黄瓜子叶离体后的一些生理变化

CHANGES OF SOME PHYSIOLOGICAL CHARACTERISTICS IN DETACHED CUCUMBER COTYLEDONS

成熟种子的子叶离体后，在无外源激素和营养供应的滤纸保湿（26±1℃，2．92Wm-2，14h光照）条件下培养。0—4d内子叶的面积大小和鲜重迅速增加而干重基本保持不变，4d后子叶面积和鲜重继续增加但速度减慢，干重迅速下降；呼吸速率和叶绿素含量4d前稳定上升，第4天达到峰值后下降．离休后6d内，子叶中矿质元素含量发生了一定的变化；除Put含量在第2天有所下降外，子叶中Spm、SPd和Cad含量均不断上升，但上升幅度不相同，因此，离体并没有削弱黄瓜子叶多胺合成；GA3和ABA含量有不同程度的上升，但IAA和ZT含量剧增，表明离休子叶有很好的激素合成能力．离体后2d内，子叶中DNA含量、RNA含量、酸溶蛋白含量均成倍增加，此后DNA含量迅速下降，酸溶蛋白含量呈彼动状，RNA含量基本保持同样水平；0—4d碱溶蛋白含量不断减少，这表明子叶离体0—4d有活跃的核酸、蛋白质代谢活动．

Excised cotyledons of mature cucumber seeds were cultured on wet filter paper without exogenous hormones and nutrients (26 ±1℃, 2.92 W m-2, 14h day length). During 0 to 4 days after excision, the size and fresh weight of cotyledons increased rapidly, and the dry weight remained almost constant. After the 4th day of culture, the fresh weight and the area of cotyledons continued to increase, although more slowly than before, while the dry weight decreased quickly (Fig. 1). Respiration intensity and chlorophyll content of the cotyledons increased quickly before the 4th day, and reached the peak simultaneously at day 4, and then declined obviously (Fig. 2). The contents of mineral elements in detached cotyledons appeared to change within 0 to the 6th day (Table 1). With the exception of putrescine content decreasing slightly in the 2nd day of culture, all of the contents of spermine. spermidine and cadaverine in cotyiedons increased steadily. butthe increment was different. Thus, polyamine synthesis in cucumber cotyledons was not generally impaired after excision (Table 2). The contents of GA3 and ABA in cotyledons were to some extent increased, and the contents of IAA and ZT increased markedly, indicating that the detached cotyledons were capable of synthesizing the hormones during this period (Table 2). The contents of DNA, RNA and acid-soluble protein increased obviously within the first 2 days, while DNA content declined quickly, and the acid-soluble protein content fluctuated, meanwhile, RNA content remained almost unchanged. In the first 4 day, the content of alkali-soluble protein decreased continuously (Fig. 3), indicating that the detached cotyledons kept metabolic activity of nucleic acids and proteins.