Sunflowers' invisible colors help them attract bees and adapt to drought

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According to a new research from the University of British Columbia, the ultraviolet colors of the flowers of sunflowers help the plant regulate water loss.

The dense collection of yellow petals of a sunflower is a familiar sight, but it's hiding something from the human eye: an ultraviolet bullseye pattern.

The bullseye patterns have been shown to improve the attractiveness of flowers to pollinators. A new paper published today in eLife shows that the same molecule that produces UV patterns in sunflowers is also involved in helping the plant respond to stresses such as drought or extreme temperatures.

We were surprised to find that the flowers of the sunflowers growing in the drier climates are able to retain water more efficiently. Dr. Marco Todesco is a research associate at the biodiversity research center and department of botany at the University of British Columbia.

In the past two years, Dr. Todesco and his colleagues have grown almost 2,000 wild sunflowers. They measured the UV patterns of the sunflowers and found that some of them had UV bullseyes that were different sizes, while others had no UV bullseyes at all. bees visited bullseyes larger than before, supporting previous research.
Most of the diversity in floral UV patterns was caused by a single gene. Plants are known to survive under different environmental stresses, such as drought or extreme temperatures, because of the production of UV-absorbing flavonol compounds. Larger floral UV patterns that have more of these compounds could help reduce the amount of water that is lost in environments with lower humidity. In hot environments, smaller UV patterns would promote this evaporation, keeping the plant cool and avoiding overheating.

The senior author of the paper says that floral UV patterns regulate water loss from flowers and that they play a dual role in adaptation. "That's not something you would expect a flower color to do, and it exemplifies the complexity and efficiency of adaptation,solving two problems with a single trait."

The industry of sunflowers is estimated to be US$20 billion in 2020. Dr. Todesco says that this research could add to knowledge about how to attract pollinators. This work helps us understand how sunflowers, and other plants, can adapt to different climates and temperatures, which is important in a warming climate.

The researchers want to better understand how HaMYB111 regulates the size of UV bullseyes, as well as examine in more detail how those patterns affect plant physiology, as well as investigate how exactly flavonol compounds affect water loss.

Marco Todesco and his team have a genetic basis and dual adaptive role of floral pigmentation in sunflowers. There is a DOI: 10.556/eLife.

The journal has information on eLife.

The sun flowers' invisible colors help them attract bees and adapt to the weather.

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