Responses of indica rice yield and quality to extreme high and low temperatures during the reproductive period

Extreme temperatures will likely occur with greater frequency and intensity under the conditions of climatic warming, presenting a serious challenge for future crop development. The responses of rice yield and quality to extreme high (HT) and low temperature (LT) during precise reproductive periods are still unclear. Therefore, we conducted a walk-in climate chamber experiment with two indica cultivars and three temperature treatments-CK: 20-28 degrees C, LT: 12-20 degrees C and HT: 28-36 degrees C as the mean values of night-day temperatures-for seven days in four key periods-the last week of pre-heading, and the first, second and third week of post-heading-, respectively. Extreme temperatures reduced rice leaf chlorophyll fluorescence, photosynthetic rate and dry matter translocation, consequently decreasing the grain yield by 5-13 percent under LT and 12-15 percent under HT. The most sensitive periods of rice yield to extreme temperatures were found during the last week of pre-heading and the first week of post-heading. Extreme temperatures significantly declined the grain appearance, milling and cooking quality traits with inversely enhanced chalkiness, broken rice and gelatinization temperature. The most responsive period of rice quality to extreme temperatures occurred during the second week of post-heading. HT exhibited a more severe impact on rice quality than by LT. Our results indicate that the responses of rice yield and quality to extreme temperatures are different among reproductive periods.