Vegetable tissues. Types of plant tissue

The works describing animals and plant tissues appeared in the 17th century. The first anatomical botanists, Grew and Malpighi, examined the most important of them, and also introduced such concepts as the prozenham and parenchyma. In general, biology studies biology. Fabrics have differences in composition, tasks, and origin. Next, let us consider in more detail the main features of these structures. The article will present a table of plant tissues. In it you can see the main categories of structures, their location and tasks.

Biology: tissues. Classification

The scheme of separation of structures in accordance with physiological tasks was developed by Haberlandt and Schwendener at the turn of the 19th and 20th centuries. Plant tissues are groups of elements having the same origin, homogeneous composition and performing one task. The classification of structures is carried out according to different criteria. For example, plant tissues include:

• Basic.
• Conductive.
• Meristems (educational).
• Coverslips.
• Exclusive.
• Mechanical.

If plant tissues consist of cells that have more or less the same structure and tasks, they are called simple. If the elements are not the same, then the whole system is called complex, or complex. Types of plant tissue of a category are divided, in turn, into groups. For example, educational structures include:

• The apical.
• Lateral - secondary (phellogen, cambium) and primary (pericyclic, procambium).
• Wounded.
• Insertion.

The types of plant tissue of the main species include the storing and assimilation parenchyma. Conductive structures consider phloem (lub) and xylem (wood).

Cover (border) plant tissues:

• External: secondary (periderum), primary (epidermis), tertiary (rhytid, or crust); Velaman, rhizoderm.
• Internal: exo- and endoderm, lining cells from conductive bundles of leaves.

Mechanical structures (skeletal, supporting) are divided into sclerenchyma (scleraids, fibers), collenchyma. And the last group is the excretory (secretory) tissue of the plant organism.

Educational structures: general information

These plant tissues (meristems) are groups of constantly young, actively dividing cells. They are located on the growth sites of various organs. For example, they can be on tops of stalks, root tips and other places. Due to the presence of plant cells in this tissue, a continuous growth of culture and the formation of permanent elements and organs takes place.

Meristem features

Depending on the location of the educational tissue of the plant cell, it can be apical (apical), lateral (lateral), intercalary (intercalary), wounded. Also, the structures are divided into secondary and primary. The latter include the apical species of plant tissue. These structures determine the growth of culture in length. In higher low-organized plants (ferns, horsetails) apical meristems are characterized by weak expression. They are represented by only one initial, or initial cell. In angiosperms and gymnosperms, the apical meristems are well expressed. They are represented by many initial cells, which form cones of growth. Lateral structures are usually secondary. Due to them, the roots, stems (axial organs as a whole) grow in thickness. Side species of plant tissue are phellogen and cambium. Due to the activity of the first, cork is formed in the roots and stems. To the same group include airing cloth - lenticles. The lateral meristem, like cambium, forms structural elements of bast and wood. In the adverse life periods of plants, the cambium slows down or completely ceases to function. Insertion meristems, as a rule, are primary. They are preserved as separate sites in areas of active growth: at the base of internodes and petioles of cereal leaves, for example.

Covering structures

The functions of the plant tissues of this group are to protect the culture from the adverse effects of environmental factors. Negative influences, in particular, should be considered excessive evaporation, solar overheating, withering wind, mechanical damage, penetration of bacteria and pathogenic fungi. There is a primary and secondary integumentary tissue. The first category includes the epilblem and the skin (epidermis). Secondary cover tissues consider phelloderm, cork cambium, cork.

Features of structures

The skin is covered with all organs of annual plants, perennial tree cultures in the current growing season - green shoots, in general the plantations - grassy overground parts. The last, in particular, are leaves, flowers, stems.

Structure of plant tissues: epidermis

As a rule, it consists of one layer of closed structural elements. There is no intercellular space. The epidermis is easily removed and is a transparent thin film. This is a living tissue, which includes a gradual layer of protoplast with a nucleus and leukoplasts, a large vacuole. The latter occupies almost the entire cell. The outer wall of the structural elements of the epidermis is more thickened, while the inner and lateral walls are thin. The latter have pores. The main task of the epidermis is the regulation of transpiration and gas exchange. It is carried out to a greater extent through the stomata. Inorganic compounds and water penetrate through the pores. In different plants, epidermal cells differ in size and shape. Many monocotyledonous cultures have structural elements elongated in length. Most dicotyledonous plantations have winding side walls. This increases the density of their connection with each other. The structure of the epidermis at the top and bottom of the leaf is different. There are more stomata from below, than from above. Aquatic plants with leaves floating on the surface (water lilies, capsules) have their own characteristics. They have stomata present only on the upper part of the plate. But in plants completely immersed in water, these formations are absent.

Stomata

These are highly specialized formations in the epidermis. The stomata consist of 2 closing cells and a gap - the formation between them. The structural elements have a semilunar form. They adjust the size of the slit-shaped formation. It, in turn, can be closed and opened in accordance with the turgor pressure in the closing elements, depending on the concentration in the atmosphere of carbon dioxide and other factors. During the day, stomatal cells take part in photosynthesis. During this period, the turgor pressure is high, and the slit-like formation is open. At night, on the contrary, it is closed. Such a phenomenon is observed both in dry times and in the withering of leaves. It is due to the ability of stomata to store moisture inside.

Basic structures

Parenchyma occupies most of the space between other permanent tissues in the stem, roots and other organs of plants. The basic structures consist mainly of living elements having various forms. Cells can be thin-walled, but sometimes thickened, lignified, with simple pores, post-cytoplasm. The parenchyma consists of the flesh of leaves and fruits, the core of rhizomes and stems, their bark. There are several subgroups of this tissue. So, among the basic structures allocate: air-bearing, water-bearing, storing and assimilation. The functions of plant tissues in this category are the storage of nutrient compounds.

Chlorophyllous parenchyma

Chlorenchyme - assimilation tissue - the structure in which photosynthesis takes place. Its elements are distinguished by thin walls. They contain a nucleus and chloroplasts. The latter, like the cytoplasm, are located postennially. There is a chlorenchyme under the skin directly. Mostly it is concentrated in green young shoots and leaves.

Aerenheim

Airborne tissue is a structure with sufficiently developed intercellular spaces in various organs. Most of all, it is characteristic of swampy, aquatic and coastal-aquatic crops, whose roots are in oxygen-poor silt. Air reaches the lower organs with the aid of transmission organs. In addition, the communication between the intercellular spaces and the atmosphere is carried out by means of peculiar pneumatodes. At the expense of the aerochyma, the specific weight of the plant decreases. This, apparently, explains the ability of aquatic cultures to maintain a vertical position, and the leaves - to be on the surface.

Aquifer structure

This tissue retains moisture in the stems and leaves of succulent plants and crops in a saline area. To the first, for example, you can include cacti, fatty, agave, aloe and others. To the second - the comber, sarsazana, solyanka and others. This tissue is well developed in sphagnum moss.

Stacking structures

In these tissues, at a certain point in the development of culture, the products of metabolism begin to be deposited. This, in particular, fats, carbohydrates and others. The cells in the storage tissue are usually thin-walled. The structure is widely represented in thickenings of roots, bulbs, tubers, the core of stems, seed embryos, endosperm and other areas.

Mechanical cover

Supporting fabrics act as a kind of armature or "stereo" (from the Greek "hard", "strong"). The main task of the structures is to provide resistance to dynamic and static loads. In accordance with this, the tissues have a definite structure. In terrestrial cultures, they are more developed in the axial part of the shoot - the stem. Cells can be located around the periphery, separate areas or a solid cylinder.

Collenchyma

It is a simple primary supporting tissue with living cellular contents: cytoplasm, nucleus, sometimes chloroplasts. There are three categories of collenchyma: loose, lamellar and angular. This classification is carried out in accordance with the nature of cell thickening. If it is in corners, then the structure is angular, if the stalk is parallel to the surface and uniformly enough, then this is a plate-like collenchyma. Formed tissue from the main meristem and located under the epidermis at a distance of one or more layers from it.

Sclerenchyma

This mechanical tissue is considered quite common. It consists of structural elements with lignified and uniformly thickened walls and slit-like pores in a small amount. The cells in the sclerenchyma are elongated in length, they are characterized by a prochenchymal shape with pointed tips.

Conductive structures

These tissues provide transportation of nutrient compounds. It is carried out in two ways. Transpiration (ascending) current of aqueous solutions and salts goes along tracheids and vessels from roots to leaves along the stem. Assimilation (descending) movement occurs from the upper parts to the subterranean by means of special phytophasic sieve tubes. Conductive tissue can in some way be compared to the circulatory system of humans, since it has a radial and axial network. Nutrients penetrate every cell of the body.

Excretory fibers

Secretory tissues are special formations that have the ability to isolate or isolate the droplet liquid environment and metabolic products. The latter are called secrets. If they leave the plant, then the tissues of the external secretion are involved, and if they remain inside, respectively, internal structures participate. Formation of liquid products is associated with the activity of membranes and the Golgi complex. Secrets of this type are designed to protect plants from destruction by animals, damage by pathogens or insects. Intrasecretory structures are represented in the form of resinous passages, idiblasts, essential oil channels, larvae, receptacles for excreta, glands and other.

Table of plant tissues