Almost everywhere the surface of the land is covered with plants, if they have not been removed by man; and even where this has been done man has usually introduced other plants to take the place of ‘those he has removed. In countries with abundant rainfall they hide the earth so complete that the landscape is almost wholly green… The bare rocks of either dry or moist countries are usually partly covered with the plants. In the waters of oceans, plants are also found in great abundance
Why should we Know about plants?
We are indebted to plants for our very existence. Green plants are the only mechanisms which can convert the raw, inorganic materials of ail and soil into complex, organic compound called foods, which are necessary for the existence of all animal life. Al! And the food we eat comes directly or indirectly from plants.
We get from the plants other necessities of our existence
Fibers for clothing, timber for shelter, drugs for our ailments, etc., —coal, paper, spices, perfumes, rubber tires for automobiles. Thus, one comes to realize magnitude of his indebtedness and significance of plaits in scheme of Nature, to appreciate the incinerates and ceaseless activities.
A liberal and balanced education is enriched by a study of plants. Education is frequently defined in terms of its desired results: the most satisfying and the most advantageous adjustment of one’s environment. The study of pant is an essential feature of effective education. In man’s environment there are two dominant, omnipresent entities-the the green vegetation cover of the earth and the Sky. The appreciation of artistic and literary work is frequently enhanced by some acquaintance with the living plants. For an intelligent appreciation of most of the phenomena which conduce not only to our maintenance of food and clothing but also to our comfort, health and aesthetic or purely intellectual pleasures, a study of plants is necessary.
Apart from its uses as training in observation and in scientific principles, the study of plants opens up a wide field of interest for an’ intelligent student.
There are philosophical rewards in the study of plants. The appreciation of the beauties of flowers, of forest, and all other aspects of plant life is sharpened and amplified by knowledge of the myriad activities which occur behind the stage of Nature and which is apparent only to those who seek them out. Further, the realization of the unifying principles – of plant and animal development and behavior, the awareness of the order and magnificent design underlying the growth and structure of plants and the discovery of the sensitive balances and counterbalances regulating the lives of all organisms, contribute to the unfolding of a sane and appreciative philosophy of life and of man’s place in nature’s economy.
Those who intend to embark upon professional careers in the applied plant Sciences-forestry, horticulture, plant breeding, soil conservation, knowledge of plants.
Variety among plants
The Plant-covering is not everywhere the same. Instead there is infinite variety, and at first sight there seems to be little System or order. The plants however, do not grow altogether at random. Each kind of plant requires for its growth certain conditions that may be partly or entirely different from the conditions required by other plants. For this reason any ‘place in which the soil, moisture, temperature, and other conditions are favorable to one or a few kinds of plants is likely to be an unfavorable place for certain Other plants. Thus the hilltop which efforts just the right conditions for the growth of oak and hickory trees is not equally favorable to the growth of elm or willow, and these are not usually found there.
Plants which can find Suitable conditions for their growth at the same place are likely to be found together. A group of plants which are commonly associated in this way is known as a plant association. There is much kind of plants association and these constitute an important subject of study. Those types of plant association in which tress are most conspicuous part are known as forests. There are other types in which grasses are more important and they are known as grasslands and meadows. Such societies imprint their characters on the landscape and ordinary language recognizes their importance in the topography of the countryside.
Geographical changes of plants
Extensive geographical and climatic changes from tropical heat to arctic cold eave been and are taking place on our earth. They have converted dry lands into sea-beds, and up heaved the bottom of the sea to form new dry lands. These climatically and physio graphical changes which take ages to come about, have had influence upon terrestrial floras. As the temperature changed and became, say, colder, one by one the warmth-loving plants died out until only a few were left; and when warmth returned. ‘Flora of warm regions returned.
Darwin made a special mention of these floral migrations one in one place after describing the close of Glacial period (epoch in the history of the earth, when vast portions of its surface were covered by ice probably 5,000 ft. thick) said: “As the warmth returned, the Arctic form would retreat north-wards, closely followed up in their retreat by the productions of the more temperate regions, and as the snow melted from the bases of the mountains, the Arctic forms would seize on the cleared and thawed ground, always ascend nag, as the warmth increased and the snow still further disappeared, higher and higher, whilst their brethren were pursuing their northern journey. Hence when the warmth had fully returned, the same species which had lately lived together on the European and North American lowlands,) would again be found in the’ Arctic regions of the Old and New Worlds, and on many isolated mountain summits far distant from each other.
Thus, we can understand the identity of many plants at points as immediately remote as the mountains of the United States and those of Europe. We can thus also understand the fact that the Alpine plants of each mountain range are more especially related to the Arctic form living due north, or nearly due north of them; for the first migration when the cold came on, and the re-migration on the returning warmth, would generally have been due south and north. The Alpine plants, for example, of Scotland, as remarked by Mr. H. C. Watson and those of Pyrenees as remarked by Raymond, are. More especially allied to the plants of northern
Scandinavia; those of the United States to Labrador; and those of the mountains of Siberia to the Arctic regions of that Country.”
The vegetable kingdom has had its ebbs and flows, its developments and degeneration. According to Mr. C. E. Taylor, the story of the life of plants is one nearly analogous to that of the men full of failures and successes, of ambitions, efforts and degeneration ending in extinction! The path of human history is thickly strewn with projects and follies, and the strata of the earth’s crust are equally abundant in the refrains of fossil plants belonging to genera no longer existing, showing us that the pedigree of the vegetable kingdom has suffered the same incidents as that of humanity.
In each case out of the weakness has evolved strength. The extinct types of plants served as platform on which more highly organized forms could be evolved—the follies of mankind have been the means of developing higher wisdom and prudence; Every generation, both in plants and man, has originated new character and unexpected habits.
A plant has need for food as we have, and in addition it has the power of making its food supply from such simple substances as carbon dioxide, water and other compounds. If t plant is not interfered with, the food which it manufactures commonly is used by it and for its own purposes.
For instance, a part of our food is commonly composed of starch from wheat grains, but if the wheat had not been disturbed, the grains would have fallen to the ground, where under favorable conditions they would have started to grow in new wheat plants. The young plants would have used the, food that was stored tip iii the grains.
Just as in man so in plants, food supply is needed not only to replenish waste but also for the growth of plants. Both the living protoplasm and the cell walls must be built up from food materials.
The food substances required
The actual food sub substances which living things use are limited. Protoplasm is a mixture of certain chemical substances called proteins and a solution of various salts in water, together with small quantities of the substances related to fats and sugar. As the source of energy, the substance usually used is ‘sugar, though fats and even proteins may be used at times. The main food requirements of all living things are, therefore, essentially the same—proteins, salts and water for growth, with sugar (and fats in some cases) for energy.
The use of food plants
If food, which is stored, is not used by men or removed in some other way, the plant will use it in its processes of growth. Take the case of beans which contain much protein material, and this is n an insoluble form, If a bean is planted and starts to grow, the protein grains in the bean will be digested by the aid of an enzyme and dissolved after which they may be carried to the growing parts, where the protein material will form additional living protein protoplasm.
This is a wonderful process. The digested and dissolved proteins are dead materials, but the protoplasm which is formed from them is a living substance. Therefore, a dead material has become a living one. Proteins – are the only materials in which life may exist, and the only known way by which non-living protein may become haying material by uniting with some already living substance and thus becoming part of it. This process whereby non-living protein material unites with the living protoplasm and thus becomes living material is called assimilation a process the exact nature of which is not known.
Precisely the same thing happens in our bodies when the digested food is dissolved, carried through the body in the blood and assimilated by the cells.