Nancy Morris, age 13, of Redwood City, Calif., for her question:
Will you explain Photosynthesis?
No one can explain photosynthesis fully because the entire process is not yet understood, Old Andy, your reporter, however, will do his best to explain in everyday language what we do know. The word photosynthesis means a putting together with light. It is the recipe by which green leaves mako plant food from air, water and sunlight. Mother Nature gave this magic recipe to all green plants. Every green plant hands the magic secret on to its daughters, generation after generation.
We know the ingredients in the recipe. We know where it is carricd out and the result. But how it is done only a green plant knows. The sunshine recipe calls for water, carbon dioxide gas and sunlight. The water comes from the soil and is toted, up to the leaves by the vascular bundles. Usually this simple sap carries chemicals dissolved from the soil, though these chemicals are not necessary to photosynthesis.
The carbon dioxide comes from the air. It enters the leaves through tiny holes called stomata. The stomata are usually on the underside of a leaf, in the shade. Otherwise too much water would escape and evaporate. An ordinary apple leaf has about 100,000 stomata on its underside, which shows you how small these 1 ittle pores are.
The sunlight for the recipe falls all around, especially on the upper sides of the leaves. Here we find most of the green coloring material called chlorophyll. It is a fluid colored green by tiny floating bodies called chloroplasts. yin area of leaf the size of a postage stamp may contain one million to two million of these chloroplasts.
The chloroplasts are the tiny chefs who cook up the secret sunshine recipe. For each molecule biscuit of plant food they take six molecules of water anal six molecules of carbon dioxide gas. A molecule of carbon dioxide is composed of one atom of carbon and two atoms of oxygen. A molecule of water is composed of one atom of oxygen and two atoms of hydrogen. The recipe therefore starts with six atoms of carbon, 18 atoms of oxygen, and 12 atoms of hydrogen.
Using sunlight as energy, the chloroplast changes the arrangement of atoms within the carbon dioxide and water molecules. The new arrangement contains six atoms of carbon, 12 atoms of hydrogen, and six atoms of oxygen. This sunshine biscuit is a moleculo of glucose, a simple plant sugar. This is the basic food from which every cell in every plant is made. Various other plant processes take over to make countless products, even the perfume of flowers.
Right now your sense of arithmetic is on its toes. In the shuffle of the sunshine recipe, 12 oxygen atoms were misplaced.: ''Whey were a waste product and oozed their way out of the stomata. They replenished the air with oxygen for ourselves and the animals to breathe. In return, we breathe out waste carbon dioxide which plants need for their photosynthesis.