Like animals, various tissues are present in the bodies of plants. They are used to build organs, which, in turn, form systems. The structural unit as a whole is still the same - the cell.
However, the tissues of plants and animals differ in structure and in function. Therefore, we will try to understand what these structures are among the representatives of the flora. In more detail, consider what is the mechanical tissue of plants.
Plant tissue
In total, 6 groups of tissues in the plant organism can be distinguished.
- Educational includes wound, apical, lateral and intercalary types. Designed to restore the structure of plants, various types of growth, takes part in the formation of other tissues, forms new cells. Depending on the function performed, it becomes clear where the sites with the educational tissue will be localized : petioles of leaves, internodes, root tip, upper part of the stem.
- The main one consists of different types of parenchyma (columnar, airborne, spongy, storage, aquifer), as well as the photosynthetic part. The function corresponds to the name: water storage, accumulation of reserve nutrients, photosynthesis, gas exchange. Localization in leaves, stems, fruits.
- Conductive tissues - xylem and phloem. The main purpose is the transportation of minerals and water to leaves and stems and the return delivery of nutrients to the places of accumulation. They are located in vessels of wood, specialized cells of the bast.
- The integumentary tissues include three main varieties: cork, peel, epidermis. Their role is primarily protective, as well as transpiration and gas exchange. Location in the plant body: surface of leaves, bark, root.
- Excretory tissues produce juice, nectars, metabolic products, and moisture. They are located in specialized structures (nectaries, lactarias, hairs).
- The mechanical tissue of plants , its structure and functions will be discussed in more detail below.
Mechanical fabrics: general description
Difficult and heterogeneous weather conditions, climatic catharsis, and not always mild changes in nature - the dwelling protects from all this person. And often it is plants that become such a refuge for animals. And who will save them themselves? Thanks to what they are able to withstand heavy winds, and earthquakes, volcanic eruptions and hail, snowfalls and tropical showers? It turns out that the structure included in the composition — mechanical tissue — helps them to survive.
Such a structure is not always evenly distributed in the same plant. Its content is also not the same for different representatives. But to one degree or another, everyone has it. The mechanical tissue of plants has its own special structure, classification and functions.
Functional significance
One name of this structure speaks of the role and significance that it has for plants - mechanical strength, protection, support. Often mechanical fabric is equated to reinforcement. That is, it is a kind of skeleton, a skeleton that gives support and strength to the whole plant body.
These functions of mechanical tissue are extremely important. Thanks to their presence, the plant is able to tolerate severe weather inclement weather, while maintaining the integrity of all parts. Often you can see how the trees sway from strong gusts of wind. However, they do not break, showing miracles of plasticity and strength. This is due to the fact that the mechanical properties of the tissues work. You can also see the stability of shrubs, tall grasses, shrubs, small trees. All of them are kept in good condition, like persistent tin soldiers.
Of course, this explains the structural features of cell structures and the types of mechanical tissues. You can divide them into groups.
Classification
Three main types of such structures are distinguished, each of which has its own structural features of mechanical tissue.
- Collenheim.
- Sklerenchyma.
- Sclereids (often considered as part of sclerenchyma).
Each of these tissues can be formed from both primary and secondary meristem. All cells of mechanical tissue have thick strong cell walls, which largely explains the ability to perform these functions. The contents of each cell can be either alive or dead.
Collenheim and its structure
The evolution of this type of structure comes from the basic tissues of plants. Therefore, most often, the collenchyma contains the chlorophyll pigment and is capable of photosynthesis. This tissue is formed only in young plants, lining their organs immediately under the coverslip, sometimes a little deeper.
A prerequisite for the collenchyma is a turgor of cells, only in this case it can fulfill the functions of reinforcement and support assigned to it. This condition is possible, since all cells of a given tissue are living, growing, and dividing. The shells are very thickened, however, pores are preserved, through which moisture is taken and a certain turgor pressure is set.
Also, the structure of mechanical tissues of this type implies several types of cell articulation. On this basis, it is customary to distinguish three types of collenchyma.
- Lamellar . The cell walls are thickened fairly evenly, are located tightly to each other, parallel to the stem. Elongated in shape (an example of a plant containing this type of tissue is sunflower).
- Corner collenchyma - the shells are thickened unevenly, in the corners and in the middle. They are interconnected by precisely these parts, forming small spaces (buckwheat, pumpkin, sorrel).
- Loose - the name speaks for itself. The cell walls are thickened, but their connection is with large intercellular spaces. Often performs a photosynthetic function (belladonna, coltsfoot).
Once again, it should be pointed out that the collenchyma is the tissue of only young, one-year-old plants and their shoots. The main places of localization in the body of the plant are petioles and main veins, in the stem on the sides in the shape of a cylinder. This mechanical tissue contains only living, non-lignified cells that do not interfere with the growth of plants and their organs.
Functions Performed
In addition to photosynthesizing, one can also call the support function as the main one. However, it does not play such a big role in this as the sclerenchyma. Nevertheless, the tensile strength of the collenchyma is comparable to the strength of metals (aluminum, for example, and lead).
In addition, the functions of mechanical tissue of this type are also explained by the ability to form secondary lignified membranes in old plant organs.
Sclerenchyma, cell types
Unlike collenchyma, the cells of this tissue most often have lignified membranes, very thickened. Living contents (protoplast) die off over time. Often, the cellular structures of sclerenchyma are impregnated with a special substance - lignin, which increases their strength many times over. The fracture strength of sclerenchyma is comparable to that of building steel.
The main types of cells that make up such tissue are as follows:
- fiber;
- scleroids;
- structures that make up the conductive tissues, xylem and phloem - bast fibers and wood (libriform).
Fibers are elongated and pointed upward prosenchymal structures with strongly thickened and lignified membranes, there are very few pores. They are localized at the places where the plant growth processes end: internodes, stem, central root, petioles.
Bast and wood fibers are of great importance as accompanying conductive tissues surrounding them.
Structural features of the mechanical tissue of the sclerenchyma consist in the fact that all cells are dead, with a firmly formed wood membrane. Together, they give colossal resistance to plants. Sclerenchyma is formed from the primary meristem, cambium and procambium. It is localized in trunks (stems), petioles, roots, pedicels, receptacle, peduncle and leaves.
Role in the plant body
The function of the mechanical tissue of the sclerenchyma is obvious - providing an integral strong frame with sufficient strength, elasticity and strength to withstand dynamic and static effects from the crown mass (in trees) and natural disasters (in all plants).
The function of photosynthesis for sclerenchymal cells is uncharacteristic due to the death of their living contents.
Scleroids
These structural elements of mechanical tissue are formed from ordinary thin-walled cells by phasing out protoplast, sclerification (lignification) of the membranes and their multiple thickening. Such cells develop in two ways:
- from the main meristem;
- from the parenchyma.
You can verify the strength and rigidity of scleroids by indicating the places of their localization in plants. They consist of nutshells, fruit seeds.
In form, these structures can be very different. So, allocate:
- short rounded stony cells (brachisclereids);
- branched;
- very elongated - fibrous;
- osteosclereids - in shape resemble human tibia.
Often such structures are found even in the pulp of fruits, which protects them from being eaten by various birds and animals. Scleroids of all types make up the features of mechanical tissues, help them perform supporting functions.
Value for plants
The role of such cells is not only in reinforcing functions. Scleroids also help plants:
- protect seeds from temperature extremes;
- Prevent fruit damage by bacteria and fungi, as well as animal bites;
- to form, in combination with other mechanical tissues, a full-fledged stable mechanical frame.
The presence of mechanical tissues in different plants
The distribution of these types of tissues is not the same for different representatives of the flora. So, for example, the lowest aquatic plants - algae - contain the least sclerenchyma. Indeed, for them, the function of support is played by water, its pressure.
Also, tropical plants, all representatives of moist habitats, are not lignified and stocked up with lignin. But the inhabitants of arid conditions with mechanical fabrics acquire to the maximum. This is reflected in their environmental name - sclerophytes.
Collenchyma is more characteristic of annual dicotyledonous representatives. Sclerenchyma, on the contrary, is mostly formed in monocotyledonous perennial grasses, shrubs and trees.