Among the numerous senses already discovered in plants, the possibility that they have something similar to our sense of hearing is becoming more and more accepted. The hypothesis that plants are able to hear is currently being investigated by Monica Gagliano and Michael Renton, researchers at the University of Western Australia and authors of a study published in the May 2013 issue of the scientific journal BMC Ecology. What they have found is that plants are not just able to ‘smell’ chemical substances and ‘see’ the light emitted by their surrounding plants, forms of communication already noted, they can even ‘hear sounds’ emitted by other plants.

A source of acoustic energy that has special importance for plants is, of course, the sound produced by insects, especially those that might attack them. A study presented at the Conference of the Entomological Society of America in November 1993 by Heidi Appel and Reginald Cocroft of the University of Missouri states that the vibrations caused by feeding insects can actually trigger the plant to emit chemical defences. Plants of Arabidopsis thaliana previously exposed to the recorded sounds of a caterpillar chewing on them triggered chemical defenses at higher levels when they were later attacked by real caterpillars.

It has been discovered that root growth produces a sound. This has been seen to be fundamental in helping the roots themselves explore the surrounding terrain and take the best growth path by acting as a kind of “radar”. Furthermore, this underground signal communicates and “speaks” to the other plants by transmitting the needed information.