Electron transport across the plasmalemma of Lemna gibba G1 |
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Authors: | B Lass G Thiel C I Ullrich-Eberius |
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Institution: | (1) Institut für Botanik der Technischen Hochschule, Schnittspahnstrasse 3, D-6100 Darmstadt, Federal Republic of Germany;(2) Fachbereich Biologie, Universität Bremen, P.O.B. 330440, D-2800 Bremen 33, Federal Republic of Germany |
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Abstract: | Lemna gibba L., grown in the presence or absence of Fe, reduced extracellular ferricyanide with a V
max of 3.09 mol · g-1 fresh weight · h-1 and a K
m of 115 M. However, Fe3+-ethylenediaminetetraacetic acid (EDTA) was reduced only after Fe-starvation. External electron acceptors such as ferricyanide, Fe3+-EDTA, 2,6-dichlorophenol indophenol or methylene blue induced a membrane depolarization of up to 100 mV, but electron donors such as ferrocyanide or NADH had no effect. Light or glucose enhanced ferricyanide reduction while the concomitant membrane depolarization was much smaller. Under anaerobic conditions, ferricyanide had no effect on electrical membrane potential difference (Em). Ferricyanide reduction induced H+ and K+ release in a ratio of 1.16 H++1 K+/2 e- (in +Fe plants) and 1.28 H++0.8 K+/2 e- (in -Fe plants). Anion uptake was inhibited by ferricyanide reduction. It is concluded that the steady-state transfer of electrons and protons proceeds by separate mechanisms, by a redox system and by a H+-ATPase.Abbreviations
E
m
electrical membrane potential difference
- EDTA
ethylenediaminetetraacetic acid
- DCPIP
dichlorophenol indophenol
- +Fe
control plant
- -Fe
iron-deficient plant
- FW
fresh weight
- H+
electrochemical proton gradient |
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Keywords: | Electron transport Ferricyanide reduction Lemna Membrane potential Proton transport Sulfate uptake |
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