In the fall, the leaves change from green to brilliant shades of scarlet, gold, orange and purple. Then eventually fall to the ground. There is a time to die: the tree or shrub is preparing for winter.
In the summer, when the period of growth slows down, a dead cell layer is formed on the base where the stem meets the trunk. This layer is called the separation layer . This does not pass through the wood fibers that connect the stem to the trunk. These fibers hold the sheets in place until the frost or the wind starts. After the leaf has fallen, the scar where the leaf was attached to the trunk is sealed and protected by the separation layer.
According to the separation layer is formed, manufacturing of food material within the leaf decreases. Cells and veins in the leaf are covered. Not produce more chlorophyll, the green color disappears. Other colors were present in the leaf, but they were hidden because the green highlighted more. Now appear in all its glory.
All leaves contain yellow pigments called carotenoids and lutenoides. The yellow pigments are formed in the protoplasm of the leaf cells. The red and purple are due to pigments called anthocyanins (anthocyanins have the great ability to act deeply in the human body to provide powerful protection. These phytonutrients essential physiological and pharmacological effects are different. Anthocyanins, along with other nutrients found in fruits and vegetables provide protection against oxidative stress-related conditions, such as cancer, heart disease and inflammation).
These are formed from the sap of cells which is rich in sugar. Sugar maples, oaks, and sycamores have the brightest colors of purple and scarlet. To develop such a high content of color they have to be exposed to sunlight. The sugar maples are too hidden under larger trees not turn red and only show a yellow color.
A frost is usually given credit for the fall colors, but in fact a particular temperature has little effect on it. It requires a combination of favorable weather. The red pigments are formed sunlight on the leaves that have kept sugar. A cloudy, rainy or hot, dry summer prevents the development of pigment. If hot days are followed by warm nights, sugar leaf filters down to the woody portions of the plant. Ideal conditions are bright sunny days followed by cool nights.
Frost is largely responsible for releasing the leaves of the branches. On a frosty night, ice crystals form in the separation layer and break the wood fibers that hold the sash in place. So when the ice melts in the morning sun, the leaves flutter in a shower of crimson and gold to the ground. In some oak separation layer is not fully developed and the leaves remain on the tree all winter.
wise gardeners and farmers do not burn the leaves falling, but that added to the compost pile. Rotting leaves (mildew) are valuable for soil conditioner.
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