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Interaction of mugineic acid with synthetically produced iron oxides

Author:
Inoue, K., Hiradate, S., Takagi, S.
Source:
Soil Science Society of America journal 1993 v.57 no.5 pp. 1254-1260
ISSN:
0361-5995
Subject:
Hordeum vulgare, iron, nutrient deficiencies, root exudates, amino acids, chelating agents, iron oxides, solubility, adsorption, nutrient uptake, plant nutrition, siderophores
Abstract:
Interactions between mugineic acid (MA) purified from root washings of Fe-deficient barley (Hordeum vulgare L., cv. Minorimugi) and synthetically produced Fe oxides (goethite, hematite, lepidocrocite, and ferrihydrite) were studied in the equilibrium pH range of 3 to 11. The amount of MA adsorbed on Fe oxides was related to their specific surface area and followed the order: ferrihydrite is much greater than goethite is greater than or equal to lepidocrocite is greater than or equal to hematite. The adsorption of Ma on Fe oxides also decreased with increasing equilibrium pH and increased with increasing MA concentration. The MAFe complexes were also adsorbed on Fe oxides, especially on ferrihydrite and goethite, at pH 3 to 7. At pH > 10, however, MAFe complexes were decomposed to MA and Fe(OH)3 colloids. The amount of Fe dissolved from Fe oxides by MA was in the following order: ferrihydrite is much greater than lepidocrocite is greater than or equal to hematite = goethite. The Fe dissolution from Fe oxides by MA was related to their crystallinity and the maximum amount of Fe dissolved by MA was in the pH range of 7 to 8. The amounts of MA adsorbed on Fe oxides and Fe dissolved by MA from Fe oxides depended on MA concentration, pH, and the type and the amount of Fe oxides added in the system. The Fe dissolution processes from Fe oxides by MA could involve two factors, namely (i) the complexation of MA with Fe exposed on the surface of Fe oxides by ligand exchange; and (ii) the release of MAFe complexes from adsorption sites on Fe oxides by nucleophilic substitution. Our data further clarify the chemistry of Fe nutrition of graminaceous plants in Fe-deficiency-causing soils.
Agid:
1425799