Plants make noises under stress
Although ultrasonic vibrations have been recorded from plants before, this is the first and only evidence that these sounds are propagated through the air. The researchers used sensitive microphones to record healthy and stressed tomato and tobacco plants, first in a soundproof acoustic chamber and then in a noisier greenhouse environment. They stressed the plants in two ways: by not watering them for a few days and by cutting their stems. To test the data, the sounds of unstressed and stressed plants were trained with machine learning algorithms.
Although the study focused on tomato and tobacco plants as they are easy to grow and standardize in the laboratory, the research team also recorded a variety of other plant species. “We’ve found that many plants — corn, wheat, grapes and cactus plants, for example — make noises when they’re stressed,” says Lilach Hadany at Tel Aviv University.
The cause of the sounds is unknown
Sound recordings of plants can be used in agricultural irrigation systems to monitor crop hydration status and help distribute water more efficiently, the authors say. Yossi Yovel, a neuro-ecologist at Tel Aviv University, said: “We know there’s a lot of ultrasound out there – whenever you use a microphone, you’ll find that many things produce sounds that we humans can’t hear – but the fact that plants make these sounds means communication, eavesdropping, and exploiting those sounds. It opens up a whole new way of opportunity for us.”