玉米幼苗叶片保护酶活性的昼夜变化

人为控制环境下，对玉米幼苗叶片中电解质外渗率、MDA含量以及保护酶活性的昼夜变化同步进行了测定。结果表明：叶片电解质外渗率的昼夜变化呈现双峰曲线，分别在光照4 h和光照后黑暗4 h达到峰值；叶片中MDA含量表现为单峰的波形曲线，黑暗开始的4 h内最高；随着光照时间的延长，SOD酶、POD酶和CAT酶活性均表现出不同程度的降低，但均在16：00（光照8 h）至20：00（光照12 h）之间达到一昼夜内的最低点。随着光照后黑暗时间的延长，各保护酶活性均增加，但增加的速率不同，至次日8：00所有保护酶活性均接近光照前水平。光照和黑暗条件下，各保护酶活性差异极显著。保护酶活性的昼夜变化与叶片中的可溶性蛋白质含量并无显著的相关关系。

Diurnal variation of cell defense enzymes activity in leaves of maize seedling

The diurnal variations of electrolyte leakage,MDA concentration and cell defense enzyme in leaves of maize seedling were synchronously measured under the artificial conditions.The results showed that the variations of electrolyte leakage over a day-night presented respectively a dual-peaked curve with the maximum after 4 h of the light and after 4 h of the dark.MDA concentration in leaves presented a simple-peaked curve with the maximum in 4 h of the dark.With light continued,the activities of SOD,POD and CAT showed different levels of descend,but they came to the minimum of a day-night between four O'clock in the afternoon and eight O'clock in the evening.With the dark continued,the activities of defense enzyme all increased.But the rates of increasing were different,until eight O'clock in the next day,the activities of defense enzyme all reached the levels similar to the light before.Under the light and dark,the activities of all kinds of defense enzyme were significantly different.The diurnal variations of the activities of cell defense enzyme didn't significantly relate to soluble protein content in leaves.