FUMIGATION, GROSS NITROGEN TRANSFORMATIONS, N-15, NITRATE, RATES, SOIL 1911 Qi, J.E., J.D. Marshall, and K.G. Mattson. 1994. High soil carbon- dioxide concentrations inhibit root respiration of douglas-fir. New 1909 Phytologist 128(3):435-442. Pushnik, J.C., R.S. Demaree, J.L.J. Houpis, W.B. Flory, S.M. Bauer, and P.D. Anderson. 1995. The effect of elevated carbon dioxide on a Total and basal respiration (R(t) and R(b), respectively) of intact and Sierra-Nevadan dominant species: Pinus ponderosa. Journal of undisturbed roots of one-year-old Douglas fir seedlings, Pseudotsuga Biogeography 22(2-3):249-254. menziesii var. glauca [Beissn] France, were measured at experimentally varied soil carbon dioxide concentrations ([CO2]). Use of specially The impact of increasing atmospheric CO2 has not been fully evaluated designed root boxes and a CO2 gas-flow compensating system designed on western coniferous forest species. Two year old seedlings of Pinus around an infrared gas analyzer (IRGA) allowed controlled delivery of ponderosa were grown in environmentally controlled chambers under CO2 to roots and simultaneous measurements of CO2 released by roots. increased CO2 conditions (525 mu L L(-1) and 700 mu L L(-1)) for 6 Root respiration rate responded to each inlet [CO2], independent of months. These trees exhibited morphological, physiological and whether the previous concentration had been higher or lower, within two biochemical alterations when compared to our controls (350 mu L L(- to three hours (paired t test = 0.041, P = 0.622, and n = 13). Total and 1)). Analysis of whole plant biomass distribution has shown no basal respiration rates decreased exponentially as soil [CO2] rose from significant treatment effect to the root to shoot ratios. However, while 130 ppm, well below atmospheric [CO2], to 7015 ppm, a concentration stem diameter and height growth generally increased with elevated CO2, not uncommon in field soils. Analyses of variance (ANOVA) showed needles exhibited an increased overall specific needle mass and a that the effects of soil [CO2] on rates of total and basal root respiration decreased total needle area. Morphological changes at the needle level were statistically significant. Root respiration rates decreased by 4 to 5 included decreased mesophyll to vascular tissue ratio and variations in nmol CO2 g(-1) dry weight of roots s(-1) for every doubling of [CO2] starch storage in chloroplasts. The elevated CO2 increased internal CO2 according to the following equations: In(R(t)) (nmol CO2 g(-1) s(-1)) = concentrations and assimilation of carbon. Biochemical assays revealed 5.24-0.30*ln[CO2] with r = 0.78, P < 0.0001, and n = 70; and ln(R(b)) that ribulose-bis-phosphate carboxylase (RuBPCase) specific activities (nmol CO2 g(-1) s(-1)) = 6.29-0.52*ln[CO2] with r = 0.82, P < 0.0001, increased on per unit area basis with CO2 treatment levels. Sucrose and n = 35. The sensitivity of root respiration to [CO2] suggests that phosphate synthase (SPS) activities exhibited an increase of 55% in the some previous laboratory measurements of root respiration at 700 mu L(-1) treatment. These results indicate that the sink-source atmospheric [CO2], which is 3 to 10-fold lower than [CO2] in field relationships of these trees have shifted carbon allocation toward above soils, overestimated root respiration in the field. Further, the potential ground growth, possibly due to transport limitations. importance of soil [CO2] indicates that it should be accounted for in models of below-ground carbon budgets. KEYWORDS: ATMOSPHERIC CO2, CO2- ENRICHMENT, FORMS, GROWTH, LEAF ANATOMY, PHOTOSYNTHETIC ACCLIMATION, KEYWORDS: CO2- ENRICHMENT, DARK RESPIRATION, EFFLUX, RADIATA, SEEDLINGS, SUCROSE PHOSPHATE SYNTHASE, TREES FIELD, GROWTH, LEAVES, LOLIUM-PERENNE, MAINTENANCE RESPIRATION, PERENNIAL RYEGRASS, SEEDLINGS 1910 Pushnik, J.C., D. Garcia-Ibilcieta, S. Bauer, P.D. Anderson, J. Bell, 1912 and J.L.J. Houpis. 1999. Biochemical responses and altered genetic Rabbinge, R., H.C. Vanlatesteijn, and J. Goudriaan. 1993. Assessing expression patterns in ponderosa pine (Pinus ponderosa Doug ex P. the greenhouse-effect in agriculture. Ciba Foundation Symposia 175:62- Laws) grown under elevated CO2. Water, Air, and Soil Pollution 116(1- 79. 2):413-422. Evidence that concentrations of CO2 and trace gases in the atmosphere Biochemical and gene expression changes in response to elevated have increased is irrefutable. Whether or not these increased atmospheric CO2 were investigated in five maternal half-sibling concentrations will lead to climate changes is still open to debate. Direct breeding families of Ponderosa pine. Seedlings were grown in a common effects of increased CO2 concentrations on physiological processes and garden located at Lawrence Livermore National Laboratory, in open- individual plants have been demonstrated and the consequences for crop topped chambers (OTC) for two years. Chamber atmospheres were growth and production under various circumstances are evaluated with maintained at ambient, ambient + 175 mu L L-1, CO2, or ambient + 350 simulation models. The consequences of CO2 enrichment are mu L L-1CO2. Growth measurements showed significant increases in considerable under optimal growing conditions. However, the majority stem volumes and volume enhancement ratios in three of the five of crops are grown under sub-optimal conditions where the effects of families studied when grown under elevated CO2. Biochemical and gene changes in CO2 are often less. The same holds for the possible indirect expression studies were undertaken to gain a mechanistic understanding effects of environmental changes such as temperature rise. Studies on of these phenotypic responses. Biochemical studies focused on sucrose individual plants under optimal conditions are therefore not sufficient phosphate synthase (SPS) specific activities at increase CO2 levels. for evaluating the effects at a farm, regional, national or supra-national Kinetic evaluations of SPS showed an increase in V-Max. Specific SPS level. Simulation studies help to bridge the gap between the various probes revealed increases in the transcriptional levels of one SPS gene aggregation levels and provide a basis for various studies of policy with exposure to increasing CO2. RT-PCR differential gene displays options at various aggregation levels. showed that overall only a small fraction of visualized gene transcripts responded to elevated CO2 (8-10%). There were also significant KEYWORDS: CARBON DIOXIDE, CO2- ENRICHMENT, GROWTH, differences between the gene expression patterns of the different PHOTOSYNTHESIS, RESPONSES, SOYBEAN LEAVES, YIELD families, some of which correlated with alterations in growth at elevated CO2 levels. 1913 KEYWORDS: ALLOCATION, ANATOMY, CARBON-DIOXIDE Rabha, B.K., and D.C. Uprety. 1998. Effects of elevated CO2 and ENRICHMENT, ENZYMES, LEAVES, METABOLISM, PROTEIN- moisture stress on Brassica juncea. Photosynthetica 35(4):597-602. PHOSPHORYLATION, SEEDLINGS, SUCROSE PHOSPHATE SYNTHASE, TREES The interactive effect of elevated CO2 (EC) and moisture stress (MS) on Brassica juncea cv. Pusa Bold was studied using open- top chambers. The EC markedly increased net photosynthetic rate and internal CO2 1918 concentration and reduced variable and maximal chlorophyll Radoglou, K.M., and P.G. Jarvis. 1992. The effects of co2 enrichment fluorescence. Under MS, EC increased water potential and relative water and nutrient supply on growth- morphology and anatomy of phaseolus- content, and reduced transpiration rate. The greater allocation of biomass vulgaris L seedlings. Annals of Botany 70(3):245-256. to the roots, which serve as a strong sink for assimilated carbon under EC, helped in better root growth. KEYWORDS: AREA, ATMOSPHERIC CARBON-DIOXIDE, FORESTS, LEAF ANATOMY, LEAVES, MINERAL NUTRITION, N,N- KEYWORDS: GROWTH, PHOTOSYNTHESIS, RESPONSES DIMETHYLFORMAMIDE, PHOTOSYNTHESIS, PLANTS, POPLAR CLONES 1914 Raddatz, R.L., and C.F. Shaykewich. 1998. Impact of warm summers 1919 on the actual evapotranspiration from spring wheat grown on the eastern Radoglou, K.M., and P.G. Jarvis. 1993. Effects of atmospheric co2 Canadian prairies. Canadian Journal of Soil Science 78(1):171-179. enrichment on early growth of vivia- faba, a plant with large cotyledons. Plant, Cell and Environment 16(1):93-98. How do warm summers (June-July-August) influence the actual evapotranspiration totals from cropped land sown to spring wheat on the Seedlings of Vicia faba L. were grown in open-top growth chambers at eastern Canadian Prairies? The eastern Prairies is a semi-arid region present (P=350 mumol-1) and at elevated (E=700 mumol mol-1) where over 60% of the land is cultivated. Over a third of the cropped atmospheric CO2 concentration. The effects Of CO2 enrichment on the land is usually sown to spring wheat. A comparison of mean summer first phase of growth after germination were examined over 45d. There temperatures and modelled evapotranspiration, for the years 1988 to were no positive effects Of CO2 enrichment on growth of the seedlings 1996, demonstrated that with the current environmental conditions and during this early phase. No differences were observed in leaf area or in farming practices, warm summers have lower actual evapotranspiration total dry weight. No differences were found in morphology or anatomy totals from spring wheat than cool summers. The average daily actual of the leaves. The numbers of stomatal and epidermal cells, thickness of evapotranspiration rate is generally higher in years