Plant root

“ The fact of outstanding importance to everyone who really looks at most plants is that part of them are above ground and part below. This simple observation carries with it the recognition of a fundamental difference of plant structure, namely roots and stem. Most plants bear obvious leaves, and at some time in their life flowers, inevitably followed by fruits and seeds. The ideally perfect plant would consist, then, of root, stem, leaves, flowers, fruit, and seed. ”

“ Fig. 83-85. Forms of tap-root.
74. Fleshy Roots are those in which the root becomes a storehouse of nourishment. Typical roots of this kind are those of such biennials as the turnip and carrot; in which the food created in the first season's vegetation is accumulated, to be expended the next season in a vigorous growth and a rapid development of flowers, fruit, and seed. By the time the seed is matured the exhausted root dies, and with it the whole plant. ”

“ Being prepared now to find among plants many things which are like roots, yet are not; you may simplify and make fast your true idea of a root as a fibre or group of fibres, which fixes, animates, and partly feeds the leaf. Then practically, as you examine plants in detail, ask first respecting them: What kind of root have they? Is it large or small in proportion to their bulk, and why is it so? What soil does it like, and what properties does it acquire from it? The endeavour to answer these questions will soon lead you to a rational inquiry into the plant's history. ”

“ The roots grow here and there in search of food, often extending much farther in all directions than the spread of the top of the plant. Roots tend to spread farther in poor soil than in rich soil, for the same size of plant. The root has no such definite form as the stem has. Roots are usually very crooked, because they are constantly turned aside by obstacles. Examine roots in stony soil. ”

“ 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. ”

“ When a seed sprouts, the root, I have told you, goes down into the ground, while the stalk goes upward into the air. The root goes down because the food of the plant is in the ground. It is the business of the root to suck up this food, so that the plant may be nourished and grow. The root is, then, a sort of stomach to the plant. If it had no root it would not grow, any more than you would if you had no stomach to put your food in. ”

“ 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. ”

“ Thus, the root is necessary, not only to form a base to support the plant and to keep it upright, but to supply it with food; and nature has given it a tendency to bury itself in the ground, not only to enable the plant to take a firm hold of the soil, but to preserve the root in a fitting state for absorbing food, which it can only do when it is kept warm, moist, and secluded from the light. ”

“ 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. ”

“ Once it finds itself firmly rooted in the stem of its victim, it begins to grow vigorously. With every few inches of its growth it sends new roots deep into this stem. And when it feels quite at home, and perfectly sure of its board, it begins to wither away below, where it is joined to its earth root. Soon it breaks off entirely from this, and draws every bit of its nourishment from the plant or plants in which it is rooted. ”

“ The most prominent of these parts are root, stem, leaf, flower, fruit, and seed. Familiar plants differ wonderfully in size and shape,—from fragile mushrooms, delicate waterweeds and pond-scums, to floating leaves, soft grasses, coarse weeds, tall bushes, slender climbers, gigantic trees, and hanging moss.
The Stem Part.—In most plants there is a main central part or shaft on which the other or secondary parts are borne. This main part is the plant axis. Above ground, in most plants, the main plant axis bears the branches, leaves, and flowers; below ground, it bears the roots. ”

“ Few people who have studied the matter attentively but have arrived at the conclusion that those plants which we cultivate for their roots were not naturally endowed with the root portion of their structure either of the size or form which would now be considered as essential for a perfect crop plant. ”

“ Each little thread makes it just so much the more difficult to uproot the plant.
I think you know already that another use of the root is to obtain nourishment for the plant.
These thread-like roots, you notice, creep out on every side in their search for food and drink. The water they are able to suck in easily by means of tiny mouths, which we cannot see. But the plant needs a certain amount of earth food, which in its solid state could not slip down these root throats any more easily than a young baby could swallow a lump of sugar. ”

“ 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 ”

“ You know that the root does the drinking for the plant; and only the newest parts of the root, the fresh root tips, are really good for work of this sort. You [Pg 163] remember that the earth food is carried up the stem to the leaves in a watery broth; and that if the water supply should give out, the new plant cells would not get the broth which helps them to grow, and to put out other cells, and so to build up the plant. ”

“ The final causes of many of these facts are easy to comprehend: the reason why a root grows down into the earth, is for the purpose of obtaining that sustenance which is necessary for the growth of the plant of which it is a part; and stems grow upwards, and towards the light, because the influence of this element is necessary for the elaboration of the sap; as a result of which process, stems grow in thickness, roots in length, flowers are developed, and the proper juices of vegetables become formed. ”

“ When living tree seeds are exposed to proper amounts of moisture, warmth and air in a fertile soil, they will sprout and grow. A root develops which pushes its way down into the soil, while the leaf-bud of the plant, which springs from the other end of the seed, works its way upward toward the light and air. This leafy part of the seed finally forms the stem of the tree. But trees may produce plenty of seed and yet fail to maintain their proper proportion in the forest. ”

“ The root of a young plant grows downward into the soil under the influence of gravity. Its tip, which has to force its way through the rough material of sand and clay, is beautifully protected by a special root-cap, which covers the growing point as with a cushion. The surface of the root-cap is slimy, to aid it in slipping forward, and its cells, which are being worn away constantly, are replaced by the growth of the interior. ”

“ Such soils not only produce roots much more rapidly than the heavier soils, but produce a root that divides easier and to better advantage. But it is with the cultivation of the plant that we are most interested. ”

“ Some roots last one year, others two, and others, like the shrubs and trees which they produce, have an indefinite period of existence; but they all consist of a collection of fibres, composed of vascular and cellular tissues, without tracheæ, or breathing-vessels. The stem is the grand distributor of the nourishment taken by the roots to the various parts of the plant. The seat of its vitality is in the point or spot called the neck, which separates the stem from the root. If the root of a young plant be cut off, it will shoot afresh; if the stem be taken away it will be renewed. ”

“ These hairs are the feeding-organs of the roots, and they are formed only near the tips of the finest roots. You see that the large, coarse roots that you are familiar with have nothing to do with absorbing plant food from the soil. They serve merely to conduct the sap and nourishment from the root-hairs to the tree. ”

“ If the ground in old-established botanic gardens be dug much deeper than ordinary, it frequently happens that species which have been long lost are recovered, from their seeds being latent in the soil, as I have been assured by Mr. Fairbairn of Chelsea garden, and others.
The integuments of the seed, having fulfilled their destined office of protection, burst and decay. The young root is the first part of the infant plant that comes forth, and by an unerring law of Nature it is sent downwards, to seek out nourishment as well as to fix the plant to the ground. ”

“ Roots are most easily extricated from light soil, and with least fracture. They are large in proportion to stem in dry soil and climate, and when they are situated near the surface of the ground.—A healthy growing plant, of firm fibre, large root, and sturdy short stem of one leader and numerous feeders, is the great desideratum: a large root is the more desirable, as a considerable part of it is generally broken off in transplanting, rendering it disproportioned to the top, which, in consequence, either languishes, or receives deterring cropping. ”

“ Whilst the root, penetrating more deeply in the direction of the earth, spreads itself with uniformity, the plant elevates itself more and more into the light, and attains a more delicate and perfect organization ”

“ STEMS AND SEED LEAVES The smaller plants usually have green stems. The larger ones have brown, woody stems, such as you see in bushes and trees; for the trunk of the biggest tree in the world is nothing but a great stem.
The delicate green stems die down to the ground during the cold winter. Sometimes the whole plant [Pg 120] dies, the root below as well as the stem above ground. But often the root (or what we usually call the root) lives, and sends up a fresh stem the next year. ”

“ Plants in their perfect form consist of four principal parts,—the Root, Stem, Leaf, and Flower. It is true that the stem and flower are parts, or remnants, or altered states, of the leaves; and that, speaking with close accuracy, we might say, a perfect plant consists of leaf and root. ”

“ The entire mass of roots of any plant is called its root system. The root system may be annual, biennial or perennial, herbaceous or woody, deep or shallow, large or small.
Kinds of Roots.—A strong leading central root, which runs directly downwards, is a tap-root. The tap-root forms [33] an axis from which the side roots may branch. The side or spreading roots are usually smaller. Plants that have such a root system are said to be tap-rooted. Examples are red clover, alfalfa, beet, turnip, radish, burdock, dandelion, hickory (Figs. 32, 33) . ”

“ It is a very good thing for us that the plants are held fast by their roots.
Well, the root hairs do the most important work of the plant after all. It is they who go poking their noses through the soil, and with their cells draw up water and potash and nitrogen and sulphur and iron and many other things which have become dissolved in the water. They are even able to dissolve rocks and such delicacies for themselves. ”

“ This small, tough, and pungent root, however, when the plant is transferred from its native woods to a deep, rich soil, and having sufficient space given to it, soon exhibits a tendency to rapid development. ”

“ Many plants are grown from roots or bulbs, but a greater majority by far come from seed. Tulips and lilies, onions and potatoes, are all instances of plants grown from roots which sprout out from the old ones. The root is in every case the beginning, the seed the ending, of the life of a plant. ”

“ The protoplasmic lining of the cell wall is such a membrane. The soil water being a weaker solution than the sap in the roots, the flow is into the root. A strong fertilizer sometimes causes a plant to wither, or “burns it.” Explain.
Structure of Roots.—The root that grows from the lower end of the caulicle is the first or primary root. Secondary roots branch from the primary root. Branches of secondary roots are sometimes called tertiary roots. Do the secondary roots grow from the cortex, or from the central cylinder of the primary root? ”