Some flowers apparently produce a blue optical effect in order to attract pollinating insects such as bees. What is a "blue halo" and how does it help with the pollination process?

"Blue Halo"

A new research details the way some flowers make an effort in order to be seen by their pollinators. The study, conducted by researchers from the University of Cambridge, the Adolphe Merkele Institute, and the Royal Botanic Gardens Kew, has found that some flowers have structures on their petals that generate a subtle optical effect, attracting pollinators such as bees.

These nanostructures scatter light particles in blue to ultraviolet shades. When they interact with light from a certain angle, it generates an optical effect called the "blue halo" because of its color shade.

Signalling Bees

Blue halos aren't exactly easy to see with the naked human eye. However, it is apparently visible to the flowers' targets which are the pollinating insects. Scientists were able to replicate the blue halos in order to test its effects on pollinating bees. They manufacture an artificial surface replicating the blue halos and found that the bees can see it. In fact, the bees responded to the blue halo and took it as a signal to locate the flowers.

Results of the experiment with the bees suggest that these blue halos actually allow them to find the flower faster. In a way, the flowers evolved to communicate with its pollinators.

In humans, our eyes can sometimes identify blue halo in flowers with dark pigments. Amazingly, in the case of bumblebees, they can distinguish which flowers have the blue halo and which ones don't, even if they are the same color.

"Unlike us, bees have enhanced photoreceptor activity in the blue-UV parts of the spectrum," said Edwige Moyroud of Cambridge's Department of Plant Sciences, lead author of the study.

Convergent Evolution

Upon studying the nanostructures further, researchers found that the structures are actually quite messy and inconsistent, with the ridges on the petal's surface in "disorder." Though the initial belief was that the disorder is just a by-product of evolution, researchers find that this is actually what helps the flowers to generate the optical effect.

"It came as a real surprise to discover that the disorder itself is what generates the important optical signal that allows bees to find the flowers more effectively," said Professor Beverley Glover of Cambridge's Botanic Garden, senior author of the study.

Further, their findings also suggest that the flowers evolved the nanostructures many times and independently of each other and yet they came to develop the same optical effect, eventually supporting their symbiotic relationship with pollinators.

The study is published in the journal Nature.