Mechanism of Short Term Fe^III Reduction by Roots

Abstract

The hypothesized role of secreted reducing compounds in Fe"' reduction has been examined with Fe-deficient peanuts (Arwchis hypogasa 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 Fe"' reduction when roots were returned to solutions. On the contrary, exposing roots to N2 decreased rates of Fel' reduction. CCCP also decreased rates of Fe"' 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

Iron Nutrition in Field Crops

“…Thus, S deficiency could potentially reduce Fe uptake in species producing riboflavin sulfates. However, the physiological significance of reductants has been frequently discounted based on a comparison of the amount of Fe reduced to the total Fe required by plants ( Barrett-Lennard et al, 1983).…”

Mutually Exclusive Alterations in Secondary Metabolism Are Critical for the Uptake of Insoluble Iron Compounds by Arabidopsis and Medicago truncatula

“…Phenolics have both chelating and reducing properties, and it has been speculated that excreted phenolic compounds could contribute to the obligatory reduction of iron. However, the reductive power of excreted flavonoids/phenolics is much lower than the rates of enzymatic reduction (Barrett-Lennard et al, 1983;Grusak et al, 1990), an observation that draws into question the biological relevance of such a mechanism. Phenolics secreted by red clover (Trifolium pratense) roots enhanced the utilization of iron pools bound to negatively charged residues in the cell wall and provided clear-cut evidence for a role of iron deficiency-induced secretion of phenolics in iron acquisition (Jin et al, 2007).…”

Depolarization of Cell Membrane Potential during Trans-Plasma Membrane Electron Transfer to Extracellular Electron Acceptors in Iron-Deficient Roots of Phaseolus vulgaris L.

“…The possibility of transplasma membrane electron transfer was already suggested by Chaney et al in 1972. Indications for such a process were found both with iron-sufficient plant cells (11,13,15) and with irondeficient roots (3,23,24). Under steady-state conditions, the charge carried by such a transfer of electrons should be balanced by an opposite charge transfer carried by electrogenic ion transport, e.g.…”