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A photo of the Arabidopsis thaliana flowering plant

Mousear cress (Arabidopsis thaliana) creates an increased amount of mustard oil, a defense meant to deter an insect attacker, when it "hears" a caterpillar chewing on its leaves.

Photograph by Nigel Cattlin, Alamy

Emma Weissmann

National Geographic

Published July 9, 2014

Plants have long been known to react to changes in their environment, and may respond to light, temperature, and touch.

But are they listening too?

For the Arabidopsis plant, the answer is a loud and clear "yes."

The distinct, high-amplitude vibrations produced by a cabbage butterfly caterpillar munching on a leaf of this flowering mustard plant, commonly called mousear cress,  throws its defenses into high gear, according to a study published in Oecologia this month by two researchers at the University of Missouri.

The study, which combined audio and chemical analysis, is the first to find evidence that plants respond to an ecologically relevant sound in the environment, said Heidi Appel, a senior research scientist in the Division of Plant Sciences at Missouri.

Appel, along with Rex Cocroft, a professor in the Division of Biological Sciences, used a laser and a small piece of reflective material to record the caterpillar's chewing vibrations, which moves an Arabidopsis leaf up and down about 1/10,000 of an inch. They then played two-hour recordings of the vibrations to one set of plants and left another set in silence.

The plants that heard the recording of chewing vibrations created an increased amount of mustard oil, a defense meant to deter an insect attacker.

"[The vibrations] trigger them to be better prepared for subsequent attacks," said Appel. "So they make more defenses, faster, when they've been primed by these feeding vibrations."

The plants were also selective about what type of vibrations they responded to. Shortly after the first experiment, Appel and Cocroft exposed the plants to other vibratory sounds, including those from the wind and nonthreatening insects. The other sounds did not trigger any response. (See "Plants 'Listen' to the Good Vibes of Other Plants.")

"We don't think it's anything as simple as some frequencies or pitches of sound are better than others," Cocroft said. "They responded to the chewing vibrations and not to the insect song, even though they had the same frequencies in them. It suggests that the plants' acoustic perception is more complicated than simply looking for a particular pitch of sound."

A photo of a cabbage butterfly caterpillar feeding on an Arabidopsis plant.
A piece of reflective tape (on leaf at upper right) helps record the vibrations this cabbage butterfly caterpillar makes when chomping on an Arabidopsis plant.
Photograph by Roger Meissen

Little Plants Have Big Ears

Appel and Cocroft predict that although their research focused on one plant and one predator, their results suggest a widespread response throughout the plant kingdom. The next phase of research will explore the phenomenon with other types of plants and herbivores. It is too early, they say, to speculate on what applications their finding may have for commercial agriculture.

Appel and Cocroft's results join "a growing list of really interesting pieces of information that we really never appreciated that is useful for plants," said John Orrock, associate professor of zoology at the University of Wisconsin-Madison.

Orrock, who studies "the ecology of fear" between plants and their predators and has researched the effect snail slime has on a plant's defense system, said he believes the Missouri findings "open up a rich array of new and interesting questions" about the field of plant behavior.

"There are so many other forms of information that we know plants respond to," he said. "We know they pay attention to light; we know they pay attention to a vast array of chemicals both in the soil and in the air around them ... Plants are balancing a lot of information at any given moment in time. And now we know that acoustic information is something they're also balancing.

"It suggests that plants, in some ways, are listening."

Follow Emma Weissmann on Twitter.

15 comments
Bill Tyler
Bill Tyler

It's fascinating that this plant, and presumably others, respond to very specific sounds. I take exception, though, to the phraseology "pay attention to". That seems to indicate a level of awareness and anthropomorphism that's way beyond anything supported by the experimental evidence. 

Shannon Sweeney
Shannon Sweeney

It seems more useful to me to think of sensory perception as different for every type of being, rather than limit to what our present understanding is, of humans' limited 5-senses and neurology. That opens my mind to more. We are designed in a particular way with senses + brain + something we can only call a 6th sense until we can develop better ways to measure and describe it. Perhaps other life forms have different design, more or less senses. You get the idea. Tricky to describe.

C. Dufour
C. Dufour

if a tree falls in the fort and no-one is there to hear it does it make a sound ---> ask the other trees

EDWIN KAMAU
EDWIN KAMAU

I think plants feel but they do not hear.... if they did so,they would hear human beings or other animals approaching to feed on them and develop a mechanism of stoping that

lewis cheu
lewis cheu

Could  plants

feel between 2o Hz to 35,000 Hz frequecy?


I know some plants could feel to touch, they even can catch the bugs.

j. williams
j. williams

they can also "feel" fibrations.  Maybe they learn the types of vibrations and what they mean

j. williams
j. williams

Maybe it's not that they are "hearing" the insects chewing on them, but "feeling" the bugs biting them!  Humans don't usually hear when bugs are biting them, they feel the bite!

Michael Wheater
Michael Wheater

I heard the flowers in the breeze make conversation with the trees. -- The Move

Paul Duke
Paul Duke

Trees communicate to each other through the wind;just a theory at this point. we know so much and so little but isn't it amazing .

Jen Carres
Jen Carres

Amazing and now you can grow a real ZOMBIE Plant at home that "Plays DEAD" when you Touch it!  Just search thinkgeek zombie plant grow kit

Mandy Thinks
Mandy Thinks

Hearing IS feeling. Our eardrums 'hear' by feeling vibrations. Their sense of hearing is just different. But it's still the sensory observation of vibrations.

Paul Scutts
Paul Scutts

@Paul Duke I've known people who communicate through the wind (sorry, couldn't resist the fart joke).

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