Going out in a blaze of glory

Now, in September, autumn is in full swing, and, hopefully, it will be accompanied by nature's annual extravaganza of colour.Trees and shrubs are in the process of seeing out the old year; but many don't go quietly.

They transform from tired green to blazing red, vibrant orange, vivid yellow.

But why is it that some trees are more eye-catching than others? What makes them go from drab to dashing in the space of just a few weeks or even days?

It's all part of a giant vast recycling programme and it's intended to make sure that, come next spring, those trees which are now shedding their foliage, will once more be clothed in fresh leaves. Basically, the trees are recovering some of the nutrients stored in their leaves.

As the days shorten and the temperature falls, trees turn off the power to their foliage.Enzymes kick in to recycle the various proteins and carbohydrates, and the first sign of this is when the green pigment, chlorophyll, is removed and put into storage.

Once the green has gone, the leaves reveal other pigments such as carotenoids (there to protect the leaves from too much light) which show up as yellow.

The reds and purples in leaves are sugars which the tree will eventually store in its roots.

Cold nights and bright days intensify the show. And by the time a leaf falls, it's usually been sucked dry of all the good things the tree needs for future growth. But it's still not finished – it breaks down to provide valuable organic matter in the soil.

Man may think he does pretty well with recycling but he's not a patch on a tree.

YP MAG 11/9/10