hyperaccumulation

Hyperaccumulation is a biological phenomenon in which certain organisms, most notably certain plants, concentrate metals or metalloids in their tissues at levels far exceeding those found in non-accumulating relatives. In plants, hyperaccumulation refers to the ability to accumulate metals in above-ground tissues at concentrations orders of magnitude higher than background soil levels, often with high efficiency of uptake and translocation from roots to shoots.

Definitions vary by element. Researchers often require that a species accumulates a given metal in shoots above a specified threshold and exhibits a high shoot-to-root translocation factor. Metals commonly studied include nickel, zinc, cadmium, copper, cobalt, and manganese. Hyperaccumulators are rare and frequently occur on metalliferous soils such as serpentine or mine wastes.

Mechanisms involve multiple coordinated processes. Uptake is mediated by membrane transporters from families such as ZIP, NRAMP, and YSL, in concert with chelators like nicotianamine and phytochelatins. Once inside cells, metals are often sequestered in vacuoles via tonoplast transporters or bound to cell walls, reducing toxicity. This compartmentalization, along with enhanced root uptake and translocation, underlies hyperaccumulation.

Ecology and evolution are closely linked to metal-rich environments. Hyperaccumulation is common on naturally metal-bearing soils and in disturbed sites, where it may deter herbivory and influence rhizosphere communities. The trait is of interest for ecological and evolutionary studies and for biotechnical applications.

Applications and implications include phytoremediation, to extract contaminants from soils, and phytomining, to recover metals from biomass. Field success depends on soil chemistry, climate, and plant productivity, and the management of biomass containing high metal concentrations remains a consideration.