Evolutionary biologists have long pondered the phenomenon of the changing colours of autumn leaves. It's possible that the red pigments are manufactured in the leaf as a side-effect of something else that's happening at this time.
While both plants and animals awaken via distinct changes in metabolic functioning, most plants prefer to err on the side of caution, waiting for hints of full-on summer before they bloom.
Light helps the body predict the future: it's a sign of how our environment will change in the coming hours and days, and our bodies prepare themselves accordingly.
Life evolved under conditions of light and darkness, light and then darkness. And so plants and animals developed their own internal clocks so that they would be ready for these changes in light. These are chemical clocks, and they're found in every known being that has two or more cells and in some that only have one cell.
A functional biological clock has three components: input from the outside world to set the clock, the timekeeping mechanism itself, and genetic machinery that allows the clock to regulate expression of a variety of genes.
Cryptochrome harnesses the energy of incoming blue light, but other molecules are probably needed to absorb light of other colors.
It was always intriguing that flies had two peaks of activity, in the morning and evening, with a siesta during the day and not very much activity at night. There are several ways to explain that, but one possibility was that there were two clocks running - one governing the morning peak and one governing the evening peak.
I knew, of course, that trees and plants had roots, stems, bark, branches and foliage that reached up toward the light. But I was coming to realize that the real magician was light itself.
Spring, when the earth tilts closer to the sun, runs a strict timetable of flowers.
