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First published online January 11, 2006; 10.1104/pp.105.073957 Plant Physiology 140:779-790 (2006) © 2006 American Society of Plant Biologists OPEN ACCESS ARTICLE
Photosynthesis, Productivity, and Yield of Maize Are Not Affected by Open-Air Elevation of CO2 Concentration in the Absence of Drought1,[OA]Institute for Genomic Biology (A.D.B.L., E.A.A., D.R.O., S.P.L.), Department of Plant Biology (A.D.B.L., E.A.A., D.R.O., S.P.L.), and Department of Crop Sciences (M.U., S.L.N., A.R., S.P.L.), University of Illinois at Urbana-Champaign, Urbana, Illinois 61801; Photosynthesis Research Unit, United States Department of Agriculture Agricultural Research Service, Urbana, Illinois 61801 (E.A.A., D.R.O.); and Environmental Sciences Department, Brookhaven National Laboratory, Upton, New York 11973 (A.R.)
While increasing temperatures and altered soil moisture arising from climate change in the next 50 years are projected to decrease yield of food crops, elevated CO2 concentration ([CO2]) is predicted to enhance yield and offset these detrimental factors. However, C4 photosynthesis is usually saturated at current [CO2] and theoretically should not be stimulated under elevated [CO2]. Nevertheless, some controlled environment studies have reported direct stimulation of C4 photosynthesis and productivity, as well as physiological acclimation, under elevated [CO2]. To test if these effects occur in the open air and within the Corn Belt, maize (Zea mays) was grown in ambient [CO2] (376 µmol mol–1) and elevated [CO2] (550 µmol mol–1) using Free-Air Concentration Enrichment technology. The 2004 season had ideal growing conditions in which the crop did not experience water stress. In the absence of water stress, growth at elevated [CO2] did not stimulate photosynthesis, biomass, or yield. Nor was there any CO2 effect on the activity of key photosynthetic enzymes, or metabolic markers of carbon and nitrogen status. Stomatal conductance was lower (–34%) and soil moisture was higher (up to 31%), consistent with reduced crop water use. The results provide unique field evidence that photosynthesis and production of maize may be unaffected by rising [CO2] in the absence of drought. This suggests that rising [CO2] may not provide the full dividend to North American maize production anticipated in projections of future global food supply.
1 This work was supported by the Illinois Council for Food and Agricultural Research, by the Archer Daniels Midland Company, by the International Arid Land Consortium, and by the U.S. Department of Agriculture Agricultural Research Service. A.R. was supported by the U.S. Department of Energy Office of Science (contract no. DE–AC02–98CH10886 to Brookhaven National Laboratory and a Laboratory Directed Research and Development award). The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Andrew D.B. Leakey (leakey{at}life.uiuc.edu). [OA] Open Access articles can be viewed online without a subscription. Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.105.073957. * Corresponding author; e-mail leakey{at}life.uiuc.edu; fax 217–265–6800. Received November 8, 2005; returned for revision December 20, 2005; accepted December 21, 2005. Related articles in Plant Physiol.:
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