中文摘要：

【目的】研究抽穗结实期不同时段高温处理对稻米品质的影响,阐明高温对稻米品质的影响机理及其时段效应。【方法】选用耐热性不同的两个水稻品系,利用人工气候室进行抽穗结实期不同时段温度试验,研究抽穗结实期高温对稻米外观品质、加工品质、直链淀粉含量、胶稠度、蛋白质含量、RVA特征谱、Mg/K及籽粒的淀粉粒结构的影响。【结果】抽穗结实期高温使两品系稻米长宽比变小,垩白粒率和垩白度增加,糙米率、精米率、整精米率降低,直链淀粉含量和蛋白质含量增加,胶稠度降低;淀粉RVA谱特征值崩解值降低,冷胶粘度、消减值和糊化温度升高,峰值时间延长,Mg、K含量增加,Mg/K比值降低;淀粉粒扫描电镜显示,高温条件下,淀粉粒间结合较为疏松,籽粒内大多以单个淀粉粒的形式存在,折光率下降,胚乳透明度降低,导致垩白形成。相同处理条件下,耐热品系996稻米品质受高温影响低于热敏感品系4628。抽穗结实期不同时段高温对稻米品质影响存在显著差异,以始穗后8—14 d对稻米品质影响最大,其次为始穗后15—21 d、1—7 d、始穗后22—28 d影响较小。【结论】始穗后8—21 d是温度对稻米品质影响的关键时期,对稻米品质形成具有决定作用,而结实后期（始穗22 d后）环境温度对稻米品质影响较弱。

英文摘要：

[ Objective ] The effects of high temperature treatment at different times during heading and filling periods on rice quality were studied to ascertain the mechanism of the effect of high temperature on rice quality and its time effect. [Method] The experiment was conducted with two rice lines, the heat-tolerant line 996 and heat-sensitive line 4628, in controlled environment chambers to investigate the effect of high temperature stress at different times during heading and filling stages on rice appearance quality, milling quality, amylose content, gel consistency, protein content, RVA characteristcs, Mg/K and starch granule structure of grain. [Result] The ratio of grain length to width, the brown rice rate, milled rice rate, head rice rate and gel consistency of both lines decreased under high temperature stress during heading and filling stages, while chalkness rate, chalkness, amylose content, protein content and gelatinization temperature increased. Under high temperature treatments, gelatinization temperature, final viscosity, set back and peak time increased, break dowm decreased, Mg content and K content increased, Mg/K decreased. The observation of starch structure with scanning electron microscope showed that the starch granules arranged loosely, most of the starch granules existed in the form of single starch granule, refractive index decreased, endosperm transparency decreased, and chalkiness was formed. Under the same treatment, the extent of rice quality of heat-tolerant line 996 affected by high temperature was lower than that of heat-sensitive line 4628. Rice qualities had different responses to different high temperature treatments, rice qualities wereaffected by high temperature treatment 8-14 d after heading mostly, moderatedly by high temperature treatment 15-21 d and 1-7 d after heading, while least by high temperature treatment 22-28 d after heading. [ Conclusion ] Eight to twenty-one days after heading is the vital stage for whole rice quality in response to higher temperature, which affec