Look away now, vegans! Scientists find plants produce ALARM SOUNDS after being cut

By William On Mar 30, 2023

The idea of a plant making noises can conjure up a vision of the mandrakes from Harry Potter.

But a new study suggests that plants really do produce distress calls when they don’t get enough water.

They also seem to produce alarm sounds after being cut, with these sounds coming from tomato and tobacco plants, as well as corn and the vines used to make Cabernet Sauvignon.

Ultrasonic vibrations have previously been recorded from plants, using sensors that touch them directly.

Now, the new study provides the first evidence that plants emit airborne sounds, which researchers estimate can be heard by animals with keen hearing, such as mice and moths, from up to five meters away.

Now a study has found that plants actually do make sounds when they’re stressed – albeit more of a bang than a scream

For humans, who don’t hear in the high-frequency “ultrasonic” range, researchers have helpfully lowered the frequency so that we can experience the plant sounds – which are emitted rather loudly at the same volume as normal human conversation.

Normally, less than once an hour, plants produce a sound similar to the popping of popcorn — believed to be caused by air bubbles bursting in their stem.

But tomato plants that had not been watered for up to five days made this popping sound much more frantic — more than once every two minutes on average.

When cut, the tomato plants sounded an alarm about every two and a half minutes.

Professor Lilach Hadany, an evolutionary biologist at Tel Aviv University and senior author on the study on hundreds of plants, said: ‘Our findings suggest that the world around us is full of plant sounds and that these sounds carry information – for example about water scarcity or injury.

‘We assume that the sounds of plants in nature are detected by nearby creatures – such as bats, rodents, various insects and possibly other plants – which can hear the high frequencies and deduce relevant information.

Normally, plants produce a noise similar to popping popcorn less than once an hour – believed to be caused by air bubbles bursting in their stem

The idea of a plant making noises can conjure up a vision of the mandrakes from Harry Potter

Do plants feel ‘pain’?

When an insect bites a plant leaf, the wound triggers the release of calcium, University of Wisconsin researchers said last year.

This causes a chain reaction in the cells lining the leaves and stem of the plant.

It takes about one to two minutes for the reaction to reach every part of the plant.

The calcium generates a hormonal response from the plant to protect the leaves.

Some plants release harmful chemicals that make it taste bad to other invading insects.

Others, such as grass, release hormones that attract nearby parasitic wasps, which eat the attacking insects.

‘We believe that people can also use this information, provided they have the right tools, such as sensors that tell growers when plants need water.

‘Apparently an idyllic field of flowers can be quite noisy. Only we can’t hear the sounds!’

The ultrasonic recordings captured by two microphones placed next to each plant in the study support the theory that they may use sound to warn each other of danger from drought or hungry animals.

If plants knew in advance that water is scarce, they could close the pores in their leaves to conserve water.

If a plant hears a noise from another plant that has had its stem cut by an animal eating it, that plant may emit volatiles to scare off the hungry animal.

The researchers used artificial intelligence algorithms to compare the sounds made by tomato and tobacco plants to those made by plants that had been cut down in a soundproof acoustic chamber or left without water for two weeks.

The team found that plants that hadn’t been watered started making distress calls before they visibly dried out, peaking after five days without water, before decreasing before the plants had completely dried out.

The sound could in the future help people use a sensor to tell when their houseplants are unhappy and need a splash of water, or help farmers save water by irrigating crops only when they become dehydrated

The sound could, in the future, help people use a sensor to tell when their houseplants aren’t happy and need a splash of water, or help farmers conserve water by irrigating crops only when they become dehydrated.

The researchers also found that plants such as vines, wheat, corn and cacti made noises when cut or dried out.

Sounds lasted longer when a plant was dried out compared to when it was cut down, and different plants seemed to make different sounds, based on factors such as sound frequency.

Experts suspect that these sounds may be useful to creatures such as moths, which lay larvae on plants, so dried-out species will be unsuitable.