Effect of monosilicate, phosphate, and carbonate on iron dissolution by mugineic acid
1994
Watanabe, S. (Tokyo Univ. (Japan)) | Matsumoto, S.
Anions adsorbed specifically onto iron minerals in soil can affect the dissolution of the minerals by phytosiderophores and the occurrence of iron deficiency in graminaceous crops. Ferrihydrite was suspended in NaCl solutions (pH 4-9) containing orthophosphate, monosilicate, or carbonate at various concentrations, and then the dissolution rates of the ferrihydrite by mugineic acid (MA) were determined. The adsorption of the anion and Ma were also quantified. All the tested anions inhibited both the iron dissolution by MA and the MA adsorption onto ferrihydrite. Monosilicate inhibited the iron dissolution severely (80%) when the pH value exceeded 8 and the final concentration exceeded 0.2 mM. The inhibition of monosilicate on iron dissolution decreased significantly with decreasing pH. On the other hand, monosilicate is commonly present in soil solutions at such high concentrations as 0.2 mM. Moreover, strict inhibition of ferrihydrite dissolution was also observed when the ferrihydrite was added to a suspension of a calcareous soil or its filtrate. These results suggest that the adsorption of monosilicate on iron minerals results in the low availability of iron to graminaceous plants which is observed commonly in calcareous soils
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