[Science News] Plants screams when stressed

by Cameron Landman April 04, 2023

Plants let out secret high-pitch screams when stressed

They sound a bit like bubble wrap being popped, apparently.

It’s the stuff of nightmares: you sit down to tuck into a tasty salad when, suddenly, one of the tomatoes starts to scream as you cut into it.

While the above scenario is a gross exaggeration, biologists from Tel Aviv University have found that plants emit sounds comparable in volume to normal human conversation when they are stressed.

Thankfully, they’re too high pitched for humans to hear but it is likely they can be heard by insects and other mammals, the researchers say.

“Even in a quiet field, there are actually sounds that we don't hear, and those sounds carry information,” said senior author Prof Lilach Hadany, an evolutionary biologist based at Tel Aviv University.

“There are animals that can hear these sounds, so there is the possibility that a lot of acoustic interaction is occurring.

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

The researchers recorded the sounds of the tomato plants using regular microphones.The researchers placed tomato and tobacco plants in a soundproofed acoustic chamber and then later in a noisy greenhouse environment. In both situations they stressed them first by not watering them for several days and then by cutting off their stems.

After recording the plants, the researchers trained a machine-learning algorithm to analyse the difference in the sounds produced by unstressed plants, thirsty plants, and cut plants.

They found that stressed plants produced around 30 to 50 high-pitched clicks or pops per hour at random intervals, while unstressed produced far fewer.

What’s more, the machine-learning algorithm was able to identify the different types of sounds produced depending on the cause of stress and also which plant they came from.

It’s not yet clear exactly how the plants are producing these sounds, though the researchers suggest that it might be due to the formation and bursting of air bubbles inside the plants.

Similarly, it’s unclear what the purpose of the sounds is. However, it’s likely that other plants and animals are ‘listening in’ to gain some sort of benefit, the researchers say.

“It’s possible that other organisms could have evolved to hear and respond to these sounds,” said Hadany.

“For example, a moth that intends to lay eggs on a plant or an animal that intends to eat a plant could use the sounds to help guide their decision.”

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

Source: Jason Goodyer, BBC Science Focus Magazine