To measure, by patch clamping, electric current through ion channels in the plasmalemma of plant cells, access to the membrane surface is required. In higher plants, this access is gained by the preparation of protoplasts by enzymic methods. In plants such as the freshwater alga Hydrodictyon africanum, which have large cells, the preparation of protoplasts by enzymic methods is not possible. In this paper we describe a non-enzymic method for gaining access to the plasmalemma of Hydrodictyon. Our initial attempts to gain access to the plasmalemma of these cells by first plasmolysing the cells, and then cutting a window in the wall, so exposing the plasmalemma, were not successful. It was possible, however, after drying the cells in air, to cut them open and obtain fragments of the cytoplasm which maintain their original curvature. Standard patch clamping methods were then used to measure currents through single ion channels in the membrane, presumed to be the plasmalemma, bounding the outer surface of the fragments, although the success rate was low. Two types of channels were observed: (a) a multistate channel whose ion specificity was not established, and which in attached patches behaved as an outward current rectifier, and in a detached patch, as both inward and outward rectifier; and (b) a Cl- channel.
Plant physiology: Ion channels in plant cells