The Electrical Properties of Plant Cell Membranes. IV. The Effects of the Nodal Conductance upon the Cable Properties and Measured Membrane Conductance of Charophytes

Abstract

A theoretical treatment of the electrical 'cable' properties of cylindrical, radially symmetric, plant cells with two concentric membranes is presented, in which the effects of additional conductance elements located at the nodes (ends) of the cell are considered. It is shown that the measured 'membrane' conductance is effectively independent of the conductance between the vacuole and exterior at the nodes, providing the nodes are at least a cable-length distant from the point of current injection. However any 'leakage' between the cytoplasm and the cell exterior at the nodes (as might occur via unsealed plasmodesmata) can drastically affect measurements made with cytoplasmic electrodes remote from the point of current injection. It is shown that isolating the nodes of the cell with insulating external barriers of a suitable width can effectively remove any error due to the electrical properties of the nodes.