A stark discovery: plants “cry” before they die…and some animals can hear it

A new study shows that “stressed plants” make sounds, and animals can hear these sounds.

But what are “stressed” plants?

According to research published in the journal Cell, “stressed” plants that have not been watered for several days, or whose stems have been severed, produce sounds.
The tests were carried out in a soundproof room and then in a noiseless environment.
The researchers trained a machine learning algorithm to distinguish between unstressed plants, thirsty plants, and cut plants.
But tomato and tobacco plants were squealed when they were dried or when their stems were cut, Sky News reported.
When these plants are placed in a “stress situation,” they make popping or clicking sounds.
A “stressed” plant made 30 to 50 clicks per hour at random intervals, but unstressed plants made very few clicks.
Plants that don’t get enough water begin to shrivel before they become visibly dry.
After 5 days without water, the sounds peaked, and eventually the sounds slowly died out as the plants completely dried out.
The types of sounds also vary depending on the cause of stress.
“Even in a quiet field, there are sounds that we don’t hear, and these sounds carry information,” said Lilac Hadani, senior author of the study. “There are animals that can hear these sounds, so there is potential for a lot of vocal communication.”
“For example, corn, wheat, grapes and cactus – we found that many plants make noise when stressed.”
“When a tomato plant is not stressed, it is very calm.”
The frequency of these sounds is reported to be too high for humans to hear, but researchers believe they can be heard by insects, mammals and possibly other plants.
The cause of the sounds emitted by plants is not yet clear, but research suggests that it may be due to the formation and bursting of air bubbles in the plant’s vascular system.
According to Hatani, other organisms may have evolved to hear and respond to these sounds.
“For example, a moth may want to lay eggs on a plant or an animal may want to eat a plant using sounds to help it make its decision (about which plant to choose),” Hatani says.