IDENTIFYING AND MANIPULATING DETERMINANTS OF PHOTOSYNTHATE PRODUCTION AND PARTITIONING
Location: Global Change and Photosynthesis Research Unit
Title: Effects of elevated temperature and CO2 on gas exchange and chlorophyll fluorescence in soybean (Glycine max (L.) Merr.) and maize (Zea mays) grown under open-air field conditions
Submitted to: Plant Biology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: June 2, 2011
Publication Date: August 6, 2011
Citation: Ruiz Vera, U.M., Siebers, M., Rosenthal, D.M., Gray, S., Ort, D.R., Bernacchi, C.J. 2011. Effects of elevated temperature and CO2 on gas exchange and chlorophyll fluorescence in soybean (Glycine max (L.) Merr.) and maize (Zea mays) grown under open-air field conditions [abstract]. American Society of Plant Biologists. Paper No. M2102.
By mid century, [CO2] is predicted to increase above 550 ppm and temperature (T) by 3.5
degrees C. Higher T can have different effects on photosynthesis depending on plant specific T optimum. An increase in [CO2] is expected to raise photosynthesis in C3 but not in C4 plants. This experiment analyzes the combined effects of higher T and [CO2] under typical Midwestern growing conditions, on soybean and maize physiology to understand the effects on photosynthesis and underlying mechanisms. We predicted that soybean in elevated [CO2] and T will provide the highest productivity while maize productivity will not change in elevated [CO2] but decrease in elevated T. Measurements were collected in 2009 and 2010, at the SoyFACE facility, as part of T by Free Air CO2 Enrichment experiment. Plants were grown in a replicated complete factorial experimental design (n=4) with ambient, elevated temperature (eT), elevated [CO2] (eC) and combined (eT+eC) plots. Photosynthesis (A), conductance gs and quantum efficiency of photosystem II were measured via an open gas exchange system coupled with a chlorophyll fluorometer, at 2 hour intervals on seven days through the growing season. In soybean when averaged across the growing season, eT+eC increased A by 13%. gs was reduced in eC by 34%, in eT by 26% and in eT+eC by 46%. eT reduced quantum efficiency of photosystem II by 6%. For maize, there were no CO2 effects on A but eT reduced A by 6% over the growing season. gs gs was reduced by 33% in eC, 5% in eT, and 24% in eT+eC. quantum efficiency of photosystem II was reduced 8% in eT and 7% in eT+eC while it was increased 2% in eC. Our data suggest that soybean and maize physiology are negatively impacted by growth in eT, but this loss in productivity is not mitigated by eC in maize.