OBS: The science of fall leaves

Last night, a piece of science journalism put me to sleep.

At about 11 oclock last night, Robert Krulwich, NPR science correspondent, delivered a delightful story about fall leaves from my iphone--propped up on the pillow next to me. I could vividly imagine his browning leaves at the end of their productive lives, cutting off contact with their parent trees: capping their stems with so-called 'abscission cells' and then, finally, fluttering off in the wind.

According to the piece, leaves don't just break off haphazardly, the choice is made by hormones in the tree itself which signal the abscission cells to do their scissor-work. Shorter fall days--famous for a less daylight--trigger the hormones and therefore the abscission process. Evidently, there is not enough light during the day to make it worth the energy it takes to make glucose in the leaves.

Fascinating. One of the beauties of science is you often find intention where accident used to be. Maybe that's comforting at the end of a hard day.