[Effect of low temperature stress on chilling tolerance and protective system against active oxygen of grafted watermelon].

This paper studied the chilling tolerance and the activity of protective system against active oxygen of own-rooted and grafted watermelon seedlings. The results showed that under low temperature stress, the chilling tolerance of the watermelon seedlings grafted on figleaf was higher than that of the seedlings grafted on Chaofeng F1, and that of the own-rooted seedlings was the lowest. The decrease of chlorophyll, ascorbate and GSH contents and superoxide dismutase, ascorbate peroxidase and dehydroascorbate reductase activities as well as the increase of MDA content in the leaves of both own-rooted and grafted watermelon seedlings indicated an injury on the protective system against active oxygen, and induced lipid peroxidation under low temperature stress. However, the activity of protective system against active oxygen was higher in grafted watermelon seedlings than in own-rooted watermelon seedlings. The activity of protective system against active oxygen in figleaf gourd-grafted watermelon seedlings with stronger chilling tolerance was higher than that of Chaofeng F1-grafted watermelon seedlings with weaker chilling tolerance. It could be concluded that the enhancement of chilling tolerance in grafted watermelon seedlings was related to the increase of antioxidants and antioxidative enzyme activities.