Red leaves indicate glucose that has been trapped in the leaves.
Red leaves indicate glucose that has been trapped in the leaves. Terry West

Why autumn is so colourful

THE weather is starting to cool and if you live on the Granite Belt you will notice the trees have changed colour and some are now losing their leaves. Why does this happen? I will try to explain the processes behind this magnificent show put on by Mother Nature.

Leaves are the plant's food factories. As moisture is drawn from the ground by the roots, leaves draw carbon dioxide from the atmosphere. The leaves use a process called photosynthesis, which means "putting together with light". This process uses sunlight to convert the water and carbon dioxide into oxygen and glucose (sugars). Oxygen is important to us as we need it to survive and the plant needs the glucose to survive.

This shows how important plants and trees are to us and how we would not survive without them. The plant uses the glucose as its food and building blocks. A chemical called chlorophyll helps make photosynthesis happen. Chlorophyll is what gives plants their green colour.

As summer comes to an end, the days start to get shorter and we enter autumn. During autumn the leaves photosynthesis processes start to shut down and the tree starts to live off the food it has stored during summer. The leaves are no longer needed and start to change colour as the chlorophyll, which is green in colour, subsides. As the green colour fades away, other colours such as orange and yellow start to appear. These colours are in the leaves throughout summer but we can't see them because of the dominance of the green chlorophyll.

Other colours, such as the deep reds and purples are produced in autumn. In some trees, maples for example, some of the glucose stays trapped in the leaves. Because of the cooler nights of autumn and the lack of sunlight this glucose starts to change into a red colour. Other trees, like oaks, have a brown colour and this is produced by waste products trapped in the leaves.

Add all the leaf colours together and you end up with Mother Nature's palette - a magnificent array of colour for us to enjoy.



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