Steady Ionic Currents Around Pea (Pisum sativum L.) Root Tips: the Effects of Tissue Wounding.

Using the vibrating probe, we measured the extracellular current pattern around 4-day-old pea (Pisum sativum L. var. Greenfeast) root tips. Currents of 1.0 µA cm-2 flow into the meristematic and elongating tip, and smaller currents (0.1 µA cm-2) leave the mature zone basipetally behind this region. Wounding the root 3 mm from the root tip causes a very large (10 µA cm-2) inward current at the wound site. This disrupts the normal extracellular current pattern around the root. This wound current is inhibitable, and we present evidence that H+, and particularly Ca2+, may be involved. The time course of these ionic current changes is described. We propose that this wound current plays a role in the establishment of a new polarity in the cortical cells adjacent to a wound in root tissue. Possible mechanisms are discussed.