水杨酸对黄瓜叶片抗氧化剂酶系的调节作用

REGULATION OF ANTIOXIDANT ENZYMES BY SALICYLIC ACID IN CUCUMBER LEAVES 

分析了水杨酸（ＳＡ）对黄瓜（ＣｕｃｕｍｉｓｓａｔｉｖｕｓＬ．）叶片抗氧化剂酶系活性及活性氧水平的调节作用。不同浓度的ＳＡ（０．５ｍｍｏｌ／Ｌ、１ｍｍｏｌ／Ｌ、２．５ｍｍｏｌ／Ｌ、５ｍｍｏｌ／Ｌ）均能显著地提高被处理叶片超氧化物歧化酶（ＳＯＤ）和过氧化物酶（ＰＯＤ）活性，而且还能诱导同株的非处理叶片中ＳＯＤ和ＰＯＤ活性增加。用１ｍｍｏｌ／ＬＳＡ处理第一片真叶，在处理后６～７２ｈ，ＰＯＤ活性增加了２２％～６７％，同株非处理的第二片真叶ＰＯＤ活性增加了１４％～８６％，但是，在ＳＡ处理后３ｈ之前以及处理９６ｈ之后，ＰＯＤ活性没有变化。ＳＡ能够显著降低超氧物阴离子含量和提高过氧化氢水平，但它对过氧化氢酶（ＣＡＴ）活性的抑制作用很弱，表明ＳＡ提高体内过氧化氢含量的原因主要是通过提高ＳＯＤ活性而不是抑制ＣＡＴ活性。同工酶分析表明，ＳＡ不能诱导新的ＳＯＤ同工酶，但可以诱导新的ＰＯＤ同工酶。

Activities of the antioxidant enzymes involved in superoxide anion (O -· 2) and hydrogen peroxide (H 2O 2) metabolism were determined and the contents of O -· 2 and H 2O 2 were also measured. All concentrations of salicylic acid (SA) tested (0.5, 1.0, 2.5 and 5.0 mmol/L) significantly enhanced superoxide dismutase (SOD) and peroxidase (POD) activities not only in the first treated true leaf (leaf 1) but also in the second untreated true leaf (leaf 2) of Cucumis sativus L. When the leaves were treated with 1 mmol/L SA within 6 to 72 h, the activity of POD increased by 22% to 67% in the treated leaf 1 and by 14% to 86% in the untreated leaf 2. However, no changes were observed during 3 h after treatment and at 96 h following treatment. Measurement of O -· 2 and H 2O 2 showed that there was a significant decrease in O -· 2 content and an increase in H 2O 2 content after SA treatment, but catalase (CAT) activity was only slightly inhibited and this suggested that the reason of the increase in H 2O 2 by SA treatment is not due to the inhibition of CAT but rather the increase in SOD activity. It was also found that SA at all concentrations tested could not induce new SOD isozyme but it induced 1 to 2 bands of new POD isozyme within one day after treatment. The results indicate that SA might involve in the regulation of antioxidant enzymes.