Inducement Of Postharvest Sodium Silicate Treatment On Activated Oxygen And Its Metabolize System In Muskmelon (cv. Yujinxiang)

For further understanding the mechanism of enhancing postharvest diseases resistance with Si treatment, sodium silicate at 100mmol/L was used as a postharvest treatment of induction resistance on muskmelon (Cucumis melon L. cv. Yujinxiang) to study inducement of ROS, 6 kinds enzymes and 2 antioxidants for ROS metabolism, moreover, 3 resisted genes were analysed by semi quantitative RT-PCR. The results indicated as below:1. Sodium silicate treatment remarkably promoted the accumulation of hydrogen peroxide (H₂O₂) and superoxide ((O₂)⁾ in fruit. The content of H₂O₂ was 36.8% higher than the control on 4th day, and the content of (O₂) was 2 times than the control on 6th day. Sodium silicate treatment evidently increased the content of MDA with 29.3% higher than the control on 4th day, obviously decreased the membrane integrity which was 89.2% of the control on 6th day.2. The activities of CAT and APX were effectively inhibited after sodium silicate treatment, CAT activity was 62.3% of the control on 4th day, and APX activity was 84% of the control on 6th day. The activities of POD, GR, SOD and NADPH oxidase increased after sodium silicate treatment. On 4th day, the activities of POD, GR and SOD were 39.4%, 24.8%, 32.3% higher than the control respectively, and the NADPH oxidase activity was 28.4 higher than the control.3. As a response of inducement, the ASA and GSH accumulated in fruit after sodium silicate treatment. The content of ASA was 69.1% higher than the control on 10th day, and the content of GSH was 3.8% higher than the control on 8th day.4. The expression of APX gene of treated fruit was inhibited, which was 66.2% of the control on 6th day. However, the expressions of POD and SOD gene were increased. The expression of POD gene was 2.14 times than the control on 4th day, and the expression of SOD gene was 1.15 times than the control on 8th day. Moreover, the trends of the expression of APX, POD and SOD gene and the activities of APX, POD and SOD were basically consistent respectively after treatment with sodium silicate.It is suggested that sodium silicate induces activated oxygen and its metabolize system in gene and biochemical level to enhance the systemic resistance of fruit.