Metal-tolerant plants function by excluding or reducing the uptake of the toxic ion, accumulating the metal in cell walls, or complexing the metal in some way to decrease its toxicity. Datura innoxia (Jimsonweed) is a cadmium-tolerant plant that synthesizes polypeptides to sequester cadmium internally in the cell and chelates heavy metal ions externally on the cell wall. The nature of the metal binding sites on the cell walls is not known, however, there are a number of functional groups derived from cell wall proteins, lipids and carbohydrates capable of coordinating metal ions. Our goal is to use X-ray absorption spectroscopy to directly probe the metal binding sites on D. innoxia cell walls, specifically Ba2+, Cu2+ and Cd2+ metal binding sites. Understanding the interaction between plant cell walls and heavy metal ions is important because metal accumulation in agriculturally important plants is the principle means by which heavy metals are introduced into the food web. In addition, removal of toxic metals from the environment by plants or plant products has potential as an effective means of remediating heavy metal and radionuclide waste.
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