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Leaves - Leaves and needles are organs uniquely constructed for trapping the energy from the sun. Click here for more on leaves. As young leaves begin to grow, they use stored energy that was made by mature leaves the previous growth period. As leaves grow and mature, chlorophyll is formed in the living cells. To form one molecule of chlorophyll, 54 carbon atoms connect with 4 nitrogen atoms, one central magnesium atom, and 72 hydrogen atoms are required. As chlorophyll is formed the first time, the elements must come from stored reserves.
    Before chlorophyll forms in a leaf, the leaf could be a color other than green depending on the first pigments that formed.
    As leaves die, chlorophyll is no longer produced, and the leaf takes on colors of the other pigments present.
    Leaves begin to die and then the abscission layer forms. Non-woody roots die after the abscission layer forms.
    Many insects and mites feed and breed on leaves. Yes, many organisms depend on healthy leaves for high quality time, such as the koalas. Koalas eat the leaves of only about six species of Eucalyptus. Their primary intake of fluids comes from the moisture of the leaves. The interesting thing is that when the trees are hurt or injured, such as digging fire trenches by humans, the leaves tan. Not good for the koalas or the trees, i.e., digging fire trenches.

Click here for leaf anatomy.

See A TOUCH OF CHEMISTRY, SHIGO, 1996

I'm sure Mother Nature cries when she sees plastic bags full of leaves going to the dump.

Click here for some pictures of leaves.

Also see "Abscission Zones".

Also see "Needles"