JXB Advance Access originally published online on March 21, 2005
Journal of Experimental Botany 2005 56(415):1335-1342; doi:10.1093/jxb/eri134
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RESEARCH PAPER |
Antioxidant responses of hyper-accumulator and sensitive fern species to arsenic
1Soil and Water Science Department, University of Florida, Gainesville, FL 32611-0290, USA
2National Botanical Research Institute, Lucknow, Uttar Pradesh, 226001, India
3Nuclear Agriculture and Biotechnology Division, Bhabha Atomic Research Centre Trombay, Mumbai, 400 085, India
* To whom correspondence should be addressed. Fax: +001 352 392 3902. E-mail: lqma{at}ifas.ufl.edu
Plant species capable of hyper-accumulating heavy metals are of considerable interest for phytoremediation, and differ in their ability to accumulate metals from the environment. This work aims to examine (i) arsenic accumulation in three fern species [Chinese brake fern (Pteris vittata L.), slender brake fern (Pteris ensiformis Burm. f.), and Boston fern (Nephrolepis exaltata L.)], which were exposed to 0, 150, or 300 µM of arsenic (Na2HAsO4.7H2O), and (ii) the role of anti-oxidative metabolism in arsenic tolerance in these fern species. Arsenic accumulation increased with an increase in arsenic concentration in the growth medium, the most being found in P. vittata fronds showing no toxicity symptoms. In addition, accumulation was highest in the fronds, followed by the rhizome, and finally the roots, in all three fern species. Thiobarbituric acid-reacting substances, indicators of stress in plants, were found to be lowest in P. vittata, which corresponds with its observed tolerance to arsenic. All three ferns responded differentially to arsenic exposure in terms of anti-oxidative defence. Higher levels of superoxide dismutase, catalase, and ascorbate peroxidase were observed in P. vittata than in P. ensiformis and N. exaltata, showing their active involvement in the arsenic detoxification mechanism. However, no significant increase was observed in either guaiacol peroxides or glutathione reductase in arsenic-treated P. vittata. Higher activity of anti-oxidative enzymes and lower thiobarbituric acid-reacting substances in arsenic-treated P. vittata correspond with its arsenic hyper-accumulation and no symptoms of toxicity.
Key words: Antioxidant responses, arsenic, hyper-accumulation, Nephrolepis exaltata, Pteris ensiformis, Pteris vittata
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