Plants aren’t silent, and make more noise when stressed, study says

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plants popping sounds that are not perceptible to the human ear according to the recording made in a new study – and they make more noises when they are thirsty or under some other kind of stress.

research shakes up the most botanists That’s all they thought they knew about the plant kingdom, which was thought to be largely silent, and suggests the world around us is a cacophony of plant sounds, said the study’s co-authors. Lilac Hadni.

She said she had long suspected that plants were completely noiseless.

Hadani said, “There are so many organisms that react to sound, I thought there was no good reason for plants to be deaf and mute.” A professor in the School of Plant Sciences and Food Security and the George S. Wise Faculty of Life Sciences at Tel Aviv University.

The first plant Hadney recorded using an ultrasonic microphone was a cactus in her lab six years earlier, but she could not rule out that the sounds she detected were made by something else in the environment. Went. Previous studies had shown that plants produce vibrations, but it was not known whether these vibrations became airborne sound waves.

to find out whether the plant really were emitting sounds, Hadney and his team commissioned soundproof acoustic boxes.

Researchers placed tobacco and tomato plants in boxes, manipulated them with ultrasonic microphones that record at frequencies between 20 and 250 kHz. (The highest frequency that a human adult ear can detect is about 16 kHz.) Some plant stems were cut or Water had not been given for five days, and others were untouched.

The team found that plants emit sounds at a frequency of 40 to 80 kHz, and when condensed and translated into a frequency that humans can hear, the noise was slightly similar to Being made to pop popcorn or burst bubble wrap.

listen to the sounds coming from the tomato plant

These are the sounds made by a dried tomato plant over a period of one hour. The audio is accelerated and taken into the audible hearing range for humans.

Source: Khait et al.

A stressed plant emits about 30 to 50 of these popping or clicking sounds per hour at random intervals, but unstressed plants emit far fewer sounds—about one per hour.

“When tomatoes are not stressed at all, they are very calm,” Hadani said.

Researchers don’t know exactly how the sound is made, but they believe the noise comes from cavitation – a process in which an air bubble in a plant’s water column collapses under some kind of pressure , causing a click or pop.

But rest assured, the bouquet of cut flowers in your vase isn’t screaming at you in pain. There is no evidence that the noise produced by the plants is intentional or a form of communication.

“This result adds to what we know about plant responses to stress. It is a useful contribution to the field and to our general appreciation that plants are organisms capable of sensitive behavior,” said Professor of Entomology at the University of California Said Richard Carbone, a distinguished professor. Davis, who studies interactions between herbivores and their host plants. He was not involved in the research.

“However, this should not be interpreted as indicating that plants are actively communicating by making sounds,” Karban said.

While plant sounds are a passive phenomenon, other organisms may be able to use plant audio signals to their advantage, said sensory ecologist Daniel Robert, professor of biobioscience at the University of Bristol’s School of Biological Sciences in the United Kingdom. He was not involved in the research.

For example, he said the sounds may signal to the female moth that a particular tomato plant is under stress and not suitable for egg-laying or eating.

“There are many sounds produced in the world that are not ‘intentional’ signals, but can still be heard and used by other organisms for their own benefit. So, the concept of communication is really a challenge… Can it It needs to be bi-directional to work and be considered as such?’ he said via email.

The study's lead authors were Yossi Yovel, left, and Lilach Hadani.  Both are professors at Tel Aviv University.

The team repeated the experiment with tobacco and tomato plants in a noisy greenhouse environment. After recording the plants, the researchers built a machine-learning algorithm that can differentiate between unstressed plants, thirsty plants, and pruned plants.

“Finding that there is information in acoustic emissions using neural network classification is exciting because (a) the technique is fast and can identify data structures that human eyes or ears cannot,” said Robert.

While the researchers used tobacco and tomato plants because they are easy to grow in a standardized way, they also recorded and detected sounds made by many other plant species, such as varieties of wheat, corn, cacti, and grapes. that they make more sounds when stressed.

As well as insects or mammals that can detect and use plant sounds, Hadney said other plants can also hear sounds and benefit from them. Previous work by Hadney and other team members has shown that when plants “hear” the sounds made by pollinators, the concentration of sugar in their nectar increases.

Hudney said she now looks at plants and flowers differently. “There are so many songs we can’t listen to.”

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