Curious Kids: Why are leaves green?

This is an article from Curious Kids, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!

Why are leaves green? – Indigo, age 6, Elwood.

The leaves of most plants are green, because the leaves are full of chemicals that are green.

The most important of these chemicals is called “chlorophyll” and it allows plants to make food so they can grow using water, air and light from the sun.

This way that a plant makes food for itself is called “photosynthesis” and it is one of the most important processes taking place on the whole planet.

Without photosynthesis there would be no plants or people on Earth. Dinosaurs would not have been able to breathe and the air and oceans would be very different from those we have today. So the green chemical chlorophyll is really important.

All leaves contain chlorophyll, but sometimes not all of the leaf has chlorophyll in it. Some leaves have green and white or green and yellow stripes or spots. Only the green bits have chlorophyll and only those bits can make food by photosynthesis.

If you’re really good at noticing things, you might have seen plants and trees with red or purple leaves – and the leaves are that colour all year round, not just in autumn.

These leaves are still full of our important green chemical, chlorophyll, just like any other ordinary green leaf. However, they also have lots of other chemicals that are red or purple – so much of them that they no longer look green. But deep down inside the leaves the chlorophyll is still there and it’s still green.

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