中文摘要：

目的：探究氮素利用相关酶对油菜中氮素再分配的贡献程度。[方法]采用单株砂培培养，严格控制氮素等营养供应，用15N饲喂追踪，分别测定在蛋白水解酶（PE）、谷氨酰胺合成酶（GS）和谷氨酸合成酶（GOGAT）抑制剂处理的情况下．两个油菜品种氮低效品种6号和氮高效品种2号的产量、籽粒氮素转运和积累量、叶片氮索损失的情况以及氮素利用率。[结果]两品种皆在抑制GOGAT活性时，氮素利用效率最低．产量最少。籽粒中氮素转运比例最低，叶片氮素损失最大，其次为PE，在抑制GS时影响最小。同时发现在生育后期，叶片中积累的氮素接近80％转运出叶片。籽粒中来源于营养器官前期积累的氮素达到50％-70％。两品种油菜呈现相同趋势。品种之间．2号油菜品种的籽粒氮素累积和产量高。氮素损失较少。氮低效品种6号和氮高效品种2号在所有受抑制情况下呈现相同规律。[结论]GOGAT是油菜氮素再利用的关键酶，品种间酶活性不同可能是品种氮素再利用效率不同的重要因素。叶片生育前期积累的氮索主要用于氮素再利用．籽粒中积累的氮素大部分来源于营养器官。

英文摘要：

[Objective] This assay was to explore the contribution of enzymes ac- counting for nitrogen reutilization in two Brassica napus varieties No.6 （low nitrogen use efficiency） and No.2 （high nitrogen use efficiency）. [Method] We measured the yield, transportation and accumulation of grain nitrogen, loss of leaf nitrogen and ni- trogen use efficiency （NUE） in the two rape varieties, by inhibiting proteolytic en- zyme （PE）, glutamine synthetase （GS） and glutamate synthetase （GOGAT） and la- beling with lSN. [Result] Under GOGAT inhibitor treatment, both of the two varieties presented minimum NUE, yield and nitrogen transportation in grain and maximum ni- trogen loss in leaf. The effect of PE inhibitor was the second greatest, and that of GS inhibitor was the lowest. Moreover, 80% of the nitrogen that had been accumu- lated in leaf was transported out during late growth stage, and 50% to 70% of the grain nitrogen derived from the nitrogen in vegetative organs. The two varieties ex- hibited the same tendency. Rape variety No.2 had higher yield, grain nitrogen accu- mulation and lower nitrogen loss compared with No.6. [Conclusion] GOGAT has the greatest effect on the accumulation of grain nitrogen, yield and nitrogen reutilization in rape. Different enzyme activity may be the major factor resulting in different nitro- gen rautilization in the two rape varieties. Nitrogen stored in leaf during early growth stage is mainly used for nitrogen remobilization. A large proportion of grain nitrogen derives from vegetative tissues.