Effects Of Silicon On Physiological Characteristics Of Longan Seedlings Under Drought Stress

In order to study the effects silicon with different concentration on drought resistance of ,Na2SiO3 was sprayed with three concentration(200 mg/L,400 mg/L,800 mg/L ) of silicon under drought stress condition.The changes of some physiological indexes including the content of chlorophyll,proline,soluable protein,starch;the activities of enzymes in antioxidant system,photosynthesis and chlorophyâ…¡fluorescence parameters in silicon were determined under different drought stress. The major findings are as follows:1 The results showed that the treatment of 400 mg/L silicon increased the content of soluable protein,relative water,soluable starch and reduced the proline,starch content and soluble sugar content under drought stress.2 After drought stress, membrane permeability, superoxide radical production rate, production rate of hydrogen peroxide and malondialdehyde were significantly increased; silicon processing leaves superoxide (O2.-) production rate, H₂O₂ and malondialdehyde (MDA), much lower than that of silicon processing, silicon under severe stress increased leaf ascorbate peroxidase (APX), superoxide dismutase (SOD) and catalase (CAT) activity.Effects of silicon reduced the ascorbic acid and GSH content in leaves of longan.3 The longan leaf chlorophyll a, chlorophyll b and carotenoid content; silicon treatment increased the chlorophyll a, chlorophyll b and carotenoid content and content;,it was beneficial to plant growth under drought stress,. Under drought stress,The silicon treatment reduced the net photosynthetic rate (Pn), transpiration rate (Tr), and increased intercellular carbon dioxide concentration (Ci).The silicon treatment increased Pn,Tr, and reduced Ci. Silicon is conducive to the conduct of plant photosynthesis.4 The main fluorescence parameters of Fo increased significantly, Fm, Fv, Fv/Fm and Fv/Fo were significantly decreased under severe stress.Under drought stress conditions, the increase of silicon processing Fv/Fo ratio was significantly higher than without silicon, it was concluded that PSâ…¡has high potential activity with silicon,reduced the inhibitory effect of drought stress on longan.