Isoenzyme Profiles of Peroxidase, Catalase and Superoxide Dismutase as Affected by Dehydration Stress and Aba during Germination of Wheat Seeds

Isoenzyme profiles of peroxidase [EC 1.11.1.7], superoxide dismutase (SOD)[EC 1.15.1.1] and catalase [EC 1.11.1.6] in the endosperm and roots of wheat seedlings germinated under chronic stress conditions were investigated. Low and high temperature, 0.2 M NaCl and 0.5 M sucrose were applied as stress factors. Germination of seeds in the presence of ABA was used as a dehydration stress confirming standard. A strong inhibition of germination rate and growth of roots by all stress factors applied was established. Significant inhibitory effects of low temperature and sucrose on the activity of anionic peroxidase isoenzymes in the endosperm was observed. ABA activated moderate moving cationic peroxidases in the roots. The activity of fast moving SOD isoenzyme decreased significantly in the endosperm and roots of seedlings subjected to salt and osmotic stress. A strong inhibitory effect of H2O2 on catalase activity was observed in the endosperm, however, in the roots a stimulation was observed. The most sensitive among the antioxidant enzymes tested was catalase. The growth retardation in wheat seedlings correlated closely with a decrease in catalase activity. The low temperature was the strongest effector among the stress factors applied. The most specific isoenzyme profile was the profile of cationic peroxidase. Tissue-specific differences were found in the response of the antioxidant enzymes to the stress factors studied. The results were discussed in terms of the importance of the antioxidant enzymes tested for the protection of germinating wheat seeds against dehydration stress.