Study on Relationship between Physiological Changes and Chilling Tolerance in Seed-used Watermelon Seedling under Low-temperature Stress

The effects of 10℃ low temperature treatment on chilling tolerance,photosynthesis characteristics and protective system against active oxygen of 3 leaf stage seedlings of two seed-used watermelon varieties,one is black(wb10),the other is red(wb7),were investigated under low temperature stress.The research aim at supply theory basis for introduction and cultivation,improving Chilling tolerance of seed-used watermelon.The results showed that compared with control,chlorophyll content,the photosynthetic rate(Pn),stomatal conductance(Gs)and intercellular CO2 concentration(Ci),transpiration rate(Tr) were declined with the time extension of low temperature treatment,the leakage of electrolytes,the content of proline and the content of MDA were increased in all the four varieties.There was a considerable difference of chilling tolerance among different varieties;Chilling tolerance from being strong to weak is wb10wb7,seedlings of variety wb10 and wb7 with stronger chilling tolerance had lower electrolytic leakage(%),lower MDA content,higher proline content in leaves than those of variety wb10 and wb7 with weaker chilling tolerance.Therefore,chilling tolerance may be related to chilling injury index、photosynthesis characteristics and membrane stability in the plants.