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THE SUN AS A CHEMIST
All living things owe their origin to the Sun, especially plants. Try and grow them in the dark, and all you will get is pale thin filaments instead of juicy green stalks. Under the action of solar light chlorophill (the colouring matter of green leaves) converts the carbon dioxide of the air into complex molecules of organic substances which constitute the bulk of the plant.
Hence, the Sun, or rather its rays, are the chief "chemist" synthesizing all the organic substances in plants. It would seem so. Not in vain has the process of assimilation of carbon dioxide by plants been named photosynthesis.
It is known that many chemical reactions occur under the action of light. There is even a special branch of chemistry which studies them, called photochemistry.
But so far the study of photochemical reactions has not yet resulted in the creation of either proteins or hydrocarbons2 in the laboratory. And it is these compounds that are the primary products of photosynthesis in plants.
At the initial stage the plant uses only carbon dioxide, water and solar light for the synthesis of very complex organic molecules. But maybe there is something else that plays a part in these processes? Imagine a factory with soda, petroleum, potassium nitrate, etc., being fed through pipes at one end, and lorries loaded with bread, and sugar driving out of its gates at the other end. This is fantasy, of course, but it is just about what happens in plants.
Plants have been found to have their catalysts, called enzymes. Each enzyme makes a reaction proceed only in a definite direction. It appears that the Sun accomplishes photosynthesis not as the sole "chemist", but in collaboration with his colleagues, the enzymes (catalysts). The Sun supplies the energy needed for the reaction and the enzymes make the reaction go in the right direction.
Though we cannot deprive nature, and partcularly plants, of their "patents" for the production of many substances, but in some cases we can already make them operate in the direction we need. Of great value to scientists in this respect were their investigations of photosynthesis processes. It has recently been found that if light of different wave-lenghts is used to illuminate the plants during photosynthesis, chemically different substances are formed. For instance, illumination with red-yellow rays resulted in carbohydrates as :he main compounds whereas blue rays give proteins.
It may therefore be expected that in the near future people will be able, with the aid of plants, to obtain the complex organic compounds they need, on a considerable scale. Indeed, instead of building factories, furnishing them with unique equipment and working out complex synthesis technologies, it will only be necessary to build hot houses and to regulate the intensity and special composition of the light rays used. Then the plants themselves will make everything required: from the simplest carbohydrates to the most" complex proteins.
ASSIGNMENTS
I Say whether the following statements are true or false:
1. Under the action of solar light chlorophill converts the carbon dioxyde of the air into complex molecules. 2. At the initial stage the plant uses only carbon dioxyde, water and solar light for the synthesis of organic molecules. 3. It may therefore be expected that in the near future people will be able to obtain complex organic compounds. 4. Then the plants themselves will make everything required.
1. What do plants need for growing? 2. What process is called photosynthesis? 3. What branch of chemistry studies chemical reactions which occur under the action of light?
a) arrange details, examples or comparisons in the order that explains your topical sentence; b) add a concluding sentence; c) check up to be sure that all ideas refer to the topical sentence.
WHAT PLANTS EAT AND WHAT CHEMISTRY HAS TO DO WITH IT
It would seem that plants were not very particular about their food. Herbs and bushes have survived in hot deserts and in the polar tundra. They may be stunted and wretched to look at, but they , have survived
There was something they needed for their development, but what? Scientists sought this mysterious "something'" for many years.
Despite all their experiments, in spite of all their discussions nothing definite was found.
The answer was finally supplied in the middle of the last century. The chemical analysis of a great variety of plants showed the latter "to be composed" of a number of chemical elements. At the outset there were not so many of them, ten in all: carbon and hydrogen, oxygen and nitrogen, calcium and potassium, phosphorus, and sulphur, magnesium and iron, But this ten elements gave rise To the vast ocean of foliage on Earth.
It followed therefore that for plants to stay alive they had somehow to assimilate, to “eat" these elements. But how? Where are the food sores of plants? Obviously, in the soil, in the water, and in the air. There were some strange things, however, that had to be explained. In some soils a plant might develop rapidly, blossom, and bear fruit, whereas in others it would droop wither and turn into a sickly freak. Evidently the latter soils lacked some element.
It was known long before that if the same agrigullural crops were sown year after year on even the most fertile soil, harvests would become worse and worse.
The soil become improverished. The plants gradually “ate up” all the chemical elements in it that they needed.
The soil had to be “fed”, that is, the supply of substances removed fronm it had to be replenished. In other words , it had to be Fertilized,as we usually say. Fertilizers were used way back in distant antiquity. They were introduced into the soil intuitively, on the basis of experience handed down from generation to generation.
Now the use of Fertilizers has been raised to the rank of a science and this science is named agrochemistry. Chemistry became servant to plant growing. It teaches people the right way to use known Fertilizers and invents new ones.
Dozens of different Fertilizers are known today. The most important of them are potassium, nitrogenous and phosphate Fertilizers, because potassium, nitrogen and phosphorus are the elements without which not a single plant can grow.