COMPARATIVE-STUDY OF THE EFFECTS OF NATURAL AND SYNTHETIC LIGANDS ON IRON UPTAKE BY PLANTS

The uptake of iron by wheat seedlings was investigated using half-strength Hoagland's nutrient solution containing 2.0 μM ferric chloride labelled with59Fe. The iron content of root tissue, which includes adsorbed iron, was depressed by the presence in the solution of the synthetic ligands EDTA and polymaleic acid (PMA) and by the natural ligands, humate, fulvate and a water-extractable soil polycarboxylate. The patterns of change in iron content of the shoots were in all cases different from those of the roots and were of two types. EDTA and humate increased the iron content of the shoots to maximum values, at ligand concentrations of 5.0 μM and 2.5 mg l-1 respectively, and decreased it at higher concentrations. Fulvate, water-extractable soil polycarboxylate and PMA increased the iron content of the shoots up to the maximum ligand concentrations tested (25 mg l-1). These results are discussed in the light of the likely solution chemistry of iron and the various ligands. © 1979 Martinus Nijhoff, The Hague/Kluwer Academic Publishers.