Post by Deleted on Oct 1, 2014 21:25:49 GMT -5
Fall Foliage: Why Do Autumn Leaves Change Color
by George and Becky Lohmiller
Why do autumn leaves change color? What type of trees—and weather—produce the most vivid fall foliage? Read on . . .
Not all leaves turn vivid colors in the fall. Only a few of our many species of deciduous trees—notably maple, aspen, oak, and gum—produce stellar performances for our annual autumn spectacular in North America.
Several factors contribute to fall color (temperature, precipitation, soil moisture), but the main agent is light, or actually the lack of it. The amount of daylight relates to the timing of the autumnal equinox. See when fall begins.
As the autumn days grow shorter, the reduced light triggers chemical changes in deciduous plants causing a corky wall to form between the twig and the leaf stalk. See how day length is changing in your area!
This "abscission layer" eventually causes the leaf to drop off in the breeze. As the corky cells multiply, they seal off the vessels that supply the leaf with nutrients and water and also block the exit vessels, trapping simple sugars in the leaves. The combination of reduced light, lack of nutrients, and no water add up to the death of the pigment chlorophyll, the "green" in leaves.
The Old FARMERS ALMANAC
by George and Becky Lohmiller
Why do autumn leaves change color? What type of trees—and weather—produce the most vivid fall foliage? Read on . . .
Not all leaves turn vivid colors in the fall. Only a few of our many species of deciduous trees—notably maple, aspen, oak, and gum—produce stellar performances for our annual autumn spectacular in North America.
Several factors contribute to fall color (temperature, precipitation, soil moisture), but the main agent is light, or actually the lack of it. The amount of daylight relates to the timing of the autumnal equinox. See when fall begins.
As the autumn days grow shorter, the reduced light triggers chemical changes in deciduous plants causing a corky wall to form between the twig and the leaf stalk. See how day length is changing in your area!
This "abscission layer" eventually causes the leaf to drop off in the breeze. As the corky cells multiply, they seal off the vessels that supply the leaf with nutrients and water and also block the exit vessels, trapping simple sugars in the leaves. The combination of reduced light, lack of nutrients, and no water add up to the death of the pigment chlorophyll, the "green" in leaves.
The Old FARMERS ALMANAC
