Accumulators and excluders ‐strategies in the response of plants to heavy metals

TLDR

Plants that colonize metal‑rich soils have evolved physiological mechanisms that tolerate toxicity by internal detoxification rather than suppressing uptake, and these mechanisms are broadly categorized as accumulators or excluders. This study examines the physiological traits of accumulator and excluder species to understand their metal tolerance mechanisms. Accumulating species concentrate metals in plant tissues, whereas excluders regulate root‑shoot transport to maintain low shoot levels across varying external concentrations, and indicator species exhibit proportional soil‑to‑plant metal relationships.

Abstract

Abstract Plants colonizing metalliferous soils have evolved physiological mechanisms which enable them to tolerate metal toxicity. These mechanisms do not generally suppress metal uptake but result in internal detoxification. Two basic strategies of plant response are suggested, accumulators and excluders. In the former, metals can be concentrated in plant parts from low or high background levels. By contrast, differential uptake and transport between root and shoot in excluders, lead to more or less constant low shoot levels over a wide range of external concentration. 'Indicators' are seen as a further mode of response where proportional relationships exist between metal levels in the soil, uptake and accumulation in plant parts. The physiological properties of accumulator and excluder species are considered in relation to metal tolerance mechanisms.