You eat to get food. A tree never eats a thing, yet it grows huge. Where does its food come from?
Key idea
Plants make their own food in their leaves. They use sunlight for energy, water from their roots and carbon dioxide, a gas in the air. They make a sugar for food and give off oxygen. This is called photosynthesis.
| Part | Job |
|---|---|
| Roots | hold the plant and take in water and minerals |
| Stem | holds the plant up and carries water and food |
| Leaves | make food from sunlight, water and air |
| Flowers | make seeds |
Why it works
Most of a tree's wood is built from carbon dioxide taken out of the air and water from the ground. The soil gives only a few minerals. Scientists weighed soil before and after growing a tree in it and found the soil had lost almost nothing.
Worked example: In the dark
A plant is kept in a dark closet for two weeks with water. What happens?
- Without light, it cannot make food.
Answer: It turns pale and weak, and it may die.
Common mistake
Thinking plants get their food from the soil. Soil gives water and minerals, but the food is made in the leaves.
Try it at home
- Put a water plant from a fish store, or a leaf, into a clear glass of water in bright sunlight.
- After an hour or two, look for tiny bubbles on the leaves. That gas is oxygen the leaf gave off.
Going further. Plants Make Food (Young Learners) for younger brothers and sisters, and Photosynthesis in Life Science.