Effects Of Low Temperature Stress On Seedling Growth And Physiological And Biochemical Properties Of Seed-used Watermelon Seedlings

The paper investigated the effects of10℃low temperature treatment on chilling tolerance.morphological index, photosynthesis characteristics and protective system against active oxygen of3leaf stage seedlings of four seed-used watermelon varieties, whf (black),wl001(red),w1007(black), w13(red) from the ten varieties under low temperature stress. The research aim was to supply theory basis for introduction and cultivation, improving chilling tolerance of seed-used watermelon. The results were as followings:1.Chilling tolerance of seedling had highly significant negative with chilling injury index under low temperature stress.The index of different material was different, Chilling toleran from being strong to weak was whf>w1007>wl001>wl3. The chilling injury was serious with the time extension of low temperature treatment, the varieties of w13was more serious than other varieties.2.Low temperature can inhibit growing height,stem diameter,the area of third leaf,fresh and dry weights of the above and under ground parts,root-top ratio(R/T)accumulation of seed-used watermelon seedlings increased slowly root-top ratio(R/T)decreased as the time prolonged under10℃temperature.The later period of low temperature,the1001and1007of the area of third leaf and fresh and dry weights of the above ground parts were declined.3.The chlorophyll content,the photosynthetic rate(Pn),stomatal conductance(Gs)and intercellular CO2concentration(Ci), transpiration rate(Tr) of seed-used watermelon seedlings were declined with the time extension of low temperature treatment.The variety of w13had largest changed that is to say it was sensitive of low temperature.4.POD and APX activities,MDA content,electrolytic leakage (%), proline content increased,while SOD and CAT activities of seed-used watermelon seedlings decreased in leaves as the time prolonged.In conclusion, low temperature would damage seed-used watermelon seedlings.The results showed that low temperature injure more serious with the time extension of low temperature treatment.Therefore,chilling tolerance of seed-used watermelon Seedings maybe related to chilling injury index,physiologicalcharacteristics,Physiological characteristics,photosynthesis characteristics and membrane stability in the plants. HeiFeng had strongest ability to endure low temperature and Chaohuhong had weakest ability to endure low temperature in four varieties.The ability of the black seed-used watermelon to endure low temperature was stronger than the red black seed-used watermelon.It is related to the seed source.So we can select HeiFeng as one of the cultivars for seed-usedwatermelon planting in spring.