EFFECT OF LEAD STRESS ON ANTIOXIDANT MECHANISM AND DNA PROFILE IN DIFFERENT WHEAT CULTIVARS

Lead (Pb) is known to cause highly toxic direct and indirect effects on plants, animals and humans. This research was an attempt to study relationship between oxidative damage and DNA structure in two wheat genotypes exposed to heavy metal lead stress. For this reason, changes in root and shoot growth, the modulation of enzymatic antioxidant system, production of reactive oxygen species (ROS) and the extent of oxidative damage (membranes and DNA structure) in a drought-tolerant (cv. Bezostaya) and drought-sensitive (cv. Alpu) cultivars of wheat under 1, 1.5 and 2 mM lead concentrations (Pb(NO3)(2)) were determined. At the 5th day of germination stage under lead stress, root and shoot lengths decreased when compared with the control for both genotypes. While the activities of superoxide dismutase (SOD), peroxidase (PDX) and ascorbate peroxidase (APX) enzymes in both of wheat varieties increased markedly, catalase (CAT) activity decreased under the stress. Lead induced oxidative stress, causing membrane injury, measured by changes in malondialdehyde (MDA) contents, superoxide anion (O-2(-)) productions and hydrogen peroxide (H2O2) level in two wheat cultivars. The increment degree of MDA in Alpu was higher than those in B ezostaya. Effects of lead stress on genetic material were determined by comparing Random Amplified Polymorphic DNA (RAPD) profiles of normal and treated-wheat seedlings. Lead treatments caused to marked DNA mutations, however, the deterioration in genetic material of sensitive species was higher than in resistant one. As a result, this study showed that Alpu cultivar was negatively affected more than the Bezostaya variety from lead-induced oxidative stress.