Increasing Night Temperature Can Reduce Seed Set and Potential Yield of Tropical Rice

Abstract

The effect of increasing day temperature on reducing seed set in rice is well established, but little is known concerning the impact of increasing night temperature relative to constant day temperature. Recent work suggests that anticipated global warming may be uneven, with a significant increase in night compared to day temperature. Sun-lit, outdoor environment chambers were used to determine the impact of increasing night temperatures at two constant day temperatures (29/21, 29/25, 29/29ºC and 33/25, 33/29 and 33/33ºC) as well as increasing day/night temperature (29/21, 33/25 and 36/29ºC) on growth and yield of rice (cv. IR 72). Increasing daylnight temperature to 36/29ºC resulted in a significant reduction in both plant biomass and grain yield at harvest. At a constant day temperature of 29ºC, increasing night temperature did not significantly alter growth or yield; however, increasing night temperature at a day temperature of 33ºC (8 h duration) resulted in a significant decline in grain yield, primarily due to reduced seed set. The decline in grain yield at 33ºC with increasing night time temperature was similar to that observed at a daylnight temperature of 36/29ºC. Data from this experiment suggest that higher night time temperatures per se could increase the susceptibility of rice to sterility with a subsequent reduction in seed set and grain yield.