How Berries Use Fat To Look Deep Blue

Some beautiful colors in nature are created by pigments, but others, especially shades of blue, by a clever way of reflecting light. Researchers have now taken this trick one step further with a blueberry.

If you see a bird with bright red wings, the pigment molecules in those feathers absorb all colors of light except red. But if you see a butterfly or a peacock with surfaces of a beautiful brilliant deep blue, then there is a structural color. This is created because light is selectively reflected off a pigment-free surface with a special structure.

When a Colorado researcher saw a blueberry in a bush with a similar bright metallic blue glow, she wanted to know: how exactly does this berry do this? Because in plants this shade is rare. She discovered that the berry uses layered fat molecules to reflect light appropriately. Only one other plant is known to do this, but the two are unrelated.

So one would think that if this is done separately by two factories, then there must be an evolutionary advantage to this trick. One theory now is that the fat layer also has a strong protective effect. Another is that the color is so beautiful that birds often use the berries as decoration in mating rituals and the plants have found their way into many gardens for the same reason.

Read more: Pigment or optical illusion? What makes this berry blue†