Abstract: The activity of peroxidase in the shoot tips and the leaves of gynoecious cucumber plants increased significantly after treatment of silver nitrate. The maximum increment was 178.2% in the shoot tips after 24 hours and 284.6% in leaves after 36 hours. Meanwhile, new isozyme bands in peroxidase, polyphenol oxidase and superoxide dismutase were developed by silver nitrate treatment. It is considere d that the response of cucumber plants to silver ion injury resulted in the rising of activity and the production of new oxidase isozymes.