Chemical Shifts in Leaves Explain the Vivid Reds, Oranges, & Yellows of Autumn
As summer slips away and autumn settles in, green foliage shifts into vibrant reds, oranges, and yellows. With autumn comes shorter days and colder weather, which turn leaves into the warm-colored staples of the fall season.
During spring and summer, leaves are rich in a pigment called chlorophyll (1). During photosynthesis, chlorophyll absorbs sunlight, which is then converted into sugars that act as energy to fuel the plant. As days get shorter and temperatures drop, there is less sunlight for chlorophyll to absorb. This causes a decline in the production of chlorophyll and results in the leaves fading from green to yellow and orange (2). The pigments of yellow and orange are called carotenoids, which are present all year round in leaves but only dominate when chlorophyll degrades (3). The color of leaves varies from tree to tree depending on the amount of leftover chlorophyll (4). In sugar maple trees, they first turn yellow and shift to a vivid orange color (3). Other trees like dogwoods and sumacs have a more red and purple color, while oak trees’ leaves are mainly brown (2).
Anthocyanin is a pigment in plants that is created prominently during the fall season. Leftover sugars in the leaves trigger anthocyanin production, creating the bright red, burgundy, and even deep purple colors seen in the leaves (5). As chlorophyll fades and other pigments emerge, the changes in the color of autumnal foliage signal a new season. The vibrant display of colors in trees makes cozy autumn an even more magical time of year!
Autumnal Foliage
Sources
- The. (1998, July 20). Chlorophyll | Definition, Function, & Facts. Encyclopedia Britannica. https://www.britannica.com/science/chlorophyll
- Why Do Leaves Change Color in the Fall? (2021, September 21). Si.edu. https://www.si.edu/stories/why-do-leaves-change-color-fall
- oakesrl1. (2010, October 29). On the Hidden Colors in Leaves: What are the Functions of Those Yellow and Orange Pigments We See in the Fall? On the Hidden Colors in Leaves: What Are the Functions of Those Yellow and Orange Pigments We See in the Fall? https://biology.appstate.edu/fall-colors/hidden-colors-leaves-what-are-functions-those-yellow-and-orange-pigments-we-see-fall
- Why Leaves Change Color. (2024, May 8). Esf.edu. https://www.esf.edu/eis/eis-leaves-color-change.php
- “Why Leaves Turn Red”—and Cranberries, Too? (2021, September 21). Wisc.edu. https://fruit.wisc.edu/2021/09/21/why-leaves-turn-red-and-cranberries-too/
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