Which tissue cells provide plant growth? Collection of tasks for preparing for the Unified State Exam

In any living or plant organism, tissue is formed by cells similar in origin and structure. Any tissue is adapted to perform one or several important functions for an animal or plant organism.

Types of tissues in higher plants

The following types of plant tissues are distinguished:

educational (meristem);
integumentary;
mechanical;
conductive;
basic;
excretory.

All these tissues have their own structural features and differ from each other in the functions they perform.

Fig.1 Plant tissue under a microscope

Educational plant tissue

Educational fabric- This is the primary tissue from which all other plant tissues are formed. It consists of special cells capable of multiple divisions. It is these cells that make up the embryo of any plant.

This tissue is retained in the adult plant. It is located:

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at the bottom of the root system and at the tops of the stems (ensures plant growth in height and development of the root system) - apical educational tissue;
inside the stem (ensures the plant grows in width and thickens) - lateral educational tissue;

Plant integumentary tissue

Covering tissue is a protective tissue. It is necessary in order to protect the plant from sudden changes in temperature, from excessive evaporation of water, from microbes, fungi, animals and from all kinds of mechanical damage.

The integumentary tissues of plants are formed by cells, living and dead, that are capable of allowing air to pass through, providing the gas exchange necessary for plant growth.

The structure of plant integumentary tissue is as follows:

first there is the skin or epidermis, which covers the leaves of the plant, stems and the most vulnerable parts of the flower; skin cells are living, elastic, they protect the plant from excessive loss of moisture;
Next is the cork or periderm, which is also located on the stems and roots of the plant (where the cork layer forms, the skin dies); The cork protects the plant from adverse environmental influences.

There is also a type of integumentary tissue known as crust. This most durable covering tissue, cork, in this case is formed not only on the surface, but also in depth, and its upper layers slowly die off. Essentially, the crust is made up of cork and dead tissue.

Fig. 2 Crust - a type of plant covering tissue

For the plant to breathe, cracks form in the crust, at the bottom of which there are special shoots, lentils, through which gas exchange occurs.

Mechanical plant tissue

Mechanical tissues give the plant the strength it needs. It is thanks to their presence that the plant can withstand strong gusts of wind and do not break under streams of rain or under the weight of fruits.

There are two main types of mechanical fabrics: bast and wood fibers.

Conductive plant tissues

Conductive fabric ensures the transport of water with minerals dissolved in it.

This tissue forms two transport systems:

upward(from roots to leaves);
downward(from leaves to all other parts of plants).

The ascending transport system consists of tracheids and vessels (xylem or wood), and vessels are more advanced conductors than tracheids.

In descending systems, the flow of water with photosynthesis products passes through sieve tubes (phloem or phloem).

Xylem and phloem form vascular-fibrous bundles - the “circulatory system” of the plant, which penetrates it completely, connecting it into one whole.

Main fabric

Ground tissue or parenchyma- is the basis of the entire plant. All other types of fabrics are immersed in it. This is living tissue and it performs different functions. It is because of this that its different types are distinguished (information about the structure and functions of different types of basic tissue is presented in the table below).

Types of main fabric	Where is it located in the plant?	Functions	Structure
Assimilation	leaves and other green parts of the plant	promotes the synthesis of organic substances	consists of photosynthetic cells
Storage	tubers, fruits, buds, seeds, bulbs, root vegetables	promotes the accumulation of organic substances necessary for plant development	thin-walled cells
Aquifer	stem, leaves	promotes water accumulation	loose tissue consisting of thin-walled cells
Airborne	stem, leaves, roots	promotes air circulation throughout the plant	thin-walled cells

Rice. 3 The main tissue or parenchyma of the plant

Excretory tissues

The name of this fabric indicates exactly what function it plays. These fabrics help saturate the fruits of plants with oils and juices, and also contribute to the release of a special aroma by the leaves, flowers and fruits. Thus, there are two types of this fabric:

endocrine tissue;
Exocrine tissue.

What have we learned?

For the biology lesson, 6th grade students need to remember that animals and plants consist of many cells, which, in turn, arranged in an orderly manner, form one or another tissue. We found out what types of tissues exist in plants - educational, integumentary, mechanical, conductive, basic and excretory. Each tissue performs its own strictly defined function, protecting the plant or providing all its parts with access to water or air.

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Educational fabrics

The function of these tissues is the formation of new cells through division. Educational tissue consists of small cells with large nuclei and without vacuoles. The cells of this tissue are constantly dividing. One part of the daughter cells, growing to the size of the mother, divides again, and the other part gradually turns into cells of permanent tissues. All tissues except educational ones are called permanent. Permanent tissue cells are usually unable to divide. Educational tissues are located at the tip of the root and at the top of the stem. They ensure constant growth of the plant in length.

Inside the roots and stems there is a ring of educational tissue made of elongated cells. It is called cambium. The cambium ensures the growth of roots and stems in thickness.

Integumentary tissues

These tissues cover the outside of the plant organs and protect them from harmful environmental influences. Plants need protection because they are immobile and cannot run or hide from pests, rain, wind, or snow. In addition, integumentary tissues protect plant organs from drying out.

Plants have several types of integumentary tissues. The leaves and young green stems are covered with a skin, which consists of a single layer of transparent cells. The transparency of the integumentary tissue is very important, since, while protecting the organ, the skin does not prevent light from entering the deeper cells with chloroplasts. The protective properties of the skin are determined by the fact that its cells are tightly closed, the outer shell of the cells is thickened and covered on top with a fatty substance, and sometimes also with wax. This protects the organs from drying out and the penetration of fungi and bacteria that cause plant diseases.

However, the plant cannot be completely separated from the air environment. It constantly needs oxygen for cell respiration and carbon dioxide for photosynthesis. In addition, the plant constantly evaporates water. In other words, gas exchange must occur in the plant all the time. The skin does not prevent this, because it has special formations for gas exchange - stomata.

The stomata is a gap surrounded by two guard cells, which, unlike skin cells, are bean-shaped. Stomata can open and close. At the same time, the guard cells diverge or come closer together. Under the stomata there are intercellular spaces through which air reaches all cells of the leaf or young stem.

In many plants (especially woody ones), the stem is covered with another integumentary tissue - cork. This is a multi-layer fabric. Its cells are tightly closed. Their living contents die, and the cell cavities are filled with air. Cork is a much more reliable protection for the plant than the skin.

In some trees (cork oak), the layer of cork can be very thick, up to 20-30 cm. The cork from such trees is cut off from time to time. It is used to make bottle caps and sound insulation. It was this kind of plug that R. Hooke examined under a microscope.

Gas exchange in plants covered with cork occurs through lentils. Lentils are breaks in the plug that allow air to enter the stem.

Supporting or mechanical tissues

The strongly dissected body of the plant requires support. Supporting tissues support and strengthen plant organs. A characteristic feature of these tissues is the strong thickening of the cell walls, which ensure the performance of their functions. Often the cell membranes become lignified, and the living contents of the cell die. The cells of the supporting tissue can have an elongated shape, then they are called fibers, but they can also be round. However, in any case, their cell walls are very thick. It often happens that the thickness of the supporting cell shell is greater than the size of its cavity. Such cells form sclerenchyma.

Collenchyma- parenchymal mechanical tissue, the cells of which in a transverse section have a varied shape, close to 4-5 sided, and in a longitudinal section they are somewhat elongated along the axis. Appears only as primary tissue and serves to strengthen young stems and leaves when cells continue to elongate in length.

Conductive fabrics

There are two types of conducting tissues in plants. One tissue consists of vessels and conducts water and minerals from the roots to the leaves. It is called xylem. Other tissue consists of sieve cells, which conduct nutrients produced in the leaves during photosynthesis down the plant. This tissue is called phloem. Vessels are formed from a number of cells that grow, elongate, their shells become lignified, the living contents die, and the transverse walls are destroyed. Tubes are obtained, and in place of the transverse partitions there remain narrow rims, by which it can be determined that the vessels were formed from a number of cells. Sieve cells have an elongated shape, which facilitates the conduction of substances. Many small holes are formed in the transverse cell membranes, which makes them look like a strainer. Hence the name of the cells - sieve. The holes facilitate the passage of nutrients from one sieve cell to another.

Assimilating tissues carry out the process of photosynthesis, which is why they are also called photosynthetic tissues. Their cells have a round or slightly elongated shape. They are closed or have intercellular spaces. Assimilating tissues are mainly found in the leaf, but green cells are also found in young stems.

Storage fabrics

In these tissues, nutrients that were formed in assimilating tissues are stored. The cells of these tissues are large, sometimes very large. For example, if you break a ripe apple or a ripe tomato, you will see small bubbles on the break. These are large cells of storage tissue, in the vacuoles of which various substances dissolved in water, including sugar, are deposited. But nutrients can be found in both the cytoplasm and leucoplasts in a solid state. For example, starch is deposited in potato tubers or wheat grains.

Main fabric

The cells of this tissue fill the spaces between specialized tissues. Its cells can be large or small, with thin or thickened membranes, tightly closed or with intercellular spaces. The main tissue in different plant organs can perform different functions: assimilating, storing, supporting.

Bibliography:

1. G.Yu. Verves, N.N. Balan. Biology. Handbook for 7th grade dark-illuminated initial mortgages. - K.: "Osvita", 2008.

2. Shabanov D.A., Shabanova G.V. Biology. Handbook for 7th grade dark-illuminated initial mortgages. - Kh.: "Osvita", 2003.

3. Yakovlev G.P., Chelombitko V.A. Botany. M.: Spectrum, 1990.

1. What is fabric? List four types of animal tissues and five types of plant tissues.

Tissue is a group of cells similar in size, structure and functions. Tissue cells are connected to each other by intercellular substance. In plants there are educational, basic, integumentary, mechanical and conductive tissues, in animals - epithelial, connective, muscle and nervous tissues.

2. Look at the picture on p. 20-21. Prove that it does not contradict the information that there are four types of animal tissues.

Animals have four types of tissue: epithelial, connective, muscle and nervous tissue.

In the figure we see epithelial and nervous tissue.

Muscle tissue is represented by two types - smooth and striated (skeletal). Their main properties are excitability and contractility.

The fourth type (connective tissue) includes bone tissue, cartilage, adipose tissue, and blood. Despite the great diversity, all types of connective tissue are united by one feature - the presence of a large amount of intercellular substance.

3.What tissues are connective?

This type includes bone tissue, cartilage, adipose tissue, blood and others. Despite the great diversity, all types of connective tissue are united by one feature - the presence of a large amount of intercellular substance. It can be dense, as in bone tissue, loose, as in the tissues that fill the space between organs, and liquid, as in blood.

4. Name the structural features of epithelial tissue.

Its cells adhere very tightly to each other, and the intercellular substance is almost absent. This structure provides protection to underlying tissues from drying out, penetration of microbes, and mechanical damage.

5. What tissue supports plant growth?

Plant growth is provided by educational tissue.

6. What tissue does a potato tuber consist of?

A potato tuber consists of a main tissue.

7. Using the text and pictures of the paragraph, make diagrams “Classification of plant tissues” and “Classification of animal tissues”.

8. What is blood?

Blood is a liquid connective tissue consisting of plasma and formed elements: erythrocytes (red blood cells), leukocytes (white blood cells), platelets (blood platelets).

9. What are the main properties of muscle tissue?

The main properties of muscle tissue are excitability and contractility.

10. How are nerve cells structured?

Any nerve cell has a body and numerous processes of varying lengths. One of them is usually particularly long, it can reach a length from several centimeters to several meters.

11. What are the structural features of the educational tissue of plant organisms?

Educational tissue is formed by small, constantly dividing cells with large nuclei; there are no vacuoles in their cytoplasm.

12. In what parts of the plant is the educational tissue located?

The plant embryo consists entirely of educational tissue. As it develops, most of it is transformed into other types of tissue, but even in the oldest tree educational tissue remains: it is preserved at the tops of all shoots, in all buds, at the tips of roots, in the cambium - cells that ensure the growth of the tree in thickness.

13. What tissue provides support for the plant body and its organs?

Mechanical tissue provides support to the plant and its organs.

14. Name the tissue through which water, mineral salts and organic substances move in plants.

Water and mineral and organic substances dissolved in it move through conducting tissues.

15. How are the structural features of tissues related to the functions they perform?

The structural features of any tissue allow it to perform certain functions. For example, integumentary tissues, if formed by dead cells, then have thick and durable membranes that do not allow water or air to pass through. They are very firmly connected to each other. So these cells provide protection to other tissues.

16. What is the significance of cell specialization for a multicellular organism?

Strict cell specialization is necessary to perform the numerous functions of a living organism. This increases the efficiency of the entire organism, complicates its structure and provides more complex forms of behavior.

The stem grows from the embryonic stem of the bud. If this is the main stem of the plant, then it develops from the embryonic bud of the seed.

After the buds swell and their protective scales move apart, the stem begins to grow and the leaves begin to unfold. In a stem growing from a bud, the length of the internodes gradually increases.

At the very top of the shoot there is a so-called apical bud. It has growth cone. The division of cells in the growth cone leads to the growth of the stem in length.

The growth cone consists of educational fabric. Its cells are capable of constant division.

On the lower cells of the growth cone, rudimentary leaves appear, the stem cells stop dividing and begin to grow. As a result, the stem itself grows, and it turns out that it grows with its upper part. So, if you apply marks along the entire length of the stem, then after some time the distance between the marks at its top will increase, since here the cells continue to grow in length. While further down the stem the distance between the marks may not change.

However, stems do not always grow in length only due to the growth cone. Many plants have intercalary growth, in which the internodes of the shoot lengthen. Typically, this causes the cells at the base of the internodes to divide and grow.

If you remove the top of a stem along with the growth cone, its growth in length will stop. But at the same time, the stem will begin to branch, that is, side shoots will begin to grow.

Stem growth in thickness

The growth of the stem in thickness is ensured by the division of cambium cells. Growth in thickness is observed in trees and shrubs, as well as in perennial grasses. In trees, the cambium is located under the bark. The cambium consists of educational tissue.

The growth of the stem in thickness occurs during a favorable period of the year. In temperate latitudes this occurs during the warm period. At this time, cambium cells are actively dividing.

In trees, those cambium cells that are closer to the bark become phloem cells. Those closest to wood become wood. Moreover, during the growing season, the tree produces more wood cells than bast cells.

In the wood that grows in the spring, fairly thick vessels with thin walls develop. The vessels of autumn wood, on the contrary, are thin with thicker shells.

Since the stem does not grow in thickness in winter, and large cells begin to form again in spring, clear transitions from small to large cells are visible on the cut of the trunk. Wood cells of one year are called tree ring. The age of the tree can be determined by the number of annual rings.

Tree rings may differ from year to year. Some may be narrower, others wider. This difference is due to different weather conditions. If the year was good, the tree received enough moisture and light, then the annual ring will be wide. Also, the width of each individual annual ring is not the same. The rings are usually wider on the south side than on the north side. This is due to the fact that on the northern side the cambium usually warms up less, and therefore its cells divide less well.

Main content.

What is a meristem?
Classification of meristematic (educational) tissues.
Characteristics of the apical (apical) meristem
Discussion of the results of home laboratory work.
Characteristics of the intercalary (intercalary) meristem

Have you ever wondered why plants got their name - PLANTS?

This is because they have the unique ability to grow throughout their lives. This is vital for them. The vast majority of plants do not have the opportunity to move to a more advantageous place, but they have found a way out - to grow - to reach for sunlight, a source of water and minerals. Plants of temperate climates shed their leaves for the winter, and in the spring they appear again, and so on from year to year, until the death of the organism.

In multicellular plants, unlike animals, growth (with the exception of the early stages of embryo development) occurs only in certain areas called meristems and continues throughout the life of the organism, hence the name PLANTS.

Meristem (educational tissue) - this is a group of cells that retain the ability to undergo mitotic division; as a result of this division, daughter cells are formed that grow and form permanent tissue from cells that are no longer capable of dividing.

Some meristem cells retain the ability to divide ( initials), part gradually differentiates, turning into cells of various permanent tissues. That. meristem initial cells remain at the embryonic stage of development throughout the life of the plant (stem cells), and their derivatives are gradually differentiated (see Scheme 1).

The plant body is a derivative of relatively few initial cells.

Meristems can persist for a very long time, throughout the life of the plant (for some trees, thousands of years), because contain a certain number of initial cells capable of dividing an indefinite number of times while maintaining their meristematic character.

Classification of meristems

Procambium – formation of primary xylem and primary phloem.

Pericycle – forms cambium and phellogen.

Phellogen – cork cambium. Located between the phellem (plug) and phelloderm, it forms periderm complex(phellogen, phellem, phelloderm).

A significant difference between these groups of plant tissues is the direction of cell division in relation to the surface of the organ.

In primary meristems cells divide in the transverse, radial and tangential (parallel to the surface) direction - therefore the cells lie randomly.

In secondary meristems– only in tangential mode, so the cells lie in clear rows.

Scheme of the location of various meristems in the plant (according to V.Kh. Tutayuk).

1 – apical (apical)

2 – intercalary (insert)

3 - lateral (side)

Types of meristems and their functions.

Meristems	Location	Role	Result
Apical (apical) Apex –lat. top	At the tips of roots and shoots	Provides primary growth, forming the primary body of the plant	Elongation
Lateral (cambium) (lateral)	In older parts of the plant; lies parallel to the long axis of the organ (for example, cork cambium - phellogen, vascular cambium)	Provides secondary growth. The vascular cambium gives rise to secondary conducting tissues; periderm (crust) is formed from phellogen, which replaces the epidermis and contains a plug	Thickening
Intercalary (insert)	Between areas of permanent tissue, for example, in the nodes of many monocots (at the base of leaves in cereals)	Allows growth in length in intermediate areas. This is essential for those plants whose apical areas are often damaged or destroyed, for example, eaten by herbivores (in cereals) or damaged by waves (in brown algae); this eliminates the need for branching	Elongation

Explanations. In plants, two types of growth lead to an increase in length and thickness: primary and secondary. First, primary growth occurs. Primary growth can result in the formation of an entire plant, and in most monocots and herbaceous dicots this is the only type of growth. Growth in length is primary growth. Primary growth involves apical (apical) and sometimes intercalary (intercalary) meristems.

In some plants (dicots and gymnosperms), primary growth is followed by secondary growth, which involves lateral meristems. It is most pronounced in shrubs and trees. (In some herbaceous plants some secondary thickening of the stem is observed, for example, the development of additional vascular bundles in sunflower). Primary meristems are characteristic of all multicellular plants (starting with brown algae). Secondary - for dicotyledonous angiosperms and gymnosperms.

Apical meristems. The apical meristem is characterized (typical) by relatively small cuboidal cells with a thin cellulose wall and dense cytoplasm. The large nucleus is located in the center of the cell. The cytoplasm contains several small vacuoles (as opposed to the large vacuoles of the main tissue cells) and also contains small undifferentiated plastids called proplastids. Mitochondria are numerous, their shell is folded and therefore they can increase in size. Meristematic cells are densely packed, incl. There are no noticeable air-filled intercellular spaces between them.

In the growth zone, daughter cells resulting from the division of initials increase in size- mainly due to the osmotic absorption of water entering the cytoplasm, and from it into the vacuoles. The growth of stems and roots in length is achieved mainly due to cell elongation occurring at this stage. Small vacuoles increase in size and eventually merge into one large vacuole.

The elongation stage in the growth of a meristematic cell

Laboratory work No. 1: “Root growth in length.”

Equipment: sprouted seeds of peas, beans or beans with a root about 2 cm long; a small jar (mayonnaise, juice); a piece of cardboard; thick cloth or blotting paper; plastic film or cover; black ink, previously poured into the lid and slightly thickened as a result of partial drying; ruler; pointed match; stationery pins.

Experience . For the experiment, you need to prepare a humid chamber. Pour water into the bottom of the jar in a layer of 0.5–1 cm, install a cardboard wall, preferably a two-layer one. The height of the wall should be slightly lower than the can, the width should be the diameter of the can opening.

The bottom edge of the cardboard should be cut in the shape of the convex bottom of the jar. Place blotting paper or thick cloth on both sides of the cardboard wall. Water will rise along it from the bottom of the jar. For the experiment, it is necessary to select 2 - 3 sprouted seeds with more or less straight roots, without signs of damage and the beginning of the formation of lateral roots. Using a finely sharpened match, apply ink marks (on one side) along the entire length of the root in the form of small but clearly visible dots or short lines at a distance of 1.5–2 mm from the other. At the same time, hold the seed by the cotyledons; touching the root with the end of the match should be very light, especially at the tip. It is better to start marking from the base of the root. Then attach the seeds with marked roots to the cardboard wall using pins (both cotyledons are pinned onto the cardboard) so that the roots touch the wet cardboard at a height of 3–4 cm above the water.

Close the jar with a lid or plastic wrap and place in a bright and warm place. To prevent the walls of the jar from fogging up, you can wipe them with a cotton swab soaked in a 1:1 mixture of glycerin and water.

Results. After 2 days, make sure that the marks have noticeably moved apart only at the tip of the root.

Answer the questions:

Why should marks be applied throughout the root, and not just on some part of it?
Why should the distances between marks be the same and small?

Intercalary (intercalary) meristems . Intercalary meristems are located at the bases of internodes; ensure stem growth in length (due to lengthening of internodes) and leaf growth.

Intercalary (intercalary) meristem at the base of the plant internode

Key findings: During the proliferation and development of cells formed by the meristem, intercellular spaces begin to form. With distance from the tops of the stems and the tips of the roots, cell division slows down and then stops.

There are three successive phases of change in young cells:

1) the division phase, caused by an increased increase in the living substance of the protoplast (the internal contents of the cell),

2) a phase of increased proliferation of cell membranes, which is not followed by the growth of protoplast substance, but cell sap appears in abundance, initially in many individual vacuoles, which soon merge into one large vacuole;

3) the determination phase, when cells become specialized to perform certain functions. In the latter case, we observe the transformation of primary educational tissue into permanent tissue.

Basic concepts: meristem, initial, apex, apical meristems, lateral meristems, intercalary meristems, primary growth, secondary growth.

Questions and tasks for review:

What are the functions of educational fabrics?
Which meristems are primary and which are secondary? Why?
The rate of cell division of educational tissue is almost the same in all plants. however, some grow at a rate of 0.7 cm per day, while others, such as bamboo, grow up to 1 m per day. Why is there such a significant difference in growth rates between individual plant species?