Conductive fabric: features of the structure

Almost all multicellular living organisms consist of different types of tissues. This is a collection of cells that are similar in structure, united by common functions. For plants and animals, they are not the same.

Variety of tissues of living organisms

First of all, all the tissues can be divided into animals and plant. They are different. Let's look at them.

What can be the animal tissue?

Animals are of the following types:

• Nervous;
• Muscular;
• Epithelial;
• Connecting.

All of them, except the first, are divided into species. Muscle tissue is smooth, striped and cardiac. Epithelial is divided into single-layered, multilayered - depending on the number of layers, as well as on cubic, cylindrical and flat - depending on the shape of the cells. Connective tissue unites such species as loose fibrous, dense fibrous, reticular, blood and lymph, fatty, bone and cartilaginous.

Variety of plant tissues

Vegetable tissues come in the following types:

• Basic;
• Integumentary;
• Conductive tissue;
• Mechanical;
• Educational.

All types of plant tissues combine several species. So, the main ones are assimilation, store, aquifer and airborne. Cover fabrics combine such species as bark, cork and epidermis. Conductive tissue includes phloem and xylem. The mechanical is divided into a collenchyma and a sclerenchyma. Educational includes lateral, apical and intercalary.

All tissues perform certain functions, and their structure corresponds to the role they perform. In this article, we will examine in more detail the conducting tissue, the structural features of its cells. Also we will talk about its functions.

Conductive fabric: features of the structure

These tissues are divided into two types: phloem and xylem. Since they are both formed from the same meristem, they are next to each other in the plant. However, the structure of the conducting tissues of the two species differs. Let's talk more about the two types of conductive tissue.

Functions of conductive tissues

Their main role is the transport of substances. However, the functions of conductive tissues that do not belong to the same species differ.

The role of xylem is to conduct solutions of chemicals from the root up to all other organs of the plant.

A function of phloem - carrying out solutions in the opposite direction - from certain organs of the plant along the stem down to the root.

What is xylem?

It is also called wood. Conductive tissue of this species consists of two different conducting elements: tracheids and vessels. It also includes mechanical elements - wood fibers, and the main elements - wood parenchyma.

How are xylem cells arranged?

The cells of the conducting tissue are divided into two types: the tracheids and the joints of the vessels. The trachea is a very long cell with undisturbed walls, in which pores are present to transport substances.

The second conducting element of the cell - the vessel - consists of several cells, which are called the joints of the vessels. These cells are located one above the other. Through the joints of the segments of the same vessel are through holes. They are called perforations. These holes are necessary for the transport of substances along the vessels. Moving a variety of solutions through the vessels occurs much faster than tracheids.

The cells of both conducting elements are dead and do not contain protoplasts (protoplasts are the contents of the cell, except for the cell wall, that is, the nucleus, organoids and cell membrane). Protoplasts are absent, since if they were in a cell, the transport of substances along it would be very difficult.

By vessels and tracheids, solutions can be transported not only vertically, but also horizontally - to living cells or neighboring conductive elements.

The walls of the conductive elements have thickenings, which give the cell strength. Depending on the type of data of the thickening, the conducting elements are divided into spiral, annular, ladder, mesh and punctate.

Functions of mechanical and basic elements of xylem

Wood fibers are also called librioform. These are elongated cells that have thickened lignified walls. They perform a supporting function that ensures the strength of the xylem.

Elements of the main tissue in the xylem are represented by the wood parenchyma. These are cells with lignified shells, in which simple pores are located. However, at the junction of the parenchyma cell with the vessel there is a bordered pore that connects with its simple at times. The cells of the wood parenchyma, unlike the cells of the vessels, are not empty. They have protoplasts. Parenchyma xylem performs a reserve function - it stores nutrients.

What is the difference between the xylem of different plants?

Since tracheids in the process of evolution arose much earlier than the vessels, these conducting elements are also present in the lower terrestrial plants. These are spore (ferns, mosses, mosses, horsetails). Most gymnosperms also possess only tracheids. However, some gymnosperms have vessels (they are present in the umbilical ones). Also, as an exception, these elements are present in some ferns and horsetails.

But angiosperms (flowering) plants all have both tracheids and vessels.

What is phloem?

Conductive tissue of this species is also called a bast.

The main part of the phloem is the sieve-like conducting elements. Also in the structure of the bast there are mechanical elements (phloem fibers) and elements of the basic tissue (phloem parenchyma).

The characteristics of the conductive tissue of this species are that the cells of the sieve elements, unlike the conductive elements of the xylem, remain alive.

The structure of the sieve elements

There are two types: sieve-like cells and sieve-like tubes. The first are elongated and have pointed ends. They are permeated with through holes, through which the transport of substances takes place. Sitovid cells are more primitive than multicellular sieve elements. They are characteristic for such plants as spore and gymnosperms.

In angiosperms plants, the conducting elements are represented by sieve tubes consisting of a plurality of cells - segments of the sieve elements. Through holes of two adjacent cells form sieve-like plates.

Unlike sitovidnyh cells, in these structural units of multicellular conducting elements there are no nuclei, however they still remain alive. An important role in the structure of the phloem of angiosperms is also played by companion cells, located next to each cell-segment of the sieve-like elements. In companions there are both organoids and nuclei. They metabolize.

Considering the fact that phloem cells are alive, this conducting tissue can not function for long. In perennial plants, the period of her life is three to four years, after which the cells of this conductive tissue die.

Additional elements of phloem

In addition to the sieve cells or tubes, this conductive tissue also contains elements of the underlying tissue and mechanical elements. The latter are represented by bast fibers (phloem) fibers. They perform a supporting function. Not all plants have phloem fibers.

Elements of the underlying tissue are represented by the phloem parenchyma. She, as well as the xylem parenchyma, performs a reserve role. It stores such substances as tannides, resins, etc. These elements of phloem are especially developed in gymnosperms.

Floema of various plant species

In lower plants, such as ferns and mosses, it is represented by sieve cells. The same phloem is characteristic of most gymnosperms.

Angiospermous plants have multicellular conductive elements: sieve tubes.

Structure of the plant's conducting system

Xylem and phloem are always located side by side and form bundles. Depending on how the two types of conductive tissue are arranged relative to one another, several types of bundles are distinguished. The most common are collateral. They are arranged in such a way that the phloem lies on one side of the xylem.

There are also concentric beams. In them, one conductive tissue surrounds the other. They are divided into two types: centrifuge and centroxylemic.

Conductive root tissue usually has radial beams. In them the rays of the xylem move away from the center, and the phloem lies between the rays of the xylem.

Collateral bundles are more characteristic of angiosperms, and concentric ones are more common for spore and gymnosperms.

Conclusion: a comparison of two types of conductive tissue

As an output, we give a table, which briefly shows the main data on the two types of conductive tissue of plants.

Now you know everything about the conducting tissues of plants: what they are, what functions they perform and how their cells are arranged.