Why Leaves Change Colour in Autumn
Leaves change colour in autumn because trees stop making chlorophyll, the green pigment that lets leaves use sunlight to make food. Chlorophyll is so strong that it masks other pigments inside the leaf all year, so the leaf simply looks green. As autumn brings shorter days and colder air, the tree senses winter is near and prepares to rest, shutting down food production in its leaves.
With less chlorophyll being made, the green slowly fades and the pigments that were hidden underneath finally show through — yellow and orange (carotenoids), and sometimes red. The leaf isn't gaining new colour; it is losing the green that covered the existing colours. Learners grasp the ideas of pigments, chlorophyll's link to sunlight and food, and how shorter days act as the tree's signal.
This also explains why Singapore's trees stay green: the weather is warm and the day length barely changes, so local trees never get the seasonal cue to slow down and reveal their hidden colours.
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A magic colour show🍂 Nature Mystery Why do leaves change colour in autumn? In some countries, trees turn from green to yellow, orange and red before winter. It looks like magic! 🌳 ➡️ 🍁 Green tree today… colourful tree in autumn! But it isn't really magic — it's science. Let's find out the secret hiding inside every leaf. Tap Next to begin! 👉
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The green food-makerLeaves are green because of a busy worker Inside every leaf there is a green colour called chlorophyll (say: KLOR-oh-fill). Chlorophyll uses sunlight to make food for the tree. That's its job all spring and summer — and it makes the leaf look green. 💡 No chlorophyll = no green. Remember that — it's the key to the whole mystery!
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Hidden rainbow insideSecret colours hide behind the green Here's the surprise: yellow and orange colours are already inside the leaf all year! The strong green just covers them up. 👉 Tap each colour to discover the worker hiding inside the leaf. 🟢 Chlorophyll Green. Makes food from sunlight. So strong it hides the others! 🟡 Xanthophyll Yellow. Already there all summer, just hidden. 🟠 Carotene Orange. The same colour found in carrots! Tap all three colours to reveal their secrets…
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Autumn gives a signalAutumn sends a message: "Time to rest!" In autumn, the days get shorter and the air gets colder. The tree senses this and gets ready to rest for winter. Drag the slider from summer to autumn and watch the day get shorter. ☀️🌙 Long summer day ☀️ ☀️ Summer🍂 Autumn Less sunlight is the tree's signal to stop making food.
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The green fades awayThe green fades, and the colours appear! With shorter days, the tree stops making chlorophyll. The green slowly fades — and now we can finally see the yellow and orange that were hiding all along! 🟢 Lots of green🍁 Green gone Slide all the way to the right to drain the green!
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You be the scientistQuick brain check 🧠 A leaf turns yellow in autumn. Why? Someone painted it yellow with a brush. 🖌️ The green chlorophyll faded, so the hidden yellow shows. 🟡 The leaf got dirty and turned yellow. 🟫 Pick the answer you think is right — you can try again!
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Why not in Singapore?So why don't leaves change in Singapore? 🇸🇬 Great question! Singapore is warm and sunny all year. The days stay about the same length, so trees never get the "time to rest" signal. Tap each tree to see what it does. 🌴 Singapore tree Warm all year → stays green and keeps its leaves! 🍁 Autumn-country tree Cold winter coming → turns colour, then drops its leaves to rest. Tap both trees to compare them. 🌿 Fun fact: Trees that lose their leaves are called deciduous. Trees that stay green, like in Singapore, are evergreen.
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You solved it!🎉🍁🎉 You solved the autumn mystery! Here's the whole story in 4 steps: 1️⃣ Leaves look green because of chlorophyll, which makes food from sunlight. 2️⃣ Yellow and orange colours hide inside the leaf all along. 3️⃣ In autumn, shorter, colder days tell the tree to rest. 4️⃣ The green fades — so the hidden colours finally show! 🍂 And in warm Singapore, trees stay evergreen all year. 🌴 Well done, young scientist — you really understand nature now! 🌟
Frequently asked questions
- Why do leaves turn yellow, orange or red in autumn?
- The tree stops making chlorophyll, the green pigment, so the green fades. Yellow and orange pigments that were hidden under the green become visible, and some trees also make red pigment.
- Are the yellow and orange colours new, or were they always there?
- They were there all along. Yellow and orange pigments stay inside the leaf throughout the year, but the strong green chlorophyll covers them until autumn.
- What is chlorophyll and what does it do?
- Chlorophyll is the green pigment in leaves. It captures sunlight so the leaf can make food for the tree, a process called photosynthesis.
- Why don't leaves change colour in Singapore?
- Singapore is warm and sunny all year and the days stay about the same length. Without colder weather and shorter days, trees never get the signal to stop making chlorophyll, so the leaves stay green.
- What makes the tree know it is time for the leaves to change?
- Shorter days and colder air in autumn act as a signal. The tree senses these changes and gets ready to rest for winter, slowing down food-making in its leaves.
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