CHARACTERISTICS OF THE WAVE OF DEPOLARIZATION INDUCED BY WOUNDING IN BIDENS-PILOSA L

Heating locally the hypocotyl of Bidens pilosa L. elicits a wave of depolarization. The mechanism of the wave has been investigated by means of microelectrophysiological techniques. The amplitude of the transmembrane potential variation induced by an extracellular ion concentration change (K+, Na+, Ca2+, Cl-) was the same in the resting conditions as during the slow wave. At pH 4.0, the amplitude of the slow wave was reduced by 56% compared with the control performed at pH 7.0. In the presence of the uncoupler CCCP, the slow wave was not observed. The Ca2+-chelator EGTA and the Ca2+-channel blocker La3+ reduced, respectively, the amplitude of the slow wave by 78% and 68%. These results indicate the involvement of Ca2+ in triggering the slow wave. A transient modification of the electrogenic H+ pump activity (inactivation-inactivation) and of the transmembrane H+ flux in the slow wave are discussed.