Cellular mechanisms for heavy metal detoxification and tolerance

Abstract

Heavy metals such as Cu and Zn are essential for normal plant growth, although elevated concentrations of both essential and non‐essential metals can result in growth inhibition and toxicity symptoms. Plants possess a range of potential cellular mechanisms that may be involved in the detoxification of heavy metals and thus tolerance to metal stress. These include roles for the following: for mycorrhiza and for binding to cell wall and extracellular exudates; for reduced uptake or efflux pumping of metals at the plasma membrane; for chelation of metals in the cytosol by peptides such as phytochelatins; for the repair of stress‐damaged proteins; and for the compartmentation of metals in the vacuole by tonoplast‐located transporters. This review provides a broad overview of the evidence for an involvement of each mechanism in heavy metal detoxification and tolerance.