Membrane Lipid Composition Under High Temperature Stress in Wheat.

High temperature is a major environmental factor that limits wheat productivity. Climate models predict greater increases in nighttime temperatures than in daytime temperatures. Cellular membranes are one of the prime targets of high temperature stress in plants. The objective of this study was to compare the effects of high daytime and/or nighttime temperatures during flowering on cellular membranes (membrane damage, lipid peroxidation, and membrane lipid profile), reactive oxygen species content, and physiological (chlorophyll a fluorescence, chlorophyll content, and leaf level photosynthesis), growth (plant height, tiller number/plant, and biomass production), and yield traits of wheat genotypes. Winter wheat genotypes (Ventnor and Karl 92) were grown at optimum temperatures (25/15°C, maximum/minimum) until the onset of flowering. Thereafter, plants were exposed to high nighttime (HN, 25/24°C), high daytime (HD, 35/15°C), high daytime and nighttime (HDN, 35/24°C), or optimum temperatures for 12 days. All traits except growth and yield traits were measured on day 1, 6, and 12 during the stress period and day 4 during the recovery period (after the stress was relieved). Growth and yield traits were measured at maturity.  Preliminary results showed that HN, HD, and HDN significantly damaged cellular membranes, influenced most of the physiological traits, and decreased growth and yield traits. This study emphasizes the importance of understanding the mechanisms of heat tolerance for developing heat tolerant wheat varieties.