Why Do Fall Leaves Change Colour?

That's the question that intrigued me recently, when Chitrakka sent me an album of fall colours in New England. In a strange moment of serendipity, just yesterday I saw a cartoon in the newspaper about a little boy asking his mum about whether she knew why leaves change colour in the fall. In the cartoon, the mom launches into a romantic explanation involving God, Nature and Beauty. The next frame shows the boy drily saying isnt it because there's less sunlight and the plants are producing less chlorophyll?!

There's so much beauty in fall colours that I just gawp at pictures, and have never found out why. (And if they did teach me in school, I've long since forgotten!) So, deciding to re-educate myself, I googled away.

National Geographic had this nice essay, where I was informed that the lower levels of light means lower levels of chlorophhyll and the caroteinoids (which were always there) begin to show themselves.

It got a bit more complicated as I read further - there is also anthocyanin produced in the cooler months (the flaming red colour-giver), though from what I read, its role is a bit of a mystery. Hmmm... Scientists are doing extensive research as to why some turn golden and some turn red. And both seem successful at keeping the tree alive!!

Well, couldn't it just be that the maple thinks red is cool and the aspen loves yellow?! I mean imagine if a Martian were trying to research why some human females chose pink dresses, others black and still others yellow, green and blue!! They will be kept busy for a long time!!

Update:

Kamini sent me these aboslutely gorgeous photos of fall colours in Westchester, USA this year.

See, some like it yellow, others red!

Lovely photos, Kamini, and thanks for sending them along!