Spatial Variation of the Electrical Properties of Chara australis. I Electrical Potentials and Membrane Conductance

Abstract

Experiments are described with cells of Chara, using a water-film technique, to determine the dependence on position along the cells of the membrane conductance, electromotive force (e.m.f.) and noise spectrum. It was found that both the e.m.f. and the conductance were far from uniform along the cells. The e.m.f. showed distinct zoning patterns, regions of greater e.m.f. (acid zones) having potentials of up to 70 mV greater than the zones of minimum e.m.f. (alkaline zones). In the alkaline zones the conductance was ≈ 3.5 times larger than in the acid zones. The noise spectra of the membrane potential in both the acid and alkaline zones were similar, despite the differences in membrane conductance. The details of the results presented are consistent with the motion that in the acid zones the potential is hyperpolarized by the operation of an active H⁺ transport system, whilst in the alkaline zones the membrane is in a proton-permeable state (in which the conduction mechanism itself may be fluctuating).