Free-air CO2 enrichment modifies maize quality only under drought stress

International audienceClimate scenarios show that atmospheric CO2 concentrations will continue to increase. As a consequence, more frequent and severe drought periods are expected. Drought will thus modify plant growth. Although maize is a major crop globally, little information is available on how atmospheric and climatic changes will change maize quality. Here, in a field experiment, maize was grown in 2007 and 2008 under ambient (380 ppm) and elevated CO2 (550 ppm) using free-air CO2 enrichment. In 2007, maize was grown under well-watered conditions only. In 2008, we applied a drought stress treatment in which the plants received only half the amount of water of the well-watered treatment. We measured the concentrations of minerals and quality-related traits in aboveground biomass and kernels at the end of each growing season. Results show first the absence of effect of elevated CO2 under well-watered conditions. By contrast, drought stress modified several traits and interactions under elevated CO2. These results support the hypothesis that the C4 plant maize does not react to an increase in atmospheric CO2 as long as no drought stress is prominent. This finding contrasts with the impact of elevated CO2 on C3 plants. Several drought stress effects found in our study will have important implications for food and feed use. However, the effects of drought stress on the traits were less pronounced under elevated CO2 than under ambient CO2 level. Hence, an elevated CO2 concentration mitigates the drought stress impacts on elemental composition and quality traits of maize