Abstract: Effects of 24-Epibrassinolide on Antioxidant System in Cucumber Seedlings Roots under Hypoxia Stress KANG Yun-yan , GUO Shi-rong , Duan Jiu-ju (College of Horticulture, Nanjing Agriculture University, Nanjing 210095) Abstract: [Objective] The aim of our work was to study the effects of exogenous 24-epibrassinolide (EBR) on ROS, activities of antioxidant enzymes and antioxidants and their time courses in cucumber (Cucumis sativus L.) seedling roots under hypoxia stress. [Method] Seedlings of a hypoxia-resistant cultivar, Lübachun No.4, and a hypoxia-sensitive cultivar, Zhongnong No.8, were subjected to nutrient solution hypoxia stress treatments. The effects of EBR on the growth, ROS, antioxidant enzymes and antioxidants in seedlings roots were investigated. [Results] Under hypoxia stress, O2– level and lipid peroxidation were significantly increased in the roots upon exposure to hypoxia stress, which were inhibited by exogenous EBR application. EBR treatment significantly increased seedlings growth, SOD、APX、GR activities and contents of AsA、GSH under hypoxia stress. [Conclusion] From the results obtained in this work it can be conclude that oxidative damage on seedling roots by hypoxia stress can be considerably alleviated, which elevated the tolerance of plants.

Key words: 24-Epibrassinolide, Cucumber seedlings, Hypoxia stress, Antioxidative system, Lipid peroxidation