Plant growth

“ There are some leaves which, if hung up, produce other leaves and little plants from their edges; and everybody must have noticed how the common stone-crops will grow and root from any little scrap or fragment or bit that falls by accident upon damp soil. If we go down to the very bottom of the matter, it is clear that the plant tends to reproduce itself, whole and complete, from every part of itself—tends to increase in its own shape, and repeat itself anew in fresh leaves and branches. Why is this? Well, such a tendency results necessarily from the fundamental principle of cell-growth. ”

“ It is apparent from the above brief discussions that the rôle of the different soil elements as plant food, and their relations to the complex processes which constitute plant growth, afford an interesting and promising field for further study. ”

“ Active motion, local and general, though usually of relatively small amount, accompanies all plant-growth. Throughout root, stem, leaf, and flower transference of material is going forward vigorously. The root hairs and stomata are working at high pressure; the chlorophyll never ceases its activities while daylight lasts. Externally, the growing branches, leaves, and flowers also display incessant movement, sweeping the air in small circles, or in the case of climbing plants in curves of considerable amplitude. ”

“ When I plant my crops I give them such attention that it seems they have every confidence that I will remove all obstructions to hinder their growth, and the young and tender plants seem to avail themselves of the situation and spring up as by magic. ”

“ The plant is thus provided with a mechanism for adapting its possibilities of growth to the supply of growth-promoting material which is available to it.
Many other plants produce far more buds than ever develop into growing tissues, and buds which, under normal conditions, remain dormant, under altered conditions start into growth and so provide for an "adaptation" of the total mass of the growing plant to correspond with the altered conditions of growth. ”

“ In other words, the plant physiologist defines rest in living plants as that period in which their buds will not open and grow even though the temperature, moisture, and other external environmental conditions are highly suitable for growth. ”

“ The plant must have good soil, water and air and sun, care and pruning, in order to grow, but it grows of itself, gains strength by proper nourishment. The [Pg 84] aggregation of material about the plant does not constitute its growth. The plant must assimilate; the juices of life must flow through it. ”

“ If you repeat this often with many plants you will find that these are the actively growing parts of the stems and roots; the individual leaves, of course, are also growing. Thus we see that growth is not a simple stretching of the whole, but that there are two definite regions where it is specially active. That of the stem and first root carry on the growth in opposite directions, as we noticed before (see p. 11) , the normal stem growing up into the air and the root down into the soil. ”

“ When the plant is young, its chief object is to grow; it must acquire size and development, to enable it to produce and bear up the enormous crop it is destined one day to yield. Hence in the early years of a tree there is none, or very little of this transformation of the buds, which are all of the pointed character, and when excited into growth, they all produce shoots and leaves only, which result in the formation of an increase of the woody fabric, that we call the tree. ”

“ In the first of these, for which we will use the term "physiological adaptation," the species of plant simply acquires the ability to exist and grow normally under conditions which formerly inhibited its growth. Thus, we may speak of the phenomena mentioned above as "acclimatization" as the physiological adaptation of the crop to the new conditions of growth. ”

“ As the kernel swells with heat and moisture, its starches and albumens get oxidised and produce the motions and rearrangements of particles that result in the growth of a new plant. First a little head rises towards the sunlight and a little root pushes downward towards the moist soil beneath. The business of the root is to collect water for the circulating medium—the sap or blood of the plant—as well as a few mineral matters required for its stem and cells ”

“ On this power of expansion in the air, by which the juices of plants are quickened and strengthened, he builds his mechanical theory of growth, according to which the plastic parts of the plant assume a state of tension, and as the air enters into combination with other substances and so becomes fixed, warmth and movement are excited, and these make the particles of sap assume by degrees a form and shape. ”

“ Corresponding to the invariable order of growth and progression in a plant as represented by the seed (enclosing the life and unifying principle) stem, branches, leaves and fruit, is the order of ascent, or perhaps it should be descent, by which Art takes concrete form. First there is the initial flow, then the root-point answering to the seed or unifying principle, then follow in turn, lines, planes, and solids. The fruit and the solids appear to be the culmination of the initial flow, but really they contain a potential power of growth in a realizable fluid motion. ”

“ The reproduction of the higher plants takes place either asexually by the formation of buds or organs answering thereto, or sexually by the production of an embryo plant within the seed. The conditions requisite for the growth, development and reproduction of plants are, in general terms, exposure, at the proper time, to suitable amounts of light, heat and moisture, and a due supply of appropriate food. ”

“ The tremendous energy of growth covers bark and branches with creeping plants innumerable, with a profusion of moss, liverworts, and ferns such as we cannot imagine from our own experiences in this country. So the roots of our orchid find on the branches rich leaf-mould, 332 and it lives happily and contentedly on the salts and moisture accumulated by the mosses and other plants. ”

“ We are not in the habit of treating dry seeds as though they were alive; beans are stored away in sacks all the winter and may be left for months in dry cellars, and the precious seeds which will give us our beautiful flowers in the summer are put away in boxes through the winter. Yet you know that if you place seeds in the earth and keep them warm and moist, little plants will come up and will grow. What gives them the power of growth which is not possessed by the stones and earth around them? ”

“ He notes the germination of the plant seed and its early growth, step by step approaching a stage of maturity; it blossoms, produces seed, and if it is an annual plant, withers and dies. If it is a perennial plant its leaves only, wither and die at the approach of winter, the plant passing into a resting stage from which it awakes the following spring to repeat again its annual cycle. ”

“ These changes, however, are not to be made in any ordinary plant, either by stimulating manures or any other kind of artificial culture; but can only be produced by observing a tendency to aberrations of growth in certain individuals of a genus, and carefully selecting the seed from those plants most inclined to exhibit such unusual or monstrous kind of growth. ”

“ The relatively rigid nature of the plant cell-wall, and the attenuated inorganic food-supply of plants, make possible and necessary a form of growth in which the greatest surface is exposed to the exterior, and thus the plant body is composed of flattened laminae and elongated branching growths. ”

“ We have considered the various chemical changes which take place within the growing plant, during the formation of its woody stem, the blossoming of its flower, and the ripening of its seed or fruit,—and have traced the further changes it undergoes, when, the functions of its short life being discharged, it hastens to serve other purposes, by mingling with the soil, and supplying food to new races. ”

“ In planting, a little extra care in the disposition of the roots in the soil will be well repaid, for plants merely thrust into the ground cannot develop that robust root growth on which the future of the crop largely depends. ”

“ They never grow into branches, but detach themselves when full grown, fall to the ground, and take root there to form new plants.
Fig. 110. Bulblets in the axils of leaves of a Tiger Lily.
117. Consolidated Vegetation. An ordinary herb, shrub, or tree is evidently constructed on the plan developing an extensive surface. In fleshy rootstocks, tubers, corms, and bulbs, the more enduring portion of the plant is concentrated, and reduced for the time of struggle (as against drought, heat, or cold) to a small amount of exposed surface, and this mostly sheltered in the soil. ”

“ The principal determining cause seems to be the influence of light upon the germination of the seeds and the growth of the young tree. In a forest of firs, for instance, the distribution of the light and shade, to the influence of which seeds and shoots are exposed, is by no means the same as in a wood of beeches or of oaks, and hence the growth of different species will be stimulated in the two forests. ”

“ This is the first process, and, properly speaking, is all that belongs to the springing or elongation of trees; and in many plants, that is, all those which are annual or deciduous, there is no other process; the plant absorbs juices from the earth, and in proportion to the quantity of these juices increases in size: it expands its blossoms, perfects its fruit, and when the ground is incapable by drought or frost of yielding any more moisture, or when the vessels of the plant are not able to draw it up, the plant perishes. ”

“ When, however, plants are expenders, namely, during their germination and first stages of growth, their degrees of growth are determined by their amounts of vital capital. It is because the young tree commences life with a ready-formed embryo and store of food sufficient to last for some time, that it is enabled to strike root and lift its head above the surrounding herbage. ”

“ Let us fix our attention on a single plant. It has a certain amount of root pasturage and space in which to grow. Since it is not permitted to produce an indefinite number of young plants, it begins to develop itself. The soil is rich, the roots are busy, and there must be an outlet. The original plant cannot form others, and therefore begins to produce fruit-crowns for the coming year. All the sap, all the increasing power of root and foliage, are directed to preparation for fruit. ”

“ The shapes of plants will depend on the character [161] of the seed, while the flower and fruit is dependent on the water and nutritive material. In all animals the first process of maturation and concoction of the nutritive liquids [162] takes place within the animal; there is no exception to this rule. But in plants the first concoction and maturation takes place in [163] the nutritive material. Every tree continues to grow up, until its growth is completed and it dies. ”

“ If I were asked to sum up the most important result of the numerous advances made during the past decade in agriculture and forestry, I should reply—the clearer and wider recognition of the fact that the plant itself is the centre of the subject, and not the soil, climate, season, or other factors of its environment. Until comparatively recent times it was the habit of farmers, foresters, planters, and gardeners, all the world over, to look upon the plant as a mere item or as a mysterious if important one in their calculations, and to regard the soil as the chief factor in their studies. ”

“ Just as that small portion of nourishing matter which is deposited in the seed feeds the embryo when it germinates, so the much larger portion deposited in the tuber nourishes its buds, or eyes, when they likewise grow, the next spring, into new plants. And the great supply enables them to shoot with a greater vigor at the beginning, and to produce a greater amount of vegetation than the seedling plant could do in the same space of time ”

“ In its simplest form fertilization in flowerless plants is characterized by one or all these processes, as it is in the ferns, while in the flowering plants, the act is accomplished by processes, discussed previously, which, in the development of the plant kingdom, mark a period only comparable, in the history of man, to such tremendous achievements as the acquirement of speech or the ability to make a fire. ”

“ It is easy to understand how an alteration of the conditions under which plants grow influences very materially the struggle we have been alluding to. A very slight change in climatal conditions—produced, for instance, by the growth of sheltering trees, or by the drainage of the soil—may be followed by the growth of quite a different set of plants from those that occupied the ground previously. The altered conditions have been advantageous to the one and disadvantageous to the other set of plants. ”

“ Horticulture, apart from the mechanical details connected with the maintenance of a garden and its appurtenances, may be considered as the application of the principles of plant physiology to the cultivation of plants from all parts of the globe, and from various altitudes, soils and situations. The lessons derived from the abstract principles enunciated by the physiologist, the chemist and the physicist require, however, to be modified to suit the special circumstances of plants under cultivation. ”