Malus hupehensis was used as experiment materials.This experiments were conducted to explore the effects of benzoic acid on the productivity of superoxide（O2 ·）,the contents of malondialdehvde（MDA）and sulfhydryl group activity（—SH）,antioxidant enzyme activity and mineral elements in roots of M.hupehensis seedlings.The results showed that there was no significant difference between the treatment of 5 mg·kg-1（soil）benzoic acid and CK in above parameters.With 25 mg·kg-1（soil）and 125 mg·kg-1（soil）benzoic acid treatments,O2 · and MDA contents increased in the early period and then declined;—SH content decreased during the treatment time;activities of SOD and POD increased firstly,then decreased,CAT activity decreased firstly and then slightly reversed,but lower than that of CK;SOD,POD and CAT had a similar trend,activities of roots increased under 5 mg·kg-1（soil）benzoic acid,while they were inhibited by 25 mg·kg-1（soil）and 125 mg·kg-1（soil）benzoic acid;mineral elements were decreased.Benzoic acid in low concentration promoted antioxidant enzyme activity,—SH content,and uptake of mineral elements,reduced O2 · and MDA contents.In conclusion,benzoic acid of 5 mg·kg-1（soil）had no effects on Membrance Lipid Peroxidation and Antioxidant enzymes in roots of M.hupehensis seedlings;at 25 mg·kg-1（soil）and 125 mg·kg-1（soil）,benzoic acid increased Membrance Lipid Peroxidationd,decreased activity of antioxidant enzymes of roots,and damaged integrity and stability of cell membrane in M.hupehensis seedlings,meanwhile,contents of mineral elements were decreased.
