Basis of limited-transpiration rate under elevated vapor pressure deficit and high temperature among sweet corn cultivars

Abstract

One plant trait that has been developed in several crop species to increase the effectiveness in water use through the cropping season is limited-transpiration under elevated atmospheric vapor pressure deficit (VPD). This trait allows water conservation early in the season so that there is more soil water available late in the season for sustained physiological activity during seed development. In sweet corn (Zea mays L. saccharata), where the quality of the kernels is important, this trait could prove to be especially beneficial. The background objective of this study was to explore 16 sweet corn cultivars for expression of the limited-transpiration trait. It was found at 32 °C that 13 of the 16 cultivars expressed the trait. It was found in a subset of eight of these cultivars, however, only half retained the limited-transpiration trait at 38 °C. The additional objectives were to explore the hypotheses that expression of the limited-transpiration trait was related to plant hydraulic conductance, and to the abundance of silver-sensitive aquaporins in the leaves. In cultivars that lost expression of the limited-transpiration trait at 38 °C there were large increases in plant hydraulic conductance at 38 °C as compared to 32 °C. Abundance of silver-sensitive aquaporins was related to the transpiration rate under low VPD conditions. That is, those cultivars with more abundant silver-sensitive aquaporins had greater transpiration rates as a result of greater stomatal conductance. These results showed that while expression of the limited-transpiration trait in sweet corn at 32 °C was common, differences in expression of the trait at 38 °C were observed due to differences in plant hydraulic conductance and stomatal conductance.