September 2, 2012

Roots ~~ 1966 GSN

(Mrs. John's note: The intent is to represent the author's intent entirely and the original wording remains intact, as published in the magazine.  It is hoped that all will read the article to enjoy and learn, regardless of personal convictions.)
Wondrously Contrived
Lucile C. Rainsberger
May/June 1966 Gesneriad SaintPaulia News, pgs 46 - 48
It has been said that if you will give your attention to producing optimum growing conditions for the root of a plant, the top will take care of itself. This is true for the most part. Certainly we must stake leaves at times in order that they may grow in a symmetrical fashion. They must also be guarded against fungus and insect attacks. The plant must receive enough light to set buds, but not so much that the foliage is damaged. General health of plant, gloss and sheen of leaf, size of blossom to the limit of its potentiality comes through the root system. You may have seen African Violets with wide leaf spread, seemingly in excellent growing condition, which with an accidental pull, lifted off roots that had rotted away. It is sometimes surprising how a very poor root system will sustain a large top. But this cannot go on. Notice these plants. They do give indications of trouble to the discerning eye. One of the first of these is the diminishing of flower bud formation and the fact that when they do bloom, the blossoms are smaller than they should be for the variety. The root system is unseen and therefore easily forgotten, but if we would have first quality plants, whether they be African Violets or trees in the yard, or anything in between, look to the health of the root system.
The root performs certain important functions, that of anchoring the plant so that the top is supported and that of absorbing water and plant nutrients from the soil. In addition roots usually store a certain amount of food, at least for a short time. Some, such as sugar beets and carrots, have as their special purpose this storage of food. Roots also conduct water and mineral salts absorbed from the soil and foods that may be stored in the roots to the stem and leaves and any other organs of the plant. In turn, food manufactured by the leaves is conducted to the roots, even to the tiniest and furthest root tips so that they may have the materials upon which they depend in order to carry on life processes. The shoot system or leafy part of the plant is completely dependent upon the root and in turn the root system is completely dependent upon the shoot system. If there is anything in growing conditions that affects one, the other is affected, either favorably or adversely. In a normal, healthy plant one balances the other. It is particularly important that the total leaf surface which is exposed to the light which supplies energy for the production of carbohydrates balances the total root system in contact with the soil from which is absorbed water and mineral nutrients. A number of things can affect this balance:
1. Keeping a soil waterlogged so that oxygen is excluded will result in root injury and death.
2. Allowing a potted plant to dry out so that the plant wilts not only results in root injury and death, but prevents absorption of water and soil nutrients which must be in solution for plant use.
3. Roots may be destroyed by careless transplanting methods.
4. Either root or shoot growth may be seriously injured by insect pests or fungus disorders, thus creating an imbalance.
Root Structure and Balance
Because it has been stated that there must be a balance between the root and shoot systems does not necessarily mean that the quantity of roots will equal the quantity of shoots. This usually is not so. Investigation into the root systems of a number of plants has revealed the great quantity of roots in relation to top growth. This is normal for the well grown plant and in this case the two can be said to be in balance. For example, in the case of a sugar beet, the top is not extensive yet the root of a mature plant at the end of its growing season has been found to be five to six feet in length and have a lateral spread of as much as six feet in diameter.
A root is made in a most marvelous way. Its study reveals that only a master mind could contrive it in all its complexity and perfection. If we study a tiny root mounted on a glass slide, the most obvious fact apparent at first glance is that it is entirely divided into a great number of small squares and oblongs, but as these appear to have depth as well as length and width, they are really minute boxes or compartments. We call them cells. Over the extreme tip of the root there is a cap also made of cells. This root cap serves a very important purpose. It protects the growing point of the root as it is pushed through the soil. Without its protection the delicate tip would be injured as it is pushed against the sand and pebbles and other obstacles in its course. Cells for the replacement of the root cap are quickly worn away and are supllied by the root tip. So also are cells for the elongation of the root itself. This adds length to the root but the section of rapid elongation is just back of this growing tip where the cells are rapidly dividing. Here most of the cells are not dividing but are elongating thus pushing the root along into a new area of soil. Back of this region of elongation is the root-hair zone. Here the elongation of cells does not occur or delicate root hairs wrapped around soil particles would be torn loose. The root-hair is a lateral outgrowth of an epidermal cell and projects sideways from the root to a maximum length of about one-half inch. It originates as a slender tube but may be greatly distorted as it searches for moisture by growing between and around soil particles. The walls are very thin so that water and mineral elements in solution, known as solutes, move readily to the interior core. Their extreme delicacy makes it almost impossible to remove a plant from the soil without destroying most of them unless the plant is carefully removed with a good ball of earth. Although the root does have the ability to develop new root tips, the plant will suffer less transplanting shock if the roots are not badly disturbed.
As the root tip grows forward, new root-hairs are produced. Older root-hairs which have absorbed all available moisture collapse and die at about the same rate that new ones are produced. Usually their period of activity is limited to a few days.
And so it goes, a seemingly never-ending process. The growing point of the root does not become appreciably larger in spite of the fact that cell division is constantly taking place. These replace worn-out cap cells or add to the length of the root. A root increases in length only near the tip, but not exactly at the tip. Division of cells becomes rarer and stops altogether finally as the cells become older and larger. Here other changes take place, changes exceedingly complex and of the utmost importance. They are transformed into various types of cells each with a special purpose to perform.
Have you ever noticed that a root does not grow upwards? No matter how careless you may have been in arranging the roots of a newly potted plant, they will soon thereafter be found growing downward. This is partially explained by the influence of gravity, but not entirely. The root can not bend down in all portions of its length but in only one which is just behind the growing tip of the root, the portion we call the section of elongation. In the growing tip there is produced a minute but powerful substance called auxin. It is this which regulates the direction in which the root grows. Remember it is the elongation of cells that pushes the root through the soil. If it is growing directly downward auxin will be deposited equally on all sides of the elongating cell. If not, the auxin will be deposited on one side. Growth will be retarded and the cell will bend downward. The bending is caused by inequality in the elongation of the two sides of the root. After the cells have finished their elongation and become mature, bending can no longer take place. If there is need for bending of the root again, it will have to take place farther along in the section of the root back of the growing tip where young cells are rapidly elongating.

Water and Nourishment
Water moves upward through the root and into the stems and leaves of the plant, not through living cells but through long narrow passages, or tubes, which were once cells, one on top of another. Now, no longer alive, they have only their walls intact. These tubes form part of what is known as the conductive sys.tern of the plant. Water, at times, moves very rapidly from the soil by way of the root system. How rapidly it moves depends largely upon the rate at which water vapor is given off by the leaves. If plants were transparent and the water within colored, we would be astounded at the rapidity of movement we could observe. The large quantities of water moved through the plant body and evaporated from the leaves must be continually replaced if the plant is to live.
Just as water is carried from the root to the shoot system of the plant, food produced in the leaves is carried downward by means of special ducts in the stems and roots to all portions of the root system, even to the most removed growing tip. It is in this way they are nourished so that they are able to carry on their own special work. These ducts are usually found alongside the water carrying tubes.
This then is a root, a complex structure admirably suited to the work it has to do. It has been wondrously contrived. Water passage channels, strengthened by woody fiber, are arranged precisely according to the function they are to perform. In the root they are situated near the center forming a solid tough core like a rope so that it cannot be easily broken. Indeed, the life of the plant depends upon this. In the stem through which the water continues to be carried, the water channels are grouped in bundles near the surface. Every builder knows that to get the most strength in a pillar from a number of rods, he must place them as far from the center as possible. The Master Builder already knew this when the world began and so arranged the stiffening elements in the walls of conductive channels so that they would remain erect. Man who has studied Nature has found many ideas and truths which he has appropriated to work for him. Ideas which we consider modern in the architecture of today have been discovered by man in his study of the work of the all-wise and all-perfect Master Builder who conceived them in the beginning of time.

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