Saturday, September 29, 2007

A Hint of Color

Driving down to the Lake of the Ozarks today, the fading greens of the September landscape were still dominant, broken only by the yellow of goldenrod, the light purple of asters, the orange-red of sumacs and the ubiquitous billboards along Missouri's highways. But there were also hints of autumn in the woodlands, where patches of olive and rust dappled the forest.

As the length of daylight wanes, chlorophyll production is shut down and the underlying leaf pigments begin to show through. While yellow pigments are present in most leaves, the reds, oranges and purples, which protect the chloroplasts from ultraviolet light, vary among plant species. Sunny conditions increase the production of these pigments and, combined with cool nights (which diminish pigment withdrawal), tend to yield the most striking autumn displays.

In central Missouri, fall colors generally peak during the third week of October. This year, since drought stress continues, the autumn show may develop early as trees discard their leaves to conserve water.