Monday, October 6, 2008

Show of Color

During the growing season deciduous trees are continuously producing chlorophyll, which gives the green color to the leaves. As night length increases in the autumn, chlorophyll production slows down and then stops and eventually all the chlorophyll is destroyed. The carotenoids and anthocyanins that are present in the leaf are then unmasked and show their colors.

Tree and plant leaves contain pigments that give them their color. Three pigments are involved in fall color:

• Chlorophyll — gives leaves their green color.
• Carotenoids — provide the yellow, orange, and brown colors
• Anthocyanins — give the red and purple colors. In contrast to the other two pigments, anthocyanins are produced in the autumn, in response to bright light and excess plant sugars in the leaf cells

The amount of color that develops each autumn season are related to weather conditions that occur before and during the time the chlorophyll in the leaves is declining. Temperature and moisture are the main influences.

Soil moisture levels also have a significant impact in the autumn color display. Like the weather, soil moisture varies greatly from year to year. These highly variable combinations of factors assure that no two autumns can be exactly alike. A late spring, or a severe summer drought, can delay the onset of fall color by a few weeks. A warm period during fall will also lower the intensity of autumn colors.