Root hairs are ... Functions of root hairs

Complex reactions of metabolism in plants are explained by the special structure of parts of their body: root, stem, leaves, called vegetative organs. They are responsible for the processes of photosynthesis, transpiration, osmosis. In this paper, we will study the structure and functions of plant elements such as root hairs. These are important structures that determine the absorption of water and mineral salts from the soil.

Root - vegetative organ of seed plants

The underground part of gymnosperms and flowering plants is represented by two types of root system: rod and fibrous. They consist of the main, lateral, accessory (in monocotyledonous plants) roots and a large number of small structures, called - root hairs.

These are the outgrowths represented by single cells of the epibblem (rhizoderm). They are called "trioblasts." Being a support and fulfilling the functions of storing organic substances, absorption and reproduction (the so-called root offshoots in cherries, willows), the root mediates also indirectly in such metabolic processes as transpiration, respiration, and photosynthesis.

Suction zone

The main root has a complex anatomical structure, and its various parts perform many functions. In connection with this, they are usually called zones. Based on the function of the root hairs (above the stretch area entering the growth zone), and a cluster of outgrowths of the integumentary tissue is located. This area is called the suction zone. It is from one to three centimeters. In this area can be located from 200 to 1500 and more elongated epibblem cells. They do not live long: from several hours to 20 days, and then die. At the same time, new structures are formed from the rhizoderm. The cell of the root hair, in contact with the soil, is capable of sucking water molecules and dissolved salts from it in the form of sodium, chlorine, magnesium, acid residues of nitrate, nitrite and phosphate acids.

Epiphblem and features of its structure

This plant tissue belongs to the group of primary meristems. By participating in division, its cells provide the formation of such elements as root hairs. This occurs in the outer layer of the educational tissue of the root - phallogen. The rhizoderm formed during the growing season dies off. In its place, young cells of periderm are formed - a secondary integumentary tissue that is incapable of absorbing soil solutions. A new root hair, the function of which is the absorption of water and mineral salts, is formed from the overlying part of the epilblem.

Functions of root hairs

These structures are formed from protrusions of the rhizoderm and represent single cells of the primary meristem, capable of absorbing the soil solution. Over time, they stretch, and the cell membrane becomes able to flow inside both hypotonic and highly concentrated solutions of salts. When mineral fertilizers, for example, nitrogen and potassium fertilizers are introduced, the content of ammonium, potassium, and nitrate ions increases in the soil. This occurs in the spring, as it is the best time to apply fertilizers of this type. The soil solution containing the above listed species of ions penetrates into the cytoplasm of the trichoblast by passive diffusion.

Autumn application of phosphorus fertilizers, which require more time for dissolution, causes the absorption of acidic residues of phosphate and metaphosphoric acids by the root hairs of ions. With the onset of sap movement in late February - early March, almost the entire volume of the cells of the rhizoderm is filled with vacuoles, the nucleus is displaced to the apex of the root hair. The cell itself is capable of secreting molecules of organic acids: oxalic, apple. They dissolve humus particles, enhancing the absorption process. Formation of root hairs occurs quickly enough. Despite a short life, they are able to absorb large amounts of soil solution. For example, in a tree plant, the suction area is about 120 to 640 m ² .

What are trioblasts?

Previously, we studied the features of the structure and functions of the primary tissue of the plant cover. It consists of one layer of cells and is called an epilblem, located on young lateral roots, growing from the main or accessory roots. Root hairs are the outgrowths of the integumentary tissue, which are strongly elongated structures. It must be remembered that all the epileptic cells are polypotent, that is, they are capable of forming root hairs. But they are formed only from trioblasts - protrusions of epibles, having the form of microscopic tubercles.

The integumentary tissue responsible for the formation of trioblasts has cytological features of the structure: thus, its cells lack a cuticle and a thick cellulose wall. In the cytoplasm there is a large number of organelles synthesizing ATP molecules, mitochondria. They are necessary, since the absorption of water and mineral salts requires energy. Trichoblasts also do not have stomata - elements of the integumentary tissue, responsible for the processes of respiration of the plant and transpiration - the evaporation of water.

How solutions of salts penetrate into the roots of plants

Trichoblast and the root hair formed from it, the function of which is the absorption of water and mineral salts from the soil, can be considered an osmotic system. The absence of a rigid cell wall and the elasticity of the membrane facilitates the transport of molecules from the external environment into the cytoplasm. In special organelles of the root hair - vacuoles, hypertensive solutions of glucose, fructose, apple, citric and oxalic acids accumulate.

Both the membrane and the tonoplast cells have selective semipermeability. Therefore, the soil solution, being less concentrated than the cell sap, penetrates the roots of the root hair according to the laws of osmosis. The water potential of solutions coming from the soil is higher than this index in the tonoplast, and the osmotic potential is lower. Water and mineral salts are transported from the root hair cell to the xylem. It is a conducting tissue that forms the vessels of plants - trachea or tracheids. On them, the soil solution moves up the stalk to the leaves and other parts of the plant.

Picks and its meaning

To increase the suction area of the root system, it is necessary to increase the number of lateral roots. Their epilobium containing trichoblasts, and will form additional root hairs. To do this, use the mechanical method of plucking the top of the root, destroying the fission zone located above the root case. It's called a picks. This method stimulates the growth of the lateral parts, on which a large number of root hairs develops. In this case, the growth of the main root is stopped in length. The large area of the suction zone positively affects the growth and development of the plant, increasing its yield and vitality.

In this article, we studied the features of the structure of the root absorption zone of angiosperms, and also found out what function the root hair, developing from the epilblem, performs.