Plant growth is ensured by cell division of which tissue. Review of educational, conductive and mechanical plant tissue. What tissue does a potato tuber consist of?
1 what cells form the leaf blade? What is the significance of the leaf skin? What tissue cells is it formed from? what are stomata and where?located? what structure do leaf pulp cells have? what type of fabric are they? Which leaf cells contain the most chloroplasts? what function do the conductive bundles of the leaf perform? What tissue cells are they formed by?
Which statements are true??? 1. all plants are made up of cells 2. Cytoplasm is the internal environment of the cell. 3.All living plant cellshave a core.
4.Vacuoles are the plastid of the cell.
5.cell sap is the contents of a living cell.
6. The movement of the cytoplasm ensures the vital activity of the cell.
7. Different plants have a set of different plastids in their cells.
8.Chlorophyll is found in chloroplasts.
9. The educational tissue is chlorophyll.
10. Cells reproduce by division.
11. Conductive tissue is vessels through which substances move only in the water direction - from the roots to the leaves.
12.Mechanical fabric ensures plant growth
13. Conductive tissue forms a continuous network of vessels in the plant.
14. Educational tissue is present only in young plants.
15. The main sign of life and cells is metabolism.
16. A micropreparation is the internal structure of a cell.
A microscope is a device for studying plants.
18. Magnifying glass and microscope - magnifying devices.
19.The vacuole always occupies a central place in cells.
Which parts of the cell are the clearest???
Add more phrases!!!
1. the green color of the plant is due to the presence in the cells
a) Plastid
B) chlorophyll
2 Cell sap is located
A) cytoplasm
B) vacuoles
c) Mekletnik
have a core
19. The vacuole always occupies a central place in cells
Which statements are true? 1. all plants consist of cells 2. cytoplasm is the internal environment of the cell 3. all living cells of the planthave a core
4. vacuoles are cell plastids
5. cell sap - the contents of a living cell
6. the movement of the cytoplasm ensures the life and activity of the cell
7. Different plants have a set of different plastids in their cells
8. chlorophyll is found in chloroplasts
9. Educational can is chlorophyll
10. cells reproduce by division
11. conductive tissue is vessels through which substances move in only one direction - from roots to leaves
12. mechanical tissue ensures plant growth
13. conducting tissue forms a continuous network of vessels in the plant
14. educational tissue is present only in young plants
15. The main sign of cell life is metabolism
16. microscopic specimen is the internal structure of a cell
17. microscope - a device for studying plants
18. magnifier and microscope - magnifying devices
19. The vacuole in cells always occupies a central place
It divides by mitosis. Educational tissue has the following characteristics: it does not have a secondary cell wall; its cells are constantly dividing; it lacks colored plastids, so it is almost transparent. The meristem is primary (procambium, intercalary, apical) and secondary (pericycle, cambium, wound meristem, phellogen
Tissues consisting of one type of cells are called simple, and those consisting of different types of cells are called complex, or complex. There are various classifications of fabrics, but they are all quite arbitrary. Plant tissues are divided into several groups depending on their main function:
1) meristems, or educational tissues (tissues consisting of living thin-walled, intensively dividing cells);
a) apical (apical) meristims (located at the tops of stems and at the ends of roots) determine the growth of these organs in length;
b) lateral merestims - cambium and phellogen (cambium provides thickening of the stem and root. Phellogen forms a plug)
2) integumentary (protect internal plant tissues from direct influence of the external environment, regulate evaporation and gas exchange)
a) epidermis; b) cork;
3) conductive (provide the conduction of water, soil solutions and assimilation products produced by leaves. Conductive tissues can be primary and secondary in origin.);
a) xelima or wood fabric (fabric that conducts water)
b) phloem or phloem (tissue that conducts organic substances formed by the plant during photosynthesis);
4) mechanical (determine the strength of the plant);
a) collenchyma (consists of parenchyma or several elongated cells with unevenly thickened cellulose walls);
b) sclerenchyma (cells have uniformly thickened lignified walls);
1) fibers; 2) sclerids;
5) basic (consisting of homogeneous parenchyma cells that fill the space between other tissues);
6) secretory or excretory (containing waste products).
Only cells of meristematic tissues are capable of division. Cells of other tissues, as a rule, are incapable of division, and their number increases due to the activity of the corresponding meristems. Such tissues are called permanent. Permanent tissues arise from meristems as a result of cellular differentiation. Differentiation lies in the fact that during the individual development of an organism (ontogenesis), qualitative differences arise between initially homogeneous cells, and the structure and functional properties of the cells change. Usually differentiation is irreversible. Its progress is influenced by substances that act as hormones.
eristems (from the Greek “meristos” - divisible), or educational tissues, have the ability to divide and form new cells. Due to meristems, all other tissues are formed and long-term (lifelong) growth of the plant occurs. Animals lack meristems, which explains their limited period of growth. Meristem cells are characterized by high metabolic activity. Some meristem cells, called initial, remain at the embryonic stage of development throughout the life of the plant, while others gradually differentiate and turn into cells of various permanent tissues. The initial cell of the meristem can, in principle, give rise to any cell of the body. The body of land plants is a derivative of relatively few initial cells.
Primary meristems have meristematic activity, that is, they are initially capable of division. In some cases, the ability to actively divide may reappear in cells that have almost lost this property. Such “newly” emerged meristems are called secondary.
In the plant body, meristems occupy different positions, which allows them to be classified. According to their position in the plant, apical or apical (from the Latin “apex” - top), lateral or lateral (from the Latin “latus” - side), and intercalary meristems are distinguished.
Apical meristems are located at the tops of the axial organs of the plant and ensure body growth in length, while lateral meristems primarily provide growth in thickness. Each shoot and root, as well as the embryonic root and bud of the embryo, have an apical meristem. Apical meristems are primary and form cones of root and shoot growth (Fig. 1).
Lateral meristems are located parallel to the lateral surfaces of the axial organs, forming a kind of cylinders that look like rings in cross sections. Some of them are primary. The primary meristems are the procambium and pericycle, the secondary ones are the cambium and phellogen.
Intercalary, or intercalary, meristems are often primary and are preserved in the form of separate sections in zones of active growth (for example, at the bases of internodes, at the bases of leaf petioles).
There are also wound meristems. They are formed in places of damage to tissues and organs and give rise to callus - a special tissue consisting of homogeneous parenchyma cells covering the site of damage. The callus-forming ability of plants is used in horticultural practice when propagating them by cuttings and grafting. The more intense the callus formation, the greater the guarantee of fusion of the rootstock with the scion and rooting of the cuttings. Callus formation is a necessary condition for plant tissue culture on artificial media.
The cells of the apical meristems are more or less isodiametric in size and polyhedral in shape. There are no intercellular spaces between them, the shells are thin and contain little cellulose. The cell cavity is filled with dense cytoplasm with a relatively large nucleus occupying a central position. Vacuoles are numerous, small, but usually not noticeable under a light microscope. Ergastic substances are usually absent. Plastids and mitochondria are few and small.
The cells of the lateral meristems vary in size and shape. They roughly correspond to the cells of those permanent tissues that later arise from them. Thus, both parenchymal and prosenchymal initials are found in the cambium. Parenchyma of conducting tissues is formed from parenchymal initials, and conducting elements are formed from prosenchymal initials.
Rice. 1. Apical meristem of Elodea shoot. A - longitudinal section; 5 - growth cone (appearance and longitudinal section); B - cells of the primary meristem;
G - parenchyma cell of the formed leaf:
1 ~ growth cone, 2 - leaf primordium, 3 - tubercle of axillary bud
23 Integumentary tissues.
Its main function is to protect internal living tissues from excess evaporation. Cover tissue protects plants from overheating, penetration of microbes, and other adverse external influences.
Integumentary tissues are primary and secondary. The primary covering tissue is epidermis, secondary – cork and crust.
The epidermis is the primary integumentary tissue. It is formed by the primary apical meristem. The functions are twofold: on the one hand, the epidermis protects the plant from unfavorable environmental factors, on the other, it ensures its close connection with the external environment, free penetration of light, and intense gas exchange. The protective function of the epidermis is enhanced by additional formations - hairs, cuticle, waxy coating.
Hairs There are two types of hairs - covering and glandular. Functions – protecting plants from excess evaporation.
Glandular hairs remain alive longer. Their cells are characterized by thin walls, contain vacuolated cytoplasm, and a large nucleus. Hairs release plant waste products into the external environment. - water, essential oils, organic acids. The functional purpose of glandular hairs is different.
Cuticle -
This is a film of the waxy substance cutin on the surface of leaves, fruits, and some plant seeds. Cutin is formed by the cytoplasm ,
permeates the cell membrane and, in contact with air, hardens, forming the cuticle. (ficus leaves, lingonberries, cranberries)
Waxy coating performs the same function as the cuticle.
Stoma. The connection of the leaf with the external environment, the gas exchange process is carried out through stomata .
This is a gap between two specialized cells of the epidermis, which are called guard cells. The movement of stomata is determined by cell turgor. With loss of turgor, the cell volume decreases somewhat and the cells collapse. A bend or protrusion appears on the thin part of the cell membrane. The projections of two adjacent guard cells touch and close the stomatal fissure.
The location of the parastomatal cells is associated with the process of stomatal formation. Peristomatal cells in some cases differ from the main cells of the epidermis in their shape and protoplast structure. It is possible that they are related to the movement of stomata.
24 Basic tissues (parenchyma). The main parenchyma occupies a significant place in the plant both in volume and in role. Conductive and mechanical tissues seem to be immersed in the main parenchyma. The pulp of fruits, seeds, and mesophyll of leaves consists of it.
The cells of the main parenchyma are varied in shape; they are round, oval, cylindrical, tabular, etc. The cytoplasm in the cells is usually located wall-to-wall. The central position is occupied by the vacuole. Common inclusions are starch grains, protein crystals, oil droplets, etc. Cell walls are often thin with simple pores, less often thickened and partially lignified.
The main function of the main parenchyma is the transformation of matter and energy. Various processes of synthesis and hydrolysis take place in its cells, and lamellar substances accumulate. Depending on its position in the plant, parenchyma can perform various functions - storage, conduction, mechanical, excretory, assimilation, and can give rise to secondary educational tissue.
In the core of the stem, the endosperm of seeds, in the cotyledons of the embryo, in tubers, pericarps, the main parenchyma is tissue storing.
In the medullary rays of the stem and root, parenchyma plays conductive role. Water, minerals and organic substances spread through it Mechanical The role of the cells of the main parenchyma is played mainly due to their turgor.
Assimilation tissue can also be considered as one of the options for “reincarnation” of the main parenchyma.
Aerenchyma- air-bearing tissue in plants, built from cells connected to each other so that large air-filled voids (large intercellular spaces) remain between them.
The development of secondary educational tissue from the main parenchyma can be observed in the central cylinder of the stem and root during the development of the cambium, during the formation of the cork cambium.
from the vascular bundle to the secretion points and is excreted through the intercellular spaces or through openings such as stomata. However, the size of the stomatal gap in the hydathode is not regulated. Droplet-liquid water is also secreted by some glandular hairs, which in such cases also play the role of hydathodes.
Mechanical fabrics.
The mechanical tissue in the plant is located in such a way that, with the least amount of material required, it ensures the greatest strength of the plant. The mechanical role of living cells is determined by their turgor. Cells saturated with water are elastic and retain their shape and volume well.
Cell turgor depends on external conditions. In cases where the turgor state is unstable or plant organs bear a large mechanical load, special mechanical tissues develop. They are diverse, but have a common feature - thick cell membranes.
Sclerenchyma– the main type of mechanical fabric. It ensures the strength of the axial organs. Sclerenchyma cells are prosenchymal in shape. Their length exceeds their width by tens and hundreds of times. Cell membranes, as a rule, become lignified. Only some have sclerenchyma, which does not lignify or lignifies weakly. Sclerenchyma has great strength and elasticity. The elasticity of bast fiber exceeds the elasticity of iron and approaches the elasticity of steel. Sclerenchyma in the plant is found in the axial organs, stems and roots. It is part of conducting bundles.
Collenchyma- parenchymal tissue. In a cross section, collenchyma cells have a variety of shapes. The membranes thicken partially and only due to fiber, so the contents of the cell do not die off, as is observed in most mechanical tissues. A characteristic feature of collenchyma is the presence of chloroplasts in its cells.
According to the nature of the thickenings, three types of collenchyma are distinguished - angular, lamellar and loose. In angular collenchyma, thickenings are located at the corners of the cell. In lamellar collenchyma, the outer and inner ones thicken. In loose collenchyma, intercellular spaces are well developed. Collenchyma is located superficially, underlies the epidermis and determines the green color of the stems of herbaceous plants and young woody shoots.
Sclereids have a parenchymal shape, round, ovoid. The membranes of these cells become very thick and lignified. Numerous channels are visible in the cell walls. The formed cells are dead, the cell cavities have no contents.
Conductive fabrics.
Conductive tissues develop very early in the plant. There are two currents of fluid in a plant, conditions called ascending and descending. The first represents a flow of water and minerals and is directed from the root to the leaves, the second - vice versa. The bed of the ascending current is a complex tissue - xylem, or wood, and the bed of the descending current is phloem, or phloem. Xylem. Xylem consists of mechanical tissue, basic parenchyma and vessels and tracheids.
Tracheids- prosenchymal cells several millimeters long, tenths and hundredths of a millimeter wide. Along with water-conducting tracheids, they also perform mechanical functions.
Vessels- these are long hollow tubes with an average length of several centimeters (sometimes up to 1 meter or more.
The cells that make up the vessel are called vessel segments; the remains of the transverse walls between the cells are called perforation plates. The shape of the vessel segments is different
In many plants, with age, the vessels become clogged with till. Tills- these are parenchyma cells that penetrate the vessel through pores in its walls, grow and clog it, making it impassable.
The second component of xylem is the mechanical tissue sclerenchyma. Sclerenchyma, which is part of the xylem, is called libriform or otherwise wood fiber.
In the vast majority of flowering plants, the xylem includes the main parenchyma, called wood Its cells are scattered throughout the xylem or adjacent to the vessels. The cells of the wood parenchyma are somewhat elongated along the axis of the organ, their membranes slightly thicken and become lignified.
There are primary and secondary xylem. Primary xylem occurs during the formation of the primary structure of the plant body from the primary lateral meristem - procambium. Its first elements are small, slightly lignified vessels, spiral and ringed, forming protoxylem. The xylem elements that develop somewhat later and are relatively larger are called metaxylem. Secondary xylem is formed from the secondary lateral meristem - cambium. Secondary tissues determine the growth of the plant in thickness. Secondary xylem is characterized by the presence of scalariform, reticulate and punctate vessels
27 Xylem performs two main functions in the plant: water moves through it along with dissolved minerals and it serves as a support for the plant’s organs. The xylem consists of four types of histological elements: tracheids, vessels, parenchyma cells and waves. Tracheids They are narrow, highly elongated dead cells with pointed ends and lignified membranes. The penetration of solutions from one tracheid into another occurs by filtration through pores - recesses covered with a membrane. Liquid flows through the tracheids slowly, since the pore membrane prevents the movement of water. Tracheids are found in all higher plants, and in most horsetails, club mosses, ferns and gymnosperms they serve as the only conducting element of the xylem. Angiosperms have vessels along with tracheids. Trachea (vessels) - these are hollow tubes consisting of individual segments located one above the other. In the segments, through holes are formed on the transverse walls - perforations, or these walls are completely destroyed, due to which the speed of the flow of solutions through the vessels increases many times over. The shells of the vessels are impregnated with lignin and give the stem additional strength. Depending on the nature of the thickening of the membranes, tracheas are distinguished as ringed, spiral, scalariform, etc. The first vessels to form - protoxylem - are laid at the top of the axial organs, directly under the apical meristem, where the surrounding cells still continue to stretch. Mature protoxylem vessels are capable of stretching simultaneously with the elongation of surrounding cells, since their cellulose walls are not yet completely lignified - lignin is deposited in them only in rings or in a spiral. These lignin deposits allow the tubes to maintain sufficient strength during stem or root growth. As the organ grows, new xylem vessels appear, which undergo more intense lignification and complete their development in the mature parts of the organ; This is how megaxshema is formed. Meanwhile, the very first vessels of the protoxylem are stretched and then destroyed. Mature metaxylem vessels are not able to stretch and grow. Are they dead, hard? completely lignified tubes. If their development was completed before the elongation of the surrounding living cells was completed, then they would greatly interfere with this process. The long, hollow xylem tubes are an ideal system for carrying water over long distances with minimal disturbance. Xylem also performs its second function - mechanical - due to the fact that it consists of a number of lignified tubes. In the primary body of the plant, the xylem in the roots occupies a central position, helping the root to resist the pulling force of the above-ground parts, bending under gusts of wind. In the stem, the vascular bundles either form a ring along the periphery, as in dicotyledons, or are arranged randomly, as in monocotyledons; in both cases, the stem is penetrated by individual strands of xylem, providing it with a certain support. The supporting function of xylem becomes especially important where secondary growth takes place. During this process, the amount of secondary xylem rapidly increases; the role of the main mechanical tissue passes to it from collenchyma and sclerenchyma, and it is this tissue that serves as a support for large tree and shrub species. The growth of trunks in thickness is determined to a certain extent by the loads to which the plant is exposed, so that sometimes additional growth is observed, the purpose of which is to strengthen the structure and provide it with maximum support. Woody xylem parenchyma is contained in both primary and secondary xylem, but in the latter its quantity is greater and its role is more important. Wood parenchyma cells, like any other parenchyma cells, have thin cellulose walls and living contents. It is believed that wood fibers, like xylem vessels, originate from tracheids. Unlike xylem vessels, wood fibers do not conduct water; therefore, they can have much thicker walls and narrower gaps, which means they are also more durable, i.e., they give the xylem additional mechanical strength.
28 PHLOEM Consists of mechanical tissue, main parenchyma and sieve tubes. Sieve tubes are functionally and morphologically the main elements of phloem. Their function is to conduct current in plastic substances.
Sieve tubes consist of a vertical row of living elongated cells, each of which is a tube segment. Typical sieve tubes consist of cylindrical cells, while more primitive ones consist of prosenchymal cells. A characteristic morphological feature of sieve tubes is the structure of the cell membrane. It is relatively thin and has numerous, usually through, pores. Through the pores, strands of cytoplasm - plasmodesmata - penetrate from one cell to another. Pores are collected in groups on the longitudinal and more often on the transverse walls of the cell. The area of the cell membrane in the sieve tube containing numerous pores is called sieve plate.
The cell sap of sieve tubes contains sugars, dextrins, proteins, amino acids, nitrites, nitrates, salts, phosphoric acids, enzymes, etc.
Phloem, like xylem, includes the mechanical tissue of sclerenchyma and the main parenchyma. The sclerenchyma of the phloem is called bast fiber, the main parenchyma is called phloem parenchyma. The main parenchyma in the phloem is scattered and, together with the sieve tubes, makes up the soft bast. The areas of bast fiber are called hard bast. Phloem, like xylem, is divided into primary and secondary. Primary phloem in turn differentiates into protophloem and metaphloem.
29 Tissues are called excretory There are excretory tissues of internal and external secretion. Excretory tissues of external secretion 1. Hydathodes are devices used to excrete water. In many plants, various organs (mainly leaves) secrete water in the form of droplets - Guttation. Guttation occurs especially intensively under conditions that impede transpiration and evaporation of water by leaves. 2. External epidermal glands are very diverse and widespread. In many plants, the skin of leaves and stems has - Glandular hairs. These hairs usually have a multicellular stalk and a rounded unicellular head. Essential oils fill the space between the cellulose membrane and the cuticle. 3. Nectaries are a special type of external secretion glands - they are located in the flower. 4. The rarest type is the Digesting glands of insectivorous plants. sundew leaves. Excretory tissues of internal secretion. Depending on the method of their formation, they are distinguished: Schizogenic receptacles are formed by the divergence of cell membranes that were initially closely adjacent to each other. Rexigenic intercellular spaces arise by rupturing entire sections of tissue, and then drying out and dying of the cells. Lysigenic containers appear during dissolution - lysis of cells and their membranes. Channel-shaped excretory devices or passages are formed mainly in stems and roots, less often in leaves. The channels are called oil, resin, mucus and gum based on their contents. A kind of tubular canals are the lactiferous vessels or lactifers - there are two types: 1) articulated and 2) non-segmented. The non-segmented lactifer is a giant multinucleated cell with one continuous vacuole. Articulated lacticifers consist of many individual lactiferous cells.
30. Primary anatomical structure of the root using the example of the iris.
In the section, even at low magnification, a small internal part is clearly visible - central cylinder, and external primary cortex, covered with a single layer of cells with root hairs - rhizoderm (epiblema).
The outer layer of the primary cortex is exodermis, consists of tightly closed polygonal cells, the walls of which are subsequently suberized and perform a protective function. Then located main parenchyma (mesoderm), constituting the main mass of the primary crust. The inner layer of the primary crust is endoderm consists of a single row of cells, with thickened radial and internal walls. Among these cells there are thin-walled living cells (located almost opposite the small xylem vessels), called passes. The outer layer of the central cylinder is the pericycle, consisting of one row of parenchyma cells. The inner part of the central cylinder is occupied by a polyarchal radial bundle.
31. Secondary anatomical structure of the root using the example of pumpkin.
At low magnification, find the central cylinder with four rays of primary xylem (tetrarchic bundle). Between them are the bases of four large open collateral vascular bundles. The endoderm is poorly visible, since only the radial walls of its cells are thickened (Caspari spots). At high magnification, it is clear that the cells of the thin-walled parenchyma lying between the xylem and phloem are separated by tangential partitions, and in some places, newly formed and not yet lignified vessels are visible inward of this layer. Between the xylem and phloem there is a wide cambial zone with uneven outlines and consisting of several rows of rather small tabular-shaped cells. Secondary thickening is associated with the formation and activity of the cambium. The secondary xylem is significantly larger in area than the phloem and lies closer to the center. It is represented by large vessels, fibers and small parenchyma cells. Secondary phloem, located on the periphery of the cambial zone, is represented by sieve tubes with simple horizontal sieve plates, companion cells and parenchyma. The primary phloem is located at the very periphery of the bundle, its sieve tubes are deformed. Between the vascular bundles there are wide primary bast woody rays formed by the interfascicular cambium. Large parenchyma cells forming rays are somewhat elongated in the radial direction. On the surface, the pumpkin root is covered with periderm. At low magnification, schematically sketch the structure of the root, indicating the primary and secondary xylem, primary and secondary phloem, cambium, secondary bark, periderm.
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.
In animals, there are 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 ensured 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 specialization of cells 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.
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 interfere with the penetration of light into 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 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 slit 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.
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. The 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.
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 in 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 able to divide.
Some meristem cells retain the ability to divide ( initials), some gradually differentiate, 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).
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1 – apical (apical) 2 – intercalary (insert) 3 - lateral (side) |
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Types of meristems and their functions.
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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. (Some herbaceous plants exhibit some secondary thickening of the stem, 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 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.
Cover 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
Main conclusions: 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 separate 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?
