RESPONSE OF ANTIOXIDANT DEFENSE SYSTEM TO OSMOTIC STRESS IN MAIZE SEEDLINGS

In order to evaluate the effects of osmotic stress on fresh weight, H2O2, MDA, total phenolics, total soluble proteins and response of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (PDX) and catalase (CAT) were mentioned. A factorial experiment was carriedout under laboratory conditions with two maize inbred lines (MO17 and B-73) and two osmotic stress levels induced by PEG (control and -6 MPa). Electrophoretic analyses were performed for SOD, PDX and CAT in leaves of maize seedlings using 8% slab polyacrylamide gels. For SOD, PDX and CAT, three, two and one isoforms wereobserved, respectively. On the basis of percent of inhibition in fresh weight under drought stress MO17 was ranked as tolerant (47% inhibition) and B-73 drought sensitive (more than 50% inhibition). Drought stress enhanced antioxidant enzymes activity and total phenolics in maize seedlings. MO17 also exhibited low levels H2O2, MDA and total soluble proteins, compared to B73. In addition, MO17 showed higher enzymatic activity of SOD1, SOD2, SODS, PDX1, PDX2, CAT and total phenolics leaves than B73. These results indicate that MO17 inbred line tolerance to drought stress during seedling is associated with enhanced activity of antioxidant enzymes. This study provides a mechanism for drought tolerance in maize seedlings.