Mechanical plant tissue: structural features and functions

Just like in animals, in the bodies of plants there are various tissues. Of these, organs are built, which, in turn, form systems. The structural unit as a whole is the same - the cell.

However, the tissues of plants and animals differ among themselves in both structure and function. So let's try to understand what these structures represent in the representatives of the flora. Let's consider in more detail what is the mechanical tissue of plants.

Fabrics of plants

In total, 6 groups of tissues can be distinguished in the plant organism.

1. Educational includes wound, apical, lateral and intercalary types. It is 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 areas with the educational tissue will be localized : the petioles of the leaves, the internodes, the tip of the root, the upper part of the stem.
2. The main one consists of different types of parenchyma (columnar, airborne, spongy, storing, aquiferous), as well as photosynthetic part. The function corresponds to the name: water storage, accumulation of reserve nutrients, photosynthesis, gas exchange. Localization in leaves, stems, fruits.
3. Conductive tissues are xylem and phloem. The main purpose is the transportation of minerals and water to the leaves and stems and the return delivery of nutrient compounds to the accumulation sites. They are located in the vessels of wood, specialized cells of the bast.
4. Cover tissues include three main varieties: cork, crust, epidermis. Their role in the first place - protective, as well as transpiration and gas exchange. Location in the body of the plant: the surface of leaves, bark, root.
5. Excretory tissues produce the production of juice, nectars, metabolic products, moisture. Are located in specialized structures (nectaries, mlechnikah, hairs).
6. The mechanical tissue of plants , its structure and functions will be discussed below in more detail.

Mechanical fabrics: general characteristics

Difficult and heterogeneous weather conditions, climatic catharsis, not always soft changes in nature - from all this person protects the dwelling. And often such a shelter for animals become plants. And who will save them themselves? Due to what they are able to withstand and heavy wind, and earthquakes, volcanic eruptions and hail, snowfalls and tropical downpours? It turns out that the structure included in the structure helps to withstand them - mechanical fabric.

Such a structure is not always evenly distributed among the same plant. Also, its content varies from representative to representative. But to some extent it is in everyone. The mechanical tissue of plants has its own special structure, classification and functions.

Functional significance

One name of this structure speaks about the role and significance it has for plants - mechanical strength, protection, support. Often, the mechanical fabric is equated to the reinforcement. That is, it is a kind of skeleton, a skeleton, which gives support and strength to the entire plant organism.

These functions of mechanical fabric are extremely important. Due to their presence, the plant is able to withstand the strongest weather conditions, while maintaining the integrity of all parts. Often you can see how the trees are swinging 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. Also it is possible to see and stability of bushes, tall grasses, half-shrubs, small trees. All of them are kept in a normal state, like persistent tin soldiers.

Of course, this explains the features of the structure of cellular structures and a variety of mechanical tissues. You can divide them into groups.

Classification

There are three main types of such structures, each of which has its own peculiarities in the structure of mechanical tissue.

1. Collenchyma.
2. Sclerenchyma.
3. Scleroids (often regarded as part of sclerenchyma).

Each of these tissues can be formed from both the primary and secondary meristems. All cells of mechanical tissue have thick, strong cell walls, which in many ways explains the ability to perform these functions. The contents of each cell can be either alive or dead.

Collenchyma and its structure

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 performing photosynthesis. This tissue is formed only in young plants, lining their organs immediately under the integument, sometimes slightly deeper.

An obligatory condition for a collenchyma is a turgor of cells, only in this case it is able to perform the functions of the armature, supports, assigned to it. Such a state is possible, since all cells of this tissue are living, growing and dividing. The shells are very thickened, but pores remain, through which moisture is collected and a certain turgor pressure is established.

Also, the structure of mechanical tissues of this type implies several types of articulation of cells. On this basis, it is customary to distinguish three types of collenchyma.

1. Plate . The cell walls are thickened evenly enough, they settle close to each other, parallel to the stem. Extruded in shape (an example of a plant containing this type of tissue is sunflower).
2. Angular collenchyma - shells are thickened unevenly, in corners and in the middle. They huddle together with these parts, forming small spaces (buckwheat, pumpkin, sorrel).
3. Loose - the name speaks for itself. The cell walls are thickened, but their connection is with large intercellular spaces. Often performs photosynthetic function (krasavka, mother-and-stepmother).

Once again, it should be pointed out that collenchyma is the tissue of only young, single-aged plants and their shoots. The main places of localization in the body of the plant are the petioles and the main veins, in the stem on the sides in the form of a cylinder. This mechanical tissue contains only living, neodrevesnevshie cells that do not interfere with the growth of plants and their organs.

Performed functions

In addition to photosynthesizing, we can also call the function of support as the main one. However, she does not play such a big role in this, as sclerenchyma. Nevertheless, the strength of the collenchyma for rupture 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 lignifying shells in old plant organs.

Sclerenchyma, cell types

In contrast to the collenchyma, the cells of this tissue are most often lignified shells, strongly thickened. Live content (protoplast) dies with time. Often cellular structures of sclerenchyma are impregnated with a special substance - lignin, which increases their strength many times. The breaking strength of sclerenchyma is comparable with the parameters of building steel.

The main types of cells that make up this tissue are:

• Fibers;
• Scleraids;
• Structures that are part of conductive tissues, xylem and phloem are bast fibers and wood (libris).

Fibers are elongated and pointed upward prozenhimnye structures with strongly thickened and lignified shells, there is very little pore. Localize in places where the plant's growth processes end: interstices, stem, central root, petioles.

Bast and wood fibers are of great importance as the accompanying conductive tissues surrounding them.

The structural features of the mechanical tissue of sclerenchyma are that all cells are dead, with a well-formed woody membrane. Together they give colossal resistance to plants. Sclerenchyma is formed from the primary meristem, cambium and procambium. Localized in trunks (stems), petioles, roots, pedicels, peduncle, pedicels and leaves.

Role in the plant

The function of the mechanical tissue of the sclerenchyma is obvious - providing an integral, strong framework that has 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 sclerenchyma cells is uncharacteristic due to the death of their living contents.

Sclereids

These structural elements of mechanical tissue are formed from ordinary thin-walled cells by phased protoplast dying, sclerosis (lignification) of the shells and their multiple thickening. Such cells develop in two ways:

• From the basic meristem;
• From the parenchyma.

Verify the strength and rigidity of scleraids can be, indicating the location of their localization in plants. Of these is a shell of nuts, seeds of fruit.

In form, these structures can be very different. So, they distinguish:

• Short rounded stony cells (brachklereids);
• Branched;
• Strongly elongated - fibrous;
• Osteoscleride - in shape resemble human tibia.

Often such structures are found even in fruit pulp, which protects them from eating by various birds and animals. Scleroids of all types make up the features of mechanical tissues, help them to perform supporting functions.

Importance for plants

The role of such cells is not only in the reinforcement functions. Also, scleraids help plants:

• Protect seeds from temperature changes;
• Do not allow the fruit to be affected by bacteria and fungi, as well as animal bites;
• Form a complete stable mechanical frame in combination with other mechanical tissues.

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 sclerenchyma contains lower aquatic plants - algae. After all, for them, the function of support is played by water, its pressure.

Also, tropical plants, all representatives of humid habitats, are not too lignified and stored in lignin. But the inhabitants of arid conditions with mechanical tissues acquire the maximum. This is reflected in their ecological name - sclerophytes.

Collenchyma is more characteristic of annual bipartite representatives. Sclerenchyma, on the other hand, is mostly formed in monocotyledonous perennial grasses, bushes and trees.