News Sci/Tech Plants: Silent Screamers Unveiled
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Plants Really Do 'Scream': Unveiling Their Hidden Voices

By Michelle Starr

02 April 2024

It seems like Roald Dahl may have been onto something after all: if you hurt a plant, it screams. Well, sort of. Not in the same way you or I might scream. Rather, they emit popping or clicking noises in ultrasonic frequencies outside the range of human hearing that increase when the plant becomes stressed. This, according to a study published in 2023, could be one of the ways in which plants communicate their distress to the world around them.

Plants' Acoustic Conversations

Evolutionary biologist Lilach Hadany of Tel Aviv University in Israel explains, "Even in a quiet field, there are actually sounds that we don't hear, and those sounds carry information. 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."

Not So Silent Under Stress

Plants under stress aren't as passive as you might think. They undergo some pretty dramatic changes, one of the most detectable of which (to us humans, at least) is the release of some pretty powerful aromas. They can also alter their color and shape. These changes can signal danger to other plants nearby, which in response boost their own defenses; or attract animals to deal with the pests that may be harming the plant.

However, whether plants emit other kinds of signals – such as sounds – has not been fully explored. A few years ago, Hadany and her colleagues found that plants can detect sound. The logical next question to ask was whether they can produce it, too.

Plant Symphony: Clicks and Pops

To find out, they recorded tomato and tobacco plants in a number of conditions. The sounds plants emit are like popping or clicking noises in a frequency far too high-pitched for humans to make out, detectable within a radius of over a meter (3.3 feet). Unstressed plants don't make much noise at all; they just hang out, quietly doing their plant thing. By contrast, stressed plants are much noisier, emitting an average of around 40 clicks per hour depending on the species. And plants deprived of water have a noticeable sound profile. They start clicking more before they show visible signs of dehydrating, escalating as the plant grows more parched, before subsiding as the plant withers away.

The team tested a variety of plants, and found that sound production appears to be a pretty common plant activity. Wheat, corn, grape, cactus, and henbit were all recorded making noise. But there are still a few unknowns. For example, it's not clear how the sounds are being produced.

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