Fall foliage offers stress re-leaf for Oklahomans

Fall foliage throughout Oklahoma Fall 2023. (THE VISTA/TROY ISBELL)

A steady drop in temperature accompanies the changing leaves this October. While many trees still remain green, the first signs of fall are beginning to show. Photographer Troy Isbell captured some of the seasonal sights around the state. 

Mother Nature creates a palette fit for a dinner table with hues of pumpkin, turmeric, and applesauce. The change comes as a result of the trees’ response to the decreasing hours of daylight. They produce less chlorophyll as the nights grow longer, eventually stopping completely. (This isn’t true for the evergreens, who keep their chlorophyll year-round.)  

As chlorophyll production hits the brakes, the other color compounds in the leaves reveal traditional autumnal hues. These compounds can include carotenoids (which humans have too!) and anthocyanin. Carotenoids are the “most widely distributed pigments in nature,” according to the National Institute of Health. In leaves, their resulting colors can range in shade from light yellow through red and dark purple. Beta-carotene is one example of a carotenoid present in the food we eat. Carrots and pumpkins would not be orange without these fat-soluble pigments.

“Light stress” is the name of the trigger of the process that begins to change the color of the carotenoid. It changes via a chemical reaction that actually changes the chemical itself. 

If someone eats enough carrots, their skin can retain a yellow-orange hue. Also according to the National Institute of Health, this occurs most commonly in children and is most prevalent in the soles of the feet and palms of the hands. One case found that a 48-year-old man complained to his doctors of discomfort and orange skin after he reported ingesting between six and seven pounds of carrots every week.

Since Oklahoma is in the Northern Hemisphere, we get less daylight from September to March. Andy Brunning, a chemistry advisor in Cambridge, explained more about the science behind why the leaves change. The production of anthocyanins, the red compound mentioned earlier, are triggered by an interaction between sunlight and increased sugar concentrations in the leaves. Brunning explains that carotenoids also degrade along with chlorophyll in the fall, but do so at a much slower rate, which explains why they stick around for longer. 

As pop-up pumpkin patches start selling out and birds fly south, many people flock to fall foliage roadtrips. Officially titled ‘leaf peeping’ is a popular hobby this time of year, with great spots including Martin Nature Park, the Myriad Gardens’ Pumpkinville display, and Fink Park in Edmond. Pumpkin-spice lattes and chais steal the spotlight at coffee shops across the country. As the leaves turn from green to gold and midterms turn into finals, evergreen season makes its way in. Observers can watch pumpkin patches turn to Christmas tree stands throughout the month of November.

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