The Chemistry of Autumn Colours / Nature

Few people can fail to be moved by the splendour of trees cloaked in their autumn finery. This occurs in the temperate zones of the world when the arrival of cool weather transforms the landscape. At this time, broadleaved trees lose their leaves to conserve water throughout the winter months. The first signs of this come as the leaves change colour from predominantly green to a dazzling array of reds, oranges, yellows and even purples.

From early October it seems that woodlands and forests become ablaze with colour. But how and why does this happen?

Chlorophyll
The green colour of plants, present in stems and leaves, is due to chlorophyll, which is present in sub-cellular structures known as chloroplasts. Chlorophyll is essential for photosynthesis, which is the process by which plants use light energy from the sun to synthesise carbohydrates from carbon dioxide and water. The carbohydrates are essentially the plants food, or energy source required for growth, reproduction and all other life processes. During this process oxygen is given off as a by-product. The water is absorbed...

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