Reduction and Coordination of Arsenic in Indian Mustard

• Published in: Plant physiology (Bethesda) Vol. 122; no. 4; pp. 1171 - 1177
• Main Authors: Pickering, Ingrid J., Prince, Roger C., Martin J. George, Smith, Robert D., George, Graham N., Salt, David E.
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01-04-2000; American Society of Plant Biologists
• Subjects: Absorption spectroscopy; Absorption. Translocation of ions and substances. Permeability; Agronomy. Soil science and plant productions; Applied sciences; Arsenates; Arsenic; Arsenic - chemistry; Arsenites; Bioaccumulation; Biological and medical sciences; Brassica - chemistry; Decontamination. Miscellaneous; Economic plant physiology; Environmental and Stress Physiology; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Hydroponics; Mustards; Nutrition. Photosynthesis. Respiration. Metabolism; Oxidation-Reduction; Phosphates; Phytoremediation; Plant roots; Plants; Pollution; Roots; Salts; Seedlings; Shoots; Soil and sediments pollution; Soil contamination; Space life sciences; Spectrum Analysis - methods; Arsenic; Coordination; Biological transport; Soil pollution; Oil plant(vegetal); Chemical reduction; Amendment; Absorption; Decontamination; Cruciferae; Dicotyledones; Angiospermae; Spermatophyta; Bioremediation; Biological accumulation; Brassica juncea
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.122.4.1171

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 $\text{As}^{\text{III}}$-tris-thiolate complex. The majority of the arsenic remains in the roots as an $\text{As}^{\text{III}}$-tris-thiolate complex, which is indistinguishable from that found in the shoots and from $\text{As}^{\text{III}}$-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.