Abstract:Catalase activity in cucumber leaves increased by 49.65% after the seedlings weresprayed with 100 mg L-1 deltamethrin for 2 days. Deltamethrin of 150 mg L-1 increased thecontents of protein, DNA and RNA by 33.25%, 15.39% and 11.49%, respectively.However, high deltamethrin concentration(500 mg L-1) decreased the catalase aCtivity by6.94%, and decreased the contents of protein, DNA and RNA by 10.22%, 9.85% and16.20%, respectively. No effect of deltamethrin on in vitro catalase activity was found. Theeffects of deltamethrin on protein content and catalase activity in cucumber leaves could bepartially inhibited by cycloheximide. The possible mechanism of the effect of deltamethrinon catalase activity was discussed.