硝态氮对双向酶—蔗糖合成酶 (SS,Sucrose Synthase,SS,EC2 .4 .1.13)的合成和分解方向酶活力影响不同 ,不同水平的硝态氮肥能不同程度地促进甜菜根和叶片中的 SS的活性 ,而且对 SS分解方向酶活力的促进作用更大 ,根中 SS合成和分解方向的酶活力远远大于叶片中的酶活力 ,根中蔗糖合成则以 SS合成酶活性为主 ,随施硝态氮水平的增加 ,SS分解方向酶活性加强 The effects of nitrate nitrogen on the biosynthesis and disassembly direction enzyme activities of SS, Sucrose Synthase (SS, EC2 .4. 1.13) were different. Nitrate fertilizer at different levels could promote the growth of beetroots and leaves in different degrees SS activity, but also had a greater effect on the SS enzyme activity. The enzyme activity in the SS synthesis and decomposition was much larger than that in the leaves. The synthesis of sucrose in the roots was dominated by SS synthase activity, With the increase of nitrate nitrogen level, SS enzyme activity was enhanced