Mechanism of short term Feˡˡˡ reduction by roots: Evidence against the role of secreted reductants

Document Type

Article

Publication Date

12-1-1983

Journal Title

Plant Physiology

ISSN

Print: 0032-0889 Electronic: 1532-2548

Keywords

Arachis hypogaea, Fe-deficient plants, secreted reducing compounds

Disciplines

Agronomy and Crop Sciences

Abstract

The hypothesized role of secreted reducing compounds in Feˡˡˡ reduction has been examined with Fe-deficient peanuts (Arachis hypogaea L. cv A124B). Experiments involved the exposure of roots to (a) different gas mixtures, (b) carbonyl cyanide m-chlorophenylhydrazone (CCCP), and (c) agents which impair membrane integrity.

Removing roots from solution and exposing them to air or N2 for 10 minutes did not result in any accumulation in the free space of compounds capable of increasing rates of Feˡˡˡ reduction when roots were returned to solutions. On the contrary, exposing roots to N2 decreased rates of Feˡˡˡ reduction. CCCP also decreased rates of Feˡˡˡ reduction.

Acetic acid and ethylenediaminetetraacetic acid (disodium salt) (EDTA) impaired the integrity and function of the plasma membranes of roots of Fe-deficient peanuts. That is, in the presence of acetic acid or EDTA, there was an efflux of K+ from the roots; K+ (86Rb) uptake was also impaired. Acetic acid increased the efflux from the roots of compounds capable of reducing Feˡˡˡ . However, both acetic acid and EDTA caused rapid decreases in rates of Feˡˡˡ reduction by the roots. In addition to peanuts, acetic acid also decreased rates of Feˡˡˡ reduction by roots of Fe-deficient sunflowers (Helianthus annuus L. cv Sobrid) but not maize (Zea mays L. cv Garbo).

These results suggest that, at least in the short term, the enhanced Feˡˡˡ reduction by roots of Fe-deficient plants is not due to the secretion of reducing compounds.

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Digital Object Identifier (DOI)

https://doi.org/10.1104/pp.73.4.893