Spontaneous oscillations of extracellular electrical potentials measured on <i>Lepidium sativum</i> L. roots

Abstract

Abstract. Electrical potential differences (PDs) were measured continuously at six points in line on the surface of primary roots of cress ( Lepidium sativum L.). The root‐to‐hypocotyl transition was used as the reference. A gradient of extracellular potentials existed along the root axis. The most negative potentials were observed at the root tip. Whenever the growth rate declined to 0·10 mm h −1 or less, the PDs were nearly constant in space and time. Otherwise, the PDs showed different types of changes with time. Roots with growth rates between 0·65 and 1·10 mm h −1 preferably showed PDs characterized by approximately sinoidal oscillations. Maximal amplitudes appeared in the middle of the elongation zone. Roots which were exposed to a N 2 ‐atmosphere exhibited a reversible disappearance of the electrical oscillations and a decrease in the PD‐gradient. Similar effects were obtained by the application of the metabolic inhibitor azide (N 3 − ). These results proved that the electrical oscillations are dependent on the aerobic cell metabolism.