Gabriela


We all enjoy the colors of autumn leaves. The changing fall foliage never fails to surprise and delight us. Did you ever wonder how and why a fall leaf changes color? Why a maple leaf turns brightred? Where do the yellows and oranges come from? To answer those questions, we first have to understand what leaves are and what they do.


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Leaves are nature's food factories. Plants take water from the ground through their roots. They take a gas called carbon dioxide from the air. Plants usesunlight to turn water and carbon dioxide into oxygen and glucose. Oxygen is a gas in the air that we need to breathe. Glucose is a kind of sugar. Plants use glucose as food for energy and as a buildingblock for growing. The way plants turn water and carbon dioxide into oxygen and sugar is called photosynthesis. That means "putting together with light." A chemical called chlorophyll helps makephotosynthesis happen. Chlorophyll is what gives plants their green color.
As summer ends and autumn comes, the days get shorter and shorter. This is how the trees "know" to begin getting ready for winter.During winter, there is not enough light or water for photosynthesis. The trees will rest, and live off the food they stored during the summer. They begin to shut down their food-making factories. Thegreen chlorophyll disappears from the leaves. As the bright green fades away, we begin to see yellow and orange colors. Small amounts of these colors have been in the leaves all along. We just can'tsee them in the summer, because they are covered up by the green chlorophyll.

The bright reds and purples we see in leaves are made mostly in the fall. In some trees, like maples, glucose istrapped 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...