Metabolic adaptations to arsenic-induced oxidative stress in Pteris vittata L and Pteris ensiformis L

This study examined the metabolic adaptations of Pteris vittata L, an arsenic hyperaccumulator, under arsenic stress as compared to Pteris ensifonnis, a non-arsenic hyperaccumulator. Both plants were grown hydroponically in 20% Hoagland medium in controlled conditions and were treated with 0, 133 or 267 mu M arsenic as sodium arsenate for 1, 5 or 10 d. The fern fronds were analysed for differences in oxidative stress and antioxidant capacities after arsenic exposure. Upon exposure to 133 mu M arsenic, concentrations of chlorophyll, protein and carotenoids increased in P. vittata whereas they decreased in P ensifortnis. The H2O2 and TBARs concentrations were greater in P. ensiformis than R vittata in all treatments, indicating greater production of reactive oxygen species (ROS) by P ensiformis. The levels of ascorbate and glutathione, and their reduced/oxidized ratios in the fronds of P vittata of the control was much greater than R ensifortnis indicating that R vittata has an inherently greater antioxidant potential than P ensiformis. The lower levels of antioxidant compounds (ascorbate, carotenoids and glutathione) in P. ensiformis than P. vittata are consistent with its greater exposure to ROS and lower scavenging ability. The results together indicate that protection from oxidative damage by a greater level of ascorbate-glutathione pool is involved in the arsenic-tolerance in arsenic-hyperaccumulator P. vittata. (c) 2005 Elsevier Ireland Ltd. All rights reserved.