A glowing blue compound could help us understand the vibrant autumn leaves

Scientists are tracing what happens in plants when chlorophyll breaks down

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a person standing looking down at red, orange, yellow, and green leaves

Photo by Fallon Michael on Unsplash 

It’s this time of the year when those of us in northern temperate zones are spectators of a fascinating natural phenomenon – the appearance of autumn leaf colors.

The leaves start to change colors as they age, or senesce. During this period a cluster of enzymes in the leaves start chewing up their green pigment, called chlorophyll. As the leaves become less green, their red, yellow, and orange pigments (known as anthocyanins and carotenes) begin to shine. However, exactly how chlorophyll breakdown works is still only partially understood.

While autumn leaves are a great example of chlorophyll breakdown, evergreen plants (those that remain green all year long), vegetables, and fruits also experience chlorophyll decay. However, this happens only under special conditions such when fruit ripen or when evergreen plants are deprived of nutrients and water. 

Banana skin is one of the few fruits where chlorophyll degradation can be mapped under ultraviolet (UV) light. As bananas ripen, their skins lose their green color – a sign of chlorophyll breakdown – and form new pigments that fluoresce blue under the UV light. Scientists know that this new pigment, known as hypermodified fluorescent chlorophyll catabolite (hmFCC), is produced very briefly in most plants. Banana skins and grapevine leaves are known to produce hmFCCs for a longer period.

Recently scientists at Instituto de la Grasa, Spain analyzed devil’s ivy, an evergreen plant, in their quest to find signs of this fluorescent compound. They activated the aging process by starving the plant, and voila! Exposure to UV light produced the blue, fluorescent pigment hmFCC. The team also observed two other newly identified compounds that will provide more insights into the evergreen chlorophyll breakdown puzzle.

Although the actual benefit of producing this blue, fluorescent compound is still a mystery, scientists think that it could provide protection against radiation or function in communication between animals and plants.