A Berry So Shiny, It's Irresistible (And Inedible)

The shiny blue berries of the tropical Pollia condensata plant rely on their looks, not nutritional content, to attract birds to spread their seeds.

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STEVE INSKEEP, HOST:?And this next story turns our gaze to something less famous than the White House, but in its own way exalted. In Great Britain, physicists have discovered that the blueberry of one tropical plant reflects light more brightly than anything else alive.

NPR's Christopher Joyce reports.

CHRISTOPHER JOYCE, BYLINE: Ullrich Steiner was spending a lot of time looking very closely at tulips and buttercups at Cambridge University in England. He was interested in their coloration. Then a colleague said hey, you've got to check out this weird blue berry from a plant called Pollia condensata.

ULLRICH STEINER: In fact, I was looking at this and I wasn't terribly impressed because it's not very big.

JOYCE: It's much smaller than a blueberry. But close up, the blue color was incredibly intense.

Steiner measured that intensity. And while most surfaces reflect just a few percent of the light that hits them, this berry reflects 30 percent of the light.

Writing in the Proceedings of the National Academy of Sciences, Steiner says no other living thing reflects light so brightly.

STEINER: We find that it is more intense than, for example, the morpho butterfly, which is usually cited for being one of the most brilliantly colorful animals.

JOYCE: The morpho butterfly and the scarab beetle are the only living things that come close. And like the beetle, the berry's skin has no pigment - no colored cells. Instead, all the cells are coiled. They come together in layers one on top of the other, like a stack of filters. Light trickles down through these filters and creates something called structural color.

STEINER: So what they do, basically, is they bounce back the blue light, and they let the rest of the light through.

JOYCE: But to give the color some kick, there are just a few cells in the berries' skin that do reflect other colors, and that gives the fruit what Steiner calls a pixilated glow.

Of course, you're wondering why a plant would go to all this effort. Well, it needs birds to take the fruit and spread its seeds. But its berry has no nutritional value. It's just a bauble - but so bright that it fascinates birds as well as physicists.

Christopher Joyce, NPR News.

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