Why do tree leaves have different shapes?
The shape of a tree’s leaves are a response to the tree species’ long term ecological and evolutionary histories. An ecosystem’s limiting factors may also modify the finished form and shape of a tree’s leaves. 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 via pores (called “stomatae”). This carbon dioxide is also needed for photosynthesis. When these leaf stomatae are open to allow the uptake of carbon dioxide, water from inside the leaf is lost to the atmosphere. 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.
