ABSTRACT
The activities of man have left many sites contaminated with one or more heavy metals. The affected land is toxic to plants and animals, including humans, and there is considerable public and legislative pressure to remediate the land, or at least alleviate many of the adverse properties of these soils. The toxicity of the metals may cause the death of the very plants being used for phytoremediation. In plants, tolerance can be defined as the ability to survive in a soil that is toxic to other plants of the same or different species. The important point is that the toxicity of the soil is defined by reference to its effects on other plants. The artificial breeding of tolerant varieties for phytoremediation will be easier if the tolerance to a range of metals is achieved by a single genetic change. The general lack of cotolerance has implications for the mechanisms of tolerance.
