十万个为什么·科学阅读30篇（3）
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Why Do Leaves Change Color in Fall?
秋天树叶为什么会变色？
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In spring and summer, leaves are green.
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They contain a green pigment called chlorophyll.
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Chlorophyll helps plants make food from sunlight.
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When days get shorter in fall, trees stop making it.
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Other colors like yellow and orange were always there.
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They just could not be seen before.
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Red color comes from sugar trapped in leaves.
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Then the leaves fall off to save water.