INSECT-INDUCED BIOELECTROCHEMICAL SIGNALS IN POTATO PLANTS

Action potentials and resting potentials were measured in potato plants (Solanum tuberosum L.) under different physiological conditions. External stimuli (e.g. changing temperature, wounding or exposing plant leaves or soil to certain chemical compounds) cause an action potential to be generated and change the resting potential from the original steady state level. The amplitude, polarity and the speed of action potential propagation depend on the type of external stimuli or stress. The kinetics and amplitude of the resting potential also change depending on the nature of the external stimuli. For example, in the presence of leaf-feeding larvae of the Colorado potato beetle (Leptinotarsa decemlineata (Say); Coleoptera: Chrysomelidae), the speed at which insect-induced action potentials moved downward through the stem was about 0.05 cm s(-1). The action potentials propagated downwards from the damaged leaf along the stem. When the upper leaves of potato plants were sprayed with 0.3 mi of 1 mM aqueous solution of pentachlorophenol, the effect was almost identical to that induced by Colorado potato beetle. To our knowledge, this is the first demonstration of action potential generation in plants induced by insect damage or chemical injury.