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Show WHY DO LEAVES CHANGE The question comes up every year about this time: Why do leaves change color in the fall? According to Ranger Rick's Nature Magazine, autumn's cooler temperatures tem-peratures and shorter days cause chlorophyll which gives leaves their green color in spring ana summer to break down and other pigments to form in the leaves. The National Wildlife Federation monthly publication for children notes that "a spectacular show of fall colors depends on the right amount of sunshine, rain, and cool temperatures." New England falls are often so beautiful, because the region's weather is usually dry, bright and cool. Like everything else in nature, no two leaves are alike and none of them will have the same splendid color combination com-bination each season. However, Ranger Rick explains that all the color variations are based on the following pigments: Yellow and Orange These pigments are in the leaves all year long, but can't be seen in the spring and summer because they are covered by the green chlorophyll. These are the same pigments that make egg yolks yellow and carrots orange. Red and Purple The bright red and purple colors of fall only show up on leaves of trees that produce a lot of sugar. P-ecause trees need very cool and dry temperatures tem-peratures to produce sugar, these colors are mostly found in New England's trees. Red maples, which normally produce a lot of sugar, usually have red. and purple leaves in autumn. But if fall temperatures . are too warm, or there isn't enough sugar in the tree, a red maple's leaves will turn orange or yellow. Brown Some leaves, like those on oak trees, do not change to bright colors in the fall, but become brown and drab. This is due to the presence of the chemical tannin, which mixes with the yellow and orange pigments, and turns the leaves brown. Fall's cooler weather also causes the food products stored in the leaves to flow to safer qua rters the tree's branches and trunk. A thin layer of cells, called the "abciss layotV' then forms across -r stem which connects" leaf to twig. With this link weakened, the leaf is broken off by on autumn breeze or eventually falls to the ground of its own weight . |
