Effects of Temperature and/or Drought Stress On Physiology, Growth and Yield of Wheat Plants.

High temperature (heat) and drought stress are among the two most important environmental factors influencing crop growth, development, and yield processes. These two stresses commonly occur in combination under field conditions. Objectives of this research were to investigate the interaction effects of high temperature and drought stress during reproductive development on physiological, vegetative, and yield traits and expression of a chloroplast protein synthesis elongation factor (EF-Tu) of wheat (Triticum aestivum L.). Two spring wheat cultivars (Pavon-76 and Seri-82) were grown at optimum temperatures (OT; day/night, 24/14°C; 16/8 h photo/dark period) from sowing to flowering. Thereafter, plants were exposed to high temperature stress (HT; 31/18ºC, Exp. 1 and 34/22ºC, Exp. 2), drought stress (withholding water for 15 d), or a combination of both HT and drought stress. There were significant influences of temperature stress and drought stress on physiological, growth, and yield traits. There was no cultivar or cultivar by temperature or cultivar by drought interaction on most traits. The interaction between HT and drought stress was significant for total dry weights, harvest index, and spikelet fertility, particularly when HT stress was severe. For leaf chlorophyll content and reproductive growth and processes such as spikelet fertility, grain yield, and harvest index, the combined effects of HT and drought were more severe than additive effects of HT or drought alone. High temperature stress and the combination of HT and drought stress but not drought stress alone resulted in overexpression of EF-Tu in both spring wheat cultivars.