Evidence for electron transport across the plasma membrane of Zea mays root cells

Exogenous ferricyanide is reduced by roots of Z. mays. In contrast to oxidation of exogenous electron donors, ferricyanide reduction occurs mostly at the apical 5 mm of the root. Using just this portion of the root, it is shown that the activity is neither a consequence of uptake of ferricyanide fol...

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Bibliographic Details
Published in:Planta 1985-01, Vol.165 (3), p.383-391
Main Authors: Qiu, Z.-S., Rubinstein, B., Stern, A.I.
Format: Article
Language:English
Subjects:
Biological and medical sciences
Cell membranes
Cell physiology
Corn
electron transport
Fundamental and applied biological sciences. Psychology
Liquids
Oxidation
Oxygen
Plant physiology and development
Plant roots
Plants
Plasma membrane and permeation
plasma membranes
Pyridine nucleotides
Root tips
roots
Zea mays
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Summary:Exogenous ferricyanide is reduced by roots of Z. mays. In contrast to oxidation of exogenous electron donors, ferricyanide reduction occurs mostly at the apical 5 mm of the root. Using just this portion of the root, it is shown that the activity is neither a consequence of uptake of ferricyanide followed by excretion of its reduced form, nor of leakage of a reductant. Addition of ferricyanide for 40 s or 5 min results in an apparent oxidation of NADPH but not of NADH; rates of ferricyanide reduction vary together with levels of NADPH but not of NADH in the presence or absence of oxygen. It is concluded that an enzyme which can oxidize cytoplasmic NADPH and transfer the electrons to an external acceptor exists at the cell surface of maize roots. This finding extends the results of others who showed similar redox activity at the surface of Fe-depleted dicotyledonous roots, and indicates that an energy source other than ATP exists at the cell surface of a variety of plants under unstressed conditions.
ISSN:0032-0935
1432-2048
DOI:10.1007/BF00392236