Effects Of High Temperature During Grain Filling Stage On Rice Grain Productivity And Quality And Physiological Mechanism

Rice grain yield and guality were affected by the environment. Temperature was a major component in environmental variation and had a marked effect on grain filling in rice. Investigating the effects of high temperature during grain filling period on guality formation and physiological mechanism was useful for understanding the mechanism of heat damage and improving rice yield and guality under high temperature stress.Rice growing in pots filled with 7.5kg loamy soil was transferred to the artificial temperature-controlled and moisture-controlled phytotron at different grain filling stages. The experiment mainly studied the effects of high temperature during grain filling period on grain yield, grain weight, seed setting rate, grain quality and its related physiological characteristics in Huajing 1 and Teyou 559. The results were as follows.1. Effects of high temperature during grain filling period on rice grain yield and grain weight and seed setting rate. The results showed that grain yield per ear , grain weight and seed setting rate at 40℃were lower than those at lower temperature from anthesis to the 10th day after anthesis. There were no significant difference in grain number per ear and grain yield per ear at 25℃, 30℃and 35℃. Effects of different day and night temperatures on grain number per ear, grain weight and grain yield per ear were significant. The results showed that seed setting rate, grain weight at the day and night temperature 35℃/ 20℃were higher than under other temperature treatments from anthesis to the 10th day after anthesis. There were no significant difference in seed setting rate, grain weight at 35℃/25℃, 35℃/ 30℃.The higher the temperature at night under the same day temperature, the lower the grain weight.2. Effects of high temperature during grain filling period on rice grain quality. There were no significant differences in processing quality among treaments. Rice grain chalkiness was increased greatly as the temperature increased. Starch contents in grains was higher at higher temperature than those at lower temperature. Higher temperature after anthesis had positive effects on protein contents in grains. Grain protein content at the temperature 40℃was higher than other treaments. Compared 40℃with 25℃, the structure of starch granules in rice grains was combined loosely. Rice grain chalkiness was increased greatly as the night temperature increased under the same day temperature during different periods. Starch contents in grains were higher at temperature 35℃/20℃than those of other treatments. Higher temperature after anthesis had positive effects on protein contents in grains.3. Effects of high temperature during grain filling period on its related physiological characteristics. The results showed that the higher the night temperature under the same day temperature was, the higher were Pro content, Q enzyme activitiy and GS enzyme activity and the lower was SOD enzyme activity. The higher the temperature was, the faster the senescence was.