Flowers Are Changing Colour To Save Pollen From Global Warming, Ozone Depletion

Just like the animal kingdom, plants adapt to the changing climate of the Earth. A new research shows the latest way in which they do so - by altering ultraviolet (UV) pigments in their petals. This means that the plants are essentially changing their colours in response to the climate change.

(Representative Image: Reuters)

The study, now published in journal Current Biology, examined a total of 1238 flowers from 42 different species, dating back to 1941. These species were collected from across North America, Europe, and Australia.

The researchers found that over the past 75 years, flowers have evolved to alter the ultraviolet (UV) pigments in their petals in response to the rising temperatures as well as the declining ozone layer of the Earth.

¡°Flowers¡¯ UV pigments are invisible to the human eye, but they attract pollinators and serve as a kind of sunscreen for plants,¡± explained Matthew Koski as per a ScienceMag report, a plant ecologist at Clemson University and the lead author of the study.

Just as UV radiation is harmful to humans, it also poses a threat to a flower¡¯s pollen. Thus, plants tend to use UV-absorbing pigment in the petals to reduce the harmful radiation from reaching its sensitive cells.

Koski and colleagues found this effect of UV radiation and temperature on flowers in their previous studies. They found that the flowers growing at higher elevations or closer to the equator with more exposure to UV rays had more UV pigment in their petals.

They then wondered if the plants reacted to human-induced changes in the Earth¡¯s environment in a similar manner. These changes were mainly the depletion in ozone layer and the global warming effect.

Flowers colour change phenomenon

To find the answers to this, Koski and colleagues used a UV-sensitive camera which captures the UV pigment levels. The team photographed flower petals from the same species collected at different times using the camera.

The observations through these images were then mapped to the data on the local ozone level and temperature.

The scientists found that the pigment in flowers increased at an average of 2% per year from 1941 to 2017 at all locations. These changes, however, were found to be different across different species.

Representative Image

In plants with exposed pollen, like buttercups, UV pigment increased when ozone levels went down and decreased in areas where ozone levels increased. In plants where the pollens were concealed within their flower petals, UV pigment was found to decrease as temperatures went up. Such plants did not respond to changes in ozone levels.

This is because pollens hidden within petals have to endure extra, trapped heat. Higher temperatures thus leave them vulnerable. Reducing UV pigments in the petals makes these flowers absorb less solar radiation, thus bringing down temperatures.

Scientists involved with the study warn that even though these changes in the pigment cannot be experienced by humans, they can have a major impact on pollinators like bees and hummingbirds, negatively affecting the plant in the wake.