Ion channels are key participants in physiological processes of plant cells. Here, we report the first characterization of a high conductance, Cl--permeable channel, present in enriched fractions of plasma membranes of bean root cells. The Cl- channel was incorporated into planar lipid bilayers and its activity was recorded under voltage clamp conditions. The channel is voltage-dependent, excludes the passage of cations (K+, Na+, and Ca2+), and is inhibited by micromolar concentrations of Zn2+. The Cl- conductance here characterized represents a previously undescribed channel of plant cells. (C) 2003 Elsevier Science (USA). All rights reserved.