![]() ![]() "The diversity in flower colors is enormous," van der Kooi said. It's also important to understand how such biodiversity in flowers arose, he said. Ultimately, this basic research may inform conservation strategies in a world where many pollinators, including some bees, are struggling, van der Kooi said. ![]() Warm flowers are also preferred by some pollinators. This raises the temperature of the blossom's center, which may promote pollen or seed maturation, van der Kooi said. (This is called heliotrophy.) The effect is to reflect light waves not toward the sky, but internally, toward the plant's reproductive organs. On overcast days, the researchers observed that buttercups close into a cup-like shape but also tilt their blossoms to follow what sunlight they can catch. The buttercups also might be acting as their own space heaters. This might make the flowers stand out to pollinators, he said. On sunny days, when the buttercup petals are spread wide to the sky, their glossiness may create a "flash" effect for passing insects, like a mirror reflecting a beam of sunlight. There are a couple of possibilities, van der Kooi said. So why might buttercups stand out in the plant kingdom as the only ones to possess these structures? Many animal species, particularly birds and butterflies, use thin films to create iridescent or glossy colors, van der Kooi said. It's used once as the light hits the epidermal layer, and then again when the light is scattered back. "The pigment is used twice, basically," van der Kooi said. The light is scattered back through the pigmented layer, intensifying the yellow color. This starch layer has a scattering effect, van der Kooi said. The light that isn't absorbed by the pigments in the epidermal layer, or the light that is bounced back, ends up passing through and hitting the starch layer below the air pockets. Oil slicks and soap bubbles get their shine from the same mechanism, van der Kooi said.īut buttercups also use pigments to great effect, according to van der Kooi. Wavelengths moving through the different layers interact in such a way to create a shiny, mirror-like effect. The interference between the smooth, single-cell epidermis and the airy layer below is what creates the thin-film effect, van der Kooi said. Between the epidermal layer and the starch are pockets of air, they added. The epidermal layer is a mere single cell thick, and it's anchored lightly to a starch layer below, the researchers said. ![]() The top layer of the buttercup petal, the epidermal layer, is ultrasmooth and contains pigments that absorb blue light (leaving longer-wavelength yellow light to reflect back to the eye). What they found was a flower with a structure never seen before. They used photography and scanning electron microscopy to examine the petal anatomy. To study this flower anomaly, van der Kooi and his colleagues analyzed buttercups from meadows around Groningen in the Netherlands. ![]()
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