Electrical properties of Lupinus angustifolius L. stem. III. RC model, time constant, latency and threshold charge

The changes of potential in the stem of Lupinus were characterized on the basis of the strength-duration relation and of electrotonic potentials. It was found that the stimulated stem behaves like an electrical RC circuit. The time constants of electrotonic potential rise and decay were determined. A simple electrical model characterizing the passive electrical properties of the Lupinus stem is suggested. The values of resistance and capacitance of the Lupinus stem were determined on the basis of the RC circuit. The resistance-capacitance properties of the stem tissues serve as basis to gain a better knowledge of the parametres describing excitation, such as the strength-duration relation or latency. These properties in the stem of Lupinus are of the same nature as those in nerves or muscles. The values of the threshold charge of the order of 10-6 C were calculated. It is suggested that the regularities occurring here may be connected with accommodation and processes regulating the resting potential of cells.