Why Do Leaves Change Colour in Autumn ?
Tree use their leaves make food. The leaves contain chlorophyll, a green pigment which together with light from the Sun, carbon dioxide and water results in glucose. Leaves normally contain red, orange and yellow pigments but these are normally masked by the green chlorophyll. The colours are the result of anthocyanins giving pink, red and purple colours and carotenoids giving yellow and orange colours.The tree uses the leaf as a way of getting rid of waste products in Winter. In Autumn the trees stop producing sap, and photosynthesis can no longer take place so the green chlorophyll breaks down and disappears. The other colours are then apparent. By putting waste products in the leaves, as the leaves fall the tree conveniently gets rid of it's rubbish.