Electroosmosis in Membranes: Effects of Unstirred Layers and Transport Numbers. II. Experimental

In an earlier paper, it was shown that the differences in transport numbers in membranes and adjacent solutions will result in a depletion and enhancement of the local concentration profiles at the appropriate interfaces. These should, in general, cause both current-induced volume flows and transient changes in membrane potential difference (PD). The predicted concentration changes were measured near an isolated segment of plant cell wall just after a current pulse. The current-induced volume flows observed were separated into a "transport number component" and an instantaneous, electroosmotic one for both cell walls and whole cells. For walls, the electroosmotic component contributed about 53 moles . Faraday(-1) to a total coefficient of 112 moles . Faraday(-1). For whole cells, the average electroosmotic component (for both hyperpolarizing and depolarizing currents) contributed about 38 moles . Faraday(-1) to a total of about 100 moles . Faraday(-1). There was good agreement between the magnitudes and time courses of the flows and membrane PD's predicted from the theory in the previous paper, and those measured in both cell walls and whole cells.