The Season of The Carotenoids
Why do the leafs on trees become yellow, orange and red in the autumn? Well, the answer is, they have these colours in the spring and summer as well. But then it is not visible because of the strong green colour reflected by chlorophyll. The colours we see are actually the colours that the tree doesn’t use in the production of sugar through photosynthesis. These colours are reflected and the light that is actually used in the photosynthesis is absorbed.
The red, orange and yellow colours we see in the leafs in the autumn is the reflection of light from carotenoids. These substances are cheap for the trees to produce, and the trees can afford to shed these. The chlorophyll on the other hand is a very precious and valuable molecule for the trees, so these are transported to the roots in the autumn leaving the carotenoids to “light up the forests in the beautiful, warm colours. Next spring the trees formes new leafs and pumps chlorophyll back into the freshly formed leafs.
Common Aspen - Populus tremula (local dialect: Osp) - has stored it's chlorophyll for the winter. This photo was shot today.
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Northern Blog-O-Sphere 
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