WHY DO LEAVES CHANGE COLOUR IN THE AUTUMN?(FALL),AND WHAT
DO THE COLOURS COMPRISE OF IF NOT CHLORPHYL?
Anthony R. Brach
What you see when leaves change color is the appearance of pigments which
are otherwise normally hidden by the presence of green chlorophyll. The
xanthopylls and cyan colors are pigments that are always present, but as
chlorophyll is broken down/resorbed by a plant, the hidden pigments become
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Richard R. Rupnik
In the fall with the diminishing daylight and cooler temperatures, deciduous
trees begin to shut down chlorophyll production. There are other colors in
the leaf besides the green of chlorophyll, such as carotenes (yellow/orange),
xanthophylls (yellow) and anthocyanins (reds). When the chlorophyll goes
away, the other colors that were there all along can show through.
Eventually, the leaf is sealed off from the tree and it turns brown and falls
off. In the spring, when the days get longer and the days warmer again, the
tree begins to produce chlorophyll again.
A brief outline is at
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Update: June 2012