Margo Hamilton,, age 12, of San Mate o, Calif.., for her questions
How does photosynthesis: work?
Some years ago, a scientist weighed a baby tree which tipped the scales at five pounds: He weighed out a certain amount of earth, put it in a solid container and set the little tree in it to grow. Ten years later he uprooted the tree and found that it now weighed one hundred pounds, He again weighed the soil and found that it had lost only a few ounces. Certainly the tree did not get all its extra weight from the soil it used only a few ounces of chemicals. Most of those extra 95 pounds were made from air and water by the magic of photosynthesis.
The word photosynthesis means put together with light. It is the magic recipe of the green plant world in which sunlight is used to make basic plant food from carbon dioxide In the air and moisture in the soil. Like Grandma s recipe for apple pie, nature's sunshine recipe is a closely guarded secret. The best minds in the world have tried to fathom it. We know the ingredients used and how they become changed step by step. But we are not yet altogether sure how it is done.
The ingredients for the sunshine recipe are plentiful and well distributed. Carbon dioxide is the gas breathed out by us, by the animal world and also poured into the air by the plants themselves. It is also given by bacteria in the process of decay, VJ?'ater is provided by the tumbling raindrops which sink into the soil.
In the kitchen, we use heat energy from a stove to bake our pie, to rearrange the raw ingredients into something different. In photosynthesis, the energy of light is used to rearrange the molecules in the raw ingredients. The finished product is glucose, the simple sugar which is the basic food for the entire plant world.
Carbon dioxide seeps through pores in the green leaves called stomata. Water seeps up through the plant cells. Light falls on the been world from dawn to sunset, even on cloudy days.
The ingredients come in contact with green chlorophyll, a clear liquid teeming with tiny bodies called chloroplasts. Scientists suspect that each chloroplast acts like a midget battery to break apart the molecules in the ingredients and rearrange them. A molecule of carbon dioxide contains one atom of carbon and two of oxygen. A molecule of water contains one atom of oxygen and two of hydrogen. Six molecules from each ingredient are needed to make one molecule of sugar, The sugar contains six atoms of carbon, 12 of hydrogen and six of oxygen.
This means that six atoms of oxygen are sent back to the air as waste material. On a grand scale, the waste oxygen from photosynthesis provides the vital oxygen needed by us, by the animal world and by plants themselves. On a grand scale, the molecules of sugar are reprocessed to make the entire plant world.