Effects of plant growth regulators on the antioxidant system in callus of two maize cultivars subjected to water stress

The effects of brassinolide, uniconazole and methyl jasmonate on several aspects of antioxidant defences, were studied in callus tissues of drought-resistant (PAN 6043) and drought-sensitive (SC 701) cultivars of maize. When regulator-treated calli were subjected to water stress with PEG for 24 h the activities of antioxidant enzymes, such as superoxide dismutase, catalase, ascorbate peroxidase, peroxidase and glutathione reductase, remained higher in callus of the drought-resistant than in callus of the drought-sensitive cultivar. Damage, as indicated by the levels of hydrogen peroxide and malondialdehyde, the reduction of ascorbate and carotenoids, and leakage of electrolytes from cells was apparent in callus of both cultivars as a consequence of the applied water stress. However, the damage was less marked in the drought-resistant cultivar. The regulator-treated callus of this cultivar also had a higher survival percentage than that of the drought-sensitive cultivar. The present results also compare the effects of growth regulators on antioxidant systems in callus tissue of different drought-resistant cultivars when exposed to paraquat and water stress.