Wednesday, November 16, 2011

Where Do Leaves Get Their Autumn Colors?

These photos were taken recently while crossing the bridge that leads to the Aquarium in Niagara Falls, New York.

If you live in one of those parts of the world where Nature has one last fling before settling down into winter's sleep consider yourself lucky. In those wondrous places, as days shorten and temperatures become crisp, the quiet green palette of summer foliage is transformed into the vivid autumn palette of reds, orange, gold, and brown before the leaves fall off the trees. On special years, the colors are truly breathtaking.

Evergreens-pines, spruces, cedars, firs, are able to survive winter because they have toughened up. Their needle or scale like foliage is covered with a heavy wax coating and the fluid inside their cells contains substances that resist freezing. Thus the foliage of evergreens can safely withstand all but the severest winter conditions, such as those in the Arctic. Evergreen needles survive for some years but eventually fall because of old age.

I lived for several years in the New England states and now I am in Western New York. Every autumn I have been able to revel in the beauty of the fall colors. The mixture of red, purple, orange and yellow is the result of chemical processes that take place in the tree as the seasons change from summer to winter.

During spring and summer the leaves have served as factories where most of the foods necessary for the tree's growth are manufactured. This food-making process takes place in the leaf in numerous cells containing chlorophyll, which gives the leaf its green color. This extraordinary chemical absorbs from sunlight the energy that is used in transforming carbon dioxide and water to carbohydrates, such as sugars and starch.

Certain colors of leaves are characteristic of particular species of trees.

-Oaks turn red, brown, or russet.

-Hickories turn golden bronze.

-Beech turns light tan.

-Red maple turns brilliant scarlet.

-Sugar maple turns orange-red.

-Black maple turns glowing yellow.

-Aspen, birch, and yellow poplar turn golden yellow.

Leaf color is most spectacular when the right combination of factors is present. Scientists don't fully understand all of the complicated interactions that cause the best display of leaf color, but they do know that leaf pigments, length of night, the type of tree, genetic variation, and the weather all play a role.

Where Do Leaves Get Their Autumn Colors?

Tree and plant leaves contain pigments that give them their color. Three pigments are involved in fall color:

· Chlorophyll — gives leaves their green color.

· Carotenoids — provide the yellow, orange, and brown colors

· Anthocyanins — give the red and purple colors.

In contrast to the other two pigments, anthocyanins are produced in the autumn, in response to bright light and excess plant sugars in the leaf cells.

During the growing season, most tree leaves are green because they are full of chlorophyll that enables them to manufacture their own food. As the days grow shorter in the fall, chlorophyll production slows down and eventually stops. The carotenoids and anthocyanins that are present in the leaf then become visible.

Fallen leaves are not wasted; they decompose and restock the soil with nutrients. The rich layer of decomposing leaves protects the roots of other plants on the forest floor and absorbs and holds rainfall. Imitating nature by mulching with shredded leaves provides similar benefits for trees and shrubs in the home landscape.

Today the temperature was in the 60's - very unusual for this time of year. I spent time working in the Peace Garden while enjoying the sunshine and the beautiful foliage and thought I would share it with you today.

photos by peacesojourner

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