Image from Wikimedia Commons
Every year many people looking forward to Fall for many reasons. Several holidays, family time, and the changes of nature that occur all around us. One of these drastic changes is the changing of the colors of leaves in trees as they fall out to prepare the trees for the winter to come. Although many people see this as a burden to rake up leaves and have to tend to their yards, several people enjoy the changes and embrace the nature in front of them. However, not many people really know how this happens. How do these leaves just change color and fall over time? What process causes this to happen?
The change in color of leaves is caused by the chemical processes that occur in the tree throughout the rest of the year. During the spring and summer for example, the leaves on the trees act as factories for food production and this causes the leaves to have large amounts of chlorophyll. Chlorophyll is defined as a green pigment, present in all green plants and in cyanobacteria, responsible for the absorption of light to provide energy for photosynthesis. Its molecule contains a magnesium atom held in a porphyrin ring. The large amounts of chlorophyll due to the light absorption cause the leaves to produce a green pigment. However, once Fall comes, because of the shorter days and less amount of light, there is less chlorophyll produced and the green pigment that appears in leaves slowly fades away, unmasking the red, yellow, and orange pigments that we see in leaves.
Although light plays a major factor in the food production of leaves and how much chlorophyll is produced, it is not the only factor that affects leaves. Temperature and water both affect the intensity of the colors shown and how long the color will last. For example, low temperatures can help produce a bright red pigment but freezing temperatures may dull this color. On a rainy or dark day, you may see the colors of the leaves more intensified.
In early September or October, you may notice that the leaves start to fall and change their colors. During this time, you will also notice that the days get much shorter and it gets darker faster. Leaves react to these changes just as we would. Due to the shorter days, we would spend less time doing tasks and finish early. Leaves react to the shorter days by producing less and less amounts of chlorophyll and as they do this, the green pigment disappears causing the changes in color that we know and love to see. Trees also need sunlight and oxygen to produce sugar and food for itself. As it produces these products it also has larger amounts of chlorophyll. When there is less sunlight during Fall, leaves have less resources to produce their food and chlorophyll and this results in the lack of green pigment in leaves.
Today, if you happen to notice the days are shorter and older, you will most likely be able to observe the changes of leaves in the trees around you. In the future, trees will continue to repeat the same processes and annually and change nature as we see it today.