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Why do leaves change color in the fall?
Why do leaves change color in the fall?📓 The short answerLeaves change color when chlorophyll (which we perceive as green) is replaced by other pigments, such as carotenoid and anthocyanin. 📚 The long answerIt’s hard to imagine autumn without colorful trees and crunchy piles of leaves. But why do leaves change color? To answer that question, let’s 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 it’s 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: "Кожура хурмы" 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, it’s a completely natural part of a leaf’s life. It’s actually a positive thing for nature as a whole! Rather than using up a tree’s 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. 📩 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.
📖 Book of the weekThe Elements of Style by William Strunk Jr. & E.B. WhiteI'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. 👀 Catch up on other curious questions
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💡 Today You Should Know
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.
Why do dogs tilt their heads when you talk to them? This question came from a reader submission (thanks Kim!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question 📓 The short answer Dogs probably tilt their heads when we talk to them for a mix of reasons: to hear you better, to see you better, to signal that they're paying attention, and to receive praise. 📚 The long answer For at least 15,000 years, dogs have lived alongside humans....
How does a thermos work? This question came from a reader submission (thanks Duncan!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question 📓 The short answer A thermos keeps hot drinks hot and cold drinks cold by blocking all three types of heat transfer: conduction, convection, and radiation. It does this with a vacuum between its double walls (which eliminates conduction and convection) and a silvered inner surface (which reflects...
Why do we feel the urge to squish cute things? 📓 The short answer Cute aggression is thought to be your brain's way of balancing out an emotional overload so you stay functional enough to actually care for the thing you're fawning over. 📚 The long answer Have you ever spotted a baby with those adorable chubby cheeks and felt the urge to…squish them? Well, you’re not alone. Source This phenomenon, known as “cute aggression,” is the paradoxical pairing of intense adoration with aggressive...