Plants emit ultrasonic sounds, beyond the range of human hearing. Plant sounds are informative: made mainly when the plant is under stress, they contain information about its condition. The researchers mainly recorded tomato and tobacco plants; wheat, maize, nopal and henbit were also registered. The researchers: “Apparently, an idyllic field of flowers can be quite a noisy place. It’s just that we can’t hear the sounds!”
Worldwide discovery: For the first time in the world, researchers at Tel Aviv University recorded and analyzed the sounds clearly produced by plants. Clicking sounds, like popping popcorn, are emitted at a volume similar to human speech, but at high frequencies beyond the range of hearing of the human ear. The investigators: “We found that plants generally make sounds when they are under stress, and that each plant and each type of stress is associated with a specific, identifiable sound. Although imperceptible to the human ear, the sounds produced by plants can probably be heard. by various animals such as bats, mice and insects“.
The study was led by Prof. Lilach Hadany of the Wise School of Plant Sciences and Food Safety along with Prof. Yossi Yovel, Director of the Sagol School of Neuroscience and faculty member of the School of Zoology and the Steinhardt Museum of Natural History. , and research students Itzhak Khait and Ohad Lewin-Epstein, in collaboration with researchers from the Raymond and Beverly Sackler School of Mathematical Sciences, the Cereal Crop Research Institute, and the Sagol School of Neuroscience, all in Tel Aviv. University. The article was published in the prestigious scientific journal Cell .
Vibrations that become sound in plants
Prof. Hadany: “From previous studies, we know that vibrometers attached to plants record vibrations. But do these vibrations also turn into sound waves in the air, that is, sounds that can be registered from a distance? Our study addressed this question, which researchers have been debating for many years.“
In the first stage of the study, the researchers placed the plants in a boombox in a quiet, isolated basement with no background noise. Ultrasonic microphones that record sounds at frequencies from 20 to 250 kilohertz (the maximum frequency detected by an adult human being is around 16 kilohertz) were installed at a distance of about 10 cm from each plant. The study focused mainly on tomato and tobacco plants, but wheat, maize, nopal and henbit were also recorded.
Prof. Hadany: “Before placing the plants in the acoustic box, we subjected them to various treatments: some plants were not watered for five days, some had their stems cut and others were intact. Our intention was to test whether plants make sounds and whether these sounds are somehow affected by the condition of the plant. Our recordings indicated that the plants in our experiment made sounds at frequencies from 40 to 80 kilohertz. Unstressed plants made less than one sound per hour, on average, while stressed plants, both dehydrated and injured, made dozens of sounds. every hour“.
Algorithms for analysis of plant sounds
Recordings collected in this way were analyzed with specially developed machine learning (AI) algorithms. The algorithms learned to distinguish between different plants and different types of sounds, and eventually were able to identify the plant and determine the type and stress level of the recordings. Furthermore, the algorithms identified and classified plant sounds even when the plants were placed in a greenhouse with a lot of background noise. In the greenhouse, the researchers monitored the dehydrated plants over time and found that the amount of noise they made increased to a certain point and then decreased.
Prof. Hadany: “In this study we solved a very old scientific controversy: we proved that plants emit sounds! Our findings suggest that the world around us is full of plant sounds and that these sounds contain information about, for example, water scarcity. or wound We assume that in nature the sounds emitted by plants are detected by nearby creatures, such as bats, rodents, various insects and possibly also other plants, which can hear the high frequencies and obtain relevant information. We believe humans can use this information too, with the right tools, like sensors that tell growers when plants need to be watered. On the surface, an idyllic field of flowers can be quite a noisy place. It’s just that we can’t hear the sounds!“
In future studies, researchers will continue to explore a variety of intriguing questions: What is the mechanism behind plant sounds? How do moths detect and react to sounds made by plants? Do other plants also hear these sounds? And more…
Link to the article: https://doi.org/10.1016/j.cell.2023.03.009