Effect Of High Day-Time And Night Temperature During Grain Filling Stage On Rice Qualities And Adjusting Effects Of Panicle Nitrogen Levels

Wuyujing3 and Zhendao88 (Japonica rice) were used to study the effect of high night temperature on dry matter accumulation in endosperm and rice quality, the different effect of high night and day-time temperature on rice quality and starch structure, and response of rice quality to high day-time temperature under different panicle nitrogen levels.1. We all know the important effect of temperature on rice yields and qualities during grain filling stage, but we overlooked the absolute effect of high night temperature. Wuyujing3 and Zhendao88 (japonica rice) were used to study the effects of high night temperature on dry matter accumulation in endosperm of rice with heater in out environment. The results showed that: the trend of dry matter accumulation in rice endosperm under high night temperature was similar to that of the control. Accumulation rate of high night temperature was slightly faster than check during 15d after heading, but the accumulation rate of check reached the peak and faster than high night temperature during 15-20d after heading. High night temperature reduced dry matter weight and weight of total starch and amylose, although increased protein content, high night temperature has no significant effect on absolute weight of protein. Two cultivars almost had same response to high night temperature.2. Two japonica rice cultivars, Wuyujing3 and Zhendao88, were used to study the effects of high night temperature on the chemical-physiological and morphological aspects of rice quality. The results showed that: grain quality of the two cultivars almost showed similar responses to temperature treatment. For grain appearance quality, as night temperature increased, brown rice rate, milled rice rate, head rice rate, and ratio of grain length to width decreased, whereas grain chalkness rate and grain chalkiness rate significantly increased. For cooking and eating quality, grains of high night temperature treatment showed lower amylase content, RVA analysis showed that effect of high night temperature varied with cultivars, peak viscosity, breakdown increased, setback decreased in both cultivars, but higher hot viscosity and final viscosity of Wuyujing3 being different from those of Zhendao88. For grain nutritional quality, high night temperature increased grain crude protein, alabumin, globulin and glutelin contents, decreased grain prolamin content. For starch structure, high night temperature increased relative crystallinity and with bigger granule on flank side, but smaller on back side, the same happened in both cultivars.3. Wuyujing3 was used to study the effects of high day-time temperature on rice qualities and starch structure with heater in out environment. The results showed that: For grain appearance quality, as day-time temperature increased, brown rice rate, milled rice rate, head rice rate, and ratio of grain length to width significantly decreased, whereas grain chalkness rate and grain chalkiness rate significantly increased. For cooking and eating quality, grains of high day-time temperature treatment showed higher amylose content, high day-time temperature increased peak viscosity, hot viscosity breakdown and Pasting Temp, decreased final viscosity and setback. For grain nutritional quality, high night temperature increased grain crude protein, alabumin, globulin and glutelin contents, decreased grain prolamin content. For starch structure, in both cultivars, high day temperature increased relative crystallinity and with smaller and more granule on flank side, with smaller granule on back side, and the space between granule on flank side was less than check.4. Effect of high day-time temperature on rice quality under different panicle nitrogen levels was investigated in this study with a japonica rice cultivar, Wuyujing3. The results showed significant difference in the influence of day-time high temperature among different nitrogen levels. For milling quality, milled rice rate and head rice rate decreased in higher day temperature treatment. Medium nitrogen treatment showed the largest influence. For appearance quality, medium nitrogen treatment also exhibited the largest effect. Grain chalkness rate and grain chalkness increased in all nitrogen treatments. However, for brown rice rate and ratio of grain length to width, there was substantial difference among nitrogen treatments, with low and medium nitrogen treatments having the lower values whereas nitrogen treatment showing higher values. Grain protein content in all nitrogen treatments showed similar increasing trend with increased day-time temperature, but temperature and nitrogen expressed nonsignificant cross-effect on it. By contrast, the influence of day-time temperature on amylose content varied with nitrogen treatments, with medium nitrogen treatment having higher value whereas low and high nitrogen treatments showing lower values. For RVA, peak viscosity and Pasting Temp increased, setback and final viscosity decreased in all nitrogen treatments, but hot viscosity and breakdown changed differently. In addition, filled grain rate and grain weight reduced in all nitrogen treatments under high day-time temperature, with medium treatment having the lowest values. Reducing and adding nitrogen could relieve the effect of high temperature, especially increasing nitrogen fertilizer.