| Its effects on the levels of superoxide radical ( O ( 2 ) ( ) ) , hydrogen peroxide ( H ( 2 ) O ( 2 ) ) and the content of catalytic Fe , the activities of several antioxidative enzymes such as superoxide dismutase ( SOD ) , catalase ( CAT ) , ascorbate peroxidase ( APX ) and glutathione reductase ( GR ) , the contents of several non enzymatic antioxidants such as ascorbate ( ASC ) , reduced glutathione ( GSH ) , alpha tocopherol ( alpha TOC ) and carotenoid ( CAR ) , and the degrees of the oxidative damage to the membrane lipids and proteins were examined . ^^^ Treatment with 10 and 100 microM ABA significantly increased the levels of O ( 2 ) ( ) and H ( 2 ) O ( 2 ) , followed by an increase in activities of SOD , CAT , APX and GR , and the contents of ASC , GSH , alpha TOC and CAR in a dose and time dependent pattern in leaves of maize seedlings . ^^^ |