黄瓜(Cucumis sativus L.)子叶发育过程中谷氨酰胺合成酶同工酶的变化

采用Native-PAGE和活性染色的方法检测黄瓜种子萌发和子叶发育过程中GS同工酶的类型和活性，以期了解同工酶在子叶发育过程中的作用，在下种子中，只观察到一种不同于GS1和GS2形式的同工酶随着发育过程迅速消失，在种子萌发和子叶发育过程中，子叶GS1活性先于GS2出现，而且两者活性均很快升高；子叶绿化后GS2是主要的，外源氮素能硅著增强它的活性；子叶发育后期这两种同工酶活性逐步下降，在真叶发育中，同样观察到两种GS同工酶，以GS2为主．在暗转光后，GS2明显被诱导；而当光／暗转换后，GS1活性在子叶和真叶中均显著增加．GS同工酶活性随发育以及环境条件的变化而改变的现象与它们在代谢上的功能需要是一致的。

Changes of Glutamine Synthetase Isozymes During the Development of Cucumber(Cucumis sativus L.) Cotyledon

In the cucumber seed germination and cotyledon development, glutamine synthetase (GS) isozymes were investigated by Native-PAGE and activity staining. In dry seeds, only one GS isozyme different from GS1 and GS2 was detected and disappeared very soon. During cotyledon development, GS1 appeared earlier than GS2 followed by the rapid activity increase of both isozymes. After the cotyledon greening, GS2 was dominant and could be remarkably enhanced by exogenous nitrate. At the late stage, both cotyledon GS1and GS2 activities declined with culture time. The GS isozymes were also determined in the early stage of the true leaf development, and GS2 was predominant. Transferring the seedlings from dark to light, GS2 was induced obviously. However, treated by converse light condition, GS1 activity was increased markedly in cotyledon and leaf. These changes of GS isozymes and their activities with development and environmental conditions show consistent with their function in the metabolism.