十万个为什么·科学启蒙30篇（1）
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How Do Plants Make Their Own Food?
植物如何自己制造食物？
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Plants don’t eat food like animals do—they create glucose using sunlight, water, and carbon dioxide.
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This process, called photosynthesis, happens mainly in leaf cells that contain a green pigment named chlorophyll.
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Chlorophyll absorbs mostly blue and red light while reflecting green, which is why leaves appear green.
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Inside tiny structures called chloroplasts, light energy splits water molecules into oxygen and hydrogen.
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The plant then combines that hydrogen with carbon dioxide from the air to build glucose molecules.
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Oxygen is released as a byproduct, and it’s the main source of breathable air for all land animals.
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On cloudy days, photosynthesis slows down because less light energy is available to drive the reactions.
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Some desert plants open their stomata only at night to save water, performing a modified version of photosynthesis.
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If you place a potted plant in total darkness for several days, its leaves will gradually lose color and energy.
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Interestingly, algae and cyanobacteria perform photosynthesis too—and they produce over half the world’s oxygen.