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 Ca²⁺ ion fluxes with extracellular ion-selective microelectrodes, we have determined that a Ca²⁺ influx (2.4 μA cm^-2), a small H⁺ influx (0.17 μA cm^-2) and a large K⁺ efflux (16 μA 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 μA cm^-2 were measured 5 min after wounding. In a more concentrated bathing medium (1/4 rather than 1/16 strength Hoagland's solution), net ion currents of 59 μA 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.