The sorption of ferric iron, copper, zinc and manganese by wheat seedling roots and by discs of cellulose filter paper was measured. The magnitude of sorption at pH 5-0 was Fe(III) > Cu(II) > Zn(II) > Mn(II). Sorption of Cu(II), Zn(II) and Mn(II) increased with increasing pH whilst sorption of Fe(III) decreased. The patterns of sorption are discussed in the light of our knowledge of the hydrolysis of the metal ions. It is suggested that metals adsorbed on root surfaces may be remobilized by organic ligands which leak from the root cells. Where an external liquid diffusion path away from the root does not exist, soluble metal ligand complexes might accumulate in the water free space and superficial water film of the root, thus facilitating their uptake into root cells and translocation within the plant. Under such conditions the amounts of metal translocated to the shoots of wheat seedlings are shown to be related to the amounts of metal adsorbed by their roots.