Color in nature is a strange thing. Usually, we see directly reflected pigments, but some animals and plants have evolved ways of displaying colors without actually having those colors — what's known as structural color. This is pretty well understood in insects, but it happens in plants, too. In fact, the most strongly blue plant in existence isn't blue at all — it's just very strangely reflective.
Pollia condensata is a berry with no nutritional value that has managed to thrive in Africa because it's just so damned shiny that birds love the thing, and use it for decoration. A new paper in PNAS delved into how these berries are "more intense than that of any previously described biological material."
More than just an astonishing shade of blue, the berries are pointillist, with an almost glittery appearance. The paper calls it the most reflective biological material ever described, reflecting up to 30% of the light that hits it.
The berry achieves this by stacking the cell walls of its skin with cellulose strands stacked as layers of helixes. The vast majority of these are spaced so that only blue light is reflected, but there's enough variance that other colors are added to the mix as well, giving a multi hued look. As the paper puts it:
The multilayered cell walls of the fruit act as curved micro-Bragg reflectors, each of which reflects a specific color that differs from cell to cell. While blue reflectance is dominant, the sparse distribution of green and red reflecting cells gives the fruit an intriguing pixellated (pointillist) appearance, not recorded in any other organism.
Not only that, but because the patterning differs from cell to cell, some reflect to the left, and some reflect to the right, which has never before been observed in a single biological tissue.
It's an example of a convergent evolution, where plants and animals have evolved structural rather than optical coloration.
The news of just how incredibly shiny these berries are has swept across the blogosphere — so I can't be the only thinking these things will soon be in every housekeeping magazine and craft store across the globe. Because just like birds, we love decorating our nests with shiny things.