ÿWPCB ûÿ2idge­ äuªë &ÆÀG«&ÆÀGƒéëæ3À^_Alphabetic List Listed with Format STRAIN Listing Created 17 Feb 1995, at 13:09 à Ã1Ä Ä° `  à ÃAckerly, D.D., J.S. Coleman, S.R. Morse, and F.A. Bazzaz.Ä Ä 1992. CO2 and Temperature Effects on Leaf Area Production in Two Annual Plant Species. ÃÃEcology 73:1260©1269.ÄÄ We studied leaf area production in two annual plant species, ÃÃAbutilon theophrastiÄÄ and ÃÃAmaranthus retroflexusÄÄ, under three day/night temperature regimes (18/14À$ÀC, 28/22À$ÀC, and 28/31À$ÀC) and two concentrations of carbon dioxide (400 and 700 uL/L). The production of whole©plant leaf area during the first 30 d of growth was analyzed in terms of the leaf initiation rate, leaf expansion, individual leaf area, and, in ÃÃAmaranthusÄÄ, production of branch leaves. Temperature and CO2 influenced leaf area production through stem (the plastochron index), and through shifts in the relationship between whole©plant leaf area and the number of main stem nodes. In ÃÃAbutilonÄÄ, leaf initiation rate was highest at 38À$ÀC, but area of individual leaves was greatest at 28À$ÀC. Total leaf area was greatly reduced at 18À$ÀC due to slow leaf initiation rates. Elevated CO2 concentration increased leaf initiation rate at 28À$ÀC, resulting in an increase in whole©plant leaf area. In ÃÃAmaranthusÄÄ, leaf initiation rate increased with temperature, and was increased by elevated CO2 at 28À$ÀC. Individual leaf area was greatest at 28À$ÀC, and was increased by elevated CO2 at 28À$ÀC but decreased at 38À$ÀC. Branch leaf area displayed a similar response to CO2, but was greater at 38À$ÀC. Overall, whole©plant leaf area was slightly increased at 38À$ÀC relative to 28À$ÀC, and elevated CO2 levels resulted in increased leaf area at 28À$ÀC but decreased leaf area at 38À$ÀC. The effects on leaf area closely parallel rates of biomass accumulation in the same experiment, suggesting that responses of developmental processes to elevated CO2 and interacting factors may play an important role in mediating effects on plant growth. Abutilon theophrasti/Amaranthus retroflexus ÃÃKEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, LEAF AREA DEVELOPMENT, OLD FIELD COMMUNITIES, PLASTOCHRON INDEX, TEMPERATUREÄÄ Ã Ã2Ä Ä° `  à ÃAcock, B.Ä Ä 1990. Effects of CO2 on Photosynthesis, Plant Growth and Other Processes. ÃÃIN: Impact of CO2, Trace Gases, and Climate Change on Global Agriculture, ASA Special Publication No. 53 (B.A. Kimball, N.J. Rosenberg, and L.H. Allen Jr., eds.), American Society of Agronomy, Madison, Wisconsin, pp. 45©60.ÄÄ ÃÃKEYWORDS: AGRICULTURE, ALLOCATION, CROPS, GROWTH, PHOTOSYNTHESIS, PHYSIOLOGICAL CO2 RESPONSES, REVIEWÄÄ Ã Ã3Ä Ä° `  à ÃAcock, B., M.C. Acock, and D. Pasternak.Ä Ä 1990. Interactions of CO2 Enrichment and Temperature on Carbohydrate Production and Accumulation in Muskmelon Leaves. ÃÃJournal of the American Society of Horticultural Science 115:525©529.ÄÄ We examined how temperature and stage of vegetative growth affect carbohydrate production and accumulation in ÃÃCucumis meloÄÄ 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 starch 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 significantly 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 higher 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]. muskmelon/Cucumis melo ÃÃKEYWORDS: CARBOHYDRATES, GROWTH ANALYSIS, GROWTH STAGES, NAR, SPAR UNITS, TEMPERATUREÄÄ Ã Ã4Ä Ä° `  à ÃAcock, B., M.C. Acock, V.R. Reddy, and D.N. Baker.Ä Ä 1985. The Simulation, with GLYCIM, of Soybean Crops Grown in the Field and at Various CO2 Concentrations in Open©top Chambers during 1982ÃÃ, 011 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C. soybean ÃÃKEYWORDS: CROP MODEL, MODELING, OPEN©TOP CHAMBERS, SIMULATIONÄÄ Ã Ã5Ä Ä° `  à ÃAcock, B., and L.H. Allen Jr.Ä Ä 1985. Crop Responses to Elevated Carbon Dioxide Concentrations. ÃÃIN: Direct Effects of Increasing Carbon Dioxide on Vegetation, DOE/ER©0238 (B.R. Strain and J.D. Cure, eds.), Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C., pp. 53©97.ÄÄ ÃÃKEYWORDS: CROP MODEL, ENVIRONMENTAL INTERACTIONS, PHOTOSYNTHESIS, REVIEW, TRANSPIRATION, WUEÄÄ Ã Ã6Ä Ä° `  à ÃAcock, B., D.N. Baker, V.R. Reddy, J.M. McKinion, F.D. Whisler, D. Del Castillo, and H.F. Hodges.Ä Ä 1982. Soybean Responses to Carbon Dioxide: Measurement and Simulation 1981ÃÃ, 004 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C. soybean/Glycine max ÃÃKEYWORDS: ALLOCATION, CANOPY PHOTOSYNTHESIS, MODELING, RESPIRATION, ROOTS, SPAR UNITSÄÄ Ã Ã7Ä Ä° `  à ÃAcock, B., and D. Pasternak.Ä Ä 1986. Effects of CO2 Concentration on Composition, Anatomy, and Morphology of Plants. ÃÃIN: Physiology, Yield and Economics, Vol. II (H.Z. Enoch and B.A. Kimball, eds.), Carbon Dioxide Enrichment of Greenhouse Crops, CRC Press, Inc., Boca Raton, Florida, pp. 41©52.ÄÄ In summary, we can say that species differ in their response to high CO2. Plants which are using CAM are relatively unresponsive. Other plants with the C4 pathway show modest dry weight gains but large reductions in transpiration rate. Plants which only have the C3 pathway, or well©watered CAM plants which are behaving like C3 plants, exhibit modest reductions in transpiration rate and large gains in dry weight, resulting in a variety of changes in plant composition, anatomy, and morphology. We know too little to even begin dividing C3 species into response groups. However, we can describe a typical or average response as follows. All organs on the plants become heavier with roots gaining proportionally more dry weight than stems, and stems more than leaves. The additional dry matter in the root is mainly used to increase root length with very little going to increase the density of the root tissue. Additional dry matter going to the stem causes increases in its height and diameter and little increase in the density of the tissue. Additional dry matter going to the leaves causes both a small increase in leaf area and a small increase in leaf thickness. There is an increase in structural dry matter 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, depending 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. ÃÃKEYWORDS: ALLOCATION, C3, C4, REVIEWÄÄ Ã Ã8Ä Ä° `  à ÃAcock, B., V.R. Reddy, D. Del Castillo, H.F. Hodges, D.N. Baker, J.M. McKinion, and F.D. Whisler.Ä Ä 1983. Soybean Responses to Carbon Dioxide: Measurement and Simulation 1982ÃÃ, 008 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C. soybean/Glycine max ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, MODELING, PHOTOSYNTHESIS MODEL, RESPIRATION, SIMULATION, SPAR UNITS, WATER STRESS, YIELDÄÄ Ã Ã9Ä Ä° `  à ÃAcock, B., V.R. Reddy, H.F. Hodges, D.N. Baker, and J.M. McKinion.Ä Ä 1985. Photosynthetic Response of Soybean Canopies to Full©Season Carbon Dioxide Enrichment. ÃÃAgronomy Journal 77:942©947.ÄÄ Global atmospheric CO2 concentration ([CO2]) is increasing as a result of the burning of fossil fuels. At present there is little information about how agronomic crops will respond to future high [CO2]. To investigate the basic process that will be most affected, soybean canopies were continuously exposed to various [CO2] and photosynthetic rates were measured throughout the growing season. Soybean was grown to physiological maturity in sunlit controlled©environment chambers in CO2 concentrations of 330, 450, 600 and 800 uL/L. Carbon dioxide fluxes were measured on the canopies at 15©min intervals every day and used to calculate photosynthetic and respiration rates. Gross photosynthetic rate increased with each increment in [CO2] regardless of stage of development, but there was considerable day©to©day and seasonal variation. Seasonal changes in photosynthetic rate were associated with developmental changes in the crop. Photosynthetic rates were low during early vegetative development, even after the canopy had closed, but increased threefold just before flowering to reach a peak during flowering at stage R2. They then decreased by 30% or more until just before the start of pod expansion (R3) when a 45% increase occurred. Thereafter, photosynthetic rates decreased slowly and continuously to final harvest. The daily curves of photosynthetic rate ÃÃvs.ÄÄ photosynthetic photon flux density were further analyzed to determine canopy light utilization efficiency (ÀÀ) and canopy conductance to CO2 transfer (À)À). Plants grown in 800 uL/L [CO2] had a value of ÀÀ that averaged about 40% higher than that for plants grown in 330 uL/L and a value of À)À that averaged about 24% lower for the season. Differences in ÀÀ between these treatments were significant throughout the season, while initial differences in À)À between treatments became less obvious after late vegetative growth stage VII. soybean/Glycine max ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CONDUCTANCE, LIGHT UTILIZATION EFFICIENCY, PHOTOSYNTHESIS MODEL, SPAR UNITSÄÄ Ã Ã10Ä Ä° `  à ÃAcock, B., V.R. Reddy, F.D. Whisler, D.N. Baker, J.M. McKinion, H.F. Hodges, and K.J. Boote.Ä Ä 1983. The Soybean Crop Simulator GLYCIM: Model DocumentationÃÃ, 002 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C. soybean/Glycine max ÃÃKEYWORDS: CROP MODEL, MODELINGÄÄ Ã Ã11Ä Ä° `  à ÃAcock, B., and A. Trent.Ä Ä 1991. The Soybean Crop Simulator GLYCIM: Documentation for the Modular Version 91ÃÃ, 017 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C. soybean/Glycine max ÃÃKEYWORDS: CROP MODEL, GENERIC MODEL, SIMULATIONÄÄ Ã Ã12Ä Ä° `  à ÃAizawa, K., Y. Nakamura, and S. Miyachi.Ä Ä 1985. Variation of Phosphoenolpyruvate Carboxylase Activity in ÃÃDunaliellaÄÄ Associated with Changes in Atmospheric CO2 Concentration. ÃÃPlant Cell Physiology 26:1199©1203.ÄÄ In ÃÃDunaliella tertiolectaÄÄ, ÃÃD. bioculataÄÄ and ÃÃD. viridisÄÄ the activities of phosphoenolpyruvate carboxylase and carbonic anhydrase were higher in the cells grown in ordinary air (low©CO2 cells) than in those grown in air enriched with 1©5% CO2 (high©CO2 cells), whereas in ÃÃPorphyridium cruentumÄÄ R©1 there was no difference in phosphoenolpyruvate carboxylase activity between these two types of cells. Apparent Km (NaHCO3) values for photosynthesis in low©CO2 cells of all species tested were smaller than those in high©CO2 cells. Most of the 14C was incorporated into 3©phosphoglycerate, sugar mono© and di©phosphates during the initial periods of photosynthetic NaH14CO3©fixation, indicating that both types of cells in ÃÃD. tertiolectaÄÄ are C3 plants. Dunaliella tertiolecta/Dunaliella bioculata/Dunaliella viridis/Porphyridium cruentum ÃÃKEYWORDS: ALGAE, AQUATIC PLANTS, CARBONIC ANHYDRASE, CELL CULTURE, ENZYMES, PHOSPHOENOLPYRUVATE CARBOXYLASEÄÄ Ã Ã13Ä Ä° `  à ÃAkey, D.H., and B.A. Kimball.Ä Ä 1989. Growth and Development of the Beet Armyworm on Cotton Grown in an Enriched Carbon Dioxide Atmosphere. ÃÃSouthwestern Entomologist 14:255©260.ÄÄ Growth and development were studied in the beet armyworm (BAW), ÃÃSpodoptera exiguaÄÄ (HÀGÀbner), reared on cotton seedlings at high (640 uL/L) or ambient (320 uL/L) carbon dioxide (CO2) levels and at two fertilizer levels. Under high fertilization, female BAW reared on CO2 enriched seedlings weighed significantly less (87.3 mg) than controls (101.0 mg) and had a significantly longer developmental time (14.2 versus 12.4 days for controls). Male BAW followed the same pattern, but the differences were not statistically significant. Combined (male and female) survival rates for BAW reared on CO2©enriched cotton seedlings on a high fertilizer level were 19.1 compared to 41.6% for controls; more females survived than males by a significant ratio of 2:1. cotton/Gossypium hirsutum ÃÃKEYWORDS: BEET ARMYWORM, INSECTS, OPEN©TOP CHAMBERS, SPODOPTERA EXIGUAÄÄ Ã Ã14Ä Ä° `  à ÃAkey, D.H., B.A. Kimball, and J.R. Mauney.Ä Ä 1988. Growth and Development of the Pink Bollworm,Ãà Pectinophora gossypiellaÄÄ (Lepidoptera: Gelechiidae), on Bolls of Cotton Grown in Enriched Carbon Dioxide Atmospheres. ÃÃEnvironmental Entomology 17:452©455.ÄÄ The pink bollworm, ÃÃPectinophora gossypiellaÄÄ (Saunders), was reared on the bolls of cotton plants grown in CO2©enriched (649 uL/L) and ambient (371 uL/L) chambers and in two open field plots, one with free©air CO2 enrichment (522 uL/L) and one without enrichment (ambient CO2, 360 uL/L). The effects of increased CO2 levels on growth and development were examined. There was no difference in pupal weights of pink bollworm raised on CO2©enriched cotton compared with those raised on ambient CO2 cotton (26.80 versus 26.64 mg, respectively). Also, there was no difference in developmental time (21©27 d). Analysis of percent seed damage by larvae showed no differences between CO2©enriched and ambient CO2 cotton. These results 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. cotton/Gossypium hirsutum ÃÃKEYWORDS: CARBON:NITROGEN RATIO, INSECTS, OPEN©TOP CHAMBERS, PECTINOPHORA GOSSYPIELLA, PINK BOLLWORM, SEED DAMAGE, SEEDSÄÄ Ã Ã15Ä Ä° `  à ÃAllen, L.H., Jr.Ä Ä 1990. Plant Responses to Rising Carbon Dioxide and Potential Interactions with Air Pollutants. ÃÃJournal of Environmental Quality 19:15©34.ÄÄ As global population increases and industrialization expands, carbon dioxide (CO2) and toxic air pollutants can be expected to be injected into the atmosphere at increasing rates. This analysis reviews a wide range of direct plant responses 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 review of effects of potential climatic change on plants is not a major objective of this analysis. Research shows that elevated CO2 increases photosynthetic rates, leaf area, biomass, and yield. Elevated CO2 also reduces transpiration rate per unit 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. ÃÃKEYWORDS: AIR POLLUTION, CLIMATE CHANGE, CONDUCTANCE, REVIEW, TRANSPIRATION, WUEÄÄ Ã Ã16Ä Ä° `  à ÃAllen, L.H., Jr.Ä Ä 1991. Effects of Increasing Carbon Dioxide Levels and Climate Change on Plant Growth, Evapotranspiration, and Water Resources. ÃÃIN: Managing Water Resources in the West under Conditions of Climate Uncertainty; 1990 Nov. 14©16; Scottsdale, Arizona (Committee on Climate Uncertainty and Water Resources Management, ed.), National Academy Press, Washington, D.C., pp. 101©147.ÄÄ soybean/Glycine max ÃÃKEYWORDS: AGRICULTURE, CLIMATE CHANGE, CLIMATE MODEL, EVAPOTRANSPIRATION, GCM'S, MODELING, REVIEW, STREAMFLOW, WUEÄÄ Ã Ã17Ä Ä° `  à ÃAllen, L.H., Jr.Ä Ä 1992. Free©Air CO2 Enrichment Field Experiments: An Historical Overview. ÃÃCritical Reviews in Plant Sciences 11:121©134.ÄÄ ÃÃKEYWORDS: EXPOSURE METHODS, FACEÄÄ Ã Ã18Ä Ä° `  à ÃAllen, L.H., Jr., and S.E. Beladi.Ä Ä 1990. Free©Air CO2 Enrichment (FACE): Analysis of Gaseous Dispersion Arrays for the Study of Rising Atmospheric CO2 Effects on Vegetation. 1983©1989 Progress ReportÃÃ, 057 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C. ÃÃKEYWORDS: EXPOSURE METHODS, FACEÄÄ Ã Ã19Ä Ä° `  à ÃAllen, L.H., Jr., E.C. Bisbal, K.J. Boote, and P.H. Jones.Ä Ä 1991. Soybean Dry Matter Allocation under Subambient and Superambient Levels of Carbon Dioxide. ÃÃAgronomy Journal 83:875©883.ÄÄ 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 [ÃÃGlycine maxÄÄ (L.) Merr.] dry matter production and allocation for two reasons: to assess response of plants to prehistoric as well as future 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 umol (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 components (petioles and stems) increased. At final harvest the respective [CO2] treatments resulted in 38, 53, 62, 100, 120 and 92% seed yield with respect to the 330 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 increase plant growth, but also that plant growth was probably seriously limited by atmospheric [CO2] in preindustrial revolution times back to the previous global glaciation. soybean/Glycine max ÃÃKEYWORDS: ALLOCATION, GROWTH, PRE©INDUSTRIAL CO2 CONCENTRATION, SPAR UNITS, YIELDÄÄ Ã Ã20Ä Ä° `  à ÃAllen, L.H., Jr., E.C. Bisbal, W.J. Campbell, and K.J. Boote.Ä Ä 1990. Carbon Dioxide Effects on Soybean Developmental Stages and Expansive Growth. ÃÃSoil and Crop Science Society of Florida, Proceedings 49:124©131.ÄÄ 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 [ÃÃGlycine maxÄÄ (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. soybean/Glycine max ÃÃKEYWORDS: GROWTH, PHENOLOGY, PRE©INDUSTRIAL CO2 CONCENTRATION, SPAR UNITSÄÄ Ã Ã21Ä Ä° `  à ÃAllen, L.H., Jr., and K.J. Boote.Ä Ä 1992. Vegetation, Effect of Rising CO2. ÃÃIN: Encyclopedia of Earth System Science, Vol. 4, Academic Press, Inc., New York, pp. 409©416.ÄÄ ÃÃKEYWORDS: AIR POLLUTION, CLIMATE, NUTRITION, REVIEW, TEMPERATURE, TRANSPIRATIONÄÄ Ã Ã22Ä Ä° `  à ÃAllen, L.H., Jr., K.J. Boote, J.W. Jones, P.H. Jones, R.R. Valle, B. Acock, H.H. Rogers, and R.C. Dahlman.Ä Ä 1987. Response of Vegetation to Rising Carbon Dioxide: Photosynthesis, Biomass, and Seed Yield of Soybean. ÃÃGlobal Biogeochemical Cycles I:1©14.ÄÄ 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. soybean/Glycine max ÃÃKEYWORDS: CARBON CYCLE, CARBON SEQUESTERING, DEFORESTATION, GROWTH MODEL, PRE©INDUSTRIAL CO2 CONCENTRATION, REVIEWÄÄ Ã Ã23Ä Ä° `  à ÃAllen, L.H., Jr., K.J. Boote, J.W. Jones, J.W. Mishoe, P.H. Jones, R.R. Valle, and E.C. Bisbal.Ä Ä 1985. Subambient and Superambient Carbon Dioxide Effects on Growth, Nonstructural Carbohydrates, Biochemistry of Photosynthesis and Transpiration of Soybeans. 1984 Progress ReportÃÃ, 031 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C. soybean/Glycine max ÃÃKEYWORDS: CARBOHYDRATES, GROWTH, PHOTOSYNTHESIS, PRE©INDUSTRIAL CO2 CONCENTRATION, RIBULOSE BISPHOSPHATE CARBOXYLASE, SPAR UNITS, TRANSPIRATIONÄÄ Ã Ã24Ä Ä° `  à ÃAllen, L.H., Jr., K.J. Boote, J.W. Jones, J.W. Mishoe, P.H. Jones, C.V. Vu, R. Valle, and W.J. Campbell.Ä Ä 1982. Effects of Increased Carbon Dioxide on Photosynthesis and Agricultural Productivity of Soybeans. 1981 Progress ReportÃÃ, 003 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C. soybean/Glycine max ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CARBOHYDRATES, CONDUCTANCE, GROWTH, GROWTH STAGES, NITROGEN, RIBULOSE BISPHOSPHATE CARBOXYLASE, SPAR UNITS, YIELDÄÄ Ã Ã25Ä Ä° `  à ÃAllen, L.H., Jr., K.J. Boote, J.W. Jones, J.W. Mishoe, P.H. Jones, C.V. Vu, R.R. Valle, W.J. Campbell, P.R. Harris, and K.F. Heimburg.Ä Ä 1984. Effects of Increased Carbon Dioxide and Water Stress Interactions on Photosynthesis, Transpiration, and Productivity of Soybeans. 1983 Progress ReportÃÃ, 014 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C. soybean/Glycine max ÃÃKEYWORDS: CI:CA, GROWTH, LEAF PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION, SPAR UNITS, TRANSPIRATION, WATER STRESS, WUE, YIELDÄÄ Ã Ã26Ä Ä° `  à ÃAllen, L.H., Jr., B.G. Drake, H.H. Rogers, and J.H. Shinn.Ä Ä 1992. Field Techniques for Exposure of Plants and Ecosystems to Elevated CO2 and Other Trace Gases. ÃÃCritical Reviews in Plant Sciences 11:85©119.ÄÄ ÃÃKEYWORDS: EXPOSURE METHODS, REVIEW, SCALINGÄÄ Ã Ã27Ä Ä° `  à ÃAllen, L.H., Jr., R.R. Valle, J.W. Mishoe, J.W. Jones, and P.H. Jones.Ä Ä 1990. Soybean Leaf Gas Exchange Responses to CO2 Enrichment. ÃÃSoil and Crop Science Society of Florida, Proceedings 49:192©198.ÄÄ Carbon dioxide concentration of the atmosphere is expected to double within the next century. This study was undertaken to determine the leaf gas exchange responses of soybean (ÃÃGlycine MaxÄÄ (L.) Merr. cv. Bragg) grown continuously at 330, 450, 600, and 800 L (CO2)/million L (air), or volume parts per million volumes (vpm), in sunlit, controlled©environment chambers. The chambers were secured to soil bins filled with a reconstructed profile of Arredondo fine sand (a loamy siliceous hyperthermic Grossarenic Paleudult). A gas exchange system was used to measure leaf and air temperatures, flow rates, cuvette input and exit CO2 concentrations and vapor pressures, and incident solar photosynthetically active radiation (PAR). These measurements were used to calculate the carbon dioxide exchange rate (CER), transpiration rate (TRATE), stomatal resistance (rs), and leaf internal airspace (intercellular) CO2 concentration (Ci) of fully expanded, sunlit leaves held in a flat, horizontal position. Results indicated that leaf CER increased linearly over the CO2 concentration range of 330 to 800 vpm. Differences in leaf transpiration rates between the 800 and 330 vpm CO2 treatment were small. Water©use efficiency, CER/TRATE, increased as CO2 level increased, mainly due to an increase in CER. Both leaf stomatal resistance and leaf temperature increased with increasing CO2 concentrations at fixed PAR. The ratio of Ci to external CO2 concentration (Ce) was approximately constant across the range of [CO2] treatments. These findings showed no tendency for CO2©saturation of soybean leaf CER (and hence no evidence of CO2©induced feedback inhibition of photosynthetic rate) over the CO2 concentration range of 330 to 800 vpm. soybean/Glycine max ÃÃKEYWORDS: CI:CA, LEAF PHOTOSYNTHESIS, PHOTOSYNTHETIC FEEDBACK INHIBITION, SPAR UNITS, TRANSPIRATION, WUEÄÄ Ã Ã28Ä Ä° `  à ÃAllen, L.H., Jr., J.C.V. Vu, R.R. Valle, K.J. Boote, and P.H. Jones.Ä Ä 1988. Nonstructural Carbohydrates and Nitrogen of Soybean Grown under Carbon Dioxide Enrichment. ÃÃCrop Science 28:84©94.ÄÄ 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 [ÃÃGlycine maxÄÄ (L.) Merr. cv. Bragg]. Plants were grown at Gainesville, FL from seed to maturity in six sunlit, controlled©environment chambers that maintained CO2 at 330, 330, 450, 600, 800, and 800 umol (CO2)/mol (air). Attached lysimeters contained Arredondo fine sand (loamy, siliceous, hyperthermic Grossarenic Paleudult). Leaflet blades were sampled five times per day at 48 and 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. soybean/Glycine max ÃÃKEYWORDS: ALLOCATION, CARBOHYDRATES, NITROGEN, SPAR UNITS, SPECIFIC LEAF WEIGHTÄÄ Ã Ã29Ä Ä° `  à ÃAllen, S.G., S.B. Idso, and B.A. Kimball.Ä Ä 1990. Interactive Effects of CO2 and Environment on Net Photosynthesis of Water©Lily. ÃÃAgriculture, Ecosystems and Environment 30:81©88.ÄÄ Water©lily (ÃÃNymphaea marliacÄÄ) 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©33.2À$ÀC 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. Nymphaea marliac/water lily ÃÃKEYWORDS: AQUATIC PLANTS, CANOPY PHOTOSYNTHESIS, LIGHT, OPEN©TOP CHAMBERS, TEMPERATUREÄÄ Ã Ã30Ä Ä° `  à ÃAllen, S.G., S.B. Idso, B.A. Kimball, and M.G. Anderson.Ä Ä 1988. Relationship between Growth Rate and Net Photosynthesis of ÃÃAzollaÄÄ in Ambient and Elevated CO2 Concentrations. ÃÃAgriculture, Ecosystems and Environment 20:137©141.ÄÄ ÃÃAzolla pinnataÄÄ was grown out©of©doors at Phoenix, AZ, U.S.A. in open©topped plastic©walled chambers supplied with either 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 CO2 concentration©environment interaction. Azolla pinnata ÃÃKEYWORDS: AQUATIC PLANTS, CANOPY PHOTOSYNTHESIS, GROWTH RATE, OPEN©TOP CHAMBERSÄÄ Ã Ã31Ä Ä° `  à ÃAllen, S.G., S.B. Idso, B.A. Kimball, J.T. Baker, L.H. Allen Jr., J.R. Mauney, J.W. Radin, and M.G. Anderson.Ä Ä 1990. Effects of Air Temperature on Atmospheric CO2©Plant Growth RelationshipsÃÃ, TR048 in Yellow Report Series, DOE/ER©0450T, Dept. of Energy, Carbon Dioxide Research ProgramÄÄ. NTIS, U.S. Dept. of Commerce, Springfield, Virginia. ÃÃKEYWORDS: CARBOHYDRATES, CONDUCTANCE, PHENOLOGY, PHOTOSYNTHESIS, REVIEW, TEMPERATURE, YIELDÄÄ Ã Ã32Ä Ä° `  à ÃAlpert, P., F.R. Warembourg, and J. Roy.Ä Ä 1992. Transport of Carbon among Connected Ramets of ÃÃEichhornia crassipesÄÄ (Pontederiaceae) at Normal and High Levels of CO2. ÃÃAmerican Journal of Botany 78:1459©1466.ÄÄ The floating stoloniferous plant, ÃÃEichhornia crassipesÄÄ, has high rates of productivity and rapidly invades new sites. 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 ÃÃE. CrassipesÄÄ. Because net photosynthesis of ÃÃE. CrassipesÄÄ is significantly higher at high levels of atmospheric CO2, we also asked if high CO2 can change patterns of carbon transport in ways that might 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 offspring 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 as 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. ÃÃE. crassipesÄÄ maintains bidirectional transport of carbon between ramets even under uniform and favorable environmental conditions and when external CO2 levels are very high. Eichhornia crassipes/water hyacinth ÃÃKEYWORDS: 14C, AQUATIC PLANTS, ASSIMILATE EXPORT, CARBON BUDGET, GREENHOUSE, HYDROPONIC CULTURE, VEGETATIVE REPRODUCTIONÄÄ Ã Ã33Ä Ä° `  à ÃAlscher, G., and H. Krug.Ä Ä 1989. On©line Control of CO2 Enrichment in Protected Cultivation. ÃÃActa Horticulturae 248:321©327.ÄÄ As a base for experiments on CO2 on©line control the CO2 fluxes in greenhouses are simulated and potential control strategies 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 differences 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. lettuce/Lactuca sativa ÃÃKEYWORDS: CO2 MEASUREMENT AND CONTROL, COMMERCIAL USE OF CO2, GREENHOUSE, INTERMITTENT ENRICHMENT, SIMULATIONÄÄ Ã Ã34Ä Ä° `  à ÃAmthor, J.S.Ä Ä 1991. Respiration in a Future, Higher©CO2 World. ÃÃPlant, Cell and Environment 14:13©20.ÄÄ 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' respiration, another major component of the carbon budget of higher plants, may be affected by a change in [CO2] independent of an increase in temperature. Literature pertaining to an impact of [CO2] on respiration rate is reviewed. With an increase in [CO2], respiration rate is increased in some cases, but decreased in others. The effects of [CO2] on respiration rate may be direct or indirect. Mechanisms responsible for various observations are proposed. These proposed mechanisms relate to changes in: (1) levels of nonstructural carbohydrates, (2) growth rate and structural phytomass accumulation, (3) composition of phytomass, (4) direct chemical interactions between CO2 and respiratory enzymes, (5) direct chemical interactions between CO2 and other cellular components, (6) dark CO2 fixation rate, and (7) ethylene biosynthesis rate. Because a range of (possibly interactive) effects exists, and present knowledge is limited, the impact of future [CO2] on respiration rate cannot be predicted. Theoretical considerations and types of experiments that can lead to an increase in the understanding of this issue are outlined. ÃÃKEYWORDS: CARBON BUDGET, RESPIRATION, REVIEWÄÄ Ã Ã35Ä Ä° `  à ÃAmthor, J.S., G.W. Koch, and A.J. Bloom.Ä Ä 1992. CO2 Inhibits Respiration in Leaves of ÃÃRumex crispusÄÄ L. ÃÃPlant Physiology 98:757©760.ÄÄ Curly dock (ÃÃRumex crispusÄÄ L.) was grown from seed in a glasshouse at an ambient CO2 partial pressure of about 35 pascals. Apparent respiration rate (CO2 efflux in the dark) of expanded leaves was then measured at ambient CO2 partial pressure 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 pressure of CO2 typically inhibited respiration by 25 to 30%, whereas a decrease in CO2 elicited a corresponding increase in respiration. These responses were readily reversible. A flexible, sensitive regulatory interaction between CO2 (a byproduct of respiration) and some component(s) of heterotrophic metabolism is indicated. Rumex crispus/curly dock ÃÃKEYWORDS: CI:CA, GREENHOUSE, RESPIRATIONÄÄ Ã Ã36Ä Ä° `  à ÃAnderson, I.H., C. Dons, S. Nilsen, and M.K. Haugstad.Ä Ä 1985. Growth, Photosynthesis and Photorespiration of ÃÃLemna gibbaÄÄ: Response to Variations in CO2 and O2 Concentrations and Photon Flux Density. ÃÃPhotosynthesis Research 6:87©96.ÄÄ Dry weight and Relative Growth Rate of ÃÃLemna gibbaÄÄ were significantly increased by CO2 enrichment up to 6000 uL CO2/L. This high CO2 optimum for growth is probably due to the presence of nonfunctional stomata. The response to high CO2 was less or absent following four days growth in 2% O2. The Leaf Area Ratio decreased in response to CO2 enrichment as a result of an increase in dry weight per frond. Photosynthetic rate was increased by CO2 enrichment up to 1500 uL CO2/L during measurement, showing only small increases with further CO2 enrichment up to 5000 uL CO2/L at a photon flux density of 210 umol/m2/s and small decreases at 2000 umol/m/s. The actual rate of photosynthesis of those plants cultivated at high CO2 levels, however, was less than the air grown plants. The response of photosynthesis to O2 indicated that the enhancement of growth and photosynthesis by CO2 enrichment was a result of decreased photorespiration. Plants cultivated in low O2 produced abnormal morphological features and after a short time showed a reduction in growth. Lemna gibba/duckweed ÃÃKEYWORDS: AQUATIC PLANTS, CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, LIGHT, OXYGEN, RESPIRATIONÄÄ Ã Ã37Ä Ä° `  à ÃAndersson, N.E.Ä Ä 1991. The Influence of Constant and Diurnally Changing CO2 Concentrations on Plant Growth and Development. ÃÃJournal of Horticultural Science 66:569©574.ÄÄ Plants of ÃÃFicus benjaminaÄÄ and miniature rose (ÃÃRosa hybridaÄÄ cv. Red Minimo) were grown under four CO2 treatments. Two had constant CO2 levels (600 and 900 ppm) and the other two had diurnal changes in CO2 levels, one increasing from 600 to 1500 ppm and one decreasing from 1500 to 600 ppm, each in four steps of 300 ppm during the day©time. In all treatments 900 ppm CO2 was maintained during the night when supplementary light was used, except in the treatment with constant 600 ppm where 600 ppm was also continued throughout the night. Plant growth was monitored under both decreasing and increasing natural daylength and irradiance. The tallest plants and greatest increment in height for ÃÃFicusÄÄ occurred with plants grown under constant CO2 concentration at 900 ppm. In both experiments with miniature roses the number of flower buds was significantly increased under diurnally changing CO2 concentration or when the CO2 level was constant at 600 ppm compared with a constant 900 ppm. Time to flowering was decreased by constant CO2 at 900 as compared with the other treatments. Ficus benjamina/Rosa hybrida ÃÃKEYWORDS: COMMERCIAL USE OF CO2, DIURNAL CYCLE, FLOWER PRODUCTION, FLOWERING, GREENHOUSE, HORTICULTURAL CROPSÄÄ Ã Ã38Ä Ä° `  à ÃAndre, M., F. Cotte, A. Gerbaud, D. Massimino, J. Massimino, and C. Richaud.Ä Ä 1989. Effect of CO2 and O2 on Development and Fructification of Wheat in Closed Systems. ÃÃAdvances in Space Research 9:(8)17©(8)28.ÄÄ The cultivation of wheat (ÃÃTriticum aestivumÄÄ L.) was performed in controlled environment chambers with the continuous monitoring of photosynthesis, dark respiration, transpiration and main nutrient uptakes. A protocol in twin chambers was developed to compare the specific effects of low O2 and high CO2. Each parameter is able to influence photosynthesis but different effects are obtained in the development, fructification and seed production, because of the different effects of each parameter on the ratio of reductive to oxidative cycle of carbon. The first main conclusion is that low level of O2, at the same rate of biomass production, strongly acts on the rate of ear appearance and on seed production. Ear appearance was delayed and seed production reduced with a low O2 treatment (about 4%). The O2 effect was not mainly due to the repression of the oxidative cycle. The high CO2 treatment (700 to 900 uL/L) delayed ear appearance by 4 days, but did not reduce 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. Triticum aestivum/wheat ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS, OXYGEN, RESPIRATION, SEED PRODUCTIONÄÄ Ã Ã39Ä Ä° `  à ÃAndre, M., and H. Du Cloux.Ä Ä 1993. Interaction of CO2 Enrichment and Water Limitations on Photosynthesis and Water©Use Efficiency in Wheat. ÃÃPlant Physiology and Biochemistry 31:103©112.ÄÄ Wheat plants (ÃÃTriticum aestivumÄÄ L. cv. Capitole) were grown in twin closed growth chambers with continuous monitoring of CO2 and water exchanges. During the vegetative stage the effect of CO2 enrichment, from 330 to 660 uL/L, was studied under an irradiance of 660 uE/m2/s with an optimum watering. Comparisons were made with successive experiments in which daily water supply was fixed to a fraction (0.62©0.5©0.25) of the maximal transpiration of previous experiments. In a well watered canopy, the doubling of CO2 decreased transpiration by only 8%. Water use efficiency was increased (factor 1.45) mainly by the stimulation of photosynthesis. Under restricted water supply, photosynthesis of plants was more limited than transpiration. The inhibition of photosynthesis and the increase of water use efficiency can be predicted by a simple diffusion model applied to the response curve of photosynthesis to CO2, measured on canopy in standard conditions of watering. The main hypothesis is that the equivalent stomatal conductance is reduced proportionally to the water availability, without closure by patching. Under enriched CO2, the same reduction of leaf surface by water limitation was observed. Photosynthesis was less affected. Therefore, water use efficiency was again increased. Doubling CO2 concentration can compensate for water stress inhibition on CO2 assimilation. That model also predicts interactions of CO2 and water stress observed on water©use©efficiency which was increased by a factor up to 5 in comparison with well©watered plants in standard atmosphere. The implications of this study on global change models are discussed. wheat/Triticum aestivum ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS, GRASSES, PHOTOSYNTHESIS MODEL, TRANSPIRATION, WATER STRESS, WUEÄÄ Ã Ã40Ä Ä° `  à ÃAndre, M., H. Du Cloux, and C. Richaud.Ä Ä 1986. Wheat Response to CO2 Enrichment: CO2 Exchanges, Transpiration and Mineral Uptakes. ÃÃIN: Controlled Ecological Life Support System: CELLS '85 Workshop, 1985 July 16©19, NASA Report TM88215 (R. MacElroy, N.V. Martello, and D. Smernoff, eds.), AMES Research Center, Moffett Field, California, pp. 405©428.ÄÄ wheat/Triticum aestivum ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH ANALYSIS, NITROGEN, NUTRITION, PHOSPHORUS, PLANT DENSITY, POTASSIUM, TRANSPIRATION, WATER STRESS, WUEÄÄ Ã Ã41Ä Ä° `  à ÃAndre, M., H. Ducloux, C. Richaud, D. Massimino, A. Daguenet, J. Massimino, and A. Gerbaud.Ä Ä 1987. Etude des Relations entre Photosynthese Respiration, Transpiration et Nutrition Minerale chez le Ble. ÃÃAdvances in Space Research 7:(4)105©(4)114.ÄÄ La croissance du Ble ÃÃTriticum aestivumÄÄ 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 prÀ)Àsentera 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. wheat/Triticum aestivum ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS, NITROGEN, NUTRITION, PHOSPHORUS, POTASSIUM, RESPIRATION, TRANSPIRATIONÄÄ Ã Ã42Ä Ä° `  à ÃAndreeva, T.F., L.E. Strogonova, S.Y. Voevudskaya, S.N. Maevskaya, and N.N. Cherkanova.Ä Ä 1989. Effect of Enhanced CO2 Concentration on Photosynthesis, Carbohydrate and Nitrogen Metabolism, and Growth Processes in Mustard Plants. ÃÃFiziologiya Rastenii 36:40©48.ÄÄ 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 (ÃÃBrassica junceaÄÄ 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 27À$À/24À$À). Starch content increases significantly in plants grown under conditions of reduced temperature compared with ones grown at a higher temperature (34.4% of leaf dry mass at 20À$À/17À$À as compared with 20.1% at 32À$À/27À$À). 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. mustard/Brassica juncea ÃÃKEYWORDS: CARBOHYDRATES, CONTROLLED ENVIRONMENT CHAMBERS, FRACTION 1 PROTEIN, NITROGEN, PHOTOSYNTHESIS, TEMPERATUREÄÄ Ã Ã43Ä Ä° `  à ÃApel, P.Ä Ä 1989. Influence of CO2 on Stomatal Numbers. ÃÃBiologia Plantarum (Praha) 3:72©74.ÄÄ 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. 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/corn ÃÃKEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, CULTIVAR RESPONSES, STOMATAL DENSITYÄÄ Ã Ã44Ä Ä° `  à ÃArnone, J.A., III.Ä Ä 1988. Photosynthesis, Carbon Allocation, and Nitrogen Fixation in Red Alder. ÃÃDoctoral Dissertation, Yale University, Dissertation Abstracts Vol.50:08©B, p.3244 (96 pp.)ÄÄ. 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 nodulation 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 nodulation, 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 over the course of the experiment. This occurred more rapidly in nodulated plants and was attributed to more rapid attainment 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. Alnus rubra/red alder ÃÃKEYWORDS: ALLOCATION, CARBON:NITROGEN RATIO, CONTROLLED ENVIRONMENT CHAMBERS, NITROGEN, NITROGEN FIXATION, TREESÄÄ Ã Ã45Ä Ä° `  à ÃArnone, J.A., III, and J.C. Gordon.Ä Ä 1990. Effect of Nodulation, Nitrogen Fixation and CO2 Enrichment on the Physiology, Growth and Dry Mass Allocation of Seedlings of ÃÃAlnus rubraÄÄ Bong. ÃÃNew Phytologist 116:55©66.ÄÄ Inoculated and uninoculated ÃÃAlnus rubraÄÄ Bong. seedlings were grown for 47 days in atmospheres containing ambient (350 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. Evidence 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. Alnus rubra ÃÃKEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, NITROGEN FIXATION, NODULATION, TREESÄÄ Ã Ã46Ä Ä° `  à ÃArp, W.J.Ä Ä 1991. Effects of Source©Sink Relations on Photosynthetic Acclimation to Elevated CO2. ÃÃPlant, Cell and Environment 14:869©875.ÄÄ 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. ÃÃKEYWORDS: PHOTOSYNTHETIC ACCLIMATION, POT VOLUME, REVIEW, ROOT:SHOOT RATIO, SOURCE©SINK BALANCEÄÄ Ã Ã47Ä Ä° `  à ÃArp, W.J.Ä Ä 1991. Vegetation of a North American Salt Marsh and Elevated Atmospheric Carbon Dioxide. ÃÃDoctoral Dissertation, Centrale Huisdrukkerij Vrije Universiteit, AmsterdamÄÄ. Distichlis spicata/Spartina patens/Scirpus olneyi ÃÃKEYWORDS: C3, C4, EVAPOTRANSPIRATION, GROWTH, HALOPHYTES, LEAF PHOTOSYNTHESIS, OPEN©TOP CHAMBERS, PHOTOSYNTHETIC ACCLIMATION, SALT MARSH, SOURCE©SINK BALANCE, SPECIES COMPETITION, WATER STATUSÄÄ Ã Ã48Ä Ä° `  à ÃArp, W.J., and B.G. Drake.Ä Ä 1991. Increased Photosynthetic Capacity of ÃÃScirpus olneyiÄÄ after 4 Years of Exposure to Elevated CO2. ÃÃPlant, Cell and Environment 14:1003©1006.ÄÄ 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 observed in other species growing in the field, which suggests that photosynthesis of certain field grown plants will continue to respond to elevated levels of atmospheric CO2. sedge/Scirpus olneyi ÃÃKEYWORDS: LEAF PHOTOSYNTHESIS, OPEN©TOP CHAMBERS, PHOTOSYNTHETIC ACCLIMATIONÄÄ Ã Ã49Ä Ä° `  à ÃArp, W.J., B.G. Drake, W.T. Pockman, P.S. Curtis, and D.F. Whigham.Ä Ä 1993. Interactions between C3 and C4 Salt Marsh Plant Species during Four Years of Exposure to Elevated Atmospheric CO2. ÃÃVegetatio 104/105:133©143.ÄÄ Elevated atmospheric CO2 is known to stimulate photosynthesis and growth of plants with the C3 pathway but less of plants 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 CO2/mol) on a salt marsh vegetation with both C3 and C4 species was investigated. Elevated CO2 increased the biomass of the C3 sedge ÃÃScirpus olneyiÄÄ growing in a pure stand, while the biomass of the C4 grass ÃÃSpartina patensÄÄ in a monospecific community 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 ÃÃSpartina patensÄÄ dominated the higher areas of the salt marsh, while the C3 sedge ÃÃScirpus olneyiÄÄ was most abundant at the lower elevations, and the mixed community occupied intermediate elevations. ÃÃScirpusÄÄ growth may have been restricted by drought and salt stress at the higher elevations, while ÃÃSpartinaÄÄ growth at the lower elevations may be affected by the higher frequency of flooding. Elevated CO2 may affect the species distribution in the salt marsh if it allows ÃÃScirpusÄÄ to grow at higher elevations where it in turn may affect the growth of ÃÃSpartinaÄÄ. Spartina patens/Scirpus olneyi/Distichlis spicata ÃÃKEYWORDS: AQUATIC PLANTS, C3, C4, COMMUNITY LEVEL CO2 RESPONSES, GROWTH, HALOPHYTES, OPEN©TOP CHAMBERS, SALT MARSH, SALT STRESS, SPECIES COMPETITION, WATER STRESSÄÄ Ã Ã50Ä Ä° `  à ÃArtus, N.N.Ä Ä 1990. Two Mutants of ÃÃArabidopsis thalianaÄÄ That Become Chlorotic in Atmospheres Enriched with CO2. ÃÃPlant, Cell and Environment 13:575©580.ÄÄ Two nonallelic, nuclear recessive mutants of ÃÃArabidopsis thalianaÄÄ (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 leaves and spreads to the tips. The injurious effects of CO2 seem to be restricted to photosynthetic tissues, since root elongation 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 mutations do not impose a requirement for photorespiration. The possibilities that the high CO2©sensitive phenotypes are caused by an effect of CO2 in stomata, on ethylene synthesis, or on mineral uptake are discussed but are considered unlikely. Arabidopsis thaliana ÃÃKEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, MUTANTÄÄ Ã Ã51Ä Ä° `  à ÃAshenden, T.W., R. Baxter, and C.R. Rafarel.Ä Ä 1992. An Inexpensive System for Exposing Plants in the Field to Elevated Concentrations of CO2. ÃÃPlant, Cell and Environment 15:365©372.ÄÄ An inexpensive, potentially mobile field exposure system is described which may be easily constructed by a small workshop. 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 relatively 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. ÃÃKEYWORDS: EXPOSURE METHODS, OUTDOOR GROWTH CHAMBERSÄÄ Ã Ã52Ä Ä° `  à ÃAston, A.R.Ä Ä 1984. The Effect of Doubling Atmospheric CO2 on Streamflow: a Simulation. ÃÃJournal of Hydrology 67:273©280.ÄÄ There is a potential for atmospheric CO2 to rise four© or six©fold, and at some time in the foreseeable future a doubling 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. ÃÃKEYWORDS: HYDROLOGIC MODEL, STREAMFLOWÄÄ Ã Ã53Ä Ä° `  à ÃAustin, M.P.Ä Ä 1992. Modelling the Environmental Niche of Plants: Implications for Plant Community Response to Elevated CO2 Levels. ÃÃAustralian Journal of Botany 40:615©630.ÄÄ 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, forest modellers using FORET type models, a symmetric curve, and community ecologists a skewed response with a tail towards high temperatures. These assumptions are reviewed in relation to niche theory, and recent propositions concerning the 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 ÃÃEucalyptus fastigataÄÄ for 8377 sites in southern New South Wales, Australia. Seven environmental variables or factors are considered: mean annual temperature, mean annual rainfall, mean monthly solar radiation, topographic position, rainfall seasonality, lithology, and soil; nutrient status. The temperature response is modelled by a ÃÃBetaÄÄ©function, log ÃÃy + a + alphaÄÄ log ÃÃ(t © a) + sigmaÄÄ log ÃÃ(b © t)ÄÄ, where ÃÃtÄÄ is temperature and letters are parameters. The probability of occurrence is shown to be a skewed function of mean annual temperature. Any process©models of climate change for vegetation incorporating temperature changes due to elevated CO2 must be capable of generating such realised environmental niche responses for species. Eucalyptus fastigata ÃÃKEYWORDS: COMMUNITY LEVEL CO2 RESPONSES, ENVIRONMENTAL INTERACTIONS, FOREST, MODELING, NICHE THEORY, SPECIES RANGEÄÄ Ã Ã54Ä Ä° `  à ÃBadger, M.Ä Ä 1992. Manipulating Agricultural Plants for a Future High CO2 Environment. ÃÃAustralian Journal of Botany 40:421©429.ÄÄ 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 temperatures, resulting from the improvement which will occur in the performance of the primary carboxylating enzyme, Rubisco. However, while growth experiments at elevated CO2 indicate that C3 plants show stimulation of dry matter accumulation, the potential gains are greatly ameliorated by a redistribution of plant resources. This primarily occurs via a reduction in the leaf area ratio which offsets increases in the net assimilation rate. In addition, there may be an overcommitment of nitrogen in key photosynthetic components such as Rubisco and the thylakoid electron transport system. It is concluded that plants 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 elevated CO2 include (1) altering source©sink relations; (2) improving the redistribution of nitrogen between the photosynthetic machinery and the rest of the plant; and (3) changing the response of stomata to CO2 and humidity to increase water©use efficiency even further than is currently predicted. ÃÃKEYWORDS: AGRICULTURE, C3, C4, ENVIRONMENTAL INTERACTIONS, GROWTH ANALYSIS, LIGHT, NITROGEN, PHENOLOGY, REVIEW, RIBULOSE BISPHOSPHATE CARBOXYLASE, SOURCE©SINK BALANCE, TEMPERATURE, WUEÄÄ Ã Ã55Ä Ä° `  à ÃBaille, A.Ä Ä 1989. Greenhouse Microclimate and Its Management in Mild Winter Climates. ÃÃActa Horticulturae 246:23©36.ÄÄ ÃÃKEYWORDS: GREENHOUSEÄÄ Ã Ã56Ä Ä° `  à ÃBailly, J., and J.R. Coleman.Ä Ä 1988. Effect of CO2 Concentration on Protein Biosynthesis and Carbonic Anhydrase Expression in ÃÃChlamydomonas reinhardtiiÄÄ. ÃÃPlant Physiology 87:833©840.ÄÄ The effect of external inorganic carbon (Ci) concentrations on protein biosynthesis and carbonic anhydrase (CA) mRNA abundance were examined in the eukaryotic alga ÃÃChlamydomonas reinhardtiiÄÄ. Transfer of high CO2 (5%) grown algae to air levels of CO2 resulted in the transitory synthesis of two polypeptides of approximately 49,000 and 52,000 daltons as well as prolonged synthesis and accumulation of the 37,000 dalton CA monomer and an unidentified 20,000 dalton polypeptide. The gene coding for carbonic anhydrase was isolated from a genomic expression library and subjected to restriction endonuclease analysis. Southern blot analysis of chromosomal DNA indicates that only a single copy of the gene is present. The 2.5 kilobase DNA fragment hybridizes specifically to a 1.4 kilobase transcript in RNA isolated from air©grown cells and from cells grown on 5% CO2 that have been exposed to air levels of CO2. Maximum mRNA abundance was observed after 1 to 3 hours of exposure to air. Transfer of air©grown cells to a high CO2 environment resulted in the elimination of the CA transcript after 60 minutes of exposure. Changes in CA transcript abundance in response to external Ci concentrations occurred in the presence or absence of light. Chlamydomonas reinhardtii ÃÃKEYWORDS: ALGAE, AQUATIC PLANTS, CARBONIC ANHYDRASE, CELL CULTURE, ENZYMES, GENE EXPRESSIONÄÄ Ã Ã57Ä Ä° `  à ÃBaker, J.T., and L.H. Allen Jr.Ä Ä 1993. Contrasting Crop Species Responses to CO2 and Temperature: Rice, Soybean and Citrus. ÃÃVegetatio 104/105:239©260.ÄÄ The continuing increase in atmospheric carbon dioxide concentration ([CO2]) and projections of possible future increases in global air temperatures have stimulated interest in the effects of these climate variables on plants and, in particular, on agriculturally important food crops. Mounting evidence from many different experiments suggests that the magnitude and even direction of crop responses to [CO2] and temperature is almost certain to be species dependent and very likely, within a species, to be cultivar dependent. Over the last decade, [CO2] and temperature experiments have been conducted on several crop species in the outdoor, naturally©sunlit, environmentally controlled, plant growth chambers by USDA©ARS and the University of Florida, at Gainesville, Florida, USA. The objectives for this paper are to summarize some of the major findings of these experiments and further to compare and contrast species responses to [CO2] and temperature for three diverse crop species: rice (ÃÃOryza sativaÄÄ, L.), soybean (ÃÃGlycine maxÄÄ, L.) and citrus (various species). Citrus had the lowest growth and photosynthetic rates but under [CO2] enrichment displayed the greatest percentage increases over ambient [CO2] control treatments. In all three species the direct effect of [CO2] enrichment was always an increase in photosynthetic rate. In soybean, photosynthetic rate depended on current [CO2] regardless of the long©term [CO2] history of the crop. In rice, photosynthetic rate measured at a common [CO2], decreased with increasing long©term [CO2] growth treatment due to a corresponding decline in RuBP carboxylase content and activity. Rice specific respiration decrease from subambient to ambient and superambient [CO2] due to a decrease in plant tissue nitrogen content and a decline in specific maintenance respiration rate. In all three species, crop water use decreased with [CO2] enrichment but increased with increases in temperature. For both rice and soybean, [CO2] enrichment increased growth and grain yield. Rice grain yields declined by roughly 10% per each 1À$ÀC rise in day/night temperature above 28/21À$ÀC. rice/Oryza sativa/soybean/Glycine max/citrus/Citrus sinensis/Poncirus trifoliata ÃÃKEYWORDS: ENVIRONMENTAL INTERACTIONS, EVAPOTRANSPIRATION, NITROGEN, PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION, PRE©INDUSTRIAL CO2 CONCENTRATION, RESPIRATION, REVIEW, RIBULOSE BISPHOSPHATE CARBOXYLASE, TEMPERATURE, WUE, YIELDÄÄ Ã Ã58Ä Ä° `  à ÃBaker, J.T., L.H. Allen Jr., and K.J. Boote.Ä Ä 1990. Growth and Yield Responses of Rice to Carbon Dioxide Concentration. ÃÃJournal of Agricultural Science, Cambridge 115:313©320.ÄÄ Rice plants (ÃÃOryza sativaÄÄ L., cv. IR30) were grown in paddy culture in outdoor, naturally sunlit, controlled©environment, plant growth chambers at Gainesville, Florida, USA, in 1987. The rice plants were exposed throughout the season to subambient (160 and 250), ambient (330) or superambient (500, 660, 900 umol CO2/mol air) CO2 concentrations. Total shoot biomass, root biomass, tillering, and final grain yield increased with increasing CO2 concentration, the greatest increase occurring between the 160 and 500 umol CO2/mol air treatments. Early in the growing season, root:shoot biomass ratio increased with increasing CO2 concentration; although the ratio decreased during the growing season, net assimilation rate increased with increasing CO2 concentration and decreased during the growing season. Differences in biomass and lamina area among CO2 treatments were largely due to corresponding differences in tillering response. The number of panicles/plant was almost entirely responsible for differences in final grain yield among CO2 treatments. Doubling the CO2 concentration from 330 to 660 umol CO2/mol air resulted in a 32% increase in grain yield. These results suggest that important changes in the growth and yield of rice may be expected in the future as the CO2 concentration of the earth's atmosphere continues to rise. rice/Oryza sativa ÃÃKEYWORDS: ALLOCATION, GROWTH ANALYSIS, PRE©INDUSTRIAL CO2 CONCENTRATION, SPAR UNITSÄÄ Ã Ã59Ä Ä° `  à ÃBaker, J.T., L.H. Allen Jr., and K.J. Boote.Ä Ä 1992. Response of Rice to Carbon Dioxide and Temperature. ÃÃAgricultural and Forest Meteorology 60:153©166.ÄÄ The current increase in atmospheric carbon dioxide concentration ([CO2]) along with predictions of possible future increases in global air temperatures have stimulated interest in the effects of [CO2] and temperature on the growth and yield of food crops. This study was conducted to determine the effects and possible interactions of [CO2] and temperature on the growth and yield of rice (ÃÃOryza sativaÄÄ L., cultivar IR©30). Rice plants were grown for a season in outdoor, naturally sunlit, controlled©environment, and plant growth chambers. Temperature treatments of 28/21/25, 34/27/31, and 40/33/37À$ÀC (daytime dry bulb air temperature/night©time dry bulb air temperature/paddy water temperature) were maintained in [CO2] treatments of 330 and 660 umol CO2/mol air. In the 40/33/37À$ÀC temperature treatment, plants in the 330 umol/mol [CO2] treatment died during stem extension while the [CO2] enriched plants survived but produced sterile panicles. Plants in the 34/27/31À$ÀC temperature treatments accumulated biomass and leaf area at a faster rate early in the growing season than plants in the 28/21/25À$ÀC temperature treatments. Tillering increased with increasing temperature treatment. Grain yield increases owing to [CO2] enrichment were small and non©significant. This lack of [CO2] response on grain yield was attributed to the generally lower levels of solar irradiance encountered during the late fall and winter when this experiment was conducted. Grain yields were affected much more strongly by temperature than [CO2] treatment. Grain yields declined by an average of approximately 7©8% per 1À$ÀC rise in temperature from the 28/21/25 to 34/27/31À$ÀC temperature treatment. The reduced grain yields with increasing temperature treatment suggests potential detrimental effects on rice production in some areas if air temperatures increase, especially under conditions of low solar irradiance. rice/Oryza sativa ÃÃKEYWORDS: GROWTH, SPAR UNITS, TEMPERATURE, YIELDÄÄ Ã Ã60Ä Ä° `  à ÃBaker, J.T., L.H. Allen Jr., and K.J. Boote.Ä Ä 1992. Temperature Effects on Rice at Elevated CO2 Concentration. ÃÃJournal of Experimental Botany 43:959©964.ÄÄ The continuing increase in atmospheric carbon dioxide concentration ([CO2]) and projections of possible future increases in global air temperatures have stimulated interest in the effects of these climate variables on agriculturally important food crops. This study was conducted to determine the effects of [CO2] and temperature on rice (ÃÃOryza sativaÄÄ L., cv. IR©30). Rice plants were grown season©long in outdoor, naturally sunlit, controlled©environment, plant growth chambers in temperature regimes ranging from 25/18/21À$ÀC to 37/30/34À$ÀC (daytime dry bulb air temperature/night©time dry bulb air temperature/paddy water temperature) and [CO2] of 660 umol CO2/mol air. An ambient chamber was maintained at a [CO2] of 330 umol/mol and temperature regime of 28/21/25À$ÀC. Carbon dioxide enrichment at 28/21/25À$ÀC increased both biomass accumulation and tillering and increased grain yield by 60%. In the 660 umol/mol [CO2] treatment, grain yield decreased from 10.4 to 1.0 Mg/ha with increasing temperature from 28/21/25À$ÀC to the 37/30/34À$ÀC temperature treatment. Across this temperature range, the number of panicles/plant nearly doubled while the number of seeds/panicle declined sharply. These results indicate that while future increase in atmospheric [CO2] are likely to be beneficial to rice growth and yield, potentially large negative effects on rice yield are possible if air temperatures also rise. rice/Oryza sativa ÃÃKEYWORDS: GROWTH, SEED PRODUCTION, SPAR UNITS, TEMPERATURE, YIELDÄÄ Ã Ã61Ä Ä° `  à ÃBaker, J.T., L.H. Allen Jr., K.J. Boote, P. Jones, and J.W. Jones.Ä Ä 1989. Response of Soybean to Air Temperature and Carbon Dioxide Concentration. ÃÃCrop Science 29:98©105.ÄÄ Documented increases in global atmospheric CO2 concentration have stimulated interest in the direct effects of CO2 on plant growth and yield as well as the interactive effects of CO2 with other major climatic variables. This study was conducted to determine the effects and interactions of CO2 concentration and air temperature on the development, growth, total nonstructural carbohydrate (TNC), and final seed yield of soybean [ÃÃGlycine maxÄÄ (L.) Merr., cv. Bragg] grown season©long in naturally lit, controlled©environment chambers. Day/night air temperatures of 26/19, 31/24 and 36/29À$ÀC were maintained in CO2 treatments of 330 and 660 umol CO2/mol air. Both CO2 enrichment and increasing air temperature decreased main stem plastochron interval, while increasing air temperature increased final mainstem node number. Leaf area and above©ground biomass increased with CO2 enrichment and with temperature from 26/19À$ÀC to 31/24À$ÀC. The nonlinear increase with temperature in leaf area, aboveground biomass, and plastochron interval was attributed to the highest temperature treatment being near or above the optimum for soybean growth and development. Seed yield increased with CO2 enrichment due mainly to an increase in seed number rather than weight per seed. Individual seed weight decreased, while seed number increased with increasing temperature. Leaflet TNC was relatively stable throughout the day. Stem TNC was less affected by CO2 than by temperature treatment and decreased with increasing temperature. These results indicate that the response of soybean to elevated CO2 concentration is highly temperature dependent. soybean/Glycine max ÃÃKEYWORDS: CARBOHYDRATES, REPRODUCTION, SEEDS, SPAR UNITS, TEMPERATURE, YIELDÄÄ Ã Ã62Ä Ä° `  à ÃBaker, J.T., L.H. Allen Jr., K.J. Boote, P. Jones, and J.W. Jones.Ä Ä 1990. Developmental Responses of Rice to Photoperiod and Carbon Dioxide Concentration. ÃÃAgricultural and Forest Meteorology 50:201©210.ÄÄ The documented increase in the carbon dioxide concentration of the Earth's atmosphere has stimulated interest in the effects of CO2 on plants and in particular the future prospects for the world's food supplies. While rice is a major food crop, relatively little is known about the effects of CO2 concentration on the timing of physiological growth stages and total growth duration, which are important aspects of a rice cultivar's adaptability to the environment of a particular geographic region. The objective of this study was to determine the developmental responses of a modern, improved rice cultivar (ÃÃOryza sativaÄÄ, cultivar 'IR©30') to a range of CO2 concentrations under two contrasting photoperiods. Rice plants were grown season©long in an outdoor, naturally lit, computer©controlled environment, plant growth chambers in CO2 concentrations of 160, 250 (subambient), 330 (ambient), 500, 660 and 900 (superambient) umol CO2/mol air. The entire experiment was conducted twice during 1987. The first or early planted rice (EPR) experiment was conducted with photoperiod extension lights during the vegetative phase of development, while the second or late©planted rice (LPR) experiment was conducted using only naturally occurring photoperiod. In both experiments, mainstem leaf developmental rates were greater during vegetative rather than reproductive growth stages and leaf appearance rates increased with CO2 treatment during vegetative development. In the LPR experiment, panicle initiation and boot stage occurred earlier and total growth duration was shortened for rice plants in the superambient compared with ambient and subambient CO2 treatments. This acceleration of plant development with increasing CO2 treatment was associated with a CO2©induced decrease in the number of mainstem leaves formed during the vegetative phase of growth. The reduced developmental response of rice plants to CO2 in the EPR compared with the LPR experiment was attributed to the artificially extended photoperiod during the EPR experiment forcing a delay in the onset of reproductive development particularly in the superambient treatments. The CO2©induced acceleration of development and shortening of total growth duration should become a topic of interest for rice agronomists and breeders involved with selecting rice cultivars and agronomic practices for a particular geographic region in view of the continued increases in global atmospheric CO2 concentration. rice/Oryza sativa ÃÃKEYWORDS: GROWTH STAGES, PHOTOPERIOD, PRE©INDUSTRIAL CO2 CONCENTRATION, SPAR UNITSÄÄ Ã Ã63Ä Ä° `  à ÃBaker, J.T., L.H. Allen Jr., K.J. Boote, P. Jones, and J.W. Jones.Ä Ä 1990. Rice Photosynthesis and Evapotranspiration in Subambient, Ambient, and Superambient Carbon Dioxide Concentrations. ÃÃAgronomy Journal 82:834©840.ÄÄ The current global rise in atmospheric carbon dioxide concentration [CO2], has stimulated interest in the response of agricultural crops to [CO2]. The objectives were to determine the effects of [CO2] on photosynthesis, evapotranspiration, and water use efficiency of rice (ÃÃOryza sativaÄÄ L., cv. IR©30). Rice plants were grown in naturally sunlit, plant growth chambers in subambient (160 and 250), ambient (330), or superambient (500, 660, and 900 umol CO2/mol air) [CO2] treatments. Photosynthetic light response curves were analyzed to obtain estimates of canopy light utilization efficiency (ÀÀ) and canopy conductance to CO2 transfer (À)À). Estimates of ÀÀ increased with increasing [CO2] treatment with the greatest increase in the 160 to 500 umol/mol treatments. Estimates of À)À were more variable than those of ÀÀ and were not different among [CO2] treatments. Photosynthetic rates increased with increasing [CO2] treatment from 160 to 500 umol/mol followed by a leveling off of the response among the superambient [CO2] treatments. Evapotranspiration decreased while water©use efficiency increased with increasing [CO2]. Short©term cross©switching of [CO2] among the chambers revealed a profound adaptive response to long©term [CO2] growth treatment. The lack of further photosynthetic response above the 500 umol/mol [CO2] treatment appears to indicate a need to select or screen rice cultivars for increased response to superambient [CO2] in order to more fully take advantage of future increases in global atmospheric [CO2]. rice/Oryza sativa ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, LIGHT, PRE©INDUSTRIAL CO2 CONCENTRATION, SPAR UNITS, TRANSPIRATION, WUEÄÄ Ã Ã64Ä Ä° `  à ÃBaker, J.T., L.H. Allen Jr., K.J. Boote, A.J. Rowland©Bamford, J.W. Jones, P.H. Jones, G. Bowes, and S.L. Albrecht.Ä Ä 1988. Response of Rice to Subambient and Superambient Carbon Dioxide Concentrations 1986©1987 Progress ReportÃÃ, 043 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C. rice/Oryza sativa ÃÃKEYWORDS: ALLOCATION, ANABAENA VARIABILIS, CANOPY PHOTOSYNTHESIS, CARBOHYDRATES, CYANOBACTERIA, GROWTH STAGES, PRE©INDUSTRIAL CO2 CONCENTRATION, RIBULOSE BISPHOSPHATE CARBOXYLASE, SPAR UNITS, STOMATAL DENSITY, TRANSPIRATION, YIELDÄÄ Ã Ã65Ä Ä° `  à ÃBaker, J.T., L.H. Allen Jr., K.J. Boote, A.J. Rowland©Bamford, J.W. Jones, P.H. Jones, G. Bowes, and F. Laugel.Ä Ä 1989. Temperature and CO2 Effects on Rice. 1988 Progress ReportÃÃ, 053 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C. Oryza sativa/rice ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CARBOHYDRATES, EVAPOTRANSPIRATION, GROWTH STAGES, RESPIRATION, RIBULOSE BISPHOSPHATE CARBOXYLASE, SPAR UNITS, SUCROSEPHOSPHATE SYNTHASE, TEMPERATURE, YIELDÄÄ Ã Ã66Ä Ä° `  à ÃBaker, J.T., F. Laugel, K.J. Boote, and L.H. Allen Jr.Ä Ä 1992. Effects of Daytime Carbon Dioxide Concentration on Dark Respiration in Rice. ÃÃPlant, Cell and Environment 15:231©239.ÄÄ Rising atmospheric carbon dioxide concentration ([CO2]) has generated considerable interest in the response of agricultural crops to [CO2]. The objectives of this study were to determine the effects of a wide range of daytime [CO2] on dark respiration of rice (ÃÃOryza sativaÄÄ L. cv. IR©30). Rice plants were grown season©long in naturally sunlit plant growth chambers in subambient (160 and 250), ambient (330), or superambient (500, 660 and 900 umol CO2/mol air) [CO2] treatments. Canopy dark respiration, expressed on a ground area basis (Rd) increased with increasing [CO2] treatments and was very similar among the superambient treatments. The trends in Rd over time and in response to increasing daytime [CO2] treatment were associated with and similar to trends previously described for photosynthesis. Specific respiration rate (Rdw) decreased with time during the growing season and was higher in the subambient than the ambient and superambient [CO2] treatments. This greater Rdw in the subambient [CO2] treatments was attributed to a higher specific maintenance respiration rate and was associated with higher plant tissue nitrogen concentration. rice/Oryza sativa ÃÃKEYWORDS: NITROGEN, PRE©INDUSTRIAL CO2 CONCENTRATION, RESPIRATION, SPAR UNITSÄÄ Ã Ã67Ä Ä° `  à ÃBaker, R.G.E., and D.J. Boatman.Ä Ä 1990. Some Effects of Nitrogen, Phosphorus, Potassium and Carbon Dioxide Concentration on the Morphology and Vegetative Reproduction of ÃÃSphagnum cuspidatumÄÄ Ehrh. ÃÃNew Phytologist 116:604©611.ÄÄ Five experiments are described which were designed to investigate the effects of varying the concentrations of nitrate, phosphate, potassium and carbon dioxide in the culture solution on the morphology and vegetative reproduction of ÃÃSphagnum cuspidatumÄÄ Ehrh. The plants were grown axenically from spores sown on agar containing inorganic salts and then transferred to aqueous culture solutions through which air containing enhanced concentrations of carbon dioxide was passed. In three of the experiments the plants were grown in a balanced inorganic salt solution at various dilutions and in two of these the concentration of carbon dioxide in the gas bubbled through the solution was varied. The concentrations of nitrogen, phosphorus and potassium were varied independently and in combination in the remaining experiments while the concentration of carbon dioxide was kept constant. In some of the experiments the minimum concentrations of nitrogen and potassium supplied were considerably below the minimum average concentrations recorded in rain but the minimum concentration of phosphorus supplied was within the upper part of the range recorded in rain. Within the ranges supplied the concentrations of all three elements and of carbon dioxide affected interfascicle length and vegetative reproduction (innovation formation) but it was concluded that the element limiting innovation formation in natural conditions is phosphorus. Sphagnum cuspidatum ÃÃKEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, NITROGEN, NUTRITION, PHOSPHORUS, POTASSIUM, VEGETATIVE REPRODUCTIONÄÄ Ã Ã68Ä Ä° `  à ÃBaldocchi, D.D., R. White, and J.W. Johnston.Ä Ä 1989. A Wind Tunnel Study to Design Large, Open©top Chambers for Whole©tree Pollutant Exposure Experiments. ÃÃJournal of the Air Pollution Control Association 39:549©1556.ÄÄ A wind tunnel study was conducted to determine the optimal design features of a large, open©top chamber, as needed for pollution exposure studies on mature trees. An optimally©designed, open©top chamber must minimize the incursion of ambient air through its opening and maintain a uniform treatment concentration throughout the chamber. The design features of interest are the diameter and height of the chamber and the deflection angle and opening size of any frustum that may be mounted on top of a model chamber. Design specifications depend on the turbulence regime about the chamber, which is influenced by the nature of the surrounding vegetation. Consequently, our investigation was performed on scale©model, open©top chambers in a wind tunnel populated with a model coniferous forest. Turbulence measurements demonstrated the similarity between the turbulence regime of the model and a natural forest. A hydrocarbon tracer was injected into the wind tunnel flow to characterize chamber performance. The main design features of open©top chambers are the velocity of air exiting through the top and the relationship between the length scale of the turbulence and the diameter of the chamber opening. As exit velocities increase, the proportion of eddies with sufficient force to penetrate into the chamber decrease. Therefore, for equal volumetric air flows, smaller opening sizes increase the exit velocities and reduce the number and extent of ambient 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 reduced when the diameter of the chamber opening is smaller than the characteristic length scale of the turbulence, a measure 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 for a smoother transition in the wind velocity streamline and is less apt to cause wake turbulence, as is the case with steeper frusta. Knowledge of the turbulence characteristics of plant canopies are readily available in the literature and can aid scientists and engineers in designing the optimal chamber and frusta dimensions for their particular application. Therefore, the empirical approach to chamber design can be avoided, and substantial savings can be realized. ÃÃKEYWORDS: AIR POLLUTION, EXPOSURE METHODS, OPEN©TOP CHAMBERSÄÄ Ã Ã69Ä Ä° `  à ÃBall, M.C., and R. Munns.Ä Ä 1992. Plant Responses to Salinity under Elevated Atmospheric Concentrations of CO2. ÃÃAustralian Journal of Botany 40:515©525.ÄÄ This review explores effects of elevated CO2 concentrations on growth in relation to water use and salt balance of halophytic and non©halophytic species. Under saline conditions, the uptake and distribution of sodium and chloride must be regulated to protect sensitive metabolic sites from salt toxicity. Salt©tolerant species exclude most of the salt from the transpiration stream, but the salt flux from a highly saline soil is still considerable. To maintain internal ion concentrations within physiologically acceptable levels, the salt influx to leaves must match the capacities of leaves for salt storage and/or salt export by either retranslocation or secretion from glands. Hence the balance between carbon gain and the expenditure of water in association with salt uptake is critical to leaf longevity under saline conditions. Indeed, one of the striking features of halophytic vegetation, such as mangroves, is the maintenance of high water use efficiencies coupled with relatively low rates of water loss and growth. These low evaporation rates are further reduced under elevated CO2 conditions. This, with increased growth, leads to even higher water use efficiency. Leaves of plants grown under elevated CO2 conditions might be expected to contain lower salt concentrations than those grown under ambient CO2 if salt uptake is coupled with water uptake. However, salt concentrations in shoot tissues are similar in plants grown under ambient and elevated CO2 conditions despite major differences in water use efficiency. This phenomenon occurs in C3 halophytes and in both C3 and C4 non©halophytes. These results imply shoot/root communication in regulation of the salt balance to adjust to 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). ÃÃKEYWORDS: C3, C4, HALOPHYTES, REVIEW, SALT STRESSÄÄ Ã Ã70Ä Ä° `  à ÃBarlow, E.W.R., and J. Conroy.Ä Ä 1988. Influence of Elevated Atmospheric Carbon Dioxide on the Productivity of Australian Forestry Plantations. ÃÃIN: Greenhouse: Planning for Climate Change (G.I. Pearman, ed.), E.J. Brill, New York, pp. 520©533.ÄÄ Australia produced $2.7 billion worth of forest products in 1983©84 but a further $1.3 billion worth, principally softwood, were imported. Because of this ever increasing demand for softwood, there is a move away from utilization of native hardwoods and by 2020 AD, when the atmospheric CO2 concentration is likely to be greater than 450 ppmv, 75% of forest products are projected to come from coniferous plantations. This move towards ÃÃPinus radiataÄÄ 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. ÃÃPinus radiataÄÄ 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 response of pines to elevated CO2 at a range of phosphorus and water levels. When phosphorus was adequate, doubling CO2 concentration more than doubled the rate of photosynthesis and increased the total plant dry weight by about 40%. However, there 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 ÃÃP. radiataÄÄ may be altered due to a reduction in water use or an increase in the drought tolerance of the trees. We found that CO2 enrichment did not affect either of these factors but the water©use efficiency was increased when phosphorus was adequate. All families of ÃÃP. radiataÄÄ do not respond to CO2 enrichment in the same manner. In a study investigating the response of four families to elevated CO2 at two phosphorus levels, we have identified a considerable variation between the families in their response to CO2 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 ÃÃP. radiataÄÄ plantations. But this will only occur if phosphorus fertilization is adequate. If the rise in CO2 results in climatic change the range of ÃÃP. radiataÄÄ may be even further 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 phosphorus and water to enable more accurate prediction of the productivity and water use of Australian native forests and eucalyptus plantations. Pinus radiata ÃÃKEYWORDS: ALLOCATION, CONDUCTANCE, FAMILY RESPONSES, FOREST, GROWTH, LEAF PHOTOSYNTHESIS, NUTRITION, PHOSPHORUS, POT VOLUME, REVIEW, TREES, WATER STRESS, WUEÄÄ Ã Ã71Ä Ä° `  à ÃBaron, J.J., and S.F. Gorski.Ä Ä 1986. Response of Eggplant to a Root Environment Enriched with CO2. ÃÃHortScience 21:495©498.ÄÄ Several elevated concentrations of CO2 were injected into the root atmosphere to determine the influence of CO2 concentration in the soil on the growth of eggplant (ÃÃSolanum melongenaÄÄ L.). Elevated CO2 levels in the root atmosphere consistently increased stem diameter while a significant increase in plant total dry weight and leaf area only occurred during long day/warm temperature conditions. Under periods of short days and low light levels, 15% CO2 reduced total dry weight and leaf area. Applications of 14©CO2 to the root zone demonstrated that 14C eggplant roots absorb CO2 from the soil environment and translocate labeled compounds into the shoot. Solanum melongena/eggplant ÃÃKEYWORDS: 14C, FIZZ IRRIGATION, HORTICULTURAL CROPS, SOIL CO2 CONCENTRATIONÄÄ Ã Ã72Ä Ä° `  à ÃBarr, A.G., K.M. King, G.W. Thurtell, and M.E.D. Graham.Ä Ä 1990. Humidity and Soil Water Influence the Transpiration Response of Maize to CO2 Enrichment. ÃÃCanadian Journal of Plant Science 70:941©948.ÄÄ The impact of increasing atmospheric CO2 on the productivity of C4 crops may vary with soil water availability. This study investigates the hypothesis that elevating CO2 in ÃÃZea maysÄÄ L. reduces the degree to which transpiration is limited by soil water at high vapor pressure deficits or low soil water contents. Plants growing in controlled environments at 300 and 600 umol/mol CO2 were exposed daily to five levels of vapor pressure deficit as water was withheld and the soil dried over an 8©d period. Doubling CO2 caused an overall reduction of 23% in the transpiration rate and 34% in the leaf conductance, but the effect of CO2 on transpiration and leaf conductance was greatest at high soil water content and low vapor pressure deficit, when soil water least limited transpiration. Implications for the productivity of C4 crops in the field are discussed. corn/Zea mays ÃÃKEYWORDS: C4, CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS, HUMIDITY, TRANSPIRATION, VPD, WATER STRESSÄÄ Ã Ã73Ä Ä° `  à ÃBarson, M.M., and R.M. Gifford.Ä Ä 1990. Carbon Dioxide Sinks: The Potential Role of Tree Planting in Australia. ÃÃIN: Greenhouse and Energy (D.J. Swain, ed.), CSIRO, Australia, pp. 433©443.ÄÄ Reforestation has been suggested as a possible policy option at several recent international 'greenhouse effect' forums. 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. Although forestry cannot in principle offer a permanent solution to continuous emission of CO2 from fossil fuel burning, its expansion 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 sequestration 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. ÃÃKEYWORDS: MODELING, REFORESTATION, TREESÄÄ Ã Ã74Ä Ä° `  à ÃBauerle, W.L., D. Kretchman, and L. Tucker©Kelly.Ä Ä 1986. CO2 Enrichment in the U.S. ÃÃIN: Status and CO2 Sources, Vol. I (H.Z. Enoch and B.A. Kimball, eds.), Carbon Dioxide Enrichment of Greenhouse Crops, CRC Press, Inc., Boca Raton, Florida, pp. 49©57.ÄÄ ÃÃKEYWORDS: COMMERCIAL USE OF CO2, GREENHOUSEÄÄ Ã Ã75Ä Ä° `  à ÃBazzaz, F.A.Ä Ä 1990. The Response of Natural Ecosystems to the Rising Global CO2 Levels. ÃÃAnnual Review of Ecology and Systematics 21:167©196.ÄÄ ÃÃKEYWORDS: CO2 ENRICHMENT STUDIES, COMMUNITY LEVEL CO2 RESPONSES, ECOSYSTEM LEVEL CO2 RESPONSES, ENVIRONMENTAL INTERACTIONS, FAMILY RESPONSES, HERBIVORY, PHYSIOLOGICAL CO2 RESPONSES, POPULATION LEVEL CO2 RESPONSES, REVIEW, SOIL MICROORGANISMS, SPECIES COMPETITION, SPECIES RANGEÄÄ Ã Ã76Ä Ä° `  à ÃBazzaz, F.A., D.D. Ackerly, F.I. Woodward, and L. Rochefort.Ä Ä 1992. CO2 Enrichment and Dependence of Reproduction on Density in an Annual Plant and a Simulation of Its Population Dynamics. ÃÃJournal of Ecology 80:643©651.ÄÄ 1. Populations of an annual plant, ÃÃAbutilon theophrastiÄÄ, 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 of demography and reproduction. Variables measured included survivorship, proportion of plants flowering and fruiting, number of fruiting individuals, number of seeds per individual, total seed production per population, mean seed mass, and 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 production 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 produced 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 simulated 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. Abutilon theophrasti ÃÃKEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, MODELING, OLD FIELD COMMUNITIES, PLANT DENSITY, POPULATION MODEL, REPRODUCTION, SIMULATION, SURVIVORSHIPÄÄ Ã Ã77Ä Ä° `  à ÃBazzaz, F.A., J.S. Coleman, and S.R. Morse.Ä Ä 1990. Growth Responses of Seven Major Co©occurring Tree Species of the Northeastern United States to Elevated CO2. ÃÃCanadian Journal of Forest Research 20:1479©1484.ÄÄ We examined how elevated CO2 affected the growth of seven co©occurring tree species: American beech (ÃÃFagus grandifoliaÄÄ Ehrh.), paper birch (ÃÃBetula papyriferaÄÄ Marsh.), black cherry (ÃÃPrunus serotinaÄÄ Ehrh.), white pine (ÃÃPinus strobusÄÄ L.), red maple (ÃÃAcer rubrumÄÄ L.), sugar maple (ÃÃAcer saccharumÄÄ Marsh.), and eastern hemlock (ÃÃTsuga canadensisÄÄ (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 from 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 pine, hemlock, sugar maple) under CO2 levels of 400 or 700 uL/L. Plants were then harvested for biomass and growth determinations. 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. Furthermore, 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 CO2 concentrations were the shade©tolerant species (i.e., beech, sugar maple, and hemlock). Thus, elevated CO2 levels may enhance 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 seedlings greatly affected their response to elevated CO2 concentration. 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 ÃÃKEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, SHADE TOLERANCE, SPECIES COMPETITION, TREESÄÄ Ã Ã78Ä Ä° `  à ÃBazzaz, F.A., and E.D. Fajer.Ä Ä 1992. Plant Life in CO2©Rich World. ÃÃScientific American 266:68©74.ÄÄ ÃÃKEYWORDS: C3, C4, CO2 ENRICHMENT STUDIES, ECOSYSTEM LEVEL CO2 RESPONSES, INSECTS, PHOTOSYNTHESIS, REVIEWÄÄ Ã Ã79Ä Ä° `  à ÃBazzaz, F.A., and K. Garbutt.Ä Ä 1988. The Response of Annuals in Competitive Neighborhoods: Effects of Elevated CO2. ÃÃEcology 69:937©946.ÄÄ Four members of an annual community were used to investigate the effects of changing neighborhood complexity and increased 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 moisture and high light. Species responded differently to enhanced CO2 level. Some species (e.g., ÃÃAbutilon theophrastiÄÄ) had increased biomass with increasing CO2, while others (e.g., ÃÃAmaranthus retroflexusÄÄ) 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 general, competitive arrays that had C3 species depressed the response of C4 species, especially ÃÃAmaranthusÄÄ. ÃÃAmbrosia artemisiifoliaÄÄ 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. Ambrosia artemisiifolia/Abutilon theophrasti/Amaranthus retroflexus/Setaria faberii ÃÃKEYWORDS: C3, C4, OLD FIELD COMMUNITIES, SPECIES COMPETITION, SUNLIT CONTROLLED ENVIRONMENT CHAMBERSÄÄ Ã Ã80Ä Ä° `  à ÃBazzaz, F.A., K. Garbutt, E.G. Reekie, and W.E. Williams.Ä Ä 1989. Using Growth Analysis to Interpret Competition between a C3 and a C4 Annual under Ambient and Elevated CO2. ÃÃOecologia 79:223©235.ÄÄ Detailed growth analysis in conjunction with information on leaf display and nitrogen uptake was used to interpret competition between ÃÃAbutilon theophrastiÄÄ, a C3 annual, and ÃÃAmaranthus retroflexusÄÄ, 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 other. Competition caused a reduction in growth in both species, but for different reasons. In ÃÃAbutilonÄÄ, decreases in leaf area ratio (LAR) were responsible, whereas decreased unit leaf rate (ULR) was involved in the case of ÃÃAmaranthusÄÄ. Mean canopy height was lower in ÃÃAmaranthusÄÄ than ÃÃAbutilonÄÄ which may explain the low ULR of ÃÃAmaranthusÄÄ in competition. The decrease in LAR of ÃÃAbutilonÄÄ was associated with an increase in root:shoot ratio implying that ÃÃAbutilonÄÄ was limited by competition for below ground resources. The root:shoot ratio of ÃÃAmaranthusÄÄ actually decreased with competition, and ÃÃAmaranthusÄÄ had a much higher rate of nitrogen uptake per unit of root than did ÃÃAbutilonÄÄ. These latter results suggest that ÃÃAmaranthusÄÄ was better able to compete for below ground resources than ÃÃAbutilonÄÄ. Although the growth of both species was reduced by competition, generally speaking, the growth of ÃÃAmaranthusÄÄ was reduced to a greater extent than that of ÃÃAbutilonÄÄ. Regression analysis suggests that the success of ÃÃAbutilonÄÄ in competition was due to its larger starting capital (seed size) which gave it an early advantage over ÃÃAmaranthusÄÄ. Elevated CO2 had a positive effect upon biomass in ÃÃAmaranthusÄÄ, and to a lesser extent, ÃÃAbutilonÄÄ. These effects were limited to the early part of the experiment in the case of the individually grown plants, however. Only ÃÃAmaranthusÄÄ 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. ÃÃAbutilonÄÄ grown in competition with ÃÃAmaranthusÄÄ had a greater final biomass than ÃÃAmaranthusÄÄ at ambient CO2 levels, but this difference disappeared to a large extent at elevated CO2. The high RGR of ÃÃAmaranthusÄÄ at elevated CO2 levels allowed it to overcome the difference in initial size between the two species. Abutilon theophrasti/Amaranthus retroflexus ÃÃKEYWORDS: C3, C4, GROWTH ANALYSIS, NITROGEN, OLD FIELD COMMUNITIES, ROOT:SHOOT RATIO, SPECIES COMPETITION, SUNLIT CONTROLLED ENVIRONMENT CHAMBERSÄÄ Ã Ã81Ä Ä° `  à ÃBazzaz, F.A., K. Garbutt, and W.E. Williams.Ä Ä 1985. Effect of Increased Atmospheric Carbon Dioxide Concentration on Plant Communities. ÃÃIN: Direct Effects of Increasing Carbon Dioxide on Vegetation, DOE/ER©0238 (B.R. Strain and J.D. Cure, eds.), U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C., pp. 155©204.ÄÄ ÃÃKEYWORDS: C3, C4, CO2 ENRICHMENT STUDIES, COMMUNITY LEVEL CO2 RESPONSES, FLOWERING, REVIEW, SPECIES COMPETITIONÄÄ Ã Ã82Ä Ä° `  à ÃBazzaz, F.A., K. Garbutt, and W.E. Williams.Ä Ä 1985. The Effect of Elevated Atmospheric CO2 on Plant CommunitiesÃÃ, TR023 in Yellow Report Series, DOE/EV/04329©5, Dept. of Energy, Carbon Dioxide Research DivisionÄÄ. NTIS, U.S. Dept. of Commerce, Springfield, Virginia. ÃÃKEYWORDS: AIR POLLUTION, C3, C4, CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, GROWTH ANALYSIS, LEAF PHOTOSYNTHESIS, LIGHT, NUTRITION, PHENOLOGY, REPRODUCTION, REVIEW, SPECIES COMPETITION, SULFUR DIOXIDE, WATER STRESS, WUEÄÄ Ã Ã83Ä Ä° `  à ÃBazzaz, F.A., and K.D.M. McConnaughay.Ä Ä 1992. Plant©plant Interactions in Elevated CO2 Environments. ÃÃAustralian Journal of Botany 40:547©563.ÄÄ Increasing atmospheric carbon dioxide concentrations present a novel resource condition for plant communities. In order 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 consequence, 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 competitors as a result of CO2 enrichment, contrary to expectations based on their photosynthetic pathways. It is now clear that individually 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 is incomplete. We urgently need information about how elevated CO2 atmospheres influence stand formation and population dynamics, specifically with regard to the identities, numbers, sizes and reproductive fitnesses of individuals within single and multiple species stands, if we are to make multi©generational predictions concerning the fate of populations and communities in an elevated CO2 world. ÃÃKEYWORDS: COMMUNITY LEVEL CO2 RESPONSES, ENVIRONMENTAL INTERACTIONS, PLANT©PLANT INTERACTIONS, REVIEW, TEMPERATUREÄÄ Ã Ã84Ä Ä° `  à ÃBeer, S.Ä Ä 1986. The Fixation of Inorganic Carbon in Plant Cells. ÃÃIN: Physiology, Yield, and Economics, Vol. II (H. Enoch and B.A. Kimball, eds.), Carbon Dioxide Enrichment of Greenhouse Crops, CRC Press, Inc., Boca Raton, Florida, pp. 3©11.ÄÄ 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 for 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 mitochondrial 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 plants, this occurs in mesophyll cells. Malate or aspartate is then transported to bundle sheath cells where it is decarboxylated, 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. ÃÃKEYWORDS: C3, C4, CAM, ENZYMES, METABOLITES, PHOTOSYNTHESIS, REVIEWÄÄ Ã Ã85Ä Ä° `  à ÃBeerling, D.J., and W.G. Chaloner.Ä Ä 1993. The Impact of Atmospheric CO2 and Temperature Change on Stomatal Density: Observations from ÃÃQuercus roburÄÄ Lammas Leaves. ÃÃAnnals of Botany 71:231©235.ÄÄ A comparative study of leaves formed on shoots during the spring and summer (lammas) of ÃÃQuercus roburÄÄ from three contrasting geographical locations (Cardiff, Durham and London) gives a measure of the effect of temperature on stomatal density. This is of value in attempting to distinguish the effects of CO2 and temperature on observed stomatal density changes under different CO2 and temperature conditions through the Quaternary. These leaves of normal and lammas shoots will have developed under similar CO2 levels but different environmental temperatures. Our results demonstrate that leaves formed under the warmer summer temperatures had reduced stomatal densities and indices from all sites, compared with their spring counterparts. This trend was also detected from measurements of spring and summer leaves made upon herbarium material collected from the same tree in 1840. The results suggest that for ÃÃQ. roburÄÄ temperature overrides the influence of irradiance intensity and small seasonal (/= 0.20 for 25% of the earth's land surface. The temperature index annually was >/= 0.50 for 81% of the earth's land surface, indicating that local temperatures do not greatly limit net CO2 uptake by this species. The water index was >/= 0.50 for 79% of the earth's surfaces for ÃÃO. ficus©indicaÄÄ which exhibits Crassulacean acid metabolism with its accompanying high water©use efficiency. Predicted productivities for ÃÃO. ficus©indicaÄÄ without irrigation were at least 10 metric tons/ha/y, the value for many important annual agronomic crops, for 41% of the earth's land area. Irrigation increased such high productivity regions to 77% of the earth's land surface area within 60À$À of the equator. For simulations that included the worldwide changes in PAR, temperature and rainfall patterns that will most likely accompany a doubling in the ambient CO2 level, the high productivity of 10 tons/ha/y was predicted to occur for 54% of the earth's land surface area. Under elevated CO2, the predicted productivity of ÃÃO. ficus©indicaÄÄ increased for most of the U.S.A. and a productivity of 32 tons/ha/y was predicted for western South America. Opuntia ficus©indica ÃÃKEYWORDS: CAM, CLIMATE, ENVIRONMENTAL INTERACTIONS, LIGHT, NET PRIMARY PRODUCTIVITY, SIMULATION, TEMPERATURE, WATER STRESSÄÄ Ã Ã198Ä Ä° `  à ÃDel Castillo, D., B. Acock, V.R. Reddy, and M.C. Acock.Ä Ä 1989. Elongation and Branching of Roots on Soybean Plants in a Carbon Dioxide©Enriched Aerial Environment. ÃÃAgronomy Journal 81:692©695.ÄÄ Plants grown in high CO2 concentrations ([CO2]) often have a higher root weight than those grown in low [CO2]. It is usually assumed that the plants with this extra root weight can explore a greater volume of soil and will, therefore, have more water available to them. To test this assumption, soybean [ÃÃGlycine maxÄÄ (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 containers in the growth chambers had a glass side and new root growth appearing at the glass was measured and marked two or three times each week. Root weight at the end of the season (93 d after emergence) was 26 to 31% higher in [CO2]©enriched 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. soybean/Glycine max ÃÃKEYWORDS: GROWTH, ROOTS, SPAR UNITSÄÄ Ã Ã199Ä Ä° `  à ÃDelgado, E., J. Azcon©Bieto, X. Aranda, J. Palazon, and H. Medrano.Ä Ä 1992. Leaf Photosynthesis and Respiration of High CO2©grown Tobacco Plants Selected for Survival under CO2 Compensation Conditions. ÃÃPlant Physiology 98:949©954.ÄÄ Four self©pollinated, doubled©haploid tobacco, (ÃÃNicotiana tabacumÄÄ 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 ÃÃa/bÄÄ 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 ÃÃversusÄÄ 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. tobacco/Nicotiana tabacum ÃÃKEYWORDS: ALKALOIDS, COMPENSATION POINT, LEAF PHOTOSYNTHESIS, NITROGEN, PIGMENTS, RESPIRATION, SULFURÄÄ Ã Ã200Ä Ä° `  à ÃDelgado, E., M.A.J. Parry, D.W. Lawlor, A.J. Keys, and H. Medrano.Ä Ä 1993. Photosynthesis, Ribulose©1,5©ÃÃbisÄÄphosphate Carboxylase and Leaf Characteristics of ÃÃNicotiana tabacumÄÄ L. Genotypes Selected by Survival at Low CO2 Concentrations. ÃÃJournal of Experimental Botany 44:1©7.ÄÄ The photosynthetic characteristics (responses to CO2 and light), ribulose©1,5©ÃÃbisÄÄphosphate carboxylase (Rubisco) properties, and the size and number of cells of the mesophyll of ÃÃNicotiana tabacumÄÄ L. leaves of genotypes selected for survival at low atmospheric CO2 concentrations are described. When grown in the greenhouse with nutrient solution, the total dry matter production of the selected genotypes was 23% greater than that of the parent genotype; this increase was related to a greater number of mesophyll cells of smaller size in the selected plants compared to the parent. However, it was not related to changes in the photosynthetic characteristics nor to Rubisco properties. These results suggest that the increased dry matter accumulation of the selected genotypes is not due to a reduction in photorespiration nor an increase in the CO2 assimilation rates. Rather, the selection of haploid tobacco plantlets in low CO2 has resulted in plants with greater leaf areas (shown in previous work), due to the produciton of more cells of smaller size and to lower respiration rates per unit of leaf dry mass (previous work), thus increasing light capture, reducing the loss of assimilates and increasing total plant dry matter production. tobacco/Nicotiana tabacum ÃÃKEYWORDS: ANATOMY, GREENHOUSE, LEAF PHOTOSYNTHESIS, RIBULOSE BISPHOSPHATE CARBOXYLASEÄÄ Ã Ã201Ä Ä° `  à Ãden Hertog, J., and I. Stulen.Ä Ä 1990. The Effects of an Elevated Atmospheric CO2©concentration on Dry Matter and Nitrogen Allocation. ÃÃIN: The Greenhouse Effect and Primary Productivity in European Agro©ecosystems; 5©10 April 1990; Wageningen, The Netherlands (J. Goudriaan, H. van Keulen, and H.H. van Laar, eds.), Pudoc, Wageningen, pp. 27©30.ÄÄ Plantago major/broadleaf plantain/Urtica dioica/stinging nettle ÃÃKEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH ANALYSIS, NITROGEN, ROOT:SHOOT RATIO, ROOTSÄÄ Ã Ã202Ä Ä° `  à Ãden Hertog, J., I. Stulen, and H. Lambers.Ä Ä 1993. Assimilation, Respiration and Allocation of Carbon in ÃÃPlantago majorÄÄ as Affected by Atmospheric CO2 Levels: A Case Study. ÃÃVegetatio 104/105:369©378.ÄÄ The response of ÃÃPlantago majorÄÄ ssp. ÃÃpleiospermaÄÄ 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. Plantago major/broadleaf plantain ÃÃKEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH ANALYSIS, HYDROPONIC CULTURE, LEAF PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION, RESPIRATIONÄÄ Ã Ã203Ä Ä° `  à ÃDeWitt, C.A., R.E. Waldron, and J.R. Lambert.Ä Ä 1983. Effects of Carbon Dioxide Enrichment on Nitrogen Fixation in Soybeans 1982ÃÃ, 010 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, and U.S. Dept. of Agriculture, Agric. Res. Serv., Washington, D.C. soybean/Glycine max ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, GROWTH, NITROGEN FIXATION, SPAR UNITS, WUEÄÄ Ã Ã204Ä Ä° `  à ÃDietz, K.©J., U. Schreiber, and U. Heber.Ä Ä 1985. The Relationship between the Redox State of Q(A) and Photosynthesis in Leaves at Various Carbon©dioxide, Oxygen and Light Regimes. ÃÃPlanta 166:219©226.ÄÄ 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 ÃÃAsarum europaeumÄÄ and ÃÃFagus sylvaticaÄÄ than in leaves of ÃÃHelianthus annuusÄÄ and ÃÃFagus sylvaticaÄÄ 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. Helianthus annuus/Fagus sylvatica/Asarum europaeum ÃÃKEYWORDS: FLUORESCENCE, LEAF PHOTOSYNTHESIS, OXYGENÄÄ Ã Ã205Ä Ä° `  à ÃDons, C.Ä Ä 1988. Effects of Long©Term CO2 Enrichment under Different Irradiance Regimes on Growth and Photosynthesis in ÃÃLemna gibbaÄÄ. ÃÃPhotosynthetica 22:328©334.ÄÄ Cultivation in CO2©enriched air increased the growth rate of ÃÃLemna gibbaÄÄ only when day/night light cycling was used. Starch content increased with CO2 enrichment and irradiance (ÃÃIÄÄ). Reduced CO2 assimilation and growth in plants grown under high continuous ÃÃIÄÄ 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. Lemna gibba/duckweed ÃÃKEYWORDS: AQUATIC PLANTS, CARBOHYDRATES, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, LIGHT, MORPHOLOGY, PHOTOSYNTHESIS, PHOTOSYNTHETIC FEEDBACK INHIBITIONÄÄ Ã Ã206Ä Ä° `  à ÃDoorduin, J.C.Ä Ä 1990. Effects of CO2 and Plant Density on Growth and Yield of Glasshouse Grown Freesias. ÃÃActa Horticulturae 268:171©177.ÄÄ 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. freesia ÃÃKEYWORDS: FLOWER PRODUCTION, GREENHOUSE, HORTICULTURAL CROPSÄÄ Ã Ã207Ä Ä° `  à ÃDownton, W.J.S., W.J.R. Grant, and E.K. Chacko.Ä Ä 1990. Effect of Elevated Carbon Dioxide on the Photosynthesis and Early growth of Mangosteen (ÃÃGarcinia mangostanaÄÄ L.). ÃÃScientia Horticulturae 44:215©225.ÄÄ 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 weight increased by 77%. The stimulatory effect of CO2 was greatest on root and stem dry weight, which doubled. Although a smaller proportion of dry weight was partitioned into leaves compared with control plants, CO2 enrichment increased average leaf size by about 10%, specific leaf dry weight by 17% and total leaf area by 28%. By comparison, plants from the same apomictic seedling population grown under shadehouse conditions in Darwin, Australia, developed more slowly, consistent with descriptions in the literature, and were substantially smaller and lower in dry weight compared to the plants grown under controlled conditions, even in the absence of CO2 enrichment, and had not developed lateral branches by harvest time. Reasons for this difference are suggested which may enable improvement of the early growth of mangosteen plants under field nursery conditions. mangosteen/Garcinia mangostana ÃÃKEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, LEAF PHOTOSYNTHESIS, LIGHT, TREESÄÄ Ã Ã208Ä Ä° `  à ÃDownton, W.J.S., W.J.R. Grant, and B.R. Loveys.Ä Ä 1987. Carbon Dioxide Enrichment Increases Yield of Valencia Orange. ÃÃAustralian Journal of Plant Physiology 14:493©501.ÄÄ The response to elevated CO2 of 3©year©old fruiting Valencia orange scions (ÃÃCitrus sinensisÄÄ (L.) Osbeck) on citrange rootstock (ÃÃC. sinensisÄÄ x ÃÃPoncirus trifoliataÄÄ (L.) Raf.) was studied over a 12©month period under controlled environmental conditions. CO2 enrichment to approx. 800 ubar CO2 which commenced just prior to anthesis shortened the period of fruitlet abscission. Trees enriched to 800 ubar CO2 retained 70% more fruit, which at harvest were not significantly smaller in diameter or lower in fresh weight than fruit from control trees grown at approx. 400 ubar CO2. Fruit from the CO2 enriched trees also did not differ from the controls in soluble solids content, dry weight, seed number or rind thickness. The progression of fruit coloration was more rapid for the CO2©enriched trees. Dry weight of leaves and branches from the scion portion of the trees and the roots and stem of the rootstock portion did not differ between treatments at time of harvest. Leaf areas were also similar. However, specific leaf dry weight was 25% greater for the CO2 enriched treatment. Changes in dry matter partitioning resulted from the greater fruit yield (58% increase in dry weight) with CO2 enrichment. Photosynthetic rates observed at intervals over the experimental period were always lower in the CO2 enriched treatment compared to controls when measured at the same partial pressure of CO2. However photosynthetic rates in the CO2 enriched cabinet were always higher because of the increased level of CO2. The extent of this difference between the treatments varied with fruit development and increased from 23% higher photosynthetic rates in the CO2 enriched chamber at the end of flowering to 77% higher rates when fruits were 5 cm in diameter and decreased to 18% higher rates when fruit coloration was well advanced. Flushes of leaves that developed during the experiment also showed similar photosynthetic responses to CO2 enrichment and their photosynthetic rates declined as fruit matured. These results indicate that crop yield by fruit trees will increase as global levels of CO2 continue to rise, at least in those species that experience source limitation during fruit development. Valencia orange/Citrus sinensis ÃÃKEYWORDS: CROPS, GREENHOUSE, LEAF PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION, REPRODUCTION, SOURCE©SINK BALANCE, TREES, YIELDÄÄ Ã Ã209Ä Ä° `  à ÃDoyle, T.W.Ä Ä 1987. Seedling Response to CO2 Enrichment under Stressed and Non©stressed Conditions. ÃÃIN: Proceedings of the International Symposium on Ecological Aspects of Tree Ring Analysis (G.C. Jacoby and J.W. Hornbeck, eds.), NTIS, Springfield, Virginia, pp. 494©500.ÄÄ Loblolly pine and sweetgum seedlings were obtained from a Duke University phytotron study, where three groups were grown in different atmospheres of CO2 (i.e., 350, 500, 650 ppmv). Seedlings were grown over three growing seasons, and included a set of water©stressed and non©stressed individuals. X©ray densitometry was used to evaluate growth and density characteristics of the wood samples. Cross©sectional discs of these samples were radiographed and scanned with a microdensitometer to determine ring width, area, density and mass for each growth year. Results indicated significant differences in wood 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, almost 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. These 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 and need to determine growth responses at preindustrial era CO2 concentrations in order to more accurately identify the postulated 'fertilizer' effect on modern forests. loblolly pine/sweetgum/Liquidambar styraciflua/Pinus taeda ÃÃKEYWORDS: GREENHOUSE, GROWTH, TREE©RING ANALYSIS, TREES, WATER STRESS, WOOD PROPERTIESÄÄ Ã Ã210Ä Ä° `  à ÃDoyle, T.W., F.G. Taylor, M.L. Parker, C.F. Cooper, and D.C. West.Ä Ä 1985. Preliminary Ring©Width and Ring©Density Data for Deriving Wood Mass Chronologies of Coniferous Species from the Northwest U.S. and CanadaÃÃ, 025 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C., and Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee. white spruce/red pine/Douglas©fir/Western hemlock/Western red cedar/Engelmann spruce/lodgepole pine/yellow cedar/black spruce ÃÃKEYWORDS: TREE©RING ANALYSIS, TREESÄÄ Ã Ã211Ä Ä° `  à ÃDrake, B., W. Arp, P.S. Curtis, P.W. Leadley, J. Sager, and D. Whigham.Ä Ä 1986. Effects of Elevated CO2 on Chesapeake Bay Wetlands. I. Description of the Study SiteÃÃ, 034 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C. Spartina patens/Distichlis spicata/Scirpus olneyi ÃÃKEYWORDS: AQUATIC PLANTS, EXPOSURE METHODS, HALOPHYTES, LITTER QUALITY, OPEN©TOP CHAMBERS, SALT MARSH, WATER STATUSÄÄ Ã Ã212Ä Ä° `  à ÃDrake, B.G.Ä Ä 1992. A Field Study of the Effects of Elevated CO2 on Ecosystem Processes in a Chesapeake Bay Wetland. ÃÃAustralian Journal of Botany 40:579©595.ÄÄ Open top chambers are being used in a long©term project to determine the effects of elevated CO2 on ecosystem processes on a Chesapeake Bay wetland. Three communities are studied: mono©specific stands of the C3 sedge, ÃÃScirpus olneyiÄÄ, and the C4 grass, ÃÃSpartina patensÄÄ, and a mixed community of these two species and the C4 grass, ÃÃDistichlis spicataÄÄ. Treatment 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, ÃÃScirpus olneyiÄÄ: 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 community of the sedge and C4 grass species, ÃÃSpartina patensÄÄ and ÃÃDistichlis spicataÄÄ, biomass of the C3 component increased over 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, ÃÃScirpus olneyiÄÄ, including: sustained high photosynthetic capacity, decreased respiration, delayed senescence, and allocation of the additional carbon to roots and rhizomes. The complex interaction of these diverse responses suggests that the rising atmospheric CO2 may have a significant impact on ecosystem processes. Spartina patens/Scirpus olneyi/Distichlis spicata ÃÃKEYWORDS: ANATOMY, AQUATIC PLANTS, C3, C4, CANOPY PHOTOSYNTHESIS, CO2 COMPENSATION POINT, ECOSYSTEM LEVEL CO2 RESPONSES, EVAPOTRANSPIRATION, GRASSES, HALOPHYTES, INSECTS, LEAF AREA DEVELOPMENT, LIGHT, NITROGEN, OPEN©TOP CHAMBERS, PIGMENTS, PLANT©FUNGUS INTERACTIONS, RESPIRATION, SALT MARSH, SPECIES COMPETITION, STOMATAL DENSITY, WUEÄÄ Ã Ã213Ä Ä° `  à ÃDrake, B.G., W. Arp, J. Craig, P.S. Curtis, P.W. Leadley, and D. Whigham.Ä Ä 1987. Effects of Elevated CO2 on Chesapeake Bay Wetlands. II. Gas Exchange and Microenvironment in Open Top ChambersÃÃ, 038 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C. Scirpus olneyi/Spartina patens/Distichlis spicata ÃÃKEYWORDS: AQUATIC PLANTS, CANOPY PHOTOSYNTHESIS, CONDUCTANCE, EXPOSURE METHODS, HALOPHYTES, OPEN©TOP CHAMBERS, PHOTOSYNTHETIC ACCLIMATION, SALT MARSHÄÄ Ã Ã214Ä Ä° `  à ÃDrake, B.G., W.J. Arp, L. Balduman, R. Cousimano, J. Dacey, D. D'Abundo, K. Hogan, S. Long, W.T. Pockman, P. Utley, A.C. Villegas, and D. Whigham.Ä Ä 1990. Effects of Elevated Co2 on Chesapeake Bay Wetlands. V. Ecosystem and Whole Plant Responses. April©November 1989ÃÃ, 055 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C. Scirpus olneyi/Spartina patens ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, ECOSYSTEM LEVEL CO2 RESPONSES, EVAPOTRANSPIRATION, HALOPHYTES, LEAF PHOTOSYNTHESIS, METHANE, NITROGEN, OPEN©TOP CHAMBERS, QUANTUM REQUIREMENT, RESPIRATION, ROOTS, SALT MARSH, WATER STATUS, WUEÄÄ Ã Ã215Ä Ä° `  à ÃDrake, B.G., W.J. Arp, L. Balduman, P.S. Curtis, J. Johnson, D. Kabara, P.W. Leadley, W.T. Pockman, D. Seliskar, M.L. Sutton, D. Whigham, and L. Ziska.Ä Ä 1989. Effects of Elevated CO2 on Chesapeake Bay Wetlands. IV. Ecosystem and Whole Plant Responses. April©November 1988ÃÃ, 051 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C. Scirpus olneyi/Spartina patens/Distichlis spicata/Glycine max/soybean/Lycopersicon esculentum/tomato/Manihot esculentum/Amaranthus hypochondriacus/amaranth/Acacia mangium/Ficus obtusifolia/Paspallum conjugatum/Pharus latifolia/Psychotria limonensis/Tabebuia rosea ÃÃKEYWORDS: AQUATIC PLANTS, C3, C4, CANOPY PHOTOSYNTHESIS, CARBON BUDGET, COMMUNITY LEVEL CO2 RESPONSES, EVAPOTRANSPIRATION, GROWTH, HALOPHYTES, LEAF PHOTOSYNTHESIS, LITTER DECOMPOSITION, LITTER QUALITY, NITROGEN, OPEN©TOP CHAMBERS, PHOTOSYNTHETIC ACCLIMATION, RESPIRATION, ROOTS, SALT MARSH, SPECIES COMPETITIONÄÄ Ã Ã216Ä Ä° `  à ÃDrake, B.G., P.S. Curtis, W.J. Arp, P.W. Leadley, J. Johnson, and D. Whigham.Ä Ä 1988. Effects of Elevated CO2 on Chesapeake Bay Wetlands. III. Ecosystem and Whole Plant Responses in the First Year of Exposure, April©November 1987ÃÃ, 044 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C. Spartina patens/Distichlis spicata/Scirpus olneyi ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, EXPOSURE METHODS, HALOPHYTES, LEAF PHOTOSYNTHESIS, NET PRIMARY PRODUCTIVITY, NITROGEN, OPEN©TOP CHAMBERS, PHOTOSYNTHESIS MODEL, SENESCENCE, WATER STATUSÄÄ Ã Ã217Ä Ä° `  à ÃDrake, B.G., and P.W. Leadley.Ä Ä 1991. Canopy Photosynthesis of Crops and Native Plant Communities Exposed to Long©term Elevated CO2. ÃÃPlant, Cell and Environment 14:853©860.ÄÄ There have been seven studies of canopy photosynthesis of plants grown in elevated atmospheric CO2: three of seed crops, two of forage crops and two of native plant ecosystems. Growth in elevated CO2 increased canopy photosynthesis in all cases. The relative effect of CO2 was correlated with increasing temperature: the least stimulation occurred in tundra vegetation grown at an average temperature near 10À$ÀC and the greatest in rice grown at 43À$ÀC. In soybean, effects of CO2 were greater during leaf expansion and pod fill than at other stages of crop maturation. In the longest running experiment with elevated CO2 treatment to date, monospecific stands of a C3 sedge, ÃÃScirpus olneyiÄÄ (Grey), and a C4 grass, ÃÃSpartina patensÄÄ (Ait.) Muhl., have been exposed to twice normal ambient CO2 concentrations for four growing seasons, in open top chambers on a Chesapeake Bay salt marsh. Net ecosystem CO2 exchange per unit green biomass (NCEb) increased by an average of 48% throughout the growing season of 1988, the second year of treatment. Elevated CO2 increased net ecosystem carbon assimilation by 88% in the ÃÃScirpus olneyiÄÄ community and 40% in the ÃÃSpartina patensÄÄ community. Scirpus olneyi/Spartina patens ÃÃKEYWORDS: AQUATIC PLANTS, C3, C4, CANOPY PHOTOSYNTHESIS, COMMUNITY LEVEL CO2 RESPONSES, HALOPHYTES, OPEN©TOP CHAMBERS, PHOTOSYNTHETIC ACCLIMATION, REVIEW, TEMPERATUREÄÄ Ã Ã218Ä Ä° `  à ÃDrake, B.G., P.W. Leadley, W.J. Arp, D. Nassiry, and P.S. Curtis.Ä Ä 1989. An Open Top Chamber for Field Studies of Elevated Atmospheric CO2 Concentration on Saltmarsh Vegetation. ÃÃFunctional Ecology 3:363©371.ÄÄ Small open top chamber (0.8 m x 1.0 m) were developed to maintain elevated CO2 concentrations in three plant communities in a brackish marsh ecosystem. Mean annual CO2 concentrations were 340 +/© 22 uL/L in chambers which received no added CO2 and 686 +/© 30 uL/L in chambers with elevated CO2 concentrations. Light quality was not effected in the photosynthetically active wavelengths but the chamber reduced light quantity by 10%. Night©time air temperatures inside the chamber (ÃÃTiÄÄ) averaged 2À$ÀC above air temperature outside the chamber (ÃÃToÄÄ) due to heating from the air blowers. Air temperature profiles through the plant canopy and boundary layer showed that daytime temperature differences (ÃÃTi ©ToÄÄ) were greater than night©time differences and this day/night difference also depended on the plant community. Effects of the chamber on the micro©environment of the plant communities resulted in a significant growth enhancement in the plant community dominated by the C3 sedge ÃÃScirpus olneyiÄÄ Grey but not in the other two communities. Scirpus olneyi/Spartina patens/Distichlis spicata ÃÃKEYWORDS: AQUATIC PLANTS, C3, C4, COMMUNITY LEVEL CO2 RESPONSES, EXPOSURE METHODS, HALOPHYTES, OPEN©TOP CHAMBERS, SALT MARSHÄÄ Ã Ã219Ä Ä° `  à ÃDrake, B.G., H.H. Rogers, and L.H. Allen Jr.Ä Ä 1985. Methods of Exposing Plants to Elevated Carbon Dioxide. ÃÃIN: Direct Effects of Increasing Carbon Dioxide on Vegetation, DOE/ER©0238 (B.R. Strain and J.D. Cure, eds.), Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C., pp. 11©51.ÄÄ ÃÃKEYWORDS: EXPOSURE METHODS, REVIEWÄÄ Ã Ã220Ä Ä° `  à ÃDubois, D., M. Winzeler, and J. Nosberger.Ä Ä 1990. Fructan Accumulation and Sucrose:sucrose fructosyltransferase Activity in Stems of Spring Wheat Genotypes. ÃÃCrop Science 30:315©319.ÄÄ Stems of wheat (ÃÃTriticum aestivumÄÄ L.) accumulate water©soluble carbohydrates (WSC) during the first 3 wk after anthesis. These reserves can later contribute to grain filling. Two spring wheat genotypes ('Kolibri' and breeding line D) were tested in growth chambers to determine if they differ in the accumulation of WSC components and in the activation of sucrose:sucrose fructosyltransferase (SST) in stem tissue. Concentration of CO2 was supplied at 1000 or 300 uL CO2/L after anthesis to alter photosynthate production. The WSC accumulation in the penultimate internode during the first 18 d post anthesis (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 comparable level for both genotypes and both CO2 treatments. Fructan synthesis was initiated at 7 DPA. At 18 DPA, fructan was the 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 internode of plants grown at 1000 and 200 uL CO2/L. There was a positive relationship between sucrose concentration and in vivo SST activity, suggesting that sucrose induced SST activity; however, Kolibri exhibited a much lower SST activity at given 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. Triticum aestivum/wheat ÃÃKEYWORDS: CARBOHYDRATES, CONTROLLED ENVIRONMENT CHAMBERS, CULTIVAR RESPONSES, ENZYMESÄÄ Ã Ã221Ä Ä° `  à ÃDuchein, M.©C., A. Bonicel, and T. Betsche.Ä Ä 1993. Photosynthetic Net CO2 Uptake and Leaf Phosphate Concentrations in CO2 Enriched Clover (ÃÃTrifolium subterraneumÄÄ L.) at Three Levels of Phosphate Nutrition. ÃÃJournal of Experimental Botany 44:17©22.ÄÄ Net CO2©uptake of sets of clover plants (ÃÃTrifolium subterraneumÄÄ L.) was measured over 3 weeks in ambient air and in a highly CO2©enriched atmosphere (400 Pa CO2). Phosphate (P) in the nutrient solution was varied between 0.05 mol/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 parameter 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 with half©strength Hoagland's solution (0.5 mol/m3 P). Leaf pools of inorganic ortho P, soluble esterified P, and total P declined markedly in high CO2 when P©nutrition had been reduced. Considerable decline also occurred in high CO2 when P©nutrition 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 CO2 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. Trifolium subterraneum/clover ÃÃKEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, NUTRITION, PHOSPHORUSÄÄ Ã Ã222Ä Ä° `  à Ãdu Cloux, H., M. Andre, A. Gerbaud, and A. Daguenet.Ä Ä 1989. Wheat Response to CO2 Enrichment: Effect on Photosynthetic and Photorespiratory Characteristics. ÃÃPhotosynthetica 23:145©153.ÄÄ The effects of doubling atmospheric CO2 concentration on photosynthesis and photorespiration were studied on wheat cultivated for 37 or 72 d in growth chambers at a density of planting of 200 and 40 plants per m2. Net photosynthetic rate (ÃÃPnÄÄ) was measured continuously during the experiments and response curves to CO2 were made at intervals. Differences observed between the CO2 curves of the plants grown in normal and CO2 enriched atmosphere could be explained by the greater leaf area of the second group of plants. Photorespiration was tested by the Warburg effect or measured directly on isolated plants by the uptake of 18©O2. Oxygen uptake was reduced by 40% by the high CO2 treatment, but high CO2 plants were identical to the control group when returned to the same conditions. The enhancement of dry matter production was due to the kinetic response of ÃÃPnÄÄ to CO2, as there was no appreciable long©term adaptation of the kinetic characteristics of photosynthesis. wheat/Triticum aestivum ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS, OXYGEN, PHOTORESPIRATION, PHOTOSYNTHETIC ACCLIMATION, PLANT DENSITYÄÄ Ã Ã223Ä Ä° `  à Ãdu Cloux, H.C., M. Andre, A. Daguenet, and J. Massimino.Ä Ä 1987. Wheat Response to CO2 Enrichment: Growth and CO2 Exchanges at Two Plant Densities. ÃÃJournal of Experimental Botany 38:1421©1431.ÄÄ The vegetative growth of wheat (ÃÃTriticum aestivumÄÄ L., var. Capitole) was followed for almost 40 d after germination 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 the experiment the CO2 gas exchanges of each canopy were measured 24 h/d. These provided a continuous growth curve for each treatment, which were compared with dry weights. After a small stimulation at the start (first 13 d), no further effect of CO2 enrichment was observed on relative growth rate (RGR). However, RGR was stimulated throughout the experiment when plotted as a function of biomass. The final stimulation of dry weight at 660 mm3/dm3 CO2 was a factor of 1.45 at high density and 1.50 at low density; contrary to other studies, no diminution of this CO2 effect on dry weight was observed over time. Nevertheless, at low density, a transient additional enhancement of biomass (up to 1.70) was obtained at a leaf area index (LAI) below 1. This effect was attributed to a different build up of the gain of carbon in the case of an isolated plant or a closed canopy. In the former, the stimulation of leaf area and the net assimilation rate are both involved; in the 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. wheat/Triticum aestivum ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH ANALYSIS, LEAF AREA DEVELOPMENT, PLANT DENSITYÄÄ Ã Ã224Ä Ä° `  à ÃDugal, A., S. Yelle, and A. Gosselin.Ä Ä 1990. Influence of CO2 Enrichment and its Method of Distribution on the Evolution of Gas Exchanges in Greenhouse Tomatoes. ÃÃCanadian Journal of Plant Science 70:345©356.ÄÄ Net photosynthesis, stomatal conductance, internal CO2 concentration and transpiration were measured on the fifth well©developed and excised leaf of tomato seedlings (ÃÃLycopersicon esculentumÄÄ Mill. 'Vedettos') 48©83 d old. These measurements were taken in order to monitor the evolution of the gas exchanges of seedlings exposed to concentrations of 330 or 1000 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 substantially increased the net photosynthesis rate of the seedlings, particularly at the beginning of the experiment. The long©term effects of CO2 enrichment subsided after a few weeks of treatment. Intermittent CO2 enrichment was partially helpful in remedying the loss of effectiveness of the CO2 after a long period of enrichment. High CO2 concentrations reduced the opening of the stomata. Our work shows that maintaining a high internal CO2 content in the leaves would indirectly reduce the stomatal conductance of the seedlings. However, our results show that the long©term loss of photosynthetic efficiency in the enriched seedlings cannot be attributed solely to an increase in the resistance of the stomata, since the internal 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. tomato/Lycopersicon esculentum ÃÃKEYWORDS: CONDUCTANCE, GREENHOUSE, HORTICULTURAL CROPS, INTERMITTENT ENRICHMENT, LEAF PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION, WUEÄÄ Ã Ã225Ä Ä° `  à ÃEamus, D.Ä Ä 1990. Carbon Dioxide and Plant Physiological Processes. ÃÃIN: The Greenhouse Effect and Terrestrial Ecosystems of the UK (M.G.R. Cannell and M.D. Hooper, eds.), Institute of Terrestrial Ecology, Natural Environment Research Council, Edinburgh Research Station, Bush Estate, Penicuik.ÄÄ ÃÃKEYWORDS: CONDUCTANCE, ENVIRONMENTAL INTERACTIONS, GROWTH, PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION, PHYSIOLOGICAL CO2 RESPONSES, RESPIRATION, REVIEWÄÄ Ã Ã226Ä Ä° `  à ÃEamus, D.Ä Ä 1992. Atmospheric CO2 and Trees, from Cellular to Regional Responses. ÃÃIN: Encyclopedia of Earth System Science, Vol. 1, Academic Press, Inc., New York, pp. 157©169.ÄÄ ÃÃKEYWORDS: ALLOCATION, CLIMATE, COMMUNITY LEVEL CO2 RESPONSES, CONDUCTANCE, ENVIRONMENTAL INTERACTIONS, GROWTH, MODELING, PHOTOSYNTHESIS, RESPIRATION, REVIEW, TREES, WUEÄÄ Ã Ã227Ä Ä° `  à ÃEamus, D.Ä Ä 1992. The Interaction of Rising CO2 and Temperatures with Water Use Efficiency. ÃÃPlant, Cell and Environment 14:843©852.ÄÄ Recent data concerning the impact of elevated atmospheric CO2 upon water use efficiency (WUE) and the related measure, instantaneous transpiration efficiency (ITE), are reviewed. It is concluded from both short and long©term studies that, at the scale of the individual leaf or plant, an increase in WUE or ITE is generally observed in response to increased atmospheric CO2 levels. However, the magnitude of this increase may decline with time. The opinion that elevated CO2 may substantially decrease transpiration at the regional scale is discussed. The mechanisms by which elevated CO2 may cause a change in these measures are discussed in terms of stomatal conductance, assimilation and respiration responses to elevated CO2. Finally, recent experimental data and model outputs concerning the impact of the interaction of increased temperature with elevated CO2 on WUE, ITE and yield are reviewed. It is concluded that substantially more data is required before reliable predictions about the regional scale response of WUE and catchment hydrology can be made. ÃÃKEYWORDS: MODELING, REVIEW, STOMATA, TEMPERATURE, TRANSPIRATION, WUEÄÄ Ã Ã228Ä Ä° `  à ÃEamus, D., and G. Duff.Ä Ä 1992. Increased Atmospheric Carbon Dioxide Levels and Vegetation Responses in the Tropics. ÃÃIN: Conservation and Development Issues in North Australia (I. Moffatt and A. Webb, eds.), North Australia Research Unit, Australian National University, Casuarina (Darwin), Northern Territory, Australia, pp. 145©154.ÄÄ ÃÃKEYWORDS: CARBOHYDRATES, CLIMATE, COMMUNITY LEVEL CO2 RESPONSES, CONDUCTANCE, MODELING, RESPIRATION, REVIEWÄÄ Ã Ã229Ä Ä° `  à ÃEamus, D., and P.G. Jarvis.Ä Ä 1989. The Direct Effects of Increase in the Global Atmospheric CO2 Concentration on Natural and Commercial Temperate Trees and Forests. ÃÃIN: Advances in Ecological Research, Vol. 19 (M. Begon, A.H. Fitter, E.D. Ford, and A. Macfadyen, eds.), Academic Press Ltd., New York, pp. 1©55.ÄÄ ÃÃKEYWORDS: ALLOCATION, CONDUCTANCE, FOREST, GROWTH, NITROGEN FIXATION, NUTRITION, PHOTOSYNTHESIS, RESPIRATION, REVIEW, STRESS, TREES, WUEÄÄ Ã Ã230Ä Ä° `  à ÃEhret, D.L., and P.A. Jolliffe.Ä Ä 1985. Leaf Injury to Bean Plants Grown in Carbon Dioxide Enriched Atmospheres. ÃÃCanadian Journal of Botany 63:2015©2020.ÄÄ Bush bean (ÃÃPhaseolus vulgarisÄÄ L.) plants grown in atmospheres enriched with CO2 (1400 uL/L) showed marked reductions in photosynthetic capacity and accelerated chlorosis of primary leaves. Leaf injury was observed only in CO2 enriched plants, but the degree of injury was regulated by secondary factors, light and temperature. Conditions of relatively high light intensity (340©370 umol/m2/s photosynthetic photon flux density) or cool temperature (20À$ÀC) promoted leaf injury of CO2©enriched plants. Leaf starch accumulation was highest under conditions that caused injury. The enhanced chlorosis and corresponding decline in photosynthetic activity, however, were not related to changes in stomatal diffusive resistance or leaf water status. Contaminant gases, such as ethylene, were not detectable in the CO2©enrichment chambers. bean/Phaseolus vulgaris ÃÃKEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, LEAF INJURY, LEAF PHOTOSYNTHESIS, LIGHT, PHOTOSYNTHETIC FEEDBACK INHIBITION, TEMPERATUREÄÄ Ã Ã231Ä Ä° `  à ÃEhret, D.L., and P.A. Jolliffe.Ä Ä 1985. Photosynthetic Carbon Dioxide Exchange of Bean Plants Grown at Elevated Carbon Dioxide Concentrations. ÃÃCanadian Journal of Botany 63:2026©2030.ÄÄ Leaves of bean plants (ÃÃPhaseolus vulgarisÄÄ L. cv. Pure Gold Wax) grown in atmospheres enriched in CO2 (1400 uL/L) showed a decrease in CO2 exchange capacity when compared with unenriched plants (340 uL/L) measured at the same CO2 concentration. The decrease was not associated with changes in chlorophyll concentration or photorespiratory activity. The decrease was less evident in older leaves, in leaves maintained at low light intensity, and in those with reduced chlorophyll contents. Respiration rates in leaves of CO2©enriched plants increased only under conditions that caused a concurrent decrease in photosynthetic capacity. Enriched leaves had higher starch contents than unenriched leaves. The results were consistent with the idea that CO2 enrichment decreases photosynthetic capacity when photoassimilate supply exceeds sink demand. Phaseolus vulgaris/bean ÃÃKEYWORDS: CARBOHYDRATES, CONTROLLED ENVIRONMENT CHAMBERS, LEAF PHOTOSYNTHESIS, PHOTOSYNTHETIC FEEDBACK INHIBITION, RESPIRATIONÄÄ Ã Ã232Ä Ä° `  à ÃEl Kohen, A., and M. Mousseau.Ä Ä 1990. Effet d'un Doublement de la Teneur en CO2 Atmospherique sur le Bilan Carbone de Jeunes Chataigniers. ÃÃBulletin de la Societe Ecophysiologique 15:135©147.ÄÄ In French. chestnut/Castanea sativa ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CARBON BUDGET, OUTDOOR GROWTH CHAMBERS, RESPIRATION, TREESÄÄ Ã Ã233Ä Ä° `  à ÃEl Kohen, A., J.©Y. Pontailler, and M. Mousseau.Ä Ä 1991. Effect of Doubling of Atmospheric CO2 Concentration on Dark Respiration in Aerial Parts of Young Chestnut Trees (ÃÃCastanea sativaÄÄ Mill.). ÃÃComptes Rendus des Sciences (Paris) t. 312, Serie III:477©481.ÄÄ Two©year©old sweet chestnut seedlings were grown in constantly ventilated tunnels at ambient (350 vpm) or double (700 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 compared 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 control plant respiration and when decreased, it enhanced CO2 enriched plant respiration. The explanation of these findings remains 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. Castanea sativa/sweet chestnut ÃÃKEYWORDS: CARBON BUDGET, OUTDOOR GROWTH CHAMBERS, RESPIRATION, TREESÄÄ Ã Ã234Ä Ä° `  à ÃEl Kohen, A., H. Rouhier, and M. Mousseau.Ä Ä 1992. Changes in Dry Weight and Nitrogen Partitioning Induced by Elevated CO2 Depend on Soil Nutrient Availability in Sweet Chestnut (ÃÃCastanea sativaÄÄ Mill.). ÃÃAnnales des Sciences Forestieres 49:83©90.ÄÄ The effect of 2 levels of atmospheric carbon dioxide (ambient, i.e. 350 ppm, and double, i.e. 700 ppm) and 2 contrasting levels of mineral nutrition on dry weight, nitrogen accumulation and partitioning were examined in 2©year©old chestnut seedlings (ÃÃCastanea sativaÄÄ Mill.), grown in pots outdoors throughout the vegetative season. Fertilization had a pronounced effect on dry weight accumulation, tree height, leaf area, and plant nitrogen content. Carbon dioxide enrichment significantly 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 diameter but not height were increased. Carbon dioxide enrichment significantly reduced the nitrogen concentration in all organs, 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. Castanea sativa/sweet chestnut ÃÃKEYWORDS: ALLOCATION, GROWTH, LITTER QUALITY, NITROGEN, NUTRITION, OUTDOOR GROWTH CHAMBERS, ROOT:SHOOT RATIO, TREESÄÄ Ã Ã235Ä Ä° `  à ÃEl Kohen, A., L. Venet, and M. Mousseau.Ä Ä 1993. Growth and Photosynthesis of Two Deciduous Forest Species at Elevated Carbon Dioxide. ÃÃFunctional Ecology 7:480©486.ÄÄ Two©year©old sweet chestnut (ÃÃCastanea sativaÄÄ Mill) and beech (ÃÃFagus sylvaticaÄÄ 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 temperate 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 weeks in sweet chestnut and then an acclimation process took place. No effect of an increased CO2 could be found on sweet chestnut leaf area or leaf number, while a significant effect was found with beech, in which total leaf area per plant increased, owing to a greater number of growth flushes, each with larger leaves. The partitioning of the biomass increase due to elevated CO2 was very different in the two species. All additional dry matter was allocated to the roots in sweet chestnut, 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. sweet chestnut/Castanea sativa/Fagus sylvatica/beech ÃÃKEYWORDS: ALLOCATION, GROWTH, OUTDOOR GROWTH CHAMBERS, PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION, TREESÄÄ Ã Ã236Ä Ä° `  à ÃEng, R.Y.N., M.J. Tsujita, and B. Grodzinski.Ä Ä 1985. The Effects of Supplementary HPS Lighting and Carbon Dioxide Enrichment on the Vegetative Growth, Nutritional Status and Flowering Characteristics of ÃÃChrysanthemum morifoliumÄÄ Ramat. ÃÃJournal of Horticultural Science 60:389©395.ÄÄ Supplementary high pressure sodium (HPS) lighting (140 umol/m2/s) and CO2 enrichment (1375 uL/L) improved the vegetative growth of ÃÃChrysanthemum morifoliumÄÄ cv Dramatic by increases in stem length, stem diameter, root weight ratio, dry weight, relative growth and net assimilation rates. Three©week©old chrysanthemums grown under CO2 enrichment and HPS lighting had lower leaf weight and stem weight ratios as well as lower foliar nutrient content than those grown under ambient CO2 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 superior to either factor used alone. With 24 h HPS supplementary lighting CO2 enrichment was most effective in improving vegetative growth and flower quality when applied during the daytime. Night CO2 enrichment was not commercially beneficial at the light levels employed in this study. Chrysanthemum morifolium/chrysanthemum ÃÃKEYWORDS: ALLOCATION, COMMERCIAL USE OF CO2, FLOWER PRODUCTION, GREENHOUSE, LIGHTÄÄ Ã Ã237Ä Ä° `  à ÃEnoch, H.Z.Ä Ä 1990. Crop Responses to Aerial Carbon Dioxide. ÃÃActa Horticulturae 268:17©32.ÄÄ 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, that a doubling will occur during the next century and that eventually values of over 2500 ppm will be reached. Until then greenhouse crops should be CO2 enriched. The potential of intermittent CO2 enrichment (pulse CO2 enrichment) for yields enhancement and pollution avoidance will be described. The main changes in crops due to elevated CO2 seem to be secondary effects of enhanced photosynthesis but some morphogenetic changes, for instance increased branching, are interpreted as partial suppression of apical dominance and appear to show that CO2 concentration has additional hormone©like effects. Though over 1000 papers on CO2 enrichment have been published there is only an incomplete understanding of whether other organs than leaves are sensitive to CO2 concentration and whether elevated CO2 has a trigger effect or a threshold effect on morphogenesis 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. ÃÃKEYWORDS: ALLOCATION, CO2 ENRICHMENT DURATION, CO2 PULSES, COMMERCIAL USE OF CO2, GREENHOUSE, REVIEWÄÄ Ã Ã238Ä Ä° `  à ÃEnoch, H.Z., and N. Zieslin.Ä Ä 1988. Growth and Development of Plants in Response to Carbon Dioxide Concentrations. ÃÃApplied Agricultural Research 3:248©256.ÄÄ Quality of protected crops can be improved by controlling the aerial carbon dioxide (CO2) in the greenhouse. The influence of atmosphere CO2 concentration on partitioning of dry matter, leaf growth and development, stem growth, root formation, branching and tillering, growth of the whole plant and on flowering is described in this review. At elevated CO2 concentrations apical dominance in C3 and C4 plants is weakened resulting in higher root©to©shoot ratios and increased side shoot development (branching, tillering, etc.). Most effects of elevated CO2 concentration appear to be secondary effects of photosynthesis enhancement leading to higher leaf weight per unit area, greater stem weight per unit length, and an increase in absolute growth rate©©but not always an increase in relative growth rate. The influence of elevated CO2 concentration 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. ÃÃKEYWORDS: ALLOCATION, COMMERCIAL USE OF CO2, FLOWER PRODUCTION, REVIEW, ROOT:SHOOT RATIOÄÄ Ã Ã239Ä Ä° `  à ÃEvans, L.S., and G.R. Hendrey.Ä Ä 1992. Responses of Cotton Foliage to Short©term Fluctuations in CO2 Partial Pressures. ÃÃCritical Reviews in Plant Sciences 11:203©212.ÄÄ cotton/Gossypium hirsutum ÃÃKEYWORDS: 14C, CO2 PULSES, CONTROLLED ENVIRONMENT CHAMBERS, LEAF PHOTOSYNTHESISÄÄ Ã Ã240Ä Ä° `  à ÃFajer, E.D., M.D. Bowers, and F.A. Bazzaz.Ä Ä 1989. The Effects of Enriched Carbon Dioxide Atmospheres on Plant©Insect Herbivore Interactions. ÃÃScience 243:1198©1200.ÄÄ Little is known about the effects of enriched CO2 atmospheres, which may exist in the next century, on natural plant©insect herbivore interactions. Larvae of a specialist insect herbivore, ÃÃJunonia coeniaÄÄ (Lepidoptera: Nymphalidae), were reared on one of its host plants, ÃÃPlantago lanceolataÄÄ (Plantaginaceae), grown in either current low (350 parts per million) or high (700 ppm) CO2©environments. Those larvae raised on high©CO2 foliage grew more slowly and experienced greater mortality, especially in early instars, than those raised on low©CO2 foliage. Poor larval performance on high©CO2 foliage was probably due to the reduced foliar water and nitrogen concentrations of those plants and not to changes in the concentration of the defensive compounds, iridoid glycosides. Adult pupal weight and female fecundity were not affected by the CO2 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. Plantago lanceolata ÃÃKEYWORDS: ALLELOCHEMICALS, CONTROLLED ENVIRONMENT CHAMBERS, HERBIVORY, INSECTS, JUNONIA COENIA, NITROGENÄÄ Ã Ã241Ä Ä° `  à ÃFajer, E.D., M.D. Bowers, and F.A. Bazzaz.Ä Ä 1990. Performance and Allocation Patterns of the Perennial Herb, ÃÃPlantago lanceolataÄÄ, in Response to Simulated Herbivory and Elevated CO2 Environments. ÃÃOecologia 87:37©42.ÄÄ We tested the prediction that plants grown in elevated CO2 environments are better able to compensate for biomass lost to herbivory than plants grown in ambient CO2 environments. The herbaceous perennial ÃÃPlantago lanceolataÄÄ (Plantaginaceae) was grown in either near ambient (380 ppm) or enriched (700 ppm) CO2 atmospheres, and then after 4 weeks, plants experienced either 1) no defoliation; 2) every fourth leaf removed by cutting; or 3) every other leaf removed by cutting. Plants were harvested at week 13 (9 weeks after simulated herbivory treatments). Vegetative and reproductive weights were compared, and seeds were counted, weighed, and germinated to assess viability. Plants grown in enriched CO2 environments had significantly greater shoot weights, leaf areas, and root weights, yet had significantly lower reproductive weights (i.e. stalks + spikes + seeds) and produced fewer seeds, than plants grown in ambient CO2 environments. Relative biomass allocation patterns further illustrated differences in plant responses to enriched CO2 atmospheres: enriched CO2©grown plants only allocated 10% of their carbon resources to reproduction whereas ambient CO2©grown plants allocated over 20%. Effects of simulated 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 plants compensated for lost above©ground tissues, and maintained comparable levels of reproductive output and seed viability, at the expense of root growth. Plantago lanceolata ÃÃKEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, HERBIVORY, REPRODUCTION, SURVIVORSHIPÄÄ Ã Ã242Ä Ä° `  à ÃFajer, E.D., M.D. Bowers, and F.A. Bazzaz.Ä Ä 1991. The Effects of Enriched CO2 Atmospheres on the Buckeye Butterfly, ÃÃJunonia coeniaÄÄ. ÃÃEcology 72:751©754.ÄÄ Plantago lanceolata ÃÃKEYWORDS: ALLELOCHEMICALS, CONTROLLED ENVIRONMENT CHAMBERS, HERBIVORY, INSECTS, JUNONIA COENIA, NITROGENÄÄ Ã Ã243Ä Ä° `  à ÃFajer, E.D., M.D. Bowers, and F.A. Bazzaz.Ä Ä 1992. The Effect of Nutrients and Enriched CO2 Environments on Production of Carbon©based Allelochemicals in ÃÃPlantago:ÄÄ A Test of the Carbon/Nutrient Balance Hypothesis. ÃÃThe American Naturalist 140:707©723.ÄÄ In a test of the carbon/nutrient (C/N) balance hypothesis, we grew the perennial herb ÃÃPlantago lanceolataÄÄ in different CO2 and nutrient environments and then (1) measured the total allocation to shoots, roots, and reproductive parts and (2) quantified aucobin, catalpol, and verbascoside contents of replicate plants of six genotypes. Plants grown under low©nutrient conditions do have higher concentrations of carbon©based allelochemicals than plants grown under high nutrient conditions. However, in contrast to the C/N balance hypothesis, plants grown in elevated (700 uL/L) CO2 conditions had similar, or lower, concentrations of carbon©based allelochemicals than plants grown in ambient (350 uL/L) CO2 conditions. We suggest that augmented substrate concentrations (i.e., excess carbohydrates) are a necessary but insufficient trigger for increased 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, reproduction, 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. Plantago lanceolata ÃÃKEYWORDS: ALLELOCHEMICALS, ALLOCATION, CARBOHYDRATES, CARBON, CARBON:NITROGEN RATIO, CONTROLLED ENVIRONMENT CHAMBERS, HERBIVORY, NUTRITIONÄÄ Ã Ã244Ä Ä° `  à ÃFarrar, J.F., and M.L. Williams.Ä Ä 1991. The Effects of Increased Atmospheric Carbon Dioxide and Temperature on Carbon Partitioning, Source©sink Relations and Respiration. ÃÃPlant, Cell and Environment 14:819©830.ÄÄ Herbaceous C3 plants grown in elevated CO2 show increases in carbon assimilation and carbohydrate accumulation (particularly starch) within source leaves. Although changes in the partitioning of biomass between root and shoot occur, the proportion of this extra assimilate made available for sink growth is not known. Root:shoot ratios tend to increase for CO2 enriched herbaceous plants and decrease for CO2©enriched trees. Root:shoot ratios for cereals tend to remain constant. In contrast, elevated temperatures decrease carbohydrate accumulation within source and sink regions of a plant and decrease root:shoot ratios. Allometric analysis of at least two species showing changes in root:shoot ratios due to elevated CO2 show no alteration in the whole©plant partitioning of biomass. Little information is available for interactions between temperature and CO2. Cold©adapted plants show little response to elevated levels of CO2, with some species showing a decline in biomass accumulation. In general though, increasing temperature will increase sucrose synthesis, transport and utilization for CO2©enriched plants and decrease carbohydrate accumulation within the leaf. Literature reports are discussed in relation to the hypothesis that sucrose is a major factor in the control of plant carbon partitioning. A model is presented in support. ÃÃKEYWORDS: ALLOCATION, CARBOHYDRATES, MODELING, RESPIRATION, REVIEW, SOURCE©SINK BALANCE, TEMPERATUREÄÄ Ã Ã245Ä Ä° `  à ÃFerguson, J.J., W.T. Avigne, L.H. Allen, and K.E. Koch.Ä Ä 1986. Growth of CO2©enriched Sour Orange Seedlings Treated with Gibberellins/Cytokinins. ÃÃProceedings of the Florida State Horticultural Society 99:37©39.ÄÄ Enriched CO2 atmospheres and specific plant growth regulators are known to stimulate plant growth, but their combined effects on citrus seedlings have not been studied. Sour orange (ÃÃCitrus aurantiumÄÄ L.) seedlings were treated with plant growth regulators (6©benzyladenine [250 ul/l]; 6 benzyladenine and gibberellic acid [250 ul/l]; gibberellin 3 [450 ul/l] and gibberellin 4+7 [250 ul/l]) and grown at either ambient or elevated CO2 levels (330 or 660 ul/l). Seedlings treated with GA4+7 and grown at elevated CO2 levels were taller and had greater leaf weight than plants given all other treatments. Leaf number increased under elevated CO2 levels when BA or GA4+7 were applied. Stem weight was 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. sour orange/Citrus aurantium ÃÃKEYWORDS: GROWTH, GROWTH REGULATORS, SPAR UNITS, TREESÄÄ Ã Ã246Ä Ä° `  à ÃFetcher, N., C.H. Jaeger, B.R. Strain, and N. Sionit.Ä Ä 1988. Long©term Elevation of Atmospheric CO2 Concentration and the Carbon Exchange Rates of Saplings of ÃÃPinus taedaÄÄ L. and ÃÃLiquidambar styracifluaÄÄ L. ÃÃTree Physiology 4:255©262.ÄÄ The relationship between carbon exchange rate (CER) and internal CO2 concentration was measured in leaves of saplings of ÃÃLiquidambar styracifluaÄÄ L. (sweetgum) and ÃÃPinus taedaÄÄ 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 response to concentration of CO2 during measurement, but was higher in both species when grown at 500 than at 350 uL/L CO2. The net effect of a long©term increase in CO2 concentration from 350 to 500 uL/L was an increase in CER of loblolly pine, but 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. sweetgum/Liquidambar styraciflua/loblolly pine/Pinus taeda ÃÃKEYWORDS: CONDUCTANCE, GREENHOUSE, LEAF PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION, RIBULOSE BISPHOSPHATE CARBOXYLASEÄÄ Ã Ã247Ä Ä° `  à ÃFrench, C.J.Ä Ä 1989. Propagation and Subsequent Growth of Rhododendron Cuttings: Varied Response to CO2 Enrichment and Supplementary Lighting. ÃÃJournal of the American Society of Horticultural Science 114:251©259.ÄÄ CO2 mist (1100 uL CO2/L) during fall propagation inhibited rooting of ÃÃRhododendronÄÄ 'Anna Rose Whitney' (ÃÃR. griersonianumÄÄ x 'Countess of Derby') and had no effect on ÃÃR.ÄÄ 'Vulcan' ('Mars' x ÃÃR. griersonianumÄÄ), ÃÃR.ÄÄ 'Unique' (ÃÃR. campylocarpumÄÄ hybrid), ÃÃR.ÄÄ 'Anah Krushke' (ÃÃR. ponticumÄÄ seedling), or ÃÃR.ÄÄ 'Pink Bountiful' (ÃÃR. williamsianumÄÄ x 'Linswegeanum'). Supplementary lighting from high©pressure sodium lamps (HPS) for 16 hr/day (0400 to 2000 hr) had no effect on rooting of any cultivar. There was an interaction between CO2 mist and HPS exposure on rooting in ÃÃR.ÄÄ '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 'Floriade' and 'Vulcan'. CO2 enrichment of stock plants prior to propagation did not affect rooting of ÃÃR.ÄÄ 'Sonata', whereas CO2 mist during propagation was inhibitory. In 'Anna Rose Whitney', there was an interaction between CO2 enrichment before and 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 ÃÃR.ÄÄ 'Matador' (ÃÃR. griersonianumÄÄ x ÃÃstrigillosumÄÄ), ÃÃR.ÄÄ 'Martha Isaacson' (ÃÃR. occidentaleÄÄ x Ostbo seedling No. 70), or ÃÃR.ÄÄ 'Elizabeth' (ÃÃR. forestiiÄÄ var ÃÃrepensÄÄ x ÃÃgriersonianumÄÄ). Supplementary HPS had no effect on rooting. A low irradiance night break treatment from incandescent lamps (2000 to 0400 hr) had no effect on rooting of 'Vulcan'. There was an 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 ÃÃRhododendronÄÄ. Rhododendron spp. ÃÃKEYWORDS: GREENHOUSE, HORTICULTURAL CROPS, LIGHT, ROOTINGÄÄ Ã Ã248Ä Ä° `  à ÃFrench, C.J.Ä Ä 1990. Rooting of Rhododendron 'Anna Rose Whitney' Cuttings as Related to Stem Carbohydrate Concentration. ÃÃHortScience 25:409©411.ÄÄ Rooting of ÃÃRhododendronÄÄ 'Anna Rose Whitney' (ÃÃR. GriersonianumÄÄ x 'Countess of Derby') was delayed in cuttings from stock plants grown in full sun, compared to cuttings from plants grown in 80% shade. In the outer stem (extracambium tissues), concentrations of glucose, sucrose, soluble carbohydrate, and total nonstructural carbohydrates were higher in cuttings from shaded stock plants. In the inner stem (intracambium tissues), where rooting originates, fructose, starch and nonstructural 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 higher than in cuttings rooted under atmospheric CO2 (340 uL/L). Under CO2 mist, total nonstructural carbohydrate concentration was higher in the inner stem throughout the rooting period. For both high stock plant irradiance and CO2 enrichment during propagation, there was an inverse relationship between fructose concentration in the inner stem and rooting. A possible mechanism for inhibition by fructose is proposed. Rhododendron spp. ÃÃKEYWORDS: CARBOHYDRATES, GREENHOUSE, HORTICULTURAL CROPS, ROOTINGÄÄ Ã Ã249Ä Ä° `  à ÃFrench, C.J., and J. Alsbury.Ä Ä 1989. Supplementary Lighting and CO2 Mist Influence Rooting of ÃÃCamellia japonicaÄÄ. ÃÃHortScience 24:452©454.ÄÄ Supplementary irradiance from high©pressure sodium lamps (HPS) at 75 umol/s/m2 stimulated rooting of difficult©to©root ÃÃCamellia japonicaÄÄ 'Lady Clare' when applied from sunrise to sunset in a heavily shaded greenhouse (20% light transmission). There was no effect of HPS on the easy©to©root cultivar Blood of China. Irradiance from HPS either at 45 umol/s/m2 for 16 hr/day or at 75 umol/s/m2 CO2 mist inhibited rooting of both cultivars when applied in fall propagation. In spring, CO2 mist during the day simulated root number of 'Lady Clare' when combined with a night©break treatment from incandescent lamps (INC). Carbon dioxide mist had little effect under a natural photoperiod, and CO2 mist was ineffective when INC were used. The effects of supplementary CO2, irradiance, and increased photoperiod on rooting varied with season and cultivar. Camellia japonica ÃÃKEYWORDS: CULTIVAR RESPONSES, ENVIRONMENTAL INTERACTIONS, GREENHOUSE, HORTICULTURAL CROPS, LIGHT, PHOTOPERIOD, ROOTINGÄÄ Ã Ã250Ä Ä° `  à ÃFried, J.S., K.A. Surano, P.F. Daley, J.H. Shinn, and P. Anderson.Ä Ä 1986. Biomass Production and Nutrient Responses of Ponderosa Pine to Long©term Elevated CO2 Concentrations. ÃÃIN: Proceedings of the Ninth North American Forest Biology Workshop; 1986 June 15©18; Stillwater, Oklahoma (C.G. Tauer and T.C. Hennessey, eds.), Society of American Foresters, Department of Forestry, Oklahoma State University, Stillwater, Oklahoma, pp. 11©18.ÄÄ Ponderosa pine saplings and seedlings were continuously exposed to elevated CO2 concentrations of ambient, and ambient +75, +150, and +300 ppm in open©top chambers for 27 months. Saplings responded by reducing above ground biomass production. Although potassium concentration in both saplings and seedlings diminished as CO2 concentration increased, no nutrients appeared to become limiting to growth as a result of elevated CO2. Concentrations of Ca, Mg and Zn in the saplings at different concentrations of CO2 mirrored root densities, indicating that an increase in root density at +150 ppm may account for greater nutrient concentrations observed in that tree. Pinus ponderosa/ponderosa pine ÃÃKEYWORDS: CALCIUM, IRON, MAGNESIUM, MANGANESE, NITROGEN, NUTRITION, OPEN©TOP CHAMBERS, PHOSPHORUS, POTASSIUM, ROOTS, SULFUR, TREES, X©RAY DENSITOMETRY, ZINCÄÄ Ã Ã251Ä Ä° `  à ÃFung, I.Y., C.J. Tucker, and K.C. Prentice.Ä Ä 1987. Application of Advanced Very High Resolution Radiometer Vegetation Index to Study Atmosphere©Biosphere Exchange of CO2. ÃÃJournal of Geophysical Research 92:2999©3015.ÄÄ Normalized difference vegetation indices derived from radiances measured by the Advanced Very High Resolution Radiometer aboard the NOAA 7 polar©orbiting satellite were used to prescribe the phasing of terrestrial photosynthesis. The satellite data were combined with field data on soil respiration and a global map of net primary productivity to obtain the seasonal 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 spatial 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 been 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. ÃÃKEYWORDS: ADVANCED VERY HIGH RESOLUTION RADIOMETER, MODELING, NET PRIMARY PRODUCTIVITY, NORMALIZED DIFFERENCE VEGETATION INDEX, PHOTOSYNTHESIS, GLOBAL, RADIATION, REFLECTANCE, REMOTE SENSINGÄÄ Ã Ã252Ä Ä° `  à ÃFurbank, R.T., and D.A. Walker.Ä Ä 1986. Chlorophyll ÃÃAÄÄ Fluorescence as a Quantitative Probe of Photosynthesis: Effects of CO2 Concentration during Gas Transients on Chlorophyll Fluorescence in Spinach Leaves. ÃÃNew Phytologist 104:207©213.ÄÄ The relationship between changes in chlorophyll ÃÃaÄÄ 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, results in a hyperbola. When these data are replotted on an inverse©reciprocal plot, an apparent Km(CO2) for the fluorescence transient can be obtained which closely approximates the Km(CO2) for carbon assimilation under similar conditions. Transitions 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. spinach/Spinacia oleracea ÃÃKEYWORDS: FLUORESCENCE, LEAF PHOTOSYNTHESISÄÄ Ã Ã253Ä Ä° `  à ÃGale, J.Ä Ä 1986. Carbon Dioxide Enhancement of Tree Growth at High Elevation. ÃÃScience 231:859©860.ÄÄ Technical comment. ÃÃKEYWORDS: ALTITUDE, PHOTOSYNTHESIS, TREE©RING ANALYSIS, TREESÄÄ Ã Ã254Ä Ä° `  à ÃGarbutt, K., W.E. Williams, and F.A. Bazzaz.Ä Ä 1990. Analysis of the Differential Response of Five Annuals to Elevated CO2 during Growth. ÃÃEcology 71:1185©1194.ÄÄ 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 species of old field annual plants ©© ÃÃAbutilon theophrastiÄÄ (C3), ÃÃAmaranthus retroflexusÄÄ (C4), ÃÃAmbrosia artemisiifoliaÄÄ (C3), ÃÃChenopodium albumÄÄ (C3) and ÃÃSetaria faberiiÄÄ (C4) ©© were grown for their entire life cycle as individuals at CO2 concentration of 350 uL/L, 500 uL/L, and 700 uL/L. Emergence time, growth rate, shoot water status, photosynthesis, conductance, 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. ÃÃAmaranthusÄÄ relative growth rate (RGR) was always higher at 700 uL/L CO2 than at 350 uL/L. In both ÃÃAbutilonÄÄ and ÃÃAmbrosiaÄÄ, 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 potential significantly increased (became less negative) with increasing CO2 in ÃÃAmaranthusÄÄ and ÃÃSetariaÄÄ. Similar but statistically nonsignificant trends were found in ÃÃChenopodiumÄÄ and ÃÃAbutilonÄÄ. Overall rate of photosynthesis increased with CO2 but 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 species, intercellular CO2 increased with external CO2. ÃÃAmaranthusÄÄ flowered significantly earlier at 700 uL/L than at 350 uL/L, and ÃÃSetariaÄÄ flowered significantly later at 700 uL/L than at either of the other CO2 levels. Both ÃÃAbutilonÄÄ and ÃÃAmbrosiaÄÄ showed a trend towards earlier flowering but this was not statistically significant. Of the morphological characters measured at the final harvest only specific leaf area (SLA) showed a consistent response to CO2, decreasing with increasing CO2. Significant CO2 x species interactions were also found for leaf area, leaf biomass, biomass of reproductive parts, 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 proportion 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 increasing CO2 in ÃÃAmaranthusÄÄ (C4) and in ÃÃChenopodiumÄÄ and ÃÃAmbrosiaÄÄ (both C3) but there was no change in ÃÃSetariaÄÄ (C4) and ÃÃAbutilonÄÄ (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. Abutilon theophrasti/Amaranthus retroflexus/Ambrosia artemisiifolia/Chenopodium album/Setaria faberii ÃÃKEYWORDS: C3, C4, COMPETITION, GROWTH ANALYSIS, LEAF PHOTOSYNTHESIS, LIGHT, NITROGEN, OLD FIELD COMMUNITIES, REPRODUCTION, SUNLIT CONTROLLED ENVIRONMENT CHAMBERSÄÄ Ã Ã255Ä Ä° `  à ÃGardestrom, P.Ä Ä 1987. Adenylate Ratios in the Cytosol, Chloroplasts and Mitochondria of Barley Leaf Protoplasts during Photosynthesis at Different Carbon Dioxide Concentrations. ÃÃFEBS Letters 212:114©118.ÄÄ Barley (ÃÃHordeum vulgareÄÄ) protoplasts were incubated in darkness and in the light at saturating and limiting CO2 concentrations. 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. barley/Hordeum vulgare ÃÃKEYWORDS: ADENYLATES, LEAF PHOTOSYNTHESIS, METABOLITESÄÄ Ã Ã256Ä Ä° `  à ÃGastal, F., and B. Saugier.Ä Ä 1989. Relationships Between Nitrogen Uptake and Carbon Assimilation in Whole Plants of Tall Fescue. ÃÃPlant, Cell and Environment 12:407©418.ÄÄ tall fescue ÃÃKEYWORDS: GRASSES, NITROGEN, NUTRITION, PHOTOSYNTHESISÄÄ Ã Ã257Ä Ä° `  à ÃGates, D.M.Ä Ä 1985. Global Biospheric Response to Increasing Atmospheric Carbon Dioxide Concentration. ÃÃIN: Direct Effects of Increasing Carbon Dioxide on Vegetation, DOE/ER©0238 (B.R. Strain and J.D. Cure, eds.), Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C., pp. 171©184.ÄÄ ÃÃKEYWORDS: BIOTIC GROWTH FACTOR, CARBON BUDGET, ECOSYSTEM LEVEL CO2 RESPONSES, NET PRIMARY PRODUCTIVITY, REVIEW, TREE©RING ANALYSISÄÄ Ã Ã258Ä Ä° `  à ÃGaudillere, J.©P., and M. Mousseau.Ä Ä 1989. Short Term Effect of CO2 Enrichment on Leaf Development and Gas Exchange of Young Poplars (ÃÃPopulus euramericanaÄÄ cv I 214). ÃÃActa Oecologica/Oecologia Plantarum 10:95©105.ÄÄ 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 area and specific weight and contained more stomata, epidermal cells and chlorophyll per unit area. Leaf developmental characteristics (Relative Leaf Expansion, Leaf Plastochron Index, Leaf Expansion Duration) were modified by the treatment. Leaves 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. On single attached leaves, an increased CO2 level during growth promoted a photosynthetic inhibition, shown by a lower ÃÃgÄÄ 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). poplars/Populus euroamericana ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH ANALYSIS, LEAF AREA DEVELOPMENT, LEAF PHOTOSYNTHESIS, RESPIRATION, STOMATAL DENSITY, STOMATAL INDEX, TREES, WUEÄÄ Ã Ã259Ä Ä° `  à ÃGeethakumari, V.L., and K. Shivashankar.Ä Ä 1991. Studies on Organic Amendment and CO2 Enrichment in ÃÃRagiÄÄ/Soybean Intercropping Systems. ÃÃIndian Journal of Agronomy 36:202©206.ÄÄ Organic amendment comprising of ÃÃragiÄÄ husk and FYM mixed in 1:1 ratio by weight promoted organic carbon content and available P status of the soil. A level of 4 t/ha of organic amendment promoted the uptake of N significantly by both ÃÃragiÄÄ and soybean. Availability of P and K were also favourably influenced. Uptake of nutrients by soybean was promoted by CO2 enrichment. Available P status was higher in intercropped ÃÃragiÄÄ and soybean as compared to pure crops but nutrient uptake was higher by pure crops. soybean/Glycine max/ragi/Eleusine coracana ÃÃKEYWORDS: ENZYMES, INTERCROPPING, NUTRITION, OPEN©TOP CHAMBERS, ORGANIC AMENDMENTSÄÄ Ã Ã260Ä Ä° `  à ÃGifford, R.M.Ä Ä 1988. Direct Effects of Higher Carbon Dioxide Concentrations on Vegetation. ÃÃIN: Greenhouse: Planning for Climate Change (G.I. Pearman, ed.), E.J. Brill, New York, pp. 506©519.ÄÄ 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 concentration 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 effect' 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 (greater 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 reduced evapotranspiration from vegetated regions, all else being equal. There are both physiological and boundary©layer meteorological 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. However, the size of the CO2©fertilizing effect on yield for a currently adapted variety is similar to that of the associated temperature©dependent reduction of yield. So the net effect on cereal yield in a region will depend on the success at introducing 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. ÃÃKEYWORDS: CLIMATE CHANGE, CONDUCTANCE, CROPS, PHOTOSYNTHESIS, REVIEW, TRANSPIRATION, YIELDÄÄ Ã Ã261Ä Ä° `  à ÃGifford, R.M.Ä Ä 1988. Interactions with Vegetation. ÃÃIN: Greenhouse: Planning for Climate Change (G.I. Pearman, ed.), E.J. Brill, New York, pp. 83©89.ÄÄ 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 significant part in determining climate by affecting the partitioning of incoming solar energy over land. This partitioning may change as a result of CO2 effects on vegetation. In one way or another vegetation contributes to and/or is affected by the other major changing components of the global atmosphere ©© O3, CH4, CFCs, N2O. Current best estimates of the scale of net deforestation of the world indicate that it is releasing about a quarter as much CO2 to atmosphere as fossil fuel burning is. However, the increasing CO2 concentration in the atmosphere is probably increasing the growth of vegetation. It is estimated that the net annual storage of extra carbon in the form of more standing biomass and soil organic matter than hitherto, may approximately equal the carbon released by net deforestation. Quantitative appraisal of the global carbon cycle reveals that to attempt to permanently remove the fossil fuel©derived CO2 from the atmosphere by massive re©afforestation or 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. ÃÃKEYWORDS: CARBON CYCLE, DEFORESTATION, REFORESTATIONÄÄ Ã Ã262Ä Ä° `  à ÃGifford, R.M.Ä Ä 1989. The Effects of the Build©up of Carbon Dioxide in the Atmosphere on Crop Productivity. ÃÃIN: Proceedings of the 5th Australian Agronomy Conference; 1989 Sept. 24©29; University of Western Australia, Perth, Western Australia, Australian Society of Agronomy.ÄÄ ÃÃKEYWORDS: AGRICULTURE, CLIMATE CHANGE, CROPS, PHOTOSYNTHESIS, REVIEW, TEMPERATUREÄÄ Ã Ã263Ä Ä° `  à ÃGifford, R.M.Ä Ä 1989. Exploiting the Fertilizer Effect of Increasing Atmospheric Carbon Dioxide. ÃÃIN: Climate and Food Security, International Symposium on Climate Variability and Food Security in Developing Countries; 1987 Feb. 5©9; New Delhi, India, International Rice Research Institute, Manila, and American Association for the Advancement of Science, Washington, D.C., pp. 477©487.ÄÄ High CO2 concentrations fertilize plants by stimulating photosynthesis, suppressing photorespiration, and reducing transpiration per unit leaf area. CO2 enhancement of growth occurs at both optimal and nonoptimal levels of other environmental variables (light, water, temperature, nitrogen nutrients, salinity). Severely phosphate©deficient plants may not respond 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 agricultural environments (e.g. adverse climatic change, soil loss and deterioration, acid precipitation). Because yield increase 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 the 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 atmospheres. Cropping boundaries may move onto more saline and drought©prone soils, although this would probably be bad policy 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. ÃÃKEYWORDS: AGRICULTURE, CLIMATE CHANGE, CULTIVAR RESPONSES, ENVIRONMENTAL INTERACTIONS, REVIEW, YIELDÄÄ Ã Ã264Ä Ä° `  à ÃGifford, R.M.Ä Ä 1990. Photosynthesis and the Greenhouse Effect. ÃÃIN: Chemistry and the Environment, Proceedings of Regional Symposium, 1989, Brisbane (B.N. Noller and M.S. Chadha, eds.), Commonwealth Science Council, London, pp. 59©71.ÄÄ The greenhouse effect, whereby atmospheric CO2 and water vapour prevent the Earth's surface from being totally frozen is likely to be amplified by the anthropogenic emissions of fossil fuel CO2. The global carbon cycle links photosynthesis to the greenhouse effect on all timescales up to millions of years. Major characteristics of the Earth's atmospheric composition, notably the low CO2 and the high oxygen concentrations were created by the evolution of plant photosynthesis. The low CO2 concentration in the atmosphere probably came about by the substantial acceleration of rock weathering that plants, especially angiosperms, cause. Calcium released by weathering moves to the oceans where it paces the formation of calcium carbonate rocks which are a massive carbon pool that dwarfs all others combined. On a timescale of millions of years the carbon from calcium carbonate is cycled back to the atmosphere via volcanoes. On shorter timescales of sociopolitical concern photosynthesis is involved with the current global change in atmospheric CO2 increase. From what we know about plant photosynthetic and growth responses to increasing CO2 concentration interacting with other limiting environmental factors, it seems very likely that the biosphere is absorbing, into standing biomass and soil organic matter, some of the CO2 emitted from fossil fuel burning and net deforestation thereby contributing to the 'missing carbon' that does not appear as an increase in atmospheric CO2 concentration. However, the scope for accelerating this CO2 sequestering process by planting 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. ÃÃKEYWORDS: CARBON CYCLE, CARBON SEQUESTERING, CLIMATE CHANGE, DEFORESTATION, PHOTOSYNTHESIS, REFORESTATION, REVIEWÄÄ Ã Ã265Ä Ä° `  à ÃGifford, R.M.Ä Ä 1992. Interaction of Carbon Dioxide with Growth©Limiting Environmental Factors in Vegetation Productivity: Implications for the Global Carbon Cycle. ÃÃIN:, Vol. I (R.L. Desjardins, R.M. Gifford, T. Nilson, and E.A.N. Greenwood, eds.), Advances in Bioclimatology, Springer Verlag, Berlin, pp. 24©58.ÄÄ ÃÃKEYWORDS: CARBON CYCLE, ENVIRONMENTAL INTERACTIONS, NET PRIMARY PRODUCTIVITY, NUTRITION, PHOTOSYNTHETIC ACCLIMATION, RESPIRATION, REVIEW, SCALING, SOURCE©SINK BALANCEÄÄ Ã Ã266Ä Ä° `  à ÃGifford, R.M., H. Lambers, and J.I.L. Morison.Ä Ä 1985. Respiration of Crop Species under CO2 Enrichment. ÃÃPhysiologia Plantarum 63:351©356.ÄÄ Respiratory characteristics of wheat (ÃÃTriticum aestivumÄÄ L. cvs Gabo and WW15), mung bean (ÃÃVigna radiataÄÄ L. Wilczek cv. Celera) and sunflower (ÃÃHelianthus annuusÄÄ L. cv. Sunfola) were studied in plants grown under a normal CO2 concentration and in air containing an additional 340 or 250 uL/L CO2. Such an increase in global atmospheric CO2 concentration has been forecast for about the middle of the next century. The aim was to measure the effect of high CO2 on respiration and its components. Polarographic and, with wheat, CO2 exchange techniques were used. The capacity of the alternative pathway of respiration in roots was determined polarographically in the presence of 0.1 mM KCN. The actual rate of alternative pathway respiration was assessed by reduction in oxygen consumption caused by 10 mM salicylhydroxamic acid. Each species responded differently. In wheat, growth in high atmospheric CO2 was associated with up to 45% reduction in respiration by both roots and whole plants. Use of respiratory inhibitors in polarographic measurements on wheat roots implicated reduction in the degree of engagement of the alternative pathway as a major contributor to this reduced respiratory activity of high©CO2 plants. No change was found in the total sugar content per unit wheat root dry weight as a result of high CO2. In none of the species was there an increase in the absolute, or relative, contribution by the alternative pathway to total respiration of the root system. Thus the improved photosynthetic assimilate supply of plants grown in high CO2 did not lead to increased diversion of carbon through the non©phosphorylating alternative pathway of respiration in the root. On the contrary, in wheat grown in high CO2, the reduced loss of carbon through that route must have contributed to their larger dry weight. wheat/Triticum aestivum/mung bean/Vigna radiata/sunflower/Helianthus annuus ÃÃKEYWORDS: ALTERNATIVE RESPIRATORY PATHWAY, CANOPY PHOTOSYNTHESIS, CARBOHYDRATES, CROPS, GREENHOUSE, RESPIRATIONÄÄ Ã Ã267Ä Ä° `  à ÃGifford, R.M., and J.I.L. Morison.Ä Ä 1985. Photosynthesis, Water Use and Growth of a C4 Grass Stand at High CO2 Concentration. ÃÃPhotosynthesis Research 7:77©90.ÄÄ Leaf photosynthesis rate of the C4 species ÃÃPaspalum plicatulumÄÄ Michx was virtually CO2©saturated at normal atmospheric CO2 concentration but transpiration decreased as CO2 was increased above normal concentrations, thereby increasing transpiration efficiency. To test whether this leaf response led growth to be CO2©sensitive when water supply was restricted, plants were grown in sealed pots of soil as miniature swards. Water was supplied either daily to maintain a constant water table, or at three growth restricting levels on a 5©day drying cycle. Plants were either in a cabinet with normal air (340 umol (CO2)/mol (air)) or with 250 umol/mol enrichment. Harvesting was by several cycles of defoliation. With abundant water supply high CO2 concentration did not cause increased growth, but it did not cause an increase in growth over a wide range of growth©limiting water supplies either. Only when water supply was less than 30©50% of the amount used by the stand with a water©table was there evidence that dry weight growth was enhanced by high CO2. In addition, with successive regrowth, the enhancing effect under a regime of minimal water allocations, became attenuated. Examination of leaf gas exchange, growth and water use data showed that in the long term stomatal conductance responses were of little significance in matching plant water use to low water allocation; regulation of leaf area was the mechanism through which consumption matched 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. Paspalum plicatulum ÃÃKEYWORDS: C4, CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS, GRASSES, GROWTH, LEAF PHOTOSYNTHESIS, WATER STRESS, WUEÄÄ Ã Ã268Ä Ä° `  à ÃGislerod, H.R., and P.V. Nelson.Ä Ä 1989. The Interaction of Relative Air Humidity and Carbon Dioxide Enrichment in the Growth of ÃÃChrysanthemum morifoliumÄÄ Ramat. ÃÃScientia Horticulturae 38:305©313.ÄÄ Plants of ÃÃChrysanthemumÄÄ x ÃÃmorifoliumÄÄ cultivar 'Fiesta' were grown hydroponically for 6 weeks in growth chambers at relative humidity (RH) levels of 50 and 95% and CO2 levels of 340 and 940 uL/L in a Latin square combination. High RH as well as high CO2 resulted in increased relative growth rate (RGR), increased dry weight of leaves, stems and roots, and increased leaf area on main and lateral stems during the first 2 weeks of growth. During this period, high CO2 levels interacted to stimulate the RH effects. During the third to sixth weeks of growth, the interaction of RH and CO2 was either lost or, as in the case of RGR and root dry weight, reversed in such a way that a negative effect of high CO2 at high RG was found. At 6 weeks there were positive main effects of RH and CO2, but no interaction on plant height, number of leaves on lateral shoots, number of lateral shoots, and length of lateral shoots. The shoot to root dry weight ratio increased at high RH. Water consumption of plants decreased sharply at high RH and moderately at the high CO2 level. Stomatal aperture was larger at high RH, but smaller at the high CO2 level. It is concluded that increased plant growth resulting from increased RH might be caused by an increase in stomatal aperture which in turn facilitates CO2 absorption and utilization. chrysanthemum/Chrysanthemum morifolium ÃÃKEYWORDS: ALLOCATION, CONDUCTANCE, FLOWER PRODUCTION, GROWTH ANALYSIS, HORTICULTURAL CROPS, HUMIDITY, HYDROPONIC CULTURE, ROOT:SHOOT RATIO, STOMATAL DENSITY, TRANSPIRATIONÄÄ Ã Ã269Ä Ä° `  à ÃGoudriaan, J.Ä Ä 1986. Simulation of Ecosystem Response to Rising CO2, with Special Attention to Interfacing with the Atmosphere. ÃÃIN: Climate Vegetation Interactions, a NASA Workshop; 1986 January 27©29; Greenbelt, Maryland (C. Rosenzweig and R. Dickinson, eds.), NASA Goddard Space Flight Center, Greenbelt, Maryland, pp. 68©75.ÄÄ ÃÃKEYWORDS: ECOSYSTEM LEVEL CO2 RESPONSES, MODELING, NET PRIMARY PRODUCTIVITY, SIMULATIONÄÄ Ã Ã270Ä Ä° `  à ÃGoudriaan, J.Ä Ä 1990. Primary Productivity and CO2. ÃÃIN: The Greenhouse Effect and Primary Productivity in European Agro©ecosystems; 5©10 April 1990; Wageningen, The Netherlands (J. Goudriaan, H. van Keulen, and H.H. van Laar, eds.), Pudoc, Wageningen, pp. 23©25.ÄÄ ÃÃKEYWORDS: AGRICULTURE, BIOTIC GROWTH FACTOR, C3, C4, CO2 COMPENSATION POINT, CROP MODEL, PHOSPHOENOLPYRUVATE CARBOXYLASE, PHOTOSYNTHETIC ACCLIMATION, REVIEW, RIBULOSE BISPHOSPHATE CARBOXYLASEÄÄ Ã Ã271Ä Ä° `  à ÃGoudriaan, J., and R.J. Bijlsma.Ä Ä 1987. Effect of CO2 Enrichment on Growth of Faba Beans at Two Levels of Water Supply. ÃÃNetherlands Journal of Agricultural Science 35:189©191.ÄÄ The occurrence of growth enhancement by increased CO2 levels is well established under optimal conditions. A growth analysis study of faba beans, grown under two CO2 levels (350 and 700 cm3/m3) in combination with two levels of water supply, 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.) Vicia faba/broad bean ÃÃKEYWORDS: GREENHOUSE, GROWTH ANALYSIS, SENESCENCE, WATER STRESS, WUEÄÄ Ã Ã272Ä Ä° `  à ÃGoudriaan, J., H. van Keulen, and H.H. van Laar Ä Ä. 1990. The Greenhouse Effect and Primary Productivity in European Agro©Ecosystems, Proceedings of the International Workshop on Primary Productivity of European Agriculture and the Greenhouse Effect, Wageningen, The Netherlands, 5©10 April 1990. ÃÃPudoc, Wageningen.ÄÄ ÃÃKEYWORDS: AGRICULTUREÄÄ Ã Ã273Ä Ä° `  à ÃGoyal, A., and N.E. Tolbert.Ä Ä 1989. Variations in the Alternative Oxidase in ÃÃChlamydomonasÄÄ Grown in Air or High CO2. ÃÃPlant Physiology 89:958©962.ÄÄ ÃÃChlamydomonasÄÄ in the resting phase of growth has an equal capacity of about 15 micromole O2 uptake per hour per milligram of chlorophyll for both the cytochrome ÃÃcÄÄ, CN©sensitive respiration, and for the alternative, salicylhydroxamic acid©sensitive respiration. Alternative respiration capacity was measured as salicylhydroxamic acid inhibited O2 uptake in the presence of CN, and cytochrome ÃÃcÄÄ respiration capacity as CN inhibition of O2 uptake in the presence of salicylhydroxamic acid. Measured total respiration was considerably less than the combined capacities for respiration. During the log phase of growth on high (2©5%) CO2, the alternative respiraiton capacity decreased about 90% but returned as the culture entered the lag phase. When the alternative oxidase capacity was low, addition of salicylic acid or cyanide induced its reappearance. When cells were grown on low (air©level) CO2, which induced a CO2 concentrating mechanism, the alternative oxidase capacity did not decrease during the growth phase. Attempts to measure ÃÃin vivoÄÄ distribution of respiration between the two pathways with either CN or salicylhydroxamic acid alone were inconclusive. Chlamydomonas reinhardtii ÃÃKEYWORDS: ALGAE, ALTERNATIVE RESPIRATORY PATHWAY, CELL CULTUREÄÄ Ã Ã274Ä Ä° `  à ÃGraham, R.L., M.G. Turner, and V.H. Dale.Ä Ä 1990. How Increasing CO2 and Climate Change Affect Forests. ÃÃBioScience 40:575©587.ÄÄ ÃÃKEYWORDS: BIOME LEVEL CO2 RESPONSES, BIOSPHERE LEVEL CO2 RESPONSES, CLIMATE CHANGE, ECOSYSTEM LEVEL CO2 RESPONSES, FOREST, MODELING, REVIEW, SPECIES RANGEÄÄ Ã Ã275Ä Ä° `  à ÃGrant, W.J.R., H.M. Fan, W.J.S. Downton, and B.R. Loveys.Ä Ä 1992. Effects of CO2 Enrichment on the Physiology and Propagation of Two Australian Ornamental Plants, ÃÃChamelaucium uncinatumÄÄ (Schauer) x ÃÃChamelaucium floriferumÄÄ (MS) and ÃÃCorrea schlechtendaliiÄÄ (Behr). ÃÃScientia Horticulturae 52:337©342.ÄÄ Root formation on both ÃÃChamelauciumÄÄ and ÃÃCorreaÄÄ cuttings maintained at high humidity in an enclosed fog tunnel was significantly enhanced when ambient CO2 was increased from 350 to 800 ubar. CO2 enrichment resulted in decreased transpiration 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. Increased starch content with CO2 enrichment was able to account for 70©90% of the dry weight increase in ÃÃCorreaÄÄ, but only for 10©30% of the dry weight increase in ÃÃChamelauciumÄÄ. It is suggested that the stimulation of rooting associated with CO2 enrichment probably derives from the improved water relations of the cuttings rather than from increased carbohydrate levels. Chamelaucium uncinatum/Chamelaucium floriferum/Correa schlechtendalii ÃÃKEYWORDS: CARBOHYDRATES, COMMERCIAL USE OF CO2, HORTICULTURAL CROPS, ROOTING, SUNLIT CONTROLLED ENVIRONMENT CHAMBERS, TRANSPIRATION, WATER STATUSÄÄ Ã Ã276Ä Ä° `  à ÃGraumlich, L.J.Ä Ä 1991. Subalpine Tree Growth, Climate, and Increasing CO2: An Assessment of Recent Growth Trends. ÃÃEcology 72:1©11.ÄÄ LaMarche et al. (Science 225: 1019©1021, 1984) hypothesized that recent trends of increasing ring widths in subalpine conifers may be due to the fertilizing effects of increased atmospheric CO2. Five tree©ring series from foxtail pine (ÃÃPinus balfourianaÄÄ), lodgepole pine (ÃÃP. murrayanaÄÄ), and western juniper (ÃÃJuniperus occidentalisÄÄ) collected in the Sierra Nevada, California, were analyzed to determine if the temporal and spatial patterns of recent growth were consistent with 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 variation. For the remaining two sites, trends in the residuals from the growth/climate models indicate systematic underestimation 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 among subalpine conifers in the Sierra Nevada. While the results presented here offer no support for the hypothesized CO2 fertilization effect, they do provide insights into the response of subalpine conifers to climatic variation. Response surfaces 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 precipitation and warm summers for all three species, substantial species©to©species variation occurs in the response to these two variables. Juniperus occidentalis/western juniper/Pinus balfouriana/foxtail pine/Pinus murrayana/lodgepole pine ÃÃKEYWORDS: ALTITUDE, CLIMATE, DENDROCHRONOLOGY, TREE©RING ANALYSIS, TREESÄÄ Ã Ã277Ä Ä° `  à ÃGraybill, D.A.Ä Ä 1985. Western U.S. Tree©Ring Index Chronology Data for Detection of Arboreal Response to Increasing Carbon DioxideÃÃ, 026 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. 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 ÃÃKEYWORDS: ALTITUDE, TREE©RING ANALYSIS, TREESÄÄ Ã Ã278Ä Ä° `  à ÃGraybill, D.A.Ä Ä 1987. A Network of High Elevation Conifers in the Western U.S. for Detection of Tree©Ring Growth Response to Increasing Atmospheric Carbon Dioxide. ÃÃIN: Proceedings of the International Symposium on Ecological Aspects of Tree©Ring Analysis. U.S. Dept. of Energy Conference Report; DOE/CONF©8608144 (G.C. Jacoby and J.W. Hornbeck, eds.), NTIS, Springfield, Virginia, pp. 463©474.ÄÄ 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 appear 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, and 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 parameters 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 increased photosynthetic capacity, increased root growth that provides greater nutrient availability and increased water use efficiency 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. Pinus aristata/Pinus longaeva ÃÃKEYWORDS: ALTITUDE, TREE©RING ANALYSIS, TREESÄÄ Ã Ã279Ä Ä° `  à ÃGrodzinski, B.Ä Ä 1992. Plant Nutrition and Growth Regulation by CO2 Enrichment. ÃÃBioScience 42:517©525.ÄÄ ÃÃKEYWORDS: ETHYLENE, GROWTH REGULATORS, LEAF PHOTOSYNTHESIS, PARTITIONING, RESPIRATION, REVIEW, RIBULOSE BISPHOSPHATE CARBOXYLASE, SOURCE©SINK BALANCE, STOMATAÄÄ Ã Ã280Ä Ä° `  à ÃGrulke, N.E., G.H. Riechers, W.C. Oechel, U. Hjelm, and C. Jaeger.Ä Ä 1990. Carbon Balance in Tussock Tundra under Ambient and Elevated Atmospheric CO2. ÃÃOecologia 83:485©494.ÄÄ Whole ecosystem CO2 flux under ambient (340 uL/L) and elevated (680 uL/L) CO2 was measured in situ in ÃÃEriophorumÄÄ tussock tundra on the North Slope of Alaska. Elevated CO2 resulted in greater carbon acquisition than control treatments and there was a net loss of CO2 under ambient conditions at this upland tundra site. These measurements indicate a current loss of carbon from upland tundra, possibly the result of recent climatic changes. Elevated CO2 for the duration of one growing 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 ecosystem 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 temperature, and air temperature were also predictive of seasonal ecosystem flux, but only at elevated CO2 levels. At any combination of physical conditions, flux of the elevated CO2 treatment was greater than that at ambient. In short©term manipulations of CO2, tundra exposed to elevated CO2 had threefold greater carbon gain, and had one half the ecosystem level, light compensation point when compared to ambient CO2 treatments. Elevated CO2©acclimated tundra had twofold greater carbon gain compared to ambient treatments, but there was no difference in ecosystem level, light compensation point between elevated and ambient CO2 treatments. The predicted future increases in cloudiness could substantially decrease the effect of elevated 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. Eriophorum vaginatum ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CARBON BUDGET, ECOSYSTEM LEVEL CO2 RESPONSES, PHOTOSYNTHETIC ACCLIMATION, RESPIRATION, TRACKING CHAMBERS, TUNDRAÄÄ Ã Ã281Ä Ä° `  à ÃGulyaev, B.I.Ä Ä 1986. Influence of CO2 Concentration on Photosynthesis, Growth and Productivity of Plants. ÃÃPhysiology and Biochemistry of Cultured Plants (Fiziologi i aibiokhimi i akultumykh Rasteni) 18:574©591.ÄÄ 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 depends 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 always 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 while 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. ÃÃKEYWORDS: CO2 ENRICHMENT STUDIES, REVIEWÄÄ Ã Ã282Ä Ä° `  à ÃGuy, M., G. Granoth, and J. Gale.Ä Ä 1990. Cultivation of ÃÃLemna gibbaÄÄ under Desert Conditions. II: The Effect of Raised Winter Temperature, CO2 Enrichment and Shading on Productivity. ÃÃBiomass 23:1©11.ÄÄ The aim of this work was to increase the productivity of ÃÃLemna gibbaÄÄ 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 attenuated photosynthetically active light by about 30%. Winter©season yields in the covered ponds, maintained at ambient CO2 concentration, were 39% higher than in the uncovered ponds. This could be ascribed to raised temperatures. Enrichment of the atmosphere with CO2 further increased yields by as much as 28%. The different treatments did not affect protein content expressed as a percentage of dry weight. Laboratory experiments indicated that the shorter the photoperiod the larger is the growth response of ÃÃLemna gibbaÄÄ to CO2 enrichment. Shading of the ponds during the June©August summer season reduced pond temperatures at midday by about 5©6À$ÀC and resulted in a 30©80% increase in growth. It was concluded that under desert conditions similar to those prevailing in this trial, high yields of ÃÃLemna gibbaÄÄ can be achieved throughout a growing 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 economics Lemna gibba/duckweed ÃÃKEYWORDS: ENVIRONMENTAL INTERACTIONS, GROWTH, GROWTH ANALYSIS, LIGHT, OUTDOOR GROWTH CHAMBERS, TEMPERATUREÄÄ Ã Ã283Ä Ä° `  à ÃGuy, R.D., and D.M. Reid.Ä Ä 1986. Photosynthesis and the Influence of CO2©Enrichment on Delta©13 C Values in a C3 Halophyte. ÃÃPlant, Cell and Environment 9:65©72.ÄÄ Shifts in [delta]©13C of the graminaceous C3 halophyte ÃÃPuccinellia nuttallianaÄÄ (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, phosphoenolpyruvate 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 concentrations 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. Puccinellia nuttalliana ÃÃKEYWORDS: C3, CI:CA, CONDUCTANCE, GRASSES, HALOPHYTES, ISOTOPE DISCRIMINATION, PHOSPHOENOLPYRUVATE CARBOXYLASE, RIBULOSE BISPHOSPHATE CARBOXYLASE, SALT STRESS, WUEÄÄ Ã Ã284Ä Ä° `  à ÃHanan, J.J.Ä Ä 1986. CO2 Enrichment for Greenhouse Rose Production. ÃÃIN: Physiology, Yield, and Economics, Vol. II (H.Z. Enoch and B.A. Kimball, eds.), Carbon Dioxide Enrichment of Greenhouse Crops, CRC Press, Inc., Boca Raton, Florida, pp. 142©149.ÄÄ The literature indicates that CO2 enrichment is a successful and important adjunct to commercial plant production, the 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, with 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 photosynthetically 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 new investigative approaches. Second, we need to emphasize the importance of plant water potential on rates if CO2 enrichment is to achieve maximum, efficient utilization. Any student of practical plant physiology learns that the major portion of radiation impinging upon a well©watered plant is converted to latent heat. The importance of this major energy redistribution 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 observation, 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. rose ÃÃKEYWORDS: COMMERCIAL USE OF CO2, ENVIRONMENTAL INTERACTIONS, FLOWER PRODUCTION, GREENHOUSE, HORTICULTURAL CROPS, REVIEW, WATER STATUSÄÄ Ã Ã285Ä Ä° `  à ÃHand, D.W.Ä Ä 1986. CO2 Sources and Problems in Burning Hydrocarbon Fuels for CO2 Enrichment. ÃÃIN: Status and CO2 Sources, Vol. I (H.Z. Enoch and B.A. Kimball, eds.), Carbon Dioxide Enrichment of Greenhouse Crops, CRC Press, Inc., Boca Raton, Florida, pp. 99©121.ÄÄ CO2 enrichment of the greenhouse atmosphere is an invaluable technique for improving the performance of high©value salad and flower crops during the difficult winter period when poor light limits growth and development. According to government statistics there are approximately 500 ha of heated glasshouses and film©plastic covered structures (greenhouses) in England and Wales equipped specifically for CO2 enrichment. Additional areas of glasshouses receive incidental enrichment when growers either use direct©fired burners for warm©air heating or grow their crops in raised beds of decomposing straw. CO2 for enrichment purposes can be either supplied in liquid form or produced directly by burning hydrocarbon fuels with a low©sulfur content in the atmosphere. Bulk storage of liquid CO2 is difficult to justify economically on small areas of glasshouses (i.e., less than 4000 m2) but handling liquid CO2 in cylinders is laborious, time©consuming and expensive. Natural gas, LPG propane, and low©sulfur grades of kerosene (paraffin) are therefore favored by many growers because the CO2 is produced comparatively cheaply and the heat of combustion can provide a significant proportion of the daytime heat requirement 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 potentially damaging for crop production. The risk to crops of injury from gaseous air pollutants has also increased as growers have endeavored to reduce heating costs by making their greenhouses more airtight. Gaseous air pollutants, two groups account for most of the injuries to crops growing in greenhouses enriched with CO2 produced from hydrocarbon fuels. These are the 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 the burner flame of a CO2 producer by the heat©promoted combination of atmospheric nitrogen and oxygen. The rate at which nitrogen oxides are generated depends essentially on flame temperature, i.e., the hotter the flame the greater the emission of nitrogen oxides. Modern CO2 producers have a high flame temperature to ensure efficient fuel combustion and the formation of nitrogen oxides is an inevitable consequence of burner design. When threefold CO2 enrichment is practiced the concentration of nitrogen oxides in the greenhouse atmosphere can be as high as 0.5 uL/L. Such a level may cause injury to crops by reducing photosynthesis, inhibiting leaf expansion, depressing growth, and decreasing yield. Ethylene emissions from CO2 producers are the result of complex reactions involved in the pyrolysis and oxidation of hydrocarbon fuels. Burner design and operating variables such as the air©fuel ratio are crucial in determining the amount of ethylene released into the greenhouse atmosphere. In a well sealed greenhouse equipped for three©fold CO2 enrichment the ethylene concentration can easily rise to a level at which the pollutant has discernible effects on crops, (i.e., between 0.01 and 0.1 uL/L). Ethylene differs from the nitrogen oxides in that it is a naturally occurring plant growth regulator and can affect many growth, developmental, and aging processes. Escape of unburnt propylene gas (a major constituent of LPG propane) from loose©fitting connections to fuel©supply lines and faulty switching of gas©solenoid valves can cause injuries to crops similar to those induced by ethylene. Propylene concentrations of between 5 and 100 uL/L are commonly found in greenhouse atmospheres polluted 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. ÃÃKEYWORDS: AIR POLLUTION, CO2 SOURCES, COMMERCIAL USE OF CO2, EXPOSURE METHODS, GREENHOUSE, NITROGEN OXIDES, REVIEWÄÄ Ã Ã286Ä Ä° `  à ÃHand, D.W.Ä Ä 1989. The 'Greenhouse Effect': Is It Best Studied in Greenhouses? ÃÃProfessional Horticulture 3:76©82.ÄÄ ÃÃKEYWORDS: COMMERCIAL USE OF CO2, GREENHOUSE, HORTICULTURAL CROPS, REVIEWÄÄ Ã Ã287Ä Ä° `  à ÃHand, D.W.Ä Ä 1990. CO2 Enrichment in Greenhouses: Problems of CO2 Acclimation and Gaseous Air Pollutants. ÃÃActa Horticulturae 268:81©97.ÄÄ CO2 enrichment of the greenhouse atmosphere greatly improves the output, quality and value of vegetables, cut©flowers and ornamental plants. Raising the greenhouse CO2 concentration enhances photosynthesis and growth by increasing the rate of CO2 fixation concomitantly with a suppression of photo©respiration. Prolonged exposure of plants to elevated CO2 concentrations can, however, greatly accelerate the decline in the photosynthetic capacity of individual leaves with age. Commercially, CO2 for enrichment is normally obtained in liquid form or produced directly in the greenhouse atmosphere by burning hydrocarbon fuels such as natural gas, LPG propane, and premium kerosene (paraffin) which all contain low and acceptable levels of sulphur. Plentiful supplies of natural gas in both Britain and The Netherlands have also encouraged growers in these countries to practise CO2 enrichment by ducting flue©gases into their greenhouses from centralized, gas©fired boiler installations. Generating CO2 from hydrocarbon fuels can give rise to several gaseous air pollutants that are potentially damaging for crop production. The pollutants that cause most of the trouble in CO2©enriched greenhouses are nitrogen oxides such as nitric oxide and nitrogen dioxide, and unburnt hydrocarbons such as ethylene and propylene. Additionally, improvements to the insulation of heated greenhouses restrict air exchange and increase the hazard of certain plasticisers such as the alkyl esters of phthalic acid which are used to give flexibility to PVC. The risk of incurring losses in yield due 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 improve 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. ÃÃKEYWORDS: AIR POLLUTION, CO2 SOURCES, COMMERCIAL USE OF CO2, GREENHOUSE, NITROGEN OXIDES, PHOTOSYNTHETIC ACCLIMATIONÄÄ Ã Ã288Ä Ä° `  à ÃHand, D.W., J.W. Wilson, and B. Acock.Ä Ä 1993. Effects of Light and CO2 on Net Photosynthetic Rates of Stands of Aubergine and ÃÃAmaranthusÄÄ. ÃÃAnnals of Botany 71:209©216.ÄÄ Net photosynthetic rates per unit ground area for plant stands of ÃÃSolanum melongenaÄÄ L. var. ÃÃesculentumÄÄ (aubergine) and ÃÃAmaranthus caudatusÄÄ L. var. ÃÃedulisÄÄ (grain amaranth) were measured over 10 min intervals in an airtight, glass, controlled©environment cabinet for a range of light flux densities provided by the diurnal variation in daylight. Light response curves for photosynthesis of stands, grown at ambient CO2 concentration, were defined at 400, 800 and 1200 vpm CO2. Light compensation points for these stands were around 20©30 J/m2/s and decreased slightly at higher CO2 concentrations. For aubergine, a C3 species, the short©term effects of CO2 enrichment were to increase the initial slope as well as the asymptote of the light response curve, reducing light saturation at moderate to high light flux densities; but for amaranthus, a C4 species, saturation was less apparent and CO2 enrichment scarcely increased photosynthesis except at light flux densities 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 flux density of about 100 J/m2/s (the optimum rose a little with CO2 enrichment) and decreased slightly with further increase in light. Maximum utilization efficiencies at 500 vpom CO2 were 8©9 ug CO2/J. Enrichment to 1200 vpm did not affect the peak utilization efficiency of the C4 amaranthus, but increased that of aubergine to 12.2 ug CO2/J (equivalent to some 14% when using the heat of combustion of plant dry matter to convert to the dimensionless form). This is among the highest recorded 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. Solanum melongena/aubergine/eggplant/Amaranthus caudatus/grain amaranth ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS, LIGHT, LIGHT UTILIZATION EFFICIENCYÄÄ Ã Ã289Ä Ä° `  à ÃHari, P., and H. Arovaara.Ä Ä 1988. Detecting CO2 Induced Enhancement in the Radial Increment of Trees. Evidence from Northern Timber Line. ÃÃScandinavian Journal of Forest Research 3:67©74.ÄÄ Annual Ring data from northern Finland was analysed in order to reveal possible trends in ring width development due to changes in environmental factors. The data was analysed using a four component multiplicative model. The components are: tree age, climatic conditions, tree position and changes in environmental conditions. Since the effect of tree age and position in the stand could be easily eliminated the main problem was thus to eliminate the effect of climatic conditions on ring width. This was based on the dependence of the daily radial increment and daily maximum temperature. The component associated with changing environmental factors, especially to CO2 enrichment, was determined using the model. The basal area development of the trees was calculated from measured and estimated ring widths. Depending on the value of the autocorrelation 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. Pinus sylvestris/Scots pine ÃÃKEYWORDS: MODELING, TREE©RING ANALYSIS, TREESÄÄ Ã Ã290Ä Ä° `  à ÃHarley, P.C., and T.D. Sharkey.Ä Ä 1991. An Improved Model of C3 Photosynthesis at High CO2: Reversed O2 Sensitivity Explained by Lack of Glycerate Reentry into the Chloroplast. ÃÃPhotosynthesis Research 27:169©178.ÄÄ Current models of C3 photosynthesis incorporate a phosphate limitation to carboxylation which arises when the capacity for starch and sucrose synthesis fails to match the capacity for the production of triose phosphates in the Calvin cycle. As a result, the release of inorganic phosphate in the chloroplast stroma fails to keep pace with its rate of sequestration into triose phosphate, and phosphate becomes limiting to photosynthesis. Such a model predicts that when phosphate is limiting, assimilation becomes insensitive to both CO2 and O2, and is thus incapable of explaining the experimental observation 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 reversed sensitivity to CO2 and O2 by invoking the net release of phosphate in the photorespiratory oxidation cycle. In order for this to occur, some fraction of the glycollate carbon which leaves the stroma and which is recycled to the chloroplast by the photorespiratory pathway as glycerate must remain in the cytosol, perhaps in the form of amino acids. In that case, 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. soybean/Glycine max/cotton/Gossypium hirsutum ÃÃKEYWORDS: LEAF PHOTOSYNTHESIS, MODELING, OXYGEN, PHOTOSYNTHESIS MODEL, PHOTOSYNTHETIC FEEDBACK INHIBITION, RESPIRATION, SIMULATIONÄÄ Ã Ã291Ä Ä° `  à ÃHarley, P.C., R.B. Thomas, J.F. Reynolds, and B.R. Strain.Ä Ä 1992. Modelling Photosynthesis of Cotton Grown in Elevated CO2. ÃÃPlant, Cell and Environment 15:271©282.ÄÄ Cotton plants were grown in CO2©controlled growth chambers in atmospheres of either 35 or 65 Pa CO2. A widely accepted model of C3 leaf photosynthesis was parameterized for leaves from both CO2 treatments using non©linear least squares regression 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 Rubisco activity (Vcmax), estimated from A versus Ci response curves measured at 29À$ÀC, was about 10% lower in leaves from plants grown in high CO2. The relationship between key model parameters and total leaf N was linear, the only difference between 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 approximately 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. cotton/Gossypium hirsutum ÃÃKEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, LEAF PHOTOSYNTHESIS, MODELING, NITROGEN, PHOTOSYNTHESIS MODEL, RIBULOSE BISPHOSPHATE CARBOXYLASEÄÄ Ã Ã292Ä Ä° `  à ÃHarley, P.C., J.A. Weber, and D.M. Gates.Ä Ä 1985. Interactive Effects of Light, Leaf Temperature, CO2 and O2 on Photosynthesis in Soybean. ÃÃPlanta 165:249©263.ÄÄ 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 parameters may be estimated from whole©leaf gas©exchange measurements. Carbon©dioxide response curves of net photosynthesis obtained using soybean plants (ÃÃGlycine maxÄÄ (L.) Merr.) at four partial pressures of oxygen and five leaf temperatures are presented, and a method for estimating the kinetic parameters of RuBP carboxylase©oxygenase, as manifested in vivo, is discussed. The kinetic parameters so obtained compare well with kinetic parameters obtained in vitro, and the model fits to the measured data give ÃÃr2ÄÄ 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 rates are applied to data collected on soybean. Combining these equations with those describing the kinetics of RuBP carboxylase©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. soybean/Glycine max ÃÃKEYWORDS: ENVIRONMENTAL INTERACTIONS, LEAF PHOTOSYNTHESIS, LIGHT, MODELING, OXYGEN, PHOTOSYNTHESIS MODEL, RESPIRATION, RIBULOSE BISPHOSPHATE CARBOXYLASE, TEMPERATUREÄÄ Ã Ã293Ä Ä° `  à ÃHartz, T.K., A. Baameur, and D.B. Holt.Ä Ä 1991. Carbon Dioxide Enrichment of High©value Crops under Tunnel Culture. ÃÃJournal of the American Society of Horticultural Science 116:970©973.ÄÄ The feasibility of field©scale CO2 enrichment of vegetable crops grown under tunnel culture was studied with cucumber (ÃÃCucumis sativusÄÄ L. cv. Dasher II), summer squash (ÃÃCucurbita pepoÄÄ L. cv. Gold Bar), and tomato (ÃÃLycopersicon esculentumÄÄ Mill. cv. Bingo) grown under polyethylene tunnels. The drip irrigation system was used to uniformly deliver a CO2©enriched 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. In 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 (ÃÃFragariaÄÄ x ÃÃananassaÄÄ Duch. cvs. Irvine and Chandler). Carbon dioxide enrichment under tunnel culture modestly increased 'Irvine' yields but did not affect 'Chandler'. Cucumis sativus/cucumber/Cucurbita pepo/squash/Lycopersicon esculentum/tomato/Fragaria ananassa/strawberry ÃÃKEYWORDS: COMMERCIAL USE OF CO2, GREENHOUSE, HORTICULTURAL CROPS, YIELDÄÄ Ã Ã294Ä Ä° `  à ÃHartz, T.K., and D.B. Holt.Ä Ä 1991. Root©zone Carbon Dioxide Enrichment in Field Does Not Improve Tomato or Cucumber Yield. ÃÃHortScience 26:1423.ÄÄ tomato/Lycopersicon esculentum/cucumber/Cucumis sativus ÃÃKEYWORDS: COMMERCIAL USE OF CO2, FIZZ IRRIGATION, SOIL CO2 CONCENTRATION, YIELDÄÄ Ã Ã295Ä Ä° `  à ÃHarvey, L.D.D.Ä Ä 1989. Effect of Model Structure on the Response of Terrestrial Biosphere Models to CO2 and Temperature Increase. ÃÃGlobal Biogeochemical Cycles 3:137©153.ÄÄ The sensitivity of a number of different globally aggregated models of the terrestrial biosphere to changes of atmospheric CO2 and temperature is investigated. Net primary production (NPP) or net photosynthesis (NP) is modeled as a logistic function, with enhancement due to increased CO2 using the beta factor widely used in global carbon cycle models. NPP also 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 transfer coefficient from the rapidly to slowly overturning reservoir is fixed; maximum sensitivity occurs if all the carbon entering the slowly overturning reservoir first passes through the rapidly overturning reservoir. If the transfer coefficient increases in parallel with the increase of soil respiration coefficient, the carbon pathway has no effect on equilibrium 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 equilibrium 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. ÃÃKEYWORDS: BIOSPHERE LEVEL CO2 RESPONSES, MODELING, NET PRIMARY PRODUCTIVITY, TEMPERATUREÄÄ Ã Ã296Ä Ä° `  à ÃHatton, T.J., J. Walker, W.R. Dawes, and F.X. Dunin.Ä Ä 1992. Simulations of Hydroecological Responses to Elevate CO2 at the Catchment Scale. ÃÃAustralian Journal of Botany 40:679©696.ÄÄ 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 ÃÃEucalyptus maculataÄÄ trees. The model was used to simulate the direct effects of a 2x elevation in atmospheric carbon dioxide at two levels of nitrogen on catchment water yield, soil moisture status and tree growth. Experimental results used to parameterise the model are detailed. 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 yield or soil moisture content) and forest growth (expressed as leaf area index, LAI) were modelled for a 2©year period, and contrasted with the effects of added nitrogen. Results were expressed as totals for the catchment or spatially distributed across the catchment. For the total catchment, water yield increased in the order: high CO2 with low N, high CO2 with high N, ambient CO2 with low N, ambient CO2 with high N. LAI increased from 3.3 to 5.76 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 findings are: (1) with elevated CO2 a new equilibrium in transpiration is established in which leaf area increases offset decreases in stomatal conductance; (2) the addition of nitrogen increases transpiration without any indication of a new equilibrium being reached during the simulated period; (3) the spatial distribution of soil moisture changes, presenting a new resource 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 changed 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. Eucalyptus maculata ÃÃKEYWORDS: COMMUNITY LEVEL CO2 RESPONSES, EVAPOTRANSPIRATION, FOREST, HYDROLOGIC MODEL, MODELING, NITROGEN, SOIL CO2 CONCENTRATIONÄÄ Ã Ã297Ä Ä° `  à ÃHavir, E.A., and N.A. McHale.Ä Ä 1989. Regulation of Catalase Activity in Leaves of ÃÃNicotiana sylvestrisÄÄ by High CO2. ÃÃPlant Physiology 89:952©957.ÄÄ The effect of high CO2 (1% CO2/21% O2) on the activity of specific forms of catalase (CAT©1, ©2, and ©3) (EA Havir, NA McHale [987] Plant Physiol 84: 450©455) in seedling leaves of tobacco (ÃÃNicotiana sylvestris, Nicotiana tabacumÄÄ) was examined. In high CO2, total catalase activity decreased by 50% in the first 2 days, followed by a more gradual decline in the next 4 days. The loss of total activity resulted primarily from a decrease in CAT©1 catalase. In contrast, the activity of CAT©3 catalase, a form with enhanced peroxidatic activity, increased 3©fold in high CO2 relative to air controls after 4 days. Short©term exposure to high CO2 indicated that the 50% loss of total activity occurs in the first 12 hours. Catalase levels increased to normal within 23 hours after seedlings were returned to air. When seedlings were transferred to air after prolonged exposure to high CO2 (13 days), the levels of CAT©1 catalase were partially restored while CAT©3 remained at its elevated level. Levels of superoxide dismutase activity and those of several peroxisomal enzymes were not affected by high CO2. Total catalase levels did not decline when seedlings were exposed to atmospheres of 0.04% CO2/5% O2 or 0.04% CO2/1% O2, indicating that regulation of catalase in high CO2 is not related directly to suppression of photorespiration. Antibodies prepared against CAT©1 catalase from ÃÃN. tabacumÄÄ reacted strongly against CAT©1 catalase from both ÃÃN. sylvestrisÄÄ and ÃÃN. tabacumÄÄ but not against CAT©3 catalase from either species. This observation, along with the rapid changes in CAT©1 and the much slower changes in CAT©3 suggest that one form is not directly derived from the other. Nicotiana sylvestris/Nicotiana tabacum/tobacco ÃÃKEYWORDS: CATALASE, ENZYMES, PEROXIDASE, PROTEINS, SUPEROXIDE DISMUTASEÄÄ Ã Ã298Ä Ä° `  à ÃHe, H., M.B. Kirkham, D.J. Lawlor, and E.T. Kanemasu.Ä Ä 1992. Photosynthesis and Water Relations of Big Bluestem (C4) and Kentucky Bluegrass (C3) under High Concentration of Carbon Dioxide. ÃÃTransactions of the Kansas Academy of Science 95:139©152.ÄÄ As the carbon dioxide (CO2) concentration in the atmosphere increases, comparing how C3 and C4 plants will respond is important. The objective of this study was to determine the photosynthetic rate, intercellular CO2 concentration, transpiration rate, stomatal resistance, leaf temperature, water potential, and water requirement of a C3 grass (Kentucky bluegrass, ÃÃPoa pratensisÄÄ L.) and a C4 grass (big bluestem, ÃÃAndropogon gerardiiÄÄ Vitman) growing in a fall in a tallgrass prairie in Kansas under two levels of CO2 (ambient and two©times ambient). Elevated CO2 increased the photosynthetic rate of Kentucky 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 concentration. Doubled CO2 reduced the transpiration rates and increased stomatal resistance of both grasses, but big bluestem was affected more than Kentucky bluegrass. The twice©ambient level of CO2 increased (between 0.2 and 0.3 MPa) the water potential of both grasses. Doubled CO2 decreased the water requirements of big bluestem and Kentucky bluegrass by 41.6% and 158%, respectively. Kentucky bluegrass/Poa pratensis/big bluestem/Andropogon gerardii ÃÃKEYWORDS: C3, C4, CI:CA, CONDUCTANCE, LEAF PHOTOSYNTHESIS, OUTDOOR GROWTH CHAMBERS, TALLGRASS PRAIRIE, TRANSPIRATION, WATER STATUS, WUEÄÄ Ã Ã299Ä Ä° `  à ÃHendrey, G.R.Ä Ä 1992. The DOE/USDA FACE Program: Goal, Objectives, and Results Through 1989. ÃÃCritical Reviews in Plant Sciences 11:75©83.ÄÄ The FACE system is a tool for studying the effects of CO2 enrichment on vegetation and natural ecosystems and the exchange 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 conditions are relatively uniform, thus permitting an evaluation of FACE performance. Cotton is a woody perennial with well©known physiological characteristics and a high level of response to CO2 enrichment. It is therefore a convenient subject for experimentation. 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 operates effectively over plant canopies ranging in stature from bare ground to 200 cm with both open and closed canopies. Control 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 described, approximately, by the diameter of the FACE array minus 4 m and is as large as 380 m2 in the largest configuration tested to date (Hendrey 1992). In 1989 a 12©m diameter 'sweet spot' in the center of the FACE array had season©long average 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 accumulation, both above ground and below ground. Soil respiration also increased in CO2 enriched plots. Enriched plants matured earlier and, in general, had greater agronomic yields. Water use efficiency increased with CO2 enrichment. The FACE system as reported here has had two years of successful biological experimentation. Results from these experiments are intended for 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. ÃÃKEYWORDS: EXPOSURE METHODS, FACEÄÄ Ã Ã300Ä Ä° `  à ÃHendrey, G.R. (ed.)Ä Ä. 1992. FACE: Free Air CO2 Enrichment for Plant Research in the Field (Vol. 11 in Critical Reviews in Plant Sciences, B.V. Conger, ed.). ÃÃCRC Press, Inc., Boca Raton, Florida.ÄÄ ÃÃKEYWORDS: EXPOSURE METHODS, FACE, REVIEWÄÄ Ã Ã301Ä Ä° `  à ÃHendrey, G.R.Ä Ä 1992. Global Greenhouse Studies: Need for a New Approach to Ecosystem Manipulation. ÃÃCritical Reviews in Plant Sciences 11:61©74.ÄÄ ÃÃKEYWORDS: CARBON CYCLE, CO2 ENRICHMENT STUDIES, COMMUNITY LEVEL CO2 RESPONSES, ECOSYSTEM LEVEL CO2 RESPONSES, EXPOSURE METHODS, REVIEW, SCALINGÄÄ Ã Ã302Ä Ä° `  à ÃHendrey, G.R., K.F. Lewin, F. Lipfert, Z. Kolber, and M. Daum.Ä Ä 1988. Free©Air Carbon Dioxide Enrichment (FACE) Facility Development: I. Concept, Prototype Design and PerformanceÃÃ, 045 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C. ÃÃKEYWORDS: EXPOSURE METHODS, FACEÄÄ Ã Ã303Ä Ä° `  à ÃHendrey, G.R., K.F. Lewin, and J. Nagy.Ä Ä 1993. Free Air Carbon Dioxide Enrichment: Development, Progress, Results. ÃÃVegetatio 104/105:17©31.ÄÄ 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 concentration. Reliable field experiments are needed to evaluate how terrestrial plants will adjust to increasing CO2 and thereby influence the rate of change of atmospheric CO2. Brookhaven National Laboratory (BNL) has developed a unique Free©Air CO2 Enrichment (FACE) system for a cooperative research program sponsored by the U.S. Department of Energy and U.S. Department of Agriculture, currently operating as the FACE User Facility at the Maricopa Agricultural Center (MAC) of the University of 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 system 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 (ÃÃGossypium hirsutumÄÄ) as the test plant, enrichment to 550 ppm CO2 resulted in significant increases in photosynthesis and biomass of leaves, stems and roots, reduced evapotranspiration, and changes in root morphology., In addition, soil respiration increased and evapotranspiration decreased. Gossypium hirsutum/cotton ÃÃKEYWORDS: CARBON:NITROGEN RATIO, EVAPOTRANSPIRATION, EXPOSURE METHODS, FACE, PHOTOSYNTHESIS, ROOTS, SOIL RESPIRATION, WATER STRESSÄÄ Ã Ã304Ä Ä° `  à ÃHendrey, G.R., F.W. Lipfert, B.A. Kimball, D.R. Hileman, and N.C. Bhattacharya.Ä Ä 1988. Free Air Carbon Dioxide Enrichment (FACE) Facility Development: II. Field Tests at Yazoo City, MS, 1987ÃÃ, 046 in Green Report Series, Response of Vegetation to Carbon DioxideÄÄ. U.S. Dept. of Energy, Carbon Dioxide Research Division, Washington, D.C. cotton/Gossypium hirsutum ÃÃKEYWORDS: CONDUCTANCE, EXPOSURE METHODS, FACE, GROWTH MODEL, LEAF PHOTOSYNTHESIS, MODELING, OPEN©TOP CHAMBERSÄÄ Ã Ã305Ä Ä° `  à ÃHendrix, D.L.Ä Ä 1992. Influence of Elevated CO2 on Leaf Starch of Field©Grown Cotton. ÃÃCritical Reviews in Plant Sciences 11:223©226.ÄÄ cotton/Gossypium hirsutum ÃÃKEYWORDS: CARBOHYDRATES, FACEÄÄ Ã Ã306Ä Ä° `  à ÃHigginbotham, K.O., J.M. Mayo, S. L'Hirondelle, and D.K. Krystofiak.Ä Ä 1985. Physiological Ecology of Lodgepole Pine (ÃÃPinus contortaÄÄ) in an Enriched CO2 Environment. ÃÃCanadian Journal of Forest Research 15:417©421.ÄÄ 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 (ÃÃPinus contortaÄÄ Dougl. var. ÃÃlatifoliaÄÄ Engelm.) 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. Significant 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 treatments. The same relationship was found in production of total leaf surface area. Increased leaf surface area yields a productive advantage to seedlings grown at concentrations of CO2 up to 2000 uL/L even if no increase in net photosynthesis is assumed. Biomass of stems, roots, and secondary leaves was increased in both elevated CO2 conditions, with root biomass approximately 15 times greater in seedlings grown at 1000 uL/L than in those grown at 330 uL CO2/L. Stomatal resistances were essentially the same for all treatments, indicating no CO2©induced stomatal closure to at least 2000 uL/L. Photosynthetic Vmax (milligrams per square decimetre per hour) for light response curves varied with CO2 concentration. If results are extrapolated 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. lodgepole pine/Pinus contorta ÃÃKEYWORDS: ALLOCATION, CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, LIGHT, PHOTOSYNTHESIS, ROOTS, TREES, WATER STRESSÄÄ Ã Ã307Ä Ä° `  à ÃHighsmith, M.Ä Ä 1989. Two Aspects of Starch Formation in Mature Soybean Leaves. ÃÃIN: Current Topics in Plant Biochemistry and Physiology: Proceedings of the Plant Biochemistry and Physiology Symposium, Vol. 8, The Interdisciplinary Plant Biochemistry and Physiology Program, University of Missouri, Columbia, p. 267.ÄÄ soybean/Glycine max ÃÃKEYWORDS: CARBOHYDRATES, CARBON BUDGET, DIURNAL CYCLEÄÄ Ã Ã308Ä Ä° `  à ÃHilbert, D.W., A. Larigauderie, and J.F. Reynolds.Ä Ä 1991. The Influence of Carbon Dioxide and Daily Photon©flux Density on Optimal Leaf Nitrogen Concentration and Root:Shoot Ratio. ÃÃAnnals of Botany 68:365©376.ÄÄ Using a cost©benefit model, the leaf nitrogen concentration and root:shoot ratio that maximize whole©plant relative growth rate are determined as a function of the above©ground environment (integrated daily photon flux density and the concentration of carbon dioxide at the site of fixation within the leaf). The major advantage of this approach is that it determines the adaptive significance of leaf physiology by considering the functional integration of leaves and roots. The predicted response to increasing daily photon flux densities is an increase in optimal leaf N concentration (Nopt) and a concomitant increase in root:shoot ratio. Increased carbon dioxide concentration, on the other hand, reduce Nopt and only slightly change root:shoot ratio. The observed increase in leaf nitrogen concentration found in plants growing at high altitudes (low CO2 partial pressure) is also predicted. Since these responses to light and CO2 maximize the whole©plant relative growth rate, the observed adjustments that plants make to light and carbon dioxide concentration appear to be adaptive. We show that the relationship between photosynthesis and leaf nitrogen concentration is complex and depends on the light and CO2 levels at which photosynthesis is measured. The shape of this function is important in determining Nopt and the opposite 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. ÃÃKEYWORDS: ALLOCATION, GROWTH MODEL, MODELING, NITROGEN, ROOT:SHOOT RATIOÄÄ Ã Ã309Ä Ä° `  à ÃHilbert, D.W., T.I. Prudhomme, and W.C. Oechel.Ä Ä 1987. Response of Tussock Tundra to Elevated Carbon Dioxide Regimes: Analysis of Ecosystem CO2 Flux through Nonlinear Modeling. ÃÃOecologia 72:466©472.ÄÄ The response of tussock tundra to elevated atmospheric concentrations of CO2 was measured at Toolik Lake, Alaska in the summer of 1983. Computer©controlled greenhouses were used to determine diurnal ecosystem flux of CO2 under four treatments: 340 ppm, 500 ppm, and 680 ppm CO2, as well as 680 ppm CO2 with a four degree centigrade increase in temperature. For the seven days of data analyzed, net daily CO2 flux was significantly different between treatments. Net uptake was positively correlated with CO2 concentration in the chamber and negatively correlated with temperature. A nonlinear model was used to analyze this data set and to determine some of the reasons for different net CO2 flux. This model allowed an estimation of light utilization efficiency, total conductance of CO2, and a comparable measure of total respiration. From this analysis we conclude that nutrient limitations in the arctic decrease the capacity of tundra plants to make use of elevated CO2 concentrations. The plants respond by decreasing conductance in the presence of elevated CO2, which results in approximately equal gross uptake rates for the three CO2 treatments. Apparent changes in system respiration result in higher net uptake under elevated CO2 but this may be due to biases in the data. The treatment with increased temperature exhibited higher conductances and, consequently, higher gross uptake of CO2 than the other treatments. Higher temperatures, however, also increase respiration with the result being lower net uptake than would be expected in the absence of temperature increases. ÃÃKEYWORDS: ECOSYSTEM LEVEL CO2 RESPONSES, PHOTOSYNTHESIS MODEL, RESPIRATION, TEMPERATURE, TRACKING CHAMBERS, TUNDRAÄÄ Ã Ã310Ä Ä° `  à ÃHildmann, H., K. Windisch, A. Heissner, W. Weber, J. Domroese, S. Weber, and A. Markert.Ä Ä 1989. Testing a Strategy of Growth and Yield Control in Greenhouse Cucumbers in a Specialized Vegetable Growing Farm. ÃÃActa Horticulturae 260:123©136.ÄÄ Cucumis sativus ÃÃKEYWORDS: HORTICULTURAL CROPS, YIELDÄÄ Ã Ã311Ä Ä° `  à ÃHileman, D.R., N.C. Bhattacharya, P.P. Ghosh, P.K. Biswas, L.H. Allen Jr., K.F. Lewin, and G.R. Hendrey.Ä Ä 1992. Distribution of Carbon Dioxide within and above a Cotton Canopy Growing in the FACE System. ÃÃCritical Reviews in Plant Sciences 11:187©194.ÄÄ ÃÃKEYWORDS: EXPOSURE METHODS, FACEÄÄ Ã Ã312Ä Ä° `  à ÃHileman, D.R., N.C. Bhattacharya, P.P. Ghosh, P.K. Biswas, K.F. Lewin, and G.R. Hendrey.Ä Ä 1992. Responses of Photosynthesis and Stomatal Conductance to Elevated Carbon Dioxide in Field©Grown Cotton. ÃÃCritical Reviews in Plant Sciences 11:227©231.ÄÄ cotton/Gossypium hirsutum ÃÃKEYWORDS: CONDUCTANCE, FACE, LEAF PHOTOSYNTHESISÄÄ Ã Ã313Ä Ä° `  à ÃHileman, D.R., P.P. Ghosh, N.C. Bhattacharya, P.K. Biswas, L.H. Allen Jr., G. Peresta, and B.A. Kimball.Ä Ä 1992. A Comparison of the Uniformity of an Elevated CO2 Environment in Three Different Types of Open©top Chambers. ÃÃCritical Reviews in Plant Sciences 11:195©202.ÄÄ Carbon dioxide levels were determined at various points inside three different types of open©top chambers (square, round without frustum and round with frustum), to compare the variability in CO2 concentrations among the different types of chambers. At similar rates of injection of CO2 into the fan housings of the three chambers, CO2 levels were highest in the round chamber with a frustum and lowest in the square chamber. The lower enrichment levels in the square chamber were most likely due to greater air movement by the fan. Variability in CO2 concentration was lowest in the round chamber with a frustum. Variability was similar in the round (without frustum) and square chambers, except at the upper heights, where variability was somewhat greater in the shorter, square chamber. These trends were true both for variability from point to point within chambers and for variability over time. In both the square chamber and the round chamber without a frustum, CO2 levels were frequently lower and more variable in the downwind side of the chamber than in the upwind side. The round chamber with the frustum showed no evidence of a wind direction effect. ÃÃKEYWORDS: EXPOSURE METHODS, OPEN©TOP CHAMBERSÄÄ Ã Ã314Ä Ä° `  à ÃHocking, P.J., and C.P. Meyer.Ä Ä 1985. Responses of Noogoora Burr (ÃÃXanthium occidentaleÄÄ Bertol.) to Nitrogen Supply and Carbon Dioxide Enrichment. ÃÃAnnals of Botany 55:835©844.ÄÄ We studied the responses of ÃÃXanthium occidentaleÄÄ (Bertol.) (cocklebur or Noogoora burr), a noxious weed, to atmospheric CO2 enrichment and nitrate©N concentrations in the root zone ranging from 0.5 to 25 mM. CO2 enrichment (1500 cm3/m3) increased dry©matter production to about the same extent (18 per cent) at all levels of supplied N: most of the increment in dry matter was distributed equally between leaves and roots so that there was little effect on shoot©to©root dry©weight ratios. Growth was stimulated greatly by N and plateaued at 12 mM supplied N. Shoot©to©root dry©weight and total N ratios increased with increasing N supply. CO2 enrichment had no effect on the total amount of N accumulated by plants, but increased the N©use efficiency of leaves. Enriched plants had lower concentrations and quantities of N in their leaves than controls, and therefore lower shoot©to©root total N ratios. Little free NO3 accumulated in organs of control or enriched plants. NO3 was a major form of N in xylem sap from detopped plants at low supplied NO3©N, but amino N was equal in importance at high supplied NO3©N in control and enriched plants. Concentrations of NO3 were lower in the xylem sap of CO2 enriched plants. It was concluded that the better N©use efficiency of CO2 enriched plants could result in increased growth of ÃÃX. occidentaleÄÄ in regions of marginal soil fertility as atmospheric levels of CO2 increase. Xanthium occidentale/cocklebur ÃÃKEYWORDS: ALLOCATION, GREENHOUSE, GROWTH, NITROGEN, NUTRITION, ROOT:SHOOT RATIOÄÄ Ã Ã315Ä Ä° `  à ÃHocking, P.J., and C.P. Meyer.Ä Ä 1991. Carbon Dioxide Enrichment Decreases Critical Nitrate and Nitrogen Concentrations in Wheat. ÃÃJournal of Plant Nutrition 14:571©584.ÄÄ Atmospheric carbon dioxide (CO2) levels are increasing, In a glasshouse experiment with wheat grown at 5 levels of nitrate (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, respectively, for control plants grown at the ambient level of CO2. However, concentrations of NO3©N in the rooting medium required to produce maximum dry matter accumulation by CO2©enriched plants were similar to those of control plants at the three growth stages. Critical concentrations of NO3©N and total©N declined with time in stem bases and leaves of plants grown at both 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. wheat/Triticum aestivum ÃÃKEYWORDS: GREENHOUSE, GROWTH, GROWTH STAGES, NITROGEN, NUTRITIONÄÄ Ã Ã316Ä Ä° `  à ÃHocking, P.J., and C.P. Meyer.Ä Ä 1991. Effects of CO2 Enrichment and Nitrogen Stress on Growth, and Partitioning of Dry Matter and Nitrogen in Wheat and Maize. ÃÃAustralian Journal of Plant Physiology 18:339©356.ÄÄ Atmospheric CO2 levels are increasing, but little is known about how this will affect tissue concentrations and the partitioning of agriculturally important nutrients such as nitrogen (N) within crop plants. To investigate this, a glasshouse experiment was conducted in which wheat, a C3 species, and maize, a C4 species, were grown for 8 weeks at high CO2 (1500 cm3/m3) on N supplies ranging from deficient (0.5 mol/m3) to more than adequate for maximum growth (25 mol/m3). Wheat responded to both CO2 enrichment and N supply; maize responded only to N supply. CO2©enriched wheat produced about twice the dry matter of control plants at all levels of N supply. Tiller and ear numbers were increased by CO2 enrichment irrespective of N supply. Enriched wheat plants had lower Leaf Area Ratio but higher Net Assimilation Rate and Relative Growth Rate than control plants. There was no effect of CO2 enrichment on specific leaf weight. The enriched plants had lower shoot to root dry matter ratios than the controls at 6 mol/m3 N and higher. Shoot to root dry matter ratios of both wheat and maize increased with increasing N supply. CO2©enriched wheat plants accumulated more N than the controls but the proportional increase in N content was not as great as that in dry matter, with the result that concentrations of total©N and nitrate©N were lower in all organs of enriched plants, including ears. Nitrate reductase activity was lower in enriched than in control wheat plants. N©use efficiency by wheat was increased by CO2 enrichment. From a practical point of view, the study indicates that critical total©N and NO3©N concentrations used to diagnose the N status of wheat will need to be reassessed as global CO2 levels increase. Elevated CO2 may also reduce the protein content of grain and thus the baking quality of hard wheats. wheat/Triticum aestivum/maize/Zea mays ÃÃKEYWORDS: ALLOCATION, C3, C4, CROPS, GREENHOUSE, GROWTH ANALYSIS, NITRATE REDUCTASE, NITROGEN, NUTRITION, ROOT:SHOOT RATIOÄÄ Ã Ã317Ä Ä° `  à ÃHoddinott, J., and P. Jolliffe.Ä Ä 1988. The Influence of Elevated Carbon Dioxide Concentrations on the Partitioning of Carbon in Source Leaves of ÃÃPhaseolus vulgarisÄÄ. ÃÃCanadian Journal of Botany 66:2396©2401.ÄÄ Plants may alter their growth pattern in response to being grown in elevated CO2 concentrations. The nature of the change in carbon partitioning underlying those alterations was investigated in ÃÃPhaseolus vulgarisÄÄ 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 concentration on plant height, leaf area, or dry weight, but the specific leaf weight increased significantly with the CO2 concentration, indicating a denser leaf structure. The starch content of the leaves also increased significantly as the CO2 level increased. A primary leaf was pulse labelled with 14©CO2 and the depletion of label from that source leaf was monitored with a GM tube. The depletion of the count rate with time was described by a nonlinear curve fitting procedure that allowed the 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 export and storage were reduced in the dark at all CO2 levels, with an increase in the residence time of carbon in the export pool. Reducing the CO2 concentration around the source leaf just after labelling did not change carbon partitioning compared 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. Phaseolus vulgaris/bean ÃÃKEYWORDS: 14C, ASSIMILATE PARTITIONING, CARBOHYDRATES, CARBON BUDGET, REMOBILIZATIONÄÄ Ã Ã318Ä Ä° `  à ÃHogan, K.P., A.P. Smith, and L.H. Ziska.Ä Ä 1991. Potential Effects of Elevated CO2 and Changes in Temperature on Tropical Plants. ÃÃPlant, Cell and Environment 14:763©778.ÄÄ Very little attention has been directed at the responses of tropical plants to increases in global atmospheric CO2 concentrations and the potential climatic changes. The available data, from greenhouse and laboratory studies, indicate that the photosynthesis, growth and water use efficiency of tropical plants can increase at higher CO2 concentrations. However, under field conditions abiotic (light, water or nutrients) or biotic (competition or herbivory) factors might limit these responses. In general, elevated atmospheric CO2 concentrations seem to increase plant tolerance to stress, including low 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 than are temperate plants, so expected changes in temperature might be relatively more important in the tropics. Reduced transpiration due to decreased stomatal conductance could modify the effects of water stress as a cue for vegetative or reproductive 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. ÃÃKEYWORDS: ALLOCATION, COMMUNITY LEVEL CO2 RESPONSES, ENVIRONMENTAL INTERACTIONS, HERBIVORY, PHENOLOGY, POPULATION LEVEL CO2 RESPONSES, REVIEW, SOIL MICROORGANISMS, SPECIES RANGE, TEMPERATURE, TROPICAL PLANTSÄÄ Ã Ã319Ä Ä° `  à ÃHollinger, D.Y.Ä Ä 1987. Gas Exchange and Dry Matter Allocation Responses to Elevation of Atmospheric CO2 Concentration in Seedlings of Three Tree Species. ÃÃTree Physiology 3:193©202.ÄÄ Photosynthetic rates of 13©month©old ÃÃPinus radiataÄÄ D. Don, ÃÃNothofagus fuscaÄÄ (Hook f.) Orst. and ÃÃPseudotsuga menziesiiÄÄ (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 grown in ambient and elevated concentrations of CO2 had similar rates of photosynthesis when measured at 620 uL/L CO2, but when measured at 310 uL/L CO2 the ÃÃP. radiataÄÄ and ÃÃN. fuscaÄÄ 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. Pinus radiata/Nothofagus fusca/Pseudotsuga menziesii/Monterey pine/New Zealand red beech/Douglas©fir ÃÃKEYWORDS: ALLOCATION, CONDUCTANCE, CONTROLLED ENVIRONMENT CHAMBERS, LEAF PHOTOSYNTHESIS, PHOTOSYNTHETIC ACCLIMATION, TREES, VPDÄÄ Ã Ã320Ä Ä° `  à ÃHoughton, R.A.Ä Ä 1987. Biotic Changes Consistent with the Increased Seasonal Amplitude of Atmospheric CO2 Concentrations. ÃÃJournal of Geophysical Research 92:4223©4230.ÄÄ Monthly estimates of gross primary production (gross uptake of CO2 by plants) and ecosystem respiration (gross release of CO2 from the ecosystem) in an oak©pine forest in the northeastern United States were used in this study to examine the types of metabolic changes in terrestrial systems that might yield the increased seasonal amplitude of CO2 concentrations observed at several monitoring stations in recent years. In this study, increases in either photosynthesis or respiration increased the amplitude of the seasonal oscillation of CO2 concentrations if the increases were predominantly in the northern hemispheric summer and winter, respectively. The quantitative changes in metabolism required to produce the observed 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. ÃÃKEYWORDS: BIOSPHERE LEVEL CO2 RESPONSES, CO2 SEASONAL FLUX, ECOSYSTEM LEVEL CO2 RESPONSES, FOREST, MODELING, NET PRIMARY PRODUCTIVITY, RESPIRATION, TERRESTRIAL METABOLISMÄÄ Ã Ã321Ä Ä° `  à ÃHoughton, R.A.Ä Ä 1987. Terrestrial Metabolism and Atmospheric CO2 Concentrations. ÃÃBioScience 37:672©678.ÄÄ ÃÃKEYWORDS: BIOSPHERE LEVEL CO2 RESPONSES, CO2 SEASONAL FLUX, ECOSYSTEM LEVEL CO2 RESPONSES, MODELING, NET PRIMARY PRODUCTIVITY, RESPIRATION, REVIEW, TERRESTRIAL METABOLISMÄÄ Ã Ã322Ä Ä° `  à ÃHoupis, J.L.J., K.A. Surano, S. Cowles, and J.H. Shinn.Ä Ä 1988. Chlorophyll and Carotenoid Concentrations in Two Varieties of ÃÃPinus ponderosaÄÄ Seedlings Subjected to Long©term Elevated Carbon Dioxide. ÃÃTree Physiology 4:187©193.ÄÄ Two varieties of ponderosa pine (ÃÃPinus ponderosaÄÄ Dougl. var. scopulorum (Rocky Mountain variety) and ÃÃP. ponderosaÄÄ 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 both varieties showed symptoms of stress including mottling, mid©needle abscission and early senescence. In both varieties, exposure to CO2 concentrations greater than ambient + 75 uL/L resulted in lower chlorophyll ÃÃaÄÄ, chlorophyll ÃÃbÄÄ and carotenoid 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 ÃÃP. ponderosaÄÄ varieties were lower than those in current©season needles. Pinus ponderosa/ponderosa pine ÃÃKEYWORDS: OPEN©TOP CHAMBERS, PIGMENTS, SENESCENCE, TREESÄÄ Ã Ã323Ä Ä° `  à ÃHoupis, J.L.J., K.A. Surano, P.F. Daley, and J.H. Shinn.Ä Ä 1986. Growth and Morphology of ÃÃPinus ponderosaÄÄ Seedlings Exposed to Long©term Elevated Atmospheric Carbon Dioxide Concentration. ÃÃIN: Proceedings of the Ninth North American Forest Biology Workshop; 1986 June 15©18; Stillwater, Oklahoma (C.G. Tauer and T.C. Hennessey, eds.), Society of American Foresters, and Department of Forestry, Oklahoma State University, pp. 19©26.ÄÄ The growth and morphology of two varieties of ÃÃPinus ponderosaÄÄ were measured after two years of continuous fumigation with carbon dioxide. After two years of treatment, the seedlings of the Rocky Mountain variety showed no significant difference 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 quite different, with those at +150 ppm and +300 ppm significantly greater in height than those at +75 ppm and those at +150 ppm 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 significantly 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. ponderosa pine/Pinus ponderosa ÃÃKEYWORDS: GROWTH, LEAF AREA DEVELOPMENT, MORPHOLOGY, OPEN©TOP CHAMBERS, TREESÄÄ Ã Ã324Ä Ä° `  à ÃHouter, G., H. Gijzen, E.M. Nederhoff, and P.C.M. Vermeulen.Ä Ä 1989. Simulation of CO2 Consumption in Greenhouses. ÃÃActa Horticulturae 248:315©320.ÄÄ In order to calculate the CO2 and heat demand in greenhouses, a simulation model is composed of a greenhouse climate submodel and a crop submodel. The purpose of the model is to use it as a management system, which can be consulted for decisions on investments in CO2 and heating equipment. The greenhouse climate submodel calculates the conditions inside the greenhouse on the basis of outside weather data and specific setpoints for the greenhouse climate. It also calculates the demand for heat and the necessity for ventilation. Both these factors are related to the CO2 fluxes to the greenhouse. The crop submodel calculates leaf photosynthesis, crop photosynthesis, dry matter production and fresh weight production. As yet, the production of a tomato and of a cucumber can be simulated. ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CO2 MEASUREMENT AND CONTROL, COMMERCIAL USE OF CO2, MODELING, SIMULATIONÄÄ Ã Ã325Ä Ä° `  à ÃHrubec, T.C., J.M. Robinson, and R.P. Donaldson.Ä Ä 1985. Effects of CO2 Enrichment and Carbohydrate Content on the Dark Respiration of Soybeans. ÃÃPlant Physiology 79:684©689.ÄÄ During the period of most active leaf expansion, the foliar dark respiration rate of soybeans (ÃÃGlycine maxÄÄ cv Williams), grown for 2 weeks in 1000 microliters CO2 per liter air, was 1.45 milligrams CO2 evolved per hour leaf density thickness, 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 (ÃÃe.g.ÄÄ sucrose and starch) in the CO2 enriched compared with CO2 normal plants. For example, leaves of enriched plants displayed levels of nonstructural carbohydrate equivalent to 174 milligrams glucose 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 strong positive correlation between respiration rate and carbohydrate content was seen in high CO2 adapted plants, but not in 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 activities of NAD+ linked isocitrate dehydrogenase and cytochrome ÃÃcÄÄ 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 adaptations 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. Glycine max/soybean ÃÃKEYWORDS: CARBOHYDRATES, CONTROLLED ENVIRONMENT CHAMBERS, ENZYMES, GROWTH, LEAF AREA DEVELOPMENT, RESPIRATIONÄÄ Ã Ã326Ä Ä° `  à ÃHuerta, A.J., and I.P. Ting.Ä Ä 1988. Effects of Various Levels of CO2 on the Induction of Crassulacean Acid Metabolism in ÃÃPortulacaria afraÄÄ (L.) Jacq. ÃÃPlant Physiology 88:183©188.ÄÄ In response to water stress, ÃÃPortulacaria afraÄÄ (L.) Jacq. (Portulacaceae) shifts its photosynthetic carbon metabolism from the Calvin©Benson cycle for CO2 fixation (C3) photosynthesis or Crassulacean acid metabolism (CAM)©cycling, during which organic acids fluctuate with a C3©type of gas exchange, to CAM. During the CAM induction, various attributes of CAM appear, such as stomatal closure during the day, increase in diurnal fluctuation of organic acids, and an increase in phosphoenolpyruvate carboxylase activity. It was hypothesized that stomatal closure due to water stress may induce changes in 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 experiment were subjected to low (40 ppm), normal (ÃÃca.ÄÄ 330 ppm), and high (950 ppm) CO2 during the day with normal concentrations 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 phosphoenolpyruvate 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 reducing 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. Portulacaria afra ÃÃKEYWORDS: CAM, CONDUCTANCE, LEAF PHOTOSYNTHESIS, METABOLITES, PHOSPHOENOLPYRUVATE CARBOXYLASE, SUNLIT CONTROLLED ENVIRONMENT CHAMBERS, WATER STRESSÄÄ Ã Ã327Ä Ä° `  à ÃHunt, R., D.W. Hand, M.A. Hannah, and A.M. Neal.Ä Ä 1991. Response to CO2 Enrichment in 27 Herbaceous Species. ÃÃFunctional Ecology 5:410©421.ÄÄ CO2©enrichment experiments were performed on 25 British native species of widely differing ecology. Two crops, one C3 (sunflower)and one C4 (maize), were also included. The background regime involved full©light, glasshouse conditions, non©limiting supplies of water and mineral nutrients and a daytime mean temperature of 18À$ÀC. 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 ÃÃvsÄÄ CO2 concentration. The functions were then used to generate predictions of Q©540/350 (the quotient of present yield 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. Agrostis capillaris/Arrhenatherum elatius/Brachypodium pinnatum/Bromus erectus/Bromus sterilis/Cerastium fontanum/Chamerion angustifolium/Chenopodium album/Dactylis glomerata/Deschampsia flexuosa/Desmazeria rigida/Digitalis purpurea/Epilobium hirsutum/Festuca ovina/Festuca rubra/Helianthemum nummularium/Holcus lanatus/Koeleria macrantha/Plantago lanceolata/Poa annua/Poa trivialis/Rumex acetosella/Urtica dioica/Zea mays/Plantago lanceolata/Lolium perenne/Helianthus annuus/Eriophorum vaginatum ÃÃKEYWORDS: GROWTH, MODELING, PLANT STRATEGIES, SPECIES COMPETITION, SUNLIT CONTROLLED ENVIRONMENT CHAMBERSÄÄ Ã Ã328Ä Ä° `  à ÃIdso, S.B.Ä Ä 1986. Industrial Age Leading to the Greening of the Earth? ÃÃNature 320:22.ÄÄ ÃÃKEYWORDS: BIOSPHERE LEVEL CO2 RESPONSES, CO2 SEASONAL FLUX, TEMPERATUREÄÄ Ã Ã329Ä Ä° `  à ÃIdso, S.B.Ä Ä 1988. Three Phases of Plant Response to Atmospheric CO2 Enrichment. ÃÃPlant Physiology 87:5©7.ÄÄ Several years of research on seven different plants (five terrestrial and two aquatic species) suggest that the beneficial effects of atmospheric CO2 enrichment may be divided into three distinct growth response phases. First is a well©watered optimum©growth©rate phase where a 300 parts per million increase in the CO2 content of the air generally increases plant 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 normally indicative of impending death, where atmospheric CO2 enrichment may actually prevent plants from succumbing to the rigors of the environment and enable them to maintain essential life processes, as life ebbs from corresponding ambient©treatment plants. Agave vilmoriniana/Daucus carota/carrot/cotton/Gossypium hirsutum/radish/Raphanus sativus/soybean/Glycine max/water fern/Azolla pinnata/water hyacinth/Eichhornia crassipes ÃÃKEYWORDS: AQUATIC PLANTS, GROWTH, OPEN©TOP CHAMBERS, WATER STRESSÄÄ Ã Ã330Ä Ä° `  à ÃIdso, S.B.Ä Ä 1989. Carbon Dioxide, Soil Moisture, and Future Crop Production. ÃÃSoil Science 147:305©307.ÄÄ 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, indicates 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. ÃÃKEYWORDS: AGRICULTURE, CLIMATE CHANGE, MODELING, REVIEW, SIMULATION, WUEÄÄ Ã Ã331Ä Ä° `  à ÃIdso, S.B.Ä Ä 1989. Three Stages of Plant Response to Atmospheric CO2 Enrichment. ÃÃPlant Physiology and Biochemistry 27:131©134.ÄÄ Weekly assessments of biomass production in water hyacinths (ÃÃEichhornia crassipesÄÄ) and daily assessments of new©leaf production in water lilies (ÃÃNymphaea marliac carneaÄÄ) demonstrate that the positive effects of atmospheric CO2 enrichment on the growth rates of these plants are considerably greater both before (I) and after (III) the primary maximum©growth©rate stage (II) characteristic of the middle portion of a plants' life cycle. For these two particular aquatic macrophytes, 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. Eichhornia crassipes/water hyacinth/water lily/Nymphaea marliac ÃÃKEYWORDS: AQUATIC PLANTS, GROWTH, OPEN©TOP CHAMBERSÄÄ Ã Ã332Ä Ä° `  à ÃIdso, S.B.Ä Ä 1990. Interactive Effects of Carbon Dioxide and Climate Variables on Plant Growth. ÃÃIN: Impact of Carbon Dioxide, Trace Gases, and Climate Change on Global Agriculture, ASA Special Publication No. 53, American Society of Agronomy, Madison, Wisconsin.ÄÄ The climate variables predicted to experience major modification as a result of future increases in atmospheric CO2 and other radiatively active trace gases are temperature and precipitation. Predicted changes in these two parameters should intensify the hydrologic cycle over the globe, but could produce opposite trends in certain regions. A 'worst©case' scenario of consequent local reductions in summer soil moisture is evaluated in terms of the beneficial effects of atmospheric CO2 enrichment on plant water use efficiency and the interactive effect of air temperature increase on the growth©enhancing effects of atmospheric CO2 enrichment. It is demonstrated that the direct biological impacts of concomitant increases in CO2 and air temperature are probably sufficient to offset the adverse effects of summer soil moisture reductions predicted by state©of©the©art climate/water balance models. It is also noted that the worst©case climate scenario is unrealistic. Consequently, plant growth the world over should be significantly stimulated by atmospheric CO2 enrichment, a phenomenon that many people feel is already evident in a number of ecological indicators. ÃÃKEYWORDS: CLIMATE CHANGE, ENVIRONMENTAL INTERACTIONS, GROWTH, HYDROLOGIC MODEL, LEAF PHOTOSYNTHESIS, TEMPERATURE, WATER STRESS, WUEÄÄ Ã Ã333Ä Ä° `  à ÃIdso, S.B.Ä Ä 1990. A Role for Soil Microbes in Moderating the Carbon Dioxide Greenhouse Effect. ÃÃSoil Science 149:179©180.ÄÄ ÃÃKEYWORDS: CARBON IN SOILS, CARBON SEQUESTERING, SOIL MICROORGANISMSÄÄ Ã Ã334Ä Ä° `  à ÃIdso, S.B.Ä Ä 1991. The Aerial Fertilization Effect of CO2 and Its Implications for Global Carbon Cycling and Maximum Greenhouse Warming. ÃÃBulletin of the American Meteorological Society 72:962©965.ÄÄ Citrus aurantium ÃÃKEYWORDS: BIOSPHERE LEVEL CO2 RESPONSES, CARBON CYCLE, CO2 SEASONAL FLUX, GROWTH, OPEN©TOP CHAMBERS, TEMPERATURE, TREESÄÄ Ã Ã335Ä Ä° `  à ÃIdso, S.B.Ä Ä 1991. 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. ÃÃTellus 43B:338©341.ÄÄ ÃÃKEYWORDS: BIOTIC GROWTH FACTOR, CO2 SEASONAL FLUX, RHIZOSPHEREÄÄ Ã Ã336Ä Ä° `  à ÃIdso, S.B.Ä Ä 1991. A General Relationship between CO2©induced Increases in Net Photosynthesis and Concomitant Reductions in Stomatal Conductance. ÃÃEnvironmental and Experimental Botany 31:381©383.ÄÄ Simultaneous measurements of net photosynthesis and stomatal conductance of leaves of sour orange trees growing in normal and CO2©enriched air, together with similar data for cotton, soybeans and water hyacinth, suggest that a plant's photosynthetic response to atmospheric CO2 enrichment is inversely proportional to its degree of CO2©induced stomatal closure. Citrus aurantium/sour orange ÃÃKEYWORDS: CONDUCTANCE, LEAF PHOTOSYNTHESIS, OPEN©TOP CHAMBERS, TREESÄÄ Ã Ã337Ä Ä° `  à ÃIdso, S.B., S.G. Allen, M.G. Anderson, and B.A. Kimball.Ä Ä 1989. Atmospheric CO2 Enrichment Enhances Survival of ÃÃAzollaÄÄ at High Temperatures. ÃÃEnvironmental and Experimental Botany 29:337©341.ÄÄ In 2 years of experimentation with ÃÃAzolla pinnataÄÄ var. ÃÃpinnataÄÄ at Phoenix, Arizona, growth rates of this floating aquatic fern first decreased, then stagnated, and finally became negative when the mean air temperature rose above 30À$ÀC. When the atmospheric CO2 content above the plants was increased from the mean ambient concentration of 340 umol CO2/mol air to 640 umol CO2/mol air, however, the debilitating effects of high temperatures were reduced: in one case to a much less severe negative growth rate, in another case to merely a short period of zero growth rate, and in a third case to no discernible ill effects whatsoever ©© in spite of the fact that the ambient treatment plants in this instance all died. With the double verification of this phenomenon provided by both weekly biomass and periodic net photosynthesis determinations, it would appear that atmospheric CO2 enrichment may be capable of preventing the deaths of some plant species in situations where their demise is normally brought about by either the direct effects of unduly high temperatures or by associated debilitating diseases. Azolla pinnata/water fern ÃÃKEYWORDS: AQUATIC PLANTS, CANOPY PHOTOSYNTHESIS, OPEN©TOP CHAMBERS, TEMPERATUREÄÄ Ã Ã338Ä Ä° `  à ÃIdso, S.B., S.G. Allen, and B.A. Kimball.Ä Ä 1990. Growth Response of Water Lily to Atmospheric CO2 Enrichment. ÃÃAquatic Botany 37:87©92.ÄÄ Hardy water lilies (ÃÃNymphaeaÄÄ cultivar 'Marliacea carnea') were grown out©of©doors at Phoenix, Arizona in sunken metal stock tanks located within open©top, clear plastic©wall, CO2©enrichment chambers; two were maintained at a CO2 concentration of 650 ppm and two were maintained at the ambient CO2 concentration of about 350 ppm. Over a 5©month period, 25 different plant properties were evaluated, each one of which showed some degree of stimulation or enhancement under CO2©enriched conditions. In particular, net photosynthesis was increased by about 49%, leaf size by 18%, and integrated leaf number x life span by 16%, which resulted in a whole©plant biomass enhancement of 270%. After 21 months, differences between treatments 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. water lily/Nymphaea ÃÃKEYWORDS: ALLOCATION, AQUATIC PLANTS, GROWTH, LEAF AREA DEVELOPMENT, OPEN©TOP CHAMBERSÄÄ Ã Ã339Ä Ä° `  à ÃIdso, S.B., K.L. Clawson, and M.G. Anderson.Ä Ä 1986. Foliage Temperature: Effects of Environmental Factors with Implications for Plant Water Stress Assessment and the CO2/Climate Connection. ÃÃWater Resources Research 22:1702©1706.ÄÄ Throughout the summer and fall of 1985, several day©long sets of foliage temperature measurements were obtained for healthy and potentially transpiring water hyacinth, cotton, and alfalfa plants growing in a sealed and unventilated greenhouse 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 obtained out of doors under natural conditions, while dead, nontranspiring stands of alfalfa and water hyacinth were also monitored, 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 measured values of plant foliage and aerodynamic resistances to water vapor transport. These findings lead to some slight adjustments in the procedure for calculating the Idso©Jackson plant water stress index and they suggest that plants can adequately respond to much greater atmospheric demands for evaporation than what has been believed possible in the past. In addition, they demonstrate that the likely net radiation enhancement due to a doubling of the atmospheric carbon dioxide concentration will have little direct effect on vegetation temperatures, but that the antitranspirant effect of atmospheric CO2 enrichment on foliage temperature may be substantial. water hyacinth/Eichhornia crassipes/cotton/Gossypium hirsutum/alfalfa/Medicago sativa ÃÃKEYWORDS: AQUATIC PLANTS, CONDUCTANCE, CROPS, TEMPERATURE, TRANSPIRATION, VPDÄÄ Ã Ã340Ä Ä° `  à ÃIdso, S.B., and B.A. Kimball.Ä Ä 1989. Growth Response of Carrot and Radish to Atmospheric CO2 Enrichment. ÃÃEnvironmental and Experimental Botany 29:135©139.ÄÄ Seven crops of carrots and 11 crops of radishes were grown from seed in open©top, clear©plastic©wall, CO2©enrichment chambers throughout the entire year at Phoenix, AZ. Cumulative dry matter production at weekly intervals was significantly increased by a 300 ppm increase in the CO2 content of the air at all temperatures encountered, but with progressively greater effects being registered at higher and higher temperatures. At 25À$ÀC, the productivity enhancement factor for radish was about 1.5, while for carrot it was approximately 2.0. When regressed upon air temperature, the productivity enhancement factors of both species decreased to a null value of 1.0 in the vicinity of 12À$ÀC. The slope of the carrot relationship was nearly 250% greater than that of the radish relationship. carrot/Daucus carota/radish/Raphanus sativus ÃÃKEYWORDS: CROPS, GROWTH, OPEN©TOP CHAMBERS, TEMPERATUREÄÄ Ã Ã341Ä Ä° `  à ÃIdso, S.B., and B.A. Kimball.Ä Ä 1991. Downward Regulation of Photosynthesis and Growth at High CO2 Levels. ÃÃPlant Physiology 96:990©992.ÄÄ Numerous photosynthesis and growth measurements of sour orange (ÃÃCitrus aurantiumÄÄ 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. sour orange/Citrus aurantium ÃÃKEYWORDS: GROWTH, OPEN©TOP CHAMBERS, TREESÄÄ Ã Ã342Ä Ä° `  à ÃIdso, S.B., and B.A. Kimball.Ä Ä 1991. Effects of Two and a Half Years of Atmospheric CO2 Enrichment on the Root Density Distribution of Three©year©old Sour Orange Trees. ÃÃAgricultural and Forest Meteorology 55:345©349.ÄÄ 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. Citrus aurantium/sour orange ÃÃKEYWORDS: GROWTH, OPEN©TOP CHAMBERS, ROOTS, TREESÄÄ Ã Ã343Ä Ä° `  à ÃIdso, S.B., and B.A. Kimball.Ä Ä 1992. Season Fine©root Biomass Development of Sour Orange Trees Grown in Atmospheres of Ambient and Elevated CO2 Concentration. ÃÃPlant, Cell and Environment 15:337©341.ÄÄ Sour orange trees have been grown from the seedling stage out©of©doors at Phoenix, Arizona, USA, in open©top enclosures with clear plastic walls for 3.5 years. For the last 3 years of this period, half of the trees have been continuously exposed to air enriched with CO2 to 300 umol/mol above the ambient concentation. At 2©month intervals over the last 12 months, we have determined the fine©root biomass in the top 0.4 m of the soil profile beneath the trees. Results from both treatments define a single relationship between fine©root biomass and trunk cross©sectional area. The data also show the CO2©enriched trees to have approximately 2©3 times more fine©root biomass in this soil layer than the trees grown in ambient air. Citrus aurantium/sour orange ÃÃKEYWORDS: OPEN©TOP CHAMBERS, ROOTS, TREESÄÄ Ã Ã344Ä Ä° `  à ÃIdso, S.B., and B.A. Kimball.Ä Ä 1993. Effects of Atmospheric CO2 Enrichment on Net Photosynthesis and Dark Respiration Rates of Three Australian Tree Species. ÃÃJournal of Plant Physiology 141:166©171.ÄÄ 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 (ÃÃBrachychiton populneumÄÄ (Schott.) R. Br.) and two eucalyptus (ÃÃEucalyptus microthecaÄÄ F. Muell. and ÃÃE. polyanthemusÄÄ 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 (ÃÃCitrus aurantiumÄÄ L.). Australian bottle tree/Brachychiton populneum/sour orange/Citrus aurantium/Eucalyptus microtheca/Eucalyptus polyanthemus ÃÃKEYWORDS: LEAF PHOTOSYNTHESIS, OPEN©TOP CHAMBERS, RESPIRATION, TREESÄÄ Ã Ã345Ä Ä° `  à ÃIdso, S.B., B.A. Kimball, and S.G. Allen.Ä Ä 1991. CO2 Enrichment of Sour Orange Trees: 2.5 Years into a Long©term Experiment. ÃÃPlant, Cell and Environment 14:351©353.ÄÄ 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. sour orange/Citrus aurantium ÃÃKEYWORDS: GROWTH, OPEN©TOP CHAMBERS, TREESÄÄ Ã Ã346Ä Ä° `  à ÃIdso, S.B., B.A. Kimball, and S.G. Allen.Ä Ä 1991. Net Photosynthesis of Sour Orange Trees Maintained in Atmospheres of Ambient and Elevated CO2 Concentration. ÃÃAgricultural and Forest Meteorology 54:95©101.ÄÄ 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 the trees have been continuously supplied with a CO2©enriched atmosphere consisting of an extra 300 cm3 of CO2 per m3 of air. Data from a comprehensive inventory of all above©ground plant parts at the conclusion of two full years of growth under these conditions have revealed that the net effect of the CO2©enriched air was to more than double the normal production of biomass over the time interval. Here we report net photosynthesis measurements made throughout the last summer of the period, which suggest that the primary impetus for this large growth response was an equivalent enhancement of the net photosynthetic rates of the CO2©enriched trees. sour orange/Citrus aurantium ÃÃKEYWORDS: GROWTH, OPEN©TOP CHAMBERS, PHOTOSYNTHESIS, TREESÄÄ Ã Ã347Ä Ä° `  à ÃIdso, S.B., B.A. Kimball, and M.G. Anderson.Ä Ä 1985. Atmospheric CO2 Enrichment of Water Hyacinths: Effects on Transpiration and Water Use Efficiency. ÃÃWater Resources Research 21:1787©1790.ÄÄ Open©top clear plastic wall chambers enclosing pairs of sunken metal stock tanks, one of each pair of which contained a full cover of water hyacinths, were maintained out©of©doors at Phoenix, Arizona for several weeks during the summer of 1984. One of these chambers represented ambient conditions, while the other three were continuously enriched with carbon dioxide to approximate target concentrations of 500, 650, and 900 ppm. During a 4©week period when plant growth was at its maximum, water hyacinth biomass production increased by 36% for a 300©600 ppm doubling of the atmospheric CO2 content, while water use efficiency, or the biomass produced per unit of water transpired, actually doubled. These results are similar 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. water hyacinth/Eichhornia crassipes ÃÃKEYWORDS: AQUATIC PLANTS, GROWTH, OPEN©TOP CHAMBERS, TRANSPIRATION, WUEÄÄ Ã Ã348Ä Ä° `  à ÃIdso, S.B., B.A. Kimball, and M.G. Anderson.Ä Ä 1986. Foliage Temperature Increases in Water Hyacinth Caused by Atmospheric CO2 Enrichment. ÃÃArchives for Meteorology, Geophysics and Bioclimatology Ser. B 36:365©370.ÄÄ 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. water hyacinth/Eichhornia crassipes ÃÃKEYWORDS: AQUATIC PLANTS, OPEN©TOP CHAMBERS, TEMPERATURE, TRANSPIRATIONÄÄ Ã Ã349Ä Ä° `  à ÃIdso, S.B., B.A. Kimball, M.G. Anderson, and J.R. Mauney.Ä Ä 1987. Effects of Atmospheric CO2 Enrichment on Plant Growth: the Interactive Role of Air Temperature. ÃÃAgriculture, Ecosystems and Environment 20:1©10.ÄÄ 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 3À$ÀC 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 ÃÃreduceÄÄ plant growth at relatively cold air temperatures, i.e. below a daily mean air temperature of approximately 18.5À$ÀC. 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. carrot/Daucus carota/radish/Raphanus sativus/water hyacinth/Eichhornia crassipes/water fern/Azolla pinnata ÃÃKEYWORDS: AQUATIC PLANTS, CROPS, GROWTH, OPEN©TOP CHAMBERS, TEMPERATUREÄÄ Ã Ã350Ä Ä° `  à ÃIdso, S.B., B.A. Kimball, M.G. Anderson, and S.R. Szarek.Ä Ä 1986. Growth Response of a Succulent Plant, ÃÃAgave vilmorinianaÄÄ, to Elevated CO2. ÃÃPlant Physiology 80:796©797.ÄÄ Large (about 200 grams dry weight) and small (about 5 grams dry weight) specimens of the leaf succulent ÃÃAgave vilmorinianaÄÄ Berger were grown outdoors at Phoenix, Arizona. Potted plants were maintained in open©top chambers constructed with clear, plastic wall material. Four CO2 concentrations of 350, 560, 675, and 885 microliters per liter were used during two growth periods and two water treatments. Small and large plants were grown for 6 months, while a few large plants were grown for 1 year. Wet©treatment plants received water twice weekly, whereas dry©treatment plants received slightly more water than they would under natural conditions. Plant growth rates in all treatments were significantly different between small and large specimens, but not between 6 month and 1 year large plants. Only the dry©treatment plants exhibited statistically different growth rates between the CO2 treatments. This productivity response was equivalent to a 28% and 3©fold increase when mathematically interpolated between CO2 concentrations of 300 and 600 microliters per liter for large and small plants, respectively. Agave vilmoriniana ÃÃKEYWORDS: CAM, GROWTH, GROWTH ANALYSIS, OPEN©TOP CHAMBERS, WATER STRESSÄÄ Ã Ã351Ä Ä° `  à ÃIdso, S.B., B.A. Kimball, and J.R. Mauney.Ä Ä 1987. Atmospheric Carbon Dioxide Enrichment Effects on Cotton Midday Foliage Temperature: Implications for Plant Water Use and Crop Yield. ÃÃAgronomy Journal 79:667©672.ÄÄ In an experiment designed to determine the likely consequences of the steadily rising carbon dioxide (CO2) concentration of Earth's atmosphere for the foliage temperature, water use, and yield of cotton (ÃÃGossypium hirsutumÄÄ L. var. Deltapine©61) plants, cotton was grown out©of©doors at Phoenix, AZ, in open©top, clear©polyethylene©wall, CO2©enrichment chambers for three summers under mean daylight CO2 concentrations of 340, 500 and 640 umol CO2/mol air on an Avondale clay loam soil [fine©loamy, mixed (calcareous), hyperthermic Anthropic Torrifluvent]. Infrared thermometer measurements of the cotton 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 1.1À$ÀC for well©watered cotton at Phoenix in the summer. This temperature increase was predicted to produce a 9% reduction in per©unit©leaf©area plant transpiration rate and an 85% increase in crop biomass production, which 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 [ÃÃEichhornia cassipesÄÄ (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. cotton/Gossypium hirsutum ÃÃKEYWORDS: CROPS, OPEN©TOP CHAMBERS, TEMPERATURE, TRANSPIRATION, VPD, WUEÄÄ Ã Ã352Ä Ä° `  à ÃIdso, S.B., B.A. Kimball, and J.R. Mauney.Ä Ä 1988. Effects of Atmospheric CO2 Enrichment on Root:Shoot Ratios of Carrots, Radish, Cotton and Soybean. ÃÃAgriculture, Ecosystems and Environment 22:293©299.ÄÄ 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. soybean/Glycine max/cotton/Gossypium hirsutum/radish/Raphanus sativus/carrot/Daucus carota ÃÃKEYWORDS: ALLOCATION, CROPS, GROWTH, OPEN©TOP CHAMBERS, ROOT:SHOOT RATIOÄÄ Ã Ã353Ä Ä° `  à ÃIdso, S.B., B.A. Kimball, and J.R. Mauney.Ä Ä 1988. Atmospheric CO2 Enrichment and Plant Dry Matter Content. ÃÃAgricultural and Forest Meteorology 43:171©181.ÄÄ Fresh and dry plant weights were measured throughout a number of different CO2 enrichment experiments with six terrestrial plants and two aquatic species. Similar data were also extracted from the literature for 18 additional plants. In general, CO2 enrichment had little effect on plant percentage dry matter content, except under conditions conducive to starch accumulation in leaves, and then it caused an increase in percentage dry matter content. carrot/Daucus carota/cotton/Gossypium hirsutum/radish/Raphanus sativus/soybean/Glycine max/water fern/Azolla pinnata/water hyacinth/Eichhornia crassipes/Agave vilmoriniana/tomato/Lycopersicon esculentum ÃÃKEYWORDS: DRY MATTER CONTENT, OPEN©TOP CHAMBERS, REVIEWÄÄ Ã Ã354Ä Ä° `  à ÃIsrael, D.W., T.W. Rufty Jr., and J.D. Cure.Ä Ä 1990. Nitrogen and Phosphorus Nutritional Interactions in a CO2 Enriched Environment. ÃÃJournal of Plant Nutrition 13:1419©1433.ÄÄ Nonnodulated soybean plants (ÃÃGlycine maxÄÄ [L.] Merr. 'Lee') were supplied with nutrient solutions containing growth limiting concentrations of N or P to examine effects on N© and P© uptake efficiencies (mg nutrient accumulated/gdw root) and utilization efficiencies in dry matter production (gdw2/mg nutrient). Nutritional treatments were imposed in aerial environments containing either 350 or 700 uL/L atmospheric CO2 to determine whether the nutrient interactions were modified when growth rates were altered. Nutrient©stress treatments decreased growth and N© and P© uptake and utilization efficiencies at 27 days after transplanting (DAT) and seed yield at maturity (98 DAT). Atmospheric CO2 enrichment increased growth and N© and P©utilization efficiencies at 27 DAT and seed yield in all nutritional treatments and did not affect N© and P©uptake efficiencies at 27 DAT. Parameter responses to nutrient stress at 27 DAT were not altered by atmospheric CO2 enrichment and vice versa. Nutrient©stress treatments lowered the relative seed yield response to atmospheric CO2 enrichment. soybean/Glycine max ÃÃKEYWORDS: ALLOCATION, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH, NITROGEN, NUTRITION, PHOSPHORUS, YIELDÄÄ Ã Ã355Ä Ä° `  à ÃIto, T.Ä Ä 1989. More Intensive Production of Lettuce under Artificially Controlled Conditions. ÃÃActa Horticulturae 260:381©389.ÄÄ lettuce/Lactuca sativa ÃÃKEYWORDS: COMMERCIAL USE OF CO2, HORTICULTURAL CROPSÄÄ Ã Ã356Ä Ä° `  à ÃJansen, C.M., S. Pot, and H. Lambers.Ä Ä 1986. The Influence of CO2 Enrichment of the Atmosphere and NaCl on Growth and Metabolism of ÃÃUrtica dioicaÄÄ L. ÃÃIN: Biological Control of Photosynthesis (R. Marcelle, H. Clijsters, and M. Van Poucke, eds.), Martinus Nijhoff Publishers, Dordrecht, The Netherlands, pp. 143©146.ÄÄ ÃÃUrtica dioicaÄÄ plants were grown at 0 and 25 mM NaCl at two concentrations to determine the effect of CO2 enrichment on their response to NaCl. Their relative growth rate was stimulated by CO2 enrichment, which can be explained by their enhanced photosynthetic rate. The relative growth rate was reduced by NaCl at both CO2 concentrations. This reduction was associated with a reduction of their photosynthetic rate. The leaf area ratio was negatively correlated with the photosynthetic rate and counteracted both the response to CO2 enrichment and to NaCl. Urtica dioica ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CONTROLLED ENVIRONMENT CHAMBERS, GROWTH ANALYSIS, RESPIRATION, SALT STRESSÄÄ Ã Ã357Ä Ä° `  à ÃJarvis, P.G.Ä Ä 1989. Atmospheric Carbon Dioxide and Forests. ÃÃPhilosophical Transactions of the Royal Society, London (Series B) 324:369©392.ÄÄ Knowledge about the effects of the rise in atmospheric CO2 concentration on trees and forest is assessed and, the converse, the possible impact of forests on the atmospheric CO2 concentration is discussed. At the cellular scale, much is known about the role of CO2 as a substrate in photosynthesis, but only little about its role as an activator and regulator. At the leaf scale, the response of CO2 assimilation to CO2 concentration has been described often and is well represented by biochemically based models, but there is inadequate information to parameterize the models of CO2©acclimated leaves. Growth and partitioning to the roots of seedlings and young trees generally increases in response to a doubling in atmospheric CO2 concentration. Experimental results are very variable, because of the differing length of the experiments, the artificial conditions and the artefactual constraints. At larger scales, direct measurements of responses to increase in atmospheric CO2 are impractical but models of canopy processes suggest that significant increases in CO2 assimilation will result from the rise in atmospheric concentration. Inferences from the increase in amplitude of the seasonal oscillation in the global atmospheric CO2 concentration at different latitudes suggest that forest is having a significant impact on the global atmospheric concentration, but it seems unlikely that expansion of the forest resource could effectively reduce the increase in atmospheric CO2. ÃÃKEYWORDS: CARBON SEQUESTERING, CO2 SEASONAL FLUX, FOREST, LEAF PHOTOSYNTHESIS, MODELING, PHOTOSYNTHETIC ACCLIMATION, REVIEW, TREESÄÄ Ã Ã358Ä Ä° `  à ÃJiao, J.Ä Ä 1989. Predicting the Growth Response of Greenhouse Roses to Aerial Environments Based on Carbon Dioxide Exchange Studies. ÃÃDoctoral Dissertation, University of Guelph, Canada, Dissertation Abstracts Vol. 50:04©B, p.1187ÄÄ. The influence of aerial environment (i.e. irradiance, CO2 concentration, and temperature) on net CO2 exchange of single©stemmed 'Samantha' roses at different stages of flowering shoot development was studied. Photosynthesis and photorespiration in leaves of different ages were similar, except in the young expanding leaves, which had lower net assimilation rates due to their lower leaf conductance and carboxylation efficiency. Long©term CO2 enrichment did not reduce photosynthetic efficiency. Leaf photosynthesis was saturated at 500 umol/m2/s photosynthetically active radiation (PAR). At saturation irradiance and ambient CO2 concentration, photosynthesis and photorespiration of mature leaves were insensitive to temperature change from 15 to 30À$ÀC. Whole plant net photosynthetic rates were similar on a leaf area basis at different stages of shoot development. Whole plants had higher saturation irradiance (1000 umol/m2/s) but lower net photosynthetic rates than those of single leaves due to mutual shading and respiration of sink organs. Second©order polynomial functions were used to predict whole plant net photosynthesis at various aerial environments. Irradiance, CO2 concentration, and temperature attributed 70%, 20%, and 5%, respectively, to the total variance explained by the model (R2=0.86). The predicted optimal temperatures for whole plant net photosynthesis increased from 19 to 25À$ÀC with increasing irradiance and CO2 concentration. The Arrhenius equation described dark respiration temperature response well. Although night respiration increased with day©time carbon (C) gain, plant daily growth was still proportional to day©time CO2 assimilation. A whole plant daily growth model was developed by combining a dark respiration model with a day©time C gain model. The use of net CO2 exchange as a nondestructive estimation of biomass production under various irradiance, CO2 concentration, and temperature conditions provided physiological basis of environmental control of plant growth and productivity. The data and models presented can be served as a guideline for setting and controlling the greenhouse environment for rose production. rose/Rosa hybrida ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CARBOXYLATION EFFICIENCY, COMMERCIAL USE OF CO2, FLOWER PRODUCTION, GREENHOUSE, HORTICULTURAL CROPS, LEAF PHOTOSYNTHESIS, LIGHT, MODELING, RESPIRATION, TEMPERATUREÄÄ Ã Ã359Ä Ä° `  à ÃJiao, J., M.J. Tsujita, and B. Grodzinski.Ä Ä 1991. Influence of Temperature on Net CO2 Exchange in Roses. ÃÃCanadian Journal of Plant Science 71:235©243.ÄÄ The effect of temperature on net CO2 exchange of source and sink tissues of the flowering shoots and of whole plants was examined using single©stemmed Samantha roses. At all stages of shoot development, the optimal temperature range for whole©plant carbon (C) gain at saturating irradiance and ambient CO2 level was between 20À$À and 25À$ÀC, narrower than the temperature range for optimal leaf net photosynthesis. Dark respiration increased more dramatically than photosynthesis with temperatures between 15À$À and 35À$ÀC. At 25À$ÀC, C loss due to respiration from the flower bud at colour bud stage accounted for 45% of the C loss of the flowering shoot. At low irradiance levels (e.g. 200 umol/m2/s) whole©plant net photosynthesis was greater at 16À$À than at 22À$ÀC because of a greater reduction in respiration. Lowering the night temperature from 27À$À to 17À$ÀC also increased daily C gain due to a reduction in the C lost at night. Whole©plant net photosynthesis of plants grown and measured at enriched (1000 +/© 100 uL/L) CO2 was greater than that of plants grown and measured at ambient (350 +/© 50 uL/L) level at temperatures between 15À$À and 35À$ÀC. Furthermore, the optimal temperatures for whole©plant net photosynthesis in CO2 enrichment was higher than at ambient CO2 level. rose/Rosa hybrida ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CARBON BUDGET, GREENHOUSE, LIGHT, MODELING, RESPIRATION, SOURCE©SINK BALANCE, TEMPERATUREÄÄ Ã Ã360Ä Ä° `  à ÃJiao, J., M.J. Tsujita, and B. Grodzinski.Ä Ä 1991. Influence of Radiation and CO2 Enrichment on Whole Plant Net CO2 Exchange in Roses. ÃÃCanadian Journal of Plant Science 71:245©252.ÄÄ At three stages of flowering shoot development, varying the irradiance and CO2 levels had a similar effect on the whole©plant net CO2 exchange rate (NCER) of Samantha rose plants. At 22À$ÀC, the NCER was saturated at 1000 umol/m2/s photosynthetically active radiation (PAR). The duration of the light period was also important in determining daily carbon (C) gain. When roses were exposed to a constant daily radiant energy dose of 17.6 umol/m2 provided either as a 12©h irradiation interval 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 irradiation at the lower photon flux density retained 80% more C. Under saturating irradiance, the net photosynthetic rate at an enriched (1000 uL/L) CO2 level was almost double that at ambient (350 uL/L) CO2. However, plants grown at ambient and enriched CO2 levels had similar whole©plant NCERs when compared at the same assay CO2 level. Under CO2 enrichment the flower stem was longer and thicker but the flower bud size at harvest was not significantly different to that of roses grown at the ambient CO2 level. rose/Rosa hybrida ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CARBON BUDGET, GREENHOUSE, LIGHT, TEMPERATUREÄÄ Ã Ã361Ä Ä° `  à ÃJiao, J., M.J. Tsujita, and B. Grodzinski.Ä Ä 1991. Optimizing Aerial Environments for Greenhouse Rose Production Utilizing Whole©plant Net CO2 Exchange. ÃÃCanadian Journal of Plant Science 71:253©261.ÄÄ A daily growth model was developed for Samantha roses based on nondestructive measurements of whole©plant net CO2 exchange rate (NCER) under various aerial environmental conditions. Irradiance, CO2 concentration, and temperature accounted for 70, 20, and 5%, respectively, of the variance in whole©plant net photosynthesis explainable by a second©order polynomial model (R2=0.86). The predicted optimal temperatures for whole©plant net photosynthesis increased from 19 to 24À$ÀC with increasing irradiance from 100 to 1200 umol/m2/s and CO2 concentration from 350 to 1500 uL/L. Dark respiration rate increased exponentially with temperature and could be predicted by the Arrhenius equation. Even though respiratory carbon (C) loss at night increased linearly with daytime C gain, daily C gain (delta C) was still proportional to daytime net photosynthesis. The relative contribution of irradiance (100©1200 umol/m2/s), day length (8©16 h), CO2 concentration (350©1500 uL/L), day temperature (15©30À$ÀC), and night temperature (15©25À$ÀC) to plant daily growth was 64, 31, 4, 0.3, and 0.7%, respectively. rose/Rosa hybrida ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CARBON BUDGET, DAYLENGTH, ENVIRONMENTAL INTERACTIONS, FLOWER PRODUCTION, GREENHOUSE, GROWTH MODEL, HORTICULTURAL CROPS, LIGHT, MODELING, RESPIRATION, TEMPERATUREÄÄ Ã Ã362Ä Ä° `  à ÃJohnson, H.B., H.W. Polley, and H.S. Mayeux.Ä Ä 1993. Increasing CO2 and Plant©plant Interactions: Effects on Natural Vegetation. ÃÃVegetatio 104/105:157©170.ÄÄ Plant species and functional groups of species show marked differences in photosynthesis and growth in relation to rising 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 from 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% as CO2 levels approached current ambient. The proposition that acclimation to rising CO2 will largely negate the fertilization effect of higher CO2 levels on C3's is not supported. No signs of photosynthetic acclimation were evident for ÃÃAvena sativa, Prosopis glandulosaÄÄ, and ÃÃSchizachyrium scopariumÄÄ plants grown in subambient CO2. The effects of changing CO2 levels on vegetation since the last glaciation are thought to have been at least as great, if not greater, than those which should be expected for a doubling of current CO2 levels. Atmospheric CO2 concentrations below 200 ppm are thought to have been instrumental in the rise of the C4 grasslands of North America and other extensive C4 grasslands and savannas of the world. Dramatic invasion of these areas by woody C3 species are accompanying the historical increase in atmospheric CO2 concentration now in progress. Prosopis glandulosa/mesquite/Schizachyrium scoparium/little bluestem/Brassica kaber/field mustard/Avena sativa/oat/Cenchrus incertus/Paspalum setaceum/Panicum cappillare/Digitaria ciliaris/Eragrostis spectabilis/Cyperus globulosus/Mollugo verticillata/Sporobolus neglectus/Euphorbia prostrata/Setaria sp./Echinochloa crus©galli/Amaranthus sp./Croton glandulosa/Verbena hastata/Verbena halei/Oenothera sp./Ratibida columnaris/Ambrosia artemisiifolia/Lesquerella sp./Gaillardia pulchella/Gaura sp./Solanum sp./Gutierrezia dracunculoides/Rudbeckia hirta/Commelina erecta/Panicum angustifolium/Croton capitatum/Monarda punctata/Croton monanthogynus/Oxalis dillenii ÃÃKEYWORDS: C3, C4, GRADIENT EXPOSURE TUNNEL, GRASSES, PLANT©PLANT INTERACTIONS, PRE©INDUSTRIAL CO2 CONCENTRATION, SPECIES COMPETITION, TREES, WEEDSÄÄ Ã Ã363Ä Ä° `  à ÃJohnson, R.H., and D.E. Lincoln.Ä Ä 1990. Sagebrush and Grasshopper Responses to Atmospheric Carbon Dioxide Concentration. ÃÃOecologia 84:103©110.ÄÄ Seed© and clonally©propagated plants of Big Sagebrush (ÃÃArtemisia tridentataÄÄ var. ÃÃtridentataÄÄ) were grown under atmospheric carbon dioxide regimes of 270, 350 and 650 uL/L and fed to ÃÃMelanoplus differentialisÄÄ and ÃÃM. sanguinipesÄÄ grasshoppers. Total shrub biomass significantly increased as carbon dioxide levels increased, as did the weight and area of individual leaves. Plants grown from seed collected in a single population exhibited a 3©5 fold variation in the concentration of leaf volatile mono© and sesquiterpenes, guaianolide sesquiterpene lactones, coumarins and flavones within each CO2 treatment. The concentration of leaf allelochemicals did not differ significantly among CO2 treatments for these seed©propagated plants. Further, when genotypic variation was controlled by vegetative propagation, allelochemical concentrations also did not differ among carbon dioxide treatments. On the other hand, overall leaf nitrogen concentration declined significantly with elevated CO2. Carbon accumulation was seen to dilute leaf nitrogen as the balance of leaf carbon versus nitrogen progressively increased as CO2 growth concentration increased. Grasshopper feeding was highest on sagebrush leaves grown under 270 and 650 uL/L CO2, but varied widely within treatments. Leaf nitrogen concentration was an important positive factor in grasshopper relative growth but had no overall effect on consumption. Potential compensatory consumption by these generalist grasshoppers was apparently limited by the sagebrush allelochemicals. Insects with a greater ability to feed on chemically defended host plants under carbon dioxide enrichment may ultimately consume leaves with a lower nitrogen concentration but the same concentration of allelochemicals. Compensatory feeding may potentially increase the amount of dietary allelochemicals ingested for each unit of nitrogen consumed. Artemisia tridentata/sagebrush ÃÃKEYWORDS: ALLELOCHEMICALS, CONTROLLED ENVIRONMENT CHAMBERS, HERBIVORY, INSECTS, MELANOPLUS DIFFERENTIALIS, MELANOPLUS SANGUINIPES, NITROGENÄÄ Ã Ã364Ä Ä° `  à ÃJohnson, R.H., and D.E. Lincoln.Ä Ä 1991. Sagebrush Carbon Allocation Patterns and Grasshopper Nutrition: The Influence of CO2 Enrichment and Soil Mineral Limitation. ÃÃOecologia 87:127©134.ÄÄ ÃÃArtemisia tridentataÄÄ 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. sagebrush/Artemisia tridentata ÃÃKEYWORDS: ALLELOCHEMICALS, CARBOHYDRATES, CARBON:NITROGEN RATIO, CONTROLLED ENVIRONMENT CHAMBERS, HERBIVORY, INSECTS, LEAF PHOTOSYNTHESIS, NITROGEN, NUTRITION, ROOT:SHOOT RATIO, TERPENESÄÄ Ã Ã365Ä Ä° `  à ÃJolliffe, P.A., and D.L. Ehret.Ä Ä 1985. Growth of Bean Plants at Elevated Carbon Dioxide Concentrations. ÃÃCanadian Journal of Botany 63:2021©2025.ÄÄ Plants of ÃÃPhaseolus vulgarisÄÄ 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. bean/Phaseolus vulgaris ÃÃKEYWORDS: CONTROLLED ENVIRONMENT CHAMBERS, GROWTH ANALYSIS, YIELDÄÄ Ã Ã366Ä Ä° `  à ÃJones, J.W., E. Dayan, H. van Keulen, and H. Challa.Ä Ä 1989. Modeling Tomato Growth for Optimizing Greenhouse Temperatures and Carbon Dioxide Concentrations. ÃÃActa Horticulturae 248:285©294.ÄÄ 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. tomato/Lycopersicon esculentum ÃÃKEYWORDS: CANOPY PHOTOSYNTHESIS, CO2 MEASUREMENT AND CONTROL, COMMERCIAL USE OF CO2, GREENHOUSE, GROWTH STAGES, HORTICULTURAL CROPS, MODELING, SPAR UNITS, TEMPERATURE, YIELDÄÄ Ã Ã367Ä Ä° `  à ÃJones, P., B.L. Roy, and J.W. Jones.Ä Ä 1989. Coupling Expert Systems and Models for the Real©time Control of Plant Environments. ÃÃActa Horticulturae 248:445©452.ÄÄ 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. ÃÃKEYWORDS: CO2 MEASUREMENT AND CONT