Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only
Publication Acceptance Date: July 30, 2003
Publication Date: December 20, 2003
Citation: LEAKEY, A.D., BERNACCHI, C.J., LONG, S.P., ORT, D.R. WILL PHOTOSYNTHESIS OF MAIZE (ZEA MAYS) IN THE U.S. CORN BELT INCREASE IN FUTURE [CO2] RICH ATMOSPHERES? AN ANALYSIS OF DIURNAL COURSES OF CO2 UPTAKE UNDER FREE-AIR CONCENTRATION ENRICHMENT (FACE). PLANT PHYSIOLOGY SUPPLEMENT. 2003. Abstract. p. 45. Technical Abstract: The C4 grass Z. mays is the third most important food crop globally in terms of production and demand is predicted to increase 45 percent from 1997 to 2020. Nonetheless, the effects of elevated [CO2] upon C4 plants, and Z. mays specifically, are not sufficiently understood to allow accurate predictions of future crop production. FACE technology allows experimental treatments to be imposed upon a complete soil-plant-atmosphere continuum while avoiding the effects of experimental enclosures on plant microclimates. A rain fed, field experiment utilizing FACE technology in the primary area of global Z. mays production (U.S. Corn Belt) was undertaken to determine the effects of elevated [CO2] on Z. mays, with direct relevance to future agricultural productivity. Enhancement of A at elevated [CO2] primarily results from improved plant water status when water stress is limiting under ambient [CO2]. Given the relatively high rainfall of Central Illinois and the absence of irrigation in typical agricultural practice of the region, it was predicted that growth at elevated [CO2] would not increase A. The diurnal course of leaf level gas exchange of Z. mays grown under ambient and elevated [CO2] was measured for five days spread across the growing season of 2002. Growth at elevated [CO2] episodically resulted in greater A by up to 41 percent (seasonal average 10 percent). Gas exchange data were consistent with elevated [CO2] resulting in: (A) higher ci that maintained saturating [CO2] for Rubisco in the bundle sheath and (B) lower crop water use, preventing shoot water stress which may periodically limit A under ambient conditions. Compared with the meteorological record (1889 - 2002) of nearby Urbana, total rainfall in 2002 was average. This, together with a substantially lower than average variation in rainfall between months, suggests that the crop did not experience atypical water stress during 2002. Therefore, there is potential for a greater future crop biomass and harvestable yield across the U.S. Corn Belt.