World’s Shiniest Fruit

You’d be forgiven if you thought the images above are of man-made baubles
but they’re actually real fruit of the African plant Pollia condensata.
What’s more, the shiny fruit got its iridescent color in a very unusual
way.

Ed Yong of Not Exactly Rocket Science explains:

Under the microscope, Vignolini saw that the outer part of the fruit
consists of three to four layers of thick-walled cells (labelled “1?
in the image below). Each cell contains yet more layers, made of cellulose
fibres. The fibres all run parallel to one another, but each layer is
slightly rotated against the one above it, producing an elegant spiral.

As light hits the top layer, some gets reflected and the rest passes
through. The same thing happens at the next layer, and the next, and
so on. Provided the layers are exactly the right distance apart, the
reflected beams of light amplify each other to produce exceptionally
strong colours. The technical term is “multilayer interference”.
Or alternatively: “Ooh, shiny!”

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