[目的]通过探究氮素粒肥缓解水稻灌浆期高温胁迫响应生理机制,为栽培措施缓解水稻高温危害提供理论基础。[方法]以‘武运粳24号’和‘宁粳3号’为材料,进行盆栽试验,于开花期进行低氮(每盆0 g纯氮)、中氮(每盆0.8 g纯氮)、高氮(每盆1.6 g纯氮)3种施氮水平处理,6 d后移入温室进行高温处理。测定了水稻叶温及穗温,净光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r),SOD、POD、NR、GS活性,MDA、可溶性蛋白及氨基酸含量等。[结果]施用氮素粒肥显著降低了水稻的叶温和穗温,减少了高温下MDA的积累,促进水稻叶片的光合作用,提高抗氧化酶活性,增强了水稻植株氮代谢,增加硝酸还原酶、谷氨酰胺合成酶活性及氨基酸的含量。灌浆期高温降低了水稻结实率和千粒质量,氮素粒肥的施用显著缓解了高温对千粒质量和稻谷产量的影响。2个品种产量在各处理间存在显著差异,产量以低氮高温处理最低,高氮常温处理最高。‘宁粳3号’对高温胁迫更为敏感,减产幅度更大。高温胁迫初期水稻叶片内氨基酸含量显著提高,但随着胁迫时间的延长,叶片内氨基酸含量呈下降态势。氮素粒肥的施用既显著提高高温胁迫下水稻灌浆早期叶片中氨基酸的含量,同时也能持续维系水稻叶片有较高的氨基酸含量,从而提高了水稻抗逆性。[结论]氮素粒肥的施用能显著提高植物体内氮代谢水平与抗氧化酶活性,并增加叶片氨基酸含量,减少高温逆境条件下水稻产量损失。 [Objective] The study aimed to study the physiological mechanism of nitrogen fertilizer in response to high temperature stress during grain filling stage and provide theoretical basis for cultivation measures to alleviate the high temperature damage in rice. [Method] With the materials of Wuyunjing 24 and Ningjing 3 as the materials, pot experiments were conducted to study the effects of low nitrogen (0 g pure nitrogen per pot), medium nitrogen (0.8 g pure nitrogen per pot) , High nitrogen (1.6 g pure nitrogen per pot), and 6 days later, they were transferred to the greenhouse for high temperature treatment. Leaf temperature, spike temperature, net photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r), SOD, POD, NR and GS activities, MDA, soluble protein and amino acid contents in rice were measured. [Result] The results showed that the application of nitrogen fertilizer significantly reduced the leaf temperature and spike temperature of rice, reduced the accumulation of MDA under high temperature, promoted the photosynthesis of rice leaves, increased the activity of antioxidant enzymes, enhanced the nitrogen metabolism of rice plants, increased nitrate reductase, Glutamine synthetase activity and amino acid content. The high temperature during grain filling reduced the seed setting rate and 1000-grain yield. The application of nitrogen fertilizer significantly alleviated the effect of high temperature on 1000-grain yield and rice yield. The yield of two cultivars was significantly different among the treatments. The yield of the two cultivars was the lowest in the treatment with low-nitrogen and the highest in the high-nitrogen. ’Ning japonica 3’ is more sensitive to high temperature stress, yield greater. The contents of amino acids in rice leaves increased significantly in the early stage of high temperature stress, but the contents of amino acids in the leaves decreased with the prolongation of stress time. The application of N fertilizer not only significantly increased the content of amino acids in the early leaves of rice under high temperature stress, but also continued to maintain the higher amino acid content of rice leaves, thereby increasing the resistance of rice. [Conclusion] The application of N fertilizer could significantly increase nitrogen metabolism and antioxidant enzyme activities in plants, increase the content of amino acids in leaves and reduce the yield loss of rice under high temperature stress.