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Slap on the edelweiss for the ultimate sunscreen
03 November 2007
NewScientist.com news service

Want to protect yourself from sun damage? Slathering yourself in edelweiss could help.

Edelweiss is a mountain flower and so is exposed to a large amount of ultraviolet light. Just how it protects itself from tissue damage at such high altitudes has been a mystery, says Jean Pol Vigneron at the University of Notre-Dame de la Paix in Namur, Belgium.

Vigneron and his colleagues measured the spectrum of light reflected from the plants and found that while most wavelengths are reflected, UV is not. "It's astonishing, but the plant completely absorbs the UV," says Vigneron.

The team then examined the tiny, white hairs that cover edelweiss leaves under a scanning electron microscope. They found that the hairs are made up of parallel fibres 0.18 micrometres across, which is close to the wavelength of UV light. This means they can interact with UV light, steering it along the length of the leaves, says Vigneron. In this way, the UV light is absorbed over a large number of hairs instead of penetrating to the plant's body (www.arxiv.org/abs/0710.2695).

The trick should be exploited to create a "natural" sunscreen for people, says Vigneron. "We currently use sunscreens made of titanium dioxide particles, but these can be absorbed through the skin and can be harmful," he says.

From issue 2628 of New Scientist magazine, 03 November 2007, page 20

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