Influence of Surround Illuminance on the Action Potentials of a Sensitive Plant, Mimosa Pudica

Abstract

A sensitive plant, Mimosa pudica, has a small and interesting sensor mechanism in the leaf which might be different from animal's one. To measure the action potentials of the plant. a wind pressure was used as a stimulus, and a stimulator was made that can change its strength continuously. Electrodes were set at pulvinule (P₁), sub-pulvinus (P₂) and petiole (P₃). Then a leaflet was stimulated by a nozzle of the stimulator and the waveforms of the action potentials were observed. It was reported in the previous paper that (1) the waveform of electrode P₁, changed in four steps with the pressure; non-oscillation type, oscillation type, simple pulse type, and three phase pulse type, and that (2) the action potentials at electrodes P₂ and P₃ appeared over a certain threshold level of the pressure. The experiment was performed under the surround illuminance of about 200lx.
The present paper deals with the experiment performed under higher illuminance condition of about 500 and 1, 500lx. The following conclusions are obtained: (1) The change of four steps is confirmed under these condition. (2) In the lower illuminance level, the peak of the action potentials are generally larger and their waveforms become more complex than those in the higher one.