writes
On Tue, 14 Nov 2006 17:20:42 +0100, "JennyC"
wrote:

It breaks down in sunlight........:
http://scifun.chem.wisc.edu/chemweek.../fallcolr.html

Thanks. That explains the Autumn colours well. What about evergreens,
why don't they lose chlorophyll?

Presumably because they continue to synthesise it all year round,
whereas deciduous trees stop replacing it prior to leaf drop. However
I've seen another reference which suggests that the breakdown of
chlorophyll is a result of reaction of the plant to the shorter days in
'sealing off' the leaf with a corky layer so that the normal circulation
no longer reaches it. This doesn't happen on a seasonal basis with
evergreens, and so they would retain their chlorophyll.

Evergreens do lose the green colour in leaves that they are about to
shed.
--
Kay