The role of electrogenic pump inChara corallina

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Abstract
The conductance,G, and the electromotive force,E, of theChara membrane were determined accurately by using the current-clamp technique. The measurements at the final steady state of inhibitor poisoning give the conductance,g 1, and the electromotive force,E 1, of the passive ion conducting pathways. By knowing these values the conductance,g 2, and the electromotive force,E 2, of the electrogenic pump can be calculated from the measuredG andE at each time during the progress of inhibitor poisoning. The local closed circuit current,i, which usually causes a hyperpolarization across the passive conducting pathways, can be calculated by usingg 1,g 2,E 1 andE 2 thus determined. The values ofg 2 andi decrease monotonically to zero with the progress of poisoning, whileE 2 approachesE 1 asymptotically after a transient hyperpolarization. During excitationi increases markedly. Such an increased inward current through the passive conducting pathways may help in accelerating the inactivation of the excitatory mechanism.