The Effects Of Exogenous Melatonin On The Growth And Yield And Quality Of Watermelon

Watermelon is a very important horticultural crop in the world,China is a major producer and consumer of watermelon.The literature indicates that exogenous melatoninapplication can promote the growth and yield of plants.The research for yield and quality by application of different Melatonin concentration and application method was rarely reported.In order to standardize the appropriate melatonin concentration and application site to get optimal growth,yield and quality of watermelon this experiment was conducted.Nonkeda No.5 variety of watermelon was used in our experiment.This variety is the first generation of early maturing hybrids.It is important variety grown in early spring in major cultivated area of Shaanxi Province.In this study,different concentrations of melatonin were used to treat the top buds and leaves of watermelon to standardize the appropriate concentration and suitable treatment site.In the first experiment,four different concentrations of melatonin were used:0,10,100,1000?mol·L^-1 on top buds and leaves of watermelon seedlings.According to the results of the experiment,seven different concentrations of melatonin were further designed:0,10,50,100,150,200,300?mol·L^-1,and applied on top bud and leaf.The test results are as follows:1.After analysis of the growth index of watermelon plants it was concluded that melatonin promoted the growth of plants in the appropriate concentration range.When the melatonin concentration was 100?mol·L^-1 to 150?mol·L^-1,the growth and development of watermelon was significantly promoted,while the concentration of more than 200?mol·L^-1have inhibited the growth and development of the plant.2.Different concentrations of melatonin have certain effects on photosynthesis of watermelon.When the melatonin concentration was 100?mol·L^-1 to 150?mol·L^-1,the net photosynthetic rate and stomatal conductance of the plants were recorded best.After the application of 100?mol·L^-1 no significant difference was recorded in the net photosynthetic rate of the treated top bud?T-M-100?and the melatonin-treated leaves?L-M-100?,over the control,significantly improved compared to the CK.3.The changes in watermelon yield and watermelon quality were similar under different treatment levels of melatonin.The yield increased significantly compared with the control,the total soluble sugar and total soluble solids content of watermelon fruit were significantly higher after application of melatonin concentration from 100?mol·L^-1 to 150?mol·L^-1on top buds and leaves.In contrast,the content of lycopene,soluble protein and vitamin C in watermelon fruit increased significantly.4.Relevant parameters showed that the growth,yield and quality of watermelon under the treatment of melatonin were the best.However,considering the economic benefits of input and production,melatonin treatment of the top buds with concentration of 100?mol·L^-1 to 150?mol·L^-1was found better over other treatments.