Features of the structure of the columnar tissue cells. Palisade (columnar) tissue of leaf of plant leaf

Differentiation of cells and tissues plays an important role in the development of the organism. Separation of duties for each cell can be compared with the division of labor in the factory: if each unit performs only its inherent function, the overall result can be obtained in a shorter period. The same applies to any living organism whose quality of life depends on its complexity of development and the occupied evolutionary niche.

What is a cell: the biology of life

A cell is a structural and functional unit of all living things. The exception is what the viruses are - the noncellular form of life. Fabric - a collection of cells and intercellular substance, having the same structure, functions and origin. The biology of a cell's function is based on its structure, which is dictated by the degree of organization of the animal or plant.

The differentiation of cells in animals and plants occurs even in ontogenesis. Each of them comes from the precursor tissue: if the animals are stem cells, then the plants are meristem.

What is a cell? The biology and structure of cells allows us to classify them into two groups.

1. Eukaryotic cells. These include the structural units of the animal and plant organism.

2. Prokaryotic cells. They are distinguished by the absence of a nucleus and other organelles. Prokaryotic organisms include bacteria.

Structure of the animal cell

Biology studies the structure of cells. The structure of the animal cell was discovered by Hooke back in the 19th century, but it was completely studied nearer to the 20th millennium.

An animal cell is a cytoplasm surrounded by a plasmalemma. In the cytoplasm, various organelles and inclusions "swim". Organelles include lysosomes, mitochondria, Golgi apparatus, endoplasmic reticulum, peroxisomes. Inclusions are substances that are dissolved in the cytosol and wait until they are needed to build the structure of the cell.

Unlike plant, in the animal cell there is no cell wall, vacuole and chloroplasts. The absence of an additional cover complex affects, for example, the features of deformation of the plasmalemma during fission.

Structure of a plant cell

The internal contents of the plant cell are much richer than the animal. First, you can find here two-membrane structures - chloroplasts. And the function is to ensure the process of photosynthesis, which is very important for plants in terms of an additional source of energy along with breathing, as well as glucose.

The plant cell from the outside is additionally covered with a cell wall. It consists of cellulose fibers, and pectin is still present at the point of contact of two adjacent cells. Here, such a powerful outdoor complex does not allow contact as animal cells do. The main role in transport is played by the structure of the cell. Grade 6, the biology in which has not yet been studied so deeply, does not provide information about desmosomes - special pores in the cell wall that serve to move substances from one cell to another. With the help of these structures, vacuoles can contact the small bridge across the diameter.

Vacuole is another difference between an animal cell and a plant cell. Its function is to store chemically active alkaloids, acids, calcium, which help stabilize the osmotic pressure. Moreover, alkaloids and acids can adversely affect the contents of the cytoplasm, so they must be in an isolated organelle with a special membrane through which it is impossible to penetrate molecules of this size. The membrane of the vacuole is called tonoplast.

All features of the structure of the columnar tissue cells are identical to the above plan for the composition of plant cells.

Prokaryotic cells

Bacteria (as representatives of prokaryotes) are evolutionarily less developed organisms. The bacterial cell is a cytosol surrounded by a membrane, a cell wall and a mucous capsule. Inside, there are no organelles that occur in eukaryotes. The nucleus is also absent, and all genetic material is present in most bacteria with only one chromosome.

Metabolism of the cell is supported by special structures - mesosomes. They represent the outgrowth of the cytoplasmic membrane inside the cell, and their function is in breathing or photosynthesis, when it comes to photosynthetic bacteria.

The absence of a nucleus helps to increase the speed of transcription and translation. Also, the speed of binary cell division increases: a colony of bacteria can double its number every 20 minutes.

Cell functions

A cell as a structural and functional unit of all living things can perform various functions related to maintaining the vital functions of the organism. The main role here is played by the structure of the cell. Grade 6, the biology in which was studied at an initial level, dictates to us the basic features of the organization of the cellular apparatus.

Determination of plant cells is a multi-step process, as a result of which many other body tissues are formed from the meristem: cover, excretory, conductive, mechanical. The cells of each of these tissues differ in structure and function. For example, the task of integumentary cells is not to allow foreign agents to enter the body, when conductive elements are needed to transport organic and mineral substances through the plant.

The interaction of cells is achieved by special contacts, which are called plasmodesmata. Regulation works at the biochemical level with the help of various enzymes and metabolites.

Leaf - vegetative organ of plants

The function of vegetative organs is to maintain the vital activity of the plant at an optimal level. The leaf also belongs to this group, therefore its main task is photosynthesis.

Column tissue is the main photosynthetic tissue of the leaf. It consists of parenchymal cells, in which there are many chloroplasts. Cells of columnar tissue are located closer to the upper surface of the leaf to receive more solar energy and, accordingly, to increase the speed and productivity of photosynthesis.

Also in the composition of the leaf is a spongy tissue, which also has chloroplasts, but their number is much smaller compared to the polysaccharous parenchyma. The fact is that the main function of cells of spongy tissue is gas exchange due to large intercellular spaces.

Features of the structure of columnar cells of leaf tissue

The parasitic parenchyma is in the upper layers of the leaf to accumulate a greater amount of solar energy. This is necessary for the efficient flow of light and dark stages of photosynthesis, which pass only in the condition of illumination.

The columnar cell is an elongated cell of a cylindrical shape, the main function of which is the process of photosynthesis. To do this, several dozens of chloroplasts are located in the cells of the columnar tissue, which are located along the periphery of the cell. Such an arrangement in the space of the cytosol is explained by an increase in the absorption surface of the sun's rays.

In C4 plants of tropical and equatorial forests, the structure of the leaf is slightly different. They have a columnar tissue in the uppermost and in the lowest layers of the organ. This is due to the peculiarities of the dark stage of photosynthesis in these plants.

Features of the structure of the columnar tissue cells are used by the plant to increase the efficiency of photosynthesis.

What is photosynthesis?

Photosynthesis is a multi-stage biochemical process, in which energy is formed in the form of ATP and glucose-carbohydrate, which is stored by the plant.

Photosynthesis is divided into two stages: light and dark. During the first stage, photolysis of water occurs, the release of oxygen as a by-product and the synthesis of ATP, NADPH. The dark stage of photosynthesis represents a cascade of consecutive reactions, as a result of which glucose or sugar analogues are synthesized.

Why do plants need photosynthesis?

To maintain normal life, the plant stores a large amount of starch. Starch is a polysaccharide, the monomer of which is glucose. It is not surprising that in the organism of a plant the greatest percentage is occupied by carbohydrates from all possible classes of organic substances.

The peculiarities of the structure of the columnar tissue cell make it possible to efficiently absorb the light energy that is necessary for the biochemical reactions of photosynthesis to proceed. During the dark stage, glucose and other hexoses are synthesized, which are stored in the form of large polymer molecules of starch in the parenchyma cells. Even in the chloroplasts themselves, sometimes starch grains can be observed.