Sunflower exposed to high-intensity microwave-frequency electromagnetic field: electrophysiological response requires a mechanical injury to initiate

Abstract

We have monitored the electrical potential variations (EPV) of sunflower plants illuminated by a high-intensity microwave-frequency (2.5 GHz, 1.5 kV/m) electromagnetic field (EMF). We have designed an appropriate set-up that allows parallel temperature and EPV measurements while part of the plant is being exposed to the field. The results show that the considered EMF does not induce plant EPV directly. This electrophysiological response appears only when the EMF leads to a mechanical injury of the tissues via a thermal effect (dielectric heating). Once the plant inner temperature reached a threshold, we systematically observed burn-like lesions associated with the bending of the stem or leaf-stalks. Theses mechanical constraints were rapidly followed by EPVs, moving through the stem.

Electrical Signaling, Photosynthesis and Systemic Acquired Acclimation

“…First, local electrical potential (LEP) is a sub-threshold response induced by environmental factors (e.g., light, cold, water status changes, phytohormones, pathogen infection). LEP is not transferred to other parts of a plant, but has an impact on the local physiological status of the cell (Yan et al, 2009 ; Roux et al, 2014 ). Second, action potential (AP) is a fast “all-or-nothing” signal, locally generated in the cell after treatment with different stimuli (light/darkness, electrical stimulation, cold, mechanical stimulus), provided that stimulus reaches a certain threshold.…”