Effect of aluminium on peroxidase activity in roots of Al-sensitive and Al-resistant barley cultivars

The effect of Al stress on peroxidase activity and peroxidase isozymes was studied in roots of two barley cultivars with contrasting sensitivity to Al. Al treatment induced a tremendous enhancement of guaiacol peroxidase activity especially in roots of Al-sensitive barley cv. Alfor. After 48 h of Al treatment activity of peroxidase in roots of cv. Alfor was up to 5.5 times higher than the control roots. In contrast, activity of peroxidase in the roots of Al-resistant cv. Bavaria was about one half than that in roots of Al-sensitive Alfor. SDS-PAGE analysis revealed that at least five peroxidase isozymes are activated by Al treatment. Using IEF we determined that three of Al-induced peroxidase isozymes are cationic with pI about 8.2, 8.4 and 8.6, while two other are anionic isoperoxidases with pI about 4.0 and 4.5. Al induced increase in the activity of root peroxidases correlated with the extent of Al induced root growth inhibition. The inhibition of root growth in Al-sensitive Alfor represented 44% but in Al-resistant Bavaria only 21% in comparison with control plants. Higher peroxidase activity, as well, as higher inhibition of root growth in Al-sensitive Alfor suggest that enhanced oxidative stress generated by Al treatment is significantly more stressful in Alfor than in the Al-resistant Bavaria.