Highly efficient xylem transport of arsenite in the arsenic hyperaccumulator Pteris vittata

The hyperaccumulator Pteris vittata translocates arsenic (As) from roots to fronds efficiently, but the form of As translocated in xylem and the main location of arsenate reduction have not been resolved. Here, P. vittata was exposed to 5 mu M arsenate or arsenite for 1-24 h, with or without 100 mu M phosphate. Arsenic speciation was determined in xylem sap, roots, fronds and nutrient solutions by high-performance liquid chromatography (HPLC) linked to inductively coupled plasma mass spectrometry (ICP-MS). The xylem sap As concentration was 18-73 times that in the nutrient solution. In both arsenate- and arsenite-treated plants, arsenite was the predominant species in the xylem sap, accounting for 93-98% of the total As. A portion of arsenate taken up by roots (30-40% of root As) was reduced to arsenite rapidly. The majority (c. 80%) of As in fronds was arsenite. Phosphate inhibited arsenate uptake, but not As translocation. More As was translocated to fronds in the arsenite-treated than in the arsenate-treated plants. There was little arsenite efflux from roots to the external solution. Roots are the main location of arsenate reduction in P. vittata. Arsenite is highly mobile in xylem transport, possibly because of efficient xylem loading, little complexation with thiols in roots, and little efflux to the external medium

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

Case Reports: Arsenic pollution in Thailand, Bangladesh and Hungary

The purpose of this review is to share information on how arsenic contamination arises and what options are available to mitigate it when it occurs. We describe how contamination arose in three countries, two Asian, and one European, and the approaches employed to resolve it. In the three selected countries, the presence of arsenic is both long term and of geological origin, yet the affected regions have distinct and contrasting concerns, both in the scale of the contamination of the abiotic environment and in the extent of human health impacts arising from arsenic exposure. Therefore, we hope that knowledge of the range of problems encountered in the three countries, and their potential solutions, will contain common themes that, at least partly, facilitate stakeholder endeavours to address arsenic contamination in other affected regions

Case Reports: Arsenic pollution in Thailand, Bangladesh and Hungary

The purpose of this review is to share information on how arsenic contamination arises and what options are available to mitigate it when it occurs. We describe how contamination arose in three countries, two Asian, and one European, and the approaches employed to resolve it. In the three selected countries, the presence of arsenic is both long term and of geological origin, yet the affected regions have distinct and contrasting concerns, both in the scale of the contamination of the abiotic environment and in the extent of human health impacts arising from arsenic exposure. Therefore, we hope that knowledge of the range of problems encountered in the three countries, and their potential solutions, will contain common themes that, at least partly, facilitate stakeholder endeavours to address arsenic contamination in other affected regions