Induced fluctuations of electric potentials in the apoplast of leaves.

Extracellular recordings of electrical potential in leaves of different species by means of band-pass amplifiers showed the occurrence of fast, small changes (spikes) with an amplitude below 1 mV. Local illumination of leaves induced temporal patterns of spikes outside the illuminated region. The light-induced patterns recorded by a given electrode in a particular experimental setup were similar for successive illuminations. The patterns recorded at different sites on the same leaf were different. Locally repetitive patterns of spikes at the electrode outside the illuminated region indicate the occurrence of some signals transmitted from this region to the cells in the neighborhood of the electrode.