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Carnivorous Plants Glow to Attract Prey

Carnivorous plants have an arsenal of tricks to entice insects into their clutches. These predatory plants have been known to use bright colors, delicious nectars, and appealing smells to make quick meals of the bugs that come to investigate—but no one knew they could also glow a bright blue.   The flesh-eating flora have special cells...

Carnivorous plants have an arsenal of tricks to entice insects into their clutches. These predatory plants have been known to use bright colors, delicious nectars, and appealing smells to make quick meals of the bugs that come to investigate—but no one knew they could also glow a bright blue.

The pitcher plant Nepenthes khasiana glows blue. Photograph courtesy Rajani Kurup, Anil J. Johnson, Sreethu Sankar, and Sabulal Baby

 

The flesh-eating flora have special cells that help them generate an ultraviolet hue, according to a new study published in the journal Plant Biology. Though invisible to the unaided human eye, the fluorescence is quite alluring to an inquisitive insect. (See pictures of killer plants.)

“To the best of our knowledge, this is the most distinct fluorescent emission found in the plant kingdom,” said study author Sabulal Baby, a plant biologist at the Jawaharlal Nehru Tropical Botanic Garden and Research Institute in India.

The glow is actually a survival technique: Carnivorous plants most often grow in nutrient-deficient soils and have to catch and kill bugs to supplement their poor diets.

Like Moths to a… Glow Stick

The plants’ light is emitted as an ultraviolet wavelength tailored to appeal to potential prey, including insects and other arthropods, the group that includes crustaceans, insects, and spiders. Insects often can see wavelengths that emphasize food sources.
For example, research suggests that honeybee eyes have evolved to pick out the brightest—and hopefully most nectar-rich—flowers.

 

carnivorous plant picture
The plant Sarracenia purpurea glows in UV light. Photograph courtesy Rajani Kurup, Anil J. Johnson, Sreethu Sankar, and Sabulal Baby

 

To an insect, the carnivorous plant’s glow probably looks like a bonfire. But to people looking at the plant under a black light, it’s something like a glow stick.

“In normal light, humans are not going to see this,” Baby said. “In the scale of a small ant, this could be a very clear light to them.” (Also see: “Glowing Animals: Beasts Shining for Science.”)

Fatal Attraction

Baby and his team examined four major types of carnivorous plants: pitfall traps, flypaper traps, snap traps, and bladder traps. Pitfall traps use pools of water or nectar to drown victims, while flypaper traps secrete sticky substances to snag a live snack.

Snap traps make some of the fastest movements in the plant kingdom, rapidly closing around prey, and bladder traps suck in prey using an internal vacuum. (Related: Tentacled, Carnivorous Plants Catapult Prey Into Traps.”)

Only the pitfall traps Nepenthes and Sarracenia and the snap trap Dionaea muscipula generated the distinct blue emissions, which turned out to be important to the plants’ survival. For instance, when scientists blacked out the ultraviolet light, the predators were less likely to attract insects. (Also see “Spiders, Carnivorous Plants Compete for Food—A First.”)

 

pitcher plant picture
The pitcher plant Nepenthes khasiana is seen in white light (left) and ultraviolet. Photograph courtesy Rajani Kurup, Anil J. Johnson, Sreethu Sankar, and Sabulal Baby

 

Though the research is incomplete, Baby also suspects that small animals like tree shrews and rats can also see the blue hue, enticing them to drink the plants’ sweet nectar. In the process, these animals drop fecal matter inside the plant, which becomes another good source of nutrients.

“The fluorescents are a very important attractant of insects, arthropods, and small animals,” he said.

Go With the Glow

Pitfall traps and snap traps aren’t the only plants to use ultraviolet frequencies. There are many species whose molecular makeup give them the ability to glow, said Howard Berg, a plant-cell biologist and the director of the Integrated Microscopy facility at the Donald Danforth Plant Science Center in Missouri.

“They have a chemical structure called conjugated double bond, and they have the ability to absorb light and re-emit it,” he said.

pitcher plant fluids picture
Fluids from a pitcher plant in the Nepenthes species fluoresce. Photograph courtesy Rajani Kurup, Anil J. Johnson, Sreethu Sankar, and Sabulal Baby

 

Berg added that the finding may even aid in future breakthroughs. Fluorescent jellyfish proteins are attached to specific markers, allowing researchers to study, for example, how cancer cells spread. The carnivorous plant’s glowing cells could potentially provide a new tracking method.

“It’s like a luggage tag,” Berg said. “You can use that as a locator. It’s really cool.”

What’s more likely, though, is the development of the ultimate bug zapper, study author Baby said.

The ultraviolet glow could work in tandem with an electric current to zap unsuspecting insects. The future of pest control—just go with the glow.

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Meet the Author

Mollie Bloudoff-Indelicato
Mollie Bloudoff-Indelicato is a science journalist who loves em dashes, ’80s music and parasites. She has a master’s degree from the Columbia University Graduate School of Journalism with concentrations in science journalism, photography, and radio reporting. Contact her at news@mbloudoff.com, and follow her on Twitter at @mbloudoff.