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As fall colors emerge, here’s something fun to learn about plant pigments.

Updated: Oct 1, 2023

I was in Steamboat this weekend, enjoying the beginning of our Colorado fall colors, and thinking about plant pigments! You might already know that the colors we see in autumn are from pigments that are always in the leaves (e.g. carotenoids and anthocyanins) but are swamped by green chlorophyll during the growing season. As the season ends, the chlorophyll breaks down, and the other pigments are unmasked. But there’s a whole other story about some of the carotenoid pigments that is critical to understanding photosynthesis in an increasingly stressful environment. The lab of William Adams and Barbara Demmig-Adams in CU’s Ecology & Evolutionary Biology Department plays a central role in telling this story, and it’s where I did my doctoral work.

Geek alert, but I enjoyed studying and thinking about this, so here’s some detail for those still with me. Exposure to high light can damage plants’ photosynthetic machinery, but hundreds of millions of years of evolution under the sun have given plants a defense system to mitigate this. Under low light levels, plants have an abundance of the carotenoid pigment, violaxanthin. When light levels increase, threatening damage to photosynthetic machinery, violaxanthin is converted to a different pigment, zeaxanthin. Zeaxanthin can actually dissipate excess light energy, preventing damage to the plant. When light levels decrease, zeaxanthin is converted back to violaxanthin. This pigment cycling (called the “xanthophyll cycle”) provides plants with a mechanism to regulate photosynthetic productivity in a variety of environments. When a plant is already undergoing other stresses (e.g. drought, high temperatures, etc.), this mechanism is especially important.

There’s plenty of work going on to understand more about photoprotection and regulation of photosynthesis as Earth temperatures rise, as the need for efficient food production increases, etc. There will be a need for policy makers who can think critically about the myriad aspects of our climate change story, and bringing a scientist’s perspective to the Colorado Capitol is one of the many reasons I’m running for House District 10.

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