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Plant Physiol. 1991 Aug;96(4):1034-7.

Plasmalemma redox activity and h extrusion in roots of fe-deficient cucumber plants.

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Department of Agronomy, Escuela T.S. Ingenieros Agrónomos, University of Córdoba, Apdo. 3048, 14080 Córdoba, Spain.


Cucumber plants (Cucumis sativus L.) with incipient Fe deficiency showed increased root capacity to reduce chelated Fe(3+) compared to Fe-sufficient plants. When Fe-ethylenediaminete-traacetate was added to the root medium of the Fe-deficient plants, the reductase activity was associated with acidification of the medium and an increase in the net apparent K(+) efflux. In the presence of the H(+)-ATPase inhibitor N,N'-dicyclohexylcarbodiimide the net apparent H(+) efflux was completely suppressed, though some reductase activity was preserved, and the net apparent K(+) efflux was significantly increased. The inhibition of the reductase activity by N,N'-dicyclohexylcarbodiimide was similar whether the pH of the medium was buffered or not. Anoxia and the protonophore carbonyl cyanide m-chlorophenyl hydrazone also caused a similar inhibition of the reductase activity. It is proposed that this redox system transports electrons only and that its activity is inhibited by plasmamembrane depolarization and anoxia. The H(+) and K(+) efflux associated with the reductase activity may be a result of the plasmamembrane depolarization it causes.

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