In our article, we will consider the zones of the root structure, which allow it to carry out the most important functions in the plant body. The internal structure of this organ is distinguished by a clear differentiation, due to which the coordinated work of the whole organism is carried out.
What is root
The root is the axial underground organ of a plant. Depending on the features of the arrangement, the main, side and subordinate are distinguished. The first type is very simple to determine. The main root of a plant is always one. On it are lateral. Together they form a core root system. It is characteristic of all representatives of the class Dicotyledonous, including the well-known families of Rosaceae, Solanaceae, Astrovidae, Cabbage, Legumes, and others. The adventitious roots depart directly from the shoot . They grow in a bunch. Such a root system, which is called fibrous, have monocotyledonous plants: Cereals, Onions and Liliaceae.
Root functions
The main task of the underground organ is to fix the plant in the soil, provide it with water and solutions of mineral substances. Using the root, nitrogen, potassium, iron, magnesium, phosphorus, and other elements are absorbed from the soil. This process is called mineral nutrition. The resulting plant substances are used for self-synthesis of organic compounds.
The root and shoot perform their functions in close interconnection. An underground organ provides the plant with water with solutions of mineral substances. They come from the root to all parts of the shoot. This is an upward current of substances. In turn, as a result of photosynthesis, organic substances are formed in the leaves. They move from the shoot to the root, carrying a downward current.
In some cases, the zones of the root of the plants are modified to perform additional functions. For example, in radishes, turnips, carrots and beets, the underground organ thickens to store reserve substances. And ivy with the help of roots-trailers reliably clings to the support. Many parasitic plants are generally not capable of photosynthesis. The nutrition of such organisms occurs exclusively due to the root system. An example of this would be a plant - a parasite dodder. With its roots, it penetrates the cells of the host body, absorbing its juices.
Plant Root Zones
If you cut the underground organ along its axis, you can easily notice the root zone. All of them are specialized, with a clear relationship between the structural features and the functions performed. Zones are located in the following sequence: root cover, division, stretching, absorption, holding. Already only by name, one can guess what elements of tissues they consist of, and what their role in the life of plant organisms is. Let's consider each of them in more detail.
Root case
To penetrate deep into the soil, the root constantly grows at its apex. This function is carried out by the root dividing zone, which is covered by the root cap. It reliably protects the cells of the educational tissue from mechanical damage, prevents damage to the top of the underground organ during its penetration into the soil.
The root cap is formed by several layers of living cells of the integumentary tissue. They are not uniform in structure. So, the cells of the outer layer are constantly destroyed by contact with soil particles. Therefore, they require recovery. This process occurs due to cell division of the educational tissue from the inside. The root cap also plays the role of a kind of "navigator" for the underground organ of plants. Since it has the ability to perceive the force of gravity, this zone determines the direction of root growth in depth.
Meristem
The following is the portion of the root that combines the two zones: division and extension. Due to these structures, an increase in its size is carried out. Therefore, it is called the root growth zone. What structural features does each of them have?
The zone of division of the root is located behind the root cap. It is completely formed by educational tissue - meristem, the length of which does not exceed 3 mm. Its cells are small, tightly adjacent to each other, have thin walls. This zone has a unique ability. During its division, cells of any other tissues are formed. This is very important for the restoration of lost or damaged parts of the organs of the plant body.
Stretching zone
Beyond the meristem, the root growth zone continues with cells of a different type. They are constantly growing, lengthening, acquiring a fixed shape and size. This is a stretch zone. Its dimensions are also insignificant: only a few mm. Increasing in size, its cells advance the meristem with the root cover deeper. A stretch zone is also created by the educational tissue. Therefore, cells of any type can form here.
Root Suction Area
The following structure is more significant, occupying a plot of 5 to 20 mm. This is the root absorption zone. Its main function is the absorption of water with a solution of nutrients from the soil. This process is carried out using root hairs, which are outgrowths of cells of the integumentary tissue. Their length varies from a few millimeters to one centimeter. Sometimes this indicator exceeds the size of the cells themselves.
Root hairs are constantly renewed formations. They live up to 20 days, after which they die. New hairs are formed from cells that are located near the growth zone. At the same time, they disappear in the upper part. Therefore, it turns out that the absorption zone, as the root grows, sinks deeper into the soil.
Root hairs are very easy to damage. Therefore, during plant transplantation, it is recommended to transfer it together with the soil in which it grew before. These structures are quite numerous. On one square millimeter several hundred root hairs are formed. This significantly increases the absorption surface, which is several hundred times larger than the shoot area of the plant.
Side roots
The zone of the root, or lateral roots, is the largest. This is the area within which the underground organ thickens and branches. Here the lateral roots of the plant are formed. There are no root hairs in the conduction zone, therefore, the absorption of nutrients from the soil is not carried out. The root zone serves as a “transport route” from the absorption zone to the ground part of the plant.
Features of the internal structure
As you can see, all zones of the root are distinguished by a clear specialization. This also applies to the internal structure of the underground organ. On the cross section of the root in the absorption zone, several layers are clearly visible. Outside is a coverslip. It is represented by a single layer of living skin cells. They form the new root hairs.
Under the skin is the bark. These are several layers of the main fabric. Through them, solutions of mineral substances from root hairs move to the elements of the conductive tissue. The inner axial part of the root is occupied by the central cylinder. This structure consists of vessels and sieve tubes, as well as elements of mechanical and storage tissue. Around the central cylinder is a layer of cells of the educational tissue, from which the lateral roots are formed.
Methods of root system formation
People have long been using knowledge about the structure and physiology of the underground organ of plants in their economic activities. So, for the formation of additional roots developing in the surface layer of the soil, it is recommended to spud the plot and add soil to the base of shoots.
To increase the number of lateral roots, the picking method is used. It is carried out during transplanting seedlings in open ground. To do this, the tip of the main root is nipped off from the seedling, as a result of which the whole system becomes more branched. Lateral roots grow, which means that soil nutrition of plants is carried out more efficiently. In addition, during hilling and picking, their predominant amount develops in the upper soil layer, which is more fertile.
So, the root zones are sections of the axial underground organ of plants that are different in structural features. All of them are distinguished by narrow specialization, due to the peculiarities of their structure. The following areas are distinguished: root cap, division, growth, including stretching and absorption zones, and conducting.