Why Do Leaves Change Colors?
By Noah Bergren on September 27, 2012, 8:41pm
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As we now are in the fall season, and the temperature continues to get cooler, and the days get shorter, one of the most loved autumn changes is the leaves on the trees, from their green color to orange, yellow, and red. But why do leaves change color in the fall season?
Well, it starts with the chemicals and pigments that are found in each leaf on a tree. The process of the color change starts with the declining length of nighttime, which triggers the chemical process of color change. Some of the chemicals involved in the reaction are:
-Chlorophyll, which is responsible for the green part of the leaf, and also is necessary for the photosynthesis process.
-Carotenoids, which yield the typical yellow/orange/gold colors found in leaves and other vegetables.
Chlorophyll and carotenoids are both present in the chloroplasts of leaf cells throughout the growing season in the leaves on trees. Chlorophyll is inside an organelle called a chloroplast. During the spring months, chlorophyll is repeatedly created and broken down chemically, producing the green color. This is because of the dominant presence of the chlorophyll pigment, which controls and hides the colors of other pigments in the leaf- leaving leaves to appear as a green color through late summer. This process is directly related to the length of nighttime, which is a major factor in the process of leaf change. Once the nights begin to get longer, the process of chlorophyll slows down and eventually comes to a halt.
Chlorophyll absorbs the suns' powerful rays and converts them into energy for the plants' food, which are responsible for the nourishment and longevity of the leaf. As I mentioned before, during the spring and summer months the tree continues to refill the supply of chlorophyll, hence leaving the leaves a green color. In late summer and early fall, as days become shorter and night's become longer, veins in the leaf that transport fluid are sealed off at the base of each leaf. As the leaves begin to loose their supply of energy (chlorophyll), the leaves loose their green color from the lack of energy. Then, the remaining pigments in the leaf can yield the colors that are left over inside, ranging from red to purple to yellow.
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