The science of autumnal beauty

This gorgeous photograph of a tree-lined avenue in Nottinghamshire, England, demonstrates a basic principle of chemistry.

Photo by Carl Mick.

Leaf cells contain a combination of chemicals which produce different colors: Chlorophyll, which creates the familiar green in leaves; carotenoids, which create yellow, orange and brown (you see them a lot in corn and carrots); and anthocyanins, which create reds (you see them in cranberries and strawberries). So why do the leaves of many trees go from green to other colors in autumn?

According to the US Forestry Service:

Both chlorophyll and carotenoids are present in the chloroplasts of leaf cells throughout the growing season. Most anthocyanins are produced in the autumn, in response to bright light and excess plant sugars within leaf cells.

During the growing season, chlorophyll is continually being produced and broken down and leaves appear green. As night length increases in the autumn, chlorophyll production slows down and then stops and eventually all the chlorophyll is destroyed. The carotenoids and anthocyanins that are present in the leaf are then unmasked and show their colors.

Depending on the type of tree and the weather, these colors will be more or less intense.

via the US Forestry Service