Effect of Exogenous ABA on Chilling Resistance and Some Physiological Index in Watermelon Seedling

The seedlings of watermelon at 3 leaf stage were treated with 5,10,15,20 and 25 mg/L of ABA and then exposed at 5 ℃ for 24 h in order to study the effects of ABA on chilling-tolerance.The chilling-tolerance of watermelon seedling can be increased with ABA treatment.The concentration of ABA at 20 mg/L showed the most effective results.The results showed that ABA could improve the activity of superoxide dismutase(SOD) and catalase(CAT),remarkably delay the decrease of chlorophyll and reduced glutathione hormone(GSH) content as well as the increase of malonaldehyde(MDA) content in the leaves of watermelon seedling during low temperature stress.On the other hand,ABA could effectively promote the increase of contents of proline and soluble sugar in the leaves of watermelon seedling during low temperature stress.The ascorbic acid(AsA) content was maintained a steady level in leaves of watermelon seedling by ABA treatment.