Friday, October 20, 2006

Red leaves

I love the brilliance of leaves as they cling to branches, as they rain down upon the streets and sidewalks in the wind. October colors too soon to become the naked branches of November.

What makes leaves red? Here's what Peter J.F. Stobie, outreach-program director at the Kalamazoo Nature Center, says (excerpted):

What makes leaves red? Remember the glucose that was produced for plant food [during spring and summer]? At the same time that the chloroplasts shut down [in the fall], a layer of cells forms between leaf stem and tree branch. Like a closed door, this stops the exchange of water and glucose between the leaf and the rest of the tree. Any glucose left over in the leaf will change to a pigment called anthocyanin [which turns the leaf red].

However, this change only occurs if the conditions are right. It requires bright, sunny days and cool but above-freezing temperatures at night. Frost kills leaves, preventing the wonderful change of glucose to anthocyanin.

I am continually amazed by the infinite details found in nature.

I agree, Mr. Stobie.

Our question next time: What makes pumpkins orange?

Addenum: Speaking of red, check out, which is raising funds to help women and children with HIV/AIDS in Africa. Catch their blog at:

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