Comparison of a lipophilic cation and microelectrodes to measure membrane potentials of the giant-celled algae,Chara australis (Charophyta) andGriffithsia monilis (Rhodophyta) |
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Authors: | Raymond J Ritchie |
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Institution: | (1) The School of Biological Sciences, The University of Sydney, Sydney, New South Wales, Australia |
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Abstract: | Summary The vacuolar equilibrium potential of the lipophilic cation TPMP+ (triphenyl methyl phosphonium) in the giant algaeChara australis andGriffithsia monilis was directly measured. The TPMP+ equilibrium potential was approximately 100mV less negative than the measured vacuolar electrical potential. Thus TPMP+ does not act as a probe of the vacuolar electrical potential and appears to be extruded against an electrochemical gradient. Measurement of the plasmalemma equilibrium potential of TPMP+ showed that extrusion of TPMP+ apparently occurred at both the tonoplast and plasmalemma inChara and at the plasmalemma inGriffithsia. It is concluded that TPMP+ cannot be used as a membrane potential probe inChara orGriffithsia. |
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Keywords: | giant algal cells membrane potentials microelectrodes lipophilic cations |
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