Electrical signals in long-distance communication in plants

Abstract

Action potentials (APs) belong to long-distance signals in plants. They fulfill the all-or-none law, propagate without decrement and their generation is limited by refractory periods. The ion mechanism of APs was elaborated in giant Characean algae and extended by another model plant - the liverwort Conocephalum conicum. It consists of an increase in cytoplasmic Ca2+ concentration ([Ca2+]cyt) which activates anion channels responsible for Cl- efflux and for membrane depolarization. Repolarization occurs after the opening of potassium channels and K+ efflux. The resting potential is restored by the electrogenic proton pump. A number of ion channels which may play a role in AP were identified by the patch-clamp technique. APs propagate on the principle of local electrical circuits. They cover whole plants, plant organs or definite tissues, mainly phloem, phloem parenchyma and protoxylem. APs mediate between local stimulation and movements in carnivorous Dionaea muscipula, Aldrovanda vesiculosa, and tigmonastic Mimosa pudica. The role of APs in regulation of respiration, photosynthesis, growth, pollination, fertilization and gene expression is well documented. An AP-coupled increase in [Ca2+]cyt seems to play a central role in signal transduction.