中文摘要：

【目的】通过对不同蛋白质含量小麦品种籽粒形成期旗叶、籽粒氮代谢主要物质及相关酶活性变化的分析,阐明其源、库氮形态以及相关酶活性对籽粒蛋白质含量的影响。【方法】选用高、中、低蛋白质含量的小麦品种各2个,研究籽粒形成期硝态氮、氨态氮与硝酸还原酶（NR）、谷氨酰胺合成酶（GS）的变化特征。【结果】不同类型小麦籽粒形成期蛋白质含量呈“高-低-高”的变化趋势,蛋白质积累量呈现为高蛋白含量品种〉中蛋白含量品种〉低蛋白含量品种。随籽粒发育,3种类型品种籽粒硝态氮含量逐渐下降,成熟时高蛋白含量品种〉中蛋白含量品种〉低蛋白含量品种。籽粒、旗叶氨态氮含量与籽粒硝态氮含量呈类似变化趋势,成熟时氨态氮含量因品种而异。旗叶NR活性随籽粒成熟而降低,低蛋白含量品种NR活性低于高、中蛋白含量品种。旗叶和籽粒GS活性均随籽粒的成熟而下降,中、高蛋白含量品种趋势相似,而低蛋白含量品种籽粒和旗叶GS活性变化趋势不同,籽粒成熟时旗叶仍保持较高的GS活性,而籽粒GS活性则降至很低。【结论】籽粒硝态氮含量与旗叶NR活性和籽粒GS活性均呈极显著正相关。籽粒氨态氮含量与旗叶NR、GS和籽粒GS活性的相关性均亦达显著或极显著水平。高蛋白含量品种由源（叶）向库（籽粒）供给硝态氮的能力强于中、低蛋白含量品种。但低蛋白含量品种对硝态氮的利用更为充分。高蛋白含量品种较高的旗叶NR活性和较高的籽粒GS活性使其氮素同化能力高于中、低蛋白含量品种，这为籽粒蛋白质合成提供了充足的底物，有利于蛋白质的积累。

英文摘要：

Objective The present study was carried out to characterize the nitrogen metabolism and activities of the related enzymes during grain filling stage among wheat cultivars differing in protein content.This information will be helpful to elucidate the effects of nitrogen form in source and sink and activities of the related enzymes on the protein content in grains of wheat and will be valuable to wheat cultivation for high quality.Method Two cultivars from each of the three types of cultivars,the high-,middle-and low-protein content cultivars, were grown in the field of the experimental station of Shandong Agricultural University in Tai＇an. The contents of nitrate nitrogen, ammonia nitrogen and activities of enzymes relating to nitrogen metabolism were tested. [Result] The protein content of wheat grains showed the change pattern of ＂high-low-high＂ during grain filling stage and the protein accumulation in the mature grains was in the order of the high- 〉middle- 〉 low-protein content cultivars. The content of nitrate nitrogen in grain decreased gradually as grain developed, and at maturity, it was in the order of the high- 〉 middle- 〉 low-protein content cultivars. The change of ammonia nitrogen content in flag leaves and grains was similar to that of nitrate nitrogen content in grains. But the ammonia nitrogen content at maturity varied with cultivars. The activities of nitrate reductase （NR） decreased as grains developed, especially, for low-protein content cultivars, the NR activity of which was lower than that of high- and middle-protein content cultivars. The activities of glutamine synthetase （GS） in grains and flag leaves decreased with grains developing in both high- and middle-content cultivars. As for low-protein content cultivars, the change of GS activities in grains was different from that in flag leaves, the later remained the higher value as compared with that of both high- and middle- protein content cultivars. [Conclusion] It was found that the content of nitrate nitrogen in