As the days grow shorter and colder towards the end of the year the green leaves that adorned deciduous trees and shrubs throughout the summer begin to change into colors of red, orange, and yellow, and fall off the tree. Most trees with broad flat leaves lose their leaves every fall, while most trees with needles and a few with flat leaves keep them throughout the winter. Leaves that stay on the tree throughout the year have specially designed protective features, such as a sturdy needle shape, or a wax coating. Most broad leaf plants do not have these features though. They must lose their large delicate leaves or risk having them destroyed by winter weather. When the days grow shorter there is less sunlight available for the tree to use in photosynthesis, which is the process by which most plants use the green pigment chlorophyll to convert water, carbon dioxide, and light into carbohydrates. Oxygen is produced as a byproduct of this chemical reaction. When the lack of su...