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Name: GEORGE
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Question:
WHY DO LEAVES CHANGE COLOUR IN THE AUTUMN?(FALL),AND WHAT DO THE COLOURS COMPRISE OF IF NOT CHLORPHYL?



Replies:
Dear George,

http://willow.ncfes.umn.edu/leaves/leaves.htm
http://www.esf.edu/pubprog/brochure/leaves/leaves.htm
http://photoscience.la.asu.edu/photosyn/education/colorchange.html

Sincerely,

Anthony R. Brach


George,

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 prominent.

Thanks for using NEWTON!

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.

Van Hoeck


A brief outline is at
http://www.flash.net/~johnrtnc/fall.htm

J. Elliott



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