Every autumn we revel in the beauty of the fall colours. The mixture of red, purple, orange and yellow is the result of chemical processes that take place in the tree as the seasons change from summer to winter.
During the spring and summer the leaves have served as factories where most of the food necessary for the tree’s growth are manufactured.[ihc-hide-content ihc_mb_type=”show” ihc_mb_who=”2,3,5″ ihc_mb_template=”1″ ] This food-making process takes place in the leaf in numerous cells containing chlorophyll, which gives the leaf its green colour.
This extraordinary chemical absorbs from sunlight the energy that is used in transforming carbon dioxide and water to carbohydrates, such as sugars and starch.
Along with the green pigment are yellow to orange pigments, carotenes and xanthophyll pigments which, for example, give the orange colour to a carrot. Most of the year these colours are masked by great amounts of green colouring.
But in the autumn, because of changes in the length of daylight and changes in temperature, the leaves stop their food-making process. The chlorophyll breaks down, the green colour disappears, and the yellow to orange colours become visible and give the leaves part of their fall splendour.
At the same time, other chemical changes may occur, which form additional colours through the development of red anthocyanin pigments. Some mixtures give rise to the reddish and purplish fall colours of trees such as dogwoods and sumacs, while others give the sugar maple its brilliant orange.
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