The effect of mechanical stimulation on the inherent E.M.F. of polar tissues

Abstract

1. The effect of mechanical stimulation of a portion of the onion root is to reduce, or reverse the sign of, the inherent E.M.F. of the cells of the stimulated region. 2. The effect upon the inherent E.M.F. of a length of root including the stimulated region is dependent upon the direction of fall of potential across the latter. Stimulation of a region whose apical end is positive in the external circuit produces a fall of total potential, while stimulation of a region whose basal end is positive produces a rise in total potential. The effect is instantaneous in all cases. 3. There is no transmission of electrical effect from the stimulated region as shown by: (a) Absence of diphasic variation when stimuli are applied between the electrodes; (b) Absence of any effect when stimuli are applied outside the electrodes; (c) Adequacy of the quadrant electrometer to register the passage of impulses whose velocity does not exceed that of the slower waves recorded for Mimosa; (d) Existence of a negative condition in the stimulated cells as shown by moving the nearer electrode to include the stimulated region. 4. Lund's theory of the origin of bioelectric currents is shown to offer a simple and logical explanation of the facts.