Have you ever wondered why the leaves change color in the fall? Well, it is such a simple question, and many people believe the leaves are just dying, but what is the science behind it?

Leaves contain three main pigments or molecules: chlorophyll, carotene, xanthophylls, and anthocyanins. Chlorophyll acquires the sun’s energy to generate food for the plant, and is the molecule for the leaves green color. Carotenes cause yellow colors and are found in carrot roots, while xanthophylls cause corn to be yellow, and anthocyanins cause beets to be red and eggplants to have their purple color.

In the latter part of the summer season, shorter days and chillier nights halt the manufacturing of fresh chlorophyll, and promote its breakdown. The other pigments in the leaves are not broken down, and are no longer disguised by the chlorophyll molecules, therefore becoming apparent. Different species, then based on different conditions, produce different hues of color. If anything stops the production of auxin, like the changing autumn weather, the stem and leaf stalk becomes structurally weaker, and allows for the leaf to break off in the wind.

During the growing season, auxin, a plant hormone, is also produced. This molecule controls a group of cells at the bottom of each leaf stem, also known as the abscission layer. If anything stops the production of auxin, like the changing autumn weather, the stem and leaf stalk becomes structurally weaker, and allows for the leaf to break off in the wind.

These reasons would have been so cool to learn as a child, not just in botany. I have also noticed that leaves have become less bright in the last ten years, specifically in my hometown, and I wonder the reason for that.  Pollution? Acid Rain? Research!

http://www.sciencedaily.com/releases/2007/10/071012104737.htm

http://faculty.ucc.edu/biology-ombrello/POW/autumn_leaf_colors.htm