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Plants "scream" when experiencing stress


A new study reveals that plants emit distress calls when under stress.

Scientists say that when in a state of stress, some plants begin to vibrate, but there is no consensus among scientists on whether these vibrations can become sound waves. However, a recent study from Tel Aviv University suggests that plants emit ultrasound, conveying what they need.

In the experiment, tomato and tobacco plants were subjected to stressful conditions first in a soundproof chamber and then in a greenhouse. Stress was induced in two ways: either the plants were not watered for an extended period or their stems were pruned. After gathering sufficient data, researchers were even able to train a computer to distinguish the sounds produced by control plants from those that were drying out or pruned.

"We found that plants typically emit sounds when they are in a state of stress, and that each plant and type of stress is associated with a specific identifiable sound," said the researchers. "Although the sounds emitted by plants are imperceptible to the human ear, they can likely be heard by various animals, such as bats, mice, and insects."

Ultrasound microphones were placed approximately 10 centimeters away from the plants and found that they could produce sounds with frequencies ranging from 20 to 250 kilohertz due to air vibrations. Since humans can only hear up to 16 kilohertz, these sounds went unnoticed.

The research team analyzed the recordings using artificial intelligence algorithms, which were able to differentiate between the sounds emitted by the plants. Plants emitted louder cries if they experienced severe stress.

"Stress-free plants emitted an average of less than one sound per hour, while stressed plants—both dehydrated and damaged—emitted dozens of sounds every hour," said researcher Layla Hadani.

Scientists aim to apply this knowledge in agriculture and farming to better care for crops. Hadani says they simply need the "right tools—such as sensors that can alert farmers when plants need watering."

According to the study, "more precise irrigation can save up to 50% of water usage and increase crop yields."

"It's clear that an idyllic field of flowers can be quite a noisy place," said Hadani. "We just can't hear these sounds."