Plants
How does a green plant make its food?
The short answer
A green plant can use light to make sugar from water and carbon dioxide from the air. This is photosynthesis, which also produces oxygen. Roots supply water and minerals; the plant does not simply eat soil as a ready-made meal.
See how it works
Blue: water entering. Teal: oxygen leaving. Purple: carbon dioxide entering. Yellow: light energy. Orange: sugar. Minerals are also needed.
1. Take up water
Roots absorb water and dissolved minerals. Water travels to the leaves. Minerals are needed but do not replace sugar production.
2. Let air into leaves
Carbon dioxide from the air can enter leaves through tiny openings. This gas is used inside for making sugar.
3. Use light
Green leaf pigment helps absorb light energy. This energy allows sugar to be built from water and carbon dioxide. Light supplies energy, not an additional solid building material.
4. Build and respire
Sugar provides material for growth and energy supply. Photosynthesis produces oxygen that can be released. Plant cells also use oxygen to release usable energy from sugar. This is called cellular respiration.
An imagined Wusel scene
Puschel and Flauschi investigate
Puschel puts a bowl of soil beside the museum model plant like lunch. Flauschi points to leaf, light and water. He replaces his meal idea with the routes by which the plant gets its materials.
Word help
- Photosynthesis
- Using light to build energy-rich substances, here illustrated by green plants.
- Carbon dioxide
- A gas in the air that plants use in photosynthesis.
Your activity
Sort cards: water, carbon dioxide and light go into photosynthesis; sugar and oxygen are produced. Draw light as an energy input, not as a lump of soil. Cards are a model, not ingredients to mix.
Quiz: understand the idea
What is the job of light in photosynthesis?
Choose a), b) or c), then explain your choice.
- a)It supplies the building material instead of carbon dioxide.
- b)It replaces minerals from the roots.
- c)It supplies energy for building sugar.
Show the explanation
Correct: c): It supplies energy for building sugar.
Light provides energy. Water and carbon dioxide provide starting materials for the process.
Try a new example
Which statement about a green plant and oxygen is right?
Choose a), b) or c), then explain your choice.
- a)It releases oxygen but never needs any itself.
- b)It needs oxygen only when growing in a pot.
- c)It releases oxygen during photosynthesis and also uses oxygen itself.
Show the explanation
Correct: c): It releases oxygen during photosynthesis and also uses oxygen itself.
Plant cells use oxygen to release energy from sugar. This is cellular respiration. Photosynthesis is a different process.
Word help
- cell
- A tiny living unit. Living things are made of cells.
- oxygen
- A gas in air that our bodies take in through breathing and need for their work.
- carbon dioxide
- A gas produced, among other ways, by working body cells and breathed out.
- mineral
- A natural substance with a particular composition and ordered internal structure.
Explore in more detail
Here you will find longer explanations and further details. You can explore them together.
More to discover
Leaves are not little mouths
The green pigment is chlorophyll. It is found in tiny parts of many plant cells called chloroplasts, where steps of photosynthesis take place. Our diagram simplifies materials and energy; it does not draw every particle or reaction step.
Pictures and sources for adults
Sources
Museum scene: AI-generated illustration, checked separately from the factual diagram. The diagrams simplify the process. Editorial source check: 19 October 2026.