黄瓜组织中几种酶活性与其对霜霉病抗性的关系

对抗，感霜霉病两类黄瓜品种的萌动种子，子叶，不同叶痊直叶及定位叶片感染霜霉病菌后叶内超氧化物歧化酶（ＳＯＤ），多酚氧化酶（ＰＰＯ）和过氧化酶（ＰＯＤ）活性的测定结果表明：抗病品种比感染品种萌动种子中的ＳＯＤ活性高５４．１５％，ＰＰＯ活性高６２．１４％；子叶中的ＳＯＤ活性高３５．５１％，ＰＰＯ活性高４０．１０％，ＰＯＤ活性高７４．４７％；不同叶位真叶内，除ＳＯＤ活性为感病品种高于抗病品种１３１．．５

The Relationships Between the Activity of Several Enzymes in Cucumber Tissues and Their Resistance to Downy Mildew of Cucumber

The activities of superoxide dismutase(SOD), peroxidase(POD) and polyphenol oxidase(PPO) in germinated seeds, cotyledons, true leaves on different nodes and the leaves inoculated with Pseudoperronospora(Berk. et Curt.) Rostov. of cucumber varieties with different resistance to downy mildew of cucumber were measured. The results showed that SOD activity in germinated seeds and cotyledons of resistant varieties were 54.15% and 35.51% higher than that of the susceptible varieties. SOD activity in true leaves on different nodes of resistant varieties was 131. 51% higher than that of the susceptible varieties. Activities of polyphenol oxidase in germinated seeds, cotyledons and true leaves on different leaf nodes of resistant varieties were 62. 14%, 60. 00%, and 12. 93% (mean of 3 leaf nodes) higher than that of the susceptible varieties respectively. Activities of prooxidase in cotyledon and true leaves on different nodes of resistant varieties were 74. 47% and 28. 76% higher than that of the susceptible varieties respectively. When the leaves on the second node was inoculated with Pseudoperonosis (Berk. et Curt. ) Rostov, the activity of polyphenol oxidase decreased with increase of the time after inoculation (i. e. increase of disease index). However, activities of two enzymes in resistant varieties were higher than those of the susceptible varieties all time,activity of SOD was going down firstly and then rising, but that of the resistant varieties was always higher than that of the susceptible varieties.It was concluded that there was a negative correlation between the activity of SOD and resistance to downy mildew of cucumber, and there were positive correlations between the activities of polyphenol oxidase and prooxidase and the resistance to downy mildew of cucumber.