Absorption of ferric iron by plants

Abstract

In an earlier publication the conclusion was reached that ferric iron is not absorbed by plant roots and that the reduction of Fe(III) to Fe(II) is an obligatory step preceding absorption of Fe(III). Inasmuch as Fe(III) is the predominant form in well‐aerated soils and its reduction is an energy‐requiring process, this conclusion appears to necessitate the continuous functioning of a special mechanism in roots for inducing Fe absorption.

Findings of the present investigation cast doubt upon the validity of the earlier conclusion and support the belief that both Fe(III) and Fe(II) ions can be absorbed. Demands upon the plant are correspondingly less and, during non‐stress periods, might be negligibly small. During non‐stress periods, rate of absorption of Fe(III) might be adequate to meet plant requirements. Reduction is viewed, not as an obligatory process, but as a supplementary process for enhancing rate of absorption of Fe particularly during stress periods. Thus the stress response mechanism, based upon acidification and extrusion of phenolics, might be a principal factor in preventing and correcting Fe deficiency stress in efficient plants.

Key words:

• Bathophenanthrolinedisulfonate (BPDS)
• Ethylenediamine‐(di(O‐hydroxyphenylacetic) acid (EDDHA)
• Gallium (Ga(III))
• Obligatory reduction
• Stress response mechanism
• Barley (Hordeum vulgare
• I)