Botanists Answer Mystery Of Glowing Buttercups
December 15, 2011

Botanists Answer Mystery Of Glowing Buttercups

As a child, did you ever shine a buttercup flower under your chin and witness a yellow glow to test whether you or your friends like butter? Well scientists have taken a closer look to better understand how this works and discovered the distinctive glossiness of the buttercup flower is related to its unique anatomical structure, according to a study published in the Royal Society journal Interface.

The bright and glossy appearance of the buttercup petals is the result of the interplay between its different layers, The Telegraph reports. The yellow reflection responsible for the illumination is due primarily to the epidermal layer of the petal reflecting yellow light with an intensity similar to glass.

The researchers also found a significant amount of UV light reflected from the flower which attracts many pollinators, including bees, which have eyes sensitive in the UV region.

As far back as 1883, researchers had noted the unusual optical properties of the buttercup, but this is the first time scientists have studied the flower´s light-reflecting qualities with modern equipment and related them to the anatomy of its petals, according to study researcher Ullrich Steiner, a professor of physics at the University of Cambridge in the United Kingdom.

Using flowers picked from meadows around Cambridge, physicists and plant biologists examined the petal and the layers within it and discovered how these layers affected the wavelengths of light passing through or reflecting off them, Wynne Parry reports for MSNBC Science.

Their research revealed how the anatomy of the petal creates the yellow glow, it turns out that light arriving at the flower petal encounters two different surfaces within its outer layer, called the epidermis.

Both surfaces are flat and each reflects light back much like a mirror would meaning the angle at which the light travels to the surface equals the angle at which it travels out, so all of the reflected light travels in the same direction.

Dr. Silvia Vignolini, from the University of Cambridge´s Department of Physics, explained the importance of the buttercup´s unique appearance, “Although many different factors, such as scent and temperature, influence the relationships between pollinators and flowers, the visual appearance of flowers is one of the most important factors in this communication.“

“Flowers develop brilliant color, or additional cues, such as glossiness - in the case of the buttercup - that contribute to make the optical response of the flower unique. Moreover, the glossiness might also mimic the presence of nectar droplets on the petals, making them that much more attractive.”

Supporting this theory, researchers discovered that the flower petals had the same glossy appearance under ultraviolet light. Light at these wavelengths is not visible to humans, but is an important visual cue for pollinating insects.


Image Caption: Buttercup under chin. Photo credit: Silvia Vignolini


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