Leaves Most of us in the Midwest at least take trees for granted. They are so common and seem to grow so easily that we fail to consider how carefully they have to be designed to survive. The leaves of trees are especially complex. Not only is their chemistry that turns sunlight and common chemicals into usable complex compounds highly sophisticated, but their physical makeup and shape are also carefully engineered.
Leaves have to be arranged on a tree so that there is an efficient interception of the sun's rays.
If you have ever stood beneath a tree and looked at its shadow, you know that very little sunlight is wasted. In addition to absorbing sunlight and carrying on photosynthesis, leaves have to be able to endure a great deal of physical abuse. In severe wind, a leaf has to have minimal drag. If the drag of leaves is high, a tree will be toppled by even moderate winds. To have a low drag, the shape is critical.