Naturally occurring iron-chelating compounds in oat- and rice-root washings

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Abstract
The root washings of water-cultured oat and rice (non-sterile) contained some sort of amphoteric, iron-solubilizing chelating (or complexing) compound(s), which could be separated into a “cationic fraction” by elution in a cation exchanger column with in NH4OH. In oats, the release of the chelator into the washings greatly increased under iron-stress conditions. Under the same condition “iron-inefficient” rice plants also increased the release of the chelator, though to a much less extent than did the oats. Further examination of the “cationic fraction” revealed that this chelator may be a heat-stable, acid-hydrolyzable non-marromolecule of extraordinarily high polarity. In the absence of interfering ions, the chelator was able to solubilize hydra ted Fe (III) oxide effectively within a range of pH 4 to 9. Its Fe-solubilizing action was inhibited by the presence of divalent metals, the extent being in the order, Cu>Cos≥Zn>Mn> Ca (no inhibition).