Effects Of Low Night Temperature On Physiological Index And Morphological Anatomy Of Grafted Watermelon Seedlings

As the main fruit vegetable in summer, watermelon plays an important role in the world horticulture industry. With the increase of consumers demand, the cultivation area of watermelon is also expanding. Grafting is the effective realization of continuous cropping, and the preferred technology to overcome soil-borne disease. It has been widely applied in watermelon production. But it is easy to suffer from low temperature stress during the grafting stage of watermelon in early spring which is the main factor in the seedling raising stage of early spring. This thesis is based on the research of physiological index and morphological anatomy structure during the healing stage of watermelon grafted seedlings under different night temperatures, to explore the influence of low temperature on the survival rate of grafted watermelon seedlings. By a better understanding of the healing process of watermelon seedlings when it encountered early spring cold stress can improve the production technology and improve the survival rates of the grafted seedling. The main results are as follows.:1?In the healing process of the grafted seedlings, with the decrease of night temperature, the protective enzyme (SOD?POD?CAT) of Watermelon Grafted seedlings can alleviate the damage of cell membrane by enhancing its activity. The lower the night temperature was, the higher the activity could be. The lower the night temperature was, the higher the content of MDA and soluble protein in grafted seedlings could be. The physiological index of watermelon grafting seedlings'junction and scion leaves showed the same developing trend. Grafted watermelon scion leaves are more sensitive to the environment, and relatively good for measuring material.2?On the tenth day after grafting, the survival rate of grafted seedlings at night temperature of 12?,15? and 18? were 88%,87.7% and 93%.When the temperature is below 18 degrees, the survival rate of grafted seedlings at night temperature of 12? and 15? was basically the same.3?Through the anatomical observation on watermelon grafting seedlings, the concrescence characteristics of watermelon graft under 18? night temperature treatment was the fastest. On the fifth day, the vascular bridges were connected, and the whole healing process has been completed. With the night temperature decreased, the healing rate was slower. The concrescence characteristics of watermelon graft under 12? night temperature treatment formed necrotic layer on the third day, and formed cambium on the fifth day. Then, the tracheary elements were appeared, and the vascular bridges were connected.4?The differences in the histology of survival and death showed that vascular bridges connected was the most important. For one thing, the rootstock and scion have wider gully spacing, the callus of both sides failed to link. It has caused watermelon grafted seedlings to die.For another, the low temperature delay the differentiation of vascular tissue, not conducive to the connection of the vascular bundle.