Biofluorescence - Carnivorous Plants' Secret Lure Revealed
Carnivorous plants, with their captivating methods of attracting insect prey, have long fascinated scientists. Beyond the known tactics of tempting nectar, scents and vibrant colours, a 2015 discovery by researchers at the Jawaharlal Nehru Tropical Botanic Garden and Research Institute in India shed light on a possible previously concealed means of beckoning. Some carnivorous plants, it turns out, may be employing biofluorescence, invisible to the human eye, to lure unsuspecting insects to their demise.
A hidden blue ring
While conducting unrelated experiments, a team led by botanist Sabulal Baby placed various carnivorous plants, including the rare Nepenthes khasiana pitcher plant native to India, under ultraviolet light. To their astonishment, the team observed a distinct blue ring on the pitcher rim, revealing UV-induced blue emissions. Then they looked at other Nepenthes species and the prey traps of other carnivorous plants, including the Venus flytrap, and consistently found UV-induced blue emissions. These colours were found in a total of twenty carnivorous plant species and documented in a study published in Plant Biology.
A lure of light
Whilst on an expedition to document Biofluorescence in Malaysia we came across a number of species of Biofluorescent pitcher plants. We saw how the intensity of the blue fluorescence changes with the age and health of each pitcher. Just like how a flower has it’s brightest most intense fluorescence when it is at it’s prime and has the highest concentration of nectar/pollen, each pitcher gives off their most intense blue light when they are at their prime and ready to catch insects. The intensity of the fluorescence slowly fades with the age of the pitcher, until it is no longer visible in old/dead pitchers.
From Insects to Mammals
Bioluorescence might serve additional purposes for pitcher plants beyond just luring insects in. Field studies in Borneo suggested a potential symbiotic relationship between certain pitcher plant species and small nocturnal mammals. These mammals, including rats, bats, and tree shrews are lured to pitcher plants by the promise of sweet nectar and in return provide the plants with nutrition in the form of faeces. Is it possible that these mammals may also be lured to pitcher plants by their biofluorescent emissions?
Unveiling the Invisible Signals
This revelation prompts further exploration into the hidden signals within the plant kingdom. Similar to the discovery of bumblebees detecting electric fields produced by flowers, there may be numerous undisclosed forms of signaling waiting to be uncovered. Sabulal Baby emphasizes the possibility of diverse communication methods, stating, “There could be many other forms of signaling out there, waiting to be found.”
Critics of this study point out one major flaw in the work – The way the researchers used acetate to block out the fluorescent signals. There are a myriad of ways that the acetate may have repelled the insects, aside from covering up the fluorescence. It is quite a mistake and one which leaves the question of whether the fluorescence is a functional lure or not right up in the air again. It would be fantastic for further studies to take place to investigate further and try to discover once and for all if the fluorescence is attracting prey in or not.
Want to learn more about Biofluorescence? Check out this article exploring biofluroescence in Mushrooms.
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