INDUCTION OF ENZYME-ACTIVITIES AND ANTIOXIDANT PRODUCTION IN BARLEY PLANTS AS A RESULT OF SO2 FUMIGATION

Two cultivars (Arda and Plaisant) of barley (Hordeum vulgare) were exp osed continuously to fumigation with low concentrations of SO, (115, 2 20 and 350 mu g/m(3)) for 34 days. The increases observed in the activ ities of catalase (EC 1.11.1.6.), superoxide dismutase (EC 1.15.1.1.), glutathione synthetase (EC 6.3.2.3.), glutathione reductase (EC 1.6.4 .2.), glutathione peroxidase (EC 1.11.1.9.) and glutathione transferas e (EC 2.5.1.18,) following fumigation were higher in Arda than in Plai sant. The ratio of reduced glutathione to oxidized glutathione (GSH/GS SG) increased significantly in Plaisant, and even more so in Arda. The antioxidant levels in lipid extracts were higher than in the control only after exposure to SO2 at the lowest concentration, while at highe r concentrations no significant changes were observed. As to free radi cals, only after fumigation with the highest levels of SO2 a 5% increa se in free organic radicals was found in Plaisant, compared to the non -treated control. In previous studies it had been shown that Arda is m ore resistant to drought than Plaisant. Our data show that also in res ponse to low SO2 concentrations Arda has a higher potential to activat e anti-oxidative stress defences. These results suggest that the pheno type that proved to be more resistant to drought may have a higher abi lity than the sensitive one to activate antioxidative defences when ex posed to SO2 at low concentrations.