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Why do leaves change color in the fall?
Why do leaves change color in the fall?๐ The short answerLeaves change color when chlorophyll (which we perceive as green) is replaced by other pigments, such as carotenoid and anthocyanin. ๐ The long answerItโs hard to imagine autumn without colorful trees and crunchy piles of leaves. But why do leaves change color? To answer that question, letโs start by understanding why spring leaves are green. The substance that makes leaves green is chlorophyll, a pigment that helps trees absorb sunlight and convert it into energy. This process is known as photosynthesis.
At the beginning of fall, the temperature drops and the nights get longer. This signals to trees that itโs almost winter and resources are becoming scarce. To conserve energy, trees stop producing chlorophyll, and the chlorophyll in their leaves begins to break down. When the chlorophyll is depleted, other pigments in the leaves take center stage. Carotenoid pigments appear as yellow or orange, while anthocyanin pigments appear as red or purple. Without chlorophyll to mask them, these pigments cause the leaves to appear yellow, orange, or red. Left: Close-up view of yellow carotenoid pigments from a persimmon rind. Right: Close-up view of purple anthocyanin pigments in an unidentified flower cell. Left: "ะะพะถััะฐ ั ััะผั" by Andrei Savitsky is licensed under CC BY 4.0. Right: "Microscopic view of unidentified flower cells with anthocyanins (4x magnification)" by Shkyrik is licensed under CC BY-SA 4.0. So why do leaves fall to the ground after they change color? Since chlorophyll produces the energy leaves need to stay alive, leaves slowly weaken without it. Throughout the fall season, they gradually separate from the tree until they fall to the ground. While this process might seem sad, itโs a completely natural part of a leafโs life. Itโs actually a positive thing for nature as a whole! Rather than using up a treeโs much-needed energy, fallen leaves are able to serve as food for animals or fertilizer for the soil. Losing leaves also helps the tree survive through the chilly winter so it can sprout new leaves the next year. ๐ฉ Subscribe to Madeline's newsletterIf you enjoyed today's post, I recommend you join Bluestocking, for more easy-to-understand breakdowns of science, history, and geography.
๐ Book of the weekโThe Elements of Styleโ by William Strunk Jr.โ & โE.B. WhiteโI've been trying to read more books on how to write better (for you, dear reader). This one is a must! I loved how this guide is concise and straight-to-the-point. There are plenty of examples to showcase okay writing vs. great writing, and I found myself noting down some key takeaways: "Omit needless words" will stay with me for life. โ ๐ Catch up on other curious questions
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Learn something new every Friday. Join 2,000+ nerds and satisfy your curiosity one question at a time with topics including science, technology, history, and more.
How do QR codes work? This question came from a reader submission (thanks Nathan!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question ๐ The short answer A QR code is a binary message your camera can read. The grid of black and white squares encodes data, while built-in structural markers tell the scanner how to orient the code, how it's formatted, and how to reconstruct any missing pieces. ๐ The long answer Back in the 1990s, Masahiro...
How do contact lenses work? This question came from a reader submission (thanks anonymous!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question ๐ The short answer Contact lenses correct refractive errors, like nearsightedness, farsightedness, and astigmatism, by using precisely shaped lenses to bend incoming light so it lands on the retina instead of in front of or behind it. ๐ The long answer As someone with a mild aversion to putting...
Why do nuthatch birds walk upside down? This question came from a reader submission (thanks Nancy!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question ๐ The short answer Nuthatches climb down trees headfirst to forage more efficiently. By approaching the bark from above, they can spot hidden food that upward-climbing birds may miss. ๐ The long answer Say hello to the nuthatch. ๐๐ "Sitta-carolinensis-001" by Mdf is licensed under CC...