Carnivorous plant species glow blue to lure prey

Peristomes of Indian pitcher plants glow blue under UV light

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Some carnivorous plants act as blue "fluorescent lamps" to lure prey, according to scientists in India.

The research team discovered blue fluorescent emissions from the plants' "capture spots" when tested in ultraviolet (UV) light.

Carnivorous plants are known to attract insects with nectar, colours and smells.

But the alluring blue glow reveals a new prey capture mechanism in some species, according to the findings.

The study, published in the journal Plant Biology, was carried out by scientists from Jawaharlal Nehru Tropical Botanic Garden and Research Institute in Thiruvananthapuram, Kerala, India.

Killer plants

Venus Fly Trap

"These distinct blue emissions were so far not known in carnivorous prey traps," said research team member Dr Sabulal Baby.

"To the best of our knowledge, this is the first study reporting such strong and distinct fluorescence emissions in the plant kingdom."

Significant signals

The team found the blue emissions, caused by molecular mechanisms, in "prey traps" of pitcher plants Nepenthes and Sarracenia and in Venus flytraps (Dionaea muscipula).

The blue glow was revealed on the inner sides of Venus flytraps when scanned at UV 366nm. And distinct blue fluorescence appeared on the lids, interior pitcher tubes and peristomes (upper rims) of pitcher plants.

Most insects and other arthropods can perceive UV regions of the electromagnetic spectrum.

To potential prey, the blue fluorescent rings emitting from the pitcher plants' peristomes may make attractive landing pads.

These fluorescent emissions would also be perceptible in low-light conditions, meaning they could also attract nocturnal prey.

Pitcher plant peristome glows blue under UV light The peristomes of Nepenthes gracilis appear like attractive landing pads for prey

The glow may also attract visits from small mammals such as rats, bats and tree shrews.

To test the significance of blue fluorescence as a prey-attracting device, the team "masked" the blue rings of Indian pitcher plants (Nepenthes khasiana) growing in the botanic gardens by coating them with a non-fluorescent extract.

The plants' prey capture success reduced drastically over the 10-day period when their blue emissions were hidden.

This indicates that blue fluorescence acts as a "very significant signal" in attracting prey, Dr Baby explained.

Invaluable insights

Found in low-nutrient soil, carnivorous plants have evolved to gather nutrients from elsewhere.

The plants use biological traps such as pitfall traps, snap traps and flypaper traps to snare animals before digesting nutrients from the prey.

For example, the Venus flytrap snaps shut around insects with one of the quickest movements in the plant kingdom, while pitcher plants have slippery edges causing prey to fall to their deaths into a pitcher of digestive fluid.

According to the study, the discovery of the plants' blue fluorescence in UV light conditions provides "a new understanding to prey capture in carnivorous plants and also [of] plant-animal interactions."

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