Chemistry: Autumn Leaves (University of Wisconsin-Madison)

"Every autumn across the Northern Hemisphere, diminishing daylight hours and falling temperatures induce trees to prepare for winter. In these preparations, they shed billions of tons of leaves. In certain regions....the shedding of leaves is preceded by a spectacular color show. Formerly green leaves turn to brilliant shades of yellow, orange, and red." -- from the website. <http://scifun.chem.wisc.edu/>