Change of Antioxidant Enzyme Activities during Heat Stress in Cucumber (Cucumis sativus L.)

This experiment was conducted to study the effect of high temperature stress on the antioxidant enzyme activity in four cucumber varieties viz.; 'Merry Swallow', 'FIVOS', 'Drawer ground frost' and 'Treasure'. Three antioxidant enzyme activities, guaiacol peroxidase (G-POD), ascorbate peroxidase (A-POD) and catalase (CAT) were further determined at vegetative and reproductive stage under heat stress. The results showed that 'Treasure' had the highest fruit production than others cultivated in net-house in Kaohsiung, Taiwan. We grouped ‘Treasure’ into heat-tolerant line, the other three cultivars into heat-sensitive lines. Besides, we found the G-POD, A-POD, and CAT activities increased significantly after expose to high temperature especially at reproductive stage in 'Treasure'. This phenomenon did not show in heat-sensitive varieties. It suggested that antioxidant enzyme activities would be closely related to heat stress tolerance. They are probably become a reliable indicators for heat tolerance to assist cucumber breeding.