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Title:   Author  item
                                            Kim, Soo Hyungitem
                                            Bae, Hanhongitem
                                            Gitz, Dennisitem
                                            Sicher  Jr, Richarditem
                                            Baker, Jeffreyitem
                                            Timlin, Dennisitem
                                            Reddy, Vangimalla
  Submitted to: BARC Poster Day
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 5/1/2003
                                    Publication  Date: 5/1/2003
                                    Citation: Kim, S., Bae, H., Gitz, D.C., Sicher  Jr, R.C., Baker, J.T., Timlin, D.J., Reddy, V. 2003. Responses of corn (zea mays l.) to elevated co2: from gene expression to whole-plants [abstract]. BARC Poster Day. Paper No. 50.Interpretive Summary:
                                Technical Abstract: Given the importance of corn in global agricultural production, it is imperative to assess how rising CO2 will affect growth, development and yield of corn plants. Studies have shown that C4 plants can accumulate more biomass under elevated CO2, whereas the underlying mechanisms of this response are unclear. Enhanced water use efficiency and photosynthetic nitrogen use efficiency were postulated as possible mechanisms for the positive response of C4 plants to elevated CO2 under water and nitrogen limiting conditions. Photosynthetic, growth and developmental responses of corn plants to elevated CO2 were investigated using molecular, biochemical, and leaf and whole-plant methodologies in order to test the hypothesis that elevated CO2 alters expression of genes, enzyme activities, leaf and whole-plant gas exchange, and biomass accumulation. Corn plants were grown in six naturally lit Soil-Plant-Atmosphere-Research (SPAR) chambers in Beltsville, MD.  These were each assigned randomly to receive either ambient (370 umol mol-1) and elevated (750 umol mol-1) CO2. All chambers were maintained at 31/25 C day/night temperatures. Plants were fertigated four times per day with complete nutrient solution. Leaf and whole-plants gas exchange properties including rates of CO2 assimilation, transpiration, and conductance to water vapor were investigated. Activities of photosynthetic enzymes involved in the C4 cycle were measured during the vegetative stages. Global changes and patterns of gene expression were compared using DNA microarrays. Total carbon and nitrogen content, and biomass accumulation were investigated. The results indicated that elevated CO2 did not alter biomass, leaf area, leaf and whole-plant CO2 assimilation rates, or the measured C4 enzyme activities. Elevated CO2 did result in decreased leaf and whole-plant transpiration rates; reduced conductance to water vapor; increased water use efficiency; and a higher leaf C/N ratio. Leaf photosynthetic acclimation appeared to occur as the carboxylation efficiency decreased under elevated CO2. Several genes were found to show different levels of expression in response to elevated CO2. Our work demonstrates that although no change in biomass accumulation was apparent, corn plants responded to elevated CO2 at various levels from patterns of gene expression to canopy water use efficiency.


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