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Plants Talk. Plants Listen. Here's How

Tuesday, April 29, 2014 - 03:00 PM

They don't have eyes. Or ears. Or what we would call a nervous system. But plants can talk. And they listen. Let me show you how.

First, we'll need a plant eater. This one's perfect: It's an aphid, a hungry little critter who loves to munch on fresh, green leaves ...

Robert Krulwich/NPR

Next, we arrange lunch. We choose a bunch of young, healthy bean plants with lots of broad, green leaves ...

Robert Krulwich/NPR

Then we carefully drop our aphid (make that many aphids) onto the bean plants, where they land and begin to chew. The aphids spread across the plant, biting the leafy surface, gobbling little bits of green, creating holes ...


Robert Krulwich/NPR

When a leafy plant is under attack, it doesn't sit quietly. Back in 1983, two scientists,Jack Schultz and Ian Baldwin, reported that young maple saplings getting bitten by insects release a spurt of chemicals that float through the air. You and I wouldn't notice, but these chemicals carry a slight odor that neighboring plants can detect. It's a little like a silent scream.

Robert Krulwich/NPR

These chemicals come from the injured parts of the plant and seem to be an alarm. Maybe not an intentional warning like, "Watch Out! Aphid Attack!" but more like a simple distress call like, "Aphids! Aphids! Aphids!" or, "Attack! Attack!" The chemicals the plants pump through the air are a blend of organic molecules — alcohols, aldehydes, ketones and esters — known as volatile organic compounds, VOCs for short.

Over the past 20 years, scientists have found that all kinds of trees and plants like sagebrush, barley, corn, and yes, bean plants, release VOCs when they're being invaded. It's a plant's way of crying out. But is anyone listening? Apparently. Because we can watch the neighbors react.

Robert Krulwich/NPR

Robert Krulwich/NPR

In our case, when the distress signal reaches the two bean plants on either side of our aphid-covered plant, they also emit VOCs — cries of their own. As you can see, they seem to be calling for help — that's my fanciful way of describing what happens next.

Some bean plants pump out chemicals specifically designed to keep aphids away. Those are smelly irritants, especially noxious to invaders. But some bean plants do double duty. They pump out attractants — perfumes designed to lure in different airborne insects — in this case, wasps. Wasps are an aphid's worst nightmare. Once they arrive, the tables are turned. The critter who was lunching now becomes lunch.

Robert Krulwich/NPR

In study after study, it appears that these chemical conversations help the neighbors. The damage is usually extensive on the first plant, but the neighbors, relatively speaking, stay pest-resistant. Apparently, they heard the alarm and knew what to do.

Robert Krulwich/NPR

Does this mean that plants talk to each other? Did the first plant in some way intentionally send its warning? Was it doing a Paul Revere? Scientists don't know. Maybe the first plant just uttered a cry of pain or was sending a message to its own branches, and so, in effect, was talking to itself (scientists call this "a soliloquy"). Perhaps the neighbors just happened to "overhear" the cry. So information was exchanged, but it wasn't a true, intentional back and forth.

Still, the more they look, the more scientists discover plants chattering. "It's pretty spectacular what plants do," Ted Farmer of the University of Lausanne told Quanta Magazine. "I'm amazed."

Not only do plants use airborne chemicals, they send signals underground, through their roots. Some make ultrasonic "clicking" sounds. What feels to us like a quiet day in the forest may in fact be a hurly-burly of wafting, pulsing, clicking plant-to-plant communication.

Robert Krulwich/NPR

And sometimes the chatter leaps across species lines. Scientists have simulated an animal attack on a sagebrush. In the American West, pronghorn antelopes regularly grab on to sage with their teeth and tear off leaves when it's time for lunch ...

In the lab version, as the animal's teeth ripped the sage leaves, scientists watched the sage plant send a chemical signal into the air, and watched as a nearby tobacco plant picked up the signal and then emitted an odor that was noxious to the animal — strong enough to repel the antelope — protecting itself, and, arguably, helping the sage. What a complex dance!

Charles Darwin, 150 years ago, imagined a world far busier, noisier and more intimate than the world we can see and hear. Our senses are weak. The world is buzzing. Darwin sensed this. "Let it be borne in mind how infinitely close-fitting are the mutual relations of all organic beings to each other," he wrote. I like that expression, "infinitely close-fitting." It suggests there's a whole lot going on, and that we're just hearing our first peep.


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Comments [10]

Jason from New Jersey

I found it cool that different genera can communicate. I had always only thought that two of the same species of plant can communicate.
Your fact checkers missed the fact that aphids do not eat leaves. They insert a stylet (mouthpart) into the leaf and rely on transpirational pull of the leaf to extract the sugars.

Nov. 14 2015 05:58 AM
Billy thompson from Colorado

o yeah that was cool they are all like do dooo doododo dodoood doo doodod dood ood

May. 06 2014 05:34 PM
Steve from Orlando

Evidentially you have not heard the grass scream when your cutting it!

May. 04 2014 10:33 PM

I remember seeing an episode of myth busters where they grew two kinds of plants. One plant grew with nice complements and classical music while the other endured harsh comments and rock music. These factors didn't seem to change the way the plant grew. Although plants won't communicate with us, it's interesting to see how they communicate with each other. They are living organisms and they are just like animals because they release toxic odors or change colors to repel predators. I think it was interesting how one plant would warn another and they would help each other out so alert the predator. It shows how diverse this world is.

May. 04 2014 09:20 PM
Joseph campbell from O town

This was a very interesting subject. Plants are in fact another form of life form in the world which has been seen. In honesty though who really does see plats as actually having a communications.

May. 04 2014 08:02 PM
john from scottsdale, az

Recall the movie AVATAR

May. 03 2014 08:08 PM
Captain Stupendous from Australia

Interesting article, especially the part about aphids chewing holes in leaves, a very difficult task when they have no chewing mouth parts. Aphids are built for piercing and sucking.

May. 02 2014 06:03 AM
Kelley from Denver

So maybe M. Knight Shyamalan's movie "The Happening" had more factual basis to it than everyone thought.... Uh Oh!

May. 01 2014 12:31 PM
ClashofClans from Indonesia

Thanks for the above post

May. 01 2014 10:54 AM
George Sherman from Nyack, NY

A fascinating report. I used to jokingly tell my vegetarian friends that I objected to the killing of plants as much as they objected to the killing of animals for food. I guess that I wasn't too far off the mark.

May. 01 2014 08:01 AM

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