TITLE: Stem and Leaf Electrical Potentials of Phaseolus vulgaris

Several previously published experiments have indicated that electrical activity is present in live plants. In order to determine the source and magnitude of plant voltages, a very high impedance measuring apparatus was constructed, and this system was attached to several Phaseolus vulgaris plants growing inside a conductive wire cage constructed as a Faraday cage to prevent external electromagnetic interference.

Several experiments were run on the plants, the results of which clearly point toward the plants generating approximately 300 mV negative relative to ground on their leaves. The experiments indicated that there are distinct voltages developed along the stem, and between the stem and the leaf. Each can be induced to generate more or less voltage by different stimuli, most notably, rapid changes in light intensity. A transition from light to full darkness causes the leaves to become approximately 20 mV more negative. Restoring the light causes the leaves to behave oppositely. Furthermore, the generation of this voltage is dependent on the amount of moisture contained within the plant’s soil. It has been hypothesized that sap transport play a major role in the voltage’s generation.