The Mechanisms Of Silicon In Alleviating Autotoxicity During Seed Germination And Seedling Growth Of Cucumber

Silicon?Si? is the second most abundant element after oxygen in the soil. Si dioxide comprises 50-70 % of the soil mass. All plants rooted in soil include some Si in their tissues. It has been demonstrated that Si can mitigate not only biotic stresses?e.g., pathogens and pests?, but also abiotic stresses such as salinity, water stress, heavy metal toxicity, and nutrient imbalance. Autotoxicity is one of many diverse abiotic stresses, and it is one of the main causes of decline in crop yield and quality, which is present widely in vegetable crops, especially cucurbit crops. Till now, the information of Si effects on autotoxicity tolerance of cucumber?Cucumis sativus L.? and its mechanism is still scant, the mechanism of silicon on crop autotoxicity is still unclear. Therefore, the purpose of this study was to investigate the effects of exogenous Si on autotoxicity in cucumber seed germination and seedling growth. To clarify the regulation mechanism of silicon alleviates autotoxicity in cucumber. The main results were presented as follows:1. Si improved the activity of amylase, and the total amylase and ?-amylase activities attained a maximum at 36 h, increased AMY??-amylase? and BMY??-amylase? transcript levels?up-regulated 2227.75 % and 259.96 % respectively?, improved the conversion rate of carbohydrates, and enhanced the growth of PA-treated plants.2. Si significantly reduced the levels of ELP, MDA, and lowered the endogenous concentrations of O₂^·-, proline, and H₂O₂, while increasing the relative activities of SOD, CAT, POD, and APX and the contents of Si, As A and GSH, alleviated lipid peroxidation damage of cucumber seedlings under PA and CA stressed.3. Si increased the number and the opening degree of stomata in the unit area leaf under CA-stressed, increased the photochemical activity of chloroplasts, alleviated the damage of PSI and PSII under CA-treated, and enhanced the ability of synthesis and accumulation of organic compounds in cucumber seedlings.4. Established the method of HPLC extraction and quantitative determination of PA in plant tissue for the first time. Si-treated was effectively restrained the absorption and accumulation of PA and CA, repaired the damage of root tip cell and chloroplast in cucumber seedlings under PA-stressed, and protecting the cell wall and membrane integrity and function. The beneficial effects of Si were more obvious under conditions of PA or CA-induced stress.