Plasmodesmata in Nitella translucens: structure and electrical resistance.

Electrical resistance measurements, made with intracellular microelectrodes on a system consisting of two giant internodal cells of Nitella translucent joined by a node, show that the specific resistance of the node is 50 times smaller than the specific resistance of the internodal cell plasmalemma. The node is a complex structure of small cells which separate the internodal cells by a single layer at the nearest point of approach. Information on the size and distribution of the plasmodesmata in the node, obtained from electron micrographs, suggests that the specific resistance of the node should be smaller than the observed value by a factor of 330. It must therefore be assumed that there is some restriction on the diffusion of ions in the plasmodesmata. The electrical coupling between some internodal cells is sufficient for an action potential in one cell to initiate an action potential in the neighbouring cell.