Although I’ve alluded to talking to plants in the title for this post, the interesting thing here is that research shows they can sense vibrations made by insects like caterpillars. This allows the plants to prepare for an attack by producing defensive chemicals.

Some research suggests that plants can even detect the sound of water, which could have implications for sewer systems. The findings open up possibilities for using sound-based interventions in agriculture, such as drones equipped with speakers to warn crops of impending pest attacks.

Plants have been evolving alongside the insects that pollinate them and eat them for hundreds of millions of years. With that in mind, Heidi Appel, a botanist now at the University of Houston, and Reginald Cocroft, an entomologist at the University of Missouri, wondered if plants might be sensitive to the sounds made by the animals with which they most often interact. The researchers recorded the vibrations made by certain species of caterpillar as they chewed on leaves. These vibrations are not powerful enough to produce sound waves in the air. But they are able to travel across leaves and branches, and even to neighbouring plants if their foliage touches.

The researchers then exposed Thale cress—the plant biologist’s version of the laboratory mouse—to the recorded vibrations while no caterpillars were actually present. Later, they put real caterpillars on the plants to see if exposure had led them to prepare for an insect attack. The results were striking. Leaves that had been exposed had significantly higher levels of defensive chemicals like glucosinolates and anthocyanins, making them much harder for the caterpillars to eat. Leaves on control plants that had not been exposed to vibrations showed no such response. Other sorts of vibration—caused by the wind, for instance, or other insects that do not eat leaves—had no effect.


The research may have practical consequences, too. “Drones armed with speakers and the right audio files could warn crops to act when pests are detected but not yet widespread,” says Dr Cocroft. Unlike chemical pesticides, sound waves leave no toxic residue. With the help of weather forecasts, the system could even be used to prepare crops for cold snaps.


Farmers monitor the health of their crops by eye. (Mosaic virus, for instance, is so named because of the mottled pattern produced on the leaves of suffering plants.) That can be hard to do properly over an entire field. But if plants are broadcasting auditory indicators of distress, then wiring a field with microphones might help farmers keep an ear out for trouble.

Source: Plants don’t have ears. But they can still detect sound | The Economist