[Effects of 24-epibrassinolide on antioxidant system and anaerobic respiratory enzyme activities in cucumber roots under hypoxia stress].

Seedlings of a hypoxia-resistant cultivar, Lübachun No.4, and a hypoxia-sensitive cultivar, Zhongnong No.8, were applied by feeding roots. The effects of exogenous 24-epibrassinolide (EBR) on lipid peroxidation, activities of major antioxidant enzymes and anaerobic respiratory enzymes and their time courses were investigated in cucumber seedling roots under hypoxia stress. Root growth was significantly inhibited under hypoxia stress, which was improved by exogenous EBR application (Figs.1,2). O(-*)(2) and H(2)O(2) level and lipid peroxidation were significantly increased in the roots upon exposure to hypoxia stress, which were inhibited by exogenous EBR application (Fig.3). EBR treatment increased SOD and POD activities under hypoxia stress (Fig.4). Hypoxia enhanced the activities of lactate dehydrogenase (LDH), alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC) whereas EBR treatment significantly increased ADH activity, but decreased LDH activity (Fig.5). There was no significant difference in CAT and PDC activities between the hypoxia stress treatment and "hypoxia+EBR" treatment (Fig.4,5). From the results obtained in this work it can be concluded that oxidative damage on seedling roots by hypoxia stress can be considerably alleviated, and alcohol fermentation can be enhanced by EBR treatment.