Effect of temperature under different evaporative demand conditions on maize leaf expansion

Leaf area affects light interception, carbon assimilation and plant growth. How maize leaf development and expansion is affected by temperature under different evaporative demand conditions is not well understood. Effects of three temperatures (21, 27 and 32 °C) under high and low evaporative demand conditions were tested in growth chambers. Leaf expansion rate (LER), leaf appearance rate (LAR), leaf number, plant height, photosynthesis (A), net assimilation rate (NAR), stomatal conductance (gs), and transpiration (E) increased with increasing temperature under low evaporative demand environments. Under high evaporative demand, while there was an increase with temperature until 27 °C, at 32 °C there was a decrease in LER, plant height, A, NAR, gs, and E. However, the variation in the rate of leaf appearance appears to be linked to temperature but not VPD. The development of stomata and epidermal cells were affected by VPD with large size stomata and more epidermal cells under low VPD. The differential responses of LER to low and high evaporative demands could be attributed to changes in expression of Expansin A2, A4, and B1 genes and XTH23. The significant effect of temperature and VPD on the expression of vacuolar H + pyrophosphatase and teosinte branched gene was detected. Overall, we found a negative effect of high VPD due to high evaporative demand for maize leaf expansion and development.