Hyperaccumulator

A hyperaccumulator is a plant that can grow in soils with very high concentrations of metals.
Featured by the BBC is a tree on the island of New Caledonia, "Pycnandra acuminata", which grows on soil rich in nickel. Many different plants do this in several different plant families.
The advantage of hyperaccumulation of metals may be that the toxic levels of heavy metals in leaves deter herbivores (defence against herbivory).
Several gene families are involved in hyperaccumulation including absorbing and storing heavy metals. The genes most usually involved are the ZIP gene family. These genes code for membrane receptors for the transport of, for example, zinc molecules.
These hyperaccumulation genes (HA genes) are found in over 450 plant species, including the model organisms "Arabidopsis" and the Brassicaceae. Expression of HA genes allows the plant to uptake and sequester metals such as As, Co, Fe, Cu, Cd, Pb, Hg, Se, Mn, Zn, Mo and Ni in 100–1000 times the concentration found in sister species or populations.