Action Potentials in Lupinus angustifolius L. Shoots: II. DETERMINATION OF THE STRENGTH-DURATION RELATION AND THE ALL-OR-NOTHING LAW

In Lupinus shoots an electrical stimulus (d.c.) produces a potentialwave analogous to the action potential wave (AP) in stimulatedsimple plant cells or in nerves. The method used (Paszewskiand Zawadzki, 1973a, b) is similar to those applied in neurophysiologyin research on the excitability of nerves. In the present paper the strength-duration relation (Eqn. (1))of the excitation in Lupinusitalic has been used to calculatethe values of the rheobase, chronaxie, and useful time of pulse.The rheobase, as a threshold value of the stimulus, is examinedin terms of the applicability of the all-or-nothing law. The results suggest that the origin and propagation of AP inplants and in nerves may occur in a similar way. The analogybetween the impulse propagation in nerve trunks and in Lupinusshoots is discussed.