The patch-clamp technique was used to study passive movements of ions through the plasmalemma of wheat leaf protoplasts. This method overcomes the problems inherent in conventional electrophysiological study of plant cells. Changes in conductance were recorded in patches excised from the plasmalemma. Two types of patches were observed: (i) regions of low channel density, where discrete single-channel currents could be resolved and conductance ranged from 10 to 200 picosiemens and (ii) regions of high channel density, where single-channel currents could not be resolved and conductance was on the order of a few nanosiemens. The results indicate a striking similarity between animal and plant cell membranes in the basic phenomena of transport. Moreover, the approach used constitutes a new degree of refinement in the study of processes of regulation, pathology, and toxicity in plants.