中文摘要：

以中熟籼稻品种沪旱15和中熟粳稻品种扬粳4038为材料，利用盆栽试验，在水稻穗分化期设置低氮（每盆0．5g尿素）、中氮（每盆1．0g尿素）和高氮（每盆2．0g尿素）3种施氮量水平，在抽穗灌浆期进行高温（白天／夜间平均温度为35．1℃／20．8℃）和正常温度（白天／夜间平均温度为29．0℃／20．8℃）处理，探讨了氮素穗肥对水稻高温灌浆过程及其产量和品质的影响。结果表明，在高温胁迫下，中氮和高氮显著增加每穗粒数、结实率、千粒重和产量，增加整精米率和支链淀粉短链比例，降低垩白米率和支链淀粉中长链的比例，其中，中氮效果更为明显。施用氮素穗肥还增加了叶片光合速率、根系氧化力和籽粒中蔗糖一淀粉代谢途径关键酶活性。说明抽穗结实期遭受高温胁迫，在穗分化期适当施用氮肥可以获得较高的产量和较好的稻米品质，根系和冠层生理活性的提高是其重要原因。

英文摘要：

Effects of application of nitrogen as panicle-promoting fertilizer on grain yield and quality was studied with two mid-season rice cultivars, Huhan 15 （indica） and Yangjing 4038 （japonica） grown in pots as materials under three nitrogen fertilizer levels, low nitrogen level（LN, 0.5 g urea per pot）, medium nitrogen level （MN, 1.0 g urea per pot）, and high nitrogen level（HN, 2.0 g urea per pot） at the panicle initiation stage under high temperature. Both high temperature （mean temperature during the day/night at 35.1℃/20.8℃） and normal temperature （mean temperature during the day/night at 29.0℃/20.8℃ ） treatments were conducted during heading and grain filling. The grain yield and rice quality were investigated under these treatments. The results showed that at the same temperature, especially under high temperature, compared with the LN, the MN and HN significantly increased spikelet number per panicle, seed-setting rate, 1000-grain weight, grain yield, head rice rate and short chain percentage in debranched amylopectin, and reduced chalky grains and long chain in debranched amylopectin, especially at MN. Application of panicle- promoting fertilizer also increased the photosynthetic rate of flag leaf, root oxidation activity, and activities of the key enzymes involved in sucrose-to-starch metabolic pathway in grains in the two cultivars. These results indicate that proper application of nitrogen as panicle fertilizer could maintain a higher grain yield and better quality of rice when subjected to high temperature during heading and grain filling, and increases in root and shoot activities contribute to the reducing adverse effects of high temperature on rice yield and quality.