Effect of Temperature on Bioelectric Oscillations of Bean Roots

Abstract

IT has been previously shown that roots of Vicia faba immersed in dilute salt solutions generate weak electric fields¹. These cause potential differences that can be measured in regions adjacent to the root. Under certain conditions, these potentials undergo spontaneous oscillations of several millivolts amplitude, with a period of about 5 min (that is, 12 cycles per hour) at 25° C (ref. 2). If the bioelectric field of a root is not oscillating spontaneously it can be forced to oscillate by subjecting it to periodic oscillations of osmotic pressure, or of concentration of the growth hormone indolyl-3-acetic acid in the surrounding medium. Under these conditions, a characteristic resonance response is observed when the enforcing oscillation has a period close to the natural period of the spontaneous oscillation³. This behaviour has been described in terms of a feedback oscillator having three exponential delay elements for which the following sequence of operations has been proposed: the potential of the cellular membrane affects migration of growth hormone electrophoretically; the hormone alters permeability of the membrane, and the resulting change in ion movement modifies the electric field, thus completing the loop. The literature on this subject has been reviewed by Scott⁴.