Effects of aluminum on nucleoli in root tip cells, root growth and the antioxidant defense system in Vicia faba L.

The effects of different concentrations of Al (10 μM, 50 μM, 100 μM) on nucleoli in root tip cells, root growth, antioxidant enzyme activity and malondialdehyde (MDA) content were investigated in hydroponically grown Vicia faba L. Aluminum significantly inhibited root growth of V. faba treated with 50 μM and 100 μM Al. In the nucleolus in root tip cells, some particulates containing argyrophilic proteins were extruded from the nucleus into the cytoplasm, and some were scattered in the nucleus after Al stress. Superoxide dismutase (SOD) activity in leaves and roots exposed to different concentrations of Al was mostly higher than in the control. Seedlings exposed to 100 μM Al showed significantly higher peroxidase (POD) activity in roots than in the control. POD activity increased much more in roots than in leaves. Catalase (CAT) activity was lower in roots than in leaves. Malondialdehyde (MDA) content in leaves and roots of plants exposed to 50 μM and 100 μM Al was significantly higher than in the other groups and the control at 6 to 9 days of treatment. These results suggest that alterations in nucleoli and altered antioxidant enzyme activity and MDA content in V. faba can serve as useful biomarkers for detection of Al toxicity. The mechanisms of Al toxicity and tolerance in V. faba are briefly discussed