Comparative analysis of antioxidant response by Pteris vittata and Vetiveria zizanioides towards arsenic stress

Abstract

Antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione peroxidase (GPX) reportedly allow plants to combat toxic metal stress. Hydroponic experiment was conducted to study the response of antioxidant enzymes under arsenic (As) stress in the fronds and roots of an Indian ecotype of Pteris vittata (As hyperaccumulator) and Vetiveria zizanioides (As non hyperaccumulator). These plants were exposed to different As levels (0, 10, 20, 30 & 50mg As L−1) for 10days in green house. In P. vittata and V. zizanioides, total As accumulation in biomass increases with increase in As concentrations. Arsenic accumulation was more in the fronds than in the roots of P. vittata, though not in case of V. zizanioides. Arsenic accumulation in total plant biomass of P. vittata and V. zizanioides was 879mg and 785mg Askg−1 respectively. Enzymatic antioxidants response in P. vittata under As stress showed increased activity in different parts in comparison to control. All enzyme activity was higher in fronds as compared to roots which corresponded to more As accumulation in fronds. Results indicate that enhanced activities of the antioxidant enzymes play a significant role in As tolerance and hyperaccumulation by P. vittata whilst changes in these enzyme activities did not show a specific trend in V. zizanioides under As stress. The results indicate that P. vittata has evolved mechanisms for As detoxification and hyperaccumulation while V. zizanioides does not, but sustains a moderate level of As stress presumably as excluder.