Effects of Temperature and Evaporative Demand on Maize Leaf Area Development.

Vapor pressure deficit (VPD), combines the effect of temperature and RH, has an effect of leaf expansion of the plants. It modifies processes directly related to leaf development both at physiological and molecular level. The objective of this study is to understand the maize leaf development, growth, and expression of genes related to leaf development to VPD and its interaction with temperature under high and low evaporative demand conditions. Controlled environment studies were conducted with potted maize plants by subjecting them to three different temperatures: 21, 27 and 32°C at low (40 to 45%) and high (80 to 85%) RH levels approximately for 36 days. The temperature and evaporative demand had a significant effect on leaf expansion with a highest mean rate of leaf area expansion observed at 27°C/low humidity. The effect of temperature on maize photosynthesis, transpiration, and biomass was significant under low and high evaporative demand conditions. The impact of temperature on the phyllochron index and plant height was observed but no significant interactions with evaporative demand were detected. Changes in evaporative demand due to low and high RH modified the development of stomata and stomatal density, with larger and fewer stomata at low evaporative demand compared to high evaporative demand conditions. Maize expansin, aquaporin, teosinte branched (TB1) and vacuolar H+-pyro phosphatase genes expression was quantified. Expansin and aquaporin genes were up and down regulated, respectively, with a substantial influence of VPD. In summary, this study suggests that the effects of temperature and evaporative demand on leaf expansion are important factors to consider when modeling leaf development in maize.