From cacti to tomatoes, from tobacco to nettles, even plants speak and they do it by emitting ultrasound: for the first time, researchers at the Israeli University of Tel Aviv have resolved an ancient scientific controversy by recording the sounds emitted by plants, similar to popping popcorn and inaudible to human ears, but probably audible to many animals, such as bats, mice, and insects.
The study, published in the journal Cell, also indicates that plants ‘talk’ above all when they are under stress: information which, thanks to special sensors, could be exploited by humans, for example to know when crops need to be watered. The researchers, coordinated by Lilach Hadany and Yossi Yovel, placed the plants in a silent and isolated place, positioning ultrasound microphones about ten centimeters from each specimen.
Above all, tomato and tobacco plants were used, as well as those of wheat, corn, cacti and nettles. The recordings revealed sounds emitted at frequencies between 40 and 80 kilohertz: for comparison, the maximum frequency detected by an adult human being reaches 16 kilohertz. Unstressed plants made about one sound per hour, while dehydrated or injured plants made dozens of sounds per hour. The collected recordings were then analyzed by specially developed Artificial Intelligence (AI) algorithms, which learned to distinguish between different plants and different types of sounds, identifying the plant and determining the type and level of stress. Furthermore, the algorithms were able to identify the ‘language’ of plants even in a greenhouse characterized by a lot of background noise. “Apparently, an idyllic field of flowers can be a very noisy place, but we can’t hear it,” comments Hadany.
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