Since it's autumn and the trees they are 'a peaking,' I thought it might be interesting to share how the various colors come into being, something I just came upon quite recently. I used to think it was utterly dependent on the amount of rain and degree of frost and stuff like that. Well, that's not entirely the story.
Leaf color comes from pigments: the yellows and oranges are carotene; the green is chlorophyll, of course; and the red is anthocyanin.
When autumn arrives, the leaves produce little or no chlorophyll, which thus allows the stored carotene to come forward as an array of magnificent golds, oranges and yellows. (In Ireland, I went to primary school on the site of an ancient fort whose old moat was ringed with beech trees and I remember staring for ages into the bright gold canopy at this time of year.) The intensity of red produced in a given year is dependent on temperature and amount of cloud in the sky. Reds are at their most impressive when there's a period of warm, sunny days followed by cool nights because during the day the trees can still produce sap in which anthocyanin is synthesized; then during cool nights, the sap does not flow to the trees extremities and all the stored anthocyanin turns the leaves into hues of brilliant red, maroon and purple--think red maples and dogwoods on the east coast.
Rain does affect the intensity of color, however. If the Fall is warm and wet, such as we've been experiencing this year, the brightness of the turning leaves is affected adversely. I'm finding this year quite strange because many trees are still green and those that are turning are very disappointing. But I suppose it takes an off-year or two to make us truly appreciate those spectacular years when the show really blazes. And lastly, an early and severe frost simply causes the leaves to turn a horrid brown immediately.
Tonight we're supposed to get our first frost and it'll be very interesting to see if my turkey vultures change color, too. Just kidding. Dear reader, you do know I'm not that naive, right?!
[technorati: Ireland, Pennsylvania, Fall, fall colors]