Abstract: In the present study the effects of different concentrations of MeJA on the activities of SOD and CAT in roots and shoots of corn seedlings were studied in two parts. In the first part, the plants were pretreated with 0, 5, 10, 20, 50 and 100 μmol methyl jasmonate 24 h before PQ application as an inducer of oxidative stress agent. In the second part, the 0, 20, 50 and 100 μmol concentrations of MeJA were used after PQ imposed oxidative stress. Subsequently, the intensity of enzymatic activities in roots and shoots were separately measured. The certainty of oxidative stress imposition by PQ was investigated by measuring the MDA levels as a product of lipid peroxidation and indicator of oxidative stress. Reducing the levels of lipid peroxidation to the control level was accomplished by increasing the activity of SOD and CAT through changes in concentration and time of application of MeJA in roots and shoots. In this relation, the 50 and 100 μmol concentrations of MeJA could decrease the lipid peroxidation with highest efficiency and meaningfully in roots and shoots as compared with controls.