为什么偏施氮肥的西瓜大而不甜西瓜叶片中蔗糖的含量与蔗糖磷酸合成酶活性有关，随着施氮量增加．有利于蔗糖合成的蔗糖磷酸合成酶的活性略为增加．但也提高了促使蔗糖分解的酸性蔗糖转化酶的活性，可见施氮过多，果实膨大速度明显促进了，但却不利于蔗糖积累，这是导致西... Why partial nitrogen fertilizer watermelon large but not sweet watermelon leaf sucrose content and sucrose phosphate synthase activity, with the amount of nitrogen increased. The activity of sucrose phosphate synthase that favors sucrose synthesis is slightly increased. But also increased the activity of acid sucrose invertase, which promotes the decomposition of sucrose. It can be seen that too much nitrogen was applied and the rate of fruit enlargement was obviously promoted, but it was not conducive to the accumulation of sucrose.