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🌳 How Plants Build Themselves from Air and Water

Uncover the surprising truth that a plant builds most of its body not from soil, but from an invisible gas in the air.

lessons

~15 min

to learn

🔬 Science

subject

Ages 6–12

level

Start the course →

What you’ll learn

The Willow Tree MysteryMeet van Helmont's willow experiment and see the clue that a plant does not build itself from soil.People once believed plants grew by eating the soil. Long ago, Jan van Helmont grew a willow tree in a pot, giving it only water for five years. The tree grew heavy, yet the soil barely lost any weight. This surprising result was the first clue that a plant's mass does not come from the soil.
Air Into WoodUnderstand that most of a plant's mass comes from carbon dioxide in the air plus water, not from soil.Most of a plant's body is built from carbon dioxide, an invisible gas in the air. Leaves take in this gas and use sunlight to pull out the carbon, which joins with water to form wood, stems, and leaves. Only a tiny part of a plant's mass comes from minerals in the soil, so a plant really does build itself from air and water.
Inside a LeafIdentify how roots take up water, leaves take in carbon dioxide through stomata, and chloroplasts build glucose.Every part of a plant has a job. The roots soak up water and minerals from the soil, the stem carries water upward, and the leaves take in carbon dioxide through tiny pores called stomata. Inside the leaves, chloroplasts use light energy to build glucose, letting the plant grow bigger from carbon and water.

Questions this course answers

In van Helmont's experiment, what happened to the weight of the soil after five years?

The willow grew much heavier, but the soil barely changed weight, showing the tree did not build itself from soil.

What did people used to wrongly believe made plants grow bigger?

People once thought a plant simply ate the soil to grow, but experiments showed this is not where its mass comes from.

Where does most of a plant's mass actually come from?

Most of a plant's body is built from the carbon in carbon dioxide gas that leaves take from the air, joined with water.

Which two things join to build most of a plant's body?

The carbon from carbon dioxide in the air joins with water to make up most of a plant's body.

What are the tiny pores on a leaf that let gases in and out called?

Stomata are tiny pores, mostly on the underside of a leaf, where carbon dioxide goes in and oxygen comes out.

What is the main job of a plant's roots?

The roots anchor the plant and soak up water and a few minerals from the soil for the plant to use.

Grounded in trusted sources

BBC Bitesize
Britannica Kids
Royal Society of Biology

Every Wunder lesson is built from real, reputable sources — never invented.

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