A sign of Autumn is when leaves on some trees start to change colour. The green colour starts to fade to be replaced by red, orange or yellow, do you know why this is?
Plants make energy by a process called photosynthesis. They convert carbon dioxide from the air, water and sunlight into energy and oxygen. A chemical pigment called chlorophyll absorbs the sunlight for photosynthesis and also gives the leaves their green colour, there is so much chlorophyll in the leaf that is masks the other colours, such as Carotene which is yellow.
In Autumn, when the temperature starts to drop the tree severs the connection with the leaves and the chlorophyll breaks down, revealing the other colours in the leaves. Eventually the leaves fall to the ground. We call these trees Deciduous.
Why do some trees stay green?
Some trees stay green all year round, we call these Evergreen. These trees keep their leaves all winter and so still need the chlorophyll to make energy. You’ll notice that the leaves on Evergreen trees are usually smaller and often have a waxy layer which helps prevent water loss in the winter, they also produce a chemical which stops them freezing! How clever is that.
- Can you go out and collect some colourful Autumn leaves?
- What could you make with them?
How about making your own Autumn tree?
Or, how about making a leaf crown like Red Ted Art?