Cactus plant with microphones. Credit: Tel Aviv University
Key points:
- For the first time, researchers have recorded and analyzed sounds emitted by plants.
- The sounds are similar to popcorn popping, but in a frequency undetectable to the human ear.
- They found that stressed plants emit many more sounds than unstressed plants.
In the first of its kind study, researchers at Tel Aviv University recorded and analyzed sounds emitted by plants. They detected a click-like sound, similar to the popping of popcorn, emitted at a volume that mimics human speech, but at frequencies outside the hearing range of the human ear.
"We found that plants usually emit sounds when they are under stress, and that each plant and each type of stress is associated with a specific identifiable sound,” said the researchers. “While imperceptible to the human ear, the sounds emitted by plants can probably be heard by various animals, such as bats, mice, and insects."
For the study, published in Cell, the researchers placed tomato and tobacco plants, as well as corn, wheat, cactus and henbit, in an acoustic box in a quiet, isolated basement with no background noise. They then set up ultrasonic microphones about 10 cm away from each plan to record sounds at frequencies of 20 to 250 kilohertz.
Before the experiment, the plants were subjected to various treatments. Some had their stems cut, some had not been watered for five days and some were untouched. The recordings indicated that the plants emitted sounds at frequencies of 40 to 80 kilohertz. Unstressed plants emitted less than one sound per hour, while the stressed plants emitted dozens of sounds every hour.
In future studies, the researchers say they will continue to explore plant sounds, including the mechanism behind them, how moths detect and react to the sounds, if other plants can hear the sounds, and more.
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