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Falling colors - Tran Le Tuy Phuong
1. FALLING COLORS Source: Internet & Trần Lê Túy-Phượng Music: Mistica – Lost in Paradise PPS: Trần Lê Túy-Phượng Click mouse
2. Why do leaves change color in the Fall ? Autumn leaf color is a phenomenon that affects the normally green leaves of many deciduous trees and shrubs by which they take on, during a few weeks in the autumn season, one or many colors that range from red to yellow. The phenomenon is commonly called fall colors and autumn colors , while the expression fall foliage usually connotes the viewing of a tree or forest whose leaves have undergone the change. In some areas of Canada and the United States, "leaf peeping" tourism is a major contribution to economic activity. Chlorophyll and the green color A green leaf is green because of the presence of a pigment known as chlorophyll. When they are abundant in the leaf's cells, as they are during the growing season, the chlorophylls' green color dominates and masks out the colors of any other pigments that may be present in the leaf. Thus the leaves of summer are characteristically green. This produces a fractal-like pattern. Chlorophyll has a vital function: that of capturing solar rays and utilizing the resulting energy in the manufacture of the plant's food—simple sugars which are produced from water and carbon dioxide. These sugars are the basis of the plant's nourishment – the sole source of the carbohydrates needed for growth and development. In their food-manufacturing process, the chlorophylls themselves break down and thus are being continually "used up." During the growing season, however, the plant replenishes the chlorophyll so that the supply remains high and the leaves stay green. In late summer, as daylight hours shorten and temperatures cool, the veins that carry fluids into and out of the leaf are gradually closed off as a layer of special cork cells forms at the base of each leaf. As this cork layer develops, water and mineral intake into the leaf is reduced, slowly at first, and then more rapidly. It is during this time that the chlorophyll begins to decrease. Often the veins will still be green after the tissues between them have almost completely changed color.
3. Carotenoids Carotenoids are present in leaves the whole year round, but their orange-yellow colors are usually masked by green chlorophyll. As autumn approaches, certain influences both inside and outside the plant cause the chlorophylls to be replaced at a slower rate than they are being used up. During this period, with the total supply of chlorophylls gradually dwindling, the "masking" effect slowly fades away. Then other pigments that have been present (along with the chlorophylls) in the cells all during the leaf's life begin to show through. These are carotenoids and they provide colorations of yellow, brown, orange, and the many hues in between. The carotenoids occur, along with the chlorophyll pigments, in tiny structures called plastids within the cells of leaves. Sometimes they are in such abundance in the leaf that they give a plant a yellow-green color, even during the summer. Usually, however, they become prominent for the first time in autumn, when the leaves begin to lose their chlorophyll. Carotenoids are common in many living things, giving characteristic color to carrots, corn, canaries, and daffodils, as well as egg yolks, rutabagas, buttercups, and bananas. Their brilliant yellows and oranges tint the leaves of such hardwood species as hickories, ash, maple, yellow poplar, aspen, birch, black cherry, sycamore, cottonwood, sassafras, and alder. Carotenoids are the dominant pigment in coloration of about 15-30% of tree species.
4. Anthocyanins The reds, the purples, and their blended combinations that decorate autumn foliage come from another group of pigments in the cells called anthocyanins. Unlike the carotenoids, these pigments are not present in the leaf throughout the growing season, but are actively produced towards the end of summer. They develop in late summer in the sap of the cells of the leaf, and this development is the result of complex interactions of many influences — both inside and outside the plant. Their formation depends on the breakdown of sugars in the presence of bright light as the level of phosphate in the leaf is reduced. Anthocyanins are present in about 10% of tree species in temperate regions, although in certain areas — most famously Maine, New England — up to 70% of tree species may produce the pigment. In autumn forests they appear vivid in the maples, oaks, sourwood, sweetgums, dogwoods, tupelos, cherry trees and persimmons. These same pigments often combine with the carotenoids' colors to create the deeper orange, fiery reds, and bronzes typical of many hardwood species. Cell walls The brown color of leaves is not the result of a pigment, but rather cell walls, which may be evident when no coloring pigment is visible. Function of autumn colors Deciduous plants were traditionally believed to shed their leaves in autumn primarily because the high costs involved in their maintenance would outweigh the benefits from photosynthesis during the winter period of low light availability and cold temperatures.
7. Now that you have a general knowledge about the phenomenon of what fall colors is all about, you are invited to join me for an out-of-this-world journey through my favorite places, in my favorite time of the year, to see a showcase of Falling Colors in one of the most beautiful geographical spots on Earth, my home sweet home, the Appalachian Mountains of the United States of America. Our first stop will be The Trinity Zen Garden in Lakes of The Woods, Virginia. Shall we start…
69. CHÚC AN LẠC Trần Lê Túy-Phượng Deep thanks to all talented photographers whose beautiful works appeared in this presentation Wishing you Peace & Happiness Photo: Trần Lê Túy-Phượng
