Archive for Thursday, November 18, 2010

Leaves are everywhere

November 18, 2010

Have you seen any leaves lately?

Today after bagging 10 big bags full just from my front yard, I had a hard time trying to forget about them.

I have always thought that the wind blew the leaves off the trees but now after looking up leaves on the Internet, I find they do not fall by themselves but are being pushed off by the trees. When the trees in the fall get less sunlight, it triggers a hormone that sends a chemical message to each leaf that says, “It is time to go.”

Once the message is received, little cells appear where the leaf stem meets the branch. They are called abscission cells. That name comes from the root word, scissors, meaning they are designed to cut the leaf from the branch. It is a little bumpy line of cells that push the leaf bit by bit, away from the stem. You cannot see this without a microscope but if you did look through one you would see the scissor cells lined up to make the cut. They dangle for a while then usually when a breeze hits them they let go and fall to the ground.

I have always loved the colors of the trees, spring, summer or fall. The energy of the sunlight absorbed by the carotene in the leaf and is transferred to chlorophyll, which uses the energy in photosynthesis and makes the leaves green.

When the seasons change and the chlorophyll disappears from the leaf, the remaining carotene causes the leaf to appear yellow. Later a third pigment, or class of pigments that occur in leaves are anthocyanins. That is what makes the leaf turn to red.

The sap of the tree has a lot to do with color. If the sap is quite acidic, the pigments impart a bright red color, if the sap is less acidic, its color is more purple. The anthocyanins pigments are responsible for fruit as well as leaves, and affect the red skin of a ripe apple or any other colorful fruit. This causes the sunny side of the apple to be red and the shady side will remain green.

Isn’t Mother Nature wonderful? I just wish she would come and help me pick up her various colored leaves.


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