UTILIZATION OF THE VIBRATING PROBE AND ION-SELECTIVE MICROELECTRODE TECHNIQUES TO INVESTIGATE ELECTROPHYSIOLOGICAL RESPONSES TO WOUNDING IN PEA ROOTS

This paper examines the ionic composition of wound-induced electrical currents in higher plant tissue, using two non-injurious electrophysiological techniques. By simultaneous recording of K+, H+, and Ca" ion fluxes with extracellular ion-selective microelectrodes, we have determined that a Ca2+ influx (2.4-mu-A cm-2). a small H+ influx (0.17-mu-A cm-2) and a large K+ efflux (16-mu-A cm-2) occur immediately after wounding in roots of Pisum sativum L. var. Greenfeast. Using an extracellular vibrating probe at the wound site, net ion currents of 26-mu-A cm-2 were measured 5 min after wounding. In a more concentrated bathing medium (1/4 rather than 1/6 strength Hoagland's solution), net ion currents of 59-mu-A cm-2 were measured, and these would appear to be the largest extracellular currents that have been measured in plants. We made a quantitative comparison of the summed ion fluxes with the net ion currents and this revealed that ion fluxes, in addition to those measured here, occur after wounding.