Abstract:Silicon (Si) is the second largest abundant mineral element in the earth‘s crust. Although Si is still not listed as an essential element for the majority of plant species, it plays important roles in stimulating plant growth and nutrition uptake and enhancing plant resistance to abiotic and biotic stresses. This paper reviewed the distribution and absorption of Si in plant and its physiological functions with focusing on the mechanisms of Si mediated pathogen resistance. Higher plants mainly take up Si in the form of \[Si(OH)4\], and there are active and passive Si uptake mechanisms. Silicon can deposit in the epidermal cell walls beneath the cuticle, form a cuticle-Si double layer and enhance cell wall mechanical strength and stability, and therefore retard and resist pathogen from penetration and spreading. More research evidence shows that Si-treated plants can significantly increase the activity of protective enzymes such as peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, etc. in leaves and the production of antifungal compounds such as phenolic metabolism product, phytoalexins, pathogenesis-related proteins, etc., which in turn activate the plant defense system and enhance the plant resistance to pathogen. Studies in molecular level show that Si can induce the expression of defense-related genes as well as interact with disease-resistant signal molecules such as salicylic acid, jasmonic acid and ethylene for signal transduction.