THE ROLE OF ELECTRICITY IN PLANT MOVEMENTS

Abstract

SUMMARYA survey has been made of the different types of reversible movements in the plant kingdom (including those of carnivorous traps, leaves, floral parts, root tips, cytoplasmic streaming, cilia and flagella) and it is suggested that many are mediated by changes in electrical potential. Many touch‐sensitive movements in higher plants are regulated by propagating electrical signals (action potentials), which relay excitation from the site of stimulation to the motor organ(s), where collapse of sensitive motor cells is brought about. The resulting change in volume of the motor cells causes movement of the entire motor organ. In some cases additional localized changes in electrical potential (receptor potentials) can be induced by external stimuli, which convert specific characteristics of the stimulus into an electrical analogue before triggering an action potential.The role of electrical activity in other plant movements is more speculative. Action potentials do not arise in light‐ or endogenous rhythm‐regulated movements, but changes in the membrane potential of motor cells concerned with these movements may also help to drive the ionic transport which leads to their turgor‐mediated motion. The significance of electrical activity associated with intracellular movements is less certain, but may become the focus of increasing attention as the regulation of actin‐directed cellular movements is further investigated. Electrical impulses comparable to those in higher plants may, however, regulate ciliar and flagellar activity in the motile gametes and spores of lower plants. Thus, it is clear that electrophysiology is an important aspect of many plant movements, and bears a remarkable similarity to excitation in animal nervous systems.