Assessing the role of transpiration in ameliorating leaf temperatures in wheat (Triticum aestivum L.) in relation to changing environmental conditions

[Truncated] High temperature can drastically reduce wheat yields. Therefore, adaptation strategies that minimise the negative impact of high temperature on wheat need to be explored. Transpiration (T_r) may play an important role in dissipating heat through evaporative cooling. This thesis assessed the role of T_r in ameliorating leaf temperature (T_leaf) in wheat in relation to changes in atmospheric vapour pressure deficit (VPD), air temperature (T_air) and soil water, and identified some of the mechanisms underlying the genotypic variability in those responses.

A morpho-physiologically diverse set of 20 wheat genotypes was assessed under ambient and elevated T_air to investigate whether greater water use aids plants to retain its biomass under high temperature. It was expected that the genotypes with greater water use would be superior in maintaing their biomass by inhibiting senescence through greater canopy cooling. A pot experiment was conducted in two partially-controlled glasshouses (ambient and elevated temperature) under wellwatered (WW) conditions. Greater water use and its effect on leaf cooling contributed to greater biomass retention under high temperature, which depended on genotype. Genotypes differed in their capacity to maintain cooler T_leaf, which did not always correlate with the Tr (VPD) response.