Root. Functions. Types of roots and root systems. Anatomical structure of the root. Mechanism of soil solution entry into the root and its movement into the stem. Root modifications. The role of mineral salts. The concept of hydroponics and aeroponics.
Higher plants, unlike lower plants, are characterized by the division of the body into organs that perform various functions. There are vegetative and generative organs of higher plants.
Vegetative organs - parts of the body of plants that perform the functions of nutrition and metabolism. Evolutionarily, they arose as a result of the complication of the body of plants when they landed and the development of air and soil environments. The vegetative organs include the root, stem and leaf.
1. Root and root systems
The root is an axial organ of plants with radial symmetry, growing due to the apical meristem and not bearing leaves. The root growth cone is protected by a root cap.
The root system is the totality of the roots of a single plant. The shape and nature of the root system are determined by the ratio of growth and development of the main, lateral and adventitious roots. The main root develops from the germinal root and has positive geotropism. Lateral roots arise on the main or adventitious roots as offshoots. They are characterized by transversal geotropism (diageotropism). Adventitious roots occur on stems, roots, and rarely on leaves. In the case when the main and lateral roots are well developed in the plant, a tap root system is formed, which may contain adventitious roots. If the adventitious roots are predominant in the plant, and the main root is invisible or absent, then a fibrous root system is formed.
Root functions:
Absorption from the soil of water with mineral salts dissolved in it. The function of absorption is performed by root hairs (or mycorrhiza) located in the absorption zone.
Anchoring the plant in the soil.
Synthesis of products of primary and secondary metabolism.
Biosynthesis of secondary metabolites (alkaloids, hormones and other biologically active substances) is carried out.
Root pressure and transpiration ensure the transport of aqueous solutions of mineral substances through the vessels of the root xylem (upward current), to the leaves and reproductive organs.
Reserve nutrients (starch, inulin) are deposited in the roots.
Synthesize in the meristematic zones the growth substances necessary for the growth and development of the aerial parts of the plant.
Carry out symbiosis with soil microorganisms - bacteria and fungi.
Provide vegetative reproduction.
Some plants (monstera, philodendron) act as a respiratory organ.
Root modifications. Very often the roots perform special functions, and in connection with this they undergo changes or metamorphoses. Root metamorphoses are fixed hereditarily.
Retractors (contractile) The roots of bulbous plants serve to immerse the bulb in the soil.
Reservers the roots are thickened and strongly parenchymatized. In connection with the accumulation of reserve substances, they acquire onion, conical, tuberous, and other forms. Storage roots include 1) roots in biennial plants. Not only the root, but also the stem (carrots, turnips, beets) takes part in their formation. 2) root tubers - thickening of adventitious roots. They are also called root cones(dahlia, sweet potato, chistyak). Necessary for the early appearance of large flowers.
Roots - trailers have climbing plants (ivy).
aerial roots characteristic of epiphytes (orchids). They provide the plant with absorption of water and minerals from the moist air.
Respiratory plants growing on waterlogged soils have roots. These roots rise above the soil surface and supply the underground parts of the plant with air.
stilted roots are formed in trees growing in the littoral of tropical seas (mangroves). Strengthens plants in loose soil.
Mycorrhiza- symbiosis of the roots of higher plants with soil fungi.
Nodules - tumor-like growths of the root bark as a result of symbiosis with nodule bacteria.
Columnar roots (roots - props) are laid as adventitious on the horizontal branches of the tree, reaching the soil, grow, supporting the crown. Indian banyan.
In some perennial plants, adventitious buds are laid in the root tissues, which later develop into ground shoots. These escapes are called root suckers, and the plants root offspring(aspen - Populustremula, raspberry - Rubusidaeus, sow thistle - Sonchusarvensis, etc.).
Anatomical structure of the root.
In a young root, 4 zones are usually distinguished in the longitudinal direction:
division zone 1 - 2 mm. Represented by the tip of the growth cone, where active cell division occurs. It consists of cells of the apical meristem, and is covered by a root cap. It performs a protective function. When in contact with the soil, the cells of the root cap are destroyed with the formation of a mucous membrane. It (the root cap) is restored due to the primary meristem, and in cereals - due to a special meristem - calyptrogen.
Stretch zone is several mm. Cell divisions are practically absent. Cells are maximally stretched due to the formation of vacuoles.
Suction zone is several centimeters. This is where cell differentiation and specialization takes place. Distinguish integumentary tissue - epiblema with root hairs. Epiblema (rhizoderma) cells are living, with a thin cellulose wall. Some cells form long outgrowths - root hairs. Their function is the absorption of aqueous solutions by the entire surface of the outer walls. Therefore, the length of the hair is 0.15 - 8 mm. On average, from 100 to 300 root hairs are formed per 1 mm 2 of the root surface. They die in 10-20 days. play a mechanical (supporting) role - they serve as a support for the tip of the root.
Venue stretches up to the root neck and makes up most of the length of the root. In this zone, there is an intensive branching of the main root and the appearance of lateral roots.
Transverse structure of the root.
On a transverse section in the absorption zone in dicotyledonous plants, and in monocotyledonous plants, in the conduction zone, three main parts are distinguished: integumentary-absorption tissue, primary cortex, and the central axial cylinder.
Integumentary-absorption tissue - rhizoderm performs integumentary, suction, and also, partially, support functions. Represented by a single layer of epiblema cells.
The primary cortex of the root is most powerfully developed. It consists of exoderm, mesoderm = parenchyma of the primary cortex and endoderm. Exoderm cells are polygonal, tightly adjacent to each other, arranged in several rows. Their cell walls are impregnated with suberin (corking) and lignin (lignification). Suberin provides impermeability of cells to water and gases. Lignin gives it strength. The water and mineral salts absorbed by the rhizodermis pass through the thin-walled cells of the exoderm = passage cells. They are located under the root hairs. As the rhizodermal cells die off, the ectoderm can also perform an integumentary function.
The mesoderm is located under the ectoderm and consists of living parenchymal cells. They perform a storage function, as well as the function of conducting water and salts dissolved in it from the root hairs to the central axial cylinder.
The inner single-row layer of the primary cortex is represented by the endoderm. There are endoderm with Casparian bands and endoderm with horseshoe-shaped thickenings.
Endoderm with Casparian bands is the initial stage of endoderm formation, in which only the radial walls of its cells are thickened due to their impregnation with lignin and suberin.
In monocotyledonous plants in the cells of the endodermis, further impregnation of the cell walls with suberin occurs. As a result, only the outer cell wall remains unthickened. Among these cells, cells with thin cellulose membranes are observed. These are checkpoints. They are usually located opposite the rays of the xylem bundle of the radial type.
It is believed that the endoderm is a hydraulic barrier, facilitating the movement of minerals and water from the primary cortex into the central axial cylinder, and preventing their reverse flow.
The central axial cylinder consists of a single-row pericycle and a radial vascular fibrous bundle. The pericycle is capable of meristematic activity. It forms lateral roots. The vascular fibrous bundle is the conducting system of the root. In the root of dicotyledonous plants, the radial bundle consists of 1–5 xylem rays. Monocots have 6 or more xylem rays. Roots have no core.
In monocotyledonous plants, the structure of the root does not undergo significant changes during the life of the plant.
For dicot plants on the border of the suction zone and the zone of strengthening (conduction), there is a transition from the primary to secondary structure root. The process of secondary changes begins with the appearance of layers of cambium under the areas of the primary phloem, inward from it. The cambium arises from the poorly differentiated parenchyma of the central cylinder (stele).
Between the rays of the primary xylem from the cells of the procambium (lateral meristem), arcs of the cambium are formed, closing on the pericycle. The pericycle partially forms the cambium and phellogen. The cambial regions arising from the pericycle form only the parenchymal cells of the medullary rays. Cambium cells lay secondary xylem toward the center, and secondary phloem outward. As a result of the activity of the cambium, open collateral vascular-fibrous bundles are formed between the rays of the primary xylem, the number of which is equal to the number of rays of the primary xylem.
At the site of the pericycle, a cork cambium (phellogen) is laid, giving rise to periderm, the secondary integumentary tissue. The cork isolates the primary cortex from the central axial cylinder. The bark dies and is shed. The periderm becomes the integumentary tissue. And the root is actually represented by the central axial cylinder. In the very center of the axial cylinder, the rays of the primary xylem are preserved, between them there are vascular-fibrous bundles. The complex of tissues outside the cambium is called the secondary cortex. That. the root of the secondary structure consists of xylem, cambium, secondary cortex and cork.
Absorption and transport of water and minerals by the root.
Absorption of water from the soil and delivery to ground organs is one of the most important functions of the root, which arose in connection with the emergence of land.
Water enters the plants through the rhizoderm, in the absorption zone, the surface of which is increased due to the presence of root hairs. Xylem is formed in this zone of the root, providing an upward flow of water and minerals.
The plant absorbs water and minerals independently of each other, because. these processes are based on different mechanisms of action. Water passes into the root cells passively due to osmosis. In the root hair there is a huge vacuole with cell sap. Its osmotic potential ensures the flow of water from the soil solution into the root hair.
Mineral substances enter the root cells mainly as a result of active transport. Their absorption is facilitated by the release of various organic acids by the root, which convert inorganic compounds into a form available for absorption.
In the root, the horizontal movement of water and minerals occurs in the following sequence: root hair, cortical parenchyma cells, endoderm, pericycle, parenchyma of the axial cylinder, root vessels. Horizontal transport of water and minerals occurs in three ways:
The path through the apoplast (a system consisting of intercellular spaces and cell walls). Primary for the transport of water and ions of inorganic substances.
The path through the symplast (a system of cell protoplasts connected by plasmodesmata). Carries out the transport of mineral and organic substances.
The vacuolar pathway is the movement from vacuole to vacuole through other components of adjacent cells (plasma membranes, cytoplasm, vacuole tonoplast). Applicable exclusively for the transport of water. For the root is insignificant.
In the root, water moves along the apoplast to the endoderm. Here, its further advance is hindered by the Caspari bands, so further water enters the stele along the symplast through the passage cells of the endoderm. This switching of pathways regulates the movement of water and minerals from the soil into the xylem. In the stele, water encounters no resistance and enters the conducting vessels of the xylem.
The vertical transport of water goes through dead cells, so the movement of water is provided by the activity of the root and leaves. The root supplies water to the vessels of the stem under pressure, called the root. It occurs as a result of the fact that the osmotic pressure in the root vessels exceeds the osmotic pressure of the soil solution due to the active release of mineral and organic substances into the vessels by the root cells. Its value is 1 - 3 atm.
Evidence of root pressure is the "weeping of the plant" and guttation.
"Crying of a plant" - the release of liquid from a cut stem.
Guttation is the release of water from an intact plant through the tips of the leaves when it is in a humid atmosphere or intensively absorbs water and minerals from the soil.
The upper force of water movement is the suction force of the leaves, provided by transpiration. Transpiration is the evaporation of water from the surface of leaves. The sucking force of leaves in trees can reach 15 - 20 atm.
In the vessels of the xylem, water moves in the form of continuous water threads. Between water molecules there are forces of adhesion (cohesion), which causes them to move one after another. The adhesion of water molecules to the walls of vessels (adhesion) provides an upward capillary flow of water. The main driving force is transpiration.
For the normal development of the plant, the roots must be provided with moisture, access to fresh air and the necessary mineral salts. All this plants are obtained from the soil, which is the top fertile layer of the earth.
To increase the fertility of the soil, various fertilizers are applied to it. Fertilizing during plant growth is called top dressing.
There are two main groups of fertilizers:
Mineral fertilizers: nitrogen (nitrate, urea, ammonium sulfate), phosphate (superphosphate), potash (potassium chloride, ash). Complete fertilizers contain nitrogen, phosphorus and potassium.
Organic fertilizers - substances of organic origin (manure, bird droppings, peat, humus).
Nitrogen fertilizers dissolve well in water, promote plant growth. They are applied to the soil before sowing. For the ripening of fruits, the growth of roots, bulbs and tubers, phosphorus and potash fertilizers are needed. Phosphate fertilizers are poorly soluble in water. They are brought in in the fall, along with manure. Phosphorus and potassium increase the cold resistance of plants.
Plants in greenhouses can be grown without soil, in an aquatic environment that contains all the elements the plant needs. This method is called hydroponics.
There is also an aeroponics method - air culture - when the root system is in the air and is periodically irrigated with a nutrient solution.
Root anatomy (part 2)
The primary structure of the root can be viewed under a microscope on a transverse section of the absorptive zone of a young root. On a similar preparation, it can be seen that the root consists of the epidermis (epiblema), which forms root hairs, primary root cortex, located under the epidermis, occupying the main part of the root and consisting of cells of the main tissue. The inside of the root is called central cylinder, which consists mainly of conductive tissues (Fig. 2).
Fig.2. Cross sections of the root:
I- the incision was made in the zone of root hairs, the epidermis with numerous root hairs, the main tissue of the cortex and the central cylinder are visible. II - root central cylinder: a - a large vessel, from which five rays of smaller vessels diverge, between them are sections of the bast (phloem); b - endoderm cells; c - passage cells, d - pericycle, or root layer.The main tissue of the root cortex cells contains a protoplast, as well as spare substances, crystals, resins, etc. The innermost layer of the cortex forms endoderm, which surrounds the central cylinder and consists of several elongated cells. On transverse sections, the radial membranes of these cells have dark spots or strongly thickened inner and lateral lignified membranes that do not allow water to pass through. Among them are vertical rows checkpoints with thin-walled cellulose shells, they are located opposite the woody vessels and serve to pass water and salts flowing from the root hairs through the bark cells into the woody vessels.
Inside of the endoderm is located central cylinder, the outer layer of which is called root layer(pericycle), as lateral roots develop from it, which then grow through the bark and go outside. The lateral roots are usually formed against the rays of the wood, and therefore they are distributed on the root in regular rows according to the number of rays of the wood, or twice as many rows.
In the central cylinder there is a conductive tissue consisting of water-bearing vessels - tracheas and tracheids, forming wood (xylem), and of sieve tubes with accompanying cells, forming a bast (phloem) and conducting organic substances. Since the primary wood at the root is located in the form of rays, the number of which varies (from 2 to 20), then areas of primary bast are distributed in the intervals between the rays of primary wood and their number corresponds to the number of rays of wood.
Trachea, or vessels, are hollow tubes, the walls of which have a variety of thickenings. Tracheids are elongated (prosenchymal) dead cells with pointed ends.
Through the tracheae and tracheids, water and dissolved salts rise along the root up and further along the stem, and through the sieve tubes of the bast, organic substances (sugar, protein substances, etc.) descend from the stem down to the root and into its branches.
The mechanical elements of bast and wood (bast fibers and wood fibers) are distributed between the cells of the conductive tissue. In the central cylinder of the root there are also living parenchymal cells.
in the roots monocot plants changes in the course of life are reduced only to the death of root hairs and corking of the cells of the outer cortex, to the appearance of mechanical tissues. Only in tree-like monocots with thickening roots and trunks (dracaena, palm trees) does cambium appear and secondary changes occur.
At dicot plants already during the first year of life, the primary structure of the root described above undergoes sharp secondary changes associated with the fact that a strip of cambium appears between the primary wood (xylem) and the primary bast (phloem); if its cells are deposited inside the root, they turn into secondary wood (xylem), and outwards - into secondary bast (phloem). Cambium cells arise from parenchymal cells located between primary wood and bast. They are divided by tangential septa (Fig. 3).
Fig.3. The beginning of secondary changes in the root of a dicotyledonous plant (common bean):
1 - the main tissue of the cortex; 2 - endoderm; 3 - root layer (pericycle); 4 - cambium; 5 - bast (phloem); 6 - primary xylem.Pericycle cells, which are against the rays of wood, divide, forming parenchymal tissue, which turns into core beam. The remaining cells of the pericycle, which are the outer layer of the central cylinder of the root, also begin to divide along their entire length, and from them cork tissue arises, separating the inner part of the root from the primary cortex, which gradually dies and is shed from the root.
cambial layer closes around the primary wood of the central cylinder, and as a result of the division of its cells, secondary wood grows inside, and a continuous bast is formed towards the periphery, moving further and further away from the primary wood. The cambium initially looks like a curved line, and later flattens out and takes the shape of a circle.
In autumn and winter, cell division of the cambium changes, and in spring it begins with renewed vigor. As a result, layers of wood are formed in perennial roots, and the root becomes similar in structure to the stem. Roots can be distinguished from stems by the primary wood remaining in the center of the root in the form of radial rays.(Fig. 2). At the root, the core rays rest against the primary wood, while in the stem they always rest against the core.
Vessels of wood and sieve tubes of the bast from the root pass directly into the stem, where they are located not in radial rays, as in the primary structure of the root, but in the form of ordinary closed (monocot) and open (bicot) vascular-fibrous bundles. The rearrangement of wood and bast occurs in the root collar in the hypocotyl knee.
K category: plant anatomy
The primary structure of the root
With a primary structure in the root, as well as in the stem, zones of the primary cortex and the central cylinder can be distinguished, however, unlike the stem, the primary cortex of the root is more strongly developed than the central cylinder.
The function of the integumentary tissue in the root is performed by the exoderm, which is formed from one or several rows of peripheral cells of the primary cortex. As the root hairs die off, the walls of the outer cells of the cortex are covered on the inside with a thin layer of suberin, which first appears on the radial walls. Suberinization causes cells to be impermeable to either water or gases. In this respect, the exoderm is similar to the cork, but unlike it, it is primary in origin. In addition, exoderm cells are not arranged in regular rows, like cork cells, but alternate with one another. The longitudinal walls of its cells often have spiral thickenings.
The exoderm sometimes retains cells with thin, non-corked walls. In roots with a weak secondary thickening, in addition to the exoderm, protective functions are also performed by the cells of the rhizoderm undergoing changes.
Under the exoderm there are living parenchymal cells of the primary cortex, located more or less loosely and forming intercellular spaces. Sometimes air cavities develop in the cortex, which provide gas exchange. It may also contain mechanical elements (sclereids, fibers, groups of cells resembling collenchyma) and various receptacles of secretions.
The inner single-row layer of tightly adjacent cells of the primary cortex is represented by the endoderm. At the early stages of development, it consists of living, somewhat elongated prismatic thin-walled cells. In the future, its cells acquire some structural features.
A change in the chemical composition of the middle part of the radial and horizontal (transverse) walls, accompanied by a slight thickening, causes the appearance of Caspari belts. Suberin and lignin can be found in them. Endoderm with Casparian bands is already present in the zone of root hairs. It regulates the flow of water and aqueous solutions from the root hairs to the central cylinder, acting as a physiological barrier. Casparian bands limit the free movement of solutions along the cell walls. They pass directly through the cytoplasm of cells, which has selective permeability.
In many dicotyledons and gymnosperms, the roots of which have a secondary thickening, the formation of Casparian belts usually ends with the differentiation of the endoderm (the first stage). In monocots, in whose roots there is no secondary thickening, further changes can occur in the cells of the endodermis. Suberin is deposited on the inner surface of the primary membrane, which isolates the Casparian bands from the cytoplasm (second stage). In the third stage of endoderm development, a thick cellulose, usually layered, secondary membrane is deposited on the suberic layer, which becomes lignified over time. The outer walls of the cells almost do not thicken.
The cells communicate in pores with the parenchymal elements of the primary cortex and retain their living contents for a long time. However, the endoderm with a horseshoe-shaped thickening of the cell walls does not participate in the conduction of aqueous solutions and performs only a mechanical function. Among the thick-walled cells in the endoderm, there are cells with thin, non-lignified walls that have only Casparian bands. These are checkpoints; apparently, through them, a physiological connection is made between the primary cortex and the central cylinder.
The pericycle is always well expressed in the central cylinder, which in young roots consists of living thin-walled parenchymal cells arranged in one or more rows.
Rice. 1. Cross section of the root of the iris in the area of conduction: epb - epiblema, specimen - three-layer exoderm, p.p.k. - storage parenchyma of the primary cortex, end - endoderm, p. class. - check cell, pc - pericycle, p. ks. - primary xylem, p. fl. - primary phloem, m. t. - mechanical tissue
Pericycle cells retain their meristematic character and the ability to form new growths longer than other root tissues. It usually plays the role of a “root layer”, since lateral roots are laid in it, which, therefore, are of endogenous origin. In the root pericycle of some plants, the rudiments of adnexal buds also appear. In dicots, it is involved in the secondary thickening of the root, forming an interfascicular cambium and often a phellogen. In old roots of monocots, the cells of the pericycle are often sclerified.
The conducting system of the root is represented by a radial bundle, in which groups of elements of the primary phloem alternate with strands of primary xylem. The number of xylem strands in different plants varies from two to many. In this regard, diarch, triarch, tetrarch, polyarch roots are distinguished. The latter type predominates in monocots.
The first conducting elements of the xylem in the root arise on the periphery of the pro-cambial cord (exar-chno), the differentiation of subsequent tracheal elements occurs in the centripetal direction, i.e., opposite to what is observed in the stem. On the border with the pericycle, there are the most narrow-lumen and the earliest in time of occurrence spiral and annular elements of the protoxylem. Later, metaxylem vessels form inward from them, with each subsequent vessel forming closer to the center. Thus, the diameter of the tracheal elements gradually increases from the periphery to the center of the stele, where the youngest, most late developed wide-lumen, usually porous vessels are located.
The primary phloem develops exarchically, as in the stem.
The phloem is separated from the rays of the primary xylem by a narrow layer of living thin-walled cells. With tangential division of these cells in dicotyledonous plants, a bundle cambium arises.
The spatial separation of strands of the primary phloem and xylem located at different radii and their exarchic origin are characteristic features of the development and structure of the central cylinder of the root and are of great biological importance. Water with mineral substances dissolved in it, which is absorbed by root hairs, as well as solutions of some organic substances synthesized by the root, move through the cells of the cortex, and then, having passed through the endodermis and thin-walled cells of the pericycle, they enter the conducting elements of the xylem and phloem in the shortest way.
The central part of the root is usually occupied by one or several large metaxylem vessels. The presence of a pith is generally atypical for a root; if it develops, it is much inferior in size to the core of the stem. It can be represented by a small area of mechanical tissue or thin-walled cells arising from the procambium.
In monocotyledonous plants, the primary structure of the root remains without significant changes throughout the life of the plant. For acquaintance with it, the roots of iris, onion, kupena, corn, asparagus and other plants are most convenient.
German iris root (Iris germanica L.)
Transverse and longitudinal sections of the root in the conduction zone must be treated with a solution of iodine in an aqueous solution of potassium iodide, and then with phloroglucinum with hydrochloric acid. On some sections, it is desirable to color test for suberin using an alcohol solution of Sudan III or IV. Sections are examined in glycerin or water at low and high magnifications of the microscope.
On a cross section at low magnification, a wide primary cortex is visible, occupying most of the root section, and a relatively narrow central cylinder.
If the cut was not far from the absorption zone, then dying cells of the epiblema with root hairs can be found on the periphery of the root.
The primary cortex begins with a two- or three-layered exoderm. Its large, usually hexagonal cells are tightly connected and often somewhat elongated in the radial direction. Cells of neighboring layers alternate with each other. On sections treated with Sudan, corky walls of exoderm cells turn pink.
The primary cortex is loose, with numerous intercellular spaces, which are usually triangular in cross sections. Large rounded parenchymal cells with slightly thickened walls are arranged in more or less regular concentric layers. There are many starch grains in the cells, sometimes calcium oxalate styloids are found.
The inner layer of tightly closed cells of the primary cortex, bordering the central cylinder, is represented by the endoderm. The radial and internal tangential walls of its cells are strongly thickened, often layered, and give a positive reaction to lignification and corking. On transverse sections, they have horseshoe-shaped outlines. On longitudinal sections one can sometimes see thin spiral thickenings of the radial walls. The outer slightly convex walls are thin, with simple pores.
With a high magnification of the microscope in the endoderm, one can also see thin-walled through cells with a dense cytoplasm and a large nucleus. Usually they are located one by one against the rays of the primary xylem.
Rice. 2. Longitudinal section of the tissues of the root of the iris: pc - pericycle, end - endoderm with horseshoe-shaped thickened walls, p.k.l. - check cell with living protoplast, sp. e. - spiral thickening of the walls of endoderm cells, l - mechanical elements with cruciform pores in the central part of the root
The inner part of the root is occupied by the central cylinder. The per and cycle is represented by a single layer of small cells rich in cytoplasm, the radial walls of which alternate with the walls of the endoderm cells.
In some sections, it is possible to see the rudiments of lateral roots, which are laid in the pericycle against the rays of the primary xylem.
The pericycle surrounds the radial conducting bundle. Elements of exarch primary xylem are arranged in radial strands. On a transverse section, a set of xylem strands, of which there may be more than eight, looks like a multi-beam star. Such a xylem is called polyarchic. Each strand of xylem in cross section is a triangle, with its apex resting on the pericycle. Here are the most narrow-lumen and the earliest in time of formation spiral and annular tracheids of protoxy-lemes. The inner, expanded part of the xylem cord consists of the youngest wide porous vessels of the metaxylem, including one to three.
The primary phloem is located in small areas between the rays of the xylem. In the phloem, several polygonal sieve tubes cut across with colorless shiny walls, small, filled with dense cytoplasm, accompanying cells and bast parenchyma, are clearly visible. From the inside, the phloem is surrounded by a thin layer of parenchymal cells.
The central part of the stele is occupied by a mechanical tissue of cells with evenly thickened lignified walls. Longitudinal sections show that the cells have a prosenchymal shape, their walls have numerous simple slit-like pores or pairs of cruciform pores. The same cells wedged between the vessels and tracheids, forming a single central strand of mechanical tissue.
Exercise.
1. With a low magnification of the microscope, draw a diagram of the structure of the root, noting: a) a wide primary cortex, consisting of a three-layer exoderm, storage parenchyma and endoderm;
b) the central Cylinder, including a single-layer parenchymal pericycle, primary xylem located in radial strands, primary phloem and mechanical tissue.
2. At high magnification draw:
a) several exoderm cells;
b) a section of the endoderm, consisting of cells with horseshoe-shaped thickened walls and passage cells;
c) parenchymal pericycle.
- The primary structure of the roottheoretical tour. Grade 9 Exercise 1. You must select only one answer .
1. Hawthorn thorn is a) a modified shoot b) a modified stipule c) a modified leaf d) the result of the growth of the peripheral layers of stem cells.
2. The appendix is a process a) large intestine b) duodenum c) caecum d) rectum.
3. The end products of metabolism are removed from the ciliates-shoes through
a) powder b) contractile vacuoles c) cell membrane d) cell mouth (leaf)
4. The process of protein breakdown begins at
a) mouth b) stomach c) small intestine d) large intestine
5. Tissues predominate in the central cylinder of the root a) integumentary b) main c) storage d) conductive
a) digestive organs b) blood c) tissue fluid d) skin
7. Unconditioned reflex a) these are reflexes that are formed when an unconditioned stimulus is combined with a conditioned stimulus b) these are congenital reflexes that are transmitted to offspring from parents and, as a rule, remain with a healthy nervous system throughout life c) unconditioned reflexes are called such reflexes that arise spontaneously, disappear without special need and with the development of higher nervous activity d) unconditioned reflexes are the reactions of the body that are not associated with hereditary mechanisms and appear without the necessary conditions for this
8. The diameter of the corn stalk is determined by the activity of the meristem
a) primary b) secondary c) primary and secondary d) first primary and then secondary.
9. The respiratory organs of a spider are
a) lung sacs b) tracheas c) lung sacs and tracheas d) skin and lungs
10. A component of photoreceptors that capture light energy is
a) lens b) enzyme c) pigment d) photocell
11. From a zygote in a pine, a a) spore b) germ c) germ d) seed
12. Spermatozoa and eggs in scyphoid jellyfish are formed
a) in the ectoderm b) in the endoderm c) in the mesoglea d) in the basement membrane
13. Electrocardiogram reflects electrical activity
a) all parts of the heart b) pacemaker (pacemaker) of the heart c) pacemaker and conduction system of the heart d) left atrium and left ventricle
14. Apple is a fruit a) upper, juicy, one-seeded b) lower, juicy, one-seeded c) upper, juicy, many-seeded d) lower, juicy, many-seeded
15. Mammal kidneys a) primary b) secondary c) protonephridia d) metanephridia.
16. Fruit-bearing strawberries have roots
a) main and lateral b) lateral and accessory c) lateral d) accessory
17. None of the following should be considered a function of the human digestive system
a) physical processing of food b) destruction of the species specificity of food components
c) release of energy in the process of oxidation of food components d) antibacterial treatment of food18. In mammals, arterial blood flows through veins, and venous blood through arteries a) in the systemic circulation b) in the March circulation c) in the portal system of the liver d) with extrasystole circulation, when blood begins to be pumped from the ventricle of the heart into the atria
19. Potato tuber is formed a) on lateral roots b) on stolons c) on adventitious roots d) on other parts of the plant
20. The life cycle of polychaete worms proceeds
a) with transformation, there is a free-swimming larval stage b) without transformation, there are no larval stages, development is direct c) with transformation, there are several larval stages d) some worms have transformation, others have direct development
21. Do not form stumps a) birches b) oaks c) pines d) poplars
22. If a unicellular protozoan amoeba and an erythrocyte are placed in distilled water
a) both cells will be destroyed b) the amoeba will die, but the erythrocyte will remain
c) the amoeba will survive, but the erythrocyte will die d) both cells will survive23. A box on a leg in representatives of bryophytes is a) fetus b) sporangium c) gametophyte d) sporophyte
24. The skin of cartilaginous fish has
a) ganoid scales b) cosmoid scales c) bony scales d) placoid scales
a) differentiation of spores in the carpel and stigma b) haploid endosperm and vascular tissues with tracheids c) heterospores and male gametes without flagella d) isogamy and wind pollination.
26. In connection with life on land, the frog's circulatory system includes
a) dorsal and abdominal vessels b) two-chambered heart c) three-chambered heart and 1 circle of blood circulation
d) three-chambered heart and 2 circles of blood circulation27. In order for the movement of xylem sap to occur under the influence of root pressure, the plant needs a) sufficient content of mineral salts in the soil b) sufficient content of water in the soil d) all of the above
28. The wings of insects are on the dorsal side.
a) thorax and abdomen b) thorax c) cephalothorax d) cephalothorax and abdomen
29. Plants, as a rule, store energy-rich substances in the form
a) glycogen b) glucose c) starch d) fat
30. For watering the garden, the hostess took water from the nearest pond. What kind of helminth can be infected if you eat poorly washed lettuce from this garden?
a) liver fluke b) tapeworm c) ascaris d) echinococcus
Task 2.Choose only those answers that you think are correct (from 0 to 5).
1. The following features are characteristic of amphibians
a) have only pulmonary respiration b) have a bladder c) excretion products are d) molting is typical for adults e) no chest
2. For all bryophytes it is characteristic
a) division into organs b) reproduction by spores c) diversity of spores d) dominance of the gametophyte over the sporophyte e) living in humid places on land
3. Spores reproduce a) hay bacillus b) chlorella c) mucor d) yeast e) hara
4. All helminths are characterized a) lack of a digestive system b) high intensity of reproduction c) absence of sensory organs d) hermaphroditism e) highly developed reproductive system
5. Mushrooms form mycorrhiza with roots a) horsetails b) club mosses c) gymnosperms d) monocotyledonous angiosperms e) dicotyledonous angiosperms
6. The organs of attachment of tapeworms are not a) coracidia b) plerocercoid c) bothridia d) oncospheres e) all answers are correct
7. There are no chlorella cells a) chloroplasts b) ocellus c) flagella d) pulsating vacuole e) pyrenoid
8. Normally reproduce by parthenogenesis a) hydra b) earthworm c) bee d) roundworm e) stick insect
9. Animals with unstable body temperature, depending on the temperature of the external environment
a) homoiothermic b) poikilothermic c) homoiosmotic d) poikiloosmotic e) no correct answer
10. A heart with two atria and one ventricle has
a) sparrows b) frogs c) rays d) carp e) salamanders
Task 3.
Solve a biological problem
In 1 cu. mm. Goat blood is 10 ml. Erythrocytes size 0.004; in human blood in 1 cu. mm. - 5 million erythrocytes with a size of 0.007; in the blood of a frog in 1 cu. mm. - 400 thousand erythrocytes with a size of 0.02. Whose blood - a man, a frog or a goat - will carry more oxygen per unit time? Why
Grade 10 Task 1. In choose only one answer.
1. Cabbage fruit a) dry single-seeded b) juicy multi-seeded c) dry multi-seeded d) juicy single-seeded
2. The human respiratory center is located in
a) medulla oblongata b) diencephalon c) cerebral cortex d) midbrain
3. The excretory organs of higher cancers are
a) maxillary glands b) antennal glands c) coxal glands d) Malpighian vessels.
4. For blood clotting, among other things,
a) iron ions b) farm ions c) ascorbic acid d) calcium ions
5. Chlorella breeds a) sexually and asexually; b) only asexually; c) under favorable conditions, asexually; under unfavorable conditions, sexually;
6. Does not participate in the metabolism of carbohydrates in the body a) adrenaline b) insulin c) glucagon d) gastrin
7. Most desert animals can live without water. A source of moisture for rodents, reptiles, some large mammals (for example, camels) can be
a) chemical reactions in cells that occur with proteins b) conversion of carbohydrates c) fat oxidation
d) decrease in the level of metabolism8. The gender of a person is determined a) during the formation of gametes in meiosis b) during the divergence of chromosomes in meiosis c) during the formation of a zygote (during the fusion of gametes) d) at the birth of a child
9. Barberry spines are a modification a) leaf b) shoot c) root d) flower
10. Pellagra disease is associated with beriberi a) C b) E c) PP d) K
11. The white-browed thrush and the song thrush living in the same forest make up
a) one population b) two populations of two species c) two populations of the same species d) one population of different species
12. Acromegaly occurs with hyperfunction of the hormone
a) adrenocorticotropic b) somatotropic c) gonadotropic d) thyrotropic
13. Phloem refers to the tissue that is a) educational b) basic c) productive d) mechanical.
14. In the temporal zone of the cerebral cortex is the highest department
a) taste analyzer b) auditory analyzer c) visual analyzer d) skin analyzer
15. Hemolymph of insects performs the functions
a) supplying tissues and organs with nutrients, reserving nutrients in the body
b) removal of metabolic end products from the hemocoel and their excretion into the hindgut
c) supplying tissues and organs with oxygen and removing carbon dioxide from them
d) supply of tissues and organs with nutrients and transport of end products of metabolism16. The breakdown of fiber in humans occurs in
a) stomach b) mouth c) large intestine d) small intestine
17. The "head" of garlic is a) modified adventitious roots b) modified shoot system c) modified shoot d) modified leaves
18. Bile secreted by the liver contributes to a) the breakdown of proteins b) the breakdown of carbohydrates c) the emulsification of fats d) the creation of conditions for the breakdown of all these organic substances
19. Reptiles differ from amphibians a) closed circulatory system b) reproductive organs open into intestines c) simple stomach with one compartment d) metanephric kidney
20. Various amino acids are found in the proteins of the human body a) 20 6) 2c) more than 20 but less than 64 d) 64
21. The maximum speed of propagation of a nerve impulse a) 30 m/s b) 60 m/s c) 120 m/s d) 240 m/s
22. In the nephron of the kidney, the process is the least selective a) secretion b) reabsorption
c) filtration d) movement through the epithelium of the collecting duct23. Of the following organs, it is not associated with the immune system a) pancreas b) lymph nodes c) thymus d) spleen
24. The AIDS virus strikes a) T-helpers (lymphocytes) b) B-lymphocytes c) antigens d) all types of lymphocytes
25.The human body is kept warm mainly by a) metabolism b) muscle tremors c) sweating d) warm clothes
26. Belonging of human blood to serotypes A, B, O is associated with a) lipids b) carbohydrates c) polypeptides d) antibodies
27. During hunger or during hibernation, the reserves of energy substrates are consumed in the following order a) fats - proteins - carbohydrates b) fats - carbohydrates - proteins c) carbohydrates - fats - proteins d) proteins - carbohydrates - fats
28. Detrital food chain a) Ecological pyramid b) Eating chain c) Decay chain d) Pyramid of numbers
29. The mineral composition of bones is disturbed with a lack of vitamin a) A1 b) B6 c) C d) E
30. Eutrophication of water bodies with poor flow leads to the appearance of an unpleasant odor, since as a result of this process a) many salts of chlorides, phosphates, nitrates are dissolved
b) organic substances, being oxidized, turn into compounds such as CO 2, H 2 SO 4, H 3 PO 4
c) organic substances are restored with the help of anaerobic bacteria, turning into CH 4, H 3 S, NH 3, PH 3 d) organic and inorganic decomposition products precipitate31. Abiotic factor, which in the process of evolution turned out to be the main regulator of seasonal phenomena in the life of plants and animals
32. The main organ that synthesizes glucose from lactic acid is
a) kidneys b) liver c) spleen d) intestinal epithelium
33. When regulating seasonal rhythms and in the process of developing methods for managing the development of plants during their year-round cultivation under artificial lighting, during winter and early planting of flowers, for the accelerated production of seedlings, such a general biological factor as
a) cold hardening b) circadian rhythm c) photoperiodism d) self-regulation
34. When looking at an object, a person's eyes move continuously because
a) light rays are directed to the yellow spot of the retina b) to prevent blinding of the eye c) image focusing on the retina is ensured d) to disadaptation of visual neurons
35. The term "ecology" is formulated a) in 1900 b) in 1866 c) in 1953 d) in 1981
36. Monitoring of the (human) environment is a) creating the best conditions for man and nature
b) tracking global processes and phenomena in the Earth's biosphere c) a set of processes related to the protection of nature and human ecology d) monitoring the state of the human environment and warning about critical situations that are dangerous to human health and all other living organisms37. Enzyme does not occur in humans a) DNA - polymerase b) hexokinase c) chitinase d) ATP - synthetase
38. Certain, relatively permanent complexes - natural communities, consisting of populations of different species living in a certain area with more or less uniform conditions of existence, are called a) waves of life b) biocenosis c) phylogenetic series d) biogeocenosis
39. Propolis is a) bee glue, a mixture of sticky secretions extracted by bees from the buds of various plants b) a pasty creamy-whitish substance produced by the glands of worker bees as food for developing queen larvae c) a mixture of secretions of the poisonous glands of the stinging apparatus of the bee
d) food of honey bees from pollen of plants, laid in cells of honeycombs and filled with honey40. The most important property of ecological systems, which is manifested in the fact that all the diverse inhabitants of such systems exist together, without completely destroying each other, but only limiting the number of individuals of each species to a certain level
a) stability b) self-renewal c) adaptability d) self-regulation
Task 2.. Choose only those answers that you think are correct.
1. A rhizome can be distinguished from a root by the following features
a) the obligatory presence of leaves, buds, internodes b) the absence of a root cap
c) the presence of scales, knots and buds d) the absence of rhizoderm e) the ability to turn green in the light2. Excitation of nerve cells is accompanied by a) the release of Na ions - from the cell b) the release of Ca ions - from the cell c) the entry of Na ions - into the cell d) the entry of K ions - into the cell e) the exit of K ions - from the cell
3. In plants, the process of photosynthesis a) proceeds only in the light b) H 2 O photolysis occurs in photosystem I c) O 2 is released as a result of the decomposition of CO 2 d) NADP is formed e) O 2 is released as a result of the decomposition of H 2 O
4. Of the hormones involved in the regulation of reproductive function in mammals a) estrogens b) thyroid hormones c) androgens d) hormones of the adrenal medulla e) prothoracotropic hormone
5. Adrenal medulla secretes a) Insulin b) Epinephrine c) Norepinephrine d) Corticosteroids e) Glucocorticoids
6. The gills of cancer and fish are organs a) similar b) homologous c) divergent d) convergent e) no correct answer
7. Excitatory postsynaptic potential (EPsP) is different from action potential
a) duration b) amplitude c) distribution distance d) decay time e) distribution speed
8. Removal of herbivores from the natural pasture ecosystem will cause
a) increasing the intensity of plant competition b) decreasing the intensity of plant competition
c) increase in the diversity of plant species d) decrease in the diversity of plant species9. Greenhouse effect associated with the accumulation of CO 2 , soot and other particulate matter
a) cause an increase in temperature b) lead to adverse changes in the biosphere
c) will not lead to noticeable changes in the biosphere d) will contribute to improving the climate on the planet
e) all of the above are correct10. Leaf fall in plant life -
a) an adaptation aimed at reducing water evaporation in winter b) protection against breaking branches with snow masses c) metabolic products are removed from plants with leaves d) adaptation to seasonal changes in day length e) freeing up space for laying new buds
eleven . Consequences of eutrophication of water bodies a) depletion of O 2 resources b) depletion of CO 2 resources
c) death of most living organisms d) accumulation of H 2 S e) increase in the number of most organismsa) the development cycle is dominated by sporophyte b) they reproduce well vegetatively c) diploid endosperm d) trees, bushes and herbaceous plants e) there are no roots
13. The growth of the body is most regulated by a set of hormones.
a) growth hormone b) insulin c) thyroid hormones d) sex hormones e) substance P
14. ATP is synthesized in human cells a) in mitochondria b) in the cytoplasm c) in the nucleus d) in chloroplasts e) in chromoplasts
15. Mother and father can be donors for their child
a) both never b) sometimes only the father c) sometimes only the mother d) sometimes both e) both always
16. In humans, proteins are digested by enzymes that secrete
a) stomach b) salivary glands c) pancreas d) liver e) small intestine
18. With a calm exhalation, the air "leaves" the lungs because
a) the volume of the chest decreases b) the muscle fibers in the walls of the lungs contract c) the diaphragm relaxes and protrudes into the chest cavity d) the muscles of the chest relax e) the muscles of the chest contract
19. Pituitary gland a) consists of one lobe b) consists of lobes d) is not connected with the hypothalamus e) consists of nerve and glandular cells
20. Blood circulation in vertebrates is carried out according to a) arteries b) arterioles c) veins d) venules e) capillaries
Task 3.
one . The nostrils of fish do not communicate with the oropharynx.
2. Moss sporophyte is incapable of photosynthesis.
3. During vaccinations, the vaccine is administered.
4. Absorption of nutrients begins in the intestines.
5. The spatial distribution of animals in populations is not regulated by their behavior.
6. Plants absorb carbon dioxide only in the light.
7. Each natural population is always homogeneous in terms of the genotypes of individuals.
8. Succession is a successive change of ecosystems that successively arise on a certain area of the earth's surface.
10. The introduction of rats and mice into houses was caused by the destruction of their natural habitats by man.
Grade 11 Exercise 1.
You need to choose only one answer, which you consider the most complete and correct.
one . Of the given pairs, it is not an example of homologous organs
a) cactus thorns and pea tendrils b) barberry thorns and strawberry tendrils c) trapping sundew leaves and juicy onion scales d) lily of the valley rhizomes and potato tubers
2. "Power stations" are the following cell organelles
a) nucleus b) ribosomes c) lysosomes d) mitochondria
3. Lemon fruit is juicy tissue a) conductive b) assimilation c) mechanical d) integumentary
4. As a result of meiosis, various gametes are formed, since
a) homologous chromosomes have a different composition b) in prophase 1 of the division of meiosis, crossing over occurs
c) non-homologous chromosomes in the 1st division of meiosis diverge independently of each other d) in the metaphase of the 2nd division of meiosis, the chromosomes diverge independently5. Plants usually store energy in the form a) glycogen b) fat c) fiber d) starch
6. Children develop new signs that are not characteristic of their parents because
a) all the gametes of the parents are of different sorts b) during fertilization, the gametes merge randomly
c) in children, parental genes are combined in new combinations d) the child receives one half of the genes from the father, and the other from the mother7. Polymorphism is
a) the presence in populations of several forms of a gene or trait b) the ability to change morphologically during life c) the diversity of offspring d) the severity of the trait (its expression)
8. Diversity in body color of algae is caused by
a) attraction of animals b) adaptation to photosynthesis c) masking d) peculiarities of reproduction
9. Of the DNA fragments, the wrong one is
a) A-T
G-Cb) G-T
T-Ac) T-A
A-Td) G-C
C-G10. Sundew grows a) in a spruce forest b) along the banks of water bodies c) in peat bogs d) in meadows
11. The process of cellular respiration (aerobic pathway for the conversion of PVC) occurs
a) in the chloroplasts of all plant organisms b) on the membranes of the endoplasmic reticulum (ER) and the Golgi apparatus c) on the inner side of the outer cell membrane d) on the inner surface of the mitochondrial membranes
12. A housefly can adapt to changing environmental conditions faster than a person, because a) it is smaller b) it flies well c) it has numerous offspring d) it has a rapid change of generations
13. Convergence results from
a) adaptive changes in the genotype under the direct influence of the environment b) mutations
c) selection of individuals with traits that are useful under given conditions from among random directed changes
d) sets of random phenomena that have been preserved due to the corresponding conditions of existence14. The process of gametogamy is that
a) cells of different organisms identical in sex merge b) the process of formation of gametes occurs
c) multiple gamete formation is carried out d) two gametes different in sex, formed by different individuals, merge15. In the ventricles of the heart of crocodiles, blood by composition
a) venous b) arterial c) venous in the right ventricle, arterial in the left d) completely mixed
e) partially mixed16. Reparative regeneration is understood as
a) the universal property of renewal of tissues and organs in the process of life and aging of cells
b) physiological changes that occur during the period of differentiation and specialization of kopets
c) restoration of organs or tissues after their violent damage d) replacement of obsolete cells with new ones17. Of the listed types of animals, a system of giant axons has
a) coelenterates, flatworms, roundworms b) flatworms, roundworms, annulus d) annulus, arthropods, mollusks e) mollusks, arthropods, chordates
18. The basis of the fundamental property of living things - the ability to reproduce their own kind are reactions
a) formation of a carbohydrate chain b) glycolysis reactions c) matrix-type reactions d) conversion of ATP to ADP
19. Differences in the mechanism of cell division in higher plants and animals
1. Division of the centromere 2. Division of the cytoplasm 3. Function of the spindle during division 4. Presence of centrioles
Correct answer a) 1.2 b) 1.4 c) 2.4 d) 3.4
20. Heterosis is a) rebirth of hybrids in the second generation b) non-fold increase in the number of chromosomes c) non-related crossing d) change, expressed in accelerating growth, increasing size, increasing viability and fertility of hybrids of the first generation
21. During the phase of general relaxation of the heart a) Crescent - open, fold - closed b) Crescent - open, fold - open c) Crescent - closed, fold - open d) Crescent - closed, fold - closed
22. Gynandromorphs are amazing creatures a) resulting from inbreeding b) descendants subjected to cell cloning c) individuals developed as a result of parthenogenesis d) individuals whose body part has a female, part - male structure
23. When the axon of the motor neuron is stimulated in the middle, the nerve impulse will propagate
a) to the body of the neuron b) to its end c) both to the body and to its end d) will not arise at all
24. A polyploid cell arises due to
a) modification b) gene mutation c) chromosomal mutation d) nondisjunction of chromosomes
25. The ability to phagocytize and kill microbes a) T - killers and macrophages b) T - killers, V - lymphocytes and macrophages c) T - lymphocytes and B - lymphocytes d) macrophages and neutrophils
26. Can enzymes catalyze not only the forward reaction, but also the reverse?
a) yes b) no c) some can, some can't d) sometimes they can, sometimes not
27. Body growth is most regulated by one of the following sets of hormones
a) growth hormone, thyroid hormones, sex hormones b) growth hormone, prolactin, insulin c) growth hormone, thyroliberin, substance P d) growth hormone, thyroid hormones
28. An example of convergent evolution is the pair
a) polar bear and koala b) oak and maple c) wolf and marsupial wolf d) skunk and raccoon
29. Growth hormone is synthesized on ribosomes
a) rough ER b) free c) free and rough ER d) mitochondrial
30. The synthesis of lipids and carbohydrates is associated with the following cell structures
a) with a nucleus b) with a smooth endoplasmic reticulum c) with lysosomes d) with ribosomes
31. Structural unit responsible for the synthesis of a specific protein molecule a) triplet b) gene c) nucleotide d) ATP
32. Chromosome morphology is determined
a) achromatin spindle b) matrix thickness c) chromosome shape d) centromere position
33. The role of rhodopsin a) participates in photosynthesis b) participates in the regulation of carbohydrate metabolism
c) mammalian muscle protein that binds oxygen d) chromoprotein present in retinal rods34. The Krebs cycle serves to a) neutralization of acetic acid b) provision of the respiratory chain with reduced coenzymes c) removal of excess ATP d) utilization of reduced coenzymes formed during glycolysis
35. What is the process of transition of Pre-RNA to mRNA called? a) splicing b) translation c) sequencing d) transformation
36. Name the fossil of the genus Nomo, related to the paleotropics
a) Australopithecus b) Pithecanthropus c) Sinatrope d) Neanderthal
37. Molar ratio of ActiGcC in a DNA molecule a) 1.0 b) 0.5 c) 0.75 d) 2.0
38. An elementary evolutionary phenomenon is called a) mutations b) non-directional change in allele frequencies in the gene pool of a population c) natural selection d) long-term irreversible directional change in the gene pool of a population
39. In meiosis divisions a) 2 b) 3 c) 4 d) 1
40. Macroergs richer in energy than ATP a) exist b) do not exist c) exist only in prokaryotes d) exist only in eukaryotes
41. Moving DNA elements in a linkage group are called
a) transposon b) orphones c) oligogenes d) operon
42. Among the structural features of flatworms, indicate the organizational features that can be attributed to idioadaptations a) bilateral symmetry of the body b) the presence of hooks and suckers c) the primary body cavity d) the formation of three germ layers
43. With incomplete dominance, AA genotypes in Gg appear with a probability of
a) 25% b) 100% c) 75% d) 12.5%
44. The distance between genes is measured in a) morganides b) % c) nm d) A
45. The adaptive nature of evolution is relative because
a) natural selection ensures the survival of the fittest and their predominant offspring b) the fitness of species on the basis of selection corresponds only to those environmental conditions in which species live for a long time c) the reactions of the organism to environmental influences are purposeful
d) man makes changes in the course of evolution using artificial selection47. In F 2 with complete dominance of the polyhybrid, phenotypic classes are formed a)2n b)3n c)4n d)(3:1)n
48. Another name for a repressor a) cistron-regulator b) operon c) exon d) intron
49. Oocyte 1 is formed from a) from an ootid b) from an oogonium c) from germ cells d) from an ovum
50. Indicate, in the presence of which of the following factors, the balance of allele frequencies in populations cannot be maintained? a) the mutation process is at a high level b) a large number of populations c) free interbreeding occurs within populations d) the population exists in a limited area
Task 2. Each of them has several possible answers. .
one . During photosynthesis, NADP+ is a) starting compound (substance) for reactions induced by light b) end product of reactions induced by light c) intermediate product of reactions induced by light d) starting compound (substance) for carbon fixation e) end product of carbon fixation
2. The hypothesis postulated by Oparin and experimentally verified by Miller is as follows a) the primary atmosphere contained molecular O 2 b) the primary ocean contained high concentrations of proteins and nucleic acids c) bacteria appeared on Earth 3.5 billion years ago d) molecules of organic substances were able to form abiogenically e) molecules of organic substances entered into the physicochemical interaction
3. Prokaryotic cells have
a) nucleotide b) plasmalemma c) cell membrane d) ribosomes e) compartments
4. Plasmolysis is only when a) turgor pressure in the cell is zero b) the cytoplasm is completely compressed and completely moved away from the cell wall c) the cell volume decreases d) the cell volume is maximum e) the cell wall can no longer stretch
5. Cytoplasmic inheritance is associated with
a) mitochondria b) nucleolus c) chloroplasts d) ribosomes e) lysosomes
6. DNA in the nucleus form a complex with
a) histones b) nonhistone proteins c) RNA d) acetylcholine e) polysaccharides
7. Mark the provisions that are valid for both chloroplasts and mitochondria,
8. There are ribosomes in the cell
a) in the nucleus b) in the cytoplasm c) in the endoplasmic reticulum d) in the cell center e) in the mitochondria
10. There is RNA in the cell a) nucleus b) cytoplasm c) mitochondria d) chloroplasts e) endoplasmic reticulum
11. In order to draw correct conclusions when studying and comparing the efficiency of energy expended by parent birds, the following conditions must be taken into account a) all chicks during the study should be approximately the same size b) all parent birds should be of the same weight c) nests should be next to each other with a friend d) food should be obtained at approximately the same distance from all nests e) all parents should feed their chicks with approximately the same energy-intensive food
12. Cytokinesis occurs during division
a) plant cells b) animal cells c) in prophase d) in anaphase e) in telophase
13. Biological progress in evolution is achieved
a) aromorphosis b) idioadaptation c) degeneration d) divergence e) convergence
14. On the ribosomes of the rough EPS are synthesized
a) Ca + - ATPase b) thyroid hormone c) lysosomal proteases d) growth hormone e) tronsferrin
15. From the following, the evidence for evolution is
a) phylogenetic series b) biogenetic law c) analogies d) transitional forms e) homology
16. The necessary conditions for speciation are
a) behavioral barriers that prevent the exchange of genes between populations b) geographical barriers; interfering with the exchange of genes between populations c) genetic barriers interfering with the exchange of genes between populations
d) environmental barriers that prevent the exchange of genes between populations;d) there is no correct answer17. Hemeralopia (inability to see in low light) is caused by a recessive gene located on the X chromosome. Healthy spouses had a child with this disease. Decide if such a birth was possible and its probability a) it is practically impossible b) 1/4 of all children may be ill c) half of all children may be ill d) all boys may be ill e) 1/2 of boys may be ill
18. Hematopoietic organs are a) bone marrow thymus; lymph nodes b) spleen, adrenal medulla, thymus c) bone marrow, thymus, spleen d) bone marrow, lymph nodes, adrenal medulla e) lymph nodes, spleen, liver
19. To reach the right hand, blood carrying nutrients from the intestines must pass through
a) heart (once) b) heart (twice) c) does not pass through the heart d) lungs e) liver
20. Which of the following functions is performed by the liver of mammals
a) the synthesis of digestive enzymes, which then enter the duodenum b) the regulation of the concentration of glucose and amino acids in the blood c) the extraction of nitrogen from excess amino acids and the formation of urine
d) synthesis of proteins and blood plasma e) detoxification of toxic substancesTask 3.Decide whether a given statement is correct or incorrect.
one . As the swim bladder enlarges, the fish becomes lighter and floats upwards.
2. The heart of a person works for half a life, and rests for half a life.
3. There are fish in which the notochord persists throughout life.
4. Adipose tissue is one of the types of connective tissue.
5. The first land plants were rhinophytes.
6. The nucleolus serves as a site for the synthesis of ribosomal proteins.
7. Evolution always leads to the complication of the organization of living beings.
8. Coacervates were the first living organisms on Earth.
9. Parthenogenesis is a variant of sexual reproduction.
10. Living organisms contain all the elements of the periodic table.
eleven . All biocenoses must necessarily include autotrophic plants.
12. Glycine is the only amino acid that does not have optical isomers.
13. The development of new habitats by organisms is not always accompanied by an increase in their level of organization.
14. In the cells of all animals and plants, an organoid called the cell center is located near the nucleus.
15. All forms of variability are one of the most important evolutionary factors.Task 4.
Solve a genetic problem.
Plants on the planet Phaethon are triploid. During the formation of gametes, the cell from which they arise is divided into three cells. At fertilization, three gametes of three parent plants merge. On this planet, F 1 was received from three parents, of which two carry only dominant alleles of a certain trait, and the third alleles of this trait are all recessive. What genotypes and in what ratio should be expected in F 2 ?
Answers
Grade 9
Exercise 1.
1-a. 2-in. 3-b, 4-6, 5-d, 6-a, 7-b, 8-a, 9-c, 10-c, 11-d, 12-a, 13-a, 14-d, 15- b, 16-b, 17-c, 18-b, 19-b, 20-a, 21-c, 22-c, 23-d, 24-d, 25-c, 26-d, 27-d, 28 - b, 29 - c, 30 - a.
Task 2.
1-b, c, e, 2-b, d, 3-b, c, d, 4-b, e, 5-c, d, e, 6-a, b, d, 7-b, c, 8-c, d, 9-b, 10-b, d.
Task 3.
For a unit of time, the blood of a goat will carry the most oxygen, then a person, and least of all a frog. The total surface of erythrocytes in a goat is 800 mm 2, in humans - 650 mm 2, in a frog - 220 mm 2.
Grade 10
Exercise 1.
1-b, 2-a, 3-b, 4-d, 5-6, 6-d, 7-c, 8-c, 9-a, 10-c. 11-b, 12-b, 13-c, 14-b, 15-d, 16-c, 17-b, 18-, 19-d, 20-c, 21-c, 22-c, 23-a , 24-a, 25-a, 26-d, 27-c, 28-c, 29-d. 30th century 31st century 32-b, 33-c, 34-d, 35-b, 36-d, 37-c, 38-c, 39-a, 40-d.
Task 2.
1-a, b, c, d, e, 2-c, e, 3-b, e, 4-a, c, 5-b, c, 6-a, 7-a, b, c, d, e, 8-a, d, 9-a, b, 10 - a, b. c, 11-a, c, d, 12-a, c, 13-a, c, d, 14-a, b, 15-b, c, d, 16-a, c, e, 17-a, b, c, d, e, 18-a, c, d, 19-b, c, e, 20 - a, b, c, d, e.
Task 3.
Correct judgments: 1,2,3,4.8.
Grade 11
Exercise 1.
1-b, 2-d, 3-d, 4-b, 5-d, 6-c, 7-a, 8-b, 9-b, 10-c, 11-d, 12-d, 13- c, 14-d, 15-d, 16-c, 17-d, 18-c, 19-c, 20-d, 21-c, 22-d, 23-c, 24-d, 25-d, 26-a, 27-a, 28-c, 29-a, 30-b, 31-b, 32-d, 33-d, 34-b, 35-a, 36-a, 37-a, 38- d, 39-a, 40-a, 41-a, 42-d, 43-a, 44-a, 45-b, 46-c, 47-a, 48-a, 49-b, 50-a.
Task 2.
1-a, e, 2-d, e, 3-a, b, c, d, 4-b, 5-a, c, 6-a, b, 7-a, b, c, e, 8- b, c, e, 9-a, c, d, e, 10-a, b, c, d, 11-a, d, e, 12-a, b, e, 13-a, b, c, 14-a, c, d, e, 15-a, b, d, e. 16-a, b, c, d, 17-b, e, 18-a, c, 19-b, d, e, 20-a, b, e,
Task 3.
Correct judgments: 1.2.3.4.5.9.12,13.
Task 4.
Splitting 26:1.
Genotypes: 8/27 AAA; 12/27 6/27 Aaa; 1/27 aaa.
Thank you, have not yet expressed ..Axial root cylinder
pericycle. In the axial cylinder of the root, one can distinguish between a complex radial conducting bundle and parenchyma - a tissue whose peripheral part, in the form of a ring of cells, is called the pericycle (Fig. 161, 162, 163). On a transverse section, the pericycle consists of one, two or several layers of cells (in walnut Juglans regia, for example, from 3-10). In many plants, the pericycle has an unequal thickness around the circumference. In sedges and conifers, for example, it is interrupted against the xylem groups, so that the protoxylem comes into direct contact with the endodermis. The pericycle may include resin passages (in some conifers), oil passages (in carrots and other umbrellas), milkers (in bellflowers and some Compositae), sclerenchyma (in buttercups - cornflower, spur). In many cereals, the cell walls of all pericyclic cells thicken greatly over time (Fig. 164) and become lignified.
In the pericycle, usually opposite the xylem groups, lateral roots originate. In several cells of the pericycle, protoplasm with a nucleus fills the entire cell cavity. These cells elongate in the radial direction, divide by tangential septa and form root arc with layers of cells functioning according to the same type as in the root tip. The young lateral root grows and breaks through the primary cortex outwards. This process occurs with the participation of a pocket - a case of cells, which is formed as a result of the division of endoderm cells located opposite the root arch (Fig. 165). With the growth of the root in length, the pocket paves the way through the primary cortex and the epiblema, acting not only mechanically, but also chemically; he highlights
enzymes that dissolve cell membranes. After the spine comes out, the pocket usually falls off (Fig. 166). The laying of the lateral roots occurs very close to the growth cone of the root that forms them, while their exit to the outside is at a considerable distance. Some
Rice. 164. Part of a cross section of an adult root of reddening erianthus ( Erianthus purpurascens):
1 - endoderm; 2 and 3 - other layers of the primary cortex adjacent to it; 4 - Razdorsky's bodies.
Rice. 165. The beginning of the formation of the lateral root of the fumes ( Fumaria sp..):1 - one of the layers of the primary cortex; 2 - endoderm; 3 - pericycle; 4 - phloem; 5 - xylem; 6, 7, 8 - initial cells of the root growth point.
In plants, root branches are laid not opposite the xylem groups, but near them or even opposite the phloem groups. This is the case, for example, in carrots, where in the pericycle opposite the xylem groups there are excretory canals, or in cereals, in which the pericycle opposite the xylem groups is interrupted or is represented, as in wheat (on a transverse section), by one very small cell. In some plants (for example, goose onion yellow Gagea lutea, in many orchids) the roots do not form lateral branches.
In the pericycle, and usually originate adnexal buds, which can develop into adventitious shoots, the so-called root growth(at the multi-colored knitter Coronilla varia, near poplars).
In some plants, however, adventitious buds are laid in the primary bark of the root (in buttercup). In many tree species (for example, in the apple tree), adventitious shoots on root cuttings are born as a result of the meristematic activity of the cells of the woody rays.
Conducting system. Inside the pericycle is the conducting system of the root in the form complex radial beam. According to the number of xylem groups ( n) and an equal number of phloem groups ( n) distinguish monarchical bundles (with n= 1), diarch (at n= 2, fig. 170, ks), triarchy (with n= 3), tetrarchic (at n= 4, fig. 163, 169 10 ). At n, equal to 5-6 or more, the bundle (and the entire root) is called polyarchic.
Monarchic roots are quite rare. Diarch roots of many dicots, including umbellate, labiate and some gymnosperms (spruce, our pine Pinus silvestris). The number of xylem groups in dicots and gymnosperms usually does not exceed 5. Among the monocots
BUT- maternal root; B- formed lateral root of the first order, breaking through the primary bark; AT- a functioning lateral root of the first order; epb- epiblema; copy- exoderm; end- endoderm; hc- pericycle; p. ks. - primary xylem; p. fl. - primary phloem; kr- secretory pocket; k.h. - root cap; m. b. to. - meristematic rudiments of lateral roots of the second order; to. in. - root hairs.
polyarchy predominates: rarely n equal to or less than 7 and in many cases reaches several tens (for some large cereals, palm trees).
Between individuals, between the roots of a given individual, and even between different sections of one long root, there may be differences in the number of rays.
Primary xylem at the root usually exarchic, or centripetal, i.e., the initiation of vessels occurs from the periphery of the central cylinder to the center of the root. Elements of protoxylem are the most narrow-lumen; by the nature of the structure, they are annular and spiral tracheids. The vessels of the metaxylem are comparatively wide-lumen; usually these are ladder, mesh, dot tracheas.
In many monocots, the formation of xylem groups occurs somewhat peculiarly: vessels closer to the root center begin to differentiate earlier, and elements closer to the endoderm form later.
primary phloem is formed in the roots in general also centripetally. Primary phloem may be seen earlier than primary xylem; usually it is destroyed earlier than the primary xylem.
Like the vessels, the sieve tubes of the primary vascular system are wider in the root than in the stem, but they are fundamentally less numerous and less differentiated than in the stem.
Xylem groups often close with each other in the center of the root, and then the middle part of the cross section is occupied by large vessels (Fig. 167), one or several.
The central region of the axial cylinder can be occupied by thin-walled parenchymal cells (Fig. 161), which often store nutrient reserves, for example, in mallows. In the core of many Compositae there are jointed lactifers (in reeds, such as dandelions) or excretory canals (in some tubulars, such as wormwood).
The core of the root can also be represented by a strand of sclerenchyma (in many barberries, iris, etc., Fig. 162).
The presence of a core for the root is not typical; it is always much less developed than in the stems.
The roots of the vast majority of monocots do not have a secondary
Rice. 167. Establishment and beginning of activity of cambium in the root of pumpkin sprout ( Cucurbita pepo):end- endoderm; hc- pericycle; p. fl. - primary phloem; in. fl. - secondary phloem; to. - cambium; p. ks. - primary xylem; in. ks. - secondary xylem.
growth. Many of them, however, undergo additional changes in the primary tissues, which increase their mechanical strength. These changes consist mainly in sclerification - in the thickening and lignification of cell membranes. The more powerful adventitious roots, which arise from the stem nodes above the soil level and then penetrate into it, are especially strongly sclerified. In such roots, the exoderm, several other outer layers of the primary cortex and most of the parenchyma of the axial cylinder (in corn) undergo sclerification with age, and in some plants, the outer and inner layers of the primary cortex and almost all tissues of the axial cylinder.
The roots of only a very few monocots have secondary thickening, namely, some of those tree-like lilies ( Dracaena, Aletris), which form a secondary growth in the stems.
The ring of thickening is usually laid down in the pericycle. In some species (in Dracaena goldiena) after the formation of a certain amount of secondary tissues, the thickening ring turns into a thick-walled permanent tissue, and another thickening ring is laid in the region of the primary cortex. Dracaena bordered ( Dracaena marginata) the ring of thickening is located from the very beginning in the area of \u200b\u200bthe primary cortex, outward from the endoderm. The production of the ring of thickening in the roots of dendritic lilies is similar to that which is formed in the stem: outwards - the secondary parenchyma, and inside - the parenchyma with vascular bundles scattered in it with sclerenchymal covers.
Some pines have about 10 rays.
In many monocots, the metaxylem vessels are not arranged along radii, like the protoxylem vessels, but are scattered throughout the tissue of the axial cylinder.
Axial cylinders of such roots are used in silk-metal production and for the manufacture of brushes.
