Characteristics of action potentials in <i>Helianthus annuus</i>

Abstract

The action potentials induced by nondamaging electrical stimuli in 16‐ to 22‐day‐old plants of Helianthus annuus were examined. Typical recordings are presented. Mean values of their amplitudes and conduction velocities in the stem, the strength‐duration relation, the ‘all‐or‐none’ law and the refractory periods have been determined. The amplitude and velocity of propagation were essentially identical in the upward and downward direction, but greater in the upper than in the lower half. In ‘electrically active’ plants, the rheobase value is 2 V, the minimum period for stimulation is 1.8 s. and the chronaxie 2.3 s. It is noted that the excitability level between similar plants on the same day and in the same plant on different days is highly variable and undergoes periodic changes.