Agnes Burns, age 12, of Wichita, Kansas, for her question:

Why must plants have sunlight?

We tend to forget that sunlight is radiant energy    but the plants do not forget. They use its energy to manufacture their foods from air, water and dissolved chemicals from the soil. The basic food, from which all others are processed, is a simple sugar. The chlorophyll of the green plant world uses energy from sunlight to create these sugar molecules from carbon dioxide taken from the air and water absorbed from the ground. This is the miraculous process called photosynthesis.

It can go on only during the daylight hours, for only then is the basic energy available. Later, a multitude of other chemical activities proceed to remodel the simple sugar into more complicated molecules. These are created to maintain living cells and to build a large assortment of fats, proteins and carbohydrates. The health and growth of the plant world depends upon the energy of sunlight to process the simple sugar from which everything else is built.