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Why do leaves change color in the fall?
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​ 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 week​The Elements of Style​ by William Strunk Jr.​ & ​E.B. White​I'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.
Can you cook pasta without boiling water? This question came from a reader submission (thanks Marc!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question 📓 The short answer Yes, the key chemical reactions that cook pasta happen at around 180°F (82°C), below the boiling point of water (212°F (100°C)). But cooking pasta at this lower temperature will require you to cook for a longer time. 📚 The long answer On the package of your favorite...
Why does oversleeping make you tired? This question came from a reader submission (thanks Rodrigo!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question 📓 The short answer Oversleeping can make you feel more tired because it throws off your internal clock. You might wake up during a deep sleep stage, miss your body’s natural cortisol boost that helps you feel alert, and wake up dehydrated – all of which can cause you to feel tired. 📚 The...
Why do flies rub their legs together? 📓 The short answer Flies rub their legs together to clean off dust, dirt, moisture, and pollen that can interfere with their senses. Staying clean helps them fly, avoid infections, an taste with their feet. 📚 The long answer You've probably spotted a fly rubbing its little legs together and wondered what that's all about. The options run through your head (memes linked for illustrative effect): (A) Plotting world domination (B) Gearing up for a delicious...