A hyperaccumulator is a plant capable of growing in soil or water with very high concentrations of metals, absorbing these metals through their roots, and concentrating extremely high levels of metals in their tissues. Expression of HA genes provides the plant with capacity to uptake and sequester metals such as As, Co, Fe, Cu, Cd, Pb, Hg, Se, Mn, Zn, Mo and Ni in 100–1000x the concentration found in sister species or populations.
From Wikipedia