Comparison of root absorption, translocation and tolerance of arsenic in the hyperaccumulator Pteris vittata and the nonhyperaccumulator Pteris tremula

Several fern species can hyperaccumulate arsenic, although the mechanisms are not fully understood. Here we investigate the roles of root absorption, translocation and tolerance in As hyperaccumulation by comparing the hyperaccumulator Pteris vittata and the nonhyperaccumulator Pteris tremula. The two species were grown in a pot experiment with 0-500 mg As kg(-1) added as arsenate, and in a short-term (8 h) uptake experiment with 5 pm arsenate under phosphorus-sufficient conditions. In the pot experiment, P. vittata accumulated up to 2500 mg As kg(-1) frond d. wt and suffered no phytotoxicity. P. tremula accumulated < 100 mg As kg(-1) frond d. wt and suffered severe phytotoxicity with additions of ! 25 mg As kg-1. In the short-term uptake experiment, P. vittata had a 2.2-fold higher rate of arsenate uptake than P. tremula, and distributed more As taken up to the fronds (76%) than did P. tremula (9%). Our results show that enhanced root uptake, efficient root-to-shoot translocation, and a much elevated tolerance through internal detoxification all contribute to As hyperaccumulation in P. vittata.