Plant Physiol. Journal of Pharmacology and Experimental Therapeutics
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Plant Physiology 61:164-169 (1978)
© 1978 American Society of Plant Biologists

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Articles

Membrane Potential in Phaeoceros laevis

Effects of Anoxia, External Ions, Light, and Inhibitors 1 ,2

Paul J. Contardi and Robert F. Davis

Department of Botany, Rutgers University, Newark, New Jersey 07102

Gametophyte cells of Phaeoceros laevis (L.) Prosk. have vacuole electric potentials (PDs) of about –175 millivolts; the steady PD is not affected by light but small transient PDs result after changing from light to darkness or darkness to light. The PD is more negative than the Nernst potentials for any of the permeating ions. Changes in the concentration of any one of the external ions between 0.1 and 10 mM have only a very small effect on the PD. Increases in external pH cause the PD to depolarize by a few millivolts. Azide, 2,4-dinitrophenol, and NH4Cl each cause rapid and reversible depressions of the PD; the effects of these agents are similar in magnitude in the light and in the dark. Anoxia depolarizes the PD by about 30 millivolts in the light and by about 60 millivolts in the dark. Ouabain and 3-(3,4-dichlorophenyl)-1,1-dimethylurea have no effects on the PD. It is concluded that the membrane potential is controlled by an electrogenic efflux pump, possibly for H+. It is also concluded that the source of energy for the pump is respiration and not photosynthesis.

1 This investigation was supported by grants to R. F. D. from the Research Council of Rutgers University, the Charles and Johanna Busch Memorial Fund, and Biomedical Grant RR7059-12.

2 Part of the work presented in this paper is from a thesis submitted to the Rutgers University Graduate School by P. J. C. in partial fulfillment of the requirements for the M.S. degree.






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Copyright © 1978 by the American Society of Plant Biologists