Impact of Nighttime Temperature on Physiology and Growth of Spring Wheat

Climate models predict greater increases in nighttime temperature in the future. The impacts of high nighttime temperature on wheat (Triticum aestivum L.) are not well understood. Objectives of this research were to quantify the impact of high nighttime temperatures during reproductive development on phenology, physiological, vegetative, and yield traits of wheat. Two spring wheat cultivars (Pavon-76 and Seri-82) were grown at optimum temperatures (day/night, 24/14 degrees C; 16/8 h light/dark photoperiod) from sowing to booting. Thereafter, plants were exposed to four different nighttime temperatures (14, 17, 20, 23 degrees C) until maturity. The daytime temperature was 24 degrees C across all treatments. There were significant influences of high nighttime temperatures on physiological, growth, and yield traits, but no cultivar or cultivar by temperature interactions were observed. High nighttime temperatures (>14 degrees C) decreased photosynthesis after 14 d of stress. Grain yields linearly decreased with increasing nighttime temperatures, leading to lower harvest indices at 20 and 23 degrees C. High nighttime temperature (>= 20 degrees C) decreased spikelet fertility, grains per spike, and grain size. Compared to the control (14 degrees C), grain filling duration was decreased by 3 and 7 d at night temperatures of 20 and 23 degrees C, respectively. High nighttime temperature increased the expression of chloroplast protein synthesis elongation factor in both cultivars suggesting possible involvement of this protein in plant response to stress.