31 January 2014

Pitcher plants glow under UV light to attract prey

It's long been known that carnivorous plants lure their insect prey in a range of ways: irresistible nectars, vivid colors and alluring scents that range from rose to rotten flesh. But recently, a group of scientists at the Jawaharlal Nehru Tropical Botanic Garden and Research Institute in India discovered a previously hidden means of beckoning among the most ruthless of greenery. Some carnivorous plants, they discovered, lure insects to their death with a fluorescent glow invisible to the human eye...

"To our great surprise, we found a blue ring on on the pitcher rim," Baby says. "Then, we looked at other Nepenthes species and the prey traps of other carnivorous plants, including the Venus flytrap, and we consistently found UV-induced blue emissions." These colors, found in a total of twenty carnivorous plant species and documented in a study published in Plant Biology, were the first time such distinct fluorescent emissions were ever detected in the plant kingdom...

An ant—which can't see red, but is extremely sensitive to blue and violet light—would see rings of blue florescence, the result of metabolic compounds in the plant that absorb UV radiation from the Sun and re-emit it as visible light...

...the plants might use their fluorescence for other purposes as well. Recent field studies in Borneo indicated that some species of pitchers may have a symbiotic relationship with small nocturnal mammals, such as rats, bats and tree shrews—these mammals come and drink nectar from the plants, and deposit nutritious feces nearby, which serve as a fertilizer.
More photos and explanation at Smithsonian.  You learn something every day.

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