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Every autumn we are surrounded by Mother Natures "carnival of colors",
as the trees are set ablaze in hues of red, purple, orange and yellow. The color changes are the
results of a chemical processes taking place in the trees, as the seasons change from summer to winter.
Surrounded by the awesome beauty, one can better understand what Isaiah must have meant by "the mountains and the
hills shall break forth into singing and all the trees of the field shall clap their hands".
During spring and summer the leaves serve as "food factories" where most of the food
necessary for the tree's growth is manufactured. This food-making process called photosynthesis,
takes place in numerous leaf cells that contain chlorophyll, which gives the leaf its green color.
Along with the green pigments are yellow (carotenes) and orange (xanthophyll) pigments.
These pigments are present in the leaves most of the year, but are masked and unseen by great
amounts of green coloring.
The shortening daylight hours and changing weather trigger the food making process to slow down. As the
chlorophyll breaks down, the green coloring slowly disappears allowing the yellows and oranges to
become more visible. At the same time other chemical changes may occur, which stimulate the production
of red and purple (anthocyanin) pigments.
All colors result from the mixing of varying amounts of chlorophyll residue and other pigments in the leaf.
Some trees show only yellow colors while others like many of the oaks, display mostly browns. Other mixtures give
rise to the reddish and purplish colors, or brilliant oranges.
Temperature, light, and water supply have an influence on the degree and the duration of fall color.
The brightest colors are seen when late summer is dry, and autumn has bright sunny days and cool nights. These are
ideal conditions for the production of anthocyanin pigments.
When high levels of both anthocyanin and carotenoid pigments are present, leaves display the deeper oranges,
fiery reds and bronzes that can light up a fall landscape. A fall with cloudy days and warm nights brings drab colors.
And an early frost quickly ends the colorful display.
As fall colors appear, other changes are taking place. At the point where the leaf stem is attached to the tree, is a
special layer of cells called the "abscission" or separation layer. During summer, small tubes pass through
this layer carring water into the leaf, and food back to the tree.
In the fall, the cells of the abscission layer begin to swell and form a cork-like material, cutting off the flow
between leaf and tree and severing the tissues that support the leaf. At the same time the tree seals the cut, so that
when the leaf is finally blown off or falls, it leaves behind a leaf sear.
Enjoy the leaves before they fall !!!
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