Propagation inVicia fabaStem of a Potential Variation Induced by Wounding

摘要

Heating of leaf blade inVicia fabatriggered bioelectrical events (“variation potential”) spreading throughout the shoot, preferentially in the acropetal direction. The spreading of a variation potential, previously described inMimosaand other plants, is related to a concomitant transport of a stimulating substance in the transpiration stream. This conclusion is supported by the observation inVicia fabastem that conduction in the basipetal direction is promoted when the transpiration stream is inverted.The conduction is promoted in the vascular bundles in direct relation with the burnt lobe of the leaf, but a lateral conduction may exist, as electrical variations are recorded in isolated bundles of the orthostichy opposite to the wounded leaf.A local cooling (1°C) of the stem has no influence on the conduction rate but it completely inhibits the bioelectrical variations in the cooled zone. This last result reinforces earlier demonstrations that the substance is transported in the vessels, according to a physical process, but that the electrical events require metabolic integrality in other cellular mem