Not only does the smaller surface area of desert plants help reduce water loss, but some also have a waxy outer coating that helps keep water in. Try this activity to show how wax keeps water in. Tear a piece of bread in half. Lay one of the bread halves on a plate. Tightly wrap the second bread half in wax paper. Lay the wrapped piece of bred beside the unwrapped bread piece. Allow the bread to remain undisturbed overnight, then compare the softness of the unwrapped and wrapped pieces of bread. The firmer the bread the more water it has lost.