River in New Hampshire is flanked by color
© Gregory G. and Mary Beth Dimijian
do leaves turn red and yellow in the fall?
It is still largely a mystery, but one hint comes from anthocyanins, the most
widespread red pigments in plants. Anthocyanins also color fruits and flowers
red. In leaves they seem to serve as a "sunscreen," protecting chlorophyll
molecules from sunburn, their color masked by the green chlorophyll. When the
photosynthetic machinery is dismantled in the fall, their color becomes visible.
Anthocyanins may also be useful as antioxidants.
(D.W.Lee and K.S. Gould, Why Leaves Turn Red,
American Scientist 90:524-531, Nov.-Dec. 2002)