While researching the pigments that create flower colors, scientists accidentally discovered a natural compound that produces a mystical green fluorescence on the petals of the Mirabilis jalapa, commonly known as the four o’clock flower.
This type of luminescence can be recognized by bees, bats, and other nocturnal pollinators, which have particularly sensitive eyes to green light. This marks the first time science has identified a plant species capable of using fluorescence to attract pollinators.
“Fluorescence may be an important signal in mate selection for the Australian long-tailed parrot and the mantis shrimp, and potentially for flowers attracting pollinating animals,” noted Fernando Gandía-Herrero and his colleagues at the University of Murcia in Spain.
Gandía-Herrero and his team extracted color pigments from the petals of the Mirabilis jalapa and found that when a pigment called betaxanthin is activated by blue light in sunlight, it emits green fluorescent light, contributing to the yellow color of certain petals.
However, on other petals, the green fluorescence is entirely absorbed by another pigment—betacyanin, which is purple—before it can be released. As a result, they create a self-filtering light system that controls the intensity and position of the green fluorescence escaping from the petals, thereby regulating the amount of green light visible to pollinating animals.
“The self-filtering effect between the two types of pigments causes a reduction in visible fluorescence in areas of the flower where both pigments are present,” the research team reported. Petals containing only betaxanthin will appear yellow under white daylight, due to the combination of green fluorescence and reflected white light.
Unfortunately for flower enthusiasts, the green fluorescent light can only be seen with special devices designed to detect this type of light.
The next step for researchers is to clarify whether the fluorescence actually makes the flower appear brighter or more attractive to pollinators. Furthermore, they need to investigate whether the luminescent form seen in four o’clock flowers originated from their ancient ancestors. This will shed light on the evolutionary advantages of this feature.
T. An
