Living organisms generate electrical fields. The conduction of electrochemical excitation is a fundamental property of living organisms. Cells, tissues, and organs transmit electrochemical signals over short and long distances. Excitation waves in higher plants are possible mechanisms for intercellular-and intracellular communication in the presence of environmental changes. Ionic channels, as natural nanodevices, control the plasma membrane potential and the movement of ions across membranes; thereby, regulating various biological functions. Some voltage-gated ion channels work as plasma membrane nanopotentiostats. Tetraethylammonium chloride and ZnCl2 block K+ and Ca2+ ionic channels. These blockers inhibit the propagation of action potentials induced by blue light, and inhibit phototropism in soybean plants. The irradiation of soybean plants at 450 +/- 50 nm induces action potentials with duration times of about 0.3 ms and amplitudes around 60 mV. The role of the electrified nanointerface of the plasma membrane in signal transduction is discussed. (C) 2005 Elsevier Ltd. All rights reserved.