CHARACTERIZATION OF ION CHANNELS IN THE PLASMA-MEMBRANE OF EPIDERMAL-CELLS OF EXPANDING PEA (PISUM-SATIVUM ARG) LEAVES

Ion channels in isolated patches of the plasma membrane of pea (Pisum sativum arg) epidermal cells were studied with the patch-clamp technique. One anion and one cation channel were dominantly present in most trials. The anion channel conducts nitrate, halides and malate, with a conductance in symmetrical 100 mM Cl- of 300 pS and can be blocked by SITS when applied to the cytoplasmic side of the membrane. The cation channel poorly discriminates between potassium, sodium and lithium, is not blocked by either TEA or Ba2+, and has a conductance of 35 pS in symmetrical 100 mM K+. The open probability of the cation channel increases with increase of the Ca2+ concentration on the cytoplasmic side of the membrane from 0.1 to 1 mu M, The possible role of these two channels in the physiology of epidermal cells is discussed.