Voltage-Dependent K-Channel in Protoplasmic Droplets of Chara corallina: A Single Channel Patch Clamp Study

Passive transport of potassium through the plasma membrane of a protoplasmic droplet isolated from large internodal cells of Chara corallina Klein ex Willd., em, R.D.W. has been investigated using the patchclamp technique. When the membrane is hyperpolarized the conductance of a single K(+)-channel is of the order of magnitude of 100 picoSiemens and is reduced by tetraethylammonium chloride. Its open time is voltage dependent. This voltage-dependent K(+)-channel displays rectifying properties. The channel density is about 0.1 channel per square micrometer of membrane. When the membrane is depolarized the conductance of a single channel is of the order of magnitude of 30 picoSiemens and is insensitive to tetraethylammonium chloride. These results suggest that K(+)-channels are incorporated in the plasma membrane during membranogenesis of a protoplasmic droplet. They constitute further evidence for the existence of voltage-dependent K(+)-channels in plant cells.