Stressed plants emit sounds detectable at more than a meter

March 30 () –

Israeli researchers have verified that stressed tomato and tobacco plants, due to dehydration or because their stems have dried up, They emit sounds of volume comparable to that of a conversation.

The frequency of these noises is too high for our ears to detect, but they can probably be heard by insects, other mammals, and possibly other plants. as published in the magazine ‘Cell’.

“Even in a quiet field there are sounds that we don’t hear that contain information,” says Lilach Hadany, an evolutionary biologist and theorist at Tel Aviv University. “There are animals that can hear those sounds, so there’s the potential for a lot of acoustic interaction to take place.”

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.

“Plants interact with insects and other animals all the time, and many of these organisms use sound to communicate, so it would be highly suboptimal for plants not to use sound at all,” Hadany explains.

The researchers used microphones to record healthy and stressed tomato and tobacco plants, first in a soundproof acoustic chamber and then in a noisier greenhouse. They subjected the plants to stress by two methods: not watering them for several days and cutting the stems.

After recording the plants, the researchers trained a machine learning algorithm to differentiate between unstressed plants, thirsty plants, and cut plants.

The team found that stressed plants make more sounds than non-stressed ones. A single stressed plant makes between 30 and 50 of these clicks per hour at seemingly random intervals, while non-stressed plants make far fewer sounds. “When tomatoes are not stressed, they are very quiet,” Hadany assures.

The water-stressed plants started making noises before they were visibly dehydrated, with the frequency of the sounds peaking after 5 days without water before decreasing again as the plants dried out completely.

The types of sound emitted differed depending on the cause of the stress. Machine learning algorithm was able to accurately differentiate between dehydration and shear stress and he was also able to discern whether the sounds were coming from a tomato or tobacco plant.

Although the study focused on tomato and tobacco plants for their ease of cultivation and standardization in the laboratory, the research team also recorded other plant species. “We discovered that many plants – corn, wheat, grapes and cacti, for example – make sounds when they are stressed,” Hadany says.

The exact mechanism behind these noises is unclear, but the researchers suggest it could be due to the formation and bursting of air bubbles in the plant’s vascular system, a process called cavitation.

It’s also unclear whether plants make these sounds to communicate with other organisms, but the fact that they exist has big ecological and evolutionary implications. “Other organisms may have evolved to hear and respond to these sounds. Hadany points out. For example, a moth trying to lay eggs on a plant or an animal trying to eat a plant might use sounds to guide their decision.”

Other plants could also be listening and benefiting from the sounds. It is known from previous research that plants can respond to sounds and vibrations. Hadany and several other team members previously showed that plants increase the concentration of sugar in their nectar when they “hear” sounds made by pollinators, and other studies have shown that plants change their gene expression in response to sounds.

“If other plants have information about stress before it actually occurs, they could prepareHadany reasons.

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

“We know there are a lot of ultrasounds out there. –every time you use a microphone, you discover that many things produce sounds that humans cannot hear–, But the fact that plants make these sounds opens up a whole new avenue of opportunities for communication, listening and exploiting these sounds,” says co-lead author Yossi Yovel, a neuroecologist at Tel Aviv University.

“Now that we know that plants make sounds, the next question is: who might be listening?” he asks. “We are currently investigating the responses of other organisms, both animal and plant, to these sounds, and we are also exploring our ability to identify and interpret sounds in completely natural settings.