The blue halo of “attracting bees and butterflies”

Rare blue flower

No blue flower can be found among the mountains and plains, and the blue flowers that I usually see are nothing more than artificial dyes. In fact, natural blue flowers are very rare. According to statistics, less than 10% of the 280,000 kinds of flowers in the world can naturally grow blue flowers.

Why are blue flowers so rare in nature?

In fact, the color of flowers depends on anthocyanins. Anthocyanin is a kind of plant pigment, which exists in the cell sap of plant cell vacuoles. With the change of pH, it will show different colors. The stronger the acidity, the redder the anthocyanin; the stronger the alkalinity, the bluer the anthocyanin; under neutral conditions, the anthocyanin will appear purple. Normally, the soil environment where plants grow is mostly neutral or weakly acidic, so it is difficult to find naturally growing blue flowers.

However, British scientists have found that pollinators such as birds and insects prefer purple and blue flowers, because such flowers are often richer in nectar and sweeter. So flowers that are neither purple nor blue are going to fall out of favor? Don’t worry, the flowers have their own tricks, they do everything they can to attract pollinators. Can’t grow naturally? Then I will make it myself!

Homemade blue halo

In order to make up for their natural shortcomings, the flowers took a different approach and created a blue halo by themselves.

The discovery of the blue halo of flowers is actually an encounter. One day, Beverly Glover, a professor of botany at the University of Cambridge, was strolling on the campus and stumbled upon a scallop flower. When you walk around the scallop flower, you will find that different angles will reflect different luster. When she reached a certain angle, she found the flower glowing with a blue halo. She was shocked! Because as a botanist, she knows how scarce blue is in flowers. She looked carefully and carefully, and found that the petals of the bellflower flower were white and nearly light yellow, but the bottom of the petals was burgundy, that is, the burgundy part of the petals was glowing blue.

Is this an accidental phenomenon? Professor Glover also studied other flowers and found that this is not accidental. Many other different types of flowers also have blue halos. The blue halos are all located at the bottom end of the petals, some of which can be directly observed with the naked eye, and some require the help of experimental equipment to see. The blue halo that is visible to the naked eye has a darker color at the bottom of the petals, such as the burgundy part of bergamot. The blue halo on the petals with lighter bottom color cannot be directly observed with our eyes, such as white or yellow background. But the sensitivity of bees to colors is different from that of the human eye. Experiments show that no matter what kind of blue halo, bees can be seen.

So how exactly is the blue halo produced?

Under the microscope, a flower with a blue halo, the cells in other parts of the petals are flat and smooth, only the cells at the bottom of the petals have many tiny folds. These folds are relatively regularly spaced, and some are similar to the grooves on a vinyl record. . These uneven structures are the cause of the blue halo. When the light pours down, these folds will selectively absorb part of the light and reflect the other part, which will produce different colors of light at different angles. Different types of flowers reflect different light due to their own structural characteristics. But coincidentally, blue halos are all produced. Previous studies have shown that bee pollinators prefer blue-violet light, so are these homemade blue halos really effective?

“Recruiting Bees and Butterflies”

In order to verify whether the blue halo can help the flowers attract pollinators, the researchers conducted a controlled experiment.

There are three groups of artificial flowers, one of which has folds, but these folds are irregular and chaotic. The second group of flowers also have folds, these folds are very regular, the spacing, size, and shape are exactly the same. The folds of the third group of flowers are similar to natural flowers. As a result, the first group of flowers did not produce any optical effects, which were unremarkable; the second group of reflections had rainbow-like colors, but no blue halo was produced. The third group produced a blue halo, the same as natural flowers. Use these three groups of flowers to attract bumblebees. Under the same conditions, bumblebees can quickly find flowers with a blue halo. It can be seen from this that these natural flowers are very clever, neither too disorderly nor too orderly, and they grow up to attract pollinators just right. It seems that the blue halo is indeed the magic weapon for the flowers to “recruit bees and butterflies” and make up for their inherent shortcomings.

These blue halos are not inherent to angiosperms. Angiosperms have existed on the earth as early as 200 million years ago, but the flower fossils of that period did not have a structure capable of producing folds. In the Cretaceous period about 100 million years ago, dinosaurs were still the overlords of the earth. Hua’er began their evolutionary journey, gradually appearing fold structures, and have evolved many times since then. And every evolution of them is in step with the evolution of insects, especially those that collect nectar.

In addition, in nature, some flowers need wind to pollinate, while others need pollinators, such as birds and insects, to help pollinate. Flowers that need insects to help pollinate naturally must be able to attract the attention of pollinators. It is not only a specific kind of flower that has evolved to produce blue halo structures. Most flowers that need insects to help pollinate have this function. Favorite blue to attract them. This is a kind of convergent evolution, in which different species have evolved the same structure due to environmental and other factors. Obviously, although the species of flowers are different, their purpose is the same. The ultimate goal of flower evolution is to “recruit bees and butterflies” to complete its own reproduction process.

The perfect structure creates a blue halo and attracts pollinators. The flower has its own tricks and no longer has to worry about whether it is blue or purple.

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