Worms and Flowers

First Blush

Posted in Scientific by Lzyjo on September 24, 2009

Autumn is truly upon us and the leaves have noticed not a moment too soon.

Photobucket

Just a few days ago, I noticed the tiniest blush of gold on the green hills.

Photobucket

When the days shorten the trees respond by storing as much energy as possible for the upcoming months. They begin by sealing off the leaf petiole, preventing chlorophyll from regenerating.

Photobucket

When the chlorophyll breaks down it leaves the more stable carotene molecules. Carotene naturally occurs in green leaves, acting as an accessory to increase absorption of certain wave lengths in the light spectrum. With the chlorophyll gone the leaf appears yellow due to light reflecting from the carotene molecules.

Photobucket

Under certain stressful circumstances, bright dry days and cool nights, the tree makes a last ditch effort to recover any remaining nutrients.  If these condition are met, a reaction between the sugars and proteins in the sap occurs, catalyzing anthocyanins, pigments that can be red to purple colored depending on the pH. Anthocyanins are responsible for the red skin of apples and the purple colors of grapes.

Photobucket

Depending on the temperature and weather conditions, fall displays can vary greatly from year to year.

Photobucket

Sources:

The Chemistry of Autumn Colors

HowStuffWorks “Why do leaves change color and turn red?”