An NADH-dependent, flavin mediated electron transport system operates in the plasmalemma of stomata

Photo credit: NCBI

Tetrazolium Reduction by Guard Cells in Abaxial Epidermis of Vicia faba: Blue Light Stimulation of a Plasmalemma Redox System

by Vani T., Raghavendra A. S. (1989)

School of Life Sciences, University of Hyderabad, Hyderabad 500 134, India

in Plant Physiol. (1989) 90, 59-62 –



The stomata in the abaxial epidermis of Vicia faba were examined for the location of redox systems using tetrazolium salts.

Three distinct redox systems could be demonstrated: chloroplast, mitochondrial, and plasmalemma. The chloroplast activity required light and NADP. Mitochondnal activity required added NADH and was suppressed by preincubation with KCN. The plasmalemma redox system in guard cells also required NADH, but was insensitive to KCN and was stimulated by blue light.

The involvement of an NADH dehydrogenase in the blue light stimulated redox system in guard cells was suggested by the sensitivity to plantanetin, an inhibitor of NADH dehydrogenase.

The redox system of mitochondria was the most active followed by that of plasmalemma. The activity of chloroplasts was the least among the three redox systems.

The plasmalemma mediated tetrazolium reduction was stimulated by exogenous flavins and suppressed by KI or phenylacetate, inhibitors of flavin excitation.

We therefore conclude that an NADH-dependent, flavin mediated electron transport system, sensitive to blue light, operates in the plasmalemma of guard cells.


Published by

Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.

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