Effect of high pH on the plasma membrane potential and conductance in Elodea densa

H Miedema*, H. Felle, H.B.A. Prins

*Corresponding author for this work

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16 Citations (Scopus)

Abstract

In leaves of Elodea densa the membrane potential measured in light equals the equilibrium potential of H+ on the morphological upper plasma membrane. The apoplastic pH on the upper side of the leaf is as high as 10.5-11.0, which indicates that alkaline pH induces an increased H+ permeability of the plasmalemma. To study this hypothesis in more detail we investigated the changes in membrane potential and conductance in response to alterations in the external pH from 7 (= control) to 9 or 11 under both light and dark conditions.

Departing from the control pH 7 condition, in light and in dark the application of pH 9 resulted in a depolarization of the membrane potential to the Nernst potential of H+. In the light but not in the dark, this depolarization was followed by a repolarization to about - 160 mV. The change to pH 9 induced, in light as well as in dark, an increase in membrane conductance.

The application of pH 11, which caused a momentary hyperor depolarization depending on the value at the time pH 11 was applied, brought the membrane potential to around - 160 mV. The membrane conductance also increased, in comparison to its value at pH 7, as a result of the application of pH 11, irrespective of the light conditions.

Original languageEnglish
Pages (from-to)63-69
Number of pages7
JournalJournal of membrane biology
Volume128
Issue number1
DOIs
Publication statusPublished - May-1992

Keywords

  • PLASMA MEMBRANE
  • H+ PERMEABILITY
  • MEMBRANE POTENTIAL
  • MEMBRANE CONDUCTANCE
  • CHARA-CORALLINA
  • EGERIA-DENSA
  • LEAF SURFACE
  • LIGHT
  • LEAVES
  • CELLS
  • ION
  • POTAMOGETON
  • TRANSPORT
  • MECHANISM

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