Effects of High Nighttime Temperature and Preventive Exogenous Effectors on Rice Physiology and Grain Characteristics.

The presence of seasonally high nighttime temperatures (HNT) along the United States Gulf Coast and in regions of similar climate, occurring during the critical stages of development, reduces rice (Oryza sativa L.) yield and quality. The objective of this study was to determine the effects of HNT and preventive exogenous effectors (α-tocopherol, glycinebetaine and salicylic acid) on rice physiology with special emphasis on grain characteristics. Plants were grown under ambient nighttime temperature (ANT) (27 ^oC) or HNT (32 ^oC) in the greenhouse. They were subjected to a HNT through use of continuously controlled infrared heaters, starting from 2000 h until 0600 h. The HNT did not affect leaf photosynthetic rates; however profound effects on leaf respiration, membrane stability, percent pollen germination, spikelet fertility and grain characteristics were observed. On average, plants grown under HNT showed a 95% decrease in yield compared to plants grown under ANT. Application of preventative exogenous effectors increased plant yield, under ANT and HNT.  We were able to identify two potential exogenous effectors (glycine betaine and salicylic acid) to diminish the negative effects of HNT.