豆科固氮植物植株茎叶、根和根瘤的δ^(15)N值变异

VARIATIONS OF δ 15 N VALUE IN SHOOTS,ROOTS AND NODULES OF N 2 FIXING PLANTS

由于生物固定的氮在植物体内迁移过程中存在着同位素分馏效应，导致豆科固氮植物不同部位的δ１５Ｎ值彼此各不相同，我们的结果证实，茎叶的１５Ｎ自然丰度普遍低于根，特别是低于根瘤。固氮百分率以茎叶的δ１５Ｎ值为参数计算较为合理。另外，砂培试验得到的δ１５Ｎａ值对于固氮百分率的计算也有很大的影响。

Because of isotopic fractionation in plant fixed N 2 transport from nodules to shoots and leaves,δ 15 N values of vrious parts of leguminous N 2 fixing plant are different.The results of the experiment demonstrated that natural 15 N abundance of the shoot is generally lower than that of the root,and especially lower than that of the nodules.It is reasonable to calculate % Ndfa by using δ 15 N value of the shoot as parameter.Moreover,δ 15 N values obtainted from sand culture experiment also have a great influence on calculation of N 2 fixing percertage.