ELECTRICAL SIGNALING IN PLANTS

Long-distance electrical signalling in plants has generally been considered to be confined to a very few plant species in which the consequence of the electrical signals is turgor-dependent leaf movements of several different kinds. Recently, it has become clear that action potentials can be produced in a wide range of species, including many common ones, by various stimuli and that these action potentials can propagate through the plant. At the same time, evidence has become available that links electrical signalling to other kinds of responses-biochemical and developmental-in plants. Perhaps the most persuasive evidence is that linking electrical signalling to the systemic synthesis of pin proteins in tomato seedlings in response to local wounding. For long distances (greater than about 1 cm) the pathway for electrical signals in plants lies within the vascular system, but for some systems where only shorter distances are involved the pathway does not involve vascular tissues. In both cases propagation of action potentials occurs via plasmodesmatal connections between relatively unspecialized cells. Electrical signalling in plants, therefore, resembles the epithelial conduction system of electrical signalling in animals rather than the more widely known nervous systems.