Plants make food with sunlight — Chemistry, 4–6 years
Green leaves use sunlight, water and carbon dioxide from the air to make sugar for the plant. Oxygen is released as part of this process, which helps animals and people breathe.
Leaves are tiny food-makers
A green plant does not get all its food from the soil. Its leaves use sunlight to join water from the roots with carbon dioxide from the air and make sugar. The green colour comes from chlorophyll, which helps capture the light.
Why a plant needs leaves
A plant needs energy to grow new roots, stems, leaves, flowers and seeds. It cannot walk to find a meal, so it makes sugar where light reaches it. People discovered this by comparing plants kept in light with plants kept in darkness and watching how they grew.
A bean in two places
Put two similar bean plants in separate places and give both the same water. Leave one near a bright window and the other in a safe, dim place. After a week, the bright plant may have greener, stronger leaves, because its leaves received light to make more sugar.
The reasonable mistake
It is easy to think plants eat soil because roots grow in it, or that leaves are only for decoration. Soil supplies water and minerals, but most of the plant’s dry food is made in green leaves. A leaf is a working part, even when it looks quiet.
Why plants matter to us
The sugars made by plants help feed the plant and the animals that eat plants. Crops such as wheat, apples and beans all depend on leaves making food. Plants also release oxygen, so gardens, forests and crops help keep the air suitable for breathing.
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