High nighttime temperatures affect rice productivity through altered pollen germination and spikelet fertility

Seasonally high nighttime temperatures (HNTs) along the United States Gulf Coast and in regions of similar climate, occurring during the critical stages of development, reduce 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, glycine betaine and salicylic acid) on growth, development, physiology and yield of rice plants. Plants were subjected to ambient nighttime temperature (ANT) (27 °C) or HNT (32 °C) 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 chlorophyll content, leaf nitrogen content, percent pollen germination and spikelet fertility were observed. In addition, HNT hastened plant development rates, as indicated by the panicle emergence date. Plants grown under HNT showed a 90% decrease in yield compared to plants grown under ANT. Dry matter partitioning to the grains of cv. Cocodrie decreased under HNT mainly due to effects on pollen germination and spikelet fertility, but not photosynthesis. Our findings indicate that exogenous application of salicylic acid reduced the negative effects of HNT by 16%.