Eco-Farm: An Acres U.S.A. Primer — Lesson 1: Photosynthesis, Part 2
This is an excerpt from Charles Walters’ Eco-Farm — An Acres U.S.A. Primer, available from the Acres U.S.A. bookstore at bookstore.acresusa.com. Read more excerpts from this book using the category “Eco-Farm.”
5. Photosynthesis
Here was a factor the great chemist hadn’t even considered. Men like Hales and Priestley didn’t work in the dark. They worked in sunlight or with the aid of candlepower, and they didn’t give the matter a thought. Yet here was the reality Ingenhousz discovered: plants kept in the dark would not purify the air. As a matter of fact, in the dark all plant parts damaged air much the same as did candles and mice. Moreover, certain parts of plants wouldn’t purify the air either. Roots wouldn’t. Old stems wouldn’t. Only leaves and young stems with green coloring seemed to do this job. Green coloring? The equation seemed to get more complicated as man’s puny mind expanded itself. First air, now green coloring seemed to walk hand in hand with that air purification task.
Once this door had been kicked open, it became more difficult to overlook contributing factors—no matter how strange—in the Creator’s handiwork. At each step along the way some investigator had a vision of what was happening. If plants didn’t get their food from the soil as a finished product, then plants—quite unlike animals—manufactured it. In the scientist’s lexicon the term of choice was synthesize. If this manufacturing chore was accomplished only in light, then photo (meaning light) and synthesize described the process.
That is, photosynthesis described what, but not how. There were all those nagging questions. If, in Hale’s experiment, the water level only rose, it meant that plants not only gave up something (oxygen), they also consumed something else. After all, those mint plants eventually died. Did they exhaust what they were taking from the air, possibly the same thing plants and animals were giving up?
Mental acuity and sound reasoning suggested a balance in nature. But it took chemistry to answer how this balance was being maintained. Laboratory experiments said that of the various substances released by animals into the environment, carbon dioxide was the one plants needed to grow. Somehow the plants combined water with carbon dioxide to produce food called glucose.
Glucose has 6 atoms of carbon, 12 atoms of hydrogen, and 6 atoms of oxygen—C6H12O6. Did the oxygen released from plant life come from the water or from the carbon dioxide? Students of agriculture will run across names such as Claude Louis Berthollet, Jean Senebier, Nicholas Theodore de Saussure as they watch the debate rage back and forth. All passed from the scene long before the question was answered, or the answer was explained. A great deal had to be learned about chemistry and the chemistry of life first, about inorganic and organic chemistry.
6. Table of known elements
Dmitri I. Mendeleyeff, the Russian chemist, first constructed his table of known elements hardly a hundred years ago. His insight into the Creator’s order was so great he supplied spaces where he believed an element should be to comply with the rhyme and reason of the supreme plan. That table still stands. The blank spots have been filled in. And the Periodic Chart of the Elements has provided a simple and beautiful picture of the order in the universe where we live. It has done more. It has opened chemistry and physics as never before, and made it possible for lesser minds to understand the structure of the atom. Moreover, it has provided facts agronomists could not ignore.
Each elemental entry features an inventory of information, starting with hydrogen, the lightest.
The atomic weight on a chart is almost always expressed as a single figure average when isotopes are involved. Isotopes are atomic brothers, so to speak, atoms of the same element which differ in weight. Hydrogen, as an example, has three isotopes. Protium hydrogen, the lightest form, has one proton and one orbiting electron.
A slightly heavier form is deuterium, sometimes called heavy hydrogen.
The heaviest form of hydrogen is called tritium.
The average of these several weights is 1.00797.
Each of the elements of life and death has an abbreviation symbol. You’ll see some on fertilizer bags, in farm literature, and even field them as slang in daily conversations.
All the elements needed for life are listed as the first 53 of 92 natural elements on planet earth. Of these, all except one falls in order among the first 42, and all except two are listed among the first 34. There is also a natural order for abundance of elements, according to atomic weight and number. The heaviest elements are the rarest. Elements with even atomic numbers are more abundant than those with odd numbers in our universe. We don’t know why, nor can we even guess.
The table itself is a veritable encyclopedia. There are series with missing electrons. As the eye moves from titanium to zinc, unfilled orbits change, an electron at a time. These transitions take place in natural order, moving across the table. There is also a vertical order to the table weight increasing as each element is listed under the one above. There are groups that figure in biology and signal the entrance and exit of disease. Henry A. Schroeder, M.D., possibly the world’s foremost authority on trace elements at the time of his death, wrote in The Trace Elements and Man, that a heavier metal can displace a lighter one in the same group in biological tissues and alter the reaction of the lighter one. He went on to say that tissues with an affinity for a certain element have an affinity for all other elements of the same group. Some elements are bone seekers. Some are thyroid seekers. All elements in two groups are liver and kidney seekers.
In terms of plant life, it is too early to say which of the elements are essential, although college texts and agronomy manuals are fond of listing 14 or 16 or 18, sometimes more.
If you look at any Periodic Chart of the Elements diagram, you will note a + symbol, designating a footnote, and the footnote says that atomic weights presented are reliable to ±3 in the last place. Other weights are reliable to ±1 in the last place. These are the isotopes. Isotopes are atoms with the same number of protons, but different number of neutrons.
The notation 168O, 178O, 188O simply denotes three stable isotopes of oxygen. The small index 8 means there are 16 – 8 = 8 neutrons in the isotope 16; 17 – 8 = 9 neutrons in the isotope 17; and 18 – 8 = 10 neutrons in the isotope 18.
This means oxygen 18 can be identified, just as in the case of those hydrogen forms illustrated earlier. It has more mass than, say, oxygen 16, and this mass can be identified by the mass spectrometer, a relatively modern instrument now available to scientific investigators. It was the development of this instrument, together with codified knowledge of the periodic table of elements, that finally served up an answer to the question: did the oxygen released from plant life come from the water or from carbon dioxide? Why is it so important to know the answer?
7. Shared, rented, occupied
There is a wonderful little book in print nowadays entitled The Lives of a Cell. In it Lewis Thomas, M.D., makes quite a point of the fact that the human system is not alone as an operating mechanism. We are shared, rented, occupied, he writes. The very interior of our cells are homesteaded by the mitochondria, small separate creatures that may or may not have entered early precursors of our eukaryotic cells, and stayed on for a few billion years. These little fellows are self sufficient sooners. They have their own DNA and RNA and replicate in their own way. Like the rhizobial bacteria on the roots of beans, they are symbionts. Except for them we couldn’t even drum a finger, much less think a thought.
Plant life is not plant life as such either. It too is rented out and occupied. Little one cell individuals are everywhere. They are so small they are invisible to the naked eye. Except for powerful microscopes, we would never lay an eye on one, and yet plant and human life depend on them, suffer disease because of them, live and die according to how life and death are balanced among them.
