A study confirms it, plants 'scream' when you cut them or lack water

The plants when they are stressed emit sounds at a frequency that humans cannot hear, but that resemble sounds bursts of a bubble wrapwhich are detected at more than a meter and their volume is similar to that of a normal conversation.

A study from the University of Tel Aviv published by Cell has studied these sounds in stressed tomato and tobacco plants, either due to lack of watering or because a stem has been cut.

The frequency of these sounds is too high for our ears to pick up, but stressed plants emit sounds that can be detected at more than one meter, so there is a possibility that a lot of acoustic interaction is taking place," said the study coordinator. Lilach Hadany from Tel Aviv University.

Although ultrasonic vibrations have already been recorded in plants, this is the first evidence that they are transmitted through the air, a fact that makes them more relevant to other organisms in the environment, the publication explains.

The plants interact with insects and other animalsmany of which use sound to communicate, “so it would be highly suboptimal for plants not to use sound at all,” Hadany said. The researchers used microphones to record healthy, stressed tomato and tobacco plants, first in a soundproof acoustic chamber and then in a noisier greenhouse.

After recording the plants, they trained a machine learning algorithm to differentiate between stressed and unstressed, as well as between thirsty and cut plants. The team found that stressed plants make more sounds than non-stressed ones, and that they sound alike. to “pops o clicks”.

A single stressed plant emits between 30 and 50 of these clicks per hour at what seem like random intervals, while healthy ones make fewer sounds. “When tomato plants are not stressed they are very, very quiet”Hadany noted.

The types of sounds emitted differed depending on the cause of the stress, and the algorithm was able to differentiate between dehydration and cutting stress, as well as discern whether the sounds were coming from a tomato or tobacco plant.

Plants stressed by lack of water emit sounds before they are visibly dehydrated and the frequency reaches its maximum after five days without watering, after which it decreases and ends up completely drying up.

Although the study focused on tomato and tobacco plants, because they are easy to grow in a standard laboratory, the team also recorded a variety of other plant species.

"We discovered that many plants - corn, wheat, grapes and cacti, for example - make sounds when they are stressed," he said. Hadany.

The exact mechanism of these noises is not clear, but the researchers suggest that it could be due to the formation and air bubble break in the plant's vascular system, a process called cavitation.

"It is possible that other organisms have evolved to hear and respond to these sounds"

It is also not known whether they produce these sounds for communicate with other organisms, but the fact that they exist has major ecological and evolutionary implications.

"It is possible that other organisms have evolved to hear and respond to these sounds", for example -explained the researcher- "a moth that intends to lay eggs on a plant or an animal that intends to eat a plant could use the sounds to guide their decision ".

Other plants could also be listening and benefiting from the sounds. Previous studies have shown that plants increase sugar concentration in their nectar when they "hear" the sounds that pollinators make, and that they change their gene expression in response to the sounds.

"If other plants have information about stress before it actually occurs, they could prepare for it," he said. Hadany.

According to the authors, the sound recordings of the plants could be used in agricultural irrigation systems to control the state of hydration crops and help distribute water more efficiently.

The fact that plants produce these sounds "opens up a whole new avenue of opportunities for communication, listening and exploitation of these sounds," said another of the authors of the research, Yossi Yovel of Tel Aviv University.

The team is now studying the responses of other organisms, both animal and plant, to these sounds, and the researchers' ability to identify and interpret sounds in completely natural settings.