The Chinese brake fern absorbs and transports toxic arsenic from roots to fronds via cellular transport channels.

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The Chinese brake fern is able to survive and thrive in toxic arsenic-laden soils. Arsenic is chemically similar to phosphate. The fern uses phosphate ion channels in root cell membranes to absorb and transport the metal to its leaves where it hyperaccumulates and functions as a deterrent to would-be predators.

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"The discovery of the Chinese brake fern (Pteris vittata L) and related species to hyperaccumulate arsenic in their fronds has led to the development of environmentally-friendly and cost-effective phytoremediation technology for remediation of arsenic contaminated sites...the global input of arsenic to soils by human activities was estimated to be between 52,000-112,000 ton per year. One of the more widespread problems is due to leaching of naturally occurring arsenic into drinking water aquifers...Arsenic is a carcinogen, and is associated with animal and human skin, lung and bladder cancers." (Rathinasabapathi et al. 2006:304)

"The fern grows in arsenic-contaminated soils and accumulates large amounts of arsenic in its aboveground biomass. Pteris vittata was tolerant of high concentrations of arsenic, up to 1,500 mg As kg-1 soil." (Rathinasabapathi et al. 2006:305)

"While many arsenic resistant plant variants resist arsenic by reducing its uptake, P. vittata resists arsenic by hyperaccumulating arsenic in its tissues...P. vittata has excellent abilities to take up and transport arsenic into its fronds and concentrate it in that tissue...Because of the structural similarity between phosphate and As(V)... As(V) is taken up by P. vittata via the phosphate transporters...As [arsenic] is transported as dimethylarsenic acid to the shoot. It may be stored as an arsenic-tris-thiolate complex." (Rathinasabapathi et al. 2006:306)

"The toxicity of As(III) results from its affinity for thiol groups in proteins. One cellular mechanism to deal with heavy metal toxicity is the chelation of metals in the cytosol by high affinity ligands such as amino acids and organic acids and two classes of thiol peptides phytochelatins (PCs) and metallothioneins. It has been shown that P. vittata synthesizes a phytochelatin in its fronds in response to increasing concentrations of arsenic." (Rathinasabapathi et al. 2006:307)

"Phytoremediation of arsenic contaminated environments will involve growing the arsenic hyperaccumulator ferns in the contaminated environment, harvesting the arsenic-rich biomass and the safe disposal of the biomass." (Rathinasabapathi et al. 2006:308)

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Arsenic hyperaccumulating ferns and their application to phytoremediation of arsenic contaminated sites

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