The influences of different rootstocks on chilling tolerance and physiological parameters in watermelon seedlings have been studied. The results showed that grafting improved the chilling tolerance. Compared with own-rooted watermelon seedlings, the grafted watermelon seedlings had lower chilling injury index, lower electrolytic leakage (%), lower malondialdehyde (MDA) content, higher chlorophyll and proline content, and higher activities of superoxide dismutase (SOD), ascorbate peroxidase (AsA-POD) and dehydroascorbate reductase (DR) in the leaves under low temperature stress. There was a considerable difference of chilling tolerance among different grafted watermelon seedlings due to the difference of rootstock chilling tolerance. After low temperature treatment, the grafted seedling with higher chilling tolerance had lower electrolytic leakage (%),lower MDA content, higher proline content and higher activities of SOD, AsA-POD and DR in the leaves compared with the grafted seedling with weaker chilling tolerance. From these, we could conclude that chilling tolerance of watermelon seedlings may be related to higher antioxidative ability and membrane stability in the plants. The chilling tolerance of grafted seedling could be properly evaluated by comprehensive physiological indexes but not a single physiological index.
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