大豆萌发过程的活性氧代谢

本文研究了大豆萌发过程中活性氧的产生与清除，并探讨了光因子在活性氧代谢中的作用。大豆呼吸强度、O产生速率及H2O2水平都在吸水后第四天达到高峰，然后下降，三者的变化趋势同步。SOD、POD及APX的活性随萌发过程而逐渐增强，最后趋于平稳。SOD同工酶谱中分别于萌发的第二、第三天各出现一条新的酶带。CAT在萌发的初期猛增50倍左右，之后趋于稳定。在三种清除H2O2的酶（CAT、POD、APX）中，CAT清除H2O2的能力远远高于POD与APX，CAT可能是大豆萌发过程中最主要的H2O2清除酶。光萌发时呼吸强度低于暗中萌发，但O产生速率与H2O2水平高于暗萌发，光萌发时O的产生占总耗氧量的1．1—2．7％，而暗中萌发为0．9—1．3％。光条件下SOD、APX活性明显高于暗中萌发，而POD与CAT则在光和暗条件下相差不大。

ACTIVE OXYGEN METABOLISM IN SOYBEAN DURING GERMINATION

The generation of active oxygen and the activities of active oxygen scavenging enzymes as well as the effect of light on active oxygen metabolism were studied in soybean during germination. The O2 uptake, the rate of O2 production, and the level of H2O2 in imbibed seeds all increased at the beginning of germination, but all decreased after 4 days of imbibition. Gradual increases in activities of superoxide dismutase (SOD), peroxidase (POD) and ascorbate peroxidase (APX) were observed at the early stage of germination, then the activities of SOD, POD, and APX tended to be in a certain level with little alteration. A new band of SOD isoenzyme presented respectively on the 2nd and 3rd day of seed imbibition. There was about a 50-fold increase in catalase (CAT) activity at the early stage of germination, and then turned stable. Among the three H2O2-scavenging enzymes (CAT, POD and APX), the capacity of CAT for scavenging H2O2 was much higher than those of POD and APX. So it seems that CAT is the most important H2O2 scavenging enzyme during germination. Although the O2 uptake of seeds germinating under light was lower than that in the dark, the rate of O2 production and the H2O2 level under light were higher than those in the dark. The ratio of O2- production to total O2 uptake was 1.1 - 2.7% in seeds germinated under light, while this ratio was 0.9 - 1.3% in the dark. The activities of SOD and APX under light were higher than those in the dark, but the activities of POD and CAT had no distinct difference under light and dark.