1^4^Ackerly,D D^Coleman,J S^Morse,S R^Bazzaz,F A^1992^1^CO2 and Temperature Effects on Leaf Area Production in Two Annual Plant Species^2^73^^1260-1269^^^^^^^^^^3^^^^^^^^^^^Abutilon theophrasti/Amaranthus retroflexus;sϝ_ZÀ}&>!&&C^1^Ecology[PQR&Dt&"O&\&D t&Du&|Au&|But&|tV2r^ZYXA^1^We studied leaf area production in two annual plant species, _Abutilon theophrasti_ and _Amaranthus retroflexus_, under three day/night temperature regimes (18/14C, 28/22C, and 28/31C) and two concentrations of carbon dioxide (400 and 700 uL/L). The production of whole-plant leaf area during the first 30 d of growth was analyzed in terms of the leaf initiation rate, leaf expansion, individual leaf area, and, in _Amaranthus_, production of branch leaves. Temperature and CO2 inf% luenced leaf area production through stem (the plastochron index), and through shifts in the relationship between whole-pl) ant leaf area and the number of main stem nodes. In _Abutilon_, leaf initiation rate was highest at 38C, but area of indi- vidual leaves was greatest at 28C. Total leaf area was greatly reduced at 18C due to slow leaf initiation rates. Elevate0 d CO2 concentration increased leaf initiation rate at 28C, resulting in an increase in whole-plant leaf area. In _Amarant3 hus_, leaf initiation rate increased with temperature, and was increased by elevated CO2 at 28C. Individual leaf area wasA greatest at 28C, and was increased by elevated CO2 at 28C but decreased at 38C. Branch leaf area displayed a similar response to CO2, but was greater at 38C. Overall, whole-plant leaf area was slightly increased at 38C relative to 28C, aDnd elevated CO2 levels resulted in increased leaf area at 28C but decreased leaf area at 38C. The effects on leaf area cTlosely parallel rates of biomass accumulation in the same experiment, suggesting that responses of developmental processesW to elevated CO2 and interacting factors may play an important role in mediating effects on plant growth.uPVښ*[2^1^Acock,B^1990^3^Effects of CO2 on Photosynthesis, Plant Growth and Other Processes^Impact of CO2, Trace Gases, and Clim^ate Change on Global Agriculture^American Society of Agronomy^Madison, Wisconsin^45-60^^^^^^^ASA Special Publication No. 53^^^^^^^^^^^^^^^^^^^^^^^^Kimball,BA^Rosenberg,NJ^Allen,LH,Jri&4t tCVt\ut t1TtJctPt=Vtb3^3^Acock,B^Acock,M C^Pasternak,D^1990^1^Interactions of CO2 Enrichment and Temperature on Carbohydrate Production and Acciumulation in Muskmelon Leaves^3^115^^525-529^^^^^^^^^^7^^^^^^^^^^^muskmelon/Cucumis meloL. XX B~. CC^5^J. Amer. Soc. Hort. Sci.6&P& &&&@&& S~X؊}ǀtttttmA^5^We examined how temperature and stage of vegetative growth affect carbohydrate production and accumulation in _Cucumisu melo_ L. 'Haogen' grown at various CO2 concentrations ([CO2]). Carbohydrate production was measured by net assimilation rate either on a leaf-area basis (NARa) or a leaf dry-weight basis (NARw); carbohydrate accumulation was measured by leaf sxtarch plus sugar content. Twenty-four- and 35-day-old muskmelon plants were grown for 11 days in artificially lighted cabinets at day/night temperatures of 20/20 or 40/20C and at [CO2] of 300 or 1500 uL/L. NARa and NARw both increased with increasing [CO2], but the CO2 effect was smaller at low temperature, especially for plants at the later stage of vegetative growth. NARw was a better indicator of total dry-weight gain than was NARa. Both suboptimal temperatures and CO2 enrichment caused carbohydrates to accumulate in the leaves at both stages of vegetative growth. NARw was correlated negatively with !leaf starch plus sugar content. The rate of decrease in NARw with increasing leaf starch plus sugar content was significan"tly greater for CO2-enriched plants. Leaf starch plus sugar content >0.03 to 0.04 kg/kg of leaf residual dry weight at the# end of a dark period may indicate that temperature is suboptimal for growth. Plants grown at the same temperature had hig$her leaf starch plus sugar content if they were CO2-enriched than if grown in ambient [CO2], suggesting that an optimal temperature for growth in ambient [CO2] may be suboptimal in elevated [CO2].@&&2'&>tQ3&6S~&Dt tS~ &4^4^Acock,B^Acock,M C^Reddy,V R^Baker,D N^1985^5^The Simulation, with GLYCIM, of Soybean Crops Grown in the Field and at V'arious CO2 Concentrations in Open-top Chambers during 1982^U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S(. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C^^^^^^^^^^^^^^^^^^^^^^^^soybean^^011 in Green Report Series^Response of Vegetation to Carbon Dioxide^^S~@&tG;u:&>u&>#w&uS~Z&S~@&uC*5^7^Acock,B^Baker,D N^Reddy,V R^McKinion,J M^Whisler,F D^Del Castillo,D^Hodges,H F^1982^5^Soybean Responses to Carbon Diox+ide: Measurement and Simulation 1981^U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture,, Agric. Res. Serv., Washington, D.C^^^^^^^^^^^^^^^^^^^^^^^^soybean/Glycine max^^004 in Green Report Series^Response of Vegetation to Carbon Dioxide^^ Dioxide^^~uG~us~~ -6Z~\~D ^~D\DD~$s~^RV.6^2^Acock,B^Allen,LH,Jr^1985^3^Crop Responses to Elevated Carbon Dioxide Concentrations^Direct Effects of Increasing Carbo/n Dioxide on Vegetation^Dept. of Energy, Carbon Dioxide Research Division^Washington, D.C.^53-97^^^^^^^DOE/ER-0238^^^^^^^^^^^^^^^^^^^^^^^^Strain,BR^Cure,JD~DDDь\s"6N~D${6N~|>N~6N~&&t 8& 17^2^Acock,B^Pasternak,D^1986^3^Effects of CO2 Concentration on Composition, Anatomy, and Morphology of Plants^Physiology, 2Yield and Economics^CRC Press, Inc.^Boca Raton, Florida^41-52^^^^II^^Carbon Dioxide Enrichment of Greenhouse Crops^^^^12^^^^^^^^^^^^^^^^^^^^^Enoch,HZ^Kimball,BAl,B A &Dt&T&D@t&Dt&tr v &Du &t⇨uZX4A^11^In summary, we can say that species differ in their response to high CO2. Plants which are using CAM are relatively u5nresponsive. Other plants with the C4 pathway show modest dry weight gains but large reductions in transpiration rate. Pla6nts which only have the C3 pathway, or well-watered CAM plants which are behaving like C3 plants, exhibit modest reduction7s in transpiration rate and large gains in dry weight, resulting in a variety of changes in plant composition, anatomy, an8d morphology. We know too little to even begin dividing C3 species into response groups. However, we can describe a typica9l or average response as follows. All organs on the plants become heavier with roots gaining proportionally more dry weigh:t than stems, and stems more than leaves. The additional dry matter in the root is mainly used to increase root length wit;h very little going to increase the density of the root tissue. Additional dry matter going to the stem causes increases ir which is probably greater than can be explained by the increase in number of mesophyll cell layers, although no one has  ?even done a definitive experiment on this. Finally, there is an increase in starch accumulating in the leaves which, depen@ding on the circumstances, can be very large. Branch and tiller numbers are frequently increased, as are the number of flowers. Either the weight or number of individual fruits is increased.8s@+CJJXS28+@I[WPS3B8^5^Acock,B^Reddy,V R^Hodges,H F^Baker,D N^McKinion,J M^1985^1^Photosynthetic Response of Soybean Canopies to Full-Season !Carbon Dioxide Enrichment^4^77^^942-947^^^^^^^^^^15^^^^^^^^^^^soybean/Glycine maxx(L.) Merr.T_PSQV5Y: |<C^13^Agron. J.5&|Du=:u2&L F&< t:T13^Y[XPSQR&tt2N$:T15:$EA^13^Global atmospheric CO2 concentration ([CO2]) is increasing as a result of the burning of fossil fuels. At present the+Fre is little information about how agronomic crops will respond to future high [CO2]. To investigate the basic process thaGt will be most affected, soybean canopies were continuously exposed to various [CO2] and photosynthetic rates were measure-Hd throughout the growing season. Soybean was grown to physiological maturity in sunlit controlled-environment chambers in 9ICO2 concentrations of 330, 450, 600 and 800 uL/L. Carbon dioxide fluxes were measured on the canopies at 15-min intervals Jevery day and used to calculate photosynthetic and respiration rates. Gross photosynthetic rate increased with each increm<Kent in [CO2] regardless of stage of development, but there was considerable day-to-day and seasonal variation. Seasonal chCLanges in photosynthetic rate were associated with developmental changes in the crop. Photosynthetic rates were low during Mearly vegetative development, even after the canopy had closed, but increased threefold just before flowering to reach a pGNeak during flowering at stage R2. They then decreased by 30% or more until just before the start of pod expansion (R3) whePOn a 45% increase occurred. Thereafter, photosynthetic rates decreased slowly and continuously to final harvest. The daily Pcurves of photosynthetic rate _vs._ photosynthetic photon flux density were further analyzed to determine canopy light utiSQlization efficiency () and canopy conductance to CO2 transfer (). Plants grown in 800 uL/L [CO2] had a value of that a\Rveraged about 40% higher than that for plants grown in 330 uL/L and a value of that averaged about 24% lower for the seaSson. Differences in between these treatments were significant throughout the season, while initial differences in betw_een treatments became less obvious after late vegetative growth stage VII.2t&G2t&G3t&G 3 t&GjU9^7^Acock,B^Reddy,V R^Whisler,F D^Baker,D N^McKinion,J M^Hodges,H F^Boote,K J^1983^5^The Soybean Crop Simulator GLYCIM: MoVdel Documentation^U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv.m$w, Washington, D.C^^^^^^^^^^^^^^^^^^^^^^^^soybean/Glycine max^^002 in Green Report Series^Response of Vegetation to Carbon {X10^7^Acock,B^Reddy,V R^Del Castillo,D^Hodges,H F^Baker,D N^McKinion,J M^Whisler,F D^1983^5^Soybean Responses to Carbon DioYxide: Measurement and Simulation 1982^U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of AgriculturZe, Agric. Res. Serv., Washington, D.C^^^^^^^^^^^^^^^^^^^^^^^^soybean/Glycine max^^008 in Green Report Series^Response of Vegetation to Carbon Dioxide^^ Dioxide^^ PSQRVU3MUEU?EU tsJ tE t%r\11^2^Acock,B^Trent,A^1991^5^The Soybean Crop Simulator GLYCIM: Documentation for the Modular Version 91^U.S. Dept. of Ener]gy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C^^^^^^^^^^^^^^^^^^^^^^^^soybean/Glycine max^^017 in Green Report Series^Response of Vegetation to Carbon Dioxide^^ Dioxide^^t-< t(< t#<t<_12^3^Aizawa,K^Nakamura,Y^Miyachi,S^1985^1^Variation of Phosphoenolpyruvate Carboxylase Activity in _Dunaliella_ Associated` with Changes in Atmospheric CO2 Concentration^128^26^^1199-1203^^^^^^^^^^21^^^^^^^^^^^Dunaliella tertiolecta/Dunaliella bioculata/Dunaliella viridis/Porphyridium cruentumm3 tփs<3;rr;r@uBy ^YCC^19^Plant Cell Physiol.&g RQ&g0uYZPSQRVWSsu^&wv&w&G'u։S&&G [P&GcA^19^In _Dunaliella tertiolecta_, _D. bioculata_ and _D. viridis_ the activities of phosphoenolpyruvate carboxylase and cadrbonic anhydrase were higher in the cells grown in ordinary air (low-CO2 cells) than in those grown in air enriched with 1e-5% CO2 (high-CO2 cells), whereas in _Porphyridium cruentum_ R-1 there was no difference in phosphoenolpyruvate carboxylasfe activity between these two types of cells. Apparent Km (NaHCO3) values for photosynthesis in low-CO2 cells of all speciegs tested were smaller than those in high-CO2 cells. Most of the 14C was incorporated into 3-phosphoglycerate, sugar mono- hand di-phosphates during the initial periods of photosynthetic NaH14CO3-fixation, indicating that both types of cells in _D. tertiolecta_ are C3 plants.y ^3 twPSQRVWb3ۊ@ ^r%2&N3ɾ &j13^3^Akey,D H^Kimball,B A^Mauney,J R^1988^1^Growth and Development of the Pink Bollworm,_ Pectinophora gossypiella_ (Lepidkoptera: Gelechiidae), on Bolls of Cotton Grown in Enriched Carbon Dioxide Atmospheres^6^17^^452-455^^^^^^^^^^24^^^^^^^^^^^cotton/Gossypium hirsutummL. FQnYsS&&W&O[ & u6& u & u &O$&O$0^NtsFC^22^Environ. Entomol.42҃t#2ᰀtt^Y PQVPQVrʚd${su^YXSnA^22^The pink bollworm, _Pectinophora gossypiella_ (Saunders), was reared on the bolls of cotton plants grown in CO2-enricohed (649 uL/L) and ambient (371 uL/L) chambers and in two open field plots, one with free-air CO2 enrichment (522 uL/L) anpd one without enrichment (ambient CO2, 360 uL/L). The effects of increased CO2 levels on growth and development were examiqned. There was no difference in pupal weights of pink bollworm raised on CO2-enriched cotton compared with those raised onr ambient CO2 cotton (26.80 versus 26.64 mg, respectively). Also, there was no difference in developmental time (21-27 d). sAnalysis of percent seed damage by larvae showed no differences between CO2-enriched and ambient CO2 cotton. These resultst were attributed to the nutritional qualities of the seed remaining the same (specifically the carbon:nitrogen ratio) despite CO2 and photosynthetic changes in the plant.t,ltr_r t _ F F ]_Y[XZR2Rv14^2^Akey,D H^Kimball,B A^1989^1^Growth and Development of the Beet Armyworm on Cotton Grown in an Enriched Carbon Dioxide Atmosphere^7^14^^255-260^^^^^^^^^^27^^^^^^^^^^^cotton/Gossypium hirsutummL.^€~ t2tĚ__rFlC^25^Southwestern Entomol.GDLVydr%^F FuPbkPr*X=o&+15^1^Allen,L H,Jr^1991^3^Effects of Increasing Carbon Dioxide Levels and Climate Change on Plant Growth, Evapotranspiration, and Water Resources^Managing Water Resources in the West under Conditions of Climate Uncertainty; 1990 Nov. 14-16; Scot-tsdale, Arizona^National Academy Press^Washington, D.C.^101-147^^^^^^^^^^^^^^^^^^^^^soybean/Glycine max^^^^^^^^^^Committee on Climate Uncertainty and Water Resources Management8r>u&]&Ùt+016^1^Allen,L H,Jr^1992^1^Free-Air CO2 Enrichment Field Experiments: An Historical Overview^8^11^^121-134^^0;9u;>t;&SC^29^Crit. Rev. Plant Sci.=?Nv;5u;6t.`T5633҇13tC9;]_^Y[V u u17^1^Allen,L H,Jr^1990^1^Plant Responses to Rising Carbon Dioxide and Potential Interactions with Air Pollutants^9^19^^15-?34^^^^^^^^^^333v&D u3&\ &t VvK^6Hdؿ9Vv&\&]&\%]E&| t&&D &d &t fKC^31^J. Environ. Qual. &DE&DE&]Y]&D2 W> uv&t&| uuK6H]3&t t@[WA^31^As global population increases and industrialization expands, carbon dioxide (CO2) and toxic air pollutants can be exNpected to be injected into the atmosphere at increasing rates. This analysis reviews a wide range of direct plant responseds to rising CO2, increasing levels of gaseous pollutants, and climate change, and potential interactions among the factors. Although several environmental interactions on stomata and foliage temperatures are reviewed briefly, a comprehensive refview of effects of potential climatic change on plants is not a major objective of this analysis. Research shows that elevwated CO2 increases photosynthetic rates, leaf area, biomass, and yield. Elevated CO2 also reduces transpiration rate per uznit leaf area, but not in proportion to reduction of stomatal conductance, because foliage temperature tends to rise. With increasing leaf area and foliage temperature, water use per unit land area is scarcely reduced by elevated CO2. Increases in photosynthetic water-use efficiency are caused primarily by increased photosynthesis rather than reduced transpiration. Gaseous pollutants (O3, SO2, NOx, H2S) affect plants adversely primarily by entry through the stomata. An example calculation showed that reduction in stomatal conductance by doubled CO2 could potentially reduce the effects of ambient O3 and SO2 by 15%. However, information on the interaction of CO2 and air pollutants is scanty. More research is needed on these interactions, because regional changes in air pollutants are occurring concurrently with global changes in CO2.o4:r$18^2^Allen,L H,Jr^Beladi,S E^1990^5^Free-Air CO2 Enrichment (FACE): Analysis of Gaseous Dispersion Arrays for the Study of Rising Atmospheric CO2 Effects on Vegetation. 1983-1989 Progress Report^U.S. Dept. of Energy, Carbon Dioxide Research Div#6ision, and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C^^^^^^^^^^^^^^^^^^^^^^^^^^057 in Green Report Seri19^4^Allen,L H,Jr^Bisbal,E C^Campbell,W J^Boote,K J^1990^1^Carbon Dioxide Effects on Soybean Developmental Stages and Expansive Growth^10^49^^124-131^^^^^^^^^^37^^^^^^^^^^^soybean/Glycine maxx(L.) Merr.ZSQRVW5NP9RTr>wC^35^Soil and Crop Sci. Soc. Fla. Proc.dfd؉=ԉ?ԸbءhYj]l n[oWpXqYrZsVtA^35^Crop productivity is expected to increase as atmospheric carbon dioxide (CO2) continues to rise. The purpose of this paper is to examine the response of soybean [_Glycine max_ (L.) Merr., cv. Bragg] stages of development and plant size to CO2 concentration during four experiments (1981-1984) in outdoor controlled-environment chambers. Attached lysimeters contained Arredondo fine sand (loamy, siliceous, hyperthermic Grossarenic Paleudult). Air temperature and dewpoint temperature were controlled to common set-points within each year with CO2 concentration being the treatment variable among chambers. Vegetative and reproductive developmental stages were determined at frequent intervals during each experiment. Growth parameters of mainstem height, total mainstem plus branch stem length, number of mainstem nodes with branches, mainstem diameter, and leaf areas were measured during at least one experiment. Vegetative stages progressed slightly faster and the final number of nodes was slightly greater with increased CO2 concentration. All size parameters clearly increased with increasing CO2 concentration. Growth responses per unit CO2 concentration change were greater over the subambient range (160 to 330 umol/mol) than over the superambient range (330 to 990 umol/mol). For soybean, plant expansive growth will increase as atmospheric CO2 continues to rise, whereas direct effects of CO2 (without interaction of potential climatic changes) will have little effect on phenology.X[1ș&X[&X[+ڋȋ&X[ȋ&X[ȋ&X[##&X[320^4^Allen,L H,Jr^Bisbal,E C^Boote,K J^Jones,P H^1991^1^Soybean Dry Matter Allocation under Subambient and Superambient Levels of Carbon Dioxide^4^83^^875-883^^^^^^^^^^40^^^^^^^^^^^soybean/Glycine maxx (L.) Merr.ƀt҃C^38^Agron. J.ڒt ҃>tƀt҃ǀt t t tA^38^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 fu-ture 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 u0mol (CO2)/mol (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/m2/d for the above respective [CO2]. Samples taken from 24 to 94 d after planting showed that the percentage of total plant mass in leaf trifoliates decreased with increasing [CO2] whereas the percentage in structural componen@ts (petioles and stems) increased. At final harvest the respective [CO2] treatments resulted in 38, 53, 62, 100, 120 and 9K2% seed yield with respect to the 330 umol/mol treatment. Total dry weight responses were similar. Late season spider mite damage of the 990 and 280 umol/mol treatments reduced yields. These data confirm not only that rising CO2 should increaseO 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~ tM&%E &!E ]EWn*_ub21^8^Allen,L H,Jr^Boote,K J^Jones,J W^Mishoe,J W^Jones,P H^Vu,C V^Valle,R^Campbell,W J^1982^5^Effects of Increased Carbon _Dioxide on Photosynthesis and Agricultural Productivity of Soybeans. 1981 Progress Report^U.S. Dept. of Energy, Carbon Diobxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C^^^^^^^^^^^^^^^^^^^^^^^^soybean/Glycine max^^003 in Green Report Series^Response of Vegetation to Carbon Dioxide^^ Dioxide^^PSQRVWU&>&[22^10^Allen,L H,Jr^Boote,K J^Jones,J W^Mishoe,J W^Jones,P H^Vu,C V^Valle,R R^Campbell,W J^Harris,P R^Heimburg,K F^1984^5^Effects of Increased Carbon Dioxide and Water Stress Interactions on Photosynthesis, Transpiration, and Productivity of Soybeans. 1983 Progress Report^U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C^^^^^^^^^^^^^^^^^^^^^^^^soybean/Glycine max^^014 in Green Report Series^Response of Vegetation to Carbon Dioxide^^n Dioxide^^&dGs6 ~| ~X u tt%523^8^Allen,L H,Jr^Boote,K J^Jones,J W^Jones,P H^Valle,R R^Acock,B^Rogers,H H^Dahlman,R C^1987^1^Response of Vegetation to Rising Carbon Dioxide: Photosynthesis, Biomass, and Seed Yield of Soybean^11^I^^1-14^^^^^^^^^^45^^^^^^^^^^^soybean/Glycine maxx (L.) Merr.H122ɿr@>' %5F %'F fP %YF_^[r;C^43^Global Biogeochem. Cycles&v = u Ms鉅Wf22sv>W>tsNV A^43^Elevated carbon dioxide throughout the lifespan of soybean causes an increase in photosynthesis, biomass, and seed yield. A rectangular hyperbola model predicts a 32% increase in soybean seed yield with a doubling of carbon dioxide from 315 to 630 ppm and shows that yields may have increased by 13% from about 1800 A.D. to the present due to global carbon dioxide increases. Several other sets of data indicate that photosynthetic and growth response to rising carbon dioxide of many species, including woody plants, is similar to that of soybean. Calculations suggest that enough carbon could be sequestered annually from increased photosynthesis and biomass production due to the rise in atmospheric carbon dioxide from 315 ppm in 1958 to about 345 ppm in 1986 to reduce the impact of deforestation in the tropics on the putative current flux of carbon from the biosphere to the atmosphere.FȉF̉F҉FЉF։F@FʉF΋3FƋ1FvĿc$6F~6F624^7^Allen,L H,Jr^Boote,K J^Jones,J W^Mishoe,J W^Jones,P H^Valle,R R^Bisbal,E C^1985^5^Subambient and Superambient Carbon Dioxide Effects on Growth, Nonstructural Carbohydrates, Biochemistry of Photosynthesis and Transpiration of Soybeans. 1984 Progress Report^U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv.," Washington, D.C^^^^^^^^^^^^^^^^^^^^^^^^soybean/Glycine max^^031 in Green Report Series^Response of Vegetation to Carbon D25^2^Allen,L H,Jr^Boote,K J^1992^3^Vegetation, Effect of Rising CO2^Encyclopedia of Earth System Science^Academic Press, Inc.^New York^409-416^^^^4^^^^^^^^^^^^^^^^^^^^^^Ƅ_^mcwW u^NV t7rp^_N]ҍ^^^^^^^^^^^^^^^^^^^^^^^^^Shands,WE^Hoffman,JSNV^ t 닋^Ftr&E-26^4^Allen,L H,Jr^Drake,B G^Rogers,H H^Shinn,J H^1992^1^Field Techniques for Exposure of Plants and Ecosystems to Elevated CO2 and Other Trace Gases^8^11^^85-119^^0~tF܉FtF׈c DŽ[Ƅ_.&t ^N&fnC^49^Crit. Rev. Plant Sci.fN6v t2J*r+*W%5)55%N%NW 27^5^Allen,L H,Jr^Valle,R R^Mishoe,J W^Jones,J W^Jones,P H^1990^1^Soybean Leaf Gas Exchange Responses to CO2 Enrichment^10^49^^192-198^^^^^^^^^^53^^^^^^^^^^^soybean/Glycine maxx (L.) Merr.[^6:s.S^r[[ a6:rad6:r F\C^51^Soil and Crop Sci. Soc. Fla. Proc.NV*6 _ZY[^K}M3ێF&Cu OFQu!3c 3VȉFƋ]28^5^Allen,L H,Jr^Vu,J C V^Valle,R R^Boote,K J^Jones,P H^1988^1^Nonstructural Carbohydrates and Nitrogen of Soybean Grown `under Carbon Dioxide Enrichment^12^28^^84-94^^^^^^^^^^56^^^^^^^^^^^soybean/Glycine maxx (L.) Merr.c 3 t<3eC^54^Crop Sci.c 3^ t<N剕A?qoc 35 t 3#, uJGusc 3 tgA^54^Carbon dioxide (CO2) concentration has been rising in the atmosphere for over a century. This study was conducted to determine the effects of anticipated future levels of CO2 on nonstructural carbohydrates and N of soybean [_Glycine max_ (jL.) Merr. cv. Bragg]. Plants were grown at Gainesville, FL from seed to maturity in six sunlit, controlled-environment chaumbers that maintained CO2 at 330, 330, 450, 600, 800, and 800 umol (CO2)/mol (air). Attached lysimeters contained Arredondyo fine sand (loamy, siliceous, hyperthermic Grossarenic Paleudult). Leaflet blades were sampled five times per day at 48 a{nd 69 d after planting (DAP). At 48 DAP, average daytime starch conc. of leaflets increased with increasing CO2 from 85 g/|kg of dry wt at 330 umol/mol to 205 g/kg at 800 umol/mol. On each date, the daytime rate of starch accumulation combined over all CO2 treatments was 6 g/kg. Specific leaf weight increased significantly throughout the day both at 48 (0.64 g/m2/h) and 69 DAP (0.29 g/m2/h). Total Kjeldahl N (TKN) conc., expressed on a g/m2 basis, showed no change over the day. Total final dry wt increased 18, 34, and 54% at 450, 600 and 800 umol/mol, respectively. The TKN harvested per plant increased 25, 26 and 45% in the 450, 600 and 800 umol/mol CO2 treatments, respectively. Plants in the 450 umol/mol CO2 treatment partitioned more biomass to seed than the other CO2 treatments. With that exception, we saw no great differences among treatment partitioning at final harvest, and thus interpret the main effect of CO2 enrichment to be enhanced photoassimilation by soybean canopies while maintaining consistent allometric relationships of the plants.&>&2&e%_ZY[QRW&L29^3^Allen,S G^Idso,S B^Kimball,B A^1990^1^Interactive Effects of CO2 and Environment on Net Photosynthesis of Water-Lily^13^30^^81-88^^^^^^^^^^59^^^^^^^^^^^Nymphaea marliac/water lilyy6&r+3ɿ & GGr&>&2>s&M'C^57^Agric. Ecosystems Environ.r&>&22&&8\ t&M'^_ZY[XPQRVWU&@&|&D2&d&L&A^57^Water-lily (_Nymphaea marliac_) plants were grown out of doors in 570-L stock tanks contained in plastic-walled, open-topped CO2-enrichment chambers continuously supplied with either 640 or 340 (ambient) uL CO2/L air. Net photosynthesis (Pn) of water-lily leaves in each CO2 treatment was measured hourly between 0800 and 1600 h MST on 26 October and 10 and 24 November 1987. Air temperature and net solar radiation were measured at the same time. The 3 days on which Pn was measured provided an air temperature range of 10.3-33.2C and a net solar radiation range of 30-659 W/m2. Significant linear relationships were established between Pn and air temperature and Pn and net solar radiation for both CO2 treatments. Significant interactive effects of CO2 and air temperature and CO2 and net solar radiation were also found to affect Pn. In conditions generally unfavorable for Pn (low light and low temperature), there was no difference in Pn rate between the two CO2 treatments. In conditions that were favorable for Pn (high light and high temperature), however, Pn in the 640 uL CO2/L air treatment was as much as 60% greater than in the ambient CO2 treatment.t Zrs Z>Xs3]_^YPSUC30^4^Allen,S G^Idso,S B^Kimball,B A^Anderson,M G^1988^1^Relationship between Growth Rate and Net Photosynthesis of _Azolla_ in Ambient and Elevated CO2 Concentrations^13^20^^137-141^^^^^^^^^^62^^^^^^^^^^^Azolla pinnataa~F33ɋ^V3C^60^Agric. Ecosystems Environ.6F߹d dÉF_^ZY[XVWu23 uφ ++r r; A^60^_Azolla pinnata_ was grown out-of-doors at Phoenix, AZ, U.S.A. in open-topped plastic-walled chambers supplied with e ither 340 or 640 uL CO2/L air. Net photosynthesis and growth rate were measured weekly between September 1985 and May 1986 and a significant (P<0.01) positive correlation was established between these two parameters in both CO2 environments. Regression coefficients for the linear regression of growth rate onto net photosynthesis were not significantly different in the two CO2 environments, indicating that the rate of growth per unit of CO2 uptake is not influenced by an atmospheric C O2 concentration-environment interaction.F&FF tFF 7X7XÚ${Ú${ÚO${Ú31^3^Alpert,P^Warembourg,F R^Roy,J^1992^1^Transport of Carbon among Connected Ramets of _Eichhornia crassipes_ (Pontederiaceae) at Normal and High Levels of CO2^14^78^^1459-1466^^^^^^^^^^65^^^^^^^^^^^Eichhornia crassipes/water hyacinth/water hyacinth66u6r9S^[r t!"C266:|S^[rT^]_YZ[PSRU2666aC^63^Amer. J. Bot.&"]Z[XPQV&=t&|t&\&"${ ^YXPSQWU싏a&;MuEX&:Mu;A^63^The floating stoloniferous plant, _Eichhornia crassipes_, has high rates of productivity and rapidly invades new site+s. Because the transport of carbon among connected ramets in known to increase the growth of clonal plants, we asked whether there is intraclonal carbon transport in _E. Crassipes_. Because net photosynthesis of _E. Crassipes_ is significantly .higher at high levels of atmospheric CO2, we also asked if high CO2 can change patterns of carbon transport in ways that m<ight modify clonal growth. We exposed individual ramets within groups of connected ramets to 14-CO2 for 15-45 min and measured the distribution of 14-C in the group after 4 days of growth at 350, 700, 1,400, or 2,800 uL/L CO2. At 350 uL/L CO2, @a parent ramet exported approximately 10% of the 14-C that it assimilated to its first rooted offspring ramet. The offspriMng exported a similar percentage of the 14-C it assimilated toward the parent; two-thirds of this 14-C was retained by the parent, and one-third moved into new offspring of the parent. In all ramets, imported carbon moved into leaves as well asP roots. At the higher levels of CO2, the percentage of assimilated carbon exported from a parent ramet to the leaf blades ^of its first offspring was lower by half. High CO2 had little other effect on carbon transport. _E. crassipes_ maintains b idirectional transport of carbon between ramets even under uniform and favorable environmental conditions and when externabl CO2 levels are very high.LD0D~t!tu t t5*s =uoF]ZXSVb腚r.&6n"32^2^Alscher,G^Krug,H^1989^1^On-line Control of CO2 Enrichment in Protected Cultivation^15^248^^321-327^^^^^^^^^^68^^^^^^^^^^^lettuce/Lactuca sativaa L.]^_ZY[XPSQRWVU这s&>t,&M&&] 2&=&E t&E u &e|rStrr C^66^Act. Hort.}0&O &E't&E' uS&2&a [0rsF]^_ZY[XPWUr&;>s&e{%A^66^As a base for experiments on CO2 on-line control the CO2 fluxes in greenhouses are simulated and potential control st&rategies presented. Some approaches are tested, others outlined for discussion. Preliminary experiments with lettuce were 'performed with CO2 supply depending on wind velocity and irradiance. Additionally, intermittent CO2 application was tested(. Results indicate that the efficiency of CO2 enrichment varies relying on season and year. If planted in October cutting )off CO2 supply led to extended growth periods with increased energy demands. If planted in January no significant differen*ces in growing periods occurred between constant CO2 treatments, intermittent CO2 supply and cutting off due to wind velocity and irradiance, except differences to the control. Simulations for optimizing CO2 on-line control are in progress.33^1^Amthor,J S^1991^1^Respiration in a Future, Higher-CO2 World^16^14^^13-20^^^^^^^^^^711 tTdؾDu&E&M#C^69^Plant, Cell and EnvironmentHr~r: sF ]^_ZY[XRPWVU˷r觔r&6&D&t&t:ŷrsF.A^69^Apart from its impact on global warming, the annually increasing atmospheric [CO2] is of interest to plant scientists/ primarily because of its direct influence on photosynthesis and photorespiration in C3 species. But in addition, 'dark' r0espiration, another major component of the carbon budget of higher plants, may be affected by a change in [CO2] independen1t of an increase in temperature. Literature pertaining to an impact of [CO2] on respiration rate is reviewed. With an incr2ease in [CO2], respiration rate is increased in some cases, but decreased in others. The effects of [CO2] on respiration r3ate may be direct or indirect. Mechanisms responsible for various observations are proposed. These proposed mechanisms rel4ate to changes in: (1) levels of nonstructural carbohydrates, (2) growth rate and structural phytomass accumulation, (3) c5omposition of phytomass, (4) direct chemical interactions between CO2 and respiratory enzymes, (5) direct chemical interac6tions between CO2 and other cellular components, (6) dark CO2 fixation rate, and (7) ethylene biosynthesis rate. Because a7 range of (possibly interactive) effects exists, and present knowledge is limited, the impact of future [CO2] on respirati8on rate cannot be predicted. Theoretical considerations and types of experiments that can lead to an increase in the understanding of this issue are outlined.5 ƚe,sG*"P7 e,sG t[2 *3>et:6bt)F:34^3^Amthor,J S^Koch,G W^Bloom,A J^1992^1^CO2 Inhibits Respiration in Leaves of _Rumex crispus_ L^17^98^^757-760^^^^^^^^^^74^^^^^^^^^^^Rumex crispus/curly dockdock^_+rXr ^o]^ZY[XˉF SVWPR2@t<u23 t 2$6F_^,C^72^Plant Physiol.b& t̀u4: Nt @suFu^~[XPSRUbۀt.0.=A^72^Curly dock (_Rumex crispus_ L.) was grown from seed in a glasshouse at an ambient CO2 partial pressure of about 35 pa>scals. Apparent respiration rate (CO2 efflux in the dark) of expanded leaves was then measured at ambient CO2 partial pres?sure of 5 to 95 pascals. Calculated intercellular CO2 partial pressure was proportional to ambient CO2 partial pressure in@ these short term experiments. The CO2 level strongly affected apparent respiration rate: a doubling of the partial pressuAre of CO2 typically inhibited respiration by 25 to 30%, whereas a decrease in CO2 elicited a corresponding increase in res!Bpiration. These responses were readily reversible. A flexible, sensitive regulatory interaction between CO2 (a byproduct o*f respiration) and some component(s) of heterotrophic metabolism is indicated.^_Y;w+PRVW363^VF-D35^4^Anderson,I H^Dons,C^Nilsen,S^Haugstad,M K^1985^1^Growth, Photosynthesis and Photorespiration of _Lemna gibba_: Respon0Ese to Variations in CO2 and O2 Concentrations and Photon Flux Density^18^6^^87-96^^^^^^^^^^77^^^^^^^^^^^Lemna gibba/duckwe3edd2F xd }2hZ-$d<(  D 6 _PSQRWV ;C^75^Photosynth. Res....&ˆFFFsvFVNF^rr^ Ffu8t2FvBtOfF6HA^75^Dry weight and Relative Growth Rate of _Lemna gibba_ were significantly increased by CO2 enrichment up to 6000 uL CO2AI/L. This high CO2 optimum for growth is probably due to the presence of nonfunctional stomata. The response to high CO2 waDJs less or absent following four days growth in 2% O2. The Leaf Area Ratio decreased in response to CO2 enrichment as a resGKult of an increase in dry weight per frond. Photosynthetic rate was increased by CO2 enrichment up to 1500 uL CO2/L duringL measurement, showing only small increases with further CO2 enrichment up to 5000 uL CO2/L at a photon flux density of 210JM umol/m2/s and small decreases at 2000 umol/m/s. The actual rate of photosynthesis of those plants cultivated at high CO2 XNlevels, however, was less than the air grown plants. The response of photosynthesis to O2 indicated that the enhancement oOf growth and photosynthesis by CO2 enrichment was a result of decreased photorespiration. Plants cultivated in low O2 prod[uced abnormal morphological features and after a short time showed a reduction in growth. t_:guZguRF?t;w uEFkQ36^1^Andersson,N E^1991^1^The Influence of Constant and Diurnally Changing CO2 Concentrations on Plant Growth and Development^19^66^^569-574^^^^^^^^^^80^^^^^^^^^^^Ficus benjamina/Rosa hybridaa&}D&=tv:/#:v*tmFC^78^J. Hort. Sci.^XPQRVWF~FFًLNLNLNLN^&2N&>N F&E'@tFVF m;VrTA^78^Plants of _Ficus benjamina_ and miniature rose (_Rosa hybrida_ cv. Red Minimo) were grown under four CO2 treatments. UTwo had constant CO2 levels (600 and 900 ppm) and the other two had diurnal changes in CO2 levels, one increasing from 600V to 1500 ppm and one decreasing from 1500 to 600 ppm, each in four steps of 300 ppm during the day-time. In all treatmentsW 900 ppm CO2 was maintained during the night when supplementary light was used, except in the treatment with constant 600 Xppm where 600 ppm was also continued throughout the night. Plant growth was monitored under both decreasing and increasingY natural daylength and irradiance. The tallest plants and greatest increment in height for _Ficus_ occurred with plants grZown under constant CO2 concentration at 900 ppm. In both experiments with miniature roses the number of flower buds was si[gnificantly 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 as compared with the other treatments.I.:]37^6^Andre,M^Cotte,F^Gerbaud,A^Massimino,D^Massimino,J^Richaud,C^1989^1^Effect of CO2 and O2 on Development and Fructification of Wheat in Closed Systems^124^9^^(8)17-(8)28^^^^^^^^^^83^^^^^^^^^^^Triticum aestivum/wheat^^^^^^^um aestivum L./whme that physiological evidence indicates the CCM is approaching maximal activity. Glycolate DH activity in 24 hour air-ad`A^81^The cultivation of wheat (_Triticum aestivum_ L.) was performed in controlled environment chambers with the continuouas monitoring of photosynthesis, dark respiration, transpiration and main nutrient uptakes. A protocol in twin chambers wasb developed to compare the specific effects of low O2 and high CO2. Each parameter is able to influence photosynthesis but cdifferent effects are obtained in the development, fructification and seed production, because of the different effects ofd each parameter on the ratio of reductive to oxidative cycle of carbon. The first main conclusion is that low level of O2,e at the same rate of biomass production, strongly acts on the rate of ear appearance and on seed production. Ear appearancfe was delayed and seed production reduced with a low O2 treatment (about 4%). The O2 effect was not mainly due to the reprgession of the oxidative cycle. The high CO2 treatment (700 to 900 uL/L) delayed ear appearance by 4 days, but did not reduhce seed production. High CO2 treatment also reduced transpiration by 20%. Two hypotheses were proposed to explain the similarities and the difference in the O2 and CO2 effects on the growth of wheat.r &W&GN3zr rr rFF^r transfer and then declines to the original level within 48 hours. The decline in PGPase activity begins at about the tik38^2^Andre,M^Du Cloux,H^1993^1^Interaction of CO2 Enrichment and Water Limitations on Photosynthesis and Water-Use Efficie ncy in Wheat^20^31^^103-112^^^^^^^^^^86^^^^^^^^^^^wheat/Triticum aestivumm L.2&3ҁ~|u &L&L&;Lt&RC^84^Plant Physiol. Biochem.OIr`t\RQ&Gt&WNYZr;&G&g}r( t~\u%6:"6:nA^84^Wheat plants (_Triticum aestivum_ L. cv. Capitole) were grown in twin closed growth chambers with continuous monitoriong of CO2 and water exchanges. During the vegetative stage the effect of CO2 enrichment, from 330 to 660 uL/L, was studiedp under an irradiance of 660 uE/m2/s with an optimum watering. Comparisons were made with successive experiments in which d!qaily water supply was fixed to a fraction (0.62-0.5-0.25) of the maximal transpiration of previous experiments. In a well 1rwatered canopy, the doubling of CO2 decreased transpiration by only 8%. Water use efficiency was increased (factor 1.45) msainly by the stimulation of photosynthesis. Under restricted water supply, photosynthesis of plants was more limited than 4ttranspiration. The inhibition of photosynthesis and the increase of water use efficiency can be predicted by a simple diffAuusion model applied to the response curve of photosynthesis to CO2, measured on canopy in standard conditions of watering.v The main hypothesis is that the equivalent stomatal conductance is reduced proportionally to the water availability, withDwout closure by patching. Under enriched CO2, the same reduction of leaf surface by water limitation was observed. PhotosynRxthesis was less affected. Therefore, water use efficiency was again increased. Doubling CO2 concentration can compensate fyor water stress inhibition on CO2 assimilation. That model also predicts interactions of CO2 and water stress observed on Uzwater-use-efficiency which was increased by a factor up to 5 in comparison with well-watered plants in standard atmospheref. The implications of this study on global change models are discussed.&&G^SRYԡ[ tgb&y >^Ԛ(6: |39^3^Andre,M^Du Cloux,H^Richaud,C^1986^3^Wheat Response to CO2 Enrichment: CO2 Exchanges, Transpiration and Mineral Uptakej}s^Controlled Ecological Life Support System: CELLS '85 Workshop^AMES Research Center^Moffett Field, California^405-428^^^^x^^^1985 July 16-19, NASA Report TM88215^^^^^^^^^^^^^^wheat/Triticum aestivum^^^^^^^^^^MacElroy,R^Martello,NV^Smernoff,D,DlXrq&GF&&G!_rY&ON&WVxXrBF t3ɋ^t XFFN^ t XFF t X|40^7^Andre,M^Ducloux,H^Richaud,C^Massimino,D^Daguenet,A^Massimino,J^Gerbaud,A^1987^1^Etude des Relations entre Photosynthese Respiration, Transpiration et Nutrition Minerale chez le Ble^124^7^^(4)105-(4)114^^^^^^^^^^90^^^^^^^^^^^wheat/Triticum aestivum^^^^^^^Triticum aestivum L.]Xse k xX^Y[F 7  F 7  >m^^^^^ Adv. Space Res. ',, &A^88^La croissance du Ble _Triticum aestivum_ a ete etudiee en environnement controle et ferme pendant une periode de 70 jours. Les echanges gazeux (Photosynthese, Respiration) hydriques (Transpiration) et al consommation en elements mineraux (Azote, Phosphore, Potassium) ont ete mesures en continu. On prsentera les relations dynamiques observees entre les differentes fonctions physiologiques, d'une part sous l'influence de la croissance et d'autre part en reponse a des modifications de l'environnement. L'influence de la teneur en CO2 pendant la croissance (teneur normale ou doublee) sera mise en evidence. In French.'-.---4,%%%%%%//,&l(l(l(l(l(l(l(l(l(l(l(l(l(l(l(l(l(l(l(l(l(l(l(l(l(l(l(41^5^Andreeva,T F^Strogonova,L E^Voevudskaya,S Yu^Maevskaya,S N^Cherkanova,N N^1989^1^Effect of Enhanced CO2 Concentration on Photosynthesis, Carbohydrate and Nitrogen Metabolism, and Growth Processes in Mustard Plants^21^36^^40-48^^^^^^^^^^93^^^^^^^^^^^mustard/Brassica junceaa L.bC    ! V~C^91^Fiziol. Rast.U(sp10h12vsb3T&d@E%-12345X@PJL RDYMSG DISPLAY = "" %-12345Xerences*p1005Xwhich*p1132Xcan*p1210A^91^We investigated prolonged (8- to 10-day) influence of enhanced carbon dioxide content (0.03-0.05%) in the air on photosynthesis of mustard plants (_Brassica juncea_ L.), on their carbohydrate and nitrogen metabolism, and on the course of growth processes. Considerable attention is devoted to the question of the effect of leaf starch excess on the rate of photosynthesis. It is demonstrated that mustard plants in the vegetative phase of growth under conditions of enhanced CO2 concentration in the air exhibit higher pure productivity of photosynthesis and a higher rate of photosynthesis than in plants growing at normal CO2 content in the atmosphere. Increase of apparent photosynthesis is realized without supplementary synthesis of fraction I protein. Increase in the rate of photosynthesis is accompanied by intensification of nitrogen metabolism, increase of growth, and accumulation of biomass. An excess of assimilates in the form of starch accumulates in the chloroplasts (25% of leaf dry mass at 27/24). Starch content increases significantly in plants grown under conditions of reduced temperature compared with ones grown at a higher temperature (34.4% of leaf dry mass at 20/17 as compared with 20.1% at 32/27). It is concluded that high starch content in the leaves is not a cause of photosynthesis suppression. Decline of photosynthesis is observed only when the starch excess disturbs structure of the chloroplasts.))42^1^Apel,P^1989^1^Influence of CO2 on Stomatal Numbers^22^3^^72-74^^^^^^^^^^96^^^^^^^^^^^Phaseolus vulgaris/Vicia faba/Lycopersicon esculentum/Acer pseudoplatanus/Triticum aestivum/Hordeum vulgare/Secale cereale/Avena sativa/Zea mays/bean/broad bean/tomato/sycamore maple/wheat/barley/rye/oat/cornmaple/wheat/barley/rye/oat/cornTUPPPUUUUUUUUUUC^94^Biol. PlantarumUUUUUUUUUUUUUUUUUUUUUUUUUUUUEDDDDDDDDDEDDDDDDDDDTDDDDDDDDDDDDDDDDP A^94^From nine different plant species grown at 1500 cm3/m3 CO2 five responded with a significant increase in stomatal numbers per mm2 as compared with plants grown under normal air conditions. Within a collection of twelve french bean cultivars remarkable cultivar differences with regard to the CO2 enhancement effect on stomatal numbers was found. 43^1^Arnone,J A,III^1988^6^Photosynthesis, Carbon Allocation, and Nitrogen Fixation in Red Alder^^Yale University^^Doctora(l Dissertation^^^Dissertation Abstracts Vol.50:08-B, p.3244 (96 pp.)^^^^^^^98^^^^^^^^^^^Alnus rubra/red alderalderA^97^Research reported in the three sections of this dissertation addresses the problem of the effect of potentially high *carbon costs of nitrogen fixation by alder-Frankia symbioses on host plant biomass productivity. Effects of root nodulatio7n and nitrogen fixation on plant biomass productivity and allocation patterns were evaluated by growing inoculated and uninoculated red alder seedlings in atmospheres containing ambient (350 uL/L) and elevated (650 uL/L) levels of CO2, with and: without combined nitrogen (20 mg/L NH4NO3) supplied in modified N-free Hoagland's nutrient solution. Effect of nodulationD, CO2 enrichment, substrate nitrogen, and the feedback interaction on early seedling development and aboveground and belowground growth were also tested using the same plant material. Root:shoot ratios for plants in all treatments decreased oveHr the course of the experiment. This occurred more rapidly in nodulated plants and was attributed to more rapid attainmentU of balanced root:shoot growth. This and evidence supporting the hypothesis that whole plant internal carbon/nitrogen balance regulated aboveground and belowground growth is presented and discussed.X44^2^Arnone,J A,III^Gordon,J C^1990^1^Effect of Nodulation, Nitrogen Fixation and CO2 Enrichment on the Physiology, Growth` and Dry Mass Allocation of Seedlings of _Alnus rubra_ Bong^23^116^^55-66^^^^^^^^^^101^^^^^^^^^^^Alnus rubrara Bong.C^99^New Phytol.cA^99^Inoculated and uninoculated _Alnus rubra_ Bong. seedlings were grown for 47 days in atmospheres containing ambient (3t50 uL CO2/L) and elevated (650 uL CO2/L) levels of CO2, with and without combined nitrogen (20 mg/L) supplied as ammonium nitrate. Five plants from each treatment were harvested 15, 30, and 47 days after exposure to CO2 treatments began. Evidenwce for the presence of a positive feedback loop between nitrogen fixation and photosynthesis was observed in nodulated plants growing at elevated CO2. These plants had greater whole-plant photosynthesis and nitrogenase activity, leaf area and nitrogen content, as well as nodule and plant dry mass, relative to nodulated plants grown at ambient CO2 and non-nodulated plants grown at both CO2 levels. This feedback may be an important way in which the potential carbon drain of nitrogen fixation on the host plant could be compensated; increased nitrogen availability resulting in stimulated leaf area growth and whole-plant photosynthesis. The relative amount of dry mass allocated to below ground decreased for all seedlings over time, and the amount allocated above ground increased. This shift in allocation occurred slowly and at a constant rate in non-nodulated plants and more rapidly and abruptly when plants were nodulated. The proportion of dry mass allocated below ground was consistently greater in non-nodulated plants grown at high CO2. Dry mass partitioning among other organs was not directly affected by nodulation, CO2 enrichment, or other treatment interactions.45^1^Arp,W J^1991^1^Effects of Source-Sink Relations on Photosynthetic Acclimation to Elevated CO2^16^14^^869-875^^^^^^^^^C^102^Plant Cell Environ. 8GA^102^While photosynthesis of C3 plants is stimulated by an increase in the atmospheric CO2 concentration, photosynthetic 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 revealed 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 reduction or an increase in this capacity. Pot volume also determined the effect of elevated CO2 on the root:shoot ratio--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.    ^10404     46^1^Arp,WJ^1991^6^Vegetation of a North American Salt Marsh and Elevated Atmospheric Carbon Dioxide^^Centrale Huisdrukkerij Vrije Universiteit, Amsterdam^^Doctoral Dissertation^^^^^^^^^^^^^^^^^^^^^Distichlis spicata/Spartina patens/Scirpus olneyi^^^^^eyi        47^2^Arp,W J^Drake,B G^1991^1^Increased Photosynthetic Capacity of _Scirpus olneyi_ after 4 Years of Exposure to Elevated CO2^16^14^^1003-1006^^^^^^^^^^108^^^^^^^^^^^sedge/Scirpus olneyiyi C^106^Plant Cell Environ. A^106^While a short-term exposure to elevated atmospheric CO2 induces a large increase in photosynthesis in many plants, long-term growth in elevated CO2 often results in a smaller increase due to reduced photosynthetic capacity. In this study,  it was shown that, for a wild C3 species growing in its natural environment and exposed to elevated CO2 for four growing (seasons, the photosynthetic capacity has actually increased by 31%. An increase in photosynthetic capacity has been observ +ed in other species growing in the field, which suggests that photosynthesis of certain field grown plants will continue t /o respond to elevated levels of atmospheric CO2.a d h? 548^5^Arp,W J^Drake,B G^Pockman,W T^Curtis,P S^Whigham,D F^1993^1^Interactions between C3 and C4 Salt Marsh Plant Species d 9uring Four Years of Exposure to Elevated Atmospheric CO2^123^104/105^^133-143^^^^^^^^^^111^^^^^^^^^^^Spartina patens/Scirp =us olneyi/Distichlis spicata^^^^^&s4&s) ي54t "k)9 &s43kean variety was more promoted by CO2 enrichment than by NO3-N application, while that of the wild one was enhanced by NO3- @A^109^Elevated atmospheric CO2 is known to stimulate photosynthesis and growth of plants with the C3 pathway but less of p Jlants with the C4 pathway. An increase in the CO2 concentration can therefore be expected to change the competitive interactions between C3 and C4 species. The effect of long term exposure to elevated CO2 (ambient CO2 concentration + 340 umol C NO2/mol) on a salt marsh vegetation with both C3 and C4 species was investigated. Elevated CO2 increased the biomass of the W C3 sedge _Scirpus olneyi_ growing in a pure stand, while the biomass of the C4 grass _Spartina patens_ in a monospecific Zcommunity was not affected. In the mixed C3/C4 community the C3 sedge showed a very large relative increase in biomass in elevated CO2 while the biomass of the C4 species declined. The C4 grass _Spartina patens_ dominated the higher areas of th ]e salt marsh, while the C3 sedge _Scirpus olneyi_ was most abundant at the lower elevations, and the mixed community occup jied intermediate elevations. _Scirpus_ growth may have been restricted by drought and salt stress at the higher elevations, while _Spartina_ growth at the lower elevations may be affected by the higher frequency of flooding. Elevated CO2 may af mfect the species distribution in the salt marsh if it allows _Scirpus_ to grow at higher elevations where it in turn may a vffect the growth of _Spartina_.is required $ Error: 80286 or higher CPU is required $ 49^1^Artus,N N^1990^1^Two Mutants of _Arabidopsis thaliana_ That Become Chlorotic in Atmospheres Enriched with CO2^16^13^^ y575-580^^^^^^^^^^114^^^^^^^^^^^Arabidopsis thalianana L.2꤀DF>?a꤀DpF>?꤀D C^112^Plant Cell Environ.DWPP^WWP^#d":ffp d#d:ZA^112^Two nonallelic, nuclear recessive mutants of _Arabidopsis thaliana_ (L.) Heynh. which become chlorotic when grown in  an atmosphere enriched to 20,000 cm3 CO2/m3 have been isolated. For one of the mutants, chlorosis begins at the veins and  gradually spreads to the interveinal regions. A minimum photon flux density of ca 50 umol/m2/s is required for this response. For the other mutant, the yellowing is independent of the light intensity and begins at the basal regions of the leav es and spreads to the tips. The injurious effects of CO2 seem to be restricted to photosynthetic tissues, since root elong ation and callus growth were not inhibited by a high atmospheric CO2 concentration for either mutant. Neither mutant became chlorotic in a low O2 atmosphere that suppressed photorespiration as effectively as the elevated CO2 does. Thus, the mut ations do not impose a requirement for photorespiration. The possibilities that the high CO2-sensitive phenotypes are caus ed by an effect of CO2 in stomata, on ethylene synthesis, or on mineral uptake are discussed but are considered unlikely.50^3^Ashenden,T W^Baxter,R^Rafarel,C R^1992^1^An Inexpensive System for Exposing Plants in the Field to Elevated Concentra tions of CO2^16^15^^365-372^^^^^^^^^^11717SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS C^115^Plant Cell Environ.SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS A^115^An inexpensive, potentially mobile field exposure system is described which may be easily constructed by a small wor kshop. It may be operated as an open-top with a frustum or covered with a polycarbonate 'lid'. The system is cost-effective for CO2 exposure work because the small size allows provision of CO2-enriched atmospheres over prolonged periods at rela tively low cost. A preliminary assessment of the chambers has been made and concentrations can be maintained at +/- 6% for  a target atmosphere of 680 cm3/m3 CO2 under normal operating conditions. Other chamber environmental conditions are reported.SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS            ! " # % & ) * + , - . 0 1 2 3 4 7 ; @  E F G H J K L M N O Q R S T V W X Y Z [ \ ] ^ _ a b c d e f g h j k l m n o p q r v w x y z { | } ~   51^1^Aston,A R^1984^1^The Effect of Doubling Atmospheric CO2 on Streamflow: a Simulation^24^67^^273-280^^^^^^^^^^1200t C^118^J. Hydrol. &Yt 8r>u&]&Ùt+ A^118^There is a potential for atmospheric CO2 to rise four- or six-fold, and at some time in the foreseeable future a dou bling of stomatal resistance seems, on present evidence, to be inevitable. A distributed deterministic process model was used to simulate the effects of changed stomatal resistance on streamflow of a 5-ha experimental catchment and a large (417  km2) water-supply area. The results indicated that we can expect streamflow to increase from 40 to 90% as a consequence of doubling of atmospheric CO2 concentration.Y]&D2 W> uv&t&| uuK6H]3&t t@[W 52^1^Austin,M P^1992^1^Modelling the Environmental Niche of Plants: Implications for Plant Community Response to Elevated CO2 Levels^25^40^^615-630^^^^^^^^^^123^^^^^^^^^^^Eucalyptus fastigatataK<}EE&&dFV&&`FV C^121^Aust. J. Bot.^NV;u;rEEEE3F^NV;u;֋NV;u;֋F^;u; u  A^121^No simple natural gradients in CO2 concentration exist for testing predictions about changes in plant communities in  response to elevated CO2. However indirect effects of CO2 via temperature increases can be tested by reference to natural  analogues. Physiologists, vegetation modellers of climate change and community ecologists assume very different temperature responses for plants. Physiologists often assume a skewed non-monotonic curve with a tail towards low temperatures, for est modellers using FORET type models, a symmetric curve, and community ecologists a skewed response with a tail towards h #igh temperatures. These assumptions are reviewed in relation to niche theory, and recent propositions concerning the continuum concept. Confusion exists between the different approaches over the shape of response curves to temperature. Distinctions 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-models 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 response of a species to temperature is provided. It is based on generalised linear modelling (GLM) of presence/absence data on _Eucalyptus fastigata_ for 8377 si 3tes in southern New South Wales, Australia. Seven environmental variables or factors are considered: mean annual temperatu >re, mean annual rainfall, mean monthly solar radiation, topographic position, rainfall seasonality, lithology, and soil; nutrient status. The temperature response is modelled by a _Beta_-function, log _y + a + alpha_ log _(t - a) + sigma_ log _ A(b - t)_, where _t_ is temperature and letters are parameters. The probability of occurrence is shown to be a skewed funct Jion of mean annual temperature. Any process-models of climate change for vegetation incorporating temperature changes due to elevated CO2 must be capable of generating such realised environmental niche responses for species.YPSQRVWUt M53^1^Badger,M^1992^1^Manipulating Agricultural Plants for a Future High CO2 Environment^25^40^^421-429^^^^^^^^^^12626 P C^124^Aust. J. Bot.&ur N?&^XW>~;6w*r&2r _ A^124^This paper discusses the potential ways in which C3 plant performance may benefit from a future high-CO2 environment!. These include increases in the efficiencies for light, nitrogen and water utilisation, particularly at elevated temperat b"ures, resulting from the improvement which will occur in the performance of the primary carboxylating enzyme, Rubisco. How n#ever, while growth experiments at elevated CO2 indicate that C3 plants show stimulation of dry matter accumulation, the po$tential gains are greatly ameliorated by a redistribution of plant resources. This primarily occurs via a reduction in the q% leaf area ratio which offsets increases in the net assimilation rate. In addition, there may be an overcommitment of nitr y&ogen in key photosynthetic components such as Rubisco and the thylakoid electron transport system. It is concluded that pl'ants may not be genetically adapted to optimise their growth and performance at elevated CO2 and that consideration should }( be given to exploring avenues for manipulating plants for more optimal responses. Targets for improvement of growth at el )evated CO2 include (1) altering source-sink relations; (2) improving the redistribution of nitrogen between the photosynth*etic machinery and the rest of the plant; and (3) changing the response of stomata to CO2 and humidity to increase water-u se efficiency even further than is currently predicted.tƀt҃ǀt t t t 54^1^Baille,A^1989^1^Greenhouse Microclimate and Its Management in Mild Winter Climates^15^246^^23-36^^28Xr uC^127^Act. Hort.\&Q9r J9rK&2Q &79rY5O&r9rr9rr֊9rϊ8rr .55^2^Bailly,J^Coleman,J R^1988^1^Effect of CO2 Concentration on Protein Biosynthesis and Carbonic Anhydrase Expression in _Chlamydomonas reinhardtii_^17^87^^833-840^^^^^^^^^^131^^^^^^^^^^^Chlamydomonas reinhardtiiiidu&^_X. ,C^129^Plant Physiol.rdۉsW3PWPryd3ҹd4Xך؇6F_ tы:_QrFw33ɋ&:w 1A^129^The effect of external inorganic carbon (Ci) concentrations on protein biosynthesis and carbonic anhydrase (CA) mRNA2 abundance were examined in the eukaryotic alga _Chlamydomonas reinhardtii_. Transfer of high CO2 (5%) grown algae to air 3levels of CO2 resulted in the transitory synthesis of two polypeptides of approximately 49,000 and 52,000 daltons as well 4as prolonged synthesis and accumulation of the 37,000 dalton CA monomer and an unidentified 20,000 dalton polypeptide. The5 gene coding for carbonic anhydrase was isolated from a genomic expression library and subjected to restriction endonuclea 6se analysis. Southern blot analysis of chromosomal DNA indicates that only a single copy of the gene is present. The 2.5 k 7ilobase DNA fragment hybridizes specifically to a 1.4 kilobase transcript in RNA isolated from air-grown cells and from ce 8lls grown on 5% CO2 that have been exposed to air levels of CO2. Maximum mRNA abundance was observed after 1 to 3 hours of 9 exposure to air. Transfer of air-grown cells to a high CO2 environment resulted in the elimination of the CA transcript a:fter 60 minutes of exposure. Changes in CA transcript abundance in response to external Ci concentrations occurred in the presence or absence of light. & tG4&_&&c&[ }r4Fr ^r$s^r&>&F^2 <56^2^Baker,R G E^Boatman,D J^1990^1^Some Effects of Nitrogen, Phosphorus, Potassium and Carbon Dioxide Concentration on th=e Morphology and Vegetative Reproduction of _Sphagnum cuspidatum_ Ehrh^23^116^^604-611^^^^^^^^^^134^^^^^^^^^^^Sphagnum cus pidatumum Ehrh.ZY[XSRQU&DžOv&t%&%N.P&%&!Y&Q&!U&tD&!vP&+Uy&!& /C^132^New Phytol.&UY&Q&U&!v]YZ[PSQRVW&6&[ oskF^Nc&E%t@A^132^Five experiments are described which were designed to investigate the effects of varying the concentrations of nitra Ate, phosphate, potassium and carbon dioxide in the culture solution on the morphology and vegetative reproduction of _Spha Bgnum cuspidatum_ Ehrh. The plants were grown axenically from spores sown on agar containing inorganic salts and then transCferred to aqueous culture solutions through which air containing enhanced concentrations of carbon dioxide was passed. In Dthree of the experiments the plants were grown in a balanced inorganic salt solution at various dilutions and in two of th Eese the concentration of carbon dioxide in the gas bubbled through the solution was varied. The concentrations of nitrogenF, phosphorus and potassium were varied independently and in combination in the remaining experiments while the concentrati Gon of carbon dioxide was kept constant. In some of the experiments the minimum concentrations of nitrogen and potassium su Hpplied were considerably below the minimum average concentrations recorded in rain but the minimum concentration of phosph Iorus supplied was within the upper part of the range recorded in rain. Within the ranges supplied the concentrations of al Jl three elements and of carbon dioxide affected interfascicle length and vegetative reproduction (innovation formation) bu t it was concluded that the element limiting innovation formation in natural conditions is phosphorus.2~FU&E0 %L57^3^Baldocchi,D D^White,R^Johnston,J W^1989^1^A Wind Tunnel Study to Design Large, Open-top Chambers for Whole-tree Pollu 'tant Exposure Experiments^27^39^^549-1556^^^^^^^^^^13737F։F@FʉF΋3FƋ1FvĿc$6F~6F6 3>C^135^JapcaFF-]6F^3&E&E&E&E &E&E"tQ!&E(&E*%&E,&E._ZY[XPSQRVW F 6OA^135^A wind tunnel study was conducted to determine the optimal design features of a large, open-top chamber, as needed f 8Por pollution exposure studies on mature trees. An optimally-designed, open-top chamber must minimize the incursion of ambi GQent air through its opening and maintain a uniform treatment concentration throughout the chamber. The design features of Rinterest are the diameter and height of the chamber and the deflection angle and opening size of any frustum that may be m JSounted on top of a model chamber. Design specifications depend on the turbulence regime about the chamber, which is influe ZTnced by the nature of the surrounding vegetation. Consequently, our investigation was performed on scale-model, open-top cUhambers in a wind tunnel populated with a model coniferous forest. Turbulence measurements demonstrated the similarity bet ]Vween the turbulence regime of the model and a natural forest. A hydrocarbon tracer was injected into the wind tunnel flow kWto characterize chamber performance. The main design features of open-top chambers are the velocity of air exiting throughX the top and the relationship between the length scale of the turbulence and the diameter of the chamber opening. As exit nYvelocities increase, the proportion of eddies with sufficient force to penetrate into the chamber decrease. Therefore, for qZ equal volumetric air flows, smaller opening sizes increase the exit velocities and reduce the number and extent of ambien t[t air incursions. Almost total exclusion of ambient air is achieved as the exit velocity of the air exceeds the magnitude \of one standard deviation of the vertical wind velocity measured at the chamber top. The incursion of ambient air is also w]reduced when the diameter of the chamber opening is smaller than the characteristic length scale of the turbulence, a meas |^ure of mean eddy size. Frusta deflect air flow over the chamber. Three prototypes, with 30-, 45- and 60-degree angles were _ tested. A 30-degree frustum slightly improves the performance of the chamber and is more effective in preventing ambient `air from entraining into the chamber opening than frusta with either a 45- or 60-degree angle. A flatter frustum allows fo ar a smoother transition in the wind velocity streamline and is less apt to cause wake turbulence, as is the case with stee bper frusta. Knowledge of the turbulence characteristics of plant canopies are readily available in the literature and can caid scientists and engineers in designing the optimal chamber and frusta dimensions for their particular application. Ther efore, the empirical approach to chamber design can be avoided, and substantial savings can be realized.[uS^v58^2^Ball,M C^Munns,R^1992^1^Plant Responses to Salinity under Elevated Atmospheric Concentrations of CO2^25^40^^515-525^^ MC^138^Aust. J. Bot.QNv^Ft6FN6FFvY[XPSQRV6@t%KKwtMt c gA^138^This review explores effects of elevated CO2 concentrations on growth in relation to water use and salt balance of hhalophytic and non-halophytic species. Under saline conditions, the uptake and distribution of sodium and chloride must be iregulated to protect sensitive metabolic sites from salt toxicity. Salt-tolerant species exclude most of the salt from the j transpiration stream, but the salt flux from a highly saline soil is still considerable. To maintain internal ion concent krations within physiologically acceptable levels, the salt influx to leaves must match the capacities of leaves for salt s ltorage and/or salt export by either retranslocation or secretion from glands. Hence the balance between carbon gain and th me expenditure of water in association with salt uptake is critical to leaf longevity under saline conditions. Indeed, one nof the striking features of halophytic vegetation, such as mangroves, is the maintenance of high water use efficiencies co oupled with relatively low rates of water loss and growth. These low evaporation rates are further reduced under elevated CpO2 conditions. This, with increased growth, leads to even higher water use efficiency. Leaves of plants grown under elevat qed CO2 conditions might be expected to contain lower salt concentrations than those grown under ambient CO2 if salt uptake r is coupled with water uptake. However, salt concentrations in shoot tissues are similar in plants grown under ambient ands elevated CO2 conditions despite major differences in water use efficiency. This phenomenon occurs in C3 halophytes and in t both C3 and C4 non-halophytes. These results imply shoot/root communication in regulation of the salt balance to adjust t uo environmental factors affecting the availability of water and ions at the roots (salinity) and those affecting carbon gain in relation to water loss at the leaves (atmospheric concentrations of water vapour and carbon dioxide).DF&DF& ^^^^^^^^14040F{s& 2& ؋&^&\^FlOriF22賱rX؋&&tt 2&&2&e'_ZYSQRWr$3ɿ & GGr&>&2&e%_ZY[QRW&L {A^141^Australia produced $2.7 billion worth of forest products in 1983-84 but a further $1.3 billion worth, principally so |ftwood, were imported. Because of this ever increasing demand for softwood, there is a move away from utilization of nativ }e hardwoods and by 2020 AD, when the atmospheric CO2 concentration is likely to be greater than 450 ppmv, 75% of forest pr~oducts are projected to come from coniferous plantations. This move towards _Pinus radiata_ is a result of both demand for  softwood and lack of indepth investigations of the potential of Australian native species, particularly eucalypts, for plantation forestry. _Pinus radiata_ is the major plantation softwood in southern Australia and is presently grown at sites where phosphorus deficiency and repeated episodes of drought are common. Consequently, we are investigating the growth res ,ponse of pines to elevated CO2 at a range of phosphorus and water levels. When phosphorus was adequate, doubling CO2 conce /ntration more than doubled the rate of photosynthesis and increased the total plant dry weight by about 40%. However, ther Pe was no response when phosphorus was deficient. In contrast, there was a slightly higher response under simulated drought conditions. A further possible effect of rising CO2 levels is that the climatic range of _P. radiata_ may be altered due Tto a reduction in water use or an increase in the drought tolerance of the trees. We found that CO2 enrichment did not aff dect either of these factors but the water-use efficiency was increased when phosphorus was adequate. All families of _P. radiata_ do not respond to CO2 enrichment in the same manner. In a study investigating the response of four families to ele gvated CO2 at two phosphorus levels, we have identified a considerable variation between the families in their response to pCO2 and phosphorus. To date our studies have indicated that the projected increase in atmospheric CO2 levels is likely to have a significant influence on the productivity of Australia's _P. radiata_ plantations. But this will only occur if phos tphorus fertilization is adequate. If the rise in CO2 results in climatic change the range of _P. radiata_ may be even furt her restricted because there will be no concomitant decrease in water use or increase in drought tolerance. There is an urgent need for complementary studies of the response of Australian native species to elevated CO2 at realistic levels of ph osphorus and water to enable more accurate prediction of the productivity and water use of Australian native forests and e ucalyptus plantations.]ZY[_^F&FF tFF 7X7XÚ${Ú${ÚO${Ú%;60^2^Baron,J J^Gorski,S F^1986^1^Response of Eggplant to a Root Environment Enriched with CO2^28^21^^495-498^^^^^^^^^^2058 eC^143^HortSci.t &\?2A'&L&8t&W326 rJ& rA&9s"s5ʋF3${r)&F |rv&<3 62^2^Barson,M M^Gifford,R M^1990^3^Carbon Dioxide Sinks: The Potential Role of Tree Planting in Australia^Greenhouse and Energy^CSIRO^Australia^433-443^^^^^^^^^^149^^^^^^^^^^^^^^^^^^^^^Swain,DJ9;5_^Y[ˀ>@ t>@ u A^148^Reforestation has been suggested as a possible policy option at several recent international 'greenhouse effect' for ums. The issue of deforestation/reforestation may be the subject of a protocol for which detailed arrangements will be developed following the establishment of a non-obligatory Framework Convention on Climate Change in the early 1990's. Althoug h forestry cannot in principle offer a permanent solution to continuous emission of CO2 from fossil fuel burning, its expa nsion could assist in slowing down net emissions. This would 'buy time' to reduce rates of CO2 emission and to develop strategies to adapt to global atmospheric and climate change. A simple model is developed to explore the dynamics of carbon s equestration by new forest plantations. The areal extent of land suitable for reforestation is also examined. It is concluded from one optimistic scenario that a program of planting 40,000 ha/y of new forest onto non-forested land could, after 20 y absorb about 5-12 Mt (C) p.a. (7-17 per cent 1987-88 total Australian emissions) as long as planting at that rate continued.F&9&uHr~r: sF ]^_ZY[XRPWVU˷r觔r&6&D&t&t:ŷrsFA^151^Increasing atmospheric carbon dioxide concentrations present a novel resource condition for plant communities. In or der to understand and predict how plant community structure and function may be altered in a high CO2 world, we need to understand how interactions among neighboring plants within a community will alter the growth and reproduction of component species. Because CO2 is readily diffusible, plants have little influence on the CO2 acquisition of their neighbors, except . within particularly dense canopies. Thus, plants seldom compete directly for CO2. Rather, CO2 availability is likely to alter plant-plant interactions indirectly through its effects on plant growth and competition for other resources. As a con 2sequence, competitive outcome under elevated CO2 atmospheres within even simple systems is not easy to predict. For example, under some conditions, C4 species in competitive assemblages have improved competitive ability relative to C3 competito 5rs as a result of CO2 enrichment, contrary to expectations based on their photosynthetic pathways. It is now clear that in Bdividually grown plants can differ substantially from those within mono- or multispecific stands in response to CO2 enrichment. At present, our understanding of how stands of interacting plants modify the availability of CO2 and other resources E is incomplete. We urgently need information about how elevated CO2 atmospheres influence stand formation and population d Synamics, specifically with regard to the identities, numbers, sizes and reproductive fitnesses of individuals within singl Ue and multiple species stands, if we are to make multi-generational predictions concerning the fate of populations and communities in an elevated CO2 world.t̀u4: Nt @suFu^~[XPSRUbۀt.0. Y353r^^]Z[XˉFV&<uFQr&<t&<u r E4:^V&<uF#r&<t&<u `r 4:^65^2^Bazzaz,F A^Garbutt,K^1988^1^The Response of Annuals in Competitive Neighborhoods: Effects of Elevated CO2^2^69^^937-9 \46^^^^^^^^^^156^^^^^^^^^^^Ambrosia artemisiifolia/Abutilon theophrasti/Amaranthus retroflexus/Setaria faberiiSetaria fabe erii Herm.^_ZY[XPQVWUd&>u6 hA^154^Four members of an annual community were used to investigate the effects of changing neighborhood complexity and inc xreased CO2 concentration on competitive outcome. Plants were grown in monoculture and in all possible combinations of two, three, and four species in CO2-controlled growth chambers at CO2 concentrations of 350, 500, and 700 uL/L with ample mois {ture and high light. Species responded differently to enhanced CO2 level. Some species (e.g., _Abutilon theophrasti_) had increased biomass with increasing CO2, while others (e.g., _Amaranthus retroflexus_) had decreased biomass with increasing CO2 concentration. In mixtures, species tended to interact strongly, and, in some cases, the interaction canceled out the  effects of CO2. Furthermore, there were clear differences in species behavior in different competitive neighbors. In gene ral, competitive arrays that had C3 species depressed the response of C4 species, especially _Amaranthus_. _Ambrosia artemisiifolia_ was the strongest competitor in the assemblage. Strong statistical interactions between CO2 and the identity of  the competing species in mixtures were found to be primarily due to the as yet unexplained response of plants with CO2 at  500 uL/L. The potential effects of CO2 on community structure could be profound, particularly at the intermediate levels of CO2 that are predicted to be reached during the first half of the next century.PSQV &}tGt)< u!&2&A 66^1^Bazzaz,F A^1990^1^The Response of Natural Ecosystems to the Rising Global CO2 Levels^30^21^^167-196^^58_rtDޚ C^157^Ann. Rev. Ecol. Syst.dPSQRVWtE&4u ?u<6}t~tGXv3ҋF&;uGG t uB:67^4^Bazzaz,F A^Ackerly,D D^Woodward,F I^Rochefort,L^1992^1^CO2 Enrichment and Dependence of Reproduction on Density in an Annual Plant and a Simulation of Its Population Dynamics^31^80^^643-651^^^^^^^^^^161^^^^^^^^^^^Abutilon theophrasti^^^^^C^159^J. Ecol.Q t t:YXPW&2&E:G _XPSQVW<f&}D&=tv:/#:v*t A^159^1. Populations of an annual plant, _Abutilon theophrasti_, were grown at four densities (100, 500, 1500 and 4000/m2)  and two CO2 concentrations (350 and 700 uL/L) to examine the influence of CO2 environment on density-dependent patterns o f demography and reproduction. Variables measured included survivorship, proportion of plants flowering and fruiting, numb er of fruiting individuals, number of seeds per individual, total seed production per population, mean seed mass, and germination of seeds produced in each environment. 2. All variables, except the number of fruiting individuals, declined with increasing density, and at the highest density no individuals set seed. The number of fruiting individuals was highest at a density of 500/m2. In the elevated CO2 environment, survivorship was significantly reduced but the proportion of plants flowering and fruiting and the number of fruiting individuals in each population all increased. Total population seed prod uction was higher in the elevated CO2 environment at all densities, although the differences were not significant. Significant effects of CO2 concentration were observed only for population-level variables, but not for mean individual fecundity  or seed size. Seed germination declined with increasing maternal density, and no germination was recorded for seeds produ ced at 1500 /m2. 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 simula ted populations exhibited damped or stable oscillations under low germination values, but displayed non-cyclic ('chaotic') 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 germination value at which the simulated populations went extinct was much lower for the elevated-CO2 than for the ambient-CO2 population.ˉN rB_r=&G &8r*&&3Ћ"r3 F&8Et &MN&M0&&O&G{r68^3^Bazzaz,F A^Coleman,J S^Morse,S R^1990^1^Growth Responses of Seven Major Co-occurring Tree Species of the Northeastern  United States to Elevated CO2^32^20^^1479-1484^^^^^^^^^^164^^^^^^^^^^^American beech/Fagus grandifolia/paper birch/Betula papyrifera/black cherry/Prunus serotina/white pine/Pinus strobus/red maple/Acer rubrum/sugar maple/Acer saccharum/eastern hemlock/Tsuga canadensis./eastern hemlock/Tsuga canadensis (L.) Carr.2ˉN0urI rA&G &C^162^Can. J. For. Res.3 F&8Et A&M&M0&&O&G$r &W&GN3zr rr rFFA^162^We examined how elevated CO2 affected the growth of seven co-occurring tree species: American beech (_Fagus grandifolia_ Ehrh.), paper birch (_Betula papyrifera_ Marsh.), black cherry (_Prunus serotina_ Ehrh.), white pine (_Pinus strobus_ L.), red maple (_Acer rubrum_ L.), sugar maple (_Acer saccharum_ Marsh.), and eastern hemlock (_Tsuga canadensis_ (L.) Carr.). We also tested whether the degree of shade tolerance of species and the age of seedlings affected plant responses to enhanced CO2 levels. Seedlings that were at least 1 year old, for all species except beech, were removed while dormant fr%om Harvard Forest, Petersham, Massachusetts. Seeds of red maple and paper birch were obtained from parent trees at Harvard& Forest, and seeds of American beech were obtained from a population of beeches in Nova Scotia. Seedlings and transplants were grown in one of four plant growth chambers for 60 d (beech, paper birch, red maple, black cherry) or 100 d (white pin*e, hemlock, sugar maple) under CO2 levels of 400 or 700 uL/L. Plants were then harvested for biomass and growth determinat2ions. The results showed that the biomass of beech, paper birch, black cherry, sugar maple, and hemlock significantly increased in elevated CO2, but the biomass of red maple and white pine only marginally increased in these conditions. Furtherm5ore, there were large differences in the magnitude of growth enhancement by increased levels of CO2 between species, so it; seems reasonable to predict that one consequence of rising levels of CO2 may be to increase the competitive ability of some species relative to others. Additionally, the three species exhibiting the largest increase in growth with increased CO>2 concentrations were the shade-tolerant species (i.e., beech, sugar maple, and hemlock). Thus, elevated CO2 levels may enHhance the growth of relatively shade-tolerant forest trees to a greater extent than growth of shade-intolerant trees, at least under the light and nutrient conditions of this experiment. We found no evidence to suggest that the age of tree seedKlings greatly affected their response to elevated CO2 concentration.6&&G^SRYԡ[ tgb&y >^Ԛ(6: S69^2^Bazzaz,F A^Fajer,E D^1992^1^Plant Life in CO2-Rich World^33^266^^68-74^^66SRb&y >^Ԛ(6: u eԋ_CC^165^Sci. Amer.u_ԋw+e+my+e+mԋw+_+kZ[nNV t~hZuNc+_@Fa+e@FW70^3^Bazzaz,F A^Garbutt,K^Williams,W E^1985^3^Effect of Increased Atmospheric Carbon Dioxide Concentration on Plant Communfities^Direct Effects of Increasing Carbon Dioxide on Vegetation^U.S. Dept. of Energy, Carbon Dioxide Research Division^Washington, D.C.^155-204^^^^^^^DOE/ER-0238^^^^^^^^^^^^^^^^^^^^^^^^Strain,BR^Cure,J D @^~t ;c u>i uc i71^3^Bazzaz,F A^Garbutt,K^Williams,W E^1985^5^The Effect of Elevated Atmospheric CO2 on Plant Communities^NTIS, U.S. Dept.q of Commerce, Springfield, Virginia^^^^^^^^^^^^^^^^^^^^^^^^^^TR023 in Yellow Report Series^DOE/EV/04329-5^Dept. of Energy, Carbon Dioxide Research Division^de Research Division^ ',, &t72^4^Bazzaz,F A^Garbutt,K^Reekie,E G^Williams,W E^1989^1^Using Growth Analysis to Interpret Competition between a C3 and a C4 Annual under Ambient and Elevated CO2^34^79^^223-235^^^^^^^^^^171^^^^^^^^^^^Abutilon theophrasti/Amaranthus retroflexusroflexus L.  (((0)9))))))(((((())))")*-*Y*L)&&&&&&&&&&'<'C^169^Oecologiap([(B(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p(p( /.,,,,, , , , , ,,,A^169^Detailed growth analysis in conjunction with information on leaf display and nitrogen uptake was used to interpret c ompetition between _Abutilon theophrasti_, a C3 annual, and _Amaranthus retroflexus_, a C4 annual, under ambient (350 uL/L ) and two levels of elevated (500 and 700 uL/L) CO2. Plants were grown both individually and in competition with each othe r. Competition caused a reduction in growth in both species, but for different reasons. In _Abutilon_, decreases in leaf a rea ratio (LAR) were responsible, whereas decreased unit leaf rate (ULR) was involved in the case of _Amaranthus_. Mean ca nopy height was lower in _Amaranthus_ than _Abutilon_ which may explain the low ULR of _Amaranthus_ in competition. The decrease in LAR of _Abutilon_ was associated with an increase in root:shoot ratio implying that _Abutilon_ was limited by competition for below ground resources. The root:shoot ratio of _Amaranthus_ actually decreased with competition, and _Amaranthus_ had a much higher rate of nitrogen uptake per unit of root than did _Abutilon_. These latter results suggest that _Amaranthus_ was better able to compete for below ground resources than _Abutilon_. Although the growth of both species was reduced by competition, generally speaking, the growth of _Amaranthus_ was reduced to a greater extent than that of _Abutilon_. Regression analysis suggests that the success of _Abutilon_ in competition was due to its larger starting capital (seed size) which gave it an early advantage over _Amaranthus_. Elevated CO2 had a positive effect upon biomass in _Amaranthus_, and to a lesser extent, _Abutilon_. These effects were limited to the early part of the experiment in the case of the individually grown plants, however. Only _Amaranthus_ exhibited a significant increase in relative growth rate (RGR). In spite of the transitory effect of CO2 upon size in individually grown plants, level of CO2 did effect final biomass of competitively grown plants. _Abutilon_ grown in competition with _Amaranthus_ had a greater final biomass than _Amaranthus_ at ambient CO2 levels, but this difference disappeared to a large extent at elevated CO2. The high RGR of _Amaranthus_ at elevated CO2 levels allowed it to overcome the difference in initial size between the two species.ddd' 73^1^Beer,S^1986^3^The Fixation of Inorganic Carbon in Plant Cells^Physiology, Yield, and Economics^CRC Press, Inc.^Boca Raton, Florida^3-11^^^^II^^Carbon Dioxide Enrichment of Greenhouse Crops^^^^173^^^^^^^^^^^^^^^^^^^^^Enoch,H^Kimball,B AB AA^172^The initial fixation of atmospheric inorganic carbon (CO2) in plant cells is carried out via either the C3 or C4 pathway. The first step of the C3 pathway is the fixation of CO2 by a five-carbon compound to yield two molecules of PGA (a three-carbon compound). PGA is subsequently reduced to form sugars. In the so-called C3 plants, this is the only pathway fo r incorporation of CO2. The enzyme (RuBPcase) catalyzing CO2 fixation in the C3 pathway may also act as an oxygenase. When! doing so, glycolate (a two-carbon compound) is formed together with PGA, and there is no net carbon gain of the process. "In the further metabolism of glycolate, CO2 is released. This is called photorespiration and its rate is, in contrast to m#itochondrial or dark respiration, strongly enhanced by O2 and light. In the C4 pathway, atmospheric CO2 is fixed, via the $enzyme PEPcase, by a three-carbon compound to yield one molecule of malate or aspartate (four-carbon compounds). In C4 pla%nts, this occurs in mesophyll cells. Malate or aspartate is then transported to bundle sheath cells where it is decarboxyl&ated, and the released CO2 is refixed via the C3 pathway. There is no apparent photorespiration in C4 plants, because CO2 'levels in the vicinity of RuBPcase are probably elevated and any CO2 released from the bundle sheath cells is efficiently (refixed via PEPcase in the mesophyll cells. In CAM plants, atmospheric CO2 is fixed into malate during the night while the) decarboxylation and refixation of CO2 occurs in the daytime. The C4 pathway provides C4 and CAM plants with an efficient *carbon-capturing system complementing the basic C3 pathway. In C4 plants this leads to a higher net CO2 incorporation rate+ than in C3 plants under high light and temperature regimes such as are found in the tropics. In CAM plants it allows for  nightly CO2 fixation in arid climates where opening of stomates during the day would cause excessive water loss..74^2^Beerling,D J^Chaloner,W G^1993^1^The Impact of Atmospheric CO2 and Temperature Change on Stomatal Density: Observatio+ns from _Quercus robur_ Lammas Leaves^35^71^^231-235^^^^^^^^^^176^^^^^^^^^^^Quercus roburur L.C^174^Ann. Bot..1A^174^A comparative study of leaves formed on shoots during the spring and summer (lammas) of _Quercus robur_ from three c92ontrasting geographical locations (Cardiff, Durham and London) gives a measure of the effect of temperature on stomatal de3nsity. This is of value in attempting to distinguish the effects of CO2 and temperature on observed stomatal density chang<4es under different CO2 and temperature conditions through the Quaternary. These leaves of normal and lammas shoots will haF5ve developed under similar CO2 levels but different environmental temperatures. Our results demonstrate that leaves formed6 under the warmer summer temperatures had reduced stomatal densities and indices from all sites, compared with their sprinI7g counterparts. This trend was also detected from measurements of spring and summer leaves made upon herbarium material coS8llected from the same tree in 1840. The results suggest that for _Q. robur_ temperature overrides the influence of irradia9nce intensity and small seasonal (75^2^Beerling,D J^Chaloner,W G^1993^1^Stomatal Density Responses of Egyptian _Olea europaea_ L. Leaves to CO2 Change Since 1327 BC^35^71^^431-435^^^^^^^^^^179^^^^^^^^^^^Olea europaea/olivelive~/C^177^Ann. Bot.AA^177^We have attempted to separate the effects of CO2 and temperature change on stomatal density by examining ancient leaBf material of _Olea europaea_ L. The distribution of this species is confined to a Mediterranean type climate, so that _O.C europaea_ leaves of different ages will have formed under similar temperatures but different CO2 levels over the last 300D0 years. Stomatal density measurements have been made upon leaves of _O. europaea_ originating from King Tutankhamun's tomEb dating from 1327 BC, and have been compared with values obtained from Egyptian _O. europaea_ material dating from pre-33F2 BC, 1818 and 1978 AD. Together, the four dates provide a record of how the plant has responded to increases in atmospherGic CO2 concentration during that time. The results demonstrate that in accordance with similar studies examining the stomaHtal density response of plants over three time scales (hundreds, thousands and tens of thousands of years) stomatal densitIy falls as CO2 levels increase. Since we have examined a natural system with leaves developing under similar environmentalJ temperatures the results confirm observations from experimental studies in which plants were grown under the same temperature but different CO2 regimes.      L76^6^Beerling,D J^Chaloner,W G^Huntley,B^Pearson,J A^Tooley,M J^Woodward,F I^1992^1^Variations in the Stomatal Density of M_Salix herbacea_ L. under the Changing Atmospheric CO2 Concentrations of Late- and Post-glacial Time^36^336^^215-224^^^^^^^^^^182^^^^^^^^^^^Salix herbaceaea L.?C^180^Phil. Trans. R. Soc. Lond. B.PA^180^The rapidly rising CO2 concentration of the past 200 years has been shown to be accompanied by a fall in stomatal deQnsity in the leaves of temperate trees. The present study attempts to investigate the relationship of atmospheric CO2 chanRge and stomatal density in the arctic-alpine shrub, _Salix herbacea_, over the longer time span of 11,500 years offered byS fossil leaves from post-glacial deposits. Comparisons of fossil material from Scotland and Norway are made with leaves frTom living populations growing in Austria, Greenland and Scotland. The Austrian material, from an altitudinal gradient betwUeen 2000 and 2670 m above sea level, gives added comparisons of contemporary differences of CO2 partial pressure with altiVtude. The results of our investigation indicate, rather surprisingly, that the rising CO2 concentration of the past 11,500W years has been accompanied by an increase in the stomatal density of _S. herbacea_ in contrast to the shorter-term observXations on the herbarium material of temperate trees. The most likely explanation appears to centre on the temperature and Ywater availability of the early post-glacial environment overriding the effect of the lower CO2 regime. However, the scaleZ of the time interval involved may also be significant. Natural selection over the 11,500 year period concerned may have f[avoured a different response to what is, in effect, an acclimatory response observed in trees within the period of rapid CO2 rise of the past 200 years..ۘ* xZ'3*p*@@ ]77^2^Beeson,R C,Jr^Graham,M E D^1991^1^CO2 Enrichment of Greenhouse Roses Affects Neither Rubisco nor Carbonic Anhydrase Activities^3^116^^1040-1045^^^^^^^^^^2059^^^^^^^^^^^Rosa hybrida/rose^^^^^  WordPerfect NC^183^J. Amer. Soc. Hort. Sci.  6.0     `78^2^Bellamy,L A^Kimball,B A^1986^3^CO2 Enrichment Duration and Heating Credit as Determined by Climate^Physiology, Yield,"a and Economics^CRC Press, Inc.^Boca Raton, Florida^168-197^^^^II^^Carbon Dioxide Enrichment of Greenhouse Crops^^^^186^^^^%^^^^^^^^^^^^^^^^^Enoch,HZ^Kimball,B AB A   (cA^185^To determine if it is economical to invest in CO2 enrichment equipment, a detailed economic analysis considering the4d increases in income and operating expenses should be performed. The procedure for such an analysis is straightforward (e.eg., Chapter 13) but it is necessary to make estimates of the percent increase in yield, the amount of CO2 used, and of any7f reduction in heating energy requirements resulting from a combustion-type CO2 generator. For any given greenhouse and croBgp, these three factors will vary with the local climate and in particular, with the outside air temperature, and global soEhlar radiation. It is practical to enrich with CO2 only while a greenhouse is closed and not ventilated. Therefore, CO2 enrPiichment duration equals day length minus ventilation time. Using Kimball's MEB program curves were generated which show thUje ventilation time fraction a 0.05 m3/m2/s capacity (47 greenhouse volume changes per hour) fan would need to operate to mYkaintain a given set point temperature as a function of transmitted solar radiation for various ambient air temperatures. S^limilar curves were generated showing the heating credit from a CO2 generator rated at 42.5 W/m2 (CO2 output 9.5 g/m2/h). Hbmourly solar radiation and temperature data for days typical of each month of the year for six climate regions were generatned using simple models from values of monthly mean minimum and maximum temperatures and mean total daily global radiation.eo Such data should be available nearby to most greenhouse locations. The hourly climate data for each of the typical monthlqpy days were used in conjunction with the ventilation time fraction curves to compute the ventilation requirement throughouqt the year for six locations--Oslo, Norway; De Bilt, Netherlands; Milan, Italy; Columbus, Ohio, U.S.; Tokyo, Japan; Tel Avuriv, Israel. The number of hours at which the greenhouse operated in five ventilation classes (0%, 0 to 20%, 20 to 50%, 50 sto 100%, 100%) for a 30C ventilation temperature setpoint were plotted. For all sites except Tel Aviv, enrichment is possxtible throughout the whole day during winter. At Oslo, a greenhouse can remain unventilated and enriched for up to 7 monthsu of the year. The areas in each ventilation class were measured to estimate the corresponding annual number of hours of povssible CO2 enrichment. From these CO2 enrichment duration values, the required amounts of CO2 can be estimated. The amountw of solar radiation received by the crop during each of the ventilation classes was also determined, so that the percent ixncrease in yield due to CO2 enrichment could be calculated. A greenhouse in Oslo can remain closed and CO2 enriched for 79y% of the total annual daylight hours, yet only 51% of the total radiation is received by the crop during this time. Using zthe assumption that yield is directly proportional to transmitted solar radiation, yields with and without CO2 enrichment {were compared for the six locations to assess the effect of climate on percent yield increase. Annual yields could be incr|eased 2% at Tel Aviv and 26% at Oslo if enrichment is limited to when the greenhouse remains completely closed. If CO2 is }pulsed into the greenhouse between intervals of fan operation, these CO2 response values can increase to 22 and 48%, respe~ctively. The effects on CO2 enrichment duration of using 'hot' CO2 from a combustion-type generator rather than 'cold' CO2 from other sources were computed for the Tel Aviv location. Using a 27C greenhouse air temperature for the ventilation setpoint, average daily CO2 enrichment duration (0% ventilation) was 4.0 hr during the winter using cold CO2, but decreased to 2.6 hr with hot CO2. Finally, the annual heating credit was determined for each of the six locations for 15C day heating setpoint, and the annual and winter savings in heating energy requirements were tabulated. The proportion of annual CO2 enrichment duration (0% ventilation) that was heating credit time ranged from 49% for Oslo to 8% for Tel Aviv."\79^2^Bentley,B L^Johnson,N D^1990^3^Plants as Food for Herbivores: The Roles of Nitrogen Fixation and Carbon Dioxide Enrichment^Plant-Animal Interactions: Evolutionary Ecology in Tropical and Temperate Regions^John Wiley & Sons, Inc.^^257-272^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^Price,PW^Lewinsotin,TM^Fernandes,GW^Benson,WWZi~~0XCF@80^2^Berntson,G M^Woodward,F I^1992^1^The Root System Architecture and Development of _Senecio vulgaris_ in Elevated CO2 and Drought^37^6^^324-333^^^^^^^^^^190^^^^^^^^^^^Senecio vulgaris^dpD$NsLp'oy!oF>^C^188^Funct. Ecol.d>$"8>F"dZz+!p'd#C@dd#CC$dCC+a *FS3A^188^1. The impact of elevated CO2 and drought on the architecture and development of root systems of _Senecio vulgaris_ was examined and implications for water and nutrient uptake discussed. Plants were grown in miniature rhizotrons to non-destructively monitor the development of roots _in situ_ at both an elevated (700 umol/mol) and ambient (350 umol/mol) atmospheric CO2 concentration and high or low supply of water. 2. CO2 and water had a significant impact on the way that _S. vulgaris_ root systems filled the soil matrix. Elevated CO2 resulted in more branched, longer root systems that foraged through larger volumes of soil. Under elevated CO2 and a low water supply, root systems had branching and foraging patterns and root length similar to those grown under ambient CO2 with a high water supply. 3. Overall, water had a more pronounced impact on the growth rate of _S. vulgaris_ roots than did CO2. The density of rooting remained unchanged across all treatments. Thus, under elevated CO2 the intensity of foraging _S. vulgaris_ root systems might be unchanged while the extent of  foraging by these root systems, as indicted by the horizontal spread of roots, may be increased.$ 6Fi?5T5Zr4581^1^Besford,R T^1990^1^The Greenhouse Effect: Acclimation of Tomato Plants Growing in High CO2, Relative Changes in Calvin Cycle Enzymes^38^136^^458-463^^^^^^^^^^192^^^^^^^^^^^Lycopersicon esculentum^^^^^^WO6P|PPGQNQQQ R"/ A^191^Tomato plants (cv. Findon Cross) were grown in a normal concentration of CO2 (approximately 340 vpm) or in elevated CO2 (1000 vpm) with a 12 h photoperiod of 400 umol quanta/m2/s, PAR. The activities of three Calvin cycle enzymes, RuBPco !(E.C. 4.1.1.39), 3 phosphoglyceric acid phosphokinase (E.C. 2.7.2.3) and NADP-dependent glyceraldehyde 3-phosphate dehydro6genase (E.C. 1.2.1.13) were determined in extracts from the unshaded 5th leaf during leaf development. RuBPco activity was reduced in the high-CO2 grown leaves at 60% expansion compared with leaves grown in 340 vpm CO2, but there were no appare9nt differences in the other two Calvin cycle enzymes at this stage of expansion. With subsequent leaf development in high FCO2 there was an accelerated decline in all three enzyme activities. The loss of RuBPco activity was studied further by raising antibodies to RuBPco and the large subunit of RuBPco (LSU) was detected in electroblotted crude extracts from normalI and high-CO2 grown plants. This specific immunoassay estimated a 75% reduction of LSU in the high-CO2 grown leaf at full Wexpansion.Xu7vX7vX7vX7vX7vX7vX7vX<8vX8vXvXvXvX7vXLvX]vXbvXlvXwvXvXvXvX4vXKvXRvXXvXvXvX[82^1^Besford,R T^1993^1^Photosynthetic Acclimation in Tomato Plants Grown in High CO2^123^104/105^^441-448^^^^^^^^^^195^^^^^^^^^^^Lycopersicon esculentum/tomato^^^^^^^^^^vX+vX+vX+vX+vX+vX+vX+vX+vX+vX,vX,vX,vX ,vX&,vX2,vXe,vX^wth and dinitrogen fixation in the vegetative growth stage were examined. 1. The whole plant weight of the cultivated soyb_A^193^The effects of prolonged CO2 enrichment of tomato plants on photosynthetic performance and Calvin cycle enzymes, including the amount and activity of ribulose-1,5-bisphosphate carboxylase (RuBPco), were determined. Also the light-saturatebd rate of photosynthesis (Pmax) of the 5th leaf throughout leaf development was predicted based on the amount and kineticso of RuBPco. With short-term CO2 enrichment, i.e. only during the photosynthesis measurements, Pmax of the young leaves did not increase while the leaves reaching full expansion more than doubled their net rate of CO2 fixation. However, with lonrger-term CO2 enrichment, i.e. growing the crop in high CO2, the plants did not maintain this photosynthetic gain. Compared| with leaves of plants grown in normal ambient CO2 the high CO2-grown leaves, when almost fully expanded, contained only about half as much RuBPco protein and Pmax in 300 and 1000 vpm CO2 was similarly reduced. The loss of RuBPco protein may be a factor associated with the accelerated fall in Pmax since Pmax was close to that predicted from the amount and kinetics of RuBPco assuming RuBP saturation. Acclimation to high CO2 is fundamentally different from acclimation to high light. In contrast to acclimation to high light, acclimation to high CO2 does not usually involve an increase in photosynthetic machinery so the synthesis and maintenance costs (as indicate by the dark respiration rate) are generally lower..0S183^2^Besford,R T^Hand,D W^1989^1^The Effects of CO2 Enrichment and Nitrogen Oxides on some Calvin Cycle Enzymes and Nitrite Reductase in Glasshouse Lettuce^39^40^^329-336^^^^^^^^^^198^^^^^^^^^^^Lactuca sativa L.N~C^196^J. Exp. Bot.A^196^Glasshouse lettuce (cvs Pascal and Talent) was grown during late autumn and early winter in an atmosphere polluted with nitrogen oxides (NOx) generated from direct-fired natural gas burners used for CO2 enrichment and warm air heating (high CO2 + NOx treatment). Concentrations of 0.3-0.4 vpm NOx were detected during the daytime when near 3-fold CO2 enrichment (1000 vpm) was practised without heating. In cold weather, the CO2 and NOx levels were dependent on the amount of heating required to maintain minimum temperatures of 5C (night) and 7C (day). Concentrations of between 2000-5000 vpm CO2 and 1-2.5 vpm NOx were recorded at night during an intensely cold period in early January just prior to sampling for leaf enzymes. The plants were compared with those grown in unpolluted atmospheres with either a natural (340 vpm) or an enriched level (1000 vpm) of CO2. Pascal grown in elevated CO2 had less activity per g fresh weight of RuBPc (E.C. 4.1.1.39), 3PGA phosphokinase (E.C. 2.7.2.3) and NADP-G3P dehydrogenase (E.C 12.1.13) than plants grown in a normal ambient CO2 atmosphere. The cytoplasmic enzyme PEPc (E.C. 4.1.1.31) was not significantly affected by the pure CO2 enrichment. With high CO2 + NOx the activities of the Calvin cycle enzymes were restored to values close to those present in non-enriched plants, while the activity of PEPc was increased. The activity of nitrite reductase (NiR) (E.C. 1.7.7.1) was increased in Pascal and Talent by high CO2 + NOx. Immunoblotting techniques were used to show that the increase in activity of this enzyme was accompanied by an increase in the steady state concentration of the protein. Only one molecular form of NiR was detected by immunoblotting, and it would appear that the 'induction' of NiR activity resulted from increased net enzyme synthesis rather than activation of pre-existing enzyme. At the time of sampling no visible damage by high CO2 and NOx was evident and the lack of symptoms may have been associated with the enhanced levels of nitrite reductase in these cultivars.84^3^Besford,R T^Ludwig,L J^Withers,A C^1990^1^The Greenhouse Effect: Acclimation of Tomato Plants Growing in High CO2, Photosynthesis and Ribulose-1, 5-_Bis_phosphate Carboxylase Protein^39^41^^925-931^^^^^^^^^^201^^^^^^^^^^^Lycopersicon esculentumumC^199^J. Exp. Bot.A^199^Tomato plants were grown in solution culture in a controlled environment at 20C with a 12 h photoperiod of 400 umol# quanta/m2/s PAR with either normal ambient CO2, approximately 340 vpm, or with 1000 vpm CO2. The short- and long-term eff/ects of CO2 enrichment on photosynthesis were determined together with the levels of ribulose-1,5-_bis_phosphate carboxyla3se (RuBPco) EC. 4.1.1.39 protein and activity throughout leaf development of the unshaded 5th leaf above the cotyledons. T6he high CO2 concentration during growth did not appreciably affect the rate of leaf expansion or final leaf area but did iBncrease the fresh weight per unit area of leaf. With short-term CO2 enrichment, i.e. only during the photosynthesis measurements, the light-saturated photosynthetic rate (Pmax) of young leaves did not increase while those reaching full expansioFn more than doubled their net rate of CO2 fixation. However, with longer term CO2 enrichment, i.e. growing the crop in higUh CO2, the plants did not maintain this photosynthetic gain. While the CO2 concentration during growth did not affect the peak in Pmax measured in 300 vpm CO2 or Pmax measured in 1000 vpm CO2, RuBPco protein or its activity, the subsequent ontoXgenetic decline in these parameters was greatly accelerated by the high CO2 treatment. Compared with plants grown in normal ambient CO2 the high CO2 grown leaves, when almost fully expanded, contained only approximately half as much RuBPco prot[ein and Pmax in 300 vpm CO2 and Pmax in 1000 vpm CO2 were similarly reduced. The loss of RuBPco protein may be a major facetor associated with the accelerated fall in Pmax since it was close to that predicted from the amount and kinetics of RubBPco assuming RuBP saturation. In the oldest leaves examined grown in high CO2 additional factors may be limiting photosynthhesis since RuBPco kinetics marginally overestimated Pmax in 300 vpm CO2 and the initial slope of photosynthesis in responrse to intercellular CO2 was also less than expected from the extractable RuBPco.@@ @ @ WPCs85^5^Betsche,T^Morin,F^Cotte,F^Gaugain,F^Andr,M^1989^3^Gas Exchanges, Chlorophyll _a_ Fluorescence, and Metabolite Levelsu in Leaves of _Trifolium subterraneum_ during Long-term Exposure to Elevated CO2^Progress in Photosynthesis Research, Proc|. VIIIth International Congress on Photosynthesis, Stockholm, Sweden, 1989^^^^^^^^^^^^^203^^^^^^^^^^^Trifolium subterraneuA^202^High CO2 stimulates photosynthesis of C3-plants initially, but then photosynthesis often declines and undesirable effects such as excessive starch accumulation and yellowing of leaves can occur. Results from chlorophyll _a_ fluorescence measurements and metabolite determinations indicate that high CO2 can perturb photosynthesis probably on the level of phosphate recycling. We propose that the absence of photorespiration in high CO2 causes phosphate deficiency in the chloroplast stroma and a low phosphorylation potential in the cytosol. Both conditions favour the synthesis of starch.86^1^Bhattacharya,N C^1992^3^Prospects of Agriculture in a Carbon Dioxide-enriched Environment^A Global Warming Forum: Scientific, Economic and Legal Overview^CRC Press, Inc.^Boca Raton, Florida^^^^^^^^^^^205^^^^^^^^^^^^^^^^^^^^^Geyer,R AA^204^The CO2 concentration in the atmosphere is steadily increasing. It has been predicted that it will double the preindustrial level (270 umol/mol) by the year 2080. Investigations conducted on different food and fiber crops in response to elevated CO2 in phytotrons, glasshouses, open-top chambers, SPAR units, and Face environments have generally showed increases in growth and yields of most of the crops, although some plants responded negatively to increased concentrations of CO2. The increased growth of plants in a CO2-enriched environment may rapidly deplete nutrients from the soil and consequently, positive effects of CO2 may not persist under low fertility levels. Similarly, interactive effects of high CO2 with high temperature may not be good for all plant species because of specific temperature requirements for each plant. In certain cases, plants may remain vegetative at high temperatures throughout the growth cycle. Therefore, cropping patterns may have to be modified with the increase in atmospheric temperature in the future world of high CO2. Interestingly, water use efficiency of plants in a CO2-enriched environment may have beneficial effects in tropical and subtropical regions of the world where water is limited for crop production. Elevated CO2 in the atmosphere results in increased concentrations of carbohydrates and 'dilution' of other metabolites such as chlorophyll, proteins, amino acids, carotene and reduced nutrients in plant tissues. Increasing atmospheric CO2 may alter plant/herbivore interactions. The impact of leaf-eating herbivores may increase as the level of atmospheric CO2 rises. Furthermore, C3 weeds may grow faster than C4 crops of agricultural importance in a CO2-enriched environment, and vice versa. In unmanaged ecosystems, these effects of elevated CO2 may cause marked changes.SUP\WP{WPC}.DLN\WP{WPC}.DLNWP}WPC{.GMKWP}WPC{.GKGMK.EXEC:\WP60\WP.FIL87^4^Bhattacharya,N C^Bhattacharya,S^Strain,B R^Biswas,PK^1989^1^Biochemical Changes in Carbohydrates and Proteins of Sweet Potato Plants (_Ipomoea batatas_ [L.] Lam.) in Response to Enriched CO2 Environment at Different Stages of Growth and Development^38^135^^261-266^^^^^^^^^^208^^^^^^^^^^^Ipomoea batatas/sweet potatosweet potatoo;5Hs8C^206^J. Plant Physiol.ggHP;5H8000A^206^Sweet potato (_Ipomoea batatas_ [L.] Lam., cv. Georgia Jet) plants were grown at different CO2 concentrations (350, 675 and 1000 umol/mol) in controlled environment conditions. The effect of CO2 enrichment on carbohydrate concentrations i n leaves, stems, roots and tubers at different stages of growth and development were investigated. The glucose, sucrose and starch concentrations in leaves increased during 0-35 days after planting as compared to stems and roots receiving incre ased CO2 concentrations. However, starch and glucose concentrations increased significantly in tubers during the 50-65 day interval which corresponded with rapid growth of tubers at high CO2 concentrations. Increasing CO2 concentrations did not raise the protein content of leaves, roots or tubers at any stages of growth and development. CO2 enrichment increased the soluble protein concentration in stems during the 20-50 day growth interval which subsequently decreased at maturity.88^5^Bhattacharya,N C^Bhattacharya,S^Strain,B R^Biswas,P K^Tolbert,M E M^1986^3^An Insight into the Mechanism of Auxin Action in Rooting Hypocotyl Cuttings of _Impatiens balsamina_ Grown in Phytotron under Enriched CO2 Environment^Proc., Thirte"enth Annual Meeting; 3-7 Aug. 1986; St. Petersburg Beach, Florida^Plant Growth Regulator Society of America, Department of( Citrus^Lake Alfred, Florida^92^^^^^^^^^^^^^^^^^^^^^Impatiens balsamina^^^^^^^^^^Wilson,WCWC\WPC60DOS\,89^3^Bhattacharya,N C^Bhattacharya,S^Strain,B R^1989^1^Isozyme Polymorphism during Rooting at Elevated CO2^28^24^^302-305^6^^^^^^^^^212^^^^^^^^^^^Impatiens balsaminana L.  """ RE:C^210^HortSci.HERC.VRSS0HGC 720x348 Monochromed>9A^210^The effects of CO2 enrichment and IAA on adventitious root formation of hypocotyl cuttings of _Impatiens balsamina_ FL. 'Camellia' were examined. Root numbers increased significantly at 675 and 1000 uL CO2/L compared to 350 uL/L. In the prIesence of IAA, the number of roots increased at 675 and 1000 uL CO2/L and the effect was most pronounced with 5 ug IAA/ml ]at 675 uL CO2/L. IAA-treated cuttings, compared to those in deionized water, exhibited slightly increased intensities of s ome of the isoperoxidases coinciding with root initiation and development in a CO2-enriched atmosphere. The data also indi`cate that at least two isozymes of peroxidase are associated with root development.VWPMAIN.WPBWPGEDIT.WPBn 90^5^Bhattacharya,N C^Biswas,P K^Bhattacharya,S^Sionit,N^Strain,B R^1985^1^Growth and Yield Response of Sweet Potato to Atmospheric CO2 Enrichment^12^25^^975-981^^^^^^^^^^215^^^^^^^^^^^sweet potato/Ipomoea batatasas (L.) Lam.z*WdWdWdqC^213^Crop Sci.   |A^213^Tuber growth of sweet potato (_Ipomoea batatas_) is a sink that may be limited by source capacity under present ambient CO2 levels. Hence, sweet potato may demonstrate more response to predicted increases in atmospheric CO2 than many other annual plants. The present investigation was undertaken to determine the long-term effects of CO2 enrichment on some physiological parameters, growth, and yield, as well as on the source-sink relationship in sweet potato at different stages of growth. Plants of the cultivar Georgia Jet were grown from stem cuttings in a mixture of gravel and vermiculite in controlled environment chambers at 350, 675, and 1000 uL/L CO2 and were irrigated with one-half strength Hoagland's solution. The temperature was 28C during 14-h days and 20C during 10-h nights. The length of main stem, total branch length, number of branches, and leaf area were increased for plants grown at 675 or 1000 uL/L CO2. The production of total dry matter of plants increased at each harvest interval in response to CO2 enrichment but it was greatest in 1000 uL/L CO2. Specific leaf weight also increased with increased CO2 concentration. The number and diameter of tubers increased at high CO2 concentration. At the final harvest, the dry weight of roots and tubers increased 1.8 and 2.6 times in plants grown at 675 and 1000 uL/L CO2, respectively, compared to those grown at 350 uL/L CO2. Carbon dioxide enrichment resulted in the modulation of sink capacity to enhance the production of tubers in sweet potato.[GH 1:&1:1: 1:1:1:^91^5^Bhattacharya,N C^Ghosh,P P^Bhattacharya,S^Hileman,D R^Biswas,P K^1988^1^Effects of Abscisic Acid on Rooting Stem Cuttings of Sweet Potato in Open Top Chambers under Enriched CO2 Environment^22^30^^204-209^^^^^^^^^^218^^^^^^^^^^^sweet potato/Ipomoea batatasas (L.) Lam.:/:/:_$` /: /:^/:/:/:&/: /:/:/:_/:/: C^216^Biol. PlantarumL0:[L0:L0:q`) :] :Q :>:`M T\::Y::[::Z::::::::::S::d:A^216^Ten centimeter long stem cuttings of sweet potato (_Ipomoea batatas_ L. cv. Georgia Jet) with intact apex and leaves were cultured in distilled water as well as in varying concentrations of abscisic acid (ABA) in open top chambers at 364,! 438 and 666 cm3/m3 CO2. Low concentration of ABA promoted rooting and elongation of roots at 364 cm3/m3 CO2 while rooting" was suppressed at enriched levels of CO2. However, biomass production in shoots and roots was higher in 666 than in 364 cm3/m3 CO2.b ?=:"?=:+-$3:2:,:/:5: 8:&: ):H8s8se9s=s =s=$92^6^Bhattacharya,N C^Hileman,D R^Ghosh,P P^Musser,R L^Bhattacharya,S^Biswas,P K^1990^1^Interaction of Enriched CO2 and Wa%ter Stress on the Physiology of and Biomass Production in Sweet Potato Grown in Open-top Chambers^16^13^^933-940^^^^^^^^^^221^^^^^^^^^^^sweet potato/Ipomoea batatas^^^^^.) Lam.=gggh~iik&' C^219^Plant Cell Environ.)0  <O$H Mk<=l=== = >@H>^>[I O O O1=>>0(A^219^The objective of this study was to investigate the effects of water stress in sweet potato (_Ipomoea batatas_ L. [La)m.] '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 concent,ration of 438 and 666 umol/mol than in plants grown at 364 umol/mol. The 364 umol/mol CO2 grown plants had to be rewatered- 2 d 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 umol/mol; the increase, however, was not linear w/ith 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.[ 193^4^Bhattacharya,S^Bhattacharya,NC^Biswas,P K^Strain,B R^1985^1^Response of Cow Pea (_Vigna unguiculata_ L.) to CO2 Enric$2hment Environment on Growth, Dry-matter Production and Yield Components at Different Stages of Vegetative and Reproductive Growth^40^105^^527-534^^^^^^^^^^224^^^^^^^^^^^cowpea/Vigna unguiculatata L..rrr?08ś@כH㛀08'&C^222^J. Agric. Sci. Camb.azmkWPCC60XX.DTL 5A^222^This study examines the effects of increased atmospheric carbon dioxide concentrations on vegetative and reproductiv*6e growth and partitioning of biomass during pod and seed development of cow pea in controlled environment chambers at 350,37 675, and 1000 uL CO2/L. The length of main stem and branches, the number of leaves and branches, and leaf area were all g8reater at high CO2 than at low CO2 concentration. The appearance of flowers was 10-12 days earlier in high CO2 than in amb89ient CO2 atmosphere. The senescence of leaves started about 7 days earlier in plants grown at 675 and 1000 uL CO2/L than i=:n those grown at 350 uL CO2/L. The rate of leaf senescence was more rapid in 1000 uL/L than in 675 uL CO2/L. The dry weigh@;t of roots, stems and leaves increased with CO2 enrichment, being greater in 675 uL/L than in 1000 uL CO2/L. Plants grown ent caused a significant increase in the total number and weight of seeds as well as pods, it did not affect the ratio of ?seed dry weight to the total dry weight of above-ground plant parts (harvest index). It is concluded from the present inveN@stigation that CO2 enrichment significantly enhanced vegetative as well as reproductive growth resulting in the increase i`n yield and early plant maturation in this leguminous crop.B94^3^Bhattacharya,S^Bhattacharya,NC^Strain,B R^1985^1^Rooting of Sweet Potato Stem Cuttings under CO2-enriched Environmentc and with IAA Treatment^28^20^^1109-1110^^^^^^^^^^227^^^^^^^^^^^sweet potato/Ipomoea batatasas (L.)n3C^225^HortSci.EA^225^Stem cuttings of sweet potato (_Ipomoea batatas_ L. 'Georgia Jet') with intact apex and leaves were cultured in wateqFr or in different concentrations of IAA and were maintained in controlled environment chambers at 350, 675, or 1000 ppm CO~G2. The temperature was 20C during a 14-hr day and 14 during a 10-hr dark period. The photosynthetic photon flux density Hwas 550 umol/s/m2 (27.7 mol/m2/day). Elevated CO2 concentrations stimulated the production of roots in the presence of IAA, and this effect was more pronounced at 675 ppm than at 1000 ppm CO2 atmosphere.J95^4^Bhattacharya,S^Eatman,J F^Biswas,P K^Tolbert,M E M^1988^1^CO2 Enrichment and its Relationship to Bioconversion of CelKlulosic Biomass of Sweet Potato (_Ipomoea batatas_ L.) into Fermentable Sugars^41^15^^259-268^^^^^^^^^^230^^^^^^^^^^^sweet potato/Ipomoea batatas^^^^^.)CC^228^BiomassNA^228^Sweet potatoes (_Ipomoea batatas_ L. (Lam.) 'Georgia-Jet') were grown in open field plots and open top chambers at COO2 concentrations of 354, 531, 506 and 659 uL/L for 90 days. The leaves and stems after the harvest were used as substratePs for the production of fermentable sugars. Elevated CO2 concentrations increased the cellulose content of stems, being moQst pronounced at 506 uL/L. Hemicellulose content of leaves and stems as well as lignin content of stems decreased as a resRult of CO2 enrichment. The increase in cellulosic biomass in plants grown in CO2 enriched environment resulted in increaseSd conversion of cellulose into fermentable sugars. The saccharification was greater in stems than in leaves. It was also fTound that chemical pretreatment of stems and leaves enhanced the enzymatic hydrolysis and the yields of glucose were higher than those from untreated stems and leaves.V96^7^Biswas,P K^Hileman,D R^Allen,J R^Bhattacharya,N C^Lu,J Y^Pace,R D^Rogers,H H^1985^5^Field Studies of Sweet Potatoes aWnd Cowpeas in Response to Elevated Carbon Dioxide^U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C.X, and Tuskegee University, Tuskegee, Alabama^^^^^^^^^^^^^^^^^^^^^^^^sweet potato/cowpea/Ipomoea batatas/Vigna unguiculata^^022 in Green Report Series^Response of Vegetation to Carbon Dioxide^^^^on Dioxide^^!~(TZ97^7^Biswas,P K^Hileman,D R^Bhattacharya,N C^Ghosh,P P^Bhattacharya,S^Johnson,J H^Mbikayi,NT^1986^5^Growth, Yield and Plan[t Water Relationships in Sweet Potatoes in Response to Carbon Dioxide Enrichment^U.S. Dept. of Energy, Carbon Dioxide Rese\arch Division, Washington, D.C., and Tuskegee University, Tuskegee, Alabama^^^^^^^^^^^^^^^^^^^^^^^^sweet potato/Ipomoea batatas^^030 in Green Report Series^Response of Vegetation to Carbon Dioxide^^Dioxide^^ioxide^^^98^1^Black,C C,Jr^1986^3^Effects of CO2 Concentration on Photosynthesis and Respiration of C4 and CAM Plants^Physiology, Y_ield, and Economics^CRC Press, Inc.^Boca Raton, Florida^29-40^^^^II^^Carbon Dioxide Enrichment of Greenhouse Crops^^^^234^^^^^^^^^^^^^^^^^^^^^Enoch,HZ^Kimball,BAAB AddU<k d f e h g j i < @)yaA^233^With C4 plants, CO2 enrichment will have a small, probably less than 25%, enhancement of plant growth or biomass probduction. However, water use efficiency will increase severalfold with a doubling or tripling of air CO2 levels. With CAM pclants, CO2 enrichment should be done at night. Little daytime CO2 uptake occurs in most CAM plants, but enrichment late ind the day and at night likely will be beneficial to growth. No long-term growth work has been done with CO2 enrichment and the production of CAM plants, but the available research indicates night enrichment should be beneficial.f99^4^Bolin,B^Doos,BR^Jager,J^Warrick,RA^1986^2^The Greenhouse Effect, Climatic Change, and Ecosystems^John Wiley & Sons^New York^^Y^^^^^^^^^^^^^^^^^^^^^^^^^^͊G{Íۍh100^3^Boone,M Y L^Rickman,R W^Whisler,F D^1990^1^Leaf Appearance Rates of Two Winter Wheat Cultivars under High Carbon Dioxide Conditions^4^82^^718-724^^^^^^^^^^238^^^^^^^^^^^wheat/Triticum aestivumum L.W#WLWpH8o LC^236^Agron. J.&7*x`GnQJ()HP LaserJet 4              kA^236^The mechanisms describing leaf appearance and tillering are vital to the modeling of wheat canopy development. How t lhese two factors will be affected by increasing global atmospheric [CO2] in cool or warm climates is not fully understood.m Two southeastern USA adapted wheat (_Triticum aestivum_ L.) cultivars, Coker 762 and Stacy, were grown under nearly nonlinmiting conditions including elevated [CO2] (600 uL/L) and under six air temperature regimes (ranging from 4/-1 to 18/7C do/night and progressively increasing to 16/4 to 29/18C d/night during the season) to observe leaf and tiller appearance ra%ptes and to compare tillering rates to those predicted by the Fibonacci series as approximated by Binet's equation. Both cuqltivars exhibited an abrupt one-time change in their phyllochron interval for all six temperatures. This change occurred j)rust prior to double ridge formation. The vegetative growth phase phyllochron interval of the two cultivars was significant2sly different only in the 21/10C temperature treatment. In the two lowest temperature treatments (16/4 and 18/7C), the cutltivars differed in phyllochron interval during the reproductive growth phase. The tillering rate of wheat followed closel6y the theoretical development predicted by Binet's equation during the vegetative phase of development.Av101^2^Bottner,P^Couteaux,M M^1991^3^Effect of Plant Activity on Decomposition: Soil-plant Interactions in Response to Incrweasing Atmospheric CO2 Concentration^Ecosystem Research Report No.1, Decomposition and Accumulation of Organic Matter in TDxerrestrial Ecosystems: Research Priorities and Approaches; 1991 Sept. 2-4; Doorwerth, The Netherlands^^^^^^^^^^^^^^^^^^^^^M^^^^^^^^^^^^^van Breemen,N@H'@@5z102^2^Bottner,P^Couteaux,M M^1992^3^Reponse de la Matiere Organique des Sols^Les Recherches en France sur les Ecosystemes PForestiers^Ministere de l'Agriculture et de la Foret^Paris^25-26^^^^^^^^^^241^^^^^^^^^^^^^^^^^^^^^Landmann,GF XA^240^In French.4(P-'0(#(#  h)}103^3^Bottomley,P A^Rogers,H H^Prior,S A^1993^1^NMR Imaging of Root Water Distribution in Intact _Vicia faba_ L. Plants in] Elevated Atmospheric CO2^16^16^^335-338^^^^^^^^^^244^^^^^^^^^^^Vicia faba/broad bean beaneiC^242^Plant Cell Environ.A^242^The effect of elevated atmospheric CO2 on water distribution in the intact roots of _Vicia faba_ L. bean seedlings ghrown in natural soil was studied noninvasively with proton (1-H) nuclear magnetic resonance (NMR) imaging. Exposure of 24-od-old plants to atmospheric CO2 enriched air at 675 cm3/m3 produced significant increase in water imaged in upper roots, hypogeal cotyledons and lower stems in response to a short-term drying-stress cycle. Above ground, drying produced negligibrle stem shrinkage and stomatal resistance was unchanged. In contrast, the same drying cycle caused significant depletion o|f water imaged in the same upper root structures in control plants subject to ambient CO2 (350 m3/m3), and stem shrinkage and increased stomatal resistance. The results suggest that inhibition of transpiration caused by elevated CO2 does not ne~cessarily result in attenuation of water transport from lower root structures. Inhibition of water loss from upper roots and lower stem in elevated CO2 environments may be a mitigating factor in assessing deleterious effects of greenhouse changes on crops during periods of dry climate.US , 104^1^Bouwman,A F^1990^2^Soils and the Greenhouse Effect^John Wiley & Sons, Ltd.^New York^^N^^^^^^^^^105^1^Bowes,G^1991^1^Growth at Elevated CO2: Photosynthetic Responses Mediated through Rubisco^16^14^^795-806^^^^^^^^^^248~C^246^Plant Cell Environ.A^246^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 reduction, and photorespiratory carbon oxidation, cycles. Both CO2 and O2 are substrates; CO2 also activates the enzyme. In C3 plants, rubisco has a low catalytic activity, operates below its Km(CO2), and is inhibited by O2. Consequently, increases in the CO2/O2 ratio stimulate C3 photosynthesis and inhibit photorespiration. CO2 enrichment usually enhances the productivity of C3 plants, but the effect is marginal in C4 species. It also causes acclimation in various ways: anatomically, 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 with CO2 enrichment, net photosynthesis often declines. This is a common acclimation phenomenon, less so in field studies, that is ultimately mediated by decline in rubisco activity, though the RuBP/Pi-regeneration capacities of the plant may play a role. The decline is due to decreased rubisco protein, activation state, and/or specific activity, and it maintains the rubisco fixation and RuBP/Pi-regeneration capacities in balance. Carbohydrate accumulation is sometimes associated with reduced net photosynthesis, possibly causing feedback inhibition of the RuBP/Pi-regeneration capacities, or chloroplast disruption. As exemplified by field-grown soybeans and salt marsh species, a reduction in net photosynthesis and rubisco activity is not inevitable under CO2 enrichment. Strong sinks or rapid translocation may avoid such acclimation responses. Over geological time, aquatic autotrophs and terrestrial C4 and CAM plants have genetically adapted to a decline in the external CO2/O2 ratio, by the development of mechanisms to concentrate CO2 internally; thus circumventing O2 inhibition of rubisco. Here rubisco affinity for CO2 is less, but its catalytic activity is greater, a situation compatible with a high-CO2 internal environment. In aquatic autotrophs, the CO2 concentrating mechanisms acclimate to the external CO2, being 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.qWP_WP_US^^^^^^^^^^^^^^^^ WPCH_*.WPMM&M&@*.WPBWPGEDIT.WPB < >   106^3^Bowes,G^Rowland-Bamford,A J^Allen,LH,Jr^1990^3^Regulation of Rubisco Activity of Carboxyarabinitol-1-Phosphate and Elevated Atmospheric CO2 in Rice and Soybean Cultivars^^Kluwer Academic Publishers^The Netherlands^399-402^^^^III^^Current Research in Photosynthesis^^^^250^^^^^^^^^^^rice/Oryza sativa/soybean/Glycine max^^^^^^^^^^Baltscheffsky,My,MA^249^The degree of rubisco dark inhibition not only shows species, but also intercultivar, and development differences. As with total activity, rubisco activation is developmentally influenced; so for rice, assays of whole leaf extracts integrate various rubisco states. The growth CO2 and temperature have interactive effects on the activity, activation, and dark inhibition of rice rubisco. Detrimental temperature effects on total rubisco activity may be compounded by elevated atmospheric CO2. $107^2^Bowman,W D^Strain,B R^1987^1^Interaction between CO2 Enrichment and Salinity Stress in the C4 Non-halophyte _Andropogon glomeratus_ (Walter) BSP^16^10^^267-270^^^^^^^^^^253^^^^^^^^^^^Andropogon glomeratusus (Walter) BSP൧,:'C^251^Plant Cell Environ.:^:: :: :Q:Q::4A^251^Increasing atmospheric CO2 may result in alleviation of salinity stress in salt-sensitive plants. In order to assess the effect of enriched CO2 on salinity stress in _Andropogon glomeratus_, a C4 non-halophyte found in the higher regions 7of salt marshes, plants were grown at 350, 500 and 650 cm3/m3 CO2 with 0 or 100 mol/m3 NaCl watering treatments. IncreasesB in leaf area and biomass with increasing CO2 were measured in salt-stressed plants, while decreases in these same parameters were measured in non-salt-stressed plants. Tillering increases substantially with increasing CO2 in salt-stressed planEts, resulting in the increased biomass. Six weeks following initiation of treatments, there was no difference in photosyntRhesis on a leaf area basis with increasing CO2 in salt-stressed plants, although short-term increases probably occurred. Stomatal conductance decreased with increasing CO2 in salt-stressed plants, resulting in higher water-use efficiency, and mUay have improved the diurnal water status of the plants. Concentrations of Na+ and Cl- were higher in salt- stressed plantls, while the converse was found for K+. There were no differences in leaf ion content between CO2 treatments in the salt-stressed plants. Decreases in photosynthesis in salt-stressed plants occurred primarily as a result of decreased internal (onon-stomatal) conductance.3*2 z108^1^Bown,A W^1985^1^CO2 and Intracellular pH^16^8^^459-465^^^^^^^^^^25656wp_wp_XX.qrsC^254^Plant Cell Environ.~DP@-5jx"}A^254^The experimental determination of cytoplasmic and vacuolar pH values is discussed. Despite variation in these values evidence indicates that intracellular pH values are normally regulated within narrow limits. The regulatory mechanisms proposed involve the metabolic consumption of OH- and the active efflux of H+. The evidence for intracellular pH modification in response to CO2 hydration and the production of HCO3- and H+ is examined. Theoretical calculations and experimental data indicate that CO2 concentrations as high as 5% will lower intracellular pH. Conversely, variation in CO2 levels around atmospheric concentrations is unlikely to perturb intracellular pH. High CO2 levels are found in bulky tissues, and flooded root systems. Evidence is presented that the slow diffusion of dissolved CO2 compared to gaseous CO2 results in its accumulation. It is proposed that the accumulation of respiratory CO2 may reduce intracellular pH values when plant tissues, cells or protoplasts are maintained in a liquid culture medium. Finally, the possible role of dark CO2 fixation and organic acid synthesis in the regulation of intracellular pH is examined. PPT:S+;V6WUlWJQQQYXZZY[ZY\X.YY&R@ R@R109^1^Bravdo,B^1986^3^Effect of CO2 Enrichment on Photosynthesis of C3 Plants^Physiology, Yield, and Economics^CRC Press, Inc.^Boca Raton, Florida^13-27^^^^II^^Carbon Dioxide Enrichment of Greenhouse Crops^^^^^^^^^^^^^^^^^^^^^^^^^Enoch,HZ^Kimball,BA AB AtI110^3^Breen,P J^Hesketh,J D^Peters,D B^1986^1^Field Measurements of Leaf Photosynthesis of C3 and C4 Species under High Irradiance and Enriched CO2^42^20^^281-285^^^^^^^^^^260^^^^^^^^^^^Glycine max/soybean/Gossypium hirsutum/cotton/Phaseolus vulgaris/bean/Vigna unguiculata/cowpea/Amaranthus hybridus/pigweednthus hybridus L./pigweedC^258^Photosynthetica 03C^264^Tree Phsiol.wxyz{|}~N113^1^Brown,K R^1989^6^Effects of Nitrogen Availability and Atmospheric Carbon Dioxide Enrichment on Growth, Water Use, and Nutrition of Seedlings of Boreal Trees^^University of Alberta^^Doctoral Dissertation^^^Dissertation Abstracts Vol. 50:07Q-B, p.2703^^^^^^^267^^^^^^^^^^^Populus tremuloides/Picea glauca*$*$*$*$*$*$*$*$*$*$*$*$*))))-7  #$##$!#bA^266^Seedlings of two boreal tree species were studied. _Populus tremuloides_ dominates early successional, relatively fertile sites; _Picea glauca_ dominates later successional sites with slower rates of nutrient turnover. Seedlings were growen for 100 days at ambient (350 uL/L) or high (750 uL/L) levels of atmospheric CO2 and fertilized with high-N (15.5 mM-N, mledium-N (1.55 mM-N), or low-N (0.155 mM-N) solutions. High CO2 increased leaf and total mass of high-N _Picea_, and root moass of low-N _Picea_ after 100 days. High CO2 increased mass, height, and leaf area of _Populus_ at 30 days in the high-N sregime, at 40 days in the medium-N regime, and at 60 days in the low-N regime; in each treatment, effects did not persist to the following harvest. High CO2 accelerated the time-dependent decreases in concentrations of N and P (all N treatmentsw) and Ca and Mg (high-N and medium-N treatments) to deficient levels, preventing the continuation of growth enhancement. In a second experiment, the effects of CO2 enrichment to 650 uL/L were examined with plant N concentrations held constant at high or low levels using the relative addition technique of nutrient supply. In the high-N regime, elemental concentrations were higher in _P. tremuloides_ than in _P. glauca_ and were unaffected by CO2 enrichment. Relative growth rates (RGR) and net assimilation rates (NAR) of _Picea_ (high-N regime) and of _Populus_ (high-N, low-N) increased with CO2 enrichment. The absolute effect of CO2 enrichment on NAR increased with foliar N content and was greater in _Populus_ at a given foliar concentration of N. Nitrogen status had greater effects on root:shoot ratios of _Picea_ than of _Populus_; CO2 enrichment did not affect root:shoot ratios in either species. High CO2 reduced transpiration by 60% in _Populus_ under both N regimes, but did not affect transpiration by _Picea_. Nitrogen productivity of _Populus_ may have increased with CO2 enrichment. Thus, methods of nutrient supply may affect plant nutrient status over time and therefore affect plant response to CO2 enrichment. The effect of CO2 enrichment increases with nutrient status and is potentially greater in early successional boreal trees, given adequate nutrient supplies..HA:\COVER.LTR 114^2^Brown,K^Higginbotham,K O^1986^1^Effects of Carbon Dioxide Enrichment and Nitrogen Supply on Growth of Boreal Tree Seedlings^43^2^^223-232^^^^^^^^^^270^^^^^^^^^^^Picea glauca/white spruce/Populus tremuloides/aspenremuloides Michx./aspenC^268^Tree Physiol.bA^268^The effects of two levels of atmospheric carbon dioxide (350 uL/L, 750 uL/L) and three levels of nitrogen (15.5 mM, 1.55 mM, 0.155 mM N) on biomass accumulation and partitioning were examined in aspen (_Populus tremuloides_ Michx.) and white spruce (_Picea glauca_ (Moench) Voss) seedlings grown in controlled environment rooms for 100 days after germination. Nitrogen supply had pronounced effects on biomass accumulation, height, and leaf area of both species. Root weight ratio of white spruce was significantly increased at the lowest level of nitrogen, whereas RWR of aspen did not change much with increasing levels of nitrogen. Carbon dioxide enrichment significantly increased (1) the leaf and total biomass of spruce seedlings grown in the high-N regime, (2) the RWR of seedlings in the medium-N regime, and (3) the root biomass of seedlings in the low-N regime after 100 days. Carbon dioxide enrichment of aspen temporarily increased biomass and height in all three nitrogen regimes. Root, stem, and leaf mass, height, and leaf area of aspen were increased only at the 30-day harvest in the high-N treatment and at 50 and 60 days in the low-N treatment. Height, stem biomass, and leaf biomass of aspen se edlings were significantly increased by CO2 enrichment after 40 days in the medium-N treatment. These effects did not persist, possibly because of the onset of mineral nutrient supply limitations with increasing plant size.*.vrs*.irs*.arsst 115^4^Brugink,G T^Wolting,H G^Dassen,J H A^Bus,V G M^1988^1^The Effect of Nitric Oxide Fumigation at Two CO2 Concentration s on Net Photosynthesis and Stomatal Resistance of Tomato (_Lycopersicon lycopersicum_ L. cv. Abunda)^23^110^^185-191^^^^^^^^^^273^^^^^^^^^^^Lycopersicon lycopersicumum L.r7:u7:{7: i7:l7: o7:H$3:%0:$3:C^271^New Phytol. >* -[](      ?* -[]      Ӗ'0( A^271^Net photosynthesis of 5-week-old tomato plants (_Lycopersicon lycopersicum_ L. cv. Abunda was measured in clean air or with NO fumigation, for five consecutive days under simulated winter glasshouse conditions: temperature 22C, VPD 0.4 kPa, irradiance 30 W/m2 and daylength 8-9 h. NO concentrations applied were 0 or 1 uL/L in combination with CO2 concentrations of 350 or 1000 uL/L. A reduction in net photosynthesis due to NO became apparent in the third day of measurement. On the fifth day this reduction was 38% of the control at 350 uL/L CO2 and 24% at 1000 uL/L CO2. The increase in photosynthesis due to CO2 enrichment was initially 50%; this effect was strongly reduced after 5 d in the presence of NO. Plants did no"t recover in the dark after the daily fumigation treatment, the level to which photosynthesis was reduced at the end of th5e day being the level at which it started the next day. The decrease in photosynthesis could not be explained by an increa9sed stomatal resistance, and the plants did not show visible symptoms of injury. Practical implications of the results are< discussed.*A)$Fn\RI ^jL8Wm=`p  ^?116^5^Brugnoli,E^Hubick,K T^von Caemmerer,S^Wong,S C^Farquhar,G D^1988^1^Correlation between the Carbon Isotope Discrimination in Leaf Starch and Sugars of C3 Plants and the Ratio of Intercellular and Atmospheric Partial Pressures of Carbon DioBxide^17^88^^1418-1424^^^^^^^^^^276^^^^^^^^^^^Populus nigra/Populus deltoides/Gossypium hirsutum/Phaseolus vulgaris^^^^^ulKgaris L. "#$%'0$*06<jqx    !"$%&(),-.2O~^-O C^274^Plant Physiol.ii_WA^274^Carbon isotope discrimination ([delta]) was analyzed in leaf starch and soluble sugars, which represent most of the recently fixed carbon. Plants of three C3 species (_Populus nigra_ L. x _P. deltoides_ Marsh., _Gossypium hirsutum_ L. andZ _Phaseolus vulgaris_ L.) were kept in the dark for 24 hours to decrease contents of starch and sugar in leaves. Then gas d!exchange measurements were made with constant conditions for 8 hours, and subsequently starch and soluble sugars were extrh"acted for analysis of carbon isotope composition. The ratio of intercellular, _Pi_, and atmospheric, _Pa_, partial pressur#es of CO2 was calculated from gas exchange measurements, integrated over time and weighted by assimilation rate, for compal$rison with the carbon isotope ratios in soluble sugars and starch. Carbon isotope discrimination in soluble sugars correlat%ted strongly (_r_=0.93) with _Pi/Pa_ in all species, as did delta in leaf starch (_r_=0.84). Starch was found to contain s&ignificantly more 13C than soluble sugar, and possible explanations are discussed. The strong correlation found between [dx'elta] and _Pi/Pa_ suggests that carbon isotope analysis in leaf starch and soluble sugars may be used for monitoring, indi(rectly, the average of _Pi/Pa_ weighted by CO2 assimilation rate, over a day. Because _Pi/Pa_ has a negative correlation w)ith transpiration efficiency (mol CO2/mol H20) of isolated plants, delta in starch and sugars may be used to predict diffe*rences in this efficiency. This new method may be useful in ecophysiological studies and in selection for improved transpiration efficiency in breeding programs for C3 species.ms*xR+xr+o*--+=<=>~~ ===/c~<~>`:~^,117^2^Bugbee,B G^Salisbury,F B^1988^1^Exploring the Limits of Crop Productivity. I. Photosynthetic Efficiency of Wheat in High Irradiance Environments^17^88^^869-878^^^^^^^^^^279^^^^^^^^^^^wheat/Triticum aestivumum L.C^277^Plant Physiol.svvyyyyyyyy/A^277^The long-term vegetative and reproductive growth rates of a wheat crop (_Triticum aestivum_ L.) were determined in t0hree separate studies (24, 45, and 79 days) in response to a wide range of photosynthetic photon fluxes (PPF, 400-2080 mic1romoles per square meter per second; 22-150 moles per square meter per day; 16-20-hour photoperiod) in a near-optimum, con2trolled-environment. The CO2 concentration was elevated to 1200 micromoles per mole, and water and nutrients were supplied3 by liquid hydroponic culture. An unusually high plant density (2000 plants per square meter) was used to obtain high yiel4ds. Crop growth rate and grain yield reached 138 and 60 grams per square meter per day, respectively; both continued to in5crease up to the highest integrated daily PPF level, which was three times greater than a typical daily flux in the field.6 The conversion efficiency of photosynthesis (energy in biomass/energy in photosynthetic photons) was over 10% at low PPF 7but decreased to 7% as PPF increased. Harvest index increased from 41 to 44% as PPF increased. Yield components for primar8y, secondary, and tertiary culms were analyzed separately. Tillering produced up to 7000 heads per square meter at the hig9hest PPF level. Primary and secondary culms were 10% more efficient (higher harvest index) than tertiary culms; hence cult:ural, environmental, or genetic changes that increase the percentage of primary and secondary culms might increase harvest; index and thus grain yield. Wheat is physiologically and genetically capable of much higher productivity and photosynthetic efficiency than has been recorded in a field environment.^YXSQ|r-D t'ttD dDDD\[DD\=118^1^Bunce,J A^1993^1^Effects of Doubled Atmospheric Carbon Dioxide Concentration on the Responses of Assimilation and Co>nductance to Humidity^16^16^^189-197^^^^^^^^^^282^^^^^^^^^^^Amaranthus hypochondriacus/amaranth/Dactylis glomerata/orchard grass/Glycine max/soybean/Helianthus annuus/sunflowerus annuus L./sunflowerSQRWttd\ t9 t43ɋDp${s -C^280^Plant Cell Environ.${"rfD${s DFE>tf>u_rZ:t!A&E%:uAFD!AA^280^Experiments were performed to determine if growth at elevated partial pressure of CO2 altered the sensitivity of leaBf water vapour conductance and rate of CO2 assimilation to the leaf-to-air difference in the partial pressure of water vapCour (delta w). Comparisons were made between plants grown and measured at 350 and 700 uPa/Pa partial pressure of CO2 for aDmaranth, soybean and sunflower grown in controlled environment chambers, soybean grown outdoors in pots, and orchard grass!E grown in field plots. In amaranth, soybean and orchard grass, both the absolute and the relative sensitivity of conductan)Fce to delta w at the leaf surface were less in plants grown and measured at elevated CO2. In sunflower, there was no changGe in the sensitivity of conductance to delta w for the two CO2 partial pressures. Tests in soybeans and amaranth showed th-Hat the change in sensitivity resulted from elevated CO2 during the measurement of the delta w response. Assimilation rate 7Iof CO2 was not altered by delta w in amaranth, which has C4 metabolism. In sunflower, the assimilation rate of plants grow;Jn and measured at elevated CO2 was insensitive to delta w, consistent with the response of assimilation rate to intercelluFKlar CO2 partial pressure in the prevailing range. In soybean, the sensitivity of assimilation rate to delta w was not diffLerent between CO2 treatments, in contrast to what would be expected from the response of assimilation rate to intercellulaJr CO2 partial pressure.P/V~ u^\SF[s\_^Y[VFDDD*^QVW|VH ^XN119^1^Bunce,J A^1992^1^Light, Temperature and Nutrients as Factors in Photosynthetic Adjustment to an Elevated Concentration of Carbon Dioxide^44^86^^173-179^^^^^^^^^^285^^^^^^^^^^^soybean/Glycine max/sugar beet/Beta vulgarisBeta vulgaris L.v[?C^283^Physiol. Plant.}PSQRV1S׍v6F;ED;|D;E| D;E2N^ZY[XPSQRVWˋ׋1Q_3XXpQA^283^The short-term stimulation of the net rate of carbon dioxide exchange of leaves by elevated concentrations of CO2 usRually observed in C3 plants sometimes does not persist. Experiments were conducted to test whether the patterns of responssSe to the environment during growth were consistent with the hypothesis that photosynthetic adjustment to elevated CO2 conc{Tentration is due to (1) feedback inhibition or (2) nutrient stress. Soybean [_Glycine max_ (L.) Merr. cv. Williams] and suUgar beet (_Beta vulgaris_ L. cv. Mono Hye-4) were grown from seed at 350 and 700 uL/L CO2 at 20 and 25C, at a photon flux~V density of 0.5 and 1.0 mmol/m2/s and with three nutrient regimes until the third trifoliate leaf of soybean or the sixth Wleaf of sugar beet had finished expanding. Net rates of CO2 exchange of the most recently expanded leaves were then measurXed at both 350 and 700 uL/L CO2. Plants grown at the elevated CO2 concentration had net rates of leaf CO2 exchange which wYere reduced by 33% in sugar beet and 23% in soybean when measured at 350 uL/L CO2 and when averaged over all treatments. NZegative photosynthetic adjustment to elevated CO2 concentration was not greater at 20 than at 25C, was not greater with l[imiting nutrients. Furthermore, in soybean, negative photosynthetic adjustment could be induced by a single night at eleva\ted CO2 concentration, with net rates of CO2 exchange the next day equal to those of leaves of plants grown from seed at t]he elevated concentration of CO2. These patterns do not support either the feedback-inhibition or the nutrient-stress hypothesis of photosynthetic adjustment to elevated concentrations of CO2.8HĉtH**tGtq_120^1^Bunce,J A^1990^1^Short- and Long-Term Inhibition of Respiratory Carbon Dioxide Efflux by Elevated Carbon Dioxide^35^65^^637-642^^^^^^^^^^288^^^^^^^^^^^tomato/soybean/Lycopersicon esculentum/Glycine max/Amaranthus hypochondriacus/amaranthahondriacus L./amaranthߒ@uu>Ru N Hrvq֒t֒ttQL u5tKX>Ru$Vrz jOC^286^Ann. Bot.֒t ֈu rG u@t>t֒t.:#t<ֈt>at->aucA^286^Dark carbon dioxide efflux rates of recently fully expanded leaves and whole plants of _Amaranthus hypochondriacus_ dL., _Glycine max_ (L.) Merr., and _Lycopersicon esculentum_ Mill. grown in controlled environments at 35 and 70 Pa carbon edioxide pressure were measured at 35 and 70 Pa carbon dioxide pressure. Harvest data and whole-plant 24-h carbon dioxide efxchange were used to determine relative growth rates, net assimilation rates, leaf area ratios, and the ratio of respiratigon to photosynthesis under the growth conditions. Biomass at a given time after planting was greater at the higher carbon hdioxide pressure in _G. max_ and _L. esculentum_, but not the C4 species, _A. hypochondriacus_. Relative growth rates for ithe same range of masses were not different between carbon dioxide treatments in the two C3 species, because higher net asjsimilation rates at the higher carbon dioxide pressure were offset by lower leaf area ratios. Whole plant carbon dioxide ekfflux rates per unit of mass were lower in plants grown and measured at the higher carbon dioxide pressure in both _G. maxl_ and _L. esculentum_, and were also smaller in relation to daytime net carbon dioxide influx. Short-term responses of resmpiration rate to carbon dioxide pressure were found in all species, with carbon dioxide efflux rates of leaves and whole plants lower when measured at higher carbon dioxide pressure in almost all cases.o121^1^Bunce,J A^1992^1^Stomatal Conductance, Photosynthesis and Respiration of Temperate Deciduous Tree Seedlings Grown Ouptdoors at an Elevated Concentration of Carbon Dioxide^16^15^^514-549^^^^^^^^^^291^^^^^^^^^^^Acer rubrum/Acer saccharinum/Quercus prinus/Quercus robur/Malus domestica^^^^^estica Borkh.^^^^^/Malus domestica Borkh.3 3 " The increase by CO2 enrichment was remarkable in the cultivated soybean variety and was negligible in the wild one. In bsA^289^Seedlings of temperate deciduous tree species were grown outdoors at ambient and at an elevated concentration of car%tbon dioxide to examine how aspects of their gas exchange would be altered by growth at elevated carbon dioxide concentrati4uon. Leaf conductances to water vapour and net carbon dioxide exchange rates were determined periodically near midday. Wholve-plant carbon dioxide efflux rates in darkness were also determined. The stomatal conductance of leaves of plants grown a7wnd measured at 700 cm3/m3 carbon dioxide did not differ from that of plants grown and measured at 350 cm3/m3 in _Malus dom@xestica_, _Quercus prinus_ and _Quercus robur_ at any measurement time. In _Acer saccharinum_, lower conductances occurred yfor plants grown and measured at elevated carbon dioxide concentration only at measurement temperature above 33C. PhotosyCznthetic 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.S N|122^2^Bunce,J A^Caulfield,F^1991^1^Reduced Respiratory Carbon Dioxide Efflux During Growth at Elevated Carbon Dioxide in TPhree Herbaceous Perennial Species^35^67^^325-330^^^^^^^^^^294^^^^^^^^^^^Dactylis glomerata/Lolium perenne/Medicago sativa~o sativa L.&g7`V4 e*<^' ,sSt Npu 6 dcU6W6 N|uF u <2tR`C^292^Ann. Bot. |u: t: ta` t< s< uf<ua`2V8V3)t$:lUA^292^Long-term effects of elevated carbon dioxide on respiration were investigated in _Dactylis glomerata_, _Lolium perenne_ and _Medicago sativa_ in controlled environment chambers, and in _D. glomerata_ and _M. sativa_ in field plots. PlantsX were grown at 35 and 70 Pa carbon dioxide pressure. Dark carbon dioxide efflux rates were determined for whole plants dur`ing the first 40 d of growth in the controlled environment chambers, and for the ecosystems during the first year of growtdh in the field. Elevated carbon dioxide increased the rate of biomass accumulation in all species. In controlled environmetnts, efflux rates per unit of biomass were 30-40% lower in the elevated carbon dioxide treatment in _L. perenne_ and _ M. sativa_ at similar relative growth rates. In _D. glomerata_, efflux rates did not differ between treatments, but relative wgrowth rate was 50% higher at the elevated carbon dioxide. In the field, _M. sativa_ plots at elevated carbon dioxide had 15% less carbon dioxide efflux per unit of ground area, in spite of greater biomass production. Plots with _D. glomerata_ had equal rates of carbon dioxide efflux, but the plot with elevated carbon dioxide had higher biomass production. Thus, in all cases respiratory carbon dioxide efflux was reduced at elevated carbon dioxide, at least relative to the biomass accumulated.Ku譗Ž&Ku**P+s3SRZ[r: [=^v${DD_^ZY[X& þLss123^1^Burch,D W^1986^3^Economics of CO2 Enrichment in Greenhouses^Physiology, Yield, and Economics^CRC Press, Inc.^Boca Raton, Florida^199-209^^^^II^^Carbon Dioxide Enrichment of Greenhouse Crops^^^^296^^^^^^^^^^^^^^^^^^^^^Enoch,H Z^Kimball,B AB At;\s;TvS..G._.G[WS_&EG?[o_G?_S..o._.[PRWs#;A^295^The economic feasibility of any long-term commitment of capital is dependent on initial capital cost and further input/output relationships and prices which normally cannot be known in advance, but about which in many instances, it may seem reasonable to surmise. In the case of CO2 enrichment of the greenhouse atmosphere, the factors of primary importance are (1) the added market value of the crop due to CO2 enrichment, (2) the cost of CO2 and other expenses, (3) any heating or tax credits, and (4) the cost of equipment and terms of financing. A comprehensive equation was presented for projecting cash flow for several years, and a criteria equation was presented to determine the internal rate of return. A numerical example illustrated use of the equation. Prospects appear to be favorable for profitability of CO2 enrichment in cold climates, where it is a recommended practice. However, costs and incremental value of production may vary widely, particularly as ventilation requirements increase in warmer climates, so each case should be examined on an individual basis. The economic analysis equations presented here offer a satisfactory framework for case-by-case evaluations of the profitability of CO2 enrichment. Moreover, they can be used to compare alternative methods of financing and even to compare the attractiveness of an investment in CO2 enrichment relative to investments in other greenhouse equipment or to investments in financial instruments.EE_^ZRR3QWVO${sE tFF!Df~~=u124^4^Burger,J^Miyachi,S^Galland,P^Senger,H^1988^1^Quantum Requirements of Photosynthetic Oxygen Evolution and 77K Fluorescence Emission Spectra in Unicellular Green Algae Grown under Low-and High-CO2-Conditions^45^101^^229-232^^^^^^^^^^299^^^^^^^^^^^Dunaliella tertiolecta/Chlamydomonas reinhardtii/Chlorella vulgaris/Chlorella pyrenoidosasaX_[tE=t}C^297^Bot. Act.WF.sr#+f~Ў.sr vF*s_^Ss[4555l5t5|555 5A^297^Quantum requirements of photosynthetic oxygen evolution at 682 nm and fluorescence spectra at liquid nitrogen temperature (77K), were investigated in _Dunaliella tertiolecta_, _Chlamydomonas reinhardtii_ C-9, _Chlorella vulgaris_ 11 g, _Chlorella vulgaris_ C3, and _Chlorella pyrenoidosa_ 8b grown under low- and high-CO2 conditions. _Dunaliella_, _Chlamydomonas_ and _C. vulgaris_ 11 g show higher quantum requirements and a higher ratio of F710-740/F680-695 fluorescence when grown under low-CO2 conditions, indicating a change in excitation energy distribution towards PS-I. In _C. pyrenoidosa_ the quantum requirement for low-CO2 grown cells is higher than in high-CO2 grown cells, but there was practically no change in the fluorescence ratio. In _C. vulgaris_ C3, the quantum requirements of low- and high-CO2 grown cells are the same, but the fluorescence ratio is higher in high-CO2 grown cells than in low-CO2 grown cells. These results indicate that most of th.e low-CO2 grown cells require more PS-I light than high-CO2 grown cells. It is possible that this energy is used for cyclic electron flow. In _C. vulgaris_ C3, a mechanism may exist for excitation energy distribution which leads to the same qua0ntum requirements under low- and high-CO2 conditions.t.L8E~rntsM^tF.T8]ZrJPsM}t&125^4^Burnett,R B^Chaudhuri,U N^Kanemasu,E T^Kirkham,M B^1985^5^Sorghum at Elevated Levels of CO2^U.S. Dept. of Energy, CaCrbon Dioxide Research Division, Washington, D.C^^^^^^^^^^^^^^^^^^^^^^^^sorghum/Sorghum bicolor^^024 in Green Report SeriesG^Response of Vegetation to Carbon Dioxide^^n Dioxide^^s~'~t"& "" _G+vFyv2FRf126^3^Butler,G D^Kimball,B A^Mauney,J R^1986^1^Populations of _Bemisia tabaci_ (Homoptera: Aleyrodidae) on Cotton Grown inJ Open-top Field Chambers Enriched with CO2^6^15^^61-63^^^^^^^^^^303^^^^^^^^^^^Gossypium hirsutum/cottonottonNuFWC^301^Environ. Entomol.^V؃Xv}Ws~FFVVVVSF؊'~t& "" B;Vr3A^301^Atmospheric CO2 levels are anticipated to rise from the current ambient level of ca. 350 uL/L to 500-600 uL/L in the[ next 50 to 75 years. Plant scientists are artificially enhancing the CO2 environment of crop plants to increase photosyntnhesis, which is currently limited by inadequate levels of CO2. It is not known how increases of CO2 might affect consumers in the food chain. Population levels of sweetpotato whitefly (SPWF), _Bemisia tabaci_ (Gennadius), were assessed with stiqcky traps placed in a field experiment wherein cotton was grown in open-top field chambers that were enriched with CO2 at }levels approaching 200% ambient concentration levels. Although trapping started at the first of June, only an occasional SPWF was caught until early August. At that time populations began to increase at an exponential rate similar to that observed in commercial cotton fields in Arizona and California in previous years. There was no difference in rate of buildup of SPWF in ambient and CO2-enriched chambers in either wet or dry irrigation treatment. Thus, it seems that raised CO2 levels, either natural or artificial, do not affect SPWF populations.n^~uă~uߋ_^ZYQRVWF P tN127^2^Byrd,G T^Brown,R H^1989^1^Environmental Effects on Photorespiration of C3-C4 Species. I. Influence of CO2 and O2 during Growth on Photorespiratory Characteristics and Leaf Anatomy^17^90^^1022-1028^^^^^^^^^^306^^^^^^^^^^^Flaveria trinervia/Flaveria floridana/Flaveria pringlei/Festuca arundinacea/Panicum milloides/Panicum laxum;z9&EvC\rC^304^Plant Physiol.Nr3ۉ\\6tC&]&E 3]^[UW~N m_]UW~N [V_]VUP&5D &EPDPA^304^The possibility of altering CO2 exchange of C3-C4 species by growing them under various CO2 and O2 concentrations was examined. Growth under CO2 concentrations of 100, 350 and 750 micromoles per mole had no significant effect on CO2 exchange characteristics or leaf anatomy of _Flaveria pringlei_ (C3), _Flaveria floridana_ (C3-C4), or _Flaveria trinervia_ (C4). Carboxylation efficiency and CO2 compensation concentrations in leaves of _F. floridana_ developed under the different CO2 concentrations were intermediate to _F. pringlei_ and _F. trinervia_. When grown for 12 days at an O2 concentration of 20 millimoles per mole, apparent photosynthesis was strongly inhibited in _Panicum milloides_ (C3-C4) and to a lesser degree in _Panicum laxum_ (C3). In _P. milloides_, acute starch buildup was observed microscopically in both mesophyll and bundle sheath cells. Even after only 4 days exposure to 20 millimoles per mole O2, the presence of starch was more pronounced in leaf cross-sections of _P. milloides_ compared to those at 100 and 210 millimoles per mole. Even though this observation suggests that _P. milloides_ has a different response to low O2 with respect to translocation of photosynthate or sink activity than C3 species, the concentration of total available carbohydrates increased in shoots of all species by 33% or more when grown at low O2. This accumulation occurred even though relative growth rates of _Festuca arundinacea_ (C3) and _P. milloides_ grown for 4 days at 210 millimoles per mole O2, were inhibited 83 and 37%, respectively, when compared to plants grown at 20 millimoles per mole O2.AvO${ssG gO ]Z[XSQWVr; t!tDTG t128^2^Campagna,M A^Margolis,H A^1989^1^Influence of Short-term Atmospheric CO2 Enrichment on Growth, Allocation Patterns, and Biochemistry of Black Spruce Seedlings at Different Stages of Development^32^19^^773-782^^^^^^^^^^309^^^^^^^^^^^Picea mariana/black sprucek spruce;6wG ;6vG;6w G ;6wZO2 Du#D;6wD;6v;6w D;6w C^307^Can. J. For. Res.3^ZYlo>u>g7tS~P2ANr.=NDCdDGgN@A^307^Black spruce seedlings (_Picea mariana_ Mill.) were exposed to either elevated (1000 ppm) or ambient (340 ppm) atmospheric CO2 levels at different stages of seedling development over a winter greenhouse production cycle. Seedlings germinated in early February and were placed in CO2 chambers for either 3 or 6 weeks during March, April, May, or August. Total seedling biomass increased under high CO2 conditions for the March, April, and May stages of development, but showed no sig nificant response in August. The greater part of the CO2 response occurred during the second 3 weeks of exposure in March and April but during the first 3 weeks of exposure in May. In September, those seedlings exposed to CO2 in April and May had 30 and 14%, respectively, greater biomass than control seedlings, but seedlings from the other stages of development no longer had significant differences remaining from the CO2 treatment. This suggests that it could be very efficient to give a short well-timed CO2 pulse at the beginning of the production cycle in hopes of producing a size difference that is maintained throughout the remainder of the greenhouse production cycle under ambient levels of CO2. Short-term exposure to elevated CO2 also increased the ratio of shoot dry weight to total height for the March, April, and May stages of development. The ratio of total nonstructural carbohydrates to free amino acids was negatively correlated (_r2_=0.98) with the allo(cation of new growth between shoots and roots as measured by the allocation coefficient, _k_ (milligrams shoot growth per milligram root growth). As seedlings developed along their seasonal growth cycle, ratios of total nonstructural carbohydra*tes to free amino acids increased and the values for _k_ decreased. The effect of CO2 enrichment on these two factors is d4iscussed. Monitoring total nonstructural carbohydrate and free amino acid concentrations in foliage could have potential as a method to predict the percentage of carbon allocation to root systems of entire forest stands as well as of individual7 tree seedlings.E3*^PsVv^r(D9DtL3ۏDD_ZY333=tӓS\^XP&P u $D D <129^2^Campbell,D E^Young,R^1986^1^Short-term CO2 Exchange Response to Temperature, Irradiance, and CO2 Concentration in Strawberry^18^8^^31-40^^^^^^^^^^312^^^^^^^^^^^strawberry/Fragaria ananassasah/D&Pt P&`X&V&T ?C^310^Photosynth. Res.BE@EsaSRWD Au#rPsD t ڻDE${PQA33X&\D t"3ro&`A^310^Relative importance of short-term environmental interaction and preconditioning to CO2 exchange response was examined in _Fragaria ananassa_ (strawberry, cv. Quinault). Tests included an orthogonal comparison of 15 to 60-min and 6 to 7-h exposures to different levels of temperature (16 to 32C), photosynthetically active radiation (PAR, 200 to 800 uE/m2/s), nand CO2 (300 to 600 uL/L) on successive days of study. Plants were otherwise maintained at 21C, 300 uE/m2/s PAR and 300-3q60 uL/L CO2 as standard conditions. Treatment was restricted to the mean interval of 14 h daily illumination and the firstz 3-4 days of each test week over a 12-week cultivation period. CO2 exchange rates were followed with each step-change in e|nvironmental level including ascending/descending temperature/PAR within a test period, initial response at standard conditions on successive days of testing, and measurement at reduced O2. Response generally supported prior concepts of leaf biochemical modeling in identifying CO2 fixation as the major site of environmental influence, while overall patterns of whole plant CO2 exchange suggested additional effects for combined environmental factors and preconditioning. These included a positive interaction between temperature and CO2 concentration on photosynthesis at high irradiance and a greater contribution by 'dark' respiration at lower PAR than previously indicated. The further importance of estimating whole plant CO2 exchange from repetitive tests and measurements was evidenced by a high correlation of response to prior treatment both during the daily test period and on consecutive days of testing. Xu$0<0tu s݃ tu Dr130^1^Caporn,S J M^1989^1^The Effects of Oxides of Nitrogen and Carbon Dioxide Enrichment on Photosynthesis and Growth of Lettuce (_Lactuca sativa_ L.)^23^111^^473-481^^^^^^^^^^315^^^^^^^^^^^lettuce/Lactuca sativava L.EuQR2;EEZY WC^313^New Phytol.E_E!tQRe!C@@E! u.F3҇ڋUE +E srO t 3ƒE!u/211^3^Eng,R Y N^Tsujita,M J^Grodzinski,B^1985^1^The Effects of Supplementary HPS Lighting and Carbon Dioxide Enrichment on the Vegetative Growth, Nutritional Status and Flowering Characteristics of _Chrysanthemum morifolium_ Ramat^19^60^^389-395^^^^^^^^^^521^^^^^^^^^^^Chrysanthemum morifolium/chrysanthemumum ;wHH.-u؋.&.-.&-!$ C^519^J. Hort. Sci.a XPSQPSQd;u> 7uEtudtY[XPQdt a$:tdd under the CO2 regime predicted for the year 2050) and Q-700/350 (the quotient of present yield predicted for a doubling of ambient CO2 concentration). Values of Q-540/350 for whole-plant dry weight ranged from below 1.01 to 1.49, the upper values being at least similar in magnitude to those already observed in C3 crops. The mean value of whole-plant Q-700/350 for 11 species of near-competitive strategy was 1.43. Four species of stress-tolerant or ruderal strategy had a mean Q-700/350 of only 1.05. High CO2 responsiveness was common only within the competitive strategy and its close relations. The fitted Q-540/350 for species of the pure strategy was 1.38. In the centre of the strategic range the fitted value was 1.12, and at the far extreme, the value for species of ruderal or stress-tolerant strategy was only 1.03.Individual leaf area waA^313^The response of glasshouse crops to the nitrogen oxide pollutants which may be generated during enrichment with CO2 has been studied in controlled environments. Lettuce (_Lactuca sativa_ L. cv. Ambassador) was grown in air containing either low CO2 (380 umol/mol), high CO2 (1200 umol/mol), or high CO2 plus oxides of nitrogen (NOx). Carbon dioxide enrichment increased the rate of emergence and expansion of leaves and the growth of young plants. Addition of NOx (2 umol/mol NO and c. 0.5 umol/mol NO2) to CO2-enriched air significantly reduced the yield, compared with the 'clean', high CO2 treatment, without producing visible symptoms of toxicity. Fumigation of single plants in high CO2 with NOx rapidly inhibited photosynthesis per unit leaf area. This did not appear to be due to a reduction in stomatal conductance. Removal of NOx from the  atmosphere caused a rapid and complete recovery in the rate of photosynthesis. Studies were made of the effects of growing plants for long periods in atmospheres containing high CO2 and NOx on the photosynthetic capacity of single leaves when m% easured in NOx-free air. The decrease in photosynthetic rate as the fourth leaf aged occurred earlier in plants grown in C O2-enriched air than in those from the low CO2 treatment. Leaves which developed in the CO2-enriched air containing NOx di* d not suffer any long-term damage to photosynthetic activity in comparison with those of the 'clean' high CO2. In mature l4eaves the principal long-term effect of enrichment (with or without NOx) was to reduce the rate of photosynthesis in saturating CO2. In contrast, there was less effect on the rate of photosynthesis in low CO2. The absence of a long-term effect 7of NOx on the photosynthetic capacity suggested that photosynthesis by the lettuce crop will be inhibited only during the Ctransient periods of NOx accumulation in the glasshouse.131^3^Caporn,S J M^Mansfield,T A^Hand,D W^1990^1^The Critical Influence of Temperature on the Inhibition of PhotosynthesisG by Oxides of Nitrogen in Lettuce^15^268^^103-110^^^^^^^^^^318^^^^^^^^^^^lettuce/Lactuca sativavaTC^316^Act. Hort.A^316^The photosynthetic response of lettuce to the oxides of nitrogen (NOx) generated during enrichment with CO2 has beenX studied at different temperatures. The steady rates of net photosynthesis of lettuce fell within several minutes followinjg the addition of nitric oxide to the cuvette. This did not appear to have been caused by a reduction in the stomatal conductance. Removal of the pollutant gas resulted in a rapid and complete recovery in the rate of photosynthesis. Gas exchangme by a small stand of lettuce was measured in a novel growth chamber with fine thermal control. In high CO2 (1000 vpm) andv at 16, 10 and 6C a transient fumigation with 2.0 vpm NO reduced CO2 uptake by 7, 11 and 29% respectively. Deposition of zNO into the canopy was 46% less at 6 than at 16C. Uptake of the pollutant, therefore, did not explain the increased inhibition of photosynthesis. The greater damage at low temperature may be due to a reduced capacity to metabolize some toxic products of NOx assimilation. Methods of CO2 enrichment which vent the flue gases from the burners directly into the glasshouse air may not be entirely suitable for winter crops grown at low temperatures.wL TUU132^3^Caporn,S J M^Mansfield,T A^Hand,D W^1991^1^Low Temperature-enhanced Inhibition of Photosynthesis by Oxides of Nitrogen in Lettuce (_Lactuca sativa_ L.)^23^118^^309-313^^^^^^^^^^321^^^^^^^^^^^lettuce/Lactuca sativava L.)yC^319^New Phytol.Gddd?()"A^319^The response of photosynthetic gas exchange to oxides of nitrogen (NOx) was studied in leaves of lettuce (_Lactuca s#ativa_ L.) at different temperatures. Exposure to high concentrations (e.g. 1.3 umol NOx/mol), similar to those often foun$d in commercial glasshouses, caused a rapid inhibition of the net assimilation of CO2. This appeared to be by a direct eff%ect on photosynthesis rather than by a change in the stomatal conductance. In ambient CO2 (345 umol/mol), the percentage i&nhibition at 10 and 5C was approximately 3x and 5x, respectively, that measured at 20C. This effect of temperature also 'occurred when measured in CO2 enriched air (1050 umol/mol), which would normally accompany NOx in a glasshouse. The extent( of photosynthetic inhibition caused by NOx was, however, always less in high than in low CO2. The results suggest that wh)en burning fuel to raise the CO2 concentration and heat the glasshouse air, growers should avoid generating high concentrations of NOx in conditions of low temperature.HP LaserJet 4              +133^2^Carlson,T N^Bunce,J A^1991^3^The Effect of Atmospheric Carbon Dioxide Doubling on Transpiration^Tenth Conference on ,Biometeorology and Aerobiology and the Special Session on Hydrometeorology; 1991 Sept. 10-13; Salt Lake City, Utah^American Meteorological Society^Boston, Massachusetts^196-199^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^Preprint Volume.134^2^Challa,H^Schapendonk,A H C M^1986^3^Dynamic Optimization of CO2 Concentration in Relation to Climate Control in Gree/nhouses^Physiology, Yield, and Economics^CRC Press, Inc.^Boca Raton, Florida^147-160^^^^II^^Carbon Dioxide Enrichment of Greenhouse Crops^^^^^^^^^^^^^^^^^^^^^^^^^Enoch,H Z^Kimball,B AB A1135^4^Chaudhuri,U N^Burnett,R B^Kanemasu,E T^Kirkham,M B^1986^5^Effect of Elevated Levels of CO2 on Winter Wheat under Two2 Moisture Regimes^U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C^^^^^^^^^^^^^^^^^^^^^^^^wheat/Triticum aestivum^^029 in Green Report Series^Response of Vegetation to Carbon Dioxide^^^^` 4136^4^Chaudhuri,U N^Burnett,R B^Kirkham,M B^Kanemasu,E T^1986^1^Effect of Carbon Dioxide on Sorghum Yield, Root Growth, and Water Use^46^37^^109-122^^^^^^^^^^327^^^^^^^^^^^sorghum/Sorghum bicoloror (L.) Moench C^325^Agric. For. Meteorol.223'7A^325^The concentration of atmospheric carbon dioxide (CO2) is rising. The effect of higher than ambient levels of CO2 on 8plants grown in the sub-humid central Great Plains of the U.S.A. has not been investigated. Therefore, an experiment was c9onducted at Manhattan, Kansas, to study the effect of elevated levels of CO2 on grain sorghum [_Sorghum bicolor_ (L.) Moen:ch]. During the summer of 1984, the sorghum was grown in rhizotrons in which root and shoot growth could be monitored thro;ughout the growth cycle. The tops of the plants were enclosed in plastic chambers, which contained one of four concentratiile depths, root numbers and weights were higher at elevated CO2 than at ambient CO2. However, water use per unit dry matt8?er of leaf, stem, root, and grain was decreased 13, 30, 31 and 29%, respectively, in plants grown at 795 uL/L CO2 compared@ to plants at 330 uL/L CO2. Although elevated CO2 levels increased the stomatal resistance and leaf temperature, an increa;se in leaf area indices resulted in a lower canopy resistance.$F B137^4^Chaudhuri,U N^Burnett,R B^Kanemasu,E T^Kirkham,M B^1987^5^Effect of Elevated Levels of CO2 on Winter Wheat under Two>C Moisture Regimes^U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C^^^^^^^^^^^^^^^^^^^^^^^^wheat/TriCticum aestivum^^040 in Green Report Series^Response of Vegetation to Carbon Dioxide^^^^E138^3^Chaudhuri,U N^Kanemasu,E T^Kirkham,M B^1989^5^Effect of Elevated Levels of CO2 on Winter Wheat under Two Moisture ReFFgimes^U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C^^^^^^^^^^^^^^^^^^^^^^^^wheat/Triticum aestivVum^^050 in Green Report Series^Response of Vegetation to Carbon Dioxide^^^^d., H139^3^Chaudhuri,U N^Kirkham,M B^Kanemasu,E T^1990^1^Carbon Dioxide and Water Level Effects on Yield and Water Use of WinteYr Wheat^4^82^^637-641^^^^^^^^^^332^^^^^^^^^^^wheat/Triticum aestivumum L.g5C^330^Agron. J..KA^330^Increasing levels of atmospheric CO2 may have major effects on yield and water use of winter wheat (_Triticum aestiviLum_ L.). The objective was to determine the effect of elevated levels of CO2 on grain yield and water use from planting toM harvest under two water levels. 'Newton' winter wheat was grown in the field under ambient (340 uL/L) and elevated levelslN (485, 660, and 825 uL/L) of CO2, during three growing seasons, in 16 underground boxes (77 cm long, 37 cm wide, and 180 coOm deep) containing a Muir silt loam (fine-silty, mixed, mesic Cumulic Haplustoll). Water in half of the boxes was maintainPed at 0.38 m3/m3 (high water level) and in the other half between 0.14 to 0.25 m3/m3 (low water level). Boxes were weighedQ in the fall and spring to determine the amount of water use by transpiration. Plastic chambers (121 by 92 by 168 cm) coveRred the boxes to maintain different CO2 levels. Grain yield of the high-water-level wheat grown under ambient CO2 was abouSt the same as the grain yield of low-water-level wheat grown at the highest level of CO2 (825 uL/L) (3-yr means: 725 and 7T07 g/m2, respectively). Similar results were obtained for yield components (spike number, spike weight, kernels/spike, andU kernel weight). High-water-level wheat grown with 825 uL/L CO2 transpired more water than low-water-level wheat grown undVer ambient levels of CO2 (3-yr means: 453 and 370 L/m2, respectively). Under high and low water levels, 29 and 31% less waWter was required, respectively, to produce a gram of grain when the CO2 concentration was raised from ambient to 825 uL/L. Results show that the water requirement of wheat is reduced by about 30% by elevated (1.4 times present ambient) CO2.Y140^3^Chaudhuri,U N^Kirkham,M B^Kanemasu,E T^1990^1^Root Growth of Winter Wheat under Elevated Carbon Dioxide and Drought^12^30^^853-857^^^^^^^^^^335^^^^^^^^^^^wheat/Triticum aestivumum L.IC^333^Crop Sci.\A^333^With the atmospheric concentration of CO2 increasing, it is important to know how this will affect crop growth. The ]objective of this study was to determine the effect of enriched CO2 on root growth of winter wheat (_Triticum aestivum_ L.^ 'Newton') under both well-watered and dry conditions. The wheat was grown for 3 yr in 16 plastic chambers (121 by 92 by 1_68 cm) in the field under ambient CO2 (340 uL/L) and elevated levels of CO2 (485, 660, and 825 uL/L). Each chamber was pla`ced over an underground box (77 by 37 cm at the top; 180 cm deep) containing a Muir silt loam (fine-silty, mixed, mesic Cuamulic Haplustoll). The boxes could be pulled out of the ground for observation of the roots. Half of the boxes were maintabined at field capacity (0.38 m3/m3) (well-watered or not stressed plants) and half between 0.14 to 0.25 m3/m3 (drought-strcessed plants). At harvest, root dry weights at different depths and stem dry weight were determined. Roots of plants grownd under the three elevated levels of CO2 penetrated to the maximum depth of observation (176 cm) before roots of plants groewn under the ambient level. At harvest, the difference in root growth between elevated and ambient levels of CO2 was most fpronounced at the top level (0- to 10-cm depth). Roots of drought-stressed plants grown with 825 uL/L CO2 had a greater drgy weight than roots of well-watered plants grown with ambient CO2. The ratio of root to stem weight usually showed no trenhd (neither increase or decrease) with increasing CO2 concentration. Total dry weight at harvest of well-watered roots grow)in at ambient CO2 (3-yr mean: 118 g/m2) was similar to that of drought-stressed roots grown at the highest level of CO2 (3-jyr mean: 123 g/m2). The results indicated that high CO2 (825 uL/L) can compensate for restrictions in root growth by droug,ht.WPxx.LEXWPSP60xx.DTL8141^2^Chaves,M M^Pereira,J S^1992^1^Water Stress, CO2 and Climate Change^39^43^^1131-1139^^^^^^^^^^33838൧,:ZC^336^J. Exp. Bot.:&: :^:: :: :Q:Q::;nA^336^Climate change may bring about increased aridity of large areas of Europe. Higher temperatures, larger water deficitLos and high light stress are likely to occur in conjunction with elevated atmospheric CO2. This raises the question whetherp a high CO2 concentration in the atmosphere can compensate for the decrease in carbon gain in water-stressed plants. The pOqrocesses which determine dry matter production and the ways they are affected by soil water deficits are discussed. It is Wrnow well established that in most species and under most circumstances stomata are the main limiting factor to carbon uptaske under water deficit, the photosynthetic machinery being highly resistant to dehydration. However, when other stresses aZtre superimposed, a decline in photosynthetic capacity may be observed. In the short term, under drought conditions, the inducrease in CO2 in the atmosphere may diminish the importance of stomatal limitation for carbon assimilation, inhibit photorvespiration, stimulate carbon partitioning to soluble sugars and increase water-use efficiency. Some recent evidence seems gwto indicate that under conditions of high irradiance, plants growing at elevated CO2 may develop protection towards photoixxnhibition, which might otherwise result in significant losses in plant production under stress conditions. In the longer tyerm though, a negative acclimation of photosynthesis appears to occur in many species, an explanation for which still need|zs to be clearly identified. Similarly, the effects of extended exposure to elevated CO2 under arid conditions are not know{n. Plant production is more closely related to the integral of photosynthesis over time and total foliage area than to the| instantaneous rates of the photosynthetic process. Water deficits result in more respiratory losses. However, experimenta}l as well as simulatory evidence suggests that doubling CO2 concentration in the air may improve carbon assimilation and c~ompensate partially for the negative effects of water stress even if we assume a down-regulation of the photosynthetic process as a result of acclimation to elevated CO2. % _2L,0"142^2^Chen,J J^Sung,J M^1990^1^Gas Exchange Rate and Yield Responses of Virginia-type Peanut to Carbon Dioxide Enrichment^12^30^^1085-1089^^^^^^^^^^341^^^^^^^^^^^peanut/Arachis hypogaeaea L.lC^339^Crop Sci.A^339^Poor seed fill and resultant seed-coat shriveling occur commonly on Virginia-type peanut (_Arachis hypogaea_ L.) grown in Taiwan. The phenomenon may be linked to the limitation in photosynthate supply at seed filling. The objective of this study was to evaluate the effect of CO2 enrichment (1000 uL CO2/L) and depegging on CO2 exchange rate (CER) and yield responses of pot-grown Virginia-type peanut. Carbon dioxide enrichments were applied to the plants at pod filling. Depegging effect was examined contrasting the controls and the plants maintaining 38 to 40 pegs throughout the growing period. The results indicated that short-term CO2 enrichment (CO2 treatment for 10 d) improved leaf and canopy CER. Long-term CO2 enrichment (CO2 treatments throughout pod filling) tended to ease leaf ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco) and chlorophyll (chl) deteriorations. Electrophoresis patterns of leaf soluble protein extracts confirmed this finding. Seed yield per plant was increased with high CO2 treatment applied at seed-filling period, but the production of marketable seeds was improved only in the plants receiving CO2 and depegging treatments. The poor seed-fill characteristic observed in Virginia-type peanut is attributed to excessive sink load and low canopy CER.WPXX.ICR.143^3^Chu,C C^Coleman,J S^Mooney,H A^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^34^89^^580-587^^^^^^^^^^344^^^^^^^^^^^radish/Raphanus sativus/Raphanus raphanistrum?-DT! @-DT!@ߓi>*?UUUUC^342^Oecologiaw )VD Jb0@P;f?&{?9B.?XoR>op|?? 8o?@?QBqq?A^342^The effects of CO2 enrichment on plant growth, carbon and nitrogen acquisition and resource allocation were investigated in order to examine several hypotheses about the mechanisms that govern dry matter partitioning between shoots and roots. Wild radish plants (_Raphanus sativus x raphanistrum_) were grown for 25 d under three different atmospheric CO2 conc entrations (200 ppm, 330 ppm and 600 ppm) with stable hydroponic 150 umol/L nitrate supply. Radish biomass accumulation, photosynthetic rate, water use efficiency, nitrogen per unit leaf area, and starch and soluble sugar levels in leaves incre ased with increasing atmospheric CO2 concentration, whereas specific leaf area and nitrogen concentration of leaves signif icantly decreased. Despite substantial changes in radish growth, resource acquisition and resource partitioning, the rate at which leaves accumulated starch over the course of the light period and the partitioning of biomass between roots and s hoots were not affected by CO2 treatment. This phenomenon was consistent with the hypothesis that root/shoot partitioning is related to the daily rate of starch accumulation by leaves during the photoperiod, but is inconsistent with hypotheses suggesting that root/shoot partitioning is controlled by some aspect of plant C/N balance. 144^2^Coleman,J S^Bazzaz,F A^1992^1^Effects of CO2 and Temperature on Growth and Resource Use of Co-occurring C3 and C4 Annuals^2^73^^1244-1259^^^^^^^^^^347^^^^^^^^^^^Amaranthus retroflexus/Abutilon theophrastiti !C^345^Ecology)A)%%P;2 ,A^345^We examined how CO2 concentrations and temperature interacted to affect growth, resource acquisition, and resource a 0llocation of two annual plants that were supplied with a single pulse of nutrients. Physiological and growth measurements =were made on individuals of _Abutilon theophrasti_ (C3) and _Amaranthus retroflexus_ (C4) grown in environments with atmospheric CO2 levels of 400 or 700 uL/L and with light/dark temperatures of 28/22 or 38/31C. Elevated CO2 and temperature A treatments had significant independent and interactive effects on plant growth, resource allocation, and resource acquisi Qtion (i.e., photosynthesis and nitrogen uptake), and the strength and direction of these effects were often dependent on p Tlant species. For example, final biomass of _Amaranthus_ was enhanced by elevated CO2 at 28 but was depressed at 38. For i _Abutilon_, elevated CO2 increased initial plant relative growth rates at 28 but not at 38, and had no significant effects on final biomass at either temperature. These results are interpreted in light of the interactive effects of CO2 and t memperature on the rates of net leaf area production and loss, and on net whole-plant nitrogen retention. At 28C, elevated | CO2 stimulated the initial production of leaf area in both species, which led to an initial stimulation of biomass accumulation at the higher CO2 level. However, in elevated CO2 at 28, the rate of net leaf area loss for _Abutilon_ increased w hile that of _Amaranthus_ decreased. Furthermore, high CO2 apparently enhanced the ability of _Amaranthus_ to retain nitro gen at this temperature, which may have helped to enhance photosynthesis, whereas nitrogen retention was unaffected in _Ab utilon_. Thus, at 28, final biomass of _Abutilon_ was not stimulated in a high CO2 environment whereas the final biomass of _Amaranthus_ was. At 38, _Abutilon_ had slightly reduced peak leaf areas under elevated CO2 in comparison to ambient C O2 grown plants, but increased rates of photosynthesis per unit leaf area early in the experiment apparently compensated f or reduced leaf area. For _Amaranthus_ at 38, peak leaf area production was not affected by CO2 treatment, but the rate of net leaf area loss hastened under elevated CO2 conditions and was accompanied by substantial reductions of whole-plant n itrogen content and leaf photosynthesis This may have led to the reduced biomass accumulation of high CO2 grown plants tha t we observed during the last 30 d of growth. Plants 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 alloca tion of biomass to roots, irrespective of temperature. Plants of both species grown under an elevated temperature regime h ad substantially decreased reproductive allocation, increased allocation to stem biomass, and increased plant water flux at both CO2 treatments. The age of plants also affected our interpretations of plant responses to CO2 and temperature treat ments. For example, significant effects of CO2 treatment on the growth of _Abutilon_ were evident early, prior to the init iation of flowering, when nitrogen availability would have been highest and pot space would not have been limited. Nevertheless, the opposite was true for _Amaranthus_, in which significant effects of CO2 treatment on plant growth were not dete ctable until the final 30 d of the experiment. Elevated CO2 interacted with temperature to affect plant productivity in di fferent ways than would have been predicted from plant responses to elevated CO2 alone. Furthermore, a majority of the interactive effects of CO2 concentration and temperature on plant growth could be interpreted in light of their effects on th e rates of net leaf area production and loss, nitrogen retention, and, to a lesser degree, photosynthesis and resource par titioning.145^4^Coleman,J S^Rochefort,L^Bazzaz,F A^Woodward,F I^1991^1^Atmospheric CO2, Plant Nitrogen Status and the Susceptibility  of Plants to an Acute Increase in Temperature^16^14^^667-674^^^^^^^^^^350^^^^^^^^^^^Abutilon theophrasti/Amaranthus retro flexus/Sinapis alba/white mustard./white mustardNG=C^348^Plant Cell Environ. A^348^Elevated levels of CO2 in the atmosphere are expected to affect plant performance and may alter global temperature p atterns. Changes in mean air temperatures that might be induced by rising levels of CO2 and other greenhouse gases could also be accompanied by increased variability in daily temperatures such that acute increases in air temperature may be more  likely than at present. Consequently, we investigated whether plants grown in a CO2 enriched atmosphere would be differen tly affected by a heat shock than plants grown at ambient CO2 levels. Plants of a C3 annual (_Abutilon theophrasti_), a C3 annual crop (_Sinapis alba_) and a C4 annual (_Amaranthus retroflexus_) were grown from seed in growth chambers under eit!her 400 or 700 cm3/m3 CO2, and were fertilized with either a high or low nutrient regime. Young seedlings of _S. alba_, as well as plants of all species in either the vegetative or reproductive phase of growth were exposed to a 4-h heat shock i!n which the temperature was raised an additional 14-23C (depending on plant age). Total biomass and reproductive biomass !were examined to determine the effect of CO2, nutrient and heat shock treatments on plant performance. Heat shock, CO2, and nutrient treatments, all had some significant effects on plant performance, but plants from both CO2 treatments responde!d similarly to heat shocks. We also found, as expected, that plants grown under high CO2 had dramatically decreased tissue N concentrations relative to plants grown under ambient conditions. We predicted that high-CO2-grown plants would be more! susceptible to a heat shock than ambient-CO2-grown plants, because the reduced N concentration of high-CO2-grown plants c!!ould result in the reduced synthesis of heat shock proteins and reduced thermotolerance. Although we did not examine heat shock proteins, our results showed little relationship between plant nitrogen status and the ability of a plant to tolerat!%e an acute increase in temperature.!-"146^3^Combe,L^Bertolini,J M^Quetin,P^1990^1^Growth and Photosynthesis of CO2-enriched Primrose^15^268^^55-62^^^^^^^^^^353^C^351^Act. Hort.!0A^351^_Primula obconica_ potted plants were cultivated in a glasshouse at normal (350 +/- 50 uL/L) or enriched (800 +/- 10!;0 uL/L) CO2 concentration in the air. Final growth and yield were measured: fresh and dry matter were significantly increa!>sed by CO2-enrichment (+94% and +77% respectively). Similarly leaf number increased but flower number did not. Plant quality was better. Net CO2-gas exchange rates were measured on a small population (10 pots =30 plants =1 m2) in a growth chamb!Aer where irradiance and CO2 could be controlled. Net photosynthesis curves were the same for both control and enriched pla!Mnts: there was no CO2 adaptive effect. The effect of temperature (14C and 18C) on photosynthesis was not significant. At!Q high irradiance (450 uE PAR/m2/s) and low CO2 concentration (<350 uL/L) some plants sets displayed lowered photosynthesis rate, probably due to photoinhibition. Ageing (5 to 13 weeks after transplantation) caused a reduction of photosynthesis !Trate except at 350 uL/L. Hence CO2-enrichment should be applied preferably at the beginning of cultivation.OPQRSTU![53Z[\]^_`abcdefghijklmnopqrstuvwxyz{|}~147^2^Combe,L^Kobilinsky,A^1985^1^Effet de la Fumure Carbonee sur la Photosynthese de Radis (_Raphanus sativus_) en Serre !^en Hiver^42^19^^550-560^^^^^^^^^^356^^^^^^^^^^^radish/Raphanus sativusus L.HIJKLPQRSTUVWXY[\]cdefg!kC^354^Photosynthetica!"#)/5;?hiopvw}~  #'*+/013   A^354^Carbon dioxide dependence of net photosynthetic rate [_Pn_(C) curves] was studied in _Raphanus sativus_ L. plants gr!nown in a greenhouse with and without CO2 enrichment [ca. 1000 and 350 cm3 (CO2)/m3] for a week. _Pn_ decreased with increa!}sing plant age (6 to 23 d); the decrease was higher under lower irradiance (_I_). CO2 concentration did not modify the age effect on _Pn_. When _I_ (400-700 nm) increased from 200 to 270 umol/m2/s (average of three days before the _Pn_ measurem!ent), _Pn_ increased unless the plants were very young (6d). The effect of _I_ was higher in old plants and under CO2 enri!chment. CO2 enrichment induced a higher decrease in _Pn_ under low _I_ and in older plants. The CO2 enrichment effect appeared only after more than one day of treatment. After the enrichment had been stopped, the effect persisted for at least o!ne day and disappeared 3 d after the treatment had been stopped. In French.  _ %(B1AC)+,97"8!:abcdef!148^1^Conroy,J P^1992^1^Influence of Elevated Atmospheric CO2 Concentrations on Plant Nutrition^25^40^^445-456^^^^^^^^^^35!C^357^Aust. J. Bot.ssvvyyyyyyyy!A^357^The rising levels of atmospheric CO2 are likely to increase biomass production of C3 species in both natural and managed ecosystems because photosynthetic rates will be higher. The greatest absolute increase in productivity will occur whe!n 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 av!ailable to maintain maximum photosynthetic activity at high CO2. C3 plants response to high CO2 because the flux of carbon! through the photoreductive cycle is increased and photorespiration is suppressed. This change in metabolism appears to al!ter the foliar nutrient concentration required to promote maximum productivity (critical concentration). Higher phosphorus! concentrations are needed at elevated CO2, whereas the nitrogen requirement is reduced by CO2 enrichment. Since critical !concentrations are used to evaluate nutrient status of crop and forest species and to manage fertiliser programs, they wil!l need reassessing as the atmospheric CO2 concentration rises. Another consequence of the altered nutrient requirement at high CO2 is that the nitrogen concentrations of foliage, roots and grain are consistently lower in plants grown at elevate"d CO2, irrespective of availability of nitrogen in the soil. In natural ecosystems,the lower nitrogen to carbon ratio of t" he litter may alter rates of nutrient cycling. For farmers, the rising CO2 concentrations could cause the reductions in grain nitrogen, and therefore protein content. This could have important implications for baking quality of hard wheats as w"ell as affecting the nutrient value of grain such as rice.QR\ t= t83ɋDp${s\${H${s D): "959r%D\T L+ً\rju;vSB!Yr[TD${sPVWNfE9NsN3Ҵ?!rQ3YF;149^3^Conroy,J^Barlow,E W^Bevege,D I^1986^1^Response of _Pinus radiata_ Seedlings to Carbon Dioxide Enrichment at Differen"t Levels of Water and Phosphorus: Growth, Morphology and Anatomy^35^57^^165-177^^^^^^^^^^362^^^^^^^^^^^Pinus radiatata D.C^360^Ann. Bot.rڋFD TD)D~t )FfLT NVB!TL\~tV39NsNQAY^3@!r\L "#A^360^Eight week old seedlings of _Pinus radiata_ D. Don, grown at three levels of phosphorus, were subjected to three wat"&ering regimes and to CO2 concentrations of either 330 or 660 uL/L for 22 weeks. Carbon dioxide enrichment increased total dry weight by an average of 30 per cent. In phosphorus deficient seedlings the increase was only 13 per cent, whereas unde"+r water stress it was 38 per cent. The NAR responded similarly to CO2. The number, length, diameter and specific weight of"4 the needles was also increased by CO2 enrichment, the effect being reduced by phosphorus deficiency but not by water stress. The increase in needle diameter was due to an increase in cell size rather than cell number. It may be inferred that i"8ncreases in the yield of field grown _P. radiata_ will occur even at sites where water limits growth. However, there is li"Attle possibility of improving growth where phosphorus deficiency is chronic.>it$\Wi2P򮿪_rѾi t Don* u+O~ z]_^ZY[XPSQRV!F:u&$,A<w:!!:u&B6!-r=tFF<tִ;!ssN V!"D 150^5^Conroy,J P^Kuppers,M^Kuppers,B^Virgona,J^Barlow,E W R^1988^1^The Influence of CO2 Enrichment, Phosphorus Deficiency "L and Water Stress on the Growth, Conductance and Water Use of _Pinus radiata_ D. Don^16^11^^91-98^^^^^^^^^^365^^^^^^^^^^^Pi"Onus radiata/Monterey pine^^^^^pine~ u^\SF[s\_^Y[VFDDD*^QVW|VH ^"T C^363^Plant Cell Environ.OXssD*_^Y˚6F5>5u 7:s5ˀ>5t5u7:58ui.NǠ8H"XA^363^Seedlings of _Pinus radiata_ D. Don were grown in growth chambers for 22 weeks with two levels of phosphorus, under "`either well-watered or water-stressed conditions at CO2 concentrations of either 330 or 660 mm3/dm3. Plant growth, water use efficiency and conductance were measured and the relationship between these and needle photosynthetic capacity, water u"cse efficiency and conductance was determined by gas exchange at week 22. Phosphorus deficiency decreased growth and foliar"s surface area at both CO2 concentrations; however, it only reduced the maximum photosynthetic rates of the needles at 660 mm3 CO2/dm3 (plants grown and measured at the same CO2 concentration). Water stress reduced growth and foliar surface area"u at both CO2 concentrations. Increases in needle photosynthetic rates appeared to be partly responsible for the increased "growth at high CO2 where phosphorus was adequate. This effect was amplified by accompanying increases in needle production. Phosphorus deficiency inhibited these responses because it severely impaired needle photosynthetic function. The relativ"e increase in growth in response to high CO2 was higher in the periodically water-stressed plants. This was not due to the" maintenance of cell volume during drought. Plant water use efficiency was increased by CO2 enrichment due to an increase "in dry weight rather than a decrease in shoot conductance and, therefore, transpirational water loss. Changes in needle conductance and water use efficiency in response to high CO2 were generally in the same direction as those at the whole plan"t level. If the atmospheric CO2 level reaches the predicted concentration of 660 mm3/dm3 by the end of the next Century, t"hen the growth of _P. radiata_ will only be increased in areas where phosphorus nutrition is adequate. Growth will be increased in drought-affected regions but total water use is unlikely to be reduced.tH**tGtq"151^3^Conroy,J P^Milham,P J^Barlow,E W R^1992^1^Effect of Nitrogen and Phosphorus Availability on the Growth Response of _"Eucalyptus grandis_ to High CO2^16^15^^843-847^^^^^^^^^^368^^^^^^^^^^^Eucalyptus grandis^^^^^Ї:XUs t'${r 3 C^366^Plant Cell Environ.uu>Ru N Hrvq֒t֒ttQL u5tKX>Ru$Vrz j""A^366^The response of _Eucalyptus grandis_ seedlings to elevated atmospheric CO2 concentrations was examined by growing se"#edlings at either 340 or 660 umol CO2/mol for 6 weeks. Graded increments of phosphorus and nitrogen fertilizers were added$ to a soil deficient in these nutrients to establish if the growth response to increasing nutrient availability was affect"%ed by CO2 concentration. At 660 umol CO2/mol, seedling dry weight was up to five times greater than at 340 umol CO2/mol. T"&he absolute response was largest when both nitrogen and phosphorus availability was high but the relative increase in dry 'weight was greatest at low phosphorus availability. At 340 umol CO2/mol and high nitrogen availability, growth was stimula"(ted by addition of phosphorus up to 76 mg/kg soil. Further additions of phosphorus had little effect. However, at 660 umol) CO2/mol, growth only began to plateau at a phosphorus addition rate of 920 mg/kg soil. At 340 umol CO2/mol and high phosp*horus availability, increasing nitrogen from 40 to 160 mg/kg soil had little effect on plant growth. At high CO2, growth r+eached a maximum at between 80 and 160 mg nitrogen/kg soil. Total uptake of phosphorus was greater at high CO2 concentrati# ,on 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 enrichment, primarily because the spec# .ific leaf weight was greater. The nitrogen and phosphorus concentration in the foliage was lower at elevated CO2 concentra#/tion partly because of the higher specific leaf weight. These results indicate that critical foliar concentrations current# 0ly used to define nutritional status and fertilizer management may need to be reassessed as the atmospheric CO2 concentration rises.3 3##2152^4^Conroy,J P^Milham,P J^Mazur,M^Barlow,E W R^1990^1^Growth, Dry Weight Partitioning and Wood Properties of _Pinus radi#-ata_ D. Don after 2 Years of CO2 Enrichment^16^13^^329-337^^^^^^^^^^371^^^^^^^^^^^Pinus radiatata X&A^2054^Leaf conductance of eggplant (_Solanum melongena_ L., cv. Cosmos) was measured comparatively in two glasshouse comp#/5A^369^Advanced selections (families 20010 and 20062) of _P. radiata_ D. Don were exposed to either 340 or 660 umol CO2/mol#46 for 2 years to establish if growth responses to high CO2 would persist during the development of woody tissues. The exper7iment was carried out in glasshouses and some of the trees at each CO2 concentration were subjected to phosphorus deficien#78cy and to periodic drought. CO2 enrichment increased whole-plant dry matter production irrespective of water availability,#C9 but only when phosphorus supply was adequate. The greatest increase occurred during the exponential period of growth and :appeared to be tied to increased rates of photosynthesis, which caused accelerated production of leaf area. The increase i#G;n whole-plant dry matter production was similar for both families; however, family 20010 partitioned larger amounts of dry#Q< weight to the trunks than family 20062, which favoured the roots and branches. Wood density was generally increased by el=evated CO2 and for family 20010 this increase was due to thickening of the tracheid walls. Tracheid length was similar at #T>both CO2 levels but differed between families. These results suggest that, as the atmospheric CO2 concentration rises, fie#e?ld-grown _P. radiata_ should produce more dry weight at sites where phosphorus is not acutely deficient, even where drough#h@t limits growth; however, increases in wood production are likely only for genotypes which continue to partition at least #{the same proportion of dry weight to wood in the trunk.ing failed, F7 exits WP without saving.&%˜.8%X.6%XSQRVWB153^4^Conroy,J P^Milham,P J^Reed,M L^Barlow,E W^1990^1^Increases in Phosphorus Requirements for CO2-Enriched Pine Species^#~17^92^^977-982^^^^^^^^^^374^^^^^^^^^^^Pinus radiata/Pinus caribaea^^^^^baea0%s$<u:;Ouu3YSQRVW.;0# C^372^Plant Physiol.&E_^ZY[t..%؋>AuڎۋAu ڋ&;]vB&U&EA^372^_Pinus radiata_ D. Don (half-sib families 20010 and 20062) and _Pinus caribaea_ var hondurensis (an open-pollinated #Ffamily) were grown for 49 weeks at seven levels of phosphorus and at CO2 concentrations of either 340 or 660 microliters p#Ger liter, to establish if the phosphorus requirements differed between the CO2 concentrations and if mycorrhizal associatiHons were affected. When soil phosphorus availability was low, phosphorus uptake was increased by elevated CO2. This may ha#Ive been related to changes in mycorrhizal competition. When the phosphorus concentration in the youngest fully expanded ne#Jedles was above 600 milligrams per kilogram the shoot weight of all pine families was greater at high CO2 due to increasesK in rates of photosynthesis. More dry weight was partitioned to the stems of _P. radiata_ family 20010 and _P. caribaea_. #LAt foliar phosphorus concentrations above 1000 milligrams per kilogram (_P. radiata_) and 700 milligrams per kilogram (_P.#M caribaea_), growth did not increase at 340 microliters of CO2 per liter. Soluble sugar levels in the same needles mirroreNd the growth response, but the starch concentration declined with increasing phosphorus. At 660 microliters of CO2 per lit#Oer, shoot weight and soluble sugar concentrations were still increasing up to a foliar P concentration of 1800 milligrams #Pper kilogram for _P. radiata_ and 1600 milligrams per kilogram for _P. caribaea_. The starch concentration did not declineQ. These results indicate that higher foliar phosphorus concentrations are required to realize the maximum growth potential# of pines at elevated CO2.t!+ X *N1:XUSQVF2&t+FuUNF $?eC^378^Plant Physiol.6F| t{^FE;FtQ t.L8E~rntsM^tF.T8]ZrJPsM}t&kA^378^Needles from phosphorus deficient seedlings of _Pinus radiata_ D. Don grown for 8 weeks at either 330 or 660 uL CO2/$DlL displayed chlorophyll _a_ fluorescence induction kinetics characteristic of structural changes within the thylakoid chlo$Pmroplast membrane, _i.e._, constant yield fluorescence (Fo) was increased and induced fluorescence ([Fp-Fi]/Fo) was reducedn. The effect was greatest in the undroughted plants grown at 660 uL CO2/L. By week 22 at 330 uL CO2/L acclimation to P def$Soiciency had occurred as shown by the similarity in the fluorescence characteristics and maximum rates of photosynthesis of$cp the needles from the two P treatments. However, acclimation did not occur in the plants grown at 660 uL CO2/L. The light qsaturated rate of photosynthesis of needles with adequate P was higher at 660 uL CO2/L than at 330 uL CO2/L, whereas photo$frsynthesis of P deficient plants showed no increase when grown at the higher CO2 concentration. The average growth increase$qs due to CO2 enrichment was 14% in P deficient plants and 32% when P was adequate. In drought stressed plants grown at 330 $ttuL CO2/L, there was a reduction in the maximal rate of quenching of fluorescence (Rq) after the major peak. Constant yieldu fluorescence was unaffected but induced fluorescence was lower. These results indicate that electron flow subsequent to p$xvhotosystem II was affected by drought stress. At 660 uL CO2/L this response was eliminated showing that CO2 enrichment imp$wroved the ability of the seedlings to acclimate to drought stress. The average growth increase with CO2 enrichment was 37% in drought stressed plants and 19% in unstressed plants.x;r ƋFF1 y~2]_^Y[XPSQVWUz%7$y156^4^Conroy,J P^Virgona,J M^Smillie,R M^Barlow,E W^1988^1^Influence of Drought Acclimation and CO2 Enrichment on Osmotic $zAdjustment and Chlorophyll _a_ Fluorescence of Sunflower during Drought^17^86^^1108-1115^^^^^^^^^^383^^^^^^^^^^^sunflower/Helianthus annuususۿ+tUP3Ҿ.rAF&u9VvtF&;v F&;Dr^&;\s&\^&D#+ҏw3;sX@Ⰻ$iC^381^Plant Physiol.+t03Ҿr &T&t&u;VrV;VrV@Ӌ+t+3Ҿ}r&T&D u;VrV;Vr$}A^381^Osmotic adjustment occurred during drought in expanded leaves of sunflowers (_Helianthus annuus_ var Hysun 30) which$~ had been continuously exposed to 660 microliters CO2 per liter or had been previously acclimated to drought. The effect was greatest when the treatments were combined and was negligible in nonacclimated plants grown at 340 microliters CO2 per $liter. The concentrations of ethanol soluble sugars and potassium increased during the drought but they did not account fo$r the osmotic adjustment. The delay in the decline in conductance and relative water content and in the loss of structural integrity with increasing drought was dependent on the degree of osmotic adjustment. Where it was greatest, conductance f$ell from 5.8 millimeters per second on the first day of drought to 1.3 millimeters per second on the fourth day and was ap$proximately the same level on the eighth day. The relative water content remained constant at 85% for three days and fell to 36% on the sixth day. There was no evidence of leaf desiccation even on the eighth day. In contrast, the conductance of$ leaves showing minimal adjustment fell rapidly after the first day of drought and was negligible after the fourth, at whi$ch time the relative water content was 36%. By the sixth day of drought, areas near the margins of the leaves were desicca$ting and the plants did not recover upon rewatering. Despite the differences in the rate of change of conductance and relative water content during drought, photosynthetic electron transport activity, inferred from measurements of chlorophyll _$a_ fluorescence _in vivo_ and PSII activity of isolated thylakoids, remained functional until desiccation occurred.G$157^1^Cooper,C F^1986^1^Carbon Dioxide Enhancement of Tree Growth at High Elevations^48^231^^859^^^^^^^^^^386^^^^^^^^^^^bristlecone pine/limber pineneRU|w LAvO${ssG gO ]Z[XSQWVr; t!tDTG t${C^384^Sciencew ;GsC ux&O;r;rO ;w;w O+G3GW+GW^_Y[QGWGD TD% A^384^Technical comment.O =tOO Y.I7PS6u7;:~r 6Gu( t<w 2H؊6;Ut % 158^3^Coudret,A^Ferron,F^Laffray,D^1985^1^High CO2 Partial Pressure Effects on Dark and Light CO2 Fixation and Metabolism %is _Vicia faba_ Leaves^18^7^^115-126^^^^^^^^^^389^^^^^^^^^^^Vicia faba^^^^^.=NDCdDGgN@C^387^Photosynth. Res.FC*XY^PV>Du4FDIDCDDD dD*r 5**^X6 H؀>!u&165^4^Curtis,P S^Balduman,L M^Drake,B G^Whigham,D F^1990^1^Elevated Atmospheric CO2 Effects on Belowground Processes in C3 and C4 Estuarine Marsh Communities^2^71^^2001-2006^^^^^^^^^^407^^^^^^^^^^^Scirpus olneyi/Spartina patens/Distichlis spica&C^405^EcologyuC"r>0 &&3&& H&&&&t 3Ҍ^s^YXPS6D36;Dt[&t&A^405^Belowground carbon allocation is a major component of a plant's carbon budget, yet relatively little is known about the response of roots to elevated atmospheric CO2. We have exposed three brackish marsh communities dominated by perennial& macrophytes to twice ambient CO2 concentrations for two full growing seasons using open top chambers. One community was d&ominated by the C3 sedge _Scirpus olneyi_, one was dominated by the C4 grass _Spartina patens_, and one was a mixture of _&S. olneyi_, _S. patens_, and _Distichlis spicata_, a C4 grass. Root and rhizome growth were studied in the 2nd yr of expos&ure by measuring growth into peat cores previously excavated and refilled with sphagnum peat devoid of roots. Growth under" elevated CO2 resulted in an 83% increase in root dry mass per core in the _Scirpus_ community. Those roots were also sign"ificantly lower in percentage of nitrogen than roots from ambient-grown plants. There was no effect of elevated CO2 on roo"t growth or nitrogen content in the _Spartina_ community or in the C4 component of the mixed community.^ZY[XWu1 r,"ta^^^^ƀt8 Ur  _SQR6>Du.6>Et&&Etu wrC sZY[6>DtPS!166^5^Curtis,P S^Drake,B G^Leadley,P W^Arp,W J^Whigham,D F^1989^1^Growth and Senescence in Plant Communities Exposed to Elevated CO2 Concentrations on an Estuarine Marsh^34^78^^20-26^^^^^^^^^^410^^^^^^^^^^^Scirpus olneyi/Spartina patens/Distichlis spicatata~&&U&eF&E_^ZY[XQVW6D6D+t u_^YÀ> uuu tsC^408^Oecologiaut!&> u&>u&t^YXSQRVW 6DH rGEFN6 EuVI6 #SA^408^Three high marsh communities on the Chesapeake Bay were exposed to a doubling in ambient CO2 concentration for one growing season. Open-top chambers were used to raise CO2 concentrations ca. 340 ppm above ambient over monospecific communigties of _Scirpus olneyi_ (C3) and _Spartina patens_ (C4), and a mixed community of _S. olneyi_, _S. patens_, and _DistichlWis spicata_ (C4). Plant growth and senescence were monitored by serial, nondestructive censuses. Elevated CO2 resulted in increased shoot densities and delayed senescence in the C3 species. This resulted in an increase in primary productivity in _S. olneyi_ growing in both the pure and mixed communities. There was no effect of CO2 on growth in the C4 species. Thes&re results demonstrate that elevated atmospheric CO2 can cause increased aboveground production in a mature, unmanaged ecos3ystem.&Ì 6;Ds & 6D !&&6+wvـPX^V&H 167^3^Curtis,P S^Drake,B G^Whigham,D F^1989^1^Nitrogen and Carbon Dynamics in C3 and C4 Estuarine Marsh Plants Grown under% Elevated CO2 _in situ_^34^78^^297-301^^^^^^^^^^413^^^^^^^^^^^Scirpus olneyi/Spartina patens/Distichlis spicatata2%C^411^Oecologia[P&}t0&Eu%t&&Ur6 Et6 E&XPSRVW6 E6& Er<6 Eu96& E%* A^411^Carbon dioxide concentrations were elevated in three estuarine communities for an entire growing season. Open top ch$e ambers were used to raise CO2 concentrations ca. 336 ppm above ambient in monospecific communities of _Scirpus olneyi_ (C3#) and _Spartina patens_ (C4), and a mixed community of _S. olneyi_, _S. patens_ and _Distichlis spicata_ (C4). Nitrogen and carbon concentration (% wt) of aboveground tissue was followed throughout growth and senescence. Green shoot %N was reduced and %C was unchanged under elevated CO2 in _S. olneyi_. This resulted in a 20%-40% increase in tissue C/N ratio. There was no effect of CO2 on either C4 species. Maximum aboveground N (g/m2) was unchanged in _S. olneyi_, indicating that increased productivity under elevated CO2 was dependent on reallocation of stored N. There was no change in the N recovery efficiency of _S. olneyi_ in pure stand and a decrease in the mixed community. Litter C/N ratio was not affected by elevated CO2 suggesting that decomposition and N mineralization rates will also remain unchanged. Continued growth responses to elevated CO2 could, however, be limited by the ability of _S. olneyi_ to increase the total aboveground N pool.G_[ 168^2^Curtis,P S^Teeri,J A^1992^1^Seasonal Responses of Leaf Gas Exchange to Elevated Carbon Dioxide in _Populus grandidentata_^32^22^^1320-1325^^^^^^^^^^416^^^^^^^^^^^Populus grandidentatata Michx.4E4Eێ8E&C;,Ev{QEg u C^414^Can. J. For. Res.E-[Z&t2E&&1SREE2E&&& & &!Z["aˋD`EYA^414^Rising atmospheric carbon dioxide concentrations may have important consequences for forest ecosystems. We studied above- and below-ground growth and leaf gas exchange responses of _Populus grandidentata_ Michx. to elevated CO2 under natural forest conditions over the course of a growing season. Recently emerged _P. grandidentata_ seedlings were grown in native, nutrient-poor soils at ambient and twice ambient (707 ubar (1 bar=100 kPa)) CO2 partial pressure for 70 days in open-top chambers in northern lower Michigan. Total leaf area and shoot and root dry weight all increased in high CO2 grown plants. Photosynthetic light and CO2 response characteristics were measured 28, 45, and 68 days after exposure to elevated CO2. In ambient grown plants, light saturated assimilation rates increased from day 28 to day 45 and then declined at day 68 (15 September). This late-season decline, typical of senescing _Populus_ leaves, was due both to a decrease in the initia!l slope of the net CO2 assimilation versus intercellular CO2 partial pressure relationship and to decreased CO2 saturated "assimilation rates. Specific leaf nitrogen (mg N/cm2 leaf area) did not change during this period, although leaf carbon co#ntent and leaf weight (mg/cm2) both increased. In ambient grown plants stomatal conductance also declined at day 68. In co$ntrast, plants grown at elevated CO2 showed no late-season decline in photosynthetic capacity or changes in leaf weight, s%uggesting a delay in senescence with long-term exposure to high CO2. High CO2 grown plants also maintained photosynthetic &sensitivity to increasing Ci throughout the exposure period, while ambient CO2 grown plants were insensitive to Ci above 4'00 ubar on day 68. These results indicate the potential for direct CO2 fertilization of _P. grandidentata_ in the field and provide evidence for a new mechanism by which elevated atmospheric CO2 could influence seasonal carbon gain. @ 169^1^Dahlman,R C^1993^1^CO2 and Plants: Revisited^123^104/105^^339-355^^^^^^^^^^419^^^^^^^^^^^^^^^^arecharacteristicwne_ _max_ L. Merr. cv. Tamahomare) were subjected to CO2 enrichment and/or NO3-N application (50 and 300 ppm), and the gro+A^417^The decade-long USA research program on the direct effects of CO2 enrichment on vegetation has achieved important mi,lestones and has produced a number of interesting and exciting findings. Research beginning in 1980 focused on field exper-iments to determine whether phenomena observed in the laboratory indeed occurred in natural environments. The answer is ye.s. Data obtained from numerous field studies show mixed response of crop and native species to CO2 enrichment however. Nea/rly all experiments demonstrate that plants exhibit positive gain when grown at elevated CO2; although the magnitude varie0s greatly. Most crop responses range from 30 to 50% increase in yield. Results from long-term experiments with woody speci1es and ecosystems are even more variable. Huge growth responses (100 to nearly 300% increase relative to controls) are rep2orted from several tree experiments and the salt-marsh ecosystem experiment. Other results from experiments with woody spe3cies and the tundra ecosystem suggest little or no effect of CO2 on physiology, growth or productivity. Numerous studies o4f the physiology of the CO2 effect are continuing in attempts to understand controlling mechanisms and to explain the vari5able growth responses. Particular emphasis needs to be given to physiological measures of interactions involving the CO2 e6ffect and other environmental influences, and to the wide-ranging observations of photosynthesis acclimation to CO2. Prospects for future research are identified.proximatedwiththehelpofthelognormalfunction.MatveyevYu8170^3^Dahlman,R C^Strain,B R^Rogers,H H^1985^1^Research on the Response of Vegetation to Elevated Atmospheric Carbon Dioxide^9^14^^1-8^^^^^^^^^^422^^^^^^^^^^^^^eview/agriculture/ecosystem level CO2 responsesationcoefficientsfordifferentlC^420^J. Environ. Qual.btainedthatallowonetojudgeaboutbaricandpressureformationsrelatedtocloudfieldformati;A^420^The global rise in atmospheric CO2 is an established phenomenon. Irrespective of whether a CO2-induced climate changease the rate of photosynthesis. Quantitative information on the CO2-induced growth response for field situations is neede?d for assessments of (i) possible benefits to agriculture, (ii) the amount of fossil C that can be sequestered by CO2-acce@lerated growth of the biosphere, and (iii) unknown or unidentified effects of CO2 on the physiology, structure, and functiAon of plants and ecosystems. Along with knowledge of CO2 effects on climate and other factors, information on direct plantB effects will be used in comprehensive evaluations of policy options related to increasing atmospheric CO2. Herein, a discCussion of the plan by the U.S. Department of Energy (DOE) to address the CO2 problem is presented along with research results from two programs, one agricultural and the other ecological.ocontainsinformationonoptical,electricalandradiatE171^2^Davis,T D^Potter,J R^1989^1^Relations between Carbohydrate, Water Status and Adventitious Root Formation in Leafy PeFa Cuttings Rooted under Various Levels of Atmospheric CO2 and Relative Humidity^44^77^^185-190^^^^^^^^^^425^^^^^^^^^^^Pisum sativumum L.ngrad,p.3749.Resultsofexperimentalresearchofhighlevelcloudmicrostructure P-(4 c9C^423^Physiol. Plant.rologicalObservatoryduringthe80iesarereviewed.ItisshownthattheparticlesizespectrumIA^423^Three levels of atmospheric CO2 and 2 levels of relative humidity (RH) during the rooting period were tested for theJir effect on several factors presumed to influence adventitious root formation in leafy pea (_Pisum sativum_ L. cv. AlaskaK) cuttings. Compared to normal CO2 levels (350 uL/L), neither 1800 nor 675 uL/L CO2 affected the rooting percentage or theL number of roots per cutting. However, 1800 uL/L CO2 increased root and shoot dry weight, root length, carbohydrate levelsM in the base of the cuttings and water potential (w) of cuttings compared to normal levels of CO2. Compared to 87% RH, 55N% RH decreased all of the above parameters, including the number of roots per cutting. A polyvinyl chloride antitranspiranOt (which partially blocks stomata and slows photosynthesis) applied simultaneously with 87% RH increased w and root lengtPh but lowered all of the other above parameters, compared to 87% RH without antitranspirant. Increasing current photosynthQate (products of photosynthetic activity after excision), carbohydrate, or w either alone or together was associated withR increased root system size but not necessarily with increased rooting percentage or root number. The data are consistent Swith a hypothesis that the number of roots per cutting increased with increasing current photosynthate and carbohydrate unTtil some other factor became limiting. Also, the effect of w on rooting percentage and root number was mediated through its effect on current photosynthate and carbohydrate.orcalculatingsmallanglescatteringoncirruscloudparticlesisshV172^2^de Bruin,H A R^Jacobs,C M^1993^1^Impact of CO2 Enrichment on the Regional Evapotranspiration of Agro-ecosystems, a Theoretical and Numerical Modelling Study^123^104/105^^307-318^^^^^^^^^^428^^^^^^^^^^^^^^^^rd,theaveragevaluesoffull)A^1073^A wild soybean variety (_Glycine_ _soja_ Sieb. and Zucc. line Nakei-No. 1) and a cultivated soybean variety (_GlyciYA^426^This paper gives a brief overview of factors determining evapotranspiration of vegetated surfaces. It indicates whicZh of these factors are sensitive to CO2 enrichment. A qualitative analysis is presented of the impact of large scale clima[te changes. Data in literature indicate that the surface resistance of vegetated areas may change within the range -25% an\d +50% if the atmospheric CO2-concentration doubles. The impact of such changes on regional scale transpiration is evaluat]ed using a numerical model in which the interaction between the evapotranspiration and the Planetary Boundary Layer is acc^ounted for. It is concluded that the impact of CO2 enrichment on the transpiration at the regional scale is relatively sma_ll for aerodynamically smooth surfaces (between +7% and -11%). For aerodynamically rough surfaces the effects are somewhat larger (between +15% and -21%).scalestructureandinparticularonthoseofitscharacteristicswhichaffecttheproca173^2^de Cortzar,V G^Nobel,P S^1990^1^Worldwide Environmental Productivity Indices and Yield Predictions for a CAM Plant,s _Opuntia ficus-indica_, Including Effects of Doubled CO2 Levels^46^49^^261-279^^^^^^^^^^431^^^^^^^^^^^Opuntia ficus-indicGC^429^Agric. For. Meteorol.uscloudparticles.RadiationPropertiesofCirrusClouds.Moscow,6572.AnensemblemethoddA^429^The productivity of _Opuntia ficus-indica_ was predicted for 253 regions on a worldwide basis using data from 1464 weeather stations within 60 of the equator. First, the climatic data were used to calculate daily values of a PAR index, a ftemperature index and a water index. These indices, each of which has a maximum value of unity when that environmental facgtor is not limiting net CO2 uptake by _O. ficus-indica_ over a 24-h period, were multiplied together to give an environmenhtal productivity index, which indicates how the three environmental factors limit net CO2 uptake and hence productivity. Tihe photosynthetically active radiation (PAR) index for a canopy of closely spaced plants that have a high productivity perj unit ground area was >/= 0.20 for 25% of the earth's land surface. The temperature index annually was >/= 0.50 for 81% ofk the earth's land surface, indicating that local temperatures do not greatly limit net CO2 uptake by this species. The watler index was >/= 0.50 for 79% of the earth's surfaces for _O. ficus-indica_ which exhibits Crassulacean acid metabolism wimth its accompanying high water-use efficiency. Predicted productivities for _O. ficus-indica_ without irrigation were at lneast 10 metric tons/ha/y, the value for many important annual agronomic crops, for 41% of the earth's land area. Irrigatioon increased such high productivity regions to 77% of the earth's land surface area within 60 of the equator. For simulatipons that included the worldwide changes in PAR, temperature and rainfall patterns that will most likely accompany a doubliqng in the ambient CO2 level, the high productivity of 10 tons/ha/y was predicted to occur for 54% of the earth's land surfrace area. Under elevated CO2, the predicted productivity of _O. ficus-indica_ increased for most of the U.S.A. and a productivity of 32 tons/ha/y was predicted for western South America.ividualparticle.Itsapplicationforcalculatingsmallacateringoncirruscloudparticlesisshownandatypicalexamplecharacterizingthephysicsoftheprocessisconsideru174^4^Del Castillo,D^Acock,B^Reddy,V R^Acock,M C^1989^1^Elongation and Branching of Roots on Soybean Plants in a Carbon Dioxide-Enriched Aerial Environment^4^81^^692-695^^^^^^^^^^434^^^^^^^^^^^soybean/Glycine maxax (L.) Merr.ingincrease.ThbC^432^Agron. J.resultsintheappearanceofnoiseintheangularbehaviorofscatteringintensity.IndicatrixmaximadecxA^432^Plants grown in high CO2 concentrations ([CO2]) often have a higher root weight than those grown in low [CO2]. It isy usually assumed that the plants with this extra root weight can explore a greater volume of soil and will, therefore, havze more water available to them. To test this assumption, soybean [_Glycine max_ (L.) Merr. cv. Forrest] plants were grown {in outdoor, sunlit plant-growth chambers in [CO2] of 330, 450, 600, and 800 uL/L throughout the growing season. The soil c|ontainers in the growth chambers had a glass side and new root growth appearing at the glass was measured and marked two o}r three times each week. Root weight at the end of the season (93 d after emergence) was 26 to 31% higher in [CO2]-enriche~d chambers compared with the 330 uL/L treatment, and cumulative root length was approximately proportional to [CO2]. However, CO2 treatment did not affect the rate of elongation of individual root axes. Instead, there was a significant linear increase in the number of actively growing roots with increased [CO2]. Plants grown in 800 uL/L had 65% more actively growing roots than plants grown in 330 uL/L. Thus, growing a plant in high [CO2] enabled it to explore a given volume of soil more thoroughly, but did not increase the volume of soil explored.cordingsfortheBlind.Ihave35daysofunusedconsul175^5^Delgado,E^Azcon-Bieto,J^Aranda,X^Palazon,J^Medrano,H^1992^1^Leaf Photosynthesis and Respiration of High CO2-grown Tobacco Plants Selected for Survival under CO2 Compensation Conditions^17^98^^949-954^^^^^^^^^^437^^^^^^^^^^^tobacco/Nicotiana tabacum^^ L. % GV 04#fU> AvC^435^Plant Physiol.anovWP( U$  HP LaserJeA^435^Four self-pollinated, doubled-haploid tobacco, (_Nicotiana tabacum_ L.) lines (SP422, SP432, SP435, and SP451), selected as haploids by survival in a low CO2 atmosphere, and the parental cv Wisconsin-38 were grown from seed in a growth room kept at high CO2 levels (600-700 parts per million). The selected plants were much larger (especially SP422, SP432, and SP451) than Wisconsin-38 nine weeks after planting. The specific leaf dry weight and the carbon (but not nitrogen and sulfur) content per unit area were also higher in the selected plants. However, the chlorophyll, carotenoid, and alkaloid contents and the chlorophyll _a/b_ ratio varied little. The net CO2 assimilation rate per unit area measured in the growth room at high CO2 was not higher in the selected plants. The CO2 assimilation rate _versus_ intercellular CO2 curve and the CO2 compensation point showed no substantial differences among the different lines, even though these plants were selected for survival under CO2 compensation point conditions. Adult leaf respiration rates were similar when expressed per unit area but were lower in the selected lines when expressed per unit dry weight. Leaf respiration rates were negatively correlated with specific leaf dry weight and with the carbon content per unit area and were positively correlated with nitrogen and sulfur content of the dry matter. The alternative pathway was not involved in respiration in the dark in these leaves. The better carbon economy of tobacco lines selected for low CO2 survival was not apparently related to an improvement of photosynthesis rate but could be related, at least partially, to a significantly reduced respiration (mainly cytochrome pathway) rate per carbon.WPSQW3&/&߁DLuY[XW,3 u<u uN;t |\t|176^5^Delgado,E^Parry,M A J^Lawlor,D W^Keys,A J^Medrano,H^1993^1^Photosynthesis, Ribulose-1,5-_bis_phosphate Carboxylase and Leaf Characteristics of _Nicotiana tabacum_ L. Genotypes Selected by Survival at Low CO2 Concentrations^39^44^^1-7^^^^^^^^^^440^^^^^^^^^^^tobacco/Nicotiana tabacumum L.Q&E>DuDD>6D_u&E6D&E8D~t&E9D3&2G*C^438^J. Exp. Bot.>Du4>t*7 jN< tF_rFNdpRr#6D8D:D6.]>!<uI!.>. from field cores appears to be related to the annual cycle of net photosynthesis in _S_. _alterniflora_._.A^441^The response of _Plantago major_ ssp. _pleiosperma_ plants, grown on nutrient solution in a climate chamber, to a doubling of the atmospheric CO2 concentration was investigated. Total dry matter production was increased by 30% after 3 weeks fo exposure, due to a transition stimulation of the relative growth rate (RGR) during the first 10 days. Thereafter RGR returned to the level of control plants. Photosynthesis, expressed per unit leaf area, was stimulated during the first two weeks of the experiment, thereafter it dropped and nearly reached the level of the control plants. Root respiration was not affected by increased atmospheric CO2 levels, whereas shoot, dark respiration was stimulated throughout the experimental period. Dry matter allocation over leaves stems and roots was not affected by the CO2 level. SLA was reduced by 10%, which can partly be explained by an increased dry matter content of the leaves. Both in the early and later stages of the experiment, shoot respiration accounted for a larger part of the carbon budget in plants grown at elevated atmospheric CO2. Shifts in the total carbon budget were mainly due to the effects on shoot respiration. Leaf growth accounted for nearly 50% of the C budget at all stages of the experiment and in both treatments.D:r@Dr0D@r%3:|. 178^2^den Hertog,J^Stulen,I^1990^3^The Effects of an Elevated Atmospheric CO2-concentration on Dry Matter and Nitrogen Allocation^The Greenhouse Effect and Primary Productivity in European Agro-ecosystems; 5-10 April 1990; Wageningen, The Netherlands^Pudoc^Wageningen^27-30^^^^^^^^^^^^^^^^^^^^^Plantago major/broadleaf plantain/Urtica dioica/stinging nettle^^^^^^^^^^Goudriaan,J^van Keulen,H^van Laar,HHar,H H`Z[X4:rFFr7DNDVr,DXr$DRrDPDTrD^r D`179^3^DeWitt,C A^Waldron,R E^Lambert,J R^1983^5^Effects of Carbon Dioxide Enrichment on Nitrogen Fixation in Soybeans 1982^U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C^^^^^^^^^^^^^^^^^^^^^^^^soybean/Glycine max^^010 in Green Report Series^Response of Vegetation to Carbon Dioxide^^ Dioxi180^3^Dietz,K-J^Schreiber,U^Heber,U^1985^1^The Relationship between the Redox State of Q(A) and Photosynthesis in Leaves a"t Various Carbon-dioxide, Oxygen and Light Regimes^51^166^^219-226^^^^^^^^^^448^^^^^^^^^^^Helianthus annuus/Fagus sylvatic!C^446^Planta W -,&-&-    13AugustA^446^The response of chlorophyll fluorescence elicited by a low-fluence-rate modulated measuring beam to actinic light and to superimposed 1-s pulses from a high-fluence-rate light source was used to measure the redox state of the primary acceptor, Q(A) of photosystem II in leaves which were photosynthesizing under steady-state conditions. The leaves were exposed to various O2 and CO2 concentrations and to different energy fluence rates of actinic light to assess the relationship between rates of photosynthesis and the redox state of Q(A). Both at low and high fluence rates, the redox state of Q(A) was little altered when the CO2 concentration was reduced from saturation to about 600 uL/L although photosynthesis was decreased particularly at high fluence rates. Upon further reduction in CO2 content the amount of reduced Q(A) increased appreciably even at low fluence rates where light limited CO2 reduction. Both in the presence and in the absence of CO2, a more reduced Q(A) was observed when the O2 concentration was below 2%. Q(A) was almost fully reduced when leaves were exposed to high fluence rates under nitrogen. Even at low fluence rates, Q(A) was more reduced in shade leaves of _Asarum europaeum_ and _Fagus sylvatica_ than in leaves of _Helianthus annuus_ and _Fagus sylvatica_ grown under high light. Also, in shade leaves the redox state of Q(A) changed more during a transition from air containing 350 uL/L CO2 to CO2-free air than in sun leaves. The results are discussed with respect to the energy status and the CO2-fixation rate of leaves.181^1^Dons,C^1988^1^Effects of Long-Term CO2 Enrichment under Different Irradiance Regimes on Growth and Photosynthesis in _Lemna gibba_^42^22^^328-334^^^^^^^^^^451^^^^^^^^^^^Lemna gibba/duckweeded@C^449^PhotosyntheticaQV @srDD Ƈ؉D^YV6؋D؋D@s^SW^ج<#t uA^449^Cultivation in CO2-enriched air increased the growth rate of _Lemna gibba_ only when day/night light cycling was used. Starch content increased with CO2 enrichment and irradiance (_I_). Reduced CO2 assimilation and growth in plants grown under high continuous _I_ and CO2-enriched air may be due to high starch levels. Changes in leaf area ratio and dry mass content were associated with increased starch content. Also morphological changes occurred in high-CO2-grown plants.O&182^1^Doorduin,J C^1990^1^Effects of CO2 and Plant Density on Growth and Yield of Glasshouse Grown Freesias^15^268^^171-177^^^^^^^^^^454^^^^^^^^^^^freesiaia9b6S~6H~>g7t2ɆkN>g7~g7H~fNkH~S~F2):&C^452^Act. Hort.NˀNPSQVWu >utV t *&G uF t3ޚ-Tr7&&2'3& lA^452^It has been demonstrated for many glasshouse crops that increasing the CO2 concentration leads to improved quality and yield, while concentrations below the ambient level lead to loss of quality and yield. Relatively few experimental data are known for freesia in this area and on freesia holdings CO2 enrichment is applied only to a limited extent. For this reason in an experiment 4 CO2 concentrations were combined with 4 plant densities to investigate the effect of CO2 on quality and yield of the cultivar 'Blue Heaven'. The CO2 concentrations realised were 265, 360, 560 and 860 ppm. Plant densities were 57, 78, 100 and 121 corms per net square metre. The concentration of 265 ppm resulted in a 20% lower yield of stems, corms and cormlets and a reduction of stem quality as compared to 360 ppm. Increasing the concentration to 560 ppm resulted in a 20% higher yield and an improved quality as compared to 360 ppm. Levels exceeding 560 ppm did not improve yield or quality. Higher plant densities did not give higher yields but evidently reduced quality. Vase life was not affected by differences in CO2 concentrations or plant densities.҆t€t%3: rƾ €t3 184^3^Downton,W J S^Grant,W J R^Chacko,E K^1990^1^Effect of Elevated Carbon Dioxide on the Photosynthesis and Early growth of Mangosteen (_Garcinia mangostana_ L.)^53^44^^215-225^^^^^^^^^^460^^^^^^^^^^^mangosteen/Garcinia mangostanana L.| tC^458^Scientia Hortic.^[XÃ'X'PPSVȚTr>et ȚTs^[Xr/' PSVȚT^[Xr''A^458^The Mangosteen is a potentially important new crop for tropical northern Australia if its long establishment time can be substantially reduced. The effect of enriching the atmosphere with up to 1000 ubar CO2 on the growth and photosynthesis of mangosteen seedlings was examined over the course of a year in an attempt to accelerate early plant development. It was initially found to be necessary to reduce photon irradiance from 450 to 200 umol photons/m2/s (400-700 nm) to overcome photoinhibition of photosynthesis, and to reduce CO2 from 1000 to 800 ubar to encourage greening of newly formed leaves. A major effect of CO2 enrichment was to stimulate earlier lateral branching which accelerated the development of leaf area and plant carbon gain. Photosynthetic rates of mangosteen leaves were found to be very low and the 800-ubar CO2 atmosphere increased CO2 fixation by 40-60% compared to control leaves measured at 400 ubar CO2. As a result, total plant dry weigh t increased by 77%. The stimulatory effect of CO2 was greatest on root and stem dry weight, which doubled. Although a smal ler proportion of dry weight was partitioned into leaves compared with control plants, CO2 enrichment increased average le af size by about 10%, specific leaf dry weight by 17% and total leaf area by 28%. By comparison, plants from the same apom ictic seedling population grown under shadehouse conditions in Darwin, Australia, developed more slowly, consistent with d escriptions in the literature, and were substantially smaller and lower in dry weight compared to the plants grown under c ontrolled conditions, even in the absence of CO2 enrichment, and had not developed lateral branches by harvest time. Reaso ns for this difference are suggested which may enable improvement of the early growth of mangosteen plants under field nursery conditions..F;Vw r;FsFVF;Vr w;FvFV;ׁw ;ՁwgvD FFDFV+FVD 185^1^Doyle,T W^1987^3^Seedling Response to CO2 Enrichment under Stressed and Non-stressed Conditions^Proceedings of the I nternational Symposium on Ecological Aspects of Tree Ring Analysis^NTIS^Springfield, Virginia^494-500^^^^^^^^^^462^^^^^^^^^^^loblolly pine/sweetgum/Liquidambar styraciflua/Pinus taeda^^^^^^^^^^Jacoby,GC^Hornbeck,JWck,JWW\D sse A^461^Loblolly pine and sweetgum seedlings were obtained from a Duke University phytotron study, where three groups were g rown in different atmospheres of CO2 (i.e., 350, 500, 650 ppmv). Seedlings were grown over three growing seasons, and incl uded a set of water-stressed and non-stressed individuals. X-ray densitometry was used to evaluate growth and density char acteristics of the wood samples. Cross-sectional discs of these samples were radiographed and scanned with a microdensitom eter to determine ring width, area, density and mass for each growth year. Results indicated significant differences in wo od production (ring width, area and mass) between the lowest treatment of CO2 (350 ppmv) and the higher concentration (500  and 650 ppmv) treatments. While only a few density parameters demonstrated significant changes with increasing CO2, almos t all showed a systematic increase in density with increasing CO2 concentration. Ring area and mass displayed the greatest  degree of change between treatments. Induced drought effects appeared only to strengthen the CO2-growth association. Thes e findings suggest that naturally stressed trees are also likely to exhibit some growth effect with increasing atmospheric  CO2. And because the greatest margin of response existed between 350 and 500 ppmv, this study emphasizes the importance a nd need to determine growth responses at preindustrial era CO2 concentrations in order to more accurately identify the postulated 'fertilizer' effect on modern forests.:^Z[XQ= sȸ3YV&&Ie;:^PRI#:r<&E&U& 186^1^Drake,B G^1992^1^A Field Study of the Effects of Elevated CO2 on Ecosystem Processes in a Chesapeake Bay Wetland^25^40^^579-595^^^^^^^^^^465^^^^^^^^^^^Spartina patens/Scirpus olneyi/Distichlis spicataasBY[QRUt}&C^463^Aust. J. Bot.&@u& t22H   &@XV *\*FJ^#:ZYUu@ A^463^Open top chambers are being used in a long-term project to determine the effects of elevated CO2 on ecosystem proces ses on a Chesapeake Bay wetland. Three communities are studied: mono-specific stands of the C3 sedge, _Scirpus olneyi_, an d the C4 grass, _Spartina patens_, and a mixed community of these two species and the C4 grass, _Distichlis spicata_. Trea tment began in the spring of 1987 and will continue through the 1994 growing season. During the first 4 years of exposure,  elevated CO2 had the following effects on mono-specific stands of the C3 sedge, _Scirpus olneyi_: increased quantum yield and photosynthetic capacity, reduced dark respiration, increased numbers of shoots, roots and rhizomes, reduced nitrogen !concentration of all tissues, increased nitrogen fixation and increased ecosystem carbon accumulation. In a mixed communit "y of the sedge and C4 grass species, _Spartina patens_ and _Distichlis spicata_, biomass of the C3 component increased ove #r 100% and this was accompanied by decreased biomass in the C4 component of the community. Elevated CO2 reduced water loss $, increased water potential and delayed senescence in all three species. Many factors contributed to CO2 stimulated carbon % accumulation in the plant community dominated by the C3 sedge, _Scirpus olneyi_, including: sustained high photosynthetic & capacity, decreased respiration, delayed senescence, and allocation of the additional carbon to roots and rhizomes. The c 'omplex interaction of these diverse responses suggests that the rising atmospheric CO2 may have a significant impact on ecosystem processes. GZ_YRVWB&wtr!:s>u>u>u>9t} e,s )187^6^Drake,B^Arp,W^Curtis,P S^Leadley,P W^Sager,J^Whigham,D^1986^5^Effects of Elevated CO2 on Chesapeake Bay Wetlands. I. * Description of the Study Site^U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C^^^^^^^^^^^^^^^^^^^^!/^^^^Spartina patens/Distichlis spicata/Scirpus olneyi^^034 in Green Report Series^Response of Vegetation to Carbon Dioxide ,188^6^Drake,B G^Arp,W^Craig,J^Curtis,P S^Leadley,P W^Whigham,D^1987^5^Effects of Elevated CO2 on Chesapeake Bay Wetlands. -II. Gas Exchange and Microenvironment in Open Top Chambers^U.S. Dept. of Energy, Carbon Dioxide Research Division, Washing .ton, D.C^^^^^^^^^^^^^^^^^^^^^^^^Scirpus olneyi/Spartina patens/Distichlis spicata^^038 in Green Report Series^Response of Vegetation to Carbon Dioxide^^3\$${_^ZX_^ZXQVu<u3ɴ@9:s:s :s tFFuȊ 0189^12^Drake,B G^Arp,W J^Balduman,L^Curtis,P S^Johnson,J^Kabara,D^Leadley,P W^Pockman,W T^Seliskar,D^Sutton,M L^Whigham,D^ 1Ziska,L^1989^5^Effects of Elevated CO2 on Chesapeake Bay Wetlands. IV. Ecosystem and Whole Plant Responses. April-November 2 1988^U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C^^^^^^^^^^^^^^^^^^^^^^^^Scirpus olneyi/Sparti 3na patens/Distichlis spicata/Glycine max/soybean/Lycopersicon esculentum/tomato/Manihot esculentum/Amaranthus hypochondria 4cus/amaranth/Acacia mangium/Ficus obtusifolia/Paspallum conjugatum/Pharus latifolia/Psychotria limonensis/Tabebuia rosea^^051 in Green Report Series^Response of Vegetation to Carbon Dioxide^^arbon Dioxide^^]] EtwM M Et 6190^12^Drake,B G^Arp,W J^Balduman,L^Cousimano,R^Dacey,J^D'Abundo,D^Hogan,K^Long,S^Pockman,W T^Utley,P^Villegas,A C^Whigham 7,D^1990^5^Effects of Elevated Co2 on Chesapeake Bay Wetlands. V. Ecosystem and Whole Plant Responses. April-November 1989^ 8U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C^^^^^^^^^^^^^^^^^^^^^^^^Scirpus olneyi/Spartina patens^^055 in Green Report Series^Response of Vegetation to Carbon Dioxide^^Ȋ2SS^'.<=s[d'.& :191^6^Drake,B G^Curtis,P S^Arp,W J^Leadley,P W^Johnson,J^Whigham,D^1988^5^Effects of Elevated CO2 on Chesapeake Bay Wetlan ;ds. III. Ecosystem and Whole Plant Responses in the First Year of Exposure, April-November 1987^U.S. Dept. of Energy, Carb 192^2^Drake,B G^Leadley,P W^1991^1^Canopy Photosynthesis of Crops and Native Plant Communities Exposed to Long-term Elevated CO2^16^14^^853-860^^^^^^^^^^473^^^^^^^^^^^Scirpus olneyi/Spartina patensns>tit3Rs C^471^Plant Cell Environ.UHϚsu&&¿XP>t t +XPR& AA^471^There have been seven studies of canopy photosynthesis of plants grown in elevated atmospheric CO2: three of seed cr Bops, two of forage crops and two of native plant ecosystems. Growth in elevated CO2 increased canopy photosynthesis in all C cases. The relative effect of CO2 was correlated with increasing temperature: the least stimulation occurred in tundra ve Dgetation grown at an average temperature near 10C and the greatest in rice grown at 43C. In soybean, effects of CO2 were E greater during leaf expansion and pod fill than at other stages of crop maturation. In the longest running experiment wit Fh elevated CO2 treatment to date, monospecific stands of a C3 sedge, _Scirpus olneyi_ (Grey), and a C4 grass, _Spartina pa Gtens_ (Ait.) Muhl., have been exposed to twice normal ambient CO2 concentrations for four growing seasons, in open top cha Hmbers on a Chesapeake Bay salt marsh. Net ecosystem CO2 exchange per unit green biomass (NCEb) increased by an average of I48% throughout the growing season of 1988, the second year of treatment. Elevated CO2 increased net ecosystem carbon assimilation by 88% in the _Scirpus olneyi_ community and 40% in the _Spartina patens_ community.Pfv DlȿD K193^5^Drake,B G^Leadley,P W^Arp,W J^Nassiry,D^Curtis,P S^1989^1^An Open Top Chamber for Field Studies of Elevated Atmosphe Lric CO2 Concentration on Saltmarsh Vegetation^37^3^^363-371^^^^^^^^^^476^^^^^^^^^^^Scirpus olneyi/Spartina patens/Distichlis spicata^^^^stichlis spicata (L.) Greene]XPV >ǿu@sv3FF~:r}]^ON=VN~u ?C^474^Funct. Ecol.u^$FNu-FV^F&EG&FFNN뜋v@s~ud^XPSVUu& OA^474^Small open top chamber (0.8 m x 1.0 m) were developed to maintain elevated CO2 concentrations in three plant communi Pties in a brackish marsh ecosystem. Mean annual CO2 concentrations were 340 +/- 22 uL/L in chambers which received no adde Qd CO2 and 686 +/- 30 uL/L in chambers with elevated CO2 concentrations. Light quality was not effected in the photosynthet Rically active wavelengths but the chamber reduced light quantity by 10%. Night-time air temperatures inside the chamber (_ STi_) averaged 2C above air temperature outside the chamber (_To_) due to heating from the air blowers. Air temperature pr Tofiles through the plant canopy and boundary layer showed that daytime temperature differences (_Ti -To_) were greater tha Un night-time differences and this day/night difference also depended on the plant community. Effects of the chamber on the V micro-environment of the plant communities resulted in a significant growth enhancement in the plant community dominated by the C3 sedge _Scirpus olneyi_ Grey but not in the other two communities.DD^2>! tE]D\ X194^3^Drake,B G^Rogers,H H^Allen,LH,Jr^1985^3^Methods of Exposing Plants to Elevated Carbon Dioxide^Direct Effects of Incr Yeasing Carbon Dioxide on Vegetation^Dept. of Energy, Carbon Dioxide Research Division^Washington, D.C.^11-51^^^^^^^DOE/ER-0238^^^^^^^^^^^^^^^^^^^^^^^^Strain,BR^Cure,JDGG^J @^Y[XPSVt7\DG@uGr [195^4^du Cloux,H C^Andre,M^Daguenet,A^Massimino,J^1987^1^Wheat Response to CO2 Enrichment: Growth and CO2 Exchanges at Two Plant Densities^39^38^^1421-1431^^^^^^^^^^480^^^^^^^^^^^wheat/Triticum aestivumum L.PQR>t9,!u MC^478^J. Exp. Bot.ZYXx778J8-1S,+(}*(JN 9 d+*#pe &3B3u   u) ^A^478^The vegetative growth of wheat (_Triticum aestivum_ L., var. Capitole) was followed for almost 40 d after germinatio _n in controlled conditions. Four different treatments were carried out by combining two air concentrations of CO2, either `normal (330 mm3/dm3) or doubled (660 mm3/dm3) with two plant densities, either 200 plants/m2 or 40 plants/m2. Throughout t ahe experiment the CO2 gas exchanges of each canopy were measured 24 h/d. These provided a continuous growth curve for each b treatment, which were compared with dry weights. After a small stimulation at the start (first 13 d), no further effect o cf CO2 enrichment was observed on relative growth rate (RGR). However, RGR was stimulated throughout the experiment when pl dotted as a function of biomass. The final stimulation of dry weight at 660 mm3/dm3 CO2 was a factor of 1.45 at high densit ey and 1.50 at low density; contrary to other studies, no diminution of this CO2 effect on dry weight was observed over tim fe. Nevertheless, at low density, a transient additional enhancement of biomass (up to 1.70) was obtained at a leaf area in gdex (LAI) below 1. This effect was attributed to a different build up of the gain of carbon in the case of an isolated pla hnt or a closed canopy. In the former, the stimulation of leaf area and the net assimilation rate are both involved; in the i latter the enhancement becomes independent of the effect on leaf area because the canopy photosynthesis per unit ground area as a function of LAI reaches a plateau.:Y[XPN+ٚNĚNXVPSQRUP/uX)t s-AAG k196^4^du Cloux,H^Andre,M^Gerbaud,A^Daguenet,A^1989^1^Wheat Response to CO2 Enrichment: Effect on Photosynthetic and Photorespiratory Characteristics^42^23^^145-153^^^^^^^^^^483^^^^^^^^^^^wheat/Triticum aestivum^^^^.WK> \C^481^Photosynthetica~ <N}>N ~' ~ NN~ <N]_ZY[X1uN1t nA^481^The effects of doubling atmospheric CO2 concentration on photosynthesis and photorespiration were studied on wheat c oultivated for 37 or 72 d in growth chambers at a density of planting of 200 and 40 plants per m2. Net photosynthetic rate p(_Pn_) was measured continuously during the experiments and response curves to CO2 were made at intervals. Differences obs qerved between the CO2 curves of the plants grown in normal and CO2 enriched atmosphere could be explained by the greater l reaf area of the second group of plants. Photorespiration was tested by the Warburg effect or measured directly on isolated s plants by the uptake of 18-O2. Oxygen uptake was reduced by 40% by the high CO2 treatment, but high CO2 plants were ident tical to the control group when returned to the same conditions. The enhancement of dry matter production was due to the ki unetic response of _Pn_ to CO2, as there was no appreciable long-term adaptation of the kinetic characteristics of photosynthesis./DADMDEDMD:D1D0D 3G s !=:Noٚ*DsN[#.T t3P.TXPP.TXX w197^3^Dubois,D^Winzeler,M^Nosberger,J^1990^1^Fructan Accumulation and Sucrose:sucrose fructosyltransferase Activity in Stems of Spring Wheat Genotypes^12^30^^315-319^^^^^^^^^^486^^^^^^^^^^^Triticum aestivum/wheat^^^^^tXVxXVZY lC^484^Crop Sci.=:\1sN1:\1sMThdRIFFWAVECreative Voice FileWVU~FSQv D F=u*rW|T zA^484^Stems of wheat (_Triticum aestivum_ L.) accumulate water-soluble carbohydrates (WSC) during the first 3 wk after ant {hesis. These reserves can later contribute to grain filling. Two spring wheat genotypes ('Kolibri' and breeding line D) we |re tested in growth chambers to determine if they differ in the accumulation of WSC components and in the activation of su }crose:sucrose fructosyltransferase (SST) in stem tissue. Concentration of CO2 was supplied at 1000 or 300 uL CO2/L after a ~nthesis to alter photosynthate production. The WSC accumulation in the penultimate internode during the first 18 d post an thesis (DPA) was substantially higher in Genotype D than in Kolibri. The WSC accumulation up to 7 DPA was due to increases in hexoses and sucrose. Sucrose concentration was initially lower in Kolibri than in Genotype D, but increased to a compa rable level for both genotypes and both CO2 treatments. Fructan synthesis was initiated at 7 DPA. At 18 DPA, fructan was t he dominant component of WSC. Under both CO2 treatments Genotype D accumulated substantially higher fructan concentrations than Kolibri. In a second experiment, induction of SST activity was observed during the first 9 DPA in the penultimate in ternode of plants grown at 1000 and 200 uL CO2/L. There was a positive relationship between sucrose concentration and in v ivo SST activity, suggesting that sucrose induced SST activity; however, Kolibri exhibited a much lower SST activity at gi ven sucrose concentration. Thus, the low fructan synthesis of Kolibri is associated with an initial lower sucrose concentration and with a less effective activation of SST by sucrose.PSQRWV;*2N)t686868688 198^3^Duchein,M-C^Bonicel,A^Betsche,T^1993^1^Photosynthetic Net CO2 Uptake and Leaf Phosphate Concentrations in CO2 Enrich ed Clover (_Trifolium subterraneum_ L.) at Three Levels of Phosphate Nutrition^39^44^^17-22^^^^^^^^^^489^^^^^^^^^^^Trifolium subterraneum/clover^^^^^ȋF3FȋF 3FFCrIF32FFH;FvFF1v76Frys3 xC^487^J. Exp. Bot.vКH${rیFv1&76FrȚ${ЋFNyNAANd${r&&GGF;Fs@FeFry& A^487^Net CO2-uptake of sets of clover plants (_Trifolium subterraneum_ L.) was measured over 3 weeks in ambient air and i n a highly CO2-enriched atmosphere (400 Pa CO2). Phosphate (P) in the nutrient solution was varied between 0.05 mol/m3 P ( reduced P) and 2.0 mol/m3 P (high P). In ambient air, the daily increments of the daily rate of net CO2-uptake (DICU; a pa rameter related to relative growth) were higher at reduced P than at high P. Stimulation by high CO2 of net CO2-uptake in the first day was less at reduced P than at high P. In the following days, high CO2 markedly inhibited DICU at reduced P, and thus growth stimulation by high CO2 ceased after between 4 and 12 d. By contrast, at high P, DICU increased more than 2-fold upon CO2-enrichment, and thus growth stimulation by high CO2 was maintained. Intermediate results were obtained wit h half-strength Hoagland's solution (0.5 mol/m3 P). Leaf pools of inorganic ortho P, soluble esterified P, and total P dec lined markedly in high CO2 when P-nutrition had been reduced. Considerable decline also occurred in high CO2 when P-nutrit ion had been increased suggesting that P-uptake was not well tuned with net CO2-uptake (growth). It is proposed that high CO2 can perturb the P-metabolism of clover, the impairment being less at high levels of P-nutrition. With regard to high C O2 as a growth stimulus, these results demonstrate that increasing P-nutrition to a level supraoptimal in ambient air can considerably improve the growth of a C3-plant in high CO2.$:Ú\GsÚ$:Ú*Ú*Ú*Ú*Ú=:({ y y 199^3^Dugal,A^Yelle,S^Gosselin,A^1990^1^Influence of CO2 Enrichment and its Method of Distribution on the Evolution of Gas Exchanges in Greenhouse Tomatoes^29^70^^345-356^^^^^^^^^^492^^^^^^^^^^^tomato/Lycopersicon esculentumum Mill.>r C^490^Can. J. Plant Sci.Y[RWU$:ru>r&} &Ess]_ZS>r >svrr&_ &GR A^490^Net photosynthesis, stomatal conductance, internal CO2 concentration and transpiration were measured on the fifth we ll-developed and excised leaf of tomato seedlings (_Lycopersicon esculentum_ Mill. 'Vedettos') 48-83 d old. These measurem ents were taken in order to monitor the evolution of the gas exchanges of seedlings exposed to concentrations of 330 or 10 00 ppm, continuously, to 1000 ppm from 06:00 h to 10:00 h or to 1000 and 330 ppm alternately every 2 h. CO2 enrichment sub stantially increased the net photosynthesis rate of the seedlings, particularly at the beginning of the experiment. The lo ng-term effects of CO2 enrichment subsided after a few weeks of treatment. Intermittent CO2 enrichment was partially helpf ul in remedying the loss of effectiveness of the CO2 after a long period of enrichment. High CO2 concentrations reduced th e opening of the stomata. Our work shows that maintaining a high internal CO2 content in the leaves would indirectly reduc e the stomatal conductance of the seedlings. However, our results show that the long-term loss of photosynthetic efficienc y in the enriched seedlings cannot be attributed solely to an increase in the resistance of the stomata, since the interna l CO2 concentration of the leaves remains very high regardless of which method of CO2 enrichment is used. Continuous CO2 enrichment improved the water uptake efficiency of the seedlings. In French.7 u F Ft a,s 200^1^Eamus,D^1992^3^Atmospheric CO2 and Trees, from Cellular to Regional Responses^Encyclopedia of Earth System Science^Academic Press, Inc.^New York^157-169^^^^1^^^^^^^^^^^^^^^^^^^^^^;~u4_;:Y[SQV6rt<u |u4 H^Yq in the cultivated one increased by CO2 enrichment in both soybean varieties, when nitrate was not applied to the plants. 201^1^Eamus,D^1990^3^Carbon Dioxide and Plant Physiological Processes^The Greenhouse Effect and Terrestrial Ecosystems of the UK^Institute of Terrestrial Ecology, Natural Environment Research Council^Edinburgh Research Station, Bush Estate, Penicuik^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^Cannell,M G R^Hooper,M DPV6t  C^507^Bull. Soc. Ecophysiol.W6WWGW&+ߌWWWJ!r[/!.{.}WWWKU.w.&yA^507^In French.dgf.{!WWJ!v svdfDds=trqv@s_^ZY[XþD E E${\ T 208^3^El Kohen,A^Pontailler,J-Y^Mousseau,M^1991^1^Effect of Doubling of Atmospheric CO2 Concentration on Dark Respiration in Aerial Parts of Young Chestnut Trees (_Castanea sativa_ Mill.)^125^t. 312, Serie III^^477-481^^^^^^^^^^512^^^^^^^^^^^Castanea sativa/sweet chestnut^^^^^^^^^^^Castanea sativa/sweet chestnutCDH *sFteW_*P֒uioxylase oxygenase. PGPase in cell extracts shows a transient increase in activity that reaches a maximum 3 to 5 hours afte A^510^Two-year-old sweet chestnut seedlings were grown in constantly ventilated tunnels at ambient (350 vpm) or double (70 0 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 compare d to control plants during the first half of the growing season. This difference decreased with time and became negligible in the fall. Atmospheric CO2 concentration acted instantaneously on the respiration rate: when doubled, it decreased cont rol plant respiration and when decreased, it enhanced CO2 enriched plant respiration. The explanation of these findings re mains hypothetical. It is concluded that the rise in carbon dioxide level of the atmosphere will affect the carbon balance of young trees not only through an increase in net photosynthesis during the day, but also at night by reducing respiratory losses. In French.FU*)PSQVWU s*r2o?t @P=rF *- s *]_^Y[XPSQRVWU 209^3^El Kohen,A^Rouhier,H^Mousseau,M^1992^1^Changes in Dry Weight and Nitrogen Partitioning Induced by Elevated CO2 Depen d on Soil Nutrient Availability in Sweet Chestnut (_Castanea sativa_ Mill.)^56^49^^83-90^^^^^^^^^^515^^^^^^^^^^^Castanea sativa/sweet chestnututt 2:2:rrC[XSQtژ*m':Y[PSQRVWU<t<\t|:uV@=!r >Di C^513^Ann. Sci. For.FFF&>DBOSD;[r=\uGasL6D!AF:\2ҴG!6D<u|\t\.s>D@r A^513^The effect of 2 levels of atmospheric carbon dioxide (ambient, i.e. 350 ppm, and double, i.e. 700 ppm) and 2 contras ting levels of mineral nutrition on dry weight, nitrogen accumulation and partitioning were examined in 2-year-old chestnu t seedlings (_Castanea sativa_ Mill.), grown in pots outdoors throughout the vegetative season. Fertilization had a pronou nced effect on dry weight accumulation, tree height, leaf area, and plant nitrogen content. Carbon dioxide enrichment sign ificantly increased total biomass by about 20%, both on fertilized and on unfertilized forest soil, only the root biomass was increased, leading to an increase in the root:shoot ratio. Contrastingly, on fertilized soil only stem biomass and dia meter but not height were increased. Carbon dioxide enrichment significantly reduced the nitrogen concentration in all org ans, irrespective of the nutrient availability. However, the biomass increase made up for this reduction in such a way that the total nitrogen pool per tree remained unchanged.DC6I ;QV0fFɼ6ǼF&D@tF&\ ~]"E$ 210^3^El Kohen,A^Venet,L^Mousseau,M^1993^1^Growth and Photosynthesis of Two Deciduous Forest Species at Elevated Carbon Dioxide^37^7^^480-486^^^^^^^^^^518^^^^^^^^^^^sweet chestnut/Castanea sativa/Fagus sylvatica/beechchInpress^^517^^^^^^^^518^^^^^^^^^^^sweet chestnut/Castanea sativa/Fagus sylvatica/beechn& u4v~s?j&tv~4sS6Ǽ& t C^516^Funct. Ecol. (Cv6C>CC ;@I ;^YPQVDfZ,sv+FA+6Ǽɼ;Z A^516^Two-year-old sweet chestnut (_Castanea sativa_ Mill) and beech (_Fagus sylvatica_ L.) seedlings were grown in large pots on the same forest soil, at ambient (+/- 350 uL/L) and double (700 uL/L) atmospheric CO2 concentration in constantly ventilated minigreenhouses during the entire growing season. CO2 enrichment caused very different changes in these two tem perate deciduous species. A 20% dry weight enhancement was obtained for sweet chestnut, while this increase amounted to 60 % in beech. This greater effect of an elevated CO2 in beech was the result of a significant increase of net photosynthesis of the seedlings occurring during the whole season. On the contrary, this increase in photosynthesis lasted only a few we eks in sweet chestnut and then an acclimation process took place. No effect of an increased CO2 could be found on sweet ch estnut leaf area or leaf number, while a significant effect was found with beech, in which total leaf area per plant incre ased, owing to a greater number of growth flushes, each with larger leaves. The partitioning of the biomass increase due t o elevated CO2 was very different in the two species. All additional dry matter was allocated to the roots in sweet chestn ut, while it was partitioned equally amongst all organs of the beech seedling. The reactions to elevated CO2 of different tree species is discussed in relation to their specific growth strategy.^^^^^^^^^^205^^^^^^^^^^^^^^^^^^^^^Geyer,R A A^519^Supplementary high pressure sodium (HPS) lighting (140 umol/m2/s) and CO2 enrichment (1375 uL/L) improved the vegeta tive growth of _Chrysanthemum morifolium_ cv Dramatic by increases in stem length, stem diameter, root weight ratio, dry w eight, relative growth and net assimilation rates. Three-week-old chrysanthemums grown under CO2 enrichment and HPS lighti ng had lower leaf weight and stem weight ratios as well as lower foliar nutrient content than those grown under ambient CO 2 and natural light. Plants grown on to maturity under CO2 enrichment and supplementary HPS lighting had the longest stem lengths, the most flowers and greatest increase in dry weight. The combination of both additional light and CO2 was superi or to either factor used alone. With 24 h HPS supplementary lighting CO2 enrichment was most effective in improving vegeta tive growth and flower quality when applied during the daytime. Night CO2 enrichment was not commercially beneficial at the light levels employed in this study.8@-:88@/:3):+:K83Ps)O88@-:88@/:3):+:212^1^Enoch,H Z^1990^1^Crop Responses to Aerial Carbon Dioxide^15^268^^17-32^^^^^^^^^^52424U8V8W8X8T8H8I8=%NC^522^Act. Hort.R8U83V8W8T8X8H8I8=%NaPQ58u%8YXôO8u$S3ێۻt'<u  A^522^Crops are subjected to a global bulk atmosphere that contains a supra-optimal oxygen concentration and a sub-optimal  carbon dioxide concentration. It is expected that the present increase in atmospheric CO2 concentration will continue, th at a doubling will occur during the next century and that eventually values of over 2500 ppm will be reached. Until then g reenhouse crops should be CO2 enriched. The potential of intermittent CO2 enrichment (pulse CO2 enrichment) for yields enh ancement and pollution avoidance will be described. The main changes in crops due to elevated CO2 seem to be secondary eff ects of enhanced photosynthesis but some morphogenetic changes, for instance increased branching, are interpreted as parti al suppression of apical dominance and appear to show that CO2 concentration has additional hormone-like effects. Though o ver 1000 papers on CO2 enrichment have been published there is only an incomplete understanding of whether other organs th an leaves are sensitive to CO2 concentration and whether elevated CO2 has a trigger effect or a threshold effect on morpho genesis of crops. Some of the research questions that should be asked in order to improve our understanding of how CO2 enrichment influences plant productivity will be discussed.D2>7.6D^PSQRVWFg7Fg7S5&}SHt+5 213^2^Enoch,H Z^Zieslin,N^1988^1^Growth and Development of Plants in Response to Carbon Dioxide Concentrations^57^3^^248-256^^^^^^^^^^52727>Du4>t*7 jN< tF_rFNdpRr#6D8D:D6..<uD<t<uGrJ.<tD>ʾ@D A^525^Quality of protected crops can be improved by controlling the aerial carbon dioxide (CO2) in the greenhouse. The inf luence of atmosphere CO2 concentration on partitioning of dry matter, leaf growth and development, stem growth, root forma tion, branching and tillering, growth of the whole plant and on flowering is described in this review. At elevated CO2 con centrations apical dominance in C3 and C4 plants is weakened resulting in higher root-to-shoot ratios and increased side s hoot development (branching, tillering, etc.). Most effects of elevated CO2 concentration appear to be secondary effects o f photosynthesis enhancement leading to higher leaf weight per unit area, greater stem weight per unit length, and an incr !ease in absolute growth rate--but not always an increase in relative growth rate. The influence of elevated CO2 concentrat "ion on flowering is discussed in detail. Examples of organ development that can be explained as secondary effects of enhanced photosynthesis, as well as exceptions, are presented.! uE2ģ=D>=D sD!! t?D $214^2^Evans,L S^Hendrey,G R^1992^1^Responses of Cotton Foliage to Short-term Fluctuations in CO2 Partial Pressures^8^11^^203-212^^^^^^^^^^^^^^^^^^^^^cotton/Gossypium hirsutumum L. C^528^Crit. Rev. Plant Sci.@ '215^2^Fajer,E D^Bazzaz,F A^1992^1^Is Carbon Dioxide a 'Good' Greenhouse Gas? Effects of Increasing Carbon Dioxide on Ecolo )gical Systems^58^^^Inpress^^531^^^^^^^^532>~D0*]^MINDSLGLC^530^Global Environ. Change=?!rKظ@?!.?.;@.?.=@.??.??.;@V?D <:u2 *A^530^Carbon dioxide (CO2) in the atmosphere, a Greenhouse gas, may also provide benefits for mankind: many plants grow be +tter under increasing CO2 concentrations. Individuals have speculated that agricultural yields will increase up to 30% und ,er future CO2 concentrations, and natural ecosystems will become more lush and resilient. However, infertile conditions an -d complex ecological interactions often limit improved plant growth under increasing CO2 atmospheres. Future policies to a .dapt to a CO2-rich world must not overstate benefits from these conditions, nor ignore their usefulness for increasing fut (ure agricultural yields or restoring degraded habitats.GGGGGGGGGCGEGGGGGGGGGGGGIGGGGGGGGG 0216^3^Fajer,E D^Bowers,M D^Bazzaz,F A^1992^1^The Effect of Nutrients and Enriched CO2 Environments on Production of Carbon 1-based Allelochemicals in _Plantago:_ A Test of the Carbon/Nutrient Balance Hypothesis^59^140^^707-723^^^^^^^^^^535^^^^^^^^^^^Plantago lanceolatata2\*\rYe2r0D@r%3:|. 4A^533^In a test of the carbon/nutrient (C/N) balance hypothesis, we grew the perennial herb _Plantago lanceolata_ in diffe 5rent CO2 and nutrient environments and then (1) measured the total allocation to shoots, roots, and reproductive parts and 6 (2) quantified aucobin, catalpol, and verbascoside contents of replicate plants of six genotypes. Plants grown under low- 7nutrient conditions do have higher concentrations of carbon-based allelochemicals than plants grown under high nutrient co 8nditions. However, in contrast to the C/N balance hypothesis, plants grown in elevated (700 uL/L) CO2 conditions had simil 9ar, or lower, concentrations of carbon-based allelochemicals than plants grown in ambient (350 uL/L) CO2 conditions. We su :ggest that augmented substrate concentrations (i.e., excess carbohydrates) are a necessary but insufficient trigger for in ;creased secondary metabolism; instead, hormonal and/or direct physical cues (such as light) may be essential to synthesize < or activate the appropriate enzyme systems. Moreover, although plant genotype significantly affected plant growth, reprod =uction, and chemistry, we never observed significant genotype-by-CO2 interactions for these factors, which suggests that changing CO2 environments may not improve the fitness of certain genotypes over others.yment   p  Iwou ?217^3^Fajer,E D^Bowers,M D^Bazzaz,F A^1989^1^The Effects of Enriched Carbon Dioxide Atmospheres on Plant-Insect Herbivore Interactions^48^243^^1198-1200^^^^^^^^^^538^^^^^^^^^^^Plantago lanceolatatanslation/interpretationandteachingfromone 2C^536^Scienceuniversities.Iamconfidentinterpretingsimultaneouslyinanyscientificfield(nuclearscienceandtech BA^536^Little is known about the effects of enriched CO2 atmospheres, which may exist in the next century, on natural plant C-insect herbivore interactions. Larvae of a specialist insect herbivore, _Junonia coenia_ (Lepidoptera: Nymphalidae), were D reared on one of its host plants, _Plantago lanceolata_ (Plantaginaceae), grown in either current low (350 parts per mill Eion) or high (700 ppm) CO2-environments. Those larvae raised on high-CO2 foliage grew more slowly and experienced greater Fmortality, especially in early instars, than those raised on low-CO2 foliage. Poor larval performance on high-CO2 foliage Gwas probably due to the reduced foliar water and nitrogen concentrations of those plants and not to changes in the concent Hration of the defensive compounds, iridoid glycosides. Adult pupal weight and female fecundity were not affected by the CO I2 environment of the host plant. These results indicate that interactions between plants and herbivorous insects will be modified under the predicted CO2 conditions of the 21st century.X 3P 3!0:0:R 3 35 3 K218^3^Fajer,E D^Bowers,M D^Bazzaz,F A^1991^1^The Effects of Enriched CO2 Atmospheres on the Buckeye Butterfly, _Junonia coenia_^2^72^^751-754^^^^^^^^^^^^^^^^^^^^^Plantago lanceolatata(3(3#(3#(33%*33<:%*3, @C^539^Ecology333 N3 N3 >3 >3 3 3 $3 $3 23 23 @3,~33*3jX&3 N219^3^Fajer,E D^Bowers,M D^Bazzaz,F A^1990^1^Performance and Allocation Patterns of the Perennial Herb, _Plantago lanceola Ota_, in Response to Simulated Herbivory and Elevated CO2 Environments^34^87^^37-42^^^^^^^^^^542^^^^^^^^^^^Plantago lanceolata~&F&EF~7 N+~uFFNvvv~LsGr~3I~)V~F2 QA^541^We tested the prediction that plants grown in elevated CO2 environments are better able to compensate for biomass lo Rst to herbivory than plants grown in ambient CO2 environments. The herbaceous perennial _Plantago lanceolata_ (Plantaginac Seae) was grown in either near ambient (380 ppm) or enriched (700 ppm) CO2 atmospheres, and then after 4 weeks, plants expe Trienced either 1) no defoliation; 2) every fourth leaf removed by cutting; or 3) every other leaf removed by cutting. Plan Uts were harvested at week 13 (9 weeks after simulated herbivory treatments). Vegetative and reproductive weights were comp Vared, and seeds were counted, weighed, and germinated to assess viability. Plants grown in enriched CO2 environments had s Wignificantly greater shoot weights, leaf areas, and root weights, yet had significantly lower reproductive weights (i.e. s Xtalks + spikes + seeds) and produced fewer seeds, than plants grown in ambient CO2 environments. Relative biomass allocati Yon patterns further illustrated differences in plant responses to enriched CO2 atmospheres: enriched CO2-grown plants only Z allocated 10% of their carbon resources to reproduction whereas ambient CO2-grown plants allocated over 20%. Effects of s [imulated herbivory on plant performance were much less dramatic than those induced by enriched CO2 atmospheres. Leaf area \removal did not reduce shoot weights or reproductive weights of plants in either CO2 treatment relative to control plants. ] However, plants from both CO2 treatments experienced reductions in root weights with leaf area removal, indicating that p ^lants compensated for lost above-ground tissues, and maintained comparable levels of reproductive output and seed viability, at the expense of root growth.e~uVL43r=u @sZYX[SS3PQRZ u e*L* `220^2^Farrar,J F^Williams,M L^1991^1^The Effects of Increased Atmospheric Carbon Dioxide and Temperature on Carbon Partitioning, Source-sink Relations and Respiration^16^14^^819-830^^^^^^^^^^54545˸vPSQRVP73/ىF)ىF&/ LC^543^Plant Cell Environ.)^ZY[X˸&jNPSQRV/5uP73-@]ٸ 1ٰ-٣_],/^ZY[XPS cA^543^Herbaceous C3 plants grown in elevated CO2 show increases in carbon assimilation and carbohydrate accumulation (part dicularly starch) within source leaves. Although changes in the partitioning of biomass between root and shoot occur, the p eroportion of this extra assimilate made available for sink growth is not known. Root:shoot ratios tend to increase for CO2 f enriched herbaceous plants and decrease for CO2-enriched trees. Root:shoot ratios for cereals tend to remain constant. In g contrast, elevated temperatures decrease carbohydrate accumulation within source and sink regions of a plant and decrease h root:shoot ratios. Allometric analysis of at least two species showing changes in root:shoot ratios due to elevated CO2 s ihow no alteration in the whole-plant partitioning of biomass. Little information is available for interactions between tem jperature and CO2. Cold-adapted plants show little response to elevated levels of CO2, with some species showing a decline kin biomass accumulation. In general though, increasing temperature will increase sucrose synthesis, transport and utilizat lion for CO2-enriched plants and decrease carbohydrate accumulation within the leaf. Literature reports are discussed in re mlation to the hypothesis that sucrose is a major factor in the control of plant carbon partitioning. A model is presented in support.F+F~ t }~5vڍ~FFEFEE6v:v}Føy o221^4^Ferguson,J J^Avigne,W T^Allen,L H^Koch,K E^1986^1^Growth of CO2-enriched Sour Orange Seedlings Treated with Gibberellins/Cytokinins^60^99^^37-39^^^^^^^^^^548^^^^^^^^^^^sour orange/Citrus aurantiumum:r~^_ZYXU&Ur/ aC^546^Proc. Fla. State Hort. Soc.D*UI&Ur3Iwr+@%+P73]ȚTSW rA^546^Enriched CO2 atmospheres and specific plant growth regulators are known to stimulate plant growth, but their combine sd effects on citrus seedlings have not been studied. Sour orange (_Citrus aurantium_ L.) seedlings were treated with plant t growth regulators (6-benzyladenine [250 ul/l]; 6 benzyladenine and gibberellic acid [250 ul/l]; gibberelli un 3 [450 ul/l] and gibberellin 4+7 [250 ul/l]) and grown at either ambient or elevated CO2 levels (330 or 66 v0 ul/l). Seedlings treated with GA4+7 and grown at elevated CO2 levels were taller and had greater leaf weight than plants w given all other treatments. Leaf number increased under elevated CO2 levels when BA or GA4+7 were applied. Stem weight wa xs unaffected by growth regulators except when GA4+7 was applied to plants grown under high CO2 levels. Stem caliper increased slightly under high CO2 levels, especially when GA4+7 was applied.r.3>~Ut@ 辯   羴 z222^4^Fetcher,N^Jaeger,C H^Strain,B R^Sionit,N^1988^1^Long-term Elevation of Atmospheric CO2 Concentration and the Carbon {Exchange Rates of Saplings of _Pinus taeda_ L. and _Liquidambar styraciflua_ L^43^4^^255-262^^^^^^^^^^551^^^^^^^^^^^sweetgum/Liquidambar styraciflua/loblolly pine/Pinus taedadaPSQRVW/ t} Y uq_^ZY[XPQVD1* pC^549^Tree Physiol..3Ú93ÚJ83ó=:ó @+>"V}D3 3 3s0:j0:p0:m0: ~A^549^The relationship between carbon exchange rate (CER) and internal CO2 concentration was measured in leaves of sapling s of _Liquidambar styraciflua_ L. (sweetgum) and _Pinus taeda_ L. (loblolly pine) grown from seed for more than 14 months at atmospheric CO2 concentrations of either 340 or 500 uL/L. An elevated concentration of CO2 during growth reduced CER at any given internal CO2 concentration in sweetgum, but not in loblolly pine. Stomatal limitation of CER showed little resp onse to concentration of CO2 during measurement, but was higher in both species when grown at 500 than at 350 uL/L CO2. Th e net effect of a long-term increase in CO2 concentration from 350 to 500 uL/L was an increase in CER of loblolly pine, bu t a slight decrease in CER of sweetgum. It is suggested that the depression of CER in sweetgum resulted from a reduction in the activity of ribulose-1,5-bisphosphate carboxylase-oxygenase.  -=:^ZY[XPSQRVF umt_<tZ|u 223^1^French,C J^1989^1^Propagation and Subsequent Growth of Rhododendron Cuttings: Varied Response to CO2 Enrichment and Supplementary Lighting^3^114^^251-259^^^^^^^^^^554^^^^^^^^^^^Rhododendron spp.p.U33҉EU X # _PSQRV |C^552^J. Amer. Soc. Hort. Sci.=w tFF9-s v{ |tP583>g7t33^ZY[XWP73_Úg0: A^552^CO2 mist (1100 uL CO2/L) during fall propagation inhibited rooting of _Rhododendron_ 'Anna Rose Whitney' (_R. griers onianum_ x 'Countess of Derby') and had no effect on _R._ 'Vulcan' ('Mars' x _R. griersonianum_), _R._ 'Unique' (_R. campy locarpum_ hybrid), _R._ 'Anah Krushke' (_R. ponticum_ seedling), or _R._ 'Pink Bountiful' (_R. williamsianum_ x 'Linswegea num'). Supplementary lighting from high-pressure sodium lamps (HPS) for 16 hr/day (0400 to 2000 hr) had no effect on rooti ng of any cultivar. There was an interaction between CO2 mist and HPS exposure on rooting in _R._ 'Floriade' ('Britannia' hybrid). CO2 mist inhibited and HPS stimulated shoot development during propagation. CO2 mist during propagation inhibited subsequent development of 'Anna Rose Whitney' and 'Vulcan'. HPS during propagation inhibited subsequent growth of 'Floria de' and 'Vulcan'. CO2 enrichment of stock plants prior to propagation did not affect rooting of _R._ 'Sonata', whereas CO2 mist during propagation was inhibitory. In 'Anna Rose Whitney', there was an interaction between CO2 enrichment before an d during propagation. Application of supplementary HPS for 16 hr/day following propagation stimulated subsequent growth of both cultivars. CO2 mist during spring propagation stimulated rooting of 'Pink Bountiful' and 'Vulcan' and had no effect on _R._ 'Matador' (_R. griersonianum_ x _strigillosum_), _R._ 'Martha Isaacson' (_R. occidentale_ x Ostbo seedling No. 70) , or _R._ 'Elizabeth' (_R. forestii_ var _repens_ x _griersonianum_). Supplementary HPS had no effect on rooting. A low ir radiance night break treatment from incandescent lamps (2000 to 0400 hr) had no effect on rooting of 'Vulcan'. There was a n interaction between night break lighting and CO2 mist on rooting in 'Unique'. CO2 mist and HPS during spring propagation had minor effects on subsequent growth of 'Matador', 'Martha Isaacson', 'Pink Bountiful', and 'Elizabeth'. CO2 mist and supplementary HPS have little value in production of _Rhododendron_.-Fˡ- ;[v[٣-ٚ7(3ˉ-&˸ jNj 224^1^French,C J^1990^1^Rooting of Rhododendron 'Anna Rose Whitney' Cuttings as Related to Stem Carbohydrate Concentration^28^25^^409-411^^^^^^^^^^557^^^^^^^^^^^Rhododendron spp.p.~ڋv^_˻+&! @ C^555^HortSci.֎ދg[3UuUu pu du X u L@u @u4 A^555^Rooting of _Rhododendron_ 'Anna Rose Whitney' (_R. Griersonianum_ x 'Countess of Derby') was delayed in cuttings fro m stock plants grown in full sun, compared to cuttings from plants grown in 80% shade. In the outer stem (extracambium tis sues), concentrations of glucose, sucrose, soluble carbohydrate, and total nonstructural carbohydrates were higher in cutt ings from shaded stock plants. In the inner stem (intracambium tissues), where rooting originates, fructose, starch and no nstructural carbohydrates were lower in cuttings from the shaded stock plants. Rooting percentage was reduced by CO2 mist during propagation. At 7 days, during rooting with a CO2 enrichment to 1100 uL/L, fructose in the inner stem was 3-fold hi gher than in cuttings rooted under atmospheric CO2 (340 uL/L). Under CO2 mist, total nonstructural carbohydrate concentrat ion was higher in the inner stem throughout the rooting period. For both high stock plant irradiance and CO2 enrichment du ring propagation, there was an inverse relationship between fructose concentration in the inner stem and rooting. A possible mechanism for inhibition by fructose is proposed.1t,31PSQR*PwP.TXXZY[XPSQRV0٢ ٢"٢#٢%٢& 225^2^French,C J^Alsbury,J^1989^1^Supplementary Lighting and CO2 Mist Influence Rooting of _Camellia japonica_^28^24^^452-454^^^^^^^^^^2061^^^^^^^^^^^Camellia japonica^^^^^]ZY[X^PSQVWU^vdU vDdpU u W C^558^HortSci.U+u:>u2@u*u""V uu}@t Du3ۉU"V u<}@u4>u,Du$3ۻ 226^3^Fung,I Y^Tucker,C J^Prentice,K C^1987^1^Application of Advanced Very High Resolution Radiometer Vegetation Index to Study Atmosphere-Biosphere Exchange of CO2^62^92^^2999-3015^^^^^^^^^^56262${Y^[XVWPSQRUPPFd3F~U u C^560^J. Geophys. Res.ؚUAssvD DDޱ:Ut:Uu)G3s !=:Nٚ*,s|~UO3U A^560^Normalized difference vegetation indices derived from radiances measured by the Advanced Very High Resolution Radiom eter aboard the NOAA 7 polar-orbiting satellite were used to prescribe the phasing of terrestrial photosynthesis. The sate llite data were combined with field data on soil respiration and a global map of net primary productivity to obtain the se asonal exchange of CO2 between the atmosphere and the terrestrial biosphere. The monthly fluxes of CO2 thus obtained were employed as source/sink functions in a global three-dimensional atmospheric tracer transport model to simulate the annual oscillations of CO2 in the atmosphere. Reasonable agreement was found between the simulated and observed annual cycles of atmospheric CO2 at the locations of the remote monitoring stations. The results demonstrate that satellite data of high sp atial and temporal resolution can be used to provide quantitative information about seasonal and longer-term variations of photosynthetic activity on a global scale. Atmospheric CO2 observations and a three-dimensional atmospheric model have be en used to validate the translation of the nondimensional satellite data into dimensional carbon fluxes. Direct calibration will require extensive ground truth and field measurements at ecosystem scales.~u*PjP.TXXZY[X_^]^_PSQR 227^2^Furbank,R T^Walker,D A^1986^1^Chlorophyll _A_ Fluorescence as a Quantitative Probe of Photosynthesis: Effects of CO2 Concentration during Gas Transients on Chlorophyll Fluorescence in Spinach Leaves^23^104^^207-213^^^^^^^^^^565^^^^^^^^^^^spinach/Spinacia oleraceaea.TXXUAsvrDID=rV.TYY.T+.T.T t B${3ًv@sU X C^563^New Phytol.1SP.TXX]_ZY[XVPSQRUP fv.TXX/t>v|t5.T9ٹDV6; A^563^The relationship between changes in chlorophyll _a_ fluorescence and changes in CO2 concentration in spinach leaves is analyzed. The height of the fluorescence excursion, when plotted against the CO2 concentration during the transient, re sults in a hyperbola. When these data are replotted on an inverse-reciprocal plot, an apparent Km(CO2) for the fluorescenc e transient can be obtained which closely approximates the Km(CO2) for carbon assimilation under similar conditions. Trans itions in CO2 concentration at 2% O2 result in deviation from this hyperbolic relationship, reducing the apparent Km(CO2) for this process. The relationship between carbon assimilation and chlorophyll fluorescence is discussed with reference to the two components of fluorescence quenching. This technique raises the possibility that chlorophyll fluorescence could be used as a quantitative as well as a qualitative tool in plant screening.{r&&GGF;Fs@FeFry&228^1^Gale,J^1986^1^Carbon Dioxide Enhancement of Tree Growth at High Elevation^48^231^^859-860^^^^^^^^^^567868688A^566^Technical comment.&&3ɾʚX-Nu8888sqF~K)tF&&H${rь 229^3^Garbutt,K^Williams,W E^Bazzaz,F A^1990^1^Analysis of the Differential Response of Five Annuals to Elevated CO2 durin g Growth^2^71^^1185-1194^^^^^^^^^^570^^^^^^^^^^^Abutilon theophrasti/Amaranthus retroflexus/Ambrosia artemisiifolia/Chenopodium album/Setaria faberiiii ; mQ' vZ;&L D hvpqA; C^568^Ecology$G%%&x&&(:(:PQVU= tL=tL%=s<.'ȃe*FE t;Fu3F]^YX A^568^In order to investigate the effects, without competition, of CO2 on germination, growth, physiological response, and reproduction, we focused on co-occurring species that are prominent members of an annual community in Illinois. Five spec ies of old field annual plants -- _Abutilon theophrasti_ (C3), _Amaranthus retroflexus_ (C4), _Ambrosia artemisiifolia_ (C 3), _Chenopodium album_ (C3) and _Setaria faberii_ (C4) -- were grown for their entire life cycle as individuals at CO2 co ncentration of 350 uL/L, 500 uL/L, and 700 uL/L. Emergence time, growth rate, shoot water status, photosynthesis, conducta nce, flowering time, nitrogen content, and biomass and reproductive biomass were measured. There was no detectable effect of enhanced CO2 on timing of emergence in any of the species. _Amaranthus_ relative growth rate (RGR) was always higher at 700 uL/L CO2 than at 350 uL/L. In both _Abutilon_ and _Ambrosia_, RGR was greater at 700 uL/L than at 350 uL/L during the first half of the experimental period, but during the second half of the period the reverse was true. Shoot water potenti al significantly increased (became less negative) with increasing CO2 in _Amaranthus_ and _Setaria_. Similar but statistic ally nonsignificant trends were found in _Chenopodium_ and _Abutilon_. Overall rate of photosynthesis increased with CO2 b ut there were no significant effects, at the species level, of CO2 on photosynthetic rates. Stomatal conductance decreased with increased CO2 at both high and low light levels in C3 species but only at high light levels in C4 species. In all sp ecies, intercellular CO2 increased with external CO2. _Amaranthus_ flowered significantly earlier at 700 uL/L than at 350 uL/L, and _Setaria_ flowered significantly later at 700 uL/L than at either of the other CO2 levels. Both _Abutilon_ and _ Ambrosia_ showed a trend towards earlier flowering but this was not statistically significant. Of the morphological charac ters measured at the final harvest only specific leaf area (SLA) showed a consistent response to CO2, decreasing with incr easing CO2. Significant CO2 x species interactions were also found for leaf area, leaf biomass, biomass of reproductive pa rts, and seed biomass indicating species-specific responses for these characters. The proportion of nitrogen declined with increasing CO2; there was also a significant CO2 x species interaction caused by the different rates of decline in propor tion of nitrogen among the species. The response of most characters had a significant species x CO2 interaction. However, this was not simply caused by the C3/C4 dichotomy. Reproductive biomass (seed, fruits, and flowers) increased with increas ing CO2 in _Amaranthus_ (C4) and in _Chenopodium_ and _Ambrosia_ (both C3) but there was no change in _Setaria_ (C4) and _ Abutilon_ (C3) showed a peak at 500 uL/L. Species of the same community differed in their response to CO2, and these differences may help explain the outcome of competitive interactions among these species above ambient CO2 levels.tFF 230^1^Gardestrom,P^1987^1^Adenylate Ratios in the Cytosol, Chloroplasts and Mitochondria of Barley Leaf Protoplasts during Photosynthesis at Different Carbon Dioxide Concentrations^63^212^^114-118^^^^^^^^^^573^^^^^^^^^^^barley/Hordeum vulgarer C^571^FEBS Lett.~9b6S~6H~>g7t2ɆkN>g7~g7H~fNkH~S~F2):&~_^ZY[XÀN A^571^Barley (_Hordeum vulgare_) protoplasts were incubated in darkness and in the light at saturating and limiting CO2 co ncentrations. The protoplasts were fractioned by a membrane filtration technique which allows quenching of the metabolism by acidification within about 0.1 s and the ATP/ADP ratios in the cytosol, chloroplasts and mitochondria were determined. It is concluded that the cytosolic ATP/ADP ratio is considerably higher during photosynthesis at limiting CO2 (which is the normal situation for a C3 plant in air) compared to photosynthesis at saturating CO2 or darkness.VP3SQRW; e L.~&~vxrcFFD<V&vP&!'2& '~bH~&H~S~TFp 231^2^Gastal,F^Saugier,B^1989^1^Relationships Between Nitrogen Uptake and Carbon Assimilation in Whole Plants of Tall Fescue^16^12^^407-418^^^^^^^^^^^^^^^^^^^^^tall fescueNFt \s_6&!['&O2A&O & ߾ C^574^Plant Cell Environ.t &O&OFFF &: v& S'&*G &G[& +F+F+F-&G߾ &O 232^1^Gates,D M^1985^3^Global Biospheric Response to Increasing Atmospheric Carbon Dioxide Concentration^Direct Effects of Increasing Carbon Dioxide on Vegetation^Dept. of Energy, Carbon Dioxide Research Division^Washington, D.C.^171-184^^^^^^^DOE/ER-0238^^^^^^^^^^^^^^^^^^^^^^^^Strain,B R^Cure,JD~0TY:!Y::T:QV8** 233^2^Gaudillere,J-P^Mousseau,M^1989^1^Short Term Effect of CO2 Enrichment on Leaf Development and Gas Exchange of Young Poplars (_Populus euramericana_ cv I 214)^64^10^^95-105^^^^^^^^^^579^^^^^^^^^^^poplars/Populus euroamericanaa'3& C^577^Acta Oecologica/Oecol. Plant.<^&!'&O2F&O s& Q&*O &O߾"Y&O A^577^Fast growing young poplar trees bearing 25 to 30 leaves were placed in a growth chamber. The air CO2 content was 330 uL/L during the first 15 days and 660 uL/L the following 15 days. The leaves in 660 uL/L CO2 in air developed a greater a rea and specific weight and contained more stomata, epidermal cells and chlorophyll per unit area. Leaf developmental char acteristics (Relative Leaf Expansion, Leaf Plastochron Index, Leaf Expansion Duration) were modified by the treatment. Lea ves developed in normal CO2 atmosphere demonstrated a significant regrowth, with increased cell and stomatal number, when exposed to the elevated CO2 treatment. Whole plant and single leaf gas exchange rates were measured at 330 and 660 uL/L. O n single attached leaves, an increased CO2 level during growth promoted a photosynthetic inhibition, shown by a lower _g_ and Pmax. Due to the greater leaf area, whole tree daily photosynthesis and respiration increased with elevated CO2, enhancing growth efficiency. Doubling the CO2 resulted in a threefold increase in whole plant water use efficiency (WUE). 234^2^Geethakumari,V L^Shivashankar,K^1991^1^Studies on Organic Amendment and CO2 Enrichment in _Ragi_/Soybean Intercropping Systems^65^36^^202-206^^^^^^^^^^2045^^^^^^^^^^^soybean/Glycine max/ragi/Eleusine coracana^^^^^coracana^^^^^>tV C^580^Indian J. Agron.*r#W~*E ~*^[23NB_^Z[YøS~VhI*y':r^RVȤ 235^1^Gifford,R M^1988^3^Direct Effects of Higher Carbon Dioxide Concentrations on Vegetation^Greenhouse: Planning for Climate Change^E.J. Brill^New York^506-519^^^^^^^^^^583^^^^^^^^^^^^^^^^^^^^^Pearman,G I !ȚTu" A^582^Higher atmospheric CO2 concentrations are potentially beneficial to agriculture because they usually stimulate plant  growth. The typical magnitude of the 'CO2 fertilizing effect' is a 30-40% increase in yield for a doubling of CO2 concent ration to 700 ppmv. Variation in responsiveness depends on plant species and environmental conditions such as temperature and rainfall which may be changing as a result of the greenhouse effect. The main mechanisms of the 'CO2-fertilizing effec t' involve several physiological phenomena, some that are certainly primary (stimulation of photosynthesis, suppression of  photorespiration, reduction in stomatal aperture) and others that seem so far to be primary but may turn out not to be (g reater leaf area development and branching, reduced stomatal frequency, reduced dark respiration, changes to reproductive development). It is often assumed that the reduction in stomatal conductance at high CO2 concentration will lead to reduce d evapotranspiration from vegetated regions, all else being equal. There are both physiological and boundary-layer meteoro logical considerations which suggest that this effect might be small though there is some argument about that. For annual crops like cereals, a warmer climate will tend to reduce yield owing to the faster attainment of physiological maturity. H owever, the size of the CO2-fertilizing effect on yield for a currently adapted variety is similar to that of the associat ed temperature-dependent reduction of yield. So the net effect on cereal yield in a region will depend on the success at i ntroducing slower maturing and CO2-responsive varieties to compensate for faster development in warm conditions, and on whether the climate change involves more or less rainfall in the region.22Z Z,s ![Z^jNN%y*: 236^1^Gifford,R M^1989^3^The Effects of the Build-up of Carbon Dioxide in the Atmosphere on Crop Productivity^Proceedings of the 5th Australian Agronomy Conference; 1989 Sept. 24-29; University of Western Australia, Perth, Western Australia^Australian Society of Agronomy^^^^^^^^^^^^^^^^^^^^^^^^^^^^nomysI-C *~t*F*@s]^_ZY[X 237^1^Gifford,R M^1989^3^Exploiting the Fertilizer Effect of Increasing Atmospheric Carbon Dioxide^Climate and Food Securi ty, International Symposium on Climate Variability and Food Security in Developing Countries; 1987 Feb. 5-9; New Delhi, In dia^International Rice Research Institute, Manila, and American Association for the Advancement of Science, Washington, D.C.^^477-487^^^^^^^^^^586^^^^^^^^^^^^^^^^ *_^ZY[XPQVd*Ct%:u QU*Y^YXˀP A^585^High CO2 concentrations fertilize plants by stimulating photosynthesis, suppressing photorespiration, and reducing t ranspiration per unit leaf area. CO2 enhancement of growth occurs at both optimal and nonoptimal levels of other environme ntal variables (light, water, temperature, nitrogen nutrients, salinity). Severely phosphate-deficient plants may not resp ond to higher CO2 concentrations. The globally increasing CO2 concentration, therefore, represents an improving component of the fitness of the environment for secure food production. This will partially counter any deteriorating aspects of agr icultural environments (e.g. adverse climatic change, soil loss and deterioration, acid precipitation). Because yield incr ease percentages in response to high CO2 are larger for drought and salt-stressed plants than for nonstressed plants, some marginal cropping sites (e.g. on arid boundaries) may show less year-to-year variation. This would be an improvement in t !he stability of food production from such sites. Because C3 species will benefit more than C4 species, substitution of C3 "for C4 crops may become more worthwhile. Communities with access to fertilizer may be better able to exploit higher CO2 at #mospheres. Cropping boundaries may move onto more saline and drought-prone soils, although this would probably be bad poli $cy in the long term. Genetic variation in within-species responsiveness to high CO2 may enable the breeding of cultivars to take greater advantage of a high CO2 atmosphere.uEvV6Ǽ&\<^tt8<ur=tW>Ǽe&=u &238^1^Gifford,R M^1988^3^Interactions with Vegetation^Greenhouse: Planning for Climate Change^E.J. Brill^New York^83-89^^^^^^^^^^588^^^^^^^^^^^^^^^^^^^^^Pearman,G IS6Ǽ& tv~s6~M$ (Cv6C>CC χ@I (A^587^Plant photosynthesis has transformed the pre-biotic anaerobic atmosphere that was rich in CO2 to a modern atmosphere ), fit for advanced life, containing 21% O2 and only a trace concentration of CO2. Modern vegetation also plays a significa *nt part in determining climate by affecting the partitioning of incoming solar energy over land. This partitioning may cha +nge as a result of CO2 effects on vegetation. In one way or another vegetation contributes to and/or is affected by the ot ,her major changing components of the global atmosphere -- O3, CH4, CFCs, N2O. Current best estimates of the scale of net d -eforestation of the world indicate that it is releasing about a quarter as much CO2 to atmosphere as fossil fuel burning i .s. However, the increasing CO2 concentration in the atmosphere is probably increasing the growth of vegetation. It is esti /mated that the net annual storage of extra carbon in the form of more standing biomass and soil organic matter than hither 0to, may approximately equal the carbon released by net deforestation. Quantitative appraisal of the global carbon cycle re 1veals that to attempt to permanently remove the fossil fuel-derived CO2 from the atmosphere by massive re-afforestation or 2 by storing felled timber is unrealistic. Refraining from continued net deforestation would, however, produce a probably detectable slowdown in the rate of build-up of atmospheric CO2.X;VW*؋*_^SQVWv~!8r\Iv 4239^1^Gifford,R M^1992^3^Interaction of Carbon Dioxide with Growth-Limiting Environmental Factors in Vegetation Productivi 5ty: Implications for the Global Carbon Cycle^^Springer Verlag^Berlin^24-58^^^^I^^Advances in Bioclimatology^^^^^^^^^^^^^^^^^^^^^^^^^Desjardins,R L^Gifford,R M^Nilson,T^Greenwood,E A N A N t+EFs_^ZY[ 7240^1^Gifford,R M^1990^3^Photosynthesis and the Greenhouse Effect^Chemistry and the Environment, Proceedings of Regional Symposium, 1989, Brisbane^Commonwealth Science Council^London^59-71^^^^^^^^^^591^^^^^^^^^^^^^^^^^^^^^Noller,BN^Chadha,MSu 9A^590^The greenhouse effect, whereby atmospheric CO2 and water vapour prevent the Earth's surface from being totally froze :n is likely to be amplified by the anthropogenic emissions of fossil fuel CO2. The global carbon cycle links photosynthesi ;s to the greenhouse effect on all timescales up to millions of years. Major characteristics of the Earth's atmospheric com ts, especially angiosperms, cause. Calcium released by weathering moves to the oceans where it paces the formation of calc ?ium carbonate rocks which are a massive carbon pool that dwarfs all others combined. On a timescale of millions of years t @he carbon from calcium carbonate is cycled back to the atmosphere via volcanoes. On shorter timescales of sociopolitical c Aoncern photosynthesis is involved with the current global change in atmospheric CO2 increase. From what we know about plan Bt photosynthetic and growth responses to increasing CO2 concentration interacting with other limiting environmental factor Cs, it seems very likely that the biosphere is absorbing, into standing biomass and soil organic matter, some of the CO2 em Ditted from fossil fuel burning and net deforestation thereby contributing to the 'missing carbon' that does not appear as Ean increase in atmospheric CO2 concentration. However, the scope for accelerating this CO2 sequestering process by plantin Fg more trees is rather limited owing to the large scale required relative to the land available and to the fact that net carbon sequestration ceases when a forest matures..³뾳L뺳 붳!벳뮚$=:Ú NÚZ,s!.χ&/χ /χ!N2χ&N2χ / H241^3^Gifford,R M^Lambers,H^Morison,J I L^1985^1^Respiration of Crop Species under CO2 Enrichment^44^63^^351-356^^^^^^^^^^594^^^^^^^^^^^wheat/Triticum aestivum/mung bean/Vigna radiata/sunflower/Helianthus annuuss annuus L.ilχkχ( C^592^Physiol. Plant.QmFFD=tNFvjr/FNȋ?~NrFQW3_Y ZFpF= KA^592^Respiratory characteristics of wheat (_Triticum aestivum_ L. cvs Gabo and WW15), mung bean (_Vigna radiata_ L. Wilcz Lek cv. Celera) and sunflower (_Helianthus annuus_ L. cv. Sunfola) were studied in plants grown under a normal CO2 concentr Mation and in air containing an additional 340 or 250 uL/L CO2. Such an increase in global atmospheric CO2 concentration ha Ns been forecast for about the middle of the next century. The aim was to measure the effect of high CO2 on respiration and O its components. Polarographic and, with wheat, CO2 exchange techniques were used. The capacity of the alternative pathway P of respiration in roots was determined polarographically in the presence of 0.1 mM KCN. The actual rate of alternative pa Qthway respiration was assessed by reduction in oxygen consumption caused by 10 mM salicylhydroxamic acid. Each species res Rponded differently. In wheat, growth in high atmospheric CO2 was associated with up to 45% reduction in respiration by bot Sh roots and whole plants. Use of respiratory inhibitors in polarographic measurements on wheat roots implicated reduction Tin the degree of engagement of the alternative pathway as a major contributor to this reduced respiratory activity of high U-CO2 plants. No change was found in the total sugar content per unit wheat root dry weight as a result of high CO2. In non Ve of the species was there an increase in the absolute, or relative, contribution by the alternative pathway to total resp Wiration of the root system. Thus the improved photosynthetic assimilate supply of plants grown in high CO2 did not lead to X increased diversion of carbon through the non-phosphorylating alternative pathway of respiration in the root. On the cont Yrary, in wheat grown in high CO2, the reduced loss of carbon through that route must have contributed to their larger dry weight.FuRF^FFFQ}v&EF&} u&Ezu FFR &EFLFFt ^v's% [242^2^Gifford,R M^Morison,J I L^1985^1^Photosynthesis, Water Use and Growth of a C4 Grass Stand at High CO2 Concentration^18^7^^77-90^^^^^^^^^^597^^^^^^^^^^^Paspalum plicatulumum Michx.^X fvLDތ،¾L&R;r{P&E IC^595^Photosynth. Res.^XrHD&E P&=t4b &&E@Qr&] &M&URSQY[gX=u۾LFN6D ^A^595^Leaf photosynthesis rate of the C4 species _Paspalum plicatulum_ Michx was virtually CO2-saturated at normal atmosph _eric CO2 concentration but transpiration decreased as CO2 was increased above normal concentrations, thereby increasing tr `anspiration efficiency. To test whether this leaf response led growth to be CO2-sensitive when water supply was restricted a, plants were grown in sealed pots of soil as miniature swards. Water was supplied either daily to maintain a constant wat ber table, or at three growth restricting levels on a 5-day drying cycle. Plants were either in a cabinet with normal air ( c340 umol (CO2)/mol (air)) or with 250 umol/mol enrichment. Harvesting was by several cycles of defoliation. With abundant dwater supply high CO2 concentration did not cause increased growth, but it did not cause an increase in growth over a wide e range of growth-limiting water supplies either. Only when water supply was less than 30-50% of the amount used by the sta fnd with a water-table was there evidence that dry weight growth was enhanced by high CO2. In addition, with successive reg growth, the enhancing effect under a regime of minimal water allocations, became attenuated. Examination of leaf gas exchan hge, growth and water use data showed that in the long term stomatal conductance responses were of little significance in m iatching plant water use to low water allocation; regulation of leaf area was the mechanism through which consumption match jed supply. Since high CO2 effects operate principally via stomatal conductance in C4 species, we postulate that for this species higher CO2 concentrations expected globally in future will not have much effect on long term growth.V FV l243^2^Gislerod,H R^Nelson,P V^1989^1^The Interaction of Relative Air Humidity and Carbon Dioxide Enrichment in the Growth of _Chrysanthemum morifolium_ Ramat^53^38^^305-313^^^^^^^^^^2046^^^^^^^^^^^chrysanthemum/Chrysanthemum morifolium^^^^^mat \C^598^Scientia Hortic. UVvFF\ZFVc6h6fFPFPFPFP<χVFu=u ^FV o244^1^Goudriaan,J^1990^3^Primary Productivity and CO2^The Greenhouse Effect and Primary Productivity in European Agro-ecos pystems; 5-10 April 1990; Wageningen, The Netherlands^Pudoc^Wageningen^23-25^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^Goudriaan,J^van Keulen,H^van Laar,H H&G_^F;s[jjFVLNPR:χVFt=t_^UVWv ~ F r245^1^Goudriaan,J^1986^3^Simulation of Ecosystem Response to Rising CO2, with Special Attention to Interfacing with the At smosphere^Climate Vegetation Interactions, a NASA Workshop; 1986 January 27-29; Greenbelt, Maryland^NASA Goddard Space Flight Center^Greenbelt, Maryland^68-75^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^Rosenzweig,C^Dickinson,Rhf66hR6^tIχ=u u246^2^Goudriaan,J^Bijlsma,R J^1987^1^Effect of CO2 Enrichment on Growth of Faba Beans at Two Levels of Water Supply^66^35^^189-191^^^^^^^^^^604^^^^^^^^^^^Vicia faba/broad beanan^&G3_^ UVW,~ v jGIχP=u C^602^Nether. J. Agric. Sci.RT_^6PFPjIχ=t6PjRT_^33_^U6PfIχ]U xA^602^The occurrence of growth enhancement by increased CO2 levels is well established under optimal conditions. A growth yanalysis study of faba beans, grown under two CO2 levels (350 and 700 cm3/m3) in combination with two levels of water supp zly, showed that the beneficial CO2 effect is maintained when there is shortage of water. The effects of additional CO2 and { water were shown to be multiplicative. (This is a short synopsis of M.S. Thesis (R.J.B.), Dept. of Theoretical Production Ecology, Wageningen Agric. Univ., Wageningen, 1983.)Cχ tju5χ=t^^&t;Fv&FFPFv P }247^3^Goudriaan,J^van Keulen,H^van Laar,H H^1990^2^The Greenhouse Effect and Primary Productivity in European Agro-Ecosyst ~ems, Proceedings of the International Workshop on Primary Productivity of European Agriculture and the Greenhouse Effect, Wageningen, The Netherlands, 5-10 April 1990^Pudoc^Wageningen^^N&\FFPF v PCχ tju5χ=t^F 248^2^Goyal,A^Tolbert,N E^1989^1^Variations in the Alternative Oxidase in _Chlamydomonas_ Grown in Air or High CO2^17^89^^958-962^^^^^^^^^^608^^^^^^^^^^^Chlamydomonas reinhardtii^^^^^^^ju5χ=t^FvFFPv vCχ tju5 vC^606^Plant Physiol.FPFv PCχ tju5χ=t^FvFFPFv PCχ tju5χ=t^ A^606^_Chlamydomonas_ in the resting phase of growth has an equal capacity of about 15 micromole O2 uptake per hour per mi lligram of chlorophyll for both the cytochrome _c_, CN-sensitive respiration, and for the alternative, salicylhydroxamic a cid-sensitive respiration. Alternative respiration capacity was measured as salicylhydroxamic acid inhibited O2 uptake in the presence of CN, and cytochrome _c_ respiration capacity as CN inhibition of O2 uptake in the presence of salicylhydrox amic acid. Measured total respiration was considerably less than the combined capacities for respiration. During the log p hase of growth on high (2-5%) CO2, the alternative respiraiton capacity decreased about 90% but returned as the culture en tered the lag phase. When the alternative oxidase capacity was low, addition of salicylic acid or cyanide induced its reap pearance. When cells were grown on low (air-level) CO2, which induced a CO2 concentrating mechanism, the alternative oxida se capacity did not decrease during the growth phase. Attempts to measure _in vivo_ distribution of respiration between the two pathways with either CN or salicylhydroxamic acid alone were inconclusive.~tFvPvvvIχ249^3^Graham,R L^Turner,M G^Dale,V H^1990^1^How Increasing CO2 and Climate Change Affect Forests^67^40^^575-587^^1033 C^609^BioSci.VRTVF^3ɋVRTVFVUV F=!s^FFUVvFVC!sF 250^4^Grant,W J R^Fan,H M^Downton,W J S^Loveys,B R^1992^1^Effects of CO2 Enrichment on the Physiology and Propagation of T wo Australian Ornamental Plants, _Chamelaucium uncinatum_ (Schauer) x _Chamelaucium floriferum_ (MS) and _Correa schlechteNndalii_ (Behr)^53^52^^337-342^^^^^^^^^^613^^^^^^^^^^^Chamelaucium uncinatum/Chamelaucium floriferum/Correa schlechtendalii rrea schlechtendalii (Behr)           =:óu u "Ru#Z C^611^Scientia Hortic.u+u,1uu(u 9uru Qu u u u uu u u u u A^611^Root formation on both _Chamelaucium_ and _Correa_ cuttings maintained at high humidity in an enclosed fog tunnel wa s significantly enhanced when ambient CO2 was increased from 350 to 800 ubar. CO2 enrichment resulted in decreased transpi ration and increased water potential of cuttings implying an effect of CO2 on stomatal conductance. CO2 enrichment led to increased starch levels in cuttings of both species probably by raising the intercellular partial pressure of CO2. Increas ed starch content with CO2 enrichment was able to account for 70-90% of the dry weight increase in _Correa_, but only for 10-30% of the dry weight increase in _Chamelaucium_. It is suggested that the stimulation of rooting associated with CO2 e nrichment probably derives from the improved water relations of the cuttings rather than from increased carbohydrate levels.u2Ҁ>҆t€t%3: rƾ €t3 _^Z[XPSRVGSu >҆t tu 251^1^Graumlich,L J^1991^1^Subalpine Tree Growth, Climate, and Increasing CO2: An Assessment of Recent Growth Trends^2^72^ ^1-11^^^^^^^^^^616^^^^^^^^^^^Juniperus occidentalis/western juniper/Pinus balfouriana/foxtail pine/Pinus murrayana/lodgepole pinene>et ȚTs^[Xr/' PSVȚT^[Xr'' @PRVƾ*r 7u^ZXgRWR C^614^Ecology:['>SU":D ^e'%][ˊ<w&˸<w&˸=s.>D A^614^LaMarche et al. (Science 225: 1019-1021, 1984) hypothesized that recent trends of increasing ring widths in subalpin e conifers may be due to the fertilizing effects of increased atmospheric CO2. Five tree-ring series from foxtail pine (_P inus balfouriana_), lodgepole pine (_P. murrayana_), and western juniper (_Juniperus occidentalis_) collected in the Sierr a Nevada, California, were analyzed to determine if the temporal and spatial patterns of recent growth were consistent wit h the hypothesized CO2-induced growth enhancement. Specifically, I address the following questions: (1) Can growth trends be explained solely in terms of climatic variation? (2) Are recent growth trends unusual with respect to long-term growth records? For three of the five sites, 20th-century growth variation can be adequately modeled as a function of climatic va riation. For the remaining two sites, trends in the residuals from the growth/climate models indicate systematic underesti mation of growth during the past decade that could be interpreted as either CO2 fertilization or as a response to extreme climatic events during the mid 1970s. At all five sites, current growth levels have been equalled or exceeded during some preindustrial periods. Taken together, these results do not indicate that CO2-induced growth enhancement is occurring amon g subalpine conifers in the Sierra Nevada. While the results presented here offer no support for the hypothesized CO2 fert ilization effect, they do provide insights into the response of subalpine conifers to climatic variation. Response surface s demonstrate that precipitation during previous winter and temperature during the current summer interact in controlling growth and that the response can be nonlinear. Although maximum growth rates occur under conditions of high winter precipi tation and warm summers for all three species, substantial species-to-species variation occurs in the response to these two variables.d*ˀ&w twˀ&w twˀ&w twˀ&w ttww eP G 252^1^Graybill,D A^1987^3^A Network of High Elevation Conifers in the Western U.S. for Detection of Tree-Ring Growth Respo nse to Increasing Atmospheric Carbon Dioxide^Proceedings of the International Symposium on Ecological Aspects of Tree-Ring Analysis. U.S. Dept. of Energy Conference Report; DOE/CONF-8608144^NTIS^Springfield, Virginia^463-474^^^^^^^^^^618^^^^^^^^^^^Pinus aristata/Pinus longaeva^^^^^^^^^^Jacoby,GC^Hornbeck,JWW/ 3 /ȚTr>etȚTr A^617^Tree-ring width growth at high elevation upper treeline sites in the western U.S.A. evidences unparalleled increase during the past century in comparison to growth records of the preceding 500 or more years. Causes for this do not yet app ear to be solely climatic in origin because it remains unclear that crucial variables affecting growth such as temperature or precipitation, have changed correspondingly during their length of record. Given the recent exponential rise of CO2, a nd its potential for affecting tree growth at high elevations, it cannot yet be ruled out as an agent of change. The rates of ring-width growth increase in some cases appear to exceed the levels of known or estimated changes in climatic paramet ers and also in CO2. This may in part be due to changes in the growth potential of the organisms themselves, providing an amplifying effect to environmental inputs. This could include changes such as increasing needle mass that provides increas ed photosynthetic capacity, increased root growth that provides greater nutrient availability and increased water use effi ciency that is critical in the arid sites. The net effect may not only be increasing growth but increasing persistence in growth variation. Ongoing analysis of data from the current study should permit further understanding of these changes.! 253^1^Graybill,D A^1985^5^Western U.S. Tree-Ring Index Chronology Data for Detection of Arboreal Response to Increasing Ca rbon Dioxide^U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C., and Environmental Sciences Division , Oak Ridge National Laboratory, Oak Ridge, Tennessee^^^^^^^^^^^^^^^^^^^^^^^^Pinus longaeva/Pinus aristata/Pinus flexilis^^026 in Green Report Series^Response of Vegetation to Carbon Dioxide^^ Xe~*em=tLuGANr@eOr9=J*254^1^Grodzinski,B^1992^1^Plant Nutrition and Growth Regulation by CO2 Enrichment^67^42^^517-525^^21ҋþrP& t& C^620^BioSci.r1&t&@uH؋v&E &U &+ET2RVWUNlr t t# >D >UNr 255^5^Grulke,N E^Riechers,G H^Oechel,W C^Hjelm,U^Jaeger,C^1990^1^Carbon Balance in Tussock Tundra under Ambient and Elevated Atmospheric CO2^34^83^^485-494^^^^^^^^^^624^^^^^^^^^^^Eriophorum vaginatumumH|J C^622^Oecologiar!|tvn`>r `>raPr%f s*վf s3 t${ t A^622^Whole ecosystem CO2 flux under ambient (340 uL/L) and elevated (680 uL/L) CO2 was measured in situ in _Eriophorum_ t ussock tundra on the North Slope of Alaska. Elevated CO2 resulted in greater carbon acquisition than control treatments an d there was a net loss of CO2 under ambient conditions at this upland tundra site. These measurements indicate a current l oss of carbon from upland tundra, possibly the result of recent climatic changes. Elevated CO2 for the duration of one gro wing season appeared to delay the onset of dormancy and resulted in approximately 10 additional days of positive ecosystem flux. Homeostatic adjustment of ecosystem CO2 flux (sum of species' response) was apparent by the third week of exposure to elevated CO2. Ecosystem dark respiration rates were not significantly higher at elevated CO2 levels. Rapid homeostatic adjustment to elevated CO2 may limit carbon uptake in upland tundra. Abiotic factors were evaluated as predictors of ecosy stem CO2 flux. For chambers exposed to ambient and elevated CO2 levels for the duration of the growing season, seasonality (Julian day) was the best predictor of ecosystem CO2 flux at both ambient and elevated CO2 levels. Light (PAR), soil temp erature, and air temperature were also predictive of seasonal ecosystem flux, but only at elevated CO2 levels. At any comb ination of physical conditions, flux of the elevated CO2 treatment was greater than that at ambient. In short-term manipul ations of CO2, tundra exposed to elevated CO2 had threefold greater carbon gain, and had one half the ecosystem level, lig ht compensation point when compared to ambient CO2 treatments. Elevated CO2-acclimated tundra had twofold greater carbon g ain compared to ambient treatments, but there was no difference in ecosystem level, light compensation point between eleva ted and ambient CO2 treatments. The predicted future increases in cloudiness could substantially decrease the effect of el evated atmospheric CO2 on net ecosystem carbon budget. These analyses suggest little if any long-term stimulation of ecosystem carbon acquisition by increases in atmospheric CO2.2.1sDO@tLPDI.UEPtE_^ZPRV3E 256^1^Gulyaev,B I^1986^1^Influence of CO2 Concentration on Photosynthesis, Growth and Productivity of Plants^68^18^^574-591^^^^^^^^^^62727FEE EEM 04]] EtwM M EtwM M ^ZXSQRVWE E#osE C^625^Physiol. Biochem. of Cultured Plants (Fiziologi i aibiokhimi i akultumykh Rasteni)~2M ~ A^625^The works aimed at studying the responses of plants to higher (up to 1000 uL/L) CO2 (Ca) concentrations are reviewed . An increase in the productivity of C3-plants under the effect of carbon dioxide enrichment (by 30-40%) of the atmosphere is, mainly, a result of the photosynthesis intensification and leaf area growth. The assimilates' pool level in plants de pends on the determination degree of vegetative growth, ability of the root system to utilize an excess of assimilates and on the environmental conditions, which explains why deep inhibition of photosynthesis under these conditions is not alway s observed. Relative effect of CO2 enrichment on the productivity is higher with lower illuminations, as the assimilates' deficiency is compensated by the photosynthesis intensification. The rate of plant development slightly depends on Ca whil e the total plants' resistance increased with Ca. Efficiency of water utilization grows almost twice with Ca duplication. CO2 enrichment makes efficiency of symbiotic nitrogen-fixation in leguminous plants higher. In Russian.UHϚ 257^3^Guy,M^Granoth,G^Gale,J^1990^1^Cultivation of _Lemna gibba_ under Desert Conditions. II: The Effect of Raised Winter Temperature, CO2 Enrichment and Shading on Productivity^41^23^^1-11^^^^^^^^^^630^^^^^^^^^^^Lemna gibba/duckweeded*Ú* C^628^Biomass1-u-u^2.uQ`2u2ud3ua3u6uIB DGc F+ A^628^The aim of this work was to increase the productivity of _Lemna gibba_ ponds under desert conditions. In the winter season, the ponds were covered with transparent plastic tents which raised water temperature. This also allowed CO2 to be added to the air in the tents to either the ambient, about 340 umol/mol, or to higher concentrations. The plastic covers a ttenuated photosynthetically active light by about 30%. Winter-season yields in the covered ponds, maintained at ambient C O2 concentration, were 39% higher than in the uncovered ponds. This could be ascribed to raised temperatures. Enrichment o f the atmosphere with CO2 further increased yields by as much as 28%. The different treatments did not affect protein cont ent expressed as a percentage of dry weight. Laboratory experiments indicated that the shorter the photoperiod the larger is the growth response of _Lemna gibba_ to CO2 enrichment. Shading of the ponds during the June-August summer season reduc ed pond temperatures at midday by about 5-6C and resulted in a 30-80% increase in growth. It was concluded that under des ert conditions similar to those prevailing in this trial, high yields of _Lemna gibba_ can be achieved throughout a growin g season of 12 months per year by covering the ponds and raising ambient [CO2] during the winter, and by shading in summer . Productivity of 7.4 +/- 1.0 g/m2/day can be maintained throughout the year. Whether or not it is worthwhile to do so is a question of local economics3)`3!áȿͿʿϿǿ̿00dayVff uj d 258^2^Guy,R D^Reid,D M^1986^1^Photosynthesis and the Influence of CO2-Enrichment on Delta-13 C Values in a C3 Halophyte^16^9^^65-72^^^^^^^^^^633^^^^^^^^^^^Puccinellia nuttallianana (Schultes) Hitch.^˾d&Ϳ&EϿ˸ C^631^Plant Cell Environ.3dHWנ̿F̿dV̿_QVWmrgF&=t5¾a A^631^Shifts in [delta]-13C of the graminaceous C3 halophyte _Puccinellia nuttalliana_ (Schultes) Hitch. can be induced by salinization. To investigate this phenomenon, three approaches were taken: assay of carboxylases, CO2-enrichment studies, and gas exchange analysis. Although ribulose-1,5-bisphosphate carboxylase activity decreased with salinity, phosphoenolpy ruvate carboxylase activity did not increase and its levels were not atypical of C3 plants. When plants were grown at four NaCl concentrations under atmospheres of 310 and 1300 cm3/m3 CO2, the CO2-enrichment enhanced the effects of salinity on [delta]-13C. This is consistent with a biophysical explanation for salt-induced shifts in [delta]-13C, whereby there is a steepening of the CO2 diffusion gradient into the leaf. Gas exchange analysis indicated that intercellular CO2 concentrati ons were depressed in the leaves of salt-affected plants. This resulted from a greatly decreased stomatal conductance coupled with only small effects on intrinsic photosynthetic capacity. Water-use efficiency was enhanced.k*9 259^1^Hanan,J J^1986^3^CO2 Enrichment for Greenhouse Rose Production^Physiology, Yield, and Economics^CRC Press, Inc.^Boca  Raton, Florida^142-149^^^^II^^Carbon Dioxide Enrichment of Greenhouse Crops^^^^635^^^^^^^^^^^rose^^^^^^^^^^Enoch,HZ^Kimball,BA AB A:|2ɋ&L 2 Qʚ*YbZY[XVT=:tV29^ٚMNȋY:&D t*&DtI&\ A^634^The literature indicates that CO2 enrichment is a successful and important adjunct to commercial plant production, t he actual practices being a function of climatic location and the particular technological surroundings. For roses, there has been a hiatus since the articles published by the Israelis and English in the 1970s. The North Europeans, particularly Danish and Dutch industry, appear to have taken the lead in instrumentation and computerization on a commercial scale, wi th actual use of CO2 monitors. However, there are some shortcomings in our practical knowledge of CO2 enrichment and rose physiology. First, we need to emphasize rates rather than simply CO2 concentration and irradiance level in the photosynthe tically active spectrum. Photosynthesis is a rate process, dependent upon several other rates. Blackman's contribution was the ability to open scientists' eyes to significant interactions in the photosynthetic process in a manner that allowed n ew investigative approaches. Second, we need to emphasize the importance of plant water potential on rates if CO2 enrichme nt is to achieve maximum, efficient utilization. Any student of practical plant physiology learns that the major portion o f radiation impinging upon a well-watered plant is converted to latent heat. The importance of this major energy redistrib ution supplies the rationale for a large portion of research at agricultural research stations. Parenthetically, more than  90% of total water withdrawals in the Southwestern U.S. is for irrigation. Based upon this review, and some 30 years of o bservation, it seems to me that manipulation of water potential to maximize CO2 uptake offers the greatest opportunity for  significant technological advance in increasing rose yields in greenhouses. This will require computers which can rapidly  process information from a number of instruments and recalculate settings of the implementation systems to control irradiance, vapor pressure deficits, CO2 levels, as well as plant temperature.}cG;k wwnkvenwvltu[w260^1^Hand,D W^1989^1^The 'Greenhouse Effect': Is It Best Studied in Greenhouses?^69^3^^76-82^^37 X m Y Z " C^636^Prof. Hort.. ' %JI'(O((p7 w'W=R^Ru>b>>a>>j>>k>>5>55> A^638^CO2 enrichment of the greenhouse atmosphere greatly improves the output, quality and value of vegetables, cut-flower s and ornamental plants. Raising the greenhouse CO2 concentration enhances photosynthesis and growth by increasing the rat e of CO2 fixation concomitantly with a suppression of photo-respiration. Prolonged exposure of plants to elevated CO2 conc entrations can, however, greatly accelerate the decline in the photosynthetic capacity of individual leaves with age. Comm ercially, CO2 for enrichment is normally obtained in liquid form or produced directly in the greenhouse atmosphere by burn !ing hydrocarbon fuels such as natural gas, LPG propane, and premium kerosene (paraffin) which all contain low and acceptab "le levels of sulphur. Plentiful supplies of natural gas in both Britain and The Netherlands have also encouraged growers i #n these countries to practise CO2 enrichment by ducting flue-gases into their greenhouses from centralized, gas-fired boil $er installations. Generating CO2 from hydrocarbon fuels can give rise to several gaseous air pollutants that are potential %ly damaging for crop production. The pollutants that cause most of the trouble in CO2-enriched greenhouses are nitrogen ox &ides such as nitric oxide and nitrogen dioxide, and unburnt hydrocarbons such as ethylene and propylene. Additionally, imp 'rovements to the insulation of heated greenhouses restrict air exchange and increase the hazard of certain plasticisers su (ch as the alkyl esters of phthalic acid which are used to give flexibility to PVC. The risk of incurring losses in yield d )ue to gaseous air pollutants can be minimized by using low-sulphur fuels, avoiding leaks of fuel gases, servicing burners *regularly, limiting fuel consumption and improving ventilation in near-airtight structures. Longer-term measures to improv +e the productivity of crops grown in polluted greenhouse atmospheres include the design of pollution-free burners, and the development and use of cultivars that are tolerant of gaseous air pollutants.vX'vX-vX3vXvXvXvXvXvXvXvX -262^1^Hand,D W^1986^3^CO2 Sources and Problems in Burning Hydrocarbon Fuels for CO2 Enrichment^Status and CO2 Sources^CRC .Press, Inc.^Boca Raton, Florida^99-121^^^^I^^Carbon Dioxide Enrichment of Greenhouse Crops^^^^642^^^^^^^^^^^^^^^^^^^^^Enoch,HZ^Kimball,BAAB AE?ZY[XvX~VvX vX6^tIV8vvX+]_^XVvXvX^ 0A^641^CO2 enrichment of the greenhouse atmosphere is an invaluable technique for improving the performance of high-value s 1alad and flower crops during the difficult winter period when poor light limits growth and development. According to gover 2nment statistics there are approximately 500 ha of heated glasshouses and film-plastic covered structures (greenhouses) in 3 England and Wales equipped specifically for CO2 enrichment. Additional areas of glasshouses receive incidental enrichment 4 when growers either use direct-fired burners for warm-air heating or grow their crops in raised beds of decomposing straw 5. CO2 for enrichment purposes can be either supplied in liquid form or produced directly by burning hydrocarbon fuels with 6 a low-sulfur content in the atmosphere. Bulk storage of liquid CO2 is difficult to justify economically on small areas of 7 glasshouses (i.e., less than 4000 m2) but handling liquid CO2 in cylinders is laborious, time-consuming and expensive. Na 8tural gas, LPG propane, and low-sulfur grades of kerosene (paraffin) are therefore favored by many growers because the CO2 9 is produced comparatively cheaply and the heat of combustion can provide a significant proportion of the daytime heat req :uirement in winter. Government statistics show that low-sulfur hydrocarbon fuels are used on 7 out of every 9 ha equipped ;for CO2 enrichment. Generating CO2 from hydrocarbon fuels can give rise to several gaseous air pollutants that are potenti nt for most of the injuries to crops growing in greenhouses enriched with CO2 produced from hydrocarbon fuels. These are t ?he nitrogen oxides such as NO and NO2 and unburnt hydrocarbons such as ethylene and propylene. Inefficient fuel combustion @ can also give rise to the formation of harmful aldehydes like formaldehyde and acrolein. Nitrogen oxides are formed in th Ae burner flame of a CO2 producer by the heat-promoted combination of atmospheric nitrogen and oxygen. The rate at which ni Btrogen oxides are generated depends essentially on flame temperature, i.e., the hotter the flame the greater the emission Cof nitrogen oxides. Modern CO2 producers have a high flame temperature to ensure efficient fuel combustion and the formati Don of nitrogen oxides is an inevitable consequence of burner design. When threefold CO2 enrichment is practiced the concen Etration of nitrogen oxides in the greenhouse atmosphere can be as high as 0.5 uL/L. Such a level may cause injury to crops F by reducing photosynthesis, inhibiting leaf expansion, depressing growth, and decreasing yield. Ethylene emissions from C GO2 producers are the result of complex reactions involved in the pyrolysis and oxidation of hydrocarbon fuels. Burner desi Hgn and operating variables such as the air-fuel ratio are crucial in determining the amount of ethylene released into the Igreenhouse atmosphere. In a well sealed greenhouse equipped for three-fold CO2 enrichment the ethylene concentration can e Jasily rise to a level at which the pollutant has discernible effects on crops, (i.e., between 0.01 and 0.1 uL/L). Ethylene K differs from the nitrogen oxides in that it is a naturally occurring plant growth regulator and can affect many growth, d Levelopmental, and aging processes. Escape of unburnt propylene gas (a major constituent of LPG propane) from loose-fitting M connections to fuel-supply lines and faulty switching of gas-solenoid valves can cause injuries to crops similar to those N induced by ethylene. Propylene concentrations of between 5 and 100 uL/L are commonly found in greenhouse atmospheres poll Outed by a leak of fuel gases from propane-fired CO2 producers. The pollutant mimics the action of ethylene, albeit at a concentration 100 times that required for injury by ethylene..BbD(ޏyKOr%" Q263^3^Hand,D W^Wilson,J W^Acock,B^1993^1^Effects of Light and CO2 on Net Photosynthetic Rates of Stands of Aubergine and _Amaranthus_^35^71^^209-216^^^^^^^^^^645^^^^^^^^^^^Solanum melongena/aubergine/eggplant/Amaranthus caudatus/grain amaranth Samaranth_A2xUE3t %M /qxDĊ ɗ ov & C^643^Ann. Bot.$" u/*r|"Qzd @?t;P! UA^643^Net photosynthetic rates per unit ground area for plant stands of _Solanum melongena_ L. var. _esculentum_ (aubergin Ve) and _Amaranthus caudatus_ L. var. _edulis_ (grain amaranth) were measured over 10 min intervals in an airtight, glass, Wcontrolled-environment cabinet for a range of light flux densities provided by the diurnal variation in daylight. Light re Xsponse curves for photosynthesis of stands, grown at ambient CO2 concentration, were defined at 400, 800 and 1200 vpm CO2. Y Light compensation points for these stands were around 20-30 J/m2/s and decreased slightly at higher CO2 concentrations. ZFor aubergine, a C3 species, the short-term effects of CO2 enrichment were to increase the initial slope as well as the as [ymptote of the light response curve, reducing light saturation at moderate to high light flux densities; but for amaranthu \s, a C4 species, saturation was less apparent and CO2 enrichment scarcely increased photosynthesis except at light flux de ]nsities above 150 J/m2/s. The canopies intercepted 93-98% of incident light. The efficiency of utilization of intercepted ^light in photosynthesis (ug CO2/J) increased from zero at the light compensation point to a maximum at an optimum light fl _ux density of about 100 J/m2/s (the optimum rose a little with CO2 enrichment) and decreased slightly with further increas `e in light. Maximum utilization efficiencies at 500 vpom CO2 were 8-9 ug CO2/J. Enrichment to 1200 vpm did not affect the apeak utilization efficiency of the C4 amaranthus, but increased that of aubergine to 12.2 ug CO2/J (equivalent to some 14% b when using the heat of combustion of plant dry matter to convert to the dimensionless form). This is among the highest re ccorded efficiencies of light utilization for stands, and relates to the exceptionally favourable environment, with optimal control of CO2 concentration, humidity, temperature, water supply and mineral nutrition. e264^2^Hari,P^Arovaara,H^1988^1^Detecting CO2 Induced Enhancement in the Radial Increment of Trees. Evidence from Northern Timber Line^70^3^^67-74^^^^^^^^^^648^^^^^^^^^^^Pinus sylvestris/Scots pineney~yy\yyyy[yy}!y!y RC^646^Scand. J. For. Res.96F)6F/6F8:8:Sy6Fw6Fx96F8:8:j6F8:x\X8:7:8:7:j6Fj6Fj6Fj6Fj6Fj6Fj6Fj hA^646^Annual Ring data from northern Finland was analysed in order to reveal possible trends in ring width development due i to changes in environmental factors. The data was analysed using a four component multiplicative model. The components ar je: tree age, climatic conditions, tree position and changes in environmental conditions. Since the effect of tree age and kposition in the stand could be easily eliminated the main problem was thus to eliminate the effect of climatic conditions lon ring width. This was based on the dependence of the daily radial increment and daily maximum temperature. The component m associated with changing environmental factors, especially to CO2 enrichment, was determined using the model. The basal a nrea development of the trees was calculated from measured and estimated ring widths. Depending on the value of the autocor orelation parameter, the effect of changes in environmental factors on the basal area increment of the trees is between 15.5-43.3% during the period from 1950 to 1983.0 2 0S / ,FbRXx`<6X9`+Co q265^2^Harley,P C^Sharkey,T D^1991^1^An Improved Model of C3 Photosynthesis at High CO2: Reversed O2 Sensitivity Explained rby Lack of Glycerate Reentry into the Chloroplast^18^27^^169-178^^^^^^^^^^651^^^^^^^^^^^soybean/Glycine max/cotton/Gossypium hirsutumpium hirsutum L.7:8:y=yVyjyly~yy\yyyy[yy}!y!y fC^649^Photosynth. Res.6F96F)6F/6F8:8:Sy6Fw6Fx96F8:8:j6F8:x\X8:7:8:7:3:3:3:3:JsO${${ uA^649^Current models of C3 photosynthesis incorporate a phosphate limitation to carboxylation which arises when the capaci vty for starch and sucrose synthesis fails to match the capacity for the production of triose phosphates in the Calvin cycl we. As a result, the release of inorganic phosphate in the chloroplast stroma fails to keep pace with its rate of sequestra xtion into triose phosphate, and phosphate becomes limiting to photosynthesis. Such a model predicts that when phosphate is y limiting, assimilation becomes insensitive to both CO2 and O2, and is thus incapable of explaining the experimental obser zvation that assimilation, under phosphate-limited conditions, frequently exhibits reversed sensitivity to both CO2 and O2, { i.e., increasing O2 stimulates assimilation and increasing CO2 inhibits assimilation. We propose a model which explains r |eversed sensitivity to CO2 and O2 by invoking the net release of phosphate in the photorespiratory oxidation cycle. In ord }er for this to occur, some fraction of the glycollate carbon which leaves the stroma and which is recycled to the chloropl ~ast by the photorespiratory pathway as glycerate must remain in the cytosol, perhaps in the form of amino acids. In that c ase, phosphate normally used in the stromal glycerate kinase reaction to generate PGA from glycerate is made available for photophosphorylation, stimulating RuBP regeneration and assimilation. The model is parameterized for data obtained on soybean and cotton, and model behavior in response to CO2, O2, and light is demonstrated.P 266^4^Harley,P C^Thomas,R B^Reynolds,J F^Strain,B R^1992^1^Modelling Photosynthesis of Cotton Grown in Elevated CO2^16^15^^271-282^^^^^^^^^^654^^^^^^^^^^^cotton/Gossypium hirsutumum L.!Dd}7  sC^652^Plant Cell Environ.0C:\WPC60DOS\VMATHSYN.WFW?t꤀D (jd>$"8>F"d@ A^652^Cotton plants were grown in CO2-controlled growth chambers in atmospheres of either 35 or 65 Pa CO2. A widely accept ed model of C3 leaf photosynthesis was parameterized for leaves from both CO2 treatments using non-linear least squares re gression techniques, but in order to achieve reasonable fits, it was necessary to include a phosphate limitation resulting from inadequate triose phosphate utilization. Despite the accumulation of large amounts of starch (>50 g/m2) in the high CO2 plants, the photosynthetic characteristics of leaves in both treatments were similar, although the maximum rate of Rub isco activity (Vcmax), estimated from A versus Ci response curves measured at 29C, was about 10% lower in leaves from pla nts grown in high CO2. The relationship between key model parameters and total leaf N was linear, the only difference betw een CO2 treatments being a slight reduction in the slope of the line relating Vcmax to leaf N in 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 only slightly less than that of leaves grown in 35 Pa CO2, net photosynthesis measured at the growth CO2, light and temperature conditions was approxim ately 25% greater in leaves of plants grown in high CO2, despite the reduction in leaf conductance. Greater assimilation rate was one factor allowing plants grown in high CO2 to incorporate 30% more biomass during the first 36 d of growth.( 267^3^Harley,P C^Weber,J A^Gates,D M^1985^1^Interactive Effects of Light, Leaf Temperature, CO2 and O2 on Photosynthesis in Soybean^51^165^^249-263^^^^^^^^^^657^^^^^^^^^^^soybean/Glycine maxax (L.) Merr.q^ C^655^Planta A^655^A biochemical model of C3 photosynthesis has been developed by G.D. Farquhar et al. (1980, Planta 149, 78-90) based on Michaelis--Menten kinetics of ribulose-1,5-bisphosphate (RuBP) carboxylase-oxygenase, with a potential RuBP limitation imposed via the Calvin Cycle and rates of electron transport. The model presented here is slightly modified so that parame ters may be estimated from whole-leaf gas-exchange measurements. Carbon-dioxide response curves of net photosynthesis obta ined using soybean plants (_Glycine max_ (L.) Merr.) at four partial pressures of oxygen and five leaf temperatures are pr esented, and a method for estimating the kinetic parameters of RuBP carboxylase-oxygenase, as manifested in vivo, is discu ssed. The kinetic parameters so obtained compare well with kinetic parameters obtained in vitro, and the model fits to the measured data give _r2_ values ranging from 0.87 to 0.98. In addition, equations developed by J.D. Tenhunen et al. (1976, Oecologia 26, 89-100, 101-109) to describe the light and temperature responses of measured CO2-saturated photosynthetic r ates are applied to data collected on soybean. Combining these equations with those describing the kinetics of RuBP carbox ylase-oxygenase allows one to model successfully the interactive effects of incident irradiance, leaf temperature, CO2 and O2 on whole-leaf photosynthesis. This analytical model may become a useful tool for plant ecologists interested in comparing photosynthetic responses of different C3 plants or of a single species grown in contrasting environments. 268^3^Hartz,T K^Baameur,A^Holt,D B^1991^1^Carbon Dioxide Enrichment of High-value Crops under Tunnel Culture^3^116^^970-97 3^^^^^^^^^^660^^^^^^^^^^^Cucumis sativus/cucumber/Cucurbita pepo/squash/Lycopersicon esculentum/tomato/Fragaria ananassa/strawberrysa Duch./strawberryU[5(5,,}h5 C^658^J. Amer. Soc. Hort. Sci.TV\:(:,,h: A^658^The feasibility of field-scale CO2 enrichment of vegetable crops grown under tunnel culture was studied with cucumbe r (_Cucumis sativus_ L. cv. Dasher II), summer squash (_Cucurbita pepo_ L. cv. Gold Bar), and tomato (_Lycopersicon escule ntum_ Mill. cv. Bingo) grown under polyethylene tunnels. The drip irrigation system was used to uniformly deliver a CO2-en riched air stream independent of irrigation. Carbon dioxide was maintained between 700 and 1000 uL/L during daylight hours . Enrichment began immediately after crop establishment and continued for about 4 weeks. At the end of the treatment phase , enrichment had significantly increased plant dry weight in the 2 years of tests. This growth advantage continued through harvest, with enriched cucumber, squash, and tomato plots yielding 30%, 20%, and 32% more fruit, respectively, in 1989. I n 1990, cucumber and squash yields were increased 20%, and 16%, respectively. As performed, the expense of CO2 enrichment represented less than a 10% increase in total preharvest costs. A similar test was conducted on fall-planted strawberries (_Fragaria_ x _ananassa_ Duch. cvs. Irvine and Chandler). Carbon dioxide enrichment under tunnel culture modestly increased 'Irvine' yields but did not affect 'Chandler'.& 269^2^Hartz,T K^Holt,D B^1991^1^Root-zone Carbon Dioxide Enrichment in Field Does Not Improve Tomato or Cucumber Yield^28^26^^1423^^^^^^^^^^^^^^^^^^^^^tomato/Lycopersicon esculentum/cucumber/Cucumis sativus sativus L. C^661^HortSci.\@\ 270^1^Harvey,L D D^1989^1^Effect of Model Structure on the Response of Terrestrial Biosphere Models to CO2 and Temperature Increase^11^3^^137-153^^^^^^^^^^665^^^^^^^^^^^^^^^^^^x (08@HPX C^663^Global Biogeochem. Cycles A^663^The sensitivity of a number of different globally aggregated models of the terrestrial biosphere to changes of atmos pheric CO2 and temperature is investigated. Net primary production (NPP) or net photosynthesis (NP) is modeled as a logist ic function, with enhancement due to increased CO2 using the beta factor widely used in global carbon cycle models. NPP al so increases with temperature using a Q10 of 1.4, while respiration and coefficients for translocation and for detritus to soil, and soil to soil, carbon transfers increase with a Q10 of 2.0. The pathway of carbon flow to the slowly overturning soil reservoir has a significant effect on equilibrium sensitivity of total carbon mass to temperature increases if the t ransfer coefficient from the rapidly to slowly overturning reservoir is fixed; maximum sensitivity occurs if all the carbo n entering the slowly overturning reservoir first passes through the rapidly overturning reservoir. If the transfer coeffi cient increases in parallel with the increase of soil respiration coefficient, the carbon pathway has no effect on equilib rium sensitivity, although the transient response depends strongly on the subdivision of the soil reservoir. Allowing the detritus to soil transfer coefficient to increase in parallel with the coefficient for detrital respiration reduces the eq uilibrium sensitivity of the total carbon mass to temperature increases by about half. The variation in model response to CO2 and temperature increase using different model structures is generally comparable to the variation resulting from uncertainty in feedback parameters.(0PX`hpx 271^4^Hatton,T J^Walker,J^Dawes,W R^Dunin,F X^1992^1^Simulations of Hydroecological Responses to Elevate CO2 at the Catchment Scale^25^40^^679-696^^^^^^^^^^668^^^^^^^^^^^Eucalyptus maculatata Hook. C^666^Aust. J. Bot. (08@HPX` A^666^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 catc hment water yield, soil moisture status and tree growth. Experimental results used to parameterise the model are detailed. Key features of the model are (1) an ability to scale hydrological processes at the catchment scale in three dimensions, and (2) a means to integrate multiple factors/stresses on plant growth. The effects of CO2 on catchment hydrology (water y ield or soil moisture content) and forest growth (expressed as leaf area index, LAI) were modelled for a 2-year period, an d contrasted with the effects of added nitrogen. Results were expressed as totals for the catchment or spatially distribut ed across the catchment. For the total catchment, water yield increased in the order: high CO2 with low N, high CO2 with h igh N, ambient CO2 with low N, ambient CO2 with high N. LAI increased from 3.3 to 5.76 in the order: ambient CO2 with low N, ambient CO2 with high N, high CO2 with low N, high CO2 with high N. These results agree with previous data. New finding s are: (1) with elevated CO2 a new equilibrium in transpiration is established in which leaf area increases offset decreas es in stomatal conductance; (2) the addition of nitrogen increases transpiration without any indication of a new equilibri um being reached during the simulated period; (3) the spatial distribution of soil moisture changes, presenting a new reso urce base for spatial changes to species composition and growth rates. The major hydroecological responses to elevated CO2 are seen as increased maximum upper canopy leaf area, increased litter inputs, especially at times of drought (hence chan ged fire regimes), changes in the composition of the understory (hence litter composition, soil microfauna, and the spatial expression of biological diversity) and a slight increase in water yield. 272^4^He,H^Kirkham,M B^Lawlor,D J^Kanemasu,E T^1992^1^Photosynthesis and Water Relations of Big Bluestem (C4) and Kentucky Bluegrass (C3) under High Concentration of Carbon Dioxide^71^95^^139-152^^^^^^^^^^671^^^^^^^^^^^Kentucky bluegrass/Poa pratensis/big bluestem/Andropogon gerardiiardii Vitman:ϜϜ̙̙ C^669^Trans. Kansas Acad. Sci.眙ǑÑ̟̜̙ A^669^As the carbon dioxide (CO2) concentration in the atmosphere increases, comparing how C3 and C4 plants will respond i s important. The objective of this study was to determine the photosynthetic rate, intercellular CO2 concentration, transp iration rate, stomatal resistance, leaf temperature, water potential, and water requirement of a C3 grass (Kentucky bluegr ass, _Poa pratensis_ L.) and a C4 grass (big bluestem, _Andropogon gerardii_ Vitman) growing in a fall in a tallgrass prai rie in Kansas under two levels of CO2 (ambient and two-times ambient). Elevated CO2 increased the photosynthetic rate of K entucky bluegrass by 151% but did not affect the photosynthetic rate of big bluestem. Intercellular CO2 concentrations of both grasses were increased by about the same amount, which was about half the increase in the atmospheric CO2 concentrati on. Doubled CO2 reduced the transpiration rates and increased stomatal resistance of both grasses, but big bluestem was af fected more than Kentucky bluegrass. The twice-ambient level of CO2 increased (between 0.2 and 0.3 MPa) the water potentia l of both grasses. Doubled CO2 decreased the water requirements of big bluestem and Kentucky bluegrass by 41.6% and 158%, respectively.UT̙灙273^1^Hendrey,G R^1992^1^The DOE/USDA FACE Program: Goal, Objectives, and Results Through 1989^8^11^^75-83^^^^^^^^^^67474 C^672^Crit. Rev. Plant Sci. A^672^The FACE system is a tool for studying the effects of CO2 enrichment on vegetation and natural ecosystems and the ex change of carbon between the biosphere and the atmosphere. FACE experiments are conducted in a true field setting without any chamber effect. FACE studies were conducted in an agronomic setting using cotton because the plant and field condition s are relatively uniform, thus permitting an evaluation of FACE performance. Cotton is a woody perennial with well-known p hysiological characteristics and a high level of response to CO2 enrichment. It is therefore a convenient subject for expe rimentation. The BNL FACE system was shown to be reliable in field experiments conducted in 1987-1989, providing effective control of CO2 concentrations in an open field setting without any type of confinement of ambient air. The system operate s effectively over plant canopies ranging in stature from bare ground to 200 cm with both open and closed canopies. Contro l of CO2 concentrations over large plots is within the criterion range +/- 20% of set point for 1-min averages at least 80 % of the time in all of these situations over both vertical and horizontal profiles. The area under effective control is d escribed, approximately, by the diameter of the FACE array minus 4 m and is as large as 380 m2 in the largest configuratio n tested to date (Hendrey 1992). In 1989 a 12-m diameter 'sweet spot' in the center of the FACE array had season-long aver age CO2 concentrations throughout the volume from ground level to the top of the canopy that were within the range of 94% to 104% of the target concentration. Operating costs for a four-array FACE system are approximately $450-650/m2 of usable plot area under effective CO2 control. Cotton grown under CO2 enrichment showed significant increases in biomass accumulat ion, both above ground and below ground. Soil respiration also increased in CO2 enriched plots. Enriched plants matured ea rlier and, in general, had greater agronomic yields. Water use efficiency increased with CO2 enrichment. The FACE system a s reported here has had two years of successful biological experimentation. Results from these experiments are intended fo r use in evaluating both the effects of CO2 on plants and ecosystems, and on the feedback processes operating between the biosphere and atmosphere that are the primary, short-term regulators of atmospheric CO2 concentration.. 274^1^Hendrey,G R^1992^2^FACE: Free Air CO2 Enrichment for Plant Research in the Field^CRC Press, Inc.^Boca Raton, Florida^^Y^^^^^^Critical Reviews in Plant Sciences^^^11^^^^^^^^^^^^^^^^^^^^^^Conger,BV^^^^^^^^^^^^ increases the internal inorganic carbon concentration and suppresses oxygenase activity of ribulose-1, 5-bisphosphate carb275^1^Hendrey,G R^1992^1^Global Greenhouse Studies: Need for a New Approach to Ecosystem Manipulation^8^11^^61-74^^78 C^677^Crit. Rev. Plant Sci.! 276^3^Hendrey,G R^Lewin,K F^Nagy,J^1993^1^Free Air Carbon Dioxide Enrichment: Development, Progress, Results^123^104/105^^17-31^^^^^^^^^^681^^^^^^^^^^^Gossypium hirsutum/cotton^^^^^^^wn to decrease after young greenhouse plants were placed in the dark. Seasonal variation in the ARA of excised plant roots A^679^Credible predictions of climate change depend in part on predictions of future CO2 concentrations in the atmosphere. Terrestrial plants are a large sink for atmospheric CO2 and the sink rate is influenced by the atmospheric CO2 concentrat ion. Reliable field experiments are needed to evaluate how terrestrial plants will adjust to increasing CO2 and thereby in fluence the rate of change of atmospheric CO2. Brookhaven National Laboratory (BNL) has developed a unique Free-Air CO2 En richment (FACE) system for a cooperative research program sponsored by the U.S. Department of Energy and U.S. Department o f Agriculture, currently operating as the FACE User Facility at the Maricopa Agricultural Center (MAC) of the University o f Arizona. The BNL FACE system is a tool for studying the effects of CO2 enrichment on vegetation and natural ecosystems, and the exchange of carbon between biosphere and the atmosphere, in open-air settings without any containment. The FACE sy stem provides stable control of CO2 at 550 ppm +/- 10%, based on 1-min averages, over 90% of the time. In 1990, this level  of control was achieved over an area as large as 380 m2, at an annual operating cost of 668/m2. During two field seasons of enrichment with cotton (_Gossypium hirsutum_) as the test plant, enrichment to 550 ppm CO2 resulted in significant incr eases in photosynthesis and biomass of leaves, stems and roots, reduced evapotranspiration, and changes in root morphology., In addition, soil respiration increased and evapotranspiration decreased.-S ~Sort by...,D%2HC~ 277^5^Hendrey,G R^Lewin,K F^Lipfert,F^Kolber,Z^Daum,M^1988^5^Free-Air Carbon Dioxide Enrichment (FACE) Facility Developmen t: I. Concept, Prototype Design and Performance^U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C^^^^^^^^^^^^^^^^^^^^^^^^^^045 in Green Report Series^Response of Vegetation to Carbon Dioxide^^ Filename @@   278^5^Hendrey,G R^Lipfert,F W^Kimball,B A^Hileman,D R^Bhattacharya,N C^1988^5^Free Air Carbon Dioxide Enrichment (FACE) Fa cility Development: II. Field Tests at Yazoo City, MS, 1987^U.S. Dept. of Energy, Carbon Dioxide Research Division, Washin!$gton, D.C^^^^^^^^^^^^^^^^^^^^^^^^cotton/Gossypium hirsutum^^046 in Green Report Series^Response of Vegetation to Carbon Di 279^1^Hendrix,D L^1992^1^Influence of Elevated CO2 on Leaf Starch of Field-Grown Cotton^8^11^^223-226^^^^^^^^^^^^^^^^^^^^^cotton/Gossypium hirsutumum L.UUÁꪪ C^684^Crit. Rev. Plant Sci.ꪪÁUUꪪǙ 280^4^Higginbotham,K O^Mayo,J M^L'Hirondelle,S^Krystofiak,D K^1985^1^Physiological Ecology of Lodgepole Pine (_Pinus contorta_) in an Enriched CO2 Environment^32^15^^417-421^^^^^^^^^^688^^^^^^^^^^^lodgepole pine/Pinus contortata C^686^Can. J. For. Res.UUÁꪪUU !A^686^Relatively little work has been done to evaluate the effects of chronically high levels of carbon dioxide on growth "and physiology of woody plants. In this study, seedlings of lodgepole pine (_Pinus contorta_ Dougl. var. _latifolia_ Engel #m.) were grown for 5-month periods at 330, 1000, or 2000 uL CO2/L. Height growth; leaf area production; biomass of leaves, $ stems, and roots; and photosynthetic responses to changing light, moisture, and CO2 concentration were measured. Signific %ant differences between treatments were found in mean seedling height on all measurement dates. Seedlings grown at 1000 uL & CO2/L were tallest, with seedlings grown in 2000 uL/L intermediate between the control (330 uL/L) and 1000 uL/L treatment 's. The same relationship was found in production of total leaf surface area. Increased leaf surface area yields a producti (ve advantage to seedlings grown at concentrations of CO2 up to 2000 uL/L even if no increase in net photosynthesis is assu )med. Biomass of stems, roots, and secondary leaves was increased in both elevated CO2 conditions, with root biomass approx *imately 15 times greater in seedlings grown at 1000 uL/L than in those grown at 330 uL CO2/L. Stomatal resistances were es +sentially the same for all treatments, indicating no CO2-induced stomatal closure to at least 2000 uL/L. Photosynthetic Vm ,ax (milligrams per square decimetre per hour) for light response curves varied with CO2 concentration. If results are extr -apolated beyond a 5-month period and into field conditions, it appears that size of trees, interactions with competitors, and ecological role of the species might be altered.!s˜ /281^1^Highsmith,M^1989^3^Two Aspects of Starch Formation in Mature Soybean Leaves^Current Topics in Plant Biochemistry and 0 Physiology: Proceedings of the Plant Biochemistry and Physiology Symposium^The Interdisciplinary Plant Biochemistry and Physiology Program, University of Missouri^Columbia^267^^^^8^^^^^^^^^^^^^^^^^soybean/Glycine max^^^^^8l8vv ``oxide^^^^ `00` f< growth rate, the observed adjustments that plants make to light and carbon dioxide concentration appear to be adaptive. W ?e show that the relationship between photosynthesis and leaf nitrogen concentration is complex and depends on the light an @d CO2 levels at which photosynthesis is measured. The shape of this function is important in determining Nopt and the oppo Asite response of leaf nitrogen to light and carbon dioxide is shown to be the result of the different effects of light and CO2 on the photosynthesis-leaf nitrogen curve.ϙ̙˙ɃꪪÙÑ C283^3^Hilbert,D W^Prudhomme,T I^Oechel,W C^1987^1^Response of Tussock Tundra to Elevated Carbon Dioxide Regimes: Analysis of Ecosystem CO2 Flux through Nonlinear Modeling^34^72^^466-472^^^^^^^^^^69696UU 4C^694^OecologiaUTÙ㌙ᙀဃꪪĜćÌ FA^694^The response of tussock tundra to elevated atmospheric concentrations of CO2 was measured at Toolik Lake, Alaska in Gthe summer of 1983. Computer-controlled greenhouses were used to determine diurnal ecosystem flux of CO2 under four treatm Hents: 340 ppm, 500 ppm, and 680 ppm CO2, as well as 680 ppm CO2 with a four degree centigrade increase in temperature. For I the seven days of data analyzed, net daily CO2 flux was significantly different between treatments. Net uptake was positi Jvely correlated with CO2 concentration in the chamber and negatively correlated with temperature. A nonlinear model was us Ked to analyze this data set and to determine some of the reasons for different net CO2 flux. This model allowed an estimat Lion of light utilization efficiency, total conductance of CO2, and a comparable measure of total respiration. From this an Malysis we conclude that nutrient limitations in the arctic decrease the capacity of tundra plants to make use of elevated NCO2 concentrations. The plants respond by decreasing conductance in the presence of elevated CO2, which results in approxi Omately equal gross uptake rates for the three CO2 treatments. Apparent changes in system respiration result in higher net Puptake under elevated CO2 but this may be due to biases in the data. The treatment with increased temperature exhibited hi Qgher conductances and, consequently, higher gross uptake of CO2 than the other treatments. Higher temperatures, however, a Rlso increase respiration with the result being lower net uptake than would be expected in the absence of temperature increases.UTꪪ T284^7^Hildmann,H^Windisch,K^Heissner,A^Weber,W^Domroese,J^Weber,S^Markert,A^1989^1^Testing a Strategy of Growth and Yield "Control in Greenhouse Cucumbers in a Specialized Vegetable Growing Farm^15^260^^123-136^^^^^^^^^^^^^^^^^^^^^Cucumis sativu V285^6^Hileman,D R^Bhattacharya,N C^Ghosh,P P^Biswas,P K^Lewin,K F^Hendrey,G R^1992^1^Responses of Photosynthesis and Stoma Wtal Conductance to Elevated Carbon Dioxide in Field-Grown Cotton^8^11^^227-231^^^^^^^^^^^^^^^^^^^^^cotton/Gossypium hirsutumum L.癌UU癙甙UT DC^698^Crit. Rev. Plant Sci.ꪪϜć Z286^2^Hocking,P J^Meyer,C P^1991^1^Carbon Dioxide Enrichment Decreases Critical Nitrate and Nitrogen Concentrations in Wheat^72^14^^571-584^^^^^^^^^^702^^^^^^^^^^^wheat/Triticum aestivumum L.UT XC^700^J. Plant Nut.UU ]A^700^Atmospheric carbon dioxide (CO2) levels are increasing, In a glasshouse experiment with wheat grown at 5 levels of n ^itrate (NO3) supply, CO2 enrichment (1500 cm3/m3) substantially decreased critical concentrations of NO3-N and total-N in _stem bases and leaves. For example, critical NO3-N concentrations in stem bases at Feekes Stages 1.5, 5, and 10.3, were 4. `5, 2.0, and 2.0 mg/g dry wt, respectively, for CO2-enriched plants, compared with 7.5, 6.2 and 6.4 mg/g dry wt, respective aly, for control plants grown at the ambient level of CO2. However, concentrations of NO3-N in the rooting medium required bto produce maximum dry matter accumulation by CO2-enriched plants were similar to those of control plants at the three gro cwth stages. Critical concentrations of NO3-N and total-N declined with time in stem bases and leaves of plants grown at bo dth ambient and elevated CO2 levels, but the decline was greater for CO2-enriched plants. It was concluded that diagnostic criteria based on current critical N concentrations may become invalid as the atmospheric level of CO2 increases. f287^2^Hocking,P J^Meyer,C P^1991^1^Effects of CO2 Enrichment and Nitrogen Stress on Growth, and Partitioning of Dry Matter and Nitrogen in Wheat and Maize^52^18^^339-356^^^^^^^^^^705^^^^^^^^^^^wheat/Triticum aestivum/maize/Zea mays mays L. [C^703^Austr. J. Plant Physiol.ꪨ iA^703^Atmospheric CO2 levels are increasing, but little is known about how this will affect tissue concentrations and the jpartitioning of agriculturally important nutrients such as nitrogen (N) within crop plants. To investigate this, a glassho kuse experiment was conducted in which wheat, a C3 species, and maize, a C4 species, were grown for 8 weeks at high CO2 (15 l00 cm3/m3) on N supplies ranging from deficient (0.5 mol/m3) to more than adequate for maximum growth (25 mol/m3). Wheat r mesponded to both CO2 enrichment and N supply; maize responded only to N supply. CO2-enriched wheat produced about twice th ne dry matter of control plants at all levels of N supply. Tiller and ear numbers were increased by CO2 enrichment irrespec otive of N supply. Enriched wheat plants had lower Leaf Area Ratio but higher Net Assimilation Rate and Relative Growth Rat pe than control plants. There was no effect of CO2 enrichment on specific leaf weight. The enriched plants had lower shoot qto root dry matter ratios than the controls at 6 mol/m3 N and higher. Shoot to root dry matter ratios of both wheat and ma rize increased with increasing N supply. CO2-enriched wheat plants accumulated more N than the controls but the proportiona sl increase in N content was not as great as that in dry matter, with the result that concentrations of total-N and nitrate t-N were lower in all organs of enriched plants, including ears. Nitrate reductase activity was lower in enriched than in c uontrol wheat plants. N-use efficiency by wheat was increased by CO2 enrichment. From a practical point of view, the study vindicates that critical total-N and NO3-N concentrations used to diagnose the N status of wheat will need to be reassessed w as global CO2 levels increase. Elevated CO2 may also reduce the protein content of grain and thus the baking quality of hard wheats.UU y288^2^Hoddinott,J^Jolliffe,P^1988^1^The Influence of Elevated Carbon Dioxide Concentrations on the Partitioning of Carbon in Source Leaves of _Phaseolus vulgaris_^54^66^^2396-2401^^^^^^^^^^708^^^^^^^^^^^Phaseolus vulgaris/bean/bean gC^706^Can. J. Bot.Ϝ |A^706^Plants may alter their growth pattern in response to being grown in elevated CO2 concentrations. The nature of the c }hange in carbon partitioning underlying those alterations was investigated in _Phaseolus vulgaris_ cv. Gold Crop grown to ~the third trifoliate leaf stage in CO2 concentrations of 380, 800, and 1400 ppm. There was no effect of the CO2 concentrat ion on plant height, leaf area, or dry weight, but the specific leaf weight increased significantly with the CO2 concentra tion, indicating a denser leaf structure. The starch content of the leaves also increased significantly as the CO2 level i ncreased. A primary leaf was pulse labelled with 14-CO2 and the depletion of label from that source leaf was monitored wit h a GM tube. The depletion of the count rate with time was described by a nonlinear curve fitting procedure that allowed t he derivation of rate constants to describe the partitioning of carbon in a two-compartment model. Rates of carbon storage decreased in the light with increasing CO2 concentrations with no effect on the rates of export or remobilization. Both e xport and storage were reduced in the dark at all CO2 levels, with an increase in the residence time of carbon in the expo rt pool. Reducing the CO2 concentration around the source leaf just after labelling did not change carbon partitioning com pared to controls. Increasing the CO2 concentration around the source leaf just after labelling increased all carbon flux rates and reduced the residence times in the leaf pools.E MATV5 .CLDjE MATVE .CLD|$E 289^3^Hogan,K P^Smith,A P^Ziska,L H^1991^1^Potential Effects of Elevated CO2 and Changes in Temperature on Tropical Plants^16^14^^763-778^^^^^^^^^^71111 MIKUL .CLDdRE MILENKY .CLDlRE MIRVIS .CLDj_ E MORA zC^709^Plant Cell Environ..CLDyPjE NAZIROV .CLDUE NEZVAL .CLD*yE NICKOLAY.CLDX A^709^Very little attention has been directed at the responses of tropical plants to increases in global atmospheric CO2 c oncentrations and the potential climatic changes. The available data, from greenhouse and laboratory studies, indicate tha t the photosynthesis, growth and water use efficiency of tropical plants can increase at higher CO2 concentrations. Howeve r, under field conditions abiotic (light, water or nutrients) or biotic (competition or herbivory) factors might limit the se responses. In general, elevated atmospheric CO2 concentrations seem to increase plant tolerance to stress, including lo w water availability, high or low temperature, and photoinhibition. Thus, some species may be able to extend their ranges into physically less favourable sites, and biological interactions may become relatively more important in determining the distribution and abundance of species. Tropical plants may be more narrowly adapted to prevailing temperature regimes tha n are temperate plants, so expected changes in temperature might be relatively more important in the tropics. Reduced tran spiration due to decreased stomatal conductance could modify the effects of water stress as a cue for vegetative or reprod uctive phenology of plants of seasonal tropical areas. The available information suggests that changes in atmospheric CO2 concentrations could affect processes as varied as plant/herbivore interactions, decomposition and nutrient cycling, local and geographic distributions of species and community types, and ecosystem productivity. However, data on tropical plants are few, and there seem to be no published tropical studies carried out in the field. Immediate steps should be undertaken to reduce our ignorance of this critical area.E WOOLFS .CLDYSE WOOLFSON.CLDzE YEGOROV 290^1^Hollinger,D Y^1987^1^Gas Exchange and Dry Matter Allocation Responses to Elevation of Atmospheric CO2 Concentration in Seedlings of Three Tree Species^43^3^^193-202^^^^^^^^^^714^^^^^^^^^^^Pinus radiata/Nothofagus fusca/Pseudotsuga menziesii/Monterey pine/New Zealand red beech/Douglas-fir pine/New Zealand red beech/Douglas-fir C^712^Tree Physiol. A^712^Photosynthetic rates of 13-month-old _Pinus radiata_ D. Don, _Nothofagus fusca_ (Hook f.) Orst. and _Pseudotsuga men ziesii_ (Mirb.) Franco seedlings grown and measured at elevated atmospheric concentrations of CO2 (about 620 uL/L) were 32 to 55% greater than those of seedlings grown and measured at ambient (about 310 uL/L) concentrations of CO2. Seedlings gr own in ambient and elevated concentrations of CO2 had similar rates of photosynthesis when measured at 620 uL/L CO2, but w hen measured at 310 uL/L CO2 the _P. radiata_ and _N. fusca_ seedlings which were grown at elevated CO2 had lower rates of photosynthesis than the seedlings grown at an ambient concentration of CO2. Stomatal conductances in general were lower when measured at 620 uL/L CO2 than at 310 uL/L CO2. 291^1^Houghton,R A^1987^1^Biotic Changes Consistent with the Increased Seasonal Amplitude of Atmospheric CO2 Concentrations^62^92^^4223-4230^^^^^^^^^^71717 C^715^J. Geophys. Res. A^715^Monthly estimates of gross primary production (gross uptake of CO2 by plants) and ecosystem respiration (gross relea se of CO2 from the ecosystem) in an oak-pine forest in the northeastern United States were used in this study to examine t he types of metabolic changes in terrestrial systems that might yield the increased seasonal amplitude of CO2 concentratio ns observed at several monitoring stations in recent years. In this study, increases in either photosynthesis or respirati on increased the amplitude of the seasonal oscillation of CO2 concentrations if the increases were predominantly in the no rthern hemispheric summer and winter, respectively. The quantitative changes in metabolism required to produce the observe d increase in amplitude, however, were too large to be explained by CO2 fertilization or by a temperature-induced increase in winter respiration. Investigations of the role of the biota in causing seasonal and year-to-year variations in atmospheric CO2 concentrations are limited by the lack of stations monitoring CO2 in continental air.=Vjl~\[292^1^Houghton,R A^1987^1^Terrestrial Metabolism and Atmospheric CO2 Concentrations^67^37^^672-678^^19^zZ:yY9 C^718^BioSci.8BxBXB8BwW7wW74w4W474vV6vV6&v&V&6&uU5rurUr5ruU5tT4dtdTd4d t T 4  293^4^Houpis,J L J^Surano,K A^Cowles,S^Shinn,J H^1988^1^Chlorophyll and Carotenoid Concentrations in Two Varieties of _Pin us ponderosa_ Seedlings Subjected to Long-term Elevated Carbon Dioxide^43^4^^187-193^^^^^^^^^^722^^^^^^^^^^^Pinus ponderosa/ponderosa pine^^^^^b'bgG'fF&TfTFT&TeE%eE%FeFEF%FdD$dD$8d8D8$8cC#cC#*c*C*#* C^720^Tree Physiol.A!hahAh!haA!`@ Z`Z@Z Z`@ A^720^Two varieties of ponderosa pine (_Pinus ponderosa_ Dougl. var. scopulorum (Rocky Mountain variety) and _P. ponderosa _ var. ponderosa (Sierran variety)) seedlings were subjected to elevated atmospheric CO2 for two and a half years. The CO2 concentrations were ambient, ambient + 75 uL/L, ambient + 150 uL/L and ambient + 300 uL/L, or approximately 350, 425, 500 and 650 uL/L CO2. After one and a half years of exposure to elevated CO2 and until the end of the study, seedlings of bot h varieties showed symptoms of stress including mottling, mid-needle abscission and early senescence. In both varieties, e xposure to CO2 concentrations greater than ambient + 75 uL/L resulted in lower chlorophyll _a_, chlorophyll _b_ and carote noid concentrations. At elevated CO2 concentrations, the concentration of pigments in needles of the Sierran variety were lower than those in the Rocky Mountain variety. Also, at elevated CO2 concentrations, the pigment concentrations in the 1-year-old needles of both _P. ponderosa_ varieties were lower than those in current-season needles.fE]_^ZY[X 294^4^Houpis,J L J^Surano,K A^Daley,P F^Shinn,J H^1986^3^Growth and Morphology of _Pinus ponderosa_ Seedlings Exposed to L ong-term Elevated Atmospheric Carbon Dioxide Concentration^Proceedings of the Ninth North American Forest Biology Workshop ; 1986 June 15-18; Stillwater, Oklahoma^Society of American Foresters, and Department of Forestry, Oklahoma State University^^19-26^^^^^^^^^^724^^^^^^^^^^^ponderosa pine/Pinus ponderosa^^^^^^^^^^Tauer,CG^Hennessey,TConderosa.d.+bAQW A^723^The growth and morphology of two varieties of _Pinus ponderosa_ were measured after two years of continuous fumigati on with carbon dioxide. After two years of treatment, the seedlings of the Rocky Mountain variety showed no significant di fference in total stem height or volume, but the basal diameters of those grown at +300 ppm CO2 were significantly greater than those grown at +0 ppm and +75 ppm. The response of the seedlings of the Sierran variety in these parameters was quit e different, with those at +150 ppm and +300 ppm significantly greater in height than those at +75 ppm and those at +150 p pm and +300 ppm significantly greater than those at +0 ppm and +75 ppm in basal diameter and stem volume. However, using a combined analysis based on percent change in height, diameter, or volume, seedlings at +150 ppm responded to a significan tly greater degree than all other levels. Thus, the beneficial effects of elevated carbon dioxide increase up to +150 ppm and begin to decrease between +150 ppm and +300 ppm.& GC.:Lr3ۀt#2"&2 & GC.:Lr3"֊2"" 295^4^Houter,G^Gijzen,H^Nederhoff,E M^Vermeulen,P C M^1989^1^Simulation of CO2 Consumption in Greenhouses^15^248^^315-320^^^^^^^^^^2056...>b.0.^.`*.^..`..B.C<uv<uOu#€t& C^725^Act. Hort.FҊ€t& Gt&G & !€t&0Gt&0G"&0...>b.0.^. 296^3^Hrubec,T C^Robinson,J M^Donaldson,R P^1985^1^Effects of CO2 Enrichment and Carbohydrate Content on the Dark Respiration of Soybeans^17^79^^684-689^^^^^^^^^^729^^^^^^^^^^^Glycine max/soybeanMerr./soybean..T.`..6U.6 C^727^Plant Physiol..R2.B2.CSW<u<uuU.T.6U.Pt32"&GC.:Lr3ۀt2& A^727^During the period of most active leaf expansion, the foliar dark respiration rate of soybeans (_Glycine max_ cv Will iams), grown for 2 weeks in 1000 microliters CO2 per liter air, was 1.45 milligrams CO2 evolved per hour leaf density thic kness, and this was twice the rate displayed by leaves of control plants (350 microliters CO2 per liter air). There was a higher foliar nonstructural carbohydrate level (_e.g._ sucrose and starch) in the CO2 enriched compared with CO2 normal pl ants. For example, leaves of enriched plants displayed levels of nonstructural carbohydrate equivalent to 174 milligrams g lucose per gram dry weight compared to the 84 milligrams glucose per gram dry weight found in control plant leaves. As the leaves of CO2 enriched plants approached full expansion, both the foliar respiration rate and carbohydrate content of the CO2 enriched leaves decreased until they were equivalent with those same parameters in the leaves of control plants. A st rong positive correlation between respiration rate and carbohydrate content was seen in high CO2 adapted plants, but not i n the control plants. Mitochondria, isolated simultaneously from the leaves of CO2 enriched and control plants, showed no difference in NADH or malate-glutamate dependent O2 uptake, and there were no observed differences in the specific activit ies of NAD+ linked isocitrate dehydrogenase and cytochrome _c_ oxidase. Since the mitochondrial O2 uptake and total enzyme activities were not greater in young enriched leaves, the increase in leaf respiration rate was not caused by metabolic a daptations in the leaf mitochondria as a response to long term CO2 enrichment. It was concluded, that the higher respiration rate in the enriched plant's foliage was attributable, in part, to a higher carbohydrate status....6b.0. 297^2^Huerta,A J^Ting,I P^1988^1^Effects of Various Levels of CO2 on the Induction of Crassulacean Acid Metabolism in _Portulacaria afra_ (L.) Jacq^17^88^^183-188^^^^^^^^^^732^^^^^^^^^^^Portulacaria afrafra (L.) Jacq.]_^ZY[Xˋ...6d C^730^Plant Physiol..^%.^%.`.+^@+ŋ.PK..U.d.+bAQRVW3..P. A^730^In response to water stress, _Portulacaria afra_ (L.) Jacq. (Portulacaceae) shifts its photosynthetic carbon metabol ism from the Calvin-Benson cycle for CO2 fixation (C3) photosynthesis or Crassulacean acid metabolism (CAM)-cycling, durin g which organic acids fluctuate with a C3-type of gas exchange, to CAM. During the CAM induction, various attributes of CA M appear, such as stomatal closure during the day, increase in diurnal fluctuation of organic acids, and an increase in ph osphoenolpyruvate carboxylase activity. It was hypothesized that stomatal closure due to water stress may induce changes i n internal CO2 concentration and that these changes in CO2 could be a factor in CAM induction. Experiments were conducted to test this hypothesis. Well-watered plants and plants from which water was withheld starting at the beginning of the exp eriment were subjected to low (40 ppm), normal (_ca._ 330 ppm), and high (950 ppm) CO2 during the day with normal concentr ations of CO2 during the night for 16 days. In water-stressed and in well-watered plants, CAM induction as ascertained by fluctuation of total titratable acidity, fluctuation of malic acid, stomatal conductance, CO2 uptake, and phosphoenolpyruv ate carboxylase activity, remained unaffected by low, normal or high CO2 treatments. In well-watered plants, however, both low and high ambient concentrations of CO2 tended to reduce organic acid concentrations, low concentrations of CO2 reduci ng the organic acids more than high CO2. It was concluded that exposing the plants to the CO2 concentrations mentioned had no effect on inducing or reducing the induction of CAM and that the effect of water stress on CAM induction is probably mediated by its effects on biochemical components of leaf metabolism..]u]_^ZY[XPSVW+@+F_^ 298^4^Hunt,R^Hand,D W^Hannah,M A^Neal,A M^1991^1^Response to CO2 Enrichment in 27 Herbaceous Species^37^5^^410-421^^^^^^^^ ^^735^^^^^^^^^^^Agrostis capillaris/Arrhenatherum elatius/Brachypodium pinnatum/Bromus erectus/Bromus sterilis/Cerastium f ontanum/Chamerion angustifolium/Chenopodium album/Dactylis glomerata/Deschampsia flexuosa/Desmazeria rigida/Digitalis purp urea/Epilobium hirsutum/Festuca ovina/Festuca rubra/Helianthemum nummularium/Holcus lanatus/Koeleria macrantha/Plantago la nceolata/Poa annua/Poa trivialis/Rumex acetosella/Urtica dioica/Zea mays/Plantago lanceolata/Lolium perenne/Helianthus annuus/Eriophorum vaginatumlantago lanceolata L./Poa annua L./Poa trivialis L./Rumex acetosella agg./Urtica dioica L./Zea ma ys L./Plantago lanceolata L./Lolium perenne L./Helianthus annuus L./Eriophorum vaginatum L.ك..`.+^A..d.+ C^733^Funct. Ecol.$F €u"Kt ʀu&G&_ rMu]_^ZY[Xˋ6>\ u(D .BD<t \.C A^733^CO2-enrichment experiments were performed on 25 British native species of widely differing ecology. Two crops, one C 3 (sunflower)and one C4 (maize), were also included. The background regime involved full-light, glasshouse conditions, non -limiting supplies of water and mineral nutrients and a daytime mean temperature of 18C. Four CO2 treatments were maintained at nominal concentrations of 350, 500, 650 or 800 v.p.m. over a 56-day period. Hyperbolic functions were fitted to yield _vs_ CO2 concentration. The functions were then used to generate predictions of Q-540/350 (the quotient of present yiel299^1^Idso,S B^1991^1^The Aerial Fertilization Effect of CO2 and Its Implications for Global Carbon Cycling and Maximum Greenhouse Warming^73^72^^962-965^^^^^^^^^^^^^^^^^^^^^Citrus aurantiumum L..;0%s$<u:;Ouu3YSQRVW.;0 C^736^Bull. Amer. Meteorol. Soc._^ZY[t..%؋>AuڎۋAu ڋ&;]vB&U&300^1^Idso,S B^1989^1^Carbon Dioxide, Soil Moisture, and Future Crop Production^74^147^^305-307^^^^^^^^^^74040;NuVNC^738^Soil Sci.u=&u!NVF;Frw;NsF^NFF؋MFC&]&]&]^NAW3pËK&E&A^738^Model simulations of the effects of increases in atmospheric carbon dioxide on air temperature, precipitation, and soil moisture suggest that the resultant 'greenhouse effect' will be bad for agriculture. Experimental evidence, however, i ndicates otherwise, demonstrating that plants can more than compensate for the predicted adverse climatic changes. Indeed, recent evidence from around the globe suggests that a carbon-dioxide-induced stimulation of the biosphere is already in progress.&Ku譗Ž&Ku**P+s3SRZ[r: [=^v${DD_^ZY[X& þLss 301^1^Idso,S B^1991^1^Comment on 'Modelling the Seasonal Contribution of a CO2 Fertilization Effect of the Terrestrial Vegetation to the Amplitude Increase in Atmospheric CO2 at Mauna Loa Observatory' by G.H. Kohlmaier et al^75^43B^^338-341^^4C^741^Telluss;TvS..G._.G[WS_&EG?[o_G?_S..o._.[PRWs#; 2tV,*0;s t^^+s#_ZXQY˱QY˱QY˱ QY˱PSRWFNvLs302^1^Idso,S B^1991^1^A General Relationship between CO2-induced Increases in Net Photosynthesis and Concomitant Reductions in Stomatal Conductance^76^31^^381-383^^^^^^^^^^745^^^^^^^^^^^Citrus aurantium/sour orangerange_Z[XQV+ˋs#+)sC^743^Environ. Exp. Bot.+t!+ t+FuUNF C^751^Plant Physiol.6F| t{^FE;FtQ t.L8E~rntsM^tF.T8]ZrJPsM}t&+A^751^Several years of research on seven different plants (five terrestrial and two aquatic species) suggest that the bene,ficial effects of atmospheric CO2 enrichment may be divided into three distinct growth response phases. First is a well-wa-tered optimum-growth-rate phase where a 300 parts per million increase in the CO2 content of the air generally increases p.lant productivity by approximately 30%. Next comes a nonlethal water-stressed phase where the same increase in atmospheric/ CO2 is more than half again as effective in increasing plant productivity. Finally, there is a water-stressed phase norma0lly indicative of impending death, where atmospheric CO2 enrichment may actually prevent plants from succumbing to the rig1ors of the environment and enable them to maintain essential life processes, as life ebbs from corresponding ambient-treatment plants.@؉Ft]ZY[PQRVU;vsF]^ZYXPQRVU;vsF]^ZYXPSQRWV+Fv+@@F3307^1^Idso,S B^1989^1^Three Stages of Plant Response to Atmospheric CO2 Enrichment^20^27^^131-134^^^^^^^^^^756^^^^^^^^^^^Eichhornia crassipes/water hyacinth/water lily/Nymphaea marliaccarnea marliac carneavV:Vr2ҋvvVOItc)C^754^Plant Physiol. Biochem.+FvرЉFF.L8ЈFF+@FF.T8ЈFFF6tL&56A^754^Weekly assessments of biomass production in water hyacinths (_Eichhornia crassipes_) and daily assessments of new-le7af production in water lilies (_Nymphaea marliac carnea_) demonstrate that the positive effects of atmospheric CO2 enrichm8ent on the growth rates of these plants are considerably greater both before (I) and after (III) the primary maximum-growt9h-rate stage (II) characteristic of the middle portion of a plants' life cycle. For these two particular aquatic macrophyt:es, the growth enhancement factor for a 300 uL/L increase in the atmospheric CO2 concentration went from a mean of 1.54 in stage I, to 1.33 in stage II, to actually approach infinity in stage III.&;Dr^&;\s&\^&D#+ҏw3;sX@Ⰻ<308^4^Idso,S B^Allen,S G^Anderson,M G^Kimball,B A^1989^1^Atmospheric CO2 Enrichment Enhances Survival of _Azolla_ at High Temperatures^76^29^^337-341^^^^^^^^^^759^^^^^^^^^^^Azolla pinnata/water fernrnE u\ T;z9&EvC\r4C^757^Environ. Exp. Bot.3ۉ\\6tC&]&E 3]^[UW~N m_]UW~N [V_]VUP&5D &EPDP?A^757^In 2 years of experimentation with _Azolla pinnata_ var. _pinnata_ at Phoenix, Arizona, growth rates of this floatin@g aquatic fern first decreased, then stagnated, and finally became negative when the mean air temperature rose above 30C.A When the atmospheric CO2 content above the plants was increased from the mean ambient concentration of 340 umol CO2/mol aBir to 640 umol CO2/mol air, however, the debilitating effects of high temperatures were reduced: in one case to a much lesCs severe negative growth rate, in another case to merely a short period of zero growth rate, and in a third case to no disDcernible ill effects whatsoever -- in spite of the fact that the ambient treatment plants in this instance all died. With Ethe double verification of this phenomenon provided by both weekly biomass and periodic net photosynthesis determinations,F it would appear that atmospheric CO2 enrichment may be capable of preventing the deaths of some plant species in situatioGns where their demise is normally brought about by either the direct effects of unduly high temperatures or by associated debilitating diseases.F^ _]UW~F^ _]UVv3ɀ<-uFњ*v 3^]UWVv~ &% t uI309^3^Idso,S B^Allen,S G^Kimball,B A^1990^1^Growth Response of Water Lily to Atmospheric CO2 Enrichment^78^37^^87-92^^^^^^^^^^762^^^^^^^^^^^water lily/Nymphaeaea&G3^_]dQQSVtw^[YSQRWU u_G=C^760^Aquat. Bot.${YDT WTWDLd*s =uDOLGO ;Nv)Nw;G r 7GWGD TO LA^760^Hardy water lilies (_Nymphaea_ cultivar 'Marliacea carnea') were grown out-of-doors at Phoenix, Arizona in sunken meMtal stock tanks located within open-top, clear plastic-wall, CO2-enrichment chambers; two were maintained at a CO2 concentNration of 650 ppm and two were maintained at the ambient CO2 concentration of about 350 ppm. Over a 5-month period, 25 difOferent plant properties were evaluated, each one of which showed some degree of stimulation or enhancement under CO2-enricPhed conditions. In particular, net photosynthesis was increased by about 49%, leaf size by 18%, and integrated leaf numberQ x life span by 16%, which resulted in a whole-plant biomass enhancement of 270%. After 21 months, differences between treRatments were not quite as dramatic; but at the conclusion of the experiment, the rhizomes in the CO2-enriched treatment were still more than two-and-a-half times greater in total biomass than their ambient-grown counterparts.HtaP>DtT310^3^Idso,S B^Clawson,K L^Anderson,M G^1986^1^Foliage Temperature: Effects of Environmental Factors with Implications forU Plant Water Stress Assessment and the CO2/Climate Connection^79^22^^1702-1706^^^^^^^^^^765^^^^^^^^^^^water hyacinth/Eichhornia crassipes/cotton/Gossypium hirsutum/alfalfa/Medicago sativaa/Medicago sativa L.D\!DtD \ND u srJC^763^Water Resources Res.D u})^spPD\+D \r^u;v^Xrl~t QL.fY+s3L\XA^763^Throughout the summer and fall of 1985, several day-long sets of foliage temperature measurements were obtained for Yhealthy and potentially transpiring water hyacinth, cotton, and alfalfa plants growing in a sealed and unventilated greenhZouse at Phoenix, Arizona, along with concurrent measurements of air temperature, vapor pressure and net radiation, plus in[ the case of water hyacinths, leaf diffusion resistance measurements. Some data for these plants were additionally obtaine\d out of doors under natural conditions, while dead, nontranspiring stands of alfalfa and water hyacinth were also monitor]ed, both out of doors and within the greenhouse. Analyses of the data revealed that plant nonwater-stressed baselines, i.e^., plots of foliage-air temperature differential versus air vapor pressure deficit for potentially transpiring vegetation,_ were (1) curvilinear, as opposed to the straight lines which have so often appeared to be the case with much smaller and `restricted data sets, and (2) that these baselines are accurately described by basic theory, utilizing independently measuared values of plant foliage and aerodynamic resistances to water vapor transport. These findings lead to some slight adjusbtments in the procedure for calculating the Idso-Jackson plant water stress index and they suggest that plants can adequatcely respond to much greater atmospheric demands for evaporation than what has been believed possible in the past. In additdion, they demonstrate that the likely net radiation enhancement due to a doubling of the atmospheric carbon dioxide concenetration will have little direct effect on vegetation temperatures, but that the antitranspirant effect of atmospheric CO2 enrichment on foliage temperature may be substantial.E@E&T t &VDD tD_Z[X3D t|g311^3^Idso,S B^Kimball,B A^Anderson,M G^1985^1^Atmospheric CO2 Enrichment of Water Hyacinths: Effects on Transpiration and Water Use Efficiency^79^21^^1787-1790^^^^^^^^^^768^^^^^^^^^^^water hyacinth/Eichhornia crassipeses (Mart.) Solms+ZXQVVC^766^Water Resources Res.D u]^Y3|tD trAPD @tk/$r-D t$L&Su &&P&&Rd &PtjA^766^Open-top clear plastic wall chambers enclosing pairs of sunken metal stock tanks, one of each pair of which containekd a full cover of water hyacinths, were maintained out-of-doors at Phoenix, Arizona for several weeks during the summer ofl 1984. One of these chambers represented ambient conditions, while the other three were continuously enriched with carbon mdioxide to approximate target concentrations of 500, 650, and 900 ppm. During a 4-week period when plant growth was at itsn maximum, water hyacinth biomass production increased by 36% for a 300-600 ppm doubling of the atmospheric CO2 content, whoile water use efficiency, or the biomass produced per unit of water transpired, actually doubled. These results are similapr to hat has been observed in several terrestrial plants and they indicate the general trend which may be expected to occur as atmospheric CO2 continues to rise in the years ahead.9=r/ t&)}3F&r312^3^Idso,S B^Kimball,B A^Mauney,J R^1987^1^Atmospheric Carbon Dioxide Enrichment Effects on Cotton Midday Foliage Temperature: Implications for Plant Water Use and Crop Yield^4^79^^667-672^^^^^^^^^^771^^^^^^^^^^^cotton/Gossypium hirsutum^^^^hC^769^Agron. J.؋%^. _ZXϋ$0<0u)u" t r>u&Ë<t <u &봀uA^769^In an experiment designed to determine the likely consequences of the steadily rising carbon dioxide (CO2) concentravtion of Earth's atmosphere for the foliage temperature, water use, and yield of cotton (_Gossypium hirsutum_ L. var. Deltawpine-61) plants, cotton was grown out-of-doors at Phoenix, AZ, in open-top, clear-polyethylene-wall, CO2-enrichment chambexrs for three summers under mean daylight CO2 concentrations of 340, 500 and 640 umol CO2/mol air on an Avondale clay loam ysoil [fine-loamy, mixed (calcareous), hyperthermic Anthropic Torrifluvent]. Infrared thermometer measurements of the cottozn foliage temperature (Tf) indicated that a 330 to 660 umol CO2/mol air doubling of the atmospheric CO2 content results in{ a midday Tf increase of 1.1C for well-watered cotton at Phoenix in the summer. This temperature increase was predicted t|o produce a 9% reduction in per-unit-leaf-area plant transpiration rate and an 85% increase in crop biomass production, wh}ich compared favorably with the measured crop biomass increase of 82% for such a doubling of the air's CO2 content. These ~findings, together with similar findings for a second plant species -- water hyacinth [_Eichhornia cassipes_ (Mart.) Solms] -- allowed us to develop a technique for assessing the effects of a 330 umol CO2/mol air CO2 concentration increase on the percentage yield increase (Y) of a crop via infrared thermometry by means of the equation Y = 7.6% x (IJ), where IJ represents the Idso-Jackson plant water stress index. If this equation holds up under further scrutiny, it could provide a rapid and efficient means for assessing the yield response of crops to atmospheric CO2 enrichment.BB. a.s.Pa$.>wte((((( (  (( (. (4 (: (@ (313^3^Idso,S B^Kimball,B A^Allen,S G^1991^1^CO2 Enrichment of Sour Orange Trees: 2.5 Years into a Long-term Experiment^16^14^^351-353^^^^^^^^^^774^^^^^^^^^^^sour orange/Citrus aurantiumum L.(((((((C^772^Plant Cell Environ.((((((l(Q(V(\(a(c(A^772^Eight sour orange trees have been grown from seedling stage in the field at Phoenix, Arizona, U.S.A., in four identically-vented, open-top, clear-plastic-wall chambers for close to 2.5 years. Half of the chambers have been maintained at ambient atmospheric CO2 concentrations over this period, while half of them have been maintained at 300 ppm (300 umol CO2 per mol air) above ambient. Initially, the trees in each treatment were essentially identical; but in less than 2 years, the trunks of the CO2 enriched trees had become twice as large as their ambient-treatment counterparts. After 2 full years of growth, the enriched trees had 79% more leaves, 56% more primary branches with 72% more volume, 70% more secondary branches with 90% more volume, and 250% more tertiary branches with 855% more volume. In addition, the CO2-enriched trees also had fourth-, fifth- and sixth-order branches, while the ambient treatment trees had no branches above third order. Total trunk plus branch volume of the CO2-enriched trees was 2.79 times that of the ambient-treatment trees after 2 full years of growth.KMOUPQZR]SQsTtSu v wXWcdnm P  _  _ *7*-J\+N314^2^Idso,S B^Kimball,B A^1991^1^Downward Regulation of Photosynthesis and Growth at High CO2 Levels^17^96^^990-992^^^^^^^^^^777^^^^^^^^^^^sour orange/Citrus aurantiumum L. J  C^775^Plant Physiol. !"#$%&'()*+,-./0123456789:;<=>zNxxx,,XxU^<A^775^Numerous photosynthesis and growth measurements of sour orange (_Citrus aurantium_ L.) trees maintained in ambient air and air enriched with an extra 300 microliters per liter of CO2 have revealed the CO2-enriched trees to have consistently sequestered approximately 2.8 times more carbon than the control trees over a period of three full years. Under field conditions in the natural environment, plants may not experience the downward regulation of photosynthetic capacity typically observed in long-term CO2 enrichment experiments with plants growing in pots.+-/537"(%$=?AEI>F315^4^Idso,S B^Kimball,B A^Anderson,M G^Mauney,J R^1987^1^Effects of Atmospheric CO2 Enrichment on Plant Growth: the Interactive Role of Air Temperature^13^20^^1-10^^^^^^^^^^780^^^^^^^^^^^carrot/Daucus carota/radish/Raphanus sativus/water hyacinth/Eichhornia crassipes/water fern/Azolla pinnataern/Azolla pinnataeEeIIIINnOoOoOoOoUuUuUC^778^Agric. Ecosystems Environ.AaAaAaCcCcCcCcDdEeEeEeEeGgGgGgGg GgGgHhHhIIIA^778^Comprehensive reviews of the plant science literature indicate that a 300 part per million (ppm) increase in atmospheric carbon dioxide (CO2) concentration generally increases plant growth by approximately 30%. Working with two species of floating aquatic plants and three terrestrial species, we demonstrate that this stimulatory effect of atmospheric CO2 enrichment is strongly temperature dependent. Indeed, our results suggest that for a 3C increase in mean surface air temperature (as is generally predicted to result from the 'greenhouse effect' of such an increase in the CO2 content of the air), the growth enhancement factor for such a CO2 increase rises from 1.30 to 1.56. If the non-CO2 trace gas greenhouse effect is equally as strong, as recent model studies suggest, the growth enhancement factor rises still higher to a value of 1.85. On the other hand, our results also indicate that atmospheric CO2 enrichment tends to _reduce_ plant growth at relatively cold air temperatures, i.e. below a daily mean air temperature of approximately 18.5C. As a result, predicting the ultimate biospheric consequences of a doubling of the Earth's atmospheric CO2 concentration may prove to be much more complex than originally anticipated. @&XSQVPYr& PXsx^Y[PrhXSQH3CY[SQ6ur &316^3^Idso,S B^Kimball,B A^Mauney,J R^1988^1^Effects of Atmospheric CO2 Enrichment on Root:Shoot Ratios of Carrots, Radish, Cotton and Soybean^13^22^^293-299^^^^^^^^^^783^^^^^^^^^^^soybean/Glycine max/cotton/Gossypium hirsutum/radish/Raphanus sativus/carrot/Daucus carotarrot/Daucus carota L. r @_ZY[XPSQRVW&> t eF3ۉ^&>uC^781^Agric. Ecosystems Environ.rF~SRZ[s-^6 E~ r6& EF& &t& &tXÃ~tA^781^Detailed analyses of root:shoot ratios, determined at weekly intervals during a succession of cropping cycles, show that the responses of root crops, such as radish and carrot, differ from those of cotton and soybean. Whereas the root:shoot ratios of the latter crops were not affected by atmospheric CO2 enrichment, increasing the CO2 concentration of the air from 340 (ambient) to 650 umol CO2/mol air significantly increased the proportions of assimilates allocated to the roots of radish and carrot. This effect increased the root:shoot ratios of both root crops by approximately 36% at all stages of plant growth, suggesting a response to atmospheric CO2 enrichment that is independent of plant size and not caused by a progressive reduction in nitrogen availability. H&&&&t 3Ҍ^s^YXPS6D36;Dt[&t317^2^Idso,S B^Kimball,B A^1991^1^Effects of Two and a Half Years of Atmospheric CO2 Enrichment on the Root Density Distribution of Three-year-old Sour Orange Trees^46^55^^345-349^^^^^^^^^^786^^^^^^^^^^^Citrus aurantium/sour orangerangeu3C^784^Agric. For. Meteorol. u42fs+6>EtururDs 6>EuX6>Dut`36D6D36;DsXA^784^Eight sour orange trees planted directly into the ground at Phoenix, Arizona, as small seedlings in July 1987 have been enclosed by four clear-plastic-wall, open-top chambers since November of that year, half of which have been continuously supplied with a CO2 enriched atmosphere consisting of an extra 300 cm3 CO2/m3 of air. Extensive soil coring of the trees' root zones conducted in July 1990 indicated that two and a half years of growth under these conditions produced a fine root biomass enhancement of 175% in the CO2 enriched trees. This growth enhancement is of the same order of magnitude as our previously reported results for net photosynthesis and trunk and branch volumes for these trees._^ZY[XWu1 r,318^2^Idso,S B^Kimball,B A^1993^1^Effects of Atmospheric CO2 Enrichment on Net Photosynthesis and Dark Respiration Rates of Three Australian Tree Species^38^141^^166-171^^^^^^^^^^789^^^^^^^^^^^Australian bottle tree/Brachychiton populneum/sour orange/Citrus aurantium/Eucalyptus microtheca/Eucalyptus polyanthemus. Muell./Eucalyptus polyanthemus Schauer2DDC^787^J. Plant Physiol.U&eF&E_^ZY[XQVW6D6D+t u_^YÀ> uuu tsA^787^Net photosynthesis and dark respiration rates of leaves of three Australian tree species exposed to a range of atmospheric CO2 concentrations were measured throughout the summer of 1991. For all three species - the Australian bottle tree (_Brachychiton populneum_ (Schott.) R. Br.) and two eucalyptus (_Eucalyptus microtheca_ F. Muell. and _E. polyanthemus_ Schauer) - dark respiration dropped by approximately 50% for a 360 to 720 uL/L doubling of the air's CO2 concentration, while net photosynthesis rose by a factor of two. These results were not significantly different from results obtained previously for the common orange tree (_Citrus aurantium_ L.).&u.& t && t &n&6DdW&t319^3^Idso,S B^Kimball,B A^Anderson,M G^1986^1^Foliage Temperature Increases in Water Hyacinth Caused by Atmospheric CO2 Enrichment^126^Ser. B 36^^365-370^^^^^^^^^^792^^^^^^^^^^^water hyacinth/Eichhornia crassipes^^^^^art.) Solms^^^^^inth/EicpJSrnia crassipes (Mart.) Solms& 6D !&&6+wvـPX^VC^790^Ser. B 36 Arch. Met. Geoph. Biocl.Ev^6EV6E^& V& !Cvq_^ZY[XSA^790^Atmospheric CO2 enrichment tends to induce partial stomatal closure in most higher plants. This phenomenon reduces per-unit-leaf-area plant transpirational water loss rates, which in turn leads to higher plant temperatures. Working in the field with water hyacinths maintained in open-top, clear-plastic wall, CO2-enrichment chambers at Phoenix, Arizona, we have quantified this relationship for a plant species which has been shown previously to react like most land plants in this regard. Our results indicate that in some parts of the world this non-greenhouse mechanism for surface temperature change may play an important role in determining future climate. Under sunlit and well-watered conditions conducive to active growth, for instance, we found water hyacinth foliage temperatures to increase by 2.7 K in response to a 300 to 600 ppm doubling of the atmospheric CO2 concentration.Hu6:E6EDD WgaQRQ@+D;rV3ҋD;D t@320^4^Idso,S B^Kimball,B A^Anderson,M G^Szarek,S R^1986^1^Growth Response of a Succulent Plant, _Agave vilmoriniana_, to Elevated CO2^17^80^^796-797^^^^^^^^^^795^^^^^^^^^^^Agave vilmorinianana BergergGY˃>EtV^PQREole-plant net CO2 exchange rate (NCER) of Samantha rose plants. At 22C, the NCER was saturated at 1000 umol/m2/s photosyn?thetically active radiation (PAR). The duration of the light period was also important in determining daily carbon (C) gai@n. When roses were exposed to a constant daily radiant energy dose of 17.6 umol/m2 provided either as a 12-h irradiation iAnterval at 410 umol/m2/s PAR or 24 h of irradiation at 204 umol/m2/s PAR, the plants exposed to 24 h of continuous irradiaBtion at the lower photon flux density retained 80% more C. Under saturating irradiance, the net photosynthetic rate at an Cenriched (1000 uL/L) CO2 level was almost double that at ambient (350 uL/L) CO2. However, plants grown at ambient and enriDched CO2 levels had similar whole-plant NCERs when compared at the same assay CO2 level. Under CO2 enrichment the flower sEtem 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.anovWP( U$  HP LaserJeG330^3^Jiao,J^Tsujita,M J^Grodzinski,B^1991^1^Optimizing Aerial Environments for Greenhouse Rose Production Utilizing Whole-plant Net CO2 Exchange^29^71^^253-261^^^^^^^^^^822^^^^^^^^^^^rose/Rosa hybridadaH9q0)\;C^820^Can. J. Plant Sci.ew RomanHd8R8%8>!8>!8>uZ&e&"8Z2[ t<JA^820^A daily growth model was developed for Samantha roses based on nondestructive measurements of whole-plant net CO2 exKchange rate (NCER) under various aerial environmental conditions. Irradiance, CO2 concentration, and temperature accountedL for 70, 20, and 5%, respectively, of the variance in whole-plant net photosynthesis explainable by a second-order polynomMial model (R2=0.86). The predicted optimal temperatures for whole-plant net photosynthesis increased from 19 to 24C with Nincreasing irradiance from 100 to 1200 umol/m2/s and CO2 concentration from 350 to 1500 uL/L. Dark respiration rate increaOsed exponentially with temperature and could be predicted by the Arrhenius equation. Even though respiratory carbon (C) loPss at night increased linearly with daytime C gain, daily C gain (delta C) was still proportional to daytime net photosyntQhesis. The relative contribution of irradiance (100-1200 umol/m2/s), day length (8-16 h), CO2 concentration (350-1500 uL/LR), day temperature (15-30C), and night temperature (15-25C) to plant daily growth was 64, 31, 4, 0.3, and 0.7%, respectively.*˴J!Kl!L!.40!<swss s4C*C%2}sk2}WWV&,&l&T331^3^Johnson,H B^Polley,H W^Mayeux,H S^1993^1^Increasing CO2 and Plant-plant Interactions: Effects on Natural Vegetation^U123^104/105^^157-170^^^^^^^^^^825^^^^^^^^^^^Prosopis glandulosa/mesquite/Schizachyrium scoparium/little bluestem/Brassica Vkaber/field mustard/Avena sativa/oat/Cenchrus incertus/Paspalum setaceum/Panicum cappillare/Digitaria ciliaris/Eragrostis Wspectabilis/Cyperus globulosus/Mollugo verticillata/Sporobolus neglectus/Euphorbia prostrata/Setaria sp./Echinochloa crus-Xgalli/Amaranthus sp./Croton glandulosa/Verbena hastata/Verbena halei/Oenothera sp./Ratibida columnaris/Ambrosia artemisiifYolia/Lesquerella sp./Gaillardia pulchella/Gaura sp./Solanum sp./Gutierrezia dracunculoides/Rudbeckia hirta/Commelina erecta/Panicum angustifolium/Croton capitatum/Monarda punctata/Croton monanthogynus/Oxalis dillenii^^^^^GrJ.<tD>ʾ@D  27%. Further evidence of the dependence of ARA on plant photosynthate was obtained when activity in excised roots was sho\A^823^Plant species and functional groups of species show marked differences in photosynthesis and growth in relation to r]ising atmospheric CO2 concentrations through the range of the 30% increase of the recent past and the 100% increase since ^the last glaciation. A large shift was found in the compositional mix of 26 species of C3's and 17 species of C4's grown f_rom a native soil seed bank in a competitive mode along a CO2 gradient that approximated the CO2 increase of the past 150 `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 25% aas CO2 levels approached current ambient. The proposition that acclimation to rising CO2 will largely negate the fertilizabtion effect of higher CO2 levels on C3's is not supported. No signs of photosynthetic acclimation were evident for _Avena csativa, Prosopis glandulosa_, and _Schizachyrium scoparium_ plants grown in subambient CO2. The effects of changing CO2 ledvels on vegetation since the last glaciation are thought to have been at least as great, if not greater, than those which eshould be expected for a doubling of current CO2 levels. Atmospheric CO2 concentrations below 200 ppm are thought to have fbeen instrumental in the rise of the C4 grasslands of North America and other extensive C4 grasslands and savannas of the gworld. Dramatic invasion of these areas by woody C3 species are accompanying the historical increase in atmospheric CO2 concentration now in progress.>>!<u>~D0*]^MINDSLGLi332^2^Johnson,R H^Lincoln,D E^1990^1^Sagebrush and Grasshopper Responses to Atmospheric Carbon Dioxide Concentration^34^84^^103-110^^^^^^^^^^828^^^^^^^^^^^Artemisia tridentata/sagebrushshs u0<tF^V3Ҵo^&CGHC^826^OecologiaDTD>Dt>6D_t>u D):sD@=!r?!r,Wu$PCuu uulA^826^Seed- and clonally-propagated plants of Big Sagebrush (_Artemisia tridentata_ var. _tridentata_) were grown under atmmospheric carbon dioxide regimes of 270, 350 and 650 uL/L and fed to _Melanoplus differentialis_ and _M. sanguinipes_ grasnshoppers. Total shrub biomass significantly increased as carbon dioxide levels increased, as did the weight and area of inodividual leaves. Plants grown from seed collected in a single population exhibited a 3-5 fold variation in the concentratipon of leaf volatile mono- and sesquiterpenes, guaianolide sesquiterpene lactones, coumarins and flavones within each CO2 tqreatment. The concentration of leaf allelochemicals did not differ significantly among CO2 treatments for these seed-propargated plants. Further, when genotypic variation was controlled by vegetative propagation, allelochemical concentrations alsso did not differ among carbon dioxide treatments. On the other hand, overall leaf nitrogen concentration declined signifitcantly with elevated CO2. Carbon accumulation was seen to dilute leaf nitrogen as the balance of leaf carbon versus nitroguen progressively increased as CO2 growth concentration increased. Grasshopper feeding was highest on sagebrush leaves growvn under 270 and 650 uL/L CO2, but varied widely within treatments. Leaf nitrogen concentration was an important positive fwactor in grasshopper relative growth but had no overall effect on consumption. Potential compensatory consumption by thesex generalist grasshoppers was apparently limited by the sagebrush allelochemicals. Insects with a greater ability to feed oyn chemically defended host plants under carbon dioxide enrichment may ultimately consume leaves with a lower nitrogen conczentration but the same concentration of allelochemicals. Compensatory feeding may potentially increase the amount of dietary allelochemicals ingested for each unit of nitrogen consumed.U!  W X,X|333^2^Johnson,R H^Lincoln,D E^1991^1^Sagebrush Carbon Allocation Patterns and Grasshopper Nutrition: The Influence of CO2 Enrichment and Soil Mineral Limitation^34^87^^127-134^^^^^^^^^^831^^^^^^^^^^^sagebrush/Artemisia tridentatata13AugustjC^829^Oecologia.B.G.Ashdown..E.H.Krieg. PossibleEmployment   p  IwouA^829^_Artemisia tridentata_ seedlings were grown under carbon dioxide concentrations of 350 and 650 uL/L and two levels of soil nutrition. In the high nutrient treatment, increasing CO2 led to a doubling of shoot mass, whereas nutrient limitation 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 apparently 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 to 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 interactive 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. Grasshopper consumption was significantly greater on host leaves grown under CO2 enrichment but was reduced on leaves grown under low nutrient availability. An overall negative relationship of consumption versus leaf volatile concentration suggests that terpenes may have been one of several important leaf characteristics limiting consumption of the low nutrient hosts. Digestibility of host leaves grown under the high CO2 treatment was significantly increased and was related to high leaf starch content. Grasshopper growth efficiency (ECI) was significantly reduced by the nutrient limitation treatment but co-varied with leaf water content.T|u%>tK4:鵀^ȚT&^ZXSUGR GSw ]334^2^Jolliffe,P A^Ehret,D L^1985^1^Growth of Bean Plants at Elevated Carbon Dioxide Concentrations^54^63^^2021-2025^^^^^^^^^^834^^^^^^^^^^^bean/Phaseolus vulgaris^^^^^^^^^^XPSQRVW҆r36:u &?%3u<@}C^832^Can. J. Bot.0 rƾ u %? p_^ZY[XPSVu2$w rƾ E^[XPSRVWA^832^Plants of _Phaseolus vulgaris_ L. cv. Pure Gold Wax were grown in controlled environment chambers at six CO2 concentrations ranging from 340 to 3000 uL/L. Data for plant growth analysis were obtained from five harvests from 11 to 55 days after planting. Growth curves were fitted to the data using a cubic spline regression procedure. CO2 enrichment caused large and rapid increases in leaf dry weight, unit leaf rate, and specific leaf weight. Smaller responses included a decrease in leaf area ratio and an increase in leaf weight ratio. Root dry weight and leaf area were not significantly affected by CO2 treatments. Relative growth rate was initially higher in CO2 enriched plants and later declined; it may not be a suitable index for the evaluation of CO2 effects during long periods of growth. The results indicate that leaf formation and expansion were not limited by assimilate supply. Maximum growth and pod yield were obtained in plants grown at 1200 uL/L CO2.SFNFF3rNFNVP5:X;t$w+؉d̎w2: +؉d̚n2:Ř*^H335^4^Jones,J W^Dayan,E^van Keulen,H^Challa,H^1989^1^Modeling Tomato Growth for Optimizing Greenhouse Temperatures and Carbon Dioxide Concentrations^15^248^^285-294^^^^^^^^^^837^^^^^^^^^^^tomato/Lycopersicon esculentum^^^^^)FtXFt C^835^Act. Hort. Ft *]XPQV鵀t*uttS Z,s9=:w^YXSW>Rt*r$rA^835^Predictions of crop yield response to a dynamic environment are essential to the development of optimal control strategies for greenhouses. A dynamic tomato growth and yield model (TOMGRO) was developed specifically for coupling to physical models of the greenhouse environment for optimizing temperature and carbon dioxide concentrations for tomato production. The model is based on development and growth components. Experiments were conducted in outdoor, computer-controlled plant growth chambers to parameterize the development, carbon exchange, and growth submodels under combinations of two CO2 (350 and 950 vpm) and three night temperatures (12, 16, and 20 C). Daytime temperatures were held to 28 for all treatments. The model successfully described development, growth, and yield for all combinations of temperature and CO2 in this experiment.F&DF&D#;FsՁׁa;FvF3Ҿ${rM&D &T F;Vw r;FsFVF;Vr w;FvFV;336^3^Jones,P^Roy,B L^Jones,J W^1989^1^Coupling Expert Systems and Models for the Real-time Control of Plant Environments^15^248^^445-452^^^^^^^^^^84040t@S3wt@x wt wt Y][˾ 9d*ˀ&w C^838^Act. Hort.ˀ&w twˀ&w ttww eP G u ePQR&fQA^838^A control system, to regulate CO2 in a plant growth chamber, based on distributed processing and a multi-tasking operating system is described. CO2 controls are based on a model of plant photosynthetic light response. Parameters in the model that change through time are automatically evaluated and updated on a 'daily' basis. The system demonstrates how separation of the processing tasks facilitates sophisticated programming. Results in terms of the quality of controls achieved are favorable. The importance of distributed processing and multi-tasking to the application of data analysis, simulation models, and expert systems in 'real-time' environmental controls is discussed. Low cost hardware and supporting software is quickly becoming available and the challenge will become practical implementation of straightforward ideas. The general conclusion is that practical application of such systems can be expected in the near term.^Z[XPQVhrAA;r+њ*^Y337^1^Kano,A^1985^6^Growth Model of Greenhouse Tomatoes with Carbon Dioxide Enrichment: Development and Experimental Tests (Simulation, Modelling)^^Texas A&M University^^Doctoral Dissertation^^^Dissertation Abstracts Vol. 46:10-B, p.3272 (147 pp.)^^^^^^^842^^^^^^^^^^^tomato/Lycopersicon esculentumMill.;#:PSQ3t@fr tRY[XPSQRVNft &A^841^A deterministic, compartmental growth model of greenhouse tomato plants, written in Pascal computer language, was developed based on a leaf assimilation model and a model of a theory that the photosynthesis rate is controlled both by the environmental conditions and by the internal carbohydrate level in the leaf. The model was tested with data obtained from two experiments conducted in 1983 through 1984 at College Station, Texas. Three 2m x 2m x 10m chambers were built in a plastic-covered greenhouse, and tomato plants were grown in the chambers at three different CO2 concentrations: 340, 700, and 1000 um3/m3. Inputs to the model were the light and CO2 levels and the air temperature. The outputs included the CO2 assimilation rate, dry-mass accumulation rate, and tomato yield, which were compared with the results from the measurements. The model underestimated the CO2 assimilation rate and dry-mass accumulation rate of tomatoes for all CO2 levels; however, it predicted the fruit growth and yield rather accurately. For a growth model with parameters taken not from the measurements, but from earlier published results, the magnitude and trend of the results of the simulation were reasonably acceptable. A potential use of the model is to predict the effects of environmental factors or to estimate the benefit from CO2 enrichment under different environmental conditions. It also can be a part of an integrated greenhouse model which predicts growth and yield of the crop in the greenhouse using the environmental conditions outside the greenhouse and the greenhouse control mechanisms and strategies.LD Dʾ*s=u D tD5*r D;DtPh:X338^2^Karvonen,T^Peltonen-Sainio,P^1990^3^The Influence of CO2 and Air Temperature on Agricultural Productivity in Northern Latitudes^The Greenhouse Effect and Primary Productivity in European Agro-ecosystems; 5-10 April 1990; Wageningen, The Netherlands^Pudoc^Wageningen^61^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^Goudriaan,J^van Keulen,H^van Laar,HHվfH]r_^[þ339^3^Kats,G^Olszyk,D M^Thompson,C R^1985^1^Open Top Experimental Chambers for Trees^27^35^^1298-1301^^45DϡD%=C^844^JapcaWQds|PY_^QWRz<tzʚ*+ GZ_YRVWB&wtr!:340^3^Kaushal,P^Guehl,J M^Aussenac,G^1989^1^Differential Growth Response to Atmospheric Carbon Dioxide Enrichment in Seedlings of _Cedrus atlantica_ and _Pinus nigra_ ssp. _Laricio_ var. _Corsicana_^32^19^^1351-1358^^^^^^^^^^848^^^^^^^^^^^Cedrus atlantica/Pinus nigrassp. Laricio var. Corsicana var. CorsicanaN&L^r$3tBwuB3u 뱋LZC^846^Can. J. For. Res.wt\;tL;\sSRVW&;*5uuuu.u09uEuGEE-A^846^Nine-month-old seedlings of _Cedrus atlantica_ Manetti and _Pinus nigra_ Arn. ssp. _Laricio_ var. _Corsicana_ were transplanted in parallelepipedal containers permitting root growth observations (minirhizotrons) and in 6 L pots and were then transferred into two polyethylene tunnels in a greenhouse, where they were submitted to atmospheric CO2 concentrations of 350 (normal) and 800 umol/mol (enriched) for their 2nd growth year. At the end of the enrichment period, the biomass of the enriched plants was 66 (_C. atlantica_) and 30% (_P. nigra_) higher than those of the plants grown at normal CO2 concentrations. The root:shoot biomass ratio remained unaffected by enrichment in both species. Height and diameter growth were 20 (_C. atlantica_) and 10% (_P. nigra_) higher in the enriched treatment. At the end of the enrichment period, the CO2 assimilation rate was no longer stimulated in the enriched _C. atlantica_ plants as compared with the normal treatment, but remained slightly stimulated in the _P. nigra_ seedlings. The differential growth response to elevated CO2 appears to be related to the distinct genetic growth pattern of the two species, namely to their different patterns of root growth before bud break and during the early aerial growth.M ~2M ~ƃ.~Eu~} 341^3^Kelly,D W^Hicklenton,P R^Reekie,E G^1991^1^Photosynthetic Response of Geranium to Elevated CO2 as Affected by Leaf Age and Time of CO2 Exposure^54^69^^2482-2488^^^^^^^^^^851^^^^^^^^^^^geranium/Pelargonium hortorumorum BailyR22C^849^Can. J. Bot.s[d'.& u@[j'. u@ZY[XPSQRUF t 2؋F3ۊ2NÉFA^849^Geranium plants were grown from seed in chambers maintained at 350 or 1000 uL/L CO2. Photosynthesis as affected by leaf age and by leaf position was determined. Elevated CO2 enhanced photosynthesis to the greatest extent in middle-aged leaves; very young leaves exhibited little enhancement, and net photosynthesis in the oldest leaves was depressed by elevated CO2. Temporary increases in net photosynthesis (relative to leaves developed at high CO2) resulted when young leaves grown at 350 uL/L CO2 were switched to 1000 uL/L CO2. Leaves switched later in development exhibited permanent enhancement. Middle-aged leaves exhibited a temporary depression followed by permanent enhancement. Leaves developed at high CO2 and switched to low CO2 did not exhibit any photosynthetic depression relative to plants grown continuously at low CO2. Similarly, leaves developed at low CO2, switched to high CO2 for various lengths of time, and returned to low CO2 showed 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 photosynthesis at low CO2 was limited by CO2 regardless of developmental environment, whereas photosynthesis at high CO2 was limited by the developmental characteristics of the leaf. Further, both biochemical and structural modifications appear to be involved in this response. Because of the very different responses of young versus old leaves, future studies should be careful to consider leaf age in assessing response to elevated CO2.f~rF~F&EI&MK^X_SRVW fV!&GD342^4^Kendall,A C^Turner,J C^Thomas,S M^Keys,A J^1985^1^Effects of CO2 Enrichment at Different Irradiances on Growth and Yield of Wheat. II. Effects on Kleiber Spring Wheat Treated from Anthesis in Controlled Environments in Relation to Effects on Photosynthesis and Photorespiration^39^36^^261-273^^^^^^^^^^854^^^^^^^^^^^wheat/Triticum aestivumum L.ȿDʿDVWC^852^J. Exp. Bot.u !=:^X_PU>u,>ƿu%2+ĿZrVzM3K2Ŀ]XPV >ǿu@sA^852^Spring wheat plants were grown in a cage with a glass roof until three days after anthesis and then subjected to treatments in constant environment rooms with any one of all combinations of four irradiances and two concentrations of carbon dioxide. The photoperiod was 16 h and day/night temperatures 19C/14C. Growth and yield of grain were saturated at the two brightest irradiances. Carbon dioxide enrichment from 350 to 1200 mm3/dm3 increased shoot dry weight and grain yield at final harvest at all irradiances, by averages of 10.5 (not significant) and 23.5 (significant) percent respectively. However, increasing the irradiance from 150 to 613 uE/m2/s caused much larger yield increases (approximately 3-fold). Increased grain production by increased light was caused by both increases in dry weight per grain and by increases in grain number per spikelet. The increase caused by CO2 enrichment was mainly because of increased dry weight per grain. Increase in ear dry weight caused by CO2 enrichment took place between 30 and 60 d after anthesis. The increase in shoot dry weight took place immediately after exposure to increased CO2 from 3 to 15 d after anthesis. Net photosynthesis by flag leaves on the main shoots was almost doubled 16 d after anthesis by the CO2 enrichment even though stomatal resistance was also doubled. However, this increase was not reflected by a proportional increase in yield, probably because increased mutual shading by bigger stems and by late tillers reduced total assimilation and because of increased respiration by the shoots. The increase in photosynthesis was not due to a decrease in photorespiration but to an increase in gross photosynthesis.^r343^3^Kendall,A C^Turner,J C^Thomas,S M^1985^1^Effects of CO2 Enrichment at Different Irradiances on Growth and Yield of Wheat^39^36^^252-260^^^^^^^^^^857^^^^^^^^^^^wheat/Triticum aestivumum L.ZYXx778J8-1S,+(}*(JN 9 d+C^855^J. Exp. Bot.   u) 6m24$2 9`7XW