbed photosynthetically active radiation, with light utilization coefficients for carbon of eps8ilon = 1.66 and 2.07 g MJ-1 derived for C(a) of 350 and 700 mumol mol-1, respectively.M8O406^2^Miglietta,F^Raschi,A^1993^1^Studying the effect of elevated co2 in the open in a naturally enriched environment in c8entral italy^24^104^^391-400^^^^^Jan^^^^^3638Nt}I604:54 PM8QA^3637^A gas vents area was recently localized in Central Italy. The gas emitted from the vents is composed by 92% of carb8Ron dioxide and this produces an anomaly in the composition of the atmosphere over an area of about 2 ha. Atmospheric carbo8Sn dioxide concentration was measured by means of an infrared gas analyzer and diffusion tubes in several points and for so8Tme days within the area. Measurements revealed that the site can be at least divided into three sub-areas having increasin8Ug CO2 concentration in the air. A preliminary analysis of natural vegetation in the area was conducted by counting stomata8Vl and epidermal cells number and measuring guard cell size on leaves of several oak trees growing both near and far away f8Wrom the vents. This analysis suggested that elevated CO2 may have reduced the size of guard cells leaving stomatal density8 and stomatal index unaltered.Thanks!8407^1^Morison,JIL^1993^1^Response of plants to co2 under water limited conditions^24^104^^193-209^^^^^Jan^^^^^36408ZA^3639^The influence of increased atmospheric CO2 on the interaction between plant growth and water use is proving to be o8[ne of the most profound impacts of the anthropogenic 'Greenhouse Effect'. This paper illustrates the interaction between C9\O2 and water in plant growth at a range of scales. Most published work has concentrated on water use efficiency, especiall9]y at shorter time scales, and has shown large increases of leaf water use efficiency with increased CO2. However, the magn9^itude of the effect is variable, and does not consistently agree with predictions from simple leaf gas exchange considerat9_ions. The longer the time scales considered, the less the information and the more the uncertainty in the response to CO2,9 ` because of the additional factors that have to be considered, such as changes in leaf area, respiration of non-photosynth9"aetic tissues and soil evaporation. The need for more detailed studies of the interactions between plant evaporation, water9.b supply, water status and growth is stressed, as increased CO2 can affect all of these either directly, or indirectly thro90ugh feedbacks with leaf gas exchange, carbon partitioning, leaf growth, canopy development and root growth.LEEGE Liss9Id408^1^Mousseau,M^1993^1^Effects of elevated co2 on growth, photosynthesis and respiration of sweet chestnut (castanea-sati9Kva mill)^24^104^^413-419^^^^^Jan^^^^^364209:05 AM 04 02 1999 -0500Joy Curley9QfA^3641^Two year old sweet chestnut seedlings (Castanea sativa Mill) were grown in pots at ambient (350 mumol.mol-1) and do9Sguble (700 mumol.mol-1) atmospheric CO2 concentration in constantly ventilated greenhouses during entire growing seasons. C9chO2 enrichment caused either no significant change or a decrease in shoot growth response, depending on yearly weather cond9eiition either reduced or unchanged under elevated CO2. However, when grown under controlled conditions in a growth chamber,9sj leaf area was enlarged with elevated CO2. The CO2 exchanges of whole plants were measured during the growing season. In e9uklevated CO2, net photosynthetic rate was maximum in May and then decreased, reaching the level of the control at the end o9lf the season. End of night dark respiration of enriched plants was significantly lower than that of control plants; this d9mifference decreased with time and became negligible in the fall. The original CO2 level acted instantaneously on the respi9nration rate: a double concentration in CO2 decreased the respiration of control plants and a reduced concentration enhance9od the respiration of enriched plants. The carbon balance of a chestnut seedling may then be modified in elevated CO2 by in9creased carbon inputs and decreased carbon outputs.e9q409^2^Nijs,I^Impens,I^1993^1^Effects of long-term elevated atmospheric carbon-dioxide on lolium-perenne and trifolium-repe9ns, using a simple photosynthesis model^24^104^^421-431^^^^^Jan^^^^^3644fZ7F6!9sA^3643^Changes in gross canopy photosynthetic rate (PGc), produced by long-term exposure to an elevated atmospheric CO2 le9tvel (626 +/- 50 mumol mol-1), were modelled for Lolium perenne L. cv. Vigor and Trifolium repens L. cv. Blanca, using a si9umple photosynthesis model, based on biochemical and physiological information (leaf gross CO2 uptake in saturating light, 9vP(max), and leaf quantum efficiency, alpha) and structural vegetation parameters (leaf area index, LAI, canopy extinction 9wcoefficient, k, leaf transmission, M). Correction of PGc for leaf respiration allowed comparison with previously measured 9xcanopy net CO2 exchange rates, with the average divergence from model prediction amounting to about 6%. Sensitivity analys9yis showed that for a three-week old canopy, the PGc increase in high CO2 could be attributed largely to changes in P(max) 9zand alpha, while differences in canopy architecture were no longer important for the PGc-stimulation (which they were in t:{he early growth stages). As a consequence of this increasing LAI with canopy age, the gain of daytime CO2 uptake is progre:|ssively eroded by the increasing burden of canopy respiration in high- CO2 grown Lolium perenne. Modelling canopy photosyn:}thesis in different regrowth stages after cutting (one week, two weeks,...), revealed that the difference in a 24-h CO2 ba:~lance between the ambient and the high CO2 treatment is reduced with regrowth time and completely disappears after 6 weeks:.9 -0500Elizabeth MarschallRe: tomorrow?:)410^1^Overdieck,D^1993^1^Elevated co2 and the mineral-content of herbaceous and woody- plants^24^104^^403-411^^^^^Jan^^^^^:+A^3645^The CO2 enrichment effects (300-650 mumol mol-1) on mineral concentration (N, P, K, Ca, Mg, Mn, Fe, Zn), absolute t:8otal mineral contents per individual and of whole stands of four herbaceous (Trifolium repens L., Trifolium pratense L., L::olium perenne L., Festuca pratensis HUDS.) and two woody species (Acer pseudo-platanus L., Fagus sylvatica L.) were invest:Rigated. In general, the mineral concentration of the plant tissues decreased (all six species: N > Ca > K > Mg) with the e:Txception of P. Mn and Fe were only determined for the tree species. Both decreased in concentration (Mn > Fe). Zn was only:_ analysed for Trifolium pratense and Festuca pratensis and decreased significantly in the grass. Despite of decreases in c:`oncentrations of as much as 20 % in some cases there were increases in absolute amounts per individual and, therefore, in :ithe whole vegetation up to 25 % because of the enhanced dry matter accumulation at elevated CO2 supply.:k3646612:14 PM 09 02 1999 -0500SWENSON Steveminitab:~411^2^Pal,RK^Buescher,RW^1993^1^Respiration and ethylene evolution of certain fruits and vegetables in response to carbon-:dioxide in controlled- atmosphere storage^215^30^1^29-32^^^^^Jan-Feb^^^^^3648sdf:A^3647^Respiration was depressed by 10-30% CO2 in ripening bananas, pink tomatoes and pickling cucumbers; increased by 20-:30% in carrot roots and unaffected by CO2 exposure in guava, orange and onion bulb. Changes in respiration seldom coincide:d with changes in C2H4 evolution. Evolution of C2H4 from guavas and tomatoes was substantially reduced by all levels of CO:2. However, 30% CO2, accelerated C2H4 evolution in bananas, carrot roots, cucumbers, onions and potatoes which may have be:en due to an early injury response.nd Tammybiopsy:412^1^Poorter,H^1993^1^Interspecific variation in the growth-response of plants to an elevated ambient co2 concentration^2:4^104^^77-97^^^^^Jan^^^^^3650No Subject:A^3649^The effect of a doubling in the atmospheric CO2 concentration on the growth of vegetative whole plants was investig:ated. In a compilation of literature sources, the growth stimulation of 156 plant species was found to be on average 37%. :This enhancement is small compared to what could be expected on the basis of CO2-response curves of photosynthesis. The ca:uses for this stimulation being so modest were investigated, partly on the basis of an experiment with 10 wild plant speci:es. Both the source-sink relationship and size constraints on growth can cause the growth-stimulating effect to be transie:nt. Data on the 156 plant species were used to explore interspecific variation in the response of plants to high CO2. The :growth stimulation was larger for C3 species than for C4 plants. However the difference in growth stimulation is not as la:rge as expected as C4 plants also significantly increased in weight (41% for C3 vs. 22 % for C4). The few investigated CAM: species were stimulated less in growth (15%) than the average C4 species. Within the group of C3 species, herbaceous crop: plants responded more strongly than herbaceous wild species (58% vs. 35%) and potentially fast-growing wild species incre:ased more in weight than slow-growing species (54% vs. 23%). C3 species capable of symbiosis with N2-fixing organisms had ; higher growth stimulations compared to other C3 species. A common denominator in these 3 groups of more responsive C3 plan;ts might be their large sink strength. Finally, there was some tendency for herbaceous dicots to show a larger response th;an monocots. Thus, on the basis of this literature compilation, it is concluded that also within the group of C3 species d;ifferences exist in the growth response to high CO2.but...;&413^2^Rogers,HH^Dahlman,RC^1993^1^Crop responses to co2 enrichment^24^104^^117-131^^^^^Jan^^^^^36529 -0500Michael ;(A^3651^Carbon dioxide is rising in the global atmosphere, and this increase can be expected to continue into the foreseeab;3le future. This compound is an essential input to plant life. Crop function is affected across all scales from biochemical;5 to agro-ecosystem. An array of methods (leaf cuvettes, field chambers, free-air release systems) are available for experi;Amental studies of CO2 effects. Carbon dioxide enrichment of the air in which crops grow usually stimulates their growth an;Dd yield. Plant structure and physiology are markedly altered. Interactions between CO2 and environmental factors that infl;Vuence plants are known to occur. Implications for crop growth and yield are enormous. Strategies designed to assure future;X global food security must include a consideration of crop responses to elevated atmospheric CO2. Future research should i;^nclude these targets: search for new insights, development of new techniques, construction of better simulation models, in;`vestigation of belowground processes, study of interactions, and the elimination of major discrepancies in the scientific ;nknowledge base.ܚg603:48 PM 16 ;p414^1^Rozema,J^1993^1^Plant-responses to atmospheric carbon-dioxide enrichment - interactions with some soil and atmospher;wic conditions^24^104^^173-190^^^^^Jan^^^^^3654C P 6!08:24 AM 17 02 1999 -0500Holly Wagner;yA^3653^In general, C3 plant species are more responsive to atmospheric carbon dioxide (CO2) enrichment than C4-plants. Inc;reased relative growth rate at elevated CO2 primarily relates to increased Net Assimilation Rate (NAR), and enhancement of; net photosynthesis and reduced photorespiration. Transpiration and stomatal conductance decrease with elevated CO2, water; use efficiency and shoot water potential increase, particularly in plants grown at high soil salinity. Leaf area per plan;t and leaf area per leaf may increase in an early growth stage with increased CO2, after a period of time Leaf Area Ratio ;(LAR) and Specific Leaf Area (SLA) generally decrease. Starch may accumulate with time in leaves grown at elevated CO2, Pl;ants grown under salt stress with increased (dark) respiration as a sink for photosynthates, may not show such acclimation; to increased atmospheric CO2 levels. Plant growth may be stimulated by atmospheric carbon dioxide enrichment and reduced ;by enhanced UV-B radiation but the limited data available on the effect of combined elevated CO2 and ultraviolet B (280-32;0 nm) (UV-B) radiation allow no general conclusion. CO2-induced increase of growth rate can be markedly modified at elevat;ed UV-B radiation. Plant responses to elevated atmospheric CO2 and other environmental factors such as soil salinity and U;V-B tend to be species-specific, because plant species differ in sensitivity to salinity and UV-B radiation, as well as to; other environmental stress factors (drought, nutrient deficiency). Therefore, the effects of joint elevated atmospheric C;O2 and increased soil salinity or elevated CO2 and enhanced UV-B to plants are physiologically complex.N;415^1^Schlesinger,WH^1993^1^Response of the terrestrial biosphere to global climate change and human perturbation^24^104^^;295-305^^^^^Jan^^^^^3656;A^3655^Despite 20 years of intensive effort to understand the global carbon cycle, the budget for carbon dioxide in the at;mosphere is unbalanced. To explain why atmospheric CO2 is not increasing as rapidly as it should be, various workers have <suggested that land vegetation acts as a sink for carbon dioxide. Here, I examine various possibilities and find that the <evidence for a sink of sufficient magnitude on land is poor. Moreover, it is unlikely that the land vegetation will act as< a sink in the postulated warmer global climates of the future. In response to rapid human population growth, destruction <$of natural ecosystems in the tropics remains a large net source of CO2 for the atmosphere, which is only partially compens<&ated by the potential for carbon storage in temperate and boreal regions. Direct and inadvertent human effects on land veg<6etation might increase the magnitude of regional CO2 storage on land, but they are unlikely to play a significant role in <8moderating the potential rate of greenhouse warming in the future.j<||~??<418^2^Viil,J^Parnik,T^1992^1^Fast regulation of ribulose-1,5-bisphosphate carboxylase oxygenase activity during light dark< light transitions^168^39^4^483-487^^^^^Jul-Aug^^^^^3662, PB 694*c16476D(016476X*p315X*p2595YDepartment of Plant Biol=A^3661^On the basis of estimates of rubisco activity in leaves of barley (Hordeum vulgare L.), we established that it decl=ined by 30-50% in 3-4 sec following disconnection of light in the presence of CO2. In a medium without CO2, rubisco activi= ty did not change in this time. Keeping leaves at elevated CO2 concentration lowered rubisco activity. This effect had a l="asting aftereffect. With a sharp change of CO2 concentration, the rate of assimilation in the first second was proportiona=3l to the increase of CO2 concentration up to at least 1000 mul- liter-1. It is recorded that CO2 binds directly with the e=5nol form of ribulose-1,5-bisphosphate (RuBP) without preliminary binding with the enzyme molecule.?==419^1^Wong,SC^1993^1^Interaction between elevated atmospheric concentration of co2 and humidity on plant-growth - comparis=?on between cotton and radish^24^104^^211-221^^^^^Jan^^^^^3664476X*p315X*p2832YSessional Lecturer. Department of Biologi=LA^3663^Cotton plants (Gossypium hirsutum L. var Deltapine 90) and radish plants (Raphanus sativus L var Round Red) were gr=Nown under full sunlight using a factorial combination of atmospheric CO2 concentrations (350 mumol mol-1 and 700 mumol mol=`-1) and humidities (35% and 90% RH at 32-degrees-C during the day). Cotton plants showed large responses to increased humi=cdity and to doubled CO2. In cotton plants, the enhanced dry matter yield due to doubled CO2 concentration was 1.6-fold gre=oater at low humidity than at high humidity. Apart from the direct effect of elevated CO2 level on photosynthesis, the grea=qter effect of doubled CO2 concentration on dry matter yield at low humidity was probably due to: (1) increased leaf water =~potential caused by reduction of transpiration resulting from the negative CO2 response of stomata to increased CO2 concen=tration the consequence being greater leaf area expansion. (2) reduction of CO2 assimilation rate at low humidity and norm=al CO2 concentration as a result of humidity response of stomata causing reduction of intercellular CO2 concentration. In =contrast, apart from the very early stage of development, radish plants do not respond to increased humidity but had a rel=atively large response to doubled CO2 concentration. Furthermore, due to the determinate growth pattern as well as having =a prominent storage root, the extra photoassimilate derived at doubled CO2 level is allocated to the storage root.c74E(s=420^2^Bachelet,D^Gay,CA^1993^1^The impacts of climate change on rice yield - a comparison of 4 model performances^81^65^1-=2^71-93^^^^^Jan^^^^^3666|?သ*c44E(s24W p *c112E(s60W@{<<8=A^3665^Increasing concentrations of carbon dioxide (CO2) and other greenhouse gases are expected to modify the climate of =the earth in the next 50-100 years. Mechanisms of plant response to these changes need to be incorporated in models that p=redict crop yield estimates to obtain an understanding of the potential consequences of such changes. This is particularly= important in Asia where demographic forecasts indicate that rice supplies worldwide will need to increase by 1.6% annuall=y to the year 2000 to match population growth estimates. The objectives of this paper are (1) to review the major hypothes=es and/or experimental results regarding rice sensitivity to climate change and (2) to evaluate the suitability of existin=g rice models for assessing the impact of global climate change on rice production. A review of four physiologically-based= rice models (RICEMOD, CERES-Rice, MACROS, RICESYS) illustrates their potential to predict rice responses to elevated CO2 =and increased temperature. RICEMOD does not respond to increases in CO2 nor to large increases in temperature. Both MACROS= and CERES (wetland rice) responses to temperature and CO2 agree with recent experimental data. RICESYS is an ecosystem mo> del which predicts herbivory and inter-species competition between rice and weeds but does not respond to CO2. Its respons>e to increasing temperature also agrees with experimental data.@|}?*c44E(s31W0<~w 0@>421^4^Bazzaz,FA^Ackerly,DD^Woodward,FI^Rochefort,L^1992^1^Co2 enrichment and dependence of reproduction on density in an a>nnual plant and a simulation of its population-dynamics^12^80^4^643-651^^^^^^^^^^3668 df9d8ef1bd8fb536275b070f8878ee61 <0>,A^3667^1. Populations of an annual plant, Abutilon theophrasti, were grown at four densities (100, 500, 1500 and 4000 m-2)>. and two CO2, concentrations (350 and 700 mul l-1) to examine the influence of CO2 environment on density-dependent patter>=ns of demography and reproduction. Variables measured included survivorship, proportion of plants flowering and fruiting, >?number of fruiting individuals, number of seeds per individual, total seed production per population, mean seed mass, and >Kgermination of seeds produced in each environment. 2. All variables, except the number of fruiting individuals, declined w>M ith increasing density, and at the highest density no individuals set seed. The number of fruiting individuals was highest>\ at a density of 500m-2. In the elevated CO2 environment, survivorship was significantly reduced but the proportion of pla>^ nts flowering and fruiting and the number of fruiting individuals in each population all increased. Total population seed >g production was higher in the elevated CO2 environment at all densities, although the differences were not significant. Sig>i nificant effects of CO2, concentration were observed only for population-level variables, but not for mean individual fecu>zndity or seed size. Seed germination declined with increasing maternal density, and no germination was recorded for seeds >|produced at 1500 m-2 3. Simple models of population dynamics, utilizing difference equations, were constructed to examine >potential population-level consequences of these density and CO2 effects. In the absence of a persistent seed pool, the si>mulated populations exhibited damped or stable oscillations under low germination values, but displayed non-cyclic ('chaot>ic') oscillations or went extinct for higher germination due to the complete failure of seed-set at high density. Because >of its higher fecundity, the elevated- CO2 population generally exhibited greater oscillations, and the critical germinati>on value at which the simulated populations went extinct was much lower for the elevated-CO2 than for the ambient-CO2 popu>lation.9ddff5c1081dd2 <0F3Z00D46217HH@mx4.osu.edu>-14-Dec-1998-15:38:32--0500-(EST 913650173 Ndel Nskip Nsave read Nget 2>422^2^Bazzaz,FA^Miao,SL^1993^1^Successional status, seed size, and responses of tree seedlings to co2, light, and nutrient>s^11^74^1^104-112^^^^^Jan^^^^^3670f95ac0aa6abe494e34efc716 <3.0.5.32.19981214150128.00827b00@spot.colorado.edu>-14-Dec-19>A^3669^We studied how an enriched CO2 atmosphere in a fully crossed design of light and nutrients, influenced 1 st-yr seed>ling growth in six New England deciduous forest tree species. The species, in the order of increasing shade tolerance, wer>e gray birch (Betula populifolia), ash (Fraxinus americana L.), red maple (Acer rubrum L.), red oak (Quercus rubra L.), ye>llow birch (Betula alleghaniensis Britton), and striped maple (Acerpensylvanicum). Elevated CO2 environments significantly> stimulated the seedling growth of all six species. Generally this was more pronounced in low light. The greatest stimulat>ion was found under the condition of low light and high nutrients. However, individual species responded differently to el>evated CO2 levels. Among the three early-successional species, gray birch, ash, and red maple, a significant increase in s>eedling growth under elevated CO2 conditions was found only with high nutrients. The three late-successional species grown? under elevated CO2 conditions (red oak, yellow birch, and striped maple) showed a greater percentage increase in seedling? ! growth in low light than in high light. Thus, for the early- successional species, the degree of enhancement of seedling ?"growth by elevated CO2 levels was more sensitive to nutrient levels, while in the late-successional species the enhancemen?#t was more sensitive to the level of light. Moreover, species with large seeds (e.g., red oak) exhibited a greater respons? $e to elevated CO2 levels under low light than species with small seeds (e.g., gray birch). The results emphasize the impor?.%tance of plant species as well as other environmental resources in modifying the response of plants to elevated CO2. Consi?0&dering the light and nutrient environment observed in forest gaps of various sizes, the results of the present experiment ??suggest seedling regeneration in New England deciduous forests may be altered in a future high CO2 environment.ES\MI?A(423^3^Deyton,DE^Sams,CE^Cummins,JC^1992^1^Application of dormant oil to peach-trees modifies bud twig internal atmosphere^?O170^27^12^1304-1305^^^^^Dec^^^^^3672MICROSOFT OFFICE\OFFICE\URGENT.DOT,Mic?Q*A^3671^Treatments of single applications of 0%, 3%, 6%, 9%, or 12% dormant oil were sprayed on peach (Prunus persica L. Ba?S+tsch) trees on 6 Feb. 1990. A repeat application of 6% oil plus 6% oil applied 6 days later was also made. Internal CO2 co?`,ncentrations of oil-treated buds and twigs were higher than the control the day after treatment and continued to be higher?b- for 6 days. The second application of 10% oil prolonged the elevated CO2 concentration. Applications of 9% or 12% oil del?n.ayed flower bud development and bloom. The repeated application of 6% oil delayed bud development and bloom more than a si?q/ngle application of 6% oil. Damage to fruit buds increased as oil concentration increased, but repeated application of 6% ?oil resulted in less damage than a single application of 12% oil.icrosoft Corporation fPROG?1424^1^Diemer,M^1992^1^Population-dynamics and spatial arrangement of ranunculus- glacialis L, an alpine perennial herb, in? permanent plots^24^103^2^159-166^^^^^Dec^^^^^3674ROSOFT OFFICE\OFFICE\XL8GALRY.XLS?3A^3673^In 1986 sixteen permanent plots (625 cm2 each) were established in scree slopes dominated by Ranunculus glacialis a?4t Mt. Glungezer, Austria (2600 m elevation) in order to document the population dynamics of herbaceous perennials near the?5 upper altitudinal limits of plant existence. The abundance and sizes of individual R. glacialis shoots, their leaf number?6s and reproductive status were evaluated over a 6-year period. On South-facing slopes the population sizes of adult and ju?7venile shoots remained constant over the years, while seedling numbers fluctuated significantly. Overall density of all de?8velopmental stages of R. glacialis was significantly lower on North-facing slopes and year-to-year fluctuations were great?9er, than on thermally-favorable Southern slopes. The spatial pattern of adult shoots and seedlings was clumped, while juve?:nile shoots had a random or clumped distribution. Fertilization had no effects on population dynamics. Proposed greenhouse?; effects, e.g. increases in CO2 and temperature, should result in population growth on North-facing slopes and may increas?e mortality on South-facing sites.SOFT OFFICE\OFFICE\FLAME.DOT,Microsoft ?=425^3^Duchein,MC^Bonicel,A^Betsche,T^1993^1^Photosynthetic net co2 uptake and leaf phosphate concentrations in co2 enriche?d clover (trifolium-subterraneum L) at 3 levels of phosphate nutrition^78^44^258^17-22^^^^^Jan^^^^^3676OFFICE\OF??A^3675^Net CO2-uptake of sets of clover plants (Trifolium subterraneum L. was measured over three weeks in ambient air and?@ in a highly CO2-enriched atmosphere (400 Pa CO2). Phosphate (P) in the nutrient solution was varied between 0-05 mol m-3 ?AP (reduced P) and 2.0 mol m-3 P (high P). In ambient air, the daily increments of the daily rate of net CO2-uptake (DICU; @Ba parameter related to relative growth) were higher at reduced P than at high P. Stimulation by high CO2 of net CO2-uptake@C in the first day was less at reduced P than at high P. In the following days, high CO2 markedly inhibited DICU at reduced@D P, and thus growth stimulation by high CO2 ceased after between 4 and 12 d. By contrast, at high P, DICU increased more t@Ehan 2- fold upon CO2-enrichment, and thus growth stimulation by high CO2 was maintained. Intermediate results were obtaine@:Fd with half-strength Hoagland's solution (0-5 mol m-3 P). Leaf pools of inorganic ortho P, soluble esterified P, and total@<G P declined markedly in high CO2 when P-nutrition had been reduced. Considerable decline also occurred in high CO2 when P-@GH nutrition had been increased suggesting that P-uptake was not well tuned with net CO2-uptake (growth). It is proposed tha@IIt high CO2 can perturb the P-metabolism of clover, the impairment being less at high levels of P-nutrition. With regard to@KJ high CO2 as a growth stimulus, these results demonstrate that increasing P-nutrition to a level supraoptimal in ambient a@Vir can considerably improve the growth of a C3-plant in high CO2.Microsoft Excel vPROGRAM F@YL426^3^Gries,C^Kimball,BA^Idso,SB^1993^1^Nutrient-uptake during the course of a year by sour orange trees growing in ambien@gt and elevated atmospheric carbon- dioxide concentrations^166^16^1^129-147^^^^^^^^^^3678IBRARY\AUTOSAVE.@iNA^3677^During the third year of a long-term carbon dioxide (CO2) enrichment study, macro- and micro-nutrient concentration@pOs in leaves and roots of sour orange trees were analyzed. Data for yearly courses of the macronutrients Ca, Mg, N, P, K, N@sPa, and S and the micronutrients B, Cu, Fe, Mn, and Zn are presented. Significantly higher concentrations of N, K, Ca, and @QMn were found in leaves of the control trees. The degree of difference varied seasonally: the greatest differences occured@ in summer, whereas essentially no differences were found in spring and winter. OFFICE\OFFICE\LIBRAR@S427^3^Lincoln,DE^Fajer,ED^Johnson,RH^1993^1^Plant insect herbivore interactions in elevated co2 environments^57^8^2^64-68^@^^^^Feb^^^^^3680LIBRARY\LOOKUP.XLA Microsoft Excel pPROGRAM FI@UA^3679^The increasing concentration of CO2 in the atmosphere is expected to lead to global changes in the physical environ@Vment of terrestrial organisms. We are beginning to understand how these changes are transmitted into pervasive effects on @Wthe interactions between plants and their leaf-feeding insect herbivores. An elevated CO2 atmosphere often stimulates plan@Xt carbon assimilation and growth and alters carbon allocation patterns. This, in turn, determines the quality of plants as@Y resources for herbivorous insects. These 'quality' factors include: the concentrations of water, nitrogen and allelochemi@Zcals in host-plant leaves, and the toughness and starch and fiber content of leaf tissue. Because these parameters change @[in plants grown in enriched CO2 environments, the doubled CO2 levels anticipated for the next century will alter the dynam@\ics of plant-insect herbivore interactions because herbivore consumption, growth and fitness are affected by the typically@ lower quality of plants grown under these conditions.oft Word 8.0 `PROGRAM FILES\MIC@428^1^Malanson,GP^1993^1^Comment on modeling ecological response to climatic-change^50^23^2^95-109^^^^^Feb^^^^^3682RAM@_A^3681^Researchers have developed many computer simulation models to project ecological responses to climatic change. Thre@`e general types of models are examined: transfer functions, stand models, and physiological models. Criteria for evaluatioAan are, first, ability to represent observed and theoretical responses to climatic change i.e., geographical migration, indA bividualistic responses, and disequilibrium or inertia, and second, ability to provide useful information on biological divAcersity and impacts on society. Because of their roots in ecological interactions at the species level, stand models best mAeet these criteria at present, but physiological models have greater potential, given unlimited computing power.ord A(e429^2^Radoglou,KM^Jarvis,PG^1993^1^Effects of atmospheric co2 enrichment on early growth of vivia- faba, a plant with largA+e cotyledons^9^16^1^93-98^^^^^Jan^^^^^3684AM FILES\MICROSOFT OFFICE\OFFICE\OCEAN.A:gA^3683^Seedlings of Vicia faba L. were grown in open-top growth chambers at present (P=350 mumol-1) and at elevated (E=700A<h mumol mol-1) atmospheric CO2 concentration. The effects Of CO2 enrichment on the first phase of growth after germination AIiwere examined over 45d. There were no positive effects Of CO2 enrichment on growth of the seedlings during this early phasAKje. No differences were observed in leaf area or in total dry weight. No differences were found in morphology or anatomy ofAMk the leaves. The numbers of stomatal and epidermal cells, thickness of leaf, of epidermis and of mesophyll cell-layers werA[le unaffected by CO2 enrichment. Also, no differences were observed in leaf concentrations of chlorophyll, reducing carbohyA]mdrates or starch. These results contrast markedly with results from similar experiments on poplar hybrids and Phaseolus vuAlnlgaris obtained in the same growth facility. It seems that the intitial growth is under internal control such that the atmAnoospheric CO2 concentration has no effects. The lack of response in this case may be attributed to the presence and longeviAyty of the large cotyledons which provided available substrate for growth.MICROSOFT OFFICE\OFFICE\A{q430^2^Samuelson,LJ^Seiler,JR^1992^1^Fraser fir seedling gas-exchange and growth in response to elevated co2^173^32^4^351-3A56^^^^^Oct^^^^^3686CE\EXAMPLES\SOLVER\SOLVSAMP.XLS State&pPROGRAAsA^3685^Growth and gas exchange characteristics were examined in Fraser fir (Abies fraseri (Pursh.) Poir.) seedlings grown Atfrom seed in elevated (713 ppm) or ambient (374 ppm) CO2 for 1 year (two artificial growing seasons) to determine the poteAuntial influence of a twice-ambient CO, concentration on this species. A subset of seedlings was transplanted from 172 cm3 Avpots into 1000 cm3 pots at 7 months to determine if CO2 effects were dependent on rooting volume. At 5 and 12 months, net Awphotosynthesis (P(net)) and leaf conductance (g1) were lower in elevated CO2-grown seedlings grown in 172 cm3 pots than inAx ambient CO2-grown seedlings when measured at either 346 or 796 ppm CO2. For 12-month-old seedlings grown in 1000 cm3 potsAy, P(net) was reduced by an elevated CO2 growth environment only when measured at 346 ppm CO2, although g1 was lower in theAzse seedlings when measured at either CO2 measurement level. Seedlings grown in both pot sizes and in elevated CO2 for 1 yeA{ar had greater height, diameter, and leaf, stem, root and total dry weights than seedlings grown in ambient CO2. Specific A|leaf weight (SLW) was greater in elevated than in ambient CO2- grown needles only in the large pot size treatment. These rA}esults suggest that Fraser fir seedling growth will increase in a future elevated CO2 environment despite changes in gas eAxchange characteristics.ROSOFT OFFICE\OFFICE\LIBRARY\BSHXL.XLAZIP CA431^3^Socias,FX^Medrano,H^Sharkey,TD^1993^1^Feedback limitation of photosynthesis of phaseolus-vulgaris L grown in elevateAd co2^9^16^1^81-86^^^^^Jan^^^^^3688ES\MICROSOFT OFFICE\OFFICE\FLAME.DOTvAA^3687^The capacity for photosynthesis is often affected when plants are grown in air with elevated CO2 partial pressure. >We grew Phaseolus vulgaris L. in 35 and 65Pa CO2 and measured photosynthetic parameters. When assayed at the growth CO2 leBvel, photosynthesis was equal in the two CO2 treatments. The maximum rate of ribulose-1,5-bisphosphate (RuBP) consumption Bwas lower in plants grown at 65Pa, but the CO2 partial pressure at which the maximum occurred was higher in the high-CO2-gBrown plants, indicating acclimation to high CO2. The acclimation of RuBP consumption to CO2 involved a reduction of the acB(tivity of RuBP carboxylase which resulted from reduced carbamylation, not a loss of protein. The rate of RuBP consumption B*declined with CO2 when the CO2 partial pressure was above 50Pa in plants grown under both CO2 levels. This was caused by fB5eedback inhibition as judged by a lack of response to removing O2 from the air stream. The rate of photosynthesis at high B7CO2 was lower in the high-CO2-grown plants and this was correlated with reduced activity of sucrose-phosphate synthase. ThBBis is only the second report Of O2-insensitive photosynthesis under growth conditions for plants grown in high CO2.AM BD432^3^Sritharan,R^Caspari,H^Lenz,F^1992^1^Influence of co2 enrichment and phosphorus supply on growth, carbohydrates and nBSitrate utilization of kohlrabi plants^172^57^5^246-251^^^^^Sep-Oct^^^^^3690ER\SOLVSAMP.XLSBUA^3689^Kohlrabi (Brassica oleracea var. gongylodes (L.) cv. Express Forcer) plants were grown in sand with adequate nutrieBbnt supply. From two weeks after germination until harvest they were treated with two levels of phosphorus supply (1.0 or 0Bd.005 mM P). Four weeks after introducing the P supply regimes the plants were exposed to either a low (300 muL CO2 L-1) orBp high (900 muL CO2 L-1) CO2 concentration in growth chambers for three weeks. At elevated CO2 concentration plants with 1.Br0 mM phosphorus produced a larger leaf area and dry matter than those grown at low CO2. At reduced P supply CO2 enrichmentB promoted leaf senescence and did not increase growth and dry matter. Phosphorus deficiency resulted in increased accumulaBtion of starch in leaves, tuber, and roots and reduced NO3-N concentrations in all plant parts. The CO2 enrichment reducedB N and NO3 concentration and increased nitrate utilization efficiency at both P levels. Phosphorus deficiency decreased niBtrogen, potassium, calcium, and magnesium concentrations in leaves particularly at high CO2.AM FILES\MICROB433^3^Vantelgen,HJ^Vanmil,A^Kunneman,B^1992^1^Effect of propagation and rooting conditions on acclimatization of micropropBagated plants^216^41^4^453-459^^^^^Dec^^^^^3692RY\LOOKUP.XLApPROGRAM FILEBA^3691^Plantlets of Calathea ornata rooted at frequencies varying between 75 and 100% irrespective of the presence of 6- bBenzylaminopurine (BAP) or indolebutyric acid (IBA). After transfer to soil all plants grew rapidly with the exception of BBAP-rooted plants, probably because these plants lacked lateral roots. Plantlets of Malus showed slightly improved rooting Band considerably improved survival at increasing sucrose concentration from 20 to 30 g l(-1) during multiplication. Their Bsurvival and performance after planting in soil depended upon the number of roots formed in rooting medium. Elevated CO2-lBevels (800 ml m-3) during acclimatization increased survival rate and plant height of rooted and non-rooted plantlets.FB434^5^Woodin,S^Graham,B^Killick,A^Skiba,U^Cresser,M^1992^1^Nutrient limitation of the long-term response of heather [calluBna-vulgaris (L) hull] to co2 enrichment^84^122^4^635-642^^^^^Dec^^^^^3694TpPROGRAM FILBA^3693^In a 27-month C2-enrichment experiment, Calluna vulgaris plants were grown on peat obtained from an upland heath inB NE Scotland and given a nutrient supply which mimicked that in precipitation in the area. Three CO2 concentrations were uBsed; ambient, + 100 ppm and + 200 ppm. Calluna showed a negative growth response to increased CO2 over the first year of tBreatment and a positive response by the end of the experiment. Final above-ground biomass was greatest in the enriched CO2C treatments, showing an increase of 30 % in + 100 ppm CO2. Determination of tissue nutrient concentration, and calculationC of total nutrient uptake, demonstrated that nutrient uptake did not increase with increased growth, resulting in significC ant dilution of elements in leaf tissue. This suggests that, in its typical, nutrient poor habitats, the growth response oC f Calluna to CO2 will be limited by nutrient deficiency, and will reach a maximum with a relatively small increase in CO2 Cconcentration. Flowering was advanced and extremely prolific in + 100 ppm CO2 grown plants, but the ecological significancCe of this is uncertain. The results highlight the need for long term studies of native species on their natural soils, usiC&ng lower CO2 concentrations than the usual 'double CO2'.fPROGRAM FILES\MICROSOFT OFFICE\C(435^2^Bertin,N^Gary,C^1993^1^Evaluation of tomgro, a dynamic-model of growth and development of tomato (lycopersicon-esculC4entum mill) at various levels of assimilate supply-and-demand^217^13^5^395-405^^^^^^^^^^3696OFFICE\OFFICE\C6A^3695^TOMGRO, a tomato growth and development model, has been examined under different levels of assimilate source and siCBnk activities, induced by CO2 enrichment and truss thinning. The main purpose was the evaluation of the assumptions on dryCD matter partitioning and fruit setting. The photosynthesis submodel has been calibrated to fit the daily dry matter producCUtion. The main input parameters to the development and growth submodels have been experimentally measured. The calibrated CWmodel provides good simulations of the leaf area expansion, but it takes no account of the variations in the assimilates sCetored in leaf blades. Total fruit growth is well simulated in spite of a small underestimation for of development and simuCglations of source/sink balance leads to good simulations of the number of set fruits. This result confirms the hypothesis Cuthat fruit set depends on the ratio between assimilate source and sink activities. This calibration with a beef tomato culCxtivar proves the robustness of the model and permits some improvements to be suggested. The surplus assimilates should be Cstored in a pool, which could exert a buffer effect during low supply periods. Sink strength of reproductive and vegetativCe parts should be measured for different cultivars, and under various climatic conditions. Finally, whether the functions Cof assimilate distribution and fruit set are still valid under very low supply conditions or whether some organs have prioCrity over the others remains to be determined.M FILES\MICROSOFT OFFICE\OFFICE\HTML.C436^2^Bertin,N^Heuvelink,E^1993^1^Dry-matter production in a tomato crop - comparison of 2 simulation-models^174^68^6^995-C1011^^^^^Nov^^^^^3698RAM FILES\MICROSOFT OFFICE\OFFICE\MIDNIGHT.DOTvCA^3697^TOMSIM(1.0) and TOMGRO(1.0) are two dynamic models for tomato growth and development. Their submodels for dry matteCr production are compared and discussed. In TOMSIM(1.0), dry matter production is simulated by a modified version of SUCROCS87 (Spitters et al., 1989). Single leaf photosynthesis rates are calculated separately for shaded and sunlit leaf area atC different depths in the canopy, according to the direct and diffuse components of light; daily crop gross assimilation raCte (A) is computed by integration of these rates over the different depths and over the day. In TOMSIM(1.0) leaf photochemCical efficiency (epsilon) and potential leaf gross photosynthesis rate at saturating light level (P(g,max)) both depend onC temperature and CO2 level. In TOMGRO(1.0) crop gross photosynthesis rate is calculated by the equation of Acock et al. (1C978); epsilon is a constant and P(g,max) is a linear function of CO2. In both models leaf photosynthesis characteristics aCre assumed to be identical in the whole canopy. Maintenance respiration (R(m)) and conversion efficiency (C(f)) are taken Cinto account in the same way, except that root maintenance respiration is neglected in TOMGRO(1.0). For both models a sensCitivity analysis was performed on the input variables (light intensity, temperature, CO2 and leaf area index (LAI)) and onD some of the model parameters. Under most conditions considered, simulated A was found to be 5-30% higher in TOMSIM(1.0) tDhan in TOMGRO(1.0). At temperatures above 18-degrees-C R(m) was also higher in TOMSIM(1.0), and C(f) was 4% higher in TOMGDRO(1.0). The two models were very sensitive to changes in epsilon and to a lesser extent to changes in the light extinctioDn coefficient, whereas the scattering coefficient of leaves had hardly any effect on the simulated A. TOMGRO(1.0) appearedD* to be rather sensitive to the CO2 use efficiency, whereas at ambient CO2 level mesophyll resistance was quite important iD,n TOMSIM(1.0). Four sets of experimental data (differences in cultivar, CO2 enrichment and planting date) from Wageningen D<(The Netherlands) and Montfavet (southern France) were used to validate the models. Average 24 h temperature and average dD>aily CO2 concentration values were used as input to the models. For the Wageningen experiments, hourly PAR values were calDKculated from the daily global radiation sum by TOMSIM(1.0) and used as input in both models. For the Montfavet experiment,DN average hourly PAR measurements were used. Also measured LAI, dry matter distribution and organ dry weights (for calculatD[ion of R(m)) were input to the simulation. In the Wageningen experiments, total dry matter production was simulated reasonD]ably well by both models, whereas in the Montfavet experiment an under- estimation of about 35% occurred. TOMGRO(1.0) and DfTOMSIM(1.0) simulated almost identical curves in all four experiments. Strong and weak points of both models are discussedDh..DOC"@PROGRAM FILES\MICROSOFT OFFICE\OFFICE\ARCTICDy437^3^Chomba,BM^Guy,RD^Weger,HG^1993^1^Carbohydrate reserve accumulation and depletion in engelmann spruce (picea-engelmanD{nii parry) - effects of cold-storage and prestorage co2 enrichment^13^13^4^351-364^^^^^Dec^^^^^3700CROSOFT OFFDA^3699^The effects of pre-storage CO2 enrichment on growth, non- structural carbohydrates and post-storage root growth potDential of Engelmann spruce (Picea engelmannii Parry) seedlings were studied. Seedlings were grown from seed for 202 days iDn growth chambers with ambient (340 mu l l(-1)) or CO(2)ched (1000 mu l l(-1)) air. Some seedlings were transferred betweeDn CO2 treatments at 60 and 120 days. Photoperiod was reduced at 100 days to induce bud set and temperature was reduced at D180 days to promote frost hardiness development for storage at -5 degrees C for 2 or 4 months. Stored seedlings were plantDed in a growth chamber after thawing for one week at +5 degrees C. At 80, 120, 140 and 202 days, and at each planting timeD after storage, seedlings were harvested for growth measurements and analysis of starch and soluble sugar concentrations. DPlanted seedlings were assessed for bud break every two days and new roots > 5 mm long were counted after four weeks. CarbDon dioxide enrichment increased root collar diameter and almost doubled seedling biomass, with the most obvious effects ocDcurring after bud set. Stem height was affected only slightly and shoot/root ratios were not affected at all. Carbon dioxiDde enrichment increased the rate of reserve carbohydrate accumulation, but did not influence the final concentration attaiDned before storage (accounting for 32% of seedling dry weight). Needles were the major storage organ for soluble sugars, wDhereas roots were the major storage organ for starch. Soluble sugars were not strongly affected by two or four months of sDtorage, but starch was reduced by more than 50% in all plant parts. None of the CO2 treatments had an impact on bud break Dor root growth potential.AM FILES\MICROSOFT OFFICE\OFFICE\PPCENTRL.PPSpE438^3^Clark,DG^Kelly,JW^Rajapakse,NC^1993^1^Production and postharvest characteristics of rosa-hybrida L meijikatar grown E in pots under carbon-dioxide enrichment^154^118^5^613-617^^^^^Sep^^^^^3702.TXTpY@ZPROGRAME A^3701^The effects of carbon dioxide enrichment on growth, photosynthesis, and postharvest characteristics of 'Meijikatar'E potted roses were determined. Plants were grown in 350, 700, or 1050 mul CO2/liter until they reached 50% flower bud coloEration and then were placed into dark storage for 5 days at 4 or 16C. Plants grown in 700 or 1050 mul CO2/liter reached thE5e harvest stage earlier and were taller at harvest than plants produced in 350 mul CO2/liter, but there were no differenceE7s in the number of flowers and flower buds per plant among CO2 treatments. Plants grown in early spring were taller and haEAd more flowers and flower buds than plants grown in late winter. Shoot and root growth of plants grown in 700 or 1050 mul ECCO2/liter were higher than in plants produced in 350 mul CO2/liter, with plants grown in early spring showing greater incrEMeases than plants grown in late winter. Immediately after storage, plants grown in 350 mul CO2/liter and stored at 4C had EOthe fewest etiolated shoots, while plants grown in 1050 mul CO2/liter and stored at 16C had the most. Five days after remoEZval from storage, chlorophyll concentration of upper and lower leaves had been reduced by almost-equal-to 50% from the dayE] of harvest. Carbon dioxide enrichment had no effect on postharvest leaf chlorosis, but plants grown in early spring and sEktored at 16C had the most leaf chlorosis while plants grown in late winter and stored at 4C had the least leaf chlorosis.Em439^2^Deng,R^Donnelly,DJ^1993^1^In-vitro hardening of red raspberry by co2 enrichment and reduced medium sucrose concentraEytion^170^28^10^1048-1051^^^^^Oct^^^^^3704FICE\OLREADME.TXT@@vPROGRAM FILE{ycine max Merrill cv. Cresir) plants at decreasing distances from natural CO2 sources of geothermal origin in central ItalEy. When compared with neighbouring controls grown under normal CO2 concentration (C), soybean leaves grown at 2 x C, 7 x CE and more than 20 x C showed a substantial reduction in the size of ascorbate pool and in the activity of Cu,Zn-superoxideE dismutase; both the content of ascorbic acid and the activity of ascorbate peroxidase declined at 2 x C and 7 x C and recEovered to the control values at 20 x C. The foliar titre of glutathione disulfide and the activities of glutathione disulfEide reductase and Mn-superoxide dismutase progressively increased as CO2 concentration increased in ambient air. The resulEts obtained suggest that the immanent risk of dioxygen toxicity associated with photosynthetic electron flow could be reduEced in the presence of high CO2 levels. On the other hand, depending on both the CO2 exposure regimes and the cell compartEment considered, high CO2 could promote oxidative processes which cause GSH oxidation and require an enhanced cellular abiElity to scavenge superoxide anion and hydrogen peroxide.OGRAM FILES\MICROSOFT OFFICE\OFFE458^3^Basile,G^Arienzo,M^Zena,A^1993^1^Soil nutrient mobility in response to irrigation with carbon- dioxide enriched wateEr^222^24^11-12^1183-1195^^^^^^^^^^3742SOLVSAMP.XLSAvPROGRAM FILES\MICEA^3703^Micropropagated 'Festival' red raspberry (Rubus idaeus L.) shoots were rooted in specially constructed plexiglass cEhambers in ambient (340 +/- 20 ppm) or enriched (1500 +/- 50 ppm) CO2 conditions on a medium containing 0, 10, 20, or 30 gE sucrose/liter. Plantlet growth and leaf (CO2)-C-14 fixation rates were evaluated before and 4 weeks after ex vitro transpElantation. In vitro CO2 enrichment promoted in vitro hardening; it increased root count and length, plantlet fresh weight,E and photosynthetic capacity but did not affect other variables such as plantlet height, dry weight, or leaf count and areFa. No residual effects of in vitro CO2 enrichment were observed on 4-week-old transplants. Sucrose in the medium promoted Fplantlet growth but depressed photosynthesis and reduced in vitro hardening. Photoautotrophic plantlets were obtained on sF  ucrose-free rooting medium under ambient and enriched CO2 conditions and they performed better ex vitro than mixotrophic pF  lantlets grown with sucrose. Root hairs were more abundant and longer on root tips of photoautotrophic plantlets than on mF ixotrophic plantlets. The maximum CO2 uptake rate of plantlet leaves was 52% that of greenhouse control plant leaves. ThisF did not change in the persistent leaves up to 4 weeks after ex vitro transplantation. The photosynthetic ability of persiF, stent and new leaves of 4-week-old ex vitro transplants related neither to in vitro CO2 nor medium sucrose concentration. F.Consecutive new leaves of transplants took up more CO2 than persistent leaves. The third new leaf of transplants had photoF>synthetic rates up to 90% that of greenhouse control plant leaves. These results indicate that in vitro CO2 enrichment wasF@ beneficial to in vitro hardening and that sucrose may be reduced substantially or eliminated from red raspberry rooting mFNedium when CO2 enrichment is used.Fwd: Post Doc Opportunity: Assistant to the Director--Ohio Seau3 FP440^2^Deng,R^Donnelly,DJ^1993^1^In-vitro hardening of red raspberry through co2 enrichment and relative-humidity reductionF` on sugar-free medium^146^73^4^1105-1113^^^^^Oct^^^^^3706#K4.  e608FbA^3705^Micropropagated shoots of red raspberry (Rubus idaeus L. 'Comet') were rooted on modified Murashige-Skoog medium laFmcking sucrose, in specially 'constructed plexiglass chambers, under ambient (340 +/- 20 ppm) or enriched (1500 +/- 50 PPM)Fo CO2 and ambient (ca. 100 %) or reduced (90 +/- 5 %) relative humidity. Cultured plantlets were evaluated for their survivF{al, rooting and relative vigor, leaf and root number, stem and root length, total leaf area, total fresh and dry weight, gF}as exchange rate, and stomatal features, prior to transplantation to soil and at intervals for 6 wk ex vitro. In vitro CO2F enrichment promoted plantlet growth, rooting and both the survival and early growth of transplants. CO2 enrichment increaFsed stomatal aperture of plantlet leaves but did not apparently increase water stress at transplantation. Reduced in vitroF RH did not affect plantlet growth but decreased stomatal apertures and stomatal index on leaves of cultured plantlets andF promoted both the survival and early growth of transplants. In vitro CO2 and RH levels did not affect the photosynthetic Frate of either plantlets or transplants. Only the stomata on leaves of plantlets from the ambient CO2 and reduced RH treatFment were functional. Normal stomatal function was not observed in persistent leaves of transplants from the other treatmeFnts, even 2 wk after transplantation. In vitro CO2 enrichment acted synergistically with RH reduction in improving growth F of plantlets both in vitro and ex vitro. Hardened red raspberry plantlets obtained through CO2 enrichment and RH reductionF! survived direct transfer to ambient greenhouse conditions without the necessity for specialized ex vitro acclimatization Ftreatment.RAM FILES\MICROSOFT OFFICE\OFFICE\LIBRARY\FILECONV.XLAF#441^4^Denmead,OT^Dunin,FX^Wong,SC^Greenwood,EAN^1993^1^Measuring water-use efficiency of eucalypt trees with chambers and Fmicrometeorological techniques^218^150^2-4^649-664^^^^^1 Oct^^^^^3708FFICE\OFFICE\LIBRARY\SUMIFF%A^3707^Enclosure appears to be the only feasible way to examine the gas exchange of small groups of trees or to answer queF&stions about the effects of increased atmospheric CO2 on the assimilation, evaporation and water use efficiency of forestsF'. To be effective, enclosures must necessarily change the microclimate, but few studies have been made of the consequencesF(. In this paper, the assimilation, evaporation and water use efficiency of a community of Eucalyptus trees inside a ventilG )ated chamber are compared with the same attributes for the surrounding forest. Assimilation and evaporation for the chambeG *r were measured by the depletion in CO2 and the enrichment in water vapour of air passing through the chamber. For the forG+est, assimilation and evaporation were determined by micrometeorological techniques based on the energy balance, and for CG,O2, additional chamber measurements of the soil efflux. Water use efficiencies were calculated as the ratio of mol CO2 assG.-imilated to mol water evaporated. There are some important microclimatic differences between chamber and forest: net radiaG0.tion is reduced by about 30% in the chamber, the vapour pressure deficit of the chamber air is lower, and the light climatGC/e there tends to be diffuse rather than direct. Despite these differences, evaporation rates for both chamber and forest wGE0ere generally similar, perhaps due to compensating effects in the chamber from higher boundary layer conductances (becauseGV1 of greater ventilation rates) and higher stomatal conductances (because of increased humidity). However, assimilation ratGX2es and water use efficiencies were markedly different for the two communities in clear sky conditions, with higher values Ge3of both being recorded in the chamber for most of the daylight hours. Only on cloudy days, when the light climate was diffGg4use in both chamber and forest, were similar assimilation rates and water use efficiencies observed. This behaviour seems Gu5to be attributable in part to the light climate in the chamber being predominantly diffuse and that in the forest predominGv6antly direct. Diffuse light enhances the photosynthesis of lower leaves in the canopy. This contention is supported by modG7el calculations of canopy assimilation under diffuse and direct radiation which produced qualitatively the same light respG8onse functions as observed for chamber and forest. The study suggests that the use of chambers for exploring questions of G9forest productivity and water use efficiency must be circumspect. The act of enclosure, by itself, can change the daily waGter use efficiency of the tree community by as much as 50%.\MICROSOFT OFFICE\OFFICE\HEADERG;442^2^Enoch,HZ^Olesen,JM^1993^1^Plant-response to irrigation with water enriched with carbon- dioxide^84^125^2^249-258^^^^G^Oct^^^^^3710NUM.XLAHh׻tPROGRAM FILES\MICROSOFT OFFICE\OFFIG=A^3709^The influence of irrigation with CO2-enriched water on plant development and yield is reviewed. The reason for irriG>gation with CO2-enriched water was - in most cases - to increase yield. The present evaluation considers results from overG? a hundred studies performed since the first experiment in 1866. Special emphasis is given to the comparison of 85 experimG@ents made by Mitscherlich in 1910 with 358 irrigation experiments made in the last 80 years. In a statistical analysis of GAthese experiments, the measured plant parameter (often growth and/or gas exchange rates) showed a highly significant mean GBincrease of 2.9 % in plants irrigated with CO2-enriched water as compared with control. Evidence of five mechanisms was foGCund. The subterranean carbon dioxide concentration influences: (a) the rate of nitrification and hence of nitrogen availabGDility; (b) the rate of weathering and pH, and hence the availability of other plant nutrients; (c) the CO2 uptake via rootDEs into the transpiration stream, contributing to the rate of leaf photosynthesis; (d) the hormone levels in the plant; andHF (e) the rate of pesticide decomposition in soils. After examining the available evidence we found that (a) and (b) in somHGe experiments are important to plant growth, since they change the physiochemical environment of the roots. On the other hHHand, while (c) could theoretically contribute up to 5% of plant carbon assimilation, it usually contributes less than 1%, HIwhile (d) contributes most of the observed effects of CO2-enriched water on plants. In addition, pesticide decomposition iHn soils can be delayed by supra- or sub-optimal CO2 concentrations.TOSAVE.XLAvHh׻`PROGRH0Q443^1^Martos,JMG^1993^1^Effect of co2 in storage atmosphere on mill olive fruit physiology^219^44^2^81-84^^^^^Mar-Apr^^^^^H2LA^3711^Olive fruits (Olea europaea) used for oil production were stored at 5-degrees-C and four different atmospheres (%COH=M2/%O2/%N2: 0/21/78; 5/20/75; 10/19/71 and 20/17/63). At 5- degrees-C the enrichment of the storage atmosphere with greaterH?N-than-or-equal-to 5% CO2 concentrations produced a proportional increase of the physiological disorder occurring in storedHLO fruits. This occurrence had a strong relationship with the appearence of fruit decay. Simple refrigeration at 5- degrees-HNPC was sufficient to mantain the same degree of ripening of olive fruits for 60 days. However, a longer period of storage aHWt 5-degrees-C originated a remarkable incidence of chilling injuries in the fruits.Hh׻fPROGRAM FILHY3712ROSOFT OFFICE\OFFICE\OLREADME.TXTHh׻rPROGRAM FILESHeS444^2^Nederhoff,EM^Degraaf,R^1993^1^Effects of co2 on leaf conductance and canopy transpiration of greenhouse-grown cucumbHger and tomato^174^68^6^925-937^^^^^Nov^^^^^3714E\HEADERS\TASKHDR.RTFtHh׻^PROGHwUA^3713^The effects of carbon dioxide (CO2) on stomatal opening and canopy transpiration were investigated in cucumber (CucHxVumis sativus L., cv. Jessica) and tomato (Lycopersicon esculentum Mill., cv. Calypso). Stomatal opening (i.e. leaf conductHWance, g) was measured with a porometer, and canopy transpiration rate (E) with weighing lysimeters on intact plants in larHXge greenhouses. Regression analysis was applied to account for the effects of radiation, air humidity, leaf temperature anHYd CO2 on g. The effect of CO2 on E, which is primarily through g and secondarily through adjusted air humidity, was investHZigated by combining the regression equation for g with the Penman- Monteith equation for E. The relative effect of CO2, asH[ calculated with the fitted regression equations, was a decrease of about 4% in g for cucumber and of about 3% for tomato,H\ per 100 muol mol-1 increase in CO2, in the range of about 300 to 1200 mumol mol-1 CO2. The effect of CO2 on E was smallerH] than on g and the extent of the effect depended on the conditions, mainly ventilation rate. The ratio K (relative change H^in calculated E divided by relative change in calculated g) was estimated at less than 0.2, except at low radiation. In reH_ality, K will be even lower, because feedback mechanisms enforce the reduction in g and counteract the reduction in E. So H`the reduction of the transpiration rate of greenhouse cucumber and tomato caused by moderate CO2 enrichment is small and mHostly negligible, except under low light conditions.NTSMART\TUTORIAL\TUTORIAL.HTMHb445^4^Poulin,MJ^Belrhlid,R^Piche,Y^Chenevert,R^1993^1^Flavonoids released by carrot (daucus-carota) seedlings stimulate hyHcphal development of vesicular-arbuscular mycorrhizal fungi in the presence of optimal co2 enrichment^112^19^10^2317-2327^^H^^^Oct^^^^^3716OSYSTEMS.DOCPCXD PROGRAM FILES\MICROSOFT OFFICIeA^3715^Carbon dioxide has been previously identified as a critical volatile factor that stimulates hyphal growth of GigaspIfora margarita, a vesicular-arbuscular mycorrhizal fungus, and we determined the optimal concentration at 2.0%. The beneficIgial effect of CO2 On fungal development is also visible in the presence of stimulatory (quercetin, myricetin) or inhibitorIhy (naringenin) flavonoids. Sterile root exudates from carrot seedlings stimulate the hyphal development of G. margarita inI3i the presence of optimal CO2 enrichment. Three flavonols (quercetin, kaempferol, rutin or quercetin 3-rutinoside) and two I5jflavones (apigenin, luteolin) were identified in carrot root exudates by means of HPLC retention time. Flavonols like querIFcetin and kaempferol are known to have stimulatory effects on hyphal growth of G. margarita.LES\MICROSOFT IHl446^2^Prade,K^Hagelgans,V^1993^1^Enrichment of n2 and ar in the atmosphere of co2-consuming soils^220^156^5^421-426^^^^^OcISt^^^^^3718EMAIL.DOT|?fPROGRAM FILES\MICROSOFT OFFICE\OFFIUnA^3717^The phenomenon of unexplained N2/Ar-enrichment in soil air is quite frequently to be encountered in soil air studieI[os on anthropogenically influenced sites. In the present study two anthropogenic deposits and a calcareous fluvisol were inI]pvestigated for their soil air composition. While in the alkaline deposits extreme enrichments of N2 and Ar (N2 + Ar: up toIdq 99%, v/v) were found as persistent site characteristics, the fluvisol showed only slight (about 1%, v/v) transient N2/Ar-Ifr enrichments in summer. All sites, which did not show substantial vertical seepage percolation, exhibited enhanced CO2-SolIssubility either due to strong calcite precipitation or dissolution. So, it was concluded that intensive continuous depletioIttn Of CO2 was responsible for the subsequent convective influx of atmospheric air. From the results obtained it was concludI}ued that an encasement of the concerned soil volume rather impermeable to gas transport as well as intense dissolution of CIO2 in the pore water are prerequisites for substantial N2/Ar-enrichments in soil air.PLATES\CONTENT\FORIw447^3^Righetti,B^Magnanini,E^Rossi,F^1993^1^Photosynthetic carbon-dioxide uptake and oxygen accumulation during in-vitro cIulture of actinidia-deliciosa CV tomuri^173^33^4^523-528^^^^^Oct^^^^^3720DOCPROGRAM FILEIyA^3719^Proliferating cultures of Actinidia deliciosa cv Tomuri were grown in vitro under a photosynthetic photon flux densIzity (PPFD) of 120 mumol m2/s. Some jars were daily enriched with 2000 mul/l CO2 administered at the end of the dark periodI{. Head space analysis revealed that CO2 accumulated up to 9500 mul/l during the dark period and was drastically reduced byI| photosynthetic activity to 150-200 mul/l during the photoperiod without any significant difference between CO2-enriched aI}nd non-enriched cultures. Oxygen concentration assayed at the end of the photoperiod showed a steady increase during the 4I~4 days of culture and was not reduced to atmospheric values by respiratory processes during the dark period. CO2 enrichmenIt enhanced O2 production and accumulation to 32.5% at the end of the culture period. Oxygen photoreduction and its photo- Ioxidative damage to green tissue cells are discussed. OFFICE\OFFICE\MACROS\SUPPORT8.DOTI448^3^Sombroek,WG^Nachtergaele,FO^Hebel,A^1993^1^Amounts, dynamics and sequestering of carbon in tropical and subtropical Isoils^221^22^7^417-426^^^^^Nov^^^^^3722CK.DOCPROGRAM FILES\MICROSOFT OFIA^3721^The organic carbon pool in the upper 1 m of the world's soils contains 1220 Gt organic carbon, 1.5 times the total Ifor the standing biomass. In the widespread deep soils in the tropics the carbon stored below 1 m may add about 50 Gt C. TIhe contributions of charcoal, roots and soil fauna should be added to these totals. The much less dynamic carbonate-carbonJ pool amounts to 720 Gt C. Changes in land use, particularly by clearing of forests, reduce organic carbon by 20 to 50% inJ  the upper soil layers, but little in deeper layers. On the other hand, there are indications that a human-induced enrichmJent of soil organic matter can be maintained over centuries. Research on the causative soil processes should be supported,J because an improved understanding of this phenomenon might lead to better management strategies and sound programs to stiJmulate organic carbon storage and fertility levels in tropical and subtropical soils. Recent research data on the CO2 fertJ%ilization effect and the associated antitranspiration effect due to an increase of CO2 in the atmosphere indicate that a pJ'ositive influence on soil organic carbon levels can be expected.ICROSOFT OFFICE\OFFICE\WEB PJ2449^6^Brown,S^Hall,CAS^Knabe,W^Raich,J^Trexler,MC^Woomer,P^1993^1^Tropical forests - their past, present, and potential fuJ4ture- role in the terrestrial carbon budget^94^70^1-4^71-94^^^^^Oct^^^^^3724OCPROGRAM FILJ:A^3723^In this paper we review results of research to summarize the state-of-knowledge of the past, present, and potentialJ< future roles of tropical forests in the global C cycle. In the pre- industrial period (ca. 1850), the flux from changes iJLn tropical land use amounted to a small C source of about 0.06 Pg yr-1. By 1990, the C source had increased to 1.7 +/- 0.5JO Pg yr-1. The C pools in forest vegetation and soils in 1990 was estimated to be 159 Pg and 216 Pg, respectively. No concrJ[ete evidence is available for predicting how tropical forest ecosystems am likely to respond to CO2 enrichment and/or climJ\ate change. However, C sources from continuing deforestation are likely to overwhelm any change in C fluxes unless land maJcnagement efforts become more aggressive. Future changes in land use under a ''business as usual'' scenario could release 4Jf1-77 Pg C over the next 60 yr. Carbon fluxes from losses in tropical forests may be lessened by aggressively pursued agricultural and forestry measures. These measures could reduce the magnitude of the tropical C source by 50 Pg by the year 2050. Policies to mitigate C losses must be multiple and concurrent, including reform of forestry, land tenure, arid agricultJural policies, forest protection, promotion of on-farm forestry, and establishment of plantations on non-forested lands. PJolicies should support improved agricultural productivity, especially replacing non-traditional slash-and-burn agricultureJ with more sustainable and approaches.STRATION.DOCPROGRAM FILES\MICROSJ450^2^Crosson,PR^Rosenberg,NJ^1993^1^An overview of the mink study^50^24^1-2^159-173^^^^^Jun^^^^^3726HOME PAGE.JA^3725^Highlights of the previous papers in this series are reviewed. Methodology developed for the MINK study has improveJd the ability of impacts analysis to deal with questions of (1) spatial and temporal variability in climate change; (2) COJ2- enrichment effects; (3) the reactions of complex enterprises (farms and forests) to climate change and their ability toJ adjust and adapt; and (4) integrated effects on current and, more particularly, on future regional economies. The methodoJlogy also provides for systematic study of adjustment and adaptation opportunities and of the inter-industry linkages thatJ determine what the overall impacts on the regional economy might be. The analysis shows that with a 1930s 'dust bowl' cliJmate the region-wide economic impacts would be small, after adjustments in affected sectors. In this final paper we considJer whether synergistic effects among sectoral impacts and more severe climate change scenarios might alter this conclusionJ. The MINK analysis, as is, leads to the conclusion that a strong research capacity will be required to ensure that technoJlogies facilitating adaptation to climate change will be available when needed. The capacity to deal with climate change aJlso requires an open economy allowing for free trade and movement of people and for institutions that protect unpriced envJironmental values. More severe climate scenarios and negative synergisms can only strengthen these conclusions.UERY\J451^6^Easterling,WE^Crosson,PR^Rosenberg,NJ^McKenney,MS^Katz,LA^Lemon,KM^1993^1^Agricultural impacts of and responses to cJlimate-change in the missouri-iowa-nebraska-kansas (mink) region^50^24^1-2^23-61^^^^^Jun^^^^^3728OFT OFFICE\OJA^3727^The climate of the 1930s was used as an analog of the climate that might occur in Missouri, Iowa, Nebraska and KansJas (the MINK region) as a consequence of global warming. The analog climate was imposed on the agriculture of the region uKnder technological and economic conditions prevailing in 1984/87 and again under a scenario of conditions that might prevaKil in 2030. The EPIC model of Williams et al. (1984), modified to allow consideration of the yield enhancing effects of COK2 enrichment, was used to evaluate the impacts of the analog climate on the productivity and water use of some 50 represenKtative farm enterprises. Before farm level adjustments and adaptations to the changed climate, and absent CO2 enrichment (Kfrom 350 to 450 ppm), production of corn, sorghum and soybeans was depressed by the analog climate in about the same perceK$nt under both current and 2030 conditions. Production of dryland wheat was unaffected. Irrigated wheat production actuallyK' increased. Farm level adjustments using low-cost currently available technologies, combined with CO2 enrichment, eliminatK+ed about 80% of the negative impact of the analog climate on 1984/87 baseline crop production. The same farm level adjustmK-ents, plus new technologies developed in response to the analog climate, when combined with CO2 enrichment, converted the K2negative impact on 2030 crop production to a small increase. The analog climate would have little direct effect on animal K4production in MINK. The effect, if any, would be by way of the impact on production of feed-grains and soybeans. Since thiKEs impact would be small after on-farm adjustments and CO2 enrichment, animal production in MINK would be little affected bKGy the analog climate.ing products to add to our existing livPROGRAMKP452^1^Frederick,KD^1993^1^Climate-change impacts on water-resources and possible responses in the mink region^50^24^1-2^83KR-115^^^^^Jun^^^^^3730L 1 GENERATOR Internet Assistant for Microsoft WorKeA^3729^The capacity to supply both instream and offstream water uses under alternative climate conditions and likely futurKge changes in population, technology, and water-using practices are examined through an adaptation of the framework developKned in the Second National Water Assessment. Two measures of the adequacy of water supplies - the availability of renewableKp supplies to provide for withdrawal and instream uses and the relation between desired instream flows and current streamflKyows - are used to examine the impact of the 1931-1940 analog climate (with and without CO2 enrichment) on Missouri, Iowa, K{Nebraska, and Kansas (MINK). The impacts of the analog climate on water supplies are estimated from actual streamflow dataK and estimates of the differences in reservoir evaporation under the 1931-1940 analog and the 1951-1980 control climates. KA modification of the Erosion Productivity Inventory Calculator (EPIC) model is used to estimate the impacts of the analogK climate (with and without CO2 enrichment) on irrigation water use. Water, which is already a scarce resource in the MINK Kregion, would become much scarcer if the climate of the 1930s were to become the norm. Mean assessed total streamflow woulKd drop to 69% of the control climate level for the Missouri River Basin, 71% for the Upper Mississippi, and 93% for the ArKkansas. Even in the absence of climate change, MINK will have less water in the year 2030 than it does today because grounKdwater stocks are being depleted and increased upstream diversions would reduce surface flows into these states. IrrigatioKn and instream uses such as navigation, hydroelectric power production, recreation, and fish and wildlife habitat would beK most adversely, impacted by the climate-induced changes in water supplies.COLUMN LAYOUT.DOC3K453^3^Julkunentiitto,R^Tahvanainen,J^Silvola,J^1993^1^Increased co2 and nutrient status changes affect phytomass and the pKroduction of plant defensive secondary chemicals in salix- myrsinifolia (salisb)^2^95^4^495-498^^^^^Oct^^^^^3732T OFKA^3731^The effect of CO2 enrichment (700 and 1050 ppm) on phytomass, soluble sugars, leaf nitrogen and secondary chemicalsK of three Salix myrsinifolia clones was studied in plants cultivated at very poor (sand seedlings) and moderate (peat seedKlings) nutrient availability and under low illumination. The total shoot phytomass production of sand seedlings was less tKhan 10% of that of the peat seedlings. Carbon dioxide increased the total shoot phytomass of peat seedlings. When the ambiKent carbon supply was doubled (to 700 ppm) the growth of sand seedlings was slightly enhanced but 1050 ppm CO2 gave growthL figures similar to those at the control CO2 level. Leaf nitrogen content and total soluble sugar contents were significanLtly higher in peat seedlings than in sand seedlings. Leaf nitrogen showed a decreasing trend in relation to CO2 increase. LOn the other hand, CO2 did not have any clear-cut effect on total sugars. At the control CO2 level the content of salicortL!in, which is a dynamic phenolic, was higher in the peat seedlings than in the sand seedlings, but salicin showed the opposL,ite trend. CO2 enrichment considerably decreased these phenolics in the peat seedlings. At the control CO2 level, the contL.ent of more static phenolics, such as proanthocyanidins, was higher in sand seedlings. An increased carbon supply considerL<ably increased static phenolics in the peat seedlings. Willow defence against generalist herbivores is moderately decreaseL>d by enhancement of atmospheric carbon dioxide.ENT\FORM - REGISTRATION.DOC8.0.3LG454^3^Tanimoto,H^Kagi,T^Morita,S^1993^1^Relationship between the utilization of sugars by cultured petiole segments of begLIoniaxhiemalis and the optimum time for co2 enrichment^180^62^2^437-441^^^^^Sep^^^^^3734GRAM FILES\MICROSLTA^3733^By monitoring the utilization of sugars by petiole segments of Begonia X hiemalis cultured in medium containing theLV plant grwoth regulators, kinetin (1 PPM), NAA (1 ppm), the optimum time for beginning the CO2 enrichment treatment was esL^tablished. The total sugar concentration in the medium decreased rapidly after 40 days of culturing. The cessation of sugaL`r depletion by the tissues after 60 days is attributed to the onset of photosynthesis by the plantlets. CO2 administrationLo at this time promoted leaf development, whereas CO2 enrichment 10 to 20 days earlier halted the development of adventitioLqus shoots. These observations suggest that the optimum period to begin CO2 enrichment to promote shoot growth and to enhanL}ce photosynthesis is about 60 days after the culturing the petiole segments.9/23/96"PROGRAM FILL455^6^West,DC^Doyle,TW^Tharp,ML^Beauchamp,JJ^Platt,WJ^Downing,DJ^1993^1^Recent growth increases in old-growth longleaf pinLe^155^23^5^846-853^^^^^May^^^^^3736"PROGRAM FILES\MICROSOFT OFFICE\OFFICE\WLA^3735^Longleaf pine (Pinus palustris Mill.) tree-ring data were obtained from an old-growth stand located in Thomas County, Georgia. The tree-ring chronology from the pine stand is composed of a collection of cores extracted from 26 trees ranging in age from approximately 100 to 400 years. These cores were prepared, dated, and measured, and the resulting data were examined with dendrochronological and statistical techniques. Beginning in approximately 1950 and continuing to the present, annual increments of all age classes examined in this study have increased. resulting in an average annual ring increment approximately 40% greater in 1987 than in 1950. When compared with expected annual increment, the increase for 100- to 150- year-old trees is approximately 45%, while the increase for 200- to 400-year-old trees is approximately 35%. In terms of stand-level aboveground biomass accumulation, the increased growth has resulted in approximately 5% more biomass than expected. The increased growth cannot be explained by disturbance; stand history; or trends in precipitation, temperature, or Palmer drought severity index over the last 57 years. Increased atmospheric CO2 is a possible explanation for initiation of the observed trend, while SO(x) and NO(x) may be augmenting continuation of this phenomenon.CDB.XLAL456^4^Wheeler,RM^Mackowiak,CL^Siegriest,LM^Sager,JC^1993^1^Supraoptimal carbon-dioxide effects on growth of soybean [glyciLne-max (L) merr]^4^142^2^173-178^^^^^Aug^^^^^3738DOCcentered.doc.PROGRAM FILELA^3737^In tightly closed environments used for human life support in space, carbon dioxide (CO2) partial pressures can reaLch 500 to 1000 Pa, which may be supraoptimal or toxic to plants used for life support. To study this, soybeans [Glycine maLx (L.) Merr. cvs. McCall and Pixie] were grown for 90 days at 50, 100, 200, and 500 Pa partial pressure CO2 (500, 1000, 20L00, and 5000 ppm). Plants were grown using recirculating nutrient film technique with a 12-h photoperiod, a 26-degrees-C/2L0-degrees-C thermoperiod, and approximately 300 mumol m-2 s-1 photosynthetic photon flux (PPF). Seed yield and total biomaLss were greatest at 100 Pa for cv. McCall, suggesting that higher CO2 levels were supraoptimal. Seed yield and total biomaLss for cv. Pixie showed little difference between CO2 treatments. Average stomatal conductance of upper canopy leaves at 5L0 Pa CO2 almost-equal-to 500 Pa > 200 Pa > 100 Pa. Total water use over 90 d for both cultivars (combined on one recirculaLting system) equalled 822 kg water for 100 Pa CO2, 845 kg for 50 Pa, 879 kg for 200 Pa, and 1194kg for 500 Pa. Water use eLfficiences for both cultivars combined equaled 3.03 (g biomass kg-1 water) for 100 Pa CO2, 2.54 g kg-1 for 200 Pa, 2.42 g Lkg-1 for 50 Pa, and 1.91 g kg-1 for 500 Pa. The increased stomatal conductance and stand water use at the highest CO2 leveLl (500 Pa) were unexpected and pose interesting considerations,for managing plants in a tightly closed system where CO2 coM ncentrations may reach high levels.E TEMPLATES\CONTENT\CALENDAR.DOCHtml.dM 457^5^Badiani,M^Dannibale,A^Paolacci,AR^Miglietta,F^Raschi,A^1993^1^The antioxidant status of soybean (glycine-max) leavesM grown under natural co2 enrichment in the field^92^20^3^275-284^^^^^^^^^^3740PROGRAM FILES\MICRMA^3739^The effects of progressively higher CO2 levels on the foliar antioxidant status were studied by growing soybean (GlM'A^3741^In our experiments, carbonated water (CW) modified the equilibria in soil. Application of CW decreased the soil pH M)about 1.5 units one hour after irrigation ended. Minimal, though well defined, differences in soil pH were observed betweeM1n the two carbonated treatments. The same relationship between the treatments was not found in pH levels of the leachate. M3This seems strictly related to the temporal and spatial changes in the carbon dioxide (CO2) acidifying effect caused by chM=emical and biological factors as water descended the soil column. The temporary reduction in soil pH in the CW treatment iM?nduced the highest nutrient mobility for most of the elements.0-(EST) 918031637 Ndel Nskip Nsave read Nget 1618428005 5bMP459^2^Beerling,DJ^Chaloner,WG^1993^1^Stomatal density responses of egyptian olea-europaea L leaves to co2 change since 132MR7 bc^52^71^5^431-435^^^^^May43ca3bbe73eaea9994f9f15ab0f661 <199902031715.MAA27750@mail2.uts.ohio-state.edu>-3-Feb-1999-12MY 460^3^Cournac,L^Dimon,B^Peltier,G^1993^1^Evidence for o-18 labeling of photorespiratory co2 in photoautotrophic cell-cultuM[res of higher-plants illuminated in the presence of o-18(2)^6^190^3^407-414^^^^^Jun^^^^^374519b0ff3ef7585fb56f9e8107 <3.0Md A^3744^The O-18-enrichment of CO2 produced in the light or during the post-illumination burst was measured by mass spectroMf metry when a photoautotrophic cell suspension of Euphorbia characias L. was placed in photorespiratory conditions in the pMmresence of molecular O-18(2). The only O-18-labeled species produced was (COO)-O-18-O-16; no (COO)-O-18-O-16 could be deteMocted. Production of (COO)-O-18-O-16 ceased after addition of two inhibitors of the photosynthetic carbon-oxidation cycle, Myaminooxyacetate or aminoacetonitrile, and was inhibited by high levels of CO2. The average enrichment during the post- illM{umination burst was estimated to be 46+/-15% of the enrichment of the O2 present during the preceding light period. AdditiMon of exogenous carbonic anhydrase, by catalyzing the exchange between CO2 and H2O, drastically diminished the O-18- enricMhment of the produced CO2. The very low carbonio-anhydrase level of the photoautotrophic cell suspension probably explainsM why the O-18 labeling of photorespiratory CO2 Could be observed for the first time. These data allow the establishment ofM a direct link between O2 consumption and CO2 production in the light, and the conclusion that CO2 produced in the light rMesults, at least partially, from the mitochondrial decarboxylation of the glycine pool synthesized through the photosyntheMtic carbon-oxidation cycle. Analysis of the (COO)-O- 18-O-16 and CO2 kinetics provides a direct and reliable way to assessM in vivo the real contribution of photorespiratory metabolism to CO2 production in the light.2:17--0500-(EST) 918466818 NM461^6^Dayan,E^Vankeulen,H^Jones,JW^Zipori,I^Shmuel,D^Challa,H^1993^1^Development, calibration and validation of a greenhouMse tomato growth-model .1. Description of the model^223^43^2^145-163^^^^^^^^^^37474020a11b2e4f99427b7@[192.168.1.31]>-8-FMA^3746^A dynamic crop growth model. TOMGRO, for an indeterminate tomato variety is presented. The model describes the phenMological development and increase in dry weight of various organs (roots, stem nodes, leaves and fruits) from planting tilMl maturity under variable environmental conditions. Phenological development is governed by genetic plant properties and eMnvironmental conditions (e.g. air temperature and CO2 level) and expressed in a plastochron index, i.e. the current stem nMode number. Total dry matter accumulation is based on a quantitative description of the carbon balance, including gross COE 2 assimilation, maintenance respiration and growth respiration. Partitioning of dry matter increase over the various organN!s is governed by their relative sink strengh, defined on the basis of a genetically determined 'potential' growth rate, acN "hieved under non-limiting carbohydrate supply. The model is both schematic and modular in set-up. This means it can be adaN#pted easily and most of its subroutines can be replaced easily by others if better descriptions become available. It can aN$lso be combined with a more comprehensive model describing greenhouse climate and appears robust for use in procedures of Neconomic optimization of climate conditions in greenhouses or for management purposes.168.1.30]>-12-Feb-1999-21:44:08--05N(&462^2^Ehler,N^Karlsen,P^1993^1^Optico - a model-based real-time expert-system for dynamic optimization of co2 enrichment oN*f greenhouse vegetable crops^174^68^4^485-494^^^^^Jul^^^^^3749read Nget 868656267 7a8089ae8b15c275ba0e5eddc02b1d61 )e system continually adapts the setpoints of a standard climate computer to the climate, the greenhouse regulation equipmeNM*nt and the crop's physiological status and stage of development. Models describing air loss and photosynthesis were used fNO+or selecting an optimized CO2 setpoint by choosing the largest positive difference between expected income and cost. DurinN[,g the autumn of 1991 the sweet pepper (Capsicum annuum L.) cv. Trophy was used as experimental plant in two standard greenN]-house compartments. One treatment used the optimized CO2 enrichment, the other a fixed CO2 level of 600 ppm. The optimizedNl. treatment resulted in greater yield using less CO2. The results stress the importance of adapting the CO2 level to the imNnmediate irradiance and current leaf area and carbon partitioning behaviour of the crop.legraph.uwyo.edu>-17-Feb-1999-18:3N0463^4^Idso,SB^Kimball,BA^Akin,DE^Kridler,J^1993^1^A general relationship between co2-induced reductions in stomatal conducNtance and concomitant increases in foliage temperature^173^33^3^443-446^^^^^Jul^^^^^37515 9d7630bb0ee8c1749e9ef9110e2cfeN2A^3750^Simultaneous measurements of the temperatures and stomatal conductances of leaves of sour orange trees growing in nN3ormal and CO2-enriched air, together with similar data for water hyacinths and cotton, suggest that a plant's foliage tempN4erature response to atmospheric CO2-enrichment is directly proportional to its degree of stomatal closure, i.e. that plantN5s that experience a greater stomatal closure in response to atmospheric CO2 enrichment experience a greater warming of theN6ir foliage. The data also suggest that this primary relationship may be modified by CO2-induced changes in leaf chlorophylNl content that may have implications for global climate change. Nsave read Nget 1755720812 166405902e59380b02bf81a1b3974N8464^3^Idso,SB^Wall,GW^Kimball,BA^1993^1^Interactive effects of atmospheric co2 enrichment and light- intensity reductions Non net photosynthesis of sour orange tree leaves^173^33^3^367-375^^^^^Jul^^^^^37539-14:10:09--0500-(EST 919866127 Ndel NsN:A^3752^In a tong-term study of the effects of a 300 mul l-1 enrichment of the air's CO2 content on the growth of sour oranN;ge trees, a comprehensive set of net photosynthesis and light intensity data was obtained. From these measurements we deriNt photosynthesis at full sunlight. Our analysis demonstrated that the positive direct effect of atmospheric CO2 enrichmentN? on net photosynthesis more than compensated for the negative self- shading effect produced by the CO2-induced proliferatiOon of leaf area.0F7O00D8SIC1W9@mx3.osu.edu>-24-Feb-1999-17:10:02--0500-(EST 919928326 Ndel Nskip Nsave read Nget 89468391OA465^2^Jacob,J^Drake,BG^1993^1^Long-term co2 enrichment effects on the rubisco content and activity in 2 field-grown C3 plaO#nts^8^102^1^46^^^^^Mayda6b172f6f27ee457a67 -24-Feb-1999-17:22:27--0500-(EST 91992O%C466^3^Prior,SA^Rogers,HH^Runion,GB^1993^1^Effects of free-air co2 enrichment on cotton root morphology^8^102^1^173^^^^^MayO2ST 919928326 Ndel Nskip Nsave read Nget 933301851 f1da0e4c3fac6cf487911863ffefb9c3 <0F7O00M7GJL8V9@mx2.osu.edu>-24-Feb-1O4N467^3^Rabbinge,R^Vanlatesteijn,HC^Goudriaan,J^1993^1^Assessing the greenhouse-effect in agriculture^224^175^^62-79^^^^^^^^O<FA^3756^Evidence that concentrations of CO2 and trace gases in the atmosphere have increased is irrefutable. Whether or notO>G these increased concentrations will lead to climate changes is still open to debate. Direct effects of increased CO2 concOJHentrations on physiological processes and individual plants have been demonstrated and the consequences for crop growth anOLId production under various circumstances are evaluated with simulation models. The consequences of CO2 enrichment are consOTJiderable under optimal growing conditions. However, the majority of crops are grown under sub-optimal conditions where theOVK effects of changes in CO2 are often less. The same holds for the possible indirect effects of environmental changes such O_Las temperature rise. Studies on individual plants under optimal conditions are therefore not sufficient for evaluating theOaM effects at a farm, regional, national or supra-national level. Simulation studies help to bridge the gap between the variOkous aggregation levels and provide a basis for various studies of policy options at various aggregation levels.9292 f5e5Om^^3757bf54cade85f44ad -25-Feb-1999-09:46:27--0500-(EST 919936414 Ndel Nskip Nsave read Nget O~P468^3^Sicher,RC^Kremer,DF^Rodermel,SR^1993^1^Role of rubisco during acclimation of transformed tobacco to co2 enriched atmOospheres^8^102^1^88^^^^^May OR469^1^Woodward,FI^1993^1^The lowland-to-upland transition modeling plant-responses to environmental-change^56^3^3^404-408^O^^^^Aug^^^^^3760ROGRAM FILES\MICROSOFT OFFICE\OFFICE\WEB PAGE TEMPLAOTA^3759^A published correlative model has predicted that the distributional limits of plants and vegetation zones on mountaOUins will increase in altitude with global warming. I test this hypothesis using results from published experimental studieOVs. Investigations and models of the responses of leaf growth to temperature are in accord with the prediction. However, thOWe individualistic responses of species to CO2 enrichment indicate that the prediction is unlikely to be true for all speciOXes: growth is stimulated by CO2 enrichment for some species but not for others. Wind speed generally increases with altituOYde on mountains, and plants from high altitude tend to be more wind resistant than species from the lowland. Therefore it OZis expected that, particularly on wind-swept mountains, global warming will not necessarily be followed by the spread of lOowland species into the uplands. Word 8.0 PROGRAM FILES\MICROSOFT OFFICE\O\470^2^Beerling,DJ^Chaloner,WG^1993^1^Evolutionary responses of stomatal density to global co2 change^225^48^4^343-353^^^^^OAprord for Windows 95 vPROGRAM FILES\MICROSOFT OFFICE\OFFICEO^471^2^Bladier,C^Chagvardieff,P^1993^1^Growth and photosynthesis of photoautotrophic callus derived from protoplasts of solOanum-tuberosum L^226^12^6^307-311^^^^^Apr^^^^^3763T OFFICE\OFFICE\LIBRARY\MSQUERY\XLQO`A^3762^We describe a photoautotrophic culture procedure of potato (cvs Kennebec, Haig, DTO-33) callus derived from mesophyOall protoplasts. The protoplast culture was initiated at very low concentration of glucose (down to 0.25 g l-1). Callus wasPb subcultured under CO2 enriched air and glucose was suppressed by the successive dilutions with glucose free media. RegenePcration was successfully obtained under photoautotrophic conditions. The characterization of oxygen exchange and of some enP dzymes and metabolites of carbon assimilation indicated that chlorophyllous callus, grown on carbohydrate free medium, devePeloped the photosynthetic pathway typical of C3 plants. By comparing the fresh weight of callus cultivated in the light or P$fin non-photosynthetic conditions (in darkness or in the light +3-(3,4-Dichlorophenyl)-1,1-dimethylurea) we concluded that P&growth depended to about 70 to 88 % on photosynthesis. P9h472^3^Dorais,M^Charbonneau,J^Gosselin,A^1993^1^Gas-exchange in greenhouse tomatoes grown under supplemental light^146^73^2P:^577-585^^^^^Apr^^^^^3765XLLLLLXPDjA^3764^This study reports on in situ gas-exchange measurements in tomatoes grown under a sequential intercropping system wPFkith supplemental lighting provided by high-pressure sodium-vapour lamps. A supplemental photosynthetic photon flux (PPF) oPYlf 150 mumol m-2 s-1 significantly increased the amount of light energy penetrating the canopy of intercropped tomato seedlP[mings. During the day, the supplemental 150 mumol m-2 s-1 light regime increased the photosynthetic rate of leaves 5 and 10Pen by 67%, while at night the increases were 93 and 12%, respectively. Regression analysis of the photosynthetic rate of leaPgoves 5 and 10 as a function of PPF received accounts for 58 and 45% of the variation, respectively. Hierarchical analysis dPvpemonstrated a significant linear relationship between PPF received during the day and photosynthetic activity of leaves 5 Pxqand 10 accounting for 46 and 28%, respectively, of the variance in the model. Regression analysis of the photosynthetic acPrtivity as a function of PPF received at night accounts for 41 and 32 %, respectively, of the variation in the photosynthetPsic rate of leaves 5 and 10. Using a high level of supplemental lighting during the day or at night had no significant effePct on stomatic conductance or on the transpiration rate of leaves.and genotypes are available with tolerance and sensitivPu473^3^Hand,DW^Wilson,JW^Acock,B^1993^1^Effects of light and co2 on net photosynthetic rates of stands of aubergine and amaPranthus^52^71^3^209-216^^^^^Mart stress and optimal temperature, and test whether differences in carbohydrate supplies duPw474^4^Holbrook,GP^Hansen,J^Wallick,K^Zinnen,TM^1993^1^Starch accumulation during hydroponic growth of spinach and basil plPants under carbon-dioxide enrichment^173^33^2^313-321^^^^^Apr^^^^^3768ht temperatures of either 33/20 or 33/30- degrees-CPyA^3767^The effects of CO2 enrichment, photoperiod duration, and inorganic phosphate levels on growth and starch accumulatiPzon by spinach and basil plants were studied in a commercial hydroponic facility. During a 3-week growth period, both speciP{es exhibited increased whole-plant fresh weight as a result of an increase in atmospheric CO2 concentration from 400 to 15P|00 mul/l. However, basil leaves exhibited a 1.5- to 2-fold greater increase in specific leaf weight (SLW), and accumulatedP} starch to much greater levels than did leaves of spinach. At 1500 mul CO2/l, starch accounted for up to 38% of SLW with bP~asil compared to < 10% of SLW with spinach. The maximum ratio of starch/chlorophyll was 55.0 in basil leaves vs 8.0 in spiPnach leaves. High ratio values were associated with the appearance of chlorotic symptoms in leaves of basil grown under COP2 enrichment (WALLICK and ZINNEN (1990) Plant Disease 74, 171-173), whereas spinach did not exhibit chlorosis. Increasing Pinorganic phosphate concentrations from 0.7 to 1.8 mM in the hydroponic medium did not appreciably affect leaf starch accuQmulation in either species. Starch accumulation in basil leaves was not consistently related to the duration of the photopQ eriod. However, photoperiod-induced changes in leaf starch levels were much greater in basil than spinach. The results cleQ arly indicate that different horticultural crops can show diverse responses to CO2 enrichment, and thus highlight the needQ to develop individual growth strategies to optimize production quality of each species.ER, JM PRESS, MC TI GROWTH-RESPONQ475^2^Hunt,R^Constable,GM^1993^1^Multifactorial growth-responses in holcus-lanatus - optima and limiting factors^52^71^4^3Q%57-368^^^^^Apr, DEPT ENVIRONM BIOL, OXFORD RD, MANCHESTER M13 9PL, LANCS, ENGLAND. DE GROWTH ANALYSIS; CO2; NITROGEN; AGRQ'476^4^Tanigawa,T^Nagaoka,M^Ikeda,H^Shimizu,A^1993^1^Effects of co-2 enrichment on growth, photosynthesis and physiologicalQ>-activity of roots of dendranthema X grandiflorum (ramat) kitamura^180^61^4^873-878^^^^^Mar^^^^^3771nd Nardus stricta L. Q@A^3770^To assess the effect of CO2 enrichment on growth of greenhouse chrysanthemum, the plants were cultivated in the phyQNtotron with 300, 600 and 1,200 ppm CO2. i. CO2 enriched plants showed a significant increase in stem length, number of leaQPves, leaf area, and fresh and dry weights. The greatest rate of increase after 60 days of CO2 enrichment was observed in tQ]he dry weight of roots (39%). Flower bud formation was delayed 3 days under CO2 enriched condition. 2. No difference in phQ_otosynthetic rates of whole plants measured in 400 and 800 ppm CO2 was observed among those grown under high CO2 (600 or 1Qn,200 ppm) and those grown in ambient air (300 ppm). After 60 days of exposure to ambient and high CO2, the photosynthetic Qprate measured in 800 PPM CO2 declined markedly compared to the rate at the beginning of the treatment. 3. TTC (2, 3, 5-triQ}phenyl tetrazolium chloride) reductive activity of roots decreased under CO2 enriched atmosphere, but it increased on a peQ~r plant basis because fresh weight of the roots increased. There was a high positive correlation between TTC reduction perQ plant and the fresh weight of the top (aerial part).al dry weight at low nitrogen whilst at high nitrogen plants grown aQ477^2^Andre,M^Ducloux,H^1993^1^Interaction of co2 enrichment and water limitations on photosynthesis and water efficiency Qin wheat^184^31^1^103-112^^^^^Jan-Feb^^^^^3773he lower nitrogen concentration was to increase partitioning to the roots wQA^3772^Wheat plants (Triticum aestivum L. cv. Capitole) were grown in twin closed growth chambers with continuous monitoriQng of CO2 and water exchanges. During the vegetative stage the effect Of CO2 enrichment, from 330 to 660 mul-1, was studieQd under irradiance of 660 muE m-2 s-1 with an optimum watering. Comparisons were made with successive experiments in whichQ daily water supply was fixed to a fraction (0.62-0.50-0.25) of the maximal transpiration of previous experiments. In a weQll- watered canopy, doubling CO2 decreased transpiration by only 8%. Water use efficiency was increased (factor 1.45) mainQly by the stimulation of photosynthesis. Under restricted water supply, photosynthesis of plants was more limited than traQnspiration. The inhibition of photosynthesis and the increase of water use efficiency can be predicted by a simple diffusiQon model applied to the response curve of photosynthesis to CO2, measured on canopy in standard conditions of watering. ThQe main hypothesis is that the equivalent stomatal conductance is reduced proportionally to the water availability, withoutQ closure by patching. Under enriched CO2, the same reduction of leaf surface by water limitation was observed. PhotosyntheQsis was less affected. Therefore, water-use-efficiency was again increased. Doubling CO2 concentration can compensate for Qwater stress inhibition on CO2 assimilation. That model also predicts interactions of CO2 and water stress observed on watQer-use- efficiency which was increased by a factor up to 5 in comparison with well-watered plants in standard atmosphere. RThe implications of this study for global change models are discussed. fluxes from losses in tropical forests may be lessR478^1^Besford,RT^1993^1^Photosynthetic acclimation in tomato plants grown in high co2^24^104^^441-448^^^^^Jan^^^^^3775souR A^3774^The effects of prolonged CO2 enrichment of tomato plants on photosynthetic performance and Calvin cycle enzymes, inR cluding the amount and activity of ribulose-1,5-bisphosphate carboxylase (RuBPco), were determined. Also the light-saturatRed rate of photosynthesis (P(max)) of the 5th leaf throughout leaf development was predicted based on the amount and kinetRics of RuBPco. With short-term CO2 enrichment, i.e. only during the photosynthesis measurements, P(max) of the young leaveR*s did not increase while the leaves reaching full expansion more than doubled their net rate of CO2 fixation. However, witR-h longer- term CO2 enrichment, i.e. growing the crop in high CO2, the plants did not maintain this photosynthetic gain. CoR9mpared with leaves of plants grown in normal ambient CO2 the high CO2-grown leaves, when almost fully expanded, contained R;only about half as much RuBPco protein and P(max) in 300 and 1000 vpm CO2 was similarly reduced. The loss of RuBPco proteiRFn may be a factor associated with the accelerated fall in P(max) since P(max) was close to that predicted from the amount RHand kinetics of RuBPco assuming RuBP saturation. Acclimation to high CO2 is fundamentally different from acclimation to hiRTgh light. In contrast to acclimation to high light, acclimation to high CO2 does not usually involve an increase in photosRVynthetic machinery so the synthesis and maintenance costs (as indicated by the dark respiration rate) are generally lower.Raetween 160-190 and 450-550 mumol m-2 s-1 in the HS and FS treatments, respectively. R(D) of leaves which were kept in darRc479^2^Debruin,HAR^Jacobs,CMJ^1993^1^Impact of co2 enrichment on the regional evapotranspiration of agroecosystems, a theorRjetical and numerical modeling study^24^104^^307-318^^^^^Jan^^^^^3777 treatments of FSA, FSE, HSA and HSE, respectively. ERlA^3776^This paper gives a brief overview of factors determining evapotranspiration of vegetated surfaces. It indicates whiRwch of these factors are sensitive to CO2 enrichment. A qualitative analysis is presented of the impact of large scale climRzate changes. Data in literature indicate that the surface resistance of vegetated areas may change within the range -25 % Rand +50 % if the atmospheric CO2-concentration doubles. The impact of such changes on regional scale transpiration is evalRuated using a numerical model in which the interaction between the evapotranspiration and the Planetary Boundary Layer is Raccounted for. It is concluded that the impact of CO2 enrichment on the transpiration at the regional scale is relatively Rsmall for aerodynamically smooth surfaces (between +7 % and -11 %). For aerodynamically rough surfaces the effects are somRewhat larger (between +15 % and -21 %).reached 6.8, 4.6, 5.7 and 3.2 kg per plant in the FSA, FSE, HSA and HSE treatmentsR480^2^Fournioux,JC^Bessis,R^1993^1^Use of carbon-dioxide enrichment to obtain adult morphology of grapevine invitro^177^33R^1^51-57^^^^^Apr^^^^^3779s the combination of moderate shading and CO2 enrichment might provide a more productive option RA^3778^A procedure has been developed for in vitro propagation of Vitis vinifera 'Pinot noir' from lateral-bud cuttings unRder high CO2 concentration (1200 mumol mol-1). Because of inhibition of rooting by CO2, this procedure requires a rooting Rpre-culture of explants on medium with sucrose before the CO2- enriched culture on sucrose-free medium. Shoot growth was eRnhanced by CO2 enrichment as a result of both a higher rate of leaf production and greater internode elongation. Leaf expaRnsion and tendril growth were promoted and better rooting was obtained. The more significant effect of CO2 enrichment was Rto promote adult morphology with, in particular, the tendril pattern. Thus, for the first time, grapevine plants have beenR produced in vitro without typical juvenile characteristics. CO2 enrichment appears to be an interesting process to improvRe the in vitro propagation of grapevines.on future regional economies. The methodology also provides for systematic studyR481^4^Grant,WJR^Fan,HM^Downton,WJS^Loveys,BR^1992^1^Effects of co2 enrichment on the physiology and propagation of 2 austrRalian ornamental plants, chamelaucium-uncinatum (schauer) X chamelaucium-floriferum (ms) and correa- schlechtendalii (behrR)^165^52^4^337-342^^^^^Dec^^^^^3781 In this final paper we consider whether synergistic effects among sectoral impacts anSA^3780^Root formation on both Chamelaucium and Correa cuttings maintained at high humidity in an enclosed fog tunnel was sSignificantly enhanced when ambient CO2 was increased from 350 to 800 mubar. CO2 enrichment resulted in decreased transpiraStion and increased water potential of cuttings implying an effect of CO2 on stomatal conductance. CO2 enrichment led to inScreased starch levels in cuttings of both species probably by raising the intercellular partial pressure of CO2. IncreasedS  starch content with CO2 enrichment was able to account for 70-90% of the dry weight increase in Correa, but only for 10-3S"0% of the dry weight increase in Chamelaucium. It is suggested that the stimulation of rooting associated with CO2 enrichmS+ent probably derives from the improved water relations of the cuttings rather than from increased carbohydrate levels., AS-482^3^Hendrey,GR^Lewin,KF^Nagy,J^1993^1^Free air carbon-dioxide enrichment - development, progress, results^24^104^^17-31^S:^^^^Jan^^^^^3783 RES UNIT, LONDON E15 4LZ, ENGLAND. ID CO2 ENRICHMENT; GROWTH; ECOSYSTEMS; SOIL; POPULATIONS; NUTRITION; S<A^3782^Credible predictions of climate change depend in part on predictions of future CO2 concentrations in the atmosphereSN. Terrestrial plants are a large sink for atmospheric CO2 and the sink rate is influenced by the atmospheric CO2 concentraSPtion. Reliable field experiments are needed to evaluate how terrestrial plants will adjust to increasing CO2 and thereby iSenfluence the rate of change of atmospheric CO2. Brookhaven National Laboratory (BNL) has developed a unique Free-Air CO2 ESgnrichment (FACE) system for a cooperative research program sponsored by the U.S. Department of Energy and U.S. Department Stof Agriculture, currently operating as the FACE User Facility at the Maricopa Agricultural Center (MAC) of the University Svof Arizona. The BNL FACE system is a tool for studying the effects of CO2 enrichment on vegetation and natural ecosystems,S and the exchange of carbon between the biosphere and the atmosphere, in open-air settings without any containment. The FASCE system provides stable control of CO2 at 550 ppm +/- 10%, based on 1- min averages, over 90% of the time. In 1990, thisS level of control was achieved over an area as large as 380 m2, at an annual operating cost of $668 m-2. During two field Sseasons of enrichment with cotton (Gossypium hirsutum) as the test plant, enrichment to 550 ppm CO2 resulted in significanSt increases in photosynthesis and biomass of leaves, stems and roots, reduced evapotranspiration, and changes in root morpShology. In addition, soil respiration increased and evapotranspiration decreased.RCES FUTURE INC, WASHINGTON, DC 20036. BS483^3^Lord,D^Morissette,S^Allaire,J^1993^1^Influence of light-intensity, nocturnal air-temperature and carbon-dioxide leveSls on greenhouse black spruce seedlings (picea-marianna)^155^23^1^101-110^^^^^Jan^^^^^3785N; CO2 AB The climate of the 19SA^3784^Growth of containerized black spruce seedlings grown in greenhouses was studied in relation to factors known to infSluence plant growth. Artificial light intensity (3.80 and 72.04 mumol.m-2.s-1) and night air temperature (5, 10, 12.5, 15,S and 20-degrees-C) were considered in a first experiment and artificial light intensity (4.24 and 59.57 mumol.m-2.s-1) andS CO2 air concentration (ambient and 1000 muL.L-1) in a second one. Higher light intensity and CO2 enrichment increased dryS biomass of seedlings as well as growth in height and stem diameter. Both factors similarly enhanced the last two parameteSrs since height/diameter ratios showed little variation among treatments. Reducing night air temperature down to 10- degreSes-C did not significantly influence height growth nor biomass increase when high intensity light was provided. Lower lighSt intensity raised the threshold to 12.5-degrees-C. Shoot height, diameter, and dry biomass as well as the number of brancShes and buds per millimeter were strongly reduced by a 5- degrees-C night air temperature. High intensity light enhanced gSrowth of containerized black spruce seedlings more than CO2 enrichment or a 5-degrees-C night air temperature. When used sSimultaneously, these growth enhancing factors had a synergistic effect during most of the treatment period; thereafter, thSe effect became partially additive. The relative growth rate peaked at the onset of exponential shoot growth and decreasedS after this point. However, the enhancing factors were still efficient since absolute growth differences between seedlingsS grown under the most-favorable conditions and controls kept increasing, The faster growing pace imposed by these growth eSnhancing conditions during the treatment period was maintained over the entire first growing season. OF CARBON FIXATION IS484^3^Pospisilova,J^Solarova,J^Catsky,J^1992^1^Photosynthetic responses to stresses during invitro cultivation^79^26^1^3-1S8^^^^^^^^^^3787IOCHEM, LICHTENBERG STR 4, W-8046 GARCHING, GERMANY. UNIV ULM, ANGEW MIKROBIOL ABT, W-7900 ULM, GERMANY. UTA^3786^Present knowledge of photosynthesis, biomass production and water relations of plantlets cultivated in vitro and thT eir responses to environmental conditions is reviewed. Acclimation of plantlets, firstly to very special in vitro conditioTns and secondly after transplantating to ex vitro conditions, is considered. Low irradiance and CO2 concentration inside cTultivation vessels restrict photosynthetic rate and accumulation of biomass by plantlets in situ. Nevertheless the photosyTnthetic apparatus is often fully developed. Therefore net photosynthetic rate and hence biomass accumulation can increase Timmediately after artificial increase in CO2 concentration inside the vessels (this enables autotrophic cultivation of plaTntlets as one of important future technologies) or after transplanting to glasshouse or field. On the other hand, under veT!ry high humidity and low irradiance in vitro, efficient regulation of gas exchange does not operate. The development of fuT,nctional stomata and cuticle requires some weeks of acclimation to natural conditions.coupling patterns suggest a novel cT. 485^2^Stulen,I^Denhertog,J^1993^1^Root-growth and functioning under atmospheric co2 enrichment^24^104^^99-115^^^^^Jan^^^^^T9bacterial production (measured in anoxic, in vitro incubations) which could account for only 50% of the whole-core flux. PT;resumably the remainder was CO2 and CH4 stored in the peat cores at the time of collection. Overall, the results suggest tTHhat a temperate climate imposed on northern peatlands could mobilize stored carbon and increase CO2 and CH4 efflux into thTJe troposphere. Studies involving peat cores must insure that CO2 and CH4 dynamics measured in vitro mimic those in situ.OTY505^3^Gong,H^Nilsen,S^Allen,JF^1993^1^Photoinhibition of photosynthesis invivo - involvement of multiple sites in a photodT[amage process under co2-free and o2- free conditions^235^1142^1-2^115-122^^^^^5 Apr^^^^^3829121, BATIMENT 362, F-91405 OTgA^3788^This paper examines the extent to which atmospheric CO2 enrichment may influence growth of plant roots and functionTi in terms of uptake of water and nutrients, and carbon allocation towards symbionts. It is concluded that changes in dry mTwatter allocation greatly depend on the experimental conditions during the experiment, the growth phase of the plant, and iTyts morphological characteristics. Under non-limiting conditions of water and nutrients for growth, dry matter partitioningT to the root is not changed by CO2 enrichment. The increase in root/shoot ratio, frequently observed under limiting conditTions of water and/or nutrients, enables the plant to explore a greater soil volume, and hence acquire more water and nutriTents. However, more data on changes in dry matter allocation within the root due to atmospheric CO2 are needed. It is concT luded that nitrogen fixation is favored by CO2 enrichment since nodule mass is increased, concomitant with an increase in T root length. The papers available so far on the influence of CO2 enrichment on mycorrhizal functioning suggest that carbonT allocation to the roots might be increased, but also here more experiments are needed. All additional dry matter was allT3789he roots in sweet chestnut, while it was partitioned equally amongst all organs of the beech seedling. 5. The reactioT 486^1^Vugts,HF^1993^1^The need for micrometeorological research of the response of the energy-balance of vegetated surfaceTs to co2 enrichment^24^104^^321-328^^^^^Jan^^^^^3791 PT J AU FIROUZBAKHT, ML SCHLYER, DJ GATLEY, SJ WOLF, AP TI A CRYOGETA^3790^A Penman-Monteith equation has been used to evaluate a change in canopy resistance on the evapotranspiration of a sTavannah and agricultural area in Botswana. After a short introduction, some problems concerning the K-theory or 'first ordTer closure' are indicated when one uses it for transport modelling within and above a canopy. The Penman-Monteith equationT was used to calculate the canopy resistance for a savannah vegetation and sorghum under the same environmental conditionsT. After that, by changing the stomatal resistance due to an increase of the CO2 content, the change in the evapotranspiratTion was estimated. Finally some recommendations for future research are given and an outline of a proposed FACE experimentT is presented.ecovered by warming the target and cryogenically transferring the gas into a storage bulb. After transfer, T487^4^Wheeler,RM^Corey,KA^Sager,JC^Knott,WM^1993^1^Gas-exchange characteristics of wheat stands grown in a closed, controlTled environment^164^33^1^161-168^^^^^Jan-Feb^^^^^3793ography and the reactivity has been verified by use in the synthesisTA^3792^Information on gas exchange of crop stands grown in controlled environments is limited, but is vital for assessing Tthe use of crops for human life-support in closed habitats envisioned for space. Two studies were conducted to measure gasU exchange of wheat stands (Triticum aestivum L. cv. Yecora Rojo) grown from planting to maturity in a large (20 m2 canopy Uarea), closed growth chamber. Daily rates of dark-period respiration and net photosynthesis of the stand were calculated fUrom rates of CO2 build-up during dark cycles and subsequent CO2 drawdown in the light (i.e., a closed-system approach). LiU ghting was provided as a 20-h photoperiod by high-pressure sodium lamps, with canopy-level photosynthetic photon flux densU"ity (PPFD) ranging from 500 to 800 mumol m-2 s-1 as canopy height increased. Net photosynthesis rates peaked near 27 mumolU9 CO2 m-2 s-1 at 25 d after planting, which corresponded closely with stand closure, and then declined slowly with age. SimU; ilarly, dark-period respiration rates peaked near 14 mumol CO2 m-2 s-1 at 25 d and then gradually declined with age. RespoUN!nses to short-term changes in irradiance after canopy closure indicated the stand light compensation point for photosyntheUP"sis to be near 200 mumol m-2 s-1 PPFD. Tests in which CO2 concentration was raised to almost-equal-to 2000 mumol mol-1 andUj# then allowed to draw down to a compensation point showed that net photosynthesis was nearly saturated at > 1000 mumol molUm$-1; below almost-equal-to 500 mumol mol-1, net photosynthesis rates dropped sharply with decreasing CO2. The CO2 compensatU%ion point for photosynthesis occurred near 50 mumol mol-1. Short-term (24 h) temperature tests showed net photosynthesis aU&t 20-degrees-C greater-than- or-equal-to 16-degrees-C > 24-degrees-C, while dark-period respiration at 24-degrees-C > 20-dU'egrees-C > 16-degrees-C. Rates of stand evapotranspiration peaked near Day 25 and remained relatively constant until aboutU( Day 75, after which rates declined slowly. Results from these tests will be used to model the use of plants for CO2 removU)al, O2 production, and water evaporation for controlled ecological life support systems proposed for extraterrestrial enviUronments.23-631 PG 9 JI Plant Cell Environ. PY 1993 PD AUG VL 16 IS 6 GA LW930 RP FLANAGAN LB J9 PLANT CELL ENVIRON ER PU+488^1^Tate,KR^1992^1^Assessment, based on a climosequence of soils in tussock grasslands, of soil carbon storage and releaUse in response to global warming^227^43^4^697-707^^^^^Dec^^^^^3795AB The capacity to supply both instream and offstream wU-A^3794^A soil climosequence in tussock grasslands in South Island, New Zealand, encompassing climates ranging from cold toU. warm temperate provided a spatial analogue of climate change for investigating the effects of global warming on soil C coU/ntents and turnover. Mean annual temperature (T) and annual precipitation (P) ranged from 2 to 10-degrees-C, and 350 to 50U000 mm, respectively. Soil C contents were curvilinearly related to T/P across the sequence (r = -0.95, significant at P < U10.01), indicating that east of the Southern Alps, increased decomposition of organic matter with global warming would provV2ide a positive feedback to further increase atmospheric CO2. This decrease in New Zealand's soil C, estimated to be up to V310% of the current content for a global temperature rise of 0.03 K a-1 to 2050, could contribute about 0.5 x 10(15) g C toV4 the atmosphere over the next 60 years. These conclusions were generally supported by changes in soil C turnover estimatedV"5 from 'bomb' C-14 enrichment. The unexpectedly slow turnover found for two soils was explained by a 'memory' effect from tV$6he former southern beech forest that grew on these soils in prehistoric times. Accumulation of Al-humus under the forest mV8ay be responsible for the slow C turnover observed.ll have less water in the year 2030 than it does today because groundwV:8489^7^Abarzua,S^Altenburger,R^Callies,R^Grimme,LH^Mayer,A^Leibfritz,D^Schiewer,U^1993^1^Ammonium rhythm in cultures of theVK cyanobacterium microcystis- firma^37^89^3^659-663^^^^^Nov^^^^^3797, and fish and wildlife habitat would be most adverselVM:A^3796^Over a period of several days, rhythmic changes in extracellular NH4+ concentration take place in cultures of the cVd;yanobacterium Microcystis firma (Breb et Lenorm.) Schmidle, strain Gromov/St. Petersb. 398, under conditions of restrictedVf< CO2 supply and light/dark alternation. The changes are enhanced by nitrate supply. Among the various processes generatingVx= intracellular NH4+ (NH4+ uptake, NO3- reduction, protein and amino acid degradation, photorespiration), NO3- reduction apVz>pears as the one most important. This can be concluded from experiments with and without nitrate and/or ammonium in the meV?dium. In the presence of saturating CO2, continuous light, or continuous darkness, rhythmic NH4+ oscillations are not induV@ced. Studies of the incorporation of NH4+ nitrogen by in vivo N-15-NMR show that if CO2 is supplied, N-15 is accumulated iVAn several components with the following time course: in the first hour in Gln (delta), in the second hour in the alpha- amVBino groups of most nonbranched amino acids, in the third hour in gamma-aminobutyric acid (GABA), Orn (delta) and Lys (epsiVClon), and in the sixth hour in Ala. Carbon limitation, however, results in accumulation of label in the amide nitrogen of Vglutamine only.se in deltaC-13 values; however, the relative content of plant products, especially of the soluble polar cVE490^6^Brailsford,RW^Voesenek,LACJ^Blom,CWPM^Smith,AR^Hall,MA^Jackson,MB^1993^1^Enhanced ethylene production by primary rooVts of zea-mays L in response to sub-ambient partial pressures of oxygen^9^16^9^1071-1080^^^^^Dec^^^^^3799, BasidiomycetesVGA^3798^Ethylene production by primary roots of 72-h-old intact seedlings of Zea mays L. cv. LG11 was studied under ambientVH and sub-ambient oxygen partial pressures (pO(2)) using a gas how- through system linked to a photoacoustic laser detectorVI. Despite precautions to minimize physical perturbation to seedlings while setting-up, ethylene production in air was fastVJer during the first 6h than later, in association with a small temporary swelling of the roots. When roots were switched fVKrom air (20.8kPa O-2) to 3 or 5kPa O-2 after 6h, ethylene production increased within 2-3h. When, the roots were returned VLto air 16h later, ethylene production decreased within 2-3h. The presence of 1OkPa CO2 did not interfere with the effect oVMf 3kPa O-2. Transferring roots from air to 12.5kPa did not change ethylene production, while a reduction to 1kPa O-2 inducVNed a small increase. The extra ethylene formed in 3 and 5kPa O-2 was associated with plagiotropism, swelling, root hair prPOoduction, and after 72h, increased amounts of intercellular space (aerenchyma) in the root cortex. Root extension was alsoWP slowed down, but the pattern of response to oxygen shortage did not always match that of ethylene production. On return tWQo air, subsequent growth patterns became normal within a few hours. In the complete absence of oxygen, no ethylene productWion was detected, even when anaerobic roots were returned to air after 16h.trogen, while elevated CO2 decreased leaf costW491^2^Denelzen,MGJ^Rotmans,J^1993^1^Modeling climate related feedback processes^228^28^9^2095-2151^^^^^^^^^^3801 reflectiWTA^3800^Feedback mechanisms play a crucial role in the climate system, amplifying or dampening the climate response to enhaW&Unced concentrations of greenhouse gases from anthropogenic perturbations. Many of these feedbacks are known, but most of tW)Vhem only potentially. This article evaluates the role of a number of these feedback processes within the climate system. IW7Wn order to assess their impact, the feedbacks which at present can be quantified reasonably are built into the Integrated W9XModel to Assess the Greenhouse Effect (IMAGE). Unlike previous studies, this study describes the scenario- and time-dependWHYent role of biogeochemical feedbacks. A number of simulation experiments are performed with IMAGE to project climate changWJZes. Besides estimates of their absolute importance, the relative importance of individual biogeochemical feedbacks is consWX[idered by calculating the gain for each feedback process. This study focuses on feedback processes in the carbon cycle andWZ\ the methane (semi-) cycle. Modeled feedbacks are then used to balance the past and present carbon budget. This results inWj] substantially lower projections for atmospheric carbon dioxide than the Intergovernmental Panel on Climate Change (IPCC) Wl^estimates. The difference is approximately 18% from the 1990 level for the IPCC ''Business-as-Usual'' scenario. FurthermorW|_e, the IPCC's ''best guess'' value of the CO2 concentration in the year 2100 falls outside the uncertainty range estimatedW}` with our balanced modeling approach. For the IPCC ''Business-as- Usual'' scenario, the calculated total gain of the feedbWaacks within the carbon cycle appears to be negative, a result of the dominant role of the fertilization feedback. This stuWbdy also shows that if temperature feedbacks on methane emissions from wetlands, rice paddies, and hydrates do materialize,Wc methane concentrations might be increased by 30% by 2100. The total effect of the methane feedbacks and the carbon dioxidWde feedbacks modeled can be expressed in the carbon dioxide- equivalent concentrations. Our simulated CO2-equivalent concenWtrations are lower than the IPCC estimates.cence or abscission was detected, suggesting that the seasonal duration of effWf492^6^Gao,K^Aruga,Y^Asada,K^Ishihara,T^Akano,T^Kiyohara,M^1993^1^Calcification in the articulated coralline alga corallinaW- pilulifera, with special reference to the effect of elevated co2 concentration^229^117^1^129-132^^^^^Sep^^^^^3803 a resWhA^3802^Calcification in Corallina pilulifera Postels et Ruprecht displayed diurnal variations in aerated (350 ppm CO2) culWiture media, with faster rates during the light than during the dark period. Addition of CO2 (air + 1250 ppm) inhibited calWjcification. This was attributable to the decreased pH resulting from CO2 addition. Both photosynthesis and calcification wWere enhanced in seawater, with elevated dissolved inorganic carbon concentrations at a constant pH of 8.2.GANIC LAKE-SEDIWl493^5^Ojima,DS^Parton,WJ^Schimel,DS^Scurlock,JMO^Kittel,TGF^1993^1^Modeling the effects of climatic and co2 changes on graWssland storage of soil-C^94^70^1-4^643-657^^^^^Oct^^^^^3805SE AB Values of deltaC-13 obtained from conventional bulk sediWnA^3804^We present results from analyses of the sensitivity of global grassland ecosystems to modified climate and atmospheWoric CO2 levels. We assess 31 grassland sites from around the world under two different General Circulation Models (GCM) doWpuble CO2 climates. These grasslands are representative of mostly naturally occurring ecosystems, however, in many regions Wqof the world, grasslands have been greatly modified by recent land use changes. In this paper we focus on the ecosystem dyXrnamics of natural grasslands. The climate change results indicate that simulated soil C losses occur in all but one grasslX sand ecoregion, ranging from 0 to 14% of current soil C levels for the surface 20 cm. The Eurasian grasslands lost the greaXttest amount of soil C (approximately 1200 g C m-2) and the other temperate grasslands losses ranged froM 0 to 1000 g C m-2Xu, averaging approximately 350 g C m-2. The tropical grasslands and savannas lost the least amount of soil C per unit area X8vranging from no change to 300 g C m-2 losses, averaging approximately 70 g C m-2. plant production varies according to modX:wifications in rainfall under the altered climate and to altered nitrogen mineralization rates. The two GCM's differed in pXHxredictions of rainfall with a doubling of CO2, and these differences are reflected in plant production. Soil decompositionXJy rates responded most predictably to changes in temperature. Direct CO2 enhancement effects on decomposition and plant proXXduction tended to reduce the net impact of climate alterations alone.CHLOROETHENE TO GROWTH SO APPLIED AND ENVIRONMENTAL XZ494^2^Woods,J^Barkmann,W^1993^1^The plankton multiplier - positive feedback in the greenhouse^230^15^9^1053-1074^^^^^Sep^^Xe|A^3806^The plankton multiplier is a positive feedback mechanism linking the greenhouse effect and biological pump (Woods,JXf}.D., Royal Commission on Environmental Pollution, 1990). As pollution increases the atmospheric concentration of carbon diXv~oxide, the enhanced greenhouse effect induces radiative forcing of the ocean, which diminishes the depth of winter convectXxion, reducing the annual resupply of nutrients to the euphotic zone and therefore the annual primary production. That weakXens the biological pump, which contributes to oceanic uptake of CO2. As the ocean takes up less CO2, more remains in the aXtmosphere, accelerating the rise in radiative forcing. We have used a mathematical model of the upper ocean ecosystem, basXed on the Lagrangian Ensemble method, to estimate the sensitivity of the biological pump to radiative forcing, which lies Xat the heart of the plankton multiplier. We conclude that increasing radiative forcing by 5 W m-2 (equivalent to doubling Xatmospheric CO2) reduces the deep flux of particulate carbon by 10%. That sensitivity is sufficient to produce significantX positive feedback in the greenhouse. It means that the plankton multiplier will increase the rate of climate change in thXe 21st century. It also suggests that the plankton multiplier is the mechanism linking the Milankovich effect to the enhanXced greenhouse effect that produces global warming at the end of ice ages.hat all electrons derived from H-2 or formate cX^^^3807e recovered in dechlorination products and biomass. Exponential growth could be achieved only in gently shaken culX495^2^Darrigo,RD^Jacoby,GC^1993^1^Tree growth-climate relationships at the northern boreal forest tree line of north-ameriXca - evaluation of potential response to increasing carbon-dioxide^137^7^3^525-535^^^^^Sep^^^^^3809nder the growth conditXA^3808^Tree growth at the northern limit of the range of boreal forests is primarily limited by temperature-related factorXs. Thus the position of this range limit, and the growth rates of trees along the northern forest border, may undergo signXificant change if predictions of enhanced greenhouse warming at northern latitudes are realized. In this paper we evaluateX tree ring width and maximum latewood density chronologies of white spruce for three temperature-sensitive tree line sitesX in northern North America: in the Brooks Range, Alaska, the Franklin Mountains, Northwest Territories, and Churchill, ManY itoba. The ring width data, which more strongly integrate low-frequency temperature trends than the density series, show oY verall enhanced growth and inferred warming during the period of anthropogenic increase in greenhouse gases. The recent grYowth at these sites equals or exceeds that which has occurred during earlier centuries of more clearly natural climate varYiability. When the ring width and density variations are estimated using temperature and precipitation data in principal cY(omponents regession analysis, no substantial residual trends are detected which might require CO2 or other nutrient fertilY+ization as an additional explanation for recent growth changes.t productivity differential to the present day. This tremeY7496^5^Hyodo,H^Hashimoto,C^Morozumi,S^Hu,WZ^Tanaka,K^1993^1^Characterization and induction of the activity of 1- aminocycloY9propane-1-carboxylate oxidase in the wounded mesocarp tissue of cucurbita-maxima^231^34^5^667-671^^^^^Jul^^^^^3811AustralYCA^3810^1-Aminocyclopropane-1-carboxylate (ACC) oxidase (ethylene- forming enzyme) was isolated from wounded mesocarp tissuYEe of Cucurbita maxima (winter squash) fruit, and its enzymatic properties were investigated. The enzyme required Fe2+ and YVascorbate for its activity as well as ACC and O2 as substrates. The in vitro enzyme activity was enhanced by CO2. The appaYXrent K(m) value for ACC was 175 muM under atmospheric conditions. The enzyme activity was inhibited by sulfhydryl inhibitoY_rs and divalent cations such as Co2+, Cu2+, and Zn2+. ACC oxidase activity was induced at a rapid rate by wounding in paraYallel with an increase in the rate of ethylene production. The exposure of excised discs of mesocarp to 2,5-norbornadiene (YqNBD), an inhibitor of ethylene action, strongly suppressed induction of the enzyme, and the application of ethylene signifYsicantly accelerated the induction of the activity of ACC oxidase in the wounded mesocarp tissue. These results suggests thY}at endogenous ethylene produced in response to wounding may function in promoting the induction of ACC oxidase.REASE; PRIY497^2^Kaufman,YJ^Chou,MD^1993^1^Model simulations of the competing climatic effects of so2 and co2^126^6^7^1241-1252^^^^^JYul^^^^^3813nd 1050 ppm) on phytomass, soluble sugars, leaf nitrogen and secondary chemicals of three Salix myrsinifolia cYA^3812^Sulfur dioxide-derived cloud condensation nuclei are expected to enhance the planetary albedo, thereby cooling the Yplanet. This effect might counteract the global warming expected from enhanced greenhouse gases. A detailed treatment of tYhe relationship between fossil fuel burning and the SO2 effect on cloud albedo is implemented in a two-dimensional model fYor assessing the climate impact. Although there are large gaps in our knowledge of the atmospheric sources and sinks of suYlfate aerosol, it is possible to reach some general conclusions. Using a conservative approach, results show that the coolYing induced by the SO2 emission can presently counteract 50% of the CO2 greenhouse warming. Since 1980, a strong warming tYrend has been predicted by the model, 0.15-degrees-C, during the 1980- 1990 period alone. The model predicts that by the yYear 2060 the SO2 cooling reduces climate warming by 0.5-degrees-C or 25% for the Intergovernmental Panel on Climate ChangeY (IPCC) business as usual (BAU) scenario and 0.2-degrees-C or 20% for scenario D (for a slow pace of fossil fuel burning).Y The hypothesis is examined that the different responses between the Northern Hemisphere (NH) and the Southern Hemisphere Y(SH) can be used to validate the presence of the SO2-induced cooling. Despite the fact that most of the SO2-induced coolinYg takes place in the Northern Hemispheric continents, the model-predicted difference in the temperature response between tYhe NH and the SH of -0.2- degrees-C in 1980 is expected to remain about the same at least until 2060. This result is a comYbined effect of the much faster response of the continents than the oceans and of the larger forcing due to CO2 than due tYo the SO2. The climatic response to a complete filtering of SO2 from the emission products in order to reduce acid rain isY also examined. The result is a warming surge of 0.4-degrees-C in the first few years after the elimination of the SO2 emiYssion.ion of toluene with methane have been compared for superbasic catalysts prepared by promoting MgO, CaO, SrO or BaO Z498^4^Lasceve,G^Gautier,H^Jappe,J^Vavasseur,A^1993^1^Modulation of the blue-light response of stomata of commelina- communZis by co2^37^88^3^453-459^^^^^Jul^^^^^3815a+ + 5 mol- % (Cs+) /CaO gave a toluene conversion as high as 45.0 mol-% and a ZA^3814^Effects of CO2 on stomatal movements of Commelina communis L. were studied with plants, epidermal strips and guard Z#cell protoplasts. With plants, the stomatal response induced by a blue light pulse was studied for different ambient CO2 cZ%oncentration ranging from CO2-deprived air to 100 Pa in darkness or under red light. It was observed that the blue light rZ0esponse could be obtained not only under a red light background but also in darkness and CO2-free air, the two responses bZ2eing quite similar. With epidermal strips, the effect of CO2 on ferricyanide reductase activity at the guard cell plasmaleZAmma was studied by transmission electron microscopy. In the presence of ferric ions, reduced ferricyanide gives an electroZCn dense precipitate of Prussian Blue. In darkness and air, no precipitate was observed. In darkness and CO2-free air as weZ[ll as under light and normal air, a precipitate was found along the plasmalemma of the guard cells, indicating a ferricyanZ]ide reductase activity. With guard cell protoplasts suspended in a medium either in equilibrium with air or in a CO2-free Zfmedium the H+ extrusion induced by a blue light pulse added to a red light background was measured. A low CO2 content was Zgobtained by adding photosynthetic algae to the suspension of guard cell protoplasts. In a CO2-free medium the rate of H+ eZnxtrusion was enhanced. The results are discussed on the basis of a possible competition for reducing power between CO2 fixZpation and a putative blue light dependent redox chain located on the plasma membrane.N SN 0269-7491 C1 UNIV MASSACHUSETTSZ499^3^Tremblin,G^Jolivet,P^Coudret,A^1993^1^Light quality effects on subsequent dark 14co2-fixation in fucus-serratus^232^Z261^^471-475^^^^^18 Jun^^^^^3817URY; WINTER CONDITIONS; VEGETABLE PLANTS; GROWTH-RESPONSE; CARBON-DIOXIDE AB The use of RZA^3816^The intensity and fate Of (CO2)-C-14-fixation in the dark are studied on Fucus serratus apices previously maintaineZd under low illumination conditions using white, blue, red or yellow isoquantic lights. In the case of a 180 s pulse, lighZt quality affected dark carbon-fixation, with a higher level of incorporation into ethanol-soluble organic matter in the cZase of yellow light cultivated apices. After a 30 s pulse C-14 was mainly fixed into glycerate and aspartate-malate pools Zwhatever the pre-treatment light conditions, with a higher level into glycerate when apices were pre-illuminated with blueZ or yellow light. After a 180 s pulse, C-14 was mainly transferred into amino acids (glutamate and alanine) at the expenseZ of aspartate and malate in red and yellow pre-illumination conditions, as found in the white light reference experiment, Zand only at the expense of glycerate in blue light pre-illumination conditions. The metabolic pathway of glycerate formatiZon, principally enhanced by blue light preillumination, remains unexplained under these non-photosynthetic conditions. ResZults are discussed with reference to CO2-fixation via phosphoenolpyruvate carboxykinase and light quality effects on its iZn vitro activity.particularly the high variability of injury and growth responses, are discussed along with possible soluZ500^2^Whiting,GJ^Chanton,JP^1993^1^Primary production control of methane emission from wetlands^36^364^6440^794-795^^^^^26Z Aug^^^^^3819ed. BP 107-138 PG 32 JI Environ. Pollut. PY 1993 VL 82 IS 2 GA LV929 J9 ENVIRON POLLUT ER PT J AU KUMAR, MDZA^3818^WETLANDS, both natural and agricultural, contribute an estimated 40 to 50% of the total methane emitted to the atmo[sphere each year. Recent efforts in atmospheric modelling1 and attempts to constrain CH4 source strengths2 have indicated [the need to delineate the processes responsible for the large variations in emission rates found within and across wetland[ types. Numerous biogeochemical factors are known to affect the activity of methanogenic bacteria3,4 and although there ha[s been some success in relating water level5-7 and temperature8,9 to CH4 emissions within particular systems, these variab['les are insufficient for predicting emissions across a variety of wetlands2,10. From simultaneous measurements of CO2 and [)CH4 exchange in wetlands extending from subarctic peatlands to subtropical marshes, we report here a positive correlation [7between CH4 emission and net ecosystem production and suggest that net ecosystem production is a master variable, integrat[9ing many factors which control CH4 emission in vegetated wetlands. We find that about 3 per cent of the daily net ecosyste[Gm production is emitted back to the atmosphere as CH4. With projected stimulation of primary production and soil microbial[I activity in wetlands associated with elevated atmospheric CO2 concentrations11, we envisage the potential for increasing [TCH4 emissions from inundated wetlands, further enhancing the greenhouse effect.rove precision and sensitivity of stable i[V501^3^Dixon,RK^Winjum,JK^Schroeder,PE^1993^1^Conservation and sequestration of carbon - the potential of forest and agrofo[qrest management-practices^233^3^2^159-173^^^^^Jun^^^^^3821e analyte in the chemical reaction interface in the presence of[sA^3820^Forests play a major role in Earth's carbon cycle through assimilation, storage, and emission of CO2. Establishment[~ and management of boreal, temperate, and tropical forest and agroforest systems could potentially enhance sequestration o[f carbon in the terrestrial biosphere. A biological and economic analysis of forest establishment and management options f[rom 94 nations revealed that forestation, agroforestry, and silviculture could be employed to conserve and sequester one P[etagram (Pg) of carbon annually over a 50-year period. The marginal cost of implementing these options to sequester 55 Pg [of carbon would be approximately $10/Mg.he state-of-the-art, which is a gas chromatograph coupled to a chemical combustor[502^1^Michaels,PJ^1993^1^Benign greenhouse^234^9^2^222-233^^^^^Spring^^^^^3823Spectrom. PY 1993 PD SEP VL 22 IS 9 GA LV94[A^3822^Several lines of evidence are emerging that suggest that the ''popular vision'' of global warming-major agricultura[l damage, disastrous sea-level rise, and ecological disequilibrium-is flawed. The popular vision is driven primarily by th[e prospect of enhanced daytime warming, particularly in summer What has been observed is a warming that is beneath the pro[jections that support the popular vision, and a warming that has occurred virtually all during the night in the Northern H[emisphere. In the Southern Hemisphere there is also evidence of disproportionate night warming. Several sources of data in[dicate that this night warming has been caused by an increase in cloudiness that could be a consequence of the greenhouse [enhancement itself. The results of the night warming-longer growing seasons, little change in moisture stress, and a possi[ble increase in ice volume-are opposite to the popular vision of climatic change., but net C accumulation may not necessa[503^2^Rosenzweig,C^Hillel,D^1993^1^Agriculture in a greenhouse world^234^9^2^208-221^^^^^Spring^^^^^3825h industrializati[A^3824^While agriculture in some temperate regions may benefit from global climate change, tropical and subtropical region\ s may suffer. Even where potential production will improve, the required adjustments may disrupt ecosystems and land-use p\ atterns. Agricultural zones will shift toward high latitudes, while heat stress and increased droughts will reduce product\ivity in lower latitudes. On the positive side, higher CO2 may enhance photosynthesis and water-use efficiency. Future haz\!ards include sea-level rise, insect infestation, and greater evaporation losses. Some agricultural activities augment the \/greenhouse effect by releasing CO2, CH4, and N2O. Understanding the potential impacts of climate change is a prerequisite \1to developing societal responses.been shown to increase with soil temperature. If plant growth increases with increased N\<504^3^Yavitt,JB^Wieder,RK^Lang,GE^1993^1^Co2 and ch4 dynamics of a sphagnum-dominated peatland in west- virginia^137^7^2^2\>59-274^^^^^Jun^^^^^3827in a net increase in CO2 efflux from forests, then a positive feedback will follow. A 2 to 4-degre\KA^3826^Climatic change could bring about net release of carbon dioxide (CO2) and/or methane (CH4) from the deep peat depos\Mits in northern peatlands into the atmosphere. To provide insight into this hypothesis, we studied net flux of CO2 and CH4\\ in Big Run Bog, West Virginia, which has a temperate climate, making it an analog to evaluate climatic change imposed on \_more northern counterparts. Net CO2 flux ranged from -564 to 300 mg C m-2 hr- 1. Measurements made during the nighttime sh\oowed that net CO2 flux increased exponentially with increasing air temperature, whereas CO2 sequestration increased with i\qncreasing air temperature for daytime measurements. Net CH4 flux ranged from -2.3 to 70 mg C m-2 hr-1, showing no consiste\nt relationship to temperature or water table level. Net efflux for both CO2 and CH4 was tenfold higher from peat cores in\cubated in a greenhouse compared to field measurements. Even cores drained and allowed to dry for 8 days showed moderately\ high flux for both CO2 and CH4. The enhanced efflux seemed to be due to altered hydrology rather than increased rates of \A^3828^Intact Lemna gibba plants were illuminated by photoinhibitory light in air, in air minus O2, in air minus CO2, and \in pure N2. In pure N2, the degree of photoinhibition increased 3-5- times compared with that in air. This high degree of \photoinhibition is described as photodamage. Photodamage was found to constitute a syndrome, that is, it is due to inactiv\ation of multiple sites. These sites include RC II component(s) from P680 to Q(A); the Q(B)-Site; and a component of PS I.\ In photodamage, the donor side of PS II and PS II excitation energy transfer remain unimpaired, but the size of the PS I \antenna seems to decrease. Photodamage is distinguishable from photoinactivation. Photoinactivation occurred in air and co\uld be attributed to inhibition of electron transport from Q(A)- to Q(B). During photoinactivation the D1 protein of RC II\ became degraded faster than the detectable inhibition of Q(B) reduction. The photoinhibition- induced rise in F0 occurred\ only during the process of photodamage but not during that of photoinactivation, and was a secondary event which arose as\ a consequence of photodamage. Atmospheric O2 alleviated photodamage but increased photoinactivation. The light-induced Dl\ degradation and inhibition of Q(A) to Q(B) electron transfer were enhanced in vivo not only by O2 but also by depletion o\f CO2.LDFTMS) ID PROPYLENE OXIDATION; BISMUTH MOLYBDATE; LI/MGO CATALYST; OXIDE AB Oxygen pathways for CH4 partial oxidat]506^3^Harrison,K^Broecker,W^Bonani,G^1993^1^A strategy for estimating the impact of co2 fertilization on soil carbon stora]ge^137^7^1^69-80^^^^^Mar^^^^^3831 initial source of oxygen in the products is masked by rapid and extensive oxygen exchan]A^3830^As soils are a likely candidate for the so-called missing carbon sink, we explore the possible impact of CO2 fertil]ization on the global humus inventory. For any given greening-induced enhancement of plant growth, the increase in soil ca]!rbon inventory will depend on the spectrum of turnover times with respect to oxidation. Here we develop estimates of carbo]2n turnover rates based on soil radiocarbon measurements.LYSIS LETT ER PT J AU MCGUIRE, AD JOYCE, LA KICKLIGHTER, DW MELI]4507^3^Nunes,MA^Ramalho,JDC^Dias,MA^1993^1^Effect of nitrogen supply on the photosynthetic performance of leaves from coffe]@e plants exposed to bright light^78^44^262^893-899^^^^^May^^^^^3833SN 0165-0009 C1 MARINE BIOL LAB, CTR ECOSYST, WOODS HO]BA^3832^Although Coffea arabica L. grows naturally in shaded habitats, it can be cultivated under high light intensity, but]N not without severe photoinhibition mainly during the period of transfer from the nursery into the field. The present work]P examines some of the changes in the photosynthetic performance induced by exposure to high light and the possibility of u]bsing enhanced nitrogen levels to overcome photoinhibition. For that purpose, young plants of Coffea arabica L. (cv. Catuai]d) grown in a shaded greenhouse were treated with 0, 1 and 2 mmol of nitrogen and 4 weeks later exposed to full solar irrad]niation, outside. Visible damage due to exposure to full sunlight appeared within 2 d in all plants, resulting in a reduced]p photosynthetic leaf area and drastic shedding of leaves in the unfertilized plants. These effects were considerably less ]yin plants with the highest N dose. After 130 d of exposure, there was 100% mortality in plants receiving no extra nitrogen]{, compared with 30% in the plants treated with 2 mmol nitrogen. Photosynthesis rates, leaf conductance and transpiration p]resented minimum values after 4 d of light stress. Large changes in the photosynthetic capacity (measured at high CO2 conc] entration and high light intensity), quantum efficiency and fluorescence yield (F(v)/F(m)) indicate that net photosynthesi]!s rate in the air had been reduced by both stomatal closure and by changes at the photochemical level. All indicators show] that N-fertilized plants were less affected by photoinhibition.t. In all regions, the response to CO2 is qualitatively d]#508^3^Hanson,JD^Baker,BB^Bourdon,RM^1993^1^Comparison of the effects of different climate change scenarios on rangeland li]vestock production^223^41^4^487-502^^^^^^^^^^3835is, respiration, and soil moisture. Also, it may not be appropriate to e]%A^3834^The effect of climate change on plant and livestock production in the Great Plains of North America is an important]& issue. The purpose of this study was to modify an existing rangeland ecosystem model and to simulate a cow/calf productio]'n system under different climate scenarios. The project required the capability of simulating rangeland livestock producti](on under different ambient CO2 concentrations, temperatures and precipitation patterns. Climate change scenarios were crea])ted from three general circulation models (GCMs): GISS (Goddard Institute for Space Studies model), GFDL (Geophysical Flui]*d Dynamic Laboratory model), and UKMO (United Kingdom Meteorological Office model). Results from the GCMs were used to mod]+ify the climate record for a site in northeastern Colorado. Concomitantly, modifications were made to the SPUR model to he],lp predict the effect of predicted climate change on selected variables of the range/livestock ecosystem. Simulation runs ]-showed that predicted climate change will affect plant and animal production for rangelands. Changes in production were mo].re closely related to changes in temperature and precipitation than to enhanced [CO2] alone. The effect of climate change ^on livestock production was very complex and results were dependent on the particular GCM scenario being simulated.Prelim^0509^4^Naidu,SL^Sullivan,JH^Teramura,AH^Delucia,EH^1993^1^The effects of ultraviolet-b radiation on photosynthesis of diffe^rent aged needles in field-grown loblolly-pine^13^12^2^151-162^^^^^Mar^^^^^3837 areas. This is composed of pioneer popula^2A^3836^We examined the effect of supplemental UV-B radiation (290-320 nm) on photosynthetic characteristics of different a^$3ged needles of 3-year-old, field-grown loblolly pine (Pinus taeda L.). Needles in four age classes were examined: I, most ^&4recently fully expanded, year 3; II, first flush, year 3; III, final flush, year 2; and IV, oldest needles still present, ^.5year 2. Enhanced UV-B radiation caused a statistically significant decrease (6%) in the ratio of variable to maximum fluor^06escence (F(v)/F(m)) following dark adaptation only in needles from the youngest age class, suggesting transient damage to ^A7photosynthesis. However, no effects of enhanced UV-B radiation on other instantaneous measures of photosynthesis, includin^D8g maximum photosynthesis, apparent quantum yield and dark respiration, were seen for needles of any age. Foliar nitrogen c^R9oncentration was unaffected by UV-B treatment. However, the C- 13/C-12 carbon isotope ratios (deltaC-13-a time integrated ^T:measure of photosynthetic function) of needles in age classes II and IV were 3% (P < 0.01) and 2% (P < 0.05) more negative^`;. respectively, in treated plants than in control plants. Exposure to enhanced UV-B radiation caused a 20% decrease in tot^bss suggest subtle damage to photosynthesis, although overall growth reductions were probably a result of decreased total l^x?eaf surface rather than decreased photosynthetic capacity. Needles of age class IV had lower light- and CO2-saturated maxi^z@mum photosynthetic rates (39%), lower dark respiration (34%), lower light saturation points (37%), lower foliar nitrogen c^Aoncentration (28%), and lower delta-C-13 (14%) values than needles of age class I. Apparent quantum yield and F(v)/F(m) di^Bd not change with needle age. The observed changes in photosynthesis and foliage chemical composition with needle age are ^Cconsistent with previous studies of coniferous trees and may represent adaptations of older needles to shaded conditions w^ithin the canopy.w stomatal conductances observed under elevated CO2 conditions. BP 599-602 PG 4 JI Oecologia PY 1993 PD ^E510^3^Nederhoff,EM^Rijsdijk,AA^Degraaf,R^1992^1^Leaf conductance and rate of crop transpiration of greenhouse grown sweet-^pepper (capsicum-annuum-L) as affected by carbon- dioxide^165^52^4^283-301^^^^^Dec^^^^^3839 INST AGROENVIRONM SCI, TSUKUB^GA^3838^The effects of carbon dioxide concentration (CO2) in the range 300-1100 mumol mol-1 on leaf conductance (g) and rat^He of crop transpiration (E) of sweet pepper (Capsicum annuum L.) were investigated in spring 1990. In two greenhouse compa^Irtments (154 m2) that were simultaneously exposed to different CO2 levels, leaf conductance of the upper leaves was measur^Jed with a steady state diffusion porometer and crop transpiration rates were measured with three weighing lysimeters per g^Kreenhouse compartment. Multiple regression equations, describing the effects of photosynthetic active radiation (PAR), vap^Lour pressure deficit (VPD)-leaf-air, CO2 and optionally leaf temperature on g, were fitted to the measured data. The fitte^Md regression curves demonstrated that 100 mumol mol-1 increase in CO2 reduced g by about 3%, at any level of CO2, VPD and ^NPAR, if VPD and PAR would remain constant. Measured rates of crop transpiration were highly correlated to radiation and we^Ore in reasonable accordance with the Penman-Monteith combination equation. With this equation it was estimated that a 10% ^Pdecrease in g would reduce E by 1.5-3% at high levels of g (high radiation) and by 4-7% at low g (dark weather), at least _Qif VPD would remain constant. In a greenhouse-crop system, however. owing to thermal and hydrologic feedbacks, an increase_R in CO2 leads to a considerable increase in VPD-leaf-air. This enforces the effect of CO2 on g and counteracts the effect _Sof CO2 on E, because the driving force for transpiration is enhanced. Thus, in general the apparent response of g to chang_es in CO2 is far greater than the mentioned percentage, whereas the apparent response of E is relatively small. AB CO2 en_U511^4^Polley,HW^Johnson,HB^Marino,BD^Mayeux,HS^1993^1^Increase in C3 plant water-use efficiency and biomass over glacial t_o present co2 concentrations^36^361^6407^61-64^^^^^7 Jan^^^^^3841es-C, +/- 15 % rel. air humidity, wind speed approximate_ WA^3840^ATMOSPHERIC CO2 concentration was 160 to 200 mumol mol-1 during the Last Glacial Maximum (LGM; about 18,000 years a_)Xgo)1, rose to about 275 mumol mol-1 10,000 years ago2,3, and has increased to about 350 mumol mol-1 since 1800 (ref. 4). H_+Yere we present data indicating that this increase in CO2 has enhanced biospheric carbon fixation and altered species abund_5Zances by increasing the water-use efficiency of biomass production of C3 plants, the bulk of the Earth's vegetation. We gr_7[ew oats (Avena sativa), wild mustard (Brassica kaber) and wheat (Triticum aestivum cv. Seri M82 and Yaqui 54), all C3 annu_@\als, and selected C4 grasses along daytime gradients of Glacial to present atmospheric CO2 concentrations in a 38-m-long c_B]hamber. We calculated parameters related to leaf photosynthesis and water-use efficiency from stable carbon isotope ratios_Z^ (C-13/C- 12) of whole leaves. Leaf water-use efficiency and above-ground biomass/plant of C3 species increased linearly a_\_nd nearly proportionally with increasing CO2 concentrations. Direct effects of increasing CO2 on plants must be considered_l when modelling the global carbon cycle and effects of climate change on vegetation.nd roots > 2 mm phi 1.7-fold more und_na512^5^Mayeux,HS^Johnson,HB^Polley,HW^Dumesnil,MJ^Spanel,GA^1993^1^A controlled environment chamber for growing plants acro_ss a subambient co2 gradient^43^7^1^125-133^^^^^^^^^^3843 system. However, if one balances CO2 gains with CO2 losses over_cA^3842^1. An elongated, controlled environment chamber is described in which a continuous, reproducible gradient of subamb_dient CO2 Concentration ([CO2]) is maintained during daylight hours to assess plant responses to past increases in atmosphe_eric [CO2]. 2. The [CO2] of air moved unidirectionally through the 37-6-m long chamber by a blower is progressively deplete_fd by photosynthesis of plants growing in the chamber. 3. Plant top- growth is contained in a transparent film tunnel which_g rests upon an enclosed soil volume that is 45 cm wide and 76 cm deep. 4. The desired minimum concentration to which CO2 i_hs depleted at the end of the chamber, usually 150 or 200 mul l-1, is maintained by varying the blower speed with a microlo_igger program dependent upon real-time sensing Of [CO2] and light intensity. 5. Dewpoint and dry bulb temperatures are also_ controlled by a micrologger- and computer-monitored air- conditioning system.SOIL POLLUT ER PT J AU OWENSBY, CE TI POTE_k513^10^Sampson,RN^Apps,M^Brown,S^Cole,CV^Downing,J^Heath,LS^Ojima,DS^Smith,TM^Solomon,AM^Wisniewski,J^1993^1^Workshop summ_xary statement - terrestrial biospheric carbon fluxes - quantification of sinks and sources of co2^94^70^1-4^3-15^^^^^Oct^^_mA^3844^Understanding the role of terrestrial ecosystems in the global carbon (C) cycle has become increasingly important a_ns policymakers consider options to address the issues associated with global change, particularly climate change. Sound sc_oientific theories are critical in predicting how these systems may respond in the future, both to climate change and human_p actions. In March 1993, 60 scientists from 13 nations gathered in Bad Harzburg, Germany, to develop a state-of-the- scien_qce assessment of the present and likely future C fluxes associated with the major components of the earth's terrestrial bi\rosphere. In the process, particular emphasis was placed on the potential for improving C sinks and managing long-term C se`squestration. The majority of the week's work was conducted in eight working groups which independently considered a partic`tular biome or subject area. The working groups considered: the Global Carbon Cycle; Boreal Forests and Tundra; Temperate F`uorests; Tropical Forests; Grasslands, Savannas and Deserts; Land and Water Interface Zones; Agroecosystems; and Biomass Ma`+vnagement. This paper presents a brief overview of their major conclusions and findings. In addition, Table 1 brings togeth`-wer the best estimates from each group as to the current magnitude and estimated future direction of changes in the terrest`9rial C fluxes. ECOSYSTEM EXPOSED TO ELEVATED CARBON-DIOXIDE SO PLANT CELL AND ENVIRONMENT SN 0140-7791 C1 KANSAS STATE UN`;^^^3845SCI, DEPT AGRON, THROCKMORTON HALL, MANHATTAN, KS 66506. KANSAS STATE UNIV AGR & APPL SCI, FT HAYS BRANCH EXPT STN`Hz514^2^Schindler,DW^Bayley,SE^1993^1^The biosphere as an increasing sink for atmospheric carbon - estimates from increased `Initrogen deposition^137^7^4^717-733^^^^^Dec^^^^^3847YCORRHIZAL FUNGI; INSECT HERBIVORE; PLANTS; GROWTH; COMMUNITIES; ENRI`T|A^3846^Estimates of carbon uptake and storage based on global nitrogen deposition, C:N ratios for typical terrestrial ecos`V}ystems, and recent ecosystem-scale nutrient studies indicate that 1.0-2.3 Gt C yr-1 of carbon storage may be stimulated by`c~ anthropogenically caused increases in nitrogen deposition in the past century. Sixty four to eighty four percent of globa`el nitrogen uptake appears to occur on northern continents, with the remainder largely in northern coastal oceans. Increase`ud nitrogen input by terrestrial ecosystems causes increased accumulation of carbon as plant tissue, with C:N ratios genera`wlly 50 to 200:1. Calculations suggest that northern continents are a major sink for carbon and that nitrogen- stimulated c`arbon uptake may more or less balance global carbon losses to the atmosphere from deforestation and agriculture. Much of t`he uptake appears to occur in aggrading forests, and the question of how long it can continue has important consequences f`or global carbon budgets.ts than in ambient CO2 PlOts. N concentration in P. pratensis aboveground biomass was lower in e`515^4^Vourlitis,GL^Oechel,WC^Hastings,SJ^Jenkins,MA^1993^1^A system for measuring insitu co2 and ch4 flux in unmanaged eco`systems - an arctic example^43^7^3^369-379^^^^^Jun^^^^^3849d CO2 than in ambient CO2 plots. Root ingrowth bag biomass N c`A^3848^1. A passive, rapid response, closed system was developed to measure in situ ecosystem CO2 and CH4 flux in 0.5-m2 p`lots over diurnal, seasonal, and annual time scales in arctic tundra ecosystems. The system consists of a chamber measurin`g 0.75 m on a side, 0.3 m in height, with acrylic sides, a mylar top, and 6-10 cm radial fans to ensure thorough mixing of` the chamber environment. 2. CO2 concentration and flux rates were measured using a Li-Cor 6200 Portable Photosynthesis Sy`stem, which is capable of measuring 0.1 p.p.m. s-1 changes in CO2 concentration. CH4 flux rates were measured by sequentia`l sampling of the CH4 concentration in the chamber over the duration of a 15-20-min incubation period. 3. Performance anal`yses indicate that light attenuation was less-than-or- equal-to 10% of ambient light. The rate of temperature increase wit`hin the chamber over the duration of the measurement period was approximately 1-5-degrees-C and 0.2-degrees-C for the majo`rity of the sampling days at tussuck tundra and wet coastal tundra sites, respectively. The maximum increase in thaw depth` due to the bases was approximately 10%, and was a function of the site water balance and the amount of time that the base`s were in place. Generally, thaw depth in plots with bases was greater when the bases were in place for a longer period of` time (greater-than-or-equal-to 1 year), while the bases that were installed during the current growing season had a small` effect on plot thaw depths. 4. The system had a minimal effect on ecosystem CO2 flux, compared to plots that lacked bases` in a wet coastal tundra and southern California turf ecosystem. 5. The system was successfully used to measure the effect` of light intensity, soil temperature, and water balance on ecosystem CO2 flux. 6. Due to the rapid response of the system`, high sensitivity to low flux rates, high portability, low cost, potential for use in field experiments, and non-invasivea sampling design, the system allows for the reliable measurement of CO2, CH4, and other trace gas flux rates in a variety aof ecosystem types. ERROR IN MEASUREMENTS OF RESPIRATION MADE WITH O2 ELECTRODES SO ANNALS OF BOTANY SN 0305-7364 C1 HEBRa516^4^Azconbieto,J^Gonzalezmeler,MA^Doherty,W^Drake,BG^1994^1^Acclimation of respiratory o-2 uptake in green tissues of fia#eld-grown native species after long-term exposure to elevated atmospheric co2^8^106^3^1163-1168^^^^^Nov^^^^^3851; PHOTOSYa%A^3850^C-3 and C-4 plants were grown in open-top chambers in the field at two CO2 concentrations, normal ambient (ambient)a; and normal ambient + 340 mu L L(-1) (elevated). Dark oxygen uptake was measured in leaves and stems using a liquid-phase a=Clark-type oxygen electrode. High CO2 treatment decreased dark oxygen uptake in stems of Scirpus olneyi (C-3) and leaves oaJf Lindera benzoin (C-3) expressed on either a dry weight or area basis. Respiration of Sparfina patens (C-4) leaves was unaLaffected by CO2 treatment. Leaf dry weight per unit area was unchanged by CO2, but respiration per unit of carbon or per ua[nit of nitrogen was decreased in the C-3 species grown at high CO2. The component of respiration in stems of S. olneyi anda^ leaves of L. benzoin primarily affected by long-term exposure to the elevated CO2 treatment was the activity of the cytocaohrome pathway. Elevated CO2 had no effect on activity and capacity of the alternative pathway in S. olneyi. The cytochromeaq c oxidase activity, assayed in a cell-free extract, was strongly decreased by growth at high CO2 in stems of S. olneyi buat it was unaffected in S. patens leaves. The activity of cytochrome c oxidase and complex III extracted from mature leavesa of L. benzoin was also decreased after one growing season of plant exposure to elevated CO2 concentration. These results ashow that in some C-3 species respiration will be reduced when plants are grown in elevated atmospheric CO2. The possible aphysiological causes and implications of these effects are discussed.bs free energy of this reaction was generally very la517^6^Baker,JT^Albrecht,SL^Pan,D^Allen,LH^Pickering,NB^Boote,KJ^1994^1^Carbon-dioxide and temperature effects on rice (oryaza-sativa L, CV ir-72)^156^53^^90-97^^^^^^^^^^3853suming that propionate, 2-propanol, caproate and valerate were converteaA^3852^The current increase in atmospheric carbon dioxide concentration ([CO2]) along with predictions of possible future aincreases in global air temperatures have stimulated interest in the effects of [CO2] and temperature on the growth and yiaeld of food crops. This study was conducted to determine the effects and possible interactions of elevated [CO2] and tempearature on the development, growth and yield of rice (Oryza sativa L., cv. IR-72). Rice plants were grown season-long in ouatdoor, naturally sunlit, controlled-environment, plant growth chambers. Chamber air temperatures were controlled to followa a continuously and diurnally varying, near sine-wave control setpoint that operated between maximum (daytime) and minimuma (nighttime) values. Day/night (maximum/minimum) air temperature treatments were: 32/23, 35/26, and 38/29-degrees-C. Dewpoaint air temperatures were maintained at 18, 21, 24- degrees-C in the 32/23, 35/26, 38/29-degrees-C dry bulb air temperaturbe treatment, respectively. Daytime [CO2] was controlled to 330 and 660 mumol CO2 mol-1 air in each of the air temperature btreatments. The time interval between appearance of successive mainstrem leaves during reproductive development was reducebd by increasing air temperature treatment (P less-than-or-equal-to 0.05) but was not affected by [CO2] enrichment. In thisb! experiment [CO2] enrichment did not affect (P less-than-or-equal-to 0.10) grain yield, components of grain yield, final ab*bove ground biomass or harvest index. Increasing temperature during growth, particularly from the 35/26 to 38/29-degrees-Cb, reduced grain yield, individual grain mass, and harvest index. The reduced grain yields with increasing temperature treatb?ment suggest potential detrimental effects on rice production in some areas if air temperatures increase.jacent to calcsibA518^2^Beerling,DJ^Woodward,FI^1994^1^The climate-change experiment (climex) - phenology and gas- exchange responses of borbOeal vegetation to global change^175^4^1^17-26^^^^^Jan^^^^^3855es in disseminated graphite flakes within adjacent metapelibQA^3854^Large-scale whole ecosystem experiments will become increasingly important for predicting and testing hypotheses ofb^ complex ecosystem responses to global change. The Climate Change Experiment (CLIMEX) uses a site with an entire undisturbb`ed boreal-forested catchment enclosed within an existing very large scale (1200m2 ground area) greenhouse. In the forthcombping year temperature will be increased stepwise to +3-degrees-C in summer, +5-degrees-C in winter and the atmospheric CO2 brconcentration enriched to 560 ppm which together simulate future changes in global climate and atmospheric composition prebdicted by GCMs. Plants growing within this low nutrient ecosystem are strongly dependent upon mycorrhizal associations forb nutrient uptake and rates of nutrient uptake. Therefore it will provide an important test of current ideas concerning howb mycorrhizas might modify plant responses to global change. We describe predictions of community phenology and gas exchangbe at the CLIMEX site; in the latter case the effects of including and excluding rates of on nutrient supply are consideredb. The results are discussed with reference to the opportunities presented by CLIMEX to reveal important aspects of the phybsiological responses of boreal ecosystems to global change.an surface. The maxmum growth rate was 0.9d-1. The ratio of inb519^2^Behboudian,MH^Lai,R^1994^1^Carbon-dioxide enrichment in virosa tomato plant - responses to enrichment duration and tbo temperature^170^29^12^1456-1459^^^^^Dec^^^^^3857by a cell were little affected by CO2 enrichment. A similar result wasbA^3856^Responses of the tomato (Lycopersicon esculentum Mill. cv. Virosa) plant to elevated CO2 concentrations applied thrboughout the photoperiod or part of it were studied under two temperature regimes. Plants were exposed to CO2 at 340 (contrbol), 700, and 1000 mul-liter-1. The highest concentration was applied only at 22/16C (day/night) and 700 mul-liter-1 at 22b/16C and 25/16C. Transpiration rates were lower and photosynthetic rates were higher under elevated CO2 than at the ambienbt level. Biomass production was higher only for plants grown at 700 mul-liter-1 and 25/16C. Concentrations of macronutrienbts were lower in plants exposed to 1000 mul CO2/liter than in the control plants. Intermittent CO2 was applied using two tbiming methods. In method 1, plants were exposed to 4- or 8-hour high-CO2 concentrations during their 12-hour photoperiod. bIn method 2, plants were exposed for 3.5 days of each week to 700 mul CO2/liter. Only two of the 8-hour exposures resultedb in greater growth than the controls. The lack of higher growth for CO2-enriched plants at 22/16C was attributed to a highcer dark respiration rate and to respiration rate and a lack of efficient transport of photosynthates out of leaves. pigs,c520^2^Boote,KJ^Pickering,NB^1994^1^Modeling photosynthesis of row crop canopies^170^29^12^1423-1434^^^^^Decnted with lincc521^6^Delgado,E^Mitchell,RAC^Parry,MAJ^Driscoll,SP^Mitchell,VJ^Lawlor,DW^1994^1^Interacting effects of co2 concentration, c.temperature and nitrogen supply on the photosynthesis and composition of winter-wheat leaves^9^17^11^1205-1213^^^^^Nov^^^^c0A^3859^Winter wheat (Triticum aestivum L., cv. Mercia) was grown at two different atmospheric CO, concentrations (350 and c<700 mu mol mol(-1)) two temperatures [ambient temperature (i.e. tracking the open air) and ambient +4 degrees C] and two rc>ates of nitrogen supply (equivalent to 489 kg ha(-1) and 87 kg ha(- 1)). Leaves grown at 700 mu mol mol(-1) CO2 had slightcGly greater photosynthetic capacity (10% mean increase over the experiment) than those grown at ambient CO2 concentration, cIbut there were no differences in carboxylation efficiency or apparent quantum yield. The amounts of chlorophyll, soluble pcUrotein and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) per unit leaf area did not change with long-term expocWsure to elevated CO2 concentration. Thus winter wheat, grown under simulated field conditions, for which total biomass wasce large compared to normal field production, did not experience loss of components of the photosynthetic system or loss of cgphotosynthetic competence with elevated CO2 concentration. However, nitrogen supply and temperature had large effects on pcphotosynthetic characteristics but did not interact with elevated CO2 concentration. Nitrogen deficiency resulted in decreacrses in the contents of protein, including Rubisco, and chlorophyll, and decreased photosynthetic capacity and carboxylatiocn efficiency. An increase in temperature also reduced these components and shortened the effective life of the leaves, redcucing the duration of high photosynthetic capacity.h concentration was not significantly affected by elevated CO2. Althouc^3860temperature increased metabolic activity, it only partially alleviated the inhibition of P(N). L. gibba exhibits a cc522^8^Estiarte,M^Penuelas,J^Kimball,BA^Idso,SB^Lamorte,RL^Pinter,PJ^Wall,GW^Garcia,RL^1994^1^Elevated co2 effects on stomactal density of wheat and sour orange trees^78^45^280^1665-1668^^^^^Nov^^^^^3862VL 28 IS 1 GA LW193 RP SMERNOFF DT J9 PHOTcA^3861^No significant differences were found in stomatal densities or stomatal indices of wheat or sour orange trees grownc at high CO2 concentrations in two different CO2 enrichment systems (Free-Air CO2 enrichment for wheat and Open-Top Chambecrs for orange trees). These results are in accordance with most of the previous results obtained in short-term experimentacl studies which suggest that plants do not acclimate to increasing CO2 concentration by changing stomatal density within ac single generation. for 9 months in enclosures in greenhouses at CO2 concentrations of 350 or 750 mumol mol-1 with eitherc523^2^Ferris,R^Taylor,G^1994^1^Increased root-growth in elevated co2 - a biophysical analysis of root cell elongation^78^4c5^280^1603-1612^^^^^Nov^^^^^3864d by CO2 enrichment. High UV treatment also shifted biomass partitioning in favor of leafcA^3863^A biophysical analysis of root expansion was conducted in four chalk downland herbs (Sanguisorba minor Scop., Lotusc corniculatus L., Anthyllis vulneraria L. and Plantago media L.) exposed to either ambient or elevated CO, in controlled ecnvironment cabinets. Measurements of fine (F) and extra-fine (EF) root extension rate (RER), water relations, and cell walcl tensiometric extensibility revealed differences in the diurnal pattern of root growth between species. After 35 d of expcosure to elevated CO2, RER of both F and EF roots increased significantly in darkness and on illumination for S. minor, whcilst for A. vulneraria (EF roots only) and L. corniculatus a significant increase occurred at night whereas for P. media ac significant increase occurred during the day. Cells measured in the zone of elongation were longer in all species exposedd to elevated CO2. Water potential (Psi), solute potential (Psi(s)), turgor pressure (P), yield turgor (Y) and effective tudrgor (Pe) were measured by stress-relaxation of excised root tips placed in psychrometers. Solute potentials decreased sigdnificantly for all species following exposure to elevated CO2. In S. minor and L. corniculatus, P and Pe, respectively, wedre higher in elevated CO2. No significant effects of CO2 on Y were observed (not shown). Root cell wall tensiometric extendsibility, measured as % plasticity, increased in all species exposed to elevated CO2. These results suggest that root growd$th is enhanced following increased cell expansion and that increased P and cell wall tensiometric extensibility are both id%mportant for root growth in elevated CO2.of inhibitor for methanogenesis, ranged from -43 to -30 parts per thousand. The d,524^3^Frick,J^Nielsen,SS^Mitchell,CA^1994^1^Yield and seed oil content response of dwarf, rapid-cycling brassica to nitrogd.en treatments, planting density, and carbon- dioxide enrichment^154^119^6^1137-1143^^^^^Nov^^^^^3866C-13 of CO2 localizedd9rature by 4 degrees C, however, reduced the total lipid content of grains. Wheat plants treated with high concentrations od;f nitrogen fertilizer accumulated less lipid compared to low nitrogen controls. Qualitative changes were also observed in dEthe proportions of non-starch and starch lipid classes. However, changes in total acyl composition were limited to starch dGgrain acyl lipids, as a result of changes in atmospheric carbon dioxide, growth temperature and nitrogen fertilizer applicdIation. The alterations in wheat lipids observed are likely to affect the properties of the flour produced from the grains.dWpleted freshwater areas. BP 4015-4027 PG 13 JI Geochim. Cosmochim. Acta PY 1993 PD AUG VL 57 IS 16 GA LW389 J9 GEOCHIM CdZA^3865^Effects of N level (15 to 30 mM), time of N increase (14 to 28 days after planting), and planting density (1163 to di2093 plants/m(2)) were determined for crop yield responses of dwarf, rapid-cycling brassica (Brassica napus L., CrGC 5-2, dkGenome: ACaacc). Crops were grown in solid-matrix hydroponic systems and under controlled-environment conditions, includindmg nonsupplemented (ambient) or elevated CO2 concentrations (998 +/- 12 mumol mol(-1)). The highest seed yield rate obtained (4.4 g.m(-2).day(-1)) occurred with the lowest N level (15 mM) applied at the latest treatment time (day 28). In all trials, CO2 enrichment reduced seed yield rate and harvest index by delaying the onset of flowering and senescence and stimuldating vegetative shoot growth. The highest shoot biomass accumulation rate (55.5 g.m-2.day(-1)) occurred with the highest d N level (30 mM) applied at the earliest time (day 14). Seed oil content was not significantly affected by CO2 enrichment. d Maximum seed oil content (30% to 34%, dry weight basis) was obtained using the lowest N level (15 mM) initiated at the latd est treatment time (day 28). In general, an increase in seed oil content was accompanied by a decrease in seed protein. Sed ed carbohydrate, moisture, and ash contents did not vary significantly in response to experimental treatments. Effects of d N level and time of N increase were consistently significant for most crop responses. Planting density was significant onldy under elevated CO2 conditions.T, NORWICH NR4 7JU, ENGLAND. DE TRITICUM-AESTIVUM; ERYSIPHE-GRAMINIS; WHEAT; POWDERY MILDd525^4^Heagle,AS^Brandenburg,RL^Burns,JC^Miller,JE^1994^1^Ozone and carbon-dioxide effects on spider-mites in white clover dand peanut^204^23^6^1168-1176^^^^^Nov-Dec^^^^^3868FERTILIZATION AB In two experiments, winter wheat (Triticum aestivum cvdA^3867^Effects of O-3 and/or elevated CO2 on two-spotted spider mites (Tetranychus urticae Koch) grown on an On-sensitive dand an O-3- resistant clone of white clover (Trifolium repens L.) were measured in greenhouse and field experiments. Peanudt (Arachis hypogeae L.) 'NC-9' was used in one greenhouse study with O-3. In field studies, O-3 treatments were charcoal feiltered air (CF), nonfiltered air (NF), and two NF treatments with On added for 12 h d(-1) at proportions of approximate teo 1.25 and 1.50 times the ambient O-3 concentration. In greenhouse studies, constant amounts of O-3 were added to CF for 6e h d(-1) to achieve mean concentrations ranging from 5 to 100 nL L(-1). For the greenhouse O-3 X CO2 experiment, CO2 conceentrations were ambient and approximately twice-ambient for 24 h d(-1). Plants were exposed to O-3 and/or CO2 for approximae%te to 7 d before infestation with mites; daily exposures continued for 14 to 28 d to allow reproduction for at least two ge'enerations. Leaves were sampled to count eggs, larvae, nymphs, and adults. Ozone caused more chlorosis and necrosis on thee3 O-3-sensitive clover clone (NC-S) than on the Oa-resistant clone (NC-R). Carbon dioxide enrichment increased shoot growthe5 of both clones by approximate to 33%. Statistical analyses indicated significant O-3 effects in some experiments and nonse@ignificant O-3 effects in others. A trend toward increased mite populations with increased O-3 occurred, however, on NC-S eBin all trials. No consistent trends occurred with NC-R. With peanut, a significant linear increase in mite population occueKrred with increased O-3. Carbon dioxide enrichment increased the rate of population increase on both clover clones, but moeMre so on NC-R. At 22 to 28 d after infestation, the total population in the twice-ambient CO2 treatment was 65% greater theZ an in the ambient treatment for NC-R and 22% greater than in the ambient treatment for NC-S. There were no statistically se\!ignificant interactive effects between CO2 and O-3 On mite population growth. The apparent clone effects on mite populatioein response to O-3 and CO2 strongly suggest that responses were mediated through the host plants.when they received suppleek526^2^Hendrey,GR^Kimball,BA^1994^1^The face program^107^70^1-4^3-14^^^^^Sep^^^^^3870as an increase in activation state. Ae$A^3869^A large, cooperative, integrated experimental program utilizing free-air CO2 enrichment (FACE) is being conducted te%o expose plants to elevated concentrations of CO2. The goals are to evaluate the effects of increasing atmospheric CO2 on e&plants and ecosystems and, in the long run, to contribute to the evaluation of terrestrial plant feedback regulation on the'e rate of change of CO2 in the atmosphere. Having no walls, the FACE system allows plants to be grown under realistic micre(oclimate and CO2 conditions expected to prevail in the mid-twenty-first century. Data obtained under such conditions are ne)eeded for validation of models being developed to predict the effects of increasing CO2 and changing climate variables on e*plants, ecosystems, agricultural productivity and water resources. Setup costs for the FACE systems used in these experimee+nts are similar to the costs of field chamber systems. Although annual operating costs are about three times the cost of fe,ield chambers, FACE plots are relatively large, leading to an economy of scale, so that per unit of treated plant materiale-, FACE systems are the least expensive approach for well- integrated field experiments. These features have provided an ine.centive to conduct comprehensive FACE experiments with many cooperating scientists working together to measure numerous ple/ant, soil and micrometeorological parameters, as described in the collection of papers in this special issue of 'Agricultueral and Forest Meterology'. water under increased CO2 concentrations in the atmosphere; the temperature response of photoe1527^2^Korner,C^Miglietta,F^1994^1^Long-term effects of naturally elevated co2 on mediterranean grassland and forest trees^e2^99^3-4^343-351^^^^^Oct^^^^^3872patterns with the consequent changes in land cover. In this paper we discuss the implemee3A^3871^We investigated the carbon supply status in species-rich mediterranean plant communities growing in a bowl-shaped 14-ha ''CO2 spring'' area near Sienna, Italy. A geothermic ''lime- kiln'' has provided these communities, for as long as his5torical records are available, with pure CO2 that mixes with ambient air at canopy level to daytime means of 500-1000 ppm b6CO2. Immediately outside the spring area similar plant communities are growing on similar substrate, and in the same climaf7te, but under ca. 355 ppm CO2. We found no evidence that plants in the CO2 spring area grow faster, flower earlier or becof8me larger. However, we found very large differences in tissue quality among the 40 species studied inside and outside the f9spring area. Depending on weather conditions, the mean concentration of total non-structural carbohydrates (TNC, sugars anf#:d starch) in leaves of herbaceous plants was 38-47% higher in the spring area. Fast growing ruderals growing on garden soif%;l inside and outside the spring area show the same response. Among trees, leaves of the deciduous Quercus pubscens containf0< twice as much TNC inside as outside the vent area, whereas evergreen Q. ilex leaves show no significant difference. TNC lf2=evels in branch wood paralleled leaf values. TNC in shade leaves was also higher. Elevated CO2 had no effect on the sugar f=>fraction, therefore differences in TNC are due to starch accumulation. Leaf nitrogen concentration decreases under elevatef??d CO2. These observations suggest that the commonly reported TNC accumulation and N depletion in leaves growing under elevfM@ated CO2 are not restricted to the artificial conditions of short-term CO2 enrichment experiments but persist over very lofQAng periods. Such an alteration of tissue composition can be expected to occur in other plant communities also if atmospherfnic CO2 levels continue to rise. Effects on food webs and nutrient cycling are likely.50 and continuing to the present, anfpC528^2^Lavola,A^Julkunentiitto,R^1994^1^The effect of elevated carbon-dioxide and fertilization on primary and secondary meftabolites in birch, betula-pendula (roth)^2^99^3-4^315-321^^^^^Oct^^^^^3874nt, the increase for 100- to 150- year-old trefEA^3873^Seedlings of European white birch (Betula pendula Roth) were grown in growth chambers for one growth season under ffFour carbon dioxide regimes (350, 700, 1050 and 1400 pm) and at three fertilization levels (0, 100 and 500 kg ha(-1) monthlfGy). The soluble carbohydrates and secondary phenolics in the leaves and stems were analysed. It was found that fertilizer fHaddition reduced the amounts of glucose and fructose while sucrose remained almost unaffected. The sugar content of leavesfI increased at 700 ppm and 1050 ppm of CO2 and decreased at the highest CO2 concentration (1400 ppm). The amounts of proantJhocyanidins and flavonoids in leaves decreased with fertilization addition and increased with CO2 enrichment. The productiKon of simple phenolic glucosides varied according to the fertilization and CO2 treatments. The triterpenoid content of stefLms seemed to increase with fertilization and CO2 addition. Our results indicate that the production of phytochemicals in tfMhe birch seedlings is very sensitive to both fertilization and CO2 addition, which is in agreement with earlier studies, afNnd thus provide some support for the hypothesis of carbon allocation to plant defence when there is an excess of carbon anfOd nutrient. The considerable variation in the production of secondary components may indicate that the synthesis of these Pdefensive metabolites can be regulated by a plant to certain extent, depending on the ability of the plant to acclimate to changes in the physical environment.2000, and 5000 ppm). Plants were grown using recirculating nutrient film technique wfR529^4^Lewin,KF^Hendrey,GR^Nagy,J^Lamorte,RL^1994^1^Design and application of a free-air carbon-dioxide enrichment facilityf^107^70^1-4^15-29^^^^^Sep^^^^^3876 greatest at 100 Pa for cv. McCall, suggesting that higher CO2 levels were supraoptimalgTA^3875^Growth chambers and other enclosures used in plant physiology and growth studies tend to introduce chamber effects gUthat alter the microclimate around the plants compared with the natural environment. A free-air (chamberless) carbon dioxigVde enrichment (FACE) system has been developed by Brookhaven National Laboratory (BNL) to provide controlled fumigation cogWnditions while minimizing the potential to impose a discernible chamber effect. This system is capable of exposing large ng,Xumbers of field-grown plants to elevated levels of atmospheric carbon dioxide (CO2) from seedling emergence until physiolog.Ygic maturity. A FACE User Facility was established at the Maricopa Agricultural Center, University of Arizona, for continug<Zous enrichment of CO2 at a set point of 550 mumol mol-1 during daylight hours throughout the cotton crop growing seasons og=[f 1989-1991. The facility consisted of four circular BNL FACE arrays and associated equipment placed in a commercial cottog?\n plantation. FACE array diameters of 23, 25, and 27 m were tested. The FACE facility included the ability to operate the gG]experimental plots under two watering regimes using an automated, sub-surface irrigation system. CO2 was stored in a 48 00gI^0 kg receiver and vaporized with a heat exchanger that used water at ambient temperature as the energy source. The 1 min agS_verage CO2 concentration was held to within +/- 20% of the set point more than 98% of the time that the arrays were operatgU`ing during all three seasons. In 1991, the long term average CO2 concentration measured at 63 points throughout the volumegea of a 20 m diameter experimental plot (ground to canopy top) centered within a 25 m diameter FACE array was 568 mumol mol-ggb1. All of the FACE arrays operated for more than 99% of the planned experimental period in 1991. These 3 years of operatiogpcn have demonstrated that the BNL FACE technology can be used as a basis for a large scale facility devoted to studying thegr fate of carbon in the terrestrial environment.gze530^3^Luo,Y^Field,CB^Mooney,HA^1994^1^Predicting responses of photosynthesis and root fraction to elevated [co2](a) - integ|ractions among carbon, nitrogen, and growth^9^17^11^1195-1204^^^^^Nov^^^^^3878Uhu">INggA^3877^At elevated atmospheric CO2 concentrations ([CO2](a)), photosynthetic capacity (A(max)) and root fraction (eta(R), ghthe ratio of root to plant dry mass) increased in some studies and decreased in others. Here, we have explored possible cagiuses of this, focusing on the relative magnitudes of the effects of elevated [CO2](a) on specific leaf (n(m)) and plant (ngj(p)) nitrogen concentrations, leaf mass per unit area (h), and plant nitrogen productivity (alpha). In our survey of 39 stgkudies with 35 species, we found that elevated [CO2](a) led to decreased n(m) and n(p) in all the studies and to increased glh and alpha in most of the studies. The magnitudes of these changes varied with species and with experimental conditions. gmBased on a model that integrated [CO2](a)-induced changes in leaf nitrogen into a biochemically based model of leaf photosgnynthesis, we predicted that, to a first approximation, photosynthesis will be upregulated (A(max) will increase) when growgoth at increased [CO2](a) leads to increases in h that are larger than decreases in n(m). Photosynthesis will be downregulagpted (A(max) will decrease) when increases in h are smaller than decreases in n(m). The model suggests that photosynthetic gqcapacity increases at elevated [CO2](a) only when additional leaf mesophyll more than compensates the effects of nitrogen grdilution. We considered two kinds of regulatory paradigms that could lead to varying responses of eta(R) to elevated [CO2]gs(a), and compared the predictions of each with the data. A simple static model based on the functional balance concept pregtdicts that eta(R) should increase when neither n(p) nor h is very responsive to elevated [CO2](a). The quantitative and qugualitative agreement of the predictions with data from the literature, however, is poor. A model that predicts eta(R) from gvthe relative sensitivities of photosynthesis and relative growth rate to elevated [CO2](a) corresponds much more closely tgwo the observations. In general, root fraction increases if the response of photosynthesis to [CO2](a) is greater than thatg of relative growth rate."T+T9TjHjNj^jfjmjsjzjjjhsA^3881^Storage of broccoli (Brassica oleracea L., Italica Group) under conditions of low O-2 concentration extends its shehlf life. Excessively low O-2, however, leads to the formation of an offensive odour which is primarily due to the emissionh of methanethiol. In this study, we investigated the initial induction and control of methanethiol production of broccoli hflorets exposed to various levels of O-2 and CO2 over short- term periods of 10 h or less. Lowering the O-2 concentration hsurrounding the broccoli florets by continuously flowing N-2 through the sample containers acted to initiate the productiohn of methanethiol within 1 h after the 0(2) concentration had reached 0.5 %. After initiation the rate of production showehd a slow but steady increase during the 10 h of experimentation. In contrast, introduction of O-2 into the sample containehrs while the broccoli florets were actively producing methanethiol led to a rapid 79% drop in the amount of methanethiol dhetected within 15 min, followed by a complete absence of methanethiol within another 15 min. Resumption of N-2 flow acted hto reinitiate methanethiol production, with the initiation requiring a lesser amount of time than that required for the inhitial induction of methanethiol production. Experiments with elevated CO2 concentrations of up to 26.5% determined that COh2 is an inhibitor of methanethiol production.ŃfqvƉch533^3^Parton,WJ^Ojima,DS^Schimel,DS^1994^1^Environmental-change in grasslands - assessment using models^50^28^1-2^111-141^h^^^^Oct^^^^^3884hA^3883^Modeling studies and observed data suggest that plant production, species distribution, disturbance regimes, grasslhand biome boundaries and secondary production (i.e., animal productivity) could be affected by potential changes in climathe and by changes in land use practices. There are many studies in which computer models have been used to assess the impacht of climate changes on grassland ecosystems. A global assessment of climate change impacts suggest that some grassland echosystems will have higher plant production (humid temperate grasslands) while the production of extreme continental steppehs (e.g., more arid regions of the temperate grasslands of North America and Eurasia) could be reduced substantially. All oif the grassland systems studied are projected to lose soil carbon, with the greatest losses in the extreme continental grai ssland systems. There are large differences in the projected changes in plant production for some regions, while alteratioins in soil C are relatively similar over a range of climate change projections drawn from various General Circulation Modeils (GCM's). The potential impact of climatic change on cattle weight gains is unclear. The results of modeling studies alsi&o suggest that the direct impact of increased atmospheric CO2 on photosynthesis and water use in grasslands must be considi(ered since these direct impacts could be as large as those due to climatic changes. In addition to its direct effects on pi9hotosynthesis and water use, elevated CO2 concentrations lower N content and reduce digestibility of the forage.i<534^4^Perezsoba,M^Vandereerden,LJM^Stulen,I^Kuiper,PJC^1994^1^Gaseous ammonia counteracts the response of scots pine needliMes to elevated atmospheric carbon-dioxide^84^128^2^307-313^^^^^Oct^^^^^3886iOA^3885^Four-year-old saplings of Scots pine (Pinus sylvestris L.) were exposed for 8 wk in controlled-environment chambersiY to charcoal-filtered air (FB), FA supplemented with 754 mg m(-3) (650 mu l l(-1)) CO2, FA supplemented with 100 mu g m(-3i[) NH3 and FA + CO2 + NH3. Elevated CO2 induced a significant increase in the concentrations of NH4+ and NO3- in the soil siholution, while exposure to NH3 enhanced the soil NH4+ concentration. Elevated CO2 significantly increased needle biomass aijnd area, and decreased specific leaf area (SLA) and N concentration in the needles. The activity of peroxidase (POD) was dixecreased, while the activities of glutamine synthetase (GS) and glutamate dehydrogenase (GDH) were only slightly affected.iz Gaseous NH3 enhanced the concentration of N, soluble proteins and the GS activity in the needles, while it decreased the iPOD and GDH activities. The effects of elevated CO2 + NH3 on needle biomass production, N metabolism and POD activity werei smaller than the effects of single exposures to elevated CO2 or NH3, suggesting that elevated CO2 and NH3 counteract eachi other and disturb needle physiology. The possible mechanisms underlying the negative interactions of elevated CO2 and NH3i are discussed. The expected stimulation of biomass production by elevated CO2 may be reduced in the presence of atmospheriic NH3.i535^2^Sicher,RC^Kremer,DF^1994^1^Responses of nicotiana-tabacum to co2 enrichment at low-photon flux-density^37^92^3^383-3i88^^^^^Nov^^^^^3888iA^3887^Effects of CO2 enrichment on photosynthesis and on dry matter allocation were examined in two tobacco (Nicotiana taibacum L.) genotypes, Samsun and W38. Plants were grown from seed in controlled environment chambers at a photosynthetic phioton flux density of 450 mu mol m(-2) s(-1). Averaged over the 9 day study, net photosynthesis rates were 14.2 +/- 0.5 andi 13.0 +/- 0.4 mu mol m(-2) s(-1) in elevated (70 Pa) and in ambient (35 Pa) CO2 air, respectively, when measured at the iriradiance and CO2 partial pressure employed for plant growth. However, photosynthesis rates of plants grown in elevated CO2i were 50% less than those of the ambient controls on the last day of treatment, when measured at 70 Pa CO2 air and an irraidiance of 900 mu mol m(-2) s(-1). Total plant dry weight and specific leaf weight were greater (P<0.05) in enriched-CO2-griown than in ambient-CO2-grown plants. Leaf starch, measured during the first hour of the photoperiod, increased over 7 dayis of treatment in elevated-CO2-grown but not in ambient-CO2-grown plants. Ribulose 1,5-bisphosphate carboxylase/oxygenase j(Rubisco) activities of tobacco plants grown at 35 and 70 Pa CO2 air were 58.5 +/- 4.5 and 48.5 +/- 3.7 mu mol m(-2) s(-1)j, respectively, between days 0 and 9 of the study. Rubisco activation stale, Rubisco protein concentration, soluble proteijn and total chlorophyll were unaffected by CO2 enrichment. The above findings demonstrated that photosynthesis was down rejgulated in tobacco plants after 7 to 9 days of CO2 enrichment at low photosynthetic photon flux density, but less than at jmoderate irradiances.j536^6^Stronach,IM^Clifford,SC^Mohamed,AD^Singletonjones,PR^Azamali,SN^Crout,NMJ^1994^1^The effects of elevated carbon-dioxj2ide, temperature and soil- moisture on the water-use of stands of groundnut (arachis- hypogaea L)^78^45^280^1633-1638^^^^^j4Nov^^^^^3890Y5Xchu}<N[!jAA^3889^Stands of groundnut (Arachis hypogaea L. cv. Kadiri 3) were grown in controlled environment glasshouses at two meanjC air temperatures (28 degrees C and 32 degrees C), two atmospheric CO2 concentrations (375 ppmv and 700 ppmv) and two soiljK moisture treatments (irrigated weekly to field capacity or allowed to dry from 22 d after sowing). The transpiration equijMvalent, Omega(W) (g kPa kg(-1))-the product of the accumulated biomass/transpired water ratio and the saturation deficit-wj_as calculated for all the treatments using aboveground harvest, root core and neutron probe measurements. Neither temperatjaure nor soil moisture treatment was found to have an effect on Omega(W). Increased CO2 concentration raised Omega(W) from jr6.21 +/- 0.30 to 7.67 +/- 0.29 g kPa kg(-1), an increase of 24% (P < 0.005). The importance of accounting for root materiajtl and pod composition when calculating Omega(W) was highlighted.j 9DJdlsyj}537^5^Taylor,G^Ranasinghe,S^Bosac,C^Gardner,SDL^Ferris,R^1994^1^Elevated co2 and plant-growth - cellular mechanisms and rejsponses of whole plants^78^45^280^1761-1774^^^^^Nov^^^^^3892UjA^3891^Much research has focused on the photosynthetic responses of plants to elevated CO2, with less attention given to tjhe post- photosynthetic events which may lead to changes in the growth of tissues, organs and whole plants. The aim of thijs review is to identify how plant growth is altered in elevated CO2 and to determine which growth processes or cellular mejchanisms are sensitive to carbon supply. For leaves, both the expansion of individual leaves and the initiation of leaf prjimordia are stimulated in elevated CO2. When lamina growth is promoted, this is usually associated with increased leaf celjl expansion rather than increased leaf cell production. Using several clones of hybrid poplar (Populus euramericana, P. injteramericana) two native herbs (Plantago media, Sanguisorba minor) and bean (Phaseolus vulgaris) we have identified the mejchanism through which leaf cell expansion is promoted in elevated CO2. Changes in the water relations, turgor pressure (P)j and yield turgor (Y) of growing leaves cannot explain increased cell expansion; this appears to occur because cell wall ljoosening is promoted, as suggested by three pieces of evidence. (i) The rate of decline of water potential (psi) with timej is accelerated when growing leaves are placed in psychrometers and allowed to relax, (ii) Instron-measured cell wall extejnsibility (WEX), is greater for leaves exposed to elevated CO2 and (iii) the activity of the putative wall loosening enzymje, XET is increased for leaves of P. vulgaris exposed to elevated CO2. Species differences do, however, exist; in the herbj Lotus corniculatus small stimulations of leaf growth in elevated CO2 are due to increased leaf cell production and decreajsed cell size in elevated CO2. These results are discussed in relation to the concept of functional types. There is evidenkce to suggest that both cell production and cell expansion are promoted in roots of plants exposed to elevated CO2. For naktive herbs (Anthyllis vulneraria, Lotus corniculatus, P. media and S. minor), increased root growth in elevated CO2 is duek to increased cell elongation. In contrast to leaves, this appears to occur because both root cell turgor pressure (P) andk" root cell wall extensibility (WEX) are promoted by exposure of shoots to elevated CO2. In longer-term studies on root grok$wth, the effects of additional carbon on the production of root primordia and root branching are of overriding importance,k8 suggesting that carbon supply may influence some aspect of the cell cycle, when effects on the extension of individual rok:ots may not be apparent.#,$,),Y,,,,,-222.262=2C2H2Q2[2v2y2z2kL538^3^Tuba,Z^Szente,K^Koch,J^1994^1^Response of photosynthesis, stomatal conductance, water-use efficiency and production kNto long-term elevated co2 in winter- wheat^4^144^6^661-668^^^^^Nov^^^^^3894k[A^3893^Responses of photosynthesis, stomatal conductance, water use efficiency (at the beginning of flowering) and productk]ion allocation (at full ear/grain ripening) to long-term elevated CO2 were assessed in winter wheat (Triticum aestivum L. kocv. MV16). Plants were grown in open top chambers under a temperate-continental climate from germination at ambient (350 mkqu molmol(-1)) and elevated (700 mu molmol(-1)) CO2 concentrations. High CO2 plants displayed a decreased initial slope of kthe A/C-i response curve, with the assimilation rate (A) continuing to increase above 400 mu molmol(-1) internal CO2 concekntration (C-i). A in the ambient plants showed P regeneration limitation while RuBP regeneration appeared to be limiting Ak in the high CO2 treatment. Variable fluorescence ratios (Rfd 690) were lower in the high CO2 plants indicating a lower poktential photochemical activity. The increase in the values for the chlorophyll fluorescence ratio F690/F735 in the high COk2 plants was in agreement with the lower chlorophyll a+b concentrations. The high CO2 plants had higher concentrations of kstarch in their leaves and roots that the ambient plants. Stomatal conductance (g(s)) was lower in the high CO2 plants at kevery CO2 concentration (C-a) and C-i and the C-i-dependent g(s) response had a large influence on the A/g(s), function. Tkhe higher water use efficiency (WUE) values (at C-a's > 350 mu molmol(-1)) in the high CO2 wheat plants were the result ofk a larger decrease in transpiration rate (E) in the high CO2 plants than in the ambient plants, and of a simultaneous largker increase in A in the range of C-a above 350 mu molmol(-1) COP. The integrated and combined effect of the photosynthetick and stomatal acclimation to elevated CO2 produced a higher C- assimilation in high CO2 plants at elevated CO2 than in thek ambient plants, however, this was not followed by an acclimation in C-allocation. These were reflected in a slightly incrkeased (6.7%) overall dry matter production and lower reproductive allocation (RA).k539^3^Williams,M^Shewry,PR^Harwood,JL^1994^1^The influence of the greenhouse-effect on wheat (triticum- aestivum L) grain klipids^78^45^279^1379-1385^^^^^Oct^^^^^3896kA^3895^There have been few studies conducted with the objective of investigating comprehensively the 'greenhouse effect' oln wheat growth using field-grown crops and even less on the effects on the lipid composition of harvested grains. Thereforle, the aim of this study was to define any changes in wheat grain acyl lipids which could result from alterations in envirlonmental growth conditions predicted to mimic the 'greenhouse effect'. Quantitative changes were recorded for both the nonl-starch and starch lipids. When supplied with low concentrations of nitrogen fertilizer, plants showed increased amounts olf total grain lipids when grown under an elevated (700 mu l l(-1)) carbon dioxide atmosphere. Increasing the ambient tempel 540^2^Winter,K^Engelbrecht,B^1994^1^Short-term co2 responses of light and dark co2 fixation in the crassulacean acid metabl"olism plant kalanchoe-pinnata^4^144^4-5^462-467^^^^^Oct^^^^^3898l2A^3897^Short-term responses of net CO2 assimilation rate (A), in the light and dark, to ambient CO2 partial pressure (betwl4een about 30 and 1000 mu bar) were studied in leaves of the crassulacean acid metabolism (CAM) plant, Kalanchoe pinnata. TlChe results show that it is possible to extrapolate from instantaneous measurements of net CO2 exchange to diurnal and noctlFurnal CO2 balances at different CO2 partial pressures. Instantaneous CO2 response curves were obtained by altering CO2 levl[els at 10-min intervals during the middle of the 12-h dark period (phase I of CAM) and during the last third of the 12-h ll] ight period (phase IV of CAM). CO2 partial pressures were also altered at longer, 12- to 24-h intervals and maximum rates lp of net CO2 uptake (A(max)) during light and dark periods were analysed in response to intercellular CO2 partial pressures lr (p(i)) occurring at the time of A(max). A(max)-p(i) relationships were identical to A-p(i)-curves from rapidly performed dlw eterminations during phases I and IV. Corresponding to previous findings with non-CAM species, A(max) and integrated net cly arbon gain during light and dark periods, respectively, showed a linear relationship. Nocturnal CO2 uptake in normal air wlas barely affected when light-period carbon gain was manipulated by alterations in CO2 partial pressure. Carbon gain durinlg light periods, measured in normal air, was also independent of CO2-related changes in nocturnal carbon gain. Only after l12 h of darkness at the lowest CO2 concentration used (about 30 mu bar), was carbon gain increased under lighted conditionls.l541^4^Baxter,R^Gantley,M^Ashenden,TW^Farrar,JF^1994^1^Effects of elevated carbon-dioxide on 3 grass species from montane plasture .2. Nutrient-uptake, allocation and efficiency of use^78^45^278^1267-1278^^^^^Sep^^^^^3900>!3;lA^3899^Agrostis capillaris L.(4), Festuca vivipara L. and Poa alpina L. were grown in outdoor open-top chambers at either lambient (340 mu mol mol(-1) or elevated (680 mu mol mol(-1)) CO2 for periods from 79 to 189 d. Under these conditions therle is increased growth of A, capillaris and P. alpina, but reduced growth of F. vivipara. Nutrient use efficiency, nutrientl productivity (total plant dry weight gain per unit of nutrient) and nutrient allocation of all three grass species were mleasured in an attempt to understand their individual growth responses further and to determine whether altered nutrient-usle efficiencies and productivities enable plants exposed to an elevated atmospheric CO2 environment to overcome potential lm imitations to growth imposed by soil fertility. Total uptake of nutrients was, in general, greater in plants of A. capillamris and P. alpina (with the exception of N and K in the latter) when grown at 680 mu mol mol(-1) CO2. In F. vivipara, howemver, uptake was considerably reduced in plants grown at the higher CO2 concentration. Overall, a doubling of atmospheric CmO2 concentration had little effect on the nutrient use efficiency or productivity of A, capillaris. Reductions in tissue nm*utrient content resulted from increased plant growth and not altered nutrient use efficiency. In P. alpina, potassium, magm,nesium and calcium productivities were significantly reduced and photosynthetic nitrogen and phosphorus use efficiencies wm7 ere doubled at elevated CO2 with respect to plants grown at ambient CO2. F. vivipara grown for 189 d showed the most markem9!d changes in nutrient use efficiency and nutrient productivity (on an extracted dry weight basis) when grown at elevated CmA"O2. F. vivipara grown at elevated CO2, however, showed large increases in the ratio of nonstructural carbohydrate to nitromC#gen content of leaves and reproductive tissues, indicating a substantial imbalance between the production and utilization mSof assimilate.FOï̯ݯ̳ճBLU^նݶøʸmU%542^8^Bhattacharya,NC^Radin,JW^Kimball,BA^Mauney,JR^Hendrey,GR^Nagy,J^Lewin,KF^Ponce,DC^1994^1^Leaf water relations of cotmaton in a free-air co2-enriched environment^107^70^1-4^171-182^^^^^Sep^^^^^3902JOmc'A^3901^As part of an intensive study of crop response to CO2 enrichment in a free-air CO2 enrichment (FACE) experiment in ms(the field, we determined aspects of the water relations of a cotton crop on selected dates in 1991. The atmosphere was enrmt)iched from 370 mumol CO2 mol-1 (control) to about 550 mumol mol-1 in free air during daylight hours. Under full irrigationm*, CO2 enrichment decreased stomatal conductance and single-leaf transpiration only toward the end of the season, and thesem+ changes led to increased leaf water potentials only at that time of year. Under water-stressed (deficit irrigation) condim,tions, CO2 enrichment decreased conductance throughout the season but there was no corresponding consistent effect on leafm- water potentials. As with the fully irrigated controls, CO2 enrichment increased leaf water potentials only at the end ofm. the season. CO2 enrichment increased season-long biomass accumulation 39% under full irrigation and 34% under deficit irrm/igation. These results are consistent with previous studies of cotton in open-top chambers that found only small effects om0f CO2 enrichment on internal water relations of cotton, and no water stress-induced increase in crop responsiveness to elemvated CO2.11|22222222e3s3t333333 444*4Z4f44495=5m2543^2^Chmora,SN^Mokronosov,AT^1994^1^The global increase of co2 in the atmosphere - adaptive strategies in plants^236^41^5m^677-685^^^^^Sep-Oct^^^^^39042DEExF~FG"GNG\GGGIIIIIIKKKKKKm4A^3903^The effects of short- and long-term exposure to increased CO2 concentrations on the life activity and productivity m5of plants are discussed. Two strategies of plant adaptation to an increasing CO2 concentration are outlined that reflect tm6he diversity of adaptive plant responses at the ecological and physiological levels: physiological adaptation that occurs m7at all organization levels from molecular to cenotic and changes in areas of species that lead to changes in ecosystem commposition occurring in correspondence to the biochemical diversity of photosynthetic pathways.n9544^3^Cotrufo,MF^Ineson,P^Rowland,AP^1994^1^Decomposition of tree leaf litters grown under elevated co2 - effect of littern quality^206^163^1^121-130^^^^^Jun^^^^^3906n;A^3905^Ash (Fraxinus excelsior L.), birch (Betula pubescens Ehrh.), sycamore (Acer pseudoplatanus L.) and Sitka spruce (Pin&nt (350 mu L L(-1) CO2) and enriched (600 mu L L(-1) CO2). Elevated CO2 significantly affected some of the major litter qun6?ality parameters, with lower N, higher lignin concentrations and higher ratios of C/N and lignin/N for litters derived fron?@m enriched CO2. Respiration rates of the deciduous species were significantly decreased for litters grown under elevated CnAAO2, and reductions in mass loss at the end of the experiment were generally observed in litters derived from the 600 ppm CnTBO2 treatment. Nutrient mineralization, dissolved organic carbon, and pH in microcosm leachates did not differ significantlnVCy between the two CO2 treatments for any of the species studied. Litter quality parameters were examined for correlations ndDwith cumulative respiration and decomposition rates: N concentration, C/N and lignin/N ratios showed the highest correlatinfEons, with differences between litter types. The results indicate that higher C storage will occur in soil as a consequencenq of litter quality changes resulting from higher atmospheric concentrations of CO2.nsG545^7^Dugas,WA^Heuer,ML^Hunsaker,D^Kimball,BA^Lewin,KF^Nagy,J^Johnson,M^1994^1^Sap flow measurements of transpiration fromn cotton grown under ambient and enriched co2 concentrations^107^70^1-4^231-245^^^^^Sep^^^^^3908@GnIA^3907^Increasing atmospheric CO2 concentration has many implications for agriculture and forestry, one of which is the efnJfect it will have on transpiration (T). The objective of this work was to quantify T of cotton (Gossypium hirsutum L.) gronKwn in the field under ambient (370 mumol mol-1) and enriched (550 mumol mol-1) CO2 concentrations. Measurements were made nLin 1990 and 1991 at the Maricopa Agricultural Center, Arizona. Constant- power sap flow gauges were used to measure T. In nM1990, three plants and in 1991, 10 plants were simultaneously instrumented with gauges in each of the CO2 treatments. LeafnN area of plants with gauges was measured. T measured by sap flow was compared with evapotranspiration (ET) calculated by wnOater balance in 1990 and with T calculated by water balance in 1991. Soil evaporation was measured using microlysimeters inPn 1991, and was found to be essentially equal (approximately 0.8 mm day-1, or about 10% of T) in the two CO2 treatments. TnQhere were no consistent differences in leaf area of plants with gauges between the two CO2 treatments. Sap flow, for perionRds from 15 min to 2 weeks, was not significantly different between the two CO2 treatments in either year, except for a fewnS days in 1990. In 1991, the coefficient of variation of daily sap flow across plants was the same (about 30%) for both CO2nT treatments throughout the year. The water balance ET (1990) and T (1991) were similar to sap flow in both years, and alsonU showed no effect of CO2 treatment. These results show that for this crop, grown under well-watered and high-fertility connVditions, there was no effect of CO2 on T, on a per unit ground area or per plant basis. These results are relevant for assnessing the effects of increasing atmospheric CO2 concentrations on transpiration by cotton.n546^1^Field,CB^1994^1^Carbon-cycle - arctic chill for co2 uptake^36^371^6497^472-473^^^^^6 OctnY547^6^Hendrix,DL^Mauney,JR^Kimball,BA^Lewin,K^Nagy,J^Hendrey,GR^1994^1^Influence of elevated co2 and mild water-stress on ononstructural carbohydrates in field-grown cotton tissues^107^70^1-4^153-162^^^^^Sep^^^^^3911o[A^3910^Root, stem and leaf tissues, from cotton plants exposed to CO2 at ambient (370 mumol mol-1 (control)) or elevated (o\550 mumol mol-1 (FACE; free-air carbon dioxide enrichment)) levels in the field during the 1990 and 1991 growing seasons, o]were analyzed for nonstructural carbohydrates (glucose, fructose, sucrose and starch). Besides the FACE treatment, these po-^lants were also exposed to two irrigation levels: 100% and 67% replacement of evapotranspiration. FACE had a greater effeco/_t upon cotton plant nonstructural carbohydrates than did irrigation treatments. Leaf carbohydrate content was increased byo7` FACE, but this increase was much more pronounced in the stems and roots. Starch and soluble sugars in leaves in FACE ploto8as tended to be consistently greater than in control leaves, without much change in carbohydrate content during the growingoJb season. In contrast, root and stem, starch and soluble sugar pools were strongly increased by FACE and fluctuated strongloLcy during the growing season. In both seasons, stem and taproot nonstructural carbohydrate content passed through a minimumo^d during periods of heavy boll set. The fluctuations in stem and root carbohydrate content were therefore probably caused bo`ey the varying metabolic demands of the developing plant. These results suggest that a significant effect of CO2 enrichmentogf on starch-accumulating plants is an increase of nonstructural carbohydrate, especially starch, in nonleaf storage pools. oigThis buildup occurs somewhat independently of the water status of the plant, and these enlarged pools can be drawn upon byo the growing plant to maintain growth during periods of high metabolic demand.oi548^9^Hileman,DR^Huluka,G^Kenjige,PK^Sinha,N^Bhattacharya,NC^Biswas,PK^Lewin,KF^Nagy,J^Hendrey,GR^1994^1^Canopy photosynthojesis and transpiration of field-grown cotton exposed to free-air co2 enrichment (face) and differential irrigation^107^70^o1-4^189-207^^^^^Sep^^^^^3913olA^3912^Growth, yield and leaf photosynthetic rates of cotton (Gossypium hirsutum L. ) all respond strongly to CO2 enrichmeomnt, but the gas exchange of whole cotton canopies grown under elevated CO2 has not been investigated. We compared the effeoncts of CO2 enrichment on both single-leaf and whole-canopy photosynthetic rates in cotton. We also determined whole- canopooy photosynthetic and transpiration rates in cotton in response to CO2 enrichment and differential irrigation. Field- grownop cotton was exposed to either 550 mumol mol-1 of CO2 using the free-air carbon dioxide enrichment (FACE) system or to 370 oqmumol mol-1 in control plots. In the second year of the experiment, half of each plot received reduced levels of irrigatioorn. Rates of photosynthesis and stomatal conductance of single leaves were determined using a portable photosynthesis systeosm and a portable steady-state porometer, respectively. Rates of whole-canopy photosynthesis and transpiration were determiotned using a custom-built chamber (about 1 m x 1 m). Midday net photosynthesis rates of both leaves and canopies were 19-41ou% higher in the CO2-enriched plots than in control plots. The CO2 effect on leaf photosynthesis was greatest in July, wherpveas the CO2 effect on canopy photosynthesis was greatest in June and decreased thereafter as mutual shading of leaves and pwthe amount of non- photosynthetic biomass increased. Midday stomatal conductance values of leaves were 13-44% greater in cpxontrol plants than in CO2-enriched plants. Except for late in the second season, canopy transpiration rates were not affecpyted by the CO2 treatment because the decrease in stomatal conductance was offset by an increase in plant size. Differentiap,zl irrigation led to no significant differences in either canopy photosynthesis or transpiration, possibly because differenp.{tial irrigation was applied only during the second half of the season. It appears that cotton crops grown in a future, higp<her-CO2 climate may have increased photosynthetic rates, but water requirements may not be reduced.p=}549^6^Huluka,G^Hileman,DR^Biswas,PK^Lewin,KF^Nagy,J^Hendrey,GR^1994^1^Effects of elevated co2 and water-stress on mineral pIconcentration of cotton^107^70^1-4^141-152^^^^^Sep^^^^^3915pKA^3914^Projected increases in atmospheric CO2 concentrations may alter mineral and protein levels in plant tissues, systemp^atically affecting growth, nutrient cycling and utilization, residue decomposition, and insect-plant interactions in the fp`uture. The free-air CO2 enrichment (FACE) system provided an opportunity to monitor seasonal trends in nutrient status andpn crude protein content of cotton (Gossypium hirsutum L. cv. Deltapine 77) grown in a natural field setting without the limppitations often imposed by growth chambers or reduced rooting volumes. In 1990, plants were exposed to two levels of atmospp|heric CO2 (FACE, almost-equal-to 550 mumol mol-1 and CONTROL, almost-equal-to 370 mumol mol-1) and two irrigation regimes p~(100% and 75% replacement of evapotranspiration) beginning in early July. Cotton leaves, stem, and roots were sampled at dpifferent times during the season and analyzed for C, N, Ca, K, Mg, P, Cu, Fe, Mn, Zn, B, Mo, Si and protein. The N and proptein concentrations of leaves, stems and roots were significantly lower in FACE plants than in CONTROL plants, but C:N ratpios were higher for the FACE plants than the CONTROL plants. Some other elements were significantly affected by CO2 enrichpment, but not for all dates and all plant tissues. There were no significant effects in any of the data because of the irrpigation treatment or the irrigation-CO2 interaction. Reductions in tissue N and protein concentrations and the increases ipn the C:N with CO2 enrichment have important implications for agricultural and natural systems and demand additional reseaprch.p550^10^Idso,SB^Kimball,BA^Wall,GW^Garcia,RL^Lamorte,R^Pinter,PJ^Mauney,JR^Hendrey,GR^Lewin,K^Nagy,J^1994^1^Effects of freep-air co2 enrichment on the light response curve of net photosynthesis in cotton leaves^107^70^1-4^183-188^^^^^Sep^^^^^3917pA^3916^Daytime measurements of leaf CO2 exchange rates in a free-air CO2 enrichment (FACE) experiment reveal that at photopsynthetically active radiation (PAR) flux rates in excess of 1000 mumol m-2 s-1, cotton leaves exposed to an atmospheric CpO2 concentration of approximately 500 mumol mol-1 exhibit net photosynthetic rates about 30% greater than those for leavesp of similar plants growing in ambient air. As PAR flux rates drop below this value, the stimulatory effect of elevated CO2p rises, suggesting that the relative benefits of atmospheric CO2 enrichment will be greater for shaded cotton leaves that pfor those exposed to full sunlight.LMNOPQRSTUVWXYZ[\]^_`pcdefghijklmnopqrstuvwxyz{|}~q551^11^Kirschbaum,MUF^King,DA^Comins,HN^McMurtrie,RE^Medlyn,BE^Pongracic,S^Murty,D^Keith,H^Raison,RJ^Khanna,PK^Sheriff,DW^q1994^1^Modeling forest response to increasing co2 concentration under nutrient-limited conditions^9^17^10^1081-1099^^^^^Ocqt^^^^^3919qA^3918^The growth rates of woody plants depend on both the rate of photosynthetic carbon gain and the availability of esseq&ntial nutrients. Instantaneous carbon gain is known to increase in response to increasing atmospheric CO2 concentration, bq(ut it is uncertain whether this will translate into increased growth in the longer term under nutrient-limited conditions.q6 An analytical model to address this question was developed by Comins and McMurtrie (1993, Ecological Applications 3, 666-q8 681). Their model was further tested and analysed. Manipulation of various assumptions in the model revealed its key assuqFmptions and allowed a more confident prediction of expected growth responses to CO2 enrichment under nutrient-limited condqGitions. The analysis indicated that conclusions about the CO2 sensitivity of production were strongly influenced by assumpqNtions about the relationship between foliar and heartwood nitrogen concentrations. With heartwood nitrogen concentration pqProportional to foliar nitrogen concentration, the model predicted a strong response of plant productivity to increasing COqb2 concentration, whereas with heartwood nitrogen concentration set constant, the model predicted only a very slight growthqd response to changing CO2 concentration. On the other hand, predictions were only slightly affected by: (1) assumptions abqnout the extent of nitrogen retranslocation out of senescing roots and foliage or wood during heartwood formation; (2) the qpeffects of nitrogen status on specific Leaf area or (3) leaf longevity; (4) carbon allocation between different plant partqs; or (5) changes in the N:C ratio of organic matter sequestered in the passive pool of soil organic matter. Modification qof the effect of foliar nitrogen concentration on the light utilization coefficient had only a small effect on the CO2 senqsitivity for pines. However, this conclusion was strongly dependent on the chosen relationship between single- leaf photosqynthesis and leaf nitrogen concentration. Overall, the analysis suggested that trees growing under nitrogen- limited condiqtions can respond to increasing atmospheric CO2 concentration with considerable increases in growth.q552^4^Lewis,JD^Griffin,KL^Thomas,RB^Strain,BR^1994^1^Phosphorus supply affects the photosynthetic capacity of loblolly-pinqe grown in elevated carbon-dioxide^13^14^11^1229-1244^^^^^Nov^^^^^3921qA^3920^Effects of phosphorus supply and mycorrhizal status on the response of photosynthetic capacity to elevated CO2 wereq investigated in loblolly pine (Pinus taeda L.) seedlings. Seedlings were grown in greenhouses maintained at either 35.5 oqr 71.0 Pa CO2 in a full factorial experiment with or without mycorrhizal inoculum (Pisolithus tinctorius (Pers.) Coker & Cqouch) and with an adequate or a limiting supply of phosphorus. Assimilation versus internal CO2 partial pressure (C(i)) cuqrves were used to estimate maximum Rubisco activity (V(c,max)), electron transport mediated ribulose 1,5-bisphosphate regeqneration capacity (J(max)), phosphate regeneration capacity (PiRC) and daytime respiration rates (R(d)). Nonmycorrhizal seqedlings grown with limiting phosphorus had significantly reduced V(c,max) and PiRC compared to seedlings in other treatmenqts. Elevated CO2 increased photosynthetic capacity in nonmycorrhizal seedlings in the low phosphorus treatment by increasiqng PiRC, whereas it induced phosphorus limitation in mycorrhizal seedlings in the low phosphorus treatment and did not affrect the photosynthetic capacity of seedlings in the high phosphorus treatment. Despite the variety of effects on photosyntrhetic capacity, seedlings in the elevated CO2 treatments had higher net assimilation rates than seedlings in the ambient CrO2 treatments. We conclude that phosphorus supply affects photosynthetic capacity during long-term exposure to elevated COr2 through effects on Rubisco activity and ribulose 1,5-bisphosphate regeneration rates.RS & FAXES\CONTEMr*553^1^Mortensen,LM^1994^1^The influence of carbon-dioxide or ozone concentration on growth and assimilate partitioning in r,seedlings of 9 conifers^200^44^3^157-163^^^^^Sep^^^^^3923FAX.DOT>@PROGRAM FILESr:A^3922^Seedlings of nine different conifers were exposed to 355 and 730 mu mol mol(-1) CO2, or low (< 15 nmol mol(-1)) andr< elevated O-3 concentration (70 nmol mol(-1)) for 81-116 days. The experiments were conducted in growth chambers placed inrA a greenhouse. Increased CO2 concentration enhanced the mean relative growth rate (RGR) and total plant dry weight by 4 anrCd 33% in Larix leptolepis, by 4 and 38% in Larix sibirica, by 7 and 47% in Picea glauca and by 3 and 16% in Picea sitchensrNis, respectively. The growth rates and dry weights of Pinus contorta, Pinus mugo and Pseudotsuga menziesii were not signifrPicantly affected. Carbon dioxide enrichment enhanced RGR of two provenances of Picea abies by 4 and 6%, respectively, whilr\e a third provenance was unaffected. In Pinus sylvestris, only the RGR of one of three provenances was stimulated by CO2 er^nrichment (4%). After two growth seasons CO2 enrichment enhanced RGR and total plant dry weight by 11 and 35% in Picea abirnes and by 12 and 36% in Pinus sylvestris, respectively. Elevated CO2 decreased the shoot:root ratio in Larix leptolepis, arpnd decreased the needle:stem ratio in Picea glauca, but increased it in Pseudotsuga menziesii. Elevated O-3 significantly rdecreased the plant dry weight in Picea sitchensis, Pseudotsuga menziesii and in one of three provenances of Pinus sylvestrris, while the other species and provenances were unaffected. Increased O-3 concentration increased the shoot:root dry weirght ratio in one of three Picea abies provenances, in all three Pinus sylvestris provenances and in Pinus contorta. The neredle:stem ratio was enhanced by O- 3 in seven of the nine species. The O-3 exposure caused chlorosis of needles in all spercies except Pseudotsuga menziesii.,,nnn,B,,r554^1^Mortensen,LM^1994^1^Effects of carbon-dioxide concentration on assimilate partitioning, photosynthesis and transpirartion of betula- pendula roth and picea-abies (L) karst seedlings at 2 temperatures^200^44^3^164-169^^^^^Sep^^^^^3925rA^3924^Seedlings of Betula pendula Roth. and Picea abies (L.) Karat. were grown at 350 and 700 mu mol mol(-1) CO2 for 35 orr 45 days at 15 and 20 degrees C in eight growth chambers. The mean photosynthetic flux was 15-22 mol m(-2) day(-1). The mrean relative growth rate was increased by 7% in Betula and by 10% in Picea at the highest CO2 concentration. This correspornded to an increase in the total plant dry weight of 20 and 19%, respectively The shoot:root and leaf:stem ratios were unarffected by the CO2 concentration in both species. High CO2 levels increased the stem diameter and the number of lateral shroots in Betula. Increasing the temperature did not affect the assimilate partitioning between leaf stem and root in Betular, but the needle:stem ratio decreased in Picea. Elevated CO2 concentration increased the number of lateral shoots in Betuls a more at 15 than at 20 degrees C, however, the total weight of the lateral shoots was not affected. With this exception ts he effect of CO2 was generally the same at both temperatures. Measurements of the CO2 exchange rates indicated that a sligsht acclimation to high CO2 had taken place at the end of the experimental period in the two species. Elevated CO2 slightlys decreased the transpiration rate of Betula.associated with differences in sensitivity to heat during reproductive develos#555^5^Nagy,J^Lewin,KF^Hendrey,GR^Hassinger,E^Lamorte,R^1994^1^Face facility co2 concentration control and co2 use in 1990 s2and 1991^107^70^1-4^31-48^^^^^Sep^^^^^3927-1. Under intermediate night temperature (33/20-degrees-C), all lines set substs4A^3926^CO2 treatment level control and CO2 use are reported for free- air carbon dioxide enrichment (FACE) facility operats6ions at the University of Arizona's Maricopa Agricultural Center in 1990 and 1991. These are required for evaluation of thsHe validity of biological experiments conducted in four replicates of paired experimental and control plots in a large cottsIon field and the cost-effectiveness of the plant fumigation facility. Gas concentration was controlled to 550 mumol mol-1 sNat the center of each experimental plot, just above the canopy. In both years, season-long (April-September) average CO2 lsPevels during treatment hours (05:00-19:00 h Mountain Standard Time) were 550 mumol mol-1 measured at treatment plot centersZs when the facility was operating. Including downtime, the season average was 548 mumol mol-1 in 1991. In 1990, the seasons\ averages for the four elevated CO2 treatments varied from 522 to 544 mumol mol-1, owing to extended periods of downtime asefter lightning damage. Ambient CO2 concentration during treatment was 370 mumol mol-1. Instantaneous measurements of CO2 csgoncentration were within 10% of the target concentration of 550 mumol mol-1 more than 65% of the time when the facility waszs operating, and 1 min averages were within 10% of the target concentration for 90% of the time. The long-term average of s|CO2 concentration measured over the 20 m diameter experimental area of one array at the height of the canopy was in the rasnge 550-580 mumol mol- 1 during July 1991, with the higher values near the edges. In 1991, CO2 demand averaged 1250 kg pers array per 14 h treatment day, or 4 kg m-2 of fumigated plant canopy. The FACE facility provided good temporal and spatials control of CO2 concentration and was a cost-effective method for large-scale field evaluations of the biological effects sof CO2.HESIS; AVAILABILITY; TEMPERATURE; IRRADIANCE AB Growth parameters of Agrostis capillaris L. and Nardus stricta L. s556^10^Oechel,WC^Cowles,S^Grulke,N^Hastings,SJ^Lawrence,B^Prudhomme,T^Riechers,G^Strain,B^Tissue,D^Vourlitis,G^1994^1^Transsient nature of co2 fertilization in arctic tundra^36^371^6497^500-503^^^^^6 Oct^^^^^3929llaris had attained approx. foursA^3928^THERE has been much debate about the effect of increased atmospheric CO2 concentrations on plant net primary producstion(1,3) and on net ecosystem CO2 flux(3-10). Apparently conflicting experimental findings could be the result of differesnces in genetic potential(11-15) and resource availability(16-20), different experimental conditions(21-24) and the fact tshat many studies have focused on individual components of the system(2,21,25-27) rather than the whole ecosystem. Here we spresent results of an in situ experiment on the response of an intact native ecosystem to elevated CO2. An undisturbed patsch of tussock tundra at Toolik Lake, Alaska, was enclosed in greenhouses in which the CO2 level, moisture and temperature scould be controlled(28), and was subjected to ambient (340 p.p.m.) and elevated (680 p.p.m.) levels of CO2 and temperaturet (+4 degrees C). Air humidity, precipitation and soil water table were maintained at ambient control levels. For a doubledt CO2 level alone, complete homeostasis of the CO2 flux was re-established within three Sears, whereas the regions exposed tto a combination of higher temperatures and doubled CO2 showed persistent fertilization effect on net ecosystem carbon seqtuestration over this time. This difference may be due to enhanced sink activity from the direct effects of higher temperattures on growth(16,29-33) and to indirect effects from enhanced nutrient supply caused by increased mineralization(10,11,19t!,27,34). These results indicate that the responses of native ecosystems to elevated CO2 may not always be positive, and art*e unlikely to be straightforward. Clearly, CO2 fertilization effects must always be considered in the context of genetic lt+imitation, resource availability and other such factors.-4330 MULHEIM, GERMANY. IOWA STATE UNIV SCI & TECHNOL, DEPT BOT, t>557^3^Pearson,M^Besford,RT^Hand,DW^1994^1^The effects of oxides of nitrogen and carbon-dioxide enrichment on growth and cotAntent of ribulose-1, 5-bisphosphate carboxylase-oxygenase and nitrite reductase in glasshouse lettuce^174^69^2^257-266^^^^tM^Mar^^^^^3931e state-of-knowledge of the past, present, and potential future roles of tropical forests in the global C cytOts. Hence the division of the normalized results of the first data set by the normalized results of the second set yields t[a representation of the increase in whole-tree net photosynthesis due to enhanced needle production caused by atmospheric t]CO2 enrichment. In the solitary trees we studied, the relative contribution of this effect increased rapidly with the CO2 toconcentration of the air to increase whole-tree net photosynthesis by nearly 50% at a CO2 concentration approximately 300 tqA^3930^Different systems of CO2 enrichment and heating were used to produce glasshouse atmospheres with varying concentrattions of NO(x) and CO2 (ambient NO(x) and CO2, ambient NO(x) and 1000 vpm CO2, and three concentrations of NO(x) varying bettween 0.5 and 2.5 vpm with concurrent CO2 concentrations between 1000- 2500 vpm). The growth response of winter lettuce int these environments was assessed for three contrasting cultivars (Ambassador, Berlo and Pascal). Contents of ribulose-1, 5t- bisphosphate carboxylase-oxygenase (RuBPco) and nitrite reductase (NiR) in the leaf tissue were also determined using imtmunoblotting and enzyme-linked immunosorbent assay (ELISA). 'Ambassador' produced the heaviest ''head'' weights, but on matrketable criteria 'Berlo' performed better. CO2 enrichment enhanced yields, but the High NO(x) treatments reduced growth rt elative to that in the Low NO(x) and unpolluted environments. Growth assessments suggested a greater tolerance of NO(x) int cvs Berlo and Pascal than in cv. Ambassador. Immunoblots showed that the antibodies used here were specific. Using these t antibodies in ELISA, 'Pascal' was found to contain more RuBPco and NiR on a leaf area basis than 'Ambassador'. There were t reductions in RuBPco and NiR contents in response to growth in elevated CO2. Elevated CO2 caused a reduction in RuBPco andt NiR in 'Ambassador', but in 'Pascal' only RuBPco levels were reduced. This may account for the greater relative tolerancet of 'Pascal' and the sensitivity of 'Ambassador' to NO(x) pollution.ospheric (A) or enriched (E) concentrations of 300-33t558^6^Pinter,PJ^Kimball,BA^Mauney,JR^Hendrey,GR^Lewin,KF^Nagy,J^1994^1^Effects of free-air carbon-dioxide enrichment on patr absorption and conversion efficiency by cotton^107^70^1-4^209-230^^^^^Sep^^^^^3933urface during the P(N) measurements rtA^3932^Anticipated changes in global climate and atmospheric CO2 concentrations have very important, albeit poorly understtood consequences for production agriculture. Effects of these changes on plants have usually been examined in controlled- uenvironment enclosures, glass-houses, or open-top field chambers. Beginning in 1989, an innovative experimental free- air uCO2 enrichment (FACE) facility was operated in central Arizona to evaluate crop response to increased CO2 levels within a ularge, open-field production environment. Cotton (Gossypium hirsutum L.) was grown for three consecutive seasons under expuosed to either ambient (control, about 370 mumol mol- 1) or elevated (FACE, 550 mumol mol-1) CO2 concentrations. Deficit iu&rrigation regimes supplying 75% (beginning in July 1990) or 67% (beginning in mid-May 1991) of the crop's evapotranspiratiu(on requirement were included as additional treatment variables. Plant growth was monitored by periodic sampling. Canopy reu*flectances in visible (blue, 0.45-0.52 mum; green, 0.05-0.59 mum; red, 0.61-0.68 mum) and near-infrared (NIR; 0.79-0.89 muu7m) wavebands were measured frequently with an Exotech radiometer and related to absorbed photosynthetically active radiatiu9on (PAR; 0.4-0.7 mum) measured with a line quantum sensor. Dry biomass of plants in the FACE treatment was significantly (uGP < 0.05) greater than control values during each year of the study. The FACE plant canopy also absorbed significantly moruIe PAR than controls during the early and middle portion of the 1990 and 1991 seasons. Light use efficiency (LUE, biomass puTroduced per unit absorbed PAR) was significantly higher in FACE plots during each year. In the well-watered irrigation treuVatment, the 3 year mean LUE was 1.97 g MJ-1 for FACE and 1.56 g MJ-1 for controls. The deficit irrigation treatment in 199ud 1 produced significantly smaller plants, which absorbed less PAR and had lower LUE than plants in the well-watered treatmeue!nt (P < 0.05). No interaction was observed between CO2 and irrigation treatments. FACE research under realistic field conduq"itions revealed positive consequences of increased CO2 on cotton plant biomass, PAR absorption, and LUE. It also demonstraus#ted the effectiveness of this new technology for examining community-level plant responses to possible changes in global eunvironment.omplex enterprises (farms and forests) to climate change and their ability to adjust and adapt; and (4) integru%559^4^Prior,SA^Rogers,HH^Runion,GB^Mauney,JR^1994^1^Effects of free-air co2 enrichment on cotton root-growth^107^70^1-4^69u-86^^^^^Sep^^^^^3935on opportunities and of the inter-industry linkages that determine what the overall impacts on the reu'A^3934^The rise in atmospheric CO2 concentration is predicted to have a positive effect on agro-ecosystem productivity. Hou(wever, an area which requires further investigation centers on responses of crop root systems to elevated atmospheric CO2 u)under field conditions. The advent of free-air CO2 enrichment (FACE) technology provides a new method of CO2 exposure withu* minimal alteration of plant microclimate. In 1990 and 1991, cotton (Gossypium hirsutum (L.) 'Deltapine 77') was grown undu+er two atmospheric CO2 levels (370 and 550 mumol mol-1) and two water regimes (wet (100% of ET replaced) and dry (75% of Eu,T replaced in 1990 and 67% in 1991)). Plant root samples were collected at early vegetative and mid-reproductive growth. Tu-aproots of CO2-enriched plants displayed greater volume, dry weight, length, and tissue density. Water treatment effects wu.ere noted for length, volume and dry weight of roots at the second sampling in 1991. In general, whole soil profile root du/ensities (both length and dry weight densities) and root weight per unit length at the initial sampling were increased undu0er CO2 enrichment at each of three positions (0.00, 0.25, and 0.50 m) from row center to the middle of the inter-row spacev1. At the second sampling, root length density and root dry weight density were generally unaffected by water stress, wherev2as root weight per unit length was somewhat higher. In addition, extra CO2 increased whole profile root length density onlv3y at the 0.50 m inter-row position, whereas whole profile root dry weight density and root weight per unit length were genv'4erally higher under elevated CO2 at all three positions. The results from this field experiment strongly indicated that inv)creased atmospheric CO2 level would enhance plant root growth.n dioxide or is due to other factors. Doubts concerning thev66560^5^Reeves,DW^Rogers,HH^Prior,SA^Wood,CW^Runion,GB^1994^1^Elevated atmospheric carbon-dioxide effects on sorghum and soyv8bean nutrient status^166^17^11^1939-1954^^^^^^^^^^3937ent limitations2,3,10. Here we present evidence that mineral nutrievF8A^3936^Increasing atmospheric carbon dioxide (CO2) concentration could have significant implications on technologies for mvH9anaging plant nutrition to sustain crop productivity in the future. Soybean (Glycine max [L.] Merr.) (C3 species) and graivU:n sorghum (Sorghum bicolor [L.] Moench) (C4 species) were grown in a replicated split-plot design using open-top field chavW;mbers under ambient (357 mu mol/mol) and elevated (705 mu mol/mol) atmospheric CO2. At anthesis, leaf disks were taken froveweight were also measured. Above-ground dry matter and seed yield were determined at maturiry. Seed yield of sorghum increvv?ased 17.5% and soybean seed yield increased 34.7% with elevated CO2. There were no differences in extractable chlorophyll v@concentration or chlorophyll meter readings due to CO2 treatment, but meter readings were reduced 6% when sorghum was growvAn in chambers as compared in the open. Leaf nitrogen (N) concentration of soybean decreased from 54.5 to 39.1 g/kg at the vBhigher CO2 concentration. Neither the chambers nor CO2 had an effect on concentrations of other plant nutrients in either vCspecies. Further work under field conditions is needed to determine if current critical values for tissue N in crops, espevcially C3 crops, should be adjusted for future increases in atmospheric CO2 concentration.d to evaluate the impacts of thvE561^6^Runion,GB^Curl,EA^Rogers,HH^Backman,PA^Rodriguezkabana,R^Helms,BE^1994^1^Effects of free-air co2 enrichment on microvbial-populations in the rhizosphere and phyllosphere of cotton^107^70^1-4^117-130^^^^^Sep^^^^^3939 sorghum and soybeans wvGA^3938^Cotton (Gossypium hirsutum L.) plants were exposed to free-air CO2 enriched (FACE = 550 mumol mol-1) or ambient (COvHNTROL = 370 mumol mol-1) levels of atmospheric CO2 and to wet (100% of evapotranspiration replaced) or dry (67% of ET replvIaced) soil water content treatments. Foliar, soil and root samples were collected in June and August 1991 to determine thevJ effects of elevated CO2 on selected groups of phyllosphere and rhizosphere microorganisms. Foliage and rhizosphere soil wvKere analyzed for bacteria and/or fungi using dilution plating. Mycorrhizal colonization of cotton roots was assessed. RootvL-zone soil was analyzed for populations of nematodes, microarthropods and Rhizoctonia using various extraction methods. A vMdehydrogenase assay for total microbial respiration and a bioassay for cotton root infecting organisms were also conductedvN using root-zone soil. Populations of fungi on cotton leaves varied, by genera, in response to CO2 enrichment, but none wavOs affected by soil water content treatments; populations of foliar bacteria were not affected by either CO2 or soil water wPcontent treatments. In August, higher total numbers of rhizosphere fungi were found under the wet compared with the dry sowQil water treatment, but differences related to CO2 were not detected. There was a trend for infestation by Rhizoctonia solwRani to be higher under FACE in the August sample, but the soil bioassay demonstrated no increase in damping-off potential.w S There was a significant interaction between CO2 concentration and soil water content for populations of saprophagous nemawTtodes; populations were different between the CO2 levels in the dry soil treatment only, with higher numbers under FACE. MwUicroarthropod numbers were low; however, there was a trend for Collembola populations to be higher under FACE in the Augusw(Vt sample and more fungi were isolated from Collembola in June. Total microbial activity was higher under FACE at both sampw*Wle dates. Effects of elevated atmospheric CO2 on plant-microbe interactions could have profound influence on the productivw6ity of agro-ecosystems, and deserve further research.eaf area or leaf number, while a significant effect was found with bw9Y562^6^Tarnawski,MG^Green,TGA^Buedel,B^Meyer,A^Zellner,H^Lange,OL^1994^1^Diel changes of atmospheric co2 concentration withw@in, and above, cryptogam stands in a new-zealand temperate rain-forest^237^32^3^329-336^^^^^^^^^^3941additional dry mattewB^3940^Atmospheric CO2 levels were determined (at 2m height) in the rainforest and in a clearing outside the forest, durinwN\g spring (November) 1991, Urewera National Park, New Zealand. CO2 levels within the forest were 30 ppm higher and showed awP] more variable diel pattern (range up to 70 ppm) than outside the forest. CO2 levels were generally higher at night than dwf^uring the day. Detailed measurements were made at several sites at a depth of 25 mm in the phylloplane of three moss speciwg_es and under, or between, the thalli of four lichen species. Mean levels were 50% (moss phylloplane) and 10% (lichen thallwp`i) higher than the levels in the clearing and, in 80% of sites, also higher than air within the rainforest. The diel pattewrarn of the CO2 concentration at each of the sites was not predictable from measurements of CO2 in the bulk air of the foresw|bt. High levels of CO2 may be important in elevating photosynthetic rates of mosses and, to a lesser extent, lichens in thew~ field. the impact of the 1931-1940 analog climate (with and without CO2 enrichment) on Missouri, Iowa, Nebraska, and Kanwd563^3^Wall,GW^Amthor,JS^Kimball,BA^1994^1^Cotco2 - a cotton growth simulation-model for global change^107^70^1-4^289-342^^w^^^Sep^^^^^3943r evaporation under the 1931-1940 analog and the 1951-1980 control climates. A modification of the ErosionwfA^3942^In conjunction with the Free-Air-CO2-Enrichment (FACE) project, a new, physiologically based, mechanistic, modular wgsimulation model of cotton (Gossypium hirsutum L.) physiology, growth, development, yield and water use has been constructwhed. It is named COTCO2 for cotton response to atmospheric CO2 concentration. The model is capable of predicting cotton crowip responses to elevated atmospheric CO2 concentrations and potential concomitant changing climate variables. The major plawjnt processes known to be influenced by CO2 are simulated explicitly, i.e. photosynthesis, photorespiration, and stomatal cwkonductance, and its role in leaf energy balance. The model explicitly simulates the impact of atmospheric CO2 concentratiowln on C3 photosynthesis and photorespiration at the level of carboxylation and oxygenation. Growth is simulated for individwmual organs, i.e. leaf blade, stem segment, taproot and lateral roots, and fruit which includes squares and bolls. Potentiawnl growth is calculated and the carbohydrate and nitrogen required to meet this potential are calculated. Actual growth is wobased on substrate availability, the potential growth, and water stress. Our intent here is to describe the overall structwpure of the model, its present status, and future development plans. Further development, documentation, calibration, and vwqalidation of the model is in progress. The long range goal of the project is to provide quantitative estimates of global cwotton production in a future higher-CO2 world. carbon dioxide availability to investigate the interactive effects of thesws564^3^Wilsey,BJ^McNaughton,SJ^Coleman,JS^1994^1^Will increases in atmospheric co2 affect regrowth following grazing in C-4x grasses from tropical grasslands - a test with sporobolus-kentrophyllus^2^99^1-2^141-144^^^^^Sep^^^^^3945after 100 days x uA^3944^We grew a C-4 grass from the Serengeti ecosystem under ambient (370 ppm) and elevated (700 ppm) CO2, and under clipxvped and unclipped conditions to test whether regrowth following grazing would be affected by elevated CO2. Above-ground prxwoductivity was slightly decreased under elevated CO2, and was similar between clipped and unclipped plants. Regrowth (clipxxping offtake) following clipping was similar in the two CO2 treatments, and there was no CO2 by clipping interaction on bix!yomass, productivity, or leaf nutrient concentrations. Based on this evidence, we suggest that C-4 grasses from the Serengex-ti will show little direct response to future increases in atmospheric CO2. photoassimilates mediated by resource availabx/{565^5^Wood,CW^Torbert,HA^Rogers,HH^Runion,GB^Prior,SA^1994^1^Free-air co2 enrichment effects on soil carbon and nitrogen^1x>07^70^1-4^103-116^^^^^Sep^^^^^3947ANGE RESPONSES OF 2 DECIDUOUS HARDWOODS DURING 3 YEARS OF GROWTH IN ELEVATED CO2 - NO Lx@}A^3946^Since the onset of the industrial revolution, atmospheric CO2 concentration has increased exponentially to the currxN~ent 370 mumol mol-1 level, and continued increases are expected. Previous research has demonstrated that elevated atmosphexPric CO2 results in larger plants returning greater amounts of C to the soil. However, the effects of elevated CO2 on C andx^ N cycling and long-term storage of C in soil have not been examined. Soil samples (in 0-50, 50-100, and 100-200 mm depth x`increments) were collected after 3 years of cotton (Gossypium hirsutum L.) production under free-air CO2 enrichment (FACE,xq at 550 mumol CO2 mol-1), in combination with 2 years of different soil moisture regimes (wet, 100% of evapotranspiration xsreplaced, or dry, 75% and 67% of evapotranspiration replaced in 1990 and 1991, respectively) on a Trix clay loam (fine, lox~amy, mixed (calcareous), hyperthermic Typic Torrifluvent) at Maricopa, Arizona. Ambient plots (370 mumol CO2 mol-1 (controxl)), in combination with the wet and dry soil moisture regimes, were also included in the study. Soil organic C and N concxentrations, potential C and N mineralization, and C turnover were measured. Increased input of cotton plant residues underx FACE resulted in treatment differences and trends toward increased organic C in all three soil depths. During the first 3x0 days of laboratory incubation, available N apparently limited potential C mineralization and C turnover in all treatmentxs. Between 30 and 60 days of incubation, soils from FACE plots had greater potential C mineralization with both water regixmes, but C turnover increased in soils from the dry treatment and decreased in soils where cotton was not water stressed. xThese data indicate that in high-CO2 environments without water stress, increased C storage in soil is likely, but it is lxess likely where water stress is a factor. More research is needed before the ability of soil to store additional C in a hxigh-CO2 world can be determined.ses, but many additional factors interact in determining whole-plant and forest responsesx566^3^Xu,DQ^Gifford,RM^Chow,WS^1994^1^Photosynthetic acclimation in pea and soybean to high atmospheric co2 partial-pressuxre^8^106^2^661-671^^^^^Oct^^^^^3949MS, AJM ZEHNDER, AJB TI A HIGHLY PURIFIED ENRICHMENT CULTURE COUPLES THE REDUCTIVE DECxA^3948^Nonnodulated pea (Pisum sativum L. cv Frosty) and soybean (Glycine max [L.] Merr. cv Wye) plants were grown under axrtificial lights from germination with ample nutrients, 600 mu mol photons m(-2) s(-1), and either 34 to 36 (control) or 6x4 to 68 Pa (enriched) CO2. For soybean, pod removal and whole-plant shading treatments were used to alter the source-sink xbalance and carbohydrate status of the plants. Growth of both species was substantially increased by CO2 enrichment despitye some down-regulation of photosynthesis rate per unit leaf area (''acclimation''). Acclimation was observed in young pea yleaves but not old and in old soybean leaves but not young. Acclimation was neither evident in quantum yield nor was it reylated to triose phosphate limitation of net photosynthesis. A correlation between levels of starch and sugars in the leaf yand the amount of acclimation was apparent but was loose and only weakly related to the source-sink balance of the plant. yA consistent feature of acclimation was reduced ribulose bisphosphate carboxylase (RuBPCase) content, although in vivo RuByPCase activity was not necessarily diminished by elevated growth CO2 owing to increased percentage of activation of the eny1zyme. A proposal is discussed that the complexity of photosynthetic acclimation responses to elevated CO2 is as an expressy3ion of re-optimization of deployment of within-plant resources at three levels of competition. temperature of 25 to 35-deyD567^4^Allen,LH^Valle,RR^Mishoe,JW^Jones,JW^1994^1^Soybean leaf gas-exchange responses to carbon-dioxide and water-stress^4yF8^86^4^625-636^^^^^Jul-Aug^^^^^3951 derived from H-2 or formate consumption were recovered in dechlorination products andy\A^3950^As global carbon dioxide concentrations rise, we need to understand the combination of direct effects of this gas ay^nd the anticipated effects of climate change, including drought, on physiology and growth of all crops. Effects Of CO2 on ycplants begin at the leaf level; our objectives, therefore, were to determine interrelationships among factors governing gayfs exchange responses of soybean [Glycine max (L.) Merr.] leaves to elevated CO2 and water stress. Photosynthetic CO2 assimyrilation and transpiration rates were measured in cuvettes on leaflets of soybean (cv. Bragg) grown in controlled- environmytent chambers at 330 and 660 mumol CO2 Mol-1 air. Leaflets at high CO2, either water-stressed or well-watered, had higher py}hotosynthetic and lower transpiration rates, and therefore higher water-use efficiencies (WUE), than those at Control CO2 ylevels. As irrigation was withheld during an 11-d period, WUE decreased about 30 to 50% with respect to the well- watered ytreatments. Midday leaf temperature and leaf-to-air vapor pressure gradient levels increased as the water stress progresseyd. For water stress treatments, midday leaf conductance (G(lw)) was generally higher and residual internal conductance (G(yr)) was generally lower in low than in high CO2. Ratios of midday G(r)/G(lc), were nearly constant throughout the period iyn both the stressed and the well-watered treatments. The ratios of intercellular C(i), to ambient C(a), CO2 concentration y(i.e., C(i)/C(a)) during the water stress period remained similar to the respective nonstressed treatments within each CO2y level. These findings support the concept that leaf conductances are governed by CO2 assimilation rates under water-stresysed as well as unstressed conditions.esis and a CO2-induced reduction in nighttime dark respiration. Measurements of thesy568^2^Brioua,AH^Wheeler,CT^1994^1^Growth and nitrogen-fixation in alnus-glutinosa (L) gaertn under carbon-dioxide enrichmeynt of the root atmosphere^206^162^2^183-191^^^^^May^^^^^3953 earth's trees, in the mean, probably share this same responsyA^3952^The effects of aeration of the N-free rooting medium with elevated CO2 on (a) acetylene reduction by perlite-grown yplants and (b) N-2-fixation and long-term growth of nutrient solution- grown plants were determined for nodulated Alnus glyutinosa (L.) Gaertn. In the former experiments, roots of intact plants were incubated in acetylene in air in darkened glasys jars for 3 hr, followed by a further 3 hr incubation period in air enriched with CO2 (0-5%). During incubation, the CO2 ycontent of the jars increased by 0.17% per hour due to respiration of the root system, so that the CO2 content at 3 hr wasu 0.5%. Additional enrichment of the rooting medium gas-phase with CO2 equivalent to 1.1% and 1.75% CO2 of the gas volume szignificantly increased nitrogenase activity (ethylene production) by 55% and 50% respectively, while enrichment with greatz er than 2.5% CO2 decreased activity. In contrast, ethylene production by control plants, where CO2 was not added to the aszsay jars, decreased by 8% over the assay period. In long-term growth experiments, nodulated roots of intact Alnus glutinosza plants were sealed into jars containing N-free nutrient solution (pH 6.3) and aerated with air, or air containing elevatzed levels of CO2 (1.5% and 5%). Comparison of the appearance of CO2-treated with air treated plants suggested that 1.5% COz)2 stimulated plant growth. However, at harvest after 5 or 6 weeks variability between plants masked the significance of diz+fferences in plant dry weight. A significant increase of 33% in total nitrogen of plants aerated with 1.5% CO2, compared wz5ith air-treated plants, was demonstrated, broadly in line with the short-term increase in acetylene reducing activity obsez7rved following incubations with similar CO2 concentrations. Shoot dry weight was not affected significantly by long-term ezBxposure to 5% CO2, the main effect on growth being a 20% reduction in dry weight of the root system, possibly through inhizDbition of root system respiration. However, in contrast to the inhibitory effects of high CO2 on acetylene reduction therezO was no significant effect on the amounts of N-2 fixed.the peat seedlings. At the control CO2 level, the content of more zQ569^2^Caulfield,F^Bunce,JA^1994^1^Elevated atmospheric carbon-dioxide concentration affects interactions between spodopterz^a-exigua (lepidoptera, noctuidae) larvae and 2 host-plant species outdoors^238^23^4^999-1005^^^^^Aug^^^^^3955ment of atmozaA^3954^Beet armyworm, Spodoptera exigua (Hubner), larvae were placed on sugarbeet (Beta vulgaris L.) and pigweed (Amaranthzpus hybridus L.) plants in outdoor chambers in which the plants were growing at either the ambient (almost-equal-to 350 mulzr liter-1) or ambient plus 350 mul liter-1 (almost-equal-to 700 mul liter-1) carbon dioxide concentration. A series of expezriments was performed to determine if larvae reduced plant growth differently at the two carbon dioxide concentrations in zeither species and if the insect growth or survival differed with carbon dioxide concentration. Leaf nitrogen, water, starzch, and soluble carbohydrate contents were measured to assess carbon dioxide concentration effects on leaf quality. Insectz feeding significantly reduced plant growth in sugarbeet plants at 350 mul liter-1 but not at 700 mul liter-1 nor in pigwezed at either carbon dioxide concentration. Larval survival was greater on sugarbeet plants at the elevated carbon dioxide zconcentration. Increased survival occurred only if the insects were at the elevated carbon dioxide concentration and consuzmed leaf material grown at the elevated concentration. Leaf quality was only marginally affected by growth at elevated carzbon dioxide concentration in these experiments. The results indicate that in designing experiments to predict effects of ezlevated atmospheric carbon dioxide concentrations on plant- insect interactions, both plants and insects should be exposedz to the experimental carbon dioxide concentrations, as well as to as realistic environmental conditions as possible.ith tz570^2^Ceulemans,R^Mousseau,M^1994^1^Tansley review no-71 - effects of elevated atmospheric co2 on woody-plants^84^127^3^42z5-446^^^^^Jul^^^^^3957lkali-promoted CaO or MgO compared to the mono-alkali ones are attributed to the synergistic increazA^3956^Because of their prominent role in the global carbon balance and their possible carbon sequestration, trees are verzy important organisms in relation to global climatic changes. Knowledge of these processes is the key to understanding thez functioning of the whole forest ecosystem which can be modelled and predicted based on the physiological process informatzion. This paper reviews the major methods and techniques used to examine the likely effects of elevated CO2 on woody plantzs, as well as the major physiological responses of trees to elevated CO2. The available exposure techniques and approachesz are described. An overview table with all relevant literature data over the period 1989-93 summarizes the percent changes{ in biomass, root/shoot ratio, photosynthesis, leaf area and water use efficiency under elevated CO2. Interaction between { growth, photosynthesis and nutrition is discussed with a special emphasis on downward regulation of photosynthesis. The st{imulation or reduction found in the respiratory processes of woody plants are reviewed, as well as the effect of elevated {CO2 on stomatal density, conductance and water use efficiency. Changes in plant quality and their consequences are examine{$d. Changes in underground processes under elevated CO2 are especially emphasized and related to the functioning of the eco{&system. Some directions for future research are put forward.luated in terms of their experimental protocols on growth con{5571^2^Cui,M^Nobel,PS^1994^1^Gas-exchange and growth-responses to elevated co2 and light levels in the cam species opuntia-{7ficus-indica^9^17^8^935-944^^^^^Aug^^^^^3959oning, the small dimensions along with short and easy culture make radish an {DA^3958^Gas exchange and dry-weight production in Opuntia ficus-indica, a CAM species cultivated worldwide for its fruit an{Fd cladodes, were studied in 370 and 750 mu mol mol(-1) CO2 at three photosynthetic photon flux densities (PPFD: 5, 13 and {T20 mol m(-2) d(-1)). Elevated CO2 and PPFD enhanced the growth of basal cladodes and roots during the 12-week study. A ris{Ve in the PPFD increased the growth of daughter cladodes; elevated CO2 enhanced the growth of first-daughter cladodes but d{becreased the growth of the second-daughter cladodes produced on them. CO2 enrichment enhanced daily net CO2 uptake during {dthe initial 8 weeks after planting for both basal and first- daughter cladodes. Water vapour conductance was 9 to 15% lowe{mr in 750 than in 370 mu mol mol(-1) CO2. Cladode chlorophyll content was lower in elevated CO2 and at higher PPFD. Soluble{o sugar and starch contents increased with time and were higher in elevated CO2 and at higher PPFD. The total plant nitroge{vn content was lower in elevated CO2. The effect of elevated CO2 on net CO2 uptake disappeared at 12 weeks after planting, {ypossibly due to acclimation or feedback inhibition, which in turn could reflect decreases in the sink strength of roots. D{espite this decreased effect on net CO2 uptake, the total plant dry weight at 12 weeks averaged 32% higher in 750 than in {370 mu mol mol(-1) CO2. Averaged for the two CO2 treatments, the total plant dry weight increased by 66% from low to mediu{m PPFD and by 37% from medium to high PPFD. tidal currents. BP 221-224 PG 4 JI Indian J. Mar. Sci. PY 1993 PD SEP VL 22 I{572^1^Diemer,MW^1994^1^Mid-season gas-exchange of an alpine grassland under elevated co2^2^98^3-4^429-435^^^^^Aug^^^^^3961{A^3960^Ecosystem net CO2 uptake, evapotranspiration (ET) and night- time CO2 efflux were measured in an alpine grassland d{ominated by Carex curvula, treated with doubled ambient partial pressure of CO2 via open-top chambers. One quarter of the {plots were treated with mineral nutrients to simulate the effect of lowland nitrogen deposition rates. Depending upon fert{ilizer supply, ecosystem net CO2 uptake per ground area in full sunlight (NCE(max)) was 41-81% higher in open-top chambers{ supplied with doubled ambient partial pressure (p(a)) of CO2 than in plots receiving ambient CO2. Short-term reversals of{ the CO2 level suggest that the extent of downward adjustment of canopy photosynthesis under elevated CO2 was 30-40%. ET t{ended to decline, while water use efficiency (WUE), expressed as the NCE(max):ET ratio, increased more than twofold under {elevated CO2. Night-time ecosystem CO2 efflux did not respond to changes in CO2 p(a). NCE(max) and night-time CO2 efflux w{ere more responsive to mineral fertilizer than the doubling of CO2. This suggests that in these alpine plant communities, {atmospheric nutrient input may induce equal or greater effects on gas exchange than increased CO2.f two compared to the V{ system, and by more than an order of magnitude compared to our older results. With the optimum system we are now able to{573^4^Garcia,RL^Idso,SB^Wall,GW^Kimball,BA^1994^1^Changes in net photosynthesis and growth of pinus-eldarica seedlings in {response to atmospheric co2 enrichment^9^17^8^971-978^^^^^Aug^^^^^3963gas chromatography/mass spectrometry and the state-{A^3962^Pinus eldarica L. trees, rooted in the natural soil of an agricultural field at Phoenix, Arizona, were grown from t| he seedling stage in clear-plastic-wall open-top enclosures maintained at four different atmospheric CO2 concentrations fo|r 15 months. Light response functions were determined for one tree from each treatment by means of whole-tree net CO2 exch|ange measurements at the end of this period, after which rates of carbon assimilation of an ambient-treatment tree were me|asured across a range of atmospheric COP concentrations. The first of these data sets incorporates the consequences of bot|h the CO2-induced enhancement of net photosynthesis per unit needle area and the CO2-induced enhancement of needle area it|%self (due primarily to the production of more needles), whereas the second data set reflects only the first of these effec|'574^2^Gay,AP^Hauck,B^1994^1^Acclimation of lolium-temulentum to enhanced carbon-dioxide concentration^78^45^277^1133-1141^|/^^^^Aug^^^^^3965n C allocation. Exposure of woody species to elevated CO2 over several years has shown that high rates of|1A^3964^Acclimation of single plants of Lolium temulentum to changing [CO2] was studied on plants grown in controlled envir|8onments at 20 degrees C with an 8 h photoperiod. In the first experiment plants were grown at 135 mu mol m(-2) s(-1) photo|:synthetic photon flux density (PPFD) at m s 415 mu l l(-1) or 550 mu l l(-1) [CO2] with some plants transferred from the l|Iower to the higher [CO2] at emergence of leaf 4. In the second experiment plants were grown at 135 and 500 mu mol m(-2) s(|K-1) PPFD at 345 and 575 mu l l(-1) [CO2]. High [CO2] during growth had little effect on stomatal density, total soluble pr|` oteins, chlorophyll a content, amount of Rubisco or cytochrome f. However, increasing [CO2] during measurement increased p|b hotosynthetic rates, particularly in high light. Plants grown in the higher [CO2] had greater leaf extension, leaf and pla|i nt growth rates in low but not in high light. The results are discussed in relation to the limitation of growth by sink ca|kpacity and the modifications in the plant which allow the storage of extra assimilates at high [CO2].n growth than is rel|r 575^2^Hoen,HF^Solberg,B^1994^1^Potential and economic-efficiency of carbon sequestration in forest biomass through silvicu|tltural management^49^40^3^429-451^^^^^Aug^^^^^3967 A 2 to 4-degrees-C increase in soil temperature could increase CO2 eff|A^3966^This paper has two main objectives: First, to discuss in principle some vital methodological issues which have to b|e considered when analyzing bow preferable measures in forestry are to decrease the atmospheric concentration of greenhous|e gases (GHGs). Economic evaluation of the flow of carbon in and out of the atmosphere is discussed, related particularly |to two important problems: (1) the determination of the utility of reducing the quantity of CO2 in the atmosphere at a giv|en point in time; and (2) the intertemporal evaluation of a flow of atmospheric CO2 reductions. The marginal cost, measure|d as the change in net present value, is proposed as a proper measure for ranking of alternative projects. Secondly, a cas|e study is reported. The case study is based on forest-level optimization with a model estimating carbon flows related to |forest biomass growth and decay, linked to a long-range forest management planning (LFMP) model. Alternative stand treatme|nt schedules are simulated, and the forest management problem is solved by linear programming in a model I type LFMP model| for the county of Buskerud, with a forest area of 574,000 ha. The potential for increasing the net carbon sequestration r|elated to timber production by changes in the forest management over a time period of 30 yr is studied. A total of 253 sta|nd treatment schedules was calculated for the 40 stand types, allowing for the following stand treatment options, (1) cont|inued growth, (2) release thinnings of young growth, (3) thinning, (4) fertilization, (5) clear felling, (6) clear felling| with retention of seed trees, and (7) planting or natural regeneration depending on the felling regime. The study shows t} hat there is a significant potential for increasing the present value of the flow of net CO2 fixations (NPV(CO2)) by chang} ing the forest management on the productive forest area of Buskerud. Compared with the NPV(CO2) obtained when the net pres}ent value of the timber cash flow (NPV(NOK)) for the area is maximized (BASE problem), an increase between 8.4%-17.9% in N} PV(CO2) can be obtained. The potential for increasing the NPV(CO2) depends on the real rate of discount. The corresponding}3! decrease in the NPV(NOK) lies between 8.1% and 14.9%. The results further indicate that a large proportion of the increas}5"e in NPV(CO2) can be obtained by changes in forest management at a moderate marginal cost. If we assume that 80% of the ma}G#ximum potential increase in NPV(CO2) is obtained, this gives a yearly increase (30-yr annuity) in net CO2 fixation in the }I$range from 145,000 to 250,000 tons (depending on the real rate of discount and assumptions about fertilization) by changin}]%g the management of the 574,000 ha of productive forestland in Buskerud, compared to the current forest management practic}_&e (BASE problem). Obtaining 80% of the maximum potential increase in NPV(CO2) imposes a decrease in the NPV(NOK) in the ra}e'nge of 22% to 65% of the total potential difference in NPV(NOK) between the BASE problem and the NPV(CO2) maximizing probl}g(em. The annual decrease (30-yr annuity) in NPV(NOK) corresponding to the 80% of the maximum potential NPV(CO2) increase, i}o)s ranging between 7.6 and 25 million NOK. The results indicate that at a RRD of 4%, 5%, and 7% p.a., 80% of the increase i}q*n NPV(CO2) can be reached at a marginal cost (shadow price) below 150 NOK (21/US$) per ton NPV(CO2). Measured per ton C, t}+he corresponding marginal cost is 551 NOK (79 US$) per ton C. For RRDs at 3% p.a. and 2% p.a., the marginal costs are sign},ificantly higher, but relaxing the NPV(CO2) constraint to 60% of the total increase brings the marginal costs down and bel}-ow half of this level (59 NOK or 8 US$ per ton NPV(CO2)) for 3% p.a. and to a comparable level (182 NOK or 26 US$ per ton }.NPV(CO2)) for 2% p.a. These results are related to changes in the management of the forested area in even-aged stands and /do not take into account measures such as afforestation of marginal agricultural land or changes of tree species. Fertiliz0ation, avoiding release thinning in young growth, and changes in clear felling priorities were the most cost-efficient cha}nges in stand treatment management in order to increase the net CO2 fixation. temperature (+0-degrees-C, +2-degrees-C, an}2576^4^Jackson,RB^Sala,OE^Field,CB^Mooney,HA^1994^1^Co2 alters water-use, carbon gain, and yield for the dominant species i}n a natural grassland^2^98^3-4^257-262^^^^^Aug^^^^^3969M and TEM estimate the total net primary productivity (NPP) for te}4A^3968^Global atmospheric CO2 is increasing at a rate of 1.5-2 ppm per year and is predicted to double by the end of the n}5ext century. Understanding how terrestrial ecosystems will respond in this changing environment is an important goal of cu}6rrent research. Here we present results from a field study of elevated CO2 in a California annual grassland. Elevated CO2 7led to lower leaf- level stomatal conductance and transpiration (approximately 50%) and higher mid-day leaf water potentia8ls (30-35%) in the most abundant species of the grassland, Avena barbata Brot. Higher CO2 concentrations also resulted in }9greater midday photosynthetic rates (70% on average). The effects of CO2 on stomatal conductance and leaf water potential }:decreased towards the end of the growing season, when Avena began to show signs of senescence. Water-use efficiency was ap~;proximately doubled in elevated CO2, as estimated by instantaneous gas-exchange measurements and seasonal carbon isotope d~577^2^McKee,IF^Woodward,FI^1994^1^Co2 enrichment responses of wheat - interactions with temperature, nitrate and phosphate~'^84^127^3^447-453^^^^^Jul^^^^^3971ANT CELL AND ENVIRONMENT SN 0140-7791 C1 INST ENVIRONM ANAL & REMOTE SENSING AGR, NATL ~)@A^3970^Rising levels of atmospheric CO2, climate change, and fertilizer pollution provide the ecological imperative for in~/Avestigating the interaction between plant responses to atmospheric CO2 concentration, temperature and nutrient supply. In ~1Bthis study spring wheat (Triticum aestivum L. cv. Wembley) was grown at 40, 50, 60 and 70 Pa atmospheric CO2 pressure and Cthree experiments were conducted to investigate interactions between growth responses to the CO2 treatment and: (i) temperDature (24/16 degrees C vs. 18/10 degrees C - day/night), (ii) nutrient solution nitrate concentration (2.5, 5, 10 and 15 m~[EM Ca(NO3)(2).4H(2)O), and (iii) phosphate concentration (0.025 and 0.5 mM KH2PO4). Dry mass and root/shoot ratio increased~]F with CO2 level at the higher temperature. These responses were reversed at the lower temperature. The increase in yield w~mGith CO2 enhancement was limited by low rates of nutrient supply in both absolute and relative terms. In the elevated CO2 t~oHreatments, the shoot nitrogen concentration was reduced, as was the proportional allocation to the uppermost leaves. These~I results are discussed with respect to possible physiological mechanisms and potential for improved crop performance in a ~future, elevated CO2 world.LL ENVIRON ER PT J AU MORSE, SR WAYNE, P MIAO, SL BAZZAZ, FA TI ELEVATED CO2 AND DROUGHT ALTE~K578^4^Morgan,JA^Hunt,HW^Monz,CA^Lecain,DR^1994^1^Consequences of growth at 2 carbon-dioxide concentrations and 2 temperatu~res for leaf gas-exchange in pascopyrum-smithii (C-3) and bouteloua-gracilis (C-4)^9^17^9^1023-1033^^^^^Sep^^^^^3973DIOXI~MA^3972^Continually rising atmospheric CO2 concentrations and possible climatic change may cause significant changes in pla~Nnt communities. This study was undertaken to investigate gas exchange in two important grass species of the short-grass st~Oeppe, Pascopyrum smithii (western wheatgrass), C-3, and Bouteloua gracilis (blue grama), C4, grown at different CO2 concen~Ptrations and temperatures. Intact soil cores containing each species were extracted from grasslands in north-eastern Color~Qado, USA, placed in growth chambers, and grown at combinations of two CO2 concentrations (350 and 700 mu mol mol(-1)) and ~Rtwo temperature regimes (field average and elevated by 4 degrees C). Leaf gas exchange was measured during the second, thi~Srd and fourth growth seasons. All plants exhibited higher leaf CO2 assimilation rates (A) with increasing measurement CO2 ~Tconcentration, with greater responses being observed in the cool-season C-3 species P. smithii. Changes in the shape of in~Utercellular CO2 response curves of A for both species indicated photosynthetic acclimation to the different growth environ~Vments, The photosynthetic capacity of P. smithii leaves tended to be reduced in plants grown at high CO2 concentrations, a~Wlthough A for plants grown and measured at 700 mu mol mol(-1) CO2 was 41% greater than that in plants grown and measured a~Xt 350 mu mol mol(-1) CO2. Low leaf N concentration may have contributed to photosynthetic acclimation to CO2. A severe red~Yuction in photosynthetic capacity was exhibited in P. smithii plants grown long-term at elevated temperatures. As a result~Z, the potential response of photosynthesis to CO2 enrichment was reduced in P. smithii plants grown long-term at the highe~r temperature.ND CARBON-DIOXIDE CONCENTRATIONS OF SOILS AS INFLUENCED BY RHIZOSPHERE OF CROPS UNDER FIELD AND POT CONDITI~\579^1^Mortensen,LM^1994^1^Effects of elevated co2 concentrations on growth and yield of 8 vegetable species in a cool clim ate^165^58^3^177-185^^^^^Jul^^^^^3975MAYS ID ROOTS; BIOSYNTHESIS; ACCUMULATION; RESPONSES; OXYGEN AB A method for collect ^A^3974^The effects of elevated CO2 concentrations on the yield of Allium cepa (onion), Allium ampeloprasum (leek), Apium g_raveolens var. dulce (celery), Apium graveolens var. rapaceum (celery root), Brassica pekinensis (chinese cabbage), Daucus` carota (carrot), Lactuca sativa (lettuce) and Petroselinum crispum (parsley) grown in containers, were studied in SiX 9-M0a2 large field plots surrounded by 1.8-m high plastic foil walls ('field chambers'). Three of the chambers were supplied wi3bth pure CO2 gas through perforated tubes. Increasing the CO2 concentration from ambient (355 mumol mol-1) to 800-900 mumolAc mol-1 increased the yield (fresh weight) by 23% in onion (two cultivars) and by 8% in carrot (three cultivars). The dry wDdeight based yield increase was 18% in lettuce (three cultivars), 19% in carrot and 17% in parsley (one cultivar). The yielSeds of leek (two cultivars), chinese cabbage (three cultivars), celery (one cultivar) and celery root (one cultivar) were nUfot significantly affected by the CO2 concentration. Generally, no 'chamber effect' was found on the yields of the differenct species.993 PD MAR VL 150 IS 2 GA LQ501 RP OTANI T J9 PLANT SOIL ER PT J AU OVERDIECK, D TI EFFECTS OF ATMOSPHERIC CO2eh580^2^Oechel,WC^Vourlitis,GL^1994^1^The effects of climate-change on land atmosphere feedbacks in arctic tundra regions^57n^9^9^324-329^^^^^Sep^^^^^3977 OKOL, KONIGIN LUISE STR 22, W-1000 BERLIN 33, GERMANY. ID ELEVATED CARBON-DIOXIDE; SEEDLINGpjA^3976^Recently reported high-latitude warming has the potential to affect arctic ecosystem structure and function in the kshort and long term. Arctic ecosystems are known sources of atmospheric CH4, and recent CO2 flux measurements indicate thalt these ecosystems are now, at least regionally, net sources of atmospheric CO2. It appears that over the short term (decamdes to centuries), arctic ecosystems may represent a positive feedback on global atmospheric CO2 concentrations and associnated greenhouse gas-induced climate change. In addition, short-term feedbacks may be large enough to affect both local ando global surface temperatures. Over the long term, changes in the structure, function and composition of arctic ecosystems may increase C accumulation relatively more than the amount lost, thus restoring the sink status of arctic ecosystems. anq581^5^Rouhier,H^Billes,G^Elkohen,A^Mousseau,M^Bottner,P^1994^1^Effect of elevated co2 on carbon and nitrogen distribution within a tree (castanea-sativa mill) soil system^206^162^2^281-292^^^^^May^^^^^3979m diameter (2 cm above the first latersA^3978^Two-year-old sweet chestnut trees were grown outside in normal or double CO2 atmospheric concentration. In spring atnd in autumn of two growing seasons, a six day labelling pulse of C- 14 labelled CO2 was used to follow the carbon assimiluation and distribution in the plant-soil system. Doubling atmospheric CO2 had a significant effect on the tree net carbon vuptake. A large proportion of the additional C uptake was 'lost' through the root system. This suggests that increased C uwptake under elevated CO2 conditions increases C cycling without necessarily increasing C storage in the plant. Total root xderived material represented a significant amount of the 'extra-assimilated' carbon due to the CO2 treatment and was stronygly correlated with the phenological stage of the tree. Increasing root rhizodeposition led to a stimulation of microbial zactivity, particularly near the end of the growing season. When plant rhizodeposition was expressed as a function of the r {oot dry weight, the effect of increasing CO2 resulted in a higher root activity. The C to N ratios were significantly high |er for trees grown under elevated CO2 except for the fine root compartment. An evaluation of the plant-soil system nitroge}n dynamics showed, during the second season of CO2 treatment, a decrease of soil N mineralization rate and total N uptake !for trees grown at elevated CO2 levels. are compared by means of mathematical modelling procedures in order to quantify C-582^5^Santrucek,J^Santruckova,H^Kveton,J^Simkova,M^Rohacek,K^1994^1^The effect of elevated co2 concentration on photosynth/etic co2 fixation, respiration and carbon economy of wheat plants^239^40^8^689-696^^^^^^^^^^3981ND ABOVEGROUND AND BELOWG;A^3980^Winter wheat plants were grown under controlled atmospheric and light conditions for 25 days to assess the response= of photosynthesis, respiration and carbon allocation to elevated ambient CO2 concentration. Daily balance of carbon fixatFion and loss was measured separately for shoots and roots including root exudation. Doubled CO2 (700 mumol CO2 mol-1) stimHulated photosynthetic CO2 uptake and dark respiration rate when calculated on the leaf area basis. However, total daily caWrbon gain per plant and total dry matter of shoot was lower for high-CO2-grown plants due to reduced leaf area. After 23 dZays of exposition to high CO2, photosynthesis was depressed probably due to limiting regeneration of ribulose bisphosphateg. Both stomatal resistance and water use efficiency were markedly higher in high-CO2-grown plants. Higher evaporative demaind in low-CO2-grown plants promoted root elongation. Total root length was 160% of that in high-CO2-grown plants. Root exuzdation of high-CO2-grown plants was higher in the first days of plant development, but the inhibition of net photosynthesi|s was followed by a decrease in exudation.more of the plant biomass directly into the detrital food chain, thereby slowin583^2^Taylor,J^Ball,AS^1994^1^The effect of plant-material grown under elevated co2 on soil respiratory activity^206^162^2^315-318^^^^^May^^^^^3983oil Pollut. PY 1993 PD OCT VL 70 IS 1-4 GA LZ846 RP OWENSBY CE J9 WATER AIR SOIL POLLUT ER PT JA^3982^The biodegradability of aerial material from a C4 plant, sorghum grown under ambient (345 mu mol mol(-1)) and elevated (700 mu mol mol(-1)) atmospheric CO2 concentrations were compared by measuring soil respiratory activity. Initial daily respiratory activity (measured over 10 h per day) increased four fold from 110 to 440 cm(3) CO2 100g dry weight soil(-1) in soils amended with sorghum grown under either elevated or ambient CO2. Although soil respiratory activity decreased over the following 30 days, respiration remained significantly higher (t-test; p>0.05) in soils amended with sorghum grown under elevated CO2 concentrations. Analysis of the plant material revealed no significant differences in C:N ratios between sorghum grown under elevated or ambient CO2. The reason for the differences in soil respiratory activity have yet to be elucidated. However if this trend is repeated in natural ecosystems, this may have important implications for C and N cycling. ground biomass were estimated by periodic sampling throughout the growing season in 1989 and 1990. In 1991, N and P c584^2^Thompson,GB^Drake,BG^1994^1^Insects and fungi on a C-3 sedge and a C-4 grass exposed to elevated atmospheric co2 concentrations in open-top chambers in the field^9^17^10^1161-1167^^^^^Oct^^^^^3985 the growing season. Total N and P in aboA^3984^The effects of elevated atmospheric CO2 concentration on plant- fungi and plant-insect interactions were studied in an emergent marsh in the Chesapeake Bay. Stands of the C-3 sedge Scirpus olneyi Grey. and the C-4 grass Spartina patens (Ait.) Muhl. have been exposed to elevated atmospheric CO2 concentrations during each growing season since 1987. In August -1991 the severities of fungal infections and insect infestations were quantified. Shoot nitrogen concentration ([N]) and w.ater content (WC) were determined. In elevated concentrations of atmospheric CO2, 32% fewer S. olneyi plants were infested4 by insects, and there was a 37% reduction in the severity of a pathogenic fungal infection, compared with plants grown in7 ambient CO2 concentrations. S. olneyi also had reduced [N], which correlated positively with the severities of fungal infections and insect infestations. Conversely, S. patens had increased WC but unchanged [N] in elevated concentrations of atmospheric CO2 and the severity of fungal infection increased. Elevated atmospheric CO2 concentration increased or decreaseOd the severity of fungal infection depending on at least two interacting factors, [N] and WC; but it did not change the nuQmber of plants that were infected with fungi. In contrast, the major results for insects were that the number of plants in^fected with insects decreased, and that the amount of tissue that each insect ate also decreased.NDIA. DE HYPERAMMONEMIA;`585^3^Vanoosten,JJ^Wilkins,D^Besford,RT^1994^1^Regulation of the expression of photosynthetic nuclear genes by co2 is mimi>cked by regulation by carbohydrates - a mechanism for the acclimation of photosynthesis to high co2^9^17^8^913-923^^^^^AugL^^^^^3987somal enriched fractions of rat cerebral cortex. Production of (CO2)-C-14 from [U-C-14] glucose was enhanced in A^3986^The abundance of transcripts of cab-7 and cab-3C, which code for the chlorophyll a/b binding proteins of the light- harvesting complexes I and II, respectively, and the abundance of transcripts of Rca, which encodes Rubisco activase, wer<e reduced in tomato plants exposed to high CO2 for up to 9d, whereas the abundance of mRNA from psa A-psa B and psb A, whi@ch encode the proteins of the core complex of PSI and the D1 protein of PSII, respectively, and the abundance of glycolate oxidase, which is involved in photorespiration, were not affected. However, the abundance of the transcript for the B subdunit of ADP-glucose pyrophosphorylase was increased after 1 d at elevated CO2. The chlorophyll am ratio decreased significdantly over 9 d of exposure to elevated CO2. The responses of the nuclear genes to high CO2 were enhanced when leaves were Jzdetached so as to deprive them of any major sink. The responses of these transcripts to high CO2 were mimicked when sucrosJ|e or glucose was supplied to the leaf tissue, whereas acetate or sorbitol had no effect. Carbohydrate analyses of leaves gGrown in high CO2 or supplied with sucrose revealed that major increases occurred in the amount of glucose and fructose. BaIsed on these and other published data, a molecular model involving the repression or activation of the transcription of nu}clear genes coding for chloroplast proteins by photosynthetic end-products is proposed to account for photosynthetic accli}mation to high CO2 in tomato plants and other species., GERMANY. DE METHANOGENESIS; GIBBS FREE ENERGY; LITTORAL SEDIMENT;f586^3^Bassow,SL^McConnaughay,KDM^Bazzaz,FA^1994^1^The response of temperate tree seedlings grown in elevated co2 to extremfe temperature events^56^4^3^593-603^^^^^Aug^^^^^3989URE; ENERGETICS; TURNOVER AB In anoxic methanogenic sediments organicA^3988^Mean global temperatures have been predicted to increase in the next century, if so the frequency of extreme temper!ature events may also increase. Extreme temperatures may damage plant tissue and consequently limit the survival of certaifn plant species in a region. Elevated concentrations of CO2 in the atmosphere alter plant allocation, physiology, and growfth, and may accentuate or ameliorate the damage from extreme temperatures. In this paper we explore the interactive effectfs of atmospheric CO2 concentration, nutrient levels, and exposure to extreme temperatures on seedlings of three species off temperate deciduous trees. A1-d exposure to extreme heat (45-degrees-C) significantly decreased conductance the following~A day and decreased biomass as measured at both 35 and 105 d following the extreme temperature event, regardless of atmosph~Ceric CO2 concentration. The most shade-tolerant species, striped maple, was most severely impacted by the extreme heat eve}nt in both CO2 environments. Furthermore, striped maple seedlings grown in elevated CO2 concentrations had a significantly} greater decrease in biomass due to the extreme heat event as compared with striped maple plants grown in ambient CO2 conc}entrations at 35 d after the heat event; however, al the end of the growing season at 105 d post treatment, this differenc}e was not significant. A one-night exposure to low temperatures (4- degrees-C) did not affect biomass for any of these spehcies. With an increase in global mean temperatures, the frequency of extreme temperature events, particularly hot weather hevents, may increase and may extend to shaded understory sites. If the frequency of extremely high temperatures increases,h the role that temperature extremes may play in changing competitive interactions and thus affecting community compositionh may increase in importance, as these temperatures appear to severely alter plant survival and growth in some species.ITE587^3^Berryman,CA^Eamus,D^Duff,GA^1994^1^Stomatal responses to a range of variables in 2 tropical tree species grown with co2, enrichment^78^45^274^539-546^^^^^May^^^^^3991es supracrustal belt of southern Kerala suggest paleo-fluid channels. WA^3990^Seedlings of Maranthes corymbosa (Blume) and Eucalyptus tetrodonta (F. Muell) were grown with or without CO2 enrichment (700 mu mol CO2 mol(-1)). The response of stomatal conductance (g(s)) to leaf drying, exogenous abscisic acid and calcium ions was investigated in M. corymbosa. Reciprocal transfer experiments were also conducted whereby plants were grown in one treatment and then transferred to the other before g(s) was measured. Stomatal conductance in M. corymbosa was more sensitive (a greater percentage decline in g(s) per unit percentage decline in leaf fresh weight) to leaf water status under conditions of CO2 enrichment compared to ambient conditions. However, the rate of reduction of g(s) in response to exogenous abscisic acid was not influenced by CO2 treatment. In contrast, the rate of reduction of g(s) in response to exogenous CaCl2 was decreased under conditions of CO2 enrichment. Reciprocal transfer experiments showed that exposure to CO2 enrichment results in a short-term, reversible decline in g(s) as a result of decreased stomatal aperture and a long-term, irreversible decline in g(s) as a result of a decreased stomatal density. Seedlings of E. tetrodonta were used to investigate the response of g(s) to light flux density, leaf-to-air vapour pressure difference (LAVPD), leaf internal CO2 concentration (C-i) and temperature. Reciprocal transfer experiments were also conducted. CO2 enrichment did not influence the pattern or sensitivity of response of g(s) to LAVPD and C-i in E. tetrodonta. In contrast, the slope of the response of g(s) to temperature decreased for trees grown under elevated [CO2](a) conditions and the equilibrium g(s) attained at saturating light was also decreased for plants grown under elevated [CO2](a) conditions.CARBON FIXATION; SEMICONTINUOUS CULTURE AB 588^4^Callaway,RM^Delucia,EH^Thomas,EM^Schlesinger,WH^1994^1^Compensatory responses of co2 exchange and biomass allocation and their effects on the relative growth-rate of ponderosa pine in different co2 and temperature regimes^2^98^2^159-166^^^^^Jul^^^^^3993 on specific growth rate was determined and formulated using a semi-continuous culture system. The specifiA^3992^Increases in the concentration of atmospheric carbon dioxide may have a fertilizing effect on plant growth by increasing photosynthetic rates and therefore may offset potential growth decreases caused by the stress associated with higher temperatures and lower precipitation. However, plant growth is determined both by rates of net photosynthesis and by proportional allocation of fixed carbon to autotrophic tissue and heterotrophic tissue. Although CO2 fertilization may enhance) growth by increasing leaf-level assimilation rates, reallocation of biomass from leaves to stems and roots in response to+ higher concentrations of CO2 and higher temperatures may reduce whole-plant assimilation and offset photosynthetic gains.1 We measured growth parameters, photosynthesis, respiration, and biomass allocation of Pinus ponderosa seedlings grown for3 2 months in 2 x 2 factorial treatments of 350 or 650mu bar CO2 and 10/25-degrees-C or 15/30-degrees-C night/day temperatuCres. After 1 month in treatment conditions, total seedling biomass was higher in elevated CO2, and temperature significantEly enhanced the positive CO2 effect. However, after 2 months the effect of CO2 on total biomass decreased and relative groWwth rates did not differ among CO2 and temperature treatments over the 2-month growth period even though photosynthetic raYtes increased almost-equal-to 7% in high CO2 treatments and decreased almost- equal-to 10% in high temperature treatments.h Additionally, CO2 enhancement decreased root respiration and high temperatures increased shoot respiration. Based on CO2 jexchange rates, CO2 fertilization should have increased relative growth rates (RGR) and high temperatures should have decrxeased RGR. Higher photosynthetic rates caused by CO2 fertilization appear to have been mitigated during the second month ozf exposure to treatment conditions by a almost-equal-to 3% decrease in allocation of biomass to leaves and a almost-equal-to 9% increase in root:shoot ratio. It was not clear why diminished photosynthetic rates and increased respiration rates at high temperatures did not result in lower RGR. Significant diametrical and potentially compensatory responses of CO2 exchange and biomass allocation and the lack of differences in RGR of ponderosa pine after 2 months of exposure of high CO2 indicate that the effects of CO2 fertilization and temperature on whole-plant growth are determined by complex shifts in biomass allocation and gas exchange that may, for some species, maintain constant growth rates as climate and atmospheric CO2 concentrations change. These complex responses must be considered together to predict plant growth reactions to global atmospheric change, and the potential of forest ecosystems to sequester larger amounts of carbon in the future.M, INST LIF589^3^Delucia,EH^Callaway,RM^Schlesinger,WH^1994^1^Offsetting changes in biomass allocation and photosynthesis in ponderosa pine (pinus-ponderosa) in response to climate-change^13^14^7-9^669-677^^^^^Jul-Sep^^^^^3995respiration and growth of LeA^3994^We examined the effect of climate on aboveground biomass allocation of ponderosa pine (Pinus ponderosa) by measuring trees in disjunct forest stands growing on the same substrate at high-elevation montane sites and low-elevation desert sites. Climatic differences between the sites were comparable to the difference between present and future climates of interior North America that is expected to result from a doubling of atmospheric CO2 concentration. Relative to the montane populations, the desert populations allocated a greater proportion of biomass to sapwood (functional xylem) at the expense of foliage. The leaf/sapwood area ratio and percent of aboveground biomass in sapwood for trees of the same height were 0.201 m2 cm-2 and 58% for montane trees and 0.104 m2 cm-2 and 71% for desert trees. In a phytotron experiment, increases in net photosynthesis and net assimilation rate for seedlings grown under future conditions of high CO2 and temperature were offset by a decrease in leaf area ratio. As was observed for large trees at different elevations, increased temperatures ca!used an increase in biomass allocation to stem in the phytotron seedlings. Thus, CO2- and temperature-driven shifts in bio#mass allocation negated the effect on growth of the CO2- driven increase in carbon assimilation rate. Our data from the co2ntrolled growth chamber and field experiments suggest that future climate conditions, including elevated atmospheric CO2, 4may not stimulate growth and productivity of ponderosa pine.ither low (0.005 to 0.3 W M-2) or high (0.25 to 0.90 W M- 2) @590^2^Elkohen,A^Mousseau,M^1994^1^Interactive effects of elevated co2 and mineral-nutrition on growth and co2 exchange of Asweet chestnut seedlings (castanea- sativa)^13^14^7-9^679-690^^^^^Jul-Sep^^^^^3997 CO2 and UV treatments decreased the dCA^3996^The effects of elevated atmospheric CO2 (700 mumol mol-1) and fertilization were investigated on 2-year-old sweet cXhestnut (Castanea sativa Mill.) seedlings grown outdoors in pots in constantly ventilated open-sided chambers. Plants wereZ divided into four groups: fertilized controls (+F/-CO2), unfertilized controls (-F/-CO2), fertilized + CO2-treated plantsk (+F/+CO2) and unfertilized + CO2-treated plants (-F/+CO2). Dry matter accumulation and allocation were measured after onem growing season and CO2 exchange of whole shoots was measured throughout the growing season. Shoot growth and total leaf area of unfertilized plants were not affected by elevated CO2, whereas both parameters were enhanced by elevated CO2 in fertilized plants. Elevated CO2 increased total biomass by about 20% in both fertilized and unfertilized plants; however, bio mass partitioning differed. In unfertilized plants, elevated CO2 caused an increase in root growth, whereas in fertilized  plants, it stimulated aboveground growth. At the whole-shoot and leaf levels, photosynthetic activity of both fertilized a nd unfertilized plants increased in response to elevated CO2, but the seasonal pattern of this enhancement varied with nut rient treatment. In unfertilized plants, a downward acclimation of photosynthesis was observed early in the season (June), and was related to reductions in nitrogen and chlorophyll content and to starch accumulation. The decrease in the slope of the A/Ci curve suggested a decrease in Rubisco activity. In both fertilized and unfertilized plants, shoot respiration decreased during the night in response to elevated CO2 until mid-July. The decrease was not related to changes in sugar concentration.ts per thousand, after acetate depletion. The deltaC- 13 value of CH4 from CO2/H-2 reduction was estimated to 591^4^Epron,D^Dreyer,E^Picon,C^Guehl,JM^1994^1^Relationship between co2-dependent o-2 evolution and photosystem-II activity in oak (quercus-petraea) trees grown in the field and in seedlings grown in ambient or elevated co2^13^14^7-9^725-733^^^^^Jul-Sep^^^^^3999dmembers of CH4, the change of acetate contribution for CH4 production was calculated: less than 12% unA^3998^The light-response of the apparent quantum yield of photosynthetic O2 evolution (PHI(O2)) under non- photorespiratory conditions was measured together with the photochemical efficiency Of PS II (DELTAF/F(m)'), the photochemical efficiency of open PS II reaction centers (F(v)'/F(m)') and the photochemical fluorescence quenching (q(p)) of leaf disks punched from oak leaves of seedlings grown in ambient (350 mumol mol-1) or elevated (700 mumol mol- 1) CO2 in a greenhouse, and from sunlit leaves of mature oak trees (Quercus petraea (Matt.) Liebl.). There were marked differences between seedlings and trees. In seedlings, CO2 concentration during growth did not modify the light response of photosynthesis or PS II activity. There was a single linear relationship between PHI(O2) and DELTAF/F(m)' in seedling leaves that was independent of the CO2 concentration imposed during growth. In contrast, this relationship was curvilinear in sunlit leaves of adult trees. In seedling leaves, the decrease in q(p) (i.e., the proportion of open PS II reaction centers) largely accounted for the decrease in DELTAF/F(m)', whereas the decrease in DELTAF/F(m)' in sunlit leaves of mature oak trees was dependent on both q(p) and F(v)'/F(m)'.eaf development, whereas CO2 enrichment 10 to 20 days earlier halted the development of adventitious sh592^2^Gloser,J^Bartak,M^1994^1^Net photosynthesis, growth-rate and biomass allocation in a rhizomatous grass calamagrostis%-epigejos grown at elevated co2 concentration^79^30^1^143-150^^^^^^^^^^4001JI J. Jpn. Soc. Hortic. Sci. PY 1993 PD SEP VL&!A^4000^Young plants of Calamagrostis epigejos (L.) Roth were grown in controlled environments with two regimes of CO2 in t,"he air: normal (350 cm(3) m(-3)) and elevated (700 cm(3) m(-3)). The relative growth rate of plants grown at elevated CO2 /#was increased by about 20 % in comparison with control plants cultivated at ambient CO2 concentration. Partitioning of ass<$imilates into roots (+ rhizomes) and shoots was the same in both treatments. Slightly lower values of specific leaf area, >%leaf mass ratio and leaf area ratio were found in the plants grown at elevated CO2. The net photosynthetic rate (P-N) was L&measured gasometrically in plants from both treatments at 350 and 700 cm(3) m(-3) CO2 in the leaf chamber. There were no sN'ignificant differences between plants grown at either CO2 concentration in their responses to radiation and CO2 conditions_( during measurements, i.e., no regulation of photosynthetic processes in response to elevated CO2 was detectable. P-N at sa)aturating irradiance and maximum apparent quantum yield of photosynthesis were always considerably higher at doubled CO2 choncentration during measurements.reased % shoot water contents. At elevated atmospheric CO2 concentrations, where plant nj+593^4^Guehl,JM^Picon,C^Aussenac,G^Gross,P^1994^1^Interactive effects of elevated co2 and soil drought on growth and transpriration efficiency and its determinants in 2 european forest tree species^13^14^7-9^707-724^^^^^Jul-Sep^^^^^4003ly treatmu-A^4002^The responses of growth and transpiration efficiency (W = biomass accumulation/water consumption) to ambient and el.evated atmospheric CO2 concentrations (350 and 700 mumol mol-1, respectively) were investigated under optimal nutrient sup/ply in well-watered and in drought conditions in two temperate- forest tree species: Quercus petraea Liebl. and Pinus pina0ster Ait. Under well-watered conditions, doubling the CO2 concentration for one growing season increased biomass growth by1 138% in Q. petraea and by 63% in P. pinaster. In contrast, under drought conditions, elevated CO2 increased biomass growt2h by only 47% in Q. petraea and had no significant effect on biomass growth in P. pinaster. Transpiration efficiency was h3igher in Q. petraea than in P. pinaster in all treatments. This difference was linked (i) to lower carbon isotope discrimi4nation (DELTA), and thus lower values of the intercellular/ambient CO2 concentration (c(i)/c(a)) ratio, in Q. petraea, (ii5) to lower values of leaf mass ratio (LMR, leaf mass/whole plant mass), which we suggest was positively related to the pro6portion of daytime carbon fixation lost by respiration (PHI), in Q. petraea, and (iii) to slightly lower C concentrations 7in Q. petraea than in P. pinaster. The CO2- promoted increase in W was higher in Q. petraea (+80%) than in P. pinaster (+580%), and the difference was associated with a more pronounced decrease in PHI in response to elevated CO2 in Q. petraea th9an in P. pinaster, which could be linked with the N dilution effect observed in Q. petraea. Because PHI also directly affe:cts growth, the CO2-induced enhancement of PHI in Q. petraea is a crucial determinant of the growth stimulation observed i;n this species. Leaf gas exchange regulation was not the only factor involved in the responses of growth and W to elevated CO2 and drought, other physiological processes that have crucial roles include carbon and N allocation and respiration.s=594^2^Israel,AA^Nobel,PS^1994^1^Activities of carboxylating enzymes in the cam species opuntia- ficus-indica grown under c urrent and elevated co2 concentrations^91^40^3^223-229^^^^^Jun^^^^^4005iron. PY 1993 PD SEP VL 16 IS 7 GA LZ893 RP TISSUE ?A^4004^Responses of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPCase@) to an elevated atmospheric CO2 concentration were determined along with net CO2 uptake rates for the Crassulacean acid mAetabolism species Opuntia ficus-indica growing in open-top chambers. During the spring 13 months after planting, total dai+Bly net CO2 uptake of basal and first-order daughter cladodes was 28% higher at 720 than at 360 mu l CO2 1(-1). The enhance-Cment, caused mainly by higher CO2 assimilation during the early part of the night, was also observed during late summer (57D months after planting) and the following winter. The activities of Rubisco and PEPCase measured in vitro were both lower 9Eat the elevated CO2 concentration, particularly under the more favorable growth conditions in the spring and late summer. BFEnzyme activity in second-order daughter cladodes increased with cladode age, becoming maximal at 6 to 10 days. The effectEG of elevated CO2 on Rubisco and PEPCase activity declined with decreasing irradiance, especially for Rubisco. Throughout tWHhe 13-month observation period, O. ficus-indica thus showed increased CO2 uptake when the atmospheric CO2 concentration waYs doubled despite lower activities of both carboxylating enzymes. well as the combined processes. The aim of this paper igJ595^2^McKee,IF^Woodward,FI^1994^1^The effect of growth at elevated co2 concentrations on photosynthesis in wheat^9^17^7^85j3-859^^^^^Jul^^^^^4007er use efficiency, CO2 fertilization decreases net C emissions, while changed decomposition rates s~LA^4006^Rising levels of atmospheric CO2 will have profound, direct effects on plant carbon metabolism. In this study we usMed gas exchange measurements, models describing the instantaneous response of leaf net CO2 assimilation rate (A) to intercNellular CO2 partial pressure (C-i), in vitro enzyme activity assay, and carbohydrate assay in order to investigate the phoOtosynthetic responses of wheat (Triticum aestivum L., cv. Wembley) to growth under elevated partial pressures of atmospherPic CO2 (C- a). At flag leaf ligule emergence, the modelled, in vivo, maximum carboxylation velocity for RuBisCO was signifQicantly lower in plants grown at elevated C-a than in plants grown at ambient C-a (70 Pa compared with 40 Pa). By 12 d aftRer ligule emergence, no significant difference in this parameter was detectable. At ligule emergence, plants grown at elevSated C-a exhibited reduced in vitro initial activities and activation states of RuBisCO. At their respective growth C-i vaTlues, the photosynthesis of 40-Pa-grown plants was sensitive to p(O-2) and to p(CO2), whereas that of 70-Pa-grown plants wUas insensitive. Both sucrose and starch accumulated more rapidly in the leaves of plants grown at 70 Pa. At flag leaf liguVle emergence, modelled non-photorespiratory respiration in the light (R(d)) was significantly higher in 70-Pa-grown plants than in 40-Pa-grown plants. By 12 d after ligule emergence no significant differences in R(d) were detectable.ical technX596^7^Murray,MB^Smith,RI^Leith,ID^Fowler,D^Lee,HSJ^Friend,AD^Jarvis,PG^1994^1^Effects of elevated co2, nutrition and climaYtic warming on bud phenology in sitka spruce (picea-sitchensis) and their impact on the risk of frost damage^13^14^7-9^691-706^^^^^Jul-Sep^^^^^4009e increase for 100- to 150- year-old trees is approximately 45%, while the increase for 200- to [A^4008^Effects of elevated CO2, clone and plant nutrition on bud dormancy of Sitka spruce (Picea sitchensis (Bong.) Carr.)\ were examined. Sitka spruce seedlings were fumigated with ambient or elevated (ambient + 350 mumol mol-1) concentrations ]of CO2 in open-top chambers for three growing seasons. In 1991 and 1992, elevated CO2 delayed bud burst in the spring and ^advanced bud set in the autumn. The effect of the open-top chamber on the thermal requirement for bud burst was greater th_an the effect of elevated CO2 (50 and 30 day degrees (D(d)), respectively). In a second study, four clones of Sitka spruce` taken from two provenances, at 43 and 54-degrees-N, were fumigated with ambient or elevated CO2. There was a large natura!al variation in the timing of bud burst and bud set among the clones. Elevated CO2 had no effect on bud dormancy of the Ski#bdegate a clone, but it reduced the growing season of the North Bend b clone by 20 days. In a third study, Sitka spruce see/cdlings growing in ambient or elevated CO2, were supplied with one of three nutrient regimes, low (0.1 x potential), medium1d (0.5 x potential) or high (2.0 x potential), using a method and solution based on the Ingestad technique. Elevated CO2 di;ed not affect bud dormancy in the high-nutrient treatment, but it reduced the growing season of plants in the low-nutrient =ftreatment by 22 days. Increasing plant nutrient supply lengthened the growing season, plants flushed earlier in the springIg and set bud later in the autumn. The effects of elevated CO2 plus a 0, 2 or 4-degrees-C climatic warming on the timing ofLh bud burst and the subsequent risk of frost damage were assessed using a simulation model and meteorological data from thrXiee sites, Edinburgh, Braemar and Masset. The model predicted that (i) doubling the CO2 concentration in die absence of cliZjmatic warming, will delay the onset of bud burst at all three sites, (ii) climatic warming in ambient CO2 will hasten bud rkburst and (iii) climatic warming in elevated CO2 will hasten bud burst at Edinburgh and Braemar but to a lesser extent thatln climatic warming alone. At Masset, a 4-degrees-C warming was required to advance the date of bud burst of seedlings in tmhe elevated CO2 treatment. At all three sites, elevated CO2 and climatic warming increased the mean daily temperature on the date of bud burst, thus reducing the risk of subsequent frost damage.) were unexpected and pose interesting considerato597^2^Overdieck,D^Forstreuter,M^1994^1^Evapotranspiration of beech stands and transpiration of beech leaves subject to atmospheric co2 enrichment^13^14^7-9^997-1003^^^^^Jul-Sep^^^^^4011PHYSIOL ER qA^4010^Beech trees (Fagus sylvatica L.) show reduced stomatal conductance and increased leaf area index in response to incrreased atmospheric CO2 concentration. To determine whether the reduction in stomatal conductance results in lower stand evsapotranspiration, we compared transpiration on a leaf-area basis and stand evapotranspiration on a ground-area basis in yotung European beech trees growing in greenhouses at ambient (360 +/- 34 mumol mol-1) and elevated (698 +/- 10 mumol mol-1) uCO2 concentrations. Trees were grown in homogenized natural soil at constant soil water supply for two growing seasons. Atv light saturation, leaf transpiration rates were, on average, 18% lower in the elevated CO2 treatment than in the ambient wC02 treatment. Mean transpiration coefficients (transpiration/net CO2 uptake) of leaves were 179 and 110 in the ambient anxd elevated CO2 treatments, respectively, indicating improved water use efficiency in trees in the elevated CO2 treatment. yTotal leaf conductance was decreased by 32% at light saturation. The elevated CO2 treatment resulted in a 14% reduction inz stand evapotranspiration. In both CO2 treatments, evapotranspiration increased linearly at a rate of 0.2 kg H2O m-2 day-1{ for each 1-degrees-C rise in air temperature between 14 and 25-degrees-C. We conclude that, under Central European conditions, water losses from deciduous forest stands will be reduced by a doubling of tropospheric CO2 concentration.33}598^2^Roth,SK^Lindroth,RL^1994^1^Effects of co2-mediated changes in paper birch and white-pine chemistry on gypsy-moth performance^2^98^2^133-138^^^^^Jul^^^^^4013JjwV1!:!@!Z!b!i!o!v!!!A^4012^We examined the effects of CO2-mediated changes in the foliar chemistry of paper birch (Betula papyrifera) and white pine (Pinus strobus) on performance of the gypsy moth (Lymantria dispar). Trees were grown under ambient or enriched CO2 conditions, and foliage was subjected to plant chemical assays and insect bioassays. Enriched CO2 atmospheres reduced foliar nitrogen levels and increased condensed tannin levels in birch but not in pine. Foliar carbohydrate concentrations wer+e not markedly altered by CO2 environment. Gypsy moth performance was significantly affected by CO2 level, species, and th-e CO2 x species interaction. Under elevated CO2 conditions, growth was reduced for larvae fed birch, while development was8 prolonged for larvae fed pine. Although gypsy moths performed better overall on birch than pine, birch-fed larvae were in:fluenced more by CO2-mediated changes in host quality.4456:::::::; ;;;D599^4^Rufty,TW^Thomas,RB^Cure,JD^Cure,WW^1994^1^Growth-response of cotton to co2 enrichment in differing light environmentFs^37^91^3^503-509^^^^^Jul^^^^^4015YA^4014^Experiments were conducted to examine the growth responses of cotton (Gossypium hirsutum L. cv. Coker 315) to CO2 e[nrichment under different light regimes. Plants were exposed to 350 or 700 mu l(-1) CO2 and six light treatments differingj in photosynthetic period length (8 or 16 h) and in photosynthetic photon flux density (PPFD) for 32 days of vegetative grlowth. Higher PPFD (1100 mu mol m(-2) s(-1)) was provided by a combination of high intensity discharge and incandescent lamyps (HID), and lower PPFD (550 mu mol m(-2) s(-1)) was provided by fluorescent and incandescent lamps (F) or HID and incand{escent lamps with shade cloth (HIDs). Growth was generally much slower with the 8-h photosynthetic periods, but the growth stimulation by CO2 enrichment was larger than with 16-h photosynthetic periods. After 28 to 32 days of treatment, the growth enhancement with CO2 enrichment was 152 and 78% for 8- and 16-h photosynthetic periods, respectively, under HID; 100 and 77% in F, and 77 and 56% in HIDs. The higher PPFD of HID positively influenced the CO2 effect only at the slower growth rate in the 8-h light period. The stimulation of leaf area expansion by CO2 enrichment was also greater with the 8-h photosynthetic period for all light sources. These results, and others on net assimilation rate, shoot to root dry weight ratios and specific leaf weights, suggest that the growth response to CO2 enrichment with the longer photosynthetic period was depressed by limiting factors, perhaps nutritional, in the growth environment. The results also show that extensive variability in CO2 response can occur under light intensities which are often used in growth chamber experiments.[600^5^Segal,M^Alpert,P^Stein,U^Mandel,M^Mitchell,MJ^1994^1^Some assessments of the potential 2 X co2 climatic effects on water-balance components in the eastern mediterranean^50^27^4^351-371^^^^^Aug^^^^^4017A^4016^General circulation model (GCM) coarse evaluations of the climatological impact in the Eastern Mediterranean due to global doubling of the atmospheriC CO2 concentration were used as input for a preliminary estimation of modifications in local processes affecting the water balance in this region. It is suggested that: (i) in the 2 x CO2 climate the average regional change of precipitation associated with typical mid-winter cyclonic systems is relatively small, however, it is associated with redistribution of the regional rainfall; (ii) in the elevated terrain in the northern part of the region, daytime snowmelt due to warm air advection may be enhanced, as much as 2.8 cm per day; and (iii) transpiration in the coasta l area of the Eastern Mediterranean may increase by approximately 13% of its current level in the summer and somewhat more in the winter.601^3^Thomas,RB^Lewis,JD^Strain,BR^1994^1^Effects of leaf nutrient status on photosynthetic capacity in loblolly-pine (pinus-taeda L) seedlings grown in elevated atmospheric co2^13^14^7-9^947-960^^^^^Jul-Sep^^^^^4019vvvv+w*A^4018^We measured needle photosynthesis of loblolly pine seedlings grown in a factorial experiment with two CO2 partial p,ressures (35 and 65 Pa) and three nutrient treatments (7 mM NH4NO3 + 1 mM PO4; 7 mM NH4NO3 + 0.2 mM PO4; 1 mM NH4NO3 + 1 m:M PO4). The data were used to parameterize a physiologically based photosynthetic model that included limitations imposed <by ribulose-1,5-bisphosphate carboxylase/oxygenase activity, electron transport capacity and inorganic phosphate availabilKity. With nonlimiting nutrients, seedlings grown at 65 Pa CO2 had significantly higher net photosynthesis and lower stomatMal conductance than seedlings grown at 35 Pa CO2. Nutrient limitations by either N or P significantly reduced photosynthet^ic capacity. When either N or P was limiting, there was no effect of growth CO2 partial pressure on photosynthesis, but st`omatal conductance was significantly lower for seedlings grown at 65 Pa CO2. Modeled biochemical parameters suggest that, qin all cases, photosynthesis was co-limited by carboxylation, electron transport and phosphate regeneration. Acclimation tso growth in elevated CO2 involved a reduction in leaf N content. In the low-N and low-P treatments, modeled parameters indicated that the biochemical processes of photosynthesis were down regulated to the point that there was no effect of increasing CO2 partial pressure. The capacity to regenerate phosphate was reduced in both low nutrient treatments, but was only reduced by elevated C02 when seedlings were grown under low soil P conditions. Increased photosynthetic water use efficiency and nutrient use efficiency in response to CO2 enrichment occurred in all three nutrient treatments and have important implications for whole-plant water and nutrient balance. These data support the contention that soil nutrient status in forest ecosystems will be a critical influence on tree seedling response to increasing atmospheric CO2 partial pressures.602^2^Thompson,GB^Woodward,FI^1994^1^Some influences of co2 enrichment, nitrogen nutrition and competition on grain-yield and quality in spring wheat and barley^78^45^276^937-942^^^^^Jul^^^^^4021A^4020^Spring wheat and spring barley were grown in elevated atmospheric CO2 in controlled environments. Wheat was grown in monoculture and in competition with three weed species. In monoculture, wheat had 30% more grain yield and 28% less grain nitrogen in elevated compared to ambient atmospheric CO2. In competition, wheat had no significant increase in yield with elevated atmospheric CO2. In competition, grain nitrogen concentration was reduced in response to CO2 with the largest reduction occurring with the smallest competitor and the smallest reduction occurring with the largest competitor. Spring barley was grown in monoculture at three nitrogen fertilizer supplies. In elevated atmospheric CO2 there were significant increases in grain yield and reductions in grain nitrogen concentration at all levels of nitrogen supply. In both species the reductions in grain nitrogen concentration were large enough to affect current bread making processes. 603^3^Vaisanen,H^Standman,H^Kellomaki,S^1994^1^A model for simulating the effects of changing climate on the functioning a nd structure of the boreal forest ecosystem - an approach based on object-oriented design^13^14^7-9^1081-1095^^^^^Jul-Sep^A^4022^We have developed a forest ecosystem model to assess the effects of climate change on the functioning and structure! Of boreal coniferoUS forests assuming that temperature and precipitation are the major variables of the niche occupied by* a tree species. We specified weather patterns to a level representing the time constant of different physiological and ec-ological processes relevant to the survival, growth and death of trees. We thereby coupled the long-term dynamics of the f?orest ecosystem with climate through physiological mechanisms such as photosynthesis and respiration in terms of energy flAow through the ecosystem. The hydrological and nutrient cycles couple the dynamics of the forest ecosystem with climate chUange through soil processes, which represent the thermal and hydraulic properties of the soil, and the decomposition of liWtter and humus with mineralization of nutrients. Simulations for southern Finland (62-degrees-N) indicated that an increasme in temperature of 5-degrees-C over one hundred years could reduce soil water in Scots pine-dominated forest ecosystems. oAt the same time, the temperature increase could enhance photosynthesis up to 6-8% under current CO2 concentrations (330 pwpm) and up to 8-10% under elevated CO2 concentrations (660 ppm). Because the elevated temperature and CO2 concentration cayused an increase in respiration (12-14% more than under the current climate), total stem production increased only up to 4% with a 5-degrees-C increase in temperature and up to 6% when temperature and atmospheric CO2 concentration were increased simultaneously. Because transpiration only increased up to 5% in response to elevated temperature and C02 Concentration, the water use efficiency of Scots-pine dominated forest ecosystems increased up to 3%, particularly during the late rotation.Lly?),-2A2^^^^4023604^5^Vandegeijn,SC^Vos,J^Groenwold,J^Goudriaan,J^Leffelaar,PA^1994^1^The wageningen rhizolab - a facility to study soil-root-shoot- atmosphere interactions in crops .1. Description of main functions^206^161^2^275-287^^^^^Apr^^^^^4025A^4024^A research facility is described for the integrated study of soil-root-shoot-atmosphere relationships in crops. The Wageningen Rhizolab has been in use since 1990, and consists of two rows, each with eight below-ground compartments aligned along a corridor. A rain shelter automatically covers the experimental area at the start of rainfall. Compartments are 125 cm x 125 cm and 200 cm deep. Each compartment has a separate drip irrigation system. Crop canopy photosynthesis, respiration, and transpiration can be measured simultaneously and continuously on four out of eight compartments at a time. Each compartment can be filled with a selected soil material (repacked soil) and is accessible from the corridor over its full depth. Multiple sensors for measuring soil moisture status, electrical conductivity, temperature, soil respiration, trace gases and oxygen are installed in spatial patterns in accordance with the requirements of the experiments. Sensors are connected to control and data-acquisition devices. Likewise, provisions have been made to sample manually the soil solution! and soil atmosphere. Root observation tubes (minirhizotrons) are installed horizontally at depth intervals ranging from 5# cm (upper soil layers) to 25 cm (below 1 m). The facility is at present in use to study growth and development of vegetat+ion (crops) in relation to drought, nutrient status, soil-borne diseases, and underground root competition. One important -application is the study of elevated CO2 concentration and climate change and the way they affect crops and their carbon e;conomy. Growth and development of field grown vegetables and winter cover crops are also evaluated. The common aspect of t=hose studies is to gain a better understanding of crop growth under varying environmental conditions, and to collect datasPets that may help to improve mechanistic crop growth simulation models that can address suboptimal growth conditions.R605^3^Wang,ZM^Lechowicz,MJ^Potvin,C^1994^1^Early selection of black spruce seedlings and global change - which genotypes s\hould we favor^56^4^3^604-616^^^^^Aug^^^^^4027         # > A B G  Vc^A^4026^We investigated the effects of both soil fertility and predicted changes in climate on the performance of differentk families of black spruce, Picea mariana (Mill.) B.S.P., during the first growing season. The results were used to examinem whether reforestation programs should consider changing their preferred family lines in anticipation of altered performan{ce given global climate change. We grew seedlings of 16 open- pollinated maternal families of black spruce under phytotron} conditions simulating present and mid-21 st century climatic conditions during the growing season. The realistic, simulated future climate included both elevated CO2 levels and seasonally appropriate increases in mean daily temperature. To explore the dependence of climatic responses on site quality, seedlings were irrigated with solutions having either 5 or 100 mg/L of nitrogen. The lower nitrogen level represents a poor site for black spruce growth and survival, but the higher level provides ample nitrogen. We also recorded seed size for each seedling to evaluate the degree to which maternal investments might buffer responses to future climate and fertility during the first year on the seedbed. Seedling survival and growth increased both under the future climate regime and with nitrogen fertilization. The two factors interacted synergistically, with nitrogen enrichment significantly enhancing the positive effects of the future climate regime. Nitrogen-poor conditions, however, did not preclude a positive seedling response to the future climate. Our results indicate that seedling survival and height growth are highly dependent upon initial seed mass: larger seeds produced more vigorous 1 st-yr seedlings. The families differed in seed mass, seed germination, and seedling survival and growth, but their relative performances did not vary significantly among the treatments. These results suggest that black spruce families selected for rapid growth under present conditions will also do well in the future, at least in terms of early establishment and performance on sites regenerated by seeding.606^3^Wilkins,D^Vanoosten,JJ^Besford,RT^1994^1^Effects of elevated co2 on growth and chloroplast proteins in prunus-avium^ 13^14^7-9^769-779^^^^^Jul-Sep^^^^^4029-R-o-w-~----------_.}.. /|/04 623^3^Polley,HW^Johnson,HB^Mayeux,HS^1994^1^Increasing co2 - comparative responses of the C-4 grass schizachyrium and grassland invader prosopis^11^75^4^976-988^^^^^Jun^^^^^4062d elevated CO2 occurred (as much as 7.1 mu mol m(-2) s(-1)) over a broad range of temperatures (17-35 C), but the temperatu"re optimum for A was similar at both 350 and 700 mu L L(-1) CO2. In 1992, no differences in A, A(max), Q(r), LCP, or R(d) $were detected when ambient and elevated CO2 plants were compared. In plants collected from field plots, R(d), LCP, and lea)f N were significantly higher than in plants within the chambers indicating that a chamber effect exists for these paramet+ers. In both years, g was significantly reduced (21%-51%) when measured at 700 vs. 350 mu L L(-1) CO2. Peak aboveground bi7omass was increased at elevated CO2 in 1991 but not in 1992. These data indicate that for C-4 grasses, effects of elevated8 CO2 may only be detectable in years with significant water stress, a common occurrence in the central North American tallCgrass prairies.EA^4028^To predict the future carbon sequestering capacity of trees, we need information about the possible acclimatory mecShanisms of plant growth and photosynthesis in rising atmospheric CO2 under a variety of environmental conditions. We have,U therefore, studied the growth response of a tree species (Prunus avium L. Stella (wild cherry)) to elevated CO2 and chara_cterized the associated changes in photosynthetic machinery of the leaf tissue. Self-pollinated seedlings and mature cuttiangs (clones) from the same parent plant of P. avium were grown for two consecutive growing seasons (about 60 days each) inr ambient CO2 (350 mumol mol-1 CO2) or elevated CO2 (700 mumol Mol-1 CO2) with a high or low nutrient supply. The degree oft acclimation of leaf biochemistry and growth response to elevated CO2 was dependent on the plant material (seedling or mat~ ure cutting) and nutrient supply. There was little or no growth response to elevated CO2 in seedlings or cuttings in the l ow nutrient supply treatments, whereas, in both seasons, there was a strongly positive growth response to elevated CO2 in  seedlings and cuttings in the high nutrient supply regimes, resulting in increases in the root/shoot ratio and in carbon a llocation to the roots. In contrast, the protein content and activity of ribulose-1,5-bisphosphate carboxylase-oxygenase ( Rubisco, EC 4.1.1.39) were down regulated in elevated CO2. The loss of Rubisco on an area basis in plants in the elevated CO2 treatments was compensated for at the canopy level by increased leaf area. The loss of Rubisco protein was accompanied by decreases in the contents of chlorophyll and the thylakoid membrane proteins D1, D2 and cytochrome f, which are involved in light harvesting and photo-electron transport. We conclude that, in the medium- to long-term, the initial stimulation of biomass production by elevated CO2 may be increasingly offset by a lower photosynthetic capacity per unit leaf area in perennial plants.%607^5^Bugbee,B^Spanarkel,B^Johnson,S^Monje,O^Koerner,G^1994^1^Co2 crop growth enhancement and toxicity in wheat and rice^240^14^11^257-267^^^^^XXX^^^^^4031A^4030^The effects of elevated CO2 on plant growth are reviewed and the implications for crop yields in regenerative systems are discussed. There is considerable theoretical and experimental evidence indicating that the beneficial effects of CO2 are saturated at about 0.12% CO2 in air. However, CO2 can easily rise above 1% of the total gas in a closed system, and we have thus studied continuous exposure to CO2 levels as high as 2%. Elevating CO2 from 340 to 1200 mu mol mol(-1) can increase the seed yield of wheat and rice by 30 to 40%; unfortunately, further CO2 elevation to 2500 mu mol mol(-1) (0.25%) has consistently reduced yield by 25% compared to plants grown at 1200 mu mol mol(-1); fortunately, there was only an addi tional 10% decrease in yield as the CO2 level was further elevated to 2% (20,000 mu mol mol(-1)). Yield increases in both rice and wheat were primarily the result of increased number of heads per m(2), with minor effects on seed number per head and seed size. Yield increases were greatest in the highest photosynthetic photon flux. We used photosynthetic gas exchange to analyze CO2 effects on radiation interception, canopy quantum yield, and canopy carbon use efficiency. We were supri,sed to find that radiation interception during early growth was not improved by elevated CO2. As expected, CO2 increased q. uantum yield, but there was also a small increase in carbon use efficiency. Super-optimal CO2 levels did not reduce vegeta>!tive growth, but decreased seed set and thus yield. The reduced seed set is not visually apparent until final yield is mea@"sured. The physiological mechanism underlying CO2 toxicity is not yet known, but elevated CO2 levels (0.1 to 1% CO2) increPase ethylene synthesis in some plants and ethylene is a potent inhibitor of seed set in wheat.Z]`cfiR$608^3^Cao,W^Tibbitts,TW^Wheeler,RM^1994^1^Carbon-dioxide interactions with irradiance and temperature in potatoes^240^14^1_1^243-250^^^^^XXX^^^^^4033}jt &eh|a&A^4032^Separate controlled environment studies were conducted to determine the interaction of CO2 with irradiance and inteo'raction of CO2 with temperature on growth of three potato cultivars. In the first study, an elevated CO2 concentration of q(1000 mu mol mol(-1) and an ambient CO2 of 350 mu mol mol(-1) were maintained at the photosynthetic photon fluxes (PPF) of })17 and 34 mol m(-2) d(-1) with 12 h photoperiod, and at the PPF of 34 and 68 mol m(-2) d(-1) with 24 h photoperiod (400 an*d 800 mu mol m(-2) s(-1) PPF at each photoperiod). Tuber and total dry weights of 90-day old potatoes were significantly i+ncreased with CO2 enrichment, but the CO2 stimulation was less with higher PPF and longer photoperiod. Shoot dry weight wa,s affected more by photoperiod than by PPF and CO2 concentrations. The elevated CO2 concentration increased leaf CO2 assim-ilation rates and decreased stomatal conductance with 12 h photoperiod, but had only a marginal effect with 24 h photoperi.od. In the second study, four CO2 concentrations of 500, 1000, 1500 and 2000 mu mol mol(-1) were combined with two air tem/perature regimes of 16 and 20 degrees C under a 12 h photoperiod. At harvest, 35 days after transplanting, tuber and total0 dry weights of potatoes reached a maximum with 1000 mu mol mol(-1) CO2 at 16 degrees C, but continued to increase up to 21000 mu mol mol(-1) CO2 at 20 degrees C. Plant growth was greater at 20 degrees C than at 16 degrees C under all CO2 concen2trations. At 16 degrees C specific leaf weight increased substantially with increasing CO2 concentrations as compared to 5300 mu mol mol(-1) CO2, but increased only slightly at 20 degrees C. This suggests a carbohydrate build-up in the leaves at4 16 degrees C temperature that reduces plant response to increased CO2 concentrations. The data in the two studies indicat5e that a PPF of 34 mol m(-2) d(-1), 20 degrees C temperature, and 1000-2000 mu mol mol(-1) CO2 produces optimal tuber yield in potatoes.55687?7H@U@@@oCtCuC~CDDHHKKKKLL L LLL7609^9^Loretan,PA^Bonsi,CK^Mortley,DG^Wheeler,RM^Mackowiak,CL^Hill,WA^Morris,CE^Trotman,AA^David,PP^1994^1^Effects of several environmental-factors on sweet-potato growth^240^14^11^277-280^^^^^XXX^^^^^4035 9A^4034^Effects of relative humidity, light intensity and photoperiod on growth of 'Ga Jet' and 'TI-155' sweetpotato cultiv :ars, using the nutrient film technique (NFT), have been reported. In this study, the effect of ambient temperature regimes; (constant 28 degrees C and diurnal 28:22 degrees C day:night) and different CO2 levels (ambient, 400,1 000, and 10 000 mu< L/L - 400, 1 000 and 10 000 ppm) on growth of one or both of these cultivars in NFT are reported. For a 24-h photoperiod,-= no storage roots were produced for either cultivar in NFT when sweetpotato plants were grown at a constant temperature of/> 28 degrees C. For the same photoperiod, when a 28:22 degrees C diurnal temperature variation was used, there were still n:?o storage roots for 'TI- 155' but the cv. 'Ga Jet' produced 537 g/plant of storage roots. For both a 12-h and 24-h photope<@riod,'Ga Jet' storage root fresh and dry weight tended to be higher with a 28:22 degrees C diurnal temperature variation tIAhan with a constant 28 degrees C temperature regime. Preliminary results with both 'Ga Jet' and 'TI-155' cultivars indicatKBe a distinctive diurnal stomatal response for sweetpotato grown in NFT under an ambient CO2 level. The stomatal conductancbCe values observed for 'Ga Jet' at elevated CO2 levels indicated that the difference between the light- and dark-period condductance rates persisted at 400, 1 000, and 10 000 mu L/L.sE610^1^Bunce,JA^1993^1^Growth, survival competition, and canopy carbon-dioxide and water-vapor exchange of 1st year alfalfau at an elevated co2 concentration^79^29^4^557-565^^^^^^^^^^4037Dr. MGA^4036^Alfalfa was grown in field plots at the current CO2 concentration (350 mumol mol-1 = c350) and at 350 mumol mol-1 aHbove the current concentration (= c700). Alfalfa and weed growth, and canopy water vapor (E) and carbon dioxide exchange (IF) were determined for the first year. Alfalfa yield summed for the three harvests.in the first year was greater for the cJ700 treatment in two of the years studied, but significantly less in a third year. Weed growth was unaffected. Survival ofK alfalfa plants was greater at c700 for years in which there was substantial mortality, even when yield was not increased Lby the c700 treatment. In spite of a persistent reduction in leaf conductance to water vapor (g(l)), total canopy conductaMnce (g(c)) to water vapor did not differ between CO2 treatments when averaged over years, because of compensating changes Nin canopy leaf area. CO2 efflux (F) at night per unit of ground area was consistently less in the c700 treatment even whenO daytime CO2 uptake was higher. Hence the periodic harvesting of alfalfa crops does not necessarily allow elevated CO2 to cause persistent growth stimulation nor reduced water use.Q611^4^Chen,DX^Coughenour,MB^Knapp,AK^Owensby,CE^1994^1^Mathematical simulation of C4 grass photosynthesis in ambient and elevated co2^81^73^1-2^63-80^^^^^May^^^^^4039 SA^4038^A mechanistic leaf photosynthesis model was developed for C4 grasses based on a general simplified scheme of C4 plaTnt carbon metabolism. In the model, the PEPcase-dependent C4-cycle was described in terms of CO2 concentration in the mesoUphyll space using Michaelis-Menten kinetics, and the activity of PEPcase was related to the incident PAR to take account oVf the influence of light on the activty of C4-cycle processes. The CO2 refixation by Rubisco in the bundle sheath was descWribed using a widely accepted C3 photosynthesis model. The model assumes a steady state balance among CO2 diffusion from sXurrounding atmosphere into the mesophyll space, CO2 transport into the bundle sheath by the C4-cycle, CO2 refixation by th Ye C3-cycle in the bundle sheath, and CO2 leakage from the bundle sheath. The response to temperature of photosynthesis wasZ incorporated via the temperature dependence of model parameters. The photosynthesis model was coupled with a stomatal con[ductance model in order to predict leaf photosynthesis rates at different atmospheric conditions. The empirical model of B\all et al. (1987) was adopted and slightly modified to describe responses in stomatal conductance. The coupled model was p]arameterized for the C4 grass Andropogon gerardii grown in both ambient (350 ppm) and elevated (700 PPM) CO2 atmospheres. ^The key parameters of the model were estimated by fitting the model to the measured data using non-linear regression. The '_model was validated by comparison the predicted photosynthetic response to PAR in both CO2-pretreatments with the measured)` data from an independent gas exchange experiment. The predicted photosynthesis and stomatal conductance matched the measu8ared data quite well for both atmospheric CO2- pretreatments. At 25-degrees-C, the estimated maximum carboxylation rate of :bRubisco V(cm,25), potential electron transport rate J(m,25) and quantum efficiency alpha were increased by CO2 enrichment.Jc The maximum PEPcase activity V(pm,25) was lower in elevated CO2. The model predicted that the light-saturated leaf photosLdynthesis will increase by about 10% with the rising of atmospheric CO2 from 350 to 700 ppm at 30-degrees-C, and that the oYeptimal temperature of photosynthesis will shift from 37 to 38.5-degrees-C. The estimated slope of the stomatal conductance[f model was increased by atmospheric CO2 enrichment. Stomatal conductance was significantly reduced by increasing atmospherhic CO2 concentration.jh612^3^Dacey,JWH^Drake,BG^Klug,MJ^1994^1^Stimulation of methane emission by carbon-dioxide enrichment of marsh vegetation^3y6^370^6484^47-49^^^^^7 Jul^^^^^4041{jA^4040^THERE is substantial evidence that many plants respond to increased concentrations of atmospheric carbon dioxide byk increasing their productivity(1-4) This observation has led to the suggestion that, by taking up CO2, the terrestrial biolsphere might mitigate the potential greenhouse warming associated with anthropogenic CO2 emissions(5). Whiting and Chantonm(6) have found, however, that for wetlands of varying productivity around the world, higher net primary production is assonciated with higher emissions of methane-another important greenhouse gas. Here we present measurements of methane emissionos from a marsh that has been exposed to twice the present ambient concentration of atmospheric CO2. We find that over a onpe-week period, the CO2-enriched sites had significantly higher emissions of methane than the control sites. Our results suqggest that future increases in atmospheric CO2 concentration may lead to significant increases in methane emissions from wetlands.՜.+,D՜.+,D hp s613^2^Delesalle,VA^Blum,S^1994^1^Variation in germination and survival among families of sagittaria-latifolia in response to salinity and temperature^104^155^2^187-195^^^^^Mar^^^^^4043 6> _PID_GUIDuA^4042^We studied seed germination and seedling growth in eight maternal families of Sagittaria latifolia (Alismataceae), va freshwater perennial, in response to salinity (four levels) and temperature effects (two levels) in the greenhouse. Saliwnity decreased germination, delayed emergence, and decreased survival and growth rates. The negative effects of salinity oxn germination were greater at the high-temperature regime, but the effects on growth were greater at the low-temperature ryegime. Some seeds were capable of germinating and surviving (with minimal growth) even in 0.8% NaCl solution. Families alszo differed in their response to salinity but not to temperature. In particular, high salinities had little effect on the g{ermination of some families. Growth rate always decreased with increasing salinity, but again the magnitude of the effect |differed among maternal families. Our data show that S. latifolia can germinate but cannot grow well under low-salinity co}nditions; thus, S. latifolia might be minimally affected by short-term salt intrusions. In order to understand how plant p ~opulations respond to disturbances, such as increased salinity or increased temperature, we need to consider the source, either environmental or genetic, of maternal effects.614^2^Downton,WJS^Grant,WJR^1994^1^Photosynthetic and growth-responses of variegated ornamental species to elevated co2^92)^21^3^273-279^^^^^^^^^^4045,A^4044^Variegated and completely green cultivars of oleander (Nerium oleander L.) and willow myrtle (Agonis flexuosa (Will;d.) Sweet) were grown in controlled environment cabinets for 3 and 5 months, respectively, under either ambient levels of =CO2 or with supplementary CO2 to a partial pressure of 800 mu bar. Photosynthesis of entirely green leaves and the green pOortions of variegated leaves on both species was greatly stimulated by high CO2 and there was no evidence of downward adjuQstment (acclimation) of photosynthetic rates to high CO2 during the experiment. Dark respiration rates of these leaves werde lowered by high CO2. The yellow portions of willow myrtle leaves showed a low level of photosynthetic activity which wasf stimulated by high CO2; however, dark respiration rates showed little response to elevated CO2. Green and yellow areas onx variegated leaves of willow myrtle had much lower dark respiration rates than completely green leaves, but this differencze was not evident for oleander. Yellow portions of oleander leaves showed little evidence of photosynthetic capacity. This was also confirmed by a low photochemical efficiency as determined by chlorophyll fluorescence. A major effect of variegation was to slow overall plant growth compared with completely green plants. The respective 3-fold and 6-7-fold differences in biomass between fully green and variegated cultivars of oleander and willow myrtle was closely related to estimated net carbon gain per day by the plant canopy. Variegation for both species averaged close to 50:50, green:yellow areas. Variegated plants developed about twice the leaf area ratio and specific leaf area compared with their completely green counterparts. The relative growth response to high CO2 was significantly greater for the variegated plants compared to the completely green plants. 615^2^Ferris,R^Taylor,G^1994^1^Elevated co2, water relations and biophysics of leaf extension in 4 chalk grassland herbs^84^127^2^297-307^^^^^Jun^^^^^4047 A^4046^Diurnal measurements of leaf or leaflet extension, water relations and cell wall extensibility (phi) were made on young growing leaves of four chalk downland herbs (Sanguisorba minor Scop., Lotus corniculatus L., Anthyllis vulneraria L. and Plantago media L.) growing in controlled environment cabinets and exposed to either ambient or elevated CO2. This study revealed differences in the effect of CO2 and the control of leaf growth between the four species. Leaf extension rate (LER) increased significantly at night (average over 8 h) in elevated CO2 for S. minor, A. vulneraria and P. media with a significant increase over the first 4 h of darkness for S. mines, L. corniculatus and P. media, whilst for S. minor and P. media average day-time LER (over 16 h) also increased significantly in elevated CO2 as compared with ambient CO2. Water potential (Psi), solute potential (Psi(s)), turgor pressure (P), yield turgor (Y) and the effective turgor for growth (Pe) were measured using psychrometers. Solute potentials of S. minor, A. vulneraria acid P. media decreased significantly following exposure to elevated CO2 with a significant reduction in Psi(s) during the day in A. vulneraria. Turgor pressure increased significantly in elevated CO2 as compared with ambient CO2 in A. vulneraria but there was no effect of elevated CO2 $on P in the other species. No effects of CO2 on Psi, Y or Pe were observed. Leaf cell wall extensibility (phi) increased s'ignificantly in leaves of S. minor, L. corniculatus and P. media exposed to elevated CO2, whereas in A. vulneraria, there 5was no effect of CO2 on extensibility. These results suggest that the mechanism by which elevated CO2 promotes leaf growth7 differs between species since in S. minor, L. corniculatus and P. media, CO2 promoted growth through an influence on cellC wall properties, whilst in A. vulneraria, higher values of P explain the increased leaf growth in elevated CO2 for this sEpecies.R616^5^Goldewijk,KK^Vanminnen,JG^Kreileman,GJJ^Vloedbeld,M^Leemans,R^1994^1^Simulating the carbon flux between the terrestrSial environment and the atmosphere^94^76^1-2^199-230^^^^^Jul^^^^^4049\A^4048^A Terrestrial C Cycle model that is incorporated in the Integrated Model to Assess the Greenhouse Effect (IMAGE 2.0^) is described. The model is a geographically explicit implementation of a model that simulates the major C fluxes in diffperent compartments of the terrestrial biosphere and between the biosphere and the atmosphere. Climatic parameters, land cosver and atmospheric C concentrations determine the result of the dynamic C simulations. The impact of changing land cover ~patterns, caused by anthropogenic activities (shifting agriculture, de- and afforestation) and climatic change are modeled implicitly. Feedback processes such as CO2 fertilization and temperature effects on photosynthesis, respiration and decomposition are modeled explicitly. The major innovation of this approach is that the consequences of climate change are taken into account instantly and that their results can be quantified on a global medium-resolution grid. The objectives of this paper are to describe the C cycle model in detail, present the linkages with other parts of the IMAGE 2.0 framework, and give an array of different simulations to validate and test the robustness of this modeling approach. The computed global net primary production (NPP) for the terrestrial biosphere in 1990 was 60.6 Gt C a-1, with a global net ecosystem production (NEP) of 2.4 Gt C a-1. The simulated C flux as result from land cover changes was 1.1 Gt C a-1, so that the terrestrial biosphere in 1990 acted as a C sink of 1.3 Gt C a-1. Global phytomass amounted 567.5 Gt C and the dead biomass pool was 1517.7 Gt C. IMAGE 2.0 simulated for the period 1970 - 2050 a global average temperature increase of 1.6-degrees-C and a global average precipitation increase of 0.1 mm/day. The CO2 concentration in 2050 was 522.2 ppm. The computed NPP for the year 2050 is 82.5 Gt C a-1, with a NEP of 8.1 Gt C a-1. Projected land cover changes result in a C flux of 0.9 Gt C a-1, so that the terrestrial biosphere will be a strong sink of 7.2 Gt C a-1. The amount of phytomass hardly changed (600.7 Gt C) but the distribution over the different regions had. Dead biomass increased significantly to 1667.2 Gt C.617^2^Idso,KE^Idso,SB^1994^1^Plant-responses to atmospheric co2 enrichment in the face of environmental constraints - a review of the past 10 years research^107^69^3-4^153-203^^^^^Jul^^^^^4051 F  X`A^4050^This paper presents a detailed analysis of several hundred plant carbon exchange rate (CER) and dry weight (DW) responses to atmospheric CO2 enrichment determined over the past 10 years. It demonstrates that the percentage increase in plant growth produced by raising the air's CO2 content is generally not reduced by less than optimal levels of light, water or soil nutrients, nor by high temperatures, salinity or gaseous air pollution. More often than not, in fact, the data show the relative growth-enhancing effects of atmospheric CO2 enrichment to be greatest when resource limitations and environ!mental stresses are most severe.'618^1^Kirschbaum,MUF^1994^1^The sensitivity of C-3 photosynthesis to increasing co2 concentration - a theoretical-analysis) of its dependence on temperature and background co2 concentration^9^17^6^747-754^^^^^Jun^^^^^4053:A^4052^The atmospheric CO2 concentration has increased from the pre- industrial concentration of about 280 mu mol mol(-1) <to its present concentration of over 350 mu mol mol(-1), and continues to increase. As the rate of photosynthesis in C-3 pIlants is strongly dependent on CO2 concentration, this should have a marked effect on photosynthesis, and hence on plant gKrowth and productivity. The magnitude of photosynthetic responses can be calculated based on the well-developed theory of \photosynthetic response to intercellular CO2 concentration. A simple biochemically based model of photosynthesis was coupl^ed to a model of stomatal conductance to calculate photosynthetic responses to ambient CO2 concentration. In the combined lmodel, photosynthesis was much more responsive to CO2 at high than at low temperatures. At 350 mu mol mol(-1), photosynthensis at 35 degrees C reached 51% of the rate that would have been possible with non-limiting CO2, whereas at 5 degrees C, 7y7% of the CO2 non-limited rate was attained. Relative CO2 sensitivity also became smaller at elevated CO2, as CO2 concentr{ation increased towards saturation. As photosynthesis was far from being saturated at the current ambient CO2 concentration, considerable further gains in photosynthesis were predicted through continuing increases in CO2 concentration. The strong interaction with temperature also leads to photosynthesis in different global regions experiencing very different sensitivities to increasing CO2 concentrations.Text version619^1^Kojima,S^1994^1^Effects of global climatic warming on the boreal forest^241^107^1085^91-97^^^^^Mar^^^^^4055A^4054^On the basis of the predictions of the global climatic warming induced by anthropogenic activities, as provided by climatologists, current state of knowledge regarding possible ecological consequences of the warming on the boreal biome was discussed. A 600 to 700 km northward advance of the biome along with the warming was predicted. Such a shift could take place for half a century or so, which would be an unprecedentedly fast rate of progression. This might cause a serious disorder in species composition of the biome, particularly in the boundary regions. As to the carbon sink or source issues, considerable uncertainties and knowledge gaps existed. Elevated temperature and CO2 levels would stimulate photosynthesis to result in an increase of CO2 uptake, while the temperature increase would promote decomposition of organic matter especially that stored in the soils to release CO2 to the atmosphere. Behaviors of northern peat bogs, where ca. 700 Gt of organic matter was thought to be accumulated, would seriously affect the balance. However, overall ecosystematic carbon balance was yet to be fully studied. It was realized that multifunctional approaches needed to be developed so as to integrate pieces of various information into a holistic picture. Need for international collaboration research efforts was also addressed.b,_QP hM605:23 PM 24 02 1999 -0500Amy E. Faivre620^1^Makino,A^1994^1^Biochemistry of C3-photosynthesis in high co2^241^107^1085^79-84^^^^^Mar^^^^^4057S A^4056^The short-term responses of C3 photosynthesis to high CO2 are described first. Regulation of photosynthesis in the short term is determined by interaction among the capacities of light harvesting, electron transport, ribulose-1, 5-bispho sphate carboxylase (Rubisco) and orthophosphate (Pi) regeneration during starch and sucrose synthesis. Photosynthesis under high CO2 conditions is limited by either electron transport or Pi regeneration capacities, and Rubisco is deactivated to maintain a balance between each step in the photosynthetic pathway. Subsequently, the long-term effects on photosynthesis are discussed. Long-term CO2 enhancement leads to carbohydrate accumulation. Accumulation of carbohydrates is not associa ted with a Pi-regeneration limitation on photosynthesis, and this limitation is apparently removed during long-term exposu.re to high CO2. Enhanced CO2 does not affect Rubisco content and electron transport capacity for a given leaf-nitrogen con0tent. In addition, the deactivated Rubisco immediately after exposure to high CO2 does not recover during the subsequent p>rolonged exposure. Such evidence may indicate that plants do not necessarily have an ideal acclimation response to high CO@2 at the biochemical level.JABLONSKI LeanneCall for 18th Polar LibrK621^2^Morse,SR^Bazzaz,FA^1994^1^Elevated co2 and temperature alter recruitment and size hierarchies in C-3 and C-4 annualsM^11^75^4^966-975^^^^^Jun^^^^^4059RE: thule ms^A^4058^In order to understand the implications of changes in global CO2 concentrations and temperature for the growth and `fitness of individual plants, performance must be investigated in relation to the performance of other plants within a popoulation. In this study we examined patterns of recruitment, mortality, and size structure of monospecific stands in responqse to ambient (400 mu L/L) and elevated CO2 concentrations (700 mu L/L) across three temperature regimes; 18 degrees, 28 dzegrees, and 38 degrees C. We created experimental populations of two annual plants that differ in their photosynthetic pat|hway and water use patterns: Abutilon theophrasti (C-3) and Amaranthus retroflexus (C-4). The effects of CO2, temperature, and their interactions on population structure were complex and species dependent. For both species increasing temperature resulted in higher germination and faster initial growth rates. These initial temperature responses increased the intensity and role of competition in determining stand size and structure. Postemergence responses to elevated CO2 differed markedly between the two species. For Abutilon, the C-3 species, serf-thinning and the mean biomass of the survivors increased under elevated CO2. For Amaranthus, survivorship, but not growth, increased under elevated CO2 conditions. We attribute differences in response between species not only to photosynthetic pathway, but also to differences in the onset of competition mediated through differences in plant form and in resource uptake and deployment. The patterns of stand development in response to CO2 and temperature suggest that the effects of changing CO2 and temperature may be understood within mechanistically based models of resource use. Temperature regulates the rate of resource use and the onset of interference among plants, while CO2 functions both as a resource and a resource regulator. Although mortality was concentrated later in stand development for Abutilon than Amaranthus, overall patterns of stand size and structure were similar for both species; mortality and size inequalities increased with increasing temperature and CO2. Because size is often correlated with fecundity, an increase in size hierarchies in response to elevated CO2, in conjunction with a decrease in survivorship, may result in a smaller effective population size. Our ability to predict changes in effective population size due to changing size hierarchies alone, however, should also consider developmental shifts in response to elevated CO2 that may result in, as in this study, a decrease in the minimum size at the onset of flowering.journal, etc.622^1^Pitelka,LF^1994^1^Ecosystem response to elevated co2^57^9^6^204-207^^^^^Jun1 02 1999 -0500CURTIS Peter A^4061^The woody C-3 Prosopis glandulosa (honey mesquite) and C-4 perennial grass Schizachyrium scoparium (little bluestem,) were grown along a gradient of daytime carbon dioxide concentrations from near 340 to 200 mu mol/mol air in a 38 m long .controlled environment chamber. We sought to determine effects of historical and prehistorical increases in atmospheric CO=2 concentration on growth, resource use, and competitive interactions of a species representative of C-4-dominated grassla@nds in the southwestern United States and the invasive legume P. glandulosa. Increasing CO2 concentration stimulated N-2 fOixation by individually grown P. glandulosa and elicited in C-3 seedlings a similar relative increase in leaf intercellulaQr CO2 concentration, net assimilation rate, and intrinsic water use efficiency (leaf net assimilation rate/stomatal conduc] tance). Aboveground biomass of P. glandulosa was not altered by CO2 concentration, but belowground biomass and whole-plant^ water and nitrogen use efficiencies increased linearly with CO2 concentration in seedlings that were grown alone. Biomassj produced by P. glandulosa that was grown with S. scoparium was not affected by CO2 concentration. Stomatal conductance del clined and leaf assimilation rates of S. scoparium at near maximum incident light increased at higher CO2 concentration, bz ut there was no effect of CO2 concentration on biomass production or whole- plant water use efficiency of the C-4 grass. R|ising CO2 concentration, especially the 27% increase since the beginning of the 19th century, may have contributed to more abundant P. glandulosa on C-4 grasslands by stimulating the shrub's growth or reducing the amount of resources that the C-3 required. Much of the potential response of P. glandulosa to CO2 concentration, however, appears to be contingent on the shrub's escaping competition with neighboring grasses.phylogeny624^3^Reekie,JYC^Hicklenton,PR^Reekie,EG^1994^1^Effects of elevated co2 on time of flowering in 4 short-day and 4 long-day species^188^72^4^533-538^^^^^Apr^^^^^4064No SubjectA^4063^This study was undertaken to determine if the effect of elevated CO2 on flowering phenology is a function of the photoperiodic response of the species involved. Four long-day plants, Achillea millefolium, Callistephus chinensis, Campanula isophylla, and Trachelium caeruleum, and four short-day plants, Dendranthema grandiflora, Kalanchoe blossfeldiana, Pharbitis nil, and Xanthium pensylvanicum, were grown under inductive photoperiods (9 h for short day and 17 h for long day) at either 350 or 1000 mu L/L CO2. Time of visible flower bud formation, flower opening, and final plant biomass were assessed. Elevated CO2 advanced flower opening in all four long-day species and delayed flowering in all four short-day species. In the long-day species, the effect of CO2 was primarily on bud initiation; all four species formed buds earlier at high CO,. Bud development, the difference in time between flower opening and bud initiation, was advanced in only one long-day species, Callistephus chinensis. Mixed results were obtained for the short-day species. Elevated CO, exerted no effects on bud initiation but delayed bud development in Dendranthema and Kalanchoe. In Xanthium, bud initiation rather than bud development was delayed. Data on bud initiation and development were not obtained for Pharbitis. The negative effect of CO, upon phenology in the short-day species was not associated with negative effects on growth. Elevated CO2 increased plant siz e in both long-day and short-day species. 1999 -0500CARTER Jody lab!625^2^Reid,CD^Strain,BR^1994^1^Effects of co(2) enrichment on whole-plant carbon budget of seedlings of fagus-grandifolia and acer-saccharum in low irradiance^2^98^1^31-39^^^^^Jun^^^^^4066apologies'#A^4065^Carbon exchange rates (CER) and whole-plant carbon balances of beech (Fagus grandifolia) and sugar maple (Acer sacc)$harum) were compared for seedlings grown under low irradiance to determine the effects of atmospheric CO2 enrichment on sh9%ade-tolerant seedlings of co-dominant species. Under contemporary atmospheric CO2, photosynthetic rate per unit mass of be;&ech was lower than for sugar maple, and atmospheric CO2 enrichment enhanced photosynthesis for beech only. Aboveground resK'piration per unit mass decreased with CO2 enrichment for both species while root respiration per unit mass decreased for sM(ugar maple only. Under contemporary atmospheric CO2, beech had lower C uptake per plant than sugar maple, while C losses pe)er plant to nocturnal aboveground and root respiration were similar for both species. Under elevated CO2, C uptake per plag*nt was similar for both species, indicating a significant relative increase in whole-seedling CER with CO2 enrich ment forz+ beech but not for sugar maple. Total C loss per plant to aboveground respiration was decreased for beech only because inc|,rease in sugar maple leaf mass counterbalanced a reduction in respiration rates. Carbon loss to root respiration per plant- was not changed by CO2 enrichment for either species. However, changes in maintenance respiration cost and nitrogen level. suggest changes in tissue composition with elevated CO2. Beech had a greater net daily C gain with CO2 enrichment than di/d sugar maple in contrast to a lower one under contemporary CO2. Elevated CO2 preferentially enhances the net C balance of0 beech by increasing photosynthesis and reducing respiration cost. In all cases, the greatest C lost was by roots, indicat1ing the importance of belowground biomass in net C gain. Relative growth rate estimated from biomass accumulation was not 2affected by CO2 enrichment for either species possibly because of slow growth under low light. This study indicates the im3portance of direct effects of CO2 enrichment when predicting potential change in species distribution with global climate change.g \I6!09:41 AM 05 02 1999 -0500Holly 5626^2^Samuelson,LJ^Seiler,JR^1994^1^Red spruce seedling gas-exchange in response to elevated co2, water-stress, and soil fertility treatments^155^24^5^954-959^^^^^May^^^^^4068 05 02 1999 -0500Jodi Carter7A^4067^The interactive influences of ambient (374 muL.L-1) or elevated (713 muL.L-1) CO2, low or high soil fertility, well8-watered or water-stressed treatment, and rooting volume on gas exchange and growth were examined in red spruce (Picea rub9ens Sarg.) grown from seed through two growing seasons. Leaf gas exchange throughout two growing seasons and growth after :two growing seasons in response to elevated CO2 were independent of soil fertility and water-stress treatments, and rootin;g volume. During the first growing season, no reduction in leaf photosynthesis of seedlings grown in elevated CO2 compared< with seedlings grown in ambient CO2 was observed when measured at the same CO2 concentration. During the second growing s=eason, net photosynthesis was up to 21% lower for elevated CO2-grown seedlings than for ambient CO2-grown seedlings when m>easured at 358 muL.L-1. Thus, photosynthetic acclimation to growth in elevated CO2 occurred gradually and was not a functi?on of root- sink strength or soil-fertility treatment. However, net photosynthesis of seedlings grown and measured at an e@levated CO2 concentration was still over 2 times greater than the photosynthesis of seedlings grown and measured at an ambAient CO2 concentration. Growth enhancement by CO2 was maintained, since seedlings grown in elevated CO2 were 40% larger in both size and weight after two growing seasons.2 1999 -0500SWENSON SteveC627^3^Seneweera,S^Milham,P^Conroy,J^1994^1^Influence of elevated co2 and phosphorus-nutrition on the growth and yield of a) short-duration rice (oryza-sativa L CV jarrah)^92^21^3^281-292^^^^^^^^^^4070family+EA^4069^The growth and development of a short-duration rice cultivar (Oryza sativa L. cv. Jarrah), grown in flooded soil wi6Fth a range of phosphorus (P) levels and exposed to atmospheric CO2 concentrations of either 350 or 700 mu L L(-1) was foll8Gowed for 146 days after planting (DAP). Development (estimated by rate of tiller production and time to flowering) was fasCHter with higher soil P levels and CO2 enrichment, the effect being more pronounced with CO2 enrichment. During the early vEIegetative phase (up to 35 DAP), when rates of tiller production were low, shoot growth and rates of leaf expansion were faPJster at elevated CO2 concentrations and high soil P levels. Rates of tiller production were greater with these treatments RKduring the 35-56 DAP period, when tillering was at a maximum. Shoot elongation was reduced at elevated CO2 levels and at h_Ligh soil P levels during this period. By 146 DAP leaf weight was greater at high P levels, but CO2 enrichment accelerated aMtiller production to such an extent that final leaf weight was lower at high CO2, probably because there were fewer, and slNmaller, leaves on each tiller. Despite this, grain yield was increased by up to 58% by CO2 enrichment, with increases occunOrring even at low soil P levels. This was due mainly to an increase in grain number per panicle, although panicle number a{Plso increased. Higher soil P levels also increased grain number and yield. The P concentration in the foliage was unaffect}Qed by the CO2 treatments and the concentration required to produce maximum yield was 0.18% (dry wt basis) at both CO2 leveRls. Greater starch accumulation in the stems of high-CO2-grown plants may have accounted for the higher number of grains in each panicle.9eV609:12 AM 10 02 1999 -0500SWENSON SteveT628^3^Sheppard,MI^Ewing,LL^Hawkins,JL^1994^1^Soil processes and chemical-transport - soil degassing of C-14 dioxide - rates and factors^204^23^3^461-468^^^^^May-Jun^^^^^4072Re: Hi!VA^4071^Soil air normally contains elevated levels of CO2 relative to the atmosphere. The primary source of soil C is plantW-root and microbial respiration. The exchange of soil and atmospheric CO2 is important to many environmental concerns, sucXh as acid rain, global warming and waste management. Proposed disposal of high- level nuclear wastes containing primarily Yinorganic C-14 may provide a source of (CO2)-C-14 to the atmosphere. Field and laboratory experiments show that (CO2)-C-14Z Soil degassing rate constants, the flux density (Bq.M2.s-1) divided by soil inventory (Bq-m-2), range from -10(-7) to -10[(-2) S-1, and that the loss of inorganic C-14 is driven primarily by gaseous diffusion. These constants are affected by so\il pH and porosity, with smaller influences of soil temperature, moisture and organic matter content. Degassing rate const]ants derived through mass balance calculations to estimate loss differ only by 20% from direct trapping methods. Frozen so^il degassing rate constants were up to 25 times smaller than lab values, indicating that annual C-14 loss rates in norther_n climates would be lower because of reduced gaseous diffusion during the winter months. Using our field data, we recommen`d an annual C- 14 soil degassing rate constant of -1 x 10(-6) s-1 for acidic soils and a value of -5 x 10(-7) S-1 for calcaareous soils. For probabilistic assessment modelling, we recommend a geometric mean degassing constant of -4.3 X 10(-7) S-b1 with a geometric standard deviation of 3.26 for three different soils. This indicates the median half-life of C-14 in su rface soils is 18 d, with a 99% confidence interval of 13 h and 640 d.d629^2^Stanghellini,C^Bunce,JA^1993^1^Response of photosynthesis and conductance to light, co2, temperature and humidity in tomato plants acclimated to ambient and elevated co2^79^29^4^487-497^^^^^^^^^^4074i>fA^4073^In tomato (Lycopersicon esculentum L.) plants, net carbon dioxide exchange rate (P(N)) response curves to both irra@gdiance (I) and short-term [CO2] were similar for plants grown at both 350 and 700 cm3(CO2) m-3. However, water vapor conduKhctance (gH2O) of plants grown at high [CO2] was less sensitive to short term [CO2] variations, when measured at low vapor Mipressure difference, and was larger than the conductance of ''ambient [CO2]'' plants when both were exposed to high [CO2].]j P(N) and g(H2O) under high I increased with temperature over the range 18 to 32-degrees-C. P(N) of plants grown in both [_kCO2] treatments increased at most about 25 % from 350 to 700 cm3 m-3 at 18 and 25-degrees-C, and decreased when exposed totl 1000 cm3 m-3 at these temperatures. Thus increasing atmospheric [CO2] might not increase P(N) by as much as expected and vwater use of crops might not decrease.home...n630^3^Williams,RS^Lincoln,DE^Thomas,RB^1994^1^Loblolly-pine grown under elevated co2 affects early instar pine sawfly performance^2^98^1^64-71^^^^^Jun^^^^^4076Re: releasepA^4075^Seedlings of loblolly pine Pinus taeda (L.), were grown in open-topped field chambers under three CO2 regimes: ambiqent, 150 mul l-1 CO2 above ambient, and 300 mul l-1 CO2 above ambient. A fourth, non-chambered ambient treatment was inclurded to assess chamber effects. Needles were used in 96 h feeding trials to determine the performance of young, second instsar larvae of loblolly pine's principal leaf herbivore, red-headed pine sawfly, Neodiprion lecontei (Fitch). The relative ctonsumption rate of larvae significantly increased on plants grown under elevated CO2, and needles grown in the highest CO2u regime were consumed 21% more rapidly than needles grown in ambient CO2. Both the significant decline in leaf nitrogen covntent and the substantial increase in leaf starch content contributed to a significant increase in the starch:nitrogen ratwio in plants grown in elevated CO2. Insect consumption rate was negatively related to leaf nitrogen content and positivelyx related to the starch:nitrogen ratio. Of the four volatile leaf monoterpenes measured, only beta-pinene exhibited a signiyficant CO2 effect and declined in plants grown in elevated CO2. Although consumption changed, the relative growth rates ofz larvae were not different among CO2 treatments. Despite lower nitrogen consumption rates by larvae feeding on the plants {grown in elevated CO2, nitrogen accumulation rates were the same for all treatments due to a significant increase in nitro|gen utilization efficiency. The ability of this insect to respond at an early, potentially susceptible larval stage to poo}rer food quality and declining levels of a leaf monoterpene suggest that changes in needle quality within pines in future ~elevated-CO2 atmospheres may not especially affect young insects and that tree-feeding sawflies may respond in a manner similar to herb-feeding lepidopterans.Կ601:25 PM 19 02 1999 -0500MOBYDOG1@aol.c%631^2^Ziska,LH^Bunce,JA^1994^1^Increasing growth temperature reduces the stimulatory effect of elevated co2 on photosynthe'sis or biomass in 2 perennial species^37^91^2^183-190^^^^^Jun^^^^^4078O2MAP7A^4077^We examined how anticipated changes in CO2 concentration and temperature interacted to alter plant growth, harvest :characteristics and photosynthesis in two cold-adapted herbaceous perennials, alfalfa (Medicago sativa L. cv. Are) and orcJhard grass (Dactylis glomerata L. cv. Potomac). Plants were grown at two CO2 concentrations (362 [ambient] and 717 [elevatLed] mu mol mol(-1) CO2) and four constant day/night temperatures of 15, 20, 25 and 30 degrees C in controlled environmental chambers. Elevated CO2 significantly increased total plant biomass and protein over a wide range of temperatures in both species. Stimulation of photosynthetic rare, however, was eliminated at the highest growth temperature in M. sativa and rrelative stimulation of plant biomass and protein at high CO2 declined as temperature increased in both species. Lack of a tsynergistic effect between temperature and CO2 was unexpected since elevated CO2 reduces the amount of carbon lost via photorespiration and photorespiration increases with temperature. Differences between anticipated stimulatory effects of CO2 and temperature and whole plant single and leaf measurements are discussed. Data from this study suggest that stimulatory effects of atmospheric CO2 on growth and photosynthesis may decline with anticipated increases in global temperature, limiting the degree of carbon storage in these two perennial species.f492a3c344c0213f31ac9296f707 -19-Jan-1999-15:46:27--0500-(EST 916760779 Ndel Nskip Nsave read Nget 19890783633^1^Amthor,JS^1994^1^Scaling co2-photosynthesis relationships from the leaf to the canopy^91^39^3^321-350^^^^^Mar^^^^^40A^4081^Responses of individual leaves to short-term changes in CO2 partial pressure have been relatively well studied. Whole-plant and plant community responses to elevated CO2 are less well understood and scaling up from leaves to canopies will be complicated if feedbacks at the small scale differ from feedbacks at the large scale. Mathematical models of leaf, ca%nopy, and ecosystem processes are important tools in the study of effects on plants and ecosystems of global environmental' change, and in particular increasing atmospheric CO2, and might be used to scale from leaves to canopies. Models are also= important in assessing effects of the biosphere on the atmosphere. Presently, multilayer and big leaf models of canopy ph?otosynthesis and energy exchange exist. Big leaf models - which are advocated here as being applicable to the evaluation of impacts of 'global change' on the biosphere - simplify much of the underlying leaf-level physics, physiology, and biochemistry, yet can retain the important features of plant- environment interactions with respect to leaf CO2 exchange processTes and are able to make useful, quantitative predictions of canopy and community responses to environmental change. The baVsis of some big leaf models of photosynthesis, including a new model described herein, is that photosynthetic capacity andg activity are scaled vertically within a canopy (by plants themselves) to match approximately the vertical profile of PPFDj. The new big leaf model combines physically based models of leaf and canopy level transport processes with a biochemicallqy based model of CO2 assimilation. Predictions made by the model are consistent with canopy CO2 exchange measurements, altshough a need exists for further testing of this and other canopy physiology models with independent measurements of canopy mass and energy exchange at the time scale of 1 h or less.el Nskip Nsave read Nget 1461501043 c6a76f94343428931802a23d482199901222244.RAA15221@mail2.uts.ohio-state.edu>-22-Jan-1999-17:44:47--0500-(EST 917253364 Ndel Nskip Nsave read Nget 10634^4^Baxter,R^Ashenden,TW^Sparks,TH^Farrar,JF^1994^1^Effects of elevated carbon-dioxide on 3 montane grass species .1. Growth and dry-matter partitioning^78^45^272^305-315^^^^^Mar^^^^^4084A03144@sideshow.stanford.edu>-24-Jan-1999-12:06:25--05A^4083^Upland grasslands are a major component of natural vegetation within the UK. Such grasslands support slow growing relatively stable plant communities. The response of native montane grass species to elevated atmospheric carbon dioxide concentrations has received little attention to date. Of such studies, most have only focused on short-term (days to weeks) responses, often under favourable controlled environment conditions. In this study Agrostis capillaris L.(5), Festuca vivipara L. and Poa alpina L. were grown under semi-natural conditions in outdoor open-top chambers at either ambient (340 mu mol mol(- 1)) or elevated (680 mu mol mol(-1)) concentrations of atmospheric carbon dioxide (CO2) for periods from 79 to 189 d, with a nutrient availability similar to that of montane Agrostis-Fescue grassland in Snowdonia, N. Wales. Whole plant dry weight was increased for A. capillaris and P. alpina, but decreased for F. vivipara, at elevated CO2. Major components of relative growth rate (RGR) contributing to this change at elevated CO2 were transient changes in specific leaf area (SLA) and leaf area ratio (LAR). Despite changes in growth rate at 680 mu mol mol(-1) CO2, partitioning of dry weight between shoot and root in plants of A. capillaris and P. alpina was unaltered. There was a significant decrease in shoot relative to root growth at elevated CO2 in F. vivipara which also showed marked discoloration of the leaves and increased senescence of the foliage.--0500-(EST 917542356 Ndel Nskip Nsave read Nget 1707357751 af2e2050f340d09f95e743283236cdbf <0F6A0 635^2^Corrigan,VK^Carpenter,A^1993^1^Effects of treatment with elevated carbon-dioxide levels on the sensory quality of asparagus^199^21^4^349-357^^^^^^^^^^4086802FB@nsfmail01.nsf.gov>-29-Jan-1999-16:39:24--0500-(EST 917627988 Ndel Nskip Nsave!A^4085^Asparagus spears (Asparagus officinalis L. cv. Limbras 10) were stored for 3-5 days in atmospheres containing betwe#en 40 and 90% carbon dioxide (CO2) to evaluate the effect of insecticidal CO2 atmospheres on sensory quality based on sens1ory panel ratings of characteristic asparagus flavour, off-flavours, flavour acceptability, and overall acceptability. Sen3sory quality of spears after 4 days storage in 60% CO2 was similar to air-stored spears but 5 days storage caused deterior;ation in the CO2-stored spears relative to the air-stored spears. Using higher CO2 levels than this for shorter storage ti>mes resulted in spears with CO2 injury and poor sensory quality. Spear quality deteriorated with shelf period but previousN CO2 treatment did not affect the rate of deterioration. Storing spears at 5-degrees-C in 60% CO2 or 0-degrees-C in air gaPve consistently higher (lower for off-flavours) sensory quality ratings for all characteristics assessed than vice versa. aThick spears had more flavour and were more acceptable than thin spears. Thick spears had more flavour than thin spears whcen stored in CO2, but thin spears had more flavour when stored in air than in CO2. In 60% CO2, spears stored dry had a more acceptable flavour and were more acceptable overall (where panellists considered aspects such as flavour, texture, and off-flavours in the overall rating) than those stored with their butts in water. Spears stored in air with their butts in water had a more acceptable flavour and were more acceptable overall, spears stored with their butts in water had less characteristic asparagus flavour than those stored dry. High levels of CO2 could be used as a disinfestation treatment of fresh asparagus spears without significant effect on spear quality (compared to spears stored in air under similar conditions) providing levels >60% CO2 are not used, and storage time in the atmosphere is kept to 4 days or less.18:53--0500-(EST) 9636^3^Curtis,PS^Snow,AA^Miller,AS^1994^1^Genotype-specific effects of elevated co2 on fecundity in wild radish (raphanus-raphanistrum)^2^97^1^100-105^^^^^Feb^^^^^4088kip Nsave read Nget 832874204 18e2380b5a87885a878dbd665db3d3af <199902051333A^4087^Rising atmospheric CO2 may lead to natural selection for genotypes that exhibit greater fitness under these conditions. The potential for such evolutionary change will depend on the extent of within-population genetic variation in CO2 responses of wild species. We tested for heritable variation in CO2- dependent life history responses in a weedy, cosmopolitan annual, Raphanus raphanistrum. Progeny from five paternal families were grown at ambient and twice ambient CO2 using outdoor open-top chambers (160 plants per CO2 treatment). Elevated CO2 stimulated net assimilation rates, especially in plants that had begun flowering. Across paternal families, elevated CO2 led to significant increases in flower and seed production (by 22% and 13% respectively), but no effect was seen on time to bolting, leaf area at bolting, fruit set, or number of seeds per fruit. Paternal families differed in their response to the CO2 treatment: in three families there were no significant CO2 effects, while in one family lifetime fecundity increased by > 50%. These genotype-specific effects altered fitness rankings among the five paternal families. Although we did not detect a significant genotype X CO2 interaction, our results provide evidence for heritable responses to elevated CO2. In a subset of plants, we found that the magnitude of CO2 effects on fecundity was also influenced by soil fertility. read Nget 860444456 9198342810b3b30479f022412649a8ad <0F6)637^1^Drake,SR^1994^1^Elevated carbon-dioxide storage of anjou pears using purge- controlled atmosphere^170^29^4^299-301^^+^^^Apr^^^^^409038.MAA21284@mail2.uts.ohio-state.edu>-10-Feb-1999-12:38:44--0500-(EST 918650321 Ndel Nskip Nsave read Nget6A^4089^'Anjou' pears (Pyrus communis L.) were placed in controlled- atmosphere (CA) storage immediately after harvest (<248 hours) or after a 10-day delay in refrigerated storage, and held there for 9 months at 1C. Oxygen in all atmospheres was E1.5% and CO2 was at either 1% or 3%. Atmospheres in the flow-through system were computer-controlled at +/- 0.1%. After reGmoval from CA storage, pears were evaluated immediately and after ripening at 21C for 8 days. Pears stored in 3% CO2 were Qfirmer, greener, and displayed less scald, internal breakdown, and stem-end decay than pears stored in 1% CO2. In additionS, no internal discoloration of 'Anjou' pears was evident when held with 3% CO2. 'Anjou' pears held in 3% CO2 retained the cability to ripen after long-term storage. A 10-day delay in atmosphere establishment had little or no influence on the loneg-term keeping quality or ripening ability of 'Anjou' pears.6403a71707d39ebcecb790 <01BE584D.1E896740@waite.biosci.ohio-st638^2^Ferris,R^Taylor,G^1994^1^Stomatal characteristics of 4 native herbs following exposure to elevated co2^52^73^4^447-4v53^^^^^Apr@[128.138.153.69]>-15-Feb-1999-13:42:13--0500-(EST 919154117 Ndel Nskip Nsave read Nget 857896666 54680d836516639^2^Gunderson,CA^Wullschleger,SD^1994^1^Photosynthetic acclimation in trees to rising atmospheric co2 - a broader perspective^91^39^3^369-388^^^^^Mar^^^^^4093<199902171340.IAA17161@mail4.uts.ohio-state.edu>-17-Feb-1999-08:41:18--0500-(EST 91A^4092^Analysis of leaf-level photosynthetic responses of 39 tree species grown in elevated concentrations of atmospheric CO2 indicated an average photosynthetic enhancement of 44% when measured at the growth [CO2]. When photosynthesis was measured at a common ambient [CO2], photosynthesis of plants grown at elevated [CO2] was reduced, on average, 21% relative to ambient-grown trees, but variability was high. The evidence linking photosynthetic acclimation in trees with changes at the biochemical level is examined, along with anatomical and morphological changes in trees that impact leaf- and canopy- level photosynthetic response to CO2 enrichment. Nutrient limitations and variations in sink strength appear to influence photosynthetic acclimation, but the evidence in trees for one predominant factor controlling acclimation is lacking. Regardless of the mechanisms that underlie photosynthetic acclimation, it is doubtful that this response will be complete. A new focus on adjustments to rising [CO2] at canopy, stand, and forest scales is needed to predict ecosystem response to a changing environment.5033746 9ac14d9ae9d4ffed4bc6997a471a895d <0F7N00744ZY90N@mx2.osu.edu>-24-Feb-1999-10:20:45--0500-(EST 9640^1^Johnsen,KH^1994^1^Growth and ecophysiological responses of black spruce seedlings to elevated co2 under varied water and nutrient additions (vol 23, pg 1033, 1993)^155^24^3^646^^^^^Mar3223bf8617c1c74bea4f <007701be6008$c495a960$3eaa9680@641^3^Knapp,AK^Hamerlynck,EP^Owensby,CE^1993^1^Photosynthetic and water relations responses to elevated co-2 in the C-4 grass andropogon-gerardii^104^154^4^459-466^^^^^Dec^^^^^4096--0500-(EST 919862857 Ndel Nskip Nsave read Nget 654854431 bdbA^4095^Undisturbed tallgrass prairie, dominated by the C-4 grass Andropogon gerardii, was exposed to ambient and elevated (double ambient) levels of atmospheric CO2 in large open-top chambers throughout the 1991 and 1992 growing seasons. Responses in leaf xylem pressure potential (psi), net photosynthesis (A), and stomatal conductance (g) were measured in both years for A. gerardii grown within chambers and from adjacent field plots. In 1992, maximum photosynthetic capacity (A(max)), apparent quantum requirement (Q(r)), the photosynthetic light compensation point (LCP), and dark respiration (R(d)) were also measured. Midday psi was significantly higher in plants grown at elevated CO2 in both years, and seasonally averaged psi was 0.48-0.70 MPa lower in 1991 (a dry year) than 1992 (a wet year). In 1991, A and g were significantly higher (regar dless of measurement CO2 level) in plants grown at elevated vs. ambient CO2. These increases were measured in well-watered# plants insuring that these plants differed only in CO2 growth conditions and previous exposure to low psi. Increased A at% 642^1^Larson,DL^1994^1^Potential effects of anthropogenic greenhouse gases on avian habitats and populations in the northe8rn great-plains^34^131^2^330-346^^^^^Apr^^^^^4098352912dd40f5f2862cd8 <0F7O00C2LK48VF@mx1.osu.edu>-24-Feb-1999-17:24:53--; A^4097^Biotic response to the buildup of greenhouse gases in Earth's atmosphere is considerably more complex than an adjusG tment to changing temperature and precipitation. The fertilization effect CO2 has on some plants, the impact UVB radiationI  has on health and productivity of organisms, and the resulting changes in competitive balance and trophic structure must S also be considered. The intent of this paper is to review direct and indirect effects of anthropogenic greenhouse gases onU  wildlife, and to explore possible effects on populations of birds and their habitats in the northern Great Plains. Many o] f the potential effects of increasing greenhouse gases, such as declining plant nutritional value, changes in timing of in_ sect emergence, and fewer and saltier wetlands, foreshadow a decline in avian populations on the Great Plains. However, otj her possible effects such as increased drought resistance and water use efficiency of vegetation, longer growing seasons, k and greater overall plant biomass promise at least some mitigation. Effects of multiple simultaneous perturbations such asz can be expected under doubled CO2 scenarios will require substantial basic research to clarify.bd332bd2ea4ff2d0026 <1999| 643^4^Nobel,PS^Cui,MY^Miller,PM^Luo,YQ^1994^1^Influences of soil volume and an elevated co2 level on growth and co2 exchange for the crassulacean acid metabolism plant opuntia-ficus-indica^37^90^1^173-180^^^^^Jan^^^^^4100Nskip Nsave read Nget A^4099^Effects of the current (38 Pa) and an elevated (74 Pa) CO2 partial pressure on root and shoot areas, biomass accumu lation and daily net CO2 exchange were determined for Opuntia ficus- indica (L.) Miller, a highly productive Crassulacean acid metabolism species cultivated worldwide. Plants were grown in environmentally controlled rooms for 18 weeks in pots o f three soil volumes (2 600, 6 500 and 26 000 cm3), the smallest of which was intended to restrict root growth. For plants  in the medium-sized soil volume, basal cladodes tended to be thicker and areas of main and lateral roots tended to be gre ater as the CO2 level was doubled. Daughter cladodes tended to be initiated sooner at the current compared with the elevat ed CO2 level but total areas were similar by 10 weeks. At 10 weeks, daily net CO2 uptake for the three soil volumes averag ed 24% higher for plants growing under elevated compared with current CO2 levels. but at 18 weeks only 3% enhancement in u ptake occurred. Dry weight gain was enhanced 24% by elevated CO2 during the first 10 weeks but only 8% over 18 weeks. Incr easing the soil volume 10-fold led to a greater stimulation of daily net CO2 uptake and biomass production than did doubli ng the CO2 level. At 18 weeks, root biomass doubled and shoot biomass nearly doubled as the soil volume was increased 10-f old; the effects of soil volume tended to be greater for elevated CO2. The amount of cladode nitrogen per unit dry weight decreased as the CO2 level was raised and increased as soil volume increased, the latter suggesting that the effects of soil volume could be due to nitrogen limitations.JECT STATUS (STANDARD).POT 644^2^Nobel,PS^Israel,AA^1994^1^Cladode development, environmental responses of co2 uptake, and productivity for opuntia-ficus-indica under elevated co2^78^45^272^295-303^^^^^Mar^^^^^4102GRAM FILES\MICROSOFT OFFICE\ A^4101^Opuntia ficus-indica, an extremely productive CAM plant cultivated in many countries, was exposed to 36, 52, and 72 !-73 Pa CO, in field plots and open-top chambers. Initiation of new cladodes (stem segments) was monitored until the canopy " closed, after which bimonthly harvests maintained the plants for one year at a cladode area per unit ground area that is  #optimal for biomass production. Doubling the CO2 partial pressure slightly increased the number of first-order daughter cl $adodes growing on the basal (planted) cladodes after 3 months and nearly doubled the number and area of second-order clado %des. When the CO2 level was doubled, cladodes were 5% thicker after a few months and 11 to 16% thicker after one year. Alt" &hough the productivity enhancement by elevated CO2 tended to decrease during the year, the annual above-ground dry-mass ga8 'in was 37 to 40% higher when the CO2 level was doubled, reaching 65 tons hectare(-1) year-l in a field plot. Well-watered : (cladodes at day/night air temperatures of 25 degrees C/15 degrees C and a total daily photosynthetic photon flux (PPF) of D )15 mol m(-2) d(-1) in controlled environment chambers had 74% more net CO2 uptake over 24 h at 73 Pa than at 37 Pa CO2. WiF *th doubled CO2, the percentage enhancement of net CO2 uptake increased as the PPF was lowered, as the temperature was raisS +ed, and during drought. Using an environmental productivity index based on such factors, net CO2 uptake and hence productiUvity of O. ficus-indica can be predicted for elevated CO2 levels and other variations accompanying global climate change.d -645^2^Pettersson,R^McDonald,AJS^1994^1^Effects of nitrogen supply on the acclimation of photosynthesis to elevated co2^91^f39^3^389-400^^^^^Mar^^^^^4104A TI INTERACTIVE EFFECTS OF HIGH-TEMPERATURE AND ELEVATED CARBON- DIOXIDE CONCENTRATION ON Cr /A^4103^A common observation in plants grown in elevated CO2 concentration is that the rate of photosynthesis is lower thans 0 expected from the dependence of photosynthesis upon CO2 concentration in single leaves of plants grown at present CO2 con 1centration. Furthermore, it has been suggested that this apparent down regulation of photosynthesis may be larger in leave 2s of plants at low nitrogen supply than at higher nitrogen supply. However, the available data are rather limited and cont 3radictory. In this paper, particular attention is drawn to the way in which whole plant growth response to N supply consti 4tutes a variable sink strength for carbohydrate usage and how this may affect photosynthesis. The need for further studies 5 of the acclimation of photosynthesis at elevated CO2 in leaves of plants whose N supply has resulted in well-defined growth rate and sink activity is emphasised, and brief consideration is made of how this might be achieved.ydrate supplies du 7646^2^Rygiewicz,PT^Andersen,CP^1994^1^Mycorrhizae alter quality and quantity of carbon allocated below ground^36^369^6475^58-60^^^^^5 May^^^^^4106ch-in growth chambers and subjected to day/night temperatures of either 33/20 or 33/30- degrees-C 9A^4105^PLANTS and sails are a critically important element in the global carbon-energy equation. It is estimated that in f :orest ecosystems over two-thirds of the carbon is contained in soils and peat deposits(1). Despite the importance of fores ;t soils in the global carbon cycle, fluxes of carbon associated with fundamental processes and soil functional groups are bon budget). The mycorrhizal symbiont reduces overall retention of carbon in the plant-fungus symbiosis by increasing carb ?on in roots and below-ground respiration and reducing its retention and release above ground. Below ground, mycorrhizal pl @ants shifted allocation of carbon to pools that are rapidly turned over, primarily to fine roots and fungal hyphae, and ho Ast root and fungal respiration. Mycorrhizae alter the size of below-ground carbon pools, the quality and, therefore, the r Betention time of carbon below ground. Our data indicate that if elevated atmospheric CO2 and altered climate stressors alter mycorrhizal colonization in forests, the role of forests in sequestering carbon could be altered.e was the most respon D647^1^Sage,RF^1994^1^Acclimation of photosynthesis to increasing atmospheric co2 - the gas-exchange perspective^91^39^3^351-368^^^^^Mar^^^^^4108 PD SEP VL 16 IS 7 GA LZ893 J9 PLANT CELL ENVIRON ER PT J AU BOWLER, JM PRESS, MC TI GROWTH-RESPON FA^4107^The nature of photosynthetic acclimation to elevated CO2 is evaluated from the results of over 40 studies focusing Gon the effect of long-term CO2 enrichment on the short-term response of photosynthesis to intercellular CO2 (the A/C-i res Hponse). The effect of CO2 enrichment on the A/C-i response was dependent on growth conditions, with plants grown in small Ipots (<5 L) or low nutrients usually exhibiting a reduction of A at a given C-i, while plants grown without nutrient defic Jiency in large pots or in the field tended to exhibit either little reduction or an enhancement of A at a given C-i follow King a doubling or tripling of atmospheric CO2 during growth. Using theoretical interpretations of A/C-i curves to assess a Lcclimation, it was found that when pot size or nutrient deficiency was not a factor, changes in the shape of A/C-i curves Mwhich are indicative of a reallocation of resources within the photosynthetic apparatus typically were not observed. Long- Nterm CO2 enrichment usually had little effect or increased the value of A at all C-i. However, a minority of species grown O at elevated CO2 exhibited gas exchange responses indicative of a reduced amount of Rubisco and an enhanced capacity to me Ptabolize photosynthetic products. This type of response was considered beneficial because it enhanced both photosynthetic Qcapacity at high CO2 and reduced resource investment in excessive Rubisco capacity. The ratio of intercellular to ambient RCO2 (the C-i/C-a ratio) was used to evaluate stomatal acclimation. Except under water and humidity stress, C-i/C-a, exhibi Sted no consistent change in a variety of C-3 species, indicating no stomatal acclimation. Under drought or humidity stress T, C-i/C-a declined in high-CO2 grown plants, indicating stomata will become more conservative during stress episodes in future high CO2 environments.hat the effect of the lower nitrogen concentration was to increase partitioning to the roots w V648^3^Smart,DR^Chatterton,NJ^Bugbee,B^1994^1^The influence of elevated co2 on nonstructural carbohydrate distribution and fructan accumulation in wheat canopies^9^17^4^435-442^^^^^Apr^^^^^4110TREXLER, MC WOOMER, P TI TROPICAL FORESTS - THEIR P XA^4109^We grew 2.4 m2 wheat canopies in a large growth chamber under high photosynthetic photon flux (1000 mumol m-2 s-1) Yand using two CO2 concentrations, 360 and 1200 mumol mol-1. Photosynthetically active radiation (400-700 nm) was attenuate Zd slightly faster through canopies grown in 360 mumol mol-1 than through canopies grown in 1200 mumol mol-1, even though h [igh- CO2 canopies attained larger leaf area indices. Tissue fractions were sampled from each 5-cm layer of the canopies. L \eaf tissue sampled from the tops of canopies grown in 1200 mumol mol-1 accumulated significantly more total non-structural ] carbohydrate, starch, fructan, sucrose, and glucose (p less- than-or-equal-to 0-05) than for canopies grown in 360 mumol ^mol-1. Non-structural carbohydrate did not significantly increase in the lower canopy layers of the elevated CO2 treatment _. Elevated CO2 induced fructan synthesis in all leaf tissue fractions, but fructan formation was greatest in the uppermost ` leaf area. A moderate temperature reduction of 10- degrees-C over 5 d increased starch, fructan and glucose levels in can aopies grown in 1200 mumol mol-1, but concentrations of sucrose and fructose decreased slightly or remained unchanged. Thos be results may correspond with the use of fructosyl-residues and release of glucose when sucrose is consumed in fructan synthesis.' scenario could release 41-77 Pg C over the next 60 yr. Carbon fluxes from losses in tropical forests may be less d649^2^Teramura,AH^Sullivan,JH^1994^1^Effects of uv-b radiation on photosynthesis and growth of terrestrial plants^91^39^3^463-473^^^^^Mar^^^^^4112Policies to mitigate C losses must be multiple and concurrent, including reform of forestry, land fA^4111^The photosynthetic apparatus of some plant species appears to be well-protected from direct damage from UV-B radiat gion. Leaf optical properties of these species apparently minimizes exposure of sensitive targets to UV-B radiation. Howeve hr, damage by UV-B radiation to Photosystem II and Rubisco has also been reported. Secondary effects of this damage may inc ilude reductions in photosynthetic capacity, RuBP regeneration and quantum yield. Furthermore, UV-B radiation may decrease jthe penetration of PAR, reduce photosynthetic and accessory pigments, impair stomatal function and alter canopy morphology k, and thus indirectly retard photosynthetic carbon assimilation. Subsequently, UV-B radiation may limit productivity in ma lny plant species. In addition to variability in sensitivity to UV- B radiation, the effects of UV-B radiation are further mconfounded by other environmental factors such as CO2, temperature, light and water or nutrient availability. Therefore, w ne need a better understanding of the mechanisms of tolerance to UV-B radiation and of the interaction between UV-B and other environmental factors in order to adequately assess the probable consequences of a change in solar radiation.2) m-2 s- p650^3^Webber,AN^Nie,GY^Long,SP^1994^1^Acclimation of photosynthetic proteins to rising atmospheric co2^91^39^3^413-425^^^^^Mar^^^^^41140 and 450-550 mumol m-2 s-1 in the HS and FS treatments, respectively. R(D) of leaves which were kept in dar rA^4113^In this review we discuss how the photosynthetic apparatus, particularly Rubisco, acclimates to rising atmospheric sCO2 concentrations (c(a)). Elevated c(a) alters the control exerted by different enzymes of the Calvin cycle on the overal tl rate of photosynthetic CO2 assimilation, so altering the requirement for different functional proteins. A decreased flux u of carbon through the photorespiratory pathway will decrease requirements for these enzymes. From modeling of the respons ve of CO2 uptake (A) to intracellular CO2 concentration (c(i)) it is shown that the requirement for Rubisco is decreased at w elevated c(a), whilst that for proteins limiting ribulose 1,5 bisphosphate regeneration may be increased. This balance ma xy be altered by other interactions, in particular plasticity of sinks for photoassimilate and nitrogen supply; hypotheses yon these interactions are presented. It is speculated that increased accumulation of carbohydrate in leaves developed at e zlevated c(a) may signal the 'down regulation' of Rubisco. The molecular basis of this 'down regulation' is discussed in te {rms of the repression of photosynthetic gene expression by the elevated carbohydrate concentrations. This molecular model is then used to predict patterns of acclimation of perennials to long term growth in elevated c(a).d treatments as compar }651^4^Weigel,HJ^Manderscheid,R^Jager,HJ^Mejer,GJ^1994^1^Effects of season-long co2 enrichment on cereals .1. Growth- performance and yield^169^48^3^231-240^^^^^Apr^^^^^4116te, even in the winter, than the conventional management of aerated gre A^4115^Two cultivars each of spring wheat (Triticum aestivum L., cultivars 'Star' and 'Turbo') and spring barley (Hordeum vulgare L., cultivars 'Alexis' and 'Arena') were exposed throughout the growing season to ambient (384 p.p.m.) and above a mbient CO2 concentrations (471, 551, 624,718 p.p.m.) in open- top chambers. Plant samples were taken four times during pla nt development and biomass partitioning into stem, leaves and ear was measured. Total above-ground biomass increased mainl y in the C02 concentration range between 400-550 p.p.m. for wheat, and between 400-700 p.p.m. for barley. Stimulation of b iomass was largely due to an increase in tillering rate. At the tiller level CO2 enrichment revealed a decrease in leaf dr y weight at anthesis stage, which was due to a reduction in leaf size (barley) and in leaf number (wheat). Specific leaf w eight of the mature flag leaf was unaffected by CO2. Stem biomass per tiller was temporarily ('Star', 'Alexis') or during the whole growth period ('Turbo', 'Arena') increased by CO2 exposure, while ear dry weight was increased (barley) or even decreased ('Star'). Except for the barley cultivar 'Arena', which showed a 84% increase in the number of grains per ear, t he number of ears was almost entirely responsible for the increased grain yield among the CO2 treatments. At the highest C O2 concentration yield increase amounted to 19% and 27% for the two wheat cultivars, and 5 2% and 8 9% for the two barley cultivars in comparison with the ambient CO2 level. Among all cultivars there was an inverse relationship between the tota l shoot biomass produced at ambient CO2 conditions and the plant's response to the CO2 enrichment. This indicates that the genetic potential of wheat unlike barley is highly adapted to present atmospheric CO2 conditions and thus responsible for the small CO2 effect on wheat.ARRIS, J MCPHERSON, E TI EVIDENCE OF A FEEDBACK MECHANISM LIMITING PLANT-RESPONSE TO ELEVA 652^1^Woodrow,IE^1994^1^Optimal acclimation of the C-3 photosynthetic system under enhanced co2^91^39^3^401-412^^^^^Mar^^^ A^4117^A range of studies of C-3 plants have shown that there is a change in both the carbon flux and the pattern of nitro gen allocation when plants are grown under enhanced CO2. This paper examines evidence that allocation of nitrogen both to and within the photosynthetic system is optimised with respect to the carbon flux. A model is developed which predicts the optimal relative allocation of nitrogen to key enzymes of the photosynthetic system as a function of CO2 concentration. I t is shown that evidence from flux control analysis is broadly consistent with this model, although at high nitrogen and u nder certain conditions at low nitrogen experimental data are not consistent with the model. Acclimation to enhanced CO2 i s also assessed in terms of resource allocation between photosynthate sources and sinks. A means of assessing the optimisa tion of this source-sink allocation is proposed, and several studies are examined within this framework. It is concluded t hat C-3 plants probably possess the genetic feedback mechanisms required to efficiently 'smooth out' any imbalance within the photosynthetic system caused by a rise in atmospheric CO2.mechanism in which elevated carbon dioxide causes an increa^^4118te release into the rhizosphere by non-mycorrhizal plants, leading to mineral nutrient sequestration by the expande 653^1^Woodrow,IE^1994^1^Control of steady-state photosynthesis in sunflowers growing in enhanced co2^9^17^3^277-286^^^^^Mar^^^^^4120 S J9 NATURE ER PT J AU EASTERLING, WE CROSSON, PR ROSENBERG, NJ MCKENNEY, MS KATZ, LA LEMON, KM TI AGRICULTUR A^4119^Control coefficients were used to describe the degree to which ribulose bisphosphate carboxylase/oxygenase (Rubisco ) limits the steady-state rate of CO2 assimilation in sunflower leaves from plants grown at high (800 mu mol mol(-1)) and low (350 mu mol mol(-1)) CO2. The magnitude of a control coefficient is approximately the percentage change in the flux th at would result from a 1% rise in enzyme active site concentration. In plants grown at low CO2, leaves of different ages v aried considerably in their photosynthetic capacities. In a saturating light flux and an ambient CO2 concentration of 350 mu mol mol(-1), the Rubisco control coefficient was about 0.7 in all leaves, indicating that Rubisco activity largely limi ted the assimilation flux. The Rubisco control coefficient for leaves grown at 350 mu mol mol(-1) CO2 dropped to about zer o when the ambient CO2 concentration was raised to 800 mu mol mol(-1). In relatively young, fully expanded leaves of plant s grown at high CO2, the Rubisco control coefficient was also about 0.7 at a saturating light flux and at the CO2 concentr ation at which the plants were grown (800 mu mol mol(- 1)). This apparently resulted from a decrease in the concentration of Rubisco active sites. In older leaves, however, the control coefficient was about 0.2. Because, on the whole, Rubisco a ctivity still largely limits the assimilation flux in plants grown at high CO2, the kinetics of this enzyme can still be u sed to model photosynthesis under these conditions. The relatively high Rubisco control coefficient under enhanced CO2 ind icates that the young sunflower leaves have the capacity to acclimate their photosynthetic biochemistry in a way consistent with an optimal use of protein resources.on 2030 crop production to a small increase. The analog climate would have lit 654^3^Wullschleger,SD^Ziska,LH^Bunce,JA^1994^1^Respiratory responses of higher-plants to atmospheric co2 enrichment^37^90^1^221-229^^^^^Jan^^^^^4122uld be small after on-farm adjustments and CO2 enrichment, animal production in MINK would be l A^4121^Although the respiratory response of native and agricultural plants to atmospheric CO2 enrichment has been reported over the past 75 years, only recently have these effects emerged as prominent measures of plant and ecosystem response to the earth's changing climate. In this review we discuss this rapidly expanding field of study and propose that both incre asing and decreasing rates of leaf and whole-plant respiration are likely to occur in response to rising CO2 concentration s. While the stimulatory effects of CO2 on respiration are consistent with our knowledge of leaf carbohydrate status and p lant metabolism, we wish to emphasize the rather surprising short-term inhibition of leaf respiration by elevated CO2 and the reported effects of long-term CO2 exposure on growth and maintenance respiration. As is being found in many studies, i t is easier to document the respiratory response of higher plants to elevated CO2 than it is to assign a mechanistic basis for the observed effects. Despite this gap in our understanding of how respiration is affected by CO2 enrichment, data ar e sufficient to suggest that changes in leaf and whole-plant respiration may be important considerations in the carbon dyn amics of terrestrial ecosystems as global CO2 continues to rise. Suggestions for future research that would enable these and other effects of CO2 on respiration to be unravelled are presented. of growth flushes, of progressively larger leaves. 655^2^Ziska,LH^Bunce,JA^1994^1^Direct and indirect inhibition of single leaf respiration by elevated co2 concentrations - interaction with temperature^37^90^1^130-138^^^^^Jan^^^^^4124oned equally amongst all organs of the beech seedling. 5. Th A^4123^Two herbaceous perennials, alfalfa (Medicago sativa L. cv. Arc) and orchard grass (Dactylus glomerata L. cv. Potoma c), were grown at ambient (367 mumol mol-1) and elevated (729 mumol mol- 1) CO2 concentrations at constant temperatures of 15, 20, 25 and 30-degrees-C in order to examine direct and indirect changes in nighttime CO2 efflux rate (respiration) of single leaves. Direct (biochemical) effects of CO2 on nighttime respiration were determined for each growth condition by brief (<30 min) exposure to each CO2 concentration. If no direct inhibition of respiration was observed, then long-term re ductions in CO2 efflux between CO2 treatments were presumed to be due to indirect inhibition, probably related to long-ter m changes in leaf composition. By this criterion, indirect effects of CO2 on leaf respiration were observed at 15 and 20- degrees-C for M. sativa on a weight basis, but not on a leaf area or protein basis. Direct effects however, were observed at 15, 20 and 25-degrees-C in D. glomerata; therefore the observed reductions in respiration for leaves grown and measured at elevated relative to ambient CO2 concentrations could not be distinguished as indirect inhibition. No inhibition of re spiration at elevated CO2 was observed at the highest growth temperature (30-degrees-C) in either species. CO2 efflux incr eased with measurement and growth temperature for M. sativa at both CO2 concentrations; however, CO2 efflux in D. glomerat a showed complete acclimation to growth temperature. Stimulation of leaf area and weight by elevated CO2 levels declined w ith growth temperature in both species. Data from the present study suggest that both direct and indirect inhibition of re spiration are possible with future increases in atmospheric CO2, and that the degree of each type of respiratory inhibition is a function of growth temperature.e states. Irrigation and instream uses such as navigation, hydroelectric power prod 656^2^Baker,JT^Allen,LH^1994^1^Assessment of the impact of rising carbon-dioxide and other potential climate changes on vegetation^35^83^1-2^223-235^^^^^^^^^^4126D JUN VL 24 IS 1-2 GA LR185 RP FREDERICK KD J9 CLIMATIC CHANGE ER PT J AU GRIFFI A^4125^The projected doubling of current levels of atmospheric carbon dioxide concentration ([CO2]) during the next centur y along with increases in other radiatively active gases have led to predictions of increases in global air temperature an d shifts in precipitation patterns. Additionally, stratospheric ozone depletion may result in increased ultraviolet-B (UV- B) radiation incident at the Earth's surface in some areas. Since these changes in the Earth's atmosphere may have profoun d effects on vegetation, the objectives of this paper are to summarize some of the recent research on plant responses to [ CO2], temperature and UV-B radiation. Elevated [CO2] increases photosynthesis and usually results in increased biomass, an d seed yield. The magnitude of these increases and the specific photosynthetic response depends on the plant species, and are strongly influenced by other environmental factors including temperature, light level, and the availability of water a nd nutrients. While elevated [CO2] reduces transpiration and increases photosynthetic water-use efficiency, increasing air temperature can result in greater water use, accelerated plant developmental rate, and shortened growth duration. Experim ents on UV-B radiation exposure have demonstrated a wide range of photobiological responses among plants with decreases in photosynthesis and plant growth among more sensitive species. Although a few studies have addressed the interactive effec ts of [CO2] and temperature on plants, information on the effects of UV-B radiation at elevated [CO2] is scarce. Since [CO 2], temperature and UV-B radiation may increase concurrently, more research is needed to determine plant responses to the interactive effects of these environmental variables. DECIDUOUS HARDWOODS DURING 3 YEARS OF GROWTH IN ELEVATED CO2 - NO L 657^3^Bazzaz,FA^Miao,SL^Wayne,PM^1993^1^Co2-induced growth enhancements of cooccurring tree species decline at different rates^2^96^4^478-482^^^^^Dec^^^^^4128DENDRON-TULIPIFERA; WHITE OAK; YELLOW- POPLAR; ELEVATED ATMOSPHERIC CARBON DIOXIDE; P A^4127^To elucidate how enriched CO2 atmospheres, soil fertility, and light availability interact to influence the long-te rm growth of tree seedlings, six co-occurring members of temperature forest communities including ash (Fraxinus americana L.), gray birch (Betula populifolia), red maple (Acer rubrum), yellow birch (Betula alleghaniensis), striped maple (Acer p ensylvanicum), and red oak (Quercus rubra L.) were raised in a glasshouse for three years in a complete factorial design. After three years of growth, plants growing in elevated CO2 atmospheres were generally larger than those in ambient CO2 at mospheres, however, magnitudes of CO2-induced growth enhancements were contingent on the availability of nitrogen and ligh t, as well as species identity. For all species, magnitudes of CO2-induced growth enhancements after one year of growth we re greater than after three years of growth, though species' growth enhancements over the three years declined at differen t rates. These results suggest that CO2-induced enhancements in forest productivity may not be sustained for long periods of time. Additionally, species' differential growth responses to elevated CO2 may indirectly influence forest productivity via long-term species compositional changes in forests.onal duration of effective gas-exchange was unaffected by CO2 tre 658^1^Betsche,T^1994^1^Atmospheric co2 enrichment - kinetics of chlorophyll a fluorescence and photosynthetic co2 uptake in individual, attached cotton leaves^173^34^1^75-86^^^^^Jan^^^^^4130as a result of acclimation to CO2 enrichment in the f A^4129^Chl fluorescence and gas exchange of attached cotton leaves (Gossypium hirsutum L.) were measured in ambient air an d in a highly CO2-enriched atmosphere (4000 mu l l(-1) CO2; photosynthetic saturation). In the shore term (hours to one da y), net CO2 uptake approximately doubled in all leaves examined. Photochemical (q(P)) and nonphotochemical (q(NP)) quenchi ng of chlorophyll fluorescence, and calculated linear photosynthetic electron Row, did not change significantly when CO2 r ose from 250 to 4000 mu l l(-1) CO2. These results show that high CO2 concentration did not inhibit photosynthesis in any leaf. In contrast, the long-term response of leaves to atmospheric CO2-enrichment was variable, Some leaves sustained the initial high level of photosynthetic stimulation for more than a week while in others photosynthetic CO2-uptake declined m ore or less. These leaves turned yellowish-green although chlorophyll content declined little. Variance in the degree of l eaf yellowing was also encountered in experiments with clover when sets of plants were CO2-enriched. Gas exchange and chi fluorescence results suggest that yellowing of cotton leaves in high CO2 was not equivalent to 'natural' senescence althou gh some chlorophyll fluorescence parameters changed similarly. During extended high CO2 treatment the level of q(NP) incre ased notably in the yellowing leaves. The high levels of q(NP) and relaxation kinetics of chi fluorescence quenching recor ded upon darkening demonstrate that thylakoid energization increased during the decline of photosynthetic CO2 uptake in hi gh CO2. This shows that the photosynthetic decline was not caused by decreasing thylakoid energization because of physical damage by oversized starch grains. Calculated photosynthetic electron flow declined little suggesting that CO2 at ribulos ebisphosphate carboxylase-oxygenase fell and thus photorespiration rose. With regard to growth limitation in high CO2 conc entration, these results support the concept that high CO2 concentration tends to induce low inorganic phosphate concentra tions (Morin et al. Plant Physiol. 99, 89-95, 1992; Duchein et al. J. Exp. Bet. 44, 17-22, 1993) which can limit chloropla st ATP synthase and thus increase thylakoid energization. It is proposed that the different responses of individual leaves to atmospheric CO2 enrichment reflects variety among leaves in the phosphate status or in the capacity for Pi-recycling (assimilate utilization).S AFFECT PHYTOMASS AND THE PRODUCTION OF PLANT DEFENSIVE SECONDARY CHEMICALS IN SALIX- MYRSINIFOL!659^3^Billes,G^Rouhier,H^Bottner,P^1993^1^Modifications of the carbon and nitrogen allocations in the plant (triticum-aestivum L) soil system in response to increased atmospheric co2 concentration^206^157^2^215-225^^^^^Dec^^^^^4132 WILLOWS AB !A^4131^The aim of this work was to examine the response of wheat plants to a doubling of the atmospheric CO2 concentration! on: (1) carbon and nitrogen partitioning in the plant, (2) carbon release by the roots; and (3) the subsequent N uptake b!y the plants. The experiment was performed in controlled laboratory conditions by exposing fast-growing spring wheat plant!s, during 28 days, to a (CO2)-C-14 concentration of 350 or 700 muL L-1 at two levels of soil nitrogen fertilization. Doubl!ing CO2 availability increased total plant production by 34% for both N treatment. In the N-fertilized soil, the CO2 enric!hment resulted in an increase in dry mass production of 41% in the shoots and 23% in the roots; without N fertilization th! is figure was 33% and 37%, respectively. In the N-fertilized soil, the CO2 increase enhanced the total N uptake by 14% and! lowered the N concentration in the shoots by 23%. The N concentration in the roots was unchanged. In the N-fertilized soi! l, doubling CO2 availability increased N uptake by 32% but did not change the N concentrations, in either shoots or roots.! The CO2 enrichment increased total root-derived carbon by 12% with N fertilization, and by 24% without N fertilization. B! etween 85 and 90% of the total root derived-C-14 came from respiration, leaving only 10 to 15% in the soil as organic C-14!. However, when total root-derived C-14 was expressed as a function of root dry weight, these differences were only slight!ly significant. Thus, it appears that the enhanced carbon release from the living roots in response to increased atmospher!ic CO2, is not due to a modification of the activity of the roots, but is a result of the increased size of the root syste!m. The increase of root dry mass also resulted in a stimulation of the soil N mineralization related to the doubling atmos!pheric CO2 concentration. The discussion is focused on the interactions between the carbon and nitrogen allocation, especially to the root system, and the implications for the acquisition of nutrients by plants in response to CO2 increase. rev!660^5^Clifford,SC^Stronach,IM^Mohamed,AD^Azamali,SN^Crout,NMJ^1993^1^The effects of elevated atmospheric carbon-dioxide an!d water- stress on light interception, dry-matter production and yield in stands of groundnut (arachis-hypogaea L)^78^44^269^1763-1770^^^^^Dec^^^^^4134terms of their experimental protocols on growth conditions and recommendations for optimal r!A^4133^Stands of groundnut (Arachis hypogaea L.), a C-3 legume, were grown in controlled-environment glasshouses at 28 deg!rees C (15 degrees C) under two levels of atmospheric CO2 (350 ppmv or 700 ppmv) and two levels of soil moisture (irrigate!d weekly or no water from 35 d after sowing). Elevated CO2 increased the maximum rate of net photosynthesis by up to 40%, !with an increase in conversion coefficient for intercepted radiation of 30% (from 1.66 to 2.16 g MJ(-1)) in well-irrigated! conditions, and 94% (from 0.64 to 1.24 g MJ(-1)) on a drying soil profile. In plants well supplied with water, elevated C!O2 increased dry matter accumulation by 16% (from 13.79 to 16.03 t ha(-1)) and pod yield by 25% (from 2.7 to 3.4 t ha(-1))!. However, the harvest index (total pod dry weight/above-ground dry weight) was unaffected by CO2 treatment. The beneficia!l effects of elevated CO2 were enhanced under severe water stress, dry matter production increased by 112% (from 4.13 to 8!.87 t ha(- 1)) and a pod yield of 1.34 t ha(-1) was obtained in elevated CO2, whereas comparable plots at 350 ppmv CO2 onl! y yielded 0.22 t ha(-1). There was a corresponding decrease in harvest index from 0.15 to 0.05. Following the withholding !!of irrigation, plants growing on a stored soil water profile in elevated CO2 could maintain significantly less negative le!"af water potentials (P<0.01) for the remainder of the season than comparable plants grown in ambient CO2, allowing prolong!#ed plant activity during drought. In plants which were well supplied with water, allocation of dry matter between leaves, !$stems, roots, and pods was similar in both CO2 treatments. On a drying soil profile, allocation in plants grown in 350 ppm!%v CO2 changed in favour of root development far earlier in the season than plants grown at 700 ppmv CO2, indicating that s!&evere water stress was reached earlier at 350 ppmv CO2. The primary effects of elevated CO2 on growth and yield of groundn!'ut stands were mediated by an increase in the conversion coefficient for intercepted radiation and the prolonged maintenance of higher leaf water potentials during increasing drought stress.in atmospheric CO2 with industrialization has been ex!)661^2^Ferris,R^Taylor,G^1993^1^Contrasting effects of elevated co2 on the root and shoot growth of 4 native herbs commonly found in chalk grassland^84^125^4^855-866^^^^^Dec^^^^^4136ing the last several decades. However, if mature trees show a !+A^4135^The aim of this study was to investigate the impact of ambient (345 mu l l(-1)) and elevated (590 mu l l(-1)) CO2 o!,n the root and shoot growth of four native chalk grassland herbs: Sanguisorba minor Scop. (salad burnet), Lotus corniculat!-us L. (birdsfoot trefoil), Anthyllis vulneraria L. (kidney vetch) and Plantage media L. (hoary plantain). Elevated CO2 had!. contrasting effects on both shoot and root growth of the four species studied. Both leaf expansion and production were st!/imulated by elevated CO2 for S. minor, L. corniculatus and P. media, whilst for A. vulneraria, only leaflet shape appeared!0 to be altered by elevated CO2, with the production of broader leaflets, compared with those produced in ambient CO2. Afte!1r 100 d shoot biomass was enhanced in elevated CO2 for S. minor and L. corniculatus, whilst there was no effect of elevate!2d CO2 on shoot biomass for A. vulneraria or P. media. Contrasting effects of CO2 were also apparent for measurements of sp!3ecific leaf area (SLA), which increased for L. corniculatus, decreased for A. vulneraria and remained unaltered for S. min!4or and P. media in elevated compared with ambient CO2. Elevated CO2 also had contrasting effects on both the growth and mo!5rphology of roots. The accumulation of root biomass was stimulated following exposure to elevated CO2 for S. minor and L. !6corniculatus whilst there was no effect on root biomass for A. vulneraria or P. media. Root length was measured on three o!7ccasions during the 100 d and revealed that exposure to elevated CO2 promoted root extension in S. minor, L. corniculatus !8and P. media, but not in A. vulneraria. Specific root length (SRL, length per unit dry weight) was increased in elevated C!9O2 for one species, P. media, whilst the root to shoot ratio of all four species remained unchanged by CO2. These results !:show that four native herbs differ in their response to CO2, suggesting that the structure of this plant community may be altered in the future.xygen exchange between the catalyst and the products CO2 and HCHO. This exchange process occurs at 662^1^Gifford,RM^1994^1^The global carbon-cycle - a viewpoint on the missing sink^92^21^1^1-15^^^^^^^^^^4138llows access !=A^4137^Atmospheric carbon budgets that ignore the possibility of terrestrial ecosystem responses to global atmospheric cha!>nge do not balance; there is a 'missing sink' of about 0.4 - 4 Gt C yr(-1). This paper argues a case that mechanistically !?it is well within the bounds of possibility that increasing carbon storage in vegetation and soils in response to the glob!@ally increasing CO2 concentration, temperature and nitrogen deposition can account for the missing C sink. Global warming !Aconditions considered alone would be unlikely to cause most ecosystems to emit CO2, because the N mineralised by any enhan!Bced soil organic matter decomposition would be largely taken up by plants and reconverted into organic matter having a muc!Ch higher C:N ratio than that in the soil. Models of the global terrestrial C cycle indicate that an extra 0.5 - 4 Gt C yr(!D-1) could well be being stored in soils and vegetation today in response to the CO2 fertilising effect, having regard for !Ethe interactions with growth restricting water, light and nitrogen levels. To obtain direct proof as to whether that this is happening or not is a major challenge.l Ecosystem Model (TEM), to the historical range of temperate forests in North A!G663^3^Knapp,AK^Fahnestock,JT^Owensby,CE^1994^1^Elevated atmospheric co2 alters stomatal responses to variable sunlight in a C-4 grass^9^17^2^189-195^^^^^Feb^^^^^4140tion of 0.5-degrees latitude by 0.5-degrees longitude. For contemporary climat!IA^4139^Native tallgrass prairie in NE Kansas was exposed to elevated (twice ambient) or ambient atmospheric CO2 levels in !Jopen-top chambers. Within chambers or in adjacent unchambered plots, the dominant C-4 grass, Andropogon gerardii, was subj!Kected to fluctuations in sunlight similar to that produced by clouds or within canopy shading (full sun > 1500 mu mol m(-2!L) s(-1) versus 350 mu mol m(-2) s(-1) shade) and responses in gas exchange were measured. These field experiments demonstr!Mated that stomatal conductance in A. gerardii achieved new steady state levels more rapidly after abrupt changes in sunlig!Nht at elevated CO2 when compared to plants at ambient CO2. This was due primarily to the 50% reduction in stomatal conduct!Oance at elevated CO2, but was also a result of more rapid stomatal responses. Time constants describing stomatal responses!P were significantly reduced (29-33%) at elevated CO2. As a result, water loss was decreased by as much as 57% (6.5% due to!Q more rapid stomatal responses). Concurrent increases in leaf xylem pressure potential during periods of sunlight variabil!Rity provided additional evidence that more rapid stomatal responses at elevated CO2 enhanced plant water status. CO2-induc!Sed alterations in the kinetics of stomatal responses to variable sunlight will likely enhance direct effects of elevated CO2 on plant water relations in all ecosystems.NING LONG- TERM RESPONSE OF VEGETATION TO RISING ATMOSPHERIC CO2 CONCENTRAT664^1^Kobayashi,K^1994^1^Mapping results of crop growth simulation in a vector-space^107^68^1-2^43-61^^^^^Mar^^^^^4142 DE!VA^4141^Crop growth models can be used to address the mode-of-action of the global change impacts on crop yield as well as !Wto predict the extent of the yield change. Presented in this paper are the framework to analyze the simulated yield change!X caused by the variations of many influencing factors and some methods to visualize the yield change. In the framework, th!Ye simulated yield change is mapped into an n-dimensional vector space, where n is the number of the simulated cases, e.g. !Zyears or locations. Yield changes owing to the individual impacts as well as the impact of simultaneous changes in all the![ factors are represented by vectors in the n-dimensional space. Contributions of the individual impacts to the simulated y!\ield change and the interrelations between the impacts can be represented by the magnitude and orientation of the vectors.!] To visualize the vectors, however, the dimension n must be three or less. This is not the case, in general, and hence som!^e methods are needed to reduce the dimension. By combining the influencing factors into three or less groups, the vectors !_for each group can be visualized in a subspace of dimension three or less. Impacts within each group may be further visual!`ized in the same way. Taking an average is another way to reduce the dimension of the vector space. With it, the n-dimensi!aonal space is partitioned into a one-dimensional space for the mean and an (n - 1)-dimensional space for the deviation of !bthe yield change. These methods were applied to an example of the simulated yield changes in soybean and maize owing to cl!cimate change (precipitation increase and temperature rise) and elevated CO2 (increases in the radiation use efficiency and!d the water use efficiency). The analyses revealed the differences between soybean and maize with respect to their response!es to the simulated impacts of the climate change and the elevated CO2. These inter-specific differences were related to th!fe differential changes in growth processes. The difference between the two impacts, i.e. the climate change and the CO2 in!gcrease, was also addressed. Utilities of the above approach were discussed and compared with the sensitivity analysis. Limitation of this approach was also discussed., plants showed a decrease in osmotic potentials of 0.15 MPa and an increase !i665^2^Korner,C^Diemer,M^1994^1^Evidence that plants from high-altitudes retain their greater photosynthetic efficiency under elevated co2^43^8^1^58-68^^^^^Feb^^^^^4144r content, while lower osmotic potentials shift the zero turgor loss point t!kA^4143^1. Herbaceous plant species native to low and high altitudes in the Alps evolved under CO2 partial pressures (P-a) !lthat differ as much as pre-industrial P-a differs from present day P-a at low altitude (e.g. 21% for a 2000-m difference i!mn altitude). 2. In a previous study we showed that the efficiency of CO2 uptake (ECU) in typical high-altitude species is !ngenerally greater than in low-altitude species. Here we investigate whether this difference prevails under longer-term exp!oosure to altered P-a. 3. Alpine and lowland species (mainly Ranunculus glacialis/R. acris and Geum reptans/G. rivale) were!p grown under various CO2 regimes in full daylight growth chambers at their respective natural growth temperature and photo!qperiod. When they were grown at twice the present CO2 level only moderate downward adjustment of photosynthesis was observ!red in both groups of species. The adjustments were not enough to compensate for the effect of increased CO2 supply. These !strends prevailed under reciprocally exchanged alpine/lowland partial pressure of CO2 at the same total atmospheric pressur!te. 4. Irrespective of altitudinal origin, greatest downward adjustment of photosynthesis was found in species with the mos!ut pronounced accumulation of non-structural carbohydrate and dilution of leaf nitrogen when grown under elevated CO2 (e.g.!v in G. rivale). 5. These results suggest that, at least initially, the alpine plant species studied may attain relatively greater carbon gains in a CO2-enriched atmosphere than comparable lowland plant species.h maize or soybean were grown. On!x666^1^Madsen,TV^1993^1^Growth and photosynthetic acclimation by ranunculus-aquatilis L in response to inorganic carbon availability^84^125^4^707-715^^^^^Dec^^^^^4146greater in rhizosphere soil (55 nL g-1 day-1) than in non- rhizosphere soil (3!zA^4145^Relative growth rates of Ranunculus aquatilis L. were measured in the laboratory at dissolved inorganic carbon (DIC!{) concentrations between 0.2 and 5.2 mM at air-equilibrium CO2 (16 mu M) and also at 0.55 mM DIC with elevated CO2 (350 mu!| M). For plants grown at air-equilibrium CO2, growth was limited by inorganic carbon below 1.6 mM DIC and the apparent hal!}f saturation constant was 0.5 mM. The growth rate at elevated CO2 was 50% higher than the carbon saturated rates obtained !~at high DIC concentrations and air-equibrium CO2, where HCO3- is dominant. This difference is suggested to be caused by di!fferences in uptake mechanisms for CO2 and HCO3-. Uptake of CO2 is a diffusive process, whereas HCO3- use is an active pro!cess which involves uptake/transport systems in the cell membranes. The plants acclimated to the DIC regime for growth by !reductions in carboxylation efficiency and bicarbonate affinity, but enhanced photosynthetic capacity at elevated DIC. Wit!hin the range of concentrations used, the acclimation to CO2 and HCO3- was quantitatively similar, except for the HCO3- up!take capacity which increased at high DIC and air-equilibrium CO2 but declined at elevated CO2. Dark respiration was unaff!ected by inorganic carbon per se, but increased with growth rate. Maintenance respiration was constant among treatments. I!t is concluded that inorganic carbon, apart from being the primary substrate for photosynthesis, has secondary growth regulatory effects which affect the photosynthetic apparatus of the plants.mini-greenhouses and, in addition, a compact mini-!667^2^Mooney,HA^Koch,GW^1994^1^The impact of rising co2 concentrations on the terrestrial biosphere^221^23^1^74-76^^^^^Feb^^^^^4148 influence of the additional CO2 supply stem diameter (2 cm above the first lateral roots) was increased by 13.5!A^4147^Large advances have been made in linking terrestrial biospheric and atmospheric processes in real time. Further, it! is now possible to model the potential response of the Earth's primary productivity to the changing climate and to change!s in atmospheric CO2 concentration. We still have limited information, however, on the total responses of ecosystems to en!hanced CO2 because of the complex web of possible interactions. What is needed are experiments on whole ecosystems under e!nhanced CO2 in which all of the potential interactions and feedbacks can be monitored, including plant- microbe, plant-her!bivore, and plant-atmosphere interactions. A global network of experiments in the major biomes of the world is being devel!oped within the International Geosphere-Biosphere Programme (IGBP) to resolve questions related to the implications of a changed pattern of biomass distribution in the biosphere.es- C amounted to 0.31 +/- 0.18 and at 700 ppmv to 0.57 +/- 0.42 !668^5^Newton,PCD^Clark,H^Bell,CC^Glasgow,EM^Campbell,BD^1994^1^Effects of elevated co2 and simulated seasonal-changes in temperature on the species composition and growth-rates of pasture turves^52^73^1^53-59^^^^^Jant the high CO2 concentratio!669^4^Rogers,GS^Payne,L^Milham,P^Conroy,J^1993^1^Nitrogen and phosphorus requirements of cotton and wheat under changing atmospheric co2 concentrations^206^156^^231-234^^^^^Oct^^^^^4151ures in order to quantify CO2 enrichment effects on beech !A^4150^The influence of increasing atmospheric CO2 on shoot growth, leaf nitrogen and phosphorus concentrations and carboh!ydrate composition was investigated in cotton and wheat. Shoot dry weight of both species was generally higher at elevated! CO2, especially at high rates of available soil N and P. Critical leaf N concentration was reduced but critical P concentration was increased in both species at high CO2.ND ECOSYSTEMS; ESTUARINE MARSH; PHOTOSYNTHETIC ACCLIMATION; COMMUNITIES;!670^3^Rogers,HH^Runion,GB^Krupa,SV^1994^1^Plant-responses to atmospheric co2 enrichment with emphasis on roots and the rhizosphere^35^83^1-2^155-189^^^^^^^^^^4153d water use efficiencies at the individual plant level. Tallgrass prairie has had!A^4152^Empirical records provide incontestable evidence of global changes; foremost among these changes is the rising conc!entration of CO2 in the earth's atmosphere. Plant growth is nearly always stimulated by elevation of CO2. Photosynthesis i!ncreases, more plant biomass accumulates per unit of water consumed, and economic yield is enhanced The profitable use of !supplemental CO2 over years of greenhouse practice points to the value of CO2 for plant production. Plant responses to CO2! are known to interact with other environmental factors, e.g. light, temperature, soil water, and humidity. Important stre!sses including drought, temperature, salinity, and air pollution have been shown to be ameliorated when CO2 levels are ele!vated In the agricultural context, the growing season has been shortened for some crops with the application of more CO2; !less water use has generally, but not always, been observed and is under further study; experimental studies have shown th!at economic yield for most crops increases by about 33% for a doubling of ambient CO2 concentration. However, there are so!me reports of negligible or negative effects. Plant species respond differently to CO2 enrichment, therefore, clearly comp!etitive shifts within natural communities could occur. Though of less importance in managed agro-ecosystems, competition b!etween crops and weeds could also be altered. Tissue composition can vary as CO2 increases (e.g. higher C:N ratios) leadin!g to changes in herbivory, but tests of crop products (consumed by man) from elevated CO2 experiments have generally not r!evealed significant differences in their quality. However, any CO2-induced change in plant chemical or structural make-up !could lead to alterations in the plant's interaction with any number of environmental factors- physicochemical or biologic!al. Host-pathogen relationships, defense against physical stressors, and the capacity to overcome resource shortages could! be impacted by rises in CO2. Root biomass is known to increase but, with few exceptions, detailed studies of root growth !and function are lacking. Potential enhancement of root growth could translate into greater rhizodeposition, which, in tur!n, could lead to shifts in the rhizosphere itself. Some of the direct effects of CO2 on vegetation have been reasonably we!ll-studied, but for others work has been inadequate. Among these neglected areas are plant roots and the rhizosphere. Ther!efore, experiments on root and rhizosphere response in plants grown in CO2-enriched atmospheres will be reviewed and, wher!e possible, collectively integrated To this will be added data which have recently been collected by us. Having looked at the available data base, we will offer a series of hypotheses which we consider as priority targets for future research.t!671^3^Sicher,RC^Kremer,DF^Rodermel,SR^1994^1^Photosynthetic acclimation to elevated co2 occurs in transformed tobacco with decreased ribulose-1,5-bisphosphate carboxylase/oxygenase content^8^104^2^409-415^^^^^Feb^^^^^4155n 1989, but did not di!A^4154^Inhibition of net carbon assimilation rates during growth at elevated CO2 was studied in transgenic tobacco (Nicoti!ana tabacum L.) plants containing zero to two copies of antisense DNA sequences to the small subunit polypeptide (rbcS) ge!ne of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). High- and low-Rubisco tobacco plants were obtained from t!he selfed progeny of the original line 3 transformant (S.R. Rodermel, M.S. Abbott, L. Bogorad [1988] Cell 55: 673-681). As!similation rates of high- and low-Rubisco tobacco plants increased 22 and 71%, respectively, when transferred from 35- to !70-Pa CO2 chamber air at 900 mu mol m(-2) s(-1) photon flux density. However, CO2-dependent increases of net carbon assimi!lation rates of high- and low-Rubisco plants virtually disappeared after 9 d of growth in elevated CO2 chamber air. Total !above-ground dry matter production of high- and low- Rubisco plants was 28 and 53% greater, respectively, after 9 d of gro!wth at 70 Pa compared with 35 Pa CO2. Most of this dry weight gain was due to increased specific leaf weight. Rubisco acti!vity, Rubisco protein, and total chlorophyll were lower in both high- and low-Rubisco plants grown in enriched compared wi!th ambient CO2 chamber air. Soluble leaf protein also decreased in response to CO2 enrichment in high- but not in low-Rubi!sco tobacco plants. Decreased Rubisco activities in CO2-adapted high- and low-Rubisco plants were not attributable to chan!ges in activation state of the enzyme. Carbonic anhydrase activities and subunit levers measured with specific antibodies !were similar in high- and low-Rubisco tobacco plants and were unchanged by CO2 enrichment. Collectively, these findings su!ggested that photosynthetic acclimation to enriched CO2 occurred in tobacco plants either with or without transgenically d!ecreased Rubisco levels and also indicated that the down-regulation of Rubisco in CO2-adapted tobacco plants was related to decreased specific activity of this enzyme.USALEM, DEPT BOT, IL-91904 JERUSALEM, ISRAEL. DE LEMNA-GIBBA; LACTUCA-SATIVA!672^2^Thomas,RB^Griffin,KL^1994^1^Direct and indirect effects of atmospheric carbon-dioxide enrichment on leaf respiration of glycine-max (L) merr^8^104^2^355-361^^^^^Feb^^^^^4157AVES; EFFLUX BP 129-131 PG 3 JI Ann. Bot. PY 1993 PD AUG VL 72 I!A^4156^Long-term and short-term effects of CO2 enrichment on dark respiration were investigated using soybean (Glycine max! [L.] Merr.) plants grown at either 35.5 or 71.0 Pa CO2. Indirect effects, or effects of growth in elevated CO2, were exam!ined using a functional model that partitioned respiration into growth and maintenance components. Direct effects, or imme!diate effects of a short-term change in CO2, were examined by measuring dark respiration, first, at the CO2 partial pressu!re at which plants were grown, and second, after equilibration in the reciprocal CO2 partial pressure. The functional comp!onent model indicated that the maintenance coefficient of respiration increased 34% with elevated CO2, whereas the growth !coefficient was not significantly affected. Changes in maintenance respiration were correlated with a 33% increase in leaf! total nonstructural carbohydrate concentration, but leaf nitrogen content of soybean leaves was not affected by CO2 enric!hment. Thus, increased maintenance respiration may be a consequence of increased nonstructural carbohydrate accumulation. !When whole soybean plants were switched from low CO2 to high CO2 for a brief period, leaf respiration was always reduced. !However, this direct effect of CO2 partial pressure was approximately 50% less in plants grown in elevated CO2. We conclud!e from this study that there are potentially important effects of CO2 enrichment on plant respiration but that the effects are different for plants given a short-term increase in CO2 partial pressure versus plants grown in elevated CO2.ose res!673^2^Tremmel,DC^Patterson,DT^1994^1^Effects of elevated co2 and temperature on development in soybean and 5 weeds^146^74^1^43-50^^^^^Jan^^^^^4159e converted via acetate and H-2 to CH4, their accumulation rates plus that of acetate accounted f!A^4158^Developmental rates of soybean [Glycine max (L.) Merr. 'Braxton'],johnsongrass [Sorghum halepense (L.) Pers.], quac!kgrass [Elytrigia repens (L.) Nevski], redroot pigweed (Amaranthus retroflexus L.), sicklepod (Cassia obtusifolia L.), and! velvetleaf (Abutilon theophrasti Medic.) were compared among plants grown in all combinations of two temperature levels (!avg. day/night of 26/19 degrees C and 30/23 degrees C) and two CO2 levels (350 and 700 ppm). Neither temperature nor CO2 a!ffected johnsongrass tillering rate, but plants began tillering earlier at higher temperatures. Adverse effects of higher !temperatures on quackgrass development were alleviated by elevated CO2 conditions. Plastochron rate was higher at higher t!emperatures in all dicot species (soybean, redroot pigweed, sicklepod, and velvetleaf), and was higher at elevated CO2 in !all dicots except velvetleaf. Calculating plastochron rates on a degree day basis removed differences between temperature !treatments, but did not affect responses to CO2. Responses of dicot branch and branch leaf production to treatments varied! among species. Branch production per day increased with higher temperatures in redroot pigweed, decreased with higher tem!peratures in sicklepod, and was unaffected by temperature in soybean. The relationship between main axis and branch develo!pmental rates was altered by temperature in soybean, and by both temperature and CO2 in sicklepod, but was unaffected by e!ither treatment in redroot pigweed. These results indicate that developmental responses to temperature and CO2 depend on both the species and the aspect of development being considered. from up to 5 parts per thousand variation in delta-C-13 a!674^3^Cipollini,ML^Drake,BG^Whigham,D^1993^1^Effects of elevated co2 on growth and carbon/nutrient balance in the deciduous woody shrub lindera benzoin (L.) blume (lauraceae)^2^96^3^339-346^^^^^Dec^^^^^4161nic carbon signatures in disseminated!A^4160^We examined the effects of elevated CO2 on growth and carbon/nutrient balance in a natural population of the decidu!ous temperate zone shrub Lindera benzoin. Our data concern whole plant, leaf, and stem growth for the first two seasons of! a long-term field experiment in which CO2 levels were manipulated in situ. In addition to growth parameters, we evaluated! changes in leaf and stem chemistry, including total nitrogen, nonstructural carbohydrates, and total phenolics. Over the !course of this study, L. benzoin appeared to respond to elevated CO2 primarily by physiological and biochemical changes, w!ith only a slight enhancement in aboveground growth (ramet height). Positive effects on aboveground growth were primarily !evident in young (nonreproductive) ramets. Our results suggest that nitrogen limitation may have constrained plants to all!ocate carbohydrates produced in response to elevated CO2 primarily to storage and belowground growth, and perhaps to incre!ased secondary chemical production, rather than to increased stem and leaf growth. We discuss our results in terms of chan!ges in carbon/nutrient balance induced by elevated CO2, and provide predictions for future changes in this system based up!on constraints imposed by intrinsic and extrinsic factors and their potential effects on the reallocation of stored reserves.ate was 0.9d-1. The ratio of inorganic carbon fixed to organic carbon fixed was about 0.1. CO2 enriched air (715 ppm) !675^3^Conway,TJ^Steele,LP^Novelli,PC^1993^1^Correlations among atmospheric co2, ch4 and co in the arctic, march 1989^242^27^17-18^2881-2894^^^^^Dec^^^^^4163 obtained for the cells after the acclimation culture where the CO2 concentration was g!A^4162^During six aircraft flights conducted as part of the third Arctic Gas and Aerosol Sampling Program (AGASP III, Marc!h 1989), 189 air samples were collected throughout the Arctic troposphere and lower stratosphere for analysis of CO2, CH4 !and CO. The mixing ratios of the three gases varied significantly both horizontally and vertically. Elevated concentration!s were found in layers with high anthropogenic aerosol concentrations (Arctic Haze), The mixing ratios of CO2, CH4 and CO !were highly correlated on all flights. A linear regression of CH4 vs CO2 for pooled data from all flights yielded a correl!ation coefficient (r(2)) of 0.88 and a slope of 13.5 ppb CH4/ppm CO2 (n = 186). For CO vs CO2 a pooled linear regression g!ave r(2) = 0.91 and a slope of 15.8 ppb CO/ppm CO2 (n = 182). Carbon dioxide, CH4 and CO also exhibited mean vertical grad!ients with slopes of 0.37, -4.4 and -4.2 ppb km(-1), respectively. Since the carbon dioxide variations observed in the Arc!tic atmosphere during winter are due primarily to variations in the emissions and transport of anthropogenic CO2 from Euro!pe and Asia, the strong correlations that we have found suggest that a similar interpretation applies to CH4 and CO. Using! reliable estimates of CO2 emissions for the source regions and the measured CH4/CO2 and CO/CO2 ratios, we estimate a regi!onal European CH4 source of 47+/-6 Tg CH4 yr(-1) that may be associated with fossil fuel combustion. A similar calculation for CO results in an estimated regional CO source of 82+/- 2Tg CO yr(-1). 5b, 7, 8, 10 and 12 were isolated, and, in severature on carbon balance of tussock tundra microcosms^2^108^4^737-748^^^^^Dec^^^^^4924ted from nine herds which were fo"676^6^Dixon,RK^Brown,S^Houghton,RA^Solomon,AM^Trexler,MC^Wisniewski,J^1994^1^Carbon pools and flux of global forest ecosystems^32^263^5144^185-190^^^^^14 Jan^^^^^4165BP 204-208 PG 5 JI Can. J. Vet. Res.-Rev. Can. Rech. Vet. PY 1993 PD JUL VL 5"A^4164^Forest systems cover more than 4.1 x 10(9) hectares of the Earth's land area. Globally, forest vegetation and soils" contain about 1146 petagrams of carbon, with approximately 37 percent of this carbon in low-latitude forests, 14 percent "in mid-latitudes, and 49 percent at high latitudes. Over two- thirds of the carbon in forest ecosystems is contained in so"ils and associated peat deposits. In 1990, deforestation in the low latitudes emitted 1.6 +/- 0.4 petagrams of carbon per "year, whereas forest area expansion and growth in mid- and high- latitude forest sequestered 0.7 +/- 0.2 petagrams of carb" on per year, for a net flux to the atmosphere of 0.9 +/- 0.4 petagrams of carbon per year. Slowing deforestation, combined" with an increase in forestation and other management measures to improve forest ecosystem productivity, could conserve or" sequester significant quantities of carbon. Future forest carbon cycling trends attributable to losses and regrowth assoc" iated with global climate and land-use change are uncertain. Model projections and some results suggest that forests could be carbon sinks or sources in the future.ted temperature increased metabolic activity, it only partially alleviated the "677^4^Gao,K^Aruga,Y^Asada,K^Kiyohara,M^1993^1^Influence of enhanced co2 on growth and photosynthesis of the red algae gracilaria sp and g-chilensis^187^5^6^563-571^^^^^Dec^^^^^4167on to elevated CO2. BP 17-28 PG 12 JI Photosynthetica PY 1993 V"A^4166^The influence of elevated CO2 concentrations on growth and photosynthesis of Gracilaria sp. and G. chilensis was in"vestigated in order to procure information on the effective utilization of CO2. Growth of both was enhanced by CO2 enrichm"ent (air + 650 ppm CO2, air + 1250 ppm CO2), the enhancement being greater in Gracilaria sp. Both species increased uptake" of NO, with CO, enrichment. Photosynthetic inorganic carbon uptake was depressed in G. chilensis by pre- culture (15 days") with CO2 enrichment, but little affected in Gracilaria sp. Mass spectrometric analysis showed that O-2 uptake was higher" in the light than in the dark for both species and in both cases was higher in Gracilaria sp. The higher growth enhancement in Gracilaria sp. was attributed to greater depression of photorespiration by the enrichment of CO2 in culture.so shif"678^5^Prusky,D^Plumbley,RA^Kobiler,I^Zauberman,G^Fuchs,Y^1993^1^The effect of elevated co2 levels on the symptom expression of colletotrichum-gloeosporioides on avocado fruits^243^42^6^900-904^^^^^Dec^^^^^41692 due to a UV induced increase in "A^4168^Exposure of freshly harvested avocado fruits to different concentrations of CO2 (11, 16 and 30%) for different leng"ths of time (4, 17 and 26 h) affected the decay development caused by Colletotrichum gloeosporioides. The delay in symptom" development depended on the treatment given, the temperature regime of the fruit and time after harvest for treatment app"lication. The most appropriate treatment was the application of 30% CO2 for 24 h at a temperature of 20-25 degrees C on th"e day of harvest. Treatment for shorter time periods, at lower temperatures or 50 h after harvest, resulted in a reduced r"esponse and, in some cases, enhanced symptom expression. Concentrations of 11 or 16% CO2 were less effective than 30% CO2 "as the fruits became more mature. It is concluded that treatment of avocado fruits with high levels of CO2 for a short period has the potential to provide an alternative means of controlling anthracnose. and isotopic compositions of CH4, CO2, "!679^2^Seaton,KA^Joyce,DC^1993^1^Effects of low-temperature and elevated co2 treatments and of heat-treatments for insect disinfestation on some native- australian cut flowers^165^56^2^119-133^^^^^Dec^^^^^4171ermentation and CO2/H-2 reduction. "#A^4170^For bioassay insects, 14 days storage at 1-degrees-C was required for 100% kill of adult flour beetles (Tribolium c"$onfusum Koch.), and 10 days at 1-degrees-C killed 100% of Mediterranean fruit fly larvae (Ceratitis capitata Wied.). A CO2"% enriched atmosphere of between 45% and 60% (11% and 8% O2, respectively) reduced the time required to achieve 100% mortal"&ity of these bioassay insects to 7 days at 1-degrees-C. Increasing the CO2 content of the atmosphere to 80% (4% O2) did no"'t further reduce the time to achieve 100% mortality. Vase life of red kangaroo paw (Anigozanthos rufus) was reduced below "(that of the unstored control after just 3.5 days at 1-degrees- C. Geraldton wax (Chamelaucium uncinatum) cultivar 'Newmarr")acarra' was similarly affected after 14 days, and acorn banksia (Banksia prionotes) after 28 days. Vase lives of Geraldton"* wax cultivar 'Newmarracarra' and of red kangaroo paw were not reduced following 7 days storage at 1-degrees-C in 15% CO2,"+ compared with controls stored in air. However, Geraldton wax and red kangaroo paw vase lives were shortened and flower co",lour was altered after storage for 7 days in 30% CO2 (15% O2). Geraldton wax and red kangaroo paw had no vase lives follow"-ing storage in 80% CO2 (4% O2) at 1-degrees-C for 3. 5 days. Heat treatments of hot water dips (46-degrees-C for 30 min or". 56-degrees-C for 10 min) and vapour heat (66-degrees-C for 10 min) killed 100% of adult flour beetles and Mediterranean fruit fly larvae, but damaged and shortened the vase lives of Geraldton wax and banksia.TR, HABIKINO, OSAKA 583, JAPAN. AB"0680^2^Idso,SB^Kimball,BA^1994^1^Effects of atmospheric co2 enrichment on biomass accumulation and distribution in eldarica pine trees^78^45^280^1669-1672^^^^^Nov^^^^^4173 time for beginning the CO2 enrichment treatment was established. The tot"2A^4172^Eight Eldarica pine tree (Pinus eldarica L.) seedlings planted directly into the ground at Phoenix, Arizona within "3four clear- plastic-wall open-top enclosures were grown for a period of 2 years at mean atmospheric CO2 concentrations of "4408, 554, 680, and 812 mu L L(-1). Biomass accumulations in needles, branches and boles were all linear functions of CO2 o"5ver this concentration range. For a 75% increase in ambient CO2, i.e. for an increase from 400-700 mu L L(-1), the trees e"6xperienced a 3.42-fold increase in total above-ground biomass; while for a CO2 concentration doubling from 400-800 mu L L("7-1), they experienced a 4.23-fold increase. Bore biomass responded similarly. Needle biomass, however, increased by a smal"8ler amount (2.84-fold and 3.45-fold, respectively, for 400-700 and 400-800 mu L L(-1) increases in CO2); while branch biomass was increased considerably more (by 4.73-fold and 5.97-fold for corresponding increases in CO2).. DE TRITICUM-AESTIVU"A681^2^Ingvardsen,C^Veierskov,B^1994^1^Response of young barley plants to co2 enrichment^78^45^279^1373-1378^^^^^Oct^^^^^41";A^4174^Barley (Hordeum vulgare L. cv. Digger) was grown for 22 d in enclosed chambers with a CO2 enrichment of 35, 155, 40"<0 or 675 mu mol CO2 mol(-1). CO2 enrichment increased photosynthetic capacity in the plants grown at either of the two hig"=hest levels of pCO(2). A CO2 enrichment of 675 mu mol CO2 caused a significant increment of shoot dry weight, whereas no c">hanges were observed in fresh weight, chlorophyll or protein levels. At a light intensity of 860 mu mol m(-2) s(-1) CO2 en"?richment caused photosynthetic capacity to increase by 250%, whereas no effect was observed at 80 mu mol m(-2) s(-1). Over"@ time, photosynthesis decreased by 70% independent of CO2. A time- dependent increase in the level of extractable fructose was observed whereas total extractable carbohydrate only changed slightly.host water content was significantly increased75erity of mildew infection was significantly increased. In a moderate water supply treatment, the plants grown in elevat"C682^4^Izrael,YA^Semenov,SM^Kunina,IM^Zamaraeva,TV^1994^1^Modification of direct effect of carbon-dioxide on higher- plants due to tropospheric ozone impact^244^338^5^711-713^^^^^Oct mildew infection appeared to be more sensitive to host water "E683^2^Lamhamedi,MS^Bernier,PY^1994^1^Ecophysiology and field performance of black spruce (picea- mariana) - a review^186^51^6^529-551^^^^^^^^^^4178OMAS, RB STRAIN, BR TI LONG-TERM EFFECTS OF ELEVATED CO2 AND NUTRIENTS ON PHOTOSYNTHESIS AND RUB"GA^4177^This paper presents a literature review of black spruce (Picea mariana [Mill] BSP) ecophysiology concerning the res"Hponse of net photosynthesis and stomata to changes in environmental factors. Current knowledge on root growth, mineral nut"Irition and response to high temperature, CO2 enrichment and climate change, frosts, water stress and flooding are also cov"Jered. The review ends with an overview of stand establishment and field performance of planted seedlings. The authors high"Klight the need for research on the long-term effects of multiple stresses, such as climate change and air pollution on the black spruce ecosystem.hree nutrient treatments (low N, low P, and high N and P). Measurements taken in late autumn (Nov"M684^11^Leavitt,SW^Paul,EA^Kimball,BA^Hendrey,GR^Mauney,JR^Rauschkolb,R^Rogers,H^Lewin,KF^Nagy,J^Pinter,PJ^Johnson,HB^1994^1^Carbon-isotope dynamics of free-air co2-enriched cotton and soils^107^70^1-4^87-101^^^^^Sep^^^^^4180evated CO2, but the"OA^4179^A role for soils as global carbon sink or source under increasing atmospheric CO2 concentrations has been speculati"Pve. Free-air carbon dioxide enrichment (FACE) experiments with cotton, conducted from 1989 to 1991 at the Maricopa Agricul"Qtural Center in Arizona, maintained circular plots at 550 mumol mol-1 CO2 with tank CO2 while adjacent ambient control plo"Rts averaged about 370 mumol mol-1 CO2. This provided an exceptional test for entry of carbon into soils because the petroc"Shemically derived tank CO2 used to enrich the air above the FACE plots was depleted in both radiocarbon (C-14 content was "T0% modern carbon (pmC)) and C-13 (delta13 C almost- equal-to -36 parts per thousand) relative to background air, thus serv"Uing as a potent isotopic tracer. Flask air samples, and plant and soil samples were collected in conjunction with the 1991"V experiment. Most of the isotopic analyses on the plants were performed on the holecellulose component. Soil organic carbo"Wn was obtained by first removing carbonate with HCl, floating off plant fragments with a NaCl solution, and picking out re"Xmaining plant fragments under magnification. The delta C-13 of the air above the FACE plots was approximately - 15 to - 19"Y parts per thousand, i.e. much more C-13 depleted than the background air of approximately -7.5parts per thousand. The del"Zta C-13 values of plants and soils in the FACE plots were 10-12 parts per thousand and 2 parts per thousand C-13-depleted,"[ respectively, compared with their control counterparts. The C-14 content of the FACE cotton plants was approximately 40 p"\mC lower than that of the control cotton, but the C-14 results from soils were conflicting and therefore not as revealing "]as the delta C-13 of soils. Soil stable-carbon isotope patterns were consistent, and mass balance calculations indicate th"^at about 10% of the present organic carbon content in the FACE soil derived from the 3 year FACE experiment. At a minimum,"_ this is an important quantitative measure of carbon turnover, but the presence of C- 13-depleted carbon, even in the reca"`lcitrant 6 N HCl resistant soil organic fraction (average age 2200 years before present (BP)), suggests that at least some"a portion of this 10% is an actual increase in carbon accumulation. Similar isotopic studies on FACE experiments in differe"bnt ecosystems could permit more definitive assessment of carbon turnover rates and perhaps provide insight into the extent to which soil organic matter can accommodate the 'missing' carbon in the global carbon cycle.havior is governed by chang"d685^3^Leonardos,ED^Tsujita,MJ^Grodzinski,B^1994^1^Net carbon-dioxide exchange-rates and predicted growth-patterns in alstr"eoemeria-jacqueline at varying irradiances, carbon- dioxide concentrations, and air temperatures^154^119^6^1265-1275^^^^^Nov^^^^^4182GROWTH INCREASES IN OLD-GROWTH LONGLEAF PINE SO CANADIAN JOURNAL OF FOREST RESEARCH-REVUE CANADIENNE DE RECHERC"gA^4181^The influence of irradiance, CO2 concentration, and air temperature on leaf and whole-plant net C exchange rate (NC"hER) of Alstroemeria 'Jacqueline' was studied. At ambient CO2, leaf net photosynthesis was maximum at irradiances above 600"i mu mol.m(-2).s(-1) photosynthetically active radiation (PAR), while whole-plant NCER required 1200 mu mol.m(-2).s(-1) PAR"j to be saturated. Leaf and whole-plant NCERs were doubled under CO2 enrichment of 1500 to 2000 mu l CO2/liter. Leaf and wh"kole-plant NCERs declined as temperature increased from 20 to 35C. Whereas the optimum temperature range for leaf net photo"lsynthesis was 17 to 23C, whole-plant NCER, even at high light and high CO2, declined above 12C. Dark respiration of leaves"m and whole plants increased with a Q(10) of approximate to 2 at 15 to 35C. In an analysis of day effects, irradiance, CO2 "nconcentration, and temperature contributed 58%, 23%, and 14%, respectively, to the total variation in NCER explained by a "osecond-order polynomial model (R(2)=0.85). Interactions among the factors accounted for 4% of the variation in day C assim"pilation. The potential whole- plant growth rates during varying greenhouse day and night temperature regimes were predicte"qd for short- and long-day scenarios. The data are discussed with the view of designing experiments to test the importance "rof C gain in supporting flowering and high yield during routine harvest of Alstroemeria plants under commercial greenhouse conditions.ought severity index over the last 57 years. Increased atmospheric CO2 is a possible explanation for initiati"t686^7^Mauney,JR^Kimball,BA^Pinter,PJ^Lamorte,RL^Lewin,KF^Nagy,J^Hendrey,GR^1994^1^Growth and yield of cotton in response to a free-air carbon- dioxide enrichment (face) environment^107^70^1-4^49-67^^^^^Sep^^^^^4184PT J AU WHEELER, RM MACKOWIAK"vA^4183^To quantify the growth and yield responses to CO2 enrichment in an open field setting, free-air CO2 enrichment (FAC"wE) technology was used to expose a cotton (Gossypium hirustum L.) crop to 550 mumol mol-1 CO2 throughout the growing seaso"xns of 1989, 1990 and 1991 in fields near Maricopa, Arizona. In 1990 and 1991 a water stress treatment was also imposed. Re"ysponse data for all years were consistent, and the data for 1991 were the least compromised by unusual weather or equipmen"zt failures. In that season the biomass was increased 37% by the 48% increase in CO2 concentration. Harvestable yield was i"{ncreased 43%. The increase in biomass and yield was attributed to increased early leaf area, more profuse flowering and a "|longer period of fruit retention. The FACE treatment increased water- use efficiency (WUE) to the same amount in the well-"}irrigated plots as in the water-stressed plots. The increase in WUE was due to the increase in biomass production rather than a reduction of consumptive use.(PPF). Seed yield and total biomass were greatest at 100 Pa for cv. McCall, suggesting"687^1^Mortensen,LM^1994^1^Effects of day-night temperature-variations on growth, morphogenesis and flowering of kalanchoe-"blossfeldiana V poelln at different co2 concentrations, daylengths and photon flux densities^165^59^3-4^233-241^^^^^Nov^^^"A^4185^Growth and flowering of Kalanchoe blossfeldiana were studied at two temperature treatments (constant, CT; day lower" than night temperature, negative DIF) in combination with two CO2 concentrations (360 and 900 mu mol mol(-1)), two daylen"gths (DL; 12 and 18 h) and two photosynthetic photon flux densities (PPFD; 85 and 130 mu mol m(-2) s(-1)). In addition to "the two temperature treatments, a 2-h low temperature pulse (DROP) was included in combination with short days and low CO2" levels. The experiment was conducted in 18 growth chambers with artificial light only. The plant dry weight at saleable s"tage was the same at the different temperature treatments irrespective of CO2 concentration, DL or PPFD. The dry weight wa"s similarly (31- 40%) increased by CO2 enrichment, or increasing DL or PPFD. Total plant height was slightly, but consiste"ntly increased by negative DIF relative to CT, irrespective of the level of the other climate factors. The DROP treatment "in short DL increased the height relative to both negative DIF and CT. Negative DIF delayed flowering by 2-4 days at 360 m"u mol mol(-1) CO2, but promoted it by 2-4 days at 900 mu mol mol(-1) CO2. Fresh weight of flowers was unaffected by temper"atun treatments irrespective of DL and PPFD. It was concluded that the best plant quality was obtained at constant temperature throughout day and night irrespective of the level of the other climate factors.^^4186"688^6^Nakayama,FS^Huluka,G^Kimball,BA^Lewin,KF^Nagy,J^Hendrey,GR^1994^1^Soil carbon-dioxide fluxes in natural and co2-enriched systems^107^70^1-4^131-140^^^^^Sep^^^^^4188"A^4187^Carbon dioxide fluxes between the soil and atmosphere were determined on the 1991 free-air carbon dioxide enrichmen"t (FACE) experiment at the Maricopa Agricultural Center, Maricopa, Arizona. The study was conducted on drip-irrigated cott"on in conjunction with other physical and physiological measurements. Fluxes were measured with a 1.6 l closed-chamber sta"tic sampling system. The main treatment for the open-air release study had two levels of CO2-ambient air with CO2 concentr"ation of approximately 370 mumol mol-1 (control) and CO2-enriched air with CO2 concentration of approximately 550 mumol mo"l-1 (FACE). The enrichment was made over the daylight hours (05:00-19:00 h). Two quantities of water application, 'wet' (1"050 mm) and 'dry' (790 mm), were superimposed on the two CO2 levels. The observed soil CO2 fluxes ranged from 2 to 8 mumol" m-2 s-1 over the cultivation period. The CO2 fluxes were significantly higher in the FACE than in the control plots, and "also higher for the wet than for the dry irrigation level. In addition, an interaction between CO2 and water levels was pr"esent. The CO2 enrichment effect on soil CO2 flux remained for approximately 4 weeks after the enrichment was ended. A det"ailed study on the procedure for determining flux indicated that some of the random and inconsistent flux values observed "in the field could be attributed to a high CO2 concentration present in the first of the two gas samples taken to estimate flux."689^8^Akin,DE^Kimball,BA^Mauney,JR^Lamorte,RL^Hendrey,GR^Lewin,K^Nagy,J^Gates,RN^1994^1^Influence of enhanced co2 concentration and irrigation on sudangrass digestibility^107^70^1-4^279-287^^^^^Sep^^^^^4190:::; ;;;"A^4189^An experimental line of sudangrass (Sorghum bicolor L. Moench) was included in the free-air CO2 enrichment (FACE) p"roject in 1991 at the University of Arizona Maricopa Agricultural Center to evaluate the effect of ambient (approximately "370 mumol mol- 1) and enriched (550 mumol mol-1) CO2 in well-watered or water- stressed plots. Our specific objective was "to determine modifications caused by these environmental effects on the percentages of morphological parts and the fiber c"omponents, and on the in vitro digestibility in vegetative and mature harvests. Enrichment with CO2 did not (P > 0.05) cha"nge the percentages of morphological parts or fiber components, or the digestibility of any of the morphological component"s. Protein levels tended to be lower in CO2-enriched plants. However, water-stressed plants tended to have a higher propor"tion of leaves (blades and sheaths) and a lower proportion of stems, were more digestible, and had lower amounts of anti-q"uality, aromatic compounds within the plant cell. Stems had the highest digestibility of all morphological components (abo"ut 75% in vegetative plants) despite the lowest levels of protein. Stems also showed the greatest changes caused by all tr"eatments, including a 20% decline in digestibility from vegetative to mature samples. The results indicate that enriching CO2 to 550 mumol mol-1 did not reduce digestibility of sudangrass.LLSSSSSSSSSS"690^2^Chalabi,ZS^Fernandez,JE^1994^1^Estimation of net photosynthesis of a greenhouse canopy using a mass-balance method and mechanistic models^107^71^1-2^165-182^^^^^Oct^^^^^4192"A^4191^Two mechanistic models for estimating net photosynthesis of a greenhouse canopy are evaluated against measurements "using mass balance of CO2 fluxes. The discrepancies observed between the mechanistic models and the CO2 mass balance measu"rement method are attributed to the underestimation of leakage rate, the error in estimating radiation transmission in direct light conditions, and the spatial inhomogeneity of the CO2 concentration inside the glasshouse."691^3^Fierro,A^Tremblay,N^Gosselin,A^1994^1^Supplemental carbon-dioxide and light improved tomato and pepper seedling growth and yield^170^29^3^152-154^^^^^Mar^^^^^4194dUd^dndddddd(eHeUeeXfHlSlYltl|l"A^4193^The experiment was conducted to determine the effects of CO2 enrichment (900 mul.liter-1, 8 hours/day) in combinati"on with supplementary lighting of 100 mumol.s-1.m-2 (16-h photoperiod) on tomato (Lycopersicon esculentum Mill.) and sweet" pepper (Capsicum annuum L.) seedling growth in the greenhouse and subsequent yield in the field. Enrichment with CO2 and "supplementary lighting for almost-equal-to 3 weeks before transplanting increased accumulation of dry matter in shoots by "almost-equal-to 50% compared with the control, while root dry weight increased 49% for tomato and 62% for pepper. Early yields increased by almost-equal-to 15% and 11% for tomato and pepper, respectively."692^3^Hdider,C^Vezina,LP^Desjardins,Y^1994^1^Short-term studies of (no3-)-n-15 and (nh4+)-n-15 uptake by micropropagated strawberry shoots cultured with or without co2 enrichment^177^37^2^185-191^^^^^May^^^^^4196tttttt"A^4195^The uptake of (NO3-)-N-15 and (NH4+)-N-15 has been examined in 5-,10- and 28-day-old micropropagated strawberry (Fr"agaria x ananassa Duch. cv. Kent) shoots rooted in one-half strength Murashige and Skoog (MS) liquid medium on cellulose p"lugs (Sorbarods). The results indicated that the plantlets absorbed both NO3- and NH4+ during the culture with a greater u"ptake of NH4+ at 5 days of culture. Furthermore, a pronounced reduction in NO3- and NH4+ uptake at 10 and 28 days of cultu"re Ras observed within 6 h of the short-term uptake study. This reduction could be explained by the low CO2 concentration "in test tubes during the photoperiod, since no reduction in nitrogen uptake occurred in the CO2 enriched condition. The re"sults are interpreted as an indication of the important role for photosynthetic CO2 fixation in the process of nitrogen uptake by the plantlets during the rooting stage.W>#.3CKQXasvw|"693^6^Hunsaker,DJ^Hendrey,GR^Kimball,BA^Lewin,KF^Mauney,JR^Nagy,J^1994^1^Cotton evapotranspiration under field conditions with co2 enrichment and variable soil-moisture regimes^107^70^1-4^247-258^^^^^Sep^^^^^4198"A^4197^The CO2 concentration of the atmosphere is predicted to double by the next century, and this is expected to increas"e significantly the growth and yield of many important agricultural crops. One consequence of larger and more vigorous pla"nts may be increased crop evapotranspiration (ET) and irrigation water requirements. The objective of this work was to det"ermine ET of cotton (Gossypium hirsutum L. cv. 'Deltapine 77') grown under ambient (about 370 mumol mol-1) and enriched (5"50 mumol mol-1) CO2 concentrations for both well- watered and water-stress irrigation managements. Studies were conducted "in 1990 and 1991 within a large, drip-irrigated cotton field in central Arizona. Cotton ET was measured during the growing" seasons using a soil water balance, based on neutron gauge soil water measurements. ET, for periods from 7 to 14 days, wa"s not significantly different between ambient and enriched CO2 treatments at the 0.05 probability level, and the total sea"sonal ET for the CO2 treatments varied by 2% or less in either year. However, water-stress treatments, which were initiate"d on 3 July (day of year (DOY) 184) in 1990 and on 20 May (DOY 128) in 1991, had significantly lower (P < 0.05) ET than we"ll-watered treatments starting at the end of July in 1990 and in early July in 1991 when the plants were about 75-90 days "old. The result that CO2 enrichment to 550 mumol mol-1 did not significantly change the ET of cotton was consistent with t"he results of co-investigators who measured ET in the same experiments using stem flow gauges and an energy balance. This "result implies that irrigation water use would not have to be increased to produce cotton in a future high-CO2 world. Howe"ver, if a concomitant change in climate occurs, such as global warming, cotton evapotranspiration may change in response to the changed weather condition."694^3^Isutsa,DK^Pritts,MP^Mudge,KW^1994^1^Rapid propagation of blueberry plants using ex-vitro rooting and controlled acclimatization of micropropagules^170^29^10^1124-1126^^^^^Oct^^^^^4200 " "A^4199^A protocol is presented that enables a propagator to produce field-sized blueberry transplants within 6 months of o"btaining microshoots from tissue culture. The protocol involves subjecting microshoots to ex vitro rooting in a fog chambe"r under 100 mumol.m-2.s-1 photosynthetic photon flux for 7 weeks, transferring plants to a fog tunnel for 2 weeks, then to" a greenhouse for 7 more weeks. Plant survival and rooting of cultivars Berkeley (Vaccinium corymbosum L.) and Northsky (V"accinium angustifolium xcorymbosum) were near 100% under these conditions. Plantlets in fog chambers receiving 100 mumol.m"-2.s-1 grew rapidly, while those at lower irradiance levels grew more slowly, and supplemental CO, enhanced growth only at" 50 mumol.m-2.s-1. Growth rates slowed when plants were moved into the fog tunnel; but by the end of 16 weeks, plants that" were under high irradiance in the fog chamber had root systems that were 15 to 30 times larger than plants under low irradiance. Within 6 months, these plants were 30 to 60 cm tall and suitable for field planting."695^12^Kimball,BA^Lamorte,RL^Seay,RS^Pinter,PJ^Rokey,RR^Hunsaker,DJ^Dugas,WA^Heuer,ML^Mauney,JR^Hendrey,GR^Lewin,KF^Nagy,J"^1994^1^Effects of free-air co2 enrichment on energy-balance and evapotranspiration of cotton^107^70^1-4^259-278^^^^^Sep^^"A^4201^The effects of free-air CO2 enrichment (FACE) at 550 mumol mol- 1 on the energy balance and evapotranspiration, ET," of cotton (Gossypium hirsutum L.) were investigated. Latent heat flux, lambdaET, was calculated as the residual in an ene"rgy balance approach from determinations of net radiation, R(n), minus surface soil heat flux, G0, minus sensible heat flu"x, H. R(n) was directly measured. G0 was determined from measurements with soil heat flux plates at 10 mm depth, corrected" for temperature changes in the soil above. H was determined from measurements of air temperature with aspirated psychrome"ters, of foliage temperature with IR thermometers, and of wind speed with cup anemometers. Under ambient CO2 (control) con"ditions (about 370 mumol mol-1), the lambdaET from the energy balance approach agreed fairly well with values from several" other methods, including the Bowen ratio method, lending credence to the technique. However, the results had an uncertain"ty of the order of 20% associated with the R(n) measurements. Therefore, an apparent increase in ET of about 13% in the FA"CE plots was judged insignificant. The conclusion that any effects of CO2 enrichment to 550 mumol mol-1 on the ET of cotto"n were too small to be detected was consistent with the results of other investigators who determined ET in the same experiment using stem flow gauges and the soil water balance.d^^^4202Q^r}Ojw^"696^10^Pinter,PJ^Idso,SB^Hendrix,DL^Rokey,RR^Rauschkolb,RS^Mauney,JR^Kimball,BA^Hendrey,GR^Lewin,KF^Nagy,J^1994^1^Effect of free-air co2 enrichment on the chlorophyll content of cotton leaves^107^70^1-4^163-169^^^^^Sep^^^^^4204"A^4203^In vivo chlorophyll concentrations were estimated using a Minolta SPAD 502 meter on upper-canopy leaves of cotton p"lants exposed to air enriched to an atmospheric CO2 concentration of approximately 550 mumol mol-1 in a free-air CO2 enric"hment (FACE) study. Measurements were made on 27 days during the final 90 days of the 1991 growing season. In both well-wa"tered and moderately water-stressed plants, leaves in the FACE plots had greater chlorophyll a concentrations than leaves "in the ambient air control plots (about 370 mumol CO2 mol-1): season- long chlorophyll a averages were 7.1% greater in the" 'wet' treatment and 8.2% greater in the 'dry' treatment. This finding differs from what has been observed in a number of "studies where experimental plants were grown in small pots. It is, however, typical of what has been observed in studies e"mploying larger pots and open fields, and is a compelling rationale for conducting additional studies of this nature in FACE projects."697^2^Buddendorfjoosten,JMC^Woltering,EJ^1994^1^Components of the gaseous environment and their effects on plant-growth and development in-vitro^245^15^1^1-16^^^^^Jul#.3PX_ejs@ ^ k "698^3^Duff,GA^Berryman,CA^Eamus,D^1994^1^Growth, biomass allocation and foliar nutrient contents of 2 eucalyptus species of the wet dry tropics of australia grown under co2 enrichment^43^8^4^502-508^^^^^Aug^^^^^4207d"A^4206^1. Seeds of Eucalyptus tetrodonta and E. miniata were sown in duplicated air-conditioned tents which were ventilate"d with either ambient or CO2-enriched (700 mumol mol-1) air. Growth, foliar nutrient content, soluble protein and biomass #allocation were investigated over the subsequent 32-week experimental period. 2. It was found that CO2 enrichment signific#antly increased the total biomass and tree height of E. tetrodonta, but had no effect on total biomass or tree height of E#. miniata. 3. Allocation of biomass to main-stem wood and main- stem leaf mass increased and allocation to branch wood and# branch leaves declined, under CO2 enrichment for E. tetrodonta. No change in allocation patterns for E miniata was observ#ed in response to CO2 enrichment. 4. Foliar nitrogen, manganese and phosphorus contents were decreased under CO2 enrichmen#t in E tetrodonta, but there was no effect of CO2 concentration in E. miniata. Soluble protein contents were not affected #by CO2 enrichment in either species. These results are discussed in relation to the competitive relationship between these two species in northern Australia.#699^2^Figueira,A^Janick,J^1994^1^Optimizing carbon-dioxide and light levels during in-vitro culture of theobroma-cacao^154^119^4^865-871^^^^^Jul^^^^^4209# A^4208^In vitro culture of axillary cotyledonary shoots of Theobroma cacao L. (cacao) under increasing CO2 concentration f# rom ambient to 24,000 ppm (culture tube levels) significantly increased total shoot elongation, number of leaves, leaf are# a per explant, and shoot dry and fresh weight. Although light was necessary for the CO2 response, the effect of various ph# oton fluxes was not significant for the measured growth parameters. Net photosynthesis estimated on the basis of CO2 deple#tion in culture tubes increased 3.5 times from 463 to 2639 ppm CO2, and increased 1.5 times from 2639 to 14,849 ppm CO2, b#ut declined from 14,849 to 24,015 ppm CO2. Ethylene concentration in culture vessels increased under enriched CO2 conditions. Depletion of nutrients (fructose, K, Ca, Mg, and P) from the medium was increased under enriched CO2 conditions.#700^2^Igamberdiev,AU^Zabrovskaya,IV^1994^1^The effect of light, carbon nutrition, and salinity on the oxidative-metabolism of wolffia-arrhiza^236^41^2^208-214^^^^^Mar-Apr^^^^^4211(p((()))//////0#A^4210^The effects of varying conditions of carbon nutrition (sucrose and an inorganic source of carbon in the growth medi#um), light, and salinity on oxidative metabolism were studied in Wolffia arrhiza (L.) Hork. ex Wimmer. In cells grown on 1#% sucrose, the level of the cyanide-resistant (CO2)-C-14 evolution from 1,4-C- 14-succinate as a respiratory substrate was# considerably higher than in autotrophically grown plants. When the medium was enriched in inorganic carbon (CO2 or bicarb#onate), the rate of metabolization of glucose and other respiratory substrates diminished, and total protein and chlorophy#ll content decreased. Light incubation enhanced glucose metabolization two- to threefold, whereas succinate transformation# was increased by a factor of 1.5 to 2, with a concomitant rise in the electron flow via the cyanide-resistant pathway. In#hibition of the photorespiratory metabolism with alpha-hydroxypyridine- 2-methanesulfonate slowed down glucose and succina#te metabolism. NaCl activated glycolate metabolism in autotrophically grown plants and did not influence the rates of gluc#ose and succinate transformation. In contrast, under photoheterotrophic (mixothrophic) growth conditions on sucrose, NaCl #added to the cultivation medium led to a considerably higher (three- to fourfold) (CO2)-C-14 evolution from 1,4-C-14- succ#inate and 1-C-14-glucose. The authors conclude that the adaptation of Wolffia plants to different environmental conditions# is accompanied by changes in the metabolic fluxes via cyanide-resistant oxidase, along the glycolate pathway, and other o# xidative pathways. These changes conform to the alterations in enzyme activities participating in the oxidative metabolism.<4[͇940#"701^2^Idso,SB^Kimball,BA^1994^1^Effects of atmospheric co2 enrichment on regrowth of sour orange trees (citrus-aurantium rutaceae) after coppicing^5^81^7^843-846^^^^^Jul^^^^^4213 "RX#$A^4212^Sixteen sour orange tree (Citrus aurantium L.) seedlings were grown out-of-doors at Phoenix, Arizona, in eight clea#%r-plastic- wall open-top enclosures maintained at four different atmospheric CO2 concentrations for a period of 2 years. O#&ver the last year of this period, the trees were coppiced five times. The amount of dry matter harvested at each of these #'cuttings was a linear function of the atmospheric CO2 concentration to which the trees were exposed. For a 75% increase in#( atmospheric CO2 from 400 to 700 microliter per liter (mu L liter(-1)), total aboveground biomass rose, in the mean, by a #)factor of 3.19; while for a 400 to 800 mu L liter(- 1) doubling of the air's CO2 content, it rose by a factor of 3.92. The#* relative summer (mean air temperature of 32.8 C) response to CO2 was about 20% greater than the relative winter (mean air temperature of 16.4 C) response.lomsHT#,702^2^Matysiak,B^Nowak,J^1994^1^Carbon-dioxide and light effects on photosynthesis, transpiration and ex-vitro growth of homalomena emerald gem plantlets^165^57^4^353-358^^^^^May^^^^^4215jn$)V[6?#.A^4214^Micropropagated plantlets of Homalomena cultivar 'Emerald Gem' were grown ex vitro at two CO2 concentrations (350 a#/nd 1200 mumol mol-1) and two light levels (50 and 150 mumol m-2 s-1 photosynthetic photon flux density (PPFD)). Plants gro#0wn at 1200 mumol mol-1 CO2 and at 150 mumol m-2 s-1 PPFD accumulated dry weight of shoots and roots three and two times hi#1gher, respectively, and had a leaf area 2.4 times higher than that of plants grown at 350 mumol mol-1 CO2 and 50 mumol m-2#2 s-1 PPFD. These plants also had the highest rate of photosynthesis. Carbon dioxide enrichment was more effective than sup#3plementary light to increase plant growth. The CO2 assimilation rate, photorespiration, transpiration and stomatal conduct#4ance to water vapour were strongly promoted by light al 150 mumol m-2 s-1, irrespective Of CO2 concentration. CO2 enrichme#5nt enhanced the CO2 assimilation rate and quantum efficiency but decreased the rate of transpiration at 50 mumol m-2 s-1 PPFD and stomatal conductance to water vapour at 50 and 150 mumol m-2 s-1 PPFD.jx!'x#7703^4^Pesheva,I^Kodama,M^Dionisiosese,ML^Miyachi,S^1994^1^Changes in photosynthetic characteristics induced by transferring air-grown cells of chlorococcum-littorale to high- co2 conditions^231^35^3^379-387^^^^^Apr^^^^^4217UV_#9A^4216^When air-grown cells of Chlorococcum littorale was enriched with CO2, growth was enhanced after a lag period of one#: to two days at 20% CO2, and 3 to 6 days at 40% CO2. Changes in the rate of photosynthesis measured as oxygen evolution an#;d CO2 fixation, were similar to those observed for growth. During the initial inhibition of photosynthesis in 40% CO2, the#< activity of PSII was suppressed. In contrast, PSI activity was greatly enhanced. Air-grown cells of C. littorale possesse#=d comparatively high carbonic anhydrase (CA) activity which was localized inside the cells and on the cell surface. Under #>high CO2 concentrations extracellular CA activity was greatly suppressed and intracellular activity almost completely abol#?ished. Phosphoenol pyruvate carboxylase activity was also suppressed in high CO2-grown cells. Ribulose-1,5-bisphosphate ca#@rboxylase activity was higher in high-CO2 grown cells than in air-grown cells. The above results indicated that the lag phase induced by 40% CO2 was due to suppression of PSII activity.704^1^Raven,JA^1994^1^Carbon fixation and carbon availability in marine-phytoplankton^91^39^3^259-273^^^^^Mar^^^^^4219#CA^4218^It is widely believed that inorganic C does not limit the rate of short-term photosynthesis, the net productivity, #Dor the maximum biomass, of marine phytoplankton. This lack of inorganic C restriction is less widely believed to hold for #Ephytoplankton in many low alkalinity freshwaters or for seaweed in nutrient-enriched rock pools. These views are examined #Fin the context of the physical chemistry of the inorganic C system in natural waters and of the ways in which various taxa#G of phytoplankton deal with inorganic C and discriminate between C- 12 and C-13. Using this information to interpret data #Hobtained in the ocean or in freshwater suggests that short-term photosynthesis, production rate, and achieved biomass, of #Iphytoplankton are rarely limited by inorganic C supply but, rather, that the widely suggested factors of limited light, ni#Jtrogen or phosphorus supply are the resource inputs which restrict productivity. Global change, by increasing atmospheric #KCO2 partial pressure and global mean temperatures, is likely to increase the mean CO2 concentration in the atmosphere, but#L the corresponding change in the oceans will be much less. There are, however, genotypic differences in the handling of in#Morganic C among the diversity of marine phytoplankton, and in impact on use of limiting nutrients, so increases in the mea#Nn CO2 and HCO3- concentrations in surface ocean waters could cause changes in species composition. However, the rarity of #Oinorganic C limitation of marine phytoplankton short-term photosynthesis, net productivity, or the maximum biomass, in today's ocean means that global change is unlikely to increase these three values in the ocean.#Q705^1^Saxe,H^1994^1^Relative sensitivity of greenhouse pot plants to long-term exposures of no-containing and no2-containing air^35^85^3^283-290^^^^^^^^^^422108 #SA^4220^Thirty-five cultivars of pot plants of 20 families were exposed for 50-64 days in a greenhouse facility to either 1#T mul litre-1 NO with 0.5 mul litre-1 NO2, or 1 mul litre-1 NO2 with 0.1 mul litre-1 NO for 15 h each day, with air which w#Uas free from these gases as the reference. A sensitivity ranking of the pot plants was compiled, with the highest priority#V on visible injuries, followed by growth reductions, primarily as a response to the NO-dominated exposures, simulating the#W NO(x)- polluted environment in direct-fired, CO2-enriched greenhouses. This treatment reduced the leaf dry weight more th#Xan the number and area of the leaves. Twenty-two cultivars were significantly injured, while two (Hibiscus sp., Epipremnum#Y pinnatum, green) were significantly improved. The NO(x)-sensitivity of pot plants was highest in cultivars with variegate#Zd, small or narrow leaves, and in the Moraceae family. Nine cultivars (Ficus elastica 'Robusta, F. benjamina, F. pumila 'S#[onny, Dieffenbachia maculata 'Camilla', F. elastica 'Tineke, Epipremnum pinnatum 'Marble Queen', Begonia elatior 'Nelson, #\Cyclamen persica, Poinsettia 'Mini) were specifically sensitive to the NO-containing exposure; six were specifically sensi#]tive to the NO2-containing exposure (F. elastica 'Robusta', Asparagus den. 'Sprengeri, Hedera helix 'Shamrock, Aspledium n#^idus, Aster novo-belgii, Hypoestes phyl. 'Betina); and 12 (Soleirolia soleirolii, Asparagus den. 'Sprengeri, H. helix 'Est#_er, Codiaeum 'Pictum, Rosa 'Minimo Red, F. benjamina 'Starlight, Saintpaulia ionantha 'light blue', F. pumila, Rhododendro#`n simsii, H. helix 'Shamrock', Hibiscus sp., E. pinnatum) were equally sensitive to mixtures dominated by either gas, as measured by at least one response parameter.#b706^3^Chagvardieff,P^Daletto,T^Andre,M^1994^1^Specific effects of irradiance and co2 concentration doublings on productivity and mineral-content in lettuce^240^14^11^269-275^^^^^Sept^^^^^4223#dA^4222^Experiments in growth chambers with controlled atmosphere were performed to compare the effects on the productivity#e of two treatments stimulating photosynthesis : the doubling of CO2 concentration, the doubling of irradiance; the combini#fng of both was also tested. A large effect of light was noticed : (i) the accumulation of carbon was, contrarily to CO2 ef#gfect, amplified within time, and led to the most important dry matter production. (ii) the specific leaf weight was about #htwo-fold increased. (iii) the nitrate content was 2-3 fold less. A significant positive effect of CO2 was detected on the #ifresh biomass production and the iron content of lettuce. A synergy was observed on dry matter production by the interaction of the two factors.#k707^4^Wheeler,RM^Mackowiak,CL^Sager,JC^Knott,WM^1994^1^Growth of soybean and potato at high co2 partial pressures^240^14^11^251-255^^^^^Sept^^^^^4225#mA^4224^Soybean and potato plants were grown in controlled environments at carbon dioxide (CO2) partial pressures ranging f#nrom 0.05 to 1.00 kPa. The highest yields of edible biomass occurred at 0.10 kPa for both species, with higher CO2 levels b#oeing supraoptimal, but not injurious to the plants. Stomatal conductance rates of upper canopy leaves were lowest at 0.10 #pkPa CO2, while conductance rates at 0.50 and 1.00 kPa were significantly greater than 0.10 kPa. Total water use by the pla#qnts was greatest at the highest CO2 pressures (i.e. 0.50 and 1.00 kPa); consequently, water use efficiencies (biomass prod#ruced / water used) were low at the highest CO2 pressures. Based on previous CO2 studies in the literature, the increased c#sonductance and water use at the highest CO2 pressures were surprising and pose interesting challenges for managing plants in a CELSS, where CO2 pressures may exceed optimal levels. 6> _PID_GUID#u708^4^Caporn,SJM^Hand,DW^Mansfield,TA^Wellburn,AR^1994^1^Canopy photosynthesis of co2-enriched lettuce (lactuca-sativa L) - response to short-term changes in co2, temperature and oxides of nitrogen^84^126^1^45-52^^^^^Jan^^^^^4227#wA^4226^The canopy net photosynthesis (P-n) of lettuce (Lactuca sativa L. cv. 'Ambassador') was analyzed under controlled c#xonditions simulating the winter glasshouse atmosphere. Prior to measurements the plants were grown in CO2- enriched air of#y 1000 mu mol mol(-1), at a photosynthetic photon flux density (PPFD) of 280 mu mol m(2) s(-1) (400-700 nm) and a day/night#z air temperature of 16/13 degrees C. Short-term changes in CO2 concentration significantly changed the initial gradient of#{ the photosynthetic response to incident PPFD. Maximum photosynthetic efficiency of the crop increased from 0.041 mol CO2 #|mol photons(-1) (equivalent to 8.2 mu g CO2 J(-1) and 9.4% on an energy basis) at 350 mu mol mol(-1) to 0.055 mol CO2 phot#}ons(-1) (10.9 mu g CO2 J(-1) and 12.7% on an energy basis) at 1000 mu mol mol(-1). Transfer from low to high CO2 also lowe#~red the light compensation point, but did not affect dark respiration. The large response of P-n to transient changes in C#O2 indicated that the lettuce canopy did not acclimate to growth in 1000 mu mol CO2 mol(-1), in contrast with the effect o#f growth in high CO2 on P-n in single mature leaves reported earlier. A reduction in air temperature from 16 to 6 degrees #C at a concentration of 1000 mu mol CO2 mol(-1) halved the rate of dark respiration and reduced the light compensation poi#nt, but had no direct effect on the maximum efficiency with which the crop utilized light. Subsequently, at low light (bel#ow 200 mu mol m(-2) s(-1)) P-n was greater at 6 than 16 degrees C. Between a PPFD of 250 and 300 mu mol m(-2) s(-1) canopy# P-n was similar at all temperatures. Addition of 2.0 mu mol mol(-1) nitric oxide to an atmosphere of 1000 mu mol CO2 mol(#-1) caused a rapid and reversible reduction of canopy P-n which was greater at the lowest temperatures. The average inhibi#tion was 6.6% at 16 degrees C and 28.8% at 6 degrees C; this was not explained by differences in the rate of pollutant upt#ake, which was less in the cooler conditions. The results are discussed in relation to development of optimal growing conditions for production of glasshouse lettuce at low light and low temperature during winter in the UK.#709^3^Chapin,FS^Rincon,E^Huante,P^1993^1^Environmental responses of plants and ecosystems as predictors of the impact of global change^246^18^4^515-524^^^^^Dec^^^^^4229#A^4228^An understanding of plant responses to fluctuations in environment is critical to predictions of plant and ecosyste#m responses to climate change. In the northern hemisphere, the northern limits of distribution of major biomes are probabl#y determined by the tolerance of their dominant physiognomic types (e.g., deciduous hardwood trees) to minimum winter temp#eratures and can thus be predicted from long-term patterns of temperature fluctuations. At a more detailed level, the resp#onses of functional groups of plants to altered climate can be predicted from their known responses to fluctuations in soi#l resources (nutrients and water) and the expected effect of climatic change on these soil resources. Laboratory and field experiments demonstrate the feasibility of this approach.#710^3^Chen,CL^Li,CC^Sung,JM^1994^1^Carbohydrate-metabolism enzymes in co2-enriched developing rice grains of cultivars varying in grain-size^37^90^1^79-85^^^^^Jan^^^^^4231/0123456789:;<=>?@#A^4230^The increased supply of photosynthate from maternal tissue is known to promote grain growth in several crop species#. However, the effect of increasing photosynthate supply on grain growth receives little attention in rice. This study was# aimed at evaluating the effect of increasing photosynthate supply through CO2 enrichment (650 mul l-1) on grain growth in# three rice cultivars differing in grain size. CO2 enrichment was applied to the pot-grown plants between anthesis and fin#al harvest. The results indicated that high CO2 treatment enhanced the CO2 exchange rate of leaf tissue, and subsequently #increased the sucrose level of peduncle exudate, but it did not promote starch accumulation in the developing grains. This# phenomenon was linked to the poor CO2 responses for the grain activities of sucrose synthase, UDP-glucose pyrophosphoryla#se, ADP-glucose pyrophosphorylase, and starch synthases involved in the converison of sucrose to starch. Significant culti#var differences also existed for the activities of sucrose to starch conversion enzymes with larger grain size cultivars tending to have higher enzymes activities (expressed on a grain basis), resulting in a greater carbohydrate accumulation.#711^4^Chen,XM^Begonia,GB^Alm,DM^Hesketh,JD^1993^1^Responses of soybean leaf photosynthesis to co2 and drought^79^29^3^447-454^^^^^^^^^^4233j#A^4232^Soybean [Glycine max (L.) Merr. cv. Jack] was grown in the field in rain-protected plots to study effects of drough#t and atmospheric CO2 enrichment. on leaf gas exchange. Midday depressions in leaf photosynthetic CO2 exchange rates (P(N)#) were found in drought-stressed plants and the diurnal changes were mostly stomatal-regulated, although accumulated droug#ht stress eventually resulted in some non-stomatal limitations. However, seasonal changes in P(N) were mostly limited by n#on- stomatal factors. Water use efficiency was always higher for drought stressed plants and depended on the severity of s#tress and associated stomatal or nonstomatal limitations. At enriched atmospheric CO2 levels, stomatal limitations to P(N)# under drought stress were less important than at ambient atmospheric CO2 levels. Morning and afternoon leaf starch levels# were enhanced in both irrigated and nonirrigated plants in enriched CO2. Afternoon starch levels were higher in stressed leaves than in non-stressed leaves at normal CO2 levels.#712^5^Flanagan,LB^Phillips,SL^Ehleringer,JR^Lloyd,J^Farquhar,GD^1994^1^Effect of changes in leaf water oxygen isotopic composition on discrimination against (coo)-o-18-o-16 during photosynthetic gas-exchange^92^21^2^221-234^^^^^^^^^^4235wit#A^4234^Photosynthetic gas exchange measurements were combined with measurements of the carbon and oxygen stable isotopic c#omposition of CO2 after it passed over a leaf of Phaseolus vulgaris or Senecio spp. plants held in a controlled environmen#t chamber. Calculations were then made of discrimination by the leaf against (CO2)-C-13 and (COO)-O-18-O- 16. Leaves were #maintained at different vapour pressure gradients in order to generate a range of leaf water O-18/O-16 ratios. The O-18 co#ntent of leaf water increased when plants were exposed to higher vapour pressure deficits. The observed (COO)-O-18-O-16 di#scrimination values also increased with an increase in the leaf-air vapour pressure gradient and the associated change in #leaf water 18/(OO)-O-16 values. In addition, the observed (COO)-O-18-O-16 discrimination values were strongly correlated with values predicted by a mechanistic model of isotopic fractionation.hted words (colored or un#713^4^Fujii,N^Watanabe,M^Watanabe,Y^Shimada,N^1994^1^Relationship between oxalate synthesis and glycolate cycle in spinach^180^62^4^789-794^^^^^Mar^^^^^4237M\infoUsing Communicator Help Kristi F#A^4236^The relationship between oxalate synthesis and glycolate pathway in spinach (Spinacia oleracea L. cv. Sunlight) was# studied by exposing seedling to 1,000 PPM CO2-enriched atmosphere. It was observed that CO2-enrichment increased the cont#ent of ascorbic acid but decreased that of oxalate. It was presumed that reducing the rate of glycolate synthesis would re#duce the content of oxalate. Mature leaves of spinach grown under normal conditions, were fed with [2-C-14] glycolate and #[1-C-14] ascorbic acid to compare their contribution as a precursor of oxalate. Using the values of the C-14 distribution #to oxalate, photorespiratory glycolate metabolic rate and the turnover rate of ascorbic acid, the rate of oxalate synthesi#s was calculated. It was observed that glycolate was more efficient as a precursor of oxalate synthesis than it was for ascorbic acid. From these results, we postulate that the oxalate synthesis is closely related to the glycolate cycle.P\N#714^1^Garcia,JM^1993^1^Effect of co2 in fruit storage atmosphere on olive oil quality^219^44^3^169-174^^^^^May-Jun^^^^^423#A^4238^Olive fruits (Olea europaea, cv. ''Picual'') were stored at 5- degrees-C and four different atmospheres (% CO2/% O2#/%N2: 0/21/78: 5/20/75; 10/19/71 and 20/17/63). At 5-degrees-C the enrichment of the fruit storage atmosphere with concent#rations of CO2 above 5% resulted in a linear increase of the acidity of extracted oils after 60 days of fruit storage time#. This fact showed a strong relationship with the appearence of fruit decay. Simple refrigeration of fruits at 5-degrees-C# for 60 days was sufficient to mantain the commercial quality of ''virgin extra'' in oil extracted from them. Oils obtaine#d from fruits stored at 5-degrees-C in CO2 enriched atmospheres showed lower peroxide index and UV absorbance (270 nm), bu#t developed off-flavor. Therefore, greater-than-or-equal-to 5% CO2 concentrations in storage atmosphere of olive fruits for oil production at 5-degrees-C must be avoided.9+bjbjَ r'#715^2^Sullivan,JH^Teramura,AH^1994^1^The effects of uv-b radiation on loblolly-pine .3. Interaction with co2 enhancement^9^17^3^311-317^^^^^Mar^^^^^4241#A^4240^Projected depletions in the stratospheric ozone layer will result in increases in solar ultraviolet-B radiation (29#0- 320nm) reaching the earth's surface, These increases will likely occur in concert with other environmental changes such# as increases in atmospheric carbon dioxide concentrations. Currently very little information is available on the effectiv#eness of UV-B radiation within a CO2-enriched atmosphere, and this is especially true for trees. Loblolly pine (Pinus taed#a L.) seedlings were grown in a factorial experiment at the Duke University Phytotron with either 0, 8.8 or 13.8 kJ m(-2) #of biologically effective UV-B radiation (UV- B-BE) The CO2 concentrations used were 350 and 650 mu mol mol(- 1). Measurem#ents of chlorophyll fluorescence were made at 5- week intervals and photosynthetic oxygen evolution and leaf pigments were# measured after 22 weeks, prior to harvest. The results of this study demonstrated a clear growth response to CO2 enrichme#nt but neither photosynthetic capacity nor quantum efficiency were altered by CO2. The higher UV-B irradiance reduced tota#l biomass by about 12% at both CO2 levels but biomass partitioning was altered by the interaction of CO2 and UV-B radiatio#n. Dry matter was preferentially allocated to shoot components by UV-B radiation at 350 mu mol mol(-1) CO2 and towards roo#t components at 650 mu mol mol(-1) CO2. These subtle effects on biomass allocation could be important in the future to seedling establishment and competitive interactions in natural as well as agricultural communities. of these cowpea lines to#716^2^Yakimchuk,R^Hoddinott,J^1994^1^The influence of ultraviolet-b light and carbon-dioxide enrichment on the growth and physiology of seedlings of 3 conifer species^155^24^1^1-8^^^^^Jan^^^^^4243 sensitivity to heat during reproductive develo#A^4242^Anthropogenic production of CO2 and stratospheric ozone depleting chemicals is altering the plant growth environmen#t. Numerous studies have examined the influence of increasing CO2 and UV-B levels on plant physiology, but few studies exa#mine their interaction. Jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana (Mill.) B.S.P.), and white spruce (#Picea glauca (Moench) Voss) were raised in growth rooms from seed for 16 weeks in air with either 350 or 700 mumol.mol-1 o#f CO2 in the presence or absence of supplemental UV-B irradiation. Classical and functional growth analyses were performed# to identify treatment effects. Biomass production in all three species was increased by high CO2 levels while UV-B light #reduced it. Shade-intolerant jack pine showed a greater production of UV-B absorbing pigments in UV-B light than did shade#-tolerant spruce species. Overall, white spruce was the most sensitive species to both treatment factors. The relative mag#nitude of the effects in the three species caused by enhanced CO2 and UV-B levels indicate that future conifer seedling growth and competitive ability will be altered by the changing environment.ith respect to flower production or pod set. Hea#717^4^Hunt,R^Hand,DW^Hannah,MA^Neal,AM^1993^1^Further responses to co2 enrichment in british herbaceous species^43^7^6^661-668^^^^^Dec^^^^^4245cts on assimilate demand than on leaf assimilate supply. The heat- tolerant line was the most respon#A^4244^1. CO2-enrichment experiments have been performed on 15 British herbaceous species of widely differing ecology The #conditions of growth were very similar to those used in a previous study and involved full-light glasshouse conditions, no#n-Limiting supplies of water and mineral nutrients and a daytime mean temperature of 18 degrees C. Four CO2 treatments wer#e maintained (350, 500, 650 or 800 vpm) over periods of 49 or 52 days. 2. Hyperbolic functions were fitted to yield vs CO2# concentration. The functions were used to generate predictions of Q(540/350) (the quotient of the 'present' yield which i#s predicted for the CO2 regime expected by the year 2050) and Q(700/350) (the quotient predicted for a doubling of the pre#sent ambient CO2 concentration). Values of Q(540/350) for whole-plant dry weight ranged from below 1.00 to 1.19. The mean #Value of whole-plant Q(700/350) for eight species of 'competitive' functional type was 1.13. Six species of 'stress- toler#ant' or 'ruderal' type had a mean Q(700/350) Of only 1.07. 3. The new data support and amplify an earlier conclusion that #high CO2 responsiveness is normal only within the competitive functional type (or 'strategy') and its close relations. A s#implified and more broadly based general prediction now gives a fitted percentage increase after approximately 7 weeks' gr#owth of 27% for species of broadly competitive strategy In the centre of the range of functional types the fitted values n#ow range from 13 to 20%, and at the far extremes, the value for species of either the ruderal or the stress-tolerant type is now 6%. The gradient of this response is statistically significant, but less steep than that previously reported.and t#718^5^Mathooko,FM^Sotokawa,T^Kubo,Y^Inaba,A^Nakamura,R^1993^1^Retention of freshness in fig fruit by co2-enriched atmosphere treatment or modified atmosphere packaging under ambient- temperature^180^62^3^661-667^^^^^Dec^^^^^4247 plants grown a#A^4246^At 20-degrees-C. freshness retention of figs (Ficus carica L. cv. Masui Dauphine) by CO2-enriched atmosphere treatm#ent or modified atmosphere packaging were studied in an attempt to reduce deterioration during transportation. CO2-enriche#d atmosphere treatment inhibited ethylene production, delayed the incidence of mold growth and promoted ethanol production#. Majority of the figs exposed to 60% or 80% CO2 for 2 days were still marketable 1 day after transfer to air at 20-degree#s-C. Based on mold growth, figs stored in air and in unperforated polyethylene bags deteriorated slightly faster than thos#e stored in perforated bags. A gas mixture of 80% CO2 +20% O2 or 100% CO2 introduced into the polyethylene bags before sea#ling were more effective in the control of mold growth compared to air or 100% N2 and equally effective in reducing ethyle#ne accumulation as 100% N2. The results suggest that postharvest deterioration of figs can be reduced by either CO2-enriched atmosphere treatment or through modified atmosphere packaging.L; SINKS; NET AB In this paper we review results of rese#719^5^Muller,C^Reuter,W^Wehrmeyer,W^Dau,H^Senger,H^1993^1^Adaptation of the photosynthetic apparatus of anacystis- nidulans to irradiance and co2-concentration^118^106^6^480-487^^^^^Dec^^^^^4249l land use amounted to a small C source of about ulses of elevated co2 in hydroponic wheat^78^46^292^1661-1667^^^^^Nov^^^^^4377 in forest vegetation and soils in 1990 was$1032^7^Maytin,CE^Acevedo,MF^Jaimez,R^Andressen,R^Harwell,MA^Robock,A^Azocar,A^1995^1^Potential effects of global climatic-change on the phenology and yield of maize in venezuela^50^29^2^189-211^^^^^Feb^^^^^4859ing deforestation are likely to $A^4248^Homocontinuous cultures of the cyanobacterium Anacystis nidulans (syn. Synechococcus sp. PCC 6301) were grown at wh$ite light intensities of 2 and 20 W/M2 , and supplied with 0.03 and 3 % CO2 enriched air. The mutual influence of these gr$owth factors on the development of the photosynthetic apparatus was studied by analyses of the pigment content, by low tem$perature absorbance and fluorescence spectroscopy, by analyses of oxygen evolution light-saturation curves, and by SDS PAG$E of isolated phycobilisomes. The two growth factors, light and CO2, distinctly affect the absorption cross section of the$ photosynthetic apparatus, which is expressed by its pigment pattern, excitation energy distribution and capacity. In resp$onse to low CO2 concentrations, the phycocyanin/allophycocyanin ratios were lower and one linker polypeptide L(R)30, of th$ e phycobilisomes was no longer detectable in SDS PAGE. Apparently, low CO2 adaptation results in shorter phycobilisome rod$ s. Specifically, upon adaptation to low light intensities, the chlorophyll and the phycocyanin content on a per cell basis$ increase by about 50 % suggesting a parallel increase in the amount of phycobilisomes and photosystem core-complexes. Low$ light adaptation and low CO2 adaptation both cause a shift of the excitation energy distribution in favor of photosystem $ I. Variations in the content of the ''anchor'' polypeptides L(CM)60 and L(CM)75 are possibly related to changes in the excitation energy transfer from phycobilisomes to the photosystem II and photosystem I core-complexes.ncentrations of 300-33$720^2^Phillips,OL^Gentry,AH^1994^1^Increasing turnover through time in tropical forests^32^263^5149^954-958^^^^^18 Feb^^^^$A^4250^Tree turnover rates were assessed at 40 tropical forest sites. Averaged across inventoried forests, turnover, as me$asured by tree mortality and recruitment, has increased since the 1950s, with an apparent pantropical acceleration since 1$980. Among 22 mature forest sites with two or more inventory periods, forest turnover also increased. The trend in forest dynamics may have profound effects on biological diversity.-2 s-1 in treatments of FSA, FSE, HSA and HSE, respectively. E^4251 CO2 concentration from 300 to 1500 g m-3 increased P(N) by 16, 28, 30 and 46% under an irradiance of 160 mumol m-2 $721^3^Palutikof,JP^Goodess,CM^Guo,X^1994^1^Climate-change, potential evapotranspiration and moisture availability in the mediterranean basin^247^14^8^853-869^^^^^Oct^^^^^42531 enhanced P(N) by 69, 78, 23 and 49% in an atmosphere of 300 g m-3 C$A^4252^Simple methods for estimating potential evapotranspiration, requiring only temperature and day length data, are com$pared by reference to the results from the Penman method. A modification of the Blaney and Criddle method, in which the c $parameter is calculated from seasonal regression equations with the mean monthly temperature as the independent variable, $is proposed and tested. It is found to work sufficiently well in the area of interest, the Mediterranean Basin. For a netw$ork of 248 Mediterranean temperature stations, present-day seasonal mean potential evapotranspiration is estimated by this$ method. Using the results from four equilibrium-mode general circulation models, seasonal mean scenarios of potential eva$potranspiration per 1-degree-C rise in global mean temperature caused by the enhanced greenhouse effect are presented. Com$parison of scenarios of the change in potential evapotranspiration and scenarios of the change in precipitation indicates $an unfavourable shift in moisture availability due to the enhanced greenhouse effect, throughout the Mediterranean region.ARMI A J9 PHOTOSYNTHETICA ER PT J AU CROSSON, PR ROSENBERG, NJ TI AN OVERVIEW OF THE MINK STUDY SO CLIMATIC CHANGE SN 01$!722^2^Eichelmann,H^Laisk,A^1994^1^Co2 uptake and electron-transport rates in wild-type and a starchless mutant of nicotian$.a-sylvestris - the role and regulation of starch synthesis at saturating co2 concentrations^8^106^2^679-687^^^^^Oct^^^^^42$#A^4254^CO2 uptake rate, chlorophyll fluorescence, and 830-nm absorbance were measured in wild-type (wt) Nicotiana sylvestr$$is (Speg. et Comes) and starchless mutant NS 458 leaves at different light intensities and CO2 concentrations. Initial slo$%pes of the relationships between CO2 uptake and light and CO2 were similar, but the maximum rate at CO2 and light saturati$&on was only 30% in the mutant compared with the wt. O-2 enhancement of photosynthesis at CO2 and tight saturation was rela$'tively much greater in the mutant than in the wt. In 21% O- 2, the electron transport rate (ETR) calculated from fluoresce$(nce peaked near the beginning of the CO2 saturation of photosynthesis. With the further increase of CO2 concentration ETR $)remained nearly constant or declined a little in the wt but drastically declined in the mutant. Absorbance measurements at$* 830 nm indicated photosystem I acceptor side reduction in both plants at saturating CO2 and light. Assimilatory charge (p$+ostillumination CO2 uptake) measurements indicated trapping of chloroplast inorganic phosphate, supposedly in hexose phosp$,hates, in the mutant. It is concluded that starch synthesis gradually substitutes for photorespiration as electron accepto$-r with increasing CO2 concentration in the wt but not in the mutant. It is suggested that starch synthesis is co-controlled by the activity of the chloroplast fructose bisphosphatase.NCE OF A FEEDBACK MECHANISM LIMITING PLANT-RESPONSE TO ELEVA55N-DIOXIDE SO NATURE SN 0028-0836 C1 NATL UNIV CORDOBA, FAC CIENCIAS EXACTAS FIS & NAT, C CORREO 495, RA-5000 CORDOBA, A$0723^2^Mikkelsen,TN^Ropoulsen,H^1994^1^Exposure of norway spruce to ozone increases the sensitivity of current year needles to photoinhibition and desiccation^84^128^1^153-163^^^^^Sep^^^^^4257; GROWTH; ECOSYSTEMS; SOIL; POPULATIONS; NUTRITION; $2A^4256^Physiological effects of ozone exposure over three consecutive growing seasons on current year needles of Norway sp$3ruce were studied in open-top chambers, during daily fumigation cycles in the summer, and after the termination of ozone f$4umigation in autumn 1990. The trees were exposed to two levels of ozone: charcoal filtered air and non-filtered air to whi$5ch 30 nl l(-1) of ozone was added in three consecutive years from 1988 to 1990, daily from May to September (8 hours a day$6). Photosynthesis, stomatal conductance, transpiration and chlorophyll fluorescence were studied on selected days. Signifi$7cant decreases in net photosynthesis and chlorophyll fluorescence (F-v/F-m) were found during periods with co- occurrence $8of high ozone concentrations and high light intensities, indicating interactions between effects of ozone and photoinhibit$9ion. After termination of fumigation enhanced rates of photosynthesis were seen in the trees which had been exposed to ozone. A significant decrease in F-v/F-m was found for twigs from ozone treated trees when exposed to severe desiccation.nde$;724^4^Ke,DY^Yahia,E^Mateos,M^Kader,AA^1994^1^Ethanolic fermentation of bartlett pears as influenced by ripening stage and atmospheric composition^154^119^5^976-982^^^^^Sep^^^^^4259 PR ROSENBERG, NJ MCKENNEY, MS KATZ, LA LEMON, KM TI AGRICULTUR$=A^4258^Changes in fermentation volatiles and enzymes were studied in preclimacteric and postclimacteric 'Bartlett' pears ($>Pyrus communis L.) kept in air, 0.25% O2, 20% O2 + 80% CO2, or 0.25% O2 + 80% CO2 at 20C for 1, 2, or 3 days. All three at$?mospheres resulted in accumulation of acetaldehyde, ethanol, and ethyl acetate. The postctimacteric pears had higher activ$@ity of pyruvate decarboxylase (PDC) and higher concentrations of fermentation volatiles than those of the preclimacteric f$Aruit. For the preclimacteric pears, the 0.25% O2 treatment dramatically increased alcohol dehydrogenase (ADH) activity, wh$Bich was largely due to the enhancement of one ADH isozyme. Exposure to 20% O2 + 80% CO2 slightly increased ADH activity, b$Cut the combination of 0.25% O2 + 80% Co2 resulted in lower ADH activity than 0.25% O2 alone. For the postclimacteric pears$D, the three atmospheres resulted in higher PDC and ADH activities than those of air control fruit. Ethanolic fermentation $Ein 'Bartlett' pears could be induced by low O2 and/or high CO2 via 1) increased amounts of PDC and ADH; 2) PDC and ADH act$Fivation caused by decreased cytoplasmic pH; or 3) PDC and ADH activation or more rapid fermentation due to increased concentrations of their substrates (pyruvate, acetaldehyde, or NADH). current and 2030 conditions. Production of dryland wheat$H725^3^Ke,DY^Zhou,LL^Kader,AA^1994^1^Mode of oxygen and carbon-dioxide action on strawberry ester biosynthesis^154^119^5^971-975^^^^^Sep^^^^^4261ichment, eliminated about 80% of the negative impact of the analog climate on 1984/87 baseline crop$JA^4260^'Chandler' strawberries (Fragaria ananassa Duck.) were kept in air, 0.25% O2, 21% O2 + 50% CO2, or 0.25 O2 + 50% CO$K2 (balance N2) at 5C for 1 to 7 days to study the effects of controlled atmospheres (CAs) on volatiles and fermentation en$Lzymes. Concentrations of acetaldehyde, ethanol, ethyl acetate, and ethyl butyrate were greatly increased, while concentrat$Mions of isopropyl acetate, propyl acetate, and butyl acetate were reduced by the three CA treatments compared to those of $Nair- control fruit. The CA treatments enhanced activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) $Obut slightly decreased activity of alcohol acetyltransferase (AAT). The results indicate that the enhanced PDC and ADH act$Pivities by CA treatments cause ethanol accumulation, which in turn drives the biosynthesis of ethyl esters. The increased $Qethanol concentration also competes with other alcohols for carboxyl groups for esterification reactions. The reduced AAT $Ractivity and limited availability of carboxyl groups due to ethanol competition decrease production of other acetate esters.bient (+/-350 mul l-1) and double (700 mul l-1) atmospheric CO2 Concentration in constantly ventilated.mini- green-hous$d726^3^Li,CS^Frolking,S^Harriss,R^1994^1^Modeling carbon biogeochemistry in agricultural soils^137^8^3^237-254^^^^^Sep^^^^^$UA^4262^An existing model of C and N dynamics in soils was supplemented with a plant growth submodel and cropping practice $Vroutines (fertilization, irrigation, tillage, crop rotation, and manure amendments) to study the biogeochemistry of soil c$Warbon in arable lands. The new model was validated against field results for short-term (1-9 years) decomposition experime$Xnts, the seasonal pattern of soil CO2 respiration, and long-term (100 years) soil carbon storage dynamics. A series of sen$Ysitivity runs investigated the impact of varying agricultural practices on soil organic carbon (SOC) sequestration. The te$Zsts were simulated for corn (maize) plots over a range of soil and climate conditions typical of the United States, The la$[rgest carbon sequestration occurred with manure additions; the results were very sensitive to soil texture (more clay led $\to greater sequestration). Increased N fertilization generally enhanced carbon sequestration, but the results were sensiti$]ve to soil texture, initial soil carbon content, and annual precipitation. Reduced tillage also generally (but not always)$^ increased SOC content, though the results were very sensitive to soil texture, initial SOC content, and annual precipitat$_ion. A series of long-term simulations investigated the SOC equilibrium for various agricultural practices, soil and clima$`te conditions, and crop rotations. Equilibrium SOC content increased with decreasing temperatures, increasing clay content$a, enhanced N fertilization, manure amendments, and crops with higher residue yield. Time to equilibrium appears to be one $bhundred to several hundred years. In all cases, equilibration time was longer for increasing SOC content than for decreasi$cng SOC content. Efforts to enhance carbon sequestration in agricultural soils would do well to focus on those specific areas and agricultural practices with the greatest potential for increasing soil carbon content. data and estimates of the d4263in reservoir evaporation under the 1931-1940 analog and the 1951-1980 control climates. A modification of the Erosion$foportion of fixed carbon retained in the leaf blade, increasing the rate of export. The favourable carbon balance of CO2 e$gnriched leaves was further enhanced by a decrease in the cost of maintenance respiration, whilst simultaneous measurements$h of CO2 efflux and O-2 uptake at night suggested a shift in the substrates metabolized at high CO2. Effects of elevated CO$i2 and O-3 on the carbon balance of individual leaf blades over a single 24 h light/dark cycle were entirely consistent wit$jh the cumulative effects of the gases on plant growth over a 30 d period. O-3 reduced the rate of plant growth (-10%), but$k there were differential effects of O-3 on the growth of root and shoot which exacerbated the decrease in assimilate avail$lability induced by O-3. In contrast the favourable effects of CO2 enrichment on the carbon balance of individual source le$maves was reflected in the enhanced accumulation of dry matter in existing sinks, and the initiation of new sinks (i.e. inc$nreased tillering). In the combined treatment (elevated CO2 + O-3), O-3 counteracted the favourable effects of CO2 enrichme$ont on the carbon balance of individual leaves, and the combined effects of the individual gases on the diel partitioning o$pf photosynthetically fixed carbon in fully expanded leaf blades was reflected in a decreased rate of plant growth at eleva$qted CO2, a situation further exacerbated by O-3-induced shifts in the relative partitioning of carbon between root and sho$rot. There was no evidence that CO2 enrichment afforded additional protection against O-3 damage: the extent of the O-3-ind$suced reduction in photosynthesis, carbohydrate availability and growth observed at elevated CO2 was similar to that induce$td by O-3 in ambient air, despite additive effects of the gases on stomatal conductance that would reduce the effective dos$ue of O-3 by approximate to 30%. The wider ecological significance of interactions between elevated CO2 and O-3 is discussed in the light of other recent findings.r such factors. decreased leaf cost by 3.5%. Nitrogen and CO2 availability had a$w728^3^Arakelyan,VV^Ibragimova,GB^Nasyrov,YS^1993^1^Effects of light, co2, and temperature on carbonic-anhydrase activity in C3-plants^236^40^6^759-767^^^^^Nov-Dec^^^^^4267is was relatively high (81.8 +/- 3.0 g glucose m-2) compared to leaves f$yA^4266^Carbonic anhydrase activity was studied in cotton (Gossypium hirsutum L.) and Triticale plants exposed to various l$zight intensities, temperatures, and CO2 concentrations in the air. The activity was measured using an original method base${d on the HCO3- dehydration reaction, which is carried out in conditions resembling those occurring in the chloroplast stro$|ma in vivo. Carbonic anhydrase activity in stromal fractions from cotton and triticale plant chloroplasts appears to respo$}nd to environmental changes. Plant exposure to increased light intensities and temperatures results in increased activity,$~ whereas high ambient CO2 concentrations lower carbonic anhydrase activity. After examining in vitro the HCO3- dehydration$ reaction, which in vivo is catalyzed by carbonic anhydrase, we concluded that the physiological role of the stromal enzym$e consists of preventing local CO2 depletion in the carboxylation sites. Thus, high temperatures and low ambient CO2 conce$ntrations enhance carbonic anhydrase activity, while impeding CO2 transport from the air to the carboxylation sites in the$ leaf. This accelerates HCO3- dehydration and reduces its concentration in the stroma, thereby producing an additional driving force for HCO3- transport to the chloroplast.et photosynthesis by 12-144% over the course of the study. Net photosyn$729^3^Hausler,RE^Lea,PJ^Leegood,RC^1994^1^Control of photosynthesis in barley leaves with reduced activities of glutamine-synthetase or glutamate synthase .2. Control of electron-transport and co2 assimilation^6^194^3^418-435^^^^^Aug^^^^^4269t$A^4268^Heterozygous plants of barley (Hordeum vulgare L. cv. Maris Mink) with activities of chloroplastic glutamine synthe$tase (GS) between 47% and 97% of the wild-type and ferredoxin- dependent glutamate synthase (Fd-GOGAT) activities down to $63% of the wild-type have been used to study the control of photosynthetic fluxes. Rates of CO2 assimilation measured over$ a range of intercellular CO2 concentrations and photon flux densities (PFDs) were little different in the wild-type and a$ mutant with 47% GS, although total activities of ribulose-1, 5- bisphosphate carboxylase/oxygenase (Rubisco) decreased by$ about 20% with a decrease in GS to 50% of the wild-type. The quantum efficiencies of photosystem II electron transport (P$hi PSII) and CO2 assimilation (Phi CO2) were determined. Phi PSII was lower than expected in mutants with 50% less GS unde$r conditions which enhance the photorespiratory flux, but were identical to the wildtype under non-photorespiratory condit$ions, suggesting that at high rates of photorespiration the electron requirement for net CO2 assimilation declines in plan$ts with decreased GS. This discrepancy in the electron requirement between the wild-type and the 47% GS mutant was enhance$d at high temperatures and low CO2, conditions which favour oxygenation by Rubisco. Photochemical and non- photochemical c$hlorophyll a fluorescence quenching as well as the quantum efficiency of excitation-energy capture by open photosystem II $reaction centres were differentially affected in mutants with less GS relative to the wild-type when CO2 was lowered or th$e PFD was varied. The quantum efficiencies of electron transport in photosystems I and II were closely correlated under a $range of PFDs and CO2 concentrations, confirming that the rate of linear electron transport was much lower in plants with $less GS. It is shown that GS exerts considerable control (flux control coefficients between 0.5 and 1.0) on the electron r$equirement for CO2 assimilation at high fluxes of photorespiration relative to CO2 assimilation. Apart from the control of$ GS on protein and Rubisco contents, GS in the wild-type has also some direct positive control on CO2 assimilation. Howeve$r, negative control on CO2 assimilation was found in mutants with 50% less GS. These data, taken with the data on electron$ requirements for CO2 assimilation, suggest that CO2-fixing processes other than that catalysed by Rubisco, such as carbox$ylation of phosphoenolpyruvate, or an inhibition of photorespiration (e.g. glycine decarboxylation), may contribute to the$ observed CO2 exchange and photosystem II electron transport in plants with less GS. In the 63%-Fd-GOGAT mutant, rates of $CO2 assimilation were appreciably lower than in the wild-type under a range of PFDs and CO2 concentrations, which largely $reflected lower contents of Rubisco in the Fd- GOGAT mutants. Assimilation of CO2 was inhibited appreciably at high CO2 co$ncentrations. There was little difference in the electron requirement for CO2 assimilation between the wild-type and mutan$ts with less Fd-GOGAT, although there were indications that a triose-phosphate/glycerate-3-phosphate shuttle or cyclic ele$ctron transport operates to balance ATP generation and NADP reduction. The latter was supported by a curvilinear relations$hip of photosystem I and II electron transport in the 63% Fd-GOGAT mutant. A positive control is exerted by Fd-GOGAT on the amounts of protein and Rubisco and on CO2 assimilation.OLIC CONSTITUENTS; PERFORMANCE; ALLOCATION; BALANCE; WILLOWS AB $870^5^Bettarini,I^Calderoni,G^Miglietta,F^Raschi,A^Ehleringer,J^1995^1^Isotopic carbon discrimination and leaf nitrogen-content of erica-arborea L along a co2 concentration gradient in a co2 spring in italy^13^15^5^327-332^^^^^May^^^^^4540 ava$A^4539^We studied a Mediterranean species (Erica arborea L.) growing in a CO2 spring in Italy that was naturally exposed f$or generations to a gradient of atmospheric CO2 concentrations. The CO2 concentration gradient to which different individu$al plants were exposed was determined by an indirect method based on radioisotope analysis. The stable carbon isotope rati$o of sampled leaves was determined by mass spectrometry, and isotopic discrimination was then calculated. Leaf nitrogen, s$pecific leaf area, total soil nitrogen, soil organic matter content and soil pH were also measured. In one group of plants$, grown on a homogeneous soil and exposed to moderate CO2 enrichment, isotopic discrimination was significantly reduced in$ response to increasing CO2 concentrations, whereas the intercellular CO2 concentration and leaf nitrogen content were alm$ost unaffected. In a second group of plants, grown along a gradient of CO2 concentration and soil nitrogen content, leaf n$itrogen content was reduced when nitrogen availability was limiting. However, when soil nitrogen was available in excess, $even very high CO2 concentrations did not result in increased discrimination or reduced leaf nitrogen content in the long $term. The results are discussed with respect to current theories about the long-term CO2 response of plants based on several years of experimentation with elevated atmospheric CO2 concentrations under controlled conditions.id not reduce vegeta$871^4^Bosac,C^Gardner,SDL^Taylor,G^Wilkins,D^1995^1^Elevated co2 and hybrid poplar - a detailed investigation of root and shoot growth and physiology of populus-euramericana, primo^45^74^1-3^103-116^^^^^Jun^^^^^4542levels (0.1 to 1% CO2) incre,A^4541^Exposure of the hybrid poplar clone 'Primo' (Populus deltoides X Populus nigra) to 580 mu l 1(-1) carbon dioxide fo$869^4^Balaguer,L^Barnes,JD^Panicucci,A^Borland,AM^1995^1^Production and utilization of assimilates in wheat (triticum- aestivum L) leaves exposed to elevated o-3 and/or co2^84^129^4^557-568^^^^^Apr^^^^^4538ied and discussed. In addition, the r$A^4537^This study examined the effects of elevated ozone (O-3) and/or carbon dioxide (CO2) on the diel allocation of photo$synthetically fixed carbon in fully expanded leaves of young (growth stages 4-5) spring wheat (Triticum aestivum L. cv. Ha$nno). Plants were grown in controlled environment chambers and exposed to two O-3 regimes ['non-polluted' air (CF), < 5 nm$ol mol(-1); 'polluted' air, CF + 75 nmol mol(-1) 7 h d(-1)] and two CO2 treatments ('ambient', 354 mu mol mol(-1); 'elevat$ed', 700 mu mol mol(-1)) over a 30 d period. Neutral sugars (predominantly sucrose) were found to be the most abundant for$m of carbohydrate accumulated by leaves during the day, but significant quantities of starch and high degree of polymeriza$tion (d.p.) fructans were also present. Elevated concentrations of O-3 and/or CO2 were found to have marked effects on die$l patterns of export, storage and respiration, whilst the proportions of fixed carbon allocated to each of these processes$ were broadly similar. O-3 depressed the rate of net CO2 assimilation (-20%) and reduced stomatal conductance (- 19%). Thi$s was reflected in a reduced amount of carbohydrate accumulated in, and exported by, source tissue during the day. Effects$ of O-3 on the rate of CO2 fixation were aggravated by an increased demand for carbon by dark respiratory processes. In co$entrast, doubling the atmospheric concentration of CO2 enhanced the rate of net CO2 assimilation (+ 47%) and reduced the pr$732^12^Alcamo,J^Vandenborn,GJ^Bouwman,AF^Dehaan,BJ^Goldewijk,KK^Klepper,O^Krabec,J^Leemans,R^Olivier,JGJ^Toet,AMC^Devries,$HJM^Vanderwoerd,HJ^1994^1^Modeling the global society-biosphere-climate system .2. Computed scenarios^94^76^1-2^37-78^^^^^Jul^^^^^4275f forests and soil warming effects on net CO2 efflux from forests. Carbon dioxide enrichment of tree seedling$A^4274^This paper presents scenarios computed with IMAGE 2.0, an integrated model of the global environment and climate ch$ange. Results are presented for selected aspects of the society- biosphere-climate system including primary energy consump$tion, emissions of various greenhouse gases, atmospheric concentrations of gases, temperature, precipitation, land cover a$nd other indicators. Included are a ''Conventional Wisdom'' scenario, and three variations of this scenario: (i) the Conve$ntional Wisdom scenario is a reference case which is partly based on the input assumptions of the IPCC's IS92a scenario; ($ii) the ''Biofuel Crops'' scenario assumes that most biofuels will be derived from new cropland; (iii) the ''No Biofuels''$ scenario examines the sensitivity of the system to the use of biofuels; and (iv) the ''Ocean Realignment'' scenario inves$tigates the effect of a large-scale change in ocean circulation on the biosphere and climate. Results of the biofuel scena$rios illustrate the importance of examining the impact of biofuels on the full range of greenhouse gases, rather than only$ CO2. These scenarios also indicate possible side effects of the land requirements for energy crops. The Ocean Realignment$ scenario shows that an unexpected, low probability event can both enhance the build-up of greenhouse gases, and at the sa$me time cause a temporary cooling of surface air temperatures in the Northern Hemisphere. However, warming of the atmosphere is only delayed, not avoided.2 efflux from forests, then a positive feedback will follow. A 2 to 4-degrees-C increase $733^5^Joles,DW^Cameron,AC^Shirazi,A^Petracek,PD^Beaudry,RM^1994^1^Modified-atmosphere packaging of heritage red raspberry $fruit - respiratory response to reduced oxygen, enhanced carbon- dioxide, and temperature^154^119^3^540-545^^^^^May^^^^^42$A^4276^'Heritage' raspberries (Rubus idaeus L.) were sealed in low- density polyethylene packages and stored at 0, 10, and$ 20C during Fall 1990 and 1991 to study respiratory responses under modified atmospheres. A range of steady-state O2 and C$O2 partial pressures were achieved by varying fruit weight in packages of a specific surface area and film thickness. Film$ permeability to O2 and CO2 was measured and combined with surface area and film thickness to estimate total package perme$ability. Rates of O2 uptake and CO2 production and respiratory quotient (RQ) were calculated using steady-state O2 and CO2$ partial pressures, total package permeability, and fruit weight. The O2 uptake rate decreased with decreasing O2 partial $pressure over the range of partial pressure studied. The Michaelis-Menten equation was used to model O2 uptake as a functi$on of O2 partial pressure and temperature. The apparent K(m) (K1/2) remained constant (5.6 kPa O2) with temperature, while$ Q10 was estimated to be 1.9. RQ was modeled as a function of O2 partial pressure and temperature. Headspace ethanol incre$ased at RQs >1.3 to 1.5. Based on RQ, ethanol production, and flavor, we recommend that raspberries be stored at O2 levels$ above 4 kPa at 0C, 6 kPa at 10C, and 8 kPa at 20C. Steady-state CO2 partial pressures of 3 to 17 kPa had little or no effect on O2 uptake or headspace ethanol partial pressures at 20C.ary climate (+0-degrees-C, 3 50 ppmv), OBM and TEM estimat77al net primary productivity (NPP) for temperate forests in North America to be 2.250 and 2.602 x 10(15) g C . yr-1, res$734^3^Nikolaidis,NP^Hu,HL^Ecsedy,C^1994^1^Effects of climatic variability on the hydrologic response of a fresh-water watershed^248^56^2^161-178^^^^^^^^^^4279 PPMV CO2, OBM and TEM predict median increases in NPP of 12.5% and 2.5%, respectivel$A^4278^A generalized watershed model was used to evaluate the effects of global climate changes on the hydrologic response$s of freshwater ecosystems. The Enhanced Trickle Down (ETD) model was applied to W-3 watershed located near Danville, Verm$ont. Eight years of field data was used to perform model calibration and verification and the results were presented in Ni$kolaidis et al., (1993). Results from the Goddard Institute for Space Studies (GISS) and the Geophysical Fluid Dynamics La$boratory (GFDL) general circulation models which simulated the doubling of present day atmospheric CO2 scenarios were used$ to perform the hydrologic simulations for the W-3 watershed. The results indicate that the W-3 watershed will experience $increases in annual evapotranspiration and decreases in annual outflow and soil moisture. Stochastic models that simulate $collective statistical properties of meteorological time series were developed to generate data to drive the ETD model in $a Monte- Carlo fashion for quantification of the uncertainty in the model predictions due to input time series. This coupl$ed deterministic and stochastic model was used to generate probable scenarios of future hydrology of the W-3 watershed. Th$e predicted evapotranspiration and soil moisture under doubling present day atmospheric CO2 scenarios exceed the present d$ay uncertainty due to input time series by a factor greater than 2. The results indicate that the hydrologic response of t$he W-3 watershed will be significantly different than its present day response. The Enhanced Trickle Down model can be used to evaluate land surface feedbacks and assessing water quantity management in the event of climate change.ome of the sp$735^3^Giordano,M^Davis,JS^Bowes,G^1994^1^Organic-carbon release by dunaliella-salina (chlorophyta) under different growth-conditions of co2, nitrogen, and salinity^249^30^2^249-257^^^^^Apr^^^^^4281trated. An azonal pattern of vegetation distri$A^4280^Two strains of Dunaliella salina (Dunal) Teod., UTEX 1644 and UTEX 200, were cultured under different growth regime$s, including 10 mM NO3- or NH4+, 1.5 or 3.0 M NaCl, and low (0.035%) or high (5%) CO2 in air. The release of C-14-labeled $dissolved organic carbon (DOC), expressed as a rate and as a percentage of photo synthetic (CO2)-C-14, assimilation, was s$ubsequently determined. The percentage of DOC released was inversely related to cell density in the assay medium, but phot$osynthesis on a per-cell basis was not. Release of DOC was low, in the range of 1-5% of photosynthesis, but during acclima$tion to growth on NH4+, it rose to 11%. The presence of NH4+ rather than NO3- in the growth medium increased the rate of r$elease by both strains, but the percentage release was stimulated only in UTEX 200 cells, because their photosynthetic ra $te was depressed by NH4+. For UTEX 1644, high, as compared to low, CO2-grown cells, had somewhat higher rates a nd percent$ages of DOC release, but release from UTEX 200 cells was unaffected by the growth-CO2. The rate of DOC release by high CO2$-grown cells was not enhanced at a low concentration of dissolved inorganic carbon, indicating that the released material $did not originate from the photorespiratory pathway. The effects of NaCl on DOC release varied with strain a nd growth con$ditions. For UTEX 200, the cells in NO3-, but not NH4+, exhibited a doubling or more in percentage Of release with a doubl$ing in NaCl concentration, irrespective of growth- CO2. With UTEX 1644 the low CO2-grown cells showed the greatest enhance%ment in 3.0 M NaCl. Organic matter accumulated on the external surface of the cell membrane and constituted a well- define%d cell-coat, which was more dense in NH4+ than in NO3-- grown cells. Microtubules, which may play a role in maintaining ce%ll shape, were observed just below the plasma membrane. From a practical viewpoint, the presence of organic material in th%e hypersaline ponds of salt-works is detrimental to salt production. When D. salina cells become abundant in such ponds, the attendant, continuous release of DOC may make a significant contribution to the problem. had the most inelastic tissue%736^2^Vanoosten,JJ^Besford,RT^1994^1^Sugar feeding mimics effect of acclimation to high co2-rapid down-regulation of rubisco small-subunit transcripts but not of the large subunit transcripts^4^143^3^306-312^^^^^Mar^^^^^4283 PY 1993 PD OCT VL %A^4282^The abundance of rbcS transcripts, derived from the nuclear gene-family coding for the small subunit of RuBisCO, wa%s dramatically reduced in tomato plants exposed to high CO2 for 4 days or more whereas the decline in the rbcL RNA transcr% ipts, from the chloroplast gene coding for the large subunit of RuBisCO, was less pronounced. The rate of decline in the a% bundance of the rbcs transcripts was enhanced when leaves were detached and supplied with water so as to deprive them of a% ny major sink and simultaneously exposed to high CO2. The reduction in the abundance of rbcS mRNA, but nor rbcL, was mimic% ked when sucrose or glucose was supplied to leaf tissue, whereas acetate or sorbitol had no effect. Based on these and oth% er published data a molecular model involving the repression of transcription of nuclear-encoded genes for chloroplast pro%teins by photosynthetic end-products is proposed to account for photosynthetic acclimation to high CO2 in tomato and other species.han in non-rhizosphere soil, especially in pot experiments. The rate of ethylene decomposition was, however, muc%737^1^Baldocchi,D^1994^1^A comparative-study of mass and energy-exchange rates over a closed C-3 (wheat) and an open C-4 (corn) crop .2. Co2 exchange and water-use efficiency^107^67^3-4^291-321^^^^^Jan^^^^^4285ere regions. The implications of %A^4284^Major differences exist between the photosynthetic and transpiration rates Of C3 and C4 leaves as a result of bioch%emical and physiological factors. Whether or not differences between CO2 and water vapor exchange rates Of C3 and C4 speci%es scale from leaf to field dimensions is poorly known. The aim of this work is to improve our understanding on how enviro%nmental, architectural and physiological variables affect the flux densities Of CO2 and water vapor over C3 and C4 crop st%ands during day and night periods. Experimental data were obtained over a closed wheat and an open com stand using the edd%y correlation method. Interpretation of the field measurements is aided by the use of a canopy photosynthesis/evaporation %model. The flux density of absorbed photosynthetically active radiation (Q(a)) had a disproportionate influence on CO2 flu%x densities measured over a closed C3 and an open C4 crop. Variations in Q(a) explained over 88% of the variance in daytim%e CO2 flux densities, F(c). At night, canopy radiative temperature was the main environmental factor controlling the respi%ratory CO2 efflux by the two crops. Leaf area index and growth stage were the plant variables that affected F(c) most. Inc%remental increases in leaf area index enhanced the com crop's ability to absorb incident solar radiation and enlarged the %com's sink strength for CO2. Heading by the wheat caused rates of daytime CO2 gains to decrease and rates of night-time CO%2 losses to increase. Water use efficiency of the wheat crop improved as the absolute humidity deficit of the atmosphere d%ecreased. Water use efficiency of the com, on the other hand, was relatively insensitive to humidity deficits. With regard% to canopy CO2 exchange and water use efficiency, differences in canopy structure between the wheat and com overwhelmed ph%!ysiological differences. The closed C3 wheat crop assimilated CO2 at a higher rate than the sparse C4 com canopy, even tho%"ugh com uses a more efficient photosynthetic pathway. Consequently, water use efficiency of the com was not greater than v%#alues measured over the wheat, Instead, water use efficiencies of the two crops were similar. The com crop assimilated CO2%$ at a lower rate than wheat because the com's canopy quantum yield was lower and because its sparse canopy absorbed less photosynthetically active radiation than the closed wheat stand.sinks for CO2. During this selected time period of 5 days 738^2^Claussen,M^Esch,M^1994^1^Biomes computed from simulated climatologies^198^9^4-5^235-243^^^^^Jan^^^^^4287f respirati%'A^4286^The biome model of Prentice et al. (1992a) is used to predict global patterns of potential natural plant formations%(, or biomes, from climatologies simulated by ECHAM, a model used for climate simulations at the Max-Planck-Institut fur Me%)teorologie, This study is undertaken in order to show the advantage of this biome model in diagnosing the performance of a%* climate model and assessing effects of past and future climate changes predicted by a climate model. Good overall agreeme%+nt is found between global patterns of biomes computed from observed and simulated data of present climate. But there are %,also major discrepancies indicated by a difference in biomes in Australia, in the Kalahari Desert, and in the Middle West %-of North America, These discrepancies can be traced back to failures in simulated rainfall as well as summer or winter tem%.peratures. Global patterns of biomes computed from an ice age simulation reveal that North America, Europe, and Siberia sh%/ould have been covered largely by tundra and taiga, whereas only small differences are seen for the tropical rain forests.%0 A potential northeast shift of biomes is expected from a simulation with enhanced CO2 concentration according to the IPCC%1 Scenario A. Little change is seen in the tropical rain forest and the Sahara. Since the biome model used is not capable o%2f predicting changes in vegetation pat terns due to a rapid climate change, the latter simulation has to be taken as a pre%3diction of changes in conditions favourable for the existence of certain biomes, not as a prediction of a future distribution of biomes.ie ecosystem level response to elevated CO2 on the C cycle could potentially increase C storage. Reduced li%5739^4^Whetton,PH^Fowler,AM^Haylock,MR^Pittock,AB^1993^1^Implications of climate-change due to the enhanced greenhouse- effect on floods and droughts in australia^50^25^3-4^289-317^^^^^Dec^^^^^4289ants would shunt more of the plant biomass dire%7A^4288^Potential impacts of climate change on heavy rainfall events and flooding in the Australian region are explored usi%8ng the results of a general circulation model (GCM) run in an equilibrium enhanced greenhouse experiment. In the doubled C%9O, simulation, the model simulates an increase in the frequency of high-rainfall events and a decrease in the frequency of%: low- rainfall events. This result applies over most of Australia, is statistically more significant than simulated change%;s in total rainfall, and is supported by theoretical considerations. We show that this result implies decreased return per%. The second part of the paper assesses the implications of climate change for drought occurrence in Australia. This is un%?dertaken using an off-line soil water balance model driven by observed time series of rainfall and potential evaporation t%@o determine the sensitivity of the soil water regime to changes in rainfall and temperature, and hence potential evaporati%Aon. Potential impacts are assessed at nine sites, representing a range of climate regimes and possible climate futures, by%B linking this sensitivity analysis with scenarios of regional climate change, derived from analysis of enhanced greenhouse%C experiment results from five GCMs. Results indicate that significant drying may be limited to the south of Australia. How%Dever, because the direction of change in terms of the soil water regime is uncertain at all sites and for all seasons, there is no basis for statements about how drought potential may change.ous herb aboveground biomass was lower and total N h%F740^4^Alcamo,J^Kreileman,GJJ^Krol,MS^Zuidema,G^1994^1^Modeling the global society-biosphere-climate system .1. Model description and testing^94^76^1-2^1-35^^^^^Jul^^^^^4291ong treatments in 2 out of 3 years. In 1990, N concentration in root in%HA^4290^This paper describes the IMAGE 2.0 model, a multi-disciplinary, integrated model designed to simulate the dynamics %Iof the global society-biosphere-climate system. The objectives of the model are to investigate linkages and feedbacks in t%Jhe system, and to evaluate consequences of climate policies. Dynamic calculations are performed to year 2100, with a spati%Kal scale ranging from grid (0.5-degrees x 0.5-degrees latitude- longitude) to world regional level, depending on the sub-m%Lodel. The model consists of three fully linked sub-systems: Energy- Industry, Terrestrial Environment, and Atmosphere-Ocea%Mn. The Energy-Industry models compute the emissions of greenhouse gases in 13 world regions as a function of energy consum%Nption and industrial production. End use energy consumption is computed from var-ious economic/demographic driving forces.%O The Terrestrial Environment models simulate the changes in global land cover on a grid-scale based on climatic and econom%Pic factors, and the flux of CO2 and other greenhouse gases from the biosphere to the atmosphere. The Atmosphere-Ocean mode%Qls compute the buildup of greenhouse gases in the atmosphere and the resulting zonal-average temperature and precipitation%R patterns. The fully linked model has been tested against data from 1970 to 1990, and after calibration can reproduce the %Sfollowing observed trends: regional energy consumption and energy-related emissions, terrestrial flux of CO2 and emissions%T of greenhouse gases, concentrations of greenhouse gases in the atmosphere, and transformation of land cover. The model can also simulate long term zonal average surface and vertical temperatures.ase (in both the directions) and synaptosomal g%V741^3^Becker,M^Nieminen,TM^Geremia,F^1994^1^Short-term variations and long-term changes in oak productivity in northeastern france - the role of climate and atmospheric co2^186^51^5^477-492^^^^^^^^^^4293al and synaptosomal fractions of cerebra%XA^4292^A dendroecological study was carried out in 2 forests in northeastern France with the aim of identifying and quanti%Yfying possible long-term trends in the radial growth of sessile oak (Quercus petraea (Matt) Liebl) and pedunculate oak (Q %Zrobur L). A total of 150 sites were selected to represent the ecological diversity of these forests. An index Cd was used %[to correct annual ring width in order to compensate for the effect of different competition situations. The data were stan%\dardized with reference to the mean curve 'basal area increment vs cambial age'. The growth index curves revealed a strong%] increase in sessile oak growth (+ 64% during the period 1888 to 1987) as well as in that of peduncutate oak (+40%). The g%^rowth increase in the 'young' rings (<60 years) of sessile oak was + 87 %, and that of young rings of pedunculate oak was %_+ 49%. The corresponding increase in the 'old' rings (>65 years) was + 48% and 15% respectively (not significant for the l%`atter). It would thus appear that pedunculate oak has benefited to a lesser extent than sessile oak from the progressive c%ahanges in its environment. Years showing a strong growth decrease are more common for pedunculate oak than for sessile oak%b. These results are consistent with a recent hypothesis about a slow but general retreat of pedunculate oak, including sev%cere episodic declines, in favour of sessile oak in many regions of France. A model was created using a combination of mete%dorological data (monthly precipitation and temperature) starting in 1881, and increasing atmospheric CO, concentrations. T%ehe model explains 78.3% of the variance for sessile oak and 74.3% for pedunculate oak. This includes some monthly paramete%frs of year y (year of ring formation), and also some parameters of the years y-1 to y-4 for sessile oak and y-1 to y-5 for%g pedunculate oak. The models satisfactorily reproduce the long-term trends and the interannual variation. The climatic var%hiables alone (ie excluding the CO, concentration) were insufficient to explain the trends observed. The possible direct and indirect effects of increasing CO2 concentration on the growth of both species are discussed.as generally very low (DEL%j742^2^Beerling,DJ^Woodward,FI^1993^1^Ecophysiological responses of plants to global environmental- change since the last glacial maximum^84^125^3^641-648^^^^^Nov^^^^^4295g that propionate, 2-propanol, caproate and valerate were converted via a%lA^4294^Ecophysiological information on the responses of plants to past global environmental changes may be obtained from Q%muaternary fossil leaves by measurements of (i) stomatal density, (ii) stomatal dimensions and (iii) C-13 discrimination (D%nELTA C-13). The stomatal density and stomatal dimensions of leaves can be used to calculate stomatal conductance, while le%oaf DELTA C-13 values provide independent information on stomatal conductance and plant water use efficiency. In this paper%p, stomatal conductance is calculated for a sequence of radiocarbon dated fossil leaves of Salix herbacea L. which, togethe%qr with herbarium and fresh material, represents a time-series spanning from the Last Glacial Maximum (LGM) (16 500 yr BP) %rto the present day. The calculated values were then tested against leaf DELTA C-13 values previously reported for the same%s material. Our calculations show that stomatal conductance is negatively correlated with increases in atmospheric CO2 conc%tentration over the last 16 500 yr. This represents the first evidence of long-term response of stomatal conductance to inc%ureases in atmospheric CO2 concentration and confirms the response observed in experimental systems exposing plants to lowe%vr-than-present CO2 concentrations in controlled environments. The calculated decrease in conductance was positively correl%wated with leaf DELTA C-13 values, supporting this interpretation. The mean leaf DELTA C-13 value for the 18th and 19th cen%xturies was significantly (P < 0.05) lower than the mean for the interval LGM-Holocene (10000 yr BP) implying an increase i%yn plant water-use-efficiency over this time. These two lines of evidence, together with the stomatal density record from a%z glacial cycle, and experimental studies growing C3 plants in glacial-to-present CO2 concentrations, strongly imply that t%{he water use efficiency of vegetation during the LGM was lower than at present and that it has increased since that time. %|Further evidence in support of this conclusion comes from the pattern of world vegetation types present during the LGM pre%}viously reconstructed using palaeoecological data. This evidence demonstrates that the distribution of vegetation types du%~ring the LGM was significantly different from that of the present day and showed a contraction in the area of rain forest and a major expansion of desert areas.ation in granulites. BP 643-651 PG 9 JI J. Geol. PY 1993 PD SEP VL 101 IS 5 GA LX14%743^6^Dehaan,BJ^Jonas,M^Klepper,O^Krabec,J^Krol,MS^Olendrzynski,K^1994^1^An atmosphere-ocean model for integrated assessment of global change^94^76^1-2^283-318^^^^^Jul^^^^^42970386-216X C1 UNIV TOKYO, DEPT CHEM ENGN, TOKYO 113, JAPAN. DE BIOCH%A^4296^This paper describes the atmosphere-ocean system of the integrated model IMAGE 2.0. The system consists of four lin%ked models, for atmospheric composition, atmospheric climate, ocean climate and for ocean biosphere and chemistry. The fir%st model is globally averaged, the latter are zonally averaged with additional resolution in the vertical. The models refl%ect a compromise between describing the physical, chemical and biological processes and moderate computational requirement%s. The system is validated with direct observations for current conditions (climate, chemistry) and is consistent with res%ults from General Circulation Model experiments. The system is used in the integrated setting of the IMAGE 2.0 model to gi%ve transient climate projections. Global surface temperature is simulated to increase by 2.5 K over the next century for s%ocio- economic scenarios with continuing economic and population growth. In a scenario study with reduced ocean circulation, the climate system and the global C cycle are found to be appreciably sensitive to such changes.six weeks. Using these744^1^Innes,JL^1994^1^Climatic sensitivity of temperature forests^35^83^1-2^237-243^^^^^^^^^^4299 global carbon balance. %A^4298^Climatic change and associated global changes are of major interest to foresters, both in terms of forest ecology a%nd of future forest production. Predicting the likely effects of global change on forests is extremely difficult due to th%e critical lack of information on regional changes in meteorological factors relevant to forests. However, existing models% of forest production and forest distribution fail to take adequate account of what is already known. Climate and carbon d%ioxide concentrations have shown substantial changes over the last 100 years. Although the rate of change is likely to inc%rease, recent proposed and implemented control strategies, together with better climatic models, are tending to suggest th%at the rate of change will be less than initially thought. This means that past changes may provide an increasingly useful% source of information. In particular, information on the impact on forests of both long-term climate change and short-term climatic events is rapidly increasing. Such information should be built into future forest response models. lincomycin,%745^6^Prentice,IC^Sykes,MT^Lautenschlager,M^Harrison,SP^Denissenko,O^Bartlein,PJ^1993^1^Modeling global vegetation patterns and terrestrial carbon storage at the last glacial maximum^175^3^3^67-76^^^^^May^^^^^4301nobacillus pleuropneumoniae be%A^4300^Global patterns of potential natural vegetation were simulated for present and last glacial maximum (LGM) climates.% The LGM simulation showed good agreement with available evidence, most importantly in the humid tropics. Simple calculati%ons based on these simulations indicate that terrestrial carbon storage increased by 300-700 Pg C after the LGM. The range% is due to uncertainties in the mean carbon storage values for different biomes, and in the amount of carbon in boreal pea%ts. These results are consistent with the global change in ocean delta-C- 13, inferred from measurements on benthic foraminifera, reflecting the increased storage of isotopically light carbon on land.SN 0300-3604 C1 NASA, AMES RES CTR, MOFFETT746^1^Vitousek,PM^1994^1^Beyond global warming - ecology and global change^11^75^7^1861-1876^^^^^Oct^^^^^4303IBBA; DESERT%A^4302^While ecologists involved in management or policy often are advised to learn to deal with uncertainty, there are a %number of components of global environmental change of which we are certain-certain that they are going on, and certain th%at they are human-caused. Some of these are largely ecological changes, and all have important ecological consequences. Th%ree of the well-documented global changes are: increasing concentrations of carbon dioxide in the atmosphere; alterations %in the biogeochemistry of the global nitrogen cycle; and ongoing land use/land cover change. Human activity-now primarily %fossil fuel combustion-has increased carbon dioxide concentrations from similar to 280 to 355 mu L/L since 1800; the incre%ase is unique, at least in the past 160 000 yr, and several lines of evidence demonstrate unequivocally that it is human-c%aused. This increase is likely to have climatic consequences-and certainly it has direct effects on biota in all Earth's t%errestrial ecosystems. The global nitrogen cycle has been altered by human activity to such an extent that more nitrogen i%s fixed annually by humanity (primarily for nitrogen fertilizer, also by legume crops and as a byproduct of fossil fuel co%mbustion) than by all natural pathways combined. This added nitrogen alters the chemistry of the atmosphere and of aquatic% ecosystems, contributes to eutrophication of the biosphere, and has effects on biological diversity in the most affected %areas. Finally, human land use/land cover change has transformed one-third to one-half of Earth's ice-free surface. This i%n and of itself probably represents the most important component of global change now and will for some decades to come; i%t has profound effects on biological diversity on land and on ecosystems downwind and downstream of affected areas. Overal%l, any clear dichotomy between pristine ecosystems and human-altered areas that may have existed in the past has vanished,% and ecological research should account for this reality. These three and other equally certain components of global envir%onmental change are the primary causes of anticipated changes in climate, and of ongoing losses of biological diversity. T%hey are caused in turn by the extraordinary growth in size and resource use of the human population. On a broad scale, the%re is little uncertainty about any of these components of change or their causes. However, much of the public believes the% causes-even the existence-of global change to be uncertain and contentious topics. By speaking out effectively, we can help to shift the focus of public discussion towards what can and should be done about global environmental change.INE SEDI%747^5^Alagusundaram,K^Jayas,DS^White,NDG^Muir,WE^Sinha,RN^1995^1^Controlling cryptolestes-ferrugineus (stephens) adults in wheat stored in bolted-metal bins using elevated carbon-dioxide^250^37^3^217-223^^^^^Jul-Sep^^^^^4305an, were carried ou%A^4304^Experiments were conducted in two 5.56 m-diameter farm bins to determine the mortality of caged adult rusty grain b%eetles, Cryptolestes ferrugineus (Stephens) (Coleoptera: cucujidae), under elevated carbon dioxide (CO2) concentrations. T%he bins were filled with wheat to a depth of 2.5 m. Dry ice was used to create high CO2 concentrations in the wheat bulks.% Two different modes of application of dry ice were used: (i) pellets on the grain surface and in the aeration duct and (i%i) pellets on the grain surface and blocks in insulated boxes on the grain surface. The pellets exposed to the ambient con%ditions on the grain surface and in the aeration duct sublimated quickly and had to be replenished at frequent intervals. %Dry ice blocks in insulated boxes, however, maintained high CO2 concentrations without replenishment for over 15 d. In bot%h modes of application, the observed CO2 concentrations in the intergranular gas were about 15% and 30% (all the CO2 conce%ntrations given in this article are on a volume basis) at 2.05 m and 0.55 m above the floor, respectively. At 0.55 m above% the floor, the mortality of rusty grain beetle adults was more than 90% while in the top portions of the bulk (2.05 m abo%ve the floor) the mortality was only 30%. On an average about two thirds of the insects were killed. The use of controlled atmosphere treatment within an integrated pest management context is outlined.ion of each biological process. Also, the %748^8^Bainbridge,G^Madgwick,P^Parmar,S^Mitchell,R^Paul,M^Pitts,J^Keys,AJ^Parry,MAJ^1995^1^Engineering rubisco to change its catalytic properties^78^46^^1269-1276^^^^^Sep^^^^^4307im. Acta PY 1993 PD AUG VL 57 IS 16 GA LW389 J9 GEOCHIM COSMOCHIM%A^4306^The initial steps of carbon assimilation and photorespiration are catalysed by ribulose-1,5-bisphosphate carboxylas%e/oxygenase (EC 4.1.1.39). Natural variation in the kinetic properties of the enzyme suggest that it is possible to alter %the enzyme to favour the carboxylation activity relative to oxygenation, Mutagenesis in vitro of the gene encoding the lar%ge subunit of the enzyme from Anacystis nidulans has been used to modify catalytic properties. Residues at the C-terminal %end of loop 6 of the beta/alpha barrel structure of the large subunit influence specificity towards the gaseous substrates%, CO2 and O-2. None of the residues altered by mutagenesis appear to interact directly with the transition state analogue %and their effect on the reaction of the enediolate intermediate with the gaseous substrates and stabilization of the resul%ting transition state intermediates by lysine 334 must be indirect. Interactions with other parts of the enzyme must also %be important in determining substrate specificity, Backbone carbonyl groups close to lysine 334 interact with lysine 128; %mutation of lysine 128 to residues of less positive polarity reduces enzyme activity and favours oxygenation relative to c%arboxylation, the likely effects on assimilation rates of altering the kinetic properties of Rubisco have been modelled. A leaf with cyanobacterial Rubisco may out-perform a higher plant Rubisco at elevated CO2 and cool temperatures., ENGLAND.%749^2^Behboudian,MH^Lai,R^1995^1^Partitioning of photoassimilates in virosa tomatoes under elevated co2 concentration^4^147^1^43-47^^^^^Oct^^^^^4309TER CONTENT ID F-SP HORDEI; CO2 ENRICHMENT; ATMOSPHERIC CO2; WINTER-WHEAT; INSECT HERBIVORE; SE%A^4308^The effect of CO2 enrichment on the distribution of assimilates in tomato plants, Lycopersicon esculentum Mill. cv.% 'Virosa', was studied using C-14-label. Plants were defoliated except for leaves 8, 9, and 10 (numbered acropetally). Dep%ending on the experiment, truss 1 or trusses 1 and 2 were maintained on the plant. Within a 24-h period, the labelled leaf% (leaf 10) retained high levels of C-14 in both control and CO2-enriched plants. Truss 1 was the dominant sink for both CO%2 treatments, drawing on a considerable supply of C-14 re-exported from leaf 8 and leaf 9. The stem and root were transito%ry sinks and had the capacity to re-export C-14 at different rates during the light and dark periods. Pattern of photoassimilate partitioning was not affected by CO2 treatment.ificantly increased, the severity of mildew infection was significa%750^2^Farnsworth,EJ^Bazzaz,FA^1995^1^Inter-generic and intra-generic differences in growth, reproduction, and fitness of 9 herbaceous annual species grown in elevated co2 environments^2^104^4^454-466^^^^^Dec^^^^^4311ldew infection was unchange%A^4310^In assessing the capacity of plants to adapt to rapidly changing global climate, we must elucidate the impacts of e%levated carbon dioxide on reproduction, fitness and evolution. We investigated how elevated CO2 influenced reproduction an%d growth of plants exhibiting a range of floral morphologies, the implications of shifts in allocation for fitness in thes%e species, and whether related taxa would show similar patterns of response. Three herbaceous, annual species each of the %genera Polygonum, Ipomoea, and Cassia were grown under 350 or 700 ppm CO2. Vegetative growth and reproductive output were %measured non-destructively throughout the full life span, and vegetative biomass was quantified for a subsample of plants %in a harvest at first flowering. Viability and germination studies of seed progeny were conducted to characterize fitness %precisely. Early vegetative growth was often enhanced in high- CO2 grown plants of Polygonum and Cassia (but not Ipomoea).% However, early vegetative growth was not a strong predictor of subsequent reproduction. Phenology and production of flora%l buds, flowers, unripe and abscised fruits differed between CO2 treatments, and genera differed in their reproductive and% fitness responses to elevated CO2. Polygonum and Cassia species showed accelerated, enhanced reproduction, while Ipomoea %species generally declined in reproductive output in elevated CO2. Seed ''quality'' and fitness (in terms of viability and% percentage germination) were not always directly correlated with quantity produced, indicating that output alone may not %reliably indicate fitness or evolutionary potential. Species within genera typically responded more consistently to CO2 th%an unrelated species. Cluster analyses were performed separately on suites of vegetative and reproductive characters. Some% species assorted within genera when these reproductive responses were considered, but vegetative responses did not reflec%t taxonomic affinity in these plants. Congeners may respond similarly in terms of reproductive output under global change,% but fitness and prognoses of population persistence and evolutionary performance can be inferred only rarely from examination of vegetative characters alone.NST PUBL HLTH & ENVIRONM PROTECT, DEPT GLOBAL CHANGE, POB 1, 3720 BA BILTHOVEN, NETHE%751^9^Galtier,N^Foyer,CH^Murchie,E^Alred,R^Quick,P^Voelker,TA^Thepenier,C^Lasceve,G^Betsche,T^1995^1^Effects of light and %atmospheric carbon-dioxide enrichment on photosynthesis and carbon partitioning in the leaves of tomato (lycopersicon-esculentum L) plants over-expressing sucrose- phosphate synthase^78^46^^1335-1344^^^^^Sep^^^^^4313re. The model explores the %A^4312^Photosynthetic carbon assimilation, carbon partitioning and foliar carbon budgets were measured in the leaves of tr%ansformed tomato plants expressing a maize sucrose-phosphate synthase (SPS) gene in addition to the native enzyme, and in %untransformed controls. The maize SPS gene was expressed under control of either the promoter of the small subunit of ribu%lose 1,5-bisphosphate carboxylase (rbcS promoter; lines 2, 9 and 18) or the 35S promoter from cauliflower mosaic virus (Ca%MV promoter; line 13). The rate of sucrose synthesis was increased relative to that of starch and sucrose/starch ratios we%re higher throughout the photoperiod in the leaves of all plants expressing high SPS activity. The leaf carbon budget over% the day/night cycle in air at low irradiance (180 mu mol photon m(- 2) s(-1)) was similar in all plants. Net photosynthes%is measured in air and at elevated CO2 (800-1500 mu l I-1) on whole plants grown in air at 400 mu mol m(-2) s(-1) irradian%ce was significantly increased in the high SPS expressors compared to the untransformed controls and was highest where SPS% activity was greatest. At high CO2 the stimulation of photosynthesis was more pronounced, We conclude that SPS activity is a major point of control of photosynthesis particularly under saturating light and CO2.6 RP VLOEDBELD M J9 WATER AIR SO%752^5^Habash,DZ^Paul,MJ^Parry,MAJ^Keys,AJ^Lawlor,DW^1995^1^Increased capacity for photosynthesis in wheat grown at elevated co2 - the relationship between electron-transport and carbon metabolism^6^197^3^482-489^^^^^Oct^^^^^4315 RIDGE NATL LAB%r elevated CO2 in both clones. The observation that interactions with leaf age and/or leaf position significantly confound% the CO2 treatment effect on stomatal and epidermal cell densities, might contribute to the elucidation of the problem of the phenomenon of stomatal density reduction under elevated atmospheric CO2.LINGS; CO2 ENRICHMENT; UNITED-STATES; COMPETI#783^2^Christ,RA^Korner,C^1995^1^Responses of shoot and root gas-exchange, leaf blade expansion and biomass production to p&A^4314^Spring wheat (Triticum aestivum L.) was grown under optimal nutrition for six weeks at 700 and 350 mu mol . mol(-1)& CO2 and simultaneous measurements of photosystem-II (PSII) chlorophyll fluorescence and gas exchange were conducted on in&tact attached leaves. Plants grown at elevated CO2 had double the concentration of CO2 at the carboxylation site (C-c) des&pite a lowered stomatal (g(s)) and mesophyll (g(m)) conductance compared with ambient-grown plants. Plants grown at elevat&ed CO2 had a higher relative quantum yield of PSII electron transport (Phi(PSII)) and a higher relative quantum yield of C&O2 fixation (Phi CO2). The higher Phi(PSII) was due to a larger proportion of open PSII centres, estimated by the coeffici&ent of photochemical quenching of fluorescence (q(p)), with no change in the efficiency of light harvesting and energy tra& nsduction by open PSII centres (F'(v)/F'(m)). Analysis of the relationship between Phi(PSII) and Phi(CO2) conducted under & various CO2 and O-2 concentrations showed that the higher Phi(CO2) for a given Phi(PSII) in leaves developed under elevate& d CO2 was similar to that obtained in leaves upon a partial reduction in photorespiration. Calculation of the allocation o& f photosynthetic electron-transport products to CO2 and O-2 showed that for leaves developed in elevated CO2, there was an& increase in both total linear electron flow and electron flow to CO2 and a decrease in electron flow to O-2. Plants devel&oped under elevated CO, showed positive acclimation manifested by a higher Phi(CO2) when measured under ambient CO2 and hi&gher assimilation rates in A/C-i curves. Initial and to tal activity of ribulose-1,5- bisphosphate carboxylase- oxygenase &(Rubisco EC 4.1.1.39) measured in vitro increased by 16 and 15% respectively in leaves from plants grown in elevated CO2, &which was in agreement with a 15% higher in vivo carboxylation efficiency. It is concluded that growth of spring wheat at &elevated CO2 enhances photosynthesis due to a change in the balance of component processes manifested as an increased capa&city for carbon fixation, total electron transport and Rubisco activity, and a concomitant partial reduction of photorespiration.d, a 26-degrees-C/20-degrees-C thermoperiod, and approximately 300 mumol m-2 s-1 photosynthetic photon flux (PPF).&753^4^Ham,JM^Owensby,CE^Coyne,PI^Bremer,DJ^1995^1^Fluxes of co2 and water-vapor from a prairie ecosystem exposed to ambient and elevated atmospheric co2^107^77^1-2^73-93^^^^^Nov^^^^^4317CO2 treatments. Average stomatal conductance of upper can&A^4316^Increasing concentrations of atmospheric CO2 may alter the carbon and water relations of prairie ecosystems. A C-4-& dominated tallgrass prairie near Manhattan, KS, was exposed to 2x ambient CO2 concentrations using 4.5 m-diameter open-to&p chambers. Whole-chamber net CO2 exchange (NCE) and evapotranspiration (ET) were continuously monitored in CO2- enriched &and ambient (no enrichment) plots over a 34-d period encompassing the time of peak biomass in July and August, 1993. Soil-&surface CO2 fluxes were measured with a portable surface chamber, and sap flow (water transport in xylem) in individual gr&ass culms was monitored with heat balance techniques. Environmental measurements were used to determine the effect of CO2 &on the surface energy balance and canopy resistances to vapor flux. In 1993, frequent rainfall kept soil water near field &capacity and minimized plant water stress. Over the 34-d measurement period, average daily NCE (canopy photosynthesis - so&il and canopy respiration) was 9.3 g CO2 m(-2) in the ambient treatment and 11.4 g CO2 m(-2) under CO2 enrichment. However& , differences in NCE were caused mainly by delayed senescence in the CO2-enriched plots at the end of the growing season. &!At earlier stages of growth, elevated CO2 had no effect on NCE. Soil-surface CO2 fluxes typically ranged from 0.4 to 0.66 &"mg CO2 m(-2) s(-1), but were slightly greater in the CO2-enriched chambers. CO2 enrichment reduced daily ET by 22%, reduce&#d sap flow by 18%, and increased canopy resistance to vapor flux by 24 s m(-1). Greater NCE and lower ET resulted in highe&$r daytime water use efficiency (WUE) under CO2 enrichment vs. ambient (9.84 vs. 7.26 g CO2 kg(-1) H2O). However, record hi&%gh precipitation during the 1993 season moderated the effect of WUE on plant growth, and elevated CO2 had no effect on pea&&k aboveground biomass. CO2-induced stomatal closure also affected the energy balance of the surface by reducing latent hea&'t flux (LE), thereby causing a consequent change in sensible heat flux (H). The daytime Bowen ratio (H/LE) for the study period was near zero for the ambient treatment and 0.21 under CO2 enrichment.-3333333333&)754^3^Holland,EA^Townsend,AR^Vitousek,PM^1995^1^Variability in temperature regulation of co2 fluxes and n mineralization from 5 hawaiian soils - implications for a changing climate^127^1^2^115-123^^^^^Apr^^^^^4319i!o!v!!!&+A^4318^We examined the possibility that microbial adaptation to temperature could affect rates of CO2, N2O and CH4 release&, from soils. Laboratory incubations were used to determine the functional relationship between temperature and CO2, N2O an&-d CH4 fluxes for five soils collected across an elevational range in Hawaii. Initial rates of CO2 production and net N min&.eralization increased exponentially from 15 degrees C to 55 degrees C; initial rates of CH4 and N2O release were more comp&/lex. No optimum temperature (in which rates decline at higher and lower temperatures) was apparent for any of the gases, b&0ut respiration declined with time at higher temperatures, suggesting rapid depletion of readily available substrate. Mean &1Q(10)s for respiration varied from 1.4 to 2.0, a typical range for tropical soils. The functional relationship between CO2&2 production and temperature was consistent among all five soils, despite the substantial differences in mean annual temper&3ature, soils, and land-use among the sites. Temperature responses of N2O and CH4 fluxes did not follow simple Q(10) relati&4onships suggesting that temperature functions developed for CO2 release from heterotrophic respiration cannot be simply ex&5trapolated. Expanding this study to tropical heterotrophic respiration, the flux is more sensitive to changes in Q(10) tha&6n to changes in temperature on a per unit basis: the partial derivative with respect to temperature is 2.4 Gt C . degrees &7C- 1, with respect to Q(10) it is 3.5 Gt C . Q(10) unit(-1). Therefore, what appears to be minor variability might still produce substantial uncertainty in regional estimates of gas exchange.TUUZZZZZZZZZZ&9755^5^Jongen,M^Jones,MB^Hebeisen,T^Blum,H^Hendrey,G^1995^1^The effects of elevated co2 concentrations on the root-growth of lolium-perenne and trifolium-repens grown in a face system^127^1^5^361-371^^^^^Oct^^^^^4321E&E3EEF&;A^4320^Lolium perenne and Trifolium repens were grown in a Free Air CO2 Enrichment (FACE) system at elevated (600 mu mol m&asting nutrient regimes was examined. Root ingrowth bags were inserted for a fixed time into the soil in order to trap roo&?ts. It was also possible to follow the mortality of roots in bags inserted for different time intervals. Root ingrowth of &@both L. perenne and T. repens increased under elevated CO2 conditions. In L. perenne, root ingrowth decreased with increas&Aing nutrient fertilizer level, but for T. repens the root ingrowth was not affected by the nutrient application rate. Besi&Bdes biomass measurements, root length estimates were made for T. repens. These showed an increase under elevated CO2 conce&Cntrations. Root decomposition appeared to decrease under elevated CO2 concentrations. A possible explanation for this effe&Dct is the observed changes in tissue composition, such as the increase in the carbon:nitrogen ratio in roots of L. perenne at elevated CO2 concentrations.&U756^1^Kennedy,AD^1995^1^Antarctic terrestrial ecosystem response to global environmental-change^27^26^^683-704^^^^^^^^^^43&GA^4322^Geographical isolation and climatic constraints are responsible for the low biodiversity and structural simplicity &Hof the antarctic terrestrial ecosystem Under projected scenarios of global change, both limiting factors may be released. &IAlien species immigration is likely to be facilitated as modified ocean and atmospheric circulation introduce exotic water&J- and air-borne propagules from neighboring continents. Elevated temperature, UV radiation, CO2, and precipitation will co&Kmbine additively and synergistically to favor new trajectories of community development. It can be predicted that existing&L patterns of colonization, recruitment, succession, phenology and mortality will be perturbed with concomitant effects for&M ecosystem function through changes in biomass, trophodynamics, nutrient cycling, and resource partitioning. Soil propagul&Ne banks will play an important role through founder effects. Uniquely in Antarctica, many of the short-term consequences o&Of global change will depend on the ecophysiological relationships of cryptogamic plants. However, in the long term, climat&Pic warming will favor an increase in phanerogamic biomass since these species are currently excluded by the low cumulative&Q degree-days > 0 degrees C. It has been suggested that antarctic communities may be particularly vulnerable to global chan&Rge: Their slow rate of development and restricted gene flow limit response to new conditions. However, vulnerability must &Sbe defined with respect to both the direction and rate of change and it is likely that some perturbations will enhance the&T complexity and productivity of the biota, with negative feedback to the global carbon cycle. The chapter concludes with a discussion of institutional issues surrounding this topic.23ÇƇLJ̇ÈЈ{ɑёؑޑ &W757^4^Kerstiens,G^Townend,J^Heath,J^Mansfield,TA^1995^1^Effects of water and nutrient availability on physiological- responses of woody species to elevated co2^251^68^4^303-315^^^^^^^^^^4325&YA^4324^The growth responses to elevated CO2 found in experiments are highly variable and depend on other experimental para&Zmeters such as irrigation, fertilization, light regime, etc. As yet, the strength or even the sign of most interactions is&[ all but impossible to predict from first principles. Experiments in ambient and CO2-enriched ambient air (+250 p.p.m.) ha&\ve been conducted in specially adapted greenhouses (Solardomes) at Lancaster University for the past four seasons on Sitka&] spruce (Picea sitchensis (Bong.) Carr.), wild cherry (Prunus avium L.), beech (Fagus sylvatica L.) and pedunculate oak (Q&^uercus robur L.). These experiments are reviewed together with other published studies on interactive effects of elevated &_CO2 and water and nutrient supply on physiological processes, in particular gas exchange, in tree species. It is often ass&`umed that drought tolerance will increase in elevated CO2 because of a suppression of stomatal conductance and an increase&a in instantaneous water use efficiency. There is, however, some evidence that such effects could be more than offset in be&bech by CO2-induced increases in leaf area. It is tentatively suggested that in beech, drought tolerance could already have been reduced by the increase in atmospheric CO2 over the last century.&d758^1^King,DA^1995^1^Equilibrium-analysis of a decomposition and yield model applied to pinus-radiata plantations on sites of contrasting fertility^81^83^3^349-358^^^^^15 Dec^^^^^4327&fA^4326^Recent models of growth and nutrient cycling relate forest productivity to canopy photosynthesis, as influenced by >he effect of nutrient cycling on foliar nitrogen concentration. A useful approach for analysing the impact of elevated CO&h2 or altered nitrogen inputs on production is to consider model solutions where recycling leaves, fine roots, litter and s&ioil organic pools of intermediate turnover time are in equilibrium, while tree stems and recalcitrant humus are accumulati&jng or releasing carbon and nitrogen. This equilibrium analysis, employed by the Generic Decomposition and Yield (G'DAY) mo&kdel, was applied to Pinus radiata plantations growing on an infertile site in Australia and a fertile site in New Zealand.&l Predicted productivities and foliar nitrogen concentrations were substantially lower than observed for the young (12-year&m- old) stands, particularly for the fertile site. The model predictions were closer to values expected for older stands la&nte in the commercial rotation cycle when reduced wood production rates reduce the net nitrogen requirements for growth. Th&oese results underscore the importance of the net release of nitrogen from soil organic matter early in the life of a stand&p and suggest that care should be taken in using equilibrium analyses to estimate the impacts of elevated [CO2] on forest production.&r759^4^Lethiec,D^Dixon,M^Loosveldt,P^Garrec,JP^1995^1^Seasonal and annual variations of phosphorus, calcium, potassium and &smanganese contents in different cross-sections of picea-abies (L) karst needles and quercus-rubra L leaves exposed to elevated co2^252^10^2^55-62^^^^^Dec^^^^^4329&uA^4328^Norway spruce and red oak trees were planted directly into the soil and enclosed in open-top chambers. For 2 years &vthe trees were exposed to both ambient and elevated CO2 concentrations (700 mu mol mol(-1)) and during this time variation&ws in nutrient concentrations were studied. CO2-treated plants had decreases in global leaf concentrations of nitrogen, pot&xassium, calcium and manganese for both species. When different areas of the foliage were analysed however, the response sh&yowed much variability between the respective sites and between species. Furthermore the nutrient concentrations changed di&zfferently as the plant material aged and this change showed inter-treatment differences. These results show how it may be important to analyse plant material of different ages and at different cell sites when studying nutrient levels.&|760^2^Manderscheid,R^Weigel,HJ^1995^1^Do increasing atmospheric co2 concentrations contribute to yield increases of german crops^161^175^2^73-82^^^^^Sep^^^^^4331&~A^4330^The global atmospheric CO2-concentration is increasing and there has been an increase in Germany of about 30 ppm fr&om 340 ppm to 370 ppm CO2 during the last two decades. The hectare yield of many crops has also increased during this time& period. The objective of the present study was to estimate whether the past and future change in the atmospheric composit&ion significantly contributes to the increase in hectare yield. Different crop species (beans, Phaseolus vulgaris, cv Pfal&zer Juni; spring barley, Hordeum vulgare L., cvs. Alexis and Arena; spring wheat, Triticum aestivum L., cvs. Star and Turb&o; maize, Zea mays L., cvs. Bonny and Boss) were grown at ambient (372 ppm) and at slightly elevated CO2-concentrations (4&59 ppm and 539 ppm) in open-top chambers and the effect of the different CO2-concentrations on the growth and yield of the& plants was measured. The past and future CO2-effect was estimated from the slope of a linear CO2-yield curve (percentage &increase in yield per ppm CO2, 100 % at 370 ppm) fitted to the data and those from previous studies on wheat and maize. Th&e percentage increase in yield per ppm CO2 is insignificant for beans, of borderline significance for silage maize (0.06 %& per ppm), and 0.35 % per ppm and 0.26 % per ppm for barley and wheat, respectively. The CO2-elevation primarily decreases& the tiller dieback of the cereals. Considering the increase in CO2 of 30 ppm and in the hectare yield of 25 % (barley) an&d 28 % (wheat) from 1970 to 1990, the contribution of CO2 to the increase in the agricultural production is estimated to b&e one fourth up to one half of the increase in hectare yield of spring cereals. Given a recent yearly increase of 2 ppm the future CO2-related increase in hectare yield is estimated to be about 0.5-0.7 % per year.&761^3^McGuire,AD^Melillo,JM^Joyce,LA^1995^1^The role of nitrogen in the response of forest net primary production to elevated atmospheric carbon-dioxide^27^26^^473-503^^^^^^^^^^4333 0Ns~&A^4332^We review experimental studies to evaluate how the nitrogen cycle influences the response of forest net primary pro&duction (NPP) to elevated CO2. The studies in our survey report that at the tissue level, elevated CO2 reduces leaf nitrog&en concentration an average 21%, but that it has a smaller effect on nitrogen concentrations in stems and fine roots. In c&ontrast, higher soil nitrogen availability generally increases leaf nitrogen concentration. Among studies that manipulate &both soil nitrogen availability and atmospheric CO2, photosynthetic response depends on a linear relationship with the res&ponse of leaf nitrogen concentration and the amount of change in atmospheric CO2 concentration. Although elevated CO2 ofte&n results in reduced tissue respiration rate per unit biomass, the link to changes in tissue nitrogen concentration is not well studied.=@    & - 3 8 A W Z [ `     E  U ^&762^1^Miao,SL^1995^1^Acorn mass and seedling growth in quercus-rubra in response to elevated co2^42^6^5^697-700^^^^^Oct^^^&A^4334^In order to explore whether seed size affects plant response to elevated CO2 plants grown from red oak (Quercus rub&ra L.) acorns were studied for differences in their first year response to CO2 concentrations of 350 and 700 ul/l. Overall&, at final harvest, total biomass of plants grown in elevated CO2 were 47 % larger than that of plants grown in ambient CO&2. There were significant interactions between CO2 treatments and initial acorn mass for total biomass, as well as for roo&t, leaf, and stem biomass. Although total biomass increased with increasing initial acorn mass for both high and ambient C&O2 plants, high CO2 plants exhibited a greater increase than ambient CO2 plants, as indicated by a steeper slope in high C&O2 plants. However, CO2 levels did not affect biomass partitioning traits, such as root/shoot ratio, leaf, stem, and root &weight ratios, and leaf area ratio. These results suggest that variation in seed size or initial plant size can cause intraspecific variation in response to elevated CO2.^^4335&763^4^Navas,ML^Guillerm,JL^Fabreguettes,J^Roy,J^1995^1^The influence of elevated co2 on community structure, biomass and carbon balance of mediterranean old-field microcosms^127^1^5^325-335^^^^^Oct^^^^^4337RACIE\95\95A1\READ&A^4336^We studied the effects of a doubling of atmospheric CO2 concentration on intact monoliths of Mediterranean grasslan&d in growth chambers where climatic field conditions were simulated. During the six month growing season, changes in commu&nity structure were monitored by quantifying species richness and cover. The CO2 exchange of microcosms was measured conti&nuously and the resulting quantity and quality of biomass were evaluated. Species richness and cover did not respond to el&evated C02. After one month of treatment, CO2 exchange measured during the day did not differ between CO2 levels but the n&ight respiration was two-fold higher under elevated CO2. Stimulations of both day and night CO2 flux by short-term CO2 enr&ichment were recorded several times during the growing season. These results suggest that despite some downward adjustment& of photosynthesis, net canopy photosynthesis was stimulated by elevated CO2, but this stimulation was compensated for by &an increased respiration. The 20% stimulation of final phytomass under elevated CO2 was not significant: it resulted from &unchanged live plant matter but a significant, 100% increase in litter accumulation. These results suggest that in low-pro&ductivity Mediterranean herbaceous systems, the greatest effect of CO2 is not on the storage of carbon in biomass but on the turnover of the carbon in the plants.S\CONVENTIONS.DOCv?`CO2MAP\BIBL&764^1^Nielsen,MV^1995^1^Photosynthetic characteristics of the coccolithophorid emiliania-huxleyi (prymnesiophyceae) exposed to elevated concentrations of dissolved inorganic carbon^249^31^5^715-719^^^^^Oct^^^^^4339BIBLIOGRAPHIES&A^4338^Light-saturated photosynthesis (P-max) of Emiliania huxleyi (Lohmann) Hay et Mohler is known to be carbon-limited a&t natural concentrations of dissolved inorganic carbon (DIC). In the present study, light-limited and light-saturated phot&osynthetic rates of E. huxleyi were studied at three concentrations of DIC (2.4, 7.4, and 12.4 mM) for high-calcite (C-in/&C-tot = 0.48) and low-calcite (C-in/C-tot = 0.08) cells of the same strain. The photosynthetic efficiency (alpha) and the &maximum quantum yield (Phi(max)) increased by more than a factor of 2 from the lowest to the highest DIC level. P-max, alp&ha, and Phi(max) were always higher for the high-calcite than for the low-calcite cells at identical DIC levels. This may &indicate that the calcification process acts as an extra supplier of CO2 for photosynthesis making the CO2 shortage at nat&ural DIC levels a little smaller for high-calcite than for low-calcite E. huxleyi. A dependency of Phi(max) on DIC has not& previously been shown for marine phytoplankton. Phi(max) is a key parameter in recent biooptical models of phytoplankton productivity, and the results from the present study are therefore important for modeling the productivity of E. huxleyi.&765^3^Norton,LR^Firbank,LG^Watkinson,AR^1995^1^Ecotypic differentiation of response to enhanced co2 and temperature levels in arabidopsis-thaliana^2^104^3^394-396^^^^^Nov^^^^^4341\97\WANG.DOC@h@*AALINKSY&A^4340^Five ecotypes of Arabidopsis thaliana, from widely dispersed origins, were grown under combinations of ambient and &elevated atmospheric CO2 concentrations and ambient and elevated temperatures within solardomes. Total above-ground plant &biomass was measured when the majority of plants across all ecotypes and treatments had formed seed pods. There were subst&antial differences in biomass between the ecotypes across all treatments. Temperature had no effect on biomass whilst CO2 &had a significant effect both alone and in interaction with ecotype. The CO2 x ecotype interaction was mostly due to the enhancement of a single ecotype from the Cape Verde Islands.TXTd@NAALINKSYS\PCMCIA766^1^Patterson,DT^1995^1^Weeds in a changing climate^253^43^4^685-700^^^^^Oct-Dec^^^^^4343T32\README.TXT&A^4342^Current and projected increases in the concentrations of CO2 and other radiatively-active gases in the Earth's atmo&sphere lead to concern over possible impacts on agricultural pests, All pests would be affected by the global warming and &consequent changes in precipitation, wind patterns, and frequencies of extreme weather events which may accompany the ''gr&eenhouse effect.'' However, only weeds are likely to respond directly to the increasing CO2 concentration, Higher CO2 will& stimulate photosynthesis and growth in C-3 weeds and reduce stomatal aperture and increase water use efficiency in both C&-3 and C-4 weeds, Respiration, and photosynthate composition, concentration, and translocation may be affected, Perennial &weeds may become more difficult to control, if increased photosynthesis stimulates greater production of rhizomes and othe&r storage organs, Changes in leaf surface characteristics and excess starch accumulation in the leaves of C-3 weeds may in&terfere with herbicidal control, Global warming and other climatic changes will affect the growth, phenology, and geograph&ical distribution of weeds, Aggressive species of tropical and subtropical origins, currently restricted to the southern U&.S., may expand northward. Any direct or indirect consequences of the CO2 increase that differentially affect the growth o&r fitness of weeds and crops will alter weed-crop competitive interactions, sometimes to the detriment of the crop and sometimes to its benefit.@`CO2MAP\BIBLIOGRAPHIES\TRACIE\96\96A1\READM&767^2^Saebo,A^Mortensen,LM^1995^1^Growth and regrowth of phleum-pratense, lolium-perenne, trifolium-repens and trifolium-pratense at normal and elevated co2 concentration^169^55^1^29-35^^^^^Aug^^^^^434596B1\README.DOCv&A^4344^The effect of elevated CO2 concentration (680 +/- 52 mu mol mol(-1)) on growth of three cultivars of Phleum pratens&e, two of Lolium perenne and one of Trifolium repens and Trifolium pratense each, was studied during one growth season inc&luding three harvests. The study was performed in ten 9 m(2) field chamber units in a cool maritime climate under long day&s (15-18 h), on the southwest coast of Norway (59 degrees N, 6 degrees E). Tillering in P. pratense and L. perenne was not& significantly affected in the first harvest (June/July), but was increased by 30% in the third harvest (September) in res&ponse to elevated CO2 concentrations. The plant height was reduced by 16-24% in P. pratense and by 25-29% in L. perenne at& high CO2. The dry weight yield of the two grass species was negatively affected by elevated CO2 in the two first harvests&, however, no effect was found in the last harvest. The total harvestable dry matter was decreased by 18% in P. pratense a&nd 13% in L. perenne. The dry matter of the stubble was increased at elevated CO2, by 18% in P. pratense and 26% in L. per&enne, leaving more of the yield in the meadow after harvest. Raising the CO2 concentration increased the dry weight by 30% in both clover species. The results are discussed in relation to the climatic conditions during the season.XTv&768^1^Sage,RF^1995^1^Was low atmospheric co2 during the pleistocene a limiting factor for the origin of agriculture^127^1^2^93-106^^^^^Apr^^^^^4347GRAPHIES\TRACIE\95\95C1\README.DOCvG `CO&A^4346^Agriculture originated independently in many distinct regions at approximately the same time in human history. This& synchrony in agricultural origins indicates that a global factor may have controlled the timing of the transition from fo&raging to food- producing economies. The global factor may have been a rise in atmospheric CO:! from below 200 to near 270& mu mol mol(-1) which occurred between 15,000 and 12,000 years ago. Atmospheric CO2 directly affects photosynthesis and pl&ant productivity, with the largest proportional responses occurring below the current level of 350 mu mol mol(-1). In the &late Pleistocene, CO2 levels near 200 mu mol mol(-1) may have been too low to support the level of productivity required f&or successful establishment of agriculture. Recent studies demonstrate that atmospheric CO2 increase from 200 to 270 mu mo&l mol(-1) stimulates photosynthesis and biomass productivity of C-3 plants by 25% to 50%, and greatly increases the perfor&mance of C-3 plants relative to weedy C-4 competitors. Rising CO2 also stimulates biological nitrogen fixation and enhance&s the capacity of plants to obtain limiting resources such as water and mineral nutrients. These results indicate that inc&reases in productivity following the late Pleistocene rise in CO2 may have been substantial enough to have affected human &subsistence patterns in ways that promoted the development of agriculture. Increasing CO2 may have simply removed a produc&tivity barrier to successful domestication and cultivation of plants. Through effects on ecosystem productivity rising CO2& may also have been a catalyst for agricultural origins by promoting population growth, sedentism, and novel social relationships that in turn led to domestication and cultivation of preferred plant resources.S\97 BIB\CONVENTI&769^6^Taylor,G^Gardner,SDL^Bosac,C^Flowers,TJ^Crookshanks,M^Dolan,L^1995^1^Effects of elevated co2 on cellular mechanisms, growth and development of trees with particular reference to hybrid poplar^251^68^4^379-390^^^^^^^^^^4349 ZCO2M&A^4348^Growth is often stimulated when C-3 plants, including trees, are exposed to elevated CO2, although evidence from th&e literature suggests that the responsiveness of trees to CO2 varies, depending on species. This paper explores some of th&e cellular mechanisms which underlie increased growth, using both the authors' own data and information from the literatur&e. Mechanisms include photosynthetic fixation of CO2 and the role of Rubisco, the link between carbon fixation and growth,& in particular, how increased carbon is thought to influence the process of plant cell expansion and cell production and f&inally the consequences of cellular effects for the growth and development of whole planes. Data are presented for the gro&wth and development of hybrid poplars in elevated CO2, following both field (open-top chambers) and laboratory experiments& which suggest that this type of tree with indeterminate, rapid growth may be favoured by the CO2 concentrations of the next century.\ODI\README.TXTJXj4AALINKSYS\NDIS2\PCNFS.TXTR&770^2^Vanoosten,JJ^Besford,RT^1995^1^Some relationships between the gas-exchange, biochemistry and molecular-biology of ph&otosynthesis during leaf development of tomato plants after transfer to different carbon-dioxide concentrations^9^18^11^1253-1266^^^^^Nov^^^^^4351ANTASTI.TXTXjpAALINKSYS\MSLANMAN.DOS\DR&A^4350^Tomato plants were exposed to four concentrations of CO2 (350, 700, 1050 or 1400 mu mol CO2 mol(-1)) for 31 d. The &light- saturated rate of photosynthesis (A) of the unshaded fifth leaf was measured at either an ambient CO2 concentration' of 350 mu mol CO2 mol(-1) [A (350)] or at the level of CO2 at which the plants were grown. The chloroplast protein compos'ition and the level of transcripts of nuclear or plastid photosynthesis- associated genes (PAGs), as well as the main carb'ohydrate content of the fifth leaf maintained horizontal and unshaded, were also measured during leaf development. At 60 a'nd 95 % leaf expansion, the A of high CO2-grown plants measured at growth CO2 was higher than the A (350) of the plants gr'own at ambient CO2. However, in the fully mature leaves, A (growth CO2) declined linearly as growth CO2 concentration incr'eased. The A (350) of plants exposed to elevated CO2 up to 60% leaf expanion had not acclimated to high CO2. At 95% leaf e'xpansion, A (350) was lower in plants grown at high CO2. A versus CO2 (C-i) for mature leaves showed that A of the plants 'grown at high CO2 was lower over the entire range than that for plants grown at present ambient CO2 concentration. Lines f'itted to the linear part of the A/C-l curves were concurrent at a C-i of 49 mu mol CO2 mol(-1) and A=-1.21 mu mol CO2 m(-2' )s(-1). This C-i value is close to Gamma* (46 mu mol CO2 mol(-1)), the compensation point at 27 degrees C calculated from ' the equation described in Brooks & Farquhar (1985, Planta 165, 397-406). This A is an estimate of respiration in the light' (R(1)) and was not affected by acclimation to elevated CO2. Thylakoid proteins (photosystem I core protein, D-1 and D-2 o' f the photosystem II core complex, cytochrome f) were all reduced by elevated CO2 only in the fully mature leaves (310 exp' osure), whereas the large and small subunits of Rubisco and Rubisco activase proteins had already declined after 22 d expo'sure. Transcript levels of the plastid-encoded FAG (rbcL, psbA, psaA-B) were reduced in the mature leaves by elevated CO2 'when expressed on a total RNA basis, but they were not sensitive to elevated CO2 when expressed on a chloroplast 16S rRNA 'basis. However, rbcS, rca and cab mRNA transcripts were lower in the plants grown at high CO2 than in control plants after' 22 d exposure when expressed on a nuclear rRNA basis. The loss of these nuclear PAGs was correlated with an accumulation of soluble sugars and starch.O2MAP\BIBLIOGRAPHIES\97 BIB\97B1\README.DOCv'771^4^Walker,RF^Geisinger,DR^Johnson,DW^Ball,JT^1995^1^Enriched atmospheric co2 and soil p effects on growth and ectomycorrhizal colonization of juvenile ponderosa pine^45^78^1-3^207-215^^^^^Oct^^^^^4353.DOCvrk=`CO2M'A^4352^Interactive effects of atmospheric CO2 enrichment and soil P fertility on above- and below-ground development of ju'venile ponderosa pine (Pinus ponderosa Dougl. ex Laws.) were examined. Seedlings were reared from seed in atmospheres with' 700 mu l l(-1), 525 mu l l(-1), or ambient CO2 concentrations, and in a potting mix with 68, 43, or 18 mu g g(-1) soil P,' and all were inoculated with the mycobiont Pisolithus tinctorius (Pers.) Coker and Couch shortly after emergence. At 4-mo'nth intervals over the 1-year duration of the study, three whole seedlings of each combination of CO2 and P treatments wer'e harvested to permit detailed assessment of shoot and root growth and ectomycorrhizal colonization. After 4 months, shoot' volume, root dry weight, and total root length of seedlings grown in 700 mu l(-1) CO2 were greater than those of seedling's grown in the other atmospheres regardless of P treatment, and shoot/root ratios decreased as the CO2 concentration incre'ased within each P treatment as well. After 8 months, the smallest shoot volumes and root weights and lengths within each 'P treatment were those of seedlings grown in ambient CO2. Root weight and total length increased as the CO2 concentration 'increased in high soil P, but the greatest root weights and lengths within the medium and low P treatments were those of s' eedlings reared in the 525 mu l(-1) CO2 atmosphere. Nevertheless, shoot/root ratios decreased with increasing CO2 in both '!high and medium soil P at the second harvest, and the highest shoot/root ratio in low P was that of seedlings grown in amb'"ient CO2. After 1 year, the largest shoot and root volumes within the high and medium P treatments were those of seedlings'# grown in intermediate CO2, while the reverse was true in low P. The effects of CO2 concentration on dry weights, total ro'$ot length, and shoot/root ratio at the final harvest were nonsignificant. As proved true with seedling growth, CO2 effects'% on ectomycorrhizal colonization varied temporally, as mycorrhizal development was not affected by the atmospheric treatme'&nts after 4 months, while seedlings grown in ambient CO2 exhibited the highest percent infections within each P treatment ''at the second harvest but those grown in 700 mu l l(-1) CO2 had the highest percentages after 1 year. These results sugges'(t that elevated CO2 exerts stimulatory effects on shoot and root development of juvenile ponderosa pine which may be dependent on P availability to some degree, but these effects are somewhat transient and vary in magnitude over time.2MAP'*772^2^Wayne,PM^Bazzaz,FA^1995^1^Seedling density modifies the growth-responses of yellow birch maternal families to elevated carbon-dioxide^127^1^5^315-324^^^^^Oct^^^^^4355DME.DOCvN`CO2MAP\BIBLIOGRA',A^4354^We studied seedling growth responses to ambient and elevated CO2 (350 and 700 mu L L(-1)) of three maternal familie'-s of yellow birch (Betula alleghaniensis), raised both individually and in high-density stands. Seedlings in competitive, '.dense stands exhibited markedly lower average CO2-induced growth enhancements than individually grown plants (16% vs. 49%)'/. Maternal families differed in their growth responses to elevated CO2. However, differences among families were contingen'0t upon density; families which exhibited the greatest CO2-induced growth at low density exhibited the least CO2- responsiv'1eness at high density. These data are discussed in two separate contexts; the reliability of estimates of the CO2 fertiliz'2ation potential of forest species based solely on individually grown plants, and the potential evolutionary consequences of rising CO2 on regenerating forest tree populations.O2MAP\CO2MAP DATA\GRASS DATA\WEIGH'4773^3^Wilks,DS^Wolfe,DW^Riha,SJ^1995^1^Simple carbon assimilation response functions from atmospheric co2, and daily temperature and shortwave radiation^127^1^5^337-346^^^^^Oct^^^^^4357DATA\GRASS DATA\WEIGHTED\GRAS'6A^4356^A global 'CO2 fertilizer effect' multiplier is often used in crop or ecosystem models because of its simplicity. Ho'7wever, this approach does not take into account the interaction between CO2, temperature and light on assimilation. This o'8mission can lead to significant under- or overestimation of the magnitude of beneficial effects from elevated CO2, dependi'9ng on environmental conditions. We use a mechanistic model of the biochemistry of photosynthesis to represent the response': of net assimilation to different levels of CO2, temperature and radiation, on the daily time scale. Instantaneous assimil';ation rates for an idealized canopy model are integrated through diurnal cycles of environmental variables derived from hi'e canopy leaf area index, and by daily values of temperature and radiation available from climatic records. These summary '?functions are suitable for incorporation into crop or ecosystem models for predicting carbon assimilation or biomass produ'@ction on a daily time step. An example application of the function reveals that for a relatively cool, high latitude locat'Aion, the beneficial effects from a CO2 doubling would be negligible during the early spring, even assuming a + 4 degrees C'B global warming scenario. In contrast, the beneficial effects from increasing CO2 at a relatively warm, lower latitude loc'Cation are greatest in the spring, but decline in late summer because of excessively warm temperatures with a + 4 degrees C global warming.TRACIE\97\97E1\README.DOCtCO2MAP\CO2MAP DATA'Y774^2^Woodward,FI^Kelly,CK^1995^1^The influence of co2 concentration on stomatal density^84^131^3^311-327^^^^^Nov^^^^^4359'FA^4358^A survey of 100 species and 122 observations has shown an average reduction in stomatal density of 14.3% (SE+/-2.2%'G) with CO2 enrichment, with 74% of the cases exhibiting a reduction in stomatal density. A sign test demonstrated that sto'Hmatal density decreases, in response to CO2, significantly more often than expected by chance. Repeated observations on th'Ie same species indicated a significant repeatability in the direction of the stomatal response. Analyses which removed the'J potential effect of taxonomy on this data set showed no significant patterns in the dependency of the degree of stomatal 'Kchange on growth form (woodiness vs. non-woodiness; trees vs. shrubs), habitat (cool vs. warm) or stomatal distribution on'L the leaf (amphi- vs. hypostomatous). Forty-three of the observations had been made in controlled environments and under a'M typical range in CO2 enrichment of 350-700 mu mol mol(-1). For these cases the average stomatal density declined by 9% (S'NE+/-3.3%) and 60% of the cases showed reductions in stomatal density. When analyses were restricted to these 43 observatio'Ons, amphistomatous samples more frequently had greater changes in stomatal density than did hypostomatous samples. The deg'Pree of reduction in stomatal density with increasing CO2 increases with initial stomatal density, after the influence of t'Qaxonomy is removed using analyses of independent contrasts. When the data were examined for patterns that might be due exp'Rlicitly to the effects of relatedness, the subclasses of the Hamamelidae and the Rosidae showed highly significant reducti'Sons in stomatal density with CO2 (87% of the species studied in the Hamamelidae and 80% of the species in the Rosidae show'Ted reduction with CO2 enrichment) and correlations between initial stomatal density and degree of reduction in stomatal de'Unsity. The species sampled in the Hamamelidae were dominantly trees, whereas herbs dominated the species in the Rosidae. T'Vhere were insufficient species studied at lower taxonomic levels to warrant further statistical analyses. This problem res'Wults from experimental and observational data being most often restricted to one species per taxonomic level, typically up'X to the level of order, a feature which can severely limit the extraction of taxonomically-related and ecologically-related plant responses.ta-Analysis ProjectPCO2MAP\CO2MAP DATA\ANTOINETTUW2.XLS4CO2 Meta-Analysis Project|CO2MAP\CO2MAP DATA\'[775^2^Ackerly,DD^Bazzaz,FA^1995^1^Plant-growth and reproduction along co2 gradients - nonlinear responses and implications for community change^127^1^3^199-207^^^^^Jun^^^^^4361GRASS DATA\WEIGHTED\GRASS WEIGHTE']A^4360^The effects of rising atmospheric CO2 concentrations on natural plant communities will depend upon the cumulative r'^esponses of plant growth and reproduction to gradual, incremental changes in climatic conditions. We analysed published st'_udies of plant responses to elevated CO2 to address whether reproductive and total biomass exhibit similar enhancement to '`elevated vs. ambient CO2 concentrations, and to assess the patterns of plant response along gradients of CO2 concentration'as. In six annual plant species, mean enhancement at double ambient vs. ambient CO2 was 1.13 for total biomass and 1.30 for'b reproductive biomass. The two measures were significantly correlated, but there was considerable scatter in the relations'chip, indicating that reproductive responses cannot be consistently predicted from enhancement of total biomass. Along expe'drimental CO2 gradients utilizing three concentrations, there was a great diversity of response patterns, including positiv'ee, negative, non-monotonic and non-significant (nat) responses. The distribution of response patterns differed for plants 'fgrown in stands compared to those grown individually. Positive responses were less frequent in competitive environments, a'gnd non- monotonic responses were more frequent. These results emphasize that interpolation of plant response based on enha'hncement ratios measured at elevated vs. ambient CO2 concentrations is not sufficient to predict community responses to inc'iremental changes in atmospheric conditions. The consequences of differential response patterns were assessed in a simulati'jon of community dynamics for four species of annual plants. The model illustrates that the final community composition at a future point in time depends critically on both the magnitude and the rate of increase of atmospheric CO2.ances 'l776^1^Amthor,JS^1995^1^Terrestrial higher-plant response to increasing atmospheric [co2] in relation to the global carbon-cycle^127^1^4^243-274^^^^^Aug^^^^^4363ata from papers prior to 1998, which repo'nA^4362^Terrestrial higher plants exchange large amounts of CO2 with the atmosphere each year; c. 15% of the atmospheric po'ool of C is assimilated in terrestrial-plant photosynthesis each year, with an about equal amount returned to the atmospher'pe as CO2 in plant respiration and the decomposition of soil organic matter and plant litter. Any global change in plant C 'qmetabolism can potentially affect atmospheric CO2 content during the course of years to decades. In particular, plant resp'ronses to the presently increasing atmospheric CO2 concentration might influence the rate of atmospheric CO2 increase throu'sgh various biotic feedbacks. Climatic changes caused by increasing atmospheric CO2 concentration may modulate plant and ec'tosystem responses to CO2 concentration. Climatic changes and increases in pollution associated with increasing atmospheric'u CO2 concentration may be as significant to plant and ecosystem C balance as CO2 concentration itself. Moreover, human act'vivities such as deforestation and livestock grazing can have impacts on the C balance and structure of individual terrestr'wial ecosystems that far outweigh effects of increasing CO2 concentration and climatic change. In short-term experiments, w'xhich in this case means on the order of 10 years or less, elevated atmospheric CO2 concentration affects terrestrial highe'yr plants in several ways. Elevated CO2 can stimulate photosynthesis, but plants may acclimate and (or) adapt to a change i'zn atmospheric CO2 concentration. Acclimation and adaptation of photosynthesis to increasing CO2 concentration is unlikely '{to be complete, however. Plant water-use efficiency is positively related to CO2 concentration, implying the potential for'| more plant growth per unit of precipitation or soil moisture with increasing atmospheric CO2 concentration. Plant respira'}tion may be inhibited by elevated CO2 concentration, and although a naive C balance perspective would count this as a bene'~fit to a plant, because respiration is essential for plant growth and health, an inhibition of respiration can be detrimen'tal. The net effect on terrestrial plants of elevated atmospheric CO2 concentration is generally an increase in growth and' C accumulation in phytomass. Published estimations, and speculations about, the magnitude of global terrestrial- plant gr'owth responses to increasing atmospheric CO2 concentration range from negligible to fantastic. Well-reasoned analyses poin't to moderate global plant responses to CO2 concentration. Transfer of C from plants to soils is likely to increase with e'levated CO2 concentrations because of greater plant growth, but quantitative effects of those increased inputs to soils on' soil C pool sizes are unknown. Whether increases in leaf-level photosynthesis and short-term plant growth stimulations ca'used by elevated atmospheric CO2 concentration will have, by themselves, significant long-term (tens to hundreds of years)' effects on ecosystem C storage and atmospheric CO2 concentration is a matter for speculation, not firm conclusion. Longte'rm field studies of plant responses to elevated atmospheric CO2 are needed. These will be expensive, difficult, and by def'inition, results will not be forthcoming for at least decades. Analyses of plants and ecosystems surrounding natural geolo'gical CO2 degassing vents may provide the best surrogates for long-term controlled experiments, and therefore the most rel'evant information pertaining to long-term terrestrial-plant responses to elevated CO2 concentration, but pollutants associ'ated with the vents are a concern in some cases, and quantitative knowledge of the history of atmospheric CO2 concentratio'ns near vents is limited. On the whole, terrestrial higher-plant responses to increasing atmospheric CO2 concentration pro'bably act as negative feedbacks on atmospheric CO2 concentration increases, but they cannot by themselves stop the fossil-'fuel-oxidation-driven increase in atmospheric CO2 concentration. And, in the very long-term, atmospheric CO2 concentration' is controlled by atmosphere-ocean C equilibrium rather than by terrestrial plant and ecosystem responses to atmospheric CO2 concentration. CO2MAP\CO2MAP DATA\GRASS PHYLOGENY\MA RESULTS\SU'777^2^Arnone,JA^Korner,C^1995^1^Soil and biomass carbon pools in model communities of tropical plants under elevated co2^2^104^1^61-71^^^^^Sep^^^^^4365A\UNWEIGHTED\GRASS UNWEIGHTED CONDITIONS.DOC'A^4364^The experimental data presented here relate to the question of whether terrestrial ecosystems will sequester more C' in their soils, litter and biomass as atmospheric CO2 concentrations rise. Similar to our previous study with relatively 'fertile growth conditions (Korner and Arnone 1992), we constructed four rather nutrient-limited model communities of moist' tropical plant species in greenhouses (approximately 7 m(2) each). Plant communities were composed of seven species (77 i'ndividuals per community) representing major taxonomic groups and various life forms found in the moist tropics. Two ecosy'stems were exposed to 340 mu l CO2 l(-1) and two to 610 mu l l(-1) for 530 days of humid tropical growth conditions. In or'der to permit precise determination of C deposition in the soil, plant communities were initially established in C-free un'washed quartz sand. Soils were then amended with known amounts of organic matter (containing C and nutrients). Mineral nut'rients were also supplied over the course of the experiment as timed-release full-balance fertilizer pellets. Soils repres'ented by far the largest repositories for fixed C in all ecosystems. Almost 5 times more C (ca. 80% of net C fixation) was' sequestered in the soil than in the biomass, but this did not differ between CO2 treatments. In addition, at the whole-ec'osystem level we found a remarkably small and statistically non-significant increase in C sequestration (+4%; the sum of C' accretion in the soil, biomass, litter and necromass). Total community biomass more than quadrupled during the experiment', but at harvest was, on average, only 8% greater (i.e. 6% per year; n.s.) under elevated CO2, mainly due to increased roo't biomass (+15%, P = 0.12). Time courses of leaf area index of all ecosystems suggested that canopy expansion was approach'ing steady state by the time systems were harvested. Net primary productivity (NPP) of all ecosystems - i.e. annual accumu'lation of biomass, necromass, and leaf litter (but not plant-derived soil organic matter) - averaged 815 and 910 g m(-2) y'ear(-1) at ambient and elevated CO2, respectively. These NPPs are remarkably similar to those of many natural moist tropic'al forested ecosystems. At the same time net productivity of soil organic matter reached 7000 g dry matter equivalent per 'm(2) and year (i.e. 3500 g C m(-2) year(-1)). Very slight yet statistically significant CO2- induced shifts in the abundan'ce of groups of species occurred by the end of the experiment, with one group of species (Elettaria cardamomum, Ficus benj'amina, F: pumila, Epipremnum pinnatum) gaining slightly, and another group (Ctenanthe lubbersiana, Heliconia humilis, Cecr'opia peltata) losing. Our results show that: (1) enormous amounts of C can be deposited in the ground which are normally n'ot accounted for in estimates of NPP and net ecosystem productivity; (2) any enhancement of C sequestration under elevated' atmospheric CO2 may be substantially smaller than is believed will occur (yet still very important), especially under gro'wth conditions which permit close to natural NPP; and (3) species dominance in plant communities is likely to change under elevated CO2, but that changes may occur rather slowly.l Hunt Jones CO2MAP\CO2MAP DA'778^5^Arnone,JA^Zaller,JG^Ziegler,C^Zandt,H^Korner,C^1995^1^Leaf quality and insect herbivory in model tropical plant- communities after long-term exposure to elevated atmospheric co2^2^104^1^72-78^^^^^Sep^^^^^4367GENY\MA RESULT'A^4366^Results from laboratory feeding experiments have shown that elevated atmospheric carbon dioxide can affect interact'ions between plants and insect herbivores, primarily through changes in leaf nutritional quality occurring at elevated CO2'. Very few data are available on insect herbivory in plant communities where insects can choose among species and position's in the canopy in which to feed. Our objectives were to determine the extent to which CO2-induced changes in plant commun'ities and leaf nutritional quality may affect herbivory at the level of the entire canopy. We introduced equivalent popula'tions of fourth instar Spodoptera eridania, a lepidopteran generalist, to complex model ecosystems containing seven specie's of moist tropical plants maintained under low mineral nutrient supply. Larvae were allowed to feed freely for 14 days, b'y which time they had reached the seventh instar. Prior to larval introductions, plant communities had been continuously e'xposed to either 340 mu l CO2 l(-1) or to 610 mu l CO2 l(-1) for 1.5 years. No major shifts in leaf nutritional quality [c'oncentrations of N, total non-structural carbohydrates (TNC), sugar, and starch; ratios of: C/N, TNC/N, sugar/N, starch/N;' leaf toughness] were observed between CO2 treatments for any of the species. Furthermore, no correlations were observed b'etween these measures of leaf quality and leaf biomass consumption. Total leaf area and biomass of all plant communities w'ere similar when caterpillars were introduced. However, leaf biomass of some species was slightly greater - and for other 'species slightly less (e.g. Cecropia peltata) - in communities exposed to elevated CO2. Larvae showed the strongest prefer'ence for C. peltata leaves, the plant species that was least abundant in all communities, and fed relatively littie on pla'nts species which were more abundant. Thus, our results indicate that leaf tissue quality, as described by these parameter's, is not necessarily affected by elevated CO2 under relatively low nutrient conditions. Hence, the potential importance o'f CO2-induced shifts in leaf nutritional quality, as determinants of herbivory, may be overestimated for many plant commun'ities growing on nutrient-poor sites if estimates are based on traditional laboratory feeding studies. Finally, slight shi'fts in the abundance of leaf tissue of various species occurring under elevated CO2 will probably not significantly affect' herbivory by generalist insects. However, generalist insect herbivores appear to become more dependent on less-preferred 'plant species in cases where elevated CO2 results in reduced availability of leaves of a favoured plant species, and this greater dependency may eventually affect insect populations adversely.NDITIONS.DOCtGRASS_WT'779^2^Baldocchi,DD^Harley,PC^1995^1^Scaling carbon-dioxide and water-vapor exchange from leaf to canopy in a deciduous forest .2. Model testing and application^9^18^10^1157-1173^^^^^Oct^^^^^4369\GRASS WEIGHTED.XLS"'A^4368^The scaling of CO2 and water vapour transfer from leaf to canopy dimensions was achieved by integrating mechanistic' models for physiological (photosynthesis, stomatal conductance and soil/root and bole respiration) and micrometeorologica'l (radiative transfer, turbulent transfer and surface energy exchanges) processes, The main objectives of this paper are t'o describe a canopy photosynthesis and evaporation model for a temperate broadleaf forest and to test it against field mea'surements, The other goal of this paper is to use the validated model to address some contemporary ecological and physiolo'gical questions concerning the transfer of carbon and water between forest canopies and the atmosphere, In particular, we 'examine the role of simple versus complex radiative transfer models and the effect of environmental (solar radiation and CO2) and ecophysiological (photosynthetic capacity) variables on canopy-scale carbon and water vapour fluxes. M'780^3^Barnes,JD^Ollerenshaw,JH^Whitfield,CP^1995^1^Effects of elevated co2 and/or o-3 on growth, development and physiology of wheat (triticum-aestivum L)^127^1^2^129-142^^^^^Apr^^^^^4371 Microsoft Excel `CO2MAP\'A^4370^Two cultivars of spring wheat (Triticum aestivum L. cvs. Alexandria and Hanno) and three cultivars of winter wheat '(cvs. Riband, Mercia and Haven) were grown at two concentrations of CO2 [ambient (355 mu mol mol(-1)) and elevated (708 mu' mol mol(-1))] under two O-3 regimes [clean air (< 5 nmol mol(-1) O- 3) and polluted air (15 nmol mol(-1) O-3 at night ris'ing to a midday maximum of 75 nmol mol(-1))] in a phytotron at the University of Newcastle-upon-Tyne. Between the two-leaf' stage and anthesis, measurements of leaf gas-exchange, non-structural carbohydrate content, visible O-3 damage, growth, d'ry matter partitioning, yield components and root development were made in order to examine responses to elevated CO2 and/'or O-3. Growth at elevated CO2 resulted in a sustained increase in the rate of CO2 assimilation, but after roughly 6 weeks'' exposure there was evidence of a slight decline in the photosynthetic rate (c.-15%) measured under growth conditions whi'ch was most pronounced in the winter cultivars. Enhanced rates of CO2 assimilation were accompanied by a decrease in stoma'tal conductance which improved the instantaneous water use efficiency of individual leaves. CO2 enrichment stimulated shoo't and root growth to an equivalent extent, and increased tillering and yield components, however, non-structural carbohydr'ates still accumulated in source leaves. In contrast, long-term exposure to O-3 resulted in a decreased CO2 assimilation r'ate (c.-13%), partial stomatal closure, and the accumulation of fructan and starch in leaves in the light. These effects w'ere manifested in decreased rates of shoot and root growth, with root growth more severely affected than shoot growth. In 'the combined treatment growth of O-3-treated plants was enhanced by elevated CO2, but there was little evidence that CO2 e'nrichment afforded additional protection against O-3 damage. The reduction in growth induced by O-3 at elevated CO2 was si'milar to that induced by O-3 at ambient CO2 despite additive effects of the individual gases on stomatal conductance that 'would be expected to reduce the O-3 flux by 20%, and also CO2-induced increases in the provision of substrates for detoxif'ication and repair processes. These observations suggest that CO2 enrichment may render plants more susceptible to O-3 damage at the cellular level. Possible mechanisms are discussed.P\CO2MAP DATA\GRASS PHYLOGENY\'781^2^Beerling,DJ^Quick,WP^1995^1^A new technique for estimating rates of carboxylation and electron-transport in leaves of C-3 plants for use in dynamic global vegetation models^127^1^4^289-294^^^^^Aug^^^^^4373&Microsoft W'A^4372^The possible responses of the terrestrial biosphere to future CO2 increases and associated climatic change are bein'g investigated using dynamic global vegetation models (DGVMs) which include the Farquhar ef al. (1980) biochemical model o'f leaf assimilation as the primary means of carbon capture. This model requires representative values of the maximum rates' of Rubisco activity, V-max, and electron transport, J(max), for different vegetation types when applied at the global sca'le. Here, we describe an approach for calculating these values based on measurements of the maximum rate of leaf photosynt'hesis (A(max)) and C-13 discrimination. The approach is tested and validated by comparison with measurements of Rubisco ac'tivity assayed directly on wild-type and transgenic Nicotiana tabacum (tobacco) plants with altered Rubisco activity grown' under ambient and elevated CO2 mole fractions with high and low N-supply. V-max and J(max) values are reported for 18 dif'ferent vegetation types with global coverage. Both variables were linearly related reinforcing the idea of optimal allocat'ion of resources to photosynthesis (light harvesting vs. Rubisco) at the global scale. The reported figures should be of value to the further development of vegetation and ecosystem models employing mechanistic DGVMs.BLIOGRAPHIES\'782^3^Ceulemans,R^Vanpraet,L^Jiang,XN^1995^1^Effects of co2 enrichment, leaf position and clone on stomatal index and epidermal-cell density in poplar (populus)^84^131^1^99-107^^^^^Sep^^^^^4375CO2MAP\COMMUNICATIONS\BUS'A^4374^The effects of CO2 enrichment and leaf position on stomatal characteristics (stomatal density, stomatal index and s'tomatal pore length) and epidermal cell density were examined for two different Populus clones, Beaupre and Robusta, grown' from cuttings in open-top chambers under ambient and elevated atmospheric CO2 conditions. Both clones had amphistomatous 'leaves, and stomatal density was significantly larger on the abaxial leaf surface than on the adaxial. Significant interac'tions between CO2 enrichment, leaf position and clone were observed for most stomatal and epidermal characteristics. A sig'nificant reduction of the number of stomata mm(-2) under elevated CO2 was observed in expanding leaves near the upper port'ion of the plant for both leaf surface sides and in both clones. For the abaxial leaf side only, this reduction under elev'ated CO2 was accompanied by a similar reduction of the stomatal index in both clones. In mature leaves on the middle and l'ower portion of the plants, there was no significant effect of the CO2 treatment on stomatal density. In young, expanding 'leaves near the upper part of the plant there were significant interactions between the CO2 treatment and leaf surface sid(e for epidermal cell density. The latter increased under elevated CO2 at the abaxial leaf surface, but decreased at the ad%axial surface on the upper part of the plant. Total epidermal cell numbers of mature, fully expanded leaves increased unde(A^4376^Short-term effects of elevated CO2 during the early life phase of plants may have long lasting consequences for gro(wth and biomass in later periods. We exposed hydroponically grown wheat seedlings to 5 d pulses of elevated CO2 while leaf( expansion growth as well as shoot and root gas exchange were measured simultaneously and continuously. Shoot photosynthes(is, night- time shoot respiration and below-ground respiration (largely by roots) roughly doubled when atmospheric CO2 con(centration was doubled. An interruption of CO2 enrichment caused CO2 assimilation and respiration to return to control lev(els, However, while the response of photosynthesis was immediate, that of respiration showed a hysteresis of about 3 d. Si(nce shoot biomass increased at elevated CO2 (with no change in allocation pattern) equal fluxes per shoot or root system a( fter a return to control CO2 concentrations indicate substantial downward adjustment of the capacity for CO2 fixation and ( release in high-CO2 grown plants. Leaf expansion growth was completely unaffected by CO2 enrichment, whereas tiller initia( tion was significantly increased (doubled in 18 d). We conclude that leaf growth in these wheat plants was already carbon-( saturated at ambient CO2 concentration at optimum mineral nutrient supply. The stimulation of growth of whole plants was exclusively due to enhanced tillering during this very early part of the life of these wheat plants.AU KORNER, C TI TOWARD(784^5^Ellsworth,DS^Oren,R^Huang,C^Phillips,N^Hendrey,GR^1995^1^Leaf and canopy responses to elevated co2 in a pine forest under free-air co2 enrichment^2^104^2^139-146^^^^^Oct^^^^^4379WITZERLAND. DE ACCLIMATION; BIOMASS; CARBON DIOXIDE; ECOSYS(A^4378^Physiological responses to elevated CO2 at the leaf and canopy- level were studied in an intact pine (Pinus taeda) (forest ecosystem exposed to elevated CO2 using a free-air CO2 enrichment (FACE) technique. Normalized canopy water-use of (trees exposed to elevated CO2 over an 8-day exposure period was similar to that of trees exposed to current ambient CO2 un(der sunny conditions. During a portion of the exposure period when sky conditions were cloudy, CO2-exposed trees showed mi(nor (less than or equal to 7%) but significant reductions in relative sap flux density compared to trees under ambient CO2( conditions. Short-term (minutes) direct stomatal responses to elevated CO2 were also relatively weak (approximate to 5% r(eduction in stomatal aperture in response to high CO2 concentrations). We observed no evidence of adjustment in stomatal c(onductance in foliage grown under elevated CO2 for nearly 80 days compared to foliage grown under current ambient CO2 so i(ntrinsic leaf water-use efficiency at elevated CO2 was enhanced primarily by direct responses of photosynthesis to CO2. We( did not detect statistical differences in parameters from photosynthetic responses to intercellular CO2 (A(net)-C-i curve(s) for Pinus taeda foliage grown under elevated CO2 (550 mu mol mol(-1)) for 50-80 days compared to those for foliage grow(n under current ambient CO2 from similar-sized reference trees nearby. In both cases, leaf net photosynthetic rate at 550 (mu mol mol(-1) CO2 was enhanced by approximately 65% compared to the rate at ambient CO2 (350 mu mol mol(-1)). A similar l(evel of enhancement under elevated CO2 was observed for daily photosynthesis under field conditions on a sunny day. While (enhancement of photosynthesis by elevated CO2 during the study period appears to be primarily attributable to direct photosynthetic responses to CO2 in the pine forest, longer-term CO2 responses and feedbacks remain to be evaluated.9) In predi( 785^3^Field,CB^Jackson,RB^Mooney,HA^1995^1^Stomatal responses to increased co2 - implications from the plant to the global-scale^9^18^10^1214-1225^^^^^Oct^^^^^4381gh these responses may overrule many of the other effects of atmospheric change,("A^4380^Increased atmospheric CO2 Often but not always leads to large decreases in leaf conductance, Decreased leaf conduct(#ance has important implications for a number of components of CO2 responses, from the plant to the global scale, All of th($e factors that are sensitive to a change in soil moisture, either amount or timing, may be affected by increased CO2. The (%list of potentially sensitive processes includes soil evaporation, run- off, decomposition, and physiological adjustments (&of plants, as well as factors such as canopy development and the composition of the plant and microbial communities, Exper('imental evidence concerning ecosystem-scale consequences of the effects of CO2 on water use is only beginning to accumulat((e, but the initial indication is that, in water-limited areas, the effects of CO2- induced changes in leaf conductance are() comparable in importance to those of CO2-induced changes in photosynthesis, Above the leaf scale, a number of processes i(*nteract to modulate the response of canopy or regional evapotranspiration to increased CO2. While some components of these(+ processes tend to amplify the sensitivity of evapotranspiration to altered leaf conductance, the most likely overall patt(,ern is one in which the responses of canopy and regional evapotranspiration are substantially smaller than the responses o(-f canopy conductance, The effects of increased CO2 on canopy evapotranspiration are likely to be smallest in aerodynamical(.ly smooth canopies with high leaf conductances, Under these circumstances, which are largely restricted to agriculture, de(/creases in evapotranspiration may be only one-fourth as large as decreases in canopy conductance, Decreased canopy conduct(0ances over large regions may lead to altered climate, including increased temperature and decreased precipitation, The sim(1ulation experiments to date predict small effects globally, but these could be important regionally, especially in combination with radiative (greenhouse) effects of increased CO2. intensified turnover of carbon dioxide. There is consequently (3786^7^Friedlingstein,P^Fung,I^Holland,E^John,J^Brasseur,G^Erickson,D^Schimel,D^1995^1^On the contribution of co2 fertilization to the missing biospheric sink^137^9^4^541-556^^^^^Dec^^^^^4383ir. A main source of emissions of methane and ammonia(5A^4382^A gridded biospheric carbon model is used to investigate the impact of the atmospheric CO2 increase on terrestrial (6carbon storage. The analysis shows that the calculated CO2 fertilization sink is dependent not just on the mathematical fo(7rmulation of the ''beta factor'' but also on the relative controls of net primary productivity (NPP), carbon residence tim(8es, and resource availability. The modeled evolution of the biosphere for the period 1850-1990 shows an increasing lag bet(9ween NPP and the heterotrophic respiration. The time evolution of the modeled biospheric sink (i.e., difference between en(:hanced NPP and enhanced respiration) does not match that obtained by deconvolution of the ice core CO2 time series. Agreem(;ent between the two is reasonable for the first half of the period, but during the recent decades the deconvoluted CO2 inc(90 integrated missing sink is due to the CO2 greening of the biosphere. The remainder may be due to the increased level of nitrogen deposition starting around 1950.ng to reduce the high emissions of methane and ammonia from this sector of agri(@787^3^Gardner,SDL^Taylor,G^Bosac,C^1995^1^Leaf growth of hybrid poplar following exposure to elevated co2^84^131^1^81-90^^^^^Sep^^^^^4385ciency of it is lowered by a factor of 1:10. In spite of a growing crisis to maintain the alimentation of (BA^4384^Leaf extension was stimulated following exposure of three interamerican hybrid poplar clones (Populus trichocarpa x(C P. deltoides); 'Unal', 'Boelare', and 'Beaupre' and a euramerican clone 'Primo' (Populus nigra x P. deltoides) to elevate(Dd CO2 in controlled environment chambers. For all three interamerican clones the evidence suggests that this was the resul(Et of increased leaf cell expansion associated with enhanced cell wall extensibility (WEx), measured as tensiometric increa(Fses in cell wall plasticity. For the interamerican clone 'Boelare', there was also a significant increase in cell wall ela(Gsticity following exposure to elevated CO2 (P less than or equal to 0.001). The effect of elevated CO2 in stimulating cell(H wall extensibility was confirmed in a detailed spatial analysis of extensibility made across the lamina of expanding leav(Ies of the clone 'Boelare'. For two of the interamerican hybrids, 'Unal' and 'Beaupre', both leaf cell water potential (psi(J) and turgor pressure (P) were lower in elevated than in ambient CO2 By contrast, no significant effects on the cell wall (Kproperties or leaf water relations for the euramerican hybrid 'Primo' were observed following exposure to elevated CO2, su(Lggesting that the mechanism for increased leaf extension in elevated CO2 differed, depending on clone. The cumulative tota(Ml length of leaves of 'Boelare' grown in elevated CO2 was significantly increased (P less than or equal to 0.05) and since(N leaf number was not significantly increased in any inter-american clone it is hypothesized that final leaf size was stimu(Olated in elevated CO2 for these clones. By contrast, there was no significant effect of CO2 on cumulative total leaf lengt(Ph for the euramerican clone 'Primo', but leaf number was significantly increased by elevated CO2. The measurements suggest(Q that total tree leaf area was stimulated for a range of poplar hybrids exposed to elevated CO2. Given the short rotation (Rof a coppiced crop, it is likely that increased leaf areas will result in enhanced stemwood production when hybrid poplars are grown in the CO2 concentrations predicted for the next century. content was generally higher with 1% CO2 enrichment (T788^3^Greer,DH^Laing,WA^Campbell,BD^1995^1^Photosynthetic responses of 13 pasture species to elevated co2 and temperature^92^22^5^713-722^^^^^^^^^^4387ease in autofluorescence of chloroplasts, but not the size, was observed with decreasing suc(VA^4386^Thirteen common pasture species, (eleven C-3 and two C-4), were grown in controlled environments at 12/7, 18/13 and(W 28/23 degrees C and at 350 and 700 ppm CO2 to evaluate the effects of elevated CO2 on their photosynthetic responses. Pho(Xtosynthesis was measured at the growth temperatures and at both 350 and 700 ppm CO2. In C-3 species, short-term (within mi(Ynutes) increases in CO2 had the greatest effect on photosynthesis, with an average of 50-60% higher rates in plants expose(Zd to 700 ppm CO2 at each temperature. However, there was a continuum of response between the C-3 species whereas C-4 speci([es were unaffected by short-term changes in CO2 There was also a long-term (4-8 weeks) response to high CO2, with an avera(\ge of about 40-50% higher rates of photosynthesis, with some response by C-4 species. Both short- and long-term responses (]were negatively correlated with the photosynthetic rate of each species at 350 ppm CO2 and all species were less efficient(^ at converting photosynthate to dry matter at elevated CO2. These data show clearly that photosynthesis of these cool temp(_erate pasture species can respond to elevated CO2, especially at low temperatures. This will have consequences for predicting the potential effects of climate change, accompanied by rising CO2, on pasture ecosystems. water regimes [leaf water (a789^4^Hutchin,PR^Press,MC^Lee,JA^Ashenden,TW^1995^1^Elevated concentrations of co2 may double methane emissions from mires^127^1^2^125-128^^^^^Apr^^^^^4389tion induced a 60 % average increase in net photosynthetic rate (P-N) under well-watered(cA^4388^The potential impact of an increase in methane emissions from natural wetlands on climate change models could be ve(dry large. We report a profound increase in methane emissions from cores of mire peat and vegetation as a direct result of (eincreasing the CO2 concentration from 355 to 550 mu mol mol(-1) (a 60% increase). Increased CH4 fluxes were observed throu(fghout the four month period of study. Seasonal variation in CH4 flux, consistent with that seen in the field, was observed(g under both ambient and elevated CO2. Under ambient CO2 methane fluxes rose from 0.02 mu mol m(-2) s(-1) in May to 0.11 mu(h mol m(-2) s(-3) in July before declining again in August. Under elevated CO2, methane fluxes were at least 100% greater t(ihroughout the experiment, rising from 0.05 mu mol m(-2) s(-1) in May to a peak of 0.27 mu mol m(-2) s(-1) in July. The sti(jmulation of CH4 emissions was accompanied by a 100% increase in rates of photosynthesis from 4.6 (+/- 0.3) under ambient CO2 to 9.3 (+/- 0.7) mu mol m(-2) s(-1). Root and shoot biomass were unaffected.AMERICAN SOCIETY FOR HORTICULTURAL SCIENCE(l790^4^Jones,MB^Brown,JC^Raschi,A^Miglietta,F^1995^1^The effects on arbutus-unedo L of long-term exposure to elevated co2^127^1^4^295-302^^^^^Aug^^^^^43915040. DE LEMON; HEAT STRESS ID PLANT-ROOT SYSTEMS; CO2 CONCENTRATIONS; ARCHITECTURAL ANALY(nA^4390^Arbutus unedo is a sclerophyllous evergreen, characteristic of Mediterranean coastal scrub vegetation. In Italy, tr(oees of A. unedo have been found close to natural CO2 vents where the mean atmospheric carbon dioxide concentration is abou(pt 2200 mu mol mol(-1). Comparisons were made between trees growing in elevated and ambient CO2 concentrations to test for (qevidence of adaptation to long-term exposure to elevated CO2. Leaves formed at elevated CO2 have a lower stomatal density (rand stomatal index and higher specific leaf area than those formed at ambient CO2, but there was no change in carbon to ni(strogen ratios of the leaf tissue. Stomatal conductance was lower at elevated CO2 during rapid growth in the spring. In mid(t-summer, under drought stress, stomatal closure of all leaves occurred and in the autumn, when stress was relieved, the co(unductance of leaves at both elevated and ambient CO2 increased. In the spring, the stomatal conductance of the new flush o(vf leaves at ambient CO2 was higher than the leaves at elevated CO2, increasing instantaneous water use efficiency at eleva(wted CO2. Chlorophyll fluorescence measurements suggested that elevated CO2 provided some protection against photoinhibitio(xn in mid- summer. Analysis of A/C-i curves showed that there was no evidence of either upward or downward regulation of ph(yotosynthesis at elevated CO2. It is therefore anticipated that A. unedo will have higher growth rates as the ambient CO2 concentrations increase.ts and the length of second-degree adventitious lateral branches were increased >50% by high tempe({791^1^Korner,C^1995^1^Towards a better experimental basis for upscaling plant- responses to elevated co2 and climate warming^9^18^10^1101-1110^^^^^Oct^^^^^4393VL 120 IS 6 GA TC365 RP MARTIN CA J9 J AMER SOC HORT SCI ER PT J AU MCKEE, IF FARAG(}A^4392^Few of the most common assumptions used in models of responses of plants and ecosystems to elevated CO2 and climate(~ warming have been tested under realistic life conditions, It is shown that some unexpected discrepancies between predicti(ons and experimental findings exist, suggesting that a better empirical basis is required for predictions, The following t(en suggestions may improve our potential to scale up from experimental scales to the real world, (1) Experiments should be( timed to account for non-linearity in system responsiveness, asynchrony of responses and developmental differences, (2) B(y altering mineral nutrient supply, a wide range of CO2 responses can be 'produced', thus requiring realistic soil conditi(ons, (3) Distinctions should be made between 'doubling CO2 supply' and biologically effective degrees of CO2 enrichment. ((4) Because of the non-linearity of plant responses to CO2, studies of at least three instead of two CO2 concentrations are( necessary to describe future trends adequately, (5) Edge effects, in particular unscreened side light, may lead to allome(tric anomalies, strongly constraining up-scaling to stand-scale CO2 responses, (6) Variables such as growth, yield, net pr(imary production and C turnover are often confused with carbon pools, carbon sequestration or net ecosystem production, (7() Mono- and interspecific interactions between individuals may lead to completely unpredictable CO2 responses, (8) Experim(ents with seedlings benefit from the absence of prehistory effects but are likely to be irrelevant for the responses of la(rger trees which, on the other hand, may be constrained by carryover effects, Tree ring research indicates immediate sensi(tivity of large trees to environmental changes, supporting their usefulness in short-term CO2-enrichment experiments, (9) (In predicting temperature responses, acclimation deserves more attention, (10) The significance of developmental responses( is largely under-represented in experimental research, although these responses may overrule many of the other effects of( atmospheric change, Results of more realistic experiments which account for these problems will provide a better basis for modelling the future of the biosphere. WASHINGTON, DC 20546. UNIV ALASKA FAIRBANKS, ALASKA COOPERAT FISH & WILDLIFE RES(792^2^Krapfenbauer,A^Wriessnig,K^1995^1^Anthropogenic environmental-pollution - the share of agriculture^254^46^3^269-283^^^^^Aug^^^^^4395A, CTR REMOTE SENSING & ENVIRONM OPT, SANTA BARBARA, CA 93106. STANFORD UNIV, DEPT BIOL SCI, STANFORD, CA(A^4394^The increase of environmental pollution is in direct relation to the consumption of fossil coal, gas and oil and th(e progressive growth of the world population. Since 1950 these issues increased considerably and they will continue to inc(rease in the future. At the moment the population increases by 1.9 %, the consumption of energy between 2 and 3 % and the (environmental pollution up to 3.5 % annually. With the progressive growth of the world population and the increase in pros(perity in the developed countries the demand for food increased also progressively and therewith the productivity index of( the units of arable land, by growing consumption of fertilizers and the installation of irrigation systems. At the same t(ime the pollution of air, water and soil caused by agriculture also grew progressively. But up to date there is still a sh(ortcoming of reliable statistical facts and figures. A higher productivity index of the units of arable land in the differ(ent ecoclimatic zones of the earth leads to higher production and consumption by an inevitably higher turnover of plant nu(trients and diverse gaseous substances, for example carbon mono- and dioxide, diverse compounds of nitrogen etc. At the sa(me time an excess of the ''critical loads'' for soil, air and water must be expected. The main items of the emissions prod(uced by an intensified agriculture are, besides carbon mono- and dioxide, methane, nitric and nitrous oxide, ammonia and d(iverse hydrocarbons. A higher productivity index is consequently related to a higher consumption. This also leads to an in(tensified turnover of carbon dioxide. There is consequently a progressive input of carbon dioxide resulting from the emiss(ions of burning fossil fuel in the recently produced and consumed biomass. This inevitably leads to a higher level of carb(on dioxide in the air. A main source of emissions of methane and ammonia is animal breeding. In Austria at this time from (each of the 3,508.000 hectars of land used by agriculture annual emissions of 63 kg methane and 11 kg ammonia are resultin(g theoretically. The use of organic and inorganic fertilizers, the growing cultivation of legumes and the emissions of nit(rogen compounds resulting from burning processes elevate likewise the pool and the annual turnover of nitrogen compounds b(y production and consumption of biomass. Inevitably related to it is a growing amount of the annual input of nitrogen comp(ounds to the air, the soil and the water. A rough approximation says that at present agriculture contributes to the global( anthropogenic pollution of the environment (air, soil and water) 85 % of the ammonia, 81 % of the nitrous oxide, 35 % of (nitric mono- and dioxide, 70 % of the methane, 52 % of the carbon monoxide and 21 % of the carbon dioxide. Not considered (in the figure for carbon dioxide is the inevitable increase of the level of CO2 in the air by the elevated turnover of bio(mass. The world population growth in the future leads to an increasing contribution of agriculture to the anthropogenic en(vironmental pollution. For the developed countries this is an obligatory challenge to avoid surplus production. On a globa(l scale there must be a sensible reduction of animal breeding to reduce the high emissions of methane and ammonia from thi(s sector of agriculture. It must also be considered, that by feeding animals with vegetable food stuff, which also could b(e used for direct nutrition of man, the efficiency of it is lowered by a factor of 1:10. In spite of a growing crisis to m(aintain the alimentation of the growing world population in many countries the nutrition of man must rapidly be centered o(n vegetable food stuff rich in protein. At the same time an essential reduction of the environmental pollution resulting f(rom animal breeding could be realized. Beside of it and other reducing issues a continuous growth of the world population,( the energy consumption and environmental pollution will make it necessary to observe the development and reactions in the( environment by monitoring and phenological observations. The results must be used to counteract finally by looking for ad(aptation strategies. Considering the realities it must be realized that by all means to mobilize for counteracting the env(ironmental pollution directly, a certain climate change will be inevitable. The consequences will also be an outstanding challenge for the agriculture.(793^4^Kwa,SH^Wee,YC^Lim,TM^Kumar,PP^1995^1^Establishment and physiological analyses of photoautotrophic callus-cultures of the fern platycerium-coronarium (koenig) desv under co2 enrichment^78^46^291^1535-1542^^^^^Oct^^^^^4397(A^4396^Gametophyte-derived callus cultures of Platycerium coronarium could be maintained under photoautotrophic conditions( on Murashige and Skoog medium supplemented with 2 mu M 2,4- dichlorophenoxyacetic acid (2,4-D) and with CO2 enrichment. P(rogressive reduction of sucrose from the medium resulted in a reduction in growth, but an increase in total chlorophyll co(ntent. When subculturing was delayed beyond 2 weeks, callus cells differentiated into gametophytes on the medium with less( than or equal to 0.2% sucrose and no CO2 enrichment. Enriching the photoautotrophic cultures on 2 mu M 2,4-D with 1% CO2 (resulted in about 1.7-fold increase in fresh weight within 42 d. Total chlorophyll content was generally higher with 1% CO(2 enrichment than with 10%. F-v/F-m ratio was higher for callus on low levels of sucrose (less than or equal to 0.5%) than( that on sucrose greater than or equal to 1.0%. An increase in autofluorescence of chloroplasts, but not the size, was obs(erved with decreasing sucrose levels in the medium. Autofluorescence decreased with increase in CO2 from 0.03%. Our data a(re in agreement with the view that long-term exposure to high levels of CO2 can cause a decrease in photosynthetic capacity.(794^3^Liang,N^Maruyama,K^Huang,Y^1995^1^Interactions of elevated co2 and drought stress in gas-exchange and water-use efficiency in 3 temperate deciduous tree species^79^31^4^529-539^^^^^^^^^^4399(A^4398^The effect of CO2 increase on gas exchange and water-use efficiency (WUE) in three temperate deciduous species (Fag(us crenata, Ginkgo biloba and Alnus firma) under gradually- developing drought-stress was assessed. Seedlings were grown w(ithin transparent open-top cabinets and maintained for 4 months at mean CO2 concentrations of either 350 (ambient; C- 350)( Or 700 mu mol mol(-1) (elevated; C-700) and combined with five water regimes [leaf water potential, Psi(w), higher than -( 0.3 (well-watered), -0.5 and -0.8 (moderate drought), -1.0 and fewer than -1.2 MPa (serious drought-stress)]. Increase in( CO2 concentration induced a 60 % average increase in net photosynthetic rate (P-N) under well-watered conditions. The eff(ect of C-700 became more pronounced with drought stress established, with an 80 % average increase in P-N at Psi(w), as lo(w as -0.8 MPa; leaf conductance to water vapour transfer (g(s)) and transpiration rate (E), however, were significantly de(creased. Consequently, WUE increased under drought, through drought stress affected potential E sooner than potential P-N.( The interaction of CO2 x drought stress on WUE was significant in that P-N was stimulated while E in C-700 enriched plant(s resembled that of C-350 plants under drought. Hence if a doubling of atmospheric CO2 concentration occurs by the mid 21((st) century, then greater P-N in F. crenata, G. biloba and A. firma may be expected and the drought susceptibility of these species will be substantially enhanced.(795^5^Martin,CA^Stutz,JC^Kimball,BA^Idso,SB^Akey,DH^1995^1^Growth and topological changes of citrus-limon (L) burm f eureka in response to high-temperatures and elevated atmospheric carbon-dioxide^154^120^6^1025-1031^^^^^Nov^^^^^4401(A^4400^Growth and topological indices of 'Eureka' lemon were measured after 6 months in well-watered and well-fertilized c(onditions and factorial combinations of moderate (29/21C day/night) or high (42/32C day/night) temperatures and ambient (3(50 to 380 mu mol . mol(-1)) or elevated (constant 680 mu mol . mol(-1)) CO2. In high temperatures, plants were smaller and( had higher levels of leaf chlorophyll alpha than in moderate temperatures. Moreover, plants in high temperatures and elev(ated CO2 had about 15% higher levels of leaf chlorophyll alpha than those in high temperatures and ambient CO2. In high te(mperatures, plant growth in elevated CO2 was about 87% more than in ambient CO2. Thus, high CO2 reduced the negative effec(t of high temperature on shoot growth, In moderate temperatures, plant growth in elevated CO2 Was only about 21% more than( in ambient CO2. Irrespective of temperature treatments, shoot branch architecture in elevated CO2 was more hierarchical t(han those in ambient CO2. Specific shoot extension, a topological measure of branch frequency, was not affected by elevate(d CO2 in moderate temperatures, but was increased by elevated CO2 enrichment in high temperatures-an indication of decreas(ed branch frequency and increased apical dominance, In moderate temperatures, plants in elevated CO2 had fibrous root bran(ch patterns that were less hierarchical than at ambient CO2. The lengths of exterior and interior fibrous roots between br(anch points and the length of second-degree adventitious lateral branches were increased >50% by high temperatures compared with moderate temperatures, Root length between branch points was not affected by CO2 levels.(796^3^McKee,IF^Farage,PK^Long,SP^1995^1^The interactive effects of elevated co2 and o-3 concentration on photosynthesis in spring wheat^91^45^2^111-119^^^^^Aug^^^^^4403(A^4402^This study investigated the interacting effects of carbon dioxide and ozone on photosynthetic physiology in the fla(g leaves of spring wheat (Triticum aestivum L. cv. Wembley), at three stages of development. Plants were exposed throughou(t their development to reciprocal combinations of two carbon dioxide and two ozone treatments: [CO2] at 350 or 700 mu mol (mol(-1), [O-3] at < 5 or 60 nmol mol(-1). Gas exchange analysis, coupled spectrophotometric assay for RuBisCO activity, an(d SDS-PAGE, were used to examine the relative importance of pollutant effects on i) stomatal conductance, ii) quantum yiel(d, and iii) RuBisCO activity, activation, and concentration. Independently, both elevated [CO2] and elevated [O-3] caused (a loss of RuBisCO protein and V-cmax. In combination, elevated [CO2] partially protected against the deleterious effects o(f ozone. It did this partly by reducing stomatal conductance, and thereby reducing the effective ozone dose. Elevated [O-3] caused stomatal closure largely via its effect on photoassimilation.(797^27^Melillo,JM^Borchers,J^Chaney,J^Fisher,H^Fox,S^Haxeltine,A^Janetos,A^Kicklighter,DW^Kittel,TGF^McGuire,AD^McKeown,R^(Neilson,R^Nemani,R^Ojima,DS^Painter,T^Pan,Y^Parton,WJ^Pierce,L^Pitelka,L^Prentice,C^Rizzo,B^Rosenbloom,NA^Running,S^Schime(l,DS^Sitch,S^Smith,T^Woodward,I^1995^1^Vegetation ecosystem modeling and analysis project - comparing biogeography and bio(geochemistry models in a continental-scale study of terrestrial ecosystem responses to climate-change and co2 doubling^137^9^4^407-437^^^^^Dec^^^^^4405(A^4404^We compare the simulations of three biogeography models (BIOME2, Dynamic Global Phytogeography Model (DOLY), and Ma(pped Atmosphere-Plant Soil System (MAPSS)) and three biogeochemistry models (BIOME-BGC (BioGeochemistry Cycles), CENTURY, (and Terrestrial Ecosystem Model (TEM)) for the conterminous United States under contemporary conditions of atmospheric CO2( and climate. We also compare the simulations of these models under doubled CO2 and a range of climate scenarios. For cont(emporary conditions, the biogeography models successfully simulate the geographic distribution of major vegetation types a(nd have similar estimates of area for forests (42 to 46% of the conterminous United States), grasslands (17 to 27%), savan(nas (15 to 25%), and shrublands (14 to 18%). The biogeochemistry models estimate similar continental-scale net primary pro(duction (NPP; 3125 to 3772 x 10(12) gC yr(-1)) and total carbon storage (108 to 118 x 10(15) gC) for contemporary conditio(ns. Among the scenarios of doubled CO2 and associated equilibrium climates produced by the three general circulation model(s (Oregon State University (OSU), Geophysical Fluid Dynamics Laboratory (GFDL), and United Kingdom Meteorological Office ((UKMO)), all three biogeography models show both gains and losses of total forest area depending on the scenario (between 3(8 and 53% of conterminous United States area). The only consistent gains in forest area with all three models (BIOME2, DOL(Y, and MAPSS) were under the GFDL scenario due to large increases in precipitation. MAPSS lost forest area under UKMO, DOL)Y under OSU, and BIOME2 under both UKMO and OSU, The variability in forest area estimates occurs because the hydrologic cy)cles of the biogeography models have different sensitivities to increases in temperature and CO2. However, in general, the) biogeography models produced broadly similar results when incorporating both climate change and elevated CO2 concentratio)ns. For these scenarios, the NPP estimated by the biogeochemistry models increases between 2% (BIOME-BGC with UKMO climate)) and 35% (TEM with UKMO climate). Changes in total carbon storage range from losses of 33% (BIOME-BGC with UKMO climate) )to gains of 16% (TEM with OSU climate). The CENTURY responses of NPP and carbon storage are positive and intermediate to t)he responses of BIOME-BGC and TEM. The variability in carbon cycle responses occurs because the hydrologic and nitrogen cy)cles of the biogeochemistry models have different sensitivities to increases in temperature and CO2. When the biogeochemis)try models are run with the vegetation distributions of the biogeography models, NPP ranges from no response (BIOME-BGCwit) h all three biogeography model vegetations for UKMO climate) to increases of 40% (TEM with MAPSS vegetation for OSU climat) e). The total carbon storage response ranges from a decrease of 39% (BIOME-BGC with MAPSS vegetation for UKMO climate) to ) an increase of 32% (TEM with MAPSS vegetation for OSU and GFDL climates). The UKMO responses of BIOME-BGC with MAPSS veget) ation are primarily caused by decreases in forested area and temperature-induced water stress, The OSU and GFDL responses of TEM with MAPSS vegetations are primarily caused by forest expansion and temperature-enhanced nitrogen cycling.)798^6^Mitchell,RJ^Runion,GB^Prior,SA^Rogers,HH^Amthor,JS^Henning,FP^1995^1^Effects of nitrogen on pinus-palustris foliar respiratory responses to elevated atmospheric co2 concentration^78^46^291^1561-1567^^^^^Oct^^^^^4407)A^4406^Indirect effects of atmospheric CO2 concentration [CO2], on longleaf pine (Pinus palustris Mill.) foliage respirati)on were studied by growing trees in a factorial arrangement of low and high [CO2] (369 and 729 mu mol CO2 mol(-1)) and low) and high N (40 and 400 kg ha(-1) yr(-1)). Direct effects of [CO2] on leaf respiration were tested by measuring respiratio)n rates of foliage from all treatments at two CO2 levels (360 and 720 mu mol CO2 mol(-1)) at the time of measurement. Elev)ated CO2 did not directly or indirectly affect leaf respiration when expressed on a leaf area or mass basis, but a signifi)cant increase in respiration per unit leaf N was observed in trees grown in elevated [CO2] (indirect response to elevated )[CO2]). The lack of a [CO2] effect on respiration, when analysed on an area or mass basis, may have resulted from combined) effects of [CO2] on factors that increase respiration (e.g. greater availability of non-structural carbohydrates stimulat)ing growth and carbon export from leaves) and on factors that decrease respiration (e.g. lower N concentration leading to )lower construction costs and maintenance requirements). Thus, [CO2] affected factors that influence respiration, but in opposing ways.)799^4^Norby,RJ^Wullschleger,SD^Gunderson,CA^Nietch,CT^1995^1^Increased growth efficiency of quercus-alba trees in a co2- enriched atmosphere^84^131^1^91-97^^^^^Sep^^^^^4409)A^4408^Forests have a prominent role in the global carbon cycle, but their response to a changing atmosphere cannot be mea)sured directly. Experimental observations of small trees in CO2- enriched atmospheres must be interpreted carefully if the)y are to be relevant to the potential responses of forest trees. We grew white oak (Quercus alba L.) saplings for four com) plete growing seasons in open-top chambers with different partial pressures of atmospheric CO2. White oak saplings produce)!d 58% more dry mass in 50 Pa CO2 and 135% more in 65 Pa, compared with plants in ambient (35 Pa) CO2. Although this result)" might suggest a substantial potential for increased carbon storage in forests, the large difference in growth rate could )#be attributed to a stimulation of growth very early in the experiment. There was not a sustained effect of CO2 on relative)$ growth rate after the first year, and the increased absolute growth rate could persist only so long as leaf area could in)%crease, a condition that would not occur indefinitely in a forest. Nevertheless, annual stem wood production per unit area)& (growth efficiency) was 37% greater in elevated CO2. This increase in growth efficiency, a response that is consistent ac)'ross diverse studies, implies a potential increase in carbon sequestration by forests, subject to critical assumptions about forest canopy development in a CO2-enriched atmosphere.))800^5^Parton,WJ^Scurlock,JMO^Ojima,DS^Schimel,DS^Hall,DO^1995^1^Impact of climate-change on grassland production and soil carbon worldwide^127^1^1^13-22^^^^^Feb^^^^^4411)+A^4410^The impact of climate change and increasing atmospheric CO2 was modelled for 31 temperate and tropical grassland si),tes, using the CENTURY model. Climate change increased net primary production, except in cold desert steppe regions, and C)-O2 increased production everywhere. Climate change caused soil carbon to decrease overall, with a loss df 4 Pg from global). grasslands after 50 years. Combined climate change and elevated CO2 increased production and reduced global grassland C l)/osses to 2 Pg, with tropical savannas becoming small sinks for soil C. Detection of statistically significant change in pl)0ant production would require a 16% change in measured plant production because of high year to year variability in plant production. Most of the predicted changes in plant production are less than 10%.)2801^2^Pearson,M^Brooks,GL^1995^1^The influence of elevated co2 on growth and age-related-changes in leaf gas-exchange^78^46^292^1651-1659^^^^^Nov^^^^^4413)4A^4412^Rumex obtusifolius plants were grown far several months in daylit environment chambers (Solardomes) force-ventilate)5d with air containing 350 or 600 mu mol mol(-1) CO2. Elevated CO2 was found to accelerate the natural ontogenic decline in)6 photosynthesis, but did not reduce leaf duration, In both CO2 treatments photosynthetic rates declined progressively with)7 increasing leaf age, the decline being greater for plants grown in elevated CO2 such that rates became lower than in ambi)8ent CO2. The degree of CO2-induced photosynthetic down-regulation as determined by A/C-I analysis was found to be dependen)9t on leaf age, The major contribution to the decline in photosynthesis was likely to be a reduction in Rubisco activity as): changes in stomatal and mesophyll limitations were small. Instantaneous water use efficiency (WUE(i)) was greater for pla);nts in elevated CO2, but these values declined rapidly with leaf age, whereas in ambient CO2 values were always lower, but)< were maintained for longer. Growth analysis indicated an increased root: shoot ratio for plants grown in elevated CO2, th)=is occurring almost entirely as a result of increased root growth. Greater root proliferation and increased WUE(i) are cha)>racteristics which should give this persistent and troublesome weed an increased competitive under projected conditions of climate change.)@802^3^Reddy,KR^Hodges,HF^McKinion,JM^1995^1^Carbon-dioxide and temperature effects on pima cotton development^48^87^5^820-826^^^^^Sep-Oct^^^^^4415)BA^4414^Predicting plant responses to changing atmospheric CO2 and to the possible global warming are important concerns. E)Cffects of CO2 on developmental events are poorly documented, as is the interaction of CO2 and other major climate variable)Ds on crop development. The objective of this experiment was to determine the effects of an altered CO2 environment and int)Eeractions of CO2 and temperature on pima cotton developmental rates. Pima cotton (Gossypium barbadense L. cv. S-6) was gro)Fwn from seed in sun-lit plant growth chambers. Air temperatures were controlled from 20/12 to 40/32 degrees C (day/night) )Gin 5-degree increments. Daytime CO2 was maintained at 350 or 700 mu L L(- 1). In a second experiment, the temperature was )Hmaintained at 30/22 degrees C day/night and the plants were grown in 350, 450, or 700 mu L L(-1) CO2. Days required to dev)Ielop nodes on the mainstem, days from emergence to first square, number of vegetative and fruiting branches, number of fru)Jiting sites produced, number of bells and squares produced, and number of bells and squares retained by the plants were de)Ktermined. Rates of mainstem node formation and the time required to produce the first square and first flower were not sen)Lsitive to atmospheric CO2, but were very sensitive to temperature. Prefruiting branch nodal positions required longer to d)Mevelop than nodes with fruiting branches. Carbon dioxide levels did not affect the time required to produce nodes. Number )Nof branches produced was sensitive to both temperature and CO2. The larger number of bells set on the lower branches of pl)Oants grown at high CO2 provided a larger sink for photosynthate than plants grown at low CO2. This may be the reason for t)Phe observed reduction in number of fruit at the upper nodes of high-CO2-grown plants. More bells and squares were produced)Q and retained on plants grown in high-CO2 environments, except that none were produced in either CO2 environment at 40/32 )Rdegrees C. Our results indicate that high-temperature-tolerant cotton cultivars would be more productive in the present-day CO2 world, and they would be essential in the future if global temperature increases.)T803^1^Reining,F^1995^1^The effect of elevated co2 concentrations on the competition between lamium-galeobdolon and stellaria-holostea^79^31^4^501-508^^^^^^^^^^4417)VA^4416^The effect of enhanced air CO2 concentrations (c(520) and c(650) = 520 and 650 cm(3) m(-3)) on the growth of Lamium)W galeobdolon and Stellaria holostea and on the competition between the two species was examined. After five months growth )Xunder CO2 enrichment the dry masses of both species increased when the plants were grown in monoculture, but the increase )Yin biomass was much more pronounced in Stellaria. When the plants were grown together in competition, the measured shoot m)Zasses of Stellaria were again higher under c(520) and c(650) than at ambient CO2 concentration (c(390) = 390 cm(3) m(-3)),)[ while the shoot masses of lamium strongly decreased at c(650) The effect of CO2 enrichment on the two plant species in mo)\noculture differed significantly from that observed in mixed cultures. In terms of plant relative yield. Stellaria benefit)]ted slightly but insignificantly from competition, while Lamium was significantly suppressed under c(650). Total community)^ production of the mixed culture was optimum at c(520), while that of the monocultures was highest at c(650) At c(390) and)_ c(520), growth of Stellaria depended strongly on irradiance in all types of culture. At c(650) no such dependence could be demonstrated.)a804^2^Roth,SK^Lindroth,RL^1995^1^Elevated atmospheric co2 effects on phytochemistry, insect performance and insect parasitoid interactions^127^1^3^173-182^^^^^Jun^^^^^4419)cA^4418^This study was conducted to examine the effects of CO2-mediated changes in tree chemistry on the performance of the)d gypsy moth (Lymantria dispar L.) and the parasitoid Cotesia melanoscela (Ratz.). We used carbon-nutrient balance theory t)eo develop hypotheses regarding changes in tree chemistry and the performance of both insects under elevated CO2. As predic)fted, levels of foliar nitrogen declined and concentrations of carbon-based compounds (e.g. starch and phenolics) increased)g under elevated CO2. Gypsy moth performance (e.g. growth, development) was altered by CO2-mediated changes in foliar chemi)hstry, but the magnitude was small and varied across tree species. Larvae feeding on high CO2 aspen exhibited the largest r)ieduction in performance, relative to larvae feeding on birch, oak, or maple. Parasitism by C. melanoscela significantly pr)jolonged gypsy moth development and reduced growth rates. Overall, the effect of parasitism on gypsy moth performance did n)kot differ between CO2 treatments. Altered gypsy moth performance on high CO2 foliage in turn affected parasitoid performan)lce, but the response was variable: parasitoid mortality increased and adult female size declined slightly under high CO2, )mwhile development time and adult male size were unaffected. Our results suggest that CO2-induced changes in plant chemistr)ny were buffered to the extent that effects on third trophic level interactions were weak to non-existent for the system examined in this study.)p805^3^Salt,DT^Brooks,GL^Whittaker,JB^1995^1^Elevated carbon-dioxide affects leaf-miner performance and plant-growth in docks (rumex spp)^127^1^2^153-156^^^^^Apr^^^^^4421)rA^4420^Exposure of R. crispus and R. obtusifolius to elevated CO2 (600 ppm) resulted in an increased C:N ratio of leaf tis)ssue and greater leaf areas. Larvae of P. nigritarsis mining leaves of X. obtusifolius during exposure produced significant)tly bigger mines in elevated than in ambient (350 ppm) conditions. There were no significant treatment effects on pupal wei)ught although in both host species mean weight was greater in ambient than in elevated conditions. These results are consis)vtent with the hypothesis that insect herbivores compensate for increased C:N ratios by increased food consumption This response by herbivores may partially offset predicted increases in plant biomass in a future high CO2 environment.806^1^Schimel,DS^1995^1^Terrestrial ecosystems and the carbon-cycle^127^1^1^77-91^^^^^Feb^^^^^4423)yA^4422^The terrestrial biosphere plays an important role in the global carbon cycle. In the 1994 Intergovernmental Panel A)zssessment on Climate Change (IPCC), an effort was made to improve the quantification of terrestrial exchanges and potentia){l feedbacks from climate, changing CO2, and other factors; this paper presents the key results from that assessment, toget)|her with expanded discussion. The carbon cycle is the fluxes of carbon among four main reservoirs: fossil carbon, the atmo)}sphere, the oceans, and the terrestrial biosphere. Emissions of fossil carbon during the 1980s averaged 5.5 Gt y(-1). Duri)~ng the same period, the atmosphere gained 3.2 Gt C y(-1), and the oceans are believed to have absorbed 2.0 Gt C y(-1). The) regrowing forests of the Northern Hemisphere may have absorbed 0.5 Gt C y(-1) during this period. Meanwhile, tropical def)orestation is thought to have released an average 1.6 Gt C y(-1) over the 1980s. While the fluxes among the four pools sho)uld balance, the average 1980s values lead to a 'missing sink' of 1.4 Gt C y(-1). Several processes, including forest regr)owth, CO2 fertilization of plant growth (c. 1.0 Gt C y(-1)), N deposition (c. 0.6 Gt C y(-1)), and their interactions, may) account for the budget imbalance. However, it remains difficult to quantify the influences of these separate but interact)ive processes. Uncertainties in the individual numbers are large, and are themselves poorly quantified. This paper present)s detail beyond the IPCC assessment on procedures used to approximate the flux uncertainties. Lack of knowledge about posi)tive and negative feedbacks from the biosphere is a major limiting factor to credible simulations of future atmospheric CO)2 concentrations. Analyses of the atmospheric gradients of CO2 and (CO2)-C-13 concentrations provide increasingly strong e)vidence for terrestrial sinks, potentially distributed between Northern Hemisphere and tropical regions, but conclusive de)tection in direct biomass and soil measurements remains elusive. Current regional-to-global terrestrial ecosystem models w)ith coupled carbon and nitrogen cycles represent the effects of CO2 fertilization differently, but all suggest long-term r)esponses to CO2 that are substantially smaller than potential leaf- or laboratory whole plant-level responses. Analyses of) emissions and biogeochemical fluxes consistent with eventual stabilization of atmospheric CO2 concentrations are sensitiv)e to the way in which biospheric feedbacks are modeled by c. 15%. Decisions about land use can have effects of 100s of Gt )C over the next few centuries, with similarly significant effects on the atmosphere. Critical areas for future research ar)e continued measurements and analyses of atmospheric data (CO2 and (CO2)-C-13) to serve as large-scale constraints, proces)s studies of the scaling from the photosynthetic response to CO2 to whole-ecosystem carbon storage, and rigorous quantification of the effects of changing land use on carbon storage.)807^2^Vandasselaar,AV^Lantinga,EA^1995^1^Modeling the carbon-cycle of grassland in the netherlands under various management strategies and environmental-conditions^179^43^2^183-194^^^^^Jun^^^^^4425)A^4424^A simulation model of the carbon cycle of grassland (CCGRASS) was developed to evaluate the long-term effects of di)fferent management strategies and various environmental conditions on carbon sequestration in the soil. The results presen)ted here refer to permanent grassland on a young sedimentary loam soil in the Netherlands. The model predicted that the ra)te of increase in the amount of soil organic carbon will be highest at low to moderate application rates of nitrogen (100 )- 250 kg N ha(-1) yr(-1)). This is due to the fact that the annual gross photosynthetic uptake of CO2 in permanent grassla)nd is hardly influenced by the level of N supply. Since N shortage stimulates the growth of the unharvested plant parts (r)oots and stubble) the carbon supply to the soil is highest at low to moderate N application rates. The rate of increase in) the amount of soil organic carbon will be higher under grazing than under mowing as a result of a greater amount of carbo)n added to the soil. Increase of atmospheric CO2 concentration may induce an increase in decomposition rate of soil organi)c matter due to simultaneously increased temperatures. At the same time: plant productivity and thus carbon supply to the )soil will be stimulated due to the CO2-fertilization effect. Under the assumption of a temperature increase of 3 degrees C) if the present atmospheric CO2 concentration doubles, the model predicted that the combined effect of elevated CO2 and te)mperature will slightly reduce the rate of increase in the amount of organic carbon in grassland soils compared to that un)der unchanged environmental conditions. There was 2% less carbon sequestration by grassland at the end of a period of 100 )years as a result of these changes in environmental conditions. The separate effects of increased temperature or elevated CO2 were 10% less and 10% more carbon storage at the end of a period of 100 years, respectively.)808^4^Vandestaaij,JWM^Huijsmans,R^Ernst,WHO^Rozema,J^1995^1^The effect of elevated uv-b (280-320 nm) radiation-levels on silene vulgaris - a comparison between a highland and a lowland population^35^90^3^357-362^^^^^^^^^^4427)A^4426^Highland (altitude 1600 m above sea level) and lowland (altitude -2 m below sea level) populations of the perennial) herb Silene vulgaris (Moench) Garcke, were tested on their response to elevated levels of UV-B radiation. Highland popula)tions typically receive high natural UV-B fluxes, whereas lowland populations receive a lower natural UV-B dose. Adaptatio)n to high UV-B levels of the highland population is to be expected. Experimental comparison of growth rates, gas exchange )rates, transpiration and biochemical parameters using adult plants as well as seedlings did not show a difference in the r)esponse to elevated UV-B levels between the two populations. Individuals of both populations were relatively insensitive t)o elevated UV-B radiation. The response of alpine and lowland populations of Silene vulgaris is discussed in relation to the dispersal of this species after the last ice age.)809^2^Vogel,CS^Curtis,PS^1995^1^Leaf gas-exchange and nitrogen dynamics of n-2-fixing field- grown alnus-glutinosa under elevated atmospheric co2^127^1^1^55-61^^^^^Feb^^^^^4429)A^4428^Few studies have investigated the effects of elevated CO2 on the physiology of symbiotic N-2-fixing trees. Tree spe)cies grown in low N soils at elevated CO2 generally show a decline in photosynthetic capacity over time relative to ambien)t CO2 controls. This negative adjustment may be due to a reallocation of leaf N away from the photosynthetic apparatus, al)lowing for more efficient use of limiting N. We investigated the effect of twice ambient CO2 on net CO2 assimilation (A), )photosynthetic capacity, leaf dark respiration, and leaf N content of N-2- fixing Alnus glutinosa (black alder) grown in f)ield open top chambers in a low N soil for 160 d. At growth CO2, A was always greater in elevated compared to ambient CO2 )plants. Late season A vs. internal leaf p(CO2) response curves indicated no negative adjustment of photosynthesis in eleva)ted CO2 plants. Rather, elevated CO2 plants had 16% greater maximum rate of CO2 fixation by Rubisco. Leaf dark respiration) was greater at elevated CO2 on an area basis, but unaffected by CO2 on a mass or N basis. In elevated CO2 plants, leaf N )content (mu g N cm(- 2)) increased 50% between Julian Date 208 and 264. Leaf N content showed little seasonal change in am)bient CO2 plants. A single point acetylene reduction assay of detached, nodulated root segments indicated a 46% increase i)n specific nitrogenase activity in elevated compared to ambient CO2 plants. Our results suggest that N-2-fixing trees will) be able to maintain high A with minimal negative adjustment of photosynthetic capacity following prolonged exposure to elevated CO2 on N-poor soils.)810^3^Woodward,FI^Smith,TM^Emanuel,WR^1995^1^A global land primary productivity and phytogeography model^137^9^4^471-490^^^^^Dec^^^^^4431)A^4430^A global primary productivity and phytogeography model is described. The model represents the biochemical processes) of photosynthesis and the dependence of gas exchange on stomatal conductance, which in turn depends on temperature and so)il moisture. Canopy conductance controls soil water loss by evapotranspiration. The assignment of nitrogen uptake to leaf )layers is proportional to irradiance, and respiration and maximum assimilation rates depend on nitrogen uptake and tempera)ture. Total nitrogen uptake is derived from soil carbon and nitrogen and depends on temperature. The long-term average ann)ual carbon and hydrological budgets dictate canopy leaf area. Although observations constrain soil carbon and nitrogen, th)e distribution of vegetation types is not specified by an underlying map. Variables simulated by the model are compared to) experimental results. These comparisons extend from biochemical processes to the whole canopy, and the comparisons are fa)vorable for both current and elevated CO2 atmospheres. The model is used to simulate the global distributions of leaf area) index and annual net primary productivity. These distributions are sufficiently realistic to demonstrate that the model is useful for analyzing vegetation responses to global environmental change.)811^3^Tschaplinski,TJ^Stewart,DB^Norby,RJ^1995^1^Interactions between drought and elevated co2 on osmotic adjustment and solute concentrations of tree seedlings^84^131^2^169-177^^^^^Oct^^^^^4433)A^4432^Although drought tolerance of tree species is a critical determinant of forest composition, how elevated CO2 affect)s drought tolerance is uncertain. Interactions between elevated CO2 and drought on osmotic potential and osmotic adjustmen)t of American sycamore (Platanus occidentalis L.), sweetgum (Liquidambar styraciflua L.), and sugar maple (Acer saccharum )Marsh.) were investigated using l-yr-old seedlings, planted in 81 pots and grown in four open-top chambers, containing eit)her ambient air or ambient air enriched with 300 mu mol mol(-1) CO2. A well-watered treatment with plants watered daily an)d a droughted treatment in which plants were subjected to a series of drought cycles were included within each chamber. Su)gar maple and sweetgum seedlings completed a total of seven drying cycles, whereas sycamore seedlings, because of their gr)eater leaf area and plant size, completed 11 cycles. The mean soil water potential at re-watering for droughted seedlings )in ambient CO2 was -0.5, -0.7, and -1.8 MPa for sugar maple, sweetgum and sycamore, respectively, compared with -0.2, -0.7), and -1.2 MPa, respectively, under elevated CO2. By contrast, all well-watered plants were maintained at soil water poten)tial >-0.1 MPa. Drought under ambient CO2 reduced osmotic potential at saturation for leaves of sycamore and sweetgum by 0).30 MPa and 0.61 MPa, respectively, but leaves of sugar maple did not display osmotic adjustment to drought. Elevated CO2 )increased osmotic potential at turgor loss for leaves of sugar maple by 0.33 MPa under well-watered conditions, and 0.48 M)Pa under drought. This response was not evident in the other species and might be related to the rapid growth of sugar map)le causing a depletion of solutes. Whereas drought reduced the total solute concentration in roots of sugar maple, primari)ly the result of a reduction in K, elevated CO2 did not alter the concentration of total solutes in roots of any of the th)ree species. Elevated CO2 has differing effects on drought tolerance among tree species, and thus might alter the competitive relations between species.)812^5^Baxter,R^Bell,SA^Sparks,TH^Ashenden,TW^Farrar,JF^1995^1^Effects of elevated co2 concentrations on 3 montane grass species .3. Source leaf metabolism and whole-plant carbon partitioning^78^46^289^917-929^^^^^Aug^^^^^4435)A^4434^Agrostis capillaris L.(5), Festuca vivipara L. and Poa alpina L. were grown in outdoor open-top chambers at either )ambient (340 +/- 3 mu mol mol(-1)) or elevated (680 +/- 4 mu mol mol(- 1)) concentrations of atmospheric carbon dioxide (G)O,) for periods from 79-189 d. Photosynthetic capacity of source leaves of plants grown at both ambient and elevated CO2 c)oncentrations was measured at saturating light and 5% CO2. Dark respiration of leaves was measured using a liquid phase ox)ygen electrode with the buffer solution in equilibrium with air (21% O-2, 0.034% CO2). Photosynthetic capacity of P. alpin)a was reduced by growth at 680 mu mol mol(-1) CO2 by 105 d, and that of F. vivipara was reduced at 65 d and 189 d after CO)2 enrichment began, suggesting down-regulation or acclimation. Dark respiration of successive leaf blades of all three spe)cies was unaltered by growth at 680 relative to 340 mu mol mol(-1) CO2. In F. vivipara, leaf respiration rate was markedly) lower at 189 d than at either 0 d or 65 d, irrespective of growth CO2 concentration. There was a significantly lower tota)l non- structural carbohydrate (TNC) concentration in the leaf blades and leaf sheaths of A. capillaris grown at 680 mu mo)l mol(-1) CO2. TNC of roots of A. capillaris was unaltered by CO2 treatment. TNC concentration was increased in both leave)s and sheaths of P. alpina and F. vivipara after 105 d and 65 d growth, respectively. A 4-fold increase in the water-solub)le fraction (fructan) in P. alpina and in all carbohydrate fractions in F. vivipara accounted for the increased TNC conten)t. In F. vivipara the relationship between leaf photosynthetic capacity and leaf carbohydrate concentration was such that )there was a strong positive correlation between photosynthetic capacity and total leaf N concentration (expressed on a per) unit structural dry weight basis), and total nitrogen concentration of successive mature leaves reduced with time, Multip)le regression of leaf photosynthetic capacity upon leaf nitrogen and carbohydrate concentrations further confirmed that le)af photosynthetic capacity was mainly determined by leaf N concentration. In P. alpina, leaf photosynthetic capacity was m)ainly determined by leaf CHO concentration. Thus there is evidence for downregulation of photosynthetic capacity in P. alp)ina resulting from increased carbohydrate accumulation in source leaves. Leaf dark respiration and total N concentration w)ere positively correlated in P. alpina and F. vivipara. Leaf dark respiration and soluble carbohydrate concentration of so)urce leaves were positively correlated in A. capillaris. Changes in source leaf photosynthetic capacity and carbohydrate c)oncentration of plants grown at ambient or elevated CO, are discussed in relation to plant growth, nutrient relations and availability of sinks for carbon.)813^4^Bazzaz,FA^Jasienski,M^Thomas,SC^Wayne,P^1995^1^Microevolutionary responses in experimental populations of plants to co2-enriched environments - parallel results from 2 model systems^255^92^18^8161-8165^^^^^29 Aug^^^^^4437) with 1.6 cm . cm(-3) in ambient CO2, with sweetgum accounting for >75% of the total RLD in both cases. These findings sug)gest that resource-rich rather than resource- poor soil environments could be the circumstances under which belowground interference from sweetgum would intensify in pine- sweetgum mixtures with rising atmospheric CO2.855^1^Loehle,C^1995^1^Anomalous responses of plants to co2 enrichment^15^73^2^181-187^^^^^Jun^^^^^4510hment (face) on forage quality of wheat^260^53^1^29-43^^^^^May^^^^^4580etreatments on decomposition on tallgrass prairie leaf-litter^206^165^1^115-127^^^^^^^^^^4722ption, are discussed.*A^4436^Despite the critical role that terrestrial vegetation plays in the Earth's carbon cycle, very little is known about* the potential evolutionary responses of plants to anthropogenically induced increases in concentrations of atmospheric CO*2. We present experimental evidence that rising CO2 concentration may have a direct impact on the genetic composition and *diversity of plant populations but is unlikely to result in selection favoring genotypes that exhibit increased productivi*ty in a CO2-enriched atmosphere. Experimental populations of an annual plant (Abutilon theophrasti, velvetleaf) and a temp*erate forest tree (Betula alleghaniensis, yellow birch) displayed responses to increased CO2 that were both strongly densi*ty-dependent and genotype-specific. In competitive stands, a higher concentration of CO2 resulted in pronounced shifts in * genetic composition, even though overall CO2-induced productivity enhancements were small, For the annual species, quantit* ative estimates of response to selection under competition were 3 times higher at the elevated CO2 level. However, genotyp* es that displayed the highest growth responses to CO2 when grown in the absence of competition did not have the highest fi* tness in competitive stands. We suggest that increased CO2 intensified interplant competition and that selection favored g* enotypes with a greater ability to compete for resources other than CO2. Thus, while increased CO2 may enhance rates of se*lection in populations of competing plants, it is unlikely to result in the evolution of increased CO2 responsiveness or t*o operate as an important feedback in the global carbon cycle, However, the increased intensity of selection and drift driven by rising CO2 levels may have an impact on the genetic diversity in plant populations.*814^2^Boese,SR^Wolfe,DW^1995^1^Elevated-temperatures limit sink development and photosynthetic benefit from elevated co2^8^108^2^26^^^^^Jun*815^2^Burton,PJ^Cumming,SG^1995^1^Potential effects of climatic-change on some western canadian forests, based on phenological enhancements to a patch model of forest succession^94^82^1-2^401-414^^^^^May^^^^^4440*A^4439^We enhanced the forest patch model, Zelig, to explore the implications of 2xCO(2) climate change scenarios on sever*al forest regions in British Columbia and Alberta, Canada. In addition to the processes and phenomena commonly represented* in individual-based models of forest stand dynamics, we added some species-specific phenology and sire-specific frost eve*nts. The consideration of bud-break heat sum requirements, growing season limits, and chilling requirements for the induct*ion of dormancy and cold hardiness slightly improved the ability of Zelig to predict the present composition of B.C. fores*ts. Simulations of the predicted effects of future climatic regimes (based on the averaged predictions of four general cir*culation models) include some major shifts in equilibrial, forest composition and productivity. Lowland temperate coastal *forests are predicted to be severely stressed because indigenous species will no longer have their winter chilling require*ments met. High-elevation coastal forests are expected to increase in productivity, while interior subalpine forests are e*xpected to remain stable in productivity but will gradually be replaced by species currently characteristic of lower eleva*tions. Dry, interior low-elevation forests in southern B.C. are likely to persist relatively unchanged, while wet interior* forests are expected to support dramatic increases in yield, primarily by western hemlock. Northern interior sub-boreal f*!orests are likewise expected to increase in productivity through enhanced growth of lodgepole pine. Conversely, the precip*"itous collapse of spruce stands in the true boreal forests of northeastern B.C. is expected to be associated with reduced *#productivity as they are replaced by pine species. Boreal-Cordilleran and Moist Boreal Mixedwood forests in Alberta are le*$ss likely to undergo compositional change, while becoming somewhat more productive. We believe these model enhancements to*% be a significant improvement over existing formulations, but the resulting predictions must still be viewed with caution.*& Model limitations include: (1) the current inability of climate models to predict future variation in monthly temperature*' and precipitation; (2) sparse information on the phenological behaviour of several important tree species; and (3) a poor understanding of the degree to which growth is constrained by different suboptimal climatic events.*)816^2^Cardon,ZG^Jckson,RB^1995^1^Root acid-phosphatase-activity in bromus-hordeaceus and avena- barbata remains unchanged under elevated [co2]^8^108^2^148^^^^^Jun*+817^3^Eamus,D^Berryman,CA^Duff,GA^1995^1^The impact of co2 enrichment on water relations in maranthes- corymbosa and eucalyptus-tetrodonta^182^43^3^273-282^^^^^^^^^^4443*-A^4442^Seeds of Maranthes corymbosa Blume and Eucalyptus tetrodonta F.Muell were sown under ambient or CO2 enriched condit*.ions (two replicate tents per treatment) in tropical Australia and allowed to grow, rooted in the ground, for 20 months. F*/or both species, periodic measurements of leaf water potential, stomatal conductance and leaf temperature were made on fou*0r replicate leaves on each of four replicate trees within each tent. Measurements were made in November (M. corymbosa) and*1 June (E. tetrodonta). At the same time, atmospheric wet and dry bulb temperatures were recorded and hence leaf-to-air vap*2our presure difference (LAVPD) calculated. Measurements of pre-dawn leaf water potential were also made on E. tetrodonta. *3Leaves were also taken to the laboratory, rehydrated to full turgor and pressure-volume analyses undertaken. For M. corymb*4osa, leaf water potential was lower throughout the day for control leaves compared to leaves growing in CO2 enriched air. *5Similarly, pre dawn leaf water potential was lower for control E. tetrodonta trees than for trees grown with CO2 enrichmen*6t. However, mid- morning and mid-afternoon values of leaf water potential for E. tetrodonta were slightly lower for plants*7 growing in CO, enriched air compared to control plants. In both species, stomatal conductance was consistently lower for *8trees grown in CO2 enriched air than for controls. Whole plant hydraulic conductivity of both species was significantly lo*9wer for trees grown in CO2 enriched air than for control trees. For both species, maximum turgor and bulk volumetric elastic modulus increased and osmotic potential at zero turgor decreased for trees grown in CO2 enriched air.*;818^2^Fiscus,EL^Reid,CD^1995^1^Pollutant ozone does not affect stomatal limitation to photosynthesis in soybean in ambient or elevated co2^8^108^2^63^^^^^Jun*=819^5^Hew,CS^Hin,SE^Yong,JWH^Gouk,SS^Tanaka,M^1995^1^In-vitro co2 enrichment of cam orchid plantlets^174^70^5^721-736^^^^^Sep^^^^^4446*?A^4445^Increased growth of an in vitro-propagated CAM orchid hybrid Mokara 'White' was obtained using a novel method of CO*@P enrichment in an optimized photoautotrophic open system compared with the conventional closed system of culture. The opt*Aimization process for the open system involved the manipulation of external CO2 concentrations (0.03%, 1% and 10%), sucros*Be requirements, light intensities (80 and 200 mu mol m(-2) s(-1)) and the venting of headspace ethylene from the culture v*Cessels. The physiological basis for increased growth in these CAM orchid plantlets after three months was attributed to th*De direct effects of elevated CO2 resulting in higher CAM activity for the plantlets and to the elevated CO2 present in the*E system which might interact with the ethylene present thereby reducing the inhibition of growth of plantlets due to ethylene.*G820^5^Houpis,JLJ^Pushnik,J^Anschel,D^Anderson,P^Demaree,R^1995^1^Intraspecific variability of photosynthetic traits of pinus- ponderosa subjected to long-term exposure to elevated co2^8^108^2^62^^^^^Jun*I821^3^Jones,P^Collins,LM^Ingram,KT^1995^1^Open-top chambers for field studies of crop response to elevated co2 and temperature^256^38^4^1195-1201^^^^^Jul-Aug^^^^^4449*KA^4448^A new design for Open Top Chambers (OTCs) is described. In addition to providing CO2 controls as do several other e*Lxisting OTCs, the system is designed to provide elevated temperature control. To provide a more natural vertical microclim*Mate profile, the newly designed system pulls air down through the chamber and out the bottom rather than injecting air at *Nthe bottom and venting it out the top of the chamber. A prototype was constructed and performance tests were conducted. Ov*Oer a 24-h test period with a CO2 concentration setpoint of 660 ppm, individual measurements of concentration taken every 5*P min averaged 660.5 ppm with a standard deviation of 26.6 ppm. Temperature controls were rested over 24-h periods for two *Qdifferent setpoints-ambient +4 degrees C and ambient +6 degrees C. For the two test periods the average chamber temperatur*Re measurements were 3.98 degrees and 5.99 degrees C above ambient, respectively. Twenty chambers based on the prototype de*Ssign were constructed and installed at the International Rice Research Institute, Los Banos, Philippines. As intended, the chambers are currently being used to conduct research on rice crop response to elevated CO2 and temperature.*U822^4^King,AW^Emanuel,WR^Wullschleger,SD^Post,WM^1995^1^In search of the missing carbon sink - a model of terrestrial biospheric response to land-use change and atmospheric co2^257^47^4^501-519^^^^^Sep^^^^^4451*WA^4450^Estimates of the net exchange of carbon between the terrestrial biosphere and the atmosphere may be too large becau*Xse the models of carbon release from changes in land use do not allow for enhanced carbon assimilation by the terrestrial *Ybiosphere in response to increasing atmospheric CO2. We address this deficiency with a model of terrestrial biosphere that*Z includes both ecosystem response to land-use perturbation and vegetation response to atmospheric CO2. Model inputs specif*[y the areas affected by land-use change since 1700. The carbon dynamics of the affected areas are described by an area dis*\tribution function for vegetation carbon density and a compartment model of carbon in vegetation, litter, and soil. Vegeta*]tion growth is modeled as the difference between net primary production (NPP) and mortality. NPP, the net flux of carbon f*^rom atmosphere to vegetation, is a logistic function of vegetation carbon density. The response of NPP to atmospheric CO2 *_is modeled with three response functions: a logarithmic, a rectangular- hyperbolic, and a response function derived from a*` biochemical model of C-3 photosynthesis. The response functions are parameterized by ecosystem type with data from CO2 ex*aposure experiments. Elevated CO2 affects the NPP of both undisturbed and recovering ecosystems. We use the model to test t*bhe hypothesis that the CO2 enhancement of terrestrial NPP explains the historical missing carbon sink of the the global ca*crbon cycle budget. Our estimates of the biosphere's CO2 enhanced carbon flux are much smaller than the reconstructed missing carbon sink. We conclude that our model results do not support the hypothesis.*e823^4^Manderscheid,R^Bender,J^Jager,HJ^Weigel,HJ^1995^1^Effects of season long co2 enrichment on cereals .2. Nutrient concentrations and grain quality^169^54^3^175-185^^^^^Jul^^^^^4453*gA^4452^Two cultivars each of spring wheat (Triticum aestivum L., cv. Star and cv. Turbo) and spring barley (Hordeum vulgar*he L., cv. Alexis and cv. Arena) were exposed season-long to ambient (384 p.p.m.) and above ambient CO2 concentrations (551*i, 718 p.p.m.) in open-top chambers. Plant samples were taken at the booting stage and at maturity. Concentrations (grams p*jer gram dry weight) of macro (Ca, K, Mg, N, P, S) and micronutrients (Fe, Mn, Zn) were measured in stems, leaves, ears and*k grains, and the amino acid composition of the grain protein was determined. For most nutrients studied the sequence and s*lize of the response of the four cereal plants to the CO, enrichment was cv. Arena < cv. Alexis < cv. Turbo < cv. Star. The*m CO2 enrichment usually produced a decrease in nutrient concentrations, which was already detectable at the booting stage *nand was further enhanced until plant maturity. Nutrient concentrations of straw were more affected than those of grains. T*ohe decrease in concentration was greatest for N followed by Mg, Ca and K, and the maximum decrease as compared with ambien*pt CO2 amounted to 43%, 35%, 33% and 21% for straw, and 30%, 13%, 28% and - 6% for grains. Concentrations of micronutrients*q were also found to be partially decreased by about 10-30%. At 718 p.p.m. CO, grain protein concentrations were 96% (cv. A*rrena), 85% (cv. Alexis), 72% (cv. Turbo) and 70% (cv. Star) of the ambient CO2 value, however, the index of essential amin*so acids was increased. Overall, the CO2 enrichment did not decrease the nutrient harvest index of all nutrients except of sulphur. Nutrient use efficiency increased by high CO2 levels for cv. Star and cv. Turbo and decreased for cv. Arena.*u824^2^McElwain,JC^Chaloner,WG^1995^1^Stomatal density and index of fossil plants track atmospheric carbon-dioxide in the paleozoic^52^76^4^389-395^^^^^Oct^^^^^4455*wA^4454^It has been demonstrated that the leaves of a range of forest tree species have responded to the rising concentrati*xon of atmospheric CO2 over the last 200 years by a decrease in both stomatal density and stomatal index. This response has*y also been demonstrated experimentally by growing plants under elevated CO2 concentrations. Investigation of Quaternary fo*zssil leaves has shown a corresponding stomatal response to changing CO2 concentrations through a glacial-interglacial cycl*{e, as revealed by ice core data. Tertiary leaves show a similar pattern of stomatal density change, using palynological ev*|idence of palaeo-temperature as a proxy measure of CO2 concentration. The present work extends this approach into the Pala*}eozoic fossil plant record. The stomatal density and index of Early Devonian, Carboniferous and Early Permian plants has b*~een investigated, to test for any relationship that they may show with the changes in atmospheric CO2 concentration, deriv*ed from physical evidence, over that period. Observed changes in the stomatal data give support to the suggestion from phy*sical evidence, that atmospheric CO2 concentrations fell from an Early Devonian high of 10-12 times its present value, to *one comparable to that of the present day by the end of the Carboniferous. These results suggest that stomatal density of *fossil leaves has potential value for assessing changes in atmospheric CO2 concentration through geological time. (C) 1995 Annals of Botany Company*825^4^Newbery,RM^Wolfenden,J^Mansfield,TA^Harrison,AF^1995^1^Nitrogen, phosphorus and potassium uptake and demand in agrostis-capillaris - the influence of elevated co2 and nutrient supply^84^130^4^565-574^^^^^Aug^^^^^4457*A^4456^Responses to elevated CO2 have been studied using Agrostis capillaris L., an upland grass which is abundant on nutr*ient- poor soils. Plants were grown in sand culture with a wide range of nitrogen, phosphorus and potassium concentrations*, and the impact of CO2 on the demand for nutrients was determined using isotopic root bioassays. Plants grown with the sm*allest concentrations of N and P showed typical foliar symptoms associated with deficiency of these elements. However, eve*n when supplies of N and P were limiting to growth, additional CO2 (250 ppm above ambient) influenced neither total N nor *total P in above-ground tissues, nor nutrient demands as indicated by the bioassay. The estimates of the demand of the pla*nts for K from the Rb-86 bioassay indicated an appreciable increase when plants were raised in elevated CO2. For plants of* the same size with the same nutrient supply, those grown in elevated CO2 consistently displayed an increased internal dem*and for K. Uptake of K was not, however, enhanced by elevated CO2 even in non-limiting conditions and it might therefore b*e limited by a factor other than K supply. The overall conclusion from the experiments is that when A. capillaris is grown* in elevated CO2, uptake of N, P and K fails to increase proportionally with dry mass. This was true even when nutrient su*pplies were adequate, and it appears that nutrient-use-efficiency might increase to enable the plants to maintain growth in elevated CO2.*826^4^Nie,GY^Hendrix,DL^Long,SP^Webber,AN^1995^1^The effect of elevated co2 concentration throughout the growth of a wheat crop in the field on the expression of photosynthetic genes in relation to carbohydrate accumulation^8^108^2^92^^^^^Jun*827^2^Nowak,EJ^Martin,CE^1995^1^Effect of elevated co2 on nocturnal malate accumulation in the cam species tillandsia-ionantha and crassula-arborescens^79^31^3^441-444^^^^^^^^^^4460*A^4459^The effect of elevated CO2 on overnight malate accumulation in the CAM epiphyte Tillandsia ionantha and the CAM ter*restrial species Crassula arborescens was compared. Both species showed an increase in nocturnal accumulation of malate wi*th increasing CO2 concentrations. This study is the first to show an increase in nighttime malate accumulation with increa*sing levels of CO2 at near-ambient concentrations in a CAM plant. The results indicate that some CAM plants can respond to increasing levels of CO2 in the atmosphere, potentially leading to an increase in productivity.*828^4^Pennanen,AH^Vu,JCV^Allen,LH^Bowes,G^1995^1^Elevated co2 and temperature effects on enzymes of sucrose and starch synthesis in soybean^8^108^2^90^^^^^Jun*829^4^Penuelas,J^Biel,C^Save,R^Estiarte,M^1995^1^Detrimental effects of fluctuating high co2 concentrations on peppers^79^31^3^361-370^^^^^^^^^^4463*A^4462^Plants of pepper (Capsicum annuum L.) were grown in controlled environment chambers at ambient (360 mu mol mol(-1))* and fluctuating pulse-enriched CO2 concentrations (700 mu mol mol(- 1) daily average, ranging from 500 to 3500 mu mol mol*(-1) = ECO(2)) under two water regimes. A decrease in plant growth and yield together with frequent visual injuries was fo*und in plants growing under ECO(2). Root/shoot ratio was greater, chlorophyll concentration and respiration rates were low*er, and stomatal conductance and relative importance of alternative pathway respiration were higher under ECO(2). The nega*tive effects of ECO(2) were more intense under high water availability. The symptoms produced by ECO(2) were similar to th*ose of resource limitation, and were alleviated with increased nutrient supply. Constant elevated CO2 concentrations (700 *mu mol mol(-1)) increased pepper production and did not produce any of the injuries described for this erratic ECO(2) trea*tment. Thus, it is probably the erratic nature of the CO2 concentration and not the gas itself that was causing the injury.4a1d21403494c5178cdc2c <36A739D9.D8A8CEB4@bellatlantic.net>-21-Jan-1999-09:45:43--0500-(EST 916912910 Ndel Nskip Nsave r*830^4^Perezsoba,M^Dueck,TA^Puppi,G^Kuiper,PJC^1995^1^Interactions of elevated co2, nh3 and o-3 on mycorrhizal infection, gas-exchange and n-metabolism in saplings of scots pine^206^176^1^107-116^^^^^Sep^^^^^4465-21-Jan-1999-12:48:33--0500-(EST*A^4464^Four-year-old saplings of Scots pine (Pinus sylvestris L.) were exposed for 11 weeks in controlled-environment cham*bers to charcoal-filtered air, or to charcoal-filtered air supplemented with NH3 (40 mu g m(-3)), O-3 (110 mu g m(-3) duri*ng day/ 40 mu g m(-3) during night) or NH3 + O-3. All treatments were carried out at ambient (350 mu L L(-1)) and at eleva*ted CO2 concentration (700 mu L L(-1)). Total tree biomass, mycorrhizal infection, net CO2 assimilation (P-n), stomatal co*nductance (g(s)), transpiration of the shoots and NH3 metabolization of the needles were measured. In ambient CO2 (1) gase*ous NH3 decreased mycorrhizal infection, without significantly affecting tree biomass or N concentration and it enhanced t*he activity of glutamine synthetase (GS) and glutamate dehydrogenase (GDH) in one-year-old needles; (2) ozone decreased my*corrhizal infection and the activity of GS in the needles, while it increased the activity of GDH; (3) exposure to NH3 + O*-3 lessened the effects of single exposures to NH3 and O-3 on reduction of mycorrhizal infection and on increase in GDH ac*tivity. Similar lessing effects on mycorrhizal infection as observed in trees exposed to NH3 + O-3 at ambient CO2, were me*asured in trees exposed to NH3 + O-3 at elevated CO2. Exposure to elevated CO2 without pollutants did not significantly af*fect any of the parameters studied, except for a decrease in the concentration of soluble proteins in the needles. Elevate*d CO2 + NH3 strongly decreased root branching and mycorrhizal infection and temporarily stimulated P-n and g(s). The expos*ure to elevated CO2 + NH3 + O-3 also transiently stimulated P-n. The possible mechanisms underlying and integrating these *effects are discussed. Elevated CO2 clearly did not alleviate the negative effects of NH3 and O-3 on mycorrhizal infection*. The significant reduction of mycorrhizal infection after exposure to NH3 or O-3, observed before significant changes in *gas exchange or growth occurred, suggest the use of mycorrhizal infection as an early indicator for NH3 and O-3 induced stress. Nskip Nsave read Nget 438005030 4f6cacad28250ce39265e555e3bce5d4 <199901270204.VAA28576@mail3.uts.ohio-state.edu>-*831^2^Piastuch,WC^Stryjewski,EC^1995^1^Arabidopsis-thaliana growth, morphology and ultrastructure at elevated and super-elevated co2 concentrations^8^108^2^62^^^^^Jun26116 Ndel Nskip Nsave read Nget 1702055713 63c939371a6c924e80852dfffc0d6f0a*832^3^Rao,MV^Hale,BA^Ormrod,DP^1995^1^Amelioration of ozone-induced oxidative damage in wheat plants grown under high-carbon dioxide - role of antioxidant enzymes^8^109^2^421-432^^^^^Oct^^^^^44680:07--0500-(EST 917451114 Ndel Nskip Nsave read *A^4467^O-3-induced changes in growth, oxidative damage to protein, and specific activities of certain antioxidant enzymes *were investigated in wheat plants (Triticum aestivum L. cv Roblin) grown under ambient or high CO2. High CO2 enhanced shoo*t biomass of wheat plants, whereas O-3 exposure decreased shoot biomass. The shoot biomass was relatively unaffected in pl*ants grown under a combination of high CO2 and O-3. O-3 exposure under ambient CO2 decreased photosynthetic pigments, solu*ble proteins, and ribulose-1,5-bisphosphate carboxylase/oxygenase protein and enhanced oxidative damage to proteins, but t*hese effects were not observed in plants exposed to O-3 under high CO2. O-3 exposure initially enhanced the specific activ*ities of superoxide dismutase, peroxidase, glutathione reductase, and ascorbate peroxidase irrespective of growth in ambie*nt or high CO2. However, the specific activities decreased in plants with prolonged exposure to O-3 under ambient CO2 but *not in plants exposed to O-3 under high CO2. Native gels revealed preferential changes in the isoform composition of super*oxide dismutase, peroxidases, and ascorbate peroxidase of plants grown under a combination of high CO2 and O-3. Furthermor*e, growth under high CO2 and O-3 led to the synthesis of one new isoform of glutathione reductase. This could explain why *plants grown under a combination of high CO2 and O-3 are capable of resisting O-3-induced damage to growth and proteins compared to plants exposed to O-3 under ambient CO2.et 1618428005 5ba3c35958c4630ecf79feab4dad08ab <199902030233.VAA08003@*833^3^Reuveni,J^Mayer,AM^Gale,J^1995^1^High ambient carbon-dioxide does not affect respiration by suppressing the alternative, cyanide-resistant pathway^52^76^3^291-295^^^^^Sep^^^^^44709-12:15:49--0500-(EST) 918044167 Ndel Nskip Nsave read Nge*A^4469^Total dark respiration (v(t)), cytochrome pathway (v(eyt)), alternative pathway (v(alt)) and residual (v(res)) resp*iration were measured in Lemna gibba plants, by the use of pathway inhibitors. NaCN was used to inhibit v(eyt) and SHAM (s*alicylhydroxamic acid) to inhibit v(alt). Residual respiration (v(res)) was about 5% of v(t). The effect of high (100 Pa) *and low (0 Pa) carbon dioxide partial pressure ([CO2) on v(t), v(cyt) and v(alt) was determined from both CO2 efflux and O*(2)uptake measurements. The higher [CO2] suppressed v(t) by about 30%. When respiration operated through the cytochrome pa*thway only. in the absence of v(alt), it was suppressed by about 12% as measured by the O-2 uptake of submerged Lemna fron*ds or by about 40% as measured by CO2 efflux from Boating fronds. The higher [CO2] treatment had only a small effect oil r*espiration, when v(alt) alone operated. There was no evidence of a specific suppression of the v(alt) pathway by high [CO2*]. Succinic dehydrogenase activity of the mitochondria of roots of Medicago sativum was reduced by 18%, when the mitochond*ria were pre-treated with 120 as compared to 34 Pa [CO2]. There was no such effect on cytochrome c oxidase activity of mit*ochondria under the same conditions. It is concluded that there is no evidence for the hypothesis that the high [CO2] supp*ression of respiration is a result of a CO2 effect on the non- phosphorylating alternative respiration pathway. (C) 1995 Annals of Botany Company Nskip Nsave read Nget 1708428122 578ce981f55a40248acf3f55a57f8ffc -25-Feb-1999-17:22:22--0500-(EST 920008932 Ndel N+A^4475^Seedlings of perennial ryegrass (Lolium perenne L. cv. Parcour) and white clover (Trifolium repens L. cv. Karina) g+rown at five different plant densities were exposed to ambient (390 ppm) and elevated (690 ppm) CO2 concentrations, After +43 d the effects of CO2 enrichment and plant density on growth of shoot and root, nitrogen concentration of tissue, and mi+crobial biomass carbon (C-mic) in soil were determined, CO2 enrichment of Lolium perenne increased shoot growth on average+ by 17% independent of plant density, while effects on root biomass ranged between -4% and +107% due to an interaction wit+ h plant density, Since tiller number per plant was unaffected by elevated CO2, the small response of shoot growth to CO2 e+ nrichment was attributed to low sink strength. A significant correlation between nitrogen concentration of total plant bio+ mass and root fraction of total plant dry matter, which was not changed by CO2 enrichment, indicates that nitrogen status + of the plant controls biomass partitioning and the effect of CO2 enrichment on root growth. Effects of elevated CO2( )and + plant density on shoot and root growth of Trifolium repens were not significantly interacting and mean CO2 related increas+e amounted to 29% and 66%, respectively, However, growth enhancement due to elevated CO2 was strongest when leaf area inde+x was lowest. Total amounts of nitrogen in shoots and roots were bigger at 690 ppm than at 390 ppm CO2. There was a significant increase in C-mic in experiments with both species whereas plant density had no substantial effect.69200.AA92006034837^1^Sicher,R^1995^1^Diurnal amylolytic activity in soybean leaves grown at ambient and elevated co2^8^108^2^55^^^^^Jun<+838^2^Stryiewski,EC^Vieglais,DA^1995^1^Changes in leaf structure of 3 native florida plant-species grown in elevated co2 concentrations^8^108^2^63^^^^^June597738 <3.0.3.32.19990226182153.00f3e45c@mail>-26-Feb-1999-18:23:17--0500-(EST 920094072839^2^Tomlinson,PT^Anderson,PD^1995^1^Elevated co2 compensates for water-stress in red oak^8^108^2^36^^^^^JunFeb-1999-09:+840^3^Torbert,HA^Prior,SA^Rogers,HH^1995^1^Elevated atmospheric carbon-dioxide effects on cotton plant residue decomposition^110^59^5^1321-1328^^^^^Sep-Oct^^^^^448102 Ndel Nskip Nsave read Nget 331599157 0ab08b70c3fa0fdfbd0820039a6b8a3a <0F7U+A^4480^Assessing the impact of elevated atmospheric CO2 concentration on the global environment is hampered due to a lack +of understanding of global C cycling. Carbon fixed within plant biomass ultimately enters the soil via plant residues, but+ the effects of elevated-CO2-grown plant material on decomposition rates and long-term soil C storage are unknown. The obj+ective of this study was to determine the decomposition rate of plant residues grown under an elevated CO2 environment as +affected by soil type. Cotton (Gossypium hirsuturn L. 'Delta Pine 77') samples were collected from a free-air CO2 enrichme+nt (550 mu L L(-1)) experiment. The plant residues were incubated under ambient CO2 conditions to determine decomposition +rates of leaves, stems, and roots and potential N and P mineralization- immobilization in three soil series: a Blanton loa+my sand (loamy siliceous, thermic Grossarenic Paleudult), a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudul+t), and a Houston clay loam (very fine, montmorillonitic Typic Chromudert). No significant difference was observed between+ plant residue grown under CO2 enrichment vs. ambient CO2 conditions for soil respiration or P mineralization- immobilizat+!ion. Significantly greater net N immobilization was observed during the incubation in all soil types for plant residue gro+"wn at elevated CO2. These results indicate that while decomposition of plant residue may not be reduced by CO2 enrichment, N dynamics may be markedly changed.x2.osu.edu>-27-Feb-1999-17:58:14--0500-(EST 920268102 Ndel Nskip Nsave read Nget 1412+$841^2^Townend,J^Dickinson,AL^1995^1^A comparison of rooting environments in containers of different sizes^206^175^1^139-146^^^^^Aug^^^^^4483e404ddca1850794927b4bf908cc62 <0F7U00MFE54PR3@mx2.osu.edu>-27-Feb-1999-17:58:15--0500-(EST 920268102 Nd+&A^4482^Experiments on plants are often carried out in growth chambers or greenhouses which necessitate the use of an artif+'icial rooting environment, though this is seldom characterized in detail. Measurements were made to compare the rooting en+(vironment in large boxes (0.25 m(3)) with that in small pots (0.19, 0.55 and 1.90 dm(3)) in naturally lit chambers. Diurna+)l temperature fluctuations of 14.6, 11.6 and 7.7 degrees C occurred in the pots compared with only 1.9 degrees C in the bo+*xes. Soil drying to a matric potential of -50 kPa was approximately 25 times faster in the pots. The mean heights of 2 yea++r old Sitka spruce (Picea sitchensis (Bong.) Carr.) seedlings grown throughout their second growing season in the three si+,zes of pots were 38, 62 and 92% of the mean height of those grown in the boxes. Soil solution nutrient concentrations in t+-he boxes were considerably increased by soil drying, an aspect which seems to have received little attention in experiment+.s involving artificially imposed drought. An alternative system of constraining the roots of individual plants within nylo+/n fabric bags, embedded in larger volumes of soil, to facilitate harvesting of complete root systems is described. The importance of the rooting environment in determining the outcome of physiological experiments is also briefly discussed.7W00+1842^6^Vose,JM^Elliott,KJ^Johnson,DW^Walker,RF^Johnson,MG^Tingey,DT^1995^1^Effects of elevated co2 and n fertilization on soil respiration from ponderosa pine (pinus-ponderosa) in open-top chambers^155^25^8^1243-1251^^^^^Aug^^^^^4485 4765446a34+3A^4484^We measured growing season soil CO2 evolution under elevated atmospheric CO2 and soil nitrogen (N) additions. Our o+4bjectives were to determine treatment effects, quantify seasonal variation, and determine regulating mechanisms. Elevated +5CO2 treatments were applied in open-top chambers containing 3-year- old ponderosa pine (Pinus ponderosa Dougl. ex Laws.) s+6eedlings. Nitrogen applications were made annually in early spring. The experimental design was a replicated factorial com+7bination of CO2 (ambient, +175, and +350 mu L . L(-1) CO2) and N (0, 10, and 20 g . m(-2) N as ammonium sulfate). Soils we+8re irrigated to maintain soil moisture at >25%. Soil CO2 evolution was measured over diurnal periods (20-22 h) in April, J+9une, and October 1993 using a flow-through, infrared gas analyzer measurement system. To examine regulating mechanisms, we+: linked our results with other studies measuring root biomass with destructive sampling and root studies using minirhizotr+;on techniques. Significantly higher soil CO2 evolution was observed in the elevated CO2 treatments in April and October; N+< effects were not significant. In October, integrated daily values for CO2 evolution ranged from 3.73 to 15.68 g CO2 . m(-+= 2)day(-1) for the ambient CO2 + 0 N and 525 mu L . L(-1) CO2 + 20 g . m(-2) N, respectively. Soil CO2 flux among treatmen+>ts was correlated with coarse root biomass (r(2) = 0.40; p >F = 0.0380), indicating that at least some of the variation ob+?served among treatments was related to variation in root respiration. Across ail sample periods and treatments, there was +@a significant correlation (r(2) = 0.63; p >F = 0.0001) between soil CO2 evolution acid percent fungal hyphae observed in m+Ainirhizotron tubes. Hence, some of the seasonal and treatment variation was also related to differences in heterotrophic activity.ycle processes. The CO2 refixation by Rubisco in the bundle sheath was described using a widely accepted C3 photo+C843^2^Ziska,LH^Bunce,JA^1995^1^Growth and photosynthetic response of 3 soybean cultivars to simultaneous increases in growth temperature and co2^37^94^4^575-584^^^^^Aug^^^^^4487refixation by the C3-cycle in the bundle sheath, and CO2 leakage f+EA^4486^Three soybean (Glycine max L. Merr.) cultivars (Maple Glen, Clark and CNS) were exposed to three CO2 concentrations+F (370, 555 and 740 mu mol mol(-1)) and three growth temperatures (20/15 degrees, 25/20 degrees and 31/26 degrees C, day/ni+Gght) to determine intraspecific differences in single leaf/whole plant photosynthesis, growth and partitioning, phenology +Hand final biomass. Based on known carboxylation kinetics, a synergistic effect between temperature and CO2 on growth and p+Ihotosynthesis was predicted since elevated CO2 increases photosynthesis by reducing photorespiration and photorespiration +Jincreases with temperature. Increasing CO2 concentrations resulted in a stimulation of single leaf photosynthesis for 40-6+K0 days after emergence (DAE) at 20/15 degrees C in all cultivars and for Maple Glen and CNS at all temperatures. For Clark+L, however, the onset of flowering at warmer temperatures coincided with the loss of stimulation in single leaf photosynthe+Msis at elevated CO2 concentrations. Despite the season-long stimulation of single leaf photosynthesis, elevated CO2 concen+Ntrations did not increase whole plant photosynthesis except at the highest growth temperature in Maple Glen and CNS, and t+Ohere was no synergistic effect on final biomass. Instead, the stimulatory effect of CO2 on growth was delayed by higher te+Pmperatures. Data from this experiment suggest that: (1) intraspecific variation could be used to select for optimum soybea+Qn cultivars with future climate change; and (2) the relationship between temperature and CO2 concentration may be expressed differently at the leaf and whole plant levels and may not solely reflect known changes in carboxylation kinetics.CEY, +S844^3^Ziska,LH^Weerakoon,W^Hong,LW^1995^1^Photosynthetic acclimation of field-grown rice to elevated co2^8^108^2^92^^^^^JunDS HOLE OCEANOG INST, WOODS HOLE, MA 02543. SMITHSONIAN ENVIRONM RES CTR, EDGEWATER, MD 21037. MICHIGAN STATE UNIV, KELL+U845^7^Clifford,SC^Black,CR^Roberts,JA^Stronach,IM^Singletonjones,PR^Mohamed,AD^Azamali,SN^1995^1^The effect of elevated atmospheric co2 and drought on stomatal frequency in groundnut (arachis-hypogaea (L))^78^46^288^847-852^^^^^Jul^^^^^4490phe+WA^4489^The effects of elevated atmospheric CO2, alone or in combination with water stress, on stomatal frequency in ground+Xnut (Arachis hypogaea (L.) cv. Kadiri-3) were investigated. CO2 exerted significant effects on stomatal frequency only in +Yirrigated plants. The effects of drought on leaf development outweighed the smaller effects of CO2 concentration, although+Z reductions in stomatal frequency induced by elevated atmospheric CO2 were still observed. When stands of groundnut were g+[rown under irrigated conditions with unrestricted root systems, an increase in atmospheric CO2 from 375 to 700 ppmv decrea+\sed stomatal frequency on both leaf surfaces by up to 16%; in droughted plants, stomatal frequency was reduced by 8% on th+]e adaxial leaf surface only, Elevated atmospheric CO2 promoted larger reductions in leaf conductance than the changes in s+^tomatal frequency, indicating partial stomatal closure. As a result, the groundnut stands grown at elevated CO2 utilized t+_he available soil moisture more slowly than those grown under ambient CO2, thereby extending the growing period. Despite t+`he large variations in cell frequencies induced by drought, there was no treatment effect on either stomatal index or the +aadaxial/abaxial stomatal frequency ratio. The data suggest that the effects of future increases in atmospheric CO2 concent+bration on stomatal frequency in groundnut are likely to be small, especially under conditions of water stress, but that th+ce combination of associated reductions in leaf conductance and enhanced assimilation at elevated CO2 will be important in semi-arid regions.d survival and growth rates. The negative effects of salinity on germination were greater at the high-t+e846^3^Eamus,D^Duff,GA^Berryman,CA^1995^1^Photosynthetic responses to temperature, light flux-density, co2 concentration and vapor-pressure deficit in eucalyptus tetrodonta crown under co2 enrichment^35^90^1^41-49^^^^^^^^^^4492inity but not to +gA^4491^Seeds of Eucalyptus tetrodonta were sown under ambient or CO2 enriched (700 mu l litre(-1)) conditions in tropical +hAustralia. Four sets of measurements were made, the first two after 12 months, on trees growing either in pots or planted +iin the ground. The third and fourth set were made after 18 and 30 months exposure to CO2 enrichment, on trees growing in t+jhe ground After 12 months exposure to CO2 enrichment, the rate of light-saturated assimilation (A(max)) of plants growing +kin the ground was determined. Responses of CO2 assimilation to variations in leaf temperature, leaf-to-air vapour,pressure+l deficit (LAVPD), Eight flux density and CO2 concentration were also measured in the laboratory using plants growing in la+mrge pots. There was no significant difference in A(max) between pot and ground located plants. Assimilation of E. tetrodon+nta was relatively insensitive to changes in LAVPD for both ambient and CO2 enriched plants but the temperature optimum of +oassimilation was increased in plants grown and measured under CO2 enrichment. Plants grown with CO2 enrichment had an incr+peased rate of light-saturated assimilation and apparent quantum yield I-vas significantly inn eased by CO2 enrichment. rn +qcontrast, carboxylation efficiency was decreased significantly by CO2 enrichment. After 18 months growth with CO2 enrichme+rnt, there was no sign of a decline in assimilation I ate compared to measurements undertaken after 12 months, At low LAVPD+s values, assimilation rate was not influenced by CO2 treatment but at moderate to high LAVPD, plants grown under CO2 enric+thment exhibited a larger assimilation rate than control plants. Specific leaf area and chlorophyll contents decreased in r+uesponse to CO2 enrichment, whilst foliar soluble protein contents and chlorophyll a/b ratios were unaffected by CO2 treatm+vent. Changes in soluble protein and chlorophyll contents in response to CO2 enrichment did not account for changes in assi+wmilation between treatments. After 30 months exposure to CO2 enrichment, the rate of light-saturated assimilation was appr+xoximately 50% larger than controls and this enhancement was larger than that observed after 18 months exposure to CO2 enrichment. 3-fold and 6-7-fold differences in biomass between fully green and variegated cultivars of oleander and willow my+z847^2^Fredeen,AL^Field,CB^1995^1^Contrasting leaf and ecosystem co2 and h2o exchange in avena- fatua monoculture - growth at ambient and elevated co2^91^43^3^263-271^^^^^Mar^^^^^4494e the leaf area ratio and specific leaf area compared with th+|A^4493^Elevated CO2 (ambient + 35 Pa) increased shoot dry mass production in Avena fatua by similar to 68% at maturity. Th+}is increase in shoot biomass was paralleled by an 81% increase in average net CO2 uptake (A) per unit of leaf area and a 6+~5% increase in average A at the 'ecosystem' level per unit of ground area. Elevated CO2 also increased 'ecosystem' A per u+nit of biomass. However, the products of total leaf area and light- saturated leaf A divided by the ground surface area ov+er time appeared to lie on a single response curve for both CO2 treatments. The approximate slope of the response suggests+ that the integrated light saturated capacity for leaf photosynthesis is similar to 10-fold greater than the 'ecosystem' r+ate. 'Ecosystem' respiration (night) per unit of ground area, which includes soil and plant respiration, ranged from -20 (+at day 19) to -18 (at day 40) mu mol m(-2) s(-1) for both elevated and ambient CO2 Avena. 'Ecosystem' below-ground respira+tion at the time of seedling emergence was similar to -10 mu mol m(-2) s(- 1), while that occuring after shoot removal at +the termination of the experiment ranged from -5 to -6 mu mol m(-2) s(-1). Hence, no significant differences between eleva+ted and ambient CO2 treatments were found in any respiration measure on a ground area basis, though 'ecosystem' respiratio+n on a shoot biomass basis was clearly reduced by elevated CO2. Significant differences existed between leaf and 'ecosyste+m' water flux. In general, leaf transpiration (E) decreased over the course of the experiment, possibly in response to lea+f aging, while 'ecosystem' rates of evapotranspiration (ET) remained constant, probably because falling leaf rates were of+fset by an increasing total leaf biomass. Transpiration was lower in plants grown at elevated CO2, though variation was hi+gh because of variability in leaf age and ambient light conditions and differences were not significant. In contrast, 'eco+system' evapotranspiration (ET) was significantly decreased by elevated CO2 on 5 out of 8 measurement dates. Photosyntheti+c water use efficiencies (A/E at the leaf level, A/ET at the 'ecosystem' level) were increased by elevated CO2. Increases were due to both increased A at leaf and 'ecosystem' level and decreased leaf E and 'ecosystem' ET.to elevated CO2, where+848^7^Grant,RF^Kimball,BA^Pinter,PJ^Wall,GW^Garcia,RL^Lamorte,RL^Hunsaker,DJ^1995^1^Carbon-dioxide effects on crop energy-balance - testing ecosys with a free-air co2 enrichment (face) experiment^48^87^3^446-457^^^^^May-Jun^^^^^4496rough an in+A^4495^Elevated CO2 concentrations (C-e) have been observed to decrease short-term plant water use under controlled condit+ions by increasing stomatal resistance. The extent to which this decrease occurs over a growing season in the held is unce+rtain, however, because stomatal resistance is only one of many mechanisms that control water use. In this study, we teste+d the ecosystem simulation model ecosys, which reproduces an hourly energy balance through soil-vegetation systems under d+efined atmospheric boundary renditions, using energy exchange data measured as part of the Free-Air CO2 Enrichment (FACE) +experiment at C-e = 550 vs. 370 mu mol mol(-1). The model reproduced reductions in measured upward latent heat fluxes that+ varied from -10 to +40 W m(-2), depending on atmospheric conditions. In the model, the primary effect of elevated C-e on +latent heat fluxes was through canopy stomatal conductance. This effect was largely offset by secondary effects through ca+nopy temperature that enabled the model to reproduce measured changes in sensible heat fluxes. The total effect simulated +by ecosys of C-e = 550 vs. 370 mu mol mol(-1) on evapotranspiration during the entire PACE experiment was a reduction of 7+%. This reduction compares with one of 11% estimated from accumulated daily measurements of latent heat flux. In the model+, the different effects of C-e on plant water use depend on atmosphere and soil boundary conditions, and are highly dynami+c. Consequently the simulated C-e-water use relationship is likely to be site-specific. The use of models such as ecosys allows site-specific boundary conditions to be considered in the study of C-e effects on plant growth and water use.obal m+849^4^Groninger,JW^Seiler,JR^Zedaker,SM^Berrang,PC^1995^1^Effects of elevated co2, water-stress, and nitrogen level on competitive interactions of simulated loblolly-pine and sweetgum stands^155^25^7^1077-1083^^^^^Jul^^^^^4498ss of this modeli+A^4497^Loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.) were grown in mixed stands and in monocult+ures at 2.54 X 2.54 cm spacing in controlled-environment chambers. Treatments consisted of present (ambient) and projected+ future (ambient + 400 ppm) carbon dioxide (CO2) concentrations, drought-stressed, and well-watered conditions, and low (2+0 kg N/ha) and high (474 kg N/ha) nitrogen application rates. After two accelerated growing cycles, total biomass of both +species was significantly greater under elevated CO2. No significant interactions between CO2 concentration and water avai+lability, nitrogen availability, or stand type were observed. Competitive interactions between loblolly pine and sweetgum +were strongly influenced by water availability, but not CO2 concentration. Assessment of species response to CO2 was depen+dent upon growth in monoculture or mixture. Under low water availability, data from monocultures suggested that sweetgum h+ad a stronger growth response to elevated CO2 concentrations than loblolly pine. In contrast, results from mixed-species s+tands showed that the competitive status of loblolly pine and sweetgum did not change under the high CO2 concentration. Th+ese results underscore the value of growing co-occurring species in mixed stands under varying levels of multiple resources for the determination of relative performance under future environments.Y; SOYBEAN CANOPY PHOTOSYNTHESIS; PINUS-TAEDA S+850^6^Hadley,P^Batts,GR^Ellis,RH^Morison,JIL^Pearson,S^Wheeler,TR^1995^1^Temperature-gradient chambers for research on glo+bal environment change .2. a twin-wall tunnel system for low- stature, field-grown crops using a split heat-pump^9^18^9^1055-1063^^^^^Sep^^^^^4500 demonstrates that the percentage increase in plant growth produced by raising the air's CO2 cont+A^4499^A temperature gradient chamber (TGC) is described which enables elevated CO2 concentrations and a dynamic temperatu+re gradient to be imposed on field crops throughout their life cycle under standard husbandry. Air is circulated through t+wo double-walled polyethylene-covered tunnels connected to a split heat pump system to give a near-linear temperature grad+ient along each tunnel, Solar energy gain along each tunnel and exchange with outer tunnel air flow contribute to the temp+erature gradient and also produce diurnal and seasonal temperature fluctuations corresponding to ambient conditions, Mean +temperature gradients of between 3 and 5 degrees C have been recorded throughout the growing seasons of crops of lettuce, +carrot, cauliflower and winter wheat, Elevated or present CO2 concentrations are maintained in each of two pairs of tunnel+s throughout the cropping season using pure CO2 injected through motorized needle valves. This system can realistically si+mulate aspects of the effects of projected future environmental change on crop growth, development and yield, and in particular the possible interaction of the effects of increased CO2 and temperature. strongly dependent on CO2 concentration, +851^5^Horie,T^Nakagawa,H^Nakano,J^Hamotani,K^Kim,HY^1995^1^Temperature-gradient chambers for research on global environment change .3. a system designed for rice in kyoto, japan^9^18^9^1064-1069^^^^^Sep^^^^^4502ercellular CO2 concentration. A +A^4501^Synthesis and validation of crop models for assessment of of the impact of elevated atmospheric CO2 concentration a+nd anticipated global warming on crop production require crop response data obtained under field-like conditions, The temp+erature gradient chamber (TGC) with the facility for CO2 enrichment allows the creation of various CO2 and temperature reg+imes for crops over the entire growth period with relatively inexpensive construction and running costs, The TGC develops +a temperature gradient along its longitudinal axis using solar energy during the day and heating at night while maintainin+g the natural diurnal cycle, The temperature gradient and the CO2 concentration in the TGC are regulated by computer contr+ol of the air ventilation rate through the TGC and of the CO2 release rate, Longitudinal gradients of CO2 concentration an+d water vapour pressure deficit of air in the TGC were generally less than 5% and +/-0.2 kPa, respectively. A CO2 enrichme+nt experiment on rice in the TGC showed that a doubling of the CO2 concentration markedly enhanced crop dry matter product+ion, Temperature had less effect on dry matter production, although panicle dry weight was greatly decreased at higher tem+perature as a result of high-temperature-induced sterility of rice spikelets, Since rice spikelets are most sensitive to h+igh temperature at the moment of flowering, and their flowering habit is highly synchronized with the diurnal courses of e+nvironmental conditions, the TGC is a useful tool in understanding rice responses to changes in atmosphere and temperature.arding possible ecological consequences of the warming on the boreal biome was discussed. A 600 to 700 km northward adva+852^2^Humphries,SW^Long,SP^1995^1^Wimovac - a software package for modeling the dynamics of plant leaf and canopy photosynthesis^258^11^4^361-371^^^^^Aug^^^^^4504 might cause a serious disorder in species composition of the biome, particularly+A^4503^The ability to predict net carbon exchange and production of vegetation in response to predicted atmospheric and cl+imate change is critical to assessing the potential impacts of these changes. Mathematical models provide an important too+l in the study of whole plant, canopy and ecosystem responses to global environmental change. Because this requires predic+tion beyond experience, mechanistic rather than empirical models are needed. The uniformity and strong understanding of th+e photosynthetic process, which is the primary point of response of plant production to global atmospheric change, provide+s a basis for such an approach. Existing modelling systems have been developed primarily for expert modellers and have not+ been easily accessible to experimentalists, managers and students. Here we describe a modular modelling system operating +within Winnows to provide this access. WIMOVAC (Windows Intuitive Model of Vegetation response to Atmosphere and Climate C+hange) is designed to facilitate the modelling of various aspects of plant photosynthesis with particular emphasis on the +effects of global climate change. WIMOVAC has been designed to run on IBM PC-compatible computers running Microsoft Window+s. The package allows the sophisticated control of the simulation processes for photosynthesis through a standardized Wind+ows user interface and provides automatically formatted results as either tabulated data or as a range of customizable gra+phs. WIMOVAC has been written in Microsoft Visual Basic, to facilitate the rapid development of user-friendly modules with+in the familiar Windows framework, while allowing a structured development. The highly interactive nature of controls adopted by WIMOVAC makes it suitable for research, management and educational purposes.to increase with the solute gas partia+853^3^Jacob,J^Greitner,C^Drake,BG^1995^1^Acclimation of photosynthesis in relation to rubisco and nonstructural carbohydra+te contents and in-situ carboxylase activity in scirpus-olneyi grown at elevated co2 in the field^9^18^8^875-884^^^^^Aug^^+A^4505^Stands of Scirpus olneyi, a native saltmarsh sedge with C-3 photosynthesis, had been exposed to normal ambient and +elevated atmospheric CO2 concentrations (C-a) in their native habitat since 1987, The objective of this investigation was +to characterize the acclimation of photosynthesis of Scirpus olneyi stems, the photosynthesizing organs of this species, t+o long-term elevated C-a treatment in relation to the concentrations of Rubisco and non-structural carbohydrates, Measurem+ents were made on intact stems in the field under existing natural conditions and in the laboratory under controlled condi+tions on stems excised in the field early in the morning, Plants grown at elevated C-a had a significantly higher (30-59%)+ net CO2 assimilation rate (A) than those grown at ambient C-a when measurements were performed on excised stems at the re+spective growth C-a. However, when measurements were made at normal ambient C-a, A was smaller (45-53%) in plants grown at+ elevated C-a than in those grown at ambient C- a. The reductions in A at normal ambient C-a, carboxylation efficiency and+ in situ carboxylase activity were caused by a decreased Rubisco concentration (30-58%) in plants grown at elevated C-a; t+hese plants also contained less soluble protein (39-52%). The Rubisco content was 43 to 58% of soluble protein, and this r+elationship was not significantly altered by the growth CO2 concentrations. The Rubisco activation state increased slightl+y, but the in situ carboxylase activity decreased substantially in plants grown at elevated C-a. When measurements were ma+de on intact stems in the field, the elevated C-a treatment caused a greater stimulation of A (100%) and a smaller reducti+on in carboxylation efficiency (which was not statistically significant) than when measurements were made on excised stems+ in the laboratory. The possible reasons for this are discussed. Plants grown at elevated C-a contained more non-structura+l carbohydrates (25-53%) than those grown at ambient C-a. Plants grown at elevated C-a appear to have sufficient sink capa+city to utilize the additional carbohydrates formed during photosynthesis. Overall, our results are in agreement with the +hypothesis that elevated C-a leads to an increased carbohydrate concentration and the ensuing acclimation of the photosynt+hetic apparatus in C-3 plants results in a reduction in the protein complement, especially Rubisco, which reduces the phot+osynthetic capacity in plants grown at elevated C-a, relative to plants grown at normal ambient C-a. Nevertheless, when co+mpared at their respective growth C-a, Scirpus olneyi plants grown at elevated C-a in their native habitat maintained a su+bstantially higher rate of photosynthesis than those grown at normal ambient C-a even after 8 years of growth at elevated C-a.999-17:44:47--0500-(EST 917253364 Ndel Nskip Nsave read Nget 1003150828 9f3d6e3cc918ab9dd4b20058c10b4103 <0F61008EIC^^^4506du>-23-Jan-1999-18:24:37--0500-(EST 917253364 Ndel Nskip Nsave read Nget 1841351348 6a2bb4999ccaacab1dfa636945174+854^3^Jifon,JL^Friend,AL^Berrang,PC^1995^1^Species mixture and soil-resource availability affect the root- growth response of tree seedlings to elevated atmospheric co21^155^25^5^824-832^^^^^May^^^^^4508ate.edu>-25-Jan-1999-11:00:26--0500-(EST+A^4507^The effects of CO2 enrichment on root proliferation of loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar sty+raciflua L.) seedlings were studied under varied water and nitrogen (N) regimes and in competitive interaction. Seedlings +of each species were grown from seed as monocultures or as 50:50 pine- sweetgum mixtures in 22-L pots filled with forest s+oil. Seedlings were exposed to either ambient (400 ppm) or CO2- enriched (ambient plus 400 ppm) air for 32 weeks in contin+uously stirred tank reactors. Detailed sampling of very fine roots (<0.5 mm diam.) showed a general increase (up to 2- fol+d) in root length density (RLD, cm . cm(-3)) with elevated CO2; however, the effects of CO2 on RLD differed according to s+pecies, culture type, water, and N availability. In monoculture, low water with low N conditions produced the largest RLD +responses to elevated CO2: 75% increase for sweetgum and 31% increase for pine. In mixed culture, by contrast, the largest, RLD responses to CO2 were observed under high water, high N regimes: pine showed a 110% increase and sweetgum a 96% incre)ase. The total RLD of the standing crop in mixture under elevated CO2, high water, and high N was 2.6 cm . cm(-3) compared,A^4509^A number of unexplained responses of plants to CO2 enrichment have been observed. These anomalies can be explained ,on the basis of growth analysis of whole plants. Some plants may fail to respond to enrichment because they are long-lived, and have conservative growth responses or come from impoverished habitats. Apparent (but not real) acclimation to CO2 enr,ichment might be observed if only part of the growth curve over the life of a perennial is studied. The apparent increased, efficiency of nitrogen use may merely be an increase in storage of nonstructural carbohydrate. A model analysis of these ,effects is presented. Discrepancies among species in relative responses of different plant parts are argued to be largely ,a function of where the plant typically stores nonstructural carbohydrates, which itself is a function of plant growth sta, ge. Thus, a closer consideration of plant growth strategies and growth partitioning is needed to properly interpret results of CO2 enrichment studies.500-(EST) 917945226 Ndel Nskip Nsave read Nget 497319216 6f03e4d12d681068482f6e6988b8c4fa <1, 856^3^Marek,MV^Kalina,J^Matouskova,M^1995^1^Response of photosynthetic carbon assimilation of norway spruce exposed to long-term elevation of co2 concentration^79^31^2^209-220^^^^^^^^^^4512tate.edu>-2-Feb-1999-09:04:18--0500-(EST) 917946337 Nd, A^4511^Young (12 years old) Norway spruce (Picea abies [L.] Karst.) trees were exposed to ambient CO2 or ambient + 350 mu ,mol(CO2) mol(-1) continuously over 2 growing seasons in open-top chambers, under field conditions of a mountain stand. Com,prehesive analysis of CO2 assimilation was performed after 4 and 22 weeks of the second growing season to evaluate the inf,luence of elevated atmospheric CO2. A combination of gas exchange and a mathematical mo del of ribulose-1,5-bisphosphate c,arboxylase/oxygenase (RuBPCO) activity was used. After 4 weeks of exposure no statistically significant stimulation of the, radiant energy and CO2 saturated rate of CO2 uptake (P-Nsat) by the elevated CO2 concentration was found. Yet after 24 we,eks a statistically significant depression of P-Nsat (38 %) and carboxylation efficiency (32 %) was observed. Depression o,f photosynthetic activity by elevated CO2 resulted from a decrease in the RuBPCO carboxylation rate. The electron transpor,t rate was also modified similarly to the rate of RuBP formation. An accompanying decrease in nitrogen content of the need,les (by 12 %) together with an increase in total saccharides (by 34 %) was observed after 24 weeks of exposure to enhanced CO2.Nget 832874204 18e2380b5a87885a878dbd665db3d3af <199902051333.IAA27267@mail2.uts.ohio-state.edu>-5-Feb-1999-08:33:4,857^6^Mitchell,RAC^Lawlor,DW^Mitchell,VJ^Gibbard,CL^White,EM^Porter,JR^1995^1^Effects of elevated co2 concentration and increased temperature on winter-wheat - test of arcwheat1 simulation-model^9^18^7^736-748^^^^^Jul^^^^^451409d34ae9214fb10a4,A^4513^Winter wheat (Triticum aestivum L., cv, Mercia) was grown in a controlled-environment facility at two CO2 concentra,tions (targets 350 and 700 mu mol mol(-1)), and two temperature regimes (tracking ambient and ambient + 4 degrees C), Obse,rvations of phenology, canopy growth, dry matter production and grain yield were used to test the ARCWHEAT1 simulation mod,el, Dry-matter production and grain yield were increased at elevated CO2 concentration (27 and 39%, respectively) and redu,ced at increased temperature (-16 and -35%, respectively), ARCWHEAT1 substantially underestimated canopy growth for all tr,eatments, However, differences in the facility environment from field conditions over the winter, indicated by the unusual, ly rapid canopy growth observed in this period, meant that empirical model relationships were being used outside the condi,!tions for which they were developed, The ARCWHEAT1 productivity submodel, given observed green area indices as inputs, ove,"restimated the effect of CO2 on productivity, An alternative, more mechanistic submodel of productivity, based on the SUCR,#OS87 and Farquhar and von Caemmerer models, simulated observed crop biomass very closely, When these productivity simulati,$ons were inputed into the ARCWHEAT1 partitioning and grain-fill submodels, grain yield was predicted poorly, mainly as a r,%esult of the assumption that the number of grains is proportional to total growth during a short preanthesis phase, While ,&yield was not correlated with growth in this phase, it was correlated with growth in longer preanthesis phases, indicating that ARCWHEAT1 could be improved by taking into account the contribution of earlier growth in determining yield.get 1759,(858^1^Mortensen,LM^1995^1^Diurnal carbon-dioxide exchange-rates of greenhouse roses under artificial-light as compared with daylight conditions in summer^200^45^2^148-152^^^^^Jun^^^^^4516A29369@mail3.uts.ohio-state.edu>-12-Feb-1999-15:12:11--0,*A^4515^Carbon dioxide exchange rates (CER) of greenhouse roses (cut flowers) were measured under daylight conditions in a ,+greenhouse in July, and under artificial light only (300 mu mol m(-2) s(-1) PPFD in 18 h day(-1)) at two CO2 concentration,,s (350 and 700 mu mol mol(-1)). The daily CER varied considerably from day to day owing to the large variation in solar ra,-diation. Light saturation of CER seemed not to be reached even on clear days, and a light dose (PAP = number of photosynth,.etic active photons) produced by variable light over one week in summer gave the same total CER as a similar PAP produced ,/by a constant PPFD. CER at constant PPFD increased rapidly during the first two hours of the photoperiod, followed by a sl,0ight increase during the subsequent hours, before CER slightly decreased towards the end of the photoperiod. Raising the C,1O2 concentration significantly increased CER during the entire photoperiod, and by 32% as a mean for the whole photoperiod,2. Elevated CO2 decreased the night respiration of the plants by 30%. As a total of the light and dark period, CO2 enrichment increased CER by 38%.7859f3167d1 <92684B9D01E8D111847E00AA00DD8FA5215D23@telegraph.uwyo.edu>-17-Feb-1999-18:39:37--050,4859^5^Nie,GY^Hendrix,DL^Webber,AN^Kimball,BA^Long,SP^1995^1^Increased accumulation of carbohydrates and decreased photosyn,Bthetic gene transcript levels in wheat grown at an elevated co2 concentration in the field^8^108^3^975-983^^^^^Jul^^^^^451,6A^4517^Repression of photosynthetic genes by increased soluble carbohydrate concentrations may explain acclimation of phot,7osynthesis to elevated CO2 concentration. This hypothesis was examined in a field crop of spring wheat (Triticum aestivum ,8L.) grown at both ambient (approximately 360 mu mol mol(-1)) and elevated (550 mu mol mol(-1)) atmospheric CO2 concentrati,9ons using free-air CO2 enrichment at Maricopa, Arizona. The correspondence of steady-state levels of mRNA transcripts (cod,:ing for the 83-kD photosystem I apoprotein, sedoheptulose-1,7-bisphosphatase, phosphoribulokinase, phosphoglycerokinase, a,;nd the large and small subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase) with leaf carbohydrate concentrations ,<(glucose-6-phosphate, glucose, fructose, sucrose, fructans, and starch) was examined at different stages of crop and leaf ,=development and through the diurnal cycle. Overall only a weak correspondence between increased soluble carbohydrate conce,>ntrations and decreased levels for nuclear gene transcripts was found. The difference in soluble carbohydrate concentratio,?n between leaves grown at elevated and current ambient CO2 concentrations diminished with crop development, whereas the di,@fference in transcript levels increased. In the flag leaf, soluble carbohydrate concentrations declined markedly with the ,Aonset of grain filling; yet transcript levels also declined. The results suggest that, whereas the hypothesis may hold well in model laboratory systems, many other factors modified its significance in this field wheat crop.ave read Nget 5363448993f070a2bf2529cdee0c8c757972 <01f101be610a$e0e00ea0$3030f4ce@kevingai>-25-Feb-1999-17:22:22--0500-(EST 920008932 Ndel N,D860^8^Nie,GY^Long,SP^Garcia,RL^Kimball,BA^Lamorte,RL^Pinter,PJ^Wall,GW^Webber,AN^1995^1^Effects of free-air co2 enrichment,E on the development of the photosynthetic apparatus in wheat, as indicated by changes in leaf proteins^9^18^8^855-864^^^^^Aug^^^^^45209--0500-(EST 920008932 Ndel Nskip Nsave read Nget 1127042849 c61d53fd7d3e9ac8610a7809e2838009 <199902261333.,GA^4519^A spring wheat crop was grown at ambient and elevated (550 mu mol mol(-1)) CO2 concentrations under free-air CO2 en,Hrichment (FACE) in the field, Four experimental blocks, each comprising 21-m-diameter FACE and control experimental areas,,I were used, CO2 elevation was maintained day and night from crop emergence to final grain harvest, This experiment provide,Jd a unique opportunity to examine the hypothesis that CO2 elevation in the field would lead to acclimatory changes within ,Kthe photosynthetic apparatus under open field conditions and to assess whether acclimation was affected by crop developmen,Ltal stage, leaf ontogeny and leaf age, Change in the photosynthetic apparatus was assessed by measuring changes in the com,Mposition of total leaf and thylakoid polypeptides separated by SDS-PAGE, For leaves at completion of emergence of the blad,Ne, growth at the elevated CO2 concentration had no apparent effect on the amount of any of the major proteins of the photo,Osynthetic apparatus regardless of the leaf examined, Leaf 5 on the main stem was in full sunlight at emergence, but then b,Pecame shaded progressively as 3-4 further leaves formed above with continued development of the crop, By 35 d following co,Qmpletion of blade emergence, leaf 5 was in shade, At this point, the chlorophyll alb ratio had declined by 26% both in pla,Rnts grown at the control CO2 concentration and in those grown at the elevated CO2 concentration, which is indicative of sh,Sade acclimation. The ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) content declined by 45% in the control leav,Tes, but by 60% in the leaves grown at the elevated CO2 concentration, The light- harvesting complex of photosystem II (LHC,UII) and the chlorophyll content showed no decrease and no difference between treatments, indicating that the decrease in R,Vubisco was not an effect of earlier senescence in the leaves at the elevated CO2 concentration. Following completion of th,We emergence of the flag-leaf blade, the elevated-CO2 treatment inhibited the further accumulation of Rubisco which was app,Xarent in control leaves over the subsequent 14 d, From this point onwards, the flag leaves from both treatments showed a l,Yoss of Rubisco, which was far more pronounced in the elevated- CO2 treatment, so that by 36 d the Rubisco content of these,Z leaves was just 70% of that of the controls and by 52 d it was only 20%, At 36 d, there was no decline in chlorophyll, LH,[CII or the chloroplast ATPase coupling factor (CFI) in the elevated CO2 concentration treatment relative to the control, B,\y 52 d, all of these proteins showed a significant decline relative to the control, This indicates that the decreased conc,]entration of Rubisco at this final stage probably reflected earlier senescence in the elevated-CO2 treatment, but that this was preceded by a CO2-concentration-dependent decline in Rubisco.661bfa89232f01b822c <0F7U001RN4MVWS@mx4.osu.edu>-27-Fe,_861^3^Pearson,M^Davies,WJ^Mansfield,TA^1995^1^Asymmetric responses of adaxial and abaxial stomata to elevated co2 - impacts on the control of gas-exchange by leaves^9^18^8^837-843^^^^^Aug^^^^^452235489176 cd8ad47eb24b34ceabb82220dd79c5f2 <0F7,aA^4521^The response of adaxial and abaxial stomatal conductance in Ruiner obtusifolius to growth at elevated atmospheric c,boncentrations of CO2 (250 mu mol mol(-1) above ambient) was investigated over two growing seasons, The conductance of both,c the adaxial and abaxial leaf surfaces was found to be reduced by elevated concentrations of CO2. Elevated CO2 caused a mu,dch greater reduction in conductance for the adaxial surface than for the abaxial surface, The absence of effects upon stom,eatal density indicated that the reductions were probably the result of changes in stomatal aperture, Partitioning of gas e,fxchange between the leaf surfaces revealed that increased concentrations of CO2 caused increased rates of photosynthesis o,gnly via the abaxial surface, Additionally, leaf thickness was found to increase during growth at elevated concentrations o,hf CO2. The tendency for these amphistomatous leaves to develop a distribution of conductance approaching that of hypostoma,itous leaves clearly reduced their maximum photosynthetic potential. This conclusion was supported by measurements of stoma,jtal limitation, which showed greater values for the adaxial surfaces, and greater values at elevated CO2. This reduction i,kn photosynthesis may in part be caused by higher diffusive limitations imposed because of increased leaf thickness, in an ,luncoupled canopy, asymmetrical stomatal responses of the kind identified here may appreciably reduce transpiration, Specie,ms which show symmetrical responses are less likely to show reduced transpirational rates, and a redistribution of water lo,nss between species may occur. The implications of asymmetrical stomatal responses for photosynthesis and canopy transpiration are discussed. 920268102 Ndel Nskip Nsave read Nget 1868572554 94204bea48dc9844d1ca89561ae497b8 <0F7V002V8ZOAN2@mx4.,p862^6^Reece,CF^Krupa,SV^Jager,HJ^Roberts,SW^Hastings,SJ^Oechel,WC^1995^1^Evaluating the effects of elevated levels of atmospheric trace gases on herbs and shrubs - a prototype dual array field exposure system^35^90^1^25-31^^^^^^^^^^4524d0149cf,rA^4523^In the context of global climate change, an understanding of the long-term effects of increasing concentrations of ,satmospheric trace gases (carbon dioxide, CO2, ozone, O-3, oxides of nitrogen, NOx etc.) on both cultivated and native vege,ttation is of utmost importance. Over the years, under field conditions, various trace gas-vegetation exposure methodologie,us with differing advantages and disadvantages have been used. Because of these variable criteria, with elevated O-3 or CO2,v levels, at the present time the approach of free-air experimental-release of the gas into study plots is attracting much ,wattention. However, in the case of CO2, this approach (using 15 m diameter study plot with a single circular array of vent,x pipes) has proven to be cost prohibitive (about $59000- 98000/year/replicate) due to the consumption of significant quant,yities of the gas to perform the experiment (CO2 level elevated to 400 ppm above the ambient). Therefore, in this paper, we,z present a new approach consisting of a dual concentric exposure array of vertical risers or vent pipes. The purpose of th,{e outer array (17 m diameter) is to vent ambient air outward and toward the incoming wind thus providing an air curtain to,| reduce the velocity of that incoming wind to simulate the mode or the most frequently occurring wind speed at the study s,}ite. The inner array (15 m diameter) vents the required elevated levels of trace gases (CO2, O-3, etc.) into the study plo,~t. This dual array system is designed to provide spatial homogeneity (shown through diffusion modeling) of the desired tra,ce-gas levels within the study plot and to also reduce its consumption. As an example, while in the single- array free-air, CO2-release system the consumption of CO2 to elevate its ambient concentration by 400 ppm is calculated to be about 980 t,ons/year/replicate, it is estimated that in the dual array system it would be approximately 590 tons/year/replicate. Thus,, the dual array system may provide substantial cost savings ($24000-39000/year/replicate) in the CO2 consumption ($60-100/,ton of CO2) alone. Similarly, benefits in the requirements of other trace gases (O-3, NOx, etc.) are expected, in future multivariate studies on global climate change.@,K 9@,K6@,K 0@,K,863^4^Seneweera,SP^Basra,AS^Barlow,EW^Conroy,JP^1995^1^Diurnal regulation of leaf blade elongation in rice by co2 - is it related to sucrose-phosphate synthase activity^8^108^4^1471-1477^^^^^Aug^^^^^4526,K 1@-K 2@-,A^4525^The relationship between leaf blade elongation rates (LER) and sucrose-phosphate synthase (SPS) activity was invest,igated at different times during ontogeny of rice (Oryza safiva L. cv Jarrah) grown in flooded soil at either 350 or 700 m,u L CO2 L(- 1). High CO2 concentrations increased LER of expanding blades and in vivo activity (V-limiting) SPS activity o,f expanded blades during the early vegetative stage (21 d after planting [DAP]), when tiller number was small and growing ,blades were strong carbohydrate sinks. Despite a constant light environment, there was a distinct diurnal pattern in LER, ,V- limiting SPS activity, and concentration of soluble sugars, with an increase in the early part of the light period and ,a decrease later in the light period. The strong correlation (r = 0.65) between LER and V-limiting SPS activity over the d,iurnal cycle indicated that SPS activity played an important role in controlling blade growth. The higher V-limiting SPS a,ctivity at elevated CO, at 21 DAP was caused by an increase in the activation state of the enzyme rather than an increase ,in V- max. Fructose and glucose accumulated to a greater extent than sucrose at high CO2 and may have been utilized for sy,nthesis of cell-wall components, contributing to higher specific leaf weight. By the mid-tillering stage (42 DAP), CO2 enr,ichment enhanced V-limiting and V-max activities of source blades. Nevertheless, LER was depressed by high CO2, probably because tillers were stronger carbohydrate sinks than growing blades. @WES @ N @SON,864^1^Townend,J^1995^1^Effects of elevated co2, water and nutrients on picea- sitchensis (bong) carr seedlings^84^130^2^193-206^^^^^Jun^^^^^4528 )i\,B TIME@$ON @B @kXq<JC1018,A^4527^Sitka spruce (Picea sitchensis (Pong.) Carr.) seedlings were grown from seed for one year in naturally lit growth c,hambers with either ambient or ambient + 250 ppm concentrations of CO2. In the following year the plants were grown in the, same CO2 treatments for the whole growing season at two concentrations of nutrients and were either well-watered or subje,cted to a long-term, gradually increasing drought. Elevated CO2 increased significantly growth in all treatments except th,e well-watered, unfertilized treatment. The relative increases in end-of-year biomass in the elevated CO2 treatment compar,ed with the ambient treatment were: well-watered, fertilized + 52%, well-watered, unfertilized + 19%, droughted, fertilize,d + 44%, and droughted, unfertilized + 49%. Growth analysis revealed that treatment effects on both unit leaf rates and le,af area duration were important in determining the final masses of the plants. Plants growing in elevated CO2 had increase,d relative growth rates in the first half of the growing season but only slightly increased or even slightly decreased rel,ative growth rates in the later part of the growing season in all water x nutrient treatments. Overall there was a signifi,cant CO2 x water x nutrient interaction on end-of-year biomass. A combination of small nutrient concentration and adequate water supply led to the smallest growth response to elevated CO2.@2@ OURIER@ TIT,865^3^Vanoosten,JJ^Wilkins,D^Besford,RT^1995^1^Acclimation of tomato to different carbon-dioxide concentrations - relationships between biochemistry and gas- exchange during leaf development^84^130^3^357-367^^^^^Jul^^^^^4530ADING@,A^4529^Tomato plants were transferred to different CO2 mole fractions (350, 700, 1050 and 1400 mu mol CO2 mol(-1)) 31 d af,ter sowing (2% of full expansion) and the light saturated rate of photosynthesis (P-max) of the unshaded 5th leaf was meas,ured at either an ambient CO2 mole fraction, C-a of 350 mu mol CO2 mol(-1) [P-max (350)] or at the mole fraction of CO2 at, which the plants were grown. At 60% and 95% leaf expansion, P-max of high CO2 grown plants measured at growth CO2, was gr,eater than the P-max (350) of the ambient CO2 grown plants. However, by leaf maturity, P-max (growth CO2) declined linearl,y as growth CO2 concentration increased. P-max (350) of plants exposed to elevated CO2 up to 60% leaf expansion had not ac,climated to high CO2. At 95% leaf expansion, P-max (350) was smaller in the high CO2 grown plants. P-max (350) was predict,ed from Rubisco in vitro carboxylation capacity using tomato Rubisco kinetic constants. By 95% leaf expansion, high CO2 gr,own plants showed similarities to the response of plants to low nitrogen supply, in terms of Rubisco and chlorophyll conte,nt. The observed and theoretical relationships between the initial slopes of the P- max/C-i responses and Rubisco activity, were statistically equivalent. Both short-term and long-term effects of elevated CO2 on dark respiration (R(n)) were also, investigated at two stages of leaf development (50 and 100% expansion). R(a) (growth CO2) was smaller for the high CO2 gr,own plants compared with the control plants, whereas R(n) (350) was either equal or greater for the plants grown in high CO2.C@uTIL@WEBFORM1@2@3@4@5@,866^4^Walker,RF^Geisinger,DR^Johnson,DW^Ball,JT^1995^1^Interactive effects of atmospheric co2 enrichment and soil n on growth and ectomycorrhizal colonization of ponderosa pine- seedlings^49^41^3^491-500^^^^^Aug^^^^^4532HHY@ H,A^4531^Interactive effects of elevated atmospheric CO2 and soil N fertility on above- and belowground development of juven,ile ponderosa pine (Pinus ponderosa Dougl, ex Laws.) were examined. Seedlings were grown from seed in atmospheres containi,ng 700 mu l l(-1), 525 mu l l(-1), or ambient CO2. Medium and high soil N treatments were created by adding sufficient (NH,4)(2)SO4 to the potting mix to increase total N by 100 mu g g(-1) and 200 mu g g(-1), respectively, while unamended mix, w,hich had a total N concentration of approximately 300 mu g g(-1), served as the low N treatment. Three whole-seedling harv,ests at 4-month intervals permitted assessment of shoot and root growth and ectomycorrhizal formation resulting from inocu,lation with Pisolithus tinctorius (Pers.) Coker and Couch. After 4 months, CO2 enrichment increased shoot volume and dry w,eight of seedlings grown in high soil N, but this result was not evident in the other N treatments and did not persist to ,the second harvest. Root weight, however, increased, and shoot/root ratio decreased as the CO2 concentration increased wit,hin all three N treatments at the first harvest. At the second harvest, root weights within the high and intermediate N tr,eatments were lowest in seedlings grown in ambient CO2 and shoot/root ratios decreased as CO2 increased in these two N tre,atments as well. Although the ectomycorrhizal infection percentage of seedlings grown in 700 mu l l(-1) CO2 was highest am,ong the seedlings grown in high N after 4 months, mycorrhizal colonization was variable overall at the first and second ha,rvests. After 1 yr, the 525 mu l l(-1) CO2 concentration stimulated above- and belowground growth more than the high CO2 a,tmosphere in both high and medium soil N. These seedlings also had relatively extensive ectomycorrhizal formation, but col,onization was again variable. Results presented here suggest the response of juvenile ponderosa pine to CO2 enrichment is ,ephemeral, with the effects on roots more pronounced and persistent overall than those on shoots, and that the response is dependent on N availability. @= KER@LARATIONS@{K E@u,867^4^Williams,M^Shewry,PR^Lawlor,DW^Harwood,JL^1995^1^The effects of elevated-temperature and atmospheric carbon- dioxide, concentration on the quality of grain lipids in wheat (triticum-aestivum L) grown at 2 levels of nitrogen application^9^18^9^999-1009^^^^^Sep^^^^^4534@)\ED @S @ING @ON@)R,A^4533^Wheat plants were cultivated under growth regimes combining two temperatures (ambient and 4 degrees C above ambient, temperature) with two concentrations of carbon dioxide (350 and 700 mu mol mol(-1)) and two nitrogen fertilizer applicati,ons (high and low), The aim of this study was to define any changes in the acyl lipid composition of wheat grains which co,uld result from alterations in the growth conditions, Qualitative and quantitative changes were observed in both non-starc,h and starch lipid fractions, Temperature was by far the most influential growth factor, although interactions between all, three growth conditions occurred, as confirmed by analysis of variance, Growth at elevated temperatures had the general e,ffect of reducing the amounts of accumulated lipids, particularly non-polar lipids (1322mg fatty acids per 100g fresh weig,ht at ambient temperatures as opposed to 777mg fatty acids per 100 g fresh weight at 4 degrees C above ambient temperature,s), There were changes in the proportions of the major non-starch as well as the starch lipids, In the former category, no,n-polar lipids (principally triacylglycerols), the membrane glycosylglycerides and phosphatidylcholine were the main const,ituents, whereas in the starch lipids, lysophosphatidylcholine and lysophosphatidylethanolamine represented over 70% of th,e total, Depending on the growth conditions, the percentages of lipids such as monogalactosyldiacylglycerol, digalactosyld,iacylglycerol and phosphatidylcholine (non-starch) or the starch lysophosphatidylethanolamine varied 2-fold or more, Signi,ficant changes in the acyl composition of individual lipids were also observed, most often in the proportions of palmitate,, oleate and linoleate, The observed alterations in wheat lipids are likely to affect the properties of any flours derived from grain grown under climate change conditions.RS@INIS @*ux:>t  @ ST,868^2^Wolfenden,J^Diggle,PJ^1995^1^Canopy gas-exchange and growth of upland pasture swards in elevated co2^84^130^3^369-380^^^^^Jul^^^^^4536 ED @ ING@' S@- EGATION@# TABLE ,A^4535^Vegetation monoliths (450 x 450 mm) from two contrasting upland grassland communities were grown in Solardomes in e,ither ambient air or ambient air enriched with 250 ppm CO2. During the first two growing seasons measurements of canopy ga,s exchange showed that rates of photosynthesis of limestone swards were enhanced by growth in elevated CO2, by approx. 50%, during spring and early summer. Although canopy respiration was also greater in elevated CO2, the overall effect was an a,verage increase of 33% in net CO2 assimilation. Enhanced respiration rates persisted into the autumn, whereas the effect o,n photosynthesis diminished through the growing season, so that in September swards growing in high CO2 had net photosynth,esis rates similar to, or even lower than those in ambient air. This response varied between swards of differing species c,omposition. In acidic grassland no significant effects of CO2 on respiration or net CO2 uptake rates were detected at any ,time. The above ground productivity of limestone grassland was measured in several harvests throughout both seasons, and w,as not affected by CO2 concentration at any time. Similarly, the acidic grassland, harvested at the end of the second seas,on, showed no significant effect of CO2 on above-ground biomass. The results suggest that increasing atmospheric CO2 concentration is unlikely to cause large changes in net primary productivity in these grasslands.@-S@q[,r just 68 days significantly (P less than or equal to 0.05) increased stem height by 13% compared with trees grown in ambi,ent CO2 concentrations. The stem diameter was significantly (P less than or equal to 0.05) increased and both total biomas,s and woody stem biomass also showed higher values (38% and 31% increases respectively) in elevated CO2. Trees in elevated, CO2 had more leaves and a greater total leaf area, whilst the specific leaf area was decreased in elevated CO2 on four ou,t of five occasions and was significantly (P less than or equal to 0.05) lower after 68 days, an effect indicating that le,aves were thicker and/or heavier. Rates of photosynthesis (A) measured after 49 and 67 days of exposure revealed that tree,s in the elevated CO2 treatment had lower values of A when measured at either 350 or 580 mu l 1(-1) CO2. Sequential harves,ts at intervals during the study in which the root and shoot components were analysed separately allowed the construction ,of root:shoot ratios and allometric coefficients; there was no significant effect on the allometric coefficient and the ro,ot:shoot ratio was significantly increased on only one occasion. However, measurements of the 'apparent' root length sugge,sted that root lengths were greater in the CO2 treatment. There was a significant increase in the number of fine root tips, visible down the surface of specially designed rooting tubes (P less than or equal to 0.05), indicating more fine roots o,r an increase in fine root branching. The growth rates of individual fine or large roots over 24 h were unaffected, again ,suggesting that increases in biomass may be due to more root segments rather than longer individual roots. Root water rela,tions were also examined and showed a tendency towards solute accumulation and increases in turgor pressure (P) and effect,ive tugor (P-e) at times when root growth was stimulated, although these were not consistent. Cell wall plasticity of the ,tips of large roots was significantly (P less than or equal to 0.01) reduced in elevated CO2, possibly indicating a greate,r tendency to divert resources to the formation of root branches. The results of the study are discussed in the light of t,he possible consequences of changes in poplar growth and physiology for forestry practice in an increased CO2 environment.u,- D ATE@'D@- %-6l S @-vING@-ON@,872^3^Ceulemans,R^Jiang,XN^Shao,BY^1995^1^Growth and physiology of one-year-old poplar (populus) under elevated atmospheric co2 levels^52^75^6^609-617^^^^^Jun^^^^^4544@q,Mx. (,S RABLE @-f E,A^4543^The effects of elevated atmospheric CO2 concentrations on the ecophysiological responses (gas exchange, chlorophyll, a fluorescence, Rubisco activity, leaf area development) as well as on the growth and biomass production of two poplar cl,ones (i.e. Populus trichocarpa x P. deltoides clone Beaupre and P. x euramericana clone Robusta) were examined under open -top chamber conditions. The elevated CO2 treatment (ambient + 350 mu mol mol-1) stimulated above-ground biomass of clones -Robusta and Beaupre after the first growing season by 55 and 38 %, respectively. This increased biomass production under e-levated CO2 was associated with a significant increase in plant height, the latter being the result of enhanced internode -elongation rather than an increased production of leaves or internodes. Both an increased leaf area index (LAI) and a stim-ulated net photosynthesis per unit leaf contributed to a significantly higher stem biomass per unit leaf area, and thus to- the increased above-ground biomass production under the elevated CO2 concentrations in both clones. The larger LAI was ca-used by a larger individual leaf size and leaf growth rate; the number of leaves was not altered by the elevated CO2 treat-ment. The higher net leaf photosynthesis was the result of an increase in the photochemical (maximal chlorophyll fluoresce-nce Fm and photochemical efficiency Fv/Fm) as well as in the biochemical (increased Rubisco activity) process capacities. - No significant differences were found in dark respiration rate, neither between clones nor between treatments, but specific leaf area significantly decreased under elevated CO2 conditions. (C) 1995 Annals of Botany CompanyNG@psA- 873^2^Cotrufo,ME^Ineson,P^1995^1^Effects of enhanced atmospheric co2 and nutrient supply on the quality and subsequent decomposition of fine roots of betula- pendula roth and picea-sitchensis (bong) carr^206^170^2^267-277^^^^^Mar^^^^^4546- A^4545^Fine root litter derived from birch (Betula pendula Roth.) and Sitka spruce (Picea sitchensis (Bong.) Carr.) plants- grown under two CO2 atmospheric concentrations (350 ppm and 600 ppm) and two nutrient regimes was used for decomposition -studies in laboratory microcosms. Although there were interactions between litter type, CO2/fertiliser treatments and deco-mposition rates, in general, an increase in the C/N ratio of the root tissue was observed for roots of both species grown -under elevated CO2 in unfertilized soil. Both weight loss and respiration of decomposing birch roots were significantly re-duced in materials derived from enriched CO2, whilst the decomposition of spruce roots showed no such effect. A parallel e-xperiment was performed using Betula pendula root litter grown under different N regimes, in order to test the relationshi-p between C/N ratio of litter and root decomposition rate. A highly significant (p < 0.001) negative correlation between C-/N ratio and root litter respiration was found, with an r(2) = 0.97. The results suggest that the increased C/N ratio of p-lant tissues induced by elevated CO2 can result in a reduction of decomposition rate, with a resulting increase in forest soil C stores.@ S@)E  TEMPLATES@ UE@+ZS@-874^4^Firbank,LG^Watkinson,AR^Norton,LR^Ashenden,TW^1995^1^Plant-populations and global environmental-change - the effects- of different temperature, carbon-dioxide and nutrient regimes on density-dependence in populations of vulpia-ciliata^43^9^3^432-441^^^^^Jun^^^^^4548@CHOTOMOUS @J@ KINSON @ OT @-A^4547^1. Monocultures of Vulpia ciliata spp. ambigua were subjected to a range of temperatures, CO2, nutrient and density- regimes in a factorial design housed within solar-domes. Temperature treatments were imposed at ambient and +3 degrees C -levels, CO2 at ambient and +340 ppm, and there were three levels of nutrients and eight levels of densities ranging from 1-56 to 31250 seeds m(-2). The abiotic treatments were imposed after emergence. 2. There was little mortality and this was u-nrelated to the treatments. Plants grew more quickly at the high temperature, high nutrient and low density regimes, and f- lowering was earlier at the high temperature regime. 3. At seed set, biomass per plant and seed production per plant were -!analysed by analysis of variance and by fitting mean yield- density models expanded to account for different environmental-" conditions. Biomass and fecundity were greatest at high temperature, high nutrient and low density regimes. Allocation of-# biomass to shoots was greater at the high temperatures, as were seed number/shoot biomass ratios. Any effects of CO2 were-$ negligible. The parameter b describing the nature of the relationship between seed production per plant and density was a-%lways less than unity but was greater at the higher temperature regime. The response to density was therefore undercompens-&ating in all conditions, implying that populations would display monotonic damping to equilibrium densities. 4. Under prop-'osed future environmental regimes, V. ciliata has the capacity for more rapid population growth from low levels and for a -(northwards range shift. However, if open ground is not maintained, its habitat may become dominated by species that are more competitive or that have a higher rate of increase. @M@u ENSION@dAL@-*875^4^Hibbs,DE^Chan,SS^Castellano,M^Niu,CH^1995^1^Response of red alder seedlings to co2 enrichment and water- stress^84^129^4^569-577^^^^^Apr^^^^^4550GBATS@ING @ O @PUT@OECIOUS-,A^4549^Red alder (Alnus rubra Bong.) is a nitrogen-fixing pioneer tree species of the Pacific Northwest of North America. --We investigated the response of different seed sources of red alder to elevated atmospheric CO2 and to varied levels of wa-.ter stress. Seeds were stratified, germinated and grown for up to 147 d under ambient (350 mu l l(-1)) or elevated (700 mu-/ l l(- 1)) CO2. There were no significant interactions of seed source latitude with either treatment, although seedlings f-0rom more northerly sources were larger. Elevated CO2 and low moisture stress resulted in larger plants with more leaf area-1; effects of the two factors appeared additive. Effects of both factors on biomass allocation, including root:shoot ratios-2, were small or nonsignificant. Elevated CO2 decreased specific nitrogenase activity and generally increased photosynthesi-3s (A) and stomatal conductance (g). The ratio A:g, potential water use efficiency, also increased when plants were under w-4ater stress. Elevated CO2 appears to improve drought tolerance in red alder. Overall, these results indicate that red alder would benefit in total plant growth from increased ambient CO2 and could tolerate changes in precipitation.pF-6876^3^Ineichen,K^Wiemken,V^Wiemken,A^1995^1^Shoots, roots and ectomycorrhiza formation of pine-seedlings at elevated atmospheric carbon-dioxide^9^18^6^703-707^^^^^Jun^^^^^4552@):ING @S@)I ROVED-8A^4551^The effect of elevated atmospheric CO2 concentration on the growth of shoots, roots, mycorrhizas and extraradical m-9ycorrhizal mycelia of pine (Pinus silvestris L.) was examined, Two and a half-month-old seedlings were inoculated axenical-:ly with the mycorrhizal fungus Pisolithus tinctorius (Pers,) by a method allowing rapid mycorrhiza formation in Petri dish-;es, The plants were then cultivated for 3 months in growth chambers with daily concentrations of 350 and 600 mu mol mol(-1-<) CO2 during the day, Whereas plants harvested after 1 and 2 months did not differ appreciably between ambient and increas-=ed CO2 concentrations, after 3 months they developed a considerably higher root biomass (+57%) at elevated CO2, but did no->t increase significantly in root length, The mycorrhizal fungus Pisolithus tinctorius, which depended entirely on the plan-?t assimilates in the model system, grew much faster at increased CO2: 3 times more mycorrhizal root clusters were formed a-@nd the extraradical mycelium produced had twice the biomass at elevated as at ambient CO2. No difference in shoot biomass -Awas found between the two treatments after 91d, However, since the total water consumption of seedlings was similar in the-B two treatments, the water use efficiency was appreciably higher for the seedlings at increased CO2 because of the higher below- ground biomass.@ GUISE@%H @ ES @  WASHER @  JUNCT-D877^3^Johnson,DW^Walker,RF^Ball,JT^1995^1^Lessons from lysimeters - soil n release from disturbance compromises controlled environment study^56^5^2^395-400^^^^^May^^^^^4554@+)>_7+S@=cHOG @-FA^4553^A controlled environment study of the effects of carbon dioxide (CO2) and nitrogen (N) on growth of ponderosa pine -Gseedlings produced results contradictory to those obtained in the field with the same species, soil, and treatments. In th-He controlled environment study, there was a significant negative growth response to N fertilization, whereas in the field -Ithere was a significant positive response to N. The difference was due to high rates of native N mineralization after soil-J disturbance during potting. This was evident from soil solution NO3- concentrations that peaked at approximate to 5000 mu-K mol/L in the unfertilized pots and 20 000 mu mol/L in the fertilized pots. These concentrations are orders of magnitude g-Lreater than those typically observed in the field. The effects of soil disturbance on N mineralization and nitrification n-Meed to be carefully considered before initiating controlled environment studies. The results of this study show that excessive N mineralization caused by soil disturbance can seriously compromise the results of controlled environment studiesT-O878^2^Larsen,M^Watkins,CB^1995^1^Firmness and concentrations of acetaldehyde, ethyl-acetate and ethanol in strawberries stored in controlled and modified atmospheres^259^5^1-2^39-50^^^^^Jan^^^^^4556TIES @ OLVED @  T-QA^4555^'Pajaro' strawberries (Fragaria x ananassa Duch.) were stored at 0 degrees C in a range of controlled atmosphere (C-RA) conditions with CO2 concentrations up to 24%, O-2 concentrations down to 1%, or a combination of 10% CO2 and 2% O-2 Ele-Svated CO2 concentrations resulted in firmer fruit, while low O-2 did not affect texture. Off-flavours developed after 3 da-Tys of storage at 20% CO2, but decreased when fruit was subsequently held for 24 h at 20 degrees C. However, off- flavours -Uwere persistent after CA storage for 7 days or more. Off-flavours were related to increases in ethyl acetate and ethanol c-Voncentrations but not to acetaldehyde. Beneficial atmospheres of close to 10% CO2 and 2% O-2 resulted in a firmer texture -Wand delayed ripening with no off-flavour development. However, fruit quality was poor when similar atmospheres were develo-Xped in modified atmosphere (MA)-producing polythene bags. Rapid imposition of CA resulted in better quality fruit than when MAs around the fruit were developed gradually.yD3@T\, /)vyD4@T\, -Z879^4^Lenssen,GM^Vanduin,WE^Jak,P^Rozema,J^1995^1^The response of aster-tripolium and puccinellia-maritima to atmospheric carbon-dioxide enrichment and their interactions with flooding and salinity^159^50^2^181-192^^^^^May^^^^^4558SION-\A^4557^The effects of 380 and 720 mumol mol-1 atmospheric CO2 on growth, dry matter allocation, net leaf photosynthesis an-]d stomatal conductance of the C3 salt marsh species Aster tripolium L. and Puccinellia maritima (Hudson) Parl. were studie-^d. Plants were grown in pots under combinations of low (50-250 mM NaCl) or high (450-550 mM NaCl) salinity and non- floode-_d or flooded salt marsh soil. High salinity reduced growth of both species, while flooding increased biomass production of-` A. tripolium. Root weight of A. tripolium and total plant weight of P. maritima was increased by atmospheric CO2 enrichme-ant when the soil was flooded. Under non-flooded conditions, the effect of elevated CO2 on growth was small (P. maritima) o-br absent (A. tripolium). The relative increase in total plant weight of both species by elevated CO2 was higher under sali-cne conditions. Dry matter allocation between root, stem and leaf, as reflected in leaf weight ratio and shoot to root rati-do, was not changed by elevated CO2, while specific leaf area was slightly decreased by CO2 enrichment. Elevated CO2 stimul-eated net leaf photosynthesis of both species, while stomatal conductance decreased. These effects were not changed by salinity or flooding treatment.3275151C@ MODULE@314CDEA@4B9453-g880^1^Leverenz,JW^1995^1^Shade shoot structure of conifers and the photosynthetic response to light at 2 co2 partial pressures^43^9^3^413-421^^^^^Jun^^^^^4560@5EEF6E1@BDF3626@562762F5-iA^4559^1. The response of net photosynthesis to irradiance was measured for shade-adapted shoots of different conifer spec-jies. Shoots were illuminated unidirectionally or in a light integrating sphere to study the effects of shoot structure. 2.-k Shoot structure was quantified as R(max) the ratio of the shoot-silhouette area to the leaf-silhouette area. 3. The initi-lal slopes and the convexities (rate of bending) of the light response curves were strongly affected by R(max) during unila-mteral illumination. There was also a strong positive effect of R(max) on the maximum efficiency of net photosynthesis and -na strong negative effect of R(max) on the light compensation point. 4. Increasing atmospheric CO2 partial pressure (C-a) f-orom 35 to 70 Pa did not affect the convexity of the light response curves nor rates of dark respiration. 5. Increasing C-a-p affected the initial slope, the light compensation point, the maximum rate of photosynthesis and the efficiency of net ph-qotosynthesis. 6. Except for the maximum rate of net photosynthesis, the responses to C-a were controlled by shoot structur-re. 7. Studies of the effect of atmospheric CO2 on photosynthesis and growth in conifers need to consider variations in shoot structure.E8F@AE4D8FE@ ILMSG@CF06732@HOST-t881^2^Liu,SY^Teskey,RO^1995^1^Responses of foliar gas-exchange to long-term elevated co2 concentrations in mature loblolly-pine trees^13^15^6^351-359^^^^^Jun^^^^^4562@q,KC-ih2@>F3SB@q-vA^4561^Branches of field-grown mature loblolly pine (Pinus taeda L.) trees were exposed for 2 years (1992 and 1993) to amb-wient or elevated CO2 concentrations (ambient + 165 mu mol mol(-1) or ambient + 330 mu mol mol(-1) CO2). Exposure to elevat-xed CO2 concentrations enhanced rates of net photosynthesis (P-n) by 53-111% compared to P-n of foliage exposed to ambient -yCO2. At the same CO2 measurement concentration, the ratio of intercellular to atmospheric CO2 concentration (C-i/C-a) and -zstomatal conductance to water vapor did not differ among foliage grown in an ambient or enriched CO2 concentration. Analys-{is of the relationship between P-n and C-i indicated no significant change in carboxylation efficiency of ribulose-1,5- bi-|sphosphate carboxylase/oxygenase during growth in elevated CO2 concentrations. Based on estimates derived from P-n/C-i cur-}ves, there were no apparent treatment differences in dark respiration, CO2 compensation point or P-n at the mean C-i. In 1-~992, foliage in the three CO2 treatments yielded similar estimates of CO2-saturated P-n (P-max), whereas in 1993, estimate-s of P-max were higher far branches grown in elevated CO2 than in ambient CO2. We conclude that field-grown loblolly pine -trees do not exhibit downward acclimation of leaf-level photosynthesis in their long-term response to elevated CO2 concentrations.m t6 ING@;S(@3A-882^4^Mathooko,FM^Kubo,Y^Inaba,A^Nakamura,R^1995^1^Induction of ethylene biosynthesis and polyamine accumulation in cucumber fruit in response to carbon-dioxide stress^259^5^1-2^51-65^^^^^Jan^^^^^4564@E @ Sp@-A^4563^Carbon dioxide stress-induced ethylene biosynthesis, respiration and polyamine accumulation in cucumber fruit (Cucu-mis sativus L, cv. Sharp-1) held at 25 degrees C was investigated. Control fruit produced little ethylene and the respirat-ion rate decreased with increase in incubation time while polyamine levels decreased. Elevated CO2 induced ethylene produc-tion, respiration and polyamine accumulation. Putrescine and spermidine levels increased in response to CO2 treatment, whe-reas spermine levels were not significantly affected. No cadaverine was detected in all treatments. The increase in ethyle-ne production paralleled increases in 1- aminocyclopropane-1-carboxylic acid (ACC) and the activities of both ACC synthase- and in vitro ACC oxidase. Infiltration of the fruit with aminooxyacetic acid, a potent inhibitor of the conversion of S-a-denosylmethionine (AdoMet) to ACC completely blocked CO2 stress-induced ethylene production. Similarly, cycloheximide, an -inhibitor of nucleocytoplasmic protein synthesis effectively blocked CO2 stress induction of polyamine accumulation, ethyl-ene production, ACC formation and the development of ACC synthase. Withdrawal of CO2 gas caused cessation of increases in -ethylene production, respiration, ACC, putrescine and the activities of ACC synthase and ACC oxidase, but caused increase -in spermidine and spermine levels. These data indicate that CO2 induces de novo synthesis of ACC synthase thereby causing -accumulation of ACC and increase in ethylene production and suggest that the conversion of AdoMet to ACC is the rate-limit-ing step in CO2 stress-induced ethylene biosynthesis. The induction, however, requires continuous presence of the stimulus-. The results also suggest that protein synthesis might be required for the CO2 stress induction of polyamine biosynthesis-. The results further suggest that in cucumber fruit under CO2 stress, at least, the ethylene and polyamine biosynthetic pathways are not competitive./     H ( -883^6^Micallef,BJ^Haskins,KA^Vanderveer,PJ^Roh,KS^Shewmaker,CK^Sharkey,TD^1995^1^Altered photosynthesis, flowering, and fruiting in transgenic tomato plants that have an increased capacity for sucrose synthesis^6^196^2^327-334^^^^^May^^^^^4566-A^4565^Photosynthesis, leaf assimilate partitioning, flowering, and fruiting were examined in two lines of Lycopersicon es-culentum Mill. transformed with a gene coding for sucrose-phosphate synthase (SPS) (EC 2.3.1.14) from Zea mays L. expresse-d from a tobacco ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) small subunit promoter. Plants were grown at ei-ther 35 or 65 Pa CO2 and high light (1000 mu mol photons . m(-2). s(-1)). Limiting and maximum SPS activities were signifi-cantly greater (up to 12 times) in the leaves of SPS-transformed lines for all treatments. Partitioning of carbon into suc-rose increased 50% for the SPS transformants. Intact leaves of the control lines exhibited CO2-insensitivity of photosynth-esis at high CO2 levels, whereas the SPS transformants did not exhibit CO2-insensitivity. The O-2-sensitivity of photosynt-hesis was also greater for the SPS-transformed lines compared to the untransformed control when measured at 65 Pa CO2. The-se data indicate that the SPS transformants had a reduced limitation on photosynthesis imposed by end-product synthesis. G-rowth at 65 Pa CO2 resulted in reduced photosynthetic capacity for control lines but not for SPS-transformed lines. When g-rown at 65 Pa CO2, SPS transformed lines had a 20% greater photosynthetic rate than controls when measured at 65 Pa CO2 an-d a 35% greater rate when measured at 105 Pa CO2. Photosynthetic rates were not different between lines when grown at 35 P-a CO2. The time to 50% blossoming was reduced and the total number of inflorescences was significantly greater for the SPS- transformants when grown at either 35 or 65 Pa CO2. At 35 Pa CO2, the total fruit number of the SPS transformants was up -to 1.5 times that of the controls, the fruit matured earlier, and there was up to a 32% increase in total fruit dry weight-. Fruit yield was not significantly different between the lines when grown at 65 Pa CO2. Therefore, there was not a strict- relationship between yield and leaf photosynthesis rate. Flowering and fruit development of the SPS-transformed lines gro-wn at 35 Pa CO2 showed similar trends to the controls grown at 65 Pa CO2. Incidences of bios som-end rot were also reduced- in the SPS-transformed lines. These data indicate that altering starch/sucrose partitioning by increasing the capacity for sucrose syn thesis can affect acclimation to elevated CO2 partial pressure and flowering and fruiting in tomato.@-884^6^Pregitzer,KS^Zak,DR^Curtis,PS^Kubiske,ME^Teeri,JA^Vogel,CS^1995^1^Atmospheric co2, soil-nitrogen and turnover of fine roots^84^129^4^579-585^^^^^Apr^^^^^45682@ LTR@ N @@-!0o& R>@ 6-A^4567^In most natural ecosystems a significant portion of carbon fixed through photosynthesis is allocated to the product-ion and maintenance of fine roots, the ephemeral portion of the root system that absorbs growth-limiting moisture and nutr-ients. In turn, senescence of fine roots can be the greatest source of C input to forest soils. Consequently, important qu-estions in ecology entail the extent to which increasing atmospheric CO2 may alter the allocation of carbon to, and demogr-aphy of, fine roots. Using microvideo and image analysis technology, we demonstrate that elevated atmospheric CO2 increase-s the rates of both fine root production and mortality. Rates of root mortality also increased substantially as soil nitro-gen availability increased, regardless of CO2 concentration. Nitrogen greatly influenced the proportional allocation of ca-rbon to leaves vs. fine roots. The amount of available nitrogen in the soil appears to be the most important factor regulating fine root demography in Populus trees.@ CANCOM@ELECTDATABASE@ -885^3^Reddy,KR^Hodges,HF^McKinion,JM^1995^1^Carbon-dioxide and temperature effects on pima cotton growth^169^54^1-2^17-29^^^^^Jun^^^^^4570HELL@ OWREF@ IEGEL @ KAPI16@ 32-A^4569^Temperature and CO2 are major environmental variables that affect plant growth and development. Limited information- is available concerning how these factors affect plants, as well as specific interactions between the two. We conducted t-wo experiments in controlled environmental chambers were temperature and CO2 were controlled and other environmental facto-rs were not limiting. The purpose was to determine how cotton grew and responded to a range of temperatures and CO2 concen-trations. During vegetative development, stem growth was quite sensitive to CO2 resulting in more effective early-season l-ight capture. Plants did not develop more nodes when exposed to additional CO2, while node number increased more at higher- temperatures. Individual leaf growth was about 18% greater at optimum temperature in 450 mul 1(-1) than in 350 mul 1(-1) -CO2, but did not increase from 450 mul 1(-1) CO2 to 700 mul 1(-1) CO2. However, the time required for a leaf to reach matu-re size was not influenced by CO2. Leaf area, on the whole plant basis, was about 33% greater on plants grown at optimum t-emperature in high CO2 than in ambient CO2. The greater leaf area on a whole plant basis was achieved by a combination of -larger leaves and additional leaves produced primarily on the branches. There was a 28% increase in number of bolls produc-ed at 700 mul 1(-1) CO2 at optimum temperature compared with bolls produced at 350 mul 1(-1) CO2. There was not, however, -an increase in boll size due to high CO2. At 35.5-degrees-C, little growth response to high CO2 environments occurred at 7-00 mul 1(-1) CO2 compared with 350 mul 1(-1) CO2, but approximately a 45% increase occurred in the plants grown at 18.9-26-.9-degrees-C. Less total biomass was produced at 35.5- degrees-C than at 26.9-degrees-C and no bolls were produced in eith-er CO2 environment at the higher temperature. The most important response to temperature and CO2 occurred at high temperat-ures where the effects of elevated CO2 on plant growth were masked by apparent high-temperature injury that limited growth of all plant organs, particularly, reproductive growth. @6 @7 @2 @0@-886^6^Robertson,EJ^Williams,M^Harwood,JL^Lindsay,JG^Leaver,CJ^Leech,RM^1995^1^Mitochondria increase 3-fold and mitochondri-al proteins and lipid change dramatically in postmeristematic cells in young wheat leaves grown in elevated co2^8^108^2^469-474^^^^^Jun^^^^^4572@ FONTS@YY @Z@&CE3 @A -A^4571^A dramatic stimulation in mitochondrial biogenesis during the very early stages of leaf development was observed in- young wheat plants (Triticum aestivum cv Hereward) grown in elevated CO2 (650 mu L L(-1)). An almost 3-fold increase in t-he number of mitochondria was observed in the very young leaf cells at the base of the first leaf of a 7-d-old wheat plant-. In the same cells large increases in the accumulation of a mitochondrial chaperonin protein and the mitochondrial 2- oxo-glutarate dehydrogenase complex and pyruvate dehydrogenase complex were detected by immunolabeling. Furthermore, the basal- segment also shows a large increase in the rate of radiolabeling of diphosphatidylglycerol, a lipid confined to the inner- mitochondrial membrane. This dramatic response in very young leaf cells to elevated CO2 suggests that the numerous documented positive effects of elevated CO2 on wheat leaf development are initiated as early as 12 h postmitosis.@SIG-887^3^Wang,ZM^Lechowicz,MJ^Potvin,C^1995^1^Responses of black spruce seedlings to simulated present versus future seedbed environments^155^25^4^545-554^^^^^Apr^^^^^4574@ @CDK @QZO @-A^4573^We investigated the effects of nitrogen availability and present versus future atmospheric environments (i.e., clim-ate) on the seedling performance of 16 open-pollinated maternal families of Picea mariana (Mill.) B.S.P. over two simulate-d growing seasons. Diurnal and seasonal patterns of temperature, relative humidity, photoperiod, and light intensity were -simulated. The simulated future climate included both elevated CO2 and seasonally appropriate increases in mean monthly te-mperatures. Compared with the present, the future climate increased seedling survival, total and root dry mass, rate of wi-nter bud development, net photosynthetic rate, and water and nitrogen use efficiencies; decreased needle nitrogen content;- and altered biomass allocation patterns. Greater nitrogen availability greatly improved seedling performance and changed -biomass allocation patterns. Climate and nitrogen level interacted synergistically to promote seedling growth (branch numb-er and root dry mass), survival, and bud development. The future climate increased seedling survival, rate of bud developm-ent, and nitrogen use efficiency much more in the low than in the high nitrogen regime. Seedling performance in the second- season was dependent on initial seed mass, but less than in the 1st year. Some of the differences among the families and -in their interactions with the climate and (or) nitrogen fertilization suggest that families selected for rapid growth und-er present conditions may not do well in the future, at least in terms of early establishment. Forest managers and tree breeders should take this possibility into consideration in their tree improvement and reforestation programs.IER-888^3^White,NDG^Jayas,DS^Muir,WE^1995^1^Toxicity of carbon-dioxide at biologically producible levels to stored-product beetles^238^24^3^640-647^^^^^Jun^^^^^4576N@$x9*qY@?( POINT-A^4575^The effect of concentrations of carbon dioxide (CO2) that can be produced by biological respiration (7.5-19.2%) on -oviposition of adult Tribolium castaneum (Herbst), Cryptolestes pusillus (Schonherr), or C. ferrugineus (Stephens) was det-ermined. Relative to controls, T. castaneum , C. pusillus , and C. ferrugineus , exposed to 7.5% CO2 for 1 wk, had numbers- of offspring reduced by 43, 94, and 50%, respectively, and the total population at 6 wk was reduced 53, 84, and 19%, resp-ectively. With levels of greater than or equal to 17.1% CO2 for 1 wk, no offspring were produced and exposed adults had hi-gh mortality. Eggs and subsequent immatures of Tribolium confusum J. du Val, T. castaneum, or C. ferrugineus were exposed -for 3 wk to elevated levels of CO2 at 22 degrees C. Insect development was similar at 7.5 and 8.6% CO2 with mean mortality- 43, 62, and 30% greater than controls for T. confusum, T. castancum, and C. ferrugineus, respectively. Also, mean levels -of 5.8-8.3% CO2 for 7 wk reduced, on all sampling dates, populations of T. confusum by 85%, T. castaneum by 99%, C. pusill-us by 68%, and C. ferrugineus by 54%. Although T. castaneum had a greater oviposition rate than C. pusillus at 7.5% CO2, i-mmature mortality was greater for T. castaneum. Based on long-term exposure to levels of CO2 which can be produced by biol-ogical activity that affects oviposition and immature development, species in increasing order of sensitivity to CO2 are C. ferrugineus, C. pusillus, T. confusum, and T. castaneum.    GQ .-889^2^Zhang,J^Lechowicz,MJ^1995^1^Responses to co2 enrichment by 2 genotypes of arabidopsis- thaliana differing in their sensitivity to nutrient availability^52^75^5^491-499^^^^^May^^^^^4578CIENCE@3YS@T\> -A^4577^The responses of two genotypes of Arabidopsis thaliana, which differ in their sensitivities to nutrients to present- and predicted future CO2 concentration were determined under rich vs. poor nutrient regimes on the basis of both single t-raits and the whole plant. Based on individual traits, the two genotypes responded similarly to CO2 enrichment for all the- traits measured except for rate of increase in crown diameter, for which a decrease was observed in the less nutrient- se-nsitive genotype grown at increased CO2. Based on the overall response of the whole plant, by analysing groups of plant tr-aits using multivariate analysis, the two genotypes differed substantially from one another and both responded more strong-ly to nutrient availability than to CO2 concentration, especially for traits measured at harvest that related to reproduct-ive fitness. The less nutrient-sensitive genotype also showed a weaker overall response to CO2, and the pattern of the ove-rall response was strikingly similar at different nutrient Supply. In contrast, the more nutrient-sensitive genotype respo-nded more strongly to CO2 than the less nutrient-sensitive genotype, and responded differently to CO2 at low vs. high nutrient availability.%S @  @ S@'x9(-^Mq REPORT@ MAND)890^8^Akin,DE^Kimball,BA^Windham,WR^Pinter,PJ^Wall,GW^Garcia,RL^Lamorte,RL^Morrison,WH^1995^1^Effect of free-air co2 enric.A^4579^Wheat (Triticum aestivum L., cultivar 'Yecora rojo') was grown in ambient (370 mu mol mol(-1)) or enriched (550 mu .mol mol(- 1)) concentrations of CO2 in the free-air CO2 enrichment (FACE) project, and components were analyzed for in vit.ro digestibility, fiber constituents, and crude protein. Four replicated plots of each CO2 treatment were split for irriga.tion: 'wet' regions received 60 cm of water and 'dry' regions received 30 cm of water through underground tubes. Enriched .CO2 concentrations had no effect on in vitro digestion of intact sections of young (26-32-day-old plants) leaf blades exce.pt at 24-27 h incubation, at which time enriched leaves were lower in digestibility than control ones. Enriched CO2 concen.trations increased the content of acid detergent fiber (ADF) and cellulose of young wet leaves, Sections of main shoots at. 26 days tended to have increased digestibility with elevated CO2 levels. Enriched CO2 concentrations did not alter the di. gestibility of flag leaves from 105-day-old plants or of flag leaves, uppermost stems, and sheaths from plants at full gra. in maturity, Enriched CO2 levels reduced the acid detergent lignin (ADL) and tended to reduce the protein of leaves from 1. 05-day-old plants. For mature leaf blades, neutral detergent fiber, ADF, and cellulose were, or tended to be, higher while. protein content tended to be lower in elevated CO2-grown plants; for both CO2 treatments, 'dry' leaves were higher in dig.estibility and lower in ADL than 'wet' samples. Mature stems plus sheaths had lower protein contents in plants grown in el.evated CO2. Results indicated that enriched CO2 concentrations to 550 mu mol mol(-1) did not substantially alter wheat in .vitro digestibility, regardless of irrigation treatment. Elevated CO2 altered fiber components and protein, but these were not consistent among parts and harvests.VL 39 IS 3 GA NP930 RP GUNDERSON CA J9 PHOTOSYNTH RES ER PT J AU JOHNSEN, KH T.891^2^Boerner,REJ^Rebbeck,J^1995^1^Decomposition and nitrogen release from leaves of 3 hardwood species grown under elevated o-3 and/or co2^206^170^1^149-157^^^^^Mar^^^^^4582REVUE CANADIENNE DE RECHERCHE FORESTIERE SN 0045-5067 C1 FORESTRY CAN.A^4581^Elevated concentrations of O-3 and CO2 have both been shown to affect structure, nutrient status, and deposition of. secondary metabolites in leaves of forest trees. While such studies have produced robust models of the effects of such ai.r pollutants on tree ecophysiology and growth, few have considered the potential for broader, ecosystem-level effects afte.r these chemically and structurally altered leaves fall as leaf litter and decay. To determine the effects of elevated O-3. and/or CO2 on the subsequent decomposition and nutrient release from the leaves grown in such altered atmospheres, we gre.w seedlings of three widespread North American forest trees, black cherry (Prunus serotina) (BC), sugar maple (Acer saccha.rum) (SM), and yellow-poplar (Liriodendron tulipifera) (YP) for two growing seasons in charcoal-filtered air (CF-air=appro.ximately 25% ambient O-3), ambient O-3 (1X) or twice-ambient O-3 (2X) in outdoor open-top chambers. We then assayed the lo.ss of mass and N from the litter derived from those seedlings through one year litterbag incubations in the forest floor o.f a neighboring forest stand. Mass loss followed linear functions and was not affected by the O-3 regime in which the leav.es were grown. Instantaneous decay rates (i.e. k values) averaged SM:-0.707 y(-1), BC:-0.613 y(-1), and YP:-0.859 y(-1). N. loss from ambient (1X) O-3-grown SM leaves was significantly greater than from CF-air leaves; N loss from BC leaves did n. ot differ among treatments. Significantly less N was released from CF-air-grown YP leaves than from 1X or 2X O-3-treated l.!eaves. YP leaves from plants grown in pots at 2X O-3 and 350 ppm supplemental CO2 in indoor pollutant fumigation chambers ."(CSTRs or Continuously Stirred Tank Reactors) loss 40% as much mass and 27% as much N over one year as did leaves from YP .#grown in CF-air or 2X O-3. Thus, for leaves from plants grown in pots in controlled environment fumigation chambers, the c.$oncentrations of both O-3 and CO2 can affect N release from litter incubated in the field whereas mass loss rate was affec.%ted only by CO2. Because both mass loss and N release from leaves grown at elevated CO2 were reduced significantly (at lea.&st for yellow-poplar), forests exposed to elevated CO2 may have significantly reduced N turnover rates, thereby resulting in increased N limitation of tree growth, especially in forests which are already N-limited.ntral North American tallgras.(892^2^Brakke,M^Allen,LH^1995^1^Gas-exchange of citrus seedlings at different temperatures, vapor-pressure deficits, and soil-water contents^154^120^3^497-504^^^^^May^^^^^4584F PHOTOSYNTHESIS, CONDUCTANCE AND WATER POTENTIAL AT THE TOP OF A LOW.*A^4583^Midday reductions of stomatal conductance and carbon dioxide assimilation rates (A(CO2)) in Citrus are typically at.+tributed to large leaf-to-air vapor-pressure differences or high atmospheric vapor-pressure deficits (VPD). This study inv.,estigated air temperature (T-a) and available soil water (ASW) level as corollary factors of atmospheric VPD that influenc.-e midday reduction of net gas exchange in citrus leaves. The influence of elevated atmospheric CO2 under conditions that i..nhibit net canopy A(CO2) was also investigated. Net canopy A(CO2) and evapotranspiration rates of Carrizo citrange [Poncir./us trifoliata Raf x Citrus sinensis (L.) Osbeck] and Swingle citrumelo (P. trifoliata Raf x C. paradisii Macf.) seedlings .0grown in outdoor controlled- environment growth chambers were measured under two levels of T-a with concomitant changes in.1 VPD and two levels of atmospheric CO2 concentration, which were changed in steps over time. Cyclical depletion of ASW was.2 allowed to occur at each set of T-a/VPD and CO2 combinations. Highest net canopy A(CO2) rates at ambient CO2 concentratio.3n (330 mu mol . mol(-1)) were obtained at the low T-a/VPD level (29C/2.4 kPa) and ASW >50%. Diurnal canopy CO2 uptake rate.4s decreased at the high T-a/VPD level (37C/3.6 kPa), and midday depression of canopy A(CO2) was observed at ASW levels <50.5%. Net canopy A(CO2) decreased at higher levels of ASW under the high T-a/VPD treatment than at the low T-a/VPD treatment..6 At the elevated CO2 concentration (840 mu mol . mol(-1)) net canopy CO2 uptake rates were double those that occurred at a.7mbient CO2 levels and they did not exhibit midday reduction. Our data indicate that, when soil water is not readily availa.8ble, citrus seedlings are more sensitive to high levels of T-a and VPD which results in reduction of CO2 uptake. The inhibitory effects of elevated VPD and reduced ASW on citrus net A(CO2) were lessened at the elevated atmospheric CO2 level.EH.:893^1^Bunce,JA^1995^1^The effect of carbon-dioxide concentration on respiration of growing and mature soybean leaves^9^18^5^575-581^^^^^May^^^^^4586for the interaction coefficient (k(ij)) of CO2/n-alkane binary systems with a translated modifi. 5d after full area expansion, The short-term response of respiration rate to the measurement CO2 concentration was also d.?etermined at each age, Respiration rates per unit of dry mass declined with age and were significantly less at a given age.@ or RGR in leaves grown and measured at the elevated CO2. The difference in respiration rate was largest in mature leaves .Aand resulted from the different measurement CO2 concentrations, The respiratory costs of the tissue synthesis, estimated f.Brom the elemental composition of the tissue, did not differ substantially between CO2 treatments, The response of respirat.Cion rate to carbon dioxide concentration was not strongly affected by the form of nitrogen supplied. Maintenance respirati.Don calculated by subtracting growth respiration from total respiration was negative in rapidly growing leaves for both CO2.E treatments, This indicates that CO2 efflux in the dark does not accurately reflect the average 24h rate of energy expenditure on growth and maintenance for soybean leaves.rtilization effect CO2 has on some plants, the impact UVB radiation has.G894^1^Bunce,JA^1995^1^Effects of elevated carbon-dioxide concentration in the dark on the growth of soybean seedlings^52^75^4^365-368^^^^^Apr^^^^^4588is to review direct and indirect effects of anthropogenic greenhouse gases on wildlife, and t.IA^4587^Previous work has shown that elevated carbon dioxide (CO2) concentrations in the dark reversibly reduce the rate of.J CO2 efflux from soybeans. Experiments were performed exposing soybean plants continually to concentrations of 350 or 700 .Kcm(3) m(-3) for 24 h d(-1), or to 350 during the day and 700 cm(3) m(-3) at night, in order to determine the importance of.L the reduced rate of dark CO2 efflux for plant growth. High CO2 applied only at night conserved carbon and increased dry m.Mass during initial growth compared with the constant 350 cm(3) m-3 treatment. Long-term net assimilation rate was increase.Nd by high CO2 in the dark, without any increase in daytime leaf photosynthesis. However, leaf area ratio was reduced by th.Oe dark CO2 treatment to values equal to those of plants continually exposed to the higher concentration. From days 14- 21,.P leaf area was less for the elevated night-time CO2 treatment than for either the constant 350 or 700 cm(3) m(-3) treatmen.Qts. For the day 7-21-period, relative growth rate was significantly reduced by the high night CO2 treatment compared with .Rthe 350 cm(3) m(-3) continuous treatment. The results indicate that some functionally significant component of respiration was reduced by the elevated CO2 concentration in the dark., practical method of estimating CO2 is needed for pediatric p.T895^3^Carter,GA^Rebbeck,J^Percy,KE^1995^1^Leaf optical-properties in liriodendron-tulipifera and pinus- strobus as influenced by increased atmospheric ozone and carbon-dioxide^155^25^3^407-412^^^^^Mar^^^^^4590for 5,159 thirty-second epochs. Al.VA^4589^Seedlings of Liriodendron tulipifera L. and Pinus strobus L. were grown in open-top chambers in the field to determ.Wine leaf optical responses to increased ozone (O-3) or O-3 and carbon dioxide (CO2). In both species, seedlings were expos.Xed to charcoal-filtered air, air with 1.3 times ambient O-3 concentrations (1.3X), or air with 1.3 times ambient O-3 and 7.Y00 mu L . L(-1) CO2 (1.3X + CO2). Exposure to 1.3X increased reflectance in the 633-697 nm range in L. tulipifera. Also, 1.Z.3X decreased transmittance within the 400-420 nm range, increased transmittance at 686-691 nm, and decreased absorptance .[at 655-695 nm. With 700 mu L . L(-1) CO2, O-3 did not affect reflectance in L. tulipifera, but decreased transmittance and.\ increased absorptance within the 400-421 nm range and increased transmittance and decreased absorptance in the 694-697 nm.] range. Under 1.3X, reflectance in P. strobus was not affected. However, 1.3X + CO2 increased pine reflectance in the 538-.^647, 650, and 691-716 nm ranges. Transmittances and absorptances were not determined for P. strobus. Reflectance in both s._pecies, and transmittance and absorptance in L. tulipifera, were most sensitive to O-3 near 695 nm. Reflectance at 695 nm,.` but particularly the ratio of reflectance at 695 nm to reflectance at 760 nm, was related closely to ozone-induced decreases in leaf chlorophyll contents, particularly chlorophyll a (r(2) = 0.82).. Rev. Respir. Dis. PY 1993 PD DEC VL 148 IS 6.b896^2^Ceulemans,R^Mousseau,M^1995^1^Effects of elevated atmospheric co2 on woody-plants (vol 12m, pg 425, 1995)^84^129^3^535^^^^^MarAND CO2 EXCHANGE FOR THE CRASSULACEAN ACID METABOLISM PLANT OPUNTIA-FICUS-INDICA SO PHYSIOLOGIA PLANTARUM SN 00.d897^3^Chen,XM^Begonia,GB^Hesketh,JD^1995^1^Soybean stomatal acclimation to long-term exposure to co2- enriched atmospheres^79^31^1^51-57^^^^^^^^^^4593IVITY; ROOT GROWTH; SHOOT GROWTH ID ATMOSPHERIC CARBON-DIOXIDE; SOURCE-SINK RELATIONS; PHOTOS.fA^4592^Soybean [Glycine max (L.) cv. Jack] grown in open top chambers under controlled laboratory and field conditions was.g used to study the acclimation of leaf gas exchange processes to CO2 enrichment. Air inside the open top chambers was main.htained at either 700-800 or 350-400 mu mol(CO2) mol(-1)(air). Leaf gas exchange rates were measured for some plants switch.ied between treatments. When measured in the CO2-enriched atmosphere, stomatal conductances (g(s)) were higher in leaves gr.jown in CO2-enriched atmospheres than in those grown under ambient conditions, and the lower g(s) values for plants in the .kCO2- enriched atmospheres were limiting to leaf net photosynthetic CO2 exchange rates (P-N). P-N of enriched leaves was hi.lgher than those of the ambient controls when measured at elevated CO2 levels in both controlled environment and field stud.mies, while it was depressed in enriched leaves when measured under ambient CO2 conditions, and this drop in P-N did not recover until 6-15 d after plants were placed back in ambient conditions. gain was enhanced 24% by elevated CO2 during the .o898^4^Ellis,RH^Craufurd,PQ^Summerfield,RJ^Roberts,EH^1995^1^Linear relations between carbon-dioxide concentration and rate - of development towards flowering in sorghum, cowpea and soybean^52^75^2^193-198^^^^^Feb^^^^^4595ass nearly doubled as .qA^4594^Negative linear relations were detected (P < 0.005) between the rate of progress from sowing to panicle initiation .rand CO2 concentration (210-720 mu mol CO2 mol(-1) air) for two genotypes of sorghum [Sorghum bicolor (L.) Moench]. Relatio.sns between CO2 concentration and the rate of progress from sewing to first flowering were also negative in soyabean [Glyci.tne max (L). Merrill] (P < 0.025), but positive in cowpea [Vigna unguiculata (L.) Walp.] (P < 0.025), albeit that in both g.urain legumes sensitivity was much less than in sorghum. Thus CO2 elevation does not delay flowering in all short-day speci.ves. The considerable effect of CO2 concentration on times to panicle initiation resulted in large differences among the so.wrghum plants at this developmental stage; with increase in CO2 concentration, plants were taller with slightly more leaves.x and more pronounced apical extension. At the same time after sowing however, sorghum plants were heavier (P < 0.05) at 21.y0 than at 360 mu mol CO2 mol(-1) air. In contrast, relations between the dry masses of the soyabean and cowpea plants and .zCO2 concentration were positive and curvilinear (P < 0.05). It is suggested that the impact of global environmental change could be severe for sorghum production in the semi-arid tropics.ants for one year at a cladode area per unit ground area.|899^1^Ericsson,T^1995^1^Growth and shoot - root ratio of seedlings in relation to nutrient availability^206^169^^205-214^^^^^Jan-Feb^^^^^4597asal (planted) cladodes after 3 months and nearly doubled the number and area of second-order cladodes.~A^4596^The influence of mineral nutrient availability, light intensity and CO2 on growth and shoot:root ratio in young pla.nts is reviewed. Special emphasis in this evaluation is given to data from laboratory experiments with small Betula pendul.a plants, in which the concept of steady-state nutrition has been applied. Three distinctly different dry matter allocatio.n patterns were observed when growth was limited by the availability of mineral nutrients: 1, Root growth was favoured whe.n N, P or S were the major growth constraints. 2, The opposite pattern obtained when K, Mg and Mn restricted growth. 3, Sh.ortage of Ca, Fe and Zn had almost no effect on the shoot:root ratio. The light regime had no effect on dry matter allocat.ion except at very low photon flux densities (< 6.5 mol m(-2) day(-1)), in which a small decrease in the root fraction was. observed. Shortage of CO2 on the other hand, strongly decreased root development, while an increase of the atmospheric CO.2 concentration had no influence on dry matter partitioning. An increased allocation of dry matter to below- ground parts .was associated with an increased amount of starch in the tissues. Depletion of the carbohydrate stores occurred under all .conditions in which root development was inhibited. It is concluded that the internal balance between labile nitrogen and .carbon in the root and the shoot system determines how dry matter is being partitioned in the plant. The consistency of this statement with literature data and existing models for shoot:root regulation is examined.own in elevated CO2 concentra.900^1^Hanninen,H^1995^1^Effects of climatic-change on trees from cool and temperate regions - an ecophysiological approach to modeling of bud burst phenology^188^73^2^183-199^^^^^Feb^^^^^4599as been suggested that this apparent down regulation.A^4598^A framework is presented for meddling bud burst phenology of trees from the cool and temperate regions. Three ecoph.ysiological aspects affecting the timing of bud burst are considered: (i) effects of environmental factors on the rest sta.tus of the bud, (ii) effect of rest status on the ability for bud burst, and (iii) direct effect of air temperature on the. rate of development towards bud burst. Any model for bud burst phenology can be presented within the framework with three. submodels, each of them addressing one of the corresponding three ecophysiological aspects. A total of 96 hypothetical mo.dels were synthesized by combining submodels presented in the literature. The models were tested in two experiments with s.aplings of Pinus sylvestris L. growing in experimental chambers at their natural site in eastern Finland. In the first exp.eriment, air temperature and (or) concentration of atmospheric CO2 was elevated. Elevation of the air temperature hastened. bud burst, whereas elevation of the concentration of CO2 did not affect it. Several models accurately predicted the timin.g of bud burst for natural conditions but too early for bud burst at the elevated temperatures. This finding suggests that. (i) the risk of a premature bud burst with subsequent frost damage, as a result of climatic warming, was overestimated in. a recent simulation study, and (ii) bud burst observations in natural conditions alone are not sufficient for the testing. of these mechanistic models. Several models did predict the timing of bud burst accurately for all treatments, but none o.f them obtained sufficiently strong support from the findings to stand out as superior or uniquely correct. In the second .experiment a photoperiod submodel for rest break was tested by exposing the saplings to short-day conditions. The short-da.y treatment had only a minor effect on the timing of bud burst. These results demonstrated the importance of the concept o.f model realism: the accuracy of a model can be lost in new conditions (e.g., global warming), unless the model correctly addresses the essential ecophysiological aspects of the regulation of timing of bud burst.mulation of microbial activity .901^4^Hunt,R^Hand,DW^Hannah,MA^Neal,AM^1995^1^Temporal and nutritional influences on the response to elevated co2 in selected british grasses^52^75^2^207-216^^^^^Feb^^^^^4601to consumption of phytodetritus. Several aspects on quality of phytod.A^4600^To investigate the duration of the CO2 response and its interaction with mineral nutrition, CO2-enrichment experime.nts were performed on four British grasses of differing ecology and functional type: Arrhenatherum elatius (L.) Beauv., Fe.stuca ovina L., Festuca rubra L. and Poa annua L. Naturally-lit, glasshouse cabinets were used, with a non-limiting water .supply and a daytime mean temperature of 18 degrees C. Two CO2 treatments were maintained at nominal concentrations of 350. and 700 vpm and were combined factorially with two levels of balanced mineral nutrition at conductivities of 0.1 and 1 mS. cm(-1). Harvests took place at planting-out, and at 16, 37 and 58 d thereafter. Fitted curves were used to derive instant.aneous values of total dry weight, relative growth rate (RGR), shoot weight fraction (SWF) and unit shoot rate (USR) for a.ll combinations of species, CO2 level, nutrient level and time of harvesting. At the higher nutrient level there was a rea.sonably close agreement with previous estimates of the CO2 response in the four species. The response, if any, most often .arose from an increase in USR being accompanied by a less than proportionate decline in SWF. Responses were sustained thro.ughout the period studied. At the lower nutrient level, all species showed a CO2 response initially, but this declined at .a rate which was inversely related to the CO2- responsiveness of the species at the higher nutrient level. The underlying .ontogenetic drift appeared to be markedly towards adjustment in SWF and away from that of USR. However, this drift was retarded, suspended or even reversed by low-nutrient conditions and/or by high CO2 responsiveness in the species itself.e pe.902^3^Johnson,DW^Ball,T^Walker,RF^1995^1^Effects of elevated co2 and nitrogen on nutrient-uptake in ponderosa pine-seedlings^206^169^^535-545^^^^^Jan-Feb^^^^^4603a 57 Torr) and 10 l min(-1) mM(-1) during exercise (arterial P-O2 during hypoxia .A^4602^This paper reports on the results of a controlled-environment study on the effects of CO2 (370, 525, and 700 mu mol. mel(-1)) and N [0, 200, and 400 mu g N g soil(-1) as (NH4)SO4] on ponderosa pine (Pinus ponderosa) seedlings. Based upon .a review of the literature, we hypothesized that N limitations would not prevent a growth response to elevated CO2. The hy.pothesis was not supported under conditions of extreme N deficiency (no fertilizer added to a very poor soil), but was sup.ported when N limitations were less severe but still suboptimal (lower rate of fertilization), The growth increases in N-f.ertilized seedlings occurred mainly between 36 and 58 weeks without any additional N uptake. Thus, it appeared that elevat.ed CO2 allowed more efficient use of internal N reserves in the previously-fertilized seedlings, whereas internal N reserv.es in the unfertilized seedlings were insufficient to allow this response, Uptake rates of other nutrients were generally .proportional to growth. Nitrogen treatment caused reductions in soil exchangeable K+, Ca2+, and Mg2+ (presumably because o.f nitrification and NO3- leaching) but increases in extractable P (presumably due to stimulation of phosphatase activity).. The results of this and other seedling studies show that elevated CO2 causes a reduction in tissue N concentration, even .under N- rich conditions. The unique response of N is consistent with the hypothesis that the efficiency of Rubisco increa.ses with elevated CO2. These results collectively have significant implications for the response of mature, N-deficient forests to elevated CO2.Measurements could be obtained for approximately 60 min following a single injection. Mice exposed .903^1^Kennedy,AD^1995^1^Temperature effects of passive greenhouse apparatus in high- latitude climate-change experiments^43^9^2^340-350^^^^^Apr^^^^^4605 the fluorescence signal recovered within 20 min. The fluorescence intensity ratio was cali.A^4604^1. Passive greenhouse apparatus is commonly used to investigate the in situ biological response of terrestrial comm.unities to global warming. 2. Although close conformity of greenhouse treatment effects to general circulation model (GCM). scenarios is widely claimed, no proof of such a relationship has yet been published. 3. Here, the relationship between pa.ssive greenhouse thermal environment and future climate conditions is considered using temperature data collected from wit.hin and without greenhouses deployed in the maritime Antarctic. It is revealed that in terms of thermal extremes, diel and. annual variation, and overall distribution across the temperature spectrum, such apparatus achieves only poor simulation .of GCM forecasts. 4. During summer, greenhouses induce an amplified daily range of temperatures, elevated maxima and accel.erated rates of change. 5. During spring and autumn, diel temperature variation continues inside the greenhouses while sno.w cover protects the controls. 6. During winter, an inverse treatment effect occurs, in which the relative depth of snow c.over causes lower temperatures in greenhouses than in controls. 7. These treatment effects differ significantly from GCM c.limate predictions. Changes recorded in the composition, structure and function of greenhouse biota may thus be artefacts .of the methodology. 8. Thorough a priori testing of greenhouse treatment effects is recommended for future climate change studies that are to be conducted in environments subject to seasonal snowfall, solar elevation and day length.ly turned o.904^1^Kerstiens,G^1995^1^Cuticular water permeance of european trees and shrubs grown in polluted and unpolluted atmospheres, and its relation to stomatal response to humidity in beech (fagus-sylvatica L)^84^129^3^495-503^^^^^Mar^^^^^4607mosph.A^4606^Cuticular water permeance (P) of astomatous adaxial surfaces of intact leaves was determined in Acer pseudoplatanus. L., Betula pubescens Ehrh., Corylus avellana L., Fagus sylvatica L. and Prunus avium L. Water evaporating from the stomat.a-bearing abaxial leaf surface could not reach the moisture analyzer and the values of P presented here are therefore free. from errors that often arise from unintentional inclusion of residual stomatal transpiration. Plants were exposed from be.fore bud- break for several months to 20-50 ppb SO2 (Fagus), a combination of 50-60 ppb SO2 and 50-60 ppb NO2 (Betula), 30.0- 400 ppb NO (Acer, Corylus, Fagus), regular ozone episodes of up to 120 ppb (Fagus, Prunus), or an elevated level of CO2. (600 ppm for 2 yr; Acer, Fagus). Permeances were in the range 0.6- 2.9 x 10(-5) m s-1 and were unaffected by most treatme.nts. In Prunus, P increased slightly but significantly in the NO treatment. In Corylus and Fagus, P was sometimes found to. be reduced by fumigation with NO, but not always. Betula leaves grown under elevated SO2 and NO2 showed higher values of .P only if they were visibly damaged. Minimum conductances (g(min) estimated from water loss rates of both sides of detache.d hypostomatous leaves were higher than P, and were more strongly affected by treatments. In these cases, the most probabl.e explanation is some damage to stomatal function resulting in a reduced ability to close after leaf excision. Effects of .growing conditions and time of year on P were found, which allowed a hypothetical interaction between P and stomatal sensitivity to air humidity to be tested in beech. No unambiguous indication of such a relationship was found.-re during heat .905^1^Koike,T^1995^1^Effects of co2 in interaction with temperature and soil fertility on the foliar phenology of alder, birch, and maple seedlings^188^73^2^149-157^^^^^Feb^^^^^4609ever, hypercapnia depressed V-o2 but did not affect T-re compa.A^4608^The foliar phenology of potted 1-year-old seedlings of alder (Alnus hirsuta Turcz.), maple (Acer mono Maxim.), and .birch (Betula platyphylla Sukatch, var. japonica Hara) was observed from May to September in eight growth environments: fa.ctorial combinations of temperatures (light:dark, 30:20 degrees C and 26:16 degrees C), CO2 level (70 and 36 Pa), and nutr.ient regime (high versus low levels of fertilization). Seedlings grown at high fertility always had more leaves, and under. high CO2, shed leaves slightly later than seedlings grown at low fertility. Except for maple, production of newly formed .shoots and leaves was accelerated by high CO2. In maple, high CO2 only increased the number of flushes of the leader shoot.. Alder and birch accelerated sylleptic shoot and leaf production at high CO2 in fertile conditions. The production of new. leaves by alder grown at high CO2 and low fertility was almost the same as that grown under normal CO2 at high fertility.. At high CO2, the timing of winter bud formation of monopodial alder and maple was delayed, while that of sympodial birch was almost the same as at ambient CO2.richment on the short-term response of photosynthesis to intercellular CO2 (the A/C.906^3^Korner,C^Pelaezriedl,S^Vanbel,AJE^1995^1^Co2 responsiveness of plants - a possible link to phloem loading^9^18^5^595-600^^^^^May^^^^^4611 usually exhibiting a reduction of A at a given C-i, while plants grown without nutrient deficiency .A^4610^Of the many responses of plants to elevated CO2, accumulation of total non-structural carbohydrates (TNC in % dry w.eight) in leaves is one of the most consistent, Insufficient sink activity or transport capacity may explain this obvious .disparity between CO2 assimilation and carbohydrate dissipation and structural investment, If transport capacity contribut.es to the problem, phloem loading may be the crucial step, It has been hypothesized that symplastic phloem loading is less. efficient than apoplastic: phloem loading, and hence plant species using the symplastic pathway and growing under high li.ght and good water supply should accumulate more TNC at any given CO2 level, but particularly under elevated CO2. We teste.d this hypothesis by carrying out CO2 enrichment experiments with 28 plant species known to belong to groups of contrastin.g phloem loading type. Under current ambient CO2 symplastic loaders were found to accumulate 36% TNC compared with only 19.% in apoplastic loaders (P = 0.0016), CO2 enrichment to 600 mu mol mol(-1) increased TNC in both groups by the same absolu.te amount, bringing the mean TNC level to 41% in symplastic loaders (compared to 25% in apoplastic loaders), which may be .close to TNC saturation (coupled with chloroplast malfunction), Eight tree species, ranked as symplastic loaders by their .minor vein companion cell configuration, showed TNC responses more similar to those of apoplastic herbaceous loaders, Simi.lar results are obtained when TNC is expressed on a unit leaf area basis, since mean specific leaf areas of groups were no.t significantly different, We conclude that phloem loading has a surprisingly strong effect on leaf tissue composition, and thus may translate into alterations of food webs and ecosystem functioning, particularly under high CO2.OLIPID- METABOL.907^3^Lindroth,RL^Arteel,GE^Kinney,KK^1995^1^Responses of 3 saturniid species to paper birch grown under enriched co2 atmospheres^43^9^2^306-311^^^^^Apr^^^^^4613eptor- and receptor-mediated mechanisms respectively. We compared the effects of t.A^4612^1. Interactions between trees and tree-feeding insects are likely to shift under conditions of enriched atmospheric. CO2 owing to changes in foliar chemical composition. This study addressed the effects of CO2-mediated changes in leaf che.mistry on performance of three silkmoth (Saturniidae) species: cecropia (Hyalophora cecropia), luna (Actias luna) and poly/phemus (Antheraea polyphemus polyphemus). 2. Growth under elevated CO2 atmospheres decreased nitrogen concentrations (23%)/ but tripled starch and doubled condensed tannin concentrations, resulting in a marked increase in foliar carbon:nitrogen /ratio. 3. Survival of first stadium larvae was marginally reduced when reared on high CO2 leaves. 4. Development rates wer/e prolonged, growth rates tended to decline, consumption increased and food processing efficiencies decreased for fourth s/tadium larvae reared on high CO2 leaves. The magnitude of responses varied among species. 5. Overall performance of these /saturniid species, at least when feeding on birch, is predicted to decline under atmospheric CO2 conditions anticipated for the next century.nd remained elevated at subsequent time points, whereas labeling of choline was higher only with ATP a908^1^Murray,DR^1995^1^Plant-responses to carbon-dioxide^5^82^5^690-697^^^^^May^^^^^4615se D by only ATP. Our studies dem/A^4614^The average atmospheric concentration of CO2 will probably double before the end of next century. Many of the conse/ quences for plant growth can and should be determined now. In this review the effects of [CO2] on a variety of plant proce/ sses are summarized: stomatal opening and closing; stomatal density; respiration; root morphogenesis; and flowering. The e/ ffects of growth under elevated [CO2] on crop yield and seed composition are also discussed. Adverse effects on the composition of C-3 cereal grains are clearly indicated.NASI 221005, UTTAR PRADESH, INDIA. ID PHOTOSYNTHETIC BACTERIA; PHOTOPROD/ 909^3^Nicolussi,K^Bortenschlager,S^Korner,C^1995^1^Increase in tree-ring width in sub-alpine pinus-cembra from the central alps that may be co2-related^252^9^4^181-189^^^^^Apr^^^^^4617, under anaerobic conditions (argon/CO2, 95/5, v/v). Among /A^4616^It has been suggested many times that elevated atmospheric CO2 levels should stimulate radial increment of stem gro/wth. However, interpretation of dendrochronologies with respect to a CO2 signal is a difficult task, since a multitude of /environmental and tree factors influence the growth of stems. Here we provide a data set from subalpine stone pine which c/overs the period from 1750 to 1988, and from which growth rings of the 80- to 90-year age class were analysed. The most co/mmon climatological effects are taken into consideration. We found a steady and significant increase of mean ring width fo/r the considered age class from approximately 1 mm per year in the middle of the last century to about 1.4 mm per year at /present. Selected periods of equal mean summer temperatures in the last century and in more recent decades still yield a m/ean stimulation of about 25% for which atmospheric CO2 enrichment appears to be the most plausible explanation. The recent/ dramatic increase of atmospheric N-deposition could confound this interpretation, but chronologies of the last 2 decades /during which wet and dry deposition of N-compounds showed the most dramatic increase exhibit no deviation from the long te/rm trend. In contrast to the so far conflicting evidence of tree- ring responses to atmospheric changes the clear signal o/btained here may be explained as follows: (1) stone pine produces little late season wood and moisture is never a limiting/ factor (particularly not in the early season); (2) comparatively good climatic records permitted the selection of thermal/ly comparable periods; (3) trees grew under little spatial competition, (4) cores were collected well below the upper alti/tudinal range-limit of stone pine, leaving enough physiological leeway under episodic climatic stress, but (5) trees grew /at altitudes high enough so that the reduction of the partial pressure of CO2 could be expected to cause CO2 to become relatively more limiting than at low elevations.d glucose (p less- than-or-equal-to 0-05) than for canopies grown in 360 mum/ 910^1^Pajari,B^1995^1^Soil respiration in a poor upland site of scots pine stand subjected to elevated-temperatures and atmospheric carbon concentration^206^169^^563-570^^^^^Jan-Feb^^^^^4619ctan formation was greatest in the uppermost leaf are/"A^4618^Soil respiration rates under elevated temperature and atmospheric CO2 concentrations were studied in eastern Finlan/#d (62 degrees 47'N, 30 degrees 58'E, 144 m.a.s.l.) around naturally regenerated 20 - 30 years old Scots pine trees, enclos/$ed in open top chambers. The production of CO2 varied spatially and temporally, but clearly followed the changes in temper/%ature measured at the soil surface. However, soil respiration in the open control was higher than that in chambers; i.e. t/&he chamber itself changed the conditions by increasing the temperature, altering the movement of water, and thereby soil m/'oisture, Nevertheless, an elevation in the concentration of atmospheric CO2 raised soil respiration and brought it nearer /(to the level in the open control. An increase in temperature seemed to inhibit this rise, possibly because of an imbalance between temperature and moisture.ZONE DEPLETION; VISIBLE-LIGHT AB The photosynthetic apparatus of some plant species app/*911^3^Penuelas,J^Biel,C^Estiarte,M^1995^1^Growth, biomass allocation, and phenology responses of pepper to elevated co2 concentrations and different water and nitrogen supply^79^31^1^91-99^^^^^^^^^^4621hotosystem II and Rubisco has also been r/,A^4620^Fifty-day old plants of Capsicum annuum L. with two developed leaves were placed into controlled environment chambe/-rs at atmospheric (350 cm(3) m(-3), ACO(2)) and elevated (700 cm(3) m(-3), ECO(2)) CO2 concentrations under different nitr/.ogen and water supply. Plant response to ECO(2) and the modulating effect of the availability of nitrogen and water were e//valuated. CO2 effects were significant only after 40 d of treatment. An increase in plant growth and yield was found in EC/0O(2) plants only under a good supply of both water (HW) and nitrogen (HN). Chlorophyll concentration responded only to N s/1upply. Root/shoot ratio was higher under ECO(2) only under low N (LN) and low water (LW) supply. Leaf area and specific le/2af area decreased under ECO2. Flowering and fructification took place earlier in ECO(2) under HN and HW. Thus, all CO2 effects were modulated by the N and water supply and the duration of exposure.H RES ER PT J AU THOMPSON, KE ADAMS, MA TI DI/4912^3^Polley,HW^Johnson,HB^Mayeux,HS^1995^1^Nitrogen and water requirements of C3 plants grown at glacial to present carbon-dioxide concentrations^43^9^1^86-96^^^^^Feb^^^^^4623DA. DE CARDIAC HYPERTROPHY; VASCULAR HYPERTROPHY; ORNITHINE DECARBO/6A^4622^1. Nitrogen- and water-use efficiencies in biomass production were determined for three C3 plant species at carbon /7dioxide concentrations ([CO2]) that spanned glacial to present atmospheric levels [200-350 mumol CO2 (mol air)-1]. The spe/8cies were annual grasses Bromus tectorum and Triticum aestivum (two cultivars) and a woody perennial Prosopis glandulosa (/9alone and in mixtures with the C4 grass, Schizachyrium scoparium). 2. Changes in nitrogen- and water- use efficiencies wer/:e used to investigate effects of increasing [CO2] on the relative requirements of C3 plants for these frequently limiting /;resources. 3. Water-use efficiency (biomass produced/evapotranspiration; WUE) increased at higher [CO2] in all species but/< relative responses to [CO2] varied among species, cultivars and watering regimes. 4. Intrinsic WUE (net assimilation/stom/=atal conductance to water), calculated from stable carbon isotopes in plants, increased by about the same relative amount />as did [CO2] in all species. 5. Nitrogen-use efficiency (biomass produced/plant N; NUE) rose at higher [CO2] only in well-/?watered B. tectorum and in P. glandulosa grown alone. 6. The more consistent increase in WUE than NUE in these species at /@higher [CO2] implies that rising [CO2] may have reduced the amount of water relative to nitrogen that some C3 plants require and thereby altered the composition and function of terrestrial ecosystems.timulating left ventricular but not vascula/B913^1^Rawson,HM^1995^1^Yield responses of 2 wheat genotypes to carbon-dioxide and temperature in-field studies using temperature-gradient tunnels^92^22^1^23-32^^^^^^^^^^4625 on the hindlimb vascular resistance properties measured at maximum di/DA^4624^Clear, plastic-coated, temperature gradient tunnels (TGTs), 8 X 1.25 X 1.25 m were designed and built to examine ho/Ew temperature and CO2 affect the yield of wheat in the field. Each of the three modules of each TGT was maintained at a di/Ffferent temperature above the ambient temperature using solar heating during the day and electric heating at night. The ma/Gximum day-time increment above ambient for the warmest module was 5 degrees C and full-season averages were close to 2 deg/Hrees C. TGTs were paired, with air in one being enriched to 700 mu L L(-1) CO2, and in the other being maintained at ambie/Int CO2. Crops were planted in the TGTs at two sites in either summer (December) or winter (April and July) and they remain/Jed there until maturity. CO2 enrichment increased the yield in summer plantings by up to 36%. In winter plantings, with me/Kan temperatures between sowing and anthesis of around 10 degrees C, the responses to CO2 were small averaging only 7% (ran/Lge 1-12%). Though yield declined with increasing temperature in the TGTs in summer, there was a clear trend for an increas/Ming response to CO2 at these higher temperatures, i.e. yield declined less. In summer, there was no convincing evidence fo/Nr a different relative response to CO2 in two isolines which differed in maturity date, though the later line yielded more/O under the highest temperature regime (mean of 22- 24 degrees C between sowing and anthesis). In winter there was a strong/P trend for the isoline requiring less vernalisation to respond more to CO2. It is suggested that early progress towards fl/Qowering might predispose wheat to a greater CO2 response. Overall, the data indicated that the positive response to CO2 in/R grain yield is likely to increase at approximately 1.8% per 1 degrees C in wheat crops that are not limited by water. Ext/Srapolation indicated that the temperature at which there was no response to CO2 was 5 degrees C. All yield responses reflected biomass responses as harvest index was unchanged by CO2.one. Meteoric diagenesis at RME occurred during rising relat/g914^1^Reich,PB^1995^1^Phenology of tropical forests - patterns, causes, and consequences^188^73^2^164-174^^^^^Feb^^^^^4627/VA^4626^Leaf phenology of tropical forests is distinct from other biomes. Unlike the marked temperature-related periodicity/W of temperate forests, development tends to be continuous in aseasonal lowland tropical rain forests and becomes more epis/Xodic in response to increasing annual drought in tropical dry forests. Hence, in tropical rain forests, foliar development/Y (production, senescence, and longevity) is largely under internal rather than environmental control. In contrast, tropica/Zl forests with marked annual dry seasons display associated seasonality of leaf production and shedding. This developmenta/[l seasonality can be explained by overlaying the influence of seasonality on trees' internally regulated development and a/\ppears to be controlled by acclimative physiological processes and not by sensitivity to photo-, thermo-periodic, or direc/]t environmental cues. Consequences of tropical phenology stem from both the variety of leaf and species ecophysiological t/^ypes common to a given moisture regime and their relative synchrony of development, and include the following: larger dive/_rsity of ecophysiological species types in rain than dry forests; differential rates of herbivory in dry than wet seasons /`and for synchronous versus asynchronous leaf flushes; ecosystems with greater canopy foliar mass per hectare in rain than /adry forests; and several leaf adaptations perhaps unique to tropical forests, such as delayed greening and seasonal leaf p/bhenotypes. Tropical forests may vary in sensitivity to predicted climate change. Phenology of rain forests should change l/cittle unless water balance changes markedly, and developmental events in rain forests may be relatively insensitive to mod/derate changes in CO2 or temperature. Phenology of dry forests could be more sensitive, and in opposite directions, to elev/eated CO2 and temperatures. Elevated CO2 might delay the onset of leaf shedding and stimulate longer life span if stand lev/fel transpiration is reduced, whereas higher temperatures could lead to more rapid water depletion, longer leafless periods, and more strongly synchronized phenology.ion of ammonia was found in the caecum (600 +/- 97 and 510 +/- 70 mug N/g, forng and adult rabbits, resp.). The lowest concentration of ammonia was in the stomach. The average pH values of the gastri/i915^2^Reinert,RA^Ho,MC^1995^1^Vegetative growth of soybean as affected by elevated carbon- dioxide and ozone^35^89^1^89-96^^^^^^^^^^4629o 7.1. The gastric content of suckling rabbits contained 29.2 +/- 6.6 mmol VFA per 1 g. These VFA (acetate /kA^4628^The effects of elevated carbon dioxide (CO2) and ozone (O-3) on soybean (Glycine max (L.) Merr. cv. Centennial) gro/lwth and biomass partitioning were evaluated under greenhouse conditions. Soybeans were exposed to CO2 concentrations at 35/m0 (ambient), 450, 550, and 650 mu l liter(-1) (ppm) for 24 h day(-1) for 5 weeks. Ozone treatments of 0 and 120 nl liter(-/n1) (ppb) for 6 h day(-1) for 5 days week-1 for 5 weeks were added in combination with the CO2 treatments. Plant dry weight/o and biomass partitioning were assessed each week. Dry weight of leaf, stem, and root, as well as the total plant dry weig/pht increased with exposure to increasing levels of CO2. Dry weight of leaf, root and total plant were suppressed significa/qntly by the O-3 treatment. Stem dry weight was not affected by O-3. Suppression of root dry weight due to O-3 at each week/rly harvest was significantly dependent on the CO2 concentration. Root growth was enhanced by CO2 at 650 mu l liter(-1) com/spared with ambient CO2 (350 mu l liter(-1)) at 5 weeks of age. At ambient CO2 in the presence of O3 the roots were only ab/tout 63% of the weight of the root grown in the absence of O-3. At 550 and 650 mu l liter(-1) CO2 the biomass of soybean ro/uots in the presence of 120 nl liter(-1) O-3 was 88.2 and 88.4% of the control, respectively. Thus, CO2 limited the amount /vof root growth suppression caused by O-3. The partitioning of leaf, stems and root dry weight in relation to total plant d/wry weight remained relatively constant across each CO2 concentration. Thus, CO2 did not affect biomass partitioning among leaves, stems and roots of soybean.sis was assessed by analyzing for select prostanoids in cerebrospinal fluid sampled fr/y916^1^Reining,E^1994^1^Acclimation of C-3 photosynthesis to elevated co2 - hypotheses and experimental-evidence^79^30^4^519-525^^^^^^^^^^4631lar diameter by 34 +/- 5%. Two cyclooxygenase inhibitors, indomethacin (5 mgikg iv) and ibuprofen (30 /{A^4630^Acclimation of the photosynthesis of C-3 plants to elevated atmospheric CO2 concentrations is frequently observed. /|Some hypotheses frequently proposed to explain this phenomenon are: (1) stomatal closure; (2) inhibition of photosynthesis/} by starch accumulation, and (3) reduced activity or concentration of ribulose-1,5-bisphosphate carboxylase/oxygenase. These hypotheses are compared with experimental evidence from the literature.ds facilitate cerebrovascular relaxation to CO2/917^3^Samarakoon,AB^Muller,WJ^Gifford,RM^1995^1^Transpiration and leaf-area under elevated co2 - effects of soil-water status and genotype in wheat^92^22^1^33-44^^^^^^^^^^4633de (guanosine 3',5'-cyclic monophosphate-mediated dilator), were par/A^4632^Transpiration rate, leaf area expansion, water use and water- use efficiency (WUE) of spaced plants of wheat (cvv. /Matong and Quarrion), were examined at ambient and twice ambient CO2 concentrations in wet and drying soil regimes. A hypo/thesis tested was that both stomatal conductance (g(s)) and leaf area development are so regulated by the plant in relatio/n to soil water status that the reduction of approximately 40% in g(s) in high CO2 has no permanent impact on whole-plant /water use. Whereas, during a soil drying cycle, leaf area increase under elevated CO2 counterbalanced closely for reduced /g(s) in terms of soil water depletion as reported elsewhere, this counterbalance was neither exact at all times, nor did i/t apply when the soil was continuously wet. In wet soil, leaf area was not enhanced much by elevated CO2, probably because/, under the high radiation and nutritional conditions used, the tillering rate was almost maximal anyway. Quarrion, having/ a 40% lower g(s) than Matong genetically, did not counterbalance a reduced transpiration rate with a larger leaf area und/er either drying or wet soil conditions. These results support rejection, for wheat, of the hypothesis posed; elevated CO2/ increased leaf area mainly by virtue of the direct photosynthetic increase rather than changed soil water status. In wet /soil, low g(s) Quarrion had a higher CO2 effect on WUE (+ 73 to 82%) than did Matong (+ 54 to 65%). In drying soil, both cultivars had a similar increase in WUE at high CO2 (+ 60 to 68%). requirements for these enzymes. From modeling of the re/918^2^Silvola,J^Ahlholm,U^1995^1^Combined effects of co2 concentration and nutrient status on the biomass production and nutrient-uptake of birch seedlings (betula-pendula)^206^169^^547-553^^^^^Jan-Feb^^^^^4635increased. This balance may be al/A^4634^Birch seedlings (Betula pendula) were grown for four months in a greenhouse at three nutrient levels (fertilization/ of 0, 100 and 500 kg ha(-1) monthly) and at four CO2 concentrations (350, 700, 1050 and 1400 ppm). The effect of CO2 conc/entration on the biomass production depended on the nutrient status. When mineralization of the soil material was the only/ source of nutrients (0 kg ha(-1)), CO2 enhancement reduced the biomass production slightly, whereas the highest productio/n increase occurred at a fertilization of 100 kg ha(-1), being over 100% between 350 and 700 ppm CO2. At 500 kg ha(-1) the/ production increase was smaller, and the production decreased beyond a CO2 concentration of 700 ppm. The CO2 concentratio/n had a slight effect on the biomass distribution, the leaves accounting for the highest proportion at the lowest CO2 conc/entration (350 ppm). An increase in nutrient status led to a longer growth period and increased the nutrient concentration/s in the plants, but the CO2 concentration had no effect on the growth rhythm and higher CO2 reduced the nutrient concentrations.ng wheat (Triticum aestivum L., cultivars 'Star' and 'Turbo') and spring barley (Hordeum vulgare L., cultivars 'Al/919^1^Teskey,RO^1995^1^A field-study of the effects of elevated co2 on carbon assimilation, stomatal conductance and leaf and branch growth of pinus-taeda trees^9^18^5^565-573^^^^^May^^^^^4637mes during plant development and biomass partitioni/A^4636^A study was conducted in 21-year-old loblolly pine (Pinus taeda L.) trees growing in plantation in north central Ge/orgia, USA, The experiment used branch chambers to impose treatments of ambient, ambient+165 and ambient+ 330 mu mol mol(-/1) CO2. After one growing season there was no indication of acclimation to elevated CO2. In August and September, carbon a/ssimilation, measured by two different methods, was twice as high at ambient +330 mu mol mol(-1) CO2 than at ambient, Dark/ respiration was suppressed by 6% at ambient+l65 and by 14% at ambient+330 mu mol mol(-1) CO2. This suppression was immedi/ate, and not an effect of exposure to elevated CO2 during growth, since respiration was reduced by the same amount in all /treatments when measured at a high CO2 concentration, Elevated CO2 increased the growth of foliage and woody tissue, It al/so increased instantaneous transpiration efficiency, but it had no effect on stomatal conductance, Since the soil at the s/tudy site had low to moderate fertility, these results suggest that the growth potential of forests on many sites may be enhanced by global increases in atmospheric CO2 concentration.O2 conditions and the plant's response to the CO2 enrichment/920^3^Wang,KY^Kellomaki,S^Laitinen,K^1995^1^Effects of needle age, long-term temperature and co2 treatments on the photosynthesis of scots pine^13^15^4^211-218^^^^^Apr^^^^^4639 PG 10 JI Agric. Ecosyst. Environ. PY 1994 PD APR VL 48 IS 3 GA NJ7/A^4638^Naturally regenerated 20-25-year-old Scots pine (Pinus sylvestris L.) trees were grown in open-top chambers in the /presence of an elevated temperature or CO2 concentration, or both. The elevated temperature treatment was administered yea/r- round for 3 years. The CO2 treatment was applied between April 15 and September 15 for 2 years. The photosynthetic resp/onses of 1- and 2-year-old needles to varying photon flux densities (0-1500 mu mol m(-2) s(-1)) and CO2 concentrations (35/0, 700 and 1400 mu mol mol(-1)) during measurement were determined. The CO2 treatment alone increased maximum photosynthet/ic rate and light-use efficiency, but decreased dark respiration rate, light compensation and light saturation regardless /of needle age. In contrast, the temperature treatment decreased maximum photosynthetic rate and photosynthetic efficiency,/ but increased dark respiration rate, light compensation and light saturation. The aging of needles affected the photosynt/hetic performance of the shoots; values of all parameters except photosynthetic efficiency were less in 2- than in I-year-/old needles. The CO2 treatment decreased and the temperature treatment enhanced the reduction in maximum photosynthesis due to needle aging.ansfers also resulted in an immediate 70% reduction in the ammonia excretion rate (J(Amm)) and a 30% in/921^2^Acock,B^Wall,GW^1995^1^A simple conductimetric co2 analyzer with automatic recalibration .1. Design, implementation, and functionality^48^87^1^70-75^^^^^Jan-Feb^^^^^4641 (J(Urea)) did not change, the contribution of J(Urea) to total N ex/A^4640^Controlled-environment plant growth cabinets may be used to investigate the long-term effect of elevated carbon dio/xide concentration ([CO2]) on plant growth. Infrared gas analyzers (IRGAs) are normally used to monitor and control [CO2] /in plant cabinets. With many cabinets in use, however, it soon becomes impractical to purchase an individual IRGA for each/ cabinet, A more economical method of monitoring and controlling [CO2] relies on the change in electrical conductivity whe/n CO2 is dissolved in demineralized water, This work describes the design, implementation, and functionality of an inexpen/sive conductimetric system for controlling [CO2] in plant growth cabinets, Regressing electrical conductivity against [CO2/] over the range 0 to 1000 mu L L(-1) yields a quadratic response. Calibration drift inherent in the conductimetric CO2 an/alyzer requires that each analyzer be recalibrated periodically. Automatically recalibrating with an IRGA every 900 s gave/ control of the [CO2] within the plant enclosures to within 10 to 15 mu L L(-1) of the set point, The [CO2] control system/ is robust enough to maintain this accuracy regardless of the desired [CO2] set point or the mass of plant material within/ the plant growth cabinet, In this approach, only one IRGA is required to control [CO2] in many plant growth cabinets if each cabinet has a dedicated conductimetric CO2 analyzer.ced CO2. This paper examines evidence that allocation of nitrogen/922^3^Archer,S^Schimel,DS^Holland,EA^1995^1^Mechanisms of shrubland expansion - land-use, climate or co-2^50^29^1^91-99^^^^^Jan^^^^^4643allocation of nitrogen to key enzymes of the photosynthetic system as a function of CO2 concentration. It i/A^4642^Encroachment of trees and shrubs into grasslands and the 'thicketization' of savannas has occurred worldwide over t/he past century. These changes in vegetation structure are potentially relevant to climatic change as they may be indicati/ve of historical shifts in climate and as they may influence biophysical aspects of land surface-atmosphere interactions a/nd alter carbon and nitro en cycles. Traditional explanations offered to account for the historic displacement of grasses /by woody plants in many arid and semi-arid ecosystems have centered around changes in climatic, livestock grazing and fire/ regimes. More recently, it has been suggested that the increase in atmospheric CO2 since the industrial revolution has be/en the driving force. In this paper we evaluate the CO2 enrichment hypotheses and argue that historic, positive correlations between woody plant expansion and atmospheric CO2 are not cause and effect.811, AUSTRALIA. DE SUNFLOWER; SENSITIVITY A/923^1^Beerling,DJ^1994^1^Modeling palaeophotosynthesis - late cretaceous to present^190^346^1318^421-432^^^^^29 Dec^^^^^46/A^4644^This paper presents an attempt to reconstruct potential changes in the photosynthetic rates of terrestrial C3 leave/s over the past 120 Ma. The approach has been to couple palaeoatmospheric reconstructions of O-2, CO2 and temperature from/ geochemical modelling, and an independent estimate of ancient CO2 changes from fossil porphyrins, with a mechanistic bioc/hemical model of C3 photosynthesis. The model accounts for the effect of each of these palaeoenvironmental changes, at the/ biochemical level, to predict leaf photosynthesis and has been parametrized for a typical gymnosperm and angiosperm. The /results indicate clear potential for increased photosynthetic C3 fixation in the warm Cretaceous for both angiosperms and /gymnosperms, despite the increased O-2 content of the atmosphere prevailing at the time. Photosynthetic rates are then pre/dicted to progressively decline into the Tertiary, as a result of global cooling. The model simulations also point towards/ some leaf-level ecophysiological explanations for the rise in angiosperm dominance and the concomitant decline in gymnosp/erms from the late Cretaceous onwards, at mid-latitudes, which have not been considered previously. This work provides a b/asis for scaling up to the canopy level to predict the primary productivity of ancient ecosystems and their possible feedback on atmospheric composition and climate.e assimilation flux in plants grown at high CO2, the kinetics of this enzyme c45be used to model photosynthesis under these conditions. The relatively high Rubisco control coefficient under enhanced /924^5^Catsky,J^Pospisilova,J^Solarova,J^Synkova,H^Wilhelmova,N^1995^1^Limitations on photosynthesis under environment-simulating culture in-vitro^261^37^1^35-48^^^^^^^^^^464710 JI Plant Cell Environ. PY 1994 PD MAR VL 17 IS 3 GA MY819 RP WOODR/A^4646^Limitations on photosynthesis, characterized by leaf CO2 exchange, chlorophyll fluorescence, and thylakoid structur/e, were studied under environmental conditions simulating culture in vitro. These were simulated by growing Phaseolus vulg/aris plants in nutrient solution under high relative humidity of air (> 90%), and CO2 concentrations (c(a)) that decreased/ with the development of photosynthetic activities during plant ontogeny (1200 to 300 mg m-3). The ontogeny of such model /plants was more rapid, primary leaves reached photosynthetic maturity 2 to 3 d earlier and their life span was 7 to 14 d s/horter than in control plants. Their photosynthetic activity in situ was limited, after reaching ''photosynthetic maturity/'', similarly to plants grown in vitro. When measured under optimal conditions, however, 50 to 70% higher net photosynthet/ic rate (P(N)) were found in leaves of different ages as compared with plants grown under c(a) of 700 mg m-3 and a lower a/ir humidity (30 - 35%). This increase in P(N) was associated with a high conductance for CO2 transfer by adaxial and abaxi/al epidermes. In model plants, the dark respiration rate (R(D)) was almost twice that in the control, while the photorespi/ration rates were similar to controls; CO2 compensation concentration was about 50% of that in controls. The ratios P(N)/R/(D) were similar in control and in model plants. Chlorophyll a+b content in leaves of the model plants was lower than that/ in the control plants. Grana extent increased with plant age in the model plants while it decreased in the control ones. /In both the stomal and granal membranes of the chloroplasts in model plants, a marked accumulation of carotenoids occurred/ independent of age. The ratio of variable to maximal fluorescence, F(v)/F(m), did not differ in the model and the control/ plants. In the control plants, photochemical quenching (qp) slightly increased with plant age and was not affected by CO2/ concentration present during measurement. In the model plants, qp increased with elevated CO2 concentration in young plan/ts and decreased in saturating CO2 concentrations in older plants. Nonphotochemical quenching (q(NP)) was lower in the mod/el plants and increased under CO2 saturating conditions. Vitality index, Rfd, was markedly lower in the model plants than in the control ones and a decline was found in saturating CO2 concentration.ES; METALS AB The high-temperature-corrosion /925^4^Clark,H^Newton,PCD^Bell,CC^Glasgow,EM^1995^1^The influence of elevated co2 and simulated seasonal-changes in tempera/ture on tissue turnover in pasture turves dominated by perennial ryegrass (lolium-perenne) and white clover (trifolium-repens)^39^32^1^128-136^^^^^Feb^^^^^4649orroded in SO2-O2, the protective chromia scale which developed on the alloy in the /0 mu mol mol(-1). No unambiguous effects of the methanol applications were detected in net photosynthesis measurements mad/e on foliage in either of the two CO2 treatments. The 75% increase in CO2 however, raised the upper-limiting leaf temperat/ure for positive net photosynthesis by approximately 7 C, which resulted in a 75% enhancement in net photosynthesis at a leaf temperature of 31 C, a 100% enhancement at a leaf temperature of 35 C, and a 200% enhancement at 42 C.94 PD FEB VL 41/961^7^Johnson,D^Geisinger,D^Walker,R^Newman,J^Vose,J^Elliot,K^Ball,T^1994^1^Soil pco(2), soil respiration, and root activity in co2- fumigated and nitrogen-fertilized ponderosa pine^206^165^1^129-138^^^^^^^^^^472031-9317 C1 USDA ARS, BELTSVILL/A^4719^The purpose of this paper is to describe the effects of CO2 and N treatments on soil pCO(2), calculated CO2 efflux,/ root biomass and soil carbon in open-top chambers planted with Pinus ponderosa seedlings. Based upon the literature, it w/as hypothesized that both elevated CO2 and N would cause increased foot biomass which would in turn cause increases in bot/h total soil CO2 efflux and microbial respiration. This hypothesis was only supported in part: both CO2 and N treatments c/aused significant increases in root biomass, soil pCO(2), and calculated CO2 efflux, but there were no differences in soil/ microbial respiration measured in the laboratory. Both correlative and quantitative comparisons of CO2 efflux rates indic/ated that microbial respiration contributes little to total soil CO2 efflux in the field. Measurements of soil pCO(2) and /calculated CO2 efflux provided inexpensive, non-invasive, and relatively sensitive indices of belowground response to CO2 and N treatments.ion. By this criterion, indirect effects of CO2 on leaf respiration were observed at 15 and 20- degrees-)962^5^Kemp,PR^Waldecker,DG^Owensby,CE^Reynolds,JF^Virginia,RA^1994^1^Effects of elevated co2 and nitrogen-fertilization pr0A^4648^1. Tissue turnover, leaf morphology and population dynamics of perennial ryegrass and white clover were studied in 0pasture turves grown at ambient (350 mu molmol(-1)) or double ambient (700 mu molmol(-1)) CO2 concentrations for 217 days 0in controlled environment rooms. The turves were subjected sequentially to three day/night temperature regimes; 10/4 degre0es C, 16/10 degrees C and 22/16 degrees C and harvested at 3-week intervals. The photoperiod was 12 hours for all of the t0emperature treatments with a mean photon flux density of 480 mu E m(-2) s(-1). 2. Ryegrass leaf extension and leaf death r0ates did not differ between CO2 treatments and there was no effect of CO2 on rates of leaf appearance in white clover. Wei0ght per unit length of ryegrass laminae was unaffected by elevated CO but lamina weight per unit area, lamina area and pet0 iole weight per unit length in white clover showed a small positive response, especially at the two higher temperatures. R0 ates of growth and senescence per ryegrass tiller were therefore similar between CO2 treatments, but rates of growth per w0 hite clover growing point were increased by 4, 23 and 13% at 10/4 degrees C, 16/10 degrees C and 22/16 degrees C, respecti0 vely, at elevated CO2. Responses to CO2 could not be attributed to any consistent change in morphological characteristics 0 in either species and exposure to elevated concentrations of CO2 did not appear to change the relationship between growth 0and senescence per meristem. 3. Total grass tiller populations were similar at both CO2 concentrations, but ryegrass tille0r densities more than halved in both CO2 treatments as the temperature was increased. The fall was most severe at 700 mu m0ol mol(-1) and at the end of the experiment ryegrass tiller densities in this treatment were only 47% of those found at 3500 mu molmol(-1). There was no consistent effect of CO2 concentration on clover growing point numbers and they increased fr0om 800 m(-2) to over 3000 m(-2) in both treatments with maximum densities occurring at 22/16 degrees C. 4. The results imp0ly that, in plant communities dominated by ryegrass and white clover, exposure to elevated CO2 concentrations will alter t0he species composition in favour of white clover. Responses in above-ground dry matter yield to elevated CO2 will be a bal0ance between the positive response shown by white clover and the negative response of perennial ryegrass. Temperature will0 have a major influence on the magnitude of this response since both the response of white clover to CO2 and the ratio of white clover growing points to ryegrass tillers are temperature-dependent.0926^5^Conroy,JP^Seneweera,S^Basra,AS^Rogers,G^Nissenwooller,B^1994^1^Influence of rising atmospheric co2 concentrations and temperature on growth, yield and grain quality of cereal crops^92^21^6^741-758^^^^^^^^^^46510A^4650^A possible scenario for the end of the 21st century is that the atmospheric CO2 concentration will be in the range 0of 510-760 mu L L(-1) and that the mean global temperature will be 1.5-4.5 degrees C higher. Further, there may be greater0 incidences of extreme climatic events, which together with the CO2 and temperature changes will influence development, gr0owth and grain yield of cereals such as rice and wheat. For these C-3, plants, the driving force for the growth response t0o elevated CO2 is higher leaf CO2 assimilation rates (4). However, the response of A to CO2 depends on temperature with ma0ximum absolute increases occuring at temperatures which do not cause flower abortion, while negligible increases are obser0 ved at low temperatures. At high temperatures, where A is reduced because of partial inactivation of photosynthetic enzyme0!s, the increase in A due to CO2 enrichment is still observed. Other factors, such as changes in shoot water relations or h0"ormone concentrations, may influence growth at elevated CO2 concentrations. Wheat and rice development is accelerated by h0#igh temperature and consequently grain yield is reduced because there is less time for radiation to be intercepted during 0$the vegetative phase. Although high CO2 also accelerates development in rice and, to a lesser extent in wheat, the extra c0%arbohydrate produced by increases in A results in at least a 40% increase in grain yield at temperatures which do not caus0&e flower abortion. This is due mainly to increased tiller numbers rather than increases in the number or weight of individ0'ual grains. However, the yield enhancement due to high CO2 will not necessarily compensate for decreases in yield caused b0(y accelerated development at high temperatures. As predicted by the response of A to high CO2, the relative increase in yi0)eld, due to rising CO2 concentrations, is smaller at lower temperatures. Elevated atmospheric CO2 may improve the toleranc0*e of plants to heat-induced drought stress by facilitating the maintenance of cell volume and photosynthetic function in t0+he leaves. Increased carbohydrate storage in the stems may also be an advantage during grain filling if the flag leaves se0,nesce prematurely. However, it is unlikely that the effect of very high temperatures on newer abortion will be ameliorated0- by high CO2. For bread making, the quality of flour produced from grain developed at high temperatures is poorer. High CO0.2 may also have an effect through a reduction in the protein content of wheat grain. For rice, the amylose content of the grain, a major determinant of cooking quality is increased under elevated CO2.00927^5^Curtis,PS^Vogel,CS^Pregitzer,KS^Zak,DR^Teeri,JA^1995^1^Interacting effects of soil fertility and atmospheric co2 on leaf-area growth and carbon gain physiology in populus X euramericana (dode) guinier^84^129^2^253-263^^^^^Feb^^^^^465302A^4652^Two important processes which may limit productivity gains in forest ecosystems with rising atmospheric CO2 are red03uction in photosynthetic capacity following prolonged exposure to high CO2 and diminution of positive growth responses whe04n soil nutrients, particularly N, are limiting. To examine the interacting effects of soil fertility and CO2 enrichment on05 photosynthesis and growth in trees we grew hybrid poplar (Populus x euramericana) for 158 d in the field at ambient and t06wice ambient CO2 and in soil with low or high N availability. We measured the timing and rate of canopy development, the s07easonal dynamics of leaf level photosynthetic capacity, respiration, and N and carbohydrate concentration, and final above08- and belowground dry weight. Single leaf net CO2 assimilation (A) increased at elevated CO2 over the majority of the grow09ing season in both fertility treatments. At high fertility, the maximum size of individual leaves, total leaf number, and 0:seasonal leaf area duration (LAD) also increased at elevated CO2, leading to a 49% increase in total dry weight. In contra0;st, at low fertility leaf area growth was unaffected by CO2 treatment. Total dry weight nonetheless increased 25% due to C0egative adjustment of photosynthesis was due to a reduction in the maximum rate of CO2 fixation by Rubisco. Maximum rate o0?f electron transport and phosphate regeneration capacity were either unaffected or declined at elevated CO2. Carbon dioxid0@e effects on leaf respiration were most pronounced at high fertility, with increased respiration mid-season and no change 0A(area basis) or reduced (mass basis) respiration late- season in elevated compared to ambient CO2 plants. This temporal va0Briation correlated with changes in leaf N concentration and leaf mass per area. Our results demonstrate the importance of 0Cconsidering both structural and physiological pathways of net C gain in predicting tree responses to rising CO2 under conditions of suboptimal soil fertility.0E928^2^Demothes,MAG^Knoppik,D^1994^1^Effects of long-term enhanced co2 partial-pressure on gas- exchange parameters and saccharide pools of wheat leaves^79^30^3^435-445^^^^^^^^^^4655&v-v3v8vAvQvcvfvgvlvzvv wwzw0GA^4654^Wheat plants were cultivated in a growth chamber at normal (35 Pa, c35 plants) and enhanced (70 Pa, c70 plants) CO20H partial pressure. In C35 plants the net photosynthetic rate (P(N)) of flag leaves and the concentrations of saccharides s0Iuch as sucrose, glucose, fructose and starch were increased. The c70 plants possessed higher chlorophyll (Chl) a and Chl b0J contents. The CO2 response of P(N) at saturating photosynthetically active radiation (PAR) was very similar for both vari0Kants. At the highest CO2 concentration saccharides accumulated in both variants as a consequence of decreased export rate.0L The response of P(N) to PAR at saturating CO2 concentrations was similar in the two variants. On the other hand, the resp0Monse of water vapour pressure conductance (gH2O) to PAR in c35 plants followed a hyperbolic response to PAR, while in the 0Nc70 plants it was linearly related to PAR up to the mean PAR used for growth. In this variant gH2O seemed to change parallelly to changes in the mesophyll demand for CO2 caused by PAR.0P929^3^Dixon,M^Lethiec,D^Garrec,JP^1995^1^The growth and gas-exchange response of soil-planted norway spruce [picea-abies (0QL) karst] and red oak (quercus-rubra L) exposed to elevated co2 and to naturally-occurring drought^84^129^2^265-273^^^^^Feb^^^^^4657[ruv{=jǕЕ0SA^4656^Norway spruce and red oak trees were planted directly into the soil and exposed to 700 mu mol mol(-1) CO2 in open-t0Top chambers. There were large inter-specific differences in response to naturally occurring drought during the second pear0U of exposure to elevated CO2. Both species had decreased assimilation rates. CO2-treated red oak had no loss of photosynth0Vetic enhancement when undroughted, whereas CO2- treated Norway spruce showed a relative increase in assimilation rates onl0Wy when droughted. The effect of CO2 on radial growth of both species was less marked in the second growing season, but thi0Xs may have been a result of different biomass partitioning as Norway spruce shoot extension had a different pattern of gro0Ywth in elevated CO2. Stomatal density and chlorophyll content were largely unaffected by the CO2 treatment. A precise method for measuring Norway spruce needle surface area was also developed. g؟-T_930^1^Field,CD^1995^1^Impact of expected climate-change on mangroves^232^295^1-3^75-81^^^^^6 Jan^^^^^46590\A^4658^There is a consensus of scientific opinion that the activities of man will cause a significant change in the global0] climate over the next hundred years. The rising level of carbon dioxide and other industrial gases in the atmosphere may 0^lead to global warming with an accompanying rise in sea-level. Mangrove ecosystems grow in the intertidal zones in tropica0_l and sub- tropical regions and are likely to be early indicators of the effects of climate change. The best estimates of 0`predicted climate change in the literature are presented. It is suggested that a rise in mean sea-level may be the most im0aportant factor influencing the future distribution of mangroves but that the effect will vary dramatically depending on th0be local rate of sea-level rise and the availability of sediment to support reestablishment of the mangroves. The predicted0c rise in mean air temperature will probably be of little consequence to the development of mangroves in general but it may0d mean that the presence of mangroves will move further north and south, though this will depend on a number of additional 0efactors. The effect of enhanced atmospheric CO2 on the growth of mangroves is unknown at this time but that there is some 0fevidence that not all species of mangroves will respond similarly. The socio- economic impacts of the effects of climate c0ghange on mangrove ecosystems may include increased risk of flooding, increased erosion of coast lines, saline intrusion and increased storm surges.0i931^2^Friend,AD^Cox,PM^1995^1^Modeling the effects of atmospheric co2 on vegetation atmosphere interactions^107^73^3-4^285-295^^^^^Mar^^^^^4661Ojw~Qly0kA^4660^The effect of doubling atmospheric CO2 concentration (C-a) on climate and vegetation is investigated using a combin0led climate-vegetation model. The vegetation model predicts the response of leaf area index, canopy transpiration (E(T)) an0md whole-plant carbon balance to changes in climate, soil moisture, and atmospheric CO2 forcing. This model has been embedd0ned in the UK Meteorological Office Single Column Model (SCM), which provides the climate feedback to the vegetation. The v0oegetation model uses an optimisation approach to predict stomatal resistance, a biochemical model to predict photosynthesi0ps and a simple carbon balance model to predict leaf area. Respiration is calculated as a function of leaf area and vegetat0qion height. Clouds are assumed to be radiatively passive in the SCM to avoid unrealistic feedbacks. Simulations were perfo0rrmed with the fully interactive vegetation-climate model for an Amazon location with the present-day value of C-a (1 x CO20s), and twice this value (2 x CO2). In addition, two other types of simulation were performed at both CO2 concentrations: o0tne in which the vegetation component was forced only with 1 x CO2, and one using a fixed surface resistance. The latter ca0use is equivalent to simulations using most current general circulation models. In all the simulations, increased atmospher0vic CO2 caused an increase in surface temperature owing to increased radiative forcing. With a fixed resistance, mean E(T) 0wwas increased by 5.6% and sensible heat flux was reduced by 3.8%. The fully interactive model had significant effects on t0xhe response of both climate and productivity to C-a. Increased C-a caused stomatal closure, which resulted in a reduction 0yin mean E(T) Of 25%. The effect of C-a on E(T) was amplified by the positive feedback resulting from the effect of increased air humidity deficit on stomatal resistance.!EPVjry=e0{932^3^Gorissen,A^Kuikman,PJ^Vandebeek,H^1995^1^Carbon allocation and water-use in juvenile douglas-fir under elevated co2^84^129^2^275-282^^^^^Feb^^^^^4663 )/CKRX]ft eY0}A^4662^In this study the impact of an elevated CO2 level on allocation of assimilates and water use efficiency of Douglas 0~fir [Pseudotsuga menziesii (Mirb.) France] was investigated. Juvenile Douglas firs were exposed to a long-term treatment a0t 350 and 700 pi l(-1) CO2 for 14 months and subsequently crosswise transferred to phytotrons for a short-term treatment w0ith 350 and 700 mu l l(-1) CO2 for 4 wk in an atmosphere continuously labelled with (CO2)-C-14. No interactive effects on 0total net uptake of (CO2)-C-14 between long-term treatment and short-term treatment were observed. The short-term treatmen0t with 700 mu l l(-1) CO2 increased the total net uptake of (CO2)-C-14 by 22%, compared with the 350 mu l l(-1) CO2 treatm0ent. The long-term pretreatment did not affect the total net uptake, suggesting that photosynthetic acclimation had not oc0curred. However, expressed per unit of needle mass a 14% reduction was observed in the trees pretreated at 700 mu l l(-1) 0CO2. This was not because of a reduced sink strength of the root system. This reduced uptake per unit of needle mass after0 long-term treatment may have implications for carbon storage in forest ecosystems. The results showed that an initial gro0wth stimulation can eventually be annulled by developing physiological or morphological adaptions. (CO2)-C-14 the root/soi0l respiration increased in the short-term treatment with 700 mu l l(-1) CO2, indicating a stimulated use of current carbon0 compounds either by roots or microorganisms. The water use efficiency during the short-term treatment with 700 mu l l(-1)0 CO2 increased by 32%, but was not affected by the long- term pretreatment. Water use per unit needle mass during the shor0t-term treatment was decreased both by the short-term treatment and by the long-term pretreatment by about 15%. Some of th0e observed effects appeared to be persistent, such as decreased water use per unit needle mass, whereas others, stimulation of total net (CO2)-C-14 uptake and water use efficiency, were transient.0933^2^Horn,ME^Widholm,JM^1994^1^Photoautotrophic growth of soybean cells in suspension-culture .3. Characterization of carbon fixation products under high and low co2 levels^177^39^3^239-244^^^^^Dec^^^^^4665(9))&*o1z11110A^4664^A photoautotrophic soybean suspension culture (SB-P) was used to study CO2 assimilation while exposed to elevated o0r ambient CO2 levels. These studies showed that under elevated CO2 (5% v/v) malate is the dominant fixation product, stron0gly suggesting that phosphoenolpyruvate carboxylase (PEPCase) is the primary enzyme involved in carbon fixation in these c0ells under their normal growth conditions. Citrate and [aspartate + glutamate] were also significant fixation products dur0ing fifteen minutes of exposure to (CO2)-C-14. During the ten minute unlabeled CO2 chase however, C-14-malate continued to0 increase while citrate and [aspartate + glutamate] declined. Fixation of (CO2)-C-14 under ambient CO2 levels (0.037%) sho0wed a very different product pattern as 3-phosphoglycerate was very high in the first one to two minutes followed by incre0ases in [serine + glycine] and [aspartate + glutamate]. Hexose phosphates were also quite high initially but then declined0 relatively rapidly. Thus, the carbon fixation pattern at ambient CO2 levels resembles somewhat that seen in C3 leaf cells0 while that seen at elevated CO2 levels more closely resembles that of a C-4 plant. The initial fixation product of C-3 pl0ants, 3-PGA, was never detectable under high CO2 conditions. These data suggest that an in vitro photoautotrophic system would be suitable for studying carbon fixation physiology during photosynthetic and non- photosynthetic growth.0934^3^Muller,M^Grill,D^Guttenberger,H^1994^1^The effects of interactions between ozone and co2 on the chromosomes of norway spruce root-meristems^262^34^2^321-335^^^^^^^^^^46670A^4666^A Norway spruce (Picea abies (L.) Karsten) test system was used to study the immediate and after effects of increas0ed ozone or elevated CO2 or both, on root tip chromosomes. Five-year-old potted spruce trees were exposed in environmental0 chambers to elevated concentrations of ozone (0.1 cm3m-3) for the study of an immediate effect and to elevated concentrat0ions of carbon dioxide (750 cm3m-3) and ozone (0.08 cm3m-3) as single variables or in combination and then transferred to 0a field for the observation of an after effect. Elevated ozone caused an increased number of chromosomal abnormalities dir0ectly after finishing the fumigation and also 21 months later. Elevated CO2 more likely induced a decrease rather than an 0increase in the number of chromosomal aberrations. The most common abnormalities were chromsome stickiness, in the form of0 connections, clumped metaphases and amorphous chromatin masses. An increased number of chromosomal aberrations especially chromosome stickiness reflects highly toxic effects, usually of an irreversible type leading to cell death.@spot.colorad0935^5^Naeem,S^Thompson,LJ^Lawler,SP^Lawton,JH^Woodfin,RM^1995^1^Empirical-evidence that declining species-diversity may alter the performance of terrestrial ecosystems^190^347^1321^249-262^^^^^28 Feb^^^^^4669skip Nsave read Nget 1553168904 000A^4668^We examined experimentally the association between species diversity and ecosystem processes in a series of terrest0rial mesocosms. We developed and maintained 14 mesocosms whose biota were assembled from a single pool of plant and animal0 species and whose environmental conditions were identically controlled. Each community contained four trophic levels: pri0mary producers (annual herbs), consumers (herbivorous molluscs and phloem sucking insects), secondary consumers (parasitoi0ds) and decomposers (earthworms, Collembola and microbes). All mesocosms received the same diurnal pattern of light, tempe0rature, relative humidity and water. The initial volume of soil, soil structure, composition, nutrient content and inocula0 of both soil microbes and nematodes were also identical among replicates. The only experimentally manipulated factor was 0the number of plant and animal species within each trophic level. High, medium and low diversity communities had nine, 15 0or 31 plant and animal species, respectively. We measured five ecosystem processes as response variables in these mesocosm0s over the course of 206 days: (i) community respiration; (ii) productivity; (iii) decomposition; (iv) nutrient retention;0 and (v) water retention. The manipulation of diversity produced communities that differed significantly in their ecosyste0m processes. Our results provide the first evidence (obtained by a direct manipulation of diversity under controlled environmental conditions) that ecosystem processes may be affected by loss of diversity.1351348 6a2bb4999ccaacab1dfa6369451740936^3^North,GB^Moore,TL^Nobel,PS^1995^1^Cladode development for opuntia-ficus-indica (cactaceae) under current and doubled co2 concentrations^5^82^2^159-166^^^^^Feb^^^^^46712.008018f0@pop.service.ohio-state.edu>-25-Jan-1999-11:00:26--0500-(EST0A^4670^Morphological and anatomical changes for first-order daughter cladodes (flattened stem segments) of a prickly pear 0cactus, Opuntia ficus-indica, were monitored to determine the effects of a doubled atmospheric CO2 concentration on their 0development and mature form. For daughter cladodes developing in controlled environment chambers for 60 d, maximal elongat0ion rates were similar under a photosynthetic photon flux density (PPFD) of 6 mol m(-2) d(-1) and a CO2 concentration of 3070 mu l liter(-1), an increased PPFD (10 mol m(-2) d(-1)), and an increased PPFD and a doubled CO2 concentration. These ma0ximal rates, however, occurred at 20, 15, and 12 d, respectively. The maximal relative growth rate under the doubled CO2 c0oncentration was about twice that under the other conditions. For cladodes at 60 d as well as after 4 and 16 mo in open-to0p chambers, doubling the CO2 concentration had no effect on final length or width. At 4 mo, cladodes under doubled CO2 wer0e 27% thicker, perhaps allowing the earlier production of second-order daughter cladodes. The chlorenchyma was then 31% th0icker and composed of longer cells. At 16 mo, the difference in cladode thickness diminished, but the chlorenchyma remaine0d thicker under doubled CO2, which may contribute to greater net CO2 uptake for O. ficus-indica under elevated CO2 concent0rations. Two other persistent differences were a 20% lower stomatal frequency and a 30% thicker cuticle with more epicuticular wax for cladodes under doubled CO2, both of which may help reduce transpirational water loss.0A0C99D5B09020802FB@nsf0937^2^Prior,SA^Rogers,HH^1995^1^Soybean growth-response to water-supply and atmospheric carbon- dioxide enrichment^166^18^4^617-636^^^^^^^^^^4673m3>-31-Jan-1999-14:28:36--0500-(EST 917793036 Ndel Nskip Nsave read Nget 855963453 057dd45da499c10A^4672^Growth response of soybean [Glycine max (L.) Merr. 'Bragg'] grown in open top field chambers at five carbon dioxide0 (CO2) concentrations ranging from 349 to 946 mu LL(-1) and under two water regimes was examined. During reproductive grow0th, plants grown under CO2 enrichment exhibited increases in total leaf area and dry weight. Water stress inhibited growth0 at all CO2 levels, but the relative enhancement of growth due to CO2 enrichment under water-stressed (WS) conditions was 0greater than under well-watered (WW) conditions. Water-stressed plants grown under 946 mu LL(-1) CO2 were larger than WW p0lants grown under 349 mu LL(-1) CO2. Reproductive yield increases were represented by increases in seed number rather than0 larger seeds. Although water stress reduced yield, the relative increase in seed number in response to elevated CO2 was g0reater for WS plants. Leaf tissue analysis suggested that a phosphorus deficiency may have restricted the seed dry weight 0response to elevated CO2. The mean relative growth rate (RGR) and mean net assimilation rate (NAR) increased with CO2 conc0entration in the first interval (5 to 14 days after planting) and diminished with time thereafter for each CO2 level. At t0he second interval (14 to 63 days), the direct effect of NAR was offset by lower leaf area ratio (LAR). However, the LAR w0as greater for WS plants but the response of RGR to CO2 was similar under both water treatments. At the third interval (630 to 98 days), the RGR for WS plants remained constant across CO2 treatments, whereas under WW conditions a level response 0of NAR coupled with a negative response of LAR resulted in a decrease in RGR under CO2-enriched conditions. The decrease in LAR was attributed to a decrease in specific leaf area. Leaf weight ratio was unaffected by Co-2.get 1380344859 f5d0880938^2^Rao,MV^Dekok,LJ^1994^1^Interactive effects of high co2 and so2 on growth and antioxidant levels in wheat^262^34^2^279-290^^^^^^^^^^4675 18e2380b5a87885a878dbd665db3d3af <199902051333.IAA27267@mail2.uts.ohio-state.edu>-5-Feb-1999-08:33:40A^4674^The impact of elevated CO2 and/or SO2 on the growth and antioxidant levels of wheat (Triticum aestivum L. cv. Urban0) plants has been studied. High CO2 (0.7 ml l-1) significantly enhanced shoot biomass and photosynthetic capacity, while e0xposure to SO2 (0.14 mul l-1) resulted in a decreased shoot biomass and in an injured photosynthetic aparatus, illustrated0 by a loss of chlorophyll and a decreased ratio of variable to maximal fluorescence (F(v)/F(m)) and A(max). However, combi0ned exposure of plants to high CO2 and SO2 eliminated the negative effects of SO2. Sulfate accumulation was almost equal i0n plants exposed to SO2 and, high CO2 and SO2. A significant increase in ascorbate, glutathione and their redox state was 0observed in plants exposed to high CO2 and SO2, compared to that of plants exposed to solely SO2. The absence of the negat0ive efects of SO2 in the presence of high CO2 might be related to a high redox state of ascorbate and glutathione. Abbrevi0ations: A(max), maximum rate of oxygen evolution at saturated light and CO2 (mumol m-2 s-1); ASA, reduced ascorbic acid; D0HA, dehydroascorbic acid; F(m), maximum emission of photosystem-II chlorophyll fluorescence; F(v), variable component of F(m); GSH, reduced glutathione; GSSG, oxidized glutathione.0`0#`0.@000@00939^3^Rattray,EAS^Paterson,E^Killham,K^1995^1^Characterization of the dynamics of C-partitioning within lolium-perenne and to the rhizosphere microbial biomass using C-14 pulse-chase^263^19^4^280-286^^^^^Mar^^^^^4677/#M2@0A^4676^The dynamics of C partitioning with Lolium perenne and its associated rhizosphere was investigated in plant-soil mi0crocosms using C-14 pulse-chase labelling. The CO2(C-14) pulse was introduced into the shoot chamber and the plants allowe0d to assimilate the label for a fixed period. The microcosm design facilitated independent monitoring of shoot and root/so0il respiration during the chase period. Partitioning between above- and below-ground pools was determined between 30 min a0nd 168 h after the pulse, and the distribution was found to vary with the length of the chase period. Initially (30 min af0ter the pulse), C-14 was predominantly (99%) in the shoot biomass and declined thereafter. The results indicate that trans0location of recent photoassimilate is rapid, with C-14 detected below ground within 30 min of pulse application. The trans0location rate of C-14 below ground was maximal (6.2% h-1) between 30 min and 3h after the pulse, with greatest incorporati0on into the microbial biomass detected at 3 h. After 3 h, the microbial biomass C-14 pool accounted for 74% of the total C0-14 rhizosphere pool. By 24 h, approximately 30% of C-14 assimilate had been translocated below ground; thereafter C-14 tr0anslocation was greatly reduced. Partitioning of recent assimilate changed with increasing CO2 concentration. The proporti0on of C-14 translocated below ground almost doubled from 17.76% at the ambient atmospheric CO2 concentration (450 ppm) to 033.73% at 750 ppm CO2 concentration. More specifically, these changes occurred in the root biomass and the total rhizosphe0re pools, with two- and threefold C-14 increases at an elevated CO2 concentration compared to ambient, respectively. The p0ulse- labelling strategy developed in this study provided sufficient sensitivity to determine perturbations in C dynamics in L. perenne, in particular rhizosphere C pools, in response to an elevated atmospheric CO2 concentration.210940^3^Raveh,E^Gersani,M^Nobel,PS^1995^1^Co2 uptake and fluorescence responses for a shade-tolerant cactus hylocereus-undatus under current and doubled co2 concentrations^37^93^3^505-511^^^^^Mar^^^^^4679`: :@:<)''=@:0A^4678^Hylocereus undatus (Haworth) Britton and Rose growing in controlled environment chambers at 370 and 740 mu mol CO2 0mol(- 1) air showed a Crassulacean acid metabolism (CAM) pattern of CO2 uptake, with 34% more total daily CO2 uptake under0 the doubled CO2 concentration and most of the increase occurring in the late afternoon. For both CO2 concentrations, 90% 0of the maximal daily CO2 uptake occurred at a total daily photosynthetic photon flux density (PPFD) of only 10 mol m(-2) d0ay(-1) and the best day/night air temperatures were 25/15 degrees C. Enhancement of the daily net CO2 uptake by doubling t0he CO2 concentration was greater under the highest PPFD (30 mol m(-2) day(-1)) and extreme day/night air temperatures (15/05 and 45/35 degrees C). After 24 days of drought, daily CO2 uptake under 370 mu mol CO2 mol(-1) was 25% of that under 740 0mu mol CO2 mol(-1). The ratio of variable to maximal chlorophyll fluorescence (F-v/F-m) decreased as the PPFD was raised a0bove 5 mol m(-2) day(-1), at extreme day/night temperatures and during drought, suggesting that stress occurred under thes1e conditions. F-v/F-m was higher under the doubled CO2 concentration, indicating that the current CO2 concentration was ap1parently limiting for photosynthesis. Thus net CO2 uptake by the shade-tolerant H. undatus, the photosynthetic efficiency 1of which was greatest at low PPFDs, showed a positive response to doubling the CO2 concentration, especially under stressful environmental conditions.M (`MN: Q`O%M`V O` Q%`M@>`*1941^2^Robertson,EJ^Leech,RM^1995^1^Significant changes in cell and chloroplast development in young wheat leaves (triticum-aestivum CV hereward) grown in elevated co2^8^107^1^63-71^^^^^Jan^^^^^4681wM UVN( //1A^4680^Cell and chloroplast development were characterized in young Triticum aestivum cv Hereward leaves grown at ambient 1(350 mu L L(-1)) or at elevated (650 mu L L(-1)) CO2. In elevated CO2, cell and chloroplast expansion was accelerated by 110 and 25%, respectively, in the first leaf of 7-d-old wheat plants without disruption to the leaf developmental pattern. E1 levated CO2 did not affect the number of chloroplasts in relation to mesophyll cell size or the linear relationship betwee1 n chloroplast number or size and mesophyll cell size. No major changes in leaf anatomy or in chloroplast ultrastructure we1 re detected as a result of growth in elevated CO2, but there was a marked reduction in starch accumulation. In leaf sectio1 ns fluorescently tagged antisera were used to visualize and quantitate the amount of cytochrome f, the alpha- and beta- su1 bunits of the coupling factor 1 in ATP synthase, D1 protein of the photosystem II reaction center, the 33-kD protein of th1e extrinsic oxygen-evolving complex, subunit II of photosystem I, and ribulose-1,5-bisphosphate carboxylase/oxygenase. A s1ignificant finding was that in 10 to 20% of the mesophyll cells grown in elevated CO2 the 33-kD protein of the extrinsic o1xygen-evolving complex of photosystem II and cytochrome f were deficient by 75%, but the other proteins accumulated normally.,hV!G" [Q(MW@WX+>,_,QO`,[`(M@ZW1942^2^Seegmuller,S^Rennenberg,H^1994^1^Interactive effects of mycorrhization and elevated carbon- dioxide on growth of young pedunculate oak (quercus-robur L) trees^206^167^2^325-329^^^^^Dec^^^^^4683MX\)+_,\X1A^4682^Pedunculate oak (Quercus robur L.) was germinated and grown at ambient CO2 level and 650 ppmv CO2 in the presence a1nd absence of the ectomycorrhizal fungus Laccaria laccata for a total of 6 month under nutrient non-limiting conditions. M1ycorrhization and elevated atmospheric CO2 each supported the growth of the trees. Stem height, stem diameter, and dry mat1ter accumulation of pedunculate oak were increased by mycorrhization. Elevated atmospheric CO2 enhanced stem height, stem 1diameter, fresh weight and dry weight, as well as lateral root formation of the trees. In combination, mycorrhization and 1elevated atmospheric CO2 had a more than additive, positive effect on tree height and biomass accumulation, and further im1proved lateral root formation of the trees. From these findings it is suggested that the efficiency of the roots in supporting the growth of the shoot is increased in mycorrhized oak trees at elevated atmospheric CO2.m)@MQ@Z1943^2^Seligman,NG^Sinclair,TR^1995^1^Global environment change and simulated forage quality of wheat .2. Water and nitrogen stress^207^40^1^29-37^^^^^Jan^^^^^4685#`T@d]@` t,@*w Z^ ) M`\`[1A^4684^Forage crops are frequently subjected to stress conditions resulting from inadequate supplies of water and N. Becau1se forages grown under these stress conditions constitute an important resource in animal agriculture, this study was unde1 rtaken to assess possible changes in the nutritive value and productivity of forage crops as a consequence of global envir1!onment change. A relatively simple, mechanistic model of wheat was extended to simulate growth and important determinants 1"of feed quality ([N], leaf:stem, dry matter digestibility) in an annual, temperate climate C-3 forage grass. Weather data 1#for a semiarid region and different levels of applied N were used to examine the response of forage productivity to variou1$s levels of water and N availability. Not surprisingly, responses to global environment change were highly dependent on th1%e availability of both water and N. When either resource was available at low levels, production of digestible dry matter 1&was nearly unchanged by elevated [CO2] or increased temperature. When compared at equivalent development stages, small inc1'reases in forage quality were simulated, mainly because higher temperature resulted in achievement of the initiation of gr1(ain fill at an earlier date. As N availability increased, differences in forage characteristics and productivity became mo1)re prominent. Elevated ambient [CO2] increased vegetative mass, digestible dry matter, and concentration of digestible dry1* matter but decreased leaf:stem and [N]. Increased temperature generally had an effect on forage traits that was opposite 1+to the elevated [CO2] response. The combined effects of both factors sometimes cancelled each other, but usually one of th1,e factors was dominant. Negative effects of temperature tended to be aggravated by dry conditions. At crop maturity, posit1-ive effects of elevated atmospheric [CO2] on forage productivity and quality were severely decreased by nutrient and physi1.ological constraints. These simulations indicate that when forage crops are grown under irrigation in semiarid regions, th1/ere may be substantial and complex changes in productivity and feed quality as a consequence of warmer temperature and ele10vated atmospheric [CO2]. Under rainfed conditions, these differences could be quite erratic and virtually unpredictable within the current range of interannual variation in forage productivity and quality. ]@+2<512944^2^Sinclair,TR^Seligman,NG^1995^1^Global environment change and simulated forage quality of wheat .1. Nonstressed conditions^207^40^1^19-27^^^^^Jan^^^^^4687 Gw@FN_ `E'V14A^4686^Projected changes in the global environment may affect both the quantity and quality of grain and forage mass produ15ced and harvested in that environment. Quality is a major factor in determining the value of a forage crop as feed for rum16inants. The objective of this study was to make a preliminary assessment of potential changes in the quantity and quality 17of forage as measured by [N] and leaf:stem of an annual, temperate climate C-3 forage crop grown under nonstressed conditi18ons. Starting with a relatively simple, well-checked mechanistic model of wheat, adaptations were added to estimate change19s in forage attributes. Increased temperature influenced both yield and nutritive value, mainly through changes in ontolog1:ical development rates. Elevated,atmospheric [CO2] resulted in greater mass accumulation, but with lower leaf:stem and [N]1;. The combined effect of increased temperature and elevated [CO2] was to decrease slightly forage yield and to increase th1 -0.1 MPa for all well-watered plants. Elevated CO2 increased relative growth rate of well- watered 1isugar maple by 181%, resulting in a 4.3-fold increase in total plant dry weight after 81 d, compared with 1.4 and 1.6-fold1j increases for sweetgum and sycamore, respectively, after 69 d. Although elevated CO2 increased net CO2 assimilation rate 1kof sugar maple by 115 %, there was a 10-fold increase in leaf area which contributed to the growth response. Although drou1lght did not eliminate a growth response of sugar maple to elevated CO2, it greatly reduced the elevated CO2- induced enhan1mcement of relative growth rate. In contrast, relative growth rates of sweetgum and sycamore were not significantly increas1ned by elevated CO2. Drought, under elevated CO2, reduced leaf area of all three species to a greater extent than it reduce1od net CO2 assimilation rate. The response ranged from no effect in sugar maple to a 40 % reduction in sycamore, with sweet1pgum exhibiting an intermediate response. Results indicate that drought may alter the growth response, gas exchange and wat1qer relations of tree species growing in an elevated CO2 atmosphere. Under high nutrient and water availability, sugar mapl1re may benefit the most (of the three species studied) from a CO2-enriched atmosphere, but productivity gains will be limited if frequent drought is prevalent.00A0000A01t948^4^Vivin,P^Gross,P^Aussenac,G^Guehl,JM^1995^1^Whole-plant co2 exchange, carbon partitioning and growth in quercus-robur seedlings exposed to elevated co2^184^33^2^201-211^^^^^Mar-Apr^^^^^4695ht v$.D!eYC1vA^4694^Pedunculate oak acorns (Quercus robur L.) were germinated and grown under nonlimiting nutritional and water conditi1wons in controlled-environment greenhouses with ambient (350 mu mol mol(-1)) or elevated (700 mu mol mol(-1)) CO2 concentra1xtions. A semiclosed gas exchange measurements, and (CO2)-C-13 labelling, system (1.5% (CO2)-C-13) was used to simultaneous1yly assess (a) the CO2 exchange of both aerial and below-ground (roots plus soil) compartments of the soil-plant system and1z (b) the partitioning of the recently photo-assimilated carbon. Measurements were made during the fast aerial growth phase1{ (July 30) and at the end of the growing season (October 15). On July 30, whole-plant dry mass had been increased by 44% s1|ince the beginning of the growing season in the elevated CO2 treatment, whereas at the end of the growing season the enhan1}cing effect was only 17%. Elevated CO2 stimulated net CO2 assimilation rate per unit leaf area (A) in July (+40%), whereas1~ in October this stimulation had disappeared. The respiratory CO2 evolution of the root-soil compartment (individual plant1 basis) was stimulated by 35% under the elevated CO2 conditions on July 30, but not on October 15. In July, relative speci1fic allocation (RSA), a parameter expressing the sink strength, was higher in all compartments under 700 mu mol mol(-1) co1mpared to 350 mu mol mol(-1). Moreover in root tips, the RSA values determined 4 h after the labelling were particularly high (7.8%)with elevated CO2, whereas under ambient CO2 RSA values were close to zero.KWAJ'1949^2^Williams,TG^Colman,B^1995^1^Quantification of the contribution of co2, hco3-, and external carbonic-anhydrase to photosynthesis at low dissolved inorganic carbon in chlorella-saccharophila^8^107^1^245-251^^^^^Jan^^^^^46971A^4696^An equation has been developed incorporating whole-cell rate constants for CO2 and HCO3- that describes accurately 1photosynthesis (Phs) in suspensions of unicellular algae at low dissolved inorganic carbon. At pH 8.0 the concentration of1 CO2 available to the algal cells depends on the rate of supply from, and the loss to, HCO3- and the rate of use by the ce1lls. At elevated cell densities (>30 mg chlorophyll [Chl] L(-1)), at which CO2 use by the cells is high, the slope of a gr1aph of absolute Phs versus Chl concentration approaches the rate of Phs on a milligram of Chl basis because of HCO3- use a1lone. The slope of a graph of Phs versus HCO3- will be the rate constant for HCO3- and for Chlorella saccharophila it was 10.16 L mg(-1) Chl h(-1). The difference between the constants for dissolved inorganic carbon (measured in cells with exter1nal carbonic anhydrase) and HCO3-1 is the constant for CO2, which was 26 L mg(-1) Chl h(-1). This difference causes the ha1lf-saturation constant for Phs to increase 5- to 6-fold at high cell densities. The increase in CO2 use as a result of external carbonic anhydrase is described mathematically as a function of cell density.1950^6^Amthor,JS^Mitchell,RJ^Runion,GB^Rogers,HH^Prior,SA^Wood,CW^1994^1^Energy content, construction cost and phytomass ac1cumulation of glycine-max (L) merr and sorghum-bicolor (L) moench grown in elevated co2 in the field^84^128^3^443-450^^^^^Nov^^^^^46991A^4698^Grain sorghum [Sorghum] bicolor (L.) Moench, a C-4 crop] and soybean [Glycine max (L.) Merr. cv. Stonewall, a C-3 c1rop] plants were grown in ambient (c. 360 mu l l(-1)) and twice- ambient (c. 720 mu l l(-1)) CO2 levels in open-top chambe1rs in soil without root constriction. Plant dry mass, energy content, composition and construction cost (i.e. amount of ca1rbohydrate required to synthesize a unit of plant dry mass) were assessed at the end of the growing season. Elevated CO2 (1a) increased phytomass accumulation (kg per plant) in both species, (b) had little affect on energy concentration (MJ kg(-11) plant) but caused large increases in the amount of plant energy per ground area (MJ m(-2) ground), and (c) did not alte1r specific growth cost (kg carbohydrate kg(-1) plant growth) but greatly increased growth cost per ground area (kg carbohy1drate m(-2) ground) because growth was enhanced. For soybean, twice-ambient CO2 resulted in a 50 % increase in the amount 1of nitrogen and energy in grain (seed plus pod) per ground area. This response to elevated CO2 has important implications 1for agricultural productivity during the next century because the rate of human population growth is exceeding the rate of increase of land used for agriculture so that future food demands can only be met by greater production per ground area.1951^2^Carlsson,BA^Callaghan,TV^1994^1^Impact of climate-change factors on the clonal sedge carer bigelowii - implications for population-growth and vegetative spread^122^17^4^321-330^^^^^Dec^^^^^4701 Ft6vvvPFFF~Q1A^4700^Hypothesized life-cycle responses to climate change for the arctic, clonal perennial Carer bigelowii are constructe1d using a range of earlier observations and experiments together with new information from monitoring and an environmental1 perturbation study. These data suggest, that under current climate change scenarios, increases in CO2, temperature and nu1trient availability would promote growth in a qualitatively similar way. The evidence suggests that both tiller size and d1aughter tiller production will increase, and be shifted towards production of phalanx tillers which have a greater propens1ity for flowering. Furthermore, age at tillering as well as tiller life span may decrease, whereas survival of younger age1 classes might be higher. Mathematical models using experimental data incorporating these hypotheses were used to a) integ1rate the various responses and to calculate the order of magnitude of changes in population growth rate (lambda), and b) t1o explore the implications of responses in individual demographic parameters for population growth rate. The models sugges1t that population growth rate following climate change might increase significantly, but not unrealistically so, with the 1younger, larger, guerilla tillers being the most important tiller categories contributing to lambda. The rate of vegetativ1e spread is calculated to more than double, while cyclical trends in flowering and population growth are predicted to decrease substantially.`0 r 0~0(0!0)0109 0A 01952^4^Chen,DX^Coughenour,MB^Eberts,D^Thullen,JS^1994^1^Interactive effects of co2 enrichment and temperature on the growth of dioecious hydrilla-verticillata^173^34^4^345-353^^^^^Oct^^^^^4703P;?0P;?/0/01A^4702^Experiments of plant growth responses to different CO2 concentrations and temperatures were conducted in growth cha1mbers to explore the interactive effects of atmospheric CO2 enrichment and temperature on the growth and dry matter alloca1tion of dioecious Hydrilla [Hydrilla verticillata (L.f.) Royle]. Hydrilla plants were exposed to two atmospheric CO2 conce1ntrations (350 and 700 ppm) and three temperatures (15, 25 and 32 degrees C) under a 12-hr photoperiod for about 2 months.1 The plant growth analysis showed that elevated CO2 appeared to enhance the growth of Hydrilla, and that the percentage of1 the enhancement is strongly temperature-dependent. Maximum biomass production was achieved at 700 ppm CO2 and 32 degrees 1C. At 15 degrees C, the total dry matter production was increased about 27% by doubling CO2, due to a 26% enhancement of l1eaf biomass, a 34% enhancement of stem biomass and 16% enhancement of root biomass. At 25 degrees C, the dry matter produc1tion was increased about 46% by doubling CO2, due to a 29% enhancement of leaf biomass, a 27% enhancement of stem biomass 1and 40% enhancement of root biomass. At 32 degrees C, however, the percentage of the enhancement of total dry matter produ1ction by doubling CO2 was only about 7%. The dry matter allocation among different plant parts was influenced by temperature but not by elevated CO2 concentration.1953^1^Crush,JR^1994^1^Elevated atmospheric co2 concentration and rhizosphere nitrogen-fixation in 4 forage plants^167^37^4^455-463^^^^^^^^^^4705 ' 'msjstick.drv1A^4704^Lolium x boucheanum (2n and 4n), Plantago lanceolata, and Pennisetum clandestinum were grown in pots of soil in gro1wth rooms with factorial combinations of 350 or 700 mul/l atmospheric CO2 and day/night temperatures of 28/23-degrees-C or1 18/13-degrees-C. Both cultivars of Lolium and P. lanceolata grew faster with elevated CO2 but P. clandestinum was unaffec1ted. Rhizosphere nitrogenase activity, assessed by acetylene reduction, was reduced by the 700 mul/l CO2 treatment in the tetraploid Lolium but otherwise did not vary significantly with CO2 level. '  '1954^4^Curtis,PS^Zak,DR^Pregitzer,KS^Teeri,JA^1994^1^Aboveground and belowground response of populus grandidentata to elevated atmospheric co2 and soil n-availability^206^165^1^45-51^^^^^^^^^^47071A^4706^Soil N availability may play an important role in regulating the long-term responses of plants to rising atmospheri1c CO2 partial pressure. To further examine the linkage between above- and belowground C and N cycles at elevated CO2, we g1rew clonally propagated cuttings of Populus grandidentata in the field at ambient and twice ambient CO2 in open bottom roo1t boxes filled with organic matter poor native soil. Nitrogen was added to all root boxes at a rate equivalent to net N mi1neralization in local dry oak forests. Nitrogen added during August was enriched with N-25 to trace the flux of N within t1he plant-soil system. Above- and belowground growth, CO2 assimilation, and leaf N content were measured non- destructively1 over 142 d. After final destructive harvest, roots, stems, and leaves were analyzed for total N and N-15. There was no CO12 treatment effect on leaf area, root length, or net assimilation prior to the completion of N addition. Following the N a1ddition, leaf N content increased in both CO2 treatments, but net assimilation showed a sustained increase only in elevate1d CO2 grown plants. Root relative extension rate was greater at elevated CO2, both before and after the N addition. Althou1gh final root biomass was greater at elevated CO2, there was no CO2 effect on plant N uptake or allocation. While low soil1 N availability severely inhibited CO2 responses, high CO2 grown plants were more responsive to N. This differential behav1ior must be considered in light of the temporal and spatial heterogeneity of soil resources, particularly N which often limits plant growth in temperate forests.1955^4^Dippery,JK^Tissue,DT^Thomas,RB^Strain,BR^1995^1^Effects of low and elevated co2 on C-3 and C-4 annuals .1. Growth and biomass allocation^2^101^1^13-20^^^^^Jan^^^^^47091A^4708^In order to study C-3 and C-4 plant growth in atmospheric CO2 levels ranging from past through predicted future lev1els, Abutilon theophrasti (C-3) and Amaran thus retroflexus (C-4) were grown from seed in growth chambers controlled at CO12 partial pressures of 15 Pa (below Pleistocene minimum) 27 Pa (pre-industrial), 35 Pa (current) and 70 Pa (predicted futu1re). After 35 days of growth, CO2 had no effect on the relative growth rate, total biomass or partitioning of biomass in t1he C- 4 species. However, the C-3 species had greater biomass accumulation with increasing CO2 partial pressure. C-3 plant1s grown in 15 Pa CO2 for 35 days had only 8% of the total biomass of plants grown in 35 Pa CO2. In 15 Pa CO2, C-3 plants h1ad lower relative growth rates and lower specific leaf mass than plants grown in higher CO2 partial pressures, and aborted1 reproduction. C-3 plants grown in 70 Pa CO2 had greater root mass and root-to-shoot ratios than plants grown in lower CO21 partial pressures. These findings support other studies that show C-3 plant growth is more responsive to CO2 partial pres1sure than C-4 plant growth. Differences in growth responses to CO2 levels of the Pleistocene through the future suggest th1at competitive interactions of C-3 and C-4 annuals have changed through geologic time. This study also provided evidence that C-3 annuals may be operating near a minimum CO2 partial pressure for growth and reproduction at 15 Pa CO2.451956^4^Epron,D^Godard,D^Cornic,G^Genty,B^1995^1^Limitation of net co2 assimilation rate by internal resistances to co2 transfer in the leaves of 2 tree species (fagus- sylvatica L and castanea-sativa mill)^9^18^1^43-51^^^^^Jan^^^^^4711tu1A^4710^Using a combination of gas-exchange and chlorophyll fluorescence measurements, low apparent CO2/O-2 specificity fac1tors (1300 mol mol(-1)) were estimated for the leaves of two deciduous tree species (Fagus sylvatica and Castanea sativa),1 These low values contrasted with those estimated for two herbaceous species and were ascribed to a drop in the CO2 mole f1raction between the intercellular airspace (C-i) and the catalytic site of Rubisco (C-c) due to internal resistances to CO12 transfer, C-c was calculated assuming a specificity of Rubisco value of 2560 mol mol(-1). The drop between C-i and C-c w1as used to calculate the internal conductance for CO2 (g(i)), A good correlation between mean values of net CO2 assimilati1on rate (A) and g(i) was observed within a set of data obtained using 13 woody plant species, including our own data, We r1eport that the relative limitation of A, which can be ascribed to internal resistances to CO2 transfer, was 24-30%, High i1nternal resistances to CO2 transfer may explain the low apparent maximal rates of carboxylation and electron transport of some woody plant species calculated from A/C-i curves.1957^3^Garcia,RL^Idso,SB^Kimball,BA^1994^1^Net photosynthesis as a function of carbon-dioxide concentration in pine trees grown at ambient and elevated co2^173^34^3^337-341^^^^^Jul^^^^^47131A^4712^Pinus eldarica seedlings were grown in a field of Avondale loam at Phoenix, Arizona within transparent open-top enc1losures maintained for 15 months at mean CO2 concentrations of 402 and 788 mu l 1(-1), after which whole-tree net photosyn1thetic rates were measured at a number of CO2 concentrations ranging from ambient (360 mu l 1(-1)) to 3000 mu l 1(-1). Rat1es of the low- CO2-treatment trees saturated at approximately five times their ambient-concentration value; while rates of1 the high-CO2- treatment trees rose linearly across the entire CO2 range investigated to more than 10 times their value al1 360 mu l 1(- 1). These findings suggest that long-term exposure to elevated CO2 can increase the ability of trees with unrestricted root systems to respond positively to still higher CO2 concentrations.1958^4^Gorissen,A^Vanginkel,JH^Keurentjes,JJB^Vanveen,JA^1995^1^Grass root decomposition is retarded when grass has been grown under elevated co2^130^27^1^117-120^^^^^Jan1959^5^Grieb,B^Gross,U^Pleschka,E^Arnholdtschmitt,B^Neumann,KH^1994^1^Embryogenesis of photoautotrophic cell-cultures of daucus- carota L^177^38^2-3^115-122^^^^^Sep^^^^^47161A^4715^In this paper photoautotrophic carrot (Daucus carota L.) suspension cultures are described which are able to produc1e somatic embryos. The development of somatic embryos, however, requires a sucrose supplement. Although an elevation of th1e CO2 concentration up to 2.3% results in the same level of dry weight production as with sucrose in the medium, somatic e1mbryos could not be observed. Results on the influence of sucrose on some aspects of the photosynthetic apparatus of cultured cells are discussed.1960^5^Idso,SB^Idso,KE^Garcia,RL^Kimball,BA^Hoober,JK^1995^1^Effects of atmospheric co2 enrichment and foliar methanol application on net photosynthesis of sour orange tree (citrus- aurantium, rutaceae) leaves^5^82^1^26-30^^^^^Jan^^^^^47181A^4717^Foliar spray applications of 40% aqueous methanol were made to sunlit leaves of sour orange trees that had been gro2wn continuously in clear-plastic-wall open-top enclosures maintained out-of-doors at Phoenix, Arizona, for over 5.5 years /in ambient air of approximately 400 mu mol mol(-1) CO2 and in air enriched with CO2 to a concentration of approximately 702A^4721^Standing dead and green foliage litter was collected in early November 1990 from Andropogon gerardii (C-4), Sorghas2trum nutans (C-4), and Poa pratensis (C-3) plants that were grown in large open-top chambers under ambient or twice ambien2t CO2 and with or without nitrogen fertilization (45 kg N ha(-1)). The litter was placed in mesh bags on the soil surface 2of pristine prairie adjacent to the growth treatment plots and allowed to decay under natural conditions. Litter bags were2 retrieved at fixed intervals and litter was analyzed for mass loss, carbon chemistry, and total Kjeldahl nitrogen and pho2sphorus. The results indicate that growth treatments had a relatively minor effect on the initial chemical composition of 2the litter and its subsequent rate of decay or chemical composition. This suggests that a large indirect effect of CO2 on 2 surface litter decomposition in the tallgrass prairie would not occur by way of changes in chemistry of leaf litter Howeve2 r, there was a large difference in characteristics of leaf Litter decomposition among the species. Paa leaf fitter had a d2 ifferent initial chemistry and decayed more rapidly than C-4 grasses. We conclude that an indirect effect of CO2 on decomp2 osition and nutrient cycling could occur if CO2 induces changes in the relative aboveground biomass of the prairie species.PROGRAM FILES\MICROSOFT OFFICE\OFFICE\WEB PAGE TEMPL2963^2^Kerstiens,G^Hawes,CV^1994^1^Response of growth and carbon allocation to elevated co2 in young cherry (prunus-avium L) saplings in relation to root environment^84^128^4^607-614^^^^^Dec^^^^^4724\PROFESSIONAL.DOT2A^4723^The hypothesis that inadequate rooting volume may reduce the growth stimulation by elevated CO2 in potted tree seed2lings and saplings was tested experimentally and by surveying the literature. One-year-old cherry saplings were grown for 2one season in naturally lit growth chambers in eight combinations of CO2 concentration (ambient; ambient + 250 ppm) and ro2ot environment (four types). The latter included (1) moderately restrictive pot volume (4 l) in combination with two level2s of fertilizer addition (1a, 1b); (2) 10 l pots with total fertilizer content per pot as in treatment 1a, and (3) 20 l po2ts with five plants sharing five times the space and nutrient resources of treatment 1a. Plants were harvested in April, M2ay, June, August and September. The overall mean effect of high CO2 plant dry mass by the end of the season was +24%. Inte2ractive effects of root environments and CO2 concentrations on dry mass were not significant at the 5% level, but repeated2 measurements of basal stem diameter of individual plants indicated a significant impact of root environment on the respon2se to CO2. Overall growth enhancement by elevated CO2 did not differ significantly between harvests, but it tended to incr2ease during the season in those root environments which restricted growth in ambient CO2 most strongly (1a and 3). The hyp2othesis was rejected for this experiment. Leaf area and stem height were not affected by any treatment. The variation of c2arbon allocation to roots and shoots with plant size was very similar in all treatments. Plants grew faster in elevated CO22 very early in the season, and this resulted in small but significant differences between seasonal patterns of biomass pa2rtitioning in ambient and elevated CO2. A survey of 33 studies on growth responses of 47 tree species to elevated CO2 (6002-800 ppm) showed that the relative change in biomass was not related to the ratio of plant biomass and pot volume found in2 either ambient or elevated CO2. We conclude that there is no evidence that inadequate pot volume had a negative impact on the stimulation of growth of tree species in elevated CO2.E\WORDMAIL\FAVORITES\HIGHTECH.L2"964^3^Kleemola,J^Peltonen,J^Peltonensainio,P^1994^1^Apical development and growth of barley under different co2 and nitrogen regimes^161^173^2^79-92^^^^^Sep^^^^^4726GRAM FILES\MICROSOFT OFFICE\OFFICE\WEB 2$A^4725^Increases in atmospheric carbon dioxide (CO2) concentration have stimulated interest in the response of agricultura2%l crops to elevated levels of CO2. Several studies have addressed the response of C3 cereals to CO2, but the interactive e2&ffect of nutrient supply and CO2 on apical development and spikelet set and survival has not been investigated thoroughly.2' Hence, an experiment was conducted in the greenhouse to evaluate the effect of high (700 mumol CO2mol-1 air) and low (4002( mumol mol- 1) levels of atmospheric CO2 on apical development, spikelet set and abortion, and pre- and post-anthesis grow2)th in spring barley (Hordeum vulgare L.) grown under high N (0.3 g N pot-1 before sowing +0.11 g N pot-1 week-1) and low N2* (0.3 g N pot-1) regimes. The plants were grown in 5 L pots. Development of spike was hastened due to CO2 enrichment, and 2+the C+ plants pollinated few days earlier than the C- plants. Carbon dioxide enrichment had no effect on date of ripening.2, Development of spike slowed following application of extra N, and plants pollinated 10 days later and matured 2 weeks lat2-er when compared with plants under low N. Carbon dioxide enrichment did not affect the number of spikelets at anthesis. Ex2.cess N decreased spikelet abortion and the increased maximum number of spikelets under both [CO2]. Barley plants did not t2/iller when grown in low [CO2] and low N. Increased endogenous IAA concentration in those plants, recorded three days befor20e tillers appeared in other treatments, may have contributed to this. Carbon dioxide enrichment increased the C concentrat21ion of plants, but decreased the N concentration under high N regime. Both the C and N concentration of plants were increa22sed under high N regime. Carbon dioxide enrichment increased the total dry matter of mature plants by 9% under high N regi23me and by 21% under low N regime. Under high [CO2] increased kernel number on tiller spikes, and increased kernel weight b24oth on main stem and on tiller spikes resulted in a 23% increase in kernel yield under low N regime and 76% increase in ke25rnel yield under high N regime. The rate of N application influenced growth and yield components to a greater extent than 26CO2 enrichment. At maturity, plant dry matter, kernel weight, the number of kernels per spike, and the number of spikes pe27r plant were higher under high N regime than under low N regime. Long days (16 h), low light intensity (280 mumol m-2s-1),28 and at constant temperature of 20-degrees-C high [CO2] increased kernel weight and the number of kernels on tiller spikes29 under high and low N application rate, but did not increase the number of kernels on main stem spike, or the number of tillers or tiller spikes per plant.B PAGE TEMPLATES\CONTENT\PERSONAL HOME PAGE.2;965^4^Knapp,AK^Cocke,M^Hamerlynck,EP^Owensby,CE^1994^1^Effect of elevated co2 on stomatal density and distribution in a C-4 grass and a C-3 forb under field conditions^52^74^6^595-599^^^^^Dec^^^^^4728OFT OFFICE\OFFICE\WOR2=A^4727^Two common tallgrass prairie species, Andropogon gerardii, the dominant C-4 grass in this North American grassland,2> and Salvia pitcheri, a C-3 forb, were exposed to ambient and elevated (twice ambient) CO2 within open-top chambers throug2?hout the 1993 growing season. After full canopy development, stomatal density on abaxial and adaxial surfaces, guard cell 2@length and specific leaf mass (SLM; mg cm(-2) were determined for plants in the chambers as well as in adjacent unchambere2Ad plots. Record high rainfall amounts during the 1993 growing season minimized water stress in these plants (leaf xylem pr2Bessure potential was usually > -1.5 MPa in A. gerardii) and also minimized differences in water status among treatments. I2Cn A. gerardii, stomatal density was significantly higher (190 +/- 7 mm(-2); mean +/- s.e.) in plants grown outside of the 2Dchambers compared to plants that developed inside the ambient CO2 chambers (161 +/- 5 mm(-2)). Thus, there was a significa2Ent 'chamber effect' on stomatal density. At elevated levels of CO2, stomatal density was even lower (P < 0.05; 121 +/- 5 m2Fm(- 2)). Most stomata were on abaxial leaf surfaces in this grass, but the ratio of adaxial to abaxial stomatal density wa2Gs greater at elevated levels of CO2. In S. pitcheri, stomatal density was also significantly lower when plants were grown 2Hin the open-top chambers (235 +/- 10 mm(-2) outside vs. 140 +/- 6 mm(-2) in the ambient CO2 chamber). However, stomatal de2Insity was greater at elevated CO2 (218 +/- 12 mm(-2)) compared to plants from the ambient CO2 chamber. The ratio of stomat2Ja on adaxial vs. abaxial surfaces did not vary significantly in this herb. Guard cell lengths were not significantly affec2Kted by growth in the chambers or by elevated CO2 for either species. Growth within the chambers resulted in lower SLM in S2L. pitcheri, but CO2 concentration had no effect. In A. gerardii, SLM was lower at elevated CO2. These results indicate tha2Mt stomatal and leaf responses to elevated CO2 are species specific, and reinforce the need to assess chamber effects along with treatment effects (CO2) when using open-top chambers.IL.LNK3 PROGRAM FILES\M2O966^2^Krapp,A^Stitt,M^1995^1^An evaluation of direct and indirect mechanisms for the sink- regulation of photosynthesis in2P spinach - changes in gas- exchange, carbohydrates, metabolites, enzyme-activities and steady-state transcript levels after cold-girdling source leaves^6^195^3^313-323^^^^^Jan^^^^^4730FILES\MICROSOFT OFFICE\OFFICE2RA^4729^Mature source leaves of spinach (Spinacia oleracea L.) plants growing hydroponically in a 9 h light (350 mu mol pho2Stons.m(- 2).s(-1))/15 h dark cycle at 20 degrees C in a climate chamber were fitted with a cold girdle around the petiole,2T 2 h into the light period. Samples were taken 1, 3 and 7 h later, and at the end of the photoperiod for the following 4 d2U. Control samples were taken from ungirdled leaves. in the first 7 h after fitting the cold girdle there was (compared to 2Vthe control leaves) a two to fivefold accumulation of sucrose, glucose, fructose and starch, a 40-50% increase of hexose-p2Whosphates and ribulose-1,5-bisphosphate, a decrease of glycerate-3-phosphate, a small decrease in sucrose-phosphate syntha2Xse activation, an increase of fructose-2,6-bisphosphate, increased activation of ribulose-1,5-bisphosphate carboxylase/oxy2Ygenase (Rubisco), but no significant change in photosynthetic rate or stomatal conductance. Steady-state transcript levels2Z for rbcS (small subunit of Rubisco) and atp-D (D-subunit of the thylakoid ATP synthase) decreased 30%, cab (chlorophyll-a2[-binding protein) decreased by 15% and agp-S (S-isoenzyme of ADP-glucose pyrophosphorylase) and nra (nitrate reductase) ro2\se twofold. On the following days, levels of carbohydrates continued to rise and the changes of metabolites were maintaine2]d. Transcripts for rbcS, cab and atpD declined to 20, 70 and 25% of the control values. From day 3 onward the maximum acti2^vity of Rubisco declined. This was accompanied by a further increase of Rubisco activation to over 90% and, from day 4 onw2_ards, an inhibition of photosynthesis which was associated with high internal CO2 concentration (c(i)), high ribulose-1,5-2`bisphosphate, and low glycerate-3-phosphate. When the cold-girdle was removed on day 5 there was a gradual recovery of pho2atosynthesis and decline of c(i) over the next 2 d. Hexose-phosphates levels and transcripts for rbcS, cab and atp-D comple2btely recovered within 2 d, even though the levels of carbohydrates had not fully recovered. Activity of Rubisco only rever2cted partly after 2 d, and Rubisco activation state and the ribulose-1,5- bisphosphate/glycerate-3-phosphate ratio were sti2dll higher than in control leaves. Transcripts for nra and agp-S were also still higher than in control leaves. It is concl2euded (i) that a reversible modulation of gene expression in response to the export rate plays a central role in the mid-te2frm feedback ''sink'' regulation of photosynthesis, and (ii) that feedback regulation of CO2 fixation by changes of P-i are2g of little importance in spinach under these conditions. Further (iii) the rapid and reciprocal changes in nra and agpS tr2hanscripts, compared to rbcS, provide evidence that gene expression could also contribute to the modulation of nitrate assimilation and carbohydrate storage in conditions of decreased sink demand./23/96"PROGRAM FILES\2j967^2^Krupa,SV^Legge,AH^1995^1^Air-quality and its possible impacts on the terrestrial ecosystems of the north-american great-plains - an overview^35^88^1^1-11^^^^^^^^^^4732ILES\MICROSOFT OFFICE\OFFICE\WEB PA2lA^4731^Over the past several decades, numerous studies have been conducted on the impacts of air pollutants (air quality) 2mon terrestrial ecosystems (crops and forests). Although ambient air is always composed of pollutant mixtures, in determini2nng the relative air quality and its ecosystem impacts at a given geographic location and time, a predominant number of stu2odies have shown that at the present time surface level O-3 is the most important phytotoxic air pollutant. Within the Nort2ph American Great Plains, the precursors; for surface-level O-3 are mainly anthropogenic NOx and VOCs (volatile organic com2qpounds). Texas and Alberta ta are the top regions of such emissions in the United States and Canada, respectively. This ap2rpears to be due mainly to the prevalence of natural gas and/or oil industry in the two regions and the consequent urbaniza2stion. Nevertheless, the total emissions of NOx and VOCs within the North American Great Plains represent only about 25- 362t% of the corresponding total emissions within the contiguous United States and the whole of Canada. Within the Great Plain2us many major crop and tree species are known to be sensitive to O-3. This sensitivity assessment, however, is based mainly2v on our knowledge from univariate (O-3 only) exposure-plant response studies. In the context of global climate change, in 2walmost all similar univariate studies, elevated CO2, concentrations have produced increases in plant biomass (both crop an2xd tree species). The question remains as to whether this stimulation will offset any adverse effects of elevated surface O2y-3 concentrations. Future research must address this important issue both for the Great Plains and for all other geographi2zc locations, taking into consideration spatial and temporal variabilities in the ambient concentrations of the two trace gases.ES\MICROSOFT OFFICE\OFFICE\WORDMAIL\FAVORITES\FLAME.LNK2|968^3^Larigauderie,A^Reynolds,JF^Strain,BR^1994^1^Root response to co2 enrichment and nitrogen supply in loblolly-pine^206^165^1^21-32^^^^^^^^^^4734S\STYLES\HARVEST.DOTharvest.dotPROGRAM2~A^4733^This paper examines how elevated CO2 and nitrogen (N) supply affect plant characteristics of loblolly pine (Pinus t2aeda L.) with an emphasis on root morphology. Seedlings were grown in greenhouses from seeds during one growing season at 2two atmospheric CO2 concentrations (375 and 710 mu L L(-1)) and two N levels (High and Low). Root morphological characteri2stics were determined using a scanner and an image analysis program on a Macintosh computer. In the high N treatment, elev2ated CO2 increased total plant dry weight by 80% and did not modify root to shoot (R/S) dry weight ratio, and leaf and pla2nt N concentration at the end of the growing season. In the low N treatment, elevated CO2 increased total dry weight by 602%. Plant and leaf N concentration declined and R/S ratio tended to increase. Nitrogen uptake rate on both a root length an2d a root dry weight basis was greater at elevated CO2 in the high N treatment and lower in the low N treatment. We argue t2hat N stress resulting from short exposures to nutrients might help explain the lower N concentrations observed at high CO22 in other experiments; Nitrogen and CO2 levels modified root morphology. High N increased the number of secondary lateral2 roots per length of first order lateral root and high CO2 increased the length of secondary lateral roots per length of f2irst order lateral root. Number and length of first order lateral roots were not modified by either treatment. Specific ro2ot length of main axis, and to a lower degree, of first order laterals, declined at high CO2, especially at high N. Basal 2stem diameter and first order root diameters increased at high CO2, especially at high N. Elevated CO2 increased the proportion of upper lateral roots within the root system.ATES\STYLES\JAZZY.DOT Microsof2969^3^Lewis,JD^Thomas,RB^Strain,BR^1994^1^Effect of elevated co2 on mycorrhizal colonization of loblolly- pine (pinus-taeda L) seedlings^206^165^1^81-88^^^^^^^^^^4736 Microsoft Corp.PROGRAM FILES\MICR2A^4735^Interactive effects of elevated atmospheric CO2 and phosphorus supply on mycorrhizal colonization rates were invest2igated using loblolly pine (Pinus taeda L.) seedlings from Florida and coastal North Carolina. Seedlings from both populat2ions were grown in greenhouses maintained at either 35.5 Pa or 71.0 Pa CO2. In both CO2 treatments, seedlings were grown i2n a full factorial experiment with or without mycorrhizal inoculum and with an adequate or a limiting supply of phosphorus2. Seedlings were harvested 60, 90 and 120 days after emergence and at each harvest root subsamples were examined to determ2ine the percent of fine roots that were mycorrhizal. Additionally, root carbohydrate and nutrient levels were measured at 2each harvest. Root starch, sugar and total non-structural carbohydrate (TNC) concentrations were increased by growth in el2evated CO2 and decreased by mycorrhizal colonization. Phosphorus stress decreased root starch concentrations, increased ro2ot sugar concentrations and did not significantly affect TNC concentrations. However, despite significant effects on root 2carbohydrate levels, there were generally no significant treatment effects on mycorrhizal colonization. Additionally, at a2ll harvests, root starch and sugar concentrations were not correlated with percent of fine roots that were mycorrhizal. Th2ese results suggest that although elevated CO2 may significantly increase root carbohydrate levels, the increases may not affect the percent of fine roots that are mycorrhizal.OFT OFFICE\OFFICE\WEB PAGE TEMPLA2970^4^Monz,CA^Hunt,HW^Reeves,FB^Elliott,ET^1994^1^The response of mycorrhizal colonization to elevated co2 and climate-change in pascopyrum-smithii and bouteloua-gracilis^206^165^1^75-80^^^^^^^^^^4738\STYLES\ELEGANT.DOT2A^4737^Large intact soil cores of nearly pure stands of Pascopyrum smithii (western wheatgrass, C-3) and Bouteloua gracili2s (blue grama, C-4) were extracted from the Central Plains Experimental Range in northeastern Colorado, USA and transferre2d to controlled environment chambers. Cores were exposed to a variety of water, temperature and CO2 regimes for a total of2 four annual growth cycles. Root subsamples were harvested after the completion of the second and fourth growth cycles at 2a time corresponding to late winter, and were examined microscopically for the presence of mycorrhizae. After two growth c2ycles in the growth chambers, 54% of the root length was colonized in P smithii, compared to 35% in blue grama. Field cont2rol plants had significantly lower colonization. Elevation of CO2 increased mycorrhizal colonization in B. gracilis by 46%2 but had no effect in P. smithii. Temperatures 4 degrees C higher than normal decreased colonization in P. smithii by 15%.2 Increased annual precipitation decreased colonization in both species. Simulated climate change conditions of elevated CO22, elevated temperature and lowered precipitation decreased colonization in P. smithii but had less effect on B. gracilis. After four growth cycles in P. smithii, trends of treatments remained similar, but overall colonization rate decreased.2971^4^Morgan,JA^Knight,WG^Dudley,LM^Hunt,HW^1994^1^Enhanced root-system C-sink activity, water relations and aspects of nutrient acquisition in mycotrophic bouteloua- gracilis subjected to co2 enrichment^206^165^1^139-146^^^^^^^^^^4740soft2A^4739^In order to better elucidate fixed-C partitioning, nutrient acquisition and water relations of prairie grasses unde2r elevated [CO2], we grew the C-4 grass Bouteloua gracilis (H.B.K.) lag ex Steud. from seed in soil-packed, column- lysime2ters in two growth chambers maintained at current ambient [CO2] (350 mu L L(-1)) and twice enriched [CO2] (700 mu L L(- 1)2). Once established, plants were deficit irrigated; growth chamber conditions were maintained at day/night temperatures of2 25/16 degrees C, relative humidities of 35%/90% and a 14-hour photoperiod to simulate summer conditions on the shortgrass2 steppe in eastern Colorado. After 11 weeks of growth, plants grown under CO2 enrichment had produced 35% and 65% greater 2total and root biomass, respectively, and had twice the level of vesicular-arbuscular mycorrhizal (VAM) infection (19.8% v2ersus 10.8%) as plants grown under current ambient [CO2]. The CO2-enriched plants also exhibited greater leaf water potent2ials and higher plant water use efficiencies. Plant N uptake was reduced by CO2 enrichment, while P uptake appeared little2 influenced by CO2 regime. Under the conditions of the experiment, CO2 enrichment increased root biomass and VAM infection via stimulated growth and adjustments in C partitioning below-ground.FICE\WEB PAGE TEMPLATES\S2972^1^Mortensen,LM^1995^1^Effect of carbon-dioxide concentration on biomass production and partitioning in betula-pubescens ehrh seedlings at different ozone and temperature regimes^35^87^3^337-343^^^^^^^^^^4742ONAL HOME PAGE.D2A^4741^Seedlings of Betula pubescens were grown at two CO2 concentrations, in combination with either two O3 concentration2s or two air temperatures, during 34-35 days at 24 h day-1 photoperiod in growth chambers placed in a greenhouse. Increasi2ng the CO2 concentration from 350 to 560 mumol mol-1 at 17-degrees-C air temperature increased the dry weight of the main 2leaves, main stem, branches and root. The mean relative growth rate (RGR) was increased 10% by CO2 enrichment, while incre2asing the O3 concentration from 7 to 62 nmol mol-1 decreased the RGR by 9%. The relative biomass distribution between the 2different plant components was not significantly affected by the CO2 concentration irrespective of the O3 concentration. N2o significant interactions between CO2 and O3 concentration were found except on leaf size, which was stimulated more by e2levated CO2 concentration at high, compared to low, O3 levels. In another experiment, elevated CO2 (700 mumol mol-1) signi2ficantly increased the dry weight of the different plant components, and more at 20-degrees-C than at 15-degrees-C. Raisin2g the CO2 concentration increased the RGR by 5 and 10% at 15 and 20-degrees-C, respectively. CO2 enrichment increased the 2branch dry weight relatively more than the dry weight of the other plant parts. Increasing the CO2 concentration or temperature increased the plant height and stem diameter, however, no interactions between CO2 and temperature were found.FA2973^1^Norby,RJ^1994^1^Issues and perspectives for investigating root responses to elevated atmospheric carbon-dioxide^206^165^1^9-20^^^^^^^^^^4744FICE\WORDMAIL\FAVORITES\OCEAN.LNK,Microsoft 2A^4743^A thorough assessment of how plants and ecosystems will respond to increasing concentrations of atmospheric CO2 req2uires that the responses of root systems and associated belowground processes be understood. Static measures of root-to-sh2oot ratio have not been satisfactory for describing the integrated responses of plants to CO2-enriched atmospheres, but re2search with a process orientation has suggested that elevated CO2 can stimulate root growth or root activity and provide a2 positive feedback on plant growth. There are, however, critical questions concerning the relevance of root data from shor2t-term studies with potted plants when scaling to questions about plants in the field. Data on root responses to CO2 enric2hment in the field are fragmentary, but they allow us to more clearly define research questions for further investigation.2 Three perspectives for analyzing the significance of root responses as a component of the overall response of the terrest2rial biosphere to increasing atmospheric CO2 are suggested: (1) roots as a platform for nutrient acquisition and a mediato2r of whole-plant response to CO2; (2) carbon storage in roots as a component of whole-plant carbon storage; and (3) effect2s of CO2 enrichment on root turnover and the implications for carbon storage as soil organic matter. The relative importan2ce of these different perspectives will vary depending on the ecosystem of interest and the larger-scale issues being considered.icrosoft Word 8.0 PROGRAM FILES\MICROSOFT OFFICE\OFFIC974^1^Oneill,EG^1994^1^Responses of soil biota to elevated atmospheric carbon-dioxide^206^165^1^55-65^^^^^^^^^^47460 2A^4745^Increasing concentrations of atmospheric CO2 could have dramatic effects upon terrestrial ecosystems including chan2ges in ecosystem structure, nutrient cycling rates, net primary production, C source-sink relationships and successional p2atterns. All of these potential changes will be constrained to some degree by below ground processes and mediated by respo2nses of soil biota to indirect effects of CO2 enrichment. A review of our current state of knowledge regarding responses o2f soil biota is presented, covering responses of mycorrhizae, N-fixing bacteria and actinomycetes, soil microbiota, plant 2pathogens, and soil fauna. Emphasis will be placed on consequences to biota of increasing C input through the rhizosphere 2and resulting feedbacks to above ground systems. Rising CO2 may also result in altered nutrient concentrations of plant li2tter, potentially changing decomposition rates through indirect effects upon decomposer communities. Thus, this review will also cover current information on decomposition of litter produced at elevated CO2.E\WEB PAGE TEMPLAT2975^3^Owensby,CE^Auen,LM^Coyne,PI^1994^1^Biomass production in a nitrogen-fertilized, tallgrass prairie ecosystem exposed to ambient and elevated levels of co2^206^165^1^105-113^^^^^^^^^^4748TEMPLATES\STYLES\COMMUNITY2A^4747^Increased biomass production in terrestrial ecosystems with elevated atmospheric CO2 may be constrained by nutrient2 limitations as a result of increased requirement or reduced availability caused by reduced turnover rates of nutrients. T2o determine the short-term impact of nitrogen (N) fertilization on plant biomass production under elevated CO2, we compare2d the response of N-fertilized tallgrass prairie at ambient and twice-ambient CO2 levels over a 2-year period. Native tall2grass prairie plots (4.5 m diameter) were exposed continuously (24 h) to ambient and twice-ambient CO2 from 1 April to 26 2October. We compared our results to an unfertilized companion experiment on the same research site. Above- and belowground2 biomass production and leaf area of fertilized plots were greater with elevated than ambient CO2 in both years. The incre2ase in biomass at high CO2 occurred mainly aboveground in 1991, a dry year, and belowground in 1990, a wet year. Nitrogen 2concentration was lower in plants exposed to elevated CO2, but total standing crop N was greater at high CO2. Increased ro2ot biomass under elevated CO2 apparently increased N uptake. The biomass production response to elevated CO2 was much grea2ter on N-fertilized than unfertilized prairie, particularly in the dry year. We conclude that biomass production response 2to elevated CO2 was suppressed by N limitation in years with below-normal precipitation. Reduced N concentration in above-2and belowground biomass could slow microbial degradation of soil organic matter and surface litter, thereby exacerbating N limitation in the long term.\STYLES\OUTDOORS.DOToutdoors.dotPROGR2976^4^Rice,CW^Garcia,FO^Hampton,CO^Owensby,CE^1994^1^Soil microbial response in tallgrass prairie to elevated co2^206^165^1^67-74^^^^^^^^^^4750rsonal.doc.PROGRAM FILES\MICROSOFT OFFICE\OFFIC2A^4749^Terrestrial responses to increasing atmospheric CO2 are important to the global carbon budget. Increased plant prod2uction under elevated CO2 is expected to increase soil C which may induce N limitations. The objectives of this study were2 to determine the effects of increased CO2 on 1) the amount of carbon and nitrogen stored in soil organic matter and micro2bial biomass and 2) soil microbial activity. A tallgrass prairie ecosystem was exposed to ambient and twice-ambient CO2 co2ncentrations in open-top chambers in the field from 1989 to 1992 and compared to unchambered ambient CO2 during the entire2 growing season. During 1990 and 1991, N fertilizer was included as a treatment. The soil microbial response to CO2 was me2asured during 1991 and 1992. Soil organic C and N were not significantly affected by enriched atmospheric CO2. The respons2e of microbial biomass to CO2 enrichment was dependent upon soil water conditions. In 1991, a dry year, CO2 enrichment sig2nificantly increased microbial biomass C and N. In 1992, a wet year, microbial biomass C and N were unaffected by the CO2 2treatments. Added N increased microbial C and N under CO2 enrichment. Microbial activity was consistently greater under CO22 enrichment because of better soil water conditions. Added N stimulated microbial activity under CO2 enrichment. Increase2d microbial N with CO2 enrichment may indicate plant production could be limited by N availability. The soil system also c2ould compensate for the limited N by increasing the labile pool to support increased plant production with elevated atmospheric CO2. Longer-term studies are needed to determine how tallgrass prairie will respond to increased C input.2977^4^Singer,A^Eshel,A^Agami,M^Beer,S^1994^1^The contribution of aerenchymal co2 to the photosynthesis of emergent and submerged culms of scirpus-lacustris and cyperus- papyrus^159^49^2-3^107-116^^^^^Aug^^^^^4752FICE\WORDMAIL\F2A^4751^In this work it was investigated whether sediment-derived aerenchymal CO2 could be utilized for photosynthesis in t3he culms of the two emergent aquatic macrophytes Scirpus lacustris L. (a C-3 plant) and Cyperus papyrus L. (a C-4 plant). 3Aerenchymal CO2 concentrations within the submerged parts of the culms were found to be 30 000-50 000, mu l l(-1), and ca.3 800 mu l l(-1) in the emergent parts of Scirpus lacustris and 2000 mu l l(-1) in Cyperus papyrus. These concentrations te3nded to be lower during the day in Cyperus, while no dear diurnal pattern was observed for Scirpus. Photosynthetic rates b3ased on fixation of external or internal CO2 were measured in situ by providing (CO2)-C-14 either externally or from the a3erenchyma (by supplying C-14-labelled CO2 through test-tubes attached to excised culms). The results showed that the contr3ibution of aerenchymal CO2 to the total photosynthesis of emergent culms was less than 0.25% in both species. This has a r3ationale in that photosynthetic rates of both species were saturated at the ambient air CO2 concentration, but it remains 3unclear why CO2 does not diffuse towards the photosynthesizing tissues. By contrast, internal CO2 appeared to be the only 3 source of inorganic carbon used for photosynthesis of young submerged green culms. It is thus suggested that the aerenchym3 a, in addition to other functions, is important in providing sediment-derived CO2 for photosynthesis in young shoots or culms if growing submerged, before they reach the water surface.OFFICE\OFFICE\WORDMAIL\FAVORI3 978^4^Tissue,DT^Griffin,KL^Thomas,RB^Strain,BR^1995^1^Effects of low and elevated co2 on C-3 and C-4 annuals .2. Photosynthesis and leaf biochemistry^2^101^1^21-28^^^^^Jan^^^^^4754ONAL.DOTPROGRAM FIL3A^4753^Abutilon theophrasti (C-3) and Amaranthus retroflexus (C-4), were grown from seed at four partial pressures of CO2:3 15 Pa (below Pleistocene minimum), 27 Pa (pre-industrial), 35 Pa (current), and 70 Pa (future) in the Duke Phytotron unde3r high light, high nutrient, and well-watered conditions to evaluate their photosynthetic response to historic and future 3levels of CO2. Net photosynthesis at growth CO2 partial pressures increased with increasing CO2, for C-3 plants, but not C3-4 plants. Net photosynthesis of Abutilon at 15 Pa CO2 was 70% less than that of plants grown at 35 Pa CO2, due to greater3 stomatal and biochemical limitations at 15 Pa CO2. Relative stomatal limitation (RSL) of Abutilon at 15 Pa CO2 was nearly3 3 times greater than at 35 Pa CO2. A photosynthesis model was used to estimate ribulose-1,5-bisphosphate carboxylase (rub3isco) activity (Vc(max)), electron transport mediated RuBP regeneration capacity (J(max)), and phosphate regeneration capa3city (PiRC) in Abutilon from net photosynthesis versus intercellular CO2 (A-C-i) curves. All three component processes dec3reased by approximately 25% in Abutilon grown at 15 Pa compared with 35 Pa CO2. Abutilon grown at 15 Pa CO2 had significan3t reductions in total rubisco activity (25%), rubisco content (30%), activation state (29%), chlorophyll content (39%), N 3content (32%), and starch content (68%) compared with plants grown at 35 Pa CO2. Greater allocation to rubisco relative to3 light reaction components and concomitant decreases in J(max) and PiRC suggest co-regulation of biochemical processes occ3urred in Abutilon grown at 15 Pa CO2. There were no significant differences in photosynthesis or leaf properties in Abutil3on grown at 27 Pa CO2 compared with 35 Pa CO2, suggesting that the rise in CO2 since the beginning of the industrial age h3as had little effect on the photosynthetic performance of Abutilon. For Amaranthus, limitations of photosynthesis were bal3anced between stomatal and biochemical factors such that net photosynthesis was similar in all CO2 treatments. Differences3 in photosynthetic response to growth over a wide range of CO2 partial pressures suggest chang es in the relative performance of C-3 and C-4 annuals as atmospheric CO2 has fluctuated over geologic time.PROGRAM F3!979^4^Wheeler,TR^Ellis,RH^Hadley,P^Morison,JIL^1995^1^Effects of co2, temperature and their interaction on the growth, development and yield of cauliflower (brassica-oleracea L botrytis)^165^60^3-4^181-197^^^^^Jan^^^^^4756VORITES\HI3#A^4755^Stands of summer cauliflower were grown within polyethylene- covered tunnels along which a temperature gradient was3$ imposed. Two tunnels were maintained at either normal or elevated CO2 concentrations. At the last harvest (88 days from t3%ransplanting) no interaction between CO2 and temperature on total biomass was detected. The total dry weight of plants gro3&wn at 531 mu mol mol-L CO2 was 34% greater than those grown at 328 mu mol mol(-1) CO2, whereas a 1 degrees C rise reduced 3'dry weight by 6%. From serial harvests the radiation conversion coefficient was 2.01 g MJ(-1) and 1.42 g MJ(-1) at 531 mu 3(mol mol(-1) CO2 and 328 mu mol mol(-1) CO2, respectively, but was not greatly affected by differences in temperature. No e3)ffect of either CO2 or temperature on the canopy light extinction coefficient was detected. The rate of progress towards c3*urd initiation increased to a maximum at 15.5 degrees C, and declined thereafter. Provided the effect of temperature was a3+ccounted for, CO2 enrichment did not affect the time of curd initiation. From serial harvests after curd initiation, the l3,ogarithm of curd weight or diameter were negative linear functions of mean temperature from initiation. Increases in curd 3-weight and diameter at 531 compared with 328 mu mol mol(- 1) CO2 were greater at warmer temperatures (27% at 13 degrees C 3.compared with 47% at 15 degrees C, 57 days after initiation). Effects of CO2 on curd diameter were less than those on curd3/ dry weight because the curd dry matter content was greater at 531 compared with 328 mu mol mol(-1) CO2. Thus, the effects30 of elevated CO2 concentrations on fresh weight based yield parameters of cauliflower were less than the increase in total dry matter production.PROGRAM FILES\MICROSOFT OFFICE\OFFICE\WEB 32980^3^Wullschleger,SD^Lynch,JP^Berntson,GM^1994^1^Modeling the belowground response of plants and soil biota to edaphic and climatic-change - what can we expect to gain^206^165^1^149-160^^^^^^^^^^4758LES\COMMUNITY.DOT34A^4757^As atmospheric CO2 concentrations continue to increase, so too will the emphasis placed on understanding the belowg35round response of plants to edaphic and climatic change. Controlled- exposure studies that address the significance of an 36increased supply of carbon to roots and soil biota, and the consequences of this to nutrient cycling will play a prominent37 role in this process. Models will also contribute to understanding the response of plants and ecosystems to changes in th38e earth's climate by incorporating experimental results into conceptual or quantitative frameworks from which potential fe39edbacks within the plant-soil system can be identified. Here we present five examples of how models can be used in this an3:alysis and how they can contribute to the development of new hypotheses in the areas of root biology, soil biota, and ecos3;ystem processes. Two examples illustrate the role of coarse and fine roots in nitrogen and phosphorus uptake from soils, t32 on root and microbial biomass, and on nutrient dynamics in the rhizosphere. Difficulties associated with modeling the co3?ntribution of mycorrhizal fungi to whole-plant growth are also discussed. Finally several broad-scale models are used to i3@llustrate the importance of root turnover, litter decomposition, and nitrogen mineralization in determining an ecosystem's3A response to atmospheric CO2 enrichment. We conclude that models are appropriate tools for use both in guiding existing st3Budies and in identifying new hypotheses for future research. Development of models that address the complexities of belowg3Cround processes and their role in determining plant and ecosystem function within the context of rising CO2 concentrations and associated climate change should be encouraged.\CONTENT\SIMPLE LAYOUT.DOC3E981^3^Wullschleger,SD^Norby,RJ^Hanson,PJ^1995^1^Growth and maintenance respiration in stems of quercus-alba after 4 years of co2 enrichment^37^93^1^47-54^^^^^Jan^^^^^4760GRAM FILES\MICROSOFT OFFICE\OFFICE\W3GA^4759^Atmospheric CO2 enrichment is increasingly being reported to inhibit leaf and whole-plant respiration. It is not kn3Hown, however, whether this response is unique to foliage or whether woody-tissue respiration might be affected as well. Th3Iis was examined for mid-canopy stem segments of white oak (Quercus alba L.) trees that had been grown in open-top field ch3Jambers and exposed to either ambient or ambient + 300 mu mol mol(-1) CO2 over a 4-year period. Stem respiration measuremen3Kts were made throughout 1992 by using an infrared nas analyzer and a specially designed in situ cuvette. Rates of woody-ti3Lssue respiration were similar between CO2 treatments prior to leaf initiation and after leaf senescence, but were several 3Mfold greater for saplings grown at elevated concentrations of CO2 during much of the growing season. These effects were mo3Nst evident on 7 July when stem respiration rates for trees exposed to elevated CO2 concentrations were 7.25 compared to 3.3O44 mu mol CO2 m(-2) s(-1) for ambient-grown saplings. While other explanations must be explored, greater rates of stem res3Ppiration for saplings grown at elevated CO2 concentrations were consistent with greater rates of stem growth and more stem3Q-wood volume present at the time of measurement. When rates of stem growth were at their maximum (7 July to 3 August), gro3Rwth respiration accounted for about 80 to 85% of the total respiratory costs of stems at both CO2 treatments, while 15 to 3S20% supported the costs of stem-wood maintenance. Integrating growth and maintenance respiration throughout the season, ta3Tking into account treatment differences in stem growth and volume, indicated that there were no significant effects of ele3Uvated CO2 concentration on either respiratory process. Quantitative estimates that could be used in modeling the costs of woody-tissue growth and maintenance respiration are provided.ES\MICROSOFT OFFICE\OFFICE\WEB3W982^6^Andrews,TJ^Hudson,GS^Mate,CJ^Voncaemmerer,S^Evans,JR^Arvidsson,YBC^1995^1^Rubisco - the consequences of altering its expression and activation in transgenic plants^78^46^^1293-1300^^^^^Sep^^^^^4762S\ELEGANT.DOT3YA^4761^Transgenic tobacco (Nicotiana tabacum W38) hemizygous for a single antisense gene directed against Rubisco's small 3Zsubunit had 35% of the Rubisco content of control leaves (15% when homozygous). CO2 assimilation (at 1000 mu mol quanta m(3[-2) s(- 1) and 350 mu bar CO2) by the hemizygous leaves was reduced to 40% of that of the controls without material effect3\ on stomatal conductance, chlorophyll content or other photosynthetic components. Leaf soluble protein was reduced commens3]urately with the reduction in Rubisco. CO2 assimilation rate in the hemizygous leaves remained limited by Rubisco activity3^ at all, even very high, CO2 concentrations. This led to a simple, hyperbolic response of photosynthesis to intraplastid C3_O2 concentration from which the in vivo catalytic properties of Rubisco were inferred and compared with those of isolated 3`Rubisco in vitro. Using a similar approach, the content of Rubisco activase was suppressed by incorporating a partial cDNA3a for activase into the tobacco genome in the antisense orientation with respect to a cauliflower mosaic virus 35S promoter3b. The progeny of a primary transformant with two anti- activase inserts had from <1% to 20% of the activase content of con3ctrol plants. Quite severe suppression of activase, to less than 5% of the amount present in control leaves, was required b3defore effects on photosynthesis and growth became apparent, indicating that one activase tetramer must be able to service,3e continuously, as many as 200 Rubisco octamers. Plants with lower activase contents could not grow unless the atmosphere w3fas enriched with CO2. Their Rubisco was less carbamylated and they had lower CO2 assimilation rates than the controls. The3g rate of release of 2'-carboxyarabinitol-1-phosphate from Rubisco after illumination of the anti-activase leaves was also 3himpaired. Older anti-activase plants accumulated increasing amounts of Rubisco in their younger leaves, but were unable to3i carbamylate it. The photosynthetic rate per carbamylated Rubisco active site in the strongly suppressed anti-activase lea3jves was only approximately 25% of that seen in control leaves, suggesting that activase may not only promote carbamylation of uncarbamylated Rubisco sites, but also accelerate turnover at carbamylated sites.NITY.DOT?3l983^5^Bolker,BM^Pacala,SW^Bazzaz,FA^Canham,CD^Levin,SA^1995^1^Species-diversity and ecosystem response to carbon-dioxide fertilization - conclusions from a temperate forest model^127^1^5^373-381^^^^^Oct^^^^^4764FFICE\WEB PAGE T3nA^4763^This paper explores how the response of a temperate forest ecosystem to climate change might depend on species dive3orsity and community change. In particular, we look at the dynamics of a model of temperate forest growth under doubled CO23p. We combine a detailed, field-calibrated model of forest dynamics (Pacala et al. 1993) with greenhouse data on the range 3qof seedling biomass growth response to doubled CO2 concentrations (Bazzaz et al. 1990; Bazzaz & Miao 1993). Because total 3recosystem response to climate change depends delicately on many environmental variables other than CO2, we isolate the eff3sects of community change by comparing runs of the regular model, allowing dynamic community change, with runs of a reduced3t model that holds species composition static by using a single tree species with average parameters. Simulations that allo3uwed community change instead of holding species composition constant showed a roughly 30% additional increase in total bas3val area over time scales of 50-150 years. Although the model omits many possible feedbacks and mechanisms associated with 3wclimate change, it suggests the large potential effects that species differences and feedbacks can have in ecosystem model3xs and reinforces the possible importance of diversity to ecosystem function (Naeem et al. 1994; Tilman & Downing 1994) over time scales within the planning horizon for global change policy.?PROGRAM FILES\MIC3z984^3^Reddy,VR^Reddy,KR^Acock,B^1995^1^Carbon-dioxide and temperature interactions on stem extension, node initiation, and fruiting in cotton^169^55^1^17-28^^^^^Aug^^^^^4766OSOFT OFFICE\OFFICE\WEB PAGE TEMPLA3|A^4765^Understanding the response of agricultural crops to rising carbon dioxide concentration (CO2) and temperature is cr3}itical for modeling the effects of future climate change on crop productivity. The objective of this study was to evaluate3~ the direct and interactive effects of temperature and CO2 on mainstem and branch expansion rates, node initiation rates, 3and fruiting in cotton to be used for the development of a cotton simulation model. Cotton plants (Gossypium hirsutum L., 3cv. DPL 50) were grown in plant growth chambers exposed to natural light levels with temperature and C4 as treatments. The3 average temperatures were 17.8, 18.7, 22.7, 26.6, and 30.6 degrees C during a 70 day experimental period with CO2 treatme3nts of 350 and 700 mu l l(-1) at each temperature. Plant height and number of mainstem nodes increased with increase in te3mperature and CO2. A nine-fold increase was observed in number of fruiting branches with increase in temperature from 17.83 to 30.6 degrees C, however, no significant differences were observed in fruiting branch number due to doubling of CO2 exc3ept at 30.6 degrees C. The number of days from emergence to first square was strongly influenced by temperature, and CO2 h3ad no effect on this process. The number of squares and bells were increased at higher temperatures, and the rate of increase was greater at 700 mu l l(-1) CO2.AGE TEMPLATES\CONTENT\PERSONAL HOME PAGE.3985^4^Tanigawa,T^Kobayashi,Y^Matsui,H^Sakai,Y^1995^1^Effects of co2 enrichment on growth and vase life of cut flowers of dendranthema-grandiflorum (ramat) kitamura^180^64^2^417-424^^^^^Sep^^^^^4768S\MICROSOFT OFFICE\OFFI3A^4767^The effects of CO2 enrichment of chrysanthemum (Dendranthema grandiflorum) on the subsequent growth and mineral and3 carbohydrate contents of the plant and on CO2 and C2H4 production and vase life of cut flowers were investigated. By enri3ching the atmosphere with 1,000 and 2,000 ppm CO2 for 2-1/2 hours each morning, stem length, fresh weight, and leaf number3 of cut flowers were increased by 3 to 11%, and vase life was extended 3 days compared with flowers grown in ambient CO2 c3oncentration of 350 ppm. N, K, Mg, and Na concentrations, especially in the lower leaves were lower, whereas P and Ca conc3entrations were either the same or higher in the CO2 treatment than they were in leaves of plants grown in the ambient CO23. Starch and sugar contents in the leaves and stem were increased under CO2 enriched condition. CO2 production in the leav3es was significantly reduced by the CO2 treatments; C2H4 production was unaffected. From these data, we propose that the d3ecline of [N+K]/Ca ratio (Funakoshi, 1984) and the increase in starch and sugar contents in the leaves and seem as a result of the CO2 enriched atmosphere effectively prolonged vase life of the cut flowers.TEMPLATES\CONTENT\3986^4^Thibaud,MC^Cortez,N^Riviere,H^Betsche,T^1995^1^Photorespiration and related enzymes in pea (pisum-sativum) grown in high co2^4^146^5-6^596-603^^^^^Sep^^^^^4770\STYLES\CONTEMPORARY.DOT@PRO3A^4769^The adaptation of pea (Pisum sativum L. cv. Douce Provence) to the low photorespiratory conditions imposed by high 3CO2 was investigated at the level of enzymes and gas exchange. Seedlings were CO2-enriched (1000 and 4800 mu L CO(2)L(-1))3 during most of the vegetative period, yielding <>. Alternatively, young plants were pre-grown in ambie3nt CO2 and then CO2-enriched, yielding <>. The level of nutrient supply was high. High CO2 did not sig3nificantly alter the specific activities of the photorespiratory enzymes glycolate oxidase, NADH- and NADPH- hydroxypyruva3te reductase and glutamine synthetase in either of the experiments. Moreover, no significant effect of high CO2 on specifi3c carboxylase activity and relative abundance of ribulose bisphosphate carboxylase-oxygenase (Rubisco) was observed. In co3ntrast, high CO2 markedly affected the photorespiratory enzymes catalase (Cat) and phosphoglycolate phosphatase, the activ3ity of the latter being increased. Decline of Cat activity was detected 1 day after transfer to high CO2 and in the course3 of 7 days, the inhibition reached values of 33% (1000 mu L CO(2)L(-1)) and 50% (4800 mu L CO(2)L(-1)). The relative abund3ance of Cat protein also declined, but no change in the isoform pattern was observed. Photorespiratory O-2 uptake, determi3ned with O-18(2), decreased by 54% in an atmosphere containing 1000 mu L CO(2)L(-1). This suggests that Rubisco-oxygenase 3activity occurred at a substantial rate at threefold that of the current atmospheric CO2 concentration. CO2 enrichment to 34000 mu L CO(2)L(-1) further inhibited photorespiratory O-2, uptake. The decline of Cat was thus positively correlated wit3h the inhibition of light O-2 uptake. In <>, Cat inhibition was slight or absent, depending on the leve3l of CO2 enrichment. This suggests that Cat inhibition in <> is a transient response that can be overcome by yet unidentified adaptative mechanisms.OT PROGRAM FILES\MICROSOFT3987^3^Torres,MP^Houpis,JLJ^Pushnik,JC^1995^1^The effects of long-term co2 enrichment on photosynthesis, stomatal conductance and internal/external co2 concentrations in pinus-ponderosa^8^108^2^113^^^^^JunB PAGE TEMPLATES\ST3988^5^Elmeskaoui,A^Damont,JP^Poulin,MJ^Piche,Y^Desjardins,Y^1995^1^A tripartite culture system for endomycorrhizal inoculation of micropropagated strawberry plantlets in-vitro^265^5^5^313-319^^^^^Jul^^^^^4773 PROGRAM 3A^4772^The objective of the current investigation was to develop a reliable method to obtain vesicular-arbuscular mycorrhi3zae (VAM) in micropropagated plantlets and to determine their influence on growth, An in vitro system for culturing the VA3 mycorrhizal fungus Glomus intraradices with Ri T-DNA- transformed carrot roots or nontransformed tomato roots was used in3 this study as a potential active source of inoculum for the colonization of micropropagated plantlets. After root inducti3on, micropropagated plantlets grown on cellulose plugs (sorbarod) were placed in contact with the primary mycorrhizae in g3rowth chambers enriched with 5000 ppm CO2 and fed with a minimal medium. After 20 days of tripartite culture, all plantlet3s placed in contact with the primary symbiosis were colonized by the VAM fungus. As inoculum source, 30-day-old VA mycorrh3izal transformed carrot roots had a substantially higher infection potential than 5-, 10- or 20-day-old VAM. Colonized pla3ntlets had more extensive root systems and better shoot growth than control plants. The VAM symbiosis reduced the plantlet3 osmotic potential. This response may be a useful pre- adaptation for plantlets during transfer to the acclimatization stage.\OFFICE\WEB PAGE TEMPLATES\CONTENT\TABLE OF CONTENTS.DOC3989^1^Keeling,RF^1995^1^The atmospheric oxygen cycle - the oxygen isotopes of atmospheric co2 and o-2 and the o-2/n-2 ratio^266^33^^1253-1262^G PROGRAM FILES\MICROSOFT OFFICE\OFFICE\3990^3^Kirdmanee,C^Kitaya,Y^Kozai,T^1995^1^Effects of co2 enrichment and supporting material in-vitro on photoautotrophic growth of eucalyptus plantlets in-vitro and ex-vitro^267^31^3^144-149^^^^^Jul-Sep^^^^^4776G PROGRAM3A^4775^Eucalyptus camaldulensis shoots were cultured photoautotrophically in vitro for 6 wk with four different types of s3upporting materials (agar matrix, Gelrite matrix, plastic net, or vermiculite) under CO2-nonenriched or CO2- enriched cond3itions. Plantlets from each treatment in vitro were then grown ex vitro in a greenhouse for 4 wk. The growth and net photo3synthetic rate of plantlets in, vitro, as well as subsequent growth, survival percentage, transpiration rate, and net phot3osynthetic rate of plantlets ex vitro were evaluated. CO2 enrichment significantly increased growth (total dry weight and 3number of primary roots) and net photosynthetic rate of plantlets in vitro, as well as the growth and survival percentage 3of plantlets ex vitro regardless of the type of supporting materials. The growth in vitro was greatest in the vermiculite,3 followed by the plastic net, Gelrite matrix, and agar matrix (in descending order) under either the CO2- nonenriched or C3O2-enriched conditions. The growth and survival percentage of plantlets ex vitro were highest in the vermiculite under the3 CO2-enriched condition. The extensive root system produced in vitro was necessary for growth and survival of plantlets ex vitro.ROSOFT OFFICE\OFFICE\WEB PAGE TEMPLATES\STYLES\HARVEST.DO3991^8^Prior,SA^Rogers,HH^Runion,GB^Kimball,BA^Mauney,JR^Lewin,KF^Nagy,J^Hendrey,GR^1995^1^Free-air carbon-dioxide enrichment of cotton - root morphological-characteristics^204^24^4^678-683^^^^^Jul-Aug^^^^^4778ILES\MICROSOFT OF3A^4777^The response of plants to rising global CO2 concentration is of critical research interest but one neglected aspect3 is its effect on roots. Root morphological changes in cotton [Gossypium hirsutum (L.) 'Delta Pine 77'] were examined in a3 2- yr held study. The test crop was grown under two water regimes (wet, 100% of evapotranspiration [ET] replaced and dry,3 75% [1990] and 67% [1991] of ET replaced) and two atmospheric CO2 concentrations (ambient = 370 mu mol mol(-1) and free-a3ir CO2 enrichment [FACE] = 550 pmol mol(-1)). A FACE technique that allows for CO2 exposure under held conditions with min3imal alteration of plant microclimate was used. Excavated root systems were partitioned into taproot and lateral roots at 3two growth phases (vegetative and reproductive). Vertical root- pulling resistance was determined at the second sampling; 3this measure was higher because of CO2 enrichment but was unaffected by water stress. Water stress affected root variables3 only at the second sampling; water stress reduced taproot variables more than lateral variables. The larger diameter tapr3oots seen at all sample dates under FACE exhibited large increases in dry weight and volume. FACE often increased lateral 3root number and lateral dry weights were higher at all sample dates. The development of more robust taproot systems in CO23-enriched environments may allow for greater carbohydrate storage for utilization during periods such as hop filling and t3o ensure root growth for continued exploration of the soil profile to meet nutrient and water demands during peak demand periods.GRAM FILES\MICROSOFT OFFICE\OFFICE\WEB PAGE TEMPLATES\STY3992^5^Ronentarazi,M^Liemanhurwitz,J^Gabay,C^Orus,MI^Kaplan,A^1995^1^The genomic region of rbcls in synechococcus sp pcc-79342 contains genes involved in the ability to crow under low co2 concentration and in chlorophyll biosynthesis^8^108^4^1461-1469^^^^^Aug^^^^^4780OFFICE\WEB PAGE TEMPLATES\STYLES\ELEGANT.DOT3A^4779^Several genes involved in the ability of Synechococcus sp. PCC 7942 to grow under different CO, concentrations were3 mapped in the genomic region of rbcLS (the operon encoding the large and small subunits of ribulose-1,5-bisphosphate carb3oxylase/oxygenase). Insertion of a cartridge encoding kanamycin resistance within open reading frame (ORF) 78, designated 3ccmJ, located 7 kb upstream of rbcLS, resulted in a kanamycin-resistant, high-CO2-requiring mutant, M3, which does not con3tain normal carboxysomes. ccmJ shows significant homology to csoS1 encoding a carboxysomal shell polypeptide in Thiobacill3us neopolitanus. Analysis of the polypeptide pattern of a carboxysome-enriched fraction indicated several differences betw3een the wild type and the mutant. The amount of the ribulose-1,5-bisphosphate carboxylase/oxygenase subunits was considera3bly smaller in the carboxysomal fraction of the mutant when compared to the wild type. On the basis of the sequence analys3es, ORF286 and ORF466, located downstream of ccmJ were identified as chit and chlN, respectively, which are involved in chlorophyll biosynthesis in the dark.RITES\FLAME.LNKCPROGRAM FILES\MI3993^3^Tubiello,FN^Rosenzweig,C^Volk,T^1995^1^Interactions of co2, temperature and management-practices - simulations with a modified version of ceres-wheat^223^49^2^135-152^^^^^^^^^^4782WORDMAIL\FAVORITES\MIDNIGHT.3A^4781^A new growth subroutine was developed for CERES-Wheat, a computer model of wheat (Triticum aestivum) growth and dev3elopment. The new subroutine simulates canopy photosynthetic response to CO2 concentrations and light levels, and includes3 the effects of temperature on canopy light-use effciency. Its performance was compared to the original CERES-Wheat V-2.103 in 30 different cases. Biomass and yield predictions of the two models were well correlated (correlation coefficient r > 30.95). As an application, summer growth of spring wheat was simulated at one site. Modeled crop responses to higher mean t3emperatures, different amounts of minimum and maximum warming, and doubled CO2 concentrations were compared to observation3s. The importance of irrigation and nitrogen fertilization in modulating the wheat crop climatic responses were also analy3zed. Specifically, in agreement with observations, rainfed crops were found to be more sensitive to CO2 increases than irr3igated ones. On the other hand, low nitrogen applications depressed the ability of the wheat crop to respond positively to3 CO2 increases. In general, the positive effects of high CO2 grain yield were found to be almost completely counterbalance3d by the negative effects of high temperatures. Depending on how temperature minima and maxima were increased, yield changes averaged across management practices ranged from -4% to 8%.\WEB PAGE TEMPLATES\STYLES\CO3994^5^Arienzo,M^Basile,G^Dandria,R^Magliulo,V^Zena,A^1995^1^Irrigation with carbonated water and nutrient availability - tests on strawberry plants^268^39^1^61-72^^^^^Jan-Feb^^^^^4784ONTENTS.DOC?PROGRAM3A^4783^A research was carried out to study the nutrient availability and yield performances of a strawberry crop cv. 'Chan3dler' in response to equivalent depths (100% of ETM) of CO2 enriched water and plain water applied with different irrigati3on frequencies. Plots were arranged in a complete randomized block design replicated four times, using mulch and a drip ir3rigation system adopting 4 1/h emitters. The crop was covered by a plastic tunnel following treatment differentiation. The3 statistical analysis revealed an increased availability of Cu, Zn, Ca, Mg, and Mn for the CO2 treatment, probably linked 3with the pH reduction (from 7,5 to 6,5). The increased nutrient uptake in the CO2 enriched water treatment may be the cause of the commercial yield enhancement (8,6 %) and reduction in the weight of deformed berries (-12,1 %).FT OFFIC3995^2^Beerling,DJ^Woodward,FI^1995^1^Leaf stable carbon-isotope composition records increased water- use efficiency of C-3 plants in response to atmospheric co2 enrichment^43^9^3^394-401^^^^^Jun^^^^^4786\PROFESSIONAL MEMO.Ding simulation methods^107^72^1-2^47-56^^^^^Dec^^^^^4857FT OFFICE\TEMPLATES\LETTERS & FA3A^4856^On the basis of observed climatic trends in Slovenia obtained from 142 years of meteorological observation in Ljubl3jana (Slovenia) 15 climatic scenarios for the next 60 years are constructed regarding temperature rise and various levels 3of increasing CO2 concentration. Yearly gross primary production of 80 year old beech stand (Fagus sylvatica) is simulated3 in daily scale by the PERUN 3 model for healthy trees assuming no water stress. The influence of increased CO2 concentrat4ion on physiological processes is assessed over enhanced maximal photosynthesis, lower compensation point and increased st*omatal resistance. Results of the simulation, giving decreased primary production of beech stand under the mentioned assum4A^4785^1. A total of 17 temperate C-3 grass and herb species were grown for 5 weeks at three mole fraction treatments of a4tmospheric CO2 (350, 525 and 700 mu mol mol(-1)). Leaf stable carbon isotope compositions (delta(13)C) were determined to 4record long-term exchange responses together with instantaneous gas exchange measurements. The isotopic composition of the4 atmospheric CO2 (delta(13)C(a)) integrated over the course of the CO2 treatments was recorded biologically using the C-4 4species Zea mays. 2. We found that increases in the mole fraction of atmospheric CO2 above current levels resulted in a su4stained increase in instantaneous (photosynthesis, A/conductance, g(s)) leaf water-use efficiency (IWUE), as calculated fr4om carbon isotope-derived p(i)/p(a) ratios. Grass species showed a marked decline in the magnitude of WUE increase as the 4 CO2 mole fraction was increased from 525 to 700 mu mol mol(-1), a response which was absent in herb species. 3. Isotopic d4 erivation of the ratio of intercellular CO2 mole fraction (p(i)) to that in the surrounding atmosphere (p(a)), considered 4 as a set point of leaf metabolism, showed no significant (P = 0.06) changes in response to increases in the mole fraction 4 of CO2, for herb and grass species. Measurements of p(i)/p(a) determined from measurements of leaf gas exchange differed s4 ignificantly (P<0.01) from those derived from stable isotope ratios. These differences are attributed to contrasting stoma4tal behaviour between herb and grass species. 4. Leaf intercellular CO2 mole fraction and previously reported above- groun4d biomass responses to CO2 increases for the same species were positively correlated (P < 0.05). This suggests that as atm4ospheric CO2 levels continue to rise species showing sustained higher rates of leaf photosynthesis, may be translated into increased productivity depending on soil water and nutrient status.xhPROGRAM FILES\MICR4996^2^Beerling,DJ^Woodward,FI^1995^1^Stomatal responses of variegated leaves to co2 enrichment^52^75^5^507-511^^^^^May^^^^4A^4787^The responses of stomatal density and stomatal index of five species of ornamental plants with variegated leaves gr4own at two mole fractions of atmospheric CO2 (350 and 700 mu mol mol(- 1)) were measured. The use of variegated leaves all4owed any potential effects of mesophyll photosynthetic capacity to be uncoupled from the responses of stomatal density to 4changes in atmospheric CO2 concentration. There was a decrease in stomatal density and stomatal index with CO2 enrichment 4on both white (unpigmented) and green (pigmented) leaf areas. A similar response of stomatal density and index was also ob4served on areas of leaves with pigmentation other than green indicating that any differences in metabolic processes associ4ated with coloured leaves are not influencing the responses of stomatal density to CO2 concentrations. Therefore the carbo4xylation capacity of mesophyll tissue has no direct influence on stomatal density and index responses as suggested previou4sly (Friend and Woodward 1990 Advances in Ecological Research 20: 59-124), instead the responses were related to leaf stru4cture. The stomatal characteristics (density and index) of homobaric variegated leaves showed a greater sensitivity to CO24 on green portions, whereas heterobaric leaves showed a greater sensitivity on white areas. These results provide evidence4 that leaf structure may play an important role in determining the magnitude of stomatal density and index responses to CO2 concentrations.LES\MICROSOFT OFFICE\TEMPLATES\LETTERS & FAXES\PROFE^4788L LETTER.DOTPROGRAM FILES\MICROSOFT OFFICE\TEMPLA4!997^2^Behboudian,MH^Tod,C^1995^1^Postharvest attributes of virosa tomato fruit produced in an enriched carbon-dioxide environment^170^30^3^490-491^^^^^Jun^^^^^4790E\WORDMAIL\FAVORITES\RAIN.LNKPR4#A^4789^The effect of preharvest CO2 enrichment (1000 mu l . liter(-1)) on postharvest quality of tomato fruit (Lycopersico4$n esculentum Mill. 'Virosa') was studied with an emphasis on soluble sugars, ripening, and mineral composition. High-CO2 f4%ruit had higher concentrations of sucrose, glucose, fructose, and total soluble solids than ambient-CO2 fruit. High-CO2 fr4&uit also ripened more slowly and was characterized by lower respiration and ethylene production rates than ambient-CO2 fru4'it. Concentrations of N, P, and K were lower in the high-CO2 fruit than in the ambient- CO2 fruit, whereas those of S, Ca,4( and Mg were the same for both treatments. Preharvest CO2 enrichment of 'Virosa' tomato enhances fruit desirability in terms of slower postharvest ripening and higher concentrations of soluble sugars and total soluble solids.PROGRAM F4*998^2^Cramer,MD^Lips,SH^1995^1^Enriched rhizosphere co2 concentrations can ameliorate the influence of salinity on hydroponically grown tomato plants^37^94^3^425-432^^^^^Jul^^^^^4792OSOFT OFFICE\TEMPLATES\LETTERS4,A^4791^Our previous work indicated that salinity caused a shift in the predominant site of nitrate reduction and assimilat4-ion from the shoot to the root in tomato plants. In the present work we tested whether an enhanced supply of dissolved ino4.rganic carbon (DIC, CO2 + HCO3-) to the root solution could increase anaplerotic provision of carbon compounds for the inc4/reased nitrogen assimilation in the root of salinity-stressed Lycopersicon esculentum (L.) Mill. cv. F144. The seedlings w40ere grown in hydroponic culture with 0 or 100 mM NaCl and aeration of the root solution with either ambient or CO2-enriche41d air (5 000 mu mol mol(-1)). The salinity-treated plants accumulated more dry weight and higher total N when the roots we42re supplied with CO2-enriched aeration than when aerated with ambient air. Plants grown with salinity and enriched DIC als43o had higher rates of NO3- uptake and translocated more NO3- and reduced N in the xylem sap than did equivalent plants gro44wn with ambient DIC. Incorporation of DIC was measured by supplying a 1-h pulse of (HCO3-)-C-14 to the roots followed by e45xtraction with 80% ethanol. Enriched DIC increased root incorporation of DIC 10- fold in both salinized and non-salinized 46plants. In salinity- stressed plants, the products of dissolved inorganic C-14 were preferentially diverted into amino aci47d synthesis to a greater extent than in non-salinized plants in which label was accumulated in organic acids. It was concl48uded that enriched DIC can increase the supply of N and anaplerotic carbon for amino acid synthesis in roots of salinized 49plants. Thus enriched DIC could relieve the limitation of carbon supply for ammonium assimilation and thus ameliorate the influence of salinity on NO3- uptake and assimilation as well as on plant growth.tPROGRAM FILES\MI4;999^3^Griffin,KL^Winner,WE^Strain,BR^1995^1^Growth and dry-matter partitioning in loblolly and ponderosa pine-seedlings in response to carbon and nitrogen availability^84^129^4^547-556^^^^^Apr^^^^^47942 <!-- --> <!--ACCESS4=A^4793^We grew loblolly pine (Pinus taeda L.) and ponderosa pine (Pinus ponderosa Dougl. ex Laws.) seedlings in a factoria4>l experiment with two CO2 partial pressures (35 and 70 Pa) and two nitrogen treatments (1.0 and 3.5 mM NH4+) for one growi4?ng season in a 'common garden' experiment designed to examine the extent that dry matter and nitrogen accumulation and par4@titioning are environmentally controlled. Ponderosa pine seedlings grown in 35 Pa CO2 and 3.5 mM NH4+ showed symptoms of n4Aitrogen toxicity, characterized by greatly reduced growth, and moderately reduced total plant N. With the exception of thi4Bs treatment combination, there were no significant differences between species in total plant dry matter or total plant ni4Ctrogen, suggesting that responses of growth to environmental conditions were stronger than heritable responses. There were4D however large differences in dry matter and N partitioning between the two species. Increases in leaf mass were largest i4En loblolly pine, whilst ponderosa pine tended to have higher root:shoot (R:S) ratios. R:S ratio of loblolly increased in r4Fesponse to C availability and decreased in response to N availability, whilst R: S ratio of ponderosa pine was much less r4Gesponsive to resource availability. Total plant N varied with N supply, and N partitioning was related to plant growth and4H carbon partitioning. Carbon and N were interactive, such that an increase in the accumulation of either resource was alwa4Iys accompanied by an increase in the other. Over several seasons the different patterns of resource acquisition and biomas4Js allocation that we observed in a uniform environment could potentially result in different growth rates at most resource levels. In the first season, contrary to our expectations, heritable differences in growth rate did not appear.wind4L1000^4^Mathooko,FM^Kubo,Y^Inaba,A^Nakamura,R^1995^1^Characterization of the regulation of ethylene biosynthesis in tomato fruit by carbon-dioxide and diazocyclopentadiene^259^5^3^221-233^^^^^Feb^^^^^4796\infoACCESSTEMPLATE4NA^4795^The regulation of ethylene biosynthesis by CO2 and diazocyclopentadiene (DACP), both inhibitors of ethylene action,4O was investigated in tomato (Lycopersicon esculentum Mill. cv. 'Momotaro') fruit held at 25 degrees C. When the tomato fru4Pit at the pink stage of ripeness were treated with 20% CO2 (+ 20% O-2 + 60% N-2) or DACP, ethylene production by the fruit4Q was rapidly decreased. The inhibition of ethylene production resulted primarily, if not solely, from the suppression of t4Rhe activities of both 1-aminocyclopropane-1- carboxylic acid (ACC) synthase and ACC oxidase. The inhibition of ACC synthas4Se activity subsequently led to low levels of ACC. CO2 treatment further inhibited ACC conjugation into 1- (malonylamino)cy4Tclopropane-1-carboxylic acid (MACC). By contrast, DACP-treated fruit maintained slightly higher levels of MACC relative to4U the control fruit. When the fruit were transferred from the CO2-enriched atmosphere to air, ethylene production, ACC and 4VMACC contents and the activities of ACC synthase and ACC oxidase increased gradually to the control level after 24 h, whil4We these values, except for MACC content, remained low in DACP-treated fruit throughout the experimental period. These resu4Xlts indicate that CO2 and DACP regulate ethylene production in tomato fruit by inhibiting ACC synthase and ACC oxidase act4Yivities and further support the hypothesis that the autocatalytic signal associated with ethylene action during fruit ripening stimulates the activities of both enzymes.ETTER.DOT2 PROGRAM FILES\MICR4[1001^4^Sallanon,H^Dimon,B^Carrier,P^Chagvardieff,P^1995^1^Effects of co2 concentration and irradiance on growth and photosynthesis of juglans-regia plantlets grown in-vitro^79^31^2^241-249^^^^^^^^^^4798EMPORARY MEMO.DOT4]A^4797^Walnut (Juglans regia L.) plantlets were incubated during micropropagation in standard vessels (quasi confined vess4^els) or in aerated vessels flushed with 360 or 20 000 cm(3)(CO2) m(- 3) under irradiances of 70 (LI) and 250 (HI) mu mol m4_(-2) s(- 1). Plantlet morphology was strongly affected by the environment: leaf surface was increased, but shoot elongatio4`n and number of stems were reduced after increasing the irradiance of culture. Gross photosynthesis (P-G) capacity measure4ad by using the O-18(2) isotope and mass-spectrometry techniques was increased by increasing photosynthetic photon flux (PP4bF) and CO2 concentration. Plantlets exhibited a potential for photorespiratory activity and Mehler-type reaction and a hig4ch rate of mitochondrial respiration in all vessel types and irradiances. When a long-term HI was applied, gas exchange rat4des (P-G and O-2 uptake) were reduced in most of the vessel and PPF conditions, except in quasi confined vessels. Under all4e the growth conditions, net photosynthetic rate (P-N) was zero or slightly positive and the dry matter accumulation was ve4fry similar. Changes in O-2 exchange, growth rate or enzyme activities linked to carbon fixation that were induced by chang4ges in PFD and CO2 concentration showed that the photosynthetic characteristics of plantlets were typical for hetero-mixotrophic tissues.AG.HTM*ACCESSTEMPLATE_TITLEpPROGRAM FILES\MICR4i1002^4^Stoffella,PJ^Li,YC^Pelosi,RR^Hamner,AM^1995^1^Citrus rootstock and carbon-dioxide enriched irrigation influence on seedling emergence, growth, and nutrient content^166^18^7^1439-1448^^^^^^^^^^4800CCESS\GRAY.HTM*A4kA^4799^Seeds of Carrizo citrange (Citrus senensis (L.) Osb. X Poncirus trifolliata (L.), Cleopatra mandarin (C. reticulata4l Bianco), Sour orange (C. aurantium L.), and Rough lemon (C. limon (Burm f.) were sown in trays, irrigated without or with4m enriched Carbon dioxide (CO2) (1,362 mg L(-1)) and evaluated for seedling emergence, growth, and nutrient contents. Rough4n lemon had a faster rate and higher percent emergence than the other rootstocks. Carrizo citrange had thicker stem diamete4ors and taller seedlings than other rootstocks. Cleopatra mandarin had the smallest seedling shoot and root weights and lar4pger shoot:root ratios than Rough lemon and Sour orange. Carrizo citrange and Cleopatra mandarin had higher leaf chlorophyl4ql-a and total chlorophyll content than Rough lemon or Sour orange. Carbon dioxide enriched irrigation had no effects on em4rergence or seedling growth variables except lower root weight. Lower media pH (6.90 versus 5.65), attributed to CO2 enrich4sed irrigation, may have adversely affected root growth as compared to shoot characteristics. Leaf nutrient contents genera4tlly differed between rootstocks but were not affected by CO2 enriched water except for higher Zn and lower Mn contents. Th4uese results indicate that citrus seedling emergence, subsequent growth and leaf nutrient content differred between rootstocks but there are no beneficial effect from CO2 enriched irrigation. Company Address$zPROGR4w1003^4^Korthals,RL^Knight,SL^Crawford,RR^Christianson,LL^1995^1^Development and testing of a simple carbon-dioxide enrichment controller for growth chambers^256^38^1^207-211^^^^^Jan-Feb^^^^^4802CE\TEMPLATES\PURCHASE OR4yA^4801^Proportional and proportional plus integral (PI) computer algorithms were implemented with a low cost pulse width m4zodulated injection system to control CO2 in a 7.8 m(3) growth chamber. Experimental studies with plants in the growth cham4{ber showed that average CO2 concentrations over 12 h were within 3 and 1 mu mol mol(-1) of set point for the proportional 4|and PI controllers, respectively. The positive offset in CO2 concentration found for the proportional control was attribut4}ed to sampled measurements and pulse width modulated CO2 injection, and discussion was presented on how true errors differ4~ from measured error estimates for pulse width modulated injection with long sampling periods relative to injection periods.O.DOTcontltr.dotPROGRAM FILES\MICROSOFT OFFICE\TEM41004^2^Krug,H^Liebig,HP^1995^1^Models for planning and control of transplant production in climate controlled greenhouses .2. Production control^172^60^1^22-28^^^^^Jan-Feb^^^^^4804\TEMPLATES\BINDERS\REPORT.OBT4A^4803^A model has been developed to control transplant growth. It is based on growth curves, derived under varied greenho4use climates (global irradiances, artificial light, air and soil heating, CO2-concentration), and corresponding growth rat4es, which were related to the intensities of the climatic factors by a regression function. The best fit for the growth ra4tes was obtained by splitting the raising period in an exponential phase, described by a constant Relative Growth Rate, an4d a linear phase, described by the Mean Growth Rate. As the frequency distribution shows, 81% of the 186 sets from October4 to March hit the 4 +/- 0.2 g data of the growth function in +/- 2 days. Simulations for the most extremes out of 36 years4 weather conditions for 5 dates from October to February show the deviations from the estimated curves based on long term 4normals, the potentials of climate control by decreasing or increasing set points of air temperature, CO2 concentration, a4nd artificial light as well as the effects of the starting point for control. Aspects of application and completion as well as the necessity of timing by CO2 enrichment and artificial lighting are discussed.ES\INVOICE1.XLT41005^3^Reddy,VR^Reddy,KR^Hodges,HF^1995^1^Carbon-dioxide enrichment and temperature effects on cotton canopy photosynthesis, transpiration, and water-use efficiency^207^41^1^13-23^^^^^Apr^^^^^4806nt JonesvPROGRAM FIL4A^4805^The objectives of this study were to evaluate effects of ambient and double ambient [CO2] at a range of growing tem4peratures on photosynthesis, respiration, transpiration, water-use efficiency and dry matter accumulation of cotton plants4 (Gossypium hirsutum L., cv. DPL 50). In Experiment I, plants were grown outdoors until first bloom, then transferred into4 naturally lit growth chambers and grown for 22 days at 30/ 18 degrees C with five CO2 concentrations varying from 350 to 4900 mu l l(-1). In Experiment II, air temperatures were maintained at 20/12, 25/17, 30/22, and 35/27 degrees C day/night d4uring a 70-day experimental period with [CO2] of 350 and 700 mu l l(-1) at each temperature, Photosynthesis increased with4 [CO2] from 350 to 700 mu l l(-1) and with temperature. Plants grown at 35/27 degrees C produced fewer bells due to abscis4sion compared with plants grown at optimum temperatures (30/20 degrees C). At higher [CO2], water-use efficiency increased4 at all temperatures due mainly to increased canopy photosynthesis but also to more limited extent to reduced canopy trans4piration. Increased photosynthesis at higher [CO2] resulted in greater dry matter accumulation at all temperatures except 4at 20/12 degrees C. Respiration increased as dry matter and temperature increased. Plants grown at higher [CO2] had less r4espiration per unit dry matter but more per unit area. These results indicate that future increases in [CO2] are likely to4 benefit cotton production by increasing carbon assimilation under temperatures favorable for cotton growth. Reduced fruit4 weights at higher temperatures indicate potential negative effects on production if air temperatures increase as projected in a high-CO2 world.ICE\TEMPLATES\HARDDATA ENTRY TEMPLATE 1.XLTI41006^9^Akin,DE^Rigsby,LL^Gamble,GR^Morrison,WH^Kimball,BA^Pinter,PJ^Wall,GW^Garcia,RL^Lamorte,RL^1995^1^Biodegradation of 4plant-cell walls, wall carbohydrates, and wall aromatics in wheat grown in ambient or enriched co2 concentrations^269^67^3^399-406^^^^^Mar^^^^^4808LetterPROGRAM FILES\MICROSOFT OFFICE\TEM4A^4807^Mature internodes from wheat (Triticum aestivum L) grown in control (ambient at c 370 mu mol mol(-1)) or enriched (4to 550 mu mol mol(-1)) concentrations of atmospheric CO2 in the free- air CO2 enrichment (FACE) system were analyzed for p4otential changes in biodegradation of constituents due to predicted increases in atmospheric levels of CO2. The first inte4rnodes below the grain were incubated with the lignocellulose- degrading white rot fungus, Phanerochaete chrysosporium K-34, or incubated without microorganisms. Plant samples were then analyzed for dry weight loss, disposition of specific cell 4types to biodegradation using electron microscopy, carbohydrates and lignin using solid state NMR spectroscopy, and ester-4 and ether-linked aromatics using gas chromatography. Phanerochaete chrysosporium extensively degraded stems cells (c 75%)4 and both carbohydrate and aromatic portions of the wheat stems proportionately more carbohydrates were removed by the fun4gus from the stems. Enriched CO2 did not affect the chemical composition of wheat stems or the biodegradation by P chrysos4porium of plant cell walls or wall components for the most part. Data from various methods all indicated that enriched CO24 did not substantially alter the biodegradation of wheat cell wall internodes or wall components. Evidence was not found for an influence on C cycling due to CO2 concentrations in this study.6I84HLU@mx2.osu.edu>-21-Jan-1999-12:48:33--0500-(EST41007^4^Chenevard,D^Jayallemand,C^Gendraud,M^Frossard,JS^1995^1^The effect of sucrose on the development of hybrid walnut m4icrocuttings (juglans-nigra X juglans-regia) - consequences on their survival during acclimatization^186^52^2^147-156^^^^^4A^4809^We studied the effect of sucrose concentration in the root- development medium on the formation of adventitious roo4ts and survival of microcuttings during acclimatization in 2 interspecific hybrid walnut (Juglans nigra n degrees 23 x J r4egia) clones. Sucrose increased the rooting percentage (fig 1), the number of adventitious roots (fig 2A) and the dry- mat4ter content (table I) per rooted shoot. These effects were due to the energy properties of sucrose rather than to its osmo4tic function. High sucrose concentrations in the root- development medium (> 20 g.l(-1)) resulted in a high soluble carboh4ydrate content in the plantlets (fig 3), mainly located in roots and callus. The 2-clones showed different capacities in r4ooting and growth. Survival of microcuttings during acclimatization was not directly influenced by the sucrose concentrati4on (fig 5) but was correlated with the number of adventitious roots (fig 6A) as well as with the number of leaves (fig 6B) present at the time of transfer to the growth chamber for each individual plant.364 Ndel Nskip Nsave read Nget 441338930^^^^^4810846690aea13f950536 <3.0.1.32.19990125110302.008018f0@pop.service.ohio-state.edu>-25-Jan-1999-11:00:26--0500-(EST41008^4^Ioslovich,I^Seginer,I^Gutman,PO^Borshchevsky,M^1995^1^Suboptimal co2 enrichment of greenhouses^195^60^2^117-136^^^^^Feb^^^^^48120-(EST 917267579 Ndel Nskip Nsave read Nget 943423951 5dcf75d26ed27284f9aaef011dd8f693 <3.0.1.32.19990125124A^4811^Greenhouse CO2 enrichment in warm climates is restricted by the need to ventilate, leading some growers to intermit4tent enrichment, where enrichment and ventilation alternate several times an hour. This strategy relies on the heat and CO42 capacity of the system, characterized by a heating time constant of the order of 10 min, during which period ventilation4 may be suspended. It is shown that, for slowly changing weather, the optimal CO2 enrichment is basically not intermittent4 (bang-bang control), but rather quasi steady state (smoothly varying singular control). As the disturbance (weather) freq4uency increases, the quasi steady-state (QSS) solution becomes less and less optimal. Nevertheless, due to the difficultie4s involved in implementing a truly optimal control (the need for accurate weather forecast and high control fluxes), the s4ub-optimal QSS control may be a better choice. We chose to try a controller which aims to follow the QSS temperature and C4O2 setpoints at all disturbance frequencies. The performance of this controller for high disturbance frequencies is a few 4per cent lower than the truly optimal solution, but over the whole season this effect may not be significant. On the other4 hand, the controller is likely to be more robust. Implementation of the QSS solution requires simulaneous ventilation and enrichment, properly balanced.0500-(EST 917627988 Ndel Nskip Nsave read Nget 645060052 e4077263575a9cb4c3d4c0ebda0f23d141009^1^Comins,HN^1994^1^Equilibrium-analysis of integrated plant-soil models for prediction of the nutrient limited growth-response to co2 enrichment^270^171^4^369-385^^^^^21 Dec^^^^^4814Feb-1999-08:55:16--0500-(EST) 917859462 Ndel Nskip Nsave4A^4813^Although higher ambient CO, concentration is known to promote increased plant productivity under optimal growing co4nditions, it is not obvious if there will be a sustained growth response in natural and plantation ecosystems, where other4 resources, such as nutrients, may become limiting. Comins and McMurtrie (1993, Ecol. Applic. 3, 666-681) have constructed4 the G'DAY (Generic Decomposition A nd Field) integrated plant-soil model to investigate this CO2-nutrient interaction, an4d have described an analytic method for predicting the long-term response of their model to a step change in CO2 concentra4tion, using the analytic ''two timing'' approximation. This analysis gives insights into the interactions of the numerous 4parameters in a comprehensive plant-soil model, and may be generalizable to other such models. The current paper explores 4the accuracy of the approximation, and discusses various generalizations of the basic model to which the analytic model ca4n still be applied. The very long-term CO2 response of G'DAY was predicted by considering the dynamics of the passive soil4 organic matter pool in the ''two timing'' approximation. It was found that the two-timing approximation underestimates th4e 50-100 year CO2 response in systems that lose a very small proportion of nitrogen per recycling cycle. The other areas c4onsidered here are as follows. (i) More complex relationships between N:C ratios and carbon allocation fractions for plant4 organs, including variable heartwood N:C ratio (which has been identified as an important determinant of long-term CO2 re4sponse). Typical results are presented for a range of sensitivities of heartwood N:C ratio to changes in foliar N:C ratio.4 (ii) Variants of the CENTURY soil model were examined, having variable N:C ratios in the soil organic matter pools and/or4 carbon flux partition fractions influenced by N:C ratios. (iii) Results are presented for a preliminary analysis of variable nitrogen fixation.Nskip Nsave read Nget 1618695245 c4d1d8ca39488c3e27fd97efd8f4672d <199902051333.IAA27299@mail2.uts41010^4^Navarro,C^Teisson,C^Cote,F^Ganry,J^1994^1^Effects of light-intensity and co2 concentration on growth of banana plan4ts (musa aaa, cultivar petite-naine) in-vitro and subsequent growth following acclimatization^165^60^1-2^41-54^^^^^Dec^^^^4A^4815^The development of micropropagated banana plants during the in vitro growth phase prior to acclimatization was stud4ied both in tight vessels under two different photosynthetic photon flux densities (PPFD of 30 and 240 mu mol m(-2) s(-1))4 and in continuously flushed vessels under three atmospheric CO2 concentrations (0.034, 0.24 and 4.0%) at 240 mu mol m(-2)4 s(-1) PPFD. In tight vessels at low PPFD, the CO2 originating from dark respiration was partially fixed during the light 4period, indicating photosynthetic activity by the plants in vitro. At high PPFD, CO2 originating from dark respiration was4 rapidly fixed in the early hours of the light period and CO2 concentration became the limiting factor for photosynthetic 4activity. Plants in vitro grown under high PPFD accumulated 2.3 times the dry matter achieved by plants in low PPFD. Howev4er, this developmental advantage acquired in vitro was not maintained ex vitro at the end of the acclimatization phase (on4 a leaf area basis). In continuously flushed vessels, treatments with 0.24% and 4.0% CO2-enriched atmospheres enhanced dry4 matter accumulation in vitro by 1.6 and 2.3 times, respectively, as compared to a 0.034% CO2 treatment. Twenty days after4 transfer ex vitro, the development of plants (on a leaf area basis) from these CO2 treatments was no longer significantly4 different. The relative growth rate ex vitro was lower for plants cultured in a CO2-enriched atmosphere in vitro than for those cultured at 0.034% CO2.6M0D@mx3.osu.edu>-10-Feb-1999-20:27:34--0500-(EST 918712256 Ndel Nskip Nsave read Nget 1759^4816ff1b551fa6abde100ee1f92a3870 <0F6Y00BEXUTW0D@mx3.osu.edu>-10-Feb-1999-20:41:31--0500-(EST 918712256 Ndel Nskip Nsave41011^1^Ottosen,CO^1994^1^Net photosynthesis of schefflera-arboricola hayata clones at different co2 concentration and photosynthetic flux densities^200^44^4^248-250^^^^^Dec 2b3534d5d5a432f9bb0d57d846d4b873 -25-Feb-1999-12:52:04--0500-(E41013^3^Qi,JE^Marshall,JD^Mattson,KG^1994^1^High soil carbon-dioxide concentrations inhibit root respiration of douglas-fir^84^128^3^435-442^^^^^Nov^^^^^4821kip Nsave read Nget 948748738 efe0e5f56c3628191042b9d813bddc98 <01c801be6100$5cd1cc20$5A^4820^Total and basal respiration (R(t) and R(b), respectively) of intact and undisturbed roots of one-year-old Douglas f5ir seedlings, Pseudotsuga menziesii var. glauca [Beissn] France, were measured at experimentally varied soil carbon dioxid5e concentrations ([CO2]). Use of specially designed root boxes and a CO2 gas-flow compensating system designed around an i5nfrared gas analyzer (IRGA) allowed controlled delivery of CO2 to roots and simultaneous measurements of CO2 released by r5oots. Root respiration rate responded to each inlet [CO2], independent of whether the previous concentration had been high5er or lower, within two to three hours (paired t test = 0.041, P = 0.622, and n = 13). Total and basal respiration rates d5ecreased exponentially as soil [CO2] rose from 130 ppm, well below atmospheric [CO2], to 7015 ppm, a concentration not unc5ommon in field soils. Analyses of variance (ANOVA) showed that the effects of soil [CO2] on rates of total and basal root 5 respiration were statistically significant. Root respiration rates decreased by 4 to 5 nmol CO2 g(-1) dry weight of roots 5 s(-1) for every doubling of [CO2] according to the following equations: In(R(t)) (nmol CO2 g(-1) s(-1)) = 5.24-0.30*ln[CO25 ] with r = 0.78, P < 0.0001, and n = 70; and ln(R(b)) (nmol CO2 g(-1) s(-1)) = 6.29-0.52*ln[CO2] with r = 0.82, P < 0.00015 , and n = 35. The sensitivity of root respiration to [CO2] suggests that some previous laboratory measurements of root res5 piration at atmospheric [CO2], which is 3 to 10-fold lower than [CO2] in field soils, overestimated root respiration in th5e field. Further, the potential importance of soil [CO2] indicates that it should be accounted for in models of below-ground carbon budgets.et 1471927362 65f7db4c733fcca6f2ce1f9a1cb4d9c0 <3.0.3.32.19990226144406.009c58f0@pilot.msu.edu>-26-Feb51014^3^Seginer,I^Gary,C^Tchamitchian,M^1994^1^Optimal temperature regimes for a greenhouse crop with a carbohydrate pool - a modeling study^165^60^1-2^55-80^^^^^Dec^^^^^4823el Nskip Nsave read Nget 209902242 cf855615cde0c561b42a8e91f609a336 <5A^4822^A simple crop model with two state variables, namely structural biomass and carbohydrate pool, was used to explore 5the effect of alternative temperature regimes on greenhouse crop production, Assuming a repeated environmental cycle, cert5ain qualitative predictions could be made. (1) The smaller the plants and the higher the light integral and CO2 enrichment5, the higher are the temperatures which lead to maximum production. (2) Day temperatures higher than night temperatures us5ually lead to higher production. On winter days, however, an inverse temperature regime may result in energy saving withou5t loss of production. (3) Temperature variations may often be tolerated, provided that the mean temperature (temperature i5ntegral) is maintained at the level appropriate for maximum production. A limited amount of published experimental data was used to fit the model, leading to a satisfactory agreement.:49--0500-(EST 920268102 Ndel Nskip Nsave read Nget 1979227551015^4^Wheeler,TR^Morison,JIL^Ellis,RH^Hadley,P^1994^1^The effects of co2, temperature and their interaction on the growth and yield of carrot (daucus-carota L)^9^17^12^1275-1284^^^^^Dec^^^^^48257-Feb-1999-17:56:00--0500-(EST 920268102 Ndel Ns5A^4824^Stands of carrot (Daucus carota L.) were grown in the field within polyethylene-covered tunnels at a range of soil 5temperatures (from a mean of 7.5 degrees C to 10.9 degrees C) at either 348 (SE = 4.7) or 551 (SE = 7.7) mu mol mol(-1) CO52. The effect of increased atmospheric CO2 concentration on root yield was greater than that on total biomass, At the last5 harvest (137 d from sowing), total biomass was 16% (95% CI=6%, 27%) greater at 551 than at 348 mu mol mol(-1) CO2, and 375 % (95% CI=30%, 44%) greater as a result of a 1 degrees C rise In soil temperature, Enrichment with CO2, or a 1 degrees C r5!ise in soil temperature increased root yield by 31% (95% CI=19%, 45%) and 34% (95% CI=27%, 42%), respectively, at this har5"vest, No effect on total biomass or root yield of an interaction between temperature and atmospheric CO2 concentration at 5#137 DAS was detected, When compared at a given leaf number (seven leaves), CO2 enrichment increased total biomass by 25% a5$nd root yields by 80%, but no effect of differences in temperature on plant weights was found, Thus, increases in total bi5%omass and root yield observed in the warmer crops were a result of the effects of temperature on the timing of crop growth5& and development, Partitioning to the storage roots during early root expansion was greater at 551 than at 348 mu mol mol(5'-1) CO2. The root to total weight ratio was unaffected by differences in temperature at 551 mu mol mol(-1) CO2, but was re5(duced by cooler temperatures at 348 mu mol mol(-1) CO2. At a given thermal time from sowing, CO2 enrichment increased the 5)leaf area per plant, particularly during early root growth, primarily as a result of an increase in the rate of leaf area expansion, and not an increase in leaf number.-18:41:34--0500-(EST 920268102 Ndel Nskip Nsave read Nget 1666648336 ac9645+1016^3^Kozai,T^Watanabe,K^Jeong,BR^1995^1^Stem elongation and growth of solanum-tuberosum L in-vitro in response to photos5>ynthetic photon flux, photoperiod and difference in photoperiod and dark period temperatures^165^64^1-2^1-9^^^^^Oct^^^^^485-A^4826^Stem elongation and growth of potato plantlets under three DIF (difference in photoperiod and dark period temperatu5.res) levels, -9, 0 and +9, combined with two PPF (photosynthetic photon flux) levels, 70 (low) and 140 (high) mu mol m(-2)5/ s(-1) provided by white cool fluorescent lamps, under 16 h day(-1) (long) or 8 h day(-1) (short) photoperiods, were studi50ed. Four nodal cuttings were cultured for 21 days on 0.6 X 10(-4) m(3) MS (Murashige and Skoog, 1962, Physiol. Plant., 15:51 473-497) agar (8 kg m(-3)) medium with no added sugar in 3.7 X 10(-3) m(3) polycarbonate boxes. Each box had two 10 mm ho52les covered with microporous filter to facilitate air exchange (3.6 air exchanges per hour). The average daily temperature53 in the culture room was set the same at 23 degrees C for all treatments, and CO2 concentration and relative humidity were54 maintained at 400-500 mu mol mol(-1) and 50-70%, respectively. Stem length was significantly suppressed under 0 or -9 DIF55, high PPF and long photoperiod. Stem diameter, leaf area and number of leaves were significantly enhanced by long photope56riod and high PPF, but affected little by DIF level. Specific leaf area was little affected by photoperiod, but decreased 57under high PPF and under low DIF. Long photoperiod and high PPF led to an increase in the fresh and dry weights maintainin58g similar percentage dry matter and to enhanced root growth. Under the same amount of integrated PPF, fresh and dry weight59s of leaf, stem, root and whole plantlet were significantly higher under the long photoperiod and low PPF conditions than 5:under the short photoperiod and high PPF conditions. Because of suppressed root growth under short photoperiod, shoot to r5;oot dry weight ratio increased under short photoperiod, but was not affected by DIF. It is suggested that under photoautot5-1-Mar-1999-11:11:46--0500-(EST) 920286956 Ndel Nskip Nsave read Nget 1698205154 #POPEND 275@1017^3^Corey,KA^Bates,ME^Adams,SL^9UNKNOWN YEAR^1^Carbon-dioxide exchange of lettuce plants under hypobaric conditions^271^^^301-308^^^^^^^^^^48295BA^4828^Growth of plants in a Controlled Ecological Life Support System (CELSS) may involve the use of hypobaric pressures 5Cenabling lower mass requirements for atmospheres and possible enhancement of crop productivity, A controlled environment p5Dlant growth chamber with hypobaric capability designed and built at Ames Research Center was used to determine if reduced 5Epressures influence the rates of photosynthesis (Ps) and dark respiration (DR) of hydroponically grown lettuce plants, The5F chamber, referred to as a plant volatiles chamber (PVC), has a growing area of about 0.2 m(2), a total gas volume of abou5Gt 0.7 m(3), and a leak rate at 50 kPa of < 0.1%/day. When the pressure in the chamber was reduced from ambient to 51 kPa, 5Hthe rate of net Ps increased by 25% and the rate of DR decreased by 40%, The rate of Ps increased linearly with decreasing5I pressure, There was a greater effect of reduced pressure at 41 Pa CO2 than at 81 Pa CO2. This is consistent with reports 5Jshowing greater inhibition of photorespiration (Pr) in reduced O-2 at low CO2 concentrations. When the partial pressure of5K O-2 was held constant but the total pressure was varied between 51 and 101 kPa, the rate of CO2 uptake was nearly constan5Lt, suggesting that low pressure enhancement of Ps may be mainly attributable to lowered partial pressure of O-2 and the ac5Mcompanying reduction in Pr, The effects of lowered partial pressure of O-2 on Ps and DR could result in substantial increa5Nses in the rates of biomass production, enabling rapid throughput of crops or allowing flexibility in the use of mass and energy resources for a CELSS.RAM FILES\MICROSOFT OFFICE\TEMPLATES\LETTERS &5P1018^3^Jauhiainen,J^Vasander,H^Silvola,J^1994^1^Response of sphagnum-fuscum to n deposition and increased co2^272^18^^83-96^^^^^^^^^^4831ES\LETTERS & FAXES\CONTEMPORARY LETTER.DOT&@5RA^4830^The length increment and production of Sphagnum fuscum with enhanced nitrogen deposition (0, 10, 30 and 100 kg N ha5S(-1) yr(-1)) and CO2 concentration (350, 700, 1000 and 2000 ppm) were measured. The experiment was carried out in the glas5Tshouse, where S. fuscum was grown with the water table maintained at 10 cm below the moss surface for 120 d. For length gr5Uowth, 10 kg N ha(-1) yr(-1): and for biomass production, 30 kg N ha(-1) yr(-1) were found to be the optimal loads. A load 5Vof 100 kg N ha(-1) yr(-1) inhibited elongation and biomass production almost completely. An increased CO2 concentration re5Wduced length increment slightly, but it did not have a significant effect on biomass production. However, above ambient CO5X2 concentrations increased capitulum density and stem dry mass per unit length. In addition, increased CO2 concentration a5Yccelerated relative growth in Sphagnum carpets when these also received additional nitrogen. The study highlights the high5Z degree of spatial variability that occurs within Sphagnum fuscum. Differences in growth and biomass production between sa5[mples, not found in natural conditions, emerged during the experiment. On the basis of our results, the present nitrogen d5\eposition load in Southern Finland (ca 6-10 kg N ha(-1) yr(-1)) is quite suitable for the growth and production of S. fuscum. If N deposition increased substantially, differences in the vitality of the species might be expected.GRAM FI5f1019^1^Patterson,DT^1995^1^Effects of environmental-stress on weed/crop interactions^253^43^3^483-490^^^^^Jul-Sep^^^^^48335_A^4832^All environmental factors that influence plant growth potentially can affect the ability of weeds and crops to expl5`oit the environmental resources for which plants compete, Stressful levels of environmental factors such as temperature, l5aight, and water and nutrient availability influence weed/crop interactions directly and also may interfere with (or enhanc5be) weed control. Weed and crop species differing in photosynthetic pathway (C-3 VS C-4) are likely to respond differently 5cto many of these factors. Long-term changes in the atmospheric concentrations of CO2 and other radiatively-active ''greenh5douse gases'' may exert direct physiological and indirect climatic effects on weed/crop interactions and influence weed man5eagement strategies. This review focuses on the effects of temperature, light, soil nutrients, water stress, and CO2 concentration on weed/crop interactions with consideration of the potential impact of climate change.& FAXES\CONTEARY FAX.DOTa@PROGRAM FILES\MICROSOFT OFFICE\TEMPLA5h1020^2^Portielje,R^Lijklema,L^1995^1^Carbon-dioxide fluxes across the air-water-interface and its impact on carbon availability in aquatic systems^273^40^4^690-699^^^^^Jun^^^^^4835SS\DEFAULT.HTMe@PROGR5jA^4834^Diffusion of CO2 across the air-water interface was analyzed with a model that simulates both transport and reactio5kn of CO2 in a stagnant boundary layer. The atmospheric C influx was determined in relation to several environmental variab5lles: pH, total dissolved inorganic C, temperature, and the thickness of the stagnant boundary layer in relation to ambient5m windspeed. We used the model to calculate the atmospheric CO2 influx into six experimental ditches for a period of 6 or 85n months, starting in early spring. Three of the six ditches were dominated by aquatic macrophytes and three by benthic alg5oae. Each series received three levels of external N and P input. A comparison with net C assimilation during the same peri5pod, as estimated from continuous oxygen measurements, showed that, especially in the ditches dominated by submersed macrop5qhytes, a sizable fraction of the C requirements during this period could have been obtained from atmospheric CO2. In the d5ritches dominated by benthic algae, this fraction was considerably less, but nonetheless substantial, and was related to th5se level of N and P loading. Increased primary production due to enhanced external N and P loading increased the atmospheri5tc C input due to the resultant higher pH values. The trophic state with respect to N and P and the availability of C are therefore interrelated.E\TEMPLATES\LETTERS & FAXES\ELEGANT FAX.DOT5v1021^3^Saebo,A^Krekling,T^Appelgren,M^1995^1^Light quality affects photosynthesis and leaf anatomy of birch plantlets in-vitro^177^41^2^177-185^^^^^May^^^^^48370v@PROGRAM FILES\MICROSOFT OFFICE5xA^4836^Cultures in vitro of Betula pendula Roth were subjected to light of different spectral qualities. Photosynthetic ca5ypacity was highest when the plantlets were exposed to blue light (max recorded photosynthesis, 82 mu mol CO2 dm(-2) h(-1))5z and lowest when irradiated with light high in red and/or far-red wave lengths (max recorded photosynthesis, 40 mu mol CO25{ dm(-2) h(- 1)). Highest chlorophyll content (2.2 mg dm(-2) leaf area) was found in cultures irradiated with blue light, w5|hich also enhanced the leaf area. Morphometric analysis of light micrographs showed that the epidermal cell areas were lar5}gest in plantlets subjected to blue light and smallest in those subjected to red light. Morphometric analysis of electron 5~micrographs of palisade cells, showed that the functional chloroplast area was largest in chloroplasts of leaves subjected5 to blue light and smallest in those exposed to red light. We suggest that light quality affects photosynthesis both through effects on the composition of the photosynthetic apparatus and on translocation of carbohydrates from chloroplasts.51022^5^Adams,RM^Fleming,RA^Chang,CC^McCarl,BA^Rosenzweig,C^1995^1^A reassessment of the economic-effects of global climate-change on US agriculture^50^30^2^147-167^^^^^Jun^^^^^4839FILES\MICROSOFT OFFICE\TEMPLATE5A^4838^This study uses recent GCM forecasts, improved plant science and water supply data and refined economic modeling ca5pabilities to reassess the economic consequences of long-term climate change on U.S. agriculture. Changes in crop yields, 5crop water demand and irrigation water arising from climate change result in changes in economic welfare. Economic consequ5ences of the three GCM scenarios are mixed; GISS and GFDL-QFlux result in aggregate economic gains, UKMO implies losses. A5s in previous studies, the yield enhancing effects of atmospheric CO2 are an important determinant of potential economic c5onsequences. Inclusion of changes in world food production and associated export changes generally have a positive affect 5on U.S. agriculture. As with previous studies, the magnitude of economic effects estimated here are a small percentage of U. S. agricultural value.M FILES\MICROSOFT OFFICE\TEMPLATES\MEMOS\CONTEMP1023^2^Craig,SG^Holmen,KJ^1995^1^Uncertainties in future co2 projections^137^9^1^139-152^^^^^Mar^^^^^4841\TEMPLAT5A^4840^The perceived budget imbalance in the global carbon cycle has been suggested to result from, among other processes,5 CO2 fertilization of the terrestrial biosphere and/or enhanced regrowth of previously felled temperate forest. These two 5processes are incorporated into a box diffusion model of the ocean-atmosphere system coupled to a five-box terrestrial bio5sphere. The extent to which historical fossil fuel and land use change emission data can be reconciled with the observed a5tmospheric CO2 concentration record is examined. Furthermore, the sensitivity of future CO2 projections to the nature of t5he budget imbalance is investigated. It is found that the CO2 record can accommodate a carbon budget balanced by CO2 ferti5lization but that the balance with forest regrowth is more difficult. Future CO2 projections are found to be sensitive to how the carbon budget is balanced, even relative to uncertainties in future emissions.LETTER.DOT51024^2^Hostetler,SW^Giorgi,F^1995^1^Effects of a 2-times-co2 climate on 2 large lake systems - pyramid lake, nevada, and yellowstone lake, wyoming^274^10^1-4^43-54^^^^^Apr^^^^^4843PROGRAM FILES\MICROSOFT OFFICE\5A^4842^The possible effects of trace-gas induced climatic changes on Pyramid and Yellowstone Lakes are assessed using a mo5del of lake temperature. The model is driven by 3 1/2 years of hourly meteorological data obtained directly from the outpu5t of doubled-CO2 experiments (2 x CO2) conducted with a regional climate model nested in a general circulation model. The 5regional atmospheric model is the climate version of the National Center for Atmospheric Research/Pennsylvania State Unive5rsity mesoscale model, MM4. Average annual surface temperature of Pyramid Lake for the 2 X CO2 climate is 15.5 +/- 5.4 deg5rees C (+/- 1 sigma), 2.8 degrees C higher than the control. Annual overturn of the lake ceases as a result of these highe5r temperatures for the 2 x CO2 climate. Evaporation increases from 1400 mm yr(-1) in the control to 1595 mm yr(-1) in the 52 X CO2 simulation, but net water supplied to the Pyramid Lake basin increases from -6 mm yr(-1) in the control to +27 mm 5yr(-1) in the 2 x CO2 simulation due to increased precipitation. For the open water periods, the average annual surface te5mperature of Yellowstone Lake is 13.2 +/- 5.1 degrees C for the 2 x CO2 climate, a temperature 1.6 degrees C higher than t5he control. The annual duration of ice cover on the lake is 152 days in the 2 X CO2 simulation, a reduction of 44 days rel5ative to the control, Warming of the lake for the 2 x CO2 climate is mostly confined to the near-surface. Simulated spring5 overturn for the 2 X CO2 climate occurs earlier in the year and fall overturn later than in the control. Evaporation incr5eases from 544 mm yr(-1) to 600 mm yr(-1) in the 2 X CO2 simulation, but net water supplied to the Yellowstone Lake basin 5increases from +373 mm yr(-1) in the control to +619 mm yr(-1) due to increased precipitation. The effects of these climat5ic changes suggest possible deterioration of water quality and productivity in Pyramid Lake and possible enhancement of productivity in Yellowstone Lake.PROGRAM FILES\MICROSOFT OFFICE\TEMPLATES\LE51025^8^Kohlmaier,GH^Hager,C^Wurth,G^Ludeke,MKB^Ramage,P^Badeck,FW^Kindermann,J^Lang,T^1995^1^Effects of the age class dist5ributions of the temperate and boreal forests on the global co2 source-sink function^257^47^1-2^212-231^^^^^Feb-Apr^^^^^485A^4844^The role of the temperate and boreal forests as a global CO2 source or sink is examined, both for the present time 5and for the next hundred years. The results of the Forest Resource Assessment for 1990 of the Economic Comission for Europ5e and the Food and Agricultural Organisation of the United Nations (1992) serve as the main database in this study. Out of5 the estimated total area of approximately 20 . 10(6) km(2) of forests and wooded lands in tile temperate and boreal zone 5only approximately fifty percent is documented within the category of exploitable Forests, which are examined in detail he5re. In this study, a general formalism of the time evolution of an ensemble of forests within an ecological province is de5veloped using the formalism of the Leslie matrix. This matrix can be formulated if the age class dependent mortalities whi5ch arise from the disturbances are known. A distinction is made between the natural disturbances by fire, wind throw and i5nsect infestations and disturbances introduced through harvesting of timber. Through the use of Richards growth function e5ach age class of a given biome is related to the corresponding biomass and annual increment. The data reported on the mean5 net annual increment and on the mean biomass serve to calibrate the model. The difference of the reported nut annual incr5ement and annual fellings of approximately 550 . 10(6) m(3) roundwood correspond to a sink of 210-330 Mt of carbon per yea5r excluding any changes in the soil balance. it could be shown that the present distribution of forest age classes for the5 United States, Canada, Europe, or the former Soviet Union does not correspond to a quasi-stationary state, in which bioma5ss is accumulated only due to a stimulated growth under enhanced atmospheric CO2 levels. The present CO, sink function wil5l not persist in the next century, if harvesting rates increase with 0.5% annually or even less. The future state will als5o be influenced by the effect of the greenhouse climate, the impact of which may range from a stimulating effect on growth5. which is calculated by the Frankfurt biosphere model, up to a transitional negative effect through a shift in vegetation zones.TTERS & FAXES\CONTEMPORARY LETTER.DOT~6PROGRAM 45\MICROSOFT OFFICE\TEMPLATES\LETTERS & FAXES\ELEGANT LETTER.51026^8^Ludeke,MKB^Donges,S^Otto,RD^Kindermann,J^Badeck,FW^Ramge,P^Jakel,U^Kohlmaier,GH^1995^1^Responses in npp and carbon 5stores of the northern biomes to a co2-induced climatic-change, as evaluated by the frankfurt biosphere model (fbm)^257^47^1-2^191-205^^^^^Feb-Apr^^^^^4847DMAIL\FAVORITES\RAIN.LNK!»PROGRAM 5A^4846^To assess the role of the boreal and temperate forests and the tundra ecosystems in a future CO2-induced climate ch5ange, the Frankfurt biosphere model(FBM) was applied to the 3xCO(2) climate as calculated by the GCM of the MPI fur Meteor5ologie in Hamburg. The FBM predicts on a 1 degrees x1 degrees spatial grid the seasonal and perannual course of leaf bioma5ss and feeder roots, woody biomass, soil carbon and soil water in response to the seasonal course of light, precipitation 5and temperature. The phenology is controlled by the flux balance of carbon gains and losses, thus being dependent on the d5riving climate and the state of vegetation. Two equilibrium runs based on the 3xCO(2) climate were performed: (1) Consider5ing the pure climate effect (with no direct CO2 fertilization) we obtained a 22% decrease of the net primary production (N5PP) due to enhanced autotrophic respiration and increased water limitation. Together with the effect on the soils this res5ults in a 170 Gt carbon source. (2) Considering a CO2-induced enhancement of the maximum photosynthesis the pure climate e5ffect is more than compensated and we predict a NPP increase of 9% and a total carbon sink of 50 Ct C. This effect may eve5n be an underestimate if one takes into consideration a shift in the optimum temperature for photosynthesis under enhanced levels of atmospheric CO2 as proposed by Long and Drake.OFT OFFICE\TEMPLATES\LETTERS & F51027^2^Moriguchi,T^Romani,RJ^1995^1^Mitochondrial self-restoration as an index to the capacity of avocado fruit to sustain atmospheric stress at 2 climacteric states^154^120^4^643-649^^^^^Jul^^^^^4849THh׻PROGRAM 5A^4848^A strong association is implicit between mitochondrial function and the energy demands of cells responding to stres5s, Yet, the dynamics of this organelle-cellular dependency have been difficult to resolve. This study examines a new diagn5ostic parameter namely, mitochondrial maintenance and self- restoration as exhibited by the course of respiratory function5s (States 3 and 4 respiratory rates, respiratory control) of mitochondria extracted during and after exposure of intact 'H5ass' avocado (Persea americana) fruit to different stress atmospheres: anoxia (100% N-2) or high (25% and 75%) CO2 for var5ying durations. Comparisons are made with direct exposure of the mitochondria themselves to similar atmospheres. In genera5l, exposure of the fruit to CO2 rich atmospheres enhanced the capacity of their mitochondria to restore energy-linked func5tions whereas anoxia caused irreparable damage. The physiological (climacteric) state of the fruit also affected the stres5s capacity of the mitochondria contained therein, anaerobiosis being more harmful to mitochondria in riper fruit. In contr5ast to their effects in vivo, in vitro anoxia appeared to sustain mitochondrial energy-linked functions, whereas high CO2 5was clearly harmful, These and other observations are discussed in the context of mitochondrial self-restoration or homeos5tasis and its relevance to postharvest stress-atmosphere storage for purposes such as pathogen suppression or insect control.T OFFICE\TEMPLATES\ACCESS\GRAY.HTM 9ʼrPROGRAM FILES51028^1^Teese,P^1995^1^Intraspecific variation for co2 compensation point and differential growth among variants in a C-3-C-4 intermediate plant^2^102^3^371-376^^^^^Jun^^^^^4851\ACCESS\GRAYST.HTM 9ʼnPRO5A^4850^CO2 compensation point (Gamma), the concentration of CO2 at which photosynthesis and respiration are at equilibrium5, is a commonly used diagnostic for the C-4 photosynthetic pathway, since it reflects the reduced photorespiration that is5 a property of C-4 photosynthesis. Geographic variation for Gamma was examined within Flaveria linearis, a C-3-C-4 interme5diate species. Collections from four widely separated Floridian populations were propagated in a greenhouse and measured f5or Gamma. Little differentiation among populations was found, but significant within-population variation was present. Tem5perature is a hypothesized selective agent for the C-4 photosynthetic pathway. To test this hypothesis, plants exhibiting 5a range of Gamma were cloned and placed in growth chambers at 25 degrees C and 40 degrees C. After 7 weeks, Gamma valves w5ere remeasured and plants were harvested and weighed. There was a poor correlation between initial and final measures of G5amma for a given genotype (r = 0.38, P > 0.1). Broad sense heritability for Gamma was computed to be 0.10. At 25 degrees C5, there was no relationship between final size and Gamma. At 40 degrees C, more C,like plants, as indicated by their low G5amma, had grown larger. Differences in relative growth rate were attributable more to differences in net assimilation rate5 than in leaf area ratio. Taken together, these results demonstrate that although significant plasticity exists in the amo5unt of photorespiration in this C-3-C-4 species, high temperature appears to be an effective selective agent for the reduction of photorespiration and the enhancement of C-4-like traits.AM FILES\MICROSOFT OFFICE\OF51029^2^Zadrazil,F^Puniya,AK^1994^1^Influence of carbon-dioxide on lignin degradation and digestibility of lignocellulosics treated with pleurotus-sajor- caju^275^33^3^237-244^^^^^^^^^^4853\URGENT.LNKPROGRAM5A^4852^This study investigates the effect of different CO2 concentrations on lignin degradation and in vitro digestibility5 of wheat straw used as growth substrate for Pleurotus sajor- caju. The degradation of wheat straw lignin by P. sajor-caju5 increased under the influence of CO2 (0-20%) in the atmosphere and then started declining at higher levels. The maximum l5oss of lignin (39.7%) was found in cultures grown with passive air exchange through cotton plugs while digestibility was h5igher in cultures actively aerated with 0-30% CO2. Aside from gases, the period of incubation, i.e. 40 days rather than 205 days, seems to be the most important variable for improving the digestibility of the product. Generally, the process effi5ciency for change in digestibility per gram loss of organic matter enhanced from 0 to 30% CO2 at a fixed level of O2 (20%) in the gaseous phase.ATION DESIGNS\HIGH VOLTAGE.POTPROGRAM FI51030^1^Borodin,VB^1995^1^Photosynthetic o-2 exchange in chlorella cells adapted to low co2 concentration under blue or red-light^236^42^1^31-36^^^^^Jan-Feb^^^^^4855OSOFT OFFICE\TEMPLATES\PRESENTATION DES5A^4854^The effect of light quality on the adaptation to low atmospheric CO2 concentration was studied on the cells of unic5ellular green al,oa Chlorella pyrenoidosa 82T grown under 2% CO2 concentration and white light. The adaptation of Chlorell5a cells was more successful under blue than under red light. Thus, the air-adapted cells under blue light showed a higher 5affinity for CO2, a higher quantum efficiency of apparent photosynthesis at CO2 limitation, and acceleration of O-2 evolut5ion at light saturation, as compared to the red- light-adapted cells. In air-adapted cells, the photosynthetic rates at lo5w CO2 concentration were enhanced with increased intensities of both blue and red light, but the differences between the t5wo treatments were retained. It was inferred that Chlorella cell adaptation depended on both light intensity and its spect5ral composition. The light intensity exerts its action via photosynthetic apparatus while spectral composition of light ex5erts its effect via a system of photoreception, which absorbs blue light. This additional blue light absorption is considered favorable for Chlorella cell adaptation to low CO2 concentration.PROGRAM FILES\MICROSOF31031^2^Kajfezbogataj,L^Hocevar,A^1994^1^Assessment of climate-change effects on productivity of beech stand in slovenia us6A^4858^Simulated impacts of global and regional climate change, induced by an enhanced greenhouse effect and by Amazonian 6deforestation, on the phenology and yield of two grain corn cultivars in Venezuela (CENIAP PB-8 and OBREGON) are reported.6 Three sires were selected: Turen, Barinas and Yaritagua, representing two important agricultural regions in the country. 6The CERES-Maize model, a mechanistic process-based model, in the Decision Support System for Agrotechnology Transfer (DSSA6T) was used for the crop simulations. These simulations assume non-limiting nutrients, no pest damage and no damage from e6xcess water; therefore, the results indicate only the difference between baseline and perturbed climatic conditions, when 6other conditions remain the same. Four greenhouse-induced global climate change scenarios, covering different sensitivity 6 levels, and one deforestation-induced regional climate change scenario were used. The greenhouse scenarios assume increase6 d air temperature, increased rainfall and decreased incoming solar radiation, as derived from atmospheric GCMs for doubled6 CO2 conditions. The deforestation scenarios assume increased air temperature, increased incoming solar radiation and decr6 eased rainfall, as predicted by coupled atmosphere- biosphere models for extensive deforestation of a portion of the Amazo6 n basin. Two baseline climate years for each site were selected, one year with average precipitation and another with lowe6r than average rainfall. Scenarios associated with the greenhouse effect cause a decrease in yield of both cultivars at al6l three sites, while the deforestation scenarios produce small changes. Sensitivity tests revealed the reasons for these r6esponses. Increasing temperatures, especially daily maximum temperatures, reduce yield by reducing the duration of the phe6nological phases of both cultivars, as expected from CERES- Maize. The reduction of the duration of the kernel filling pha6se has the largest effect on yield. Increases of precipitation associated with greenhouse warming have no effects on yield6, because these sites already have adequate precipitation; however, the crop model used here does not simulate potential n6egative effects of excess water, which could have important consequences in terms of soil erosion and nutrient leaching. I6ncreases in solar radiation increased yields, according to the non-saturating light response of the photosynthesis rate: o6f a C-4 plant like corn, compensating for reduced yields from increased temperatures in deforestation scenarios. In the gr6eenhouse scenarios, reduced insolation (due to increased cloud cover) and increased temperatures combine to reduce yields; a combination of temperature increase with a reduction in solar radiation produces fewer and lighter kernels.CROSO6$1033^1^Schimel,DS^1995^1^Terrestrial biogeochemical cycles - global estimates with remote-sensing^102^51^1^49-56^^^^^Jan^^6A^4860^The carbon rand nitrogen cycles are crucial for understanding the changing Earth system, influencing atmospheric co6ncentrations of greenhouse gases, primary productivity of the biosphere, and biogenic emissions of reactive trace species.6 The carbon budget of the terrestrial biosphere has attracted special attention because of its role in atmospheric changes6 in carbon dioxide. The terrestrial biosphere influences atmospheric CO2 through three main modes: First, large, nearly ba6lanced fluxes of CO2 in photosynthesis and respiration exhibit a degree of interannual variability which can influence atm6ospheric CO2, at feast on annual to decadal time scales. Second, land use changes release CO2 to the atmosphere. Third, po6 orly understood processes are likely resulting in enhanced uptake of CO2 in certain ecosystems, acting as a sink in the gl6!obal carbon cycle. This sink may result from forest demographics, atmospheric N deposition, or direct CO2 fertilizatian, o6"r some synergistic combination of those processes. Global estimates of terrestrial carbon cycle components requires the us6#e of remote observations; however, the appropriate remote sensing strategies are quite different for the various components.TION DESIGNS\FIREBALL.POTPROGRAM FILES\MICROSOFT O^^^4861EMPLATES\PRESENTATION DESIGNS\PORTRAIT NOTEBOOK.POT6&1034^4^Takle,ES^Bramer,DJ^Heilman,WE^Thompson,MR^1994^1^A synoptic climatology for forest-fires in the ne US and future implications from gcm simulations^276^4^4^217-224^^^^^Dec^^^^^4863 FILES\MICROSOFT OFFICE\TEMP6(A^4862^We studied surface-pressure patterns corresponding to reduced precipitation, high evaporation potential, and enhanc6)ed forest- fire danger for West Virginia, which experienced extensive forest-fire damage in November 1987. From five years6* of daily weather maps we identified eight weather patterns that describe distinctive flow situations throughout the year.6+ Map patterns labeled extended-high, back-of-high, and pre-high were the most frequently occurring patterns that accompany6, forest fires in West Virginia and the nearby four-stare region. Of these, back- of-high accounted for a disproportionatel6-y large amount of fire-related damage. Examination of evaporation acid precipitation data showed that these three patterns6. and high- to-the-south patterns ail led to drying conditions and all other patterns led to moistening conditions. Surface6/-pressure fields generated by the Canadian Climate Centre global circulation model for simulations of the present (1xCO(2)60) climate and 2xCO(2) climate were studied to determine whether forest-fire potential would change under increased atmosph61eric CO2. The analysis showed a tendency for increased frequency of drying in the NE US, but the results were not statistically significant.ES\MICROSOFT OFFICE\TEMPLATES\PRESENTATION DESIGNS\631035^5^Hurry,V^Tobiaeson,M^Kromer,S^Gardestrom,P^Oquist,G^1995^1^Mitochondria contribute to increased photosynthetic capacity of leaves of winter rye (secale-cereale L) following cold- hardening^9^18^1^69-76^^^^^Jan^^^^^4865S\MICROSO65A^4864^Cold-hardening of winter rye (Secale cereale L. cv. Musketeer) increased dark respiration from -2.2 to -3.9 mu mol 66O-2 m(- 2)s(-1) and doubled light- and CO2-saturated photosynthesis at 20 degrees C from 18.1 to 37.0 mu mol O-2 m(-2) s(-671). We added oligomycin at a concentration that specifically inhibits oxidative phosphorylation to see whether the observe68d increase in dark respiration reflected an increase in respiration in the light, and whether this contributed to the enha69nced photosynthesis of cold-hardened leaves, Oligomycin inhibited light- and CO2-saturated rates of photosynthesis in non-6: hardened and cold-hardened leaves by 14 and 25%, respectively, and decreased photochemical quenching of chlorophyll a flu6;orescence to a greater degree in cold-hardened than in non- hardened leaves, These data indicate an increase both in the r6hate, This limitation was particularly severe in cold-hardened leaves, and the resulting low 3-phosphoglycerate pools led 6?to a feed-forward inhibition of sucrose-phosphate synthase activity, Thus, it does not appear that oxidative phosphorylati6@on supports the increase in photosynthetic O-2 evolution following cold-hardening by increasing the availability of cytoso6Alic ATP, The data instead support the hypothesis that the mitochondria function in the light by using the reducing equivalents generated by nan-cyclic photosynthetic electron transport.PROGRAM FILES\MICROSOFT OF6C1036^2^Pons,TL^Pearcy,RW^1994^1^Nitrogen reallocation and photosynthetic acclimation in response to partial shading in soybean plants^37^92^4^636-644^^^^^Dec^^^^^4867PLATES\PRESENTATION DESIGNS\CONTEMPORA6EA^4866^The first trifoliate of soybean was shaded when fully expanded, while the plant remained in high light; a situation6F representative for plants growing in a closed crop. Leaf mass and respiration rate per unit area declined sharply in the 6Gfirst few days upon shading and remained rather constant during the further 12 days of the shading treatment. Leaf nitroge6Hn per unit area decreased gradually until the leaves were shed. Leaf senescence was enhanced by the shading treatment in c6Iontrast to control plants growing in low light. Shaded leaves on plants grown at low nutrient availability senesced earlie6Jr than shaded leaves on plants grown at high nutrient availability. The light saturated rate of photosynthesis decreased a6Klso gradually during the shading treatment, but somewhat faster than leaf N, whereas chlorophyll contents declined somewha6Lt slower than leaf N. Partitioning of N in the leaf over main photosynthetic functions was estimated from parameters deriv6Med from the response of photosynthesis to CO2. It appeared that the N exported from the leaf was more at the expense of co6Nmpounds that make up photosynthetic capacity than of those involved in photon absorption, resulting in a change in partiti6Ooning of N within the photosynthetic apparatus. Photosynthetic nitrogen use efficiency increased during the shading treatm6Pent, which was for the largest part due to the decrease in leaf N content, to some extent to the decrease in respiration rate and only for a small part to change in partitioning of N within the photosynthetic apparatus.PLATES\PRESE6R1037^5^Vangardingen,PR^Grace,J^Harkness,DD^Miglietta,F^Raschi,A^1995^1^Carbon-dioxide emissions at an italian mineral spring - measurements of average co2 concentration and air-temperature^107^73^1-2^17-27^^^^^Feb^^^^^4869 P6TA^4868^Emissions of carbon dioxide from vents at the Bossoleto mineral spring in Central Italy have been calculated to exc6Ueed 12 t day(-1), This emission leads to enhanced atmospheric concentrations of CO2 over an area of more than 3000 m(2). T6Vhe vent gas is over 99% pure CO2, with a characteristic isotopic signature that is totally depleted in C-14. At night, con6Wcentrations at the bottom of the bowl-like depression can increase to levels approaching 75%. In the morning, this high co6Xncentration of CO2 is associated with a rapid temperature increase of over 10 degrees C before the CO2 disperses. This sit6Ye is being used in a number of studies of the response of plant communities to long-term enhanced CO2 concentrations. The 6Zproblem of defining CO2 concentrations in these studies was approached by comparing estimates determined by gas analysis m6[easurements and isotopic analysis of leaf material, The isotopic method used C-14 as a tracer, integrating effective conce6\ntration over the life of a leaf by calculating from the ratio of C-14 measurements of plant material growing near the spr6]ing and at a control site. The estimates obtained using isotopic analysis of leaf material were similar to gas analysis me6^asurements obtained during the day. This suggests that plants at this site are responding to the concentrations during the day, rather than the much higher night-time concentrations, making the system useful for biological research.ICE\T6`1038^1^Beerling,DJ^1994^1^Predicting leaf gas-exchange and delta-C-13 responses to the past 30000 years of global environmental-change^84^128^3^425-433^^^^^Nov^^^^^4871S\PRESENTATION DESIGNS\FANS.POT16bA^4870^Theoretical developments in our understanding of leaf gas exchange processes and carbon isotope composition (delta(6c13)C) mean that it should now be possible to model their responses to global environmental change. Such a model would be o6df use for process-based interpretations of historical changes in leaf delta(13)C and for understanding the global stable c6earbon isotope balance. This paper describes the development and validation of a model towards this aim. The resulting mode6fl is used to simulate changes in leaf photosynthesis, stomatal conductance and delta(13)C of limber pine (Pinus flexilis) 6gin response to the past 30000 y of global environmental change. The predictions of needle delta(13)C are in line with repo6hrted measurements of delta(13)C from fossilized Pinus flexilis needles preserved in packrat middens in western USA. Leaf g6ias exchange predictions show that the increased water use efficiency (WUE) of these trees growing in present-day environme6jnts, relative to the past, was brought about through an increase in photosynthetic rates and a decrease in stomatal conduc6ktance. This contrasts with the explanation of the recent (past 200 y) increase in the WUE of temperate and Mediterranean e6lcosystems inferred from delta(13)C measurements which are predicted by the model to have arisen largely by a decrease in s6mtomatal conductance in response to increases in the concentration of atmospheric CO2 since the pre-industrial era. The mod6nel as described offers the potential to contribute to our understanding of vegetation effects on the global carbon isotope6o balance during the glacial periods, and therefore to provide a further constraint on the carbon cycle models used to explain the low concentrations of atmospheric CO2 at these times.ARY.POT1 PROGRAM FILES6q1039^3^Beerling,DJ^Huntley,B^Bailey,JP^1995^1^Climate and the distribution of fallopia-japonica - use of an introduced species to test the predictive capacity of response surfaces^42^6^2^269-282^^^^^Apr^^^^^4873PRESENTATION DES6sA^4872^The relationship between present climate and the distribution in Europe of the aggressively invasive exotic Fallopi6ta japonica is described by fitting a response surface based on three bioclimatic variables: mean temperature of the coldes6ut month, the annual temperature sum > 5 degrees C, and the ratio of actual to potential evapotranspiration. The close fit 6vbetween the observed and simulated distributions suggests that the species' European distribution is climatically determin6wed. The response surface also provides a simulation of the extent of the area of native distribution of F. japonica in Sou6xtheast Asia that is generally accurate, confirming the robustness of the static correlative model upon which it is based. 6ySimulations of the potential distribution of F. japonica under two alternative 2 x CO2 climate change scenarios indicate t6zhe likelihood of considerable spread into higher latitudes and possible eventual exclusion of the species from central Eur6{ope. However, despite the robustness of the response surface with present-day climate, the reliability of these simulation6|s as forecasts is likely to be limited because no account is taken of the direct effects of CO2 and their interaction with6} the species' physiological responses to climate. Similarly, no account is taken of the potential impact of interactions w6~ith 'new' species as ecosystems change in composition in response to climate change. Nevertheless, the simulations indicat6e both the possible magnitude of the impacts of forecast climate changes and the regions that may be susceptible to invasion by F. japonica.L MEMO.DOT,Microsoft CorporationPROGRAM FIL1040^1^Dixon,RK^1995^1^Agroforestry systems - sources or sinks of greenhouse gases^277^31^2^99-116^^^^^^^^^^4875 AND6A^4874^The prominent role of forestry and agroforestry systems in the flux and long-term storage of carbon (C) in the terr6estrial biosphere has increased global interest in these land-use options to stabilize greenhouse gas (GHG) emissions. Pre6liminary assessments suggest that some agroforestry systems (e.g., agrosilvicultural) can be CO2 sinks and temporarily sto6re C, while other systems (e.g., ruminant-based silvopastoral systems) are probably sources of GHG (e.g., CH4). Agroforest6ry;systems can be significant sources of GHG emissions, especially at low latitudes. Practices such as tillage, burning, m6anuring, chemical fertilization, and frequent disturbance can lead to emission of CO2, CH4, and N2O from soils and vegetat6ion to the atmosphere. Establishment and management of agroforestry systems incompatible with prevailing edaphic and clima6tic conditions can accelerate soil GHG emissions. Non-sustainable agroforestry systems are quickly degraded, and woody and6 herbaceous crops can become significant GHG sources. Silvopastoral systems can result in soil compaction and erosion with6 significant loss of labile C and N compounds to the atmosphere. Ruminant-based silvopastoral systems and rice paddy agris6ilvicultural systems are well documented sources of CH4 which significantly contribute to the global CH4 budget. Early ass6essments of national and global terrestrial CO2 sinks reveal two primary beneficial attributes of agroforestry systems: 1)6 direct near-term C storage (decades to centuries) in trees and soils, and, 2) potential to offset immediate GHG emissions6 associated with deforestation and subsequent shifting agriculture. Within the tropical latitudes, it is estimated that on6e ha of sustainable agroforestry can provide goods and services which potentially offset 5-20 ha of deforestation. At a gl6obal scale, agroforestry systems could potentially be established on 585-1275 x 10(6) ha of technically suitable land, and these systems could store 12-228 (median 95) Mg C ha(-1) under current climate and edaphic conditions.CONTEMPOR61041^2^Ehleringer,JR^Cerling,TE^1995^1^Atmospheric co2 and the ratio of intercellular to ambient co2 concentrations in plants^13^15^2^105-111^^^^^Feb^^^^^4877PRESENTATION DESIGNS\NOTEBOOK.POT*Micr6A^4876^Much attention is focused today on predicting how plants will respond to anticipated changes in atmospheric composi6tion and climate, and in particular to increases in CO2 concentration. Here we review the long-term global fluctuations in6 atmospheric CO2 concentration as a framework for understanding how current trends in atmospheric CO2 concentration fit in6to a selective, evolutionary context. We then focus on an integrated approach for understanding how gas exchange metabolis6m responds to current environmental conditions, how it previously responded to glacial-interglacial conditions, and how it may respond to future changes in atmospheric CO2 concentration.SOFT OFFICE\TEMPLATES\PRESEN61042^1^Kennedy,AD^1995^1^Simulated climate-change - are passive greenhouses a valid microcosm for testing the biological effects of environmental perturbations^127^1^1^29-42^^^^^Feb^^^^^4879NTATION DESIGNS\MEADOW.POT6A^4878^This paper considers the use of passive greenhouse apparatus in field experiments investigating the biological cons6equences of climate change. The litreature contains many accounts of such experiments claiming relevance of greenhouse tre6atment effects to global change scenarios. However, inadequacies in microclimate monitoring, together with incomplete unde6rstanding of greenhouse modes of action, cast doubt upon such claims. Here, treatment effects upon temperature (magnitude,6 range, variation, rates of change), moisture (humidity, precipitation, soil water content), light (intensity, spectral di6stribution), gas composition, snow cover, and wind speed are reviewed in the context of Intergovernmental Panel on Climate6 Change (IPCC) predictions. It is revealed that greenhouses modify each of these potentially limiting factors in a complex6 and interactive manner, but that the relationship between this modification and forecast conditions of climate change is 6poor. Interpretation of biological responses, and their extrapolation to predictive models, is thus unreliable. In order t6hat future greenhouse experiments may overcome criticisms of artefact and lack of rigour, two amendments to methodology ar6e proposed: (1) objective-orientated design of greenhouse apparatus (2) multiple controls addressing individual environmental factors. The importance of a priori testing of microclimate treatment effects is stressed.AM FILES\MICR61043^2^Lechowicz,MJ^Koike,T^1995^1^Phenology and seasonality of woody-plants - an unappreciated element in global change research^188^73^2^147-148^^^^^Feb0 PROGRAM FILES\MICROSOFT OFFICE\TEMPLATE61044^2^Mackay,RM^Khalil,MAK^1995^1^Doubled co2 experiments with the global-change-research-center 2-dimensional statistical dynamical climate model^278^100^D10^21127-21135^^^^^20 Oct^^^^^4882PLATES\OTHER DOCUMENTS\MOR6A^4881^The zonally averaged response of the Global Change Research Center two-dimensional (2-D) statistical dynamical clim6ate model (GCRC 2-D SDCM) to a doubling of atmospheric carbon dioxide (350 parts per million by volume (ppmv) to 700 ppmv)6 is reported. The model solves the two-dimensional primitive equations in finite difference form (mass continuity, Newton'6s second law, and the first law of thermodynamics) for the prognostic variables: zonal mean density, zonal mean zonal velo6city, zonal mean meridional velocity, and zonal mean temperature on a grid that has 18 nodes in latitude and 9 vertical no6des (plus the surface). The equation of state, p = rho RT, and an assumed hydrostatic atmosphere, Delta p = -rho g Delta z6, are used to diagnostically calculate the zonal mean pressure and vertical velocity for each grid node, and the moisture 6balance equation is used to estimate the precipitation rate. The model includes seasonal variations in solar intensity, in6cluding the effects of eccentricity, and has observed land and ocean fractions set for each zone. Seasonally varying value6s of cloud amounts, relative humidity profiles, ozone, and sea ice are all prescribed in the model. Equator to pole ocean 6heat transport is simulated in the model by turbulent diffusion. The change in global mean annual surface air temperature 6due to a doubling of atmospheric CO2 in the 2-D model is 1.61 K, which is close to that simulated by the one- dimensional 6(1-D) radiative convective model (RCM) which is at the heart of the 2-D model radiation code (1.67 K for the moist adiabat6ic lapse rate assumption in 1-D RCM). We find that the change in temperature structure of the model atmosphere has many of6 the characteristics common to General Circulation Models, including amplified warming at the poles and the upper tropical6 troposphere, and stratospheric cooling. Because of the potential importance of atmospheric circulation feedbacks on clima6te change, we have also investigated the response of the zonal wind field to a doubling of CO2 and have found distinct pat6terns of change that are related to the change in temperature structure. In addition, we find that both the global mean ki6netic energy and simulated Hadley circulation increase when CO2 is doubled. The increase in mean kinetic energy is a resul6t of the increase in upper level meridional temperature gradients simulated by the model. It is stressed that changes in a6tmospheric dynamics associated with increased carbon dioxide may also be very important to the final steady state distribution of such greenhouse gases as ozone and water vapor. Hence further research in this regard is warranted.N DESIG61045^8^McKane,RB^Rastetter,EB^Melillo,JM^Shaver,GR^Hopkinson,CS^Fernandes,DN^Skole,DL^Chomentowski,WH^1995^1^Effects of global change on carbon storage in tropical forests of south-america^137^9^3^329-350^^^^^Sep^^^^^4884On-scr6A^4883^We used a process-based model of ecosystem biogeochemistry (MEL-GEM) to evaluate the effects of global change on ca6rbon (C) storage in mature tropical forest ecosystems in the Amazon Basin of Brazil. We first derived a single parameteriz6ation of the model that was consistent with all the C stock and turnover data from three intensively studied sites within 6the Amazon Basin that differed in temperature, rainfall, and cloudiness. The range in temperature, soil moisture, and phot6osynthetically active radiation (PAR) among these sites is about as large as the anticipated changes in these variables in6 the tropics under CO2-induced climate change. We then tested the parameterized model by predicting C stocks along a 2400-6km transect in the Amazon Basin. Comparison of predicted and measured vegetation and soil C stocks along this transect sug6gests that the model provides a reasonable approximation of how climatic and hydrologic factors regulate present-day C sto6cks within the Amazon Basin. Finally, we used the model to predict and analyze changes in ecosystem C stocks under project6ed changes in atmospheric CO2 and climate. The central hypothesis of this exercise is that changes in ecosystem C storage 6in response to climate and CO2 will interact strongly with changes in other element cycles, particularly the nitrogen (N) 6and phosphorus (P) cycles. We conclude that C storage will increase in Amazonian forests as a result of(1) redistribution 6of nutrients from soil (with low C:nutrient ratios) to vegetation (with high C:nutrient ratios), (2) increases in the C:nu6trient ratio of vegetation and soil, and (3) increased sequestration of external nutrient inputs by the ecosystem. Our ana6lyses suggest that C:nutrient interactions will constrain increases in C storage to a maximum of 63 Mg/ha during the next 6200 years, or about 16% above present-day stocks. However, it is impossible to predict how much smaller the actual increas6e in C storage will be until more is known about the controls on soil P availability. On the basis of these analyses, we identify several topics for further research in the moist tropics that must be addressed to resolve these uncertainties.O61046^4^Oechel,WC^Vourlitis,GL^Hastings,SJ^Bochkarev,SA^1995^1^Change in arctic co2 flux over 2 decades - effects of climate- change at barrow, alaska^56^5^3^846-855^^^^^Aug^^^^^4886ATES\PRESENTATION DESIGNS\RIBBO6A^4885^A significant difference in net ecosystem carbon balance of wet sedge ecosystems in the Barrow, Alaska region was o6bserved between CO2 flux measurements obtained during the International Biological Program in 1971 and measurements made d6uring the 1991-1992 growing seasons. Currently, high-center polygons are net sources of CO2 to the atmosphere of approxima6te to 14 gC . m(-2). yr(-1), while low-center polygons are losing approximate to 3.6 gC . m(-2). yr(-1), and ice wedge hab6itats are accumulating 4.0 gC . m(-2). yr(-1). On average, moist meadow habitats characteristic of the IBP-II site are cur6rently sources of approximate to 1.3 gC . m(-2). yr(-1) to the atmosphere compared to the reported accumulation of approxi6mate to 25 gC . m(-2). yr(-1) determined in 1971. This difference in ecosystem function over the last two decades may be d6ue to the recently reported increase in surface temperatures resulting in decreases in the soil moisture status. These res6ults point to the importance of long-term research sites and databases for determining the potential effects of climate change on ecosystem function.BBONS.POTPROGRAM FILES\MICROSOFT OF61047^2^Price,DT^Apps,MJ^1995^1^The boreal forest transect case-study - global change effects on ecosystem processes and carbon dynamics in boreal canada^94^82^1-2^203-214^^^^^May^^^^^4888PRESENTATION DESIGNS\FIREBAL6A^4887^The Boreal Forest Transect Case Study (BFTCS) is a multi- disciplinary ecological study organised around a 1000 km 6transect located in central Canada. The transect is oriented along an ecoclimatic gradient in a region likely to undergo s6ignificant environmental change within the next: few decades, and crosses the climate-sensitive boreal forest biome, inclu6ding the transitions north and south into tundra and grassland respectively. Originally conceived as an extension to the B6OReal Ecosystem Atmosphere Study (BOREAS), the 10-year BFTCS project projects the intensive canopy-scale measurements and 6modelling advances obtained from BOREAS to a wider range of sites with a longer-term perspective. In addition to consideri6ng ecophysiological processes with time-frames of the order of one year or shorter, BFTCS addresses the effects of larger 6scale, longer term processes including vegetation succession and ecosystem disturbances. The BFTCS currently provides prac6tical linkages among ecosystem monitoring, field experiments and regional scale modelling. It will ultimately provide a kn6owledge-base of key processes and their environmental sensitivities, and assessments of possible climate feedbacks, which can be used to assess the possible consequences of global change both regionally and globally.POT61048^13^Sellers,P^Hall,F^Margolis,H^Kelly,B^Baldocchi,D^Denhartog,G^Cihlar,J^Ryan,MG^Goodison,B^Crill,P^Ranson,KJ^Lettenma6ier,D^Wickland,DE^1995^1^The boreal ecosystem-atmosphere study (boreas) - an overview and early results from the 1994 field year^279^76^9^1549-1577^^^^^Sep^^^^^4890SIGNS\MEADOW.POTPROGRAM FIL6A^4889^The Boreal Ecosystem Atmosphere Study (BOREAS) is a large-scale international field experiment that has the goal of6 improving our understanding of the exchanges of radiative energy, heat, water, CO2, and trace gases between the boreal fo6rest and the lower atmosphere. An important objective of BOREAS is to collect the data needed to improve computer simulati6on models of the processes controlling these exchanges so that scientists can anticipate the effects of global change. Fro6m August 1993 through September 1994, a continuous set of monitoring measurements-meteorology, hydrology, and satellite re6mote sensing-were gathered over the 1000 x 1000 km BOREAS study region that covers most of Saskatchewan and Manitoba, Cana6da. This monitoring program was punctuated by six campaigns that saw the deployment of some 300 scientists and aircrew int6o the field, supported by 11 research aircraft. The participants were drawn primarily from U.S. and Canadian agencies and 6universities, although there were also important contributions from France, the United Kingdom, and Russia. The field camp6aigns lasted for a total of 123 days and saw the compilation of a comprehensive surface-atmosphere flux dataset supported 6by ecological, trace gas, hydrological, and remote sensing science observations. The surface-atmosphere fluxes of sensible6 heat, latent heat, CO2, and momentum were measured using eddy correlation equipment mounted on a surface network of 10 to6wers complemented by four flux-measurement aircraft. All in all, over 350 airborne missions (remote sensing and eddy corre7lation) were flown during the 1994 field year. Preliminary analyses of the data indicate that the area-averaged photosynth7etic capacity of the boreal forest is much less than that of the temperate forests to the south. This is reflected in very7 low photosynthetic and carbon drawdown rates, which in turn are associated with low transpiration rates (less than 2 mm d7ay-1 over the growing season for the coniferous species in the area). The strong sensible fluxes generated as a result of 7this often lead to the development of a deep dry planetary boundary layer over the forest, particularly during the spring 7and early summer. The effects of frozen soils and the strong physiological control of evapotranspiration in the biome do n7ot seem to be well represented in most operational general circulation models of the atmosphere. Analyses of the data will continue through 1995 and 1996. Some limited revisits to the field are anticipated.FILES\MICROSOFT OF71049^1^Huntley,B^1995^1^Plant-species response to climate-change - implications for the conservation of european birds^280^137^^S127-S138^^^^^Jan^^^^^4892OFT OFFICE\TEMPLATES\PRESENTATION DESIGNS\PR7 A^4891^Wildlife conservation faces new and extreme challenges in adapting to the accelerating dynamics of a world respondi7 ng to global change, The Quaternary record shows that migration has been the usual response of organisms to environmental 7 change, This record also reveals that forecast future climate changes are of a magnitude and in a direction unprecedented 7 in recent earth history: the rate of these changes is likely also to surpass that of any comparable change during the last7 2.4 million years, The relationship between a species' geographical distribution and present climate may be modelled by a7 surface representing the probability of encountering that species under given combinations of climate conditions, This 'c7limate response surface' then may be used to simulate potential future distributions of the species in response to forecas7t climate scenarios, Such simulations reveal the magnitude of the impacts of these forecast climate changes. Although to d7ate this approach has been applied in Europe only to plants, it promises to be valuable also for other groups of organisms7, including birds. Some bird species, however, may respond more directly to either habitat structure or presence of specif7ic food plants; such factors may be incorporated into the models when required, The magnitude of likely vegetation changes7 necessitates a global approach to conservation if there is to be any hope of long-term success, Successful conservation o7f global biodiversity will depend upon conservation of the global environment and limitation of the human population much more than upon parochial efforts to conserve locally rare organisms or habitats.ENTATION DESIGNS\ANG71050^3^Bartak,M^Nijs,I^Impens,I^1996^1^The effect of long-term exposure of Lolium perenne L plants to elevated CO2 and/or elevated air temperature on quantum yield of photosystem 2 and net photosynthesis^79^32^4^549-562^^^^^^^^^^4894MICRO7A^4893^The effects of long-term exposure of Lolium perenne L. plants to CO2 concentration elevated to 700 mu mol (CO2) mol7(-1) (EC) and air temperature elevated by 4 degrees C (ET) on the quantum yield of electron transport of photosystem 2, PS72 (phi(2)) and on the potential yield of photochemical reactions of PS2 (F- v/F-m) measured by the chlorophyll (Chl) fluor7escence method, were studied. The plants were exposed for 6 months in opened field greenhouses to four treatments simulati7ng global atmospheric changes: (1) ambient CO2 (AC) and ambient air temperature, AT (ACAT - control), (2) EC and AT (ECAT)7, (3) AC and ET (ACET), and (4) EC and ET (ECET). When the plants were exposed to stepwise increased irradiance, a decreas7 e in phi(2) was found under both AC and EC measuring concentrations. At high irradiances a significantly higher yield of P7!S2 was detected when measured under EC compared to AC regardless of long-term CO2 and temperature treatment (i.e., positiv7"e short- term. effect of EC). The short-term effect of EC on phi(2) as related to net photosynthetic rate (P-N) Shift was 7#detected from irradiance response curves. At high irradiances and AC, phi(2) was reduced in comparison to control for the 7$plants of EC and ET treatments (i.e., negative long-term effect of treatment). The long-term effect of both EC and ET on t7%he yield of PS2 was attributed to a down-regulation of P-N caused by the treatment. The phi(2) was related to the actual r7&ate of photosynthesis and the relationship between phi(2) and phi(CO2) was linear over a wide range of irradiances. No eff7'ect of long- term treatments on the dark-adapted F-v/F-m ratio was found in plants cultivated under natural greenhouse irradiance.\TEMPLATES\PRESENTATION DESIGNS\CONTEMPORARY PORTRAIT.PO7)1051^4^Bassirirad,H^Griffin,KL^Strain,BR^Reynolds,JF^1996^1^Effects of CO2 enrichment on growth and root (NH4+)-N-15 uptake rate of loblolly pine and ponderosa pine seedlings^13^16^11-12^957-962^^^^^Nov-Dec^^^^^4896OGRAM FILES\MI7+A^4895^We examined changes in root growth and (NH4+)-N-15 uptake capacity of loblolly pine (Pinus taeda L.) and ponderosa 7,pine (Pinus ponderosa Douglas. Ex Laws.) seedlings that were grown in pots in a phytotron at CO2 partial pressures of 35 o7-r 70 Pa with NH4+ as the sole N source. Kinetics of N-15-labeled NH4+ uptake were determined in excised roots, whereas tot7.al NH4+ uptake and uptake rates were determined in intact root systems following a 48-h labeling of intact seedlings with 7/N-15. In both species, the elevated CO2 treatment caused a significant downregulation of (NH4+)-N-15 uptake capacity in ex70cised roots as a result of a severe inhibition of the maximum rate of root (NH4+)-N-15 uptake (V-max). Rates of (NH4+)-N-1715 uptake in intact roots were, however, unaffected by CO2 treatment and were on average 4- to 10-fold less than the V-max 72in excised roots, suggesting that (NH4+)-N-15 absorption from the soil was not limited by the kinetics of root (NH4+)-N-1573 uptake. Despite the lack of a CO2 effect on intact root absorption rates, (NH4+)-N-15 uptake on a per plant basis was enh74anced at high CO2 concentrations in both species, with the relative increase being markedly higher in ponderosa pine than 75in loblolly pine. High CO2 concentration increased total (NH4+)-N-15 uptake and the fraction of total biomass allocated to76 fine roots (< 2 mm in diameter) to a similar relative extent. We suggest that the increased uptake on a per plant basis in response to CO2 enrichment is largely the result of a compensatory increase in root absorbing surfaces.ER DOCUM781052^4^Beerling,DJ^Heath,J^Woodward,FI^Mansfield,TA^1996^1^Drought-CO2 interactions in trees: Observations and mechanisms^84^134^2^235-242^^^^^Oct^^^^^4898TES\PRESENTATION DESIGNS\ANGLES.POT7:A^4897^It is sometimes assumed that because increases in atmospheric CO2 concentration usually enhance water use efficienc7;y per unit leaf area, there will be a tendency for plants to show greater drought tolerance as well as increased biomass i7isplay minimal stomatal closing responses to elevated CO2, and in the case of F. sylvatica the stomatal control of transpi7?ration per unit leaf area appears to be unable to compensate for the greater development of leaf area. By contrast, the st7@omata of oak (Quercus robur L.) close appreciably in elevated CO2, to an extent which might be sufficient to compensate fo7Ar an increase in total leaf area. A simple model for the controls on water supply and consumption for the whole tree sugge7Bsts that in F. sylvatica the potential height attainment for a given sapwood area might decrease as the atmospheric CO2 co7Cncentration rises. The conclusions drawn from experimental data and from modelling are supported by field observations mad7De in the UK in 1995, when the three species responded very differently to severe drought. We suggest that the progressive 7Eincrease in the concentration of atmospheric CO2 over the past 200 yr might have accentuated differences in drought sensitivity between these species.TES\PRESENTATION DESIGNS\DADS TIE.POT7G1053^6^Blumenthal,C^Rawson,HM^McKenzie,E^Gras,PW^Barlow,EWR^Wrigley,CW^1996^1^Changes in wheat grain quality due to doubling the level of atmospheric CO2^281^73^6^762-766^^^^^Nov-Dec^^^^^4900\MICROSOFT OFFICE\TEMPLATE7IA^4899^Elevated levels of atmospheric CO2 have been shown to increase grain yield and reduce grain nitrogen concentration.7J The object of this study was to determine whether elevated CO2 levels would modify other aspects of grain quality relevan7Kt to processing, particularly protein and starch quality. Wheat of two genotypes (Hartog and Late Hartog) was grown in the7L field in controlled-atmosphere tunnels at either the ambient level of CO2 (350 mu l/L) or an elevated level (700 mu l/L).7M This elevated level of CO2 produced significant increases in grain yield, but decreases in 1,000-kernel weight. Grain gro7Nwn in the elevated CO2 atmosphere produced poorer dough and decreased loaf volume, farinograph development time, and dough7O extensibility. These changes were largely attributable to the lower protein content of the grain grown at elevated CO2. T7Phere did not appear to be major changes in protein composition or in the functional properties of the protein. Grain produ7Qced at elevated CO2 yielded starch with a significantly higher proportion of large (A-type) starch granules but no overall7R change in amylose-to-amylopectin ratio. These studies indicate that elevated levels of CO2 may result in decreased quality of bread wheats largely due to lowered protein content.@PROGRAM FILES\MICROSOF7T1054^5^Bowes,G^Vu,JCV^Hussain,MW^Pennanen,AH^Allen,LH^1996^1^An overview of how rubisco and carbohydrate metabolism may be regulated at elevated atmospheric [CO2] and temperature^282^5^3^261-270^^^^^^^^^^4902OTHER DOCUMENTS\E7VA^4901^Although atmospheric CO2 concentration ([CO2]) has been up to 16-fold higher than at present, the past several mill7Wion years have seen atypically low values. Thus, modern-day plants are adapted to cope with a low [CO2]/[O-2] ratio. The p7Xresent [CO2] does nor saturate C-3 photosynthesis, so its doubling produces an ''efficiency effect'', but it is not always7Y fully realized. Acclimation to high [CO2] during growth can down-regulate photosynthesis, presumably to optimize carbon a7Zcquisition and utilization. A primary factor in acclimation is a reduction in rubisco. Two crops, rice and soybean, were u7[sed to study this phenomenon. Rice photosynthesis and growth peaked at 500 mu mol mol(-1), whereas soybean responded up to7\ 990 mu mol mol(-1) Rubisco concentration declined under CO2-enrichment and increasing temperatures, more so in rice than 7]soybean. The rubisco k(cat) Of rice was unaffected by growth [CO2] or temperature, but that from soybean was increased by 7^both. In rice the capacity to handle carbohydrate, as measured by sucrose phosphate synthase activity was up-regulated by 7_CO2- enrichment, but not by temperature. Leaf carbohydrates were increased by [CO2], but decreased by higher temperatures,7` starch more so than sucrose. Even though C-3 species differ in response to [CO2] and temperature, CO2-enrichment can moderate adverse effects of temperature extremes.PROGRAM FILES\MICROSOFT OFFICE\TEMPLA7b1055^3^Brklacich,M^Curran,P^Brunt,D^1996^1^The application of agricultural land rating and crop models to CO2 and climate change issues in Northern regions: The Mackenzie Basin case study^282^5^3^351-365^^^^^^^^^^4904NTS\ELEGANT R7dA^4903^The Mackenzie Basin in northwestern Canada covers approximately 1.8 million km(2) and extends from 52 degrees N to 7e70 degrees N. Much of the Basin is currently too cool and remote from markets to support a viable agricultural sector, but7f the southern portion of the Basin has the physical potential to support commercial agriculture. This case study employed 7gagricultural land rating and crop models to estimate the degree to which a CO2-induced global warming might alter the phys7hical potential for commercial agriculture throughout the Basin. The two climate change scenarios considered in this analys7iis would relax the current constraints imposed by a short and cool frost-free season, but without adaptive measures, drier7j conditions and accelerated crop development rates were estimated to offset potential gains stemming from elevated CO2 lev7kels and warmer temperatures. In addition to striving for a better understanding of the extent to which physical constraint7ls on agriculture might be modified by climate change, there is a need to expand the research context and to consider the capacity of agriculture to adapt to altered climates.HER DOCUMENTS\ELEGANT RESUME.DOT7n1056^2^Buse,A^Good,JEG^1996^1^Synchronization of larval emergence in winter moth (Operophtera brumata L) and budburst in pedunculate oak (Quercus robur L) under simulated climate change^283^21^4^335-343^^^^^Nov^^^^^4906MICROSOFT OF7pA^4905^1. The hypothesis that a 3 degrees C elevation in temperature and doubled CO2 concentration would have no effect on7q the synchronization of winter moth egg hatch with budburst in oak was tested by comparing the separate and interactive ef7rfects of ambient and elevated (+ 3 degrees C) temperature and ambient and elevated (doubled to 340 p.p.m.) CO2 in eight ex7sperimental Solardomes. In addition, an outdoor control was compared with the ambient temperature/CO2 treatment combination7t. 2. Elevated temperature accelerated darkening (preceding egg hatch by about 5-10 days) and hatching of eggs developing o7uff the trees; elevated CO2 had no effect. The same effects were observed in eggs developing on the trees. 3. Within treatm7vents, date of egg hatch was the same on trees with early or late budburst. 4. Egg darkening and budburst were closely sync7whronized at both ambient and elevated temperatures. 5. Both eggs and trees required fewer cumulative heat units (day degre7xes > 4 degrees C), for hatching and budburst, respectively, at ambient than elevated temperatures. The requirements in the7y outdoor control treatment were similar to those in the ambient Solardome treatment. 6. Egg hatch between 10 and 25 degree7zs C, on a temperature gradient in the laboratory, required a constant number of heat units; fewer were required below 10 d7{egrees C. 7. Elevated temperatures, in the Solardomes and the field, delayed adult emergence from the pupae. 8. The result7|s suggest that a general increase in temperature with climatic change would not affect the closeness of the synchronization between egg hatch of winter moth and budburst of oak.PROGRAM FILES\MICROSOFT OFFICE\T7~1057^3^Chemeris,YK^Venediktov,PS^Rubin,AB^1996^1^Role of chloroplast respiration in the inactivation of photosystem II in Chlorella^236^43^6^716-723^^^^^Nov-Dec^^^^^4908TEMPLATES\PRESENTATION DESIGNS\PULSE.7A^4907^Nitrogen deficiency, dark incubation on glucose, and dark incubation at an elevated temperature (41 degrees C) were7 previously shown to inactivate photosystem II (PS LI) in Chlorella pyrenoidosa Chick, strain CALU-175. These treatments a7lso increased chloroplast respiration by 7-11 times, At the same time, any attempt to inhibit the accumulation of substrat7es for chloroplast respiration (CO2 deprivation during nitrogen starvation, inhibition of glucose metabolism by a nonmetab7olizable analog of glucose, 2-deoxy-D-glucose, or inhibition of protein synthesis by cycloheximide during dark incubation 7on glucose or by heat shock) prevented the stimulation of chloroplast respiration and PS II inactivation, Inhibition of th7e oxygen-dependent oxidation of the plastoquinone pool under anaerobic conditions or in the presence of salicylhydroxamate7, an inhibitor of chloroplast oxidases, markedly increased the extent and rate of PS II inactivation in cells subjected to7 heat shock. The dependencies of chloroplast respiration and the PS II inactivation rate on the hear-shock temperature exa7ctly matched one another. Diuron, an inhibitor of photosynthetic electron transport between the primary and secondary quin7one electron accepters, did not affect the rate of chloroplast respiration, but prevented PS II inactivation. We propose t7hat the inactivation of PS II caused by these treatments is due to the loss of the primary quinone electron acceptor as a 7consequence of its two-electron reduction from the plastoquinone reduced by the electron flow from the substrates of chloroplast respiration. OFFICE\TEMPLATES\PRESENTATION DESIGNS\SERENE.POT71058^3^Farnsworth,EJ^Ellison,AM^Gong,WK^1996^1^Elevated CO2 alters anatomy, physiology, growth, and reproduction of red mangrove (Rhizophora mangle L)^2^108^4^599-609^^^^^Dec^^^^^4910RAM FILES\MICROSOFT OFFICE\TEM7A^4909^Mangroves, woody halophytes restricted to protected tropical coasts, form some of the most productive ecosystems in7 the world, but their capacity to act as a carbon source or sink under climate change is unknown. Their ability to adjust 7growth or to function as potential carbon sinks under conditions of rising atmospheric CO2 during global change may affect7 global carbon cycling, but as yet has not been investigated experimentally. Halophyte responses to CO2 doubling may be co7nstrained by the need to use carbon conservatively under water-limited conditions, but data are lacking to issue general p7redictions. We describe the growth, architecture, biomass allocation, anatomy, and photosynthetic physiology of the predom7inant neotropical mangrove tree, Rhizophora mangle L., grown solitarily in ambient (350 mu ll(-1)) and double-ambient (7007 mu ll(-1)) CO2 concentrations for over 1 year. Mangrove seedlings exhibited significantly increased biomass, total stem l7ength, branching activity, and total leaf area in elevated CO2. Enhanced total plant biomass under high CO2 was associated7 with higher root:shoot ratios, relative growth rates, and net assimilation rates, but few allometric shifts were attribut7able to CO2 treatment independent of plant size. Maximal photosynthetic rates were enhanced among high-CO2 plants while st7omatal conductances were lower, but the magnitude of the treatment difference declined over time, and high-CO2 seedlings s7howed a lower P-max at 700 mu ll(-1) CO2 than low-CO2 plants transferred to 700 mu ll(-1) CO2: possible evidence of downre7gulation. The relative thicknesses of leaf cell layers were not affected by treatment. Stomatal density decreased as epide7rmal cells enlarged in elevated CO2. Foliar chlorophyll, nitrogen, and sodium concentrations were lower in high CO2. Mangr7oves grown in high CO2 were reproductive after only 1 year of growth (fully 2 years before they typically reproduce in the7 field), produced aerial roots, and showed extensive lignification of the main stem; hence, elevated CO2 appeared to accel7erate maturation as well as growth. Data from this long- term study suggest that certain mangrove growth characters will c7hange flexibly as atmospheric CO2 increases, and accord with responses previously shown in Rhizophora apiculata. Such resu7lts must be integrated with data from sea-level rise studies to yield predictions of mangrove performance under changing climate. PROGRAM FILES\MICROSOFT OFFICE\TEMPLATES\PRESENTATIO71059^4^GonzalezMeler,MA^RibasCarbo,M^Siedow,JN^Drake,BG^1996^1^Direct inhibition of plant mitochondrial respiration by elevated CO2^8^112^3^1349-1355^^^^^Nov^^^^^4912S\FIREBALL.POTF# PROGRAM FILE7A^4911^Doubling the concentration of atmospheric CO2 often inhibits plant respiration, but the mechanistic basis of this e7ffect is unknown. We investigated the direct effects of increasing the concentration of CO2 by 360 mu L L(-1) above ambien7t on O-2 uptake in isolated mitochondria from soybean (Glycine max L. cv Ransom) cotyledons. Increasing the CO2 concentrat7ion inhibited the oxidation of succinate, external NADH, and succinate and external NADH combined. The inhibition was grea7ter when mitochondria were preincubated for 10 min in the presence of the elevated CO2 concentration prior to the measurem7ent of O-2 uptake. Elevated CO2 concentration inhibited the salicylhydroxamic acid-resistant cytochrome pathway, but had n7o direct effect on the cyanide-resistant alternative pathway. We also investigated the direct effects of elevated CO2 conc7entration on the activities of cytochrome c oxidase and succinate dehydrogenase (SDH) and found that the activity of both 7enzymes was inhibited. The kinetics of inhibition of cytochrome c oxidase were time-dependent. The level of SDH inhibition7 depended on the concentration of succinate in the reaction mixture. Direct inhibition of respiration by elevated CO2 in plants and intact tissues may be due at least in part to the inhibition of cytochrome c oxidase and SDH.@r71060^2^Hakala,K^Mela,T^1996^1^The effects of prolonged exposure to elevated temperatures and elevated CO2 levels on the growth, yield and dry matter partitioning of field-sown meadow fescue^282^5^3^285-298^^^^^^^^^^4914PLATES\PRESE7A^4913^Field-sown meadow fescue (Festuca pratensis, cv. Kalevi) stands were exposed to elevated temperatures (+3 degrees C7) and elevated CO2 (700 ppm) levels in two experiments conducted in 1992-1993 (experiment 1) and in 1994-1995 (experiment 72). Total aboveground yield was, on average, 38% higher at elevated than at ambient temperatures. At ambient temperatures 7elevated CO2 increased the number of tillers by 63% in 1992, 24% in 1993, 90% in 1994 and 14% in 1995. At elevated tempera7tures, the increase in tiller number in elevated CO2 was seen only in the first growing seasons after sowing. The total yi7eld in a growing season was about 10% higher in elevated CO2 in experiment 1. In experiment 2 the yield was more than 20% 7higher in elevated CO2 at elevated temperatures, whereas at ambient temperatures the rise in CO2 level had no effect on th7e yield; the root biomass, however, increased by more than 30%. In elevated CO2 at ambient temperatures the root biomass a7lso increased in experiment 1, but at elevated temperatures there was no consistent change. The soluble carbohydrate conte7nt of above-ground biomass was 5-48% higher in elevated CO2 at most of the measuring times during the growing season, but 7the nitrogen content did not show a clear decrease. The reasons for the lack of a marked increase in biomass in elevated CO2 despite a 40-60% increase in photosynthesis are discussed.PROGRAM FILES\MICROSOFT OFFICE71061^4^Hibberd,JM^Richardson,P^Whitbread,R^Farrar,JF^1996^1^Effects of leaf age, basal meristem and infection with powdery mildew on photosynthesis in barley grown in 700 mu mol mol(-1) CO2^84^134^2^317-325^^^^^Oct^^^^^4916MPORARY RE7A^4915^The rate of net photosynthesis in the second leaf of barley was higher in 700 than 350 mu mol mol(-1) CO2 when meas7ured in the CO2 concentration in which the plants were grown, but the magnitude of this difference decreased as the leaf a7ged. Infection by powdery mildew accelerated the decline in net photosynthesis of leaves grown in either 350 or 700 mu mol7 mol(-1) CO2. A/C-i curves allowed the reduction in net photosynthesis of plants exposed to 700 mu mol mol(-1) CO2 or afte7r infection by powdery mildew to be related to changes in the carboxylation efficiency or in the regeneration of ribulose 71,5-bisphosphate. The carboxylation efficiency declined in plants exposed to 700 mu mol mol(-1) CO2. In plants infected wi7th powdery mildew, the reduction in net photosynthesis was associated with both reduced carboxylation efficiency and reduc7ed ability to regenerate ribulose 1,5-bisphosphate. Reduced carboxylation efficiency of the second leaf of plants grown in7 700 mu mol mol(-1) CO2 was not associated with a reduction in the concentration of rubisco within the leaf. In contrast t7o the presence of a close exogenous sink, leaf age had large effects on the acclimation of photosynthesis to 700 mu mol mol(-1) CO2.CROSOFT OFFICE\TEMPLATES\PRESENTATION DESIGNS\FANS.POT71062^3^Hibberd,JM^Whitbread,R^Farrar,JF^1996^1^Effect of 700 mu mol mol(-1) CO2 and infection with powdery mildew on the growth and carbon partitioning of barley^84^134^2^309-315^^^^^Oct^^^^^4918 FILES\MICROSOFT OFFICE\7A^4917^The dry weight of barley plants in 700 mu mol mol(-1) CO2 was increased by 19 d after planting relative to plants g7rown in 350 mu mol mol(-1) CO2. Infection of the second leaf by powdery mildew led to reduced growth rates in both 350 and7 700 mu mol mol(-1) CO2, but the reduction in growth was transitory in 350 mu mol mol(-1) CO2. Neither the alIometric coef7ficient k between shoot and root, nor the leaf weight ratio, was altered by growth in 700 mu mol mol(-1) CO2 or by infecti7on with powdery mildew. The number of tillers produced increased per plant but not per unit d. wt in 700 mu mol mol(-1) CO72. The growth response of barley to increased concentrations of CO2 and/or to infection with powdery mildew was not associ7ated with alterations in net carbon partitioning, so a change in the ratio of photosynthetic to non-photosynthetic tissue,7 contributed to neither the growth response of barley to 700 mu mol mol(-1) CO2 nor to infection with powdery mildew. The 7increase in the growth rate of barley in 700 mu mol mol(-1) CO2 and the reduction in the growth rate after infection occurred at the same time as increased and reduced rates of net photosynthesis respectively.FICE\TEMPLATES\PR71063^6^Hogan,KP^Whitehead,D^Kallarackal,J^Buwalda,JG^Meekings,J^Rogers,GND^1996^1^Photosynthetic activity of leaves of Pinus radiata and Nothofagus fusca after 1 year of growth at elevated CO2^92^23^5^623-630^^^^^^^^^^4920Hh׻7A^4919^Radiata pine (Pinus radiata D.Don) and red beech (Nothofagus fused (Hook.f.) Oerst.) were grown for over 1 year at 7elevated (ELEV, 64 Pa) and ambient (AMB, 38 Pa) CO2 partial pressure in open-top chambers. Springtime measurements of over7wintering leaves showed that light- and CO2-saturated photosynthetic rates (A,,) of pine leaves were similar for the two t7reatments (AMB: 6.7 +/- 1.08 mu mol m(-2) s(-1), mean +/- 1 s.e.; ELEV: 6.6 +/- 0.47) but, for beech leaves, A(max) was gr7eater for AMB plants (8.8 +/- 0.90 mu mol m(-2) s(-1)) than for ELEV plants (6.10 +/- 0.71). Summertime measurements of le7aves grown that spring showed that for pine, A(max) was similar in the two CO2 treatments (AMB 14.9 mu mol m(-2) s(-1) +/-7 0.80; ELEV: 13.5 +/- 1.9) while, for beech, A(max) was higher in AMB plants (21.0 +/- 1.1) than in ELEV plants (17.2 +/- 71.9), although the difference was not statistically significant. These results indicate downregulation of photosynthetic c7apacity of beech but not pine. V-cmax did not differ between treatments within species, suggesting that there was no accli7mation of rubisco activity. Triose phosphate utilisation limitation may have contributed to the downregulation of A(max) i7n beech. For pine, photosynthesis at treatment CO2 partial pressures was greater in ELEV plants in both spring and summer.7 For beech measured at treatment CO2 partial pressures, photosynthesis was greater in ELEV plants in summer, but was similar between treatments in the springtime.TEMPLATES\PRESENTATIONS\CORPORATE HOME P71064^4^Ingestad,T^Hellgren,O^Hesseldahl,H^Ingestad,ABL^1996^1^Methods and applications to control the uptake rate of carbon^37^98^3^667-676^^^^^Nov^^^^^4922PORATE HOME PAGE (ONLINE).POT PROGR7A^4921^Methods to control carbon and nutrient uptake at different availability of carbon were tested on plants of birch (B7etula pendula Roth.) and tomato (Lycopersicon esculentum Mill. cv. Solentos). The present paper accounts for the methods a7nd the possibility to maintain steady-state, i.e., a long-term and stable physiological state of acclimated plants. Steady7-state comprises, by definition, equality between constant relative growth rates, and relative uptake rates of carbon and 7nutrients. Two methods were tested. The first, not previously applied, method (a), was based on a constant relative additi7on rate of carbon, R(AC). In the second method (b), a constant concentration of CO2 in the air, c(a), was used to attain n7on- limiting conditions. The methods are analogous to those used by us to control plant nutrition, and the generality of f7luxes to quantify supply as well as uptake and growth was verified. Thus, different R(AC) resulted suited in clear-cut res7ponses, from strong reduction to non-limitation of uptake and growth, whereas different c(a) levels in the range 100 to 7070 ppm had comparatively small effects, with an unclear causality. Non- limiting conditions were achieved at c(a) greater t7han or equal to 200 ppm. Effects reported in the literature have been based upon the control of c(a), similarly to method 7(b), whereas results comparable to those obtained with method (a) are lacking. Transpiration rate increased rapidly at c(a7) < 200 ppm CO2, and at low R(AC) levels, less than or equal to 0.1 day(- 1), wilting tendencies were observed. Elevated c7(a) 500 or 700 ppm, did not increase the relative growth rate (R(G)) but reduced transpiration and increased both nitrogen7 productivity (growth rate per unit of nitrogen in the plant) and transpiration productivity (growth rate per unit of wate7r transpired by the plant). Obviously, effects of c(a) may be due to changed transpiration rate rather than to changed qua7ntitative availability of CO2. Relative uptake (R(OC)) and growth (R(G)) rates were closely equal to the R(AC) applied (R(7AC) approximate to R(UC) approximate to R(G)); i.e., the purely mathematical conditions defining steady-state were fulfill7ed. This unambiguous and straightforward test of reliability confirms that experimental artefacts did not produce uncontro7lled or unintended effects, so that the new technique allows an accurate control of CO2 uptake and plant growth. The resul7ts add to previous databases and reference systems, where limiting conditions grade and classify plant performance as devi7ations from maximum growth. Evidently, methodology in experimentation and in evaluation of plant responses, can be based upon unifying concepts and general theories.OFFICE\TEMPLATES\PRESENTATIONS\CORPORAT"1065^7^Johnson,LC^Shaver,GR^Giblin,AE^Nadelhoffer,KJ^Rastetter,ER^Laundre,JA^Murray,GL^1996^1^Effects of drainage and temp8A^4923^We examined the importance of temperature (7 degrees C or 15 degrees C) and soil moisture regime (saturated or fiel8d capacity) on the carbon (C) balance of arctic tussock tundra microcosms (intact blocks of soil and vege tation) in growt8h chambers over an 81-day simulated growing season. We measured gaseous CO2 exchanges, methane (CH4) emissions, and dissol8ved C losses on intact blocks of tussock (Eriophorum vaginatum) and in tertussock (moss-dominated). We hypothesized that u8nder increased temperature and/or enhanced drainage, C losses from ecosystem respiration (CO2 respired by plants and heter8otrophs) would exceed gains from gross photosynthesis causing tussock tundra to become a net source of C to the atmosphere8. The field capacity moisture regime caused a decrease in net CO2 storage (NEP) in tussock tundra microcosms. This resulte8 d from a stimulation of ecosystem respiration (probably mostly microbial) with enhanced drainage, rather than a decrease i8 n gross photosynthesis. Elevated temperature alone had no effect on NEP because CO2 losses from increased ecosystem respir8 ation at elevated temperature were compensated by increased CO2 uptake (gross photosynthesis). Although CO2 losses from ec8 osystem respiration were primarily limited by drainage, CH4 emissions, in contrast, were dependent on temperature. Further8 more, substantial dissolved C losses, especially organic C, and important microhabitat differences must be considered in e8stimating C balance for the tussock tundra system. As much as similar to 20% of total C fixed in photosynthesis was lost a8s dissolved organic C. Tussocks stored similar to 2x more C and emitted 5x more methane than intertussocks. In spite of th8e limitations of this microcosm experiment, this study has further elucidated the critical role of soil moisture regime and dissolved C losses in regulating net C balance of arctic tussock tundra.USINESS PLAN (STANDARD)81066^2^Jones,MB^Jongen,M^1996^1^Sensitivity of temperate grassland species to elevated atmospheric CO2 and the interaction with temperature and water stress^282^5^3^271-283^^^^^^^^^^4926 PROGRAM FILES\MICROSOFT8A^4925^The annual cycle of growth of many temperate grasses is limited by low temperatures during the winter and spring an8d water stress during the summer. Climate change, induced by increase in the concentration of greenhouse gases in the atmo8sphere, can affect the growth and community structure of temperature grasslands in two ways. The first is directly through8 changes in atmospheric concentration of CO2 and the second is indirectly through changes in temperature and rainfall. At 8higher latitudes, where growth is largely temperature limited, it is probable that the direct effects of enhanced CO2 will8 be less than at low latitudes. However, interactions with increasing temperature and water stress are complex. Temperate 8grasslands range from intensively managed monocultures of sown species to species-rich natural and semi-natural communitie8s whose local distributions are controlled by variations in soil type and drainage. The different species can show marked 8differences in their responses to increasing CO2 concentrations, rising temperatures and water stress. This will probably 8result in major alterations in the community structure of temperate grasslands in the future. In addition to impacts on pr8imary productivity and community structure, a long-term effect of elevated CO2 on grasslands is likely to be a significant increase in soil carbon storage. However, this may be counteracted by increases in temperature.\MICROSOFT O8 1067^3^Lee,JJ^Phillips,DL^Dodson,RF^1996^1^Sensitivity of the US corn belt to climate change and elevated CO2 .2. Soil erosion and organic carbon^223^52^4^503-521^^^^^Dec^^^^^4928TES\PRESENTATION DESIGNS\WHIRLPO8"A^4927^Climate models indicate that increasing atmospheric concentrations of carbon dioxide and other greenhouse gases cou8#ld alter climate globally. The EPIC (Erosion/Productivity Impact Calculator) model was used to examine the sensitivity of 8$soil erosion (wind, water) and soil organic carbon (SOC) (15 cm and 1 m depth) across the US corn belt to changes in tempe8%rature (+2 degrees C), precipitation (+/-10%, +/-20%), wind speed (+/-10%, +/-20%), and atmospheric CO2 concentration (3508&, 625 ppmv). One-hundred-year simulations were run for each of 100 sites under 36 climate/CO2 regimes. The 100-year region8'ally aggregated mean water erosion rates increased linearly with precipitation, whereas the wind erosion rates decreased a8(nd total erosion rates increased by 15-18%. Total erosion increased with increased temperature. Increasing CO2 from 350 to8) 625 ppmv (with temperature increased by 2 degrees C and mean wind speed held constant) had no effect on water erosion, de8*spite increases in annual total and peak runoff; this was attributed to increased vegetation cover. Wind erosion decreased8+ by 4-11% under increased CO2. Wind erosion was very sensitive to mean wind speed, increasing four-fold and decreasing 10-8,fold for a 20% increase or decrease in mean wind speed, respectively. This was attributed to a threshold effect. SOC to 1 8-m decreased 4.8 Mg-C ha(-1) from an initial value of 18.1 Mg-C ha(-1) during the 100-year baseline simulation. About 50% o8.f this loss (2.3 Mg-C ha(-1)) was due to transport off- site by soil erosion. SOC in the top 15 cm decreased 0.8 Mg-C ha(-8/1) from an initial value of 4.9 Mg-C ha(-1). Increased temperature and precipitation accelerated these losses of SOC, whereas increased CO2 slowed the losses. Copyright (C) 1996 Published by Elsevier Science LtdFT OFFICE\TEMPLA811068^1^Medlyn,BE^1996^1^The optimal allocation of nitrogen within the C-3 photosynthetic system at elevated CO2^92^23^5^593-603^^^^^^^^^^4930\TEMPLATES\PRESENTATIONS\H.R. INFORMATION KIOSK (ST83A^4929^The distribution of nitrogen among compounds involved in photosynthesis varies in response to changes in environmen84tal conditions such as photon flux density. However, the extent to which the nitrogen distribution within leaves adjusts i85n response to increased atmospheric CO2 is unclear. A model was used to determine the nitrogen distribution which maximise86s photosynthesis under realistic light regimes at both current and elevated levels of CO2, and a comparison was made with 87observed leaf nitrogen distributions reported in the literature. The model accurately predicted the distribution of nitrog88en within the photosynthetic system for leaves grown at current levels of CO2, except at very high leaf nitrogen contents.89 The model predicted that, under a doubling of CO2 concentration from its current level, the ratio of electron transport c8:apacity to Rubisco activity (J(max):V-cmax) should increase by 40%. In contrast, measurements of J(max):V-cmax taken from 8;the literature show a slight but non-significant increase in response to an increase in CO2. The discrepancy between predi8crease in the conductance to CO2 transfer between the intercellular spaces and the sites of carboxylation at elevated CO2.OFT OFFICE\TEMPLATES\PRESENTATIONS\GENERIC (ONLINE).POT8@1069^7^Pfirrmann,T^Barnes,JD^Steiner,K^Schramel,P^Busch,U^Kuchenhoff,H^Payer,HD^1996^1^Effects of elevated CO2, O-3 and K deficiency on Norway spruce (Picea abies): Nutrient supply, content and leaching^84^134^2^267-278^^^^^Oct^^^^^4932SOF8BA^4931^Two clones of 5-yr-old Norway spruce (Picea abies [L.] Karst.) were exposed to two atmospheric concentrations of CO8C2 (350 and 750 mu mol mol(-1)) and of O-3 (20 and 75 nmol mol(-1)) in a phytotron at the GSF-Forschungszentrum (Munich) ov8Der the course of a single season (April-October). The phytotron was programmed to recreate an artificial climate similar t8Eo that at a high elevation site in the Inner Bavarian forest, and trees were grown in 401 containers of soil (pH 3.5) fert8Filized to achieve two levels of potassium nutrition; well fertilized and K-deficient. Foliar nutrient analyses performed a8Gt the beginning of the exposure indicated that the fertilization programmes achieved their goal without significantly alte8Hring the levels of other nutrients or the soil pH. At the beginning of the fumigation, foIiar K concentrations were 7-9 mg8I g(-1) d. wt for well fertilized trees and 4-5 mg g(-1) d. wt for trees receiving no supplemental K. Over the course of th8Je season, differences between K treatments intensified so that by the end of the experiment there was a five to sixfold di8Kfference between foliar K concentrations. This was associated with slight, but significant (P < 0.05), decreases in S and 8LZn (and of Cu in the 1989 needle year age class) and higher levels of C, N and Mg in K-deficient trees. Foliar N concentra8Mtions were low for all trees (9-15 mg g(-1) needle d. wt) but were similar to levels found in the field. Elevated O-3 was 8Nfound to decrease significantly the C (P < 0.05) and N (P < 0.001) content of both current-year (1989) and previous-pear (8O1988) needles independent of CO2 concentration, but apart from some minor changes in the concentrations of Cu and Mn in th8Pe current-year needles no other effects of the pollutant on plant nutrient status were found. In contrast, CO2 enrichment 8Qresulted in significantly (P < 0.01) lower concentrations of K and P (effects on Mg were also on the borderlines of statis8Rtical significance) in current-year needles, but there was no influence on the nutrient composition of the previous- year 8Sneedles (although effects on N were on the borderlines of statistical significance). CO2 enrichment also increased (P < 0.8T05) the C:N ratio of both current-year and previous-year needles. One factor contributing to the decline in foIiar K at el8Uevated CO2 appeared to be a marked increase (25-30%) in the rate at which cations were leached from the canopy by repeated8V simulated acid mist (pH 4.0) events, and this effect occurred independently of the O-2 concentration. The information pre8Wsented will aid the interpretation of parallel studies examining the effects of elevated CO2 and/or O-2 on seasonal change8Xs in photosynthesis, non-structural carbohydrate content, antioxidants, tree growth and water use efficiency, and sheds fu8Yrther light on the growing scepticism concerning the role of O-2 in the development of Mg and K-deficiency symptoms characteristic of certain types of forest decline in central Europe.M FILES\MICROSOFT OFFICE\TEMP8[1070^3^Phillips,DL^Lee,JJ^Dodson,RF^1996^1^Sensitivity of the US corn belt to climate change and elevated CO2 .1. Corn and soybean yields^223^52^4^481-502^^^^^Dec^^^^^4934FFICE\TEMPLATES\PRESENTATIONS\FACILI8]A^4933^Climate models indicate that increasing atmospheric concentrations of CO2 and other greenhouse gases could alter cl8^imate globally. The EPIC (Erosion Productivity Impact Calculator) model was used to examine the sensitivity of corn and so8_ybean yields over the US corn belt to changes in temperature, precipitation, wind and atmospheric CO2 concentration. A sta8`tistically representative sample of 100 corn and soybean production sites was selected from the 1987 National Resources In8aventory (NRI). One-hundred-year simulations were run for each site under 36 different climate/CO2 scenarios. The results w8bere area weighted according to the NRI area expansion factor's to produce a regionally aggregated estimate of yields. EPIC8c did an excellent job of reproducing current regional mean expected yields under the baseline scenario. There were 3% decr8deases in both corn and soybean yields in response to a 2 degrees C temperature increase at baseline precipitation levels, 8ewith larger and smaller temperature effects under drier and wetter conditions, respectively. Crop yields increased and dec8freased in response to increases and decreases of 10% or 20% precipitation. A 10% precipitation increase roughly balanced t8ghe negative effect of the 2 degrees C temperature increase. Whether the precipitation changes resulted from altered precip8hitation event frequency or amount per event had little effect on mean crop yields; however interannual yield variability w8ias higher when precipitation decreases were due to frequency rather than intensity. The opposite was true, though to a les8jser extent, far precipitation increases. Potential evapotranspiration responded linearly to changes in mean wind speed, le8kading to modest changes of 1-3 days of water stress per growing season, yield increases of up to 2% for decreased wind, an8ld yield decreases of up to 6% for increased wind. Elevated CO2 concentrations of 625 ppmv gave the greatest yield increase8ms, +17% for corn and +27% for soybean at baseline temperature and precipitation levels. The relative CO2 effect was larger under drier conditions. Copyright (C) 1996 Published by Elsevier Science LtdES\PRESENTATIONS\COMPA8o1071^5^Rosenzweig,C^Phillips,J^Goldberg,R^Carroll,J^Hodges,T^1996^1^Potential impacts of climate change on citrus and potato production in the US^223^52^4^455-479^^^^^Dec^^^^^4936ESENTATIONS\COMPANY MEETING (STA8qA^4935^Potential impacts of global climate change on fruit and vegetable yield in the US were investigated through simulat8rions of citrus and potato. Simulated treatments included combinations of three increased temperature regimes (+1.5, +2.5 a8snd +5.0 degrees C), and estimates of the impact of three levels of atmospheric carbon dioxide (440, 530, and 600 ppm) in a8tddition to control runs representing current climatic conditions. Adaptive planting dates of -28, -14, +14 and +28 days we8ure included in the potato simulations for current and increased temperature regimes. Twenty-two sites were simulated for c8vitrus yields and 12 sites for potato, using climate records from 1951 to 1980. Response surfaces were developed for all co8wmbinations of increased temperature and CO2. Results of citrus simulations without CO2-induced yield improvement indicate 8xthat production may shift slightly northward in the southern states, but yields may decline in southern Florida and Texas 8ydue to excessive heat during the winter. CO2 effects tended to counteract the decline in simulated citrus yields. Fall pot8zato production under current management practices appears vulnerable to an increase in temperature in the northern states;8{ increased CO2 and changes in planting date were estimated to have minimal compensating impacts on simulated potato yields.D).POTGeneralPROGRAM FILES\MICROSOFT OFFICE\TEMPLAT8}1072^5^Ross,DJ^Saggar,S^Tate,KR^Feltham,CW^Newton,PCD^1996^1^Elevated CO2 effects on carbon and nitrogen cycling in grass/clover turves of a Psammaquent soil^206^182^2^185-198^^^^^May^^^^^4938ATIONS\GENERIC (ONLINE).P8A^4937^Effects of elevated CO2 (525 and 700 mu L L(-1)), and a control (350 mu L L(-1) CO2), on biochemical properties of 8a Mollic Psammaquent soil in a well-established pasture of C3 and C4 grasses and clover were investigated with continuousl8y moist turves in growth chambers over four consecutive seasonal temperature regimes from spring to winter inclusive. Afte8r a further 'spring' period, half of the turves under 350 and 700 mu L L(-1) were subjected to 'summer' drying and were th8en re- wetted before a further 'autumn' period; the remaining turves were kept continuously moist throughout these additio8nal three consecutive 'seasons'. The continuously moist turves were then pulse-labelled with C-14-CO2 to follow C pathways8 in the plant/soil system during 35 days. Growth rates of herbage during the first four 'seasons' averaged 4.6 g m(-2) day8(-1) under 700 mu L L(-1) CO2 and were about 10% higher than under the other two treatments. Below-ground net productivity8 at the end of these 'seasons' averaged 465, 800 and 824 g m(-2) in the control, 525 and 700 mu L L(-1) treatments, respec8tively. In continuously moist soil, elevated CO2 had no overall effects on total, extractable or microbial C and N, or inv8ertase activity, but resulted in increased CO2-C production from soil, and from added herbage during the initial stages of8 decomposition over 21 days; rates of root decomposition were unaffected. CO2 produced h(-1) mg(-1) microbial C was about 810% higher in the 700 mu L L(-1) CO2 treatment than in the other two treatments. Elevated CO2 had no clearly defined effec8ts on N availability, or on the net N mineralization of added herbage. In the labelling experiment, relatively more C-14 i8n the plant/soil system occurred below ground under elevated CO2, with enhanced turnover of C-14 also being suggested. Dry8ing increased levels of extractable C and organic-N, but decreased mineral-N concentrations; it had no effect on microbial8 C, but resulted in lowered microbial N in the control only. In soil that had been previously 'summer'-dried, CO2 producti8on was again higher, but net N mineralization was lower, under elevated CO2 than in the control after 'autumn' pasture gro8wth. Over the trial period of 422 days, elevated CO2 generally appears to have had a greater effect on soil C turnover than on soil C pools in this pasture ecosystem.ROSOFT OFFICE\TEMPLATES\PRESENTATION D81073^5^Rudorff,BFT^Mulchi,CL^Fenny,P^Lee,EH^Rowland,R^1996^1^Wheat grain quality under enhanced tropospheric CO2 and O-3 concentrations^204^25^6^1384-1388^^^^^Nov-Dec^^^^^4940TIONS\FLYER (ONLINE).POT2Micro8A^4939^It is expected that the progressive increase of tropospheric trace gases such as CO2 and O-3 will have a significan8t impact on agricultural production. The single and combined effects of CO2 enrichment and tropospheric O-3 on grain quali8ty characteristics in soft red winter wheat (Triticum aestivum L.) were examined in held studies using 3 m in diam. open-t8op chambers. Wheat cultivars 'Massey' (1991) and 'Saluda' (1992) were exposed to two CO2 concentrations (350 vs. 590 mu mo8l CO2 mol(-1); 12 h d(-1)) in combination with two O-3 regimes (charcoal-filtered air vs. ambient air + 40 +/- 20 nmol O-38 mol(-1), 7 h d(-1) Monday to Friday) from late March until maturity in June. Grain quality characteristics investigated i8ncluded: test weight, milling and baking quality, flour yield, protein content, softness equivalent, alkaline water retent8ion capacity, and cookie diameter. In general, exposure of plants to either elevated CO2 or weekly chronic O-3 episodes ca8used only small changes in grain quality. Milling and baking quality score were not significantly changed in response to t8reatments in both years. Flour yield was increased by elevated CO2 but this increase was counteracted when elevated CO2 wa8s combined with chronic O-3 exposure. Flour protein contents were increased by enhanced O-3 exposure and reduced by elevat8ed CO2. Softness equivalent was increased by 2.4% by enhanced O-3 exposure but unaffected by O-3 under elevated CO2. Altho8ugh the single effect of either CO2 enrichment or chronic O-3 exposure had some impact on grain quality characteristic, it8 was noted that the combined effect of these gases was minor. It is Likely that the concomitant increase of CO2 and O-3 in the troposphere will have no significant impact on wheat grain quality.PROGRAM FILES\MICROSOFT 81074^3^Ruget,F^Bethenod,O^Combe,L^1996^1^Repercussions of increased atmospheric CO2 on maize morphogenesis and growth for various temperature and radiation levels^284^41^3^181-191^^^^^^^^^^4942E\TEMPLATES\PRESENTATIONS8A^4941^The effect of atmospheric CO2 enhancement on maize production was studied through four crops in two glasshouse comp8artments, with and without CO2 enrichment. Development (number of organs, duration of phenological phases) was measured du8ring cultivation and growth (dry matter production) was measured at flowering and at final harvest. The main results were 8as follows: The number of initiated organs (florets and leaves) was not affected by the CO2 enrichment. According to the r8uns, aerial and whole plant production were significantly or not increased in the enriched compartment. The production inc8rease was significantly different bem een treatments under poor radiation or high plant demand conditions. The balance bet8ween supply and demand enabled or not the effect of CO2 enhancement to be expressed. Among the four crops, the light conve8rsion efficiency was significantly modified by CO2 enrichment only in one run. The dry matter increase was not equally par8titioned between the organs. It was higher in stem, husks and cob than in leaves and grains. These organs have a morphogen8etically limited size (through the number of grains). This controlled the expression of the effect of CO2 enhancement in t8hese runs and explained why the conversion efficiency only increased in one run, which was not morphogenetically limited. 8These crops proved the interactions between CO2 concentration and the other main climatic factors (temperature and radiation) and the need to know the morphogenesis in order to be able to estimate the effects of CO2 enrichment correctly.FIC81075^3^Salt,DT^Fenwick,P^Whittaker,JB^1996^1^Interspecific herbivore interactions in a high CO2 environment: Root and shoot aphids feeding on Cardamine^15^77^2^326-330^^^^^Nov^^^^^4944\TEMPLATES\PRESENTATIONS\COMP8A^4943^This study investigated the effects of elevated CO2 on populations of root and/or shoot aphids and their effects on8 partitioning in Cardamine pratensis. Total plant biomass in elevated (approximate to 600 ppm) CO2 of uninfested Cardamine8 plants was 52% higher than in ambient (approximate to 350 ppm) concentrations but CO2 effects were not statistically sign8ificant. In elevated CO2, feeding by shoot aphids (Aphis fabae fabae) alone and in combination with root aphids (Pemphigus8 populitransversus), and root aphids alone had no significant effect on plant biomass. No significant effects of elevated 8CO2 were detected on population size of the shoot or root-feeding species. Interspecific effects were detected between the8 root and shoot species. Root aphid populations were significantly smaller in the presence of shoot aphids on the same pla8nts. In this system plant growth was unaffected by an elevated CO2 environment. Plant species which are more sensitive to elevated CO2 may show a modified response to herbivore pressure in a future atmospheric environment.-screen Sh81076^6^Thomas,SM^Whitehead,D^Adams,JA^Reid,JB^Sherlock,RR^Leckie,AC^1996^1^Seasonal root distribution and soil surface car8bon fluxes for one-year-old Pinus radiata trees growing at ambient and elevated carbon dioxide concentration^13^16^11-12^1015-1021^^^^^Nov-Dec^^^^^4946EMPLATES\PRESENTATION DESIGNS\WHIRLPOOL.POT8A^4945^The increase in number of fine (< 0.5 mm diameter) roots of one-year-old clonal Pinus radiata D. Don trees grown in8 large open-top field chambers at ambient (362 mu mol mol(-1)) or elevated (654 mu mol mol(-1)) CO2 concentration was esti8mated using minirhizotron tubes placed horizontally at a depth of 0.3 m. The trees were well supplied with water and nutri8ents. Destructive harvesting of roots along an additional tube showed that there was a linear relationship between root nu8mber estimated from the minirhizotron and both root length density, L(v), and root carbon density, C-v, in the surrounding8 soil. Root distribution decreased with horizontal distance from the tree. At a depth of 0.3 m, 88% of the total C-v was c8oncentrated within a 0.15-m radius from tree stems in the elevated CO2 treatment, compared with 35% for trees in the ambie8nt CO2 treatment. Mean C-v along the tubes ranged up to 5 x 10(-2) mu g mm(-3) and tended to be greater for trees grown at8 elevated CO2 concentration, although the differences between CO2 treatments were not significant. Root growth started in 8spring and continued until late summer. There was no significant difference in seasonal rates of increase in C-v between t8reatments, but roots were observed four weeks earlier in the elevated CO2 treatment. No root turnover occurred at a depth 8of 0.3 m during the first year after planting. Mean values of carbon dioxide flux density at the soil surface, F, increase8d from 0.02 to 0.13 g m(-2) h(-1) during the year, and F was 30% greater for trees grown at elevated CO2 concentration tha8n at ambient CO2. Diurnal changes in F were related to air temperature. The seasonal increase in F continued through the s8ummer and early autumn, well after air temperature had begun to decline, suggesting that the increase was partly caused by increase in C-v as the roots colonized the soil profile.C (ONLINE).POTPROGRA81077^5^Tingey,DT^Johnson,MG^Phillips,DL^Johnson,DW^Ball,JT^1996^1^Effects of elevated CO2 and nitrogen on the synchrony of shoot and root growth in ponderosa pine^13^16^11-12^905-914^^^^^Nov-Dec^^^^^4948ICE\TEMPLATES\PRESEN8A^4947^We monitored effects of elevated CO2 and N fertilization on shoot and fine root growth of Pinus ponderosa Dougl. ex8 P. Laws. and C. Laws. grown in native soil in open-top field- exposure chambers at Placerville, CA, over a 2-year period.8 The experimental design was a replicated 3 x 3 factorial with the center treatment missing; plants were exposed to ambien8t (similar to 365 mu mol mol(-1)) air or ambient air plus either 175 or 350 mu mol mol(-1) CO2 in combination with one of 8three rates of N addition (0, 100 or 200 kg ha(-1) year(-1)). All CO2 by N interactions were nonsignificant. Both the CO2 8and N treatments increased plant height, stem diameter and leaf area index (LAI). Elevated CO2 increased fine root area de8nsity and the occurrence of mycorrhizae, whereas N fertilization increased coarse root area density but had no effect on f8ine root area density. Spring flushes of shoot height and diameter growth were initiated concurrently with the increase in8 new root area density but height and diameter growth reached their maxima before that of fine roots. The temporal pattern8s of root and shoot growth were not altered by providing additional CO2 or N. Greatest root loss occurred in the summer, i8mmediately following the period of greatest new fine root growth. Elevated N initially reduced the fine root area density/8LAI ratio independently of CO2 treatment, indicating that the relationship between fine roots and needles was not changed by CO2 exposure.Y.POTPROGRAM FILES\MICROSOFT OFFICE\TEMP81078^4^Veisz,O^Harnos,N^Szunics,L^Tischner,T^1996^1^Overwintering of winter cereals in Hungary in the case of global warming^181^92^1-2^249-253^^^^^^^^^^4950TES\PRESENTATIONS\FACILITATING A MEETING - 8A^4949^Under phytotronic conditions investigations were made on the effect of important environmental factors, such as tem8perature, water and an increasing concentration of atmospheric CO2, on the hardening of young cereal plants. In all the va8rieties derived from the major wheat growing regions of the world the hardening process was favourably influenced by a dou8bling of atmospheric CO2 content, so that a significantly larger number of plants survived the frost test than for plants 8of the same variety raised under normal conditions. A reduction in freezing temperature and an increase in soil moisture c8ontent caused a slight reduction in survival % for varieties with excellent frost resistance and a great reduction for tho8se with medium or poor frost resistance. Predictions suggest that in Central Europe, as the result of global climatic chan8ges, there will be a reduction in the quantity of winter precipitation, a considerable rise in winter temperatures and an 8increase in atmospheric CO2 concentration. Judging by the experimental results, these changes could improve the overwinter8ing of winter cereals; at the same time, however, a number of factors (mainly the reduction of precipitation) leading to yield losses must be expected during the vegetation period.TATIONS\FLYER (ONLINE).POT81079^3^Watada,AE^Ko,NP^Minott,DA^1996^1^Factors affecting quality of fresh-cut horticultural products^259^9^2^115-125^^^^^Nov^^^^^4952E).POTPROGRAM FILES\MICROSOFT OFFICE\TEMPL8A^4951^Fresh-cut products, also known as lightly or minimally processed products, are highly perishable because a large pr8oportion of their surface area is without epidermis, the outer protective layer of tissue. Temperature, atmosphere, relati8ve humidity and sanitation must be regulated to maintain quality of fresh-cuts. In the 0-10 degrees C range, Q(10) of resp8iration rates ranged from 2.0 to 8.6 among various fresh- cut fruits and vegetables. Low Oz and elevated CO2 atmosphere re8duced the respiration rate; however, the respiratory quotient approached 3.0 with some fresh-cuts. Film bags or coatings a8re necessary to maintain high relative humidity. Microorganisms were present in chlorine-washed spinach, and populations i8ncreased during storage. Stress from the physical action of processing and low O-2 atmosphere affects physiology and bioch8emistry of the fresh-cuts, which can affect quality and shelf-life. Research in all of these areas is needed to ensure that wholesome, high-quality fresh-cut products are marketed to consumers.ILES\MICROSOFT OFFICE\TEM81080^7^Andriolo,JL^LeBot,J^Gary,C^Sappe,G^Orlando,P^Brunel,B^Sarrouy,C^1996^1^An experimental set-up to study carbon, water and nitrate uptake rates by hydroponically grown plants^166^19^10-11^1441-1462^^^^^^^^^^4954S\PRESENTATIO8A^4953^The experimental system described allows concomitant hourly measurements of CO2, H2O, and NO3 uptake rates by plant8s grown hydroponically in a greenhouse. Plants are enclosed in an airtight chamber through which air flows at a controlled8 speed. Carbon dioxide exchange and transpiration rates are determined from respective differences of concentrations of CO82 and water vapor of the air at the system inlet and outlet. This set-up is based on the ''open-system'' principle with im8provements made on existing systems. For instance, propeller anemometers are used to monitor air flow rates in the chamber8. From their signal it is possible to continuously adjust air speed to changing environmental conditions and plant activit9y. The air temperature inside the system therefore never rises above that outside. Water and NO3 uptake rates are calculat9ed at time intervals from changes in the volume and the NO3 concentration of the nutrient solution in contact with the roo9ts. The precise measurement of the volume of solution is achieved using a balance which has a higher precision than any li9quid level sensors. Nitrate concentration is determined in the laboratory from aliquots of solution sampled at time interv9als. A number of test runs are reported which validate the measurements and confirm undisturbed conditions within the system. Results of typical diurnal changes in CO2, H2O, and NO3 uptake rates by fruiting tomato plants are also presented.R91081^1^Beerling,DJ^1996^1^C-13 discrimination by fossil leaves during the late-glacial climate oscillation 12-10 ka BP: Measurements and physiological controls^2^108^1^29-37^^^^^Oct^^^^^4956 FILES\MICROSOFT OFFICE\TE9A^4955^The late-glacial climatic oscillation, 12-10 ka BP, is characterised in ice core oxygen isotope profiles by a rapid9 and abrupt return to glacial climate. Recent work has shown that associated with this cooling was a drop in atmospheric C9 O2 concentration of ca. 50 ppm. In this paper, the impact of these environmental changes on C-13 discrimination is reporte9 d, based on measurements made on a continuous sequence of fossil Salix herbacea leaves from a single site. The plant respo9 nses were interpreted using an integrated model of stomatal conductance, CO2 assimilation and intercellular CO2 concentrat9 ion, influenced by external environmental factors. According to the model, temperature exerts a marked influence on C-13 d9iscrimination by leaves and the pattern of C-13 changes recorded by the fossil leaves is consistent with other palaeotempe9rature curves for 12-10 ka BP, particularly the deuterium isotope record from Alaskan Salix woods, which generally reflect9s ocean temperatures. The gas exchange model correctly accounts for these changes and so permits the reconstruction of anc9ient rates of leaf CO2 uptake and loss of water vapour in response to the abrupt late-glacial changes in global climate an9d CO2. The approach provides the required physiological underpinning for extracting quantitative estimates of past temperatures and for contributing an ecophysiological explanation for changes in C-13 discrimination in the fossil record.S\P91082^2^Bertoni,GP^Becker,WM^1996^1^Expression of the cucumber hydroxypyruvate reductase gene is down-regulated by elevated CO2^8^112^2^599-605^^^^^Oct^^^^^4958MPLATES\PRESENTATIONS\CORPORATE HOME PAGE 9A^4957^We examined the effects of CO2 concentration on the white- light-stimulated expression of the cucumber (Cucumis sat9ivus L.) Hpr gene. Hpr encodes hydroxypyruvate reductase, an enzyme important in the photorespiratory glycolate pathway, w9hich plays an integral role in carbon allocation in C-3 plants. Because CO2 is an end product of this pathway and because 9increased CO2 concentrations lessen the need for photorespiration, we tested whether exposure of plants to elevated CO2 wo9uld affect white-light-stimulated Hpr gene expression. Exposure of dark-adapted cucumber seedlings to elevated CO2 (2 to 39 times ambient) during a 4-h white-light irradiation significantly inhibited the accumulation of Hpr mRNA. Increasing the 9CO2 concentration during irradiation to 6 or 9 times ambient did not further inhibit Hpr mRNA accumulation. The depressing9 effect of high CO2 on Hpr mRNA accumulation was seen in both high and low light, but was more pronounced in higher light.9 These results suggest that maximum sensitivity to CO2 occurs in conditions near those normally encountered by the plant (9high light, CO2 concentration near ambient) and support a model in which white-light-regulated Hpr expression is modulated in part by environmental CO2 concentration.NE).POT @PROGRAM FILES\MICRO9!1083^5^Biswas,PK^Hileman,DR^Ghosh,PP^Bhattacharya,NC^McCrimmon,JN^1996^1^Growth and yield responses of field-grown sweetpotato to elevated carbon dioxide^164^36^5^1234-1239^^^^^Sep-Oct^^^^^4960LATES\PRESENTATIONS\GENER9#A^4959^Root crops are important in developing countries, where food supplies are frequently marginal. Increases in atmosph9$eric CO2 usually lead to increases in plant growth and yield, but little is known about the response of root crops to CO2 9%enrichment under field conditions, This experiment was conducted to investigate the effects of CO2 enrichment on growth an9&d yield of field-grown sweetpotato [Ipomoea batatas (L.) Lam.]. Plants were grown in open-top chambers in the field at fou9'r CO2 levels ranging from 354 (ambient) to 665 mu mol mol(-1) in two growing seasons, Shoot growth was not affected signif9(icantly by elevated CO2. Yield of storage roots increased 46 and 75% at the highest CO2 level in the 2 yr, The yield enhan9)cement occurred through increases in the number of storage roots in the first year and through increases in both the numbe9*r and size of the storage roots in the second year, Storage- root/shoot ratios increased 44% and leaf nitrogen concentrati9+ons decreased by 24% at the highest CO2 level, A comparison of plants grown in the open field to plants grown in open-top 9,chambers at ambient CO2 concentrations indicated that open-top chambers reduced shoot growth in the first year and storage9--root yield in both years, These results are consistent with the majority of CO2-enrichment studies done on pot-grown sweetpotato.TE FINANCIAL OVERVIEW (STANDARD).POT(@PROGRAM 9/1084^3^Casella,E^Soussana,JF^Loiseau,P^1996^1^Long-term effects of CO2 enrichment and temperature increase on a temperate grass sward .1. Productivity and water use^206^182^1^83-99^^^^^May^^^^^4962ES\MICROSOFT OFFICE\TEM91A^4961^Perennial ryegrass swards were grown in large containers on a soil, at two N fertilizer supplies, and were exposed 92over two years in highly ventilated plastic tunnels to elevated (700 mu L L(-1) [CO2]) or ambient atmospheric CO2 concentr93ation at outdoor temperature and to a 3 degrees C increase in air temperature in elevated CO2. These swards were either fu94lly irrigated (kept at field capacity) in each climatic condition (W+), or received the same amount of water in the three 95climate treatments (W-). In the latter case, the irrigation was adjusted to obtain a soil water deficit during summer and 96drainage in winter. Using a lysimeter approach, the evapotranspiration, the soil water balance, the productivity (dry-matt97er yield) and the water use efficiency of the grass swards were measured. During both years, elevated CO2 increased the an98nual above-ground drymatter yield of the W-swards, by 19% at N- and by 14% at N+. Elevated CO2 modified yield to a variabl99e extent during the growing season: a small, and sometime not significant effect (+6%, on average) was obtained in spring 9:and in autumn, while the summer growth response was stronger (+48%, on average). In elevated CO2, the temperature increase9; effect on the annual above-ground dry-matter yield was not significant, due to a gain in dry-matter yield in spring and i9 drainage by 29-34%, whereas the evapotranspiration was increased by 8 and 63% during the growing season and in winter, re9?spectively. During the growing season, the soil moisture content at W- and at the high N supply declined gradually in the 9@control climate, down to 20- 30% of the water holding capacity at the last cut (September) before rewatering. This decline9A was partly alleviated under elevated CO2 in 1993, but not in 1994, and was enhanced at +3 degrees C in elevated CO2. The 9Bwater use efficiency of the grass sward increased in elevated CO2, on average, by 17 to 30% with no significant interactio9Cn with N supply or with the soil water deficit. The temperature increase effect on the annual mean of the water use effici9Dency was not significant. Highly significant multiple regression models show that elevated CO2 effect on the dry-matter yi9Eeld increased with air temperatures above 14.5 degrees C and was promoted by a larger soil moisture in elevated compared t9Fo ambient CO2. The rate of change in relative dry-matter yield at +3 degrees C in elevated CO2 became negative for air tem9Gperatures above 18.5 degrees C and was reduced by a lower soil moisture at the increased air temperature. Therefore, the a9Hltered climatic conditions acted both directly on the productivity and on the water use of the grass swards and, indirectly, through changes in the soil moisture content.NLINE).POT`b@PROGRAM FILES\9J1085^3^Devakumar,AS^Udayakumar,M^Prasad,TG^1996^1^A simple technique to expose tree seedlings to elevated CO2 for increased initial growth rates^285^71^6^469-472^^^^^25 Sep^^^^^4964GRAM FILES\MICROSOFT OFFICE\TEM9LA^4963^Initial growth rates of most tree species that are used in afforestation programmes are very low. Therefore, polyba9Mg planted seedlings have to be maintained in the nurseries for a long period of time. Growing plants in an elevated CO2 at9Nmosphere increases the growth rates as well as biomass production in many annual crop and tree species. Higher temperature9O and relative humidity in association with elevated CO2 concentration helps to boost the biomass and leaf area production.9P We demonstrate here an easy and cost-effective method for obtaining elevated CO2 concentrations for better growth of tree seedlings in the nursery. - DALE CARNEGIE TRAINING (R).POTs@PR9R1086^4^Ferris,R^Nijs,I^Behaeghe,T^Impens,I^1996^1^Elevated CO2 and temperature have different effects on leaf anatomy of perennial ryegrass in spring and summer^52^78^4^489-497^^^^^Oct^^^^^4966LES\MICROSOFT OFFICE\TEMP9TA^4965^Mature second leaves of Lolium perenne L. cv. Vigor, were sampled in a spring and summer regrowth period. Effects o9Uf CO2 enrichment and increased air temperature on stomatal density, stomatal index, guard cell length, epidermal cell dens9Vity, epidermal cell length and mesophyll cell area were examined for different positions on the leaf and seasons of growth9W. Leaf stomatal density was smaller in spring but greater in summer in elevated CO2 and higher in both seasons in elevated9X temperature and in elevated CO2 x temperature relative to the respective controls. In spring, leaf stomatal index was red9Yuced in elevated CO2 but in summer it varied with position on the leaf. In elevated temperature, stomatal index in both se9Zasons was lower at the tip/middle of the leaf but slightly higher at the base. In elevated CO2 x temperature, stomatal ind9[ex varied with position on the leaf and between seasons. Leaf epidermal cell density was higher in all treatments relative9\ to controls except in elevated CO2 (spring) and elevated CO2 x temperature (summer), it was reduced at the leaf base. In 9]all treatments, stomatal density and epidermal cell density declined from leaf tip to base, whilst guard cell length showe9^d an inverse relationship, increasing towards the base. Leaf epidermal cell length and mesophyll cell area increased in el9_evated CO2 in spring and decreased in summer. In elevated CO2 x temperature leaf epidermal cell length remained unaltered 9`in spring compared to the control but decreased in summer. Stomatal conductance was lower in all treatments except in summ9aer in elevated CO2 it was higher than in the ambient CO2. These contrasting responses in anatomy to elevated CO2 and tempe9brature provide information that might account. for differences in seasonal leaf area development observed in L. perenne under the same conditions. (C) 1996 Annals of Botany Company.&@6Х 483Ѓ92Х30ҿ91eW9d1087^3^Gebauer,RLE^Reynolds,JF^Strain,BR^1996^1^Allometric relations and growth in Pinus taeda: The effect of elevated CO2 and changing N availability^84^134^1^85-93^^^^^Sep^^^^^4968JO@0Ѓ 4Х2Х 662561Ή 8710899fA^4967^Loblolly pine (Pinus taeda L.) seedlings were grown for 138 d at two CO2 partial pressures (35 and 70 Pa CO2) and f9gour N solution concentrations (0.5, 1.5, 3.5 and 6.5 mM NH4NO3). Allometric regression analysis was used to determine whet9hher patterns of biomass allocation among functionally distinct plant-parts were directly controlled by CO2 and N availabil9iity or whether differences between treatments were the result of size-dependent changes in allocation. Both CO2 and N avai9jlability affected growth of loblolly pine. Growth stimulation by CO2 at nonlimiting N solution concentrations (3.5 and 6.59k mM NH4NO3) was c. 90%. At the lowest N solution concentration (0.5 mM NH4NO3), total plant biomass was still enhanced by 9l35% under elevated CO2. Relative growth rates were highly correlated with net assimilation rates, whereas leaf mass ratio 9mremained unchanged under the wide range of CO2 and N solution concentrations. When differences in plant size were adjusted9n apparent CO2 effects on biomass allocation among different plant parts disappeared, indicating that CO2 only indirectly a9offected allocation through accelerated growth. N availability, by contrast, had a direct effect on biomass allocation, but9p primarily at the lowest N solution concentration (0.5 mM NH4NO3). Loblolly pine compensated for N limitation by increasin9qg specific lateral root length and proportional biomass allocation to the lateral root system. The results emphasize the s9rignificance of distinguishing size- dependent effects on biomass allocation from functional adjustments made in direct response to changing resource availability.Ѓ8π4138Ѓ 88832P9Ѓ1Ѓ 659007GMi59t1088^7^Griffin,KL^Ross,PD^Sims,DA^Luo,Y^Seemann,JR^Fox,CA^Ball,JT^1996^1^EcoCELLs: Tools for mesocosm scale measurements of gas exchange^9^19^10^1210-1221^^^^^Oct^^^^^49704538624P52Х 25984GMi5@ 5Ѓ 283199vA^4969^We describe the use of a unique plant growth facility, which has as its centerpiece four 'EcoCELLs', or 5x7 m mesoc9wosms designed as open-flow, mass-balance systems for the measurement of carbon, water and trace gas fluxes. This system is9x unique in that it was conceived specifically to bridge the gap between measurement scales during long-term experiments ex9yamining the function and development of model ecosystems. There are several advantages to using EcoCELLs, including (i) th9ze same theory of operation as leaf level gas exchange systems, but with continuous operation at a much larger scale; (ii) 9{the ability to independently evaluate canopy-level and ecosystem models; (iii) simultaneous manipulation of environmental 9|factors and measurement of system-level responses, and (iv) maximum access to, and manipulation of, a large rooting volume9}. In addition to discussing the theory, construction and relative merits of EcoCELLs, we describe the calibration and use 9~of the EcoCELLs during a 'proof of concept' experiment, This experiment involved growing soybeans under two ambient CO2 co9ncentrations (similar to 360 and 710 mu mol mol(-1)). During this experiment, we asked 'How accurate is the simplest model9 that can be used to scale from leaf-level to canopy-level responses?' in order to illustrate the utility of the EcoCELLs in validating canopy-scale models.3ӷxj 515ο216Ѓ3267Ѓ515ο888ο933Ѓ91089^4^Hirose,T^Ackerly,DD^Traw,MB^Bazzaz,FA^1996^1^Effects of CO2 elevation on canopy development in the stands of two co-occurring annuals^2^108^2^215-223^^^^^Oct^^^^^49726719ӷxj5ӥW 882Ѓ9ο6҈072Ѓ489A^4971^Elevated CO2 may increase dry mass production of canopies directly through increasing net assimilation rate of leav9es and also indirectly through increasing leaf area index (LAI). We studied the effects of CO2 elevation on canopy product9ivity and development in monospecific and mixed (1:1) stands of two co- occurring C-3 annual species, Abutilon theophrasti9 and Ambrosia artemisiifolia. The stands were established in the glasshouse with two CO2 levels (360 and 700 mu l/l) under9 natural light conditions. The planting density was 100 per m(2) and LAI increased up to 2.6 in 53 days of growth. Root co9mpetition was excluded by growing each plant in an individual pot. However, interference was apparent in the amount of pho9tons absorbed by the plants and in photon absorption per unit leaf area. Greater photon absorption by Abutilon in the mixe9d stand was due to different canopy structures: Abutilon distributed leaves in the upper layers in the canopy while Ambros9ia distributed leaves more to the lower layers. CO2 elevation did not affect the relative performance and light intercepti9on of the two species in mixed stands. Total aboveground dry mass was significantly increased with CO2 elevation, while no9 significant effects on leaf area development were observed. CO2 elevation increased dry mass production by 30-50%, which 9was mediated by 35-38% increase in the net assimilation rate (NAR) and 37-60% increase in the nitrogen use efficiency (NUE9, net assimilation rate per unit leaf nitrogen). Since there was a strong overall correlation between LAI and aboveground 9nitrogen and no significant difference was found in the regression of LAI against aboveground nitrogen between the two CO29 levels, we hypothesized that leaf area development was controlled by the amount of nitrogen taken up from the soil. This 9hypothesis suggests that the increased LAI with CO2 elevation observed by several authors might be due to increased uptake of nitrogen with increased root growth.24Х72Ѓ 512P9ӑCMD.&@HБNqTH91090^3^Klironomos,JN^Rillig,MC^Allen,MF^1996^1^Below-ground microbial and microfaunal responses to Artemisia tridentata grown under elevated atmospheric CO2^43^10^4^527-534^^^^^Aug^^^^^49741A`8Ѓ2俞P56Х7264819A^4973^1. Soil microbes are fed primarily by root-derived substrates, fulfil functions such as mineralization, immobilizat9ion, decomposition, pathogeneity and improvement of plant nutrition, and form the basis of the below-ground food web. Hith9erto, belowground processes have generally been monitored using a 'black-box' approach, thereby ignoring effects of global9 change at a finer level of resolution. We describe shifts in the activity between microbial functional groups associated 9with roots of Artemisia tridentata, and the influence of this change on higher trophic levels, 2. We tested the hypothesis9 that elevated atmospheric CO2 causes the soil community to change qualitatively. We measured the responses of several soi9l microbe and soil microfaunal parameters to a double-ambient CO2 concentration and nutrient additions. The soil community9, as measured by those parameters, showed great changes in response to the treatments. There was a very strong interaction9 between elevated CO2 and the nutrient addition. 3. Under low nutrient conditions, total microbial biomass did not change 9under elevated atmospheric CO2, but doubled under conditions of elevated CO2 and added nutrients. As we increased the reso9lution of our analysis, however, results shifted. Under low nutrient conditions, mycorrhizal fungi responded positively to9 elevated CO2, whereas with added soil nutrients they responded negatively to the same elevated CO2 concentration. Bacteri9a and non-mycorrhizal fungi did not respond under the former conditions but more than doubled in biomass under conditions 9of elevated CO2 and added nutrients. Soil fauna was also affected by the treatments. Overall, elevated CO2 shifted carbon 9flow in the plant-soil system to a more mutualistic-closed, mycorrhizal-dominated system, whereas the combination of eleva9ted CO2 and nutrient addition shifted carbon flow to a more opportunistic-open, saprobe/pathogen-dominated one. 4. This in9dicates that elevated atmospheric CO2 may lead to far less predictable feedback patterns than previously thought and that qualitative shifts in the soil community may be far more important than mere changes in total C sink strength.EЊ9591091^4^Knapp,AK^Hamerlynck,EP^Ham,JM^Owensby,CE^1996^1^Responses in stomatal conductance to elevated CO2 in 12 grassland species that differ in growth form^24^125^1^31-41^^^^^Jul^^^^^497676GMi5@ 5244Ѓ964246Ѓ 729A^4975^Responses in stomatal conductance (g(st)) and leaf xylem pressure potential (psi(leaf)) to elevated CO2 (2x ambient9) were compared among 12 tallgrass prairie species that differed in growth form and growth rate. Open-top chambers (OTCs, 94.5 m diameter, 4.0 m in height) were used to expose plants to ambient and elevated CO2 concentrations from April through 9November in undisturbed tallgrass prairie in NE Kansas (USA). In June and August, psi(leaf) was usually higher in all spec9ies at elevated CO2 and was lowest in adjacent field plots (without OTCs). During June, when water availability was high, 9elevated CO2 resulted in decreased g(st) in 10 of the 12 species measured. Greatest decreases in g(st) (ca. 50%) occurred 9in growth forms with the highest potential growth rates (C-3 and C-4 grasses, and C-3 ruderals). In contrast, no significa9nt decrease in g(st) was measured in the two C-3 shrubs. During a dry period in September, reductions in g(st) at elevated9 CO2 were measured in only two species (a C-3 ruderal and a C-4 grass) whereas increased g(st) at elevated CO2 was measure9d in the shrubs and a C-3 forb. These increases in g(st) were attributed to enhanced psi(leaf) in the elevated CO2 plants 9resulting from increased soil water availability and/or greater root biomass. During a wet period in September, only reduc9tions in g(st) were measured in response to elevated CO2. Thus, there was significant interspecific variability in stomata9l responses to CO2 that may be related to growth form or growth rate and plant water relations. The effect of growth in th9e OTCs, relative to field plants, was usually positive for g(st) and was greatest (> 30%) when water availability was low,9 but only 6-12% when psi(leaf) was high. The results of this study confirm the importance of considering interactions betw9een indirect effects of high CO2 of plant water relations and direct effects of elevated CO2 on g(st), particularly in eco9systems such as grasslands where water availability often limits productivity. A product of this interaction is that the potential exists for either positive or negative responses in g(st) to be measured at elevated levels of CO2.000Ѓ91092^4^Luo,YQ^Jackson,RB^Field,CB^Mooney,HA^1996^1^Elevated CO2 increases belowground respiration in California grasslands^2^108^1^130-137^^^^^Oct^^^^^49785Ӄ+y 708ЃLGMi5@ MP6400Ѓ 722048GMi5@ 79A^4977^This study was designed to identify potential effects of elevated CO2 on belowground respiration (the sum of root a9nd heterotrophic respiration) in field and microcosm ecosystems and on the annual carbon budget. We made three sets of res9piration measurements in two CO2 treatments, i.e., (1) monthly in the sandstone grassland and in microcosms from November 91993 to June 1994; (2) at the annual peak of live biomass (March and April) in the serpentine and sandstone grasslands in 91993 and 1994; and (3) at peak biomass in the microcosms with monocultures of seven species in 1993. To help understand ec9osystem carbon cycling, we also made supplementary measurements of belowground respiration monthly in sandstone and serpen9tine grasslands located within 500 m of the CO2 experiment site. The seasonal average respiration rate in the sandstone gr9assland was 2.12 mu mol m(-2) s(-1) in elevated CO2, which was 32% higher than the 1.49 mu mol m(-2) s(-1) measured in amb9ient CO2 (P = 0.007). Studies of seven individual species in the microcosms indicated that respiration was positively corr9elated with plant biomass and increased, on average, by 70% with CO2. Monthly measurements revealed a strong seasonality i9n belowground respiration, being low (0-0.5 mu mol CO2 m(-2) s(-1) in the two grasslands adjacent to the CO2 site) in the 9summer dry season and high (2-4 mu mol CO2 m(- 1) s(-1) in the sandstone grassland and 2-7 mu mol CO2 m(-1) s(-1) in the m9icrocosms) during the growing season from the onset of fall rains in November to early spring in April and May. Estimated 9annual carbon effluxes from the soil were 323 and 440 g C m(-2) year(-1) for the sandstone grasslands in ambient and eleva9ted CO2. That CO2-stimulated increase in annual soil carbon efflux is more than twice as big as the increase in abovegroun9d net primary productivity (NPPa) and approximately 60% of NPPa in this grassland in the current CO2 environment. The resu9lts of this study suggest that below- ground respiration can dissipate most of the increase in photosynthesis stimulated by elevated CO2.7553Ѓ86Ѓ5Ө5@0267Ѓ 40Ѓ 392384P860Ѓ6Mq8 017291093^2^Majeau,N^Coleman,JR^1996^1^Effect of CO2 concentration on carbonic anhydrase and ribulose- 1,5-biphosphate carboxylase/oxygenase expression in pea^8^112^2^569-574^^^^^Oct^^^^^498056Х 66562Ѓ770Ѓ8000Ѓ19A^4979^The effect of external CO2 concentration on the expression of carbonic anhydrase (CA) and ribulose-1,5-bisphosphate9 carboxylase/oxygenase (Rubisco) was examined in pea (Pisum sativum cv Little Marvel) leaves. Enzyme activities and their 9transcript levels were reduced in plants grown at 1000 mu L/L CO2 compared with plants grown in ambient air. Growth at 1609 mu L/L CO2 also appeared to reduce steady-state transcript levels for rbcS, the gene encoding the small subunit of Rubisc9o, and for ca, the gene encoding CA; however, rbcS transcripts were reduced to a greater extent at this concentration. Rub9isco activity was slightly lower in plants grown at 160 mu L/L CO2, and CA activity was significantly higher than that obs9erved in air-grown plants. Transfer of plants from 1000 mu L/L to air levels of CO2 resulted in a rapid increase in both c9a and rbcS transcript abundance in fully expanded leaves, followed by an increase in enzyme activity. Plants transferred f9rom air to high-CO2 concentrations appeared to modulate transcript abundance and enzyme activity less quickly. Foliar carb9ohydrate levels were also examined in plants grown continuously at high and ambient CO2, and following changes in growth conditions that rapidly altered ca and rbcS transcript abundance and enzyme activities.7456ӷxj 488704G91094^2^McElwain,JC^Chaloner,WG^1996^1^The fossil cuticle as a skeletal record of environmental change^286^11^4^376-388^^^^^Aug^^^^^49826688GMi5@ 5҈ 393151Ә6҈1468Ѓ 241280ӷxj6Ѓ7)09A^4981^The plant cuticle with its stomatal pores represents an important interface between the plant and its surrounding e9nvironment. The potential of cuticular features such as cuticle thickness, stomatal density, stomatal index and stomatal r9atio to signal the environment in which they grew and developed have been reviewed. In particular new stomatal data from t9hree Yorkshire Middle Jurassic species, Brachyphyllum crucis Kendall, Brachyphyllum mamillare Lindley and Hutton and Ginkg9o huttonii (Sternberg) Heer, have been compared with those of two selected nearest living equivalent (NLE) species Athrota9xis cupressoides and Ginkgo biloba, in an attempt to deduce the atmospheric carbon dioxide concentration from that time, I9t appears that the development of a thick cuticle can represent an adaptation to more than one kind of environmental const9raint and evidently is a feature of certain taxonomic groups. It was concluded therefore that cuticle thickness, taken on 9its own was nor a suitable palaeo-ecological indicator In contrast however stomatal parameters of fossil plants seem to ha9ve great potential as palaeo-atmospheric indicators of carbon dioxide and in this sense as ''skeletal evidence of palaeo-e9cological change.'' The stomatal density and index results of the Jurassic species were significantly lower (P < 0.0001) t9han those of their selected NLE species, therefore indicating elevated atmospheric CO2 concentrations for the Middle Juras9sic. In addition the stomatal ratios of the Jurassic species were in agreement with those of previous Devonian and Carboni9ferous stomatal ratio results. These results are consistent with the evidence from carbon cycle modelling and carbon isoto9pic data which infer elevated atmospheric CO2 concentrations curing the Middle Jurassic of 4 to 5 times and 6 to 10 times the present atmospheric level respectively.5EЊ8Mq8038Ѓ 6Ѓ454Ѓ727Ѓ9҈045691095^5^Nijs,I^Teughels,H^Blum,H^Hendrey,G^Impens,I^1996^1^Simulation of climate change with infrared heaters reduces the productivity of Lolium perenne L in summer^173^36^3^271-280^^^^^Oct^^^^^498419P 343807GMi5@ 572Ѓ9A^4983^Field-grown perennial ryegrass was subjected to climate warming and elevated CO2 concentration during summer in fre9e air conditions (no enclosure of the vegetation). Increased foliage temperature (2.5 degrees C above fluctuating ambient)9 was induced by heating the stand with infrared radiation sources, modulated by an electronic control device (FATI, Free A9ir Temperature Increase). Enhanced CO2 was produced by a FACE system (Free Air CO2 Enrichment). Exposure to simulated clim9ate warming drastically reduced above-ground harvestable dry matter (52% loss). The nitrogen allocated to the leaf fractio9n was thus concentrated into less dry matter, which enhanced the nitrogen concentration on a mass basis (+17%) but also pe9r unit leaf area (+47%). As a consequence, CO, assimilation rates were not affected in these slower growing plants in the 9+2.5 degrees C treatment, and the photochemical efficiency of non-cyclic electron transport of photosystem II was also una9ffected. Although the plants were grown in the field without root restrictions, long-term exposure to elevated CO, concent9ration induced noticeable acclimation of the photosynthetic apparatus (40% loss of fixation potential), which largely outw9eighed the direct stimulation in this summer period. Part of the reduced rates could be attributed to lower N concentratio9n on a leaf area basis. The results are compared with responses of this species in sunlit conditioned greenhouses, which i9ndicates that experiments in enclosures may underestimate effects in the field. This also emphasizes the need to validate other plant responses to climate warming and CO2 enrichment in free air conditions.436Ѓ591Ѓ6395:1096^1^Nobel,PS^1996^1^Responses of some North American CAM plants to freezing temperatures and doubled CO2 concentrations: Implications of global climate change for extending cultivation^287^34^2^187-196^^^^^Oct^^^^^498691Ѓ6e:A^4985^Environmental influences on the cultivation of Crassulacean acid metabolism (CAM) plants, which are especially well: adapted to arid regions with limited rainfall, were evaluated with respect to two aspects of global climate change. Cellu:lar uptake of a vital stain, which occurs in living cells only, was halved at -6+/-1 degrees C for the cultivated CAM spec:ies Agave salmiana, Opuntia ficus indica and Stenocereus queretaroensis growing at day/night air temperatures of 30 degree:s C/20 degrees C compared with -12 degrees C for the wild species Opuntia humifusa. When plants were grown at reduced temp:eratures of 10 degrees C/0 degrees C, stain uptake was halved at about -8 degrees C for the cultivated species but at -24 :degrees C for O. humifusa. The greater low-temperature sensitivity and the lesser low-temperature acclimation of the culti: vated species severely limit the regions where they can presently be grown, but such regions will expand as air temperatur: es rise accompanying global climate change. When the atmospheric CO2 concentration was doubled from the current ambient va: lue of 360 mu mol mol(-1) to 7201 mu mol mol(-1), net CO2 uptake over 24-h periods increased 36% for A. salmiana and S. qu: eretaroensis; about one-third of the increase resulted from higher net CO2 uptake rates in the last 4 h of daytime and two: -thirds from higher rates during the first 8 h of the night. The doubled atmospheric CO, concentration predicted to occur :before the end of the twenty-first century will increase CO2 uptake and hence biomass productivity of such CAM species, further expanding the regions where they may be profitably cultivated. (C) 1996 Academic Press Limited.ӷxj7S#:1097^10^Penuelas,J^Estiarte,M^Kimball,BA^Idso,SB^Pinter,PJ^Wall,GW^Garcia,RL^Hansaker,DJ^LaMorte,RL^Hendrix,DL^1996^1^Variety of responses of plant phenolic concentration to CO2 enrichment^78^47^302^1463-1467^^^^^Sep^^^^^49880Ѓ92Х :A^4987^A wide range of responses to elevated CO2 was found for leaf total phenolic concentration of one grass species (whe:at) growing in a Free-Air CO2 Enrichment (FACE) system and two woody species (orange and pine trees) growing in Open-Top C:hambers (OTC). The total phenolic concentration of wheat flag leaves grown at elevated [CO2] was increased for most of the: grain-filling stages studied; there was no significant change in phenolic concentration of CO2-enriched orange tree leave:s and CO2-enriched pine tree needles had reduced total phenolic concentration. There was an inverse relationship between t:he increase in leaf total phenolic concentration and increase in biomass of these pine trees. Different rates of increase :in growth (carbon sink) produced by different environmental conditions or different resource availabilities apart from CO2 itself must be considered in order to understand the response of carbon-based-secondary-compounds to elevated CO2.87:1098^5^Polley,HW^Johnson,HB^Mayeux,HS^Tischler,CR^Brown,DA^1996^1^Carbon dioxide enrichment improves growth, water relations and survival of droughted honey mesquite (Prosopis glandulosa) seedlings^13^16^10^817-823^^^^^Oct^^^^^4990h 700:A^4989^Low water availability reduces the establishment of the invasive shrub Prosopis on some grasslands. Water deficit s:urvival and traits that may contribute to the postponement or tolerance of plant dehydration were measured on seedlings of: Fl glandulosa Torr. var. glandulosa (honey mesquite) grown at CO2 concentrations of 370 (ambient), 710, and 1050 mu mol m:ol(-1). Because elevated CO2 decreases stomatal conductance, the number of seedlings per container in the elevated CO2 tre: atments was increased to ensure that soil water content was depleted at similar rates in all treatments. Seedlings grown a:!t elevated CO2 had a greater root biomass and a higher ratio of lateral root to total root biomass than those grown at amb:"ient CO2 concentration; however, these seedlings also shed more leaves and retained smaller leaves. These changes, togethe:#r with a reduced transpiration/leaf area ratio at elevated CO2, may have contributed to a slight increase in xylem pressur:$e potentials of seedlings in the 1050 mu mol mol(-1) CO2 treatment during the first 37 days of growth (0.26 ro 0.40 MPa). :%Osmotic potential was not affected by CO2 treatment. Increasing the CO2 concentration to 710 and 1050 mu mol mol(-1) more :&than doubled the percentage survival of seedlings from which water was withheld for 65 days. Carbon dioxide enrichment sig:'nificantly increased survival from 0% to about 40% among seedlings that experienced the lowest soil water content. By incr:(easing seedling survival of drought, rising atmospheric CO2 concentration may increase abundance of P. glandulosa on grasslands where low water availability limits its establishment.ӷxj 984064GMi5@ 512Х 4699:*1099^5^Rudorff,BFT^Mulchi,CL^Lee,E^Rowland,R^Pausch,R^1996^1^Photosynthetic characteristics in wheat exposed to elevated O-3 and CO2^164^36^5^1247-1251^^^^^Sep-Oct^^^^^4992Ѓ3qO q4gected in increased predictions in the magnitude, variation, and range of the climate variables. Simulations used a 40 yr h:?istorical climate record, and 2 stand and site conditions to standardize the total NPP response estimates for eighteen 1x1:@ degrees grid cells across the southern United States, Contemporary NPP and NPP response estimates from the 18 cells were :Asmoothed using a cell search algorithm to obtain an NPP response index matrix for the entire loblolly pine (Pinus taeda) f:Borest-type. We conducted a sensitivity analysis of the environmental variables projected to change in a 2xCO(2) environmen:Ct to help interpret simulation output. Contemporary NPP varied from 2.5 to 8.5 Mg C ha(-1) yr(-1) over the range of loblol:Dly pine, High leaf area index (LAI) simulations had 1.5 to 2 times the productivity of low LAI simulations, but the region:Eal patterns were similar; NPP was correlated with regional differences in precipitation and temperature. The NPP response :Fto future climate and atmospheric changes depended on the GCM used, and on the stand and site condition assumed. Inter-ann:Gual estimates for the 18 cell simulations resulted in a +22 to +84% NPP response for the GFDL climate projections and a -3:H0 to +94% NPP response for the UKMO climate projections. The 40-year average NPP response for the smoothed data ranged fro:Im +43 to +65% and -1 to +94% for the GFDL and the UKMO climate projections, respectively. Consequently, the magnitude and :Jrange of the 40-year average NPP response to the climate projections was directly correlated with the GCM CO2 sensitivity.:K Although increased CO2 sensitivity resulted in broader extremes in the predicted temperature response, precipitation resp:Lonse for the 2 models was similar. The NPP response was also correlated with the patterns in predicted climate change, wit:Mh regional differences coupled to local climatic conditions. Climate projections from both models produced similar NPP res:Nponses when predicted temperatures and precipitation regimes were similar. Elevated ambient CO2 had a greater effect on NP:OP response than temperature or precipitation in the sensitivity comparisons. Simulations indicate that a CO2 fertilizer ef:Pfect, assuming no CO2 acclimation, more than compensates for declines in productivity over most of the loblolly pine fores:Qt-type associated with projected decreased precipitation and/or projected low to moderate increases in temperature and, therefore, increased maintenance respiration costs.ȷ969ԤA=%HFҕ0ΰLSνPBTJRTJνV:S1101^3^Schenk,U^Jager,HJ^Weigel,HJ^1996^1^Nitrogen supply determines responses of yield and biomass partitioning of perennial ryegrass to elevated atmospheric carbon dioxide concentrations^166^19^10-11^1423-1440^^^^^^^^^^4996TIONк:UA^4995^Perennial ryegrass (Lolium perenne L. cv. Parcour) grown at eight levels of nitrogen (N) fertilization (0-765 mg/po:Vt) was exposed to ambient (390 ppm) and elevated (690 ppm) carbon dioxide (CO2) concentrations for 83 days. Plants were cu:Wt three times and dry matter yields determined for each harvest. At final harvest, dry weight of root and stubble biomass :Xwas determined, as N concentrations of all plant fractions were determined. Carbon dioxide enrichment effects on yield and:Y total plant biomass increased with increasing N fertilization. The weaker CO2-related yield enhancement at low N supply w:Zas due to the plants inability to increase tiller number. Root fraction of total plant biomass at final harvest was increa:[sed by high CO2 and decreased by N supply. Root biomass was significantly increased by CO2 enrichment and for both CO2 tre:\atments the N supply for maximum root mass coincided with the N supply for reaching maximum total plant biomass. A signifi:]cant correlation between root fraction of total plant dry matter and N concentration of total plant biomass, which was not:^ changed by CO2 enrichment, indicates that biomass partitioning between shoot and root is controlled by the internal N status of the plant.1Ԥ27Ԥ31Ԥ56Ԥ61Ԥ95Ԥ446Ԥ66Ԥ73Ԥ5Ԥ506Ԥ1102^2^Smit,B^Cai,YL^1996^1^Climate change and agriculture in China^233^6^3^205-214^^^^^Jul^^^^^499863Ԥ8Ԥ9:aA^4997^The implications of climate change for agriculture and food are global concerns, and they are very important for Ch:bina, The country depends on an agricultural system which has evolved over thousands of years to intensively exploit enviro:cnmental conditions. The pressures on the resource base are accentuated by the prospect of climate change, This paper synth:desizes information from a variety of studies on Chinese agriculture and climate. Historical studies document the impacts o:ef past climate changes and extremes, and the types of adjustments which have occurred, the vulnerability of Chinese agricu:flture to climate change, Climate change scenarios are assessed relative to the current distribution of agro-climatic regio:gns and systems, Notwithstanding the enhancing effects of warming and elevated CO2 levels, expected moisture deficits and u:hncertain changes in the timing and frequency of critical conditions indicate that there are serious threats to the stability and adaptability of China's food production system. Copyright (C) 1996 Elsevier Science Ltd187Ѓ 206656Ә:j1103^3^Soussana,JF^Casella,E^Loiseau,P^1996^1^Long-term effects of CO2 enrichment and temperature increase on a temperate grass sward .2. Plant nitrogen budgets and root fraction^206^182^1^101-114^^^^^May^^^^^5000tl16168982180E:lA^4999^Perennial ryegrass swards were grown in large containers on a soil and were exposed during two years to elevated (7:m00 mu L L(-1)) or ambient atmospheric CO2 concentration at outdoor temperature and to a 3 degrees C increase in air temper:nature in elevated CO2. The nitrogen nutrition of the grass sward was studied at two sub-optimal (160 and 530 kg N ha(-1) y:o(-1)) and one non-limiting (1000 kg N ha(-1) y(-1)) N fertilizer supplies. At cutting date, elevated CO2 reduced by 25 to :p33%, on average, the leaf N concentration per unit mass. Due to an increase in the leaf blade weight per unit area in elev:qated CO2, this decline did not translate for all cuts in a lower N concentration per unit leaf blade area. With the non-li:rmiting N fertilizer supply, the leaf N concentration (% N) declined with the shoot dry-matter (DM) according to highly sig:snificant power models in ambient (% N=4.9 DM(-0.38)) and in elevated (% N=5.3 DM(-0.52)) CO2. The difference between both :tregressions was significant and indicated a lower critical leaf N concentration in elevated than in ambient CO2 for high, :ubut not for low values of shoot biomass. With the sub-optimal N fertilizer supplies, the nitrogen nutrition index of the g:vrass sward, calculated as the ratio of the actual to the critical leaf N concentration, was significantly lowered in eleva:wted CO2. This indicated a lower inorganic N availability for the grass plants in elevated CO2, which was also apparent fro:xm the significant declines in the annual nitrogen yield of the grass sward and in the nitrate leaching during winter. For :ymost cuts, the harvested fraction of the plant dry-matter decreased in elevated CO2 due, on average, to a 45-52% increase :zin the root phytomass. In the same way, a smaller share of the plant total nitrogen was harvested by cutting, due, on aver:{age, to a 25-41% increase in the N content of roots. The annual means of the DM and N harvest indices were highly correlat:|ed to the annual means of the nitrogen nutrition index. Changes in the harvest index and in the nitrogen nutrition index b:}etween ambient and elevated CO2 were also positively correlated. The possible implication of changes in the soil nitrogen cycle and of a limitation in the shoot growth potential of the grass in elevated. CO2 is discussed. 58Ѓ 63680:1104^3^Spring,GM^Priestman,GH^Grime,JP^1996^1^A new field technique for elevating carbon dioxide levels in climate change experiments^43^10^4^541-545^^^^^Aug^^^^^50024Ѓ4Ϛ):A000Ѓ493Ѓ59Ѓ5Ր,  073536:A^5001^1. A compact, low-cost, free-air carbon dioxide enrichment system for use in climate change experiments is describe:d, The system has been used in a small-scale study of the effects of an enriched carbon dioxide atmosphere on the growth a:nd functioning of a natural plant community, 2. The experiment ran for 4 months in summer on a nutrient-poor limestone gra:ssland in Derbyshire, The study examined the separate and combined effects of elevated CO2, temperature and soil nutrient :status on the growth of seedlings of obligate mycorrhizal and non- mycorrhizal plant species native to the site. 3. It was: demonstrated that the CO2 elevation could be controlled within the limits set for 64% of the time. Significant effects of: elevated CO2 on the growth and recruitment of seedlings were found in the presence of added nutrients and elevated temperatures.400Ѓ 1629696373EЊ 51Ѓ6Ѓ952Ѓ5ӈ27a7 052928GMi5@ 5:1105^3^Traw,MB^Lindroth,RL^Bazzaz,FA^1996^1^Decline in gypsy moth (Lymantria dispar) performance in an elevated CO2 atmosphere depends upon host plant species^2^108^1^113-120^^^^^Oct^^^^^5004A 1Ѓ5҈ 187071P30Ѓ :A^5003^Plant species differ broadly in their responses to an elevated CO2 atmosphere, particularly in the extent of nitrog:en dilution of leaf tissue. Insect herbivores are often limited by the availability of nutrients, such as nitrogen, in the:ir host plant tissue and may therefore respond differentially on different plant species grown in CO2-enriched environment:s. We reared gypsy moth larvae (Lymantria dispar) in situ on seedlings of yellow birch (Betula allegheniensis) and gray bi:rch (B. populifolia) grown in an ambient (350 ppm) or elevated (700 ppm) CO2 atmosphere to test whether larval responses i:n the elevated CO2 atmosphere were species- dependent. We report that female gypsy moths (Lymantria dispar) reared on gray: birch (Betula populifolia) achieved similar pupal masses on plants grown at an ambient or an elevated CO2 concentration. :However, on yellow birch (B. allegheniensis), female pupal mass was 38% smaller on plants in the elevated-CO2 atmosphere. :Larval mortality was significantly higher on yellow birch than gray birch, but did not differ between the CO2 treatments. :Relative growth rate declined more in the elevated CO2 atmosphere for larvae on yellow birch than for those on gray birch.: In preference tests, larvae preferred ambient over elevated CO2-grown leaves of yellow birch, but showed no preference be:tween gray birch leaves from the two CO2 atmospheres. This differential response of gypsy moths to their host species corr:esponded to a greater decline in leaf nutritional quality in the elevated CO2 atmosphere in yellow birch than in gray birc:h. Leaf nitrogen content of yellow birch dropped from 2.68% to 1.99% while that of gray birch leaves only declined from 3.:23% to 2.63%. Meanwhile, leaf condensed tannin concentration increased from 8.92% to 11.45% in yellow birch leaves while g:ray birch leaves only increased from 10.72% to 12.34%. Thus the declines in larval performance in a future atmosphere may be substantial and host-species-specific.GMi5@ 1Ѓ40948264307EЊ 10623Ә5088Ѓ:1106^2^VanOosten,JJ^Besford,RT^1996^1^Acclimation of photosynthesis to elevated CO2 through feedback regulation of gene expression: Climate of opinion^91^48^3^353-365^^^^^Jun^^^^^5006133206EЊ9012Ѓ92ХC2U2L2T2:A^5005^Although down-regulation of photosynthesis in higher C-3 plants exposed to long-term elevated CO2 has been recogniz:ed in plants with low sink activity or poor nutrient status, the underlying molecular mechanisms remain unclear. This revi:ew covers aspects of rising CO2 on plant productivity in general, and then focuses on photosynthesis, biochemistry (stroma: and thylakoid proteins, Rubisco activities and metabolites), and gene expression in tomato plants grown under ambient or :elevated CO2. Taking into account these data and the recent discovery that glucose triggers repression of photosynthetic g:ene transcription, a molecular mechanism is proposed for feedback regulation of photosynthesis under high CO2. Different l:iving organisms such as bacteria, yeast, and mammals have been investigated for the sensing mechanisms of the carbohydrate: status of their cells, and this information is used together with some recent data obtained for plants to propose how hexose levels might be sensed in higher plant cells.Ѓ853Ѓ9Ԇ33673304982EЊ5x:#fȒn:1107^3^Vidal,R^Gerbaud,A^Vidal,D^1996^1^Short-term effects of high light intensities on soybean nodule activity and photosynthesis^173^36^3^349-357^^^^^Oct^^^^^500886Ѓ9ϼP:00Ѓ 0Ѓ40Ѓ67Ѓ:A^5007^There is little information available on the effects of highlight intensity (HLI) on nitrogenase activity in legume: nodules. Inhibitory as well as stimulatory effects have been described. The hypothesis that an increase in carbohydrate p:roduction is involved in these effects was tested by comparing the effects of high light, high CO2, or low O-2 exposure of: the shoot. The HLI treatment consisted of tripling the light intensity to 1200 mu E m(-2) s(-1), compared with the growth: intensity of 400 mu E m(-2) s(-1). Acetylene reduction activity (ARA) measuring nitrogenase activity was studied in relat:ion to shoot CO:! exchange. HLI stimulated ARA. The stimulation was progressive and reached 17% after 10 hr of treatment. :Photosynthesis (P) was initially doubled, but photoinhibition appeared after about 8 hr of HLI. Under HLI, P became limite:d by N fixation. Other treatments increasing photosynthesis were compared with HLI: elevating the ambient CO2 concentratio:n around the shoot to 900 ppm, or lowering the O-2 concentration to 2%, increased photosynthesis, respectively, by 55% and: 70% without effect on ARA. It is concluded that ARA was not regulated by the availability of carbon assimilates and that specific factors promoting or inhibiting ARA are produced by leaves under HLI.Ԥ634Ԥ2ϳFpYP6< :1108^1^Wilsey,BJ^1996^1^Urea additions and defoliation affect plant responses to elevated CO2 in a C-3 grass from Yellowstone National Park^2^108^2^321-327^^^^^Oct^^^^^5010Ҹ054Ѓ8304Ѓ5@ 28641Ή997Ѓ6҈:A^5009^A common grass from Yellowstone National Park, Stipa occidentalis, was grown in a factorial experiment to determine: if its response to the direct effects of elevated CO2 would be affected by defoliation, and urea additions simulating the: N in a urine hit. Plants were grown in tall pots (to mimic rooting depth in the field) in growth chambers under elevated :(700 ppm) and ambient (370 ppm) CO2, were defoliated or left undefoliated, and given N-supply rates based on field mineral:ization rates (untreated) or with an additional 40 g N/m(2). Growth increases in response to elevated CO2 were largest whe:n plants remained unclipped and received urea additions, and were found primarily in crowns and roots (storage organs). Ab:oveground biomass, which is the part of the plant consumed by grazing mammals, was not affected by elevated CO2. The eleva:ted CO2 treatment caused a reduction in leaf percent N. However, there was a significant interaction between the CO2 and u:rea treatments, resulting in a larger difference in leaf percent N between urea-treated and control plants under elevated :than under ambient CO2. Hence, elevations in atmospheric CO2 may cause an increase in the amount of urine- hit-induced spa:tial variability in temperate grasslands. Since food quantity remained largely unchanged in response to elevated CO2, and forage N content went down, grazing mammals may be negatively affected by increases in atmospheric CO2.87744E:1109^9^Zanetti,S^Hartwig,UA^Luscher,A^Hebeisen,T^Frehner,M^Fischer,BU^Hendrey,GR^Blum,H^Nosberger,J^1996^1^Stimulation of :symbiotic N-2 fixation in Trifolium repens L under elevated atmospheric pCO(2) in a grassland ecosystem^8^112^2^575-583^^^^^Oct^^^^^50127136Ѓ 3Ѓ2Х3Ѓ28Х30Ѓ40Ѓ96127650811EЊ627:A^5011^Symbiotic N-2 fixation is one of the main processes that introduces N into terrestrial ecosystems. As such, it may :be crucial for the sequestration of the extra C available in a world of continuously increasing atmospheric CO2 partial pr:essure (pCO(2)). The effect of elevated pCO(2) (60 Pa) on symbiotic N-2 fixation (N-15-isotope dilution method) was invest:igated using Free-Air-CO2-Enrichment technology over a period of 3 years. Trifolium repens was cultivated either alone or :together with Lolium perenne (a nonfixing reference crop) in mixed swards. Two different N fertilization levels and defoli:ation frequencies were applied. The total N yield increased consistently and the percentage of plant N derived from symbio:tic N-2 fixation increased significantly in T. repens under elevated pCO(2). All additionally assimilated N was derived fr:om symbiotic N-2 fixation, not from the soil. In the mixtures exposed to elevated pCO(2), an increased amount of symbiotic:ally fixed N (+7.8, 8.2, and 6.2 g m(-2) a(-1) in 1993, 1994, and 1995, respectively) was introduced into the system. Incr:eased N-2 fixation is a competitive advantage for T. repens in mixed swards with pasture grasses and may be a crucial factor in maintaining the C:N ratio in the ecosystem as a whole.35Ѓ616Ѓ 684Ѓ97428588427E:1110^3^Ziska,LH^Manalo,PA^Ordonez,RA^1996^1^Intraspecific variation in the response of rice (Oryza sativa L) to increased CO2 and temperature: Growth and yield response of 17 cultivars^78^47^302^1353-1359^^^^^Sep^^^^^5014SZ0Ѓ 7536:A^5013^Seventeen rice (Oryza sativa L.) cultivars of contrasting ecosystems and origins were exposed to two CO2 concentrat:ions (373 [ambient] and 664 mu l l(-1) CO2 [elevated]) at two different day/night temperatures (29/21 degrees C and 37/29 :degrees C) in glasshouses at the International Rice Research Institute phytotron during the dry seasons of 1994 and 1995, :Growth at elevated CO2 (as determined by total plant biomass at maturity) increased by an average of 70% and 22%, respecti:vely, for all cultivars for growth temperatures of 29/21 degrees C and 37/29 degrees C relative to the ambient CO2 treatme:nt. At the 29/21 degrees C optimal growth temperature, grain yield increased on average c. 50% with enriched CO2. In contr:ast, at the higher growth temperature (37/29 degrees C), grain yield was almost zero, presumably due, in part, to temperat:ure- induced infertility (i.e. the percentage of filled spikelets was < 1%), Among cultivars, IAC 165, a tropical japonica: from Brazil, showed the largest relative increase in both biomass and grain yield, While the range of responses to increa:sed CO2 and/or temperature were quite large (e.g. 10-250%) and may not be applicable to field conditions, data indicate th:at lines are available which could maximize productivity as CO2 concentration increases. Additional work, however, would be needed to identify cultivars which would maintain maximum yields in a high CO2, high temperature environment.00Х:1111^1^Agren,GI^1996^1^Nitrogen productivity or photosynthesis minus respiration to calculate plant growth?^15^76^3^529-535^^^^^Sep^^^^^50161Ѓ898Ѓ948626Ѓ 72Ѓ58630007076EЊ72Ѓ6Х9:A^5015^One approach to calculate plant growth rate is from models of photosynthesis, respiration and allocation. This requ:ires that processes with characteristic time constants of seconds to minutes be scaled to hours or days. Another approach :is to use aggregate models defined at the time scale of growth, hours and days. I use such an aggregate model, the nutrien:t productivity, to compare the performance of the two approaches on growth experiments with small, nitrogen-limited birch :plants. The problems of error aggregation when using the large number of parameters required to scale from the detailed le:vel of photosynthesis and respiration to the aggregate level of growth are in this case such that whole plant growth rate is more accurately predicted with the nutrient productivity model.alias "MARION Giles" gmarion@hanover-crrel.army.mil al:1112^4^Bassirirad,H^Tissue,DT^Reynolds,JF^Chapin,FS^1996^1^Response of Eriophorum vaginatum to CO2 enrichment at different soil temperatures: Effects on growth, root respiration and PO43- uptake kinetics^84^133^3^423-430^^^^^Jul^^^^^5018 Two" :A^5017^In a phytotron experiment, we examined responses of a tussock sedge, Eriophorum vaginatum L., to changes in atmosph:eric CO2 concentration and soil temperature. We were particularly interested in phosphorus (P) acquisition and below groun:d plant characteristics that regulated its uptake in response to CO2 enrichment. Plants were grown at two CO2 partial pres:sures, 35 and 70 Pa, three soil temperature regimes, 5, 15 and 25 degrees C and a constant ambient air temperature of 15 d:egrees C. Elevated CO2 increased total plant biomass production, but decreased tissue P concentration. Although high CO2 e:nhanced root carbohydrate concentration, it inhibited root respiration with no significant effect on root PO43- absorption: capacity or root:shoot ratio. Surprisingly, there were no significant interactions between CO2 and soil temperature. The :inability of Eriophorum to exhibit root-level compensatory adjustments, e.g. increased root:shoot ratio or PO43- absorptio:n capacity, was largely responsible for the observed decline in tissue P concentration under elevated CO2 conditions. This: could ultimately limit longterm growth responses of Eriophorum to CO2 enrichment in the field where P availability is lim:iting. We found that uptake of PO43- in response to elevated CO2 was independent of changes in root respiration, but chang:es in root respiration could have important implications for ecosystem carbon budget under elevated CO2 levels. Our data i:ndicated that although root respiration on a per unit biomass basis declined in response to CO2 enrichment, this effect wa:s counterbalanced by increased root biomass, so that high CO2 stimulated root respiration on a whole-plant basis by 30%. This might help to explain why long-term exposure to high CO2 increases CO2 efflux from Eriophorum-dominated ecosystems. :1113^5^Batts,GR^Wheeler,TR^Morison,JIL^Ellis,RH^Hadley,P^1996^1^Developmental and tillering responses of winter wheat (Triticum aestivum) crops to CO2 and temperature^178^127^^23-35^^^^^Aug^^^^^5020OHNSON Tracie" Tracie Johnson vertebrates food webs significantly enhanced decomposition of all the chemical components. By adding different groups of a;?nimals, some limiting factors were overcome and new substrates were liberated for microbial decomposition. It was hypothesized that the decomposition process was controlled by the interaction between lignin and nitrogen.28` rPr r*tr;B1118^4^denHertog,J^Stulen,I^Fonseca,F^Delea,P^1996^1^Modulation of carbon and nitrogen allocation in Urtica dioica and Pla;Cntago major by elevated CO2: Impact of accumulation of nonstructural carbohydrates and ontogenetic drift^37^98^1^77-88^^^^^Sep^^^^^5030nabound.com/images/tn_prev06_jpg.jpgiD66b M1C8E6ID.JPG;EA^5029^Doubling the atmospheric CO2 concentration from 350 to 700 mu l l(-1) increased the relative growth rate (RGR) of h;Fydroponically grown Urtica dioica L. and Plantago major ssp. pleiosperma Pilger only for the first 10-14 days. Previous ex;Gperiments with P. major led to the conclusion that RGR did not respond in proportion to the rate of photosynthesis. The pr;Hesent paper is focussed on the analysis of the impact of changes in leaf morphology, dry matter partitioning, dry matter c;Ihemical composition and ontogenetic drift on this discrepancy. Soon after the start of the treatment, carbohydrate concent;Jrations were higher at elevated CO2; a reaction that was largely due to starch accumulation. An increase in the percentage;K of leaf dry matter and decreases in the specific leaf area (SLA) and the shoot nitrogen concentration were correlated wit;Lh an increase in the total nonstructural carbohydrate concentration (TNC). A combination of accumulation of soluble sugars;M and starch and ontogenetic drift explains the decrease in SLA at the elevated CO2 level. A similar ontogenetic effect of ;Nelevated CO2 was observed on the specific root length (SRL). Other variables such as shoot nitrogen concentration and perc;Oentage leaf dry matter were not affected by correction of data for TNC levels. The net diurnal fluctuation of the carbohyd;Prate pool in P. major was equal for both CO2 concentrations, indicating that the growth response to elevated CO2 may be ru;Qled by variables other than photosynthesis, as for instance sink strength. Elevated CO2 did not greatly influence the part;Ritioning of nitrogen between soluble and insoluble, reduced N and nitrate, nor the allocation of dry matter between leaf, ;Sstem and root. The finding that the root to shoot ratio (R/S) was not affected by elevated CO2 implies that, in order to m;Taintain a balanced activity between roots and shoot, no shift in partitioning of dry matter upon doubling of the atmospher;Uic CO2 concentration is required. Our data on R/S are in good agreement with the response of R/S to high CO2 predicted by models based on such a theorem. M0J6ITC3.JPGiD66b M1C8E6ID.JPG;W1119^6^Docherty,M^Hurst,DK^Holopainen,JK^Whittaker,JB^Lea,PJ^Watt,AD^1996^1^Carbon dioxide-induced changes in beech foliage cause female beech weevil larvae to feed in a compensatory manner^127^2^4^335-341^^^^^Aug^^^^^5032s...ing for reply...;YA^5031^The phenology of Fagus sylvatica was unaffected by exposure to an atmosphere of elevated CO2 (600 mu L L(-1)) after;Z two years of fumigation. Non-significant changes in nitrogen and phenolic content of the leaves decreased the nutritional;[ status of beech for female larvae in elevated CO2 such that they responded by eating in a compensatory manner; males were;\ unaffected. Rates of development, mortality and adult biomass of Rhynchaenus fagi were no different from those in ambient;] CO2 concentrations (355 mu L L(-1)). It is possible that, with the changes in leaf chemistry affecting the females, fecundity will be altered, with important consequences for populations of beech weevil.;_1120^4^Ferris,R^Nijs,I^Behaeghe,T^Impens,I^1996^1^Contrasting CO2 and temperature effects on leaf growth of perennial ryegrass in spring and summer^78^47^301^1033-1043^^^^^Aug^^^^^5034;aA^5033^The effects of increased atmospheric carbon dioxide (CO2) of 700 mu mol mol(-1) and increased air temperature of +4;b degrees C were examined in Lolium perenne L. cv. Vigor, growing in semi-controlled greenhouses, Leaf growth, segmental el;congation rates (SER), water relations, cell wall (tensiometric) extensibility (%P) and epidermal cell lengths (ECL) were m;deasured in expanding leaves in spring and summer. In elevated CO2, shoot dry weight (SDW) increased in mid-summer, In both;e seasons, SDW decreased in elevated air temperatures with this reduction being greater in summer as compared to spring, Sp;fecific leaf area (SLA) decreased in elevated CO2 and in CO2 x temperature in both seasons, In spring, increased leaf exten;gsion and SER in elevated CO2 were linked with increased ECL, %P and final leaf size whilst in summer all were reduced, In ;hhigh temperature, leaf extension, SER, %P and final leaf size were reduced in both seasons. In elevated CO2 x temperature,;i leaf extension, SER, %P, and ECL increased in spring, but final leaf size remained unaltered, whilst in summer all decrea;jsed. Mid-morning water potential did not differ with CO2 or temperature treatments. Leaf turgor pressure increased in elev;kated CO2 in spring and remained similar to the control in summer whilst solute potential decreased in spring and increased;l in summer, Contrasting seasonal growth responses of L. perenne in response to elevated CO2 and temperature suggests pastu;mre management may change in the future, The grazing season may be prolonged, but whole season productivity may become more variable than today.;o1121^2^Korner,C^Wurth,M^1996^1^A simple method for testing leaf responses of tall tropical forest trees to elevated CO2^2^107^4^421-425^^^^^Sep^^^^^5036;qA^5035^The effects of atmospheric CO2 enrichment on mature trees in their natural environment are largely unknown. Here we;r present a new, and inexpensive technique which can be used in situ to address some key physiological questions related to;s the CO2 problem. Small, light-weight cups mounted on the lower side of rigid leaves at the top of tall tropical forest tr;tees were supplied with CO2-enriched air derived from a low-technology air mixing device utilizing forest floor CO2 evoluti;uon. We present the scientific rationale for such field experiments, technical details, an assessment of potential cup arti;vfacts and first results illustrating effects of elevated CO2 on stomata and carbohydrate accumulation in the canopies of mature trees.;x1122^4^Kubo,Y^Hirata,O^Inaba,A^Nakamura,R^1996^1^Respiration and ethylene production in fruits and vegetables held in carb;on dioxide-enriched atmospheres - Effects of temperature and carbon dioxide concentration^180^65^2^403-408^^^^^Sep^^^^^503;zA^5037^The rates of respiration and ethylene production in various fruits and vegetables held in 0.60% CO2 at 25 degrees C;{ or 60% CO2 at 5-25 degrees C were determined by an automated microcomputer system. In peaches, apples, tomatoes, and broc;|coli, dose-dependent decreases of O-2 uptake and C2H4 production were observed during treatment with various concentration;}s of CO2 at 25 degrees C. Oxygen uptake in bananas was inhibited at 10% CO2 and higher, whereas C2H4 production increased ;~as the ambient CO2 concentration was elevated. CO2 concentration had little or no effect on O-2 uptake in satsuma mandarin;. Oxygen uptake in lettuce at 20% CO2 and below was similar to that under air, whereas induction of C2H4 production and an; enhanced O-2 uptake were observed in lettuce held in 40% CO2 and higher. Inhibition of O-2 uptake and C2H4 production in ;peaches by 60% CO2 declined as the temperature was lowered to the range of 5-25 degrees C. In broccoli held in 60% CO2, th;e inhibition of O-2 uptake was temperature-dependent, but C2H4 production was suppressed to trace level at all temperature;s. The induction of C2H4 production and enhancement of O-2 uptake in lettuce by 60% CO2 occurred distinctly at 25 degrees C, slightly at 15 degrees C, but not at 10 degrees C and 5 degrees C.8;1123^2^Lewis,JD^Strain,BR^1996^1^The role of mycorrhizas in the response of Pinus taeda seedlings to elevated CO2^84^133^3^431-443^^^^^Jul^^^^^5040;A^5039^The effects of mycorrhizal status, phosphorus supply and CO2 partial pressure on production and allocation of bioma;ss in seedlings from two populations of Pinus taeda L. were examined. Seedlings from a North Carolina and a Florida popula;tion were grown in sterile soil in a full-factorial experiment with one of two phosphorus treatments (low P, high P) and a;t one of two CO2 partial pressures (35.5, 71.0 Pa). One half of the seedlings were inoculated with Pisolithus tinctorius (;Pers.) Coker & Couch hyphae and spores. Seedlings were harvested 60, 90 and 120 d after emergence. Elevated CO2 significan;tly increased total seedling dry mass in all treatments at all three harvests. Phosphorus limitation reduced seedling grow;th, and mycorrhizas increased seedling growth in seedlings limited by phosphorus supply. Generally, however, there were no; interactions between CO2, phosphorus supply and mycorrhizal status on dry mass of seedlings. Mycorrhizas probably did not; affect the response of dry mass to elevated CO2 because phosphorus limitation did not reduce response of dry mass to elev;ated CO2. Phosphorus-limited seedlings responded to elevated CO2 as a result of increased phosphorus uptake, resulting fro;m increased total root dry mass, and increased phosphorus use efficiency. Although mycorrhizal colonization did not affect; the response of biomass to elevated CO2, it significantly reduced the response of needle area. As a result, specific leaf; area (leaf area per unit plant biomass) was lower in mycorrhizal seedlings grown in elevated CO2 than in mycorrhizal seed;lings grown in ambient CO2. Because there were no effects on relative growth rate or seedling dry mass, reductions in specific leaf area suggest that elevated CO2 reduced the relative cost of the symbiosis.;1124^2^Mackowiak,CL^Wheeler,RM^1996^1^Growth and stomatal behavior of hydroponically cultured potato (Solanum tuberosum L) at elevated and super-elevated CO2^4^149^1-2^205-210^^^^^Jul^^^^^5042 %sBookmarks for %s%satically generated file;A^5041^Potato cultivars Denali and Norland were grown in a controlled environment under low irradiance and CO2 partial pre;ssures of 50, 100, 500, and 1000 Pa. The highest CO2 partial pressures, 500 and 1000 Pa, reduced tuber yield when compared; to 100 Pa CO2. Upper canopy stomatal conductance was greatest at the higher CO2 partial pressures (500 and 1000 Pa) for b;oth cultivars, and conductance of Denali was consistently higher than Norland. Stomatal conductance tended to decline soon;er with plant age at 50 and 100 Pa CO2 than at 500 and 1000 Pa. Water uptake was also greatest at the higher CO2 partial p;ressures, which resulted in lowest water-use efficiencies at 500 and 1000 Pa. These observations suggest that stomatal fun;ction under very high CO2 partial pressures (500-1000 Pa) does not follow known patterns observed at moderate partial pres;sures (50-100 Pa). Although there is little concern about CO2 partial pressures reaching extreme levels in the natural env;ironment, this information should be useful for controlled environments or space life support systems (e.g. space vehicles or habitats), where CO2 partial pressures of 500-1000 Pa are common.;1125^3^Miglietta,F^Giuntoli,A^Bindi,M^1996^1^The effect of free air carbon dioxide enrichment (FACE) and soil nitrogen availability on the photosynthetic capacity of wheat^91^47^3^281-290^^^^^Mar^^^^^5044;A^5043^A. simple system for free air carbon dioxide enrichment (FACE) was recently developed and it is here briefly descri;bed. Such a MiniFACE system allowed the elevation of CO2 concentration of small field plots avoiding the occurrence of lar;ge spatial and temporal fluctuations. A CO2 enrichment field experiment was conducted in Italy in the season 1993-1994 wit;h wheat (cv. Super-dwarf Mercia). A randomized experimental design was used with the treatment combination CO2 x soil N, r;eplicated twice. Gas exchange measurements showed that photosynthetic capacity was significantly decreased in plants expos;ed to elevated CO2 and grown under nitrogen deficiency. Photosynthetic acclimation was, in this case, due to the occurrenc;e of reduced rates of rubP saturated and rubP regeneration limited photosynthesis. Gas exchange measurements did not inste;ad reveal any significant effect of elevated CO2 on the photosynthetic capacity of leaves of plants well fertilized with n;itrogen, in spite of a transitory negative effect on rubP regeneration limited photosynthesis that was detected to occur i;n the central part of a day with high irradiance. It is concluded that the levels of nitrogen fertilization will play a su;bstantial role in modulating CO2 fertilization effects on growth and yields of wheat crops under the scenario of future climate change. It will be read and overwritten.tscape was rece;1126^3^Mjwara,JM^Botha,CEJ^Radloff,SE^1996^1^Photosynthesis, growth and nutrient changes in non-nodulated Phaseolus vulgaris grown under atmospheric and elevated carbon dioxide conditions^37^97^4^754-763^^^^^Aug^^^^^5046;A^5045^The response of Phaseolus vulgaris L. cv. Contender grown under controlled environment at either ambient or elevate;d (360 and 700 mu mol mol(-1), respectively) CO2 concentrations ([CO2]), was monitored from 10 days after germination (DAG;) until the onset of senescence. Elevated CO2 had a pronounced effect on total plant height (TPH), leaf area (LA), leaf dr;y weight (LD), total plant biomass (TB) accumulation and specific leaf area (SLA). All of these were significantly increas;ed under elevated carbon dioxide with the exception of SLA which was significantly reduced. Other than high initial growth; rates in CO2-enriched plants, relative growth rates remained relatively unchanged throughout the growth period. While the; trends in growth parameters were dearly different between [CO2], some physiological processes were largely transient, in ;particular, net assimilation rate (NAR) and foliar nutrient concentrations of N, Mg and Cu. CO2 enrichment significantly i;ncreased NAR, but from 20 DAG, a steady decline to almost similar levels to those measured in plants grown under ambient C;O2 occurred. A similar trend was observed for leaf N content where the loss of leaf nitrogen in CO2-enriched plants after ;20 DAG, was significantly greater than that observed for ambient-CO2 plants. Under enhanced CO2, the foliar concentrations; of K and Mn were increased significantly whilst P, Ca, Fe and Zn were reduced significantly. Changes in Mg and Cu concent;rations were insignificant. In addition, high CO2 grown plants exhibited a pronounced leaf discoloration or chlorosis, coupled with a significant reduction in leaf longevity.;1127^4^Randlett,DL^Zak,DR^Pregitzer,KS^Curtis,PS^1996^1^Elevated atmospheric carbon dioxide and leaf litter chemistry: Influences on microbial respiration and net nitrogen mineralization^110^60^5^1571-1577^^^^^Sep-Oct^^^^^5048 ;A^5047^Elevated atmospheric CO2 has the potential to influence rates of C and N cycling in terrestrial ecosystems by alter;ing plant litter chemistry and slowing rates of organic matter decomposition, We tested the hypothesis that the chemistry ;of leaf litter produced at elevated CO2 would slow C and N transformations in soil. Soils were amended with Populus leaf l;itter produced under two levels of atmospheric CO2 (ambient and twice-ambient) and soil N availability (low and high). Kin;etic parameters for microbial respiration and net N mineralization were determined on soil with and without litter during ;a 32-wk lab incubation, Product accumulation curves for CO2-C and inorganic N were fit to a first order rate equation [y =; A(1 - e(-kt))] using nonlinear regression analyses, Although CO2 treatment affected soluble sugar concentration in leaf l;itter (ambient = 120 g kg(-1), elevated = 130 g kg(-1)), it did not affect starch concentration or C/N ratio, Microbial re;spiration, microbial biomass, and leaf litter C/N ratio were affected by soil N availability but not by atmospheric CO2, N;et N mineralization was a linear function of time and was not significantly different for leaves grown at ambient (50 mg N; kg(-1)) and elevated CO2 (35 mg N kg(-1)). Consequently, we found no evidence for the hypothesis that leaf litter produced at elevated atmospheric CO2 will dampen the rates of C and N cycling in soil. t Scots pine grown at elevated CO2 or elevated temperature, compared to those grown in the ambient conditions, did not sho 30 degrees C), the elevated CO2 treatment significantly decreased 72% at elevated CO2, because grain numb BFJNRVZ^b-25-Ja-9-Feb-1999-10:51:08--0500-(EST) 918557438 N<1145^2^Hattenschwiler,S^Korner,C^1996^1^System-level adjustments to elevated CO2 in model spruce ecosystems^127^2^4^377-387^^^^^Aug^^^^^5084save read Nget 2050691262 e13c05191278f934106c426e953648ec <199902101738.MAA21284@mail2.uts.ohio-state-24-Feb-1999-10:20:45--0500-(EST 919852011 Ndel Nskip Nsave<1146^4^He,P^Radunz,A^Bader,KP^Schmid,GH^1996^1^Influence of CO2 and SO2 on growth and structure of photosystem II of the Chinese tung-oil tree Aleurites montana^291^51^7-8^441-453^^^^^Jul-Aug^^^^^5086c495a960$3eaa9680@rhilderb.nsf.gov>-24-Feb--28-F=1147^3^Hibberd,JM^Whitbread,R^Farrar,JF^1996^1^Carbohydrate metabolism in source leaves of barley grown in 700 mu mol mol(-1) CO2 and infected with powdery mildew^84^133^4^659-671^^^^^Aug^^^^^50882302663 89495aa75d93651ce9b8105ce00aaaad <1DDF=A^5087^Soluble carbohydrate accumulated faster in second leaf blades of barley when plants were grown in 700 mu mol mol(-1=) CO2 rather than 350 mu mol mol(-1) CO2. Infection of the second leaf blade by powdery mildew had no effect on the concen=tration of soluble carbohydrate until 6 d after inoculation when it was lower than in controls. The accumulation of solubl=e carbohydrate in the second leaf of uninfected plants grown in 700 mu mol mol(-1) CO2 was due largely to earlier and fast=er accumulation of fructan. TLC showed that the series of fructan was not different in plants grown in 700 mu mol mu mol(-=1) CO2 relative to plants grown in 350 mu mol mol(-1) CO2, neither did infection by powdery mildew affect the series of fr=uctan present in the second leaf blade. The rate constant for phloem loading obtained by compartmental analysis of C-14 ef=flux from the leaf blade was not reduced in plants grown in 700 mu mol mol(-1) CO2, indicating that carbohydrate accumulation was not caused by reduced ability of the leaf to export carbon.2@aol.com>-1-Mar-1999-19:08:30--0500-(EST) 920353317 N=!1148^2^Kellomaki,S^Wang,KY^1996^1^Photosynthetic responses to needle water potentials in Scots pine after a four-year exposure to elevated CO2 and temperature^13^16^9^765-772^^^^^Sep^^^^^5090ab141ca39 <199903021329.IAA26203@mail2.uts.ohio-stat=#A^5089^Effects of needle water potential (psi(1)) on gas exchange of Scots pine (Pinus sylvestris L.) grown for 4 years in=$ open-top chambers with elevated temperature (ET), elevated CO2 (EC) or a combination of elevated temperature and CO2 (EC =%+ ET) were examined at a high photon flux density (PPFD), saturated leaf to air water vapor pressure deficit (VPD) and opt=&imal temperature (T). We used the Farquhar model of photosynthesis to estimate the separate effects of psi 1 and the treat='ments on maximum carboxylation efficiency (V-c,V-max), ribulose-1 ,5- bisphosphate regeneration capacity (J), rate of resp=(iration in the light (R(d)), intercellular partial pressure of CO2 (Ci) and stomatal conductance (G(s)). Depression of CO2=) assimilation rate at low psi(1) was the result of both stomatal and non- stomatal limitations on photosynthetic processes=*; however, stomatal limitations dominated during short-term water stress (psi(1)<-1.2 MPa), whereas nonstomatal limitation=+s dominated during severe water stress. Among the nonstomatal components, the decrease in J contributed more to the declin=,e in photosynthesis than the decrease in Long-term elevation of CO2 and temperature led to differences in the maximum valu=-es of the parameters, the threshold values of psi(1) and the sensitivity of the parameters to decreasing psi(1). The CO2 t=.reatment decreased the maximum values of V-c,V-max J and R(d) but significantly increased the sensitivity of V-c,V-max J a=/nd Rd to decreasing psi(1) (P < 0.05). The effects of the ET and EC + ET treatments on V-c,V-max J and R(d) were opposite =0to the effects of the EC treatment on these parameters. The values of G(s), which were measured simultaneously with maximu=1m net rate of assimilation (A(max)), declined in a curvilinear fashion as psi(1) decreased. Both the EC + ET and ET treatm=2ents significantly decreased the sensitivity of G(s) to decreasing psi(1-). We conclude that, in the future, acclimation to increased atmospheric CO2 and temperature could increase the tolerance of Scots pine to water stress.=41149^3^Klieber,A^Ratanachinakorn,B^Simons,DH^1996^1^Effects of low oxygen and high carbon dioxide on tomato cultivar 'Bermuda' fruit physiology and composition^165^65^4^251-261^^^^^Aug^^^^^5092 =6A^5091^Breaker stage tomatoes (Lycopersicon esculentum Mill., cultivar 'Bermuda') were treated in air, 0.5% or 1.0% oxygen=7 (O-2) in nitrogen (N-2) or 80% carbon dioxide (CO2) in air for 1, 3, 5 or 7 days at 22 degrees C, A 1 day low O-2 treatme=8nt delayed ripening after treatment by 1-2 days compared to a ripening period of 4 days for the control; elevated CO2 for =91 day had no effect on ripening after treatment, Low O-2 increased production of ethanol and acetaldehyde compared to the =:control and high CO2. Fruit treated for 3 or more days in low O-2 or high CO2 showed skin injury and blotchy ripening. Dis=;ease incidence increased with treatment time, but could be controlled in 1 day treatments by reducing relative humidity to=< about 70%, Firmness, total soluble solids, titratable acidity and pH of pericarp and gel of 1 day treated fruit were not different from the control.#FFFFFF"> getUTCMinuteshttp://ads.lycos.com/ads/att-tel=>1150^2^Leadley,PW^Stocklin,J^1996^1^Effects of elevated CO2 on model calcareous grasslands: Community, species, and genotype level responses^127^2^4^389-397^^^^^Aug^^^^^5094`L`!co@ th0 f=@A^5093^We investigated the responses of model calcareous grassland communities to three CO2 concentrations: 330, 500, and =A660 mu L L(-1). The communities were composed of six species, Bromus erectus Hudson, Festuca ovina L., Prunella vulgaris L=B., Prunella grandiflora (L.) Scholler, Hieracium pilosella L., and Trifolium repens L., that are native to the calcareous =Cgrasslands of Europe. Genotypic variation in CO2 response was studied in Bromus erectus and Festuca ovina. Plants were har=Dvested after c. 126 days of growth. We found that: 1 At the community level, there were marginally significant (0.1 greate=Er than or equal to P > 0.05) increases in leaf and litter dry weight with increasing CO2 concentration. 2 There were signi=Fficant differences between species in CO2 response, including both negative and positive responses. Prunella vulgaris had =Ga significant negative response; Hieracium pilosella and Festuca ovina had significant positive responses; Prunella grandi=Hflora had a marginally significant positive response; and Bromus erectus and Trifolium repens did not have significant res=Iponses. 3 There was significant variation among genotypes in the response to elevated CO2 in Bromus erectus, but not in Fe=Jstuca ovina. Based on the observed species- and genotype-level variation in CO2 response of calcareous grassland plants in=K this and other studies, we speculate that increasing atmospheric CO2 concentrations will alter community structure in calcareous grasslands.`ܪ43 f)F`E9ӽjava/util/zip/DataFormatException.class$_m p$=1155^2^Nijs,I^Impens,I^1996^1^Effects of elevated CO2 concentration and climate-warming on photosynthesis during winter in Lolium perenne^78^47^300^915-924^^^^^Jul^^^^^5104%L9PΨl`@%$www.nsf.gov1abo=A^5103^Long-term effects of atmospheric carbon dioxide concentration (ambient or 700 mu mol mol(-1)) and air temperature (=simulation of field conditions or +4 degrees C) on leaf photosynthetic rate were examined in Lolium perenne L. cv. Vigor, =exposed to natural illumination during winter. Photosynthetic capacity was compared over a range of air temperatures and p=hoton flux densities of photosynthetically active radiation which were representative of winter climate (5-15 degrees C an=d 0-500 mu mol m(-2) s(-1)), with CO2 level during measurement similar to that during the experimental period, Long-term e=xposure to increased air temperature reduced leaf CO2 fixation capacity by 23% (averaged over all measurement conditions),= resulting from a decline in light-saturated uptake rate, but not in incident- light quantum efficiency, CO2-stimulation w=as largely absent in plants grown in ambient temperature, but pronounced in plants grown under +4 degrees C, where it comp=ensated for two-thirds of the 23% drop. This enhancing effect of elevated CO2 level on leaf CO2 uptake rate observed in th=e warmer treatment, was strongly dependent on measurement temperature, increasing from 5% at 5 degrees C, to up to 32% at =15 degrees C. Measurements of chlorophyll fluorescence and dry matter corresponded with the observed changes in assimilati=on capacity, which could not be attributed to a deteriorated nitrogen status of the leaves as there was a similar N content on an area basis. Several hypotheses are considered to explain the observed CO2- temperature interactions.rdcorebiz-x1.=1156^2^Pearson,M^Brooks,GL^1996^1^The effect of elevated CO2 and grazing by Gastrophysa viridula on the physiology and regrowth of Rumex obtusifolius^84^133^4^605-616^^^^^Aug^^^^^5106 ,+-$java/io/OutputSt=A^5105^Plants of Rumex obtusifolius L. were grown in Solardomes under ambient and elevated (+ 250 mu mol mol-l) mole fract=ions of CO2 and were exposed to two levels of herbivory by Gastrophysa viridula Degeer larvae. The herbivory treatment las=ted 1 month, thereafter half of the plants were harvested and over the following month during a period of regrowth physiol=ogical measurements were made on the remaining plants. At the termination of the herbivory treatment uninfested plants sho=wed no damage, whereas the low and high herbivore treatments caused 20-40% and 50-70% loss of leaf area as a proportion of= total leaf area, respectively. The CO2 treatment did not affect the degree of defoliation. Total leaf area was not signif=icantly affected by either CO2 or herbivory. Uninfested plants grown in elevated concentrations of CO2 showed increased gr=owth, root- to-shoot ratios (RS), rates of photosynthesis and reduced stomatal conductance compared with uninfested plants= grown in ambient CO2. A/C-i analysis revealed that plants grown in elevated CO2 showed reductions in Vc(max). For plants =grown in ambient CO2 the high herbivory treatment led to increased rates of photosynthesis and decreased rates of dark res=piration per unit leaf area, and caused increases in stomatal conductance and RS. For plants grown in elevated CO2 the hig=h herbivory treatment increased plant biomass and RS. The increases in RS in response to elevated CO2 and herbivory appear=ed to be additive. Defoliation did not reduce the degree of photosynthetic down-regulation caused by growth in elevated concentrations of CO2, but appeared to reduce the rate of ontogenic decline in photosynthesis in ambient CO2.>zb=1157^4^Rouhier,H^Billes,G^Billes,L^Bottner,P^1996^1^Carbon fluxes in the rhizosphere of sweet chestnut seedlings (Castanea= sativa) grown under two atmospheric CO2 concentrations: C-14 partitioning after pulse labelling^206^180^1^101-111^^^^^Mar^^^^^5108ov/home/ssi/help-off.gif/home/nsforg/icons/yell_bak.gifsun/awt/windows/WPanelPeer.classntents.htm(=A^5107^Partitioning of C-14 was assessed in sweet chestnut seedlings (Castanea sativa Mill.) grown in ambient and elevated= atmospheric [CO2] environments during two vegetative cycles. The seedlings were exposed to (CO2)-C-14 atmosphere in both =high and low [CO2] environments for a 6-day pulse period under controlled laboratory conditions. Six days after exposure t=o (CO2)-C-14, the plants were harvested, their dry mass and the radioactivity were evaluated. C-14 concentration in plant =tissues, root-soil system respiratory outputs and soil residues (rhizodeposition) were measured. Root production and rhizo=deposition were increased in plants growing in elevated atmospheric [CO2]. When measuring total respiration, i.e. CO2 rele=ased from the root/soil system, it is difficult to separate CO2 originating from roots and that coming from the rhizospher=ic microflora. For this reason a model accounting for kinetics of exudate mineralization was used to estimate respiration =of rhizospheric microflora and roots separately. Root activity (respiration and exudation) was increased at the higher atm=ospheric CO2 concentration. The proportion attributed to root respiration accounted for 70 to 90% of the total respiration=. Microbial respiration was related to the amount of organic carbon available in the rhizosphere and showed a seasonal var=iation dependent upon the balance of root exudation and respiration. The increased carbon assimilated by plants grown under elevated atmospheric [CO2] stayed equally distributed between these increased root activities.nsun/awt/windows/=1158^5^Roumet,C^Bel,MP^Sonie,L^Jardon,F^Roy,J^1996^1^Growth response of grasses to elevated CO2: A physiological plurispecific analysis^84^133^4^595-603^^^^^Aug^^^^^5110EieǰdV1wJ?>ە=A^5109^The effect of CO2 enrichment on the growth and the economy of carbon and nitrogen of 11 Mediterranean grass species= was investigated in order to determine the underlying causes of the large variation observed between species in their res=ponses to elevated CO2. Plants were grown for 26-43 d (depending on species growth rate) under productive conditions at am=bient (350 mu mol mol(-1)) and elevated (700 mu mol mol(-1)) concentrations of CO2. Plant parameters were determined at a =common biomass of 0.15 g to determine the CO2 effect independent of ontogenic effects. The effect of CO2 on RGR ranged fro=m -6.7 to 22.5%, with a mean stimulation of 10.3%. Averaged over the 11 species, the growth enhancement resulted from an i=ncrease in net assimilation rate per unit leaf d. wt. (NAR(w)) of 10.6%. This was the result of a large increase (18.7%) i=n NAR per unit leaf area (NAR(a)) associated with a 8.1% decrease in the specific leaf area (SLA). This decrease in SLA wa=s due to a large increase of the non-structural carbohydrates. The increase in shoot activity was balanced by a 7.6% incre=ase in the specific absorption rate of nitrogen (SAR). AS a result, plant nitrogen content was not modified. Leaf nitrogen= productivity was significantly increased (14.9%). Shoot vs. root allocation of biomass and nitrogen was not modified. An =analysis across the 11 species of the relationships between the stimulation of RGR and the alteration in RGR components sh=owed a significant correlation only with increases in NAR(w), SAR and nitrogen productivity. The co- ordinated increase in= these three parameters constitutes a single response syndrome, whose intensity is responsible for most of the species variability.http://www.nsf.gov/home/ssi/info-on.gifs/imagesjava/io/ByteArrayOutputStream.class_mw r`t=1159^4^Sommerfeld,RA^Massman,WJ^Musselman,RC^Mosier,AR^1996^1^Diffusional flux of CO2 through snow: Spatial and temporal variability among alpine-subalpine sites^137^10^3^473-482^^^^^Sep^^^^^5112yReader.class`tuv ,u=A^5111^Three alpine and three subalpine sites were monitored for up to 4 years to acquire data on the temporal and spatial= variability of CO2 flux through snowpacks. We conclude that the snow formed a passive cap which controlled the concentrat=ion of CO2 at the snow-soil interface, while the flux of CO2 into the atmosphere was controlled by CO2 production in the s=oil. Seasonal variability in the flux at all sites was characterized by early winter minima followed by a rise in flux tha=t averaged 70% above the minima over about a I-month period. The seasonal variability was not related to soil temperatures= which remained relatively constant. Interannual variability was small, and spatial variability was smaller than previousl=y reported. Spatial variability on a scale of 1 to 10 m was less than 30% of the average fluxes and not significantly grea=ter than estimated error in most cases. Spatial variability on a scale of 10- to 100-m was about a factor of 2 and on a sc=ale of 100 to 1000 m was about a factor of 4. The 100- to 1000-m variability was complicated by the fact that the sites we=re in different ecosystems, alpine and subalpine, and at different elevations. We attribute the small variability at the 1=- to 10- m scale to the deep snow cover, from 1.4 to 5 m. We hypothesize that horizontal diffusion under the snow cover re=duced small- scale horizontal gradients, while the insulating effect of the deep snow cover kept the soil temperature and =moisture relatively constant. Equivalent annual wintertime flux averaged about 95 g C m(-2) yr(-1) in the alpine and about= 232 g C m(-2) yr(-1) in the subalpine sites. Measurements of CO2 concentrations at 0.2 and 0.5 m in the soil of one of th=e subalpine sites indicated that production early in the snow season occurred at or below 0.5 m while production between 0.5 m, and the surface became important after the start of the melt season.=1160^2^Stewart,J^Potvin,C^1996^1^Effects of elevated CO2 on an artificial grassland community: Competition, invasion and neighbourhood growth^43^10^2^157-166^^^^^Apr^^^^^5114feredReader.classf r A~y{iitID98=A^5113^1. We analysed the effect of CO2 enrichment on plant-plant interactions in an artificial community dominated by Tri=folium repens and Poa pratensis. Plants were enriched either in open- tops or growth chambers. 2. Our main hypotheses were= supported, i.e. elevated CO2 increased the strength and number of plant- plant interactions and Trifolium benefited more =than Poa from a high CO2 concentration. However, responses differed depending on whether plants were enriched in open-top =or in growth chambers. These differences are discussed regarding possible density dependence. 3. This study emphasizes the= importance of invasions in the dynamics of our artificial community. Invasiveness was best predicted by traits pertaining= to space acquisition. 4. To provide insights into evolutionary processes, phenotypic plasticity and genetic correlation o=f individual traits were analysed across environments. Our results suggest that little opportunity had occurred for adaptive plasticity to evolve for most characters.,`sun/awt/macos/InterfaceEvent.class=1161^3^Sykes,MT^Prentice,IC^Cramer,W^1996^1^A bioclimatic model for the potential distributions of north European tree species under present and future climates^134^23^2^203-233^^^^^Mar^^^^^5116.transvestite.com/counter/counter.cgi?516773?516=A^5115^A bioclimatic model based on physiological constraints to plant growth and regeneration is used here in an empirica=l way to describe the present natural distributions of northern Europe's major trees. Bioclimatic variables were computed =from monthly means of temperature, precipitation and sunshine (%) interpolated to a 10' grid taking into account elevation=. Minimum values of mean coldest-month temperature (T-c) and 'effective' growing degree days (GDD*) were fitted to species=' range limits. GDD* is total annual growing degree days (GDD) minus GDD to budburst (GDD(o)). Each species was assigned t=o one of the chilling-response categories identified by Murray, Cannell & Smith (1989) to calculate GDD(o). Maximum T-c va=lues were fitted to continental species' mild-winter limits and other deciduous species' warm-winter limits. Minimum value=s of relative growing-season moisture availability (alpha*) were estimated from silvics. Growth indices were calculated ba=sed on potential net assimilation (a quadratic in daily temperature) and alpha*. Growth can be rapid near a range limit, e=.g. Picea abies (L.) Karsten in southern Sweden. Climate changes expected for CO2 doubling were projected on to the grid. =Simulated distribution changes reflected interspecific differences in response to changing seasonality. Chilling responses= proved important, e.g. the predicted range limit of Fagus sylvatica L. contracts in the west while expanding northwards a=s winters warm more than summers. Transient responses to climate change can be modelled using the same information provide=d that fundamental and realized niche limitations are distinguished-a caveat that underlines the dearth of experimental information on the climatic requirements for growth, and especially regeneration, of many important trees.N,Tnzrk=1162^1^Wang,KY^1996^1^Apparent quantum yield in Scots pine after four years of exposure to elevated temperature and CO2^79^32^3^339-353^^^^^^^^^^5118b_m, sun/awt/PhysicalDrawingSurface.class  =A^5117^The carbon-dioxide and temperature responses of the apparent quantum yield, alpha(A), were measured in a uniform, d=iffuse radiation field for two shoot age classes of Scots pine (Pinus sylvestris L.) that had been exposed to elevated CO2= and temperature for four years (1991-4) in open-top chambers. The treatments were (I) ambient temperature and CO2 concent=ration (ACT), (2) elevated temperature (ET), (3) elevated CO2 concentration (EC), and (4) elevated CO2 concentration and t>emperature (ECT). ET and ECT increased alpha(A) in the one- year-old shoots, but did not affect alpha(A) in the current- y>ear shoots. When measured at the same partial pressure of CO2 and a leaf temperature of 20 degrees C, EC had no significan>t effect on alpha(A) in two shoot age classes. However, when the comparison was made between shoots grown in and measured >in 35 Pa CO2 and those grown in and measured in 70 Pa CO2, EC and ECT led to a significant increase in alpha(A), by 22.4 a>nd 24.5 %, respectively, for the current-year shoots and by 21.6 and 27.5 %, respectively, for one-year-old shoots. Furthe>rmore, in the one-year-old shoots, ET and ECT led to relatively higher alpha(A) values at higher temperatures, but EC alon>e led to relatively lower values of alpha(A). In contrast, this effect was not significant in the current-year shoots. The> differences in alpha(A) between different treatments and between the shoot age classes could be attributed separately to >changes in the efficiency of radiant energy capture. The Kok effect was observed at all partial pressures of CO2 during me> asurements. However, with an increase in the partial pressure of CO2, a parallel decrease was observed in both the measure> d rate of dark respiration, R(D), and the regressed rate of dark respiration, R(r). This decrease occurred regardless of g> rowth treatment and age class. Consequently, the ratio of R(r)/R(D) was nearly identical in all treatments and age classes having a mean of 0.69.MScrollbarPeer.class2пBuz;yIkLd;d˴fG='fM2> 1163^10^Williams,M^Rastetter,EB^Fernandes,DN^Goulden,ML^Wofsy,SC^Shaver,GR^Melillo,JM^Munger,JW^Fan,SM^Nadelhoffer,KJ^1996>^1^Modelling the soil-plant-atmosphere continuum in a Quercus-Acer stand at Harvard forest: The regulation of stomatal conductance by light, nitrogen and soil/plant hydraulic properties^9^19^8^911-927^^^^^Aug^^^^^5120,sun/awt/macos/MM>A^5119^Our objective is to describe a multi-layer model of C-3-canopy processes that effectively simulates hourly CO2 and >latent energy (LE) fluxes in a mixed deciduous Quercus-Acer (oak- maple) stand in central Massachusetts, USA, The key hypo>thesis governing the biological component of the model is that stomatal conductance (g(s)) is varied so that daily carbon >uptake per unit of foliar nitrogen is maximized within the limitations of canopy water availability, The hydraulic system >is modelled as an analogue to simple electrical circuits in parallel, including a separate soil hydraulic resistance, plan>t resistance and plant capacitance for each canopy layer, Stomatal opening is initially controlled to conserve plant water> stores and delay the onset of water stress, Stomatal closure at a threshold minimum leaf water potential prevents xylem c>avitation and controls the maximum rate of water flux through the hydraulic system, We show a strong correlation between p>redicted hourly CO2 exchange rate (r(2) = 0 . 86) and LE (r(2) = 0 . 87) with independent whole-forest measurements made b>y the eddy correlation method during the summer of 1992, Our theoretical derivation shows that observed relationships betw>een CO2 assimilation and LE flux can be explained on the basis of stomatal behaviour optimizing carbon gain, and provides an explicit link between canopy structure, soil properties, atmospheric conditions and stomatal conductance./awt/macos/MM>1164^2^Woolgrove,CE^Woodin,SJ^1996^1^Ecophysiology of a snow-bed bryophyte Kiaeria starkei during snowmelt and uptake of nitrate from meltwater^188^74^7^1095-1103^^^^^Jul^^^^^5122p0WhiteitID88>A^5121^Snow is a very efficient scavenger of atmospheric pollutants and because of the dynamics of snowmelt, much of the p>ollutant load of a snowpack is released at very high concentrations in episodes known as the acid flush. The ecological ef> fects of this are largely unknown, but any effects on the bryophyte- dominated vegetation of snow beds will depend in part>! on the physical environment and physiological state of plants under and just out of snow cover. These factors were invest>"igated at a snow bed in the Cairngorm Mountains, Scotland. The subnivean environment is characterized by slightly elevated># CO2 concentrations (up to 70 mu L/L above ambient), temperatures at and just above 0 degrees C, and very low light intens>$ity, with no light penetrating through more than 50 cm depth of snow. Despite overwinter storage in these conditions, the >%bryophyte Kiaeria starkei is shown to be capable of photosynthetic activity immediately after removal of snow cover, and t>&issue chlorophyll and carbohydrate concentrations increase by 250 and 60%, respectively, during the 2 weeks thereafter. Co>'mparison of photosynthetic light responses at 5 and 18 degrees C in plants collected from under and out of snow cover demo>(nstrates acclimatization to seasonal environmental change that must enable maximization of growth during the short growing>) season available. Kiaeria starkei is also shown to be capable of nitrate reductase activity even at 2 degrees C and to as>*similate more than 90% of the pollutant nitrate coming into contact with it in snowmelt. As nitrate is known to be damagin>+g to bryophytes in excess, this demonstrates a real threat of pollutant deposition to rare snow-bed communities in Scotland today and is an important warning for other regions where snow- bed vegetation is important.>-1165^3^Bremer,DJ^Ham,JM^Owensby,CE^1996^1^Effect of elevated atmospheric carbon dioxide and open-top chambers on transpiration in a tallgrass prairie^204^25^4^691-701^^^^^Jul-Aug^^^^^5124>/A^5123^Increasing concentrations of atmospheric carbon dioxide (CO2) may influence plant-water relations in natural and ag>0ricultural ecosystems. A tallgrass prairie near Manhattan, KS, was exposed to elevated atmospheric CO2 using open-top cham>1bers (OTCs). Heat balance sap Bow gauges were used to measure transpiration in ironweed [Vernonia baldwini var. interior (>2Small) Schub.], a C-3 forb, and on individual grass culms of big bluestem (Andropogon gerardii Vitman) and indiangrass [So>3rghastrum nutans (L.) Nash], both C-4 grasses, in each of three treatments: (i) CE (chamber enriched, 2x ambient CO2); (ii>4) CA (chamber ambient, no CO2 enrichment); and (iii) NC (no chamber, no CO2 enrichment). Sap Bow data were coupled with me>5asurements of stomatal conductance, plant/canopy resistance, and whole- chamber evapotranspiration (ET) to determine the e>6ffect of elevated CO2 on water use at different scales. Because of frequent rainfall during the study, all data were colle>7cted under well-watered conditions, Comparisons of CE and CA showed that sap Bow was reduced by 33% in ironweed, 18% in bi>8g bluestem, and 22% in indiangrass under CO2 enrichment. Whole- chamber ET was reduced by 23 to 27% under CO2 enrichment. >9Comparisons of CA and NC showed that the environmental effect of the OTCs caused a 21 to 24% reduction in transpiration, S>:tomatal conductance decreased from 7.9 to 3.6 mm s(-1) in big bluestem and from 5.3 to 3.2 mm s(-1) in indiangrass under C>;O2 enrichment. Soil water was consistently highest under elevated CO2, reflecting the large reductions in transpiration, D>>1166^2^Cotrufo,MF^Ineson,P^1996^1^Elevated CO2 reduces field decomposition rates of Betula pendula (Roth) leaf litter^2^106^4^525-530^^^^^Jun^^^^^5126>@A^5125^The effect of elevated atmospheric CO2 and nutrient supply on elemental composition and decomposition rates of tree>A leaf litter was studied using litters derived from birch (Betula pendula Roth.) plants grown under two levels of atmosphe>Bric CO2 (ambient and ambient+250 ppm) and two nutrient regimes in solar domes. CO2 and nutrient treatments affected the ch>Cemical composition of leaves, both independently and interactively. The elevated CO2 and unfertilized soil regime signific>Dantly enhanced lignin/N and C/N ratios of birch leaves. Decomposition was studied using field litter-bags, and marked diff>Eerences were observed in the decomposition rates of litters derived from the two treatments, with the highest weight remai>Fning being associated with litter derived from the enhanced CO2 and unfertilized regime. Highly significant correlations w>Gere shown between birch litter decomposition rates and lignin/N and C/N ratios. It can be concluded, from this study, that>H at levels of atmospheric CO2 predicted for the middle of the next century a deterioration of litter quality will result i>In decreased decomposition rates, leading to reduction of nutrient mineralization and increased C storage in forest ecosyst>Jems. However, such conclusions are difficult to generalize, since tree responses to elevated CO2 depend on soil nutritional status.>L1167^4^Csintalan,Z^Tuba,Z^Lichtenthaler,HK^Grace,J^1996^1^Reconstitution of photosynthesis upon rehydration in the desiccated leaves of the poikilochlorophyllous shrub Xerophyta scabrida at elevated CO2^4^148^3-4^345-350^^^^^May^^^^^5128>NA^5127^We report the resynthesis of the photosynthetic apparatus and the restoration of its function in the monocotyledono>Ous C-3 shrub Xerophyta scabrida (Pax) Th. Dur. et Schinz (Velloziaceae) following a period of 5 years in the air-dried sta>Pte. Detached leaves were rehydrated at present (350 mu mol mol(-1)) and at elevated CO2 (700 mu mol mol(-1)). Elevated CO2>Q concentration had no effect on the rate of rehydration, nor on the de novo resynthesis pattern of the chlorophylls and ca>Rrotenoids or the development of photochemical activity in the reviving desiccated leaves. The time required to fully recon>Sstitute the photosynthetic apparatus and its function in the air-dried achlorophyllous leaves on rehydration did not diffe>Tr at the two CO2 concentrations. However, respiratory activity during rehydration was more intensive and of longer duratio>Un at high CO2 and net CO2 assimilation first became apparent 12 h later than in the leaves rehydrated at present CO2. Afte>Vr reconstitution of the photosynthetic apparatus, the net CO2 assimilation rate was higher in the high CO2 leaves, however>W it rapidly declined to a value lower than that in the present CO2 plants due to acclimation. This acclimation to elevated>X CO2 occurred only after complete reconstitution of the photosynthetic apparatus. The downward acclimation of photosynthes>Yis was accompanied by a decrease in content of photosynthetic pigments (chlorophyll a + b and carotenoids x + c) and stoma>Ztal conductance. The initial slope of the A/c(i) curve for the high CO2 leaves was much lower and net CO2 assimilation rat>[es were lower at all c(i)'s than in the present CO2 plants. The rate of respiration also decreased and the C- balance of the high CO2 leaves therefore remained similar to that of leaves in present CO2.>]1168^4^Damesin,C^Galera,C^Rambal,S^Joffre,R^1996^1^Effects of elevated carbon dioxide on leaf gas exchange and growth of cork-oak (Quercus suber L) seedlings^186^53^2-3^461-467^^^^^^^^^^5130 ~WRL2318.tmpsave of 4c>_A^5129^Leaf gas exchange and growth were determined on cork-oak (Quercus suber L) seedlings which were grown from acorns f>`or periods of up to 4 months in greenhouses at ambient (350 mu mol mol(-1)) and at elevated (700 mu mol mol(-1)) concentra>ations of carbon dioxide. In well-watered conditions, daily maximum photosynthesis (15 mu mol m(-2) s(-1)) and stomatal con>bductance (440 mmol m(-2) s(-1)) of plants grown and measured at 700 mu mol mol(-1) CO2 did not differ from those of plants>c grown and measured at 350 mu mol mol(-1). In conditions of moderate drought, net CO2 assimilation was at least twice as g>dreat in elevated CO2, but stomatal conductance was unchanged. Elevated CO2 affected total biomass production, the average >eincrease being 76 and 97% at 3 and 4 months, respectively. Shoot biomass, root biomass, stem height and total leaf area we>fre increased by elevated CO2. Root and stem ramification were also enhanced by elevated CO2, but no change in root/shoot ratio was observed.>h1169^1^Diemer,M^1996^1^The incidence of herbivory in high-elevation populations of Ranunculus glacialis: A re-evaluation of stress-tolerance in alpine environments^15^75^3^486-492^^^^^Apr^^^^^5132>jA^5131^Growing conditions in the upper alpine zone are characterized by low temperature, low partial pressures of CO2 and,>k in the temperate zone, a short growing period. The plants which have evolved under these conditions presumably share a nu>lmber of characteristics that were ascribed to stress-tolerance, namely slow growth, extended longevity, resource limitatio>mn and low palatability to herbivores. Hence chronic biomass removals by herbivores should be a threat to plant persistence>n in alpine environments. as predicted by Grime's C-S-R theory. I tested this hypothesis on populations of an alpine butter>ocup, Ranunculus glacialis. A survey along an altitudinal transect in the Central Alps of Austria indicated that between 15>p and 26% of the R. glacialis plants in each population examined exhibited signs of herbivory damage. Merely a small popula>qtion, isolated by glaciers, at the highest site (3310 m a.s.l.) showed no traces of herbivory. Ar two sites (2600 m and 31>r80 m a.s.l.) twenty plants each were tagged and examined for a two- year period. Herbivory damage was considerable: on an >saverage nearly 25% of a plant's total leaf area was removed in 1987. primarily by snow mice (Microtus nivalis). Infloresce>tnces of 65-85% of all flowering plants were removed as well. Ar the lower sire (2600 m, roughly 600 m above the treeline) >uup to 5 g dry matter and 140 mg nitrogen m(-2) were consumed in one season. Despite the magnitude of these losses both rep>vroductive investment and the number of leaves initiated per plant did not change appreciably in the subsequent year. Since>w populations of R. glacialis are able to support populations of herbivores at the altitudinal limits of plant growth witho>xut obvious reductions in vigor,these plants and other food species (e.g. Oxyria digyna) cannot fit the stress-tolerator sc>yheme proposed by Grime. The widespread occurrence of herbivory at high elevations and plant traits challenge the concept of stress- tolerance as it is commonly applied to alpine environments.>{1170^4^Fangmeier,A^Gruters,U^Vermehren,B^Jager,HJ^1996^1^Responses of some cereal cultivars to CO2 enrichment and tropospheric ozone at different levels of nitrogen supply^292^70^1-2^12-18^^^^^May^^^^^5134>}A^5133^Two cultivars of spring wheat (Triticum aestivum L. cv. 'Nandu' and cv. 'Minaret') and one cultivar of spring barle>~y (Hordeum vulgare L. cv. 'Alexis') were exposed to CO2 enrichment (concentrations ranging from 363 to 650 mu l l(-1)), oz>one (ambient and 1.7 times ambient levels) at different levels of nitrogen nutrition in open-top field chambers from sowin>g to maturity. CO2 increased grain yield and shoot biomass, barley showing the smallest response and wheat 'Nandu' being m>ost responsive. The cultivars were rather insensitive to ozone, however, a decrease of thousand grain weight was observed >in one of the wheat cultivars ('Minaret') at high ozone levels. In this cultivar, interactions between CO2 and ozone were >observed. Elevated CO2 appeared to be protective against impairments caused by ozone. CO2 and nitrogen supply strongly int>eracted. CO2 fertilizing effects on grain yield of wheat 'Minaret' ranged from 22.9 % at 120 kg N ha(-1) to 47.4 % at 330 >kg N ha(-1). Increase in grain yield by CO2 was accompanied with a decrease of grain nitrogen content. Grain yield increas>e and grain nitrogen content depression exactly compensated each other and led to constant amounts of nitrogen stored in t>he grains on an area unit basis independent from the applied CO2 concentration. The grain quality, assessed as nitrogen co>ntent, was severely decreased by CO2 enrichment. The regressions obtained from the data suggest that nearly twice the nitr>ogen supply will be required to maintain the nitrogen content in grains at the same level if CO2 concentrations rise from the current 363 mu l l(-1) (seasonal mean 1994) to 650 mu l l(-1).P`@>1171^3^George,V^Gerant,D^Dizengremel,P^1996^1^Photosynthesis, Rubisco activity and mitochondrial malate oxidation in pedun>culate oak (Quercus robur L) seedlings grown under present and elevated atmospheric CO2 concentrations^186^53^2-3^469-474^^^^^^^^^^5136"@B@VV"V@ -lV4V(RV HC:\PROGRAM FILES\NOR>A^5135^Pedunculate oak seedlings were grown at 350 and 700 mu L/L CO2 in controlled chambers. After 130 days at elevated C>O2, the biomass of the whole plant did not significantly increase. Photosynthesis, Rubisco activity, mitochondrial malate >oxidation, carbohydrates and nitrogen contents were examined in the fourth growth flush. At 700 mu L/L CO2, the leaf net p>hotosynthetic rate was 220% higher than at 350 mu L/L CO2. The decreased activity of Rubisco was accompanied by an accumul>ation of sucrose and glucose. The decreased oxidative capacity of crude leaf mitochondria from elevated CO2 plants was dri>ven by the lower nitrogen and protein contents rather than by the higher carbohydrates contents in the leaves. Nevertheless, direct effects of elevated CO2 on the respiratory biochemistry cannot be excluded.0 h h >1172^2^Gorny,JR^Kader,AA^1996^1^Controlled-atmosphere suppression of ACC synthase and ACC oxidase in 'Golden Delicious' apples during long-term cold storage^154^121^4^751-755^^^^^Jul^^^^^51380. 0/ 06 07 0>A^5137^Preclimacteric 'Golden Delicious' apples (Malus domestica Borkh.) were stored at 0 degrees C in: air; air + 5% CO2;> 2% O- 2 + 98% N-2; or 2% O-2 + 5% CO2 + 93% N-2, and sampled monthly for 4 months to investigate the mechanism(s) by whic>h reduced O-2 and/or elevated CO2 atmospheres inhibit C2H4 biosynthesis. Ethylene biosynthesis rates and in vitro ACS acti>vity were closely correlated in all treatments, while in vitro ACO activity significantly increased over time regardless o>f the treatment. Only a small amount of C2H4 biosynthesis inhibition by lowered O-2 and/or elevated CO2 atmospheres could >be accounted for by suppressed induction of ACO activity, Western blot analysis demonstrated that apples held for 2 months> in lowered O-2 and/or elevated CO2 atmospheres had significantly reduced abundance of ACO protein, compared to fruit held> in air. Northern blot analysis of ACS and ACO transcript abundance revealed that reduced O-2 and/or elevated CO2 atmosphe>res delay induction and reduce the abundance of both transcripts, Reduced O-2 and/or elevated CO2 atmospheres reduce C2H4 >biosynthesis by delaying and suppressing expression of ACS at the transcriptional level and by reducing the abundance of a>ctive ACO protein. Chemical names used: 1-aminocyclopropane-1- carboxylic acid (ACC), ACC synthase (ACS), ACC oxidase (ACO), ethylene (C2H4), S-adenosylmethionine (AdoMet).ap8@.rsrcPDP>1173^5^Henning,FP^Wood,CW^Rogers,HH^Runion,GB^Prior,SA^1996^1^Composition and decomposition of soybean and sorghum tissues grown under elevated atmospheric carbon dioxide^204^25^4^822-827^^^^^Jul-Aug^^^^^5140$>A^5139^It has been hypothesized that changes in both quantity and quality of plant residue inputs to soils as atmospheric >carbon dioxide (CO2) concentration increases may alter carbon (C) and nitrogen (N) turnover rates and pool sizes, We deter>mined the effect of elevated atmospheric CO2 on plant tissue quality, and flow modifications in tissue quality affect C an>d N mineralization. Soybean [C-3; Glycine max (L.) Merr. cv. Stonewall] and sorghum [C-4; Sorghum bicolor (L.) Moen, cv. S>avanna 5] were grown under elevated (704.96 +/- 0.33 mu mol CO2 mol(-1)) and ambient (357.44 +/- 0.12 mu mol CO2 mol(-1)) >atmospheric CO2 in open-top chambers, Leaf and stem tissues were separated from harvested plants and analyzed for C, N, li>gnin, and cellulose. Tissues were applied to Norfolk loamy sand (fine-loamy, siliceous, thermic Typic Kandiudult) and aero>bically incubated for 70-d to determine C and N mineralization, C turnover, relative N mineralization, and C/N mineralized>. Elevated CO2 had no effect on plant residue C concentration, but N concentration of soybean leaves and stems and sorghum> stems was reduced; however, CO2 enrichment increased C/N ratio and lignin concentration for only sorghum stems and soybea>n leaves, respectively. Source of plant residue (i.e., produced under either elevated or ambient CO2) had no impact on soi>l C turnover, relative N mineralization, cumulative C and N mineralization, and C/N mineralized, These data suggest that i>ncreasing atmospheric CO2 will have little effect on composition or decomposition of field crop residues. Thus, since CO2 >enrichment results in increased photosynthetic C fixation, the possibility exists For increased soil C storage under field crops in an elevated CO2 world.р|7D 0@P`p>1174^3^Islam,MS^Matsui,T^Yoshida,Y^1996^1^Effect of carbon dioxide enrichment on physico-chemical and enzymatic changes in tomato fruits at various stages of maturity^165^65^2-3^137-149^^^^^Jun^^^^^5142VV$P W>A^5141^The influence of CO2 enrichment on fruit growth, firmness and colour, together with its effect on the concentration>s of ascorbic acid, organic acids and sugars, and the activities of sucrose synthase (SS) (UDP glucose: D-fructose 2- gluc>osyltransferase, E. C. 2, 4, 1, 13) and sucrose phosphate synthase (SPS) (UDP glucose: D-fructose-6-phosphate 2- glucosylt>ransferase, E. C. 2. 4. 1. 14) were determined at various stages of maturity in fruits of tomato (Lycopersicon esculentum >Mill. cv. Momotaro), CO2 enriched tomatoes had lower amounts of citric, malic and oxalic acids, and higher amounts of asco>rbic acid, fructose, glucose and sucrose synthase activity than the control. Elevated CO2 enhanced fruit growth and colour>ing during development. Citric acid was the primary organic acid followed by malic and oxalic acids. The concentration of >organic acids (mg g(-1) fresh weight) and of ascorbic acid (mg 100g(-1) fresh weight) increased with the maturity of fruit>s; their maximum concentrations were found at the pink stage of ripening, but declined slightly at the red stage. The amou>nt of reducing sugars (mg g(-1) fresh weight) increased with the advancement of maturity, with fructose being the predomin>ant sugar. The decrease in SS activity was accompanied by an increase in the concentrations of reducing sugars. There were> no significant differences in fruit firmness, sucrose concentration and SPS activity between the treatments. The SPS acti>vity did not change, but remained relatively constant throughout fruit development. The results also suggest that SS levels correlated positively with sucrose concentration but negatively with the concentration of reducing sugars.WW>1175^3^King,JS^Thomas,RB^Strain,BR^1996^1^Growth and carbon accumulation in root systems of Pinus taeda and Pinus ponderosa seedlings as affected by varying CO2, temperature and nitrogen^13^16^7^635-642^^^^^Jul^^^^^5144*W $C:\WINDOWS\S>A^5143^It has been hypothesized that increasing atmospheric CO2 concentration enhances accumulation of carbon in fine root>s, thereby altering soil carbon dynamics and nutrient cycling. To evaluate possible changes to belowground pools of carbon> and nitrogen in response to elevated CO2, an early and a late successional species of pine (Pinus taeda L. and Pinus pond>erosa Dougl. ex Laws, respectively) were grown from seed for 160 days in a 35 or 70 Pa CO2 partial pressure at low or high> temperature (30-year weekly mean and 30 year weekly mean + 5 degrees C) and a soil solution nitrogen concentration of 1 o>r 5 mM NH4NO3 at the Duke University Phytotron. Seedlings were harvested at monthly intervals and growth parameters of the> primary root, secondary root and tap root fractions evaluated. Total root biomass of P. ponderosa showed a positive CO2 r>esponse (105% increase) (P = 0.0001) as a result of significant increases in all root fractions in the elevated CO2 treatm>ent, but all other main effects and interactions were insignificant. In I? taeda, there were significant interactions betw>een CO2 and temperature (P = 0.04) and CO2 and nitrogen (P = 0.04) for total root biomass. An allometric analysis indicate>d that modulation of the secondary root fraction was the main response of the trees to altered environmental conditions. I>n P. ponderosa, there was an increase in the secondary root fraction relative to the primary and tap root fractions under >conditions of low temperature. In P. taeda, there was a shift in carbon accumulation to the secondary roots relative to th>e primary roots under low temperature and low nitrogen. Neither species exhibited shifts in carbon accumulation in respons>e to elevated CO2. We conclude that both species have the potential to increase be lowground biomass substantially in resp>onse to rising atmospheric CO2 concentration, and this response is sensitive to temperature and nitrogen in P. taeda. Both> species displayed small shifts in belowground carbon accumulation in response to altered temperature and nitrogen that may have substantial ecosystem consequences over time.>1176^2^Li,W^Campbell,WJ^1996^1^Response of rubisco activase protein levels in two species following grown at elevated CO2^8^111^2^347^^^^^JunW4l$4X4X A>1177^3^Madsen,TV^Maberly,SC^Bowes,G^1996^1^Photosynthetic acclimation of submersed angiosperms to CO2 and HCO3-^159^53^1-2^15-30^^^^^Mar^^^^^5147 ` 4X>A^5146^Photosynthetic acclimation after growth under a factorial combination of three concentrations of CO2 (1, 16 and 910> mu M) and two concentrations of HCO3- (0.2 and 1.5 mM) was measured for Callitriche cophocarpa Sendt., Elodea canadensis >L.C. Rich. and Ranunculus peltatus Schrank. Callitriche cophocarpa was restricted to CO2 as a carbon source while the othe>r two species also used HCO3-. None of the species showed C-4-like photosynthesis as evidenced by low activities of phosph>oenolpyruvate carboxylase. Carbon exchange characteristics and biochemical capacities were down-regulated in response to i>ncreasing inorganic carbon during growth. In all three species, P-max initial slope of net photosynthesis versus [CO2], ru>bisco activity, protein content and chlorophyll content decreased, and CO2 compensation concentration increased with incre>ased inorganic carbon, In addition, for the two HCO3- users, the rate of HCO3--dependent photosynthesis at zero [CO2] and >1.5 mM HCO3- decreased with inorganic carbon. The response to increased [GO,] was greater than that to increased [HCO3-]. >Morphological acclimation to inorganic carbon was evident in all species. The root/shoot ratio increased with increasing [>CO2] but was unaffected by [HCO3-]. The specific leaf area declined with carbon availability in Callitriche and Ranunculus>, whereas no change was observed in Elodea. There was a significant positive correlation between various carbon exchange c>haracteristics and between these and the chlorophyll content and rubisco activity, suggesting that carbon exchange, light >capture and carbon fixation are regulated in parallel in response to carbon availability. The general down-regulation resp>onse shown by these aquatic plants to elevated inorganic carbon resembles the response of some terrestrial C-3 species to elevated CO2.>1178^2^Marks,S^Lincoln,DE^1996^1^Antiherbivore defense mutualism under elevated carbon dioxide levels: A fungal endophyte and grass^238^25^3^618-623^^^^^Jun^^^^^5149 4XMXMXLc:\WIN>A^5148^Previous studies have shown that insects commonly consume more when fed leaf tissue grown under CO2 enrichment, but> with few negative effects on growth. However, lepidopteran larvae fed tissue infected with Balansiae fungal endophytes (w>hich produce toxic alkaloids) typically eat less but also suffer negative effects on growth and survival. This study was c>arried out to understand how these 2 factors may interact to affect larval consumption and growth in fall armyworm, Spodop>tera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae). Infected and uninfected ramets of a single genotype of tall fescue>, Festuca arundinacea Schreb., were grown under CO2 concentrations of 400 and 700 mu l CO2/liter of air. Relative consumpt>ion of leaf tissue by larvae was 32% greater in the high CO2 treatment compared with leaves grown under low CO2 concentrat>ions, but was not influenced by infection. As expected, larvae had significantly decreased relative growth rates when fed >infected tissue, with their growth rates somewhat increased under high CO2 levels increased CO2 level and infection both l>ed to significantly reduced efficiency of conversion of ingested food. These 2 factors also interacted so that the lowest >efficiency of conversion of ingested food was seen when both infection and an enriched atmospheric CO2 environment were pr>esent. As global atmospheric CO2 levels continue to increase, it appears that fungal endophytes will continue to be import>ant in turfgrasses as protection against insect herbivores and may lead to increased fitness for infected plant genotypes.W4XWAB7IWͥ,W4XGTb1B>1179^3^Morokuma,M^Yajima,M^Yonemura,S^1996^1^Effects of elevated CO2 concentration and warming on growth and yield of rice^160^65^2^222-228^^^^^Jun^^^^^5151o cause nutrient deficiencies over the approximate 1-year duration of these studies. 4X>1230^7^Kull,O^Sober,A^Coleman,MD^Dickson,RE^Isebrands,JG^Gagnon,Z^Karnosky,DF^1996^1^Photosynthetic responses of aspen clones to simultaneous exposures of ozone and CO2^155^26^4^639-648^^^^^Apr^^^^^5250HXHXSep^^^^^5664W8NE0LL0e0e 0e|7 ?A^5150^Effects of combined treatments of CO2 (400, 660, 1200 ppm) and air temperature (outdoor tracking, outdoor+2 degrees? C) on growth and yield of rice (Oryza sativa L. cv. Nipponbare) grown in growth chambers under natural sunlight were inve?stigated. The effects of container size (tank, 3.5 l pot) on growth and yield were also examined. Plants were grown under ?simulated paddyfield conditions. Growth parameters under the elevated CO2 and temperature conditions were promoted at the ?maximum tiller number stage but nor at the heading stage, without appreciable difference in such parameters. In the 660HT ?plot, dry weight increased about 30% at both stages compared with the 400NT plot. In the 1200HT plot, it increased more th?an that of the 660HT plot at the maximum tiller number stage but at the heading stage, the degree of promotion was decreas? ed substantially. Dry matter distribution to leaf blades was reduced, and the nitrogen ratio in leaf blades were low in pl? ants grown in both 660HT and 1200HT plants. In the 1200HT plot, the yield was remarkably reduced probably due to the high ? temperature sterility. Potted, limited-root-space plants grew smaller above-ground parts than did tank plants (less limite? d), without any difference in root production. From these results, the production processes of rice crop are discussed in terms of climate conditions predicted for the future.`|7dh|7l?1180^4^Newton,PCD^Clark,H^Bell,CC^Glasgow,EM^1996^1^Interaction of soil moisture and elevated CO2 on the above- ground growth rate, root length density and gas exchange of turves from temperate pasture^78^47^299^771-779^^^^^Jun^^^^^5153WX8;e?A^5152^Interactions between water availability and elevated atmospheric CO2 concentrations have the potential to be import?ant factors in determining future forage supply from temperate pastures, Using large turves from an established pasture, t?he response of these communities at 350 or 700 mu l l(-1) CO2 to a soil moisture deficit and to recovery from the deficit ?in comparison to turves that were well-watered throughout was measured, Prior to this experiment the turves had been expos?ed to the CO2 treatments for 324 d. Net CO2 exchange continued at elevated CO2 even when the volumetric soil moisture cont?ent was less than 0.10 m(3) m(-3) soil; at the same moisture deficit gas exchange at ambient CO2 was zero. The additional ?carbon fixed by the elevated CO2 turves was primarily allocated below-ground as shown by the maintenance of root length de?nsity at the same level as in well-watered turves, When the dry turves were rewatered there was compensatory growth at amb?ient CO2 so that the above-ground growth rate exceeded that of turves that had not experienced a moisture deficit, At the ?start of this experiment, the turves that were growing at 700 mu l l(-1) CO2 had a greater proportion of legume (principal?ly white clover, Trifolium repens L.) in the harvested herbage, There was a trend for the legume content at elevated CO2 t?o be reduced under a soil moisture deficit. The results indicate different strategies in response to soil moisture deficit?s depending on the CO2 concentration, At ambient CO2, growth stopped, but plants were able to respond strongly on rewateri?ng; while at elevated CO2 growth continued (particularly belowground), but no additional growth was evident on rewatering.? Ecosystem gas exchange measurements taken at the end of the experiment (after 429 d of exposure to CO2) showed 33% more CO2 was fixed at elevated CO2 with only a small (12%) and nonsignificant downward regulation.^X_X:1181^1^Norby,RJ^1996^1^Oaks in a high-CO2 world^186^53^2-3^413-429^^^^^^^^^^5155_Xl_XQ>_4IX4IX$?!A^5154^The concentration of carbon dioxide in the atmosphere is one environmental factor that is certain to influence the ?"physiology and productivity of oak trees everywhere. Direct assessment of the impact of increasing CO2 is very difficult, ?#however, because of the long-term nature of CO2 effects and the myriad potential interactions between CO2 and other enviro?$nmental factors that can influence the physiological and ecological relationships of oaks. The CO2 responses of at least 1?%1 Quercus species have been investigated, primarily in experiments with seedlings. The growth response varies considerably?& among these experiments, and there appears to be no basis for differentiating the response of oaks as a group from those ?'of other woody plants. The more important challenge is to find a basis for addressing questions about the responses of oak?( forest ecosystems from experimental data on individual seedlings and saplings. A series of experiments with white oak (Qu?)ercus alba L) seedlings and saplings was focused toward larger-scale questions, such as whether N limitations would preclu?*de growth responses to elevated CO2 and whether short- term physiological responses could be sustained over longer time sc?+ales. These experiments suggested three issues that are particularly important for addressing forest responses: leaf area ?,dynamics, fine root production, and biotic interactions. By focusing seedling and sapling experiments toward these issues,?- we gain insight into the important processes that will influence ecosystem response and, at least in a qualitative sense, the sensitivity of those processes to elevated CO2.$WlXDWW$?/1182^3^Picon,C^Guehl,JM^Aussenac,G^1996^1^Growth dynamics, transpiration and water-use efficiency in Quercus robur plants submitted to elevated CO2 and drought^186^53^2-3^431-446^^^^^^^^^^5157dIXdIX$,XXhD?1A^5156^Seedlings of pedunculate oak (Quercus robur L) were grown for one growing season under ambient (350 mu mol mol(-1))?2 and elevated (700 mu mol mol(-1)) atmospheric CO2 concentration ([CO2]) either in well-watered or in droughted (the water?3 supply was 40% of the well-watered plants transpiration in both [CO2]) conditions. In the droughted conditions, gravimetr?4ic soil water content (SWC) was on average 4 10(-2) g g(-1) lower under elevated [CO2]. In well-watered conditions, biomas?5s growth was 39% higher in the elevated [CO2] treatment than under ambient [CO2]. However relative growth rate (RGR) was s?6timulated by the elevated [CO2] only for 17 days, in July, at the end of the stem elongation phase (third growing flush), ?7which corresponded also to the phase of maximum leaf expansion rate. Both the number of leaves per plant and the plant lea?8f area were 30% higher in the elevated [CO2] treatment than under ambient [CO2]. In the droughted conditions, no significa?9nt enhancement in biomass growth and in plant leaf area was brought about by the elevated [CO2]. Transpiration rate was lo?:wer in the elevated [CO2] conditions, but whole plant water use was similar in the two [CO2] treatments, reflecting a comp?;ensation between leaf area and stomatal control of transpiration. Transpiration efficiency (W = biomass accumulation/plant?< water use) was improved by 47% by the elevated [CO2] in well-watered conditions but only by 18% in the droughted conditio?=ns. Carbon isotope discrimination (Delta) was decreased by drought and was increased by the elevated [CO2]. A negative lin?>ear relationship was found between transpiration efficiency divided by the atmospheric [CO2] and Delta, as predicted by theory./x,|n,N?@1183^2^Roden,JS^Ball,MC^1996^1^The effect of elevated [CO2] on growth and photosynthesis of two eucalyptus species exposed to high temperatures and water deficits^8^111^3^909-919^^^^^Jul^^^^^5159o€ŀ8ƀ:Ȁ?BA^5158^Two species of eucalyptus (Eucalyptus macrorhyncha and Eucalyptus rossii) were grown for 8 weeks in either ambient ?C(350 mu L L(-1)) or elevated (700 mu L L(-1)) CO2 concentrations, either well watered or without water additions, and subj?Dected to a daily, 3-h high-temperature (45 degrees C, maximum) and high-light (1250 mu mol photons m(-2) s(-1), maximum) s?Etress period. Water-stressed seedlings of E. macrorhyncha had higher leaf water potentials when grown in elevated [CO2]. G?Frowth analysis indicated that increased [CO2] may allow eucalyptus species to perform better during conditions of low soil?G moisture. A down-regulation of photosynthetic capacity was observed for seedlings grown in elevated [CO2] when well water?Hed but not when water stressed. Well-watered seedlings grown in elevated [CO2] had lower quantum efficiencies as measured ?Iby chlorophyll fluorescence (the ratio of variable to maximal chlorophyll fluorescence [F- v/F-m]) than seedlings grown in?J ambient [CO2] during the high- temperature stress period. However, no significant differences in F-v/F-m were observed be?Ktween CO2 treatments when water was withheld. The reductions in dark-adapted F-v/F-m for plants grown in elevated [CO2] we?Lre not well correlated with increased xanthophyll cycle photoprotection. However, reductions in the F-v/F-m were correlate?Md with increased levels of nonstructural carbohydrates. The reduction in quantum efficiencies for plants grown in elevated?N [CO2] is discussed in the context of feedback inhibition of electron transport associated with starch accumulation and variation in sink strength._/^/>tBF  A?P1184^3^Rosenqvist,E^Pedersen,H^Ottosen,CO^1996^1^Effects of elevated CO2 on growth and photosynthesis in dendranthema grandiflorum^8^111^2^355^^^^^JuntF g/f/>tBF  A?R1185^2^Rosenzweig,C^Tubiello,FN^1996^1^Effects of changes in minimum and maximum temperature on wheat yields in the central US - A simulation study^107^80^2-4^215-230^^^^^Jul^^^^^5162tBF  A?TA^5161^Recent observations and general circulation models indicate that future temperature changes linked to global warmin?Ug might be characterized by a marked asymmetry between daytime maxima and nighttime minima. We investigate the importance ?Vof such a pattern in determining future wheat (Triticum aestivum) yields in the Central United States by using a dynamic c?Wrop growth model, CERES-Wheat, modified to include physiological effects of temperature and CO2 on canopy photosynthesis. ?XSimulations are run at four sites spanning a north-south transect of the Central US; four mean temperatures increases (1-4?Y degrees C) are applied to baseline daily climate data (1951-1980). The effects of two different scenarios of temperature ?Zchange (minimum and maximum temperatures equally raised; minima increased three times as much as maxima in agreement with ?[recent observations) are analyzed under both current (330 ppm) and elevated (550 ppm) CO2 concentrations. The main mechani?\sms controlling the simulated wheat responses are direct and indirect temperature effects on wheat phenological developmen?]t. Negative effects of temperature on simulated wheat yields are reduced when minima increase more than maxima. Yield chan?^ges are consistently negative under temperature change and current CO2 concentration, while they range from positive to ne?_gative under temperature change and elevated CO2 concentration. Responses vary across the transect, with larger negative effects occurring at the southernmost site.dR GOSF"f ?ߌ~KO&%?a1186^2^Saebo,A^Mortensen,LM^1996^1^Growth, morphology and yield of wheat, barley and oats grown at elevated atmospheric CO2 concentration in a cool, maritime climate^169^57^1^9-15^^^^^15 Apr^^^^^5164xeeee^eje?cA^5163^The effects of elevated CO, concentration on the growth, yield and quality of spring wheat (Triticum aestivum L., c?dv. 'Sport'), barley( Hordeum vulgare, cv. 'Thule') and oats(Avena sativa, cv. 'Kapp') were studied. The study was performe?ed from 20 April to 24 August in ten field chamber units each of 9 m(2) in a cool (12.6 degrees C) maritime climate under l?fong days (14.6-18.1 h), on the southwest coast of Norway (59 degrees N, 6 degrees E). The total biomass increased at high ?gCO2 concentration, by 11% and 20% in wheat and barley, respectively. The proportion of small grains increased by 6% in whe?hat and 26% in barley, but the total grain yield was not affected. The weight of chaff increased by 9% and 19% in wheat and?i barley, respectively. Plant height was significantly reduced during the growing season at elevated CO2, by 8-19% in barle?jy and by 9-25% in oats until 6 July when no significant difference in height was found. After 6 July, barley plants at ele?kvated CO2 were significantly taller than at ambient CO2 concentration and oats were not affected. Elongation in wheat was ?lnot affected by CO2 concentration at any time in the growing season. No difference in developmental rate could be detected?m between plants at normal and elevated CO2 concentrations. The protein content of the grain decreased by 8% in barley, but was not significantly affected in the other species.p0{{{{{sppp70{{{pww?o1187^3^Schwanz,P^Haberle,KH^Polle,A^1996^1^Interactive effects of elevated CO2, ozone and drought stress on the activities?p of antioxidative enzymes in needles of Norway spruce trees (Picea abies, [L] Karsten) grown with luxurious N- supply^4^148^3-4^351-355^^^^^May^^^^^516688x3xxxx Ѐ?rA^5165^The aim of the present study was to address the complex interactions of environmental constraints, ozone and drough?st stress, with elevated atmospheric CO2 on the activities of antioxidative enzymes and soluble protein contents in needles?t of Norway spruce trees (Picea abies L.). Five-year-old spruce trees were kept from bud break in June until January of the?u following year in phytochambers under climatic conditions similar to those of a natural site in the Bavarian forest. The ?vtrees were well-supplied with nitrogen and exposed to either elevated CO2 (ambient + 200 mu LL(-1)), elevated ozone (80 nL?wL(-1), from June to October) or to a combination of both factors. Controls were grown with 20 nLL(-1) O-3 and ambient CO2 ?xlevels. In each chamber, a subset of trees was subjected to episodical drought stress in summer. Needles from controls inv?yestigated in October (summer conditions) and January (winter conditions) showed little seasonal variation of superoxide di?zsmutase (SOD), an approximately 2-fold reduction in catalase (CAT), and a 2-fold increase in guaiacol peroxidase (POD) act?{ivity. Exposure to elevated CO2 did not affect the activities of any of these enzymes in October and January, respectively?|, but caused a significant reduction in soluble protein. Ozone had no significant effect. Drought stress caused memory eff?}ects. In January, needles from trees drought-stressed in summer contained higher activities of defence enzymes and soluble?~ protein contents than needles from well-watered trees. Three weeks after the end of a drought episode in summer, needles ?from spruce trees grown at elevated CO2 contained increased CAT and POD activities as compared to needles from trees grown? at ambient CO2. This response was increased, if elevated ozone was present as an additional stress factor. These observat?ions suggest that Norway spruce trees grown under elevated atmospheric CO2 concentrations might better be able to compensate environmental stresses than trees grown at ambient atmospheric CO2 concentrations.?1188^4^Tausz,M^DeKok,LJ^Stulen,I^Grill,D^1996^1^Physiological responses of Norway spruce trees to elevated CO2 and SO2^4^148^3-4^362-367^^^^^May^^^^^5168?A^5167^Young Norway spruce (Picea abies (L.) Karst.) trees were exposed to elevated CO2 (0.8 mL L(-1)), SO2 (0.06 mu L L(-?1)), and elevated CO2 and SO2 (0.8 mL L(-1) and 0.06 mu L L(-1), respectively) for three months. Exposure to elevated CO2 ?resulted in an increased biomass production of the needles, while the pigment content was decreased. Exposure to SO2 hardl?y affected growth and pigment contents. Chlorophyll/carotenoid- and chlorophyll a/chlorophyll b-ratios were not affected b?y either CO2 or SO2. The epoxidation state of the xanthophyll- cycle was changed upon SO2-exposure, due to a higher zeaxan?thin and a lower violaxanthin content. Chlorophyll fluorescence measurements showed F-v/F-m-ratios of 0.7 or higher for al?l needles, which indicated a healthy photosynthetic apparatus. Exposure to SO2 resulted in increased foliar contents of su?lfate, total glutathione (reduced and oxidized form), cyst(e)ine, and a slightly more reduced redox state of glutathione. ?Exposure to elevated CO2 resulted in a slight decrease in glutathione contents, but it did not affect sulfate or cyst(e)in?e contents of the spruce needles. Neither ascorbic acid content nor its redox state were affected by CO2 or SO2. The effects of CO2 and SO2 were independent from each other, since significant interactions CO(2)xSO(2) were not observed.?1189^5^Tognetti,R^Giovannelli,A^Longobucco,A^Miglietta,F^Raschi,A^1996^1^Water relations of oak species growing in the natural CO2 spring of Rapolano (central Italy)^186^53^2-3^475-485^^^^^^^^^^5170?A^5169^The effect of elevated atmospheric carbon dioxide on water relations was examined on downy oak (Quercus pubescens) ?and helm oak (Q ilex) trees. The study was conducted on trees growing in a naturally enriched CO2 spring. Sap velocity and? sap flow were measured by the heat pulse technique. On the same trees, daily courses of xylem water potential, leaf condu?ctance and transpiration were monitored. Plant water relations were evaluated by pressure-volume analysis method on shoots?; on the same branches, relative conductivity of xylem was measured. Both species exhibited increased osmotic potential an?d decreased symplasmic fraction of water in trees adapted to increased CO2. Downy oak showed lower stomatal conductance un?der elevated CO2, but helm oak did not. Both species displayed higher sap flow in control trees. In both species, increased carbon dioxide did not influence xylem embolism formation.?1190^6^Torbert,HA^Prior,SA^Rogers,HH^Schlesinger,WH^Mullins,GL^Runion,GB^1996^1^Elevated atmospheric carbon dioxide in agroecosystems affects groundwater quality^204^25^4^720-726^^^^^Jul-Aug^^^^^5172?A^5171^Increasing atmospheric carbon dioxide (CO2) concentration has led to concerns about global changes to the environme?nt, One area of global change that has not been addressed is the effect of elevated atmospheric CO2 on ground water qualit?y below agroecosystems, Elevated CO2 concentration alterations of plant growth and C/N ratios may modify C and N cycling i?n soil and affect nitrate (NO3-) leaching to groundwater. This study was conducted to examine the effects of a legume {soy?bean [Glycine max (L.) Merr.]} and a nonlegume {grain sorghum [Sorghum bicolor (L.) Moench]} CO2-enriched agroecosystems o?n NO3- movement below the root zone in a Blanton loamy sand (loamy siliceous, thermic, Grossarenic Paleudults). The study ?was a split-plot design replicated three times with plant species (soybean and grain sorghum) as the main plots and CO2 co?ncentration (approximate to 360 and similar to 720 mu L L(-1) CO2) as subplots using open-top held chambers. Fertilizer ap?plication was made with N-15-depleted NH4NO3 to act as a fertilizer tracer, Soil solution samples were collected weekly at? 90-cm depth for a 2-yr period arid monitored for NO3-N concentrations. Isotope analysis of soil solution indicated that t?he decomposition ol organic matter was the primary source of NO3--N in soil solution below the root zone through most of t?he monitoring period. Significant differences were observed for NO3--N concentrations between soybean and grain sorghum, w?ith soybean having the higher NO3--N concentrations. Elevated CO2 increased total dry weight, total N content, and C/N rat?io of residue returned to soil in both years. Elevated CO2 significantly decreased NO3--N concentrations below the root zo?ne in both soybean and grain sorghum. The results of this study indicate that retention of N in organic pools because of e?levated atmospheric CO2 could reduce the nitrate concentration in groundwater beneath agroecosystems as indicated by NO3- movement.?1191^5^Tuba,Z^Szente,K^Nagy,Z^Csintalan,Z^Koch,J^1996^1^Responses of CO2 assimilation, transpiration and water use efficiency to long-term elevated CO2 in perennial C-3 xeric loess steppe species^4^148^3-4^356-361^^^^^May^^^^^5174?A^5173^CO2 assimilation (A), transpiration (E), water use efficiency (WUE), leaf-nitrogen and carbohydrate responses to 11? months elevated (700 mu mol mol(-1)) CO2 exposure in four perennial C- 3 species (Festuca rupicola, Dactylis glomerata, F?ilipendula vulgaris, Salvia nemorosa) from a xeric temperate loess steppe are reported. The responses in the species varie?d greatly owing to their differing acclimation. The acclimation of photosynthesis was somewhat downward in F. rupicola, fu?lly downward in D. glomerata, and upward in S. nemorosa and F. vulgaris. The reduction in the initial slope of the A/c(i) ?response curve in E rupicola and D. glomerata suggested a decrease in Rubisco capacity. Net CO2 assimilation at 700 mu mol? mol(-1) CO2 c(a) in the high CO2 F. rupicola was higher than in those grown at present (350 mu mol mol(-1)) CO2; there wa?s no difference in D. glomerata. The initial slope of the A/c(i) curve indicated an increased Rubisco capacity in high CO2? F. vulgaris and S. nemorosa. Their net CO2 assimilation was higher in the plants grown in the high CO2 treatment at c(i)'?s over 200 mu mol mol(-1) than that in the plants grown at present CO2. The A/c(i) response curves, which were saturated i?n all species grown at present CO2, did not reach saturation in the plants grown at elevated CO2, reflecting that the Pi l?imitation of CO2 assimilation was alleviated in the plants grown at high CO2. Transpiration decreased with an increase in ?c(i) in both the present and elevated CO2 F. rupicola and D. glomerata. In F. vulgaris, an increase in ci caused a reducti?on in transpiration in the plants grown at high CO2 only. Transpiration rate in both the present and elevated CO2 S. nemor?osa was not affected by any change in c(i). It is suggested then that long-term exposure to high CO2 causes a similar accl?imation of stomatal regulation and transpiration to that of photosynthesis. High CO2 caused a significant decrease in prot?ein-nitrogen content only in D. glomerata. Starch increased in F. rupicola and D. glomerata and soluble sugar content was ?higher in all species grown at high CO2 than at ambient. Instantaneous WUE significantly increased in ail species grown at elevated CO2.ԁ?1192^4^Vivin,P^Guehl,JM^Clement,AM^Aussenac,G^1996^1^The effects of elevated CO2 and water stress on whole plant CO2 exchange, carbon allocation and osmoregulation in oak seedlings^186^53^2-3^447-459^^^^^^^^^^5176?A^5175^Seedlings of Quercus robur L grown under present (350 mu mol mol(-1)) or twice the present (700 mu mol mol(-1)) atm?ospheric CO2 concentrations, were either maintained well-watered or subjected to a drought constraint late in the growing ?season (25 August 1993). Despite an initial stimulation of biomass growth (+44%) by elevated CO2, there was no significant? difference in plant dry weight at the end of the growing season (15 October 1993) between the two CO2 treatments, irrespe?ctive of watering regime. Under drought conditions, although there was no growth increase in response to elevated CO2 conc?entration, there was a stimulation in net photosynthesis. In addition, the respiration rate of the root + soil system (roo?t dry matter basis) was slightly lower in the elevated than in the ambient CO2 concentration. These results, together with? the results from short-term C-13 labelling, suggest enhanced plant carbon losses through processes not assessed here (aer?ial respiration, root exudation, etc) under elevated CO2 concentration. In the droughted conditions, new carbon relative s?pecific allocation values (RSA) were greater under elevated CO2 than under ambient CO2 concentration in both leaf and root? compartments. Osmotic potentials at full turgor (pi(o)) were lowered in response to water stress in leaves by 0.4 MPa for the elevated CO2 treatment only. In roots, osmotic adjustment (0.3 MPa) occurred in both the CO2 treatments.?1193^1^Wilsey,BJ^1996^1^Plant responses to elevated atmospheric CO2 among terrestrial biomes^15^76^1^201-206^^^^^May^^^^^5?A^5177^Although many researchers have stressed the importance of among-species variation in plant response to elevated CO2?, none have quantitatively tested whether variation exists among biomes. I compiled data from the literature and found tha?t, although C-3 plants did respond more than C-4 plants (as predicted), biome origin was a better predictor (accounted for? more of the variation) of plant response to elevated CO2 than mode of photosynthesis, Variation in plant response among b?iomes was found both between and within latitudinal zones, with plant species from tropical and temperate biomes respondin?g more than plant species from a polar biome. Within the temperate zone, species from forested biomes responded more than ?species from a grassland biome, and this provides further evidence that forests are acting as major sinks for increasing l?evels of atmospheric CO2. A more than 4-fold difference was found among ecosystems in coefficients of variation (calculate?d across mean species response within each ecosystem). Based on this difference, I suggest that ecosystems may vary in the amount of change in species composition in response to elevated CO2.178?1194^5^Andalo,C^Godelle,B^Lefranc,M^Mousseau,M^TillBottraud,I^1996^1^Elevated CO2 decreases seed germination in Arabidopsis thaliana^127^2^2^129-135^^^^^Apr^^^^^5180?A^5179^The impact of elevated [CO2] on seed germination was studied in different genotypes of Arabidopsis thaliana from na?tural populations. Two generations of seeds were studied: the maternal generation was produced in the greenhouse (present-?day conditions), the offspring generation was produced in two chambers where the CO2 concentration was either the present ?atmospheric concentration (about 350 ppm) or elevated (700 ppm). The seeds were tested for proportion of germinated seeds ?and mean germination time in both chambers to study the impact of elevated [CO2] during seed production and germination. E?levated [CO2] during maturation of seeds on the mother-plants decreased the proportion of germinated seeds, while elevated? [CO2] during germination had no effect on the proportion of germinated seeds. However, when seeds were both produced and ?germinated under elevated [CO2] (situation expected by the end of next century), germination was slow and low. Moreover, t?he effect of the [CO2] treatment differs among genotypes of Arabidopsis: there is a strong treatment x genotype interactio?n. This means that there is ample genetic variance for a selective response modiying the effects of high levels of [COP] i?n natural populations of Arabidopsis thaliana. The outcome at the community level will depend on what seeds are available, when they germinate and the resulting competition following germination.?1195^7^Balaguer,L^Valladares,F^Ascaso,C^Barnes,JD^DelosRios,A^Manrique,E^Smith,EC^1996^1^Potential effects of rising tropospheric concentrations of CO2 and O-3 on green-algal lichens^84^132^4^641-652^^^^^Apr^^^^^5182?A^5181^Parmelia sulcata Taylor was used as a model to examine the effects of elevated CO2 and/or O-3 on green algal lichen?s. Thalli were exposed for 30 d in duplicate controlled- environment chambers to two atmospheric concentrations of CO2 ('a?mbient' [350 mu mol mol(-1)] and 'elevated' [700 mu mol mol(-1)] 24 h d(-1)) and two O-3 regimes ('non-polluted' air [CF, ?< 5 nmol mol(-1)] and 'polluted' air [15 nmol mol(-1) overnight rising to a midday maximum of 75 nmol mol(-1)]), in a fact?orial design. Elevated CO2 or elevated O-3 depressed the light saturated rate of CO2 assimilation (A(sat)) measured at amb?ient CO2 by 30%, and 18%, respectively. However, despite this effect ultrastructural studies revealed increased lipid stor?age in cells of the photobiont in response to CO2- enrichment. Simultaneous exposure to elevated O-3 reduced CO2- induced ?lipid accumulation and reduced A(sat) in an additive manner. Gold-antibody labelling revealed that the decline in photosyn?thetic capacity induced by elevated CO2 and/or O-3 was accompanied by a parallel decrease in the concentration of Rubisco ?in the algal pyrenoid (r = 0.93). Interestingly, differences in the amount of Rubisco protein were not correlated with cha?nges in pyrenoid volume. Measurements of in vivo chlorophyll-fluorescence induction kinetics showed that the decline in A(?sat) induced by elevated CO2 and/or O-3 was not associated with significant changes in the photochemical efficiency of pho?tosystem (PS)II. Although the experimental conditions inevitably imposed some stress on the thalli, revealed a significant? decline in the efficiency of PS II photochemistry, and enhanced starch accumulation in the photobiont over the fumigation? period, the study shows that the green-algal lichen symbiosis might be influenced by future changes in atmospheric compos?ition. Photosynthetic capacity, measured at ambient CO2, was found to be reduced after a controlled 30 d exposure to eleva?ted CO2 and/or O-3 and this effect was associated with a parallel decline in the amount of Rubisco in the pyrenoid of algal chloroplasts.?1196^1^Bunce,JA^1996^1^Growth at elevated carbon dioxide concentration reduces hydraulic conductance in alfalfa and soybean^127^2^2^155-158^^^^^Apr^^^^^5184