Abstract
Bean roots subjected to oscillations in osmotic pressure or in the auxin concentration of their weakly conducting bathing medium exhibit corresponding oscillations in their bioelectric fields with a resonance at the natural period of oscillation (approximately 5 minutes). The amplitude and phase responses, expressed as a function of the periods of the applied oscillations, are in agreement with those predicted from a theoretical model of a feedback loop. A physiological model compatible with the theoretical one is suggested.