INSECT-INDUCED BIOELECTROCHEMICAL SIGNALS IN POTATO PLANTS

Action potentials and resting potentials were measured in potato plant s (Solanum tuberosum L.) under different physiological conditions. Ext ernal stimuli (e.g. changing temperature, wounding or exposing plant l eaves or soil to certain chemical compounds) cause an action potential to be generated and change the resting potential from the original st eady state level. The amplitude, polarity and the speed of action pote ntial propagation depend on the type of external stimuli or stress. Th e kinetics and amplitude of the resting potential also change dependin g on the nature of the external stimuli. For example, in the presence of leaf-feeding larvae of the Colorado potato beetle (Leptinotarsa dec emlineata (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 dama ged leaf along the stem. When the upper leaves of potato plants were s prayed 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.