The Beautiful Leaves

This week’s blog was written by Laura M., a Bass alumni. She writes about the reasons why leaves change their colors during the fall season.

Autumn is a wonderful time of year. The leaves on trees change color and make everything outside look very beautiful. But why do leaves change colors in autumn and eventually fall from the trees?

In order to absorb light to create energy, pigments are produced in leaves. The primary pigment in these leaves is chlorophyll, and this pigment is what is responsible for the green color of leaves. Chlorophyll is produced and used quickly by trees in the growing season when it is warm out. As a result, the leaves of trees stay green. However, as temperatures drop, trees stop the production of chlorophyll since it requires too much energy to do so. As a result, other pigments in the leaves, such as carotenoids, become visible. This causes the leaves to look orange, yellow, and brown. In addition, red and purple pigments, called anthocyanins, are produced. These help to lower the freezing point of the liquid in leaves, allowing them to remain on the tree for a little while longer than they would without the pigment. Eventually, temperatures become too cold for the trees. They need to do everything they can to preserve energy. Leaves are too susceptible to the cold and would be damaged too easily. As a result, the trees lose their leaves. Once a tree senses that days are becoming too short (they sense light using chemical light receptors called phytochrome and cryptochrome), trees stop the flow of water to the leaves. Eventually, the leaves will completely dry out and fall to the ground.

Beautiful yellow leaves still on the tree.

While all of this is the case for deciduous trees, this is not the case for evergreen trees. Evergreen trees are able to keep their leaves due to two special properties. One property is a special wax coating that is on the outside of the leaves that insulates them from the cold. In addition, the cells of the leaves contain special anti-freeze chemicals that help them survive through the harsh cold.

A giant leaf pile my brother and I made when we were younger.

As fall approaches, take time to go outside and see the stunning colors. Go for a walk in the forest, or even just down the street. Kids love a leaf pile – start raking and have some fun.

All photos in this blog belong to the author