CHAPTER 5: Hyperaccumulation by Plants

Society has long recognised that certain plant species can infer the existence of minerals in the underlying soil but only in the later years of the 20th century was the ability of some plants to accumulate heavy metals reliably quantified. The term hyperaccumulation was introduced to describe such plants. Of the many metals that can be hyperaccumulated, two of the more interesting are nickel and gold. Nickel is naturally hyperaccumulated by around 450 plant species, while plants can be forced to accumulate gold if the metal is made soluble in the soil (induced hyperaccumulation). The phytoextraction of metal from low‐grade ore, waste rock or contaminated soil represents a remediation technique, or in some cases an economically viable option for metal recovery. In some scenarios, the recovery of gold from a crop of plants can provide revenue for the remediation of more toxic metals from contaminated soil. In another, nickel farming may be an alternative livelihood for communities growing food on poor‐yielding metalliferous soils. As society progresses through the 21st century, the sustainability of the metals extractive industry must be improved. Hyperaccumulation will never replace conventional mining but it is a physiological trait that can be used for sustainable development. There are opportunities for ‘green technologies’ to support phytoextraction by better biomass processing and the realisation of specific applications for metal accumulated by plants.