Scientists explain how the buttercup got its glow
11 January 2012
Scientists have at last explained why the flowers of buttercups Ranunculus repens reflect yellow back onto people's skins – and it has nothing to do with whether or not they like butter.
The mystery of how buttercups reflect bright yellow light from their petals has existed for as long as the children's game.
But now researchers from Cambridge University have found the flowers have a highly transparent, glass-like outer epidermal layer which interacts with an underlying, starchy layer to allow petals to reflect ultraviolet light, the only wavelength visible to many pollinators.
An air gap between the layers allows the reflection to intensify and become strongly directional – appearing as a flash which would further attract the attention of pollinators as well as producing the characteristic yellow light shining on to someone's chin.
The team likened the effect to the difference between uncoated paper, which scatters light in a diffuse way, like other types of flower petals, and coated glossy paper which reflects, like buttercup petals.
'This phenomenon has intrigued scientists and laymen alike for centuries,' said Dr Beverley Glover, of the University's Department of Plant Sciences. 'Our research provides exciting insight into not only a children's game but also into the lengths to which flowers will go to attract pollinators.'