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Wednesday, January 18, 2006

Function of Leaf

Each plant has a basic limb, branch, and leaf structure that has been adapted by this plant's to meet it's habits. A conifer will have thin leaves to reduce water and sun requirements The habits of trees make it possible to identify and classify each tree.

What are leaves?

To a plant, leaves are
food producing organs. Leaves "absorb" some of the energy in the sunlight and takes in carbon dioxide from the surrounding air in order to create photosynthesis.

The green color of leaves, in fact, is caused by a pigment "chlorophyll" that is the specific chemical agent that acts to capture the sunlight energy needed for photosynthesis. The products of photosynthesis are sugars and polysaccharides. An important "waste product" of photosynthesis is oxygen.

Leaf Shapes on tree leaves

The shape of a tree's leaves are a response to the tree species' long term ecological and evolutionary histories. Understanding of the "logic" behind the varied forms of leaves is facilitated by a firm grasp of the precise functions a leaf must accomplish.

1. A leaf must "capture" sunlight for photosynthesis (and as it does this it may also absorb a great deal of heat!)

2. A leaf must take in carbon dioxide from the surrounding air. When these leaf stomatae are open to allow the uptake of carbon dioxide, water from inside the leaf is lost to the atmosphere.

3. The leaf, then, is affected by these balancing acts: enough sunlight and carbon dioxide to run photosynthesis, but not too much associated heat absorption or water loss. The shape and design of the leaf is to adjust for the plant requirements.

Leaves high in the tree canopy receive a great deal of sunlight and tend to be smaller in size. Needle-shaped leaves have a very low light absorptive surface area and also have a very thick, outer cuticle coating and is not able to capture very much sunlight energy for photosynthesis and is designed to prevent excessive water loss.


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