Electrostatic detection and electric signalling in plants: do flowers act as antennas?

Abstract

Flying insect pollinators are electrically charged. As bumblebees (Bombus terrestris) and honeybees (Apis mellifera) are almost always positively charged, they present a static electric field that is modulated by the harmonic motion of their wings. Previous research has demonstrated that as a bee approaches a flower, there is a change in the stem potential of the plant, even before the bee lands, suggesting a capacity for flowers to sense the approaching bee through its electric field. Using a combination of laboratory and field studies, we explore the potential for flowers to act as receiving antennas for electrical signals, and to transmit these signals to neighbouring plants. Results show that flowers can detect non-contact electric stimuli, presumably by charge induction, and appear not to be tuned to a specific frequency. In the field, non-contact electric stimuli can also be detected in neighbouring flowers that did not receive the aerial stimulus. This evidence demonstrates the ability of flowers to capture local, aerial electrical signals, and the plant to then transmit signals through the soil to neighbouring plants. This work highlights the significance of environmental electric fields in pollination biology.