Leaves are nature’s food factories.



Why do they change colour?

Autumn LeavesLeaves are nature’s food factories.

Plants take water from the ground through their roots.  They also take in a gas called carbon dioxide from the air.  The plants use sunlight to turn this water and the gas into glucose. Glucose is a kind of sugar.   

Plants use the sugar as food for energy and to grow. The way the plants turn the water and gas into sugar is called photosynthesis.

A chemical gives the plants their green colour. This chemical is called chlorophyll.

When summer ends and autumn comes, the days get shorter and shorter. This is how the trees ‘know’ that they must begin to get ready for winter.

During winter, there is not enough light or water for the trees to make food through photosynthesis.  The trees rest and live off the food they stored during the summer. They shut down their food making factories and the green colour - the chemical chlorophyll, disappears from the leaves. Why does the green colour disappear?

As the bright green fades away, we see yellow and orange colours.  Small amounts of these colours have been in the leaves all along. We just can’t see them in the summer, because they are covered up by the green colour.  Some leaves are red. This colour is made by food trapped in the leaves.  Brown colours are also made in the autumn. They come from wastes left in the leaves.

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