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This article in SSSAJ

  1. Vol. 38 No. 4, p. 597-602
    Received: Sept 26, 1973
    Accepted: Mar 18, 1974

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Effect of Macronutrient Ions on the Availability of Iron from a Chelated Source1

  1. J. J. Oertli and
  2. A. A. Opoku2



The uptake of Fe from FeEDDHA [ferric chelate of ethylenediamine di (o-hydroxyphenylacetic acid)] during periods of 1 to 2 days was studied with 10- to 11-day-old corn plants (Zea mays L.) grown in nutrient solutions. The Fe in roots and tops was markedly affected by the composition of the nutrient solution. Cations stimulated Fe in plants in the following order: K> Na > Mg > Ca, and anions SO4 > Cl > NO3. The stimulation was the greater the more the pH declined during the absorption experiment; hence it was concluded that the effect of nutrient solution composition on Fe nutrition must be attributed to the imbalance of cation and anion uptake rather than to a specific nutrient. The pH decline and, in general, the associated stimulation of Fe uptake were enhanced by increasing concentrations of the interfering ions and by time. However, when the pH fell toward a value of 4, injury to roots occurred and Fe uptake was reduced in spite of a higher supply. The composition of the nutrient solution was also effective in long-term experiments in regulating Fe uptake. A decrease in pH resulting from excess cation uptake favors the formation of less dissociated forms of the free ligand, namely of (ligand-H)3-, (ligand-H2)2-, etc., instead of the reactive ligand, (ligand)4- and equilibrium can be maintained only if more FeEDDHA dissociates, liberating Fe3+ for uptake.

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