Reduction and coordination of arsenic in Indian mustard.
The bioaccumulation of arsenic by plants may provide a means of removing this element from contaminated soils and waters. However, to optimize this process it is important to understand the biological mechanisms involved. Using a combination of techniques, including x-ray absorption spectroscopy, we have established the biochemical fate of arsenic taken up by Indian mustard (Brassica juncea). After arsenate uptake by the roots, possibly via the phosphate transport mechanism, a small fraction is exported to the shoot via the xylem as the oxyanions arsenate and arsenite. Once in the shoot, the arsenic is stored as an As(III)-tris-thiolate complex. The majority of the arsenic remains in the roots as an As(III)-tris-thiolate complex, which is indistinguishable from that found in the shoots and from As(III)-tris-glutathione. The thiolate donors are thus probably either glutathione or phytochelatins. The addition of the dithiol arsenic chelator dimercaptosuccinate to the hydroponic culture medium caused a 5-fold-increased arsenic level in the leaves, although the total arsenic accumulation was only marginally increased. This suggests that the addition of dimercaptosuccinate to arsenic-contaminated soils may provide a way to promote arsenic bioaccumulation in plant shoots, a process that will be essential for the development of an efficient phytoremediation strategy for this element.
Pickering
I J
IJ
Stanford Synchrotron Radiation Laboratory, Stanford University, Stanford Linear Accelerator Center, Stanford, California 94309, USA.
Prince
R C
RC
George
M J
MJ
Smith
R D
RD
George
G N
GN
Salt
D E
DE
D001151:Arsenic / Q000737:chemistry*; D001937:Brassica / Q000737:chemistry*; D010084:Oxidation-Reduction; D013057:Spectrum Analysis / Q000379:methods
D001151:Arsenic