Name: Jesse R.
Why do trees have many small leaves instead of fewer
Some kinds of trees have large leaves, and other kinds of trees have small
leaves. Some trees that grow in wet places and others that grow in the tropical
rainforests have very large leaves. Other trees that grow in dry places,
especially on mountain sides, often have small leaves, as an adaptation to
conserve/save water. Needles (of conifers or "Christmas trees") and spines
(of cactus) are actually very small leaves to save water.
Anthony Brach, Ph.D
The function of leaves is to gather energy from sunlight, and exchange
carbon dioxide and oxygen with the air in the process of photosynthesis.
Different leaf shapes and sizes have evolved to best do these things. In the
temperate zones of North America leaves in the shade are often larger than
leaves that get more sunlight, on the same species of tree, or even on the
same tree, for example. In the tropics some plants have very large leaves.
The anatomy and growth of leaves is complex, and there are other factors
like efficiency of transfer of materials that help determine leaf size and
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Update: June 2012