To ascertain the roles of exogenous salicylic acid on gray mold (Botrytis cinerea Pers. ), the defense enzyme activities and pathogenesis-related substance contents in cucumber seedlings were determined. The results showed that exogenous salicylic acid significantly decreased the disease index (n=9, P<0. 01), improved the activities of phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD), and also increased total polyphenol, flavonoid and lignin contents by 12. 0%, 32. 3% and 31....