Impairment of C4 photosynthesis by drought is exacerbated by limiting nitrogen and ameliorated by elevated CO2 in maize
Journal of Experimental Botany, 62 (9):
3235--3246 (May 1, 2011)DOI: 10.1093/jxb/err056
Abstract
Predictions of future ecosystem function and food supply from staple C4 crops, such as maize, depend on elucidation of the mechanisms by which environmental change and growing conditions interact to determine future plant performance. To test the interactive effects of elevated CO2, drought, and nitrogen (N) supply on net photosynthetic CO2 uptake (A) in the world's most important C4 crop, maize (Zea mays) was grown at ambient CO2 (∼385 ppm) and elevated CO2 (550 ppm) with either high N supply (168 kg N ha−1 fertilizer) or limiting N (no fertilizer) at a site in the US Corn Belt. A mid-season drought was not sufficiently severe to reduce yields, but caused significant physiological stress, with reductions in stomatal conductance (up to 57\%), A (up to 44\%), and the in vivo capacity of phosphoenolpyruvate carboxylase (up to 58\%). There was no stimulation of A by elevated CO2 when water availability was high, irrespective of N availability. Elevated CO2 delayed and relieved both stomatal and non-stomatal limitations to A during the drought. Limiting N supply exacerbated stomatal and non-stomatal limitation to A during drought. However, the effects of limiting N and elevated CO2 were additive, so amelioration of stress by elevated CO2 did not differ in magnitude between high N and limiting N supply. These findings provide new understanding of the limitations to C4 photosynthesis that will occur under future field conditions of the primary region of maize production in the world.