September 10, 2008

Autumn Colors

Autumn Colors One of the greatest shows in the natural world takes place every year in the forests of eastern Canada and the United States, as turning leaves paint the landscape spectacular colors from yellow, to orange, to deepest red and purple. How do leaves change color? - Leaves are nature's food factories. Plants take water from the ground and a gas called carbon dioxide from air. They use sunlight to turn water and carbon dioxide into glucose (this process is called photosynthesis), which they use as a food for energy and as a building block for growing. A group of pigments present in the leaf that helps the photosynthesis to happen and gives the leaf a green color is called chlorophylls. During the growing season, the plant replenishes the chlorophyll so that the supply remains high and the leaves stay green. In the late summer, the veins that carry materials from the leaf to the branch and minerals from the roots into the leaves are closed off as a special layer (cork cells) forms at the base of each leaf. It is during this time that the chlorophyll begins to decrease and disappears completly in relatively short time period.

autumn colors
This is when autumn colors are revealed. As the bright green fades away, we begin to see yellow and orange colors. These colors are present in the leaf throughout the growing season but are not visible as they are covered up by the green chlorophyll. In some trees like, maples, glucose is trapped in the leaves after photosynthesis stops. Sunlight and the cool nights of autumn cause the leaves turn this glucose into a red color. The brown color of trees like oaks is made from wastes left in the leaves.

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