Honey, It's Electric: Bees Sense Charge On Flowers
Flowers are nature's ad men. They'll do anything to attract the attention of the pollinators that help them reproduce. That means spending precious energy on bright pigments, enticing fragrances and dazzling patterns.
Now, scientists have found another element that contributes to flowers' brand: their distinct electric field.
Anne Leonard, who studies bees at the University of Nevada, says our understanding of pollinator-flower communication has been expanding for decades.
"Flowers do a lot of things you might not expect," Leonard says. "We observe they have these distinct bright, beautiful colors, patterns, scents."
But we don't often stop to consider that this incredible display is all an attempt to attract bees and other pollinators. These displays don't just consist of things humans notice. There are also patterns in the ultraviolet spectrum, petal temperatures and textures and shapes.
"We've found that by producing these combinations of sensory stimuli, the plant basically makes its flowers easier for the bee to learn and remember," Leonard says.
That means the bee can forage more efficiently, and flowers are more likely to be pollinated.
"This is a magnificent interaction where you have an animal and a plant, and they both want this to go as well as possible," says Gregory Sutton of the University of Bristol in the U.K. "The flowers are trying to make themselves look as different as possible. This is to establish the flower's brand."
Sutton and a team of researchers led by Daniel Robert have just uncovered a whole new layer to flower brands.
"We found that flowers can use electric fields," Sutton says.
That's right — electric fields. It turns out flowers have a slight negative charge relative to the air around them. Bumblebees have a charge, too.
"When bees are flying through the air, just the friction of the air and the friction of the body parts on one another causes the bee to become positively charged," Sutton says.
It's like shuffling across a carpet in wool socks. When a positively charged bee lands on a flower, the negatively charged pollen grains naturally stick to it. The Bristol team wondered if bees were aware of this electrostatic interaction.
So, they designed an experiment — one described in this week's Science magazine. The researchers built a small arena full of fake flowers. Each flower was simple — a stalk with a small steel dish at the top. Half of the "flowers" held delicious sugar water. The other half held quinine, a substance that bees find bitter and disgusting.
When bumblebees explored this false flower patch, they moved around randomly. They chose to land on sweet flowers just about as often as bitter flowers.
But when the sweet flowers carried a small charge, the bees learned pretty quickly to choose the charged flowers. And when the electric charge was removed? They went back to their random foraging.
The bees had recognized the electric field, and had learned to use it to find sweet flowers. But that's not all.
"In the seconds just before the bee lands, there is electrical activity in the plant," Sutton says.
The plant's electric field is changed by the proximity of that positively charged bee. And once the bee leaves, the field stays changed for 100 seconds or so. That's long enough for the altered field to serve as a warning for the next bee that buzzes by. She won't stop to investigate a flower that's already been visited.
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Transcript
LINDA WERTHEIMER, HOST:
It's MORNING EDITION from NPR News. I'm Linda Wertheimer.
STEVE INSKEEP, HOST:
And I'm Steve Inskeep.
We have a shocking development in the relationship between bees and flowers. Scientists have learned something about how bumblebees do their jobs. Turns out they're not really bumbling around. They apparently can sense the electric field around flowers and use that to help them to find nectar.
NPR's Adam Cole reports.
ADAM COLE, BYLINE: Flowers are in the ad business. If they can't attract pollinators, they won't be able to reproduce. So they really have to push their brand.
(SOUNDBITE OF AD)
UNIDENTIFIED PEOPLE: (Singing) Our nectar will make you say yum. So why not try chrysanthemum?
COLE: They may not resort cheesy jingles, but according to Dr. Anne Leonard, flowers have plenty of other strategies.
ANNE LEONARD: Oh yeah, flowers do...
(LAUGHTER)
LEONARD: ...I mean they do a lot of things that you might not expect.
COLE: Leonard is a professor at the University of Nevada who studies the relationship between bees and flowers.
LEONARD: We all see flowers every day. We observe they have these distinct bright beautiful colors, patterns, scents.
COLE: But we don't often stop to think about what this incredible display is all for: to attract bees and other pollinators. And it's not just things we humans notice; there's also patterns in the ultraviolet spectrum, petal temperatures and textures and shapes - and they all add up to the flower's particular brand.
LEONARD: And we found that by producing these combinations of sensory stimuli, the plant basically makes its flowers easier for the bee to learn and remember.
COLE: That means the bee can forage more efficiently and flowers are more likely to be pollinated.
GREGORY SUTTON: This is a magnificent interaction where you have an animal and a plant working together, and they both want this to go as well as possible.
COLE: That's Dr. Gregory Sutton. He and his colleagues at the University of Bristol have just uncovered a whole new layer to flower brands.
SUTTON: We found that the flowers actually can use electric fields.
COLE: That's right, electric fields. It turns out flowers have a slight negative charge relative to the air around them. And bumblebees have a charge too.
(SOUNDBITE OF BUZZING)
SUTTON: When bees are flying through the air, just the friction of the air and the friction of the body parts with one another causes a bee to be positively charged.
COLE: It's like shuffling across a carpet in wool socks. When a positively charged buzz bee lands on a flower, the negatively charged pollen grains naturally stick to it.
SUTTON: We wondered if this electrostatic interaction could actually be perceived by the bee.
COLE: So here's what they did. They set up a fake little flower patch with fake little flowers. And in half the flowers they put something nectar-like - basically just sugar water. And in the other half they put quinine - that stuff in tonic water.
SUTTON: The bees can't smell quinine but it's bitter to them and they don't like it.
COLE: When bumblebees were allowed explore this flower patch, they moved around randomly. They chose to land on sweet flowers just about as often as bitter flowers. But when the sweet flowers carried a small charge, the bees learned pretty quickly to choose the charged flowers.
SUTTON: They get to about 80 percent successful.
COLE: The bees had recognized the electric field and had learned to use it to find sweet flowers. The results are published in this week's Science magazine. And there's more to it.
SUTTON: So, in the seconds just before the bee lands there is electrical activity in the plant.
COLE: The plant's electric field is changed by the proximity of that positively charged bee. And once the bee leaves, the field stays changed for 100 seconds or so. Sutton says this probably helps the next bee that buzzes by. She won't stop to investigate a flower that's already been visited.
Adam Cole, NPR News. Transcript provided by NPR, Copyright NPR.
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