Temperature dependence of growth, development, and photosynthesis in maize under elevated CO2

Global atmospheric carbon dioxide concentrations (Ca) are rising. As a consequence, recent climate models have projected that global surface air temperature may increase 1.4–5.8 °C with the doubling of Ca by the end of the century. Because, changes in Ca and temperature are likely to occur concomitantly, it is important to evaluate how the temperature dependence of key physiological processes are affected by rising Ca in major crop plants including maize (Zea mays L.), a globally important grain crop with C4 photosynthetic pathway. We investigated the temperature responses of photosynthesis, growth, and development of maize plants grown at five temperature regimes ranging from 19/13 to 38.5/32.5 °C under current (370 μmol mol−1) and doubled (750 μmol mol−1) Ca throughout the vegetative stages using sunlit controlled environmental chambers in order to test if the temperature dependence of these processes was altered by elevated Ca. Leaf and canopy photosynthetic rates, C4 enzyme activities, leaf appearance rates, above ground biomass accumulation and leaf area were measured. We then applied temperature response functions (e.g., Arrhenius and Beta distribution models) to fit the measured data in order to provide parameter estimates of the temperature dependence for modeling photosynthesis and development at current and elevated Ca in maize. Biomass, leaf area, leaf appearance rate, and photosynthesis measured at growth Ca was not changed in response to CO2 enrichment. Carboxylation efficiency and the activities of C4 enzymes were reduced with CO2 enrichment indicating possible photosynthetic acclimation of the C4 cycle. All measured parameters responded to growth temperatures. Leaf appearance rate and leaf photosynthesis showed curvilinear response with optimal temperatures near 32 and 34 °C, respectively. Total above ground biomass and leaf area were negatively correlated with growth temperature. The dependence of leaf appearance rate, biomass, leaf area, leaf and canopy photosynthesis, and C4 enzyme activities on growth temperatures was comparable between current and elevated Ca. The results of this study suggest that the temperature effects on growth, development, and photosynthesis may remain unchanged in elevated Ca compared with current Ca in maize.