十万个为什么·科学启蒙30篇（1）

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植物如何自己制造食物？

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