Various terrestrial plants are shown to phytostabilise heavy metals , generally due to the negative charge of the cellular walls that can attract and compartmentalise heavy metal cations . For example, when exposed to a group of metals including copper, a low shrub succulent, Tetraena qataranse (Hadidi) Beier & Thulin, accumulated 22.4 mg/kg of copper in the roots, whilst 6.2 mg/kg translocated into the shoots, compared to 5.7 mg/kg left in the soil . Moreover, plants are natural bio-adsorbents of sulfate , as plants assimilate then store or metabolise the anion .