By: MICHELLE PARK
Staff Writer
You can see the trees at the school turning red, yellow, or brown. We know empirically that in the fall, trees that were once green will turn red or yellow. However, how do leaves change color?
Many plants do mostly photosynthesis. Photosynthesis is the process of producing carbohydrates and oxygen from carbon dioxide (CO2) and water (H2O) by using light energy. Plants have chloroplasts, which contain chlorophyll, a pigment that absorbs light, and various other pigments. Chlorophyll makes the leaves of plants green. However, chlorophyll contains not only green pigments, but also pigments such as carotenes, xanthophylls, and tannins. Carotene, which is also included in carrots and egg yolks, is the pigment that gives it an orange color, and xanthophyll is a pigment that gives it a yellowish color.
In the fall, trees cannot continue photosynthesizing their leaves due to the dry air and lack of sunlight. Chlorophyll, which has become unable to photosynthesize, is destroyed, revealing pigments such as carotene, xanthophyll, and tannin that were hidden by chlorophyll. This process is the fall foliage. It is not that the green leaves turn red or yellow, but that other colors that were hidden by the green appear as the green disappears.