Chemical plant

“ Although the action occurring during the night is the reverse of that which takes place during the day, it is in no degree to be attributed to a re-oxidation of the carbon which had been deposited in the tissues of the plant. It appears, on the contrary, to be a purely mechanical, and not a chemical process. ”

“ Chemical analysis has shown that plants are composed of water, organic or combustible matters, and inorganic or mineral matters. Water constitutes by far the greater part of a living plant; a grass crop will contain about 75% of water, a turnip crop 89 or 90%. The organic or combustible matters are those which are lost, along with the water, when the plant is burnt; the inorganic or mineral matters are those which are left behind as an “ash” after the burning. The combustible matter is composed of six elements: carbon, hydrogen, oxygen, nitrogen, sulphur and a little phosphorus. ”

“ The chemical constitution of the vegetable kingdom yields to analysis only three or four ultimate elements, viz., oxygen, hydrogen, and carbon, and sometimes nitrogen. The most active agent in the process of decomposition is the oxygen contained in the dead plant, whether such decomposition proceed under the rapid influence of fermentation, or be produced more slowly by the operation of the law which renders decay the necessary consequence of organization. ”

“ Hence, reactions between organic compounds, even when they are in solution, proceed very slowly unless carried on at high temperatures, under increased pressure, or under the influence of some catalytic agent. Even under the stimulation of these reaction-accelerating agencies, most chemical changes in organic compounds when carried on in the laboratory, require several hours or even days and sometimes weeks, for their completion. But when similar reactions take place in living organisms, they proceed with velocities which resemble those of inorganic compounds in the laboratory. ”

“ So the synthesis of a single organic compound sufficed at a blow to break down the chemical barrier which the imagination of the fathers of the science had erected between animate and inanimate nature. Thenceforth the philosophical chemist would regard the plant and animal organisms as chemical laboratories in which conditions are peculiarly favorable for building up complex compounds of a few familiar elements, under the operation of universal chemical laws. ”

“ The mineral constituents of plants are all taken up by the roots in the form of solution, water being the great carrier by which plants are supplied.
The following substances are invariably present in all agricultural plants, and in many others, viz.: Potash, soda, lime, magnesia, oxide of iron, chlorine, sulphuric acid, phosphoric acid, silicic acid, and carbonic acid. The chemical composition of different specimens of the same plant is found to be quite uniform. ”

“ In many of the processes the materials do not appear to the naked eye after their introduction into the first plant unit, being fed by gravity or pressure from one enclosed apparatus to another. It would be absolutely essential for any inspection to conduct chemical tests at the different stages. ”

“ Nitrogen in a Usable Form necessary for Growth of Plants.—A chemical element needed by the plant to make protoplasm is nitrogen. The air can be proven by experiment to be made up of about four fifths nitrogen, but this element cannot be taken from either soil, water, or air in a pure state, but is usually obtained from the organic matter in the soil, where it exists with other substances in the form of nitrates. Ammonia and other organic compounds which contain nitrogen are changed by two groups of little plants called bacteria, first into nitrites and then nitrates. ”

“ In the leaf of every plant are thousands of little chemical laboratories; CO2 diffused in small quantities in the air passes, together with a very little H2O, into the leaf, usually from its under side, and is decomposed by the radiant energy of the sun. The C is built into the woody fiber of the tree, and the O is ready to be re-breathed or burned again. CO2 contributes to the growth of plants, O to that of animals ”

“ If such a plant is brought into the light, its dormant powers are awakened, and, instead of being little other than a sponge through which fluids circulate, it exerts most remarkable chemical powers; the carbonic acid of the air and water is decomposed; its charcoal is retained to add to the wood of the plant, and the oxygen is set free again to the atmosphere. ”

“ Not only is the quantity of valuable matters existing in the soluble state materially increased, whereby the dung is enabled to act with greater rapidity, but, owing to evaporation and the escape of carbonic acid, produced by the decomposition of the organic substances, the proportion of those constituents which are most important to the plant is increased. ”

“ Now, in order that a plant may grow, its four organic constituents must be absorbed by it, and that this absorption may take place, it is essential that they be presented to it in suitable forms. A seed may be planted in pure carbon, and supplied with unlimited quantities of hydrogen, nitrogen, oxygen, and inorganic substances, and it will not germinate; and a plant, when placed in similar circumstances, shows no disposition to increase, but rapidly languishes and dies. ”

“ Water, earth salts, and the gases—the raw materials which the plants suck up—are changed within the cells into starch and sugar, gum and woody fiber., albumen and wax, oil and resin, into powerful medicines and deadly poisons. The simplest plant possesses an art which the most skillful chemist has not been able to learn from it. It is true that the chemist can artificially prepare in his laboratory many of the substances which the plant-cell likewise produces ”

“ For we must never forget that all plants mainly grow, not, as most people suppose, from the earth, but from the air. They are for the most part mere masses of carbon-compounds, and the carbon in them comes from the carbonic acid diffused through the atmosphere around, and is separated by the sunlight acting in the leaves. There it mixes with small quantities of hydrogen and nitrogen brought by the roots from soil and water; and the starches or other bodies thus formed are then conveyed by the sap to the places where they will be required in the economy of the plant system. ”

“ The organic compounds required to extend the fabric, are formed by the plant, instead of being supplied from without. The tissues of the green surface of the stem and leaves have the peculiar power, when acted on by light, of generating, at the expense of carbonic acid, water and ammonia, with various ternary and quarternary organic compounds, such as chlorophyll, starch, oil and albumen. ”

“ His first publication on this subject was Die Chemie in ihrer Anwendung auf Agricultur und Physiologie in 1840, which was at once translated into English by Lyon Playfair. Rejecting the old notion that plants derive their nourishment from humus, he taught that they get carbon and nitrogen from the carbon dioxide and ammonia present in the atmosphere, these compounds being returned by them to the atmosphere by the processes of putrefaction and fermentation—which latter he regarded as essentially chemical in nature—while their potash, soda, lime, sulphur, phosphorus, &c., come from the soil. ”

“ Withdraw any one of these three from the world, and all vital phenomena come to an end. They are related to the protoplasm of the plant, as the protoplasm of the plant is to that of the animal. Carbon, hydrogen, oxygen, and nitrogen are all lifeless bodies. Of these, carbon and oxygen unite in certain proportions, and under certain conditions, to give rise to carbonic acid; hydrogen and oxygen produce water; nitrogen and hydrogen give rise to ammonia. ”

“ Many things, doubtless, you will say, since this precious liquid is the prime source of all that the plant contains in itself. If such is your thought, undeceive yourselves: ascending sap is little more than clear water, and often it is very difficult for science to prove beyond a doubt the presence in it of various substances in solution, so minute a fraction of the whole do they compose. Among these substances the most frequent are compounds of potash, of lime, of carbonic acid gas, traces of phosphates, and compounds of nitrogen or ammonia. ”

“ But this sliding scale of solid compounds, which we designate by the names given above, is not the only product of the natural and spontaneous distillation of plant tissue. Part of the original organic mass remains, though constantly wasting, to represent it; another part escapes, either completely oxidized as carbonic acid and water, or in a volatile or liquid form, still retaining its organic character, and destined to future oxidation, known as carbureted hydrogen, olefiant gas, petroleum, etc. ”

“ Oxygen exists in the air, and is directly absorbed both by the leaves and by the roots of plants; while nitrogen, though it forms a large part of the atmosphere, is not supposed to enter directly into plants in any considerable quantity.
The whole of the carbon and hydrogen, and the greater part of the oxygen and nitrogen also, enter into plants in a state of chemical combination with other substances; the carbon chiefly in the state of carbonic acid, and of certain other soluble compounds which exist in the soil ”

“ From the standpoint of the sum total of its activities, a green plant is essentially an absorber of solar energy and a synthetizer of organic substances. Each individual autotrophic plant takes up certain amounts of the anergic foods which are discussed in the preceding chapter and manufactures from them a great variety of complex organic compounds, using the energy of the sun's rays, absorbed by chlorophyll, as the source for the energy necessary to accomplish these synthetic reactions. ”

“ If certain functions are dependent for their very occurrence upon the presence of even minute traces of any element, then surely that element is as essentially a nutrient element, as vital to the well-being of the plant as is such an element as carbon or nitrogen or phosphorus, even though the latter occurs in far greater quantity. It is necessary that one should free one’s mind from the idea that the quantity of an element present in a plant is an index of its value to the plant. ”

“ And, as these small quantities of the more important substances are capable of supplying the wants of the plant, it must be obvious that a very small fraction of the silica, oxide of iron, and alumina, which the soils contain, would afford to it the whole quantity of these substances it requires, and that the remainder must have some other functions to perform.
The soil must be considered not merely as the source of the inorganic food of plants, for it has to act also as a support for them while growing, and to retain a sufficient quantity of moisture to support their life ”

“ A plant supplied with pure carbon, hydrogen, oxygen, and nitrogen, phosphorus, sulphur, and the like, would as infallibly die as the animal in his bath of smelling-salts, though it would be surrounded by all the constituents of protoplasm. Nor, indeed, need the process of simplification of vegetable food be carried so far as this, in order to arrive at the limit of the plant's thaumaturgy. Let water, carbonic acid, and all the other needful constituents be supplied except nitrogenous salts, and an ordinary plant will still be unable to manufacture protoplasm. ”

“ I need take no notice of the modifications derived from a mixture of animal matter in these experiments, as it is not my desire to enter into a discussion of the general question, but to state such chemical facts as arose in the experiments I undertook. And since it is certain that vegetables alone are competent to the production of bitumen, and that the geological history of coal does not justify a supposition that animals have been concerned in its production, it is perhaps unnecessary to investigate that question further. ”

“ When, on the other hand, one compound body is so changed as to be converted into two or more substances different from itself, it is decomposed. Carbon, hydrogen, &c., are chemically combined in the interior of the plant during the formation of wood: wood, again, is decomposed when by the vinegar-maker it is converted among other substances into charcoal and wood-vinegar, and the flour of grain when the brewer or distiller converts it into ardent spirits. ”

“ The primary purpose of the activities of a soil organism is to obtain energy and cell material for itself; any benefit to the plant is purely incidental. For cell material it must have nitrogen and phosphorus; here it competes with the plant. If it produces more ammonia than it utilises—in other words, if it is driven to nitrogen compounds for its energy, then the plant benefits. ”

“ The habitual use of chemical analyses of fertilizers is rendering nitrogen, potash, and phosphoric acid almost as familiar terms as air, soil, and water, and thus is contributing in no small degree to the education of farmers. ”

“ This supposition, which could only be sustained at a time when analysis was imperfect, has been long since disproved and abandoned, and it has been distinctly shown by repeated experiment that not only are these inorganic substances necessary to the plant, but that every one of them, however small its quantity, must be present if it is to grow luxuriantly and arrive at a healthy maturity. ”