Depolarization of cell membrane potential during trans-plasma membrane electron transfer to extracellular electron acceptors in iron-deficient roots of Phaseolus vulgaris L

• Published in: Plant physiology (Bethesda) 1984-12, Vol.76 (4), p.943-946
• Main Authors: Sijmons, P.C, Lanfermeijer, F.C, Boer, A.H. de, Prins, H.B.A, Bienfiat, H.F
• Format: Article
• Language: English
• Subjects: Absorption. Translocation of ions and substances. Permeability; Agronomy. Soil science and plant productions; Biological and medical sciences; CELL MEMBRANE POTENTIAL; Cell membranes; Cell physiology; Depolarization; Economic plant physiology; ELECTRON TRANSFER; Electrons; FER; Fundamental and applied biological sciences. Psychology; HIERRO; Ions; IRON; Membrane potential; Nutrition. Photosynthesis. Respiration. Metabolism; PHASEOLUS; Phaseolus vulgaris; Plant cells; Plant physiology and development; Plant roots; Plants; Plasma membrane and permeation; Protons; RACINE; RAICES; ROOTS
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.76.4.943

Transfer of electrons from the cytosol of bean (Phaseolus vulgaris L.) root cells to extracellular acceptors such as ferricyanide and FeIIIEDTA causes a rapid depolarization of the membrane potential. This effect is most pronounced (30-40 millivolts) with root cells of Fe-deficient plants, which have an increased capacity to reduce extracellular ferric salts. Ferrocyanide has no effect. In the state of ferricyanide reduction, H+ ($1\text{H}^{+}$/2 electrons) and K+ ions are excreted. The reduction of extracellular ferric salts by roots of Fe-deficient bean plants is driven by cellular NADPH (Sijmons, van den Briel, Bienfait 1984 Plant Physiol 75: 219-221). From this and from the membrane potential depolarization, we conclude that trans-plasma membrane electron transfer from NADPH is the primary process in the reduction of extracellular ferric salts.