Chemical speciation of accumulated metals in plants: evidence from X-ray absorption spectroscopy

For centuries, man has been fascinated by the almost magical ability of plants to grow and reproduce on the simplest of materials - sunlight, air, water and minerals. As part of this conjuring act, plants require roots to acquire essential minerals such as iron, copper, nickel, zinc and selenium from the soil. Though these elements are essential, they are also potentially toxic, so plants possess complex biochemistry to control them. For reasons that are not yet clear, plants also have the ability to acquire and detoxify non-essential elements such as arsenic, cadmium, chromium and lead. Using X-ray absorption spectroscopy to probe the oxidation state and chemical speciation of a number of essential and non-essential elements, we have been able to identify certain common themes in the physiology and biochemistry of trace element (hyper)accumulation by plants. (C) 2002 Elsevier Science B.V. All rights reserved.