get their green color from chlorophyll, but they also contain other
pigments whose colors are masked during the growing season:
carotenoids (yellow) and anthocyanins (orange and red). Why the fall
emergence of these other pigments?
autumn, trees break down their chlorophyll and draw some of the
components back into their tissues. Conventional wisdom regards
autumn colors as the product of the remaining pigments, which were
finally unmasked. In other words, autumn leaves were a treeís gray
in recent years, scientists have recognized that autumn colors
probably play an important role in the life of many trees. [...]
Trees need energy to make carotenoids and anthocyanins, but they can
not reclaim that energy because the pigments stay in a leaf when it
dies. If the pigments did not help the tree to survive, they would
be a waste. Whatís more, leaves actually start producing a lot of
new anthocyanin when autumn arrives.
scientists do agree on one thing: the colors are for something. That
represents a major shift in thinking.
Zimmer: Those brilliant fall outfits may be saving trees, The
New York Times, Oct. 19, 2004.