Microwave radiation alters burn injury-evoked electric potential in Nicotiana benthamiana

Abstract

The dielectric effect enforced on charged ions and dipolar molecules by the oscillating electric field of microwaves may influence electric signaling in plants. In the present study, the exposure of Nicotiana benthamiana plants to continuous wave 2.45 GHz microwave radiation with 1.9 - 2.1 W m^-2 power density significantly reduced the amplitude of leaf burning-induced variation potential along the plant stem. The change in amplitude of the variation potential occurred mainly because of a significant reduction of the depolarization rate. This effect was not observed during the post-microwave exposure period. The unique characteristics observed in the variation potentials were also observed under microwave exposure, suggesting unaffected information delivery to distant locations or unaffected transport of specific chemicals generated by the injury.

Keywords: Abiotic stress; electromagnetic radiation; non-thermal effect; plant signaling; wounding.

Figure 1.

A representative image of Nicotiana benthamiana wildtype plant during electric potential recording. Letters a, b and c represent top hanging transmission microstrip antenna, reading glass electrode, and reference glass electrode respectively.

Figure 2.

Microscopic images of a Nicotiana benthamiana leaf without injury and after burn injury. Leaf tip destroyed by flame exposure and fading brown color toward the unexposed area.

Figure 3.

(a) Resting potential of a matured Nicotiana benthamiana plant without microwave exposure; (b) Three electric potential signals propagated after burning injury was inflicted without EMR exposure on first (left side signal), second (middle signal) and third leaf (right side signal) of the plant (fully emerged leaves were counted from the top downward). Arrows indicate EP spikes and dashed circles indicate observed slowing of signal repolarization rate. The example is representative of at least four similar experiments.

Figure 4.

(a) Resting potential of a matured Nicotiana benthamiana plant during pre-microwave exposure (pre), on-microwave exposure (on) and post-microwave duration (post); (b) Three electric potential signals propagated after burning injury was inflicted during, pre-microwave exposure to first leaf (left side signal), on-microwae exposure to second leaf (middle signal) and post-microwave exposure to third leaf (right side signal) of the plant (fully emerged leaves were counted from the top downward). The example is representative of at least four similar experiments.