The effect of silica nano-particles,tetraethyl orthosilicate (TEOS) and sodium silicate in solution culture on wheat powdery mildew and its action mechanism to pathogen attack were studied. The results showed that wheat seedlings cultured in nutrient solution with silicon compounds alleviated wheat powdery mil-dew,the control efficacies of TEOS and sodium silicate treatments were 54.08% and 51.36%,respectively,but that of silica nano-particles treatment was only 1.02%. Scanning electron micrograph and X-ray energy dispersive analysis (SEM-EDX) showed that wheat leaves cultured in nutrient solution with TEOS and sodium silicate had more silicon deposition than that of silica nano-particles. It indicated that wheat possessed the equal good imbibe ability to TEOS and sodium silicate,but poor to silicate nano-particles. When wheat leaves were infected with Blumeria graminisf.sptritici,silicon might has a physical prohibition effect to pathogen spore penetration.
