The science behind why the leaves change colors
COLORADO SPRINGS, Colo. (KRDO) - With fall starting we are experiencing the leaves change colors. Have you asked yourself how they do that?
There are three factors that influence the colors of leaves these are leaf pigments, length of night, and weather
A pigment is any colored material that is found in a plant or animal cell. For humans, they are what give the color of our skin, hair, and eyes. For plants, it's what gives them their colors. These colors appear because they absorb and reflect different wavelengths of light.
There are three major leaf pigments carotenoids which produce yellow, orange, and brown colors. Examples of these would be corn, carrots, and buttercups. The second is anthocyanin which produces red and purples such as strawberries, cherries, and plums. The final one which we all know of is chlorophyll which produces a green color. Examples of these would be spinach, broccoli, and green beans.
During the growing season, summer and spring, we see a lot of chlorophyll because it is continually being produced and broken down so leaves appear green. Carotenoids are also present but they only show in a few plants. During the fall our nights become longer so the production of chlorophyll decreases and eventually stops. This allows the carotenoids and anthocyanin that are present in the leaf to become seen and show their colors.
Colors of the leaves can be characteristics of a species and they can vary species by species as well. In Colorado, cottonwood trees turn yellow in fall but maple trees for example can be different colors from each other. Red maple leaves turn red while black maple turns yellow.
Length of night is the second influence in leaves changing colors.
When the nights become longer the veins in leaves that carry fluid in and out of the leaf gradually close as a layer of cells forms at the base of the leaf. The clogged veins trap sugars in the leaf and promote the production of anthocyanin red and purple. Once this separation layer is complete and the connecting tissues are sealed off, the leaf is ready to fall.
The third and final influence of the leaf's color change is weather!
Temperatures and moisture are the two biggest weather factors that affect the colors of leaves.
Having multiple warm and sunny days and cool, crisp not freezing nights brings out the best colors. During these days sugar is produced in the leaf but during the cool nights along with the gradual closing of the veins, this prevents sugar from moving out. When you have lots of sugar and sunny days this allows for vibrant reds and purples. Because carotenoids are always present in leaves yellow and gold colors remain fairly constant.
The final weather impact on leaves is moisture, especially soil moisture
A late spring or severe summer drought can delay fall colors by a few weeks. A warm period during the fall can also lower the intensity of fall colors. A warm, wet spring, favorable summer, and warm sunny fall days with cool nights can produce vibrant autumn colors. This past year in Colorado we had a mild and wet summer along with an above-average snowpack therefore there is a lot of moisture available. But we have also experienced a slightly above-normal start to September so only time will tell how vibrant and how long the fall colors will last.
