Flowers 'hear' bee sounds and make sweeter nectar in response

https://www.earth.com/news/flowers-hear-bee-sounds-and-make-sweeter-nectar-in-response/

In terms of pollination, much of the spotlight shines on the color and scent of flowers. These features attract insects, especially bees, who help transfer pollen and ensure plant reproduction. But beneath this visual and olfactory spectacle, another sense may quietly shape this relationship: sound.

Scientists have long studied how flowers use color and scent to communicate with their pollinators. But could they also be listening?

For years, researchers overlooked the possibility that flowers might respond to the sounds of visiting pollinators. The low-volume acoustic signals created by insects during flight and foraging were simply too subtle, they thought.

However, a growing body of evidence suggests that these floral visitors generate more than just physical contact. They bring with them a unique sound signature. And now, thanks to a recent international collaboration, the science community is finally beginning to hear what the flowers may already know.

Flowers respond to pollinator sounds

Francesca Barbero, a professor of zoology at the University of Turin, is leading a new wave of research into how flowers detect and respond to vibroacoustic signals.

Her work brings together an unusual alliance: entomologists, plant physiologists, and sound engineers from Spain and Australia. Their shared mission is to understand how the faint buzzes and wing flaps of pollinators influence plant biology.

This novel approach centers on using sound recordings instead of intrusive instruments. By capturing the natural buzz of pollinators and replaying them near flowers, the team can observe how plants react without physically disturbing them.

The results offer a new method for monitoring pollinator activity. They also suggest that the link between plants and insects is more complex than previously imagined.

Barbero and her team will present their findings at the joint 188th Meeting of the Acoustical Society of America and the 25th International Congress on Acoustics, taking place May 18 to 23.

Flowers change nectar and sugar levels

To study how flowers respond to sound, the researchers focused on a specific flower-pollinator pairing: snapdragons and Rhodanthidium sticticum, a bee species also known as the snail shell bee.

This insect is a known pollinator of snapdragons, making it an ideal subject for testing acoustic communication between these species.

The researchers recorded the buzzing of this bee and played the audio back in the vicinity of blooming snapdragons. What happened next surprised even the seasoned scientists.

The flowers responded to the buzzing by increasing the amount of sugar in their nectar. They also boosted overall nectar volume. On a molecular level, the plants even altered their gene expression, particularly the genes involved in sugar transport and nectar production.

This reaction suggests that flowers can perceive and act on sound cues, adjusting their internal processes to match the identity of the pollinator they anticipate.

Flowers use sound to boost pollination

“Plant-pollinator coevolution has been studied primarily by assessing the production and perception of visual and olfactory cues, even though there is growing evidence that both insects and plants can sense and produce, or transmit, vibroacoustic signals,” Barbero explained.

This shift toward understanding acoustic signals opens a new chapter in coevolution. It proposes that plants are not just responding passively to insects but actively modifying themselves based on the specific visitor.

If a plant recognizes a pollinator by its buzz, it may enhance its attractiveness by adjusting nectar rewards. In doing so, it may increase the time that pollinators spend within its flowers and build pollinator loyalty.

“The ability to discriminate approaching pollinators based on their distinctive vibroacoustic signals could be an adaptive strategy for plants,” Barbero added.

“By replying to their proper vibroacoustic signal, for instance, an efficient pollinator’s, plants could improve their reproductive success if their responses drive modifications in pollinator behavior.”

While the evidence for plants detecting and responding to pollinator sound is growing, the reverse question now arises. Can plants themselves use sound to influence insects?

The answer is not yet clear, but the implications are compelling. “If this response from insects is confirmed, sounds could be used to treat economically relevant plants and crops, and increase their pollinators’ attraction,” Barbero noted.

In agricultural settings, this idea could revolutionize how we manage crops. If scientists can learn to replicate the right buzzing sounds, they might coax more pollinators to visit key crops without needing chemical attractants.

It opens the possibility of acoustic farming, where soundscapes become tools for boosting yields and biodiversity.

From pollinators to nectar robbers

The team’s work does not stop with one type of bee. They are now examining how snapdragons react to other visitors, including nectar robbers. These insects take nectar without providing any pollination service.

The comparisons may reveal whether plants can distinguish helpful insects from freeloaders using sound alone.

“The multitude of ways plants can perceive both biotic factors, such as beneficial and harmful insects, [and] other neighboring plants, and abiotic cues, like temperature, drought, and wind in their surroundings, is truly astonishing,” Barbero said.

This line of inquiry reveals that plants are far more perceptive than we assumed. They do not simply react to light and water. They sense their environment in complex, dynamic ways, including listening to the sounds of insects that surround them.

Flowers listen and adapt to insect sounds

This innovative research is part of a larger project titled “Good Vibes: How do plants recognise and respond to pollinator vibroacoustic signals,” and it is supported by the Human Frontier Science Program.

It involves multiple international partners: the University of Turin, I²SysBio in Valencia, and the Centre for Audio, Acoustics and Vibration at the University of Technology, Sydney.

Their work highlights how sound can be a bridge between species. In a world filled with pesticides, habitat loss, and climate stress, understanding how flowers communicate through vibrations may offer new tools for protecting pollinators and the plants they serve.

Through these discoveries, sound is being given its rightful place in the story of pollination. Flowers, it turns out, are not just beautiful – they are also listeners. And what they hear may shape their survival.

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From Human Frontier Science Program.

Good vibes: how do plants recognise and respond to pollinator vibroacoustic signals?