As the days grow long and the years grow old, a special change occurs that signifies a special time of year. As long as there has been “time”, leaves have been changing to alarm the coming of winter. This occurrence happens every year bringing cold air, shorter days and even snow. This natural changing of the trees has a very intriguing science.

Leaves act as natural food-producer for trees. Three crucial components are needed for leaves to produce energy. Plants absorb water from the ground through their roots. Gas called carbon dioxide is absorbed from the air surrounding the trees. Plants use sunlight to turn water and carbon dioxide into glucose, a special kind of sugar. Plants use glucose as food for energy and as an aid for growing. The way plants turn water and carbon dioxide into sugar is called photosynthesis. A chemical called chlorophyll helps make photosynthesis happen. Chlorophyll’s pigment color is green, hence the green color in leaves.

As summer dwindles to a close, the days become shorter and shorter. This tells trees that it is time to start storing energy. During winter two of the ingredients in energy production, light and water, become scarce. This causes the process of photosynthesis to bog down, producing a shortage of chlorophyll. Two pigments that remain in leaves all year long, carotenoid and anthocyanin, now can be observed. Carotenoid creates bright yellows and oranges, similarly seen in carrots. Anthocyanins produce the bright reds in the leaves, also in cranberries and apples.

Several factors can change the brilliance of these pigments. Temperature and moisture have the biggest effect on the color of the leaves. A succession of warm, sunny days and cool, crisp but not freezing nights seems to bring about the most spectacular color displays. A wide variety of colors from year to year are caused from different soil moistures from year to year. A warm wet spring, favorable summer weather, and warm sunny fall days with cool nights should produce the most brilliant autumn colors.

Lastly, leaves completely fall off of the trees when the cold weather arrives. The veins that carry the water to and from the leaves begin to seal off. After the discontinuation of fluid exchange, the leaf dies, falling to the ground.

If the Sumerians and Egyptians had not created some form of the clock, time would move on without hesitation. Seasons will always continue to change year after year. Winter is acknowledged by snow, summer by hot days, and autumn by leaves changing colors. Glucose is created by a mixture of carbon dioxide and water, which aids in the process of photosynthesis. Chlorophyll, or the green pigment, in leaves is formed by photosynthesis. Shorter days cause photosynthesis to dwindle, decreasing the amounts of chlorophyll apparent in leaves. This allows other colors to show through. The science of “falling leaves” is an interesting natural occurrence that will always signify autumn.