Why buttercups glow yellow under your chinPublished On: Wed, Dec 14th, 2011 | Children's Health | By BioNews
The distinctive glossiness of the buttercup flower (Ranunculus repens), which children like to shine under the chin to test whether their friends like butter, is related to its unique anatomical structure, scientists have revealed.
The researchers discovered that the buttercup petal’s unique bright and glossy appearance is the result of the interplay between its different layers.
In particular, the strong yellow reflection responsible for the chin illumination is mainly due to the epidermal layer of the petal that reflects yellow light with an intensity that is comparable to glass.
This new study shows how the buttercup’s exceptionally bright appearance is a result of a special feature of the petal structure.
The epidermal layer of cells has not one but two extremely flat surfaces from which light is reflected. One is the top of the cells, the other exists because the epidermis is separated from the lower layers of the petal by an air gap.
Reflection of light by the smooth surface of the cells and by the air layer effectively doubles the gloss of the petal, explaining why buttercups are so much better at reflecting light under your chin than any other flower.
The researchers also found that the buttercup reflects a significant amount of UV light. As many pollinators, including bees, have eyes sensitive in the UV region, this provides insight into how the buttercup uses its unique appearance to attract insects.
“This phenomenon has intrigued scientists and laymen alike for centuries. 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,” said Dr Beverley Glover, from the University of Cambridge’s Department of Plant Sciences.
Their findings have been published in the Royal Society journal Interface.