Antioxidative protection in wheat varieties under severe recoverable drought at seedling stage

The antioxidative protection in leaves of four winter wheat (Triticum aestivum L.) varieties with different field drought resistance was studied under severe recoverable soil drought at seedling stage by withholding irrigation for 7 days (57-59% leaf water deficit) followed by rewatering. A 3-fold raise in electrolyte leakage and a sharp increase in proline accumulation corresponded to drought severity. Hydrogen peroxide content and catalase (CAT) activity were maintained low under stress. Peroxidase (GPX) activity increased, whereas superoxide dismutase (SOD) activity only slightly changed. The content of ascorbate and low-molecular thiols diminished under severe drought and was restored in recovery. Malondialdehyde level was not changed significantly in drought-treated plants but raised after re-watering. In recovery CAT activity became significantly higher whereas GPX activity diminished. Three isoforms of SOD, one of catalase and three of GPX were revealed. Proline accumulation had a predominant role in drought response. As for varieties, drought sensitivity or tolerance was not necessarily correlated with differences in the antioxidative response at early vegetative stage.