What are the mechanisms of zinc uptake by plants?
Zinc appears to be absorbed by roots primarily as Zn2+ from the soil solution and its uptake is mediated by a protein with a strong affinity for zinc. Kochian (50) proposed that the transport of zinc across the plasma membrane was towards a large negative electrical potential so that the process is thermodynamically passive. This negative electrical potential of the plasma membrane is the driving force for zinc by means of a divalent cation channel in dicotyledons and monocotyledons other than the Poaceae. In the Poacae, Kochian proposed that non-protein amino acids called ‘phytosiderophores’ or ‘phytometallophores’ form a complex with zinc and transport it to the outer face of the root-cell plasma membrane. These phytosidero-phores are released from the roots as a result of iron or zinc deficiency. This complex is then transported to the cell via a transport protein. Nambiar (51) showed that plants could take up zinc from dry soil (matrix potential < –1.5 MPa) via excreted mucilage bu
