I read somewhere that botanists still don't know why trees change their colours in the fall. It gives them no advantage to do so and, in fact, it tires them out before the long winter.
I'm very grateful for their sheer exuberance.
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During winter, there is not enough light or water for photosynthesis. The trees will rest, and live off the food they stored during the summer.
ReplyDeleteAs summer ends and autumn comes, the days get shorter and shorter, meaning fewer and fewer daylight hours. This is how the trees "know" to begin getting ready for winter.
In the fall, they begin to shut down their food-making factories. The green chlorophyll disappears from the leaves. As the bright green fades away, we begin to see yellow and orange colours. These colours have been in the leaves all along. We just can't see them in the summer, because they are covered up by the green chlorophyll. Some forest researchers say that the amount of these colours in the leaves depends upon the minerals in the soil surrounding the tree, and the amount of these minerals that have been drawn up into the leaves during the summer.
The bright reds and purples we see in leaves are made mostly in the fall. In some trees, like maples, glucose is trapped in the leaves after photosynthesis stops. Sunlight and the cool nights of autumn cause the leaves turn this glucose into a red color. The brown color of trees like oaks is made from wastes left in the leaves.
It is the combination of all these things that make the beautiful colours we enjoy in the fall. I hope I haven't destroyed the magic for you!!
(Brought to you through a $40,000 forestry technician diploma and a quick search on the internet.)
Glad to see all that education being put to good use!
ReplyDeleteThe magic's still there. I like the thought that the colours are there right through the summer, just waiting for their chance to shine.
Thanks for the lesson!