Tag: Chlorophyll

Slowly Slowly

Slowly, slowly, autumn’s full blown color palette is creeping in. Right now it is: “Oh! Look at that tree!” Not a hillside of color but just a few leaves here and there turning with all their might to a spectacle of hues.

Changes in a leaf’s world, encourages slowing and stopping of photosynthesis which makes the leaf lose its chlorophyll and its green coloring. Depending on what compounds are most prominent in the leaf, determines its autumn color.

Carotenoids, and flavonoids both contribute yellows, while carotenoids also include oranges and reds in their repertoire. Both these compounds deminish, like the chlorophylls, but more slowly, allowing their colors to shine through autumn.

Another set of compounds, anthocyanins, a member of the flavonoids family, plays a part in some autumn leaf color. While carotenoids and flavonoids are present in the leaves during the growing season, anthocyanins are not. Autumn is the time for some leaves to manufacture this compound through increased sugar concentrations exposed to sunlight. This gives way to rich red, purple and magenta coloring in the those leaves.

Soon we’ll be at peak leaf season. I can’t wait.

Autumn Color Change

Sassafras (Sassafras albidum)

During the summer months the trees around us are covered with green leaves. The green color in those leaves is thanks to a green pigment, chlorophyll, that the leaves use to capture the sun’s energy. That energy is used to change water and carbon dioxide into glucose and oxygen, in a process called photosynthesis. Glucose is used by plants for energy and to create other materials such as cellulose, and starch. But how do we end up with the warm colors of autumn? The reds, yellows and oranges?

Virginia Creeper (Parthenocissus quinquefolia)

The principal pigments that produce color within a leaf are: chlorophyll (green); xanthophylls (yellow); carotenoids (orange); and anthocyanins (reds and purples). 

Gray Dogwood (Cornus racemosa)

During the summer there is an abundance of chlorophyll as the leaves work to provide energy for the tree, this gives the leaves their green color. As summer winds down trees will pick up signals that the seasons are changing. Those signals? Days that are becoming shorter and cooling temperatures. In response photosynthesis slows and the amount of chlorophyll drops drastically, leaving the other pigments within the leaf more plentiful, changing the colors. Yellows, oranges, reds and sometimes even purples. And we have AUTUMN.