Arsenic metabolism in freshwater and terrestrial plants

Abstract

Freshwater and terrestrial plants differ markedly in their ability to metabolize arsenate. In experiments with higher terrestrial plants, e.g. tomato, Lycopersicon esculentum Mill. cv. Better boy, 74As‐arsenate was readily taken up and reduced to arsenite. Methylation and reduction to methanearsonic acid, methanearsinic acid (indicated for the first time) and dimethylarsinic acid were apparent only in phosphate deficient plants. Lower and higher freshwater plants, e.g. Nitella tenuissima Kütz. and Lemna minima Phill., not only methylated arsenic but also produced considerable amounts of an arsoniumphospholipid previously identified in marine algae. These differences indicate that freshwater but not terrestrial plants have evolved mechanisms for rapid detoxication of arsenate, arsenite and other toxic arsenic species.

Toxicity of arsenate in Silene vulgaris, accumulation and degradation of arsenate‐induced phytochelatins

“…It is not likely that methylation occurred in our experiment since the plants were not P-deficient -growth of the control plants under both high-and low-phosphate treatments was identical ( Fig. 1) (Nissen & Benson, 1982).…”

“…It is not likely that methylation occurred in our experiment since the plants were not P-deficient -growth of the control plants under both high-and low-phosphate treatments was identical (Fig. 1) (Nissen & Benson, 1982).The formation of arsenite-thiol complexes such as (cys) $ -As and (GS) $ -As has been demonstrated both in vivo and in vitro (Jocelyn, 1972 ;Vahter & Envall, 1983 ;Gyurasics et al, 1991 ;Li & Chou, 1992 ;Scott et al, 1993 ; Delnomdedieu et al, 1994 ;Hall et al, 1997). Under alkaline conditions these complexes dissociate, according to :…”

“…However, considering work published earlier (Nissen & Benson, 1982 ; for reviews see Manzo et al, 1992 ;Thompson, 1993), it might be expected that As will be taken up as arsenate and reduced in the cytosol by glutathione to arsenite. It is not likely that methylation occurred in our experiment since the plants were not P-deficient -growth of the control plants under both high-and low-phosphate treatments was identical ( Fig.…”

“…Once the arsenate, As(V), is taken up it is reduced to arsenite, As(III), by glutathione (GSH) (Thompson, 1993). Only in phosphate-deficient conditions is arsenate subsequently methylated in plants (Nissen & Benson, 1982). Between the successive methylation steps, GSH serves to reduce the intermediate products (Scott et al, 1993 ;Thompson, 1993).…”

“…Between the successive methylation steps, GSH serves to reduce the intermediate products (Scott et al, 1993 ;Thompson, 1993). Arsoniumphospholipids in freshwater plants (Nissen & Benson, 1982) and arsenic sugars in marine brown algae (Edmonds & Francesconi, 1981) have also been identified.Mostly there is little transport of As to the aboveground parts of the plants. Dicotyledonous plants appear to transport more As to the shoots than monocotyledonous plants (Otte, 1991).…”