Effects of high temperature stress during anthesis and grain filling periods on photosynthesis, lipids and grain yield in wheat

Background : Short episodes of high temperature (HT) stress during reproductive stages of development cause significant yield losses in wheat ( Triticum aestivum L.). Two independent experiments were conducted to quantify the effects of high temperature (HT) during anthesis and grain filling periods on photosynthesis, leaf lipidome, and yield traits in wheat. In experiment I, wheat genotype Seri82 was exposed to optimum temperature (OT; 22/14 °C; day/night) or HT (32/22 °C) for 14 d during anthesis stage. In experiment II, the plants were exposed to OT or HT for 14 d during grain filling stage. During the HT stress, chlorophyll index, thylakoid membrane damage, stomatal conductance, photosynthetic rate and leaf lipid composition were measured. At maturity, grain yield and its components were quantified. Results : HT stress during anthesis or grain filling stage decreased photosynthetic rate (17 and 25%, respectively) and grain yield plant -1 (29 and 44%, respectively), and increased thylakoid membrane damage (61 and 68%, respectively) compared to their respective control (OT). HT stress during anthesis or grain filling stage increased the levels of less unsaturated lipid species [36:5- monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG)]. However, at grain filling stage, HT stress decreased the levels of more unsaturated lipid species (36:6- MGDG and DGDG). There was a significant positive relationship between photosynthetic rate and grain yield plant -1 , and a negative relationship between thylakoid membrane damage and photosynthetic rate. Conclusions : The study suggests that maintaining thylakoid membrane stability, and seed-set percent and individual grain weight under HT stress can improve photosynthetic rate and grain yield, respectively.