Question: why do leaves turn orange in the autumn?

Jess Wade answered on 19 Jun 2015:

Leaves grow on plants, which take water from the ground and take it through their roots. They use carbon dioxide in the air, and use carbon dioxide to turn water into oxygen and glucose. Oxygen is a gas in the air that we need to breathe. Glucose is a kind of sugar. Plants use glucose as food for energy and as a building block for growing. When summer ends and the days get shorter and there isn’t much sun, they know it is going to be winter. During winter they can’t do the chemical reactions that use light and water for energy, so they begin to sleep and rest. The chemicals that change the gases and water and light disappear from the leaves. As these chemicals disappear, yellow and orange colours form. It is basically sunlight and cool air that causes the glucose in plants to turn red!