The Science of Festive Fall Colors

Written by CNC Communications Intern, Delaney Osmond

As the season changes from summer to autumn, the green leaves on trees change to the vibrant reds, oranges, and yellows we all love. But why do leaves change color?

During the spring and summer, leaves maintain their beautiful green color because of chlorophyll. Chlorophyll is a green pigment found in leaves that makes it possible for a plant to make its own food through photosynthesis.

Throughout the year there are several other pigment molecules exist within leaf cells as well, including xanthophylls (yellow pigment), carotenoids (orange pigment), and anthocyanins (red pigment). However, these colors are masked by the massive amount of green chlorophyll in plant cells.

When the weather gets cooler and day-length becomes shorter during the autumn months, the plant stops energy production. Because photosynthesis is no longer needed, chlorophyll production stops, making the leaves lose their green color and the other colors more prominent. During this process, abscisic acid (ABA) will form an “abscission layer” between the leaf and the branch of the tree. This barrier prevents water from reaching the leaf and prevents the exchange of chemicals from the leaf to the tree which speeds up the breakdown of green pigmentation.

The weather occurring between summer and autumn determines how fast the color of leaves will change. If the days are dry and hot and the nights are cool, the leaf drop process is accelerated. Whereas when there is little temperature difference during the day and night, and it is more wet and humid, it will take longer for the leaves to drop.

This year, Carpenter Nature Center was graced with a lovely array of fall colors. The gallery of pictures bellow is a mixture of photos taken by our current Communications intern Delaney, and pictures found in our photo archive.