Vegetative organs
Lecture 2. Root and root systems
The root is an axial body with the ability to unlimited growth and the property of positive geotrophism. Root functions. The root performs several functions, focus on the main:
Strengthening plants in the soil and holding the above-ground part of the plant;
Absorption of water and minerals;
Conducting substances;
Can serve as a place of accumulation of spare nutrients;
Can serve an organ vegetative reproduction.
Fig. Types of roots:
1 - main root; 2 - apparent roots; 3 - side roots
Orphology root . By origin, the roots are divided into the main, side and apparent (Fig.). The main root is a root that develops from the embryonic root. It is characterized by unlimited growth and positive geotropism. The main root has the most active top ignite. Side roots - roots, developing on another root of any origin and being the formations of the second and subsequent branching orders. The formation of these roots begins with the division of cells of the special meristem - pericycles, located on the periphery of the central cylinder of the root. P
Ridge roots - roots, developing from stalks, leaves, old roots. They appear due to the activity of secondary meristems. Zones of a young root. The zones of the young root are different parts of the root along the length that perform unequal functions and characterized by certain morphological features. The young root usually distinguish 4 zones (Fig. 9): The division zone. The top of the root, 1-2 mm long and is called the division zone. Here is the primary apicial root meristem. Due to the division of the cells of this zone, there is a constant formation of new cells. The Picked Root Merist is protected by a root case. It is formed by alive cells that are constantly generated by the meristem. Often contain starch grains (provide positive geotropy). The outer cells produce a mucus that facilitates the progress of the root in the soil. Growth zone, or stretching. The length of the zone is a few millimeters. In this zone, cell divisions are practically absent, the cells are stretched as much as possible by the formation of vacuoles. Suction zone , or zone root hairs. The length of the zone is a few centimeters. There is differentiation and cell specialization. Here already distinguish the outer layer of epibers (risodermas) with root hairs, a layer of primary bark and a central cylinder. Root hairs is a side increase of epibloma cells (risoderma). Almost the entire cage occupies a vacuole, surrounded by thin layer cytoplasm. Vacuol creates high osmotic pressure, due to which water with dissolved salts is absorbed by the cell. The length of the root hairs is up to 8 mm. On average, 1 mm 2 root surfaces are formed from 100 to 300 root hairs. As a result, the total area of \u200b\u200bthe suction zone is larger than the surface area of \u200b\u200bthe surface organs (in the plant of winter wheat, 130 times, for example). The surface of root hairs is eased and glued with soil particles, which facilitates the flow of water and mineral substances into the plant. The absorption contributes to the excretion of acidic acids dissolving mineral salts. Root hairs are short-lived, die in 10-20 days. There are new (at the top of the zone), new (at the bottom of the zone) come to replace (at the top of the zone). Due to this suction zone, it is always at the same distance from the tip of the root, and all the time moves to new parts of the soil. Zone holding located above the suction zone . In this zone, water and mineral salts extracted from the soil move from the roots up to the stalk and leaves. Here, due to the formation of lateral roots, the root branching occurs. Primary and secondary structure of the root.The primary root structure is formed by primary meristems, characteristic of the young roots of all groups of plants. On the cross section of the root in the suction zone, three parts can be distinguished: the epibline, primary bark and the central axial cylinder (stele) (Fig. 10). In plauen, horsages, ferns and monocoan plants persists throughout life. EpiBleme, or Skin - Primary coating fabric root. It consists of one row of tightly closed cells, in the suction zone of having grows - root hairs. Primary bark The three clearly different layers are presented: directly under the epibloma is the exoderma, the outer part of the primary bark. As EpiBlemes die out, it turns out on the surface of the root and in this case performs the role of coating fabric: it is thickening and the fabrication of cell membranes, and the elimination of the contents of the cells. The exoderma is located, the main layer of the primary cortex cells is located. Here there is a movement of water in the axial cylinder of the root, the nutrients are accumulated. The inner layer of primary cortex is accumulated - an endoderma formed by one cell layer. In bicycle plants, the cells of the endoderma have thickening on radial walls (cappar belts), impregnated with a loose-like substance - subsener. Among them are living thin-walled cells - throughput cells, also having a belt of cappar. Endoderm cells with a live protoplast control the flow of water and dissolved in it minerals from the bark in the central cylinder and back organic substances. Central cylinder, axial cylinder, or stela . The outer layer of stele, adjacent to the endoderm, is called pericycle. His cells have long retained the ability to divide. Here there is a locking of side roots. In the central part of the axial cylinder there is a vascular fibrous beam. Xilema forms a star, and the Floem is located between its rays. The number of rays of xylems is different from two a few dozen. Outdoor to five, in one-bedroom - five or more than five. In the very center of the cylinder can be elements of xylems, scleroshend or thin-walled parenchyma.
Fig. . The inner structure of the root.
And - the primary and secondary structure of the root; B - internal structure the root of a monocryon plant; B - internally the structure of the roototal plant.
1 - epibloma; 2 - primary bark; 3 - pericycle; 4 - Floem; 5 - xylem; 6 - Cambi; 7 - stele; 8 - endoderma; 9 - Endoderma throughput cells.
Risry The secondary structure of the root.In bicycle and gone plants, the primary structure of the root is preserved for a short time. As a result of the activity of secondary meristems, the secondary structure of the root is formed. The process of secondary changes begins with the appearance of Cambias between Floem and Ksil. Cambier arises from the weakly differentiated parenchyma of the central cylinder. Inside, it is postponing elements of secondary xylems (wood), outward elements of the secondary flolam (Luba). First, the layers of Cambia are separated, then closed, forming a solid layer. When dividing cambium cells, radial symmetry disappears, characteristic of the primary structure of the root. In pericycle, cork cambiums occurs (Fellogen). It lays out the outside layers of the cells of secondary coating fabric - traffic jams. The primary bark gradually devies and lisches. TO
Fig. 11. Types of root systems.
Ornemy systems . Root system is a combination of all plant roots. The main root, side and apparent roots participate in the formation of the root system. The form distinguishes 2 main types of root systems (Fig. 11): The rod root system is a root system with a well-pronounced main root. Characteristic for bipartal plants. The urine root system is the root system formed by side and apparent roots. The main root grows weakly and early ceases its growth. Typical for monocotional plants. Physiology root.The root has unlimited growth. It grows by the top, on which the apical meristem is located. Take 3-4 day seedlings of the bean seeds, we will apply thin tags to the developing root at a distance of 1 mm from each other and put them in a wet chamber. A few days later you can find that the distance between the labels at the root tip increased, while in higher areas of the root it does not change. This experience proves the top root growth (Fig. 12). The fact is used in human practical activity. When transplanting seedlings of cultivated plants spend pikirovka - Removal of the root top. This leads to the cessation of the growth of the main root and causes the increased development of the side roots. As a result, the suction area of \u200b\u200bthe root system increases significantly, all roots are arranged in the upper most fertile soil layers, which leads to an increase in plant yields.
Fig. . Right roots.
A - the growth of the root in length; B - root picking; B - the development of the apparent roots when emphasis.
Absorption to the root and movement of water and minerals. Absorption from the soil and movement to ground organs of water and mineral substances is one of the most important functions of the root. This feature originated in plants due to access to land. The root structure is adapted for the absorption of water and nutritional elements. Water enters the body of the plant through risoderm, the surface of which is much increased due to the presence of root hairs. In this zone, the root system is formed in the root stele, which is necessary to provide ascending current of water and mineral substances. The volume of water and mineral substances by plant occurs independently of each other, since these processes are based on various mechanisms of action. Water passes into the root cells passively, and minerals enter the root cells mainly as a result of active transport that goes with energy costs. AT
Fig. Horizontal vehicles of water.
1 - root hairs; 2 - apoplast path; 3 - Symplase path; 4 - epibloma (risoderma) 5 - endoderma; 6 - pericycle; 7 - Cweill vessels; 8 - primary bark; 9 - plasmodesma; 10 - Kaspari's beliefs.
Oda enters the plant mainly according to the law of osmosis. Root hairs have a huge vacuole with a large osmotic potential, which provides water from the soil solution in the root hairs. Horizontal transport substances. At the root, the horizontal movement of water and mineral substances is carried out in the following order: root hairs, primary cortex cells (exoderma, mesoderma, endoderma), stela cells - pericycle, axial cylinder parenchyma, root vessels. Horizontal vehicles of water and mineral substances occurs in three ways (Fig. 14): Path through apoplast , symplast and vacuolar . Poplast path includes all intercellular spaces and cell walls. This path is the main for the transport of water and ions of inorganic substances. Put through the symplast - the system of protoplasts of cells connected by means of plasmodesm. It serves to transport mineral and organic substances. Vacuolar path. Water moves from vacuole to vacuol through other components of adjacent cells (plasma membranes, cytoplasm and vacuolet tip). This path is used exclusively for water transport. Movement over the vacuolar path in the root is negligible. In the root, the water moves along apoplast to the endoderma. Here, its further advancement interferes with waterproof cell walls impregnated with Subperin (Kaspari's belts). Therefore, water enters stele through the symplast through the throughput cells (water passes through the plasma membrane under the control of the cytoplasm of the endoderma bandwidth). Due to this, there is regulation of the movement of water and mineral substances from the soil in xylem. In the stele, the water no longer meets the resistance and enters the conductive elements of xylems. Vertical vehicles substances.The roots not only absorb water and mineral substances from the soil, but also serve them to the above-ground organs. Vertical movement of water occurs through dead cells that are not capable of push water to the leaves. Vertical vehicles of water and solutes are ensured by the activity of the root and leaves. The root is nizhny end engine , feeding water into the vessels of the stem under pressure, called root. Under root pressure, they understand the strength with which the root is injected into the stem. Root pressure occurs mainly as a result of an increase in osmotic pressure in the root vessels over the osmotic pressure of the soil solution. It is a consequence of the active separation by cells of the root of mineral and organic substances in the vessels. The magnitude of the root pressure is usually 1-3 atm. Proof of the presence of root pressure serves guttech and selection easy . The utility is the release of water from an intact plant through water duitsa - guidates that are on the tips of the leaves. Passoy is a liquid that is distinguished from the cut stem. Upper end engine , providing vertical vehicles of water - the suction force of the leaves. It arises as a result of transpiration - evaporation of water from the surface of the leaves. With continuous evaporation of water, it is possible for a new flow of water to leaves. The sucking power of the leaves in the trees can reach 15-20 atm. In the vessels of xylems, water moves in the form of continuous water yarns. When moving up the water molecule is connected to each other (cohesion), which makes them move with each other. In addition, water molecules are capable of sticking to the walls of vessels (adhesion). Thus, the water lift on the plant is carried out due to the upper and lower engine current and the clutch forces of water molecules in the vessels. The main driving force is transpiration. Channel modifications. Often the roots are performed by other functions, while different modifications of roots arise. Flashing roots. Often the root performs the function of the accumulation of nutrient stock. Such roots are called stocking. From typical roots, they are distinguished by the strong development of the inquiring parenchyma, which can be in the primary (in monocotional) or secondary crust, as well as in wood or core (in two-charts). Among the stocking roots differ root tubers and root. Root tubers They are characteristic both for dicotyledan and monocotyledonic plants, and are formed as a result of modifying side or apparent roots (purple, yatryshnik, lubbar). Due to limited growth in length, they may have an oval, belief-shaped form and are not branched. Most of the types of bipartal and monocoan tube are only part of the root, and otherwise the root has a typical structure and branching (Batat, Georgin, Lily). Korneflod It is formed mainly as a result of the thickening of the main root, but the stem is also involved. Roots are also characteristic of many cultural vegetable, forage and technical domestic plants, and for wild herbaceous perennial plants (chicory, dandelion, ginseng, horseradish). Surrounding the roots are formed as a result of secondary root thickening (carrots, parsnips, parsley, celery, repa, radish, radishes). At the same time, the basic fabric can develop both in xylene and floeme. In the thickening of the main root can also take part and pericycle, forming additional cambial rings (at beets). Surveillance, growing on the swamps, often form roots growing up - respiratory roots , Pneumatophores. In such roots are well developed aeronous parenchyma. Thus, the roots of swolate plants receive a sufficient amount of oxygen.
Fig. . Channel modifications.
Key terms and concepts
1. Root. 2. The main root, side and apparent roots. 3. Primary root structure. 4. Secondary root structure. 5. Primary bark. 6. Axial cylinder, root stele. 7. Kaspari's beliefs. 8. Pericycle. 9. Root system. 10. Picking. 11. Apoplast, simplict route of transport. 12. Root pressure. 13. Guttling. 14. Passoy. 15. Roots. 16. Cornklubny. 17. Respiratory roots. 18. Air roots, Velen. 19. Nodule bacteria.
Basic questions for repetition
What is root?
What roots are called main, apparent, side?
What is the difference between the root systems of the bomb and monocotyledonic plants?
Root zones.
Three layers of primary root cortex?
Fabric axial cylinder root.
Ways of horizontal vehicles substances by root?
Bottom and upper water currents on stalk and leaves?
Channel modifications.
Root. Functions. Types of roots and root systems. Anatomical root structure. The mechanism of the arrival of the soil solution to the root and its movement in the stem. Channel modifications. The role of mineral salts. The concept of hydroponics and aircraft.
Higher plants in contrast to the lower characterized by the dismemberment of the body on the organs performing various functions. The vegetative and generative organs of higher plants are distinguished.
Vegetativeorgans - parts of the body of plants that perform batteries and metabolism. Evolutionarily arose as a result of the complication of the body of plants when they exit them to the land and the development of air and soil environments. Vegetative organs include root, stem and leaf.
1. Root and root systems
The root is an axial organ of plants with radial symmetry increasing due to the apical meristem and not carrying leaves. Root growth cone is protected by root case.
Root system - the totality of the roots of one plant. The shape and character of the root system is determined by the growth ratio and the development of the main, side and pressing roots. The main root develops from the embryonic root and has positive geotropism. Side roots arise on the main or apparent roots as branches. They are characterized by transversal geotropism (diagotropism). Putting roots arise on stems, roots and rarely on the leaves. In the case when the plant is well developed main and side roots, a rod root system is formed, which may contain and apparent roots. If the plant's prevailing development is obtained by the predominant development, and the main root is inconspicuous or absent, the urine root system is formed.
Root functions:
Suction from the soil of water with mineral salts dissolved in it, the root hairs (or mycorrhizes) are performed in the suction zone.
Fixing plants in the soil.
Synthesis of primary and secondary metabolic products.
The biosynthesis of secondary metabolites (alkaloids, hormones and other BAV) is carried out.
Root pressure and transpiration provide the transport of aqueous solutions of mineral substances according to the Ksili root vessels (ascending current), to leaves and reproductive organs.
Spread nutrients (starch, inulin) are deposited in the roots.
The growth substances necessary for the growth and development of the elevated parts of the plant are synthesized in meristematic zones.
Exercise symbiosis with soil microorganisms - bacteria and mushrooms.
Provide vegetative reproduction.
In some plants (monster, phyloodendron) perform the function of the respiratory body.
Channel modifications.Very often roots perform special functions, and in this regard, they undergo changes or metamorphosis. Metamorphose roots are inherited.
Retractive (powers) roots u. bulbous plants Serve for immersion bulbs in the soil.
Paintingroots are thickened and strongly parenchymalized. Due to the accumulation of spares, they acquire the repfature, cone-shaped, tuberous and other forms. Painter roots include 1) rootsat domestic plants. In their formation takes part not only root, but also stem (carrots, turnips, beet). 2) Cornklubny - thickening of the apparent roots. They are also called root cones(Georgin, Batat, Church). We are necessary for the early appearance of large flowers.
Roots - barshave climbing plants (ivy).
Air rootscharacteristic for epiphytes (orchids). They provide a plant suction from wet air water and mineral substances.
Respiratoryroots have plants growing on marshy soils. These roots are lifted above the surface of the soil and supply underground parts of the plant with air.
Walkersroots are formed in trees growing at the littoral of the tropical seas (Mangra). Strengthen the plants in the primer.
Mikoriza- The symbiosis of the roots of higher plants with soil mushrooms.
Tubes -tumor-shaped radiances of the root cortex as a result of symbiosis with nodule bacteria.
Pillar roots (roots - backups) are laid as apparent on horizontal branches of the tree, reaching soil, grow, supporting the crown. Indian banyan.
In some perennial plants in the root tissues, pressing kidneys are laid, developing further into terrestrial shoots. These shoots are called root offsand plants - kornotpryskovy(Aspen -PopulustRemula, Malina -Rubusidaeus, Osim --Sonchusarvensisi dr.).
Anatomical structure of the root.
The young root in the longitudinal direction usually distinguish 4 zones:
Seed zone 1 - 2 mm. Posted by the top of the cone of the increase, where the cell division occurs. Consists of apical meristem cells, and covered with root case. It performs a protective function. In contact with the soil cell of the root case, they are destroyed with the formation of the mucous membrane. It is restored (root case) due to the primary meristem, and in cellars - at the expense of a special meristema - Calipotrogen.
Zone stretching Makes up a few mm. Cell divisions are practically absent. Cells are maximally stretched due to vacuole formation.
Suction zone Makes up a few centimeters. It occurs differentiation and cell specialization. There are a coating fabric - an epibline with root hairs. Epibloma cells (risodermas) are alive, with a thin pulp wall. Some cells are formed long grown - root hairs. Their function is the absorption of aqueous solutions with the entire surface of the outer walls. Therefore, the length of the hair is 0.15 - 8 mm. On average, 1 mm 2 root surfaces are formed from 100 to 300 root hairs. They die in 10 to 20 days. Play mechanical (reference) role - serve as a support for the root tip.
Zone holding stretches up to the root neck and makes up most The length of the root. In this zone there is an intense branching of the main root and the appearance of side roots.
Cross structure root.
On the cross section in the suction zone in dicotrentic plants, and in monocoons - and in the zone of conducting, there are three main parts: covering and absorbing tissue, primary bark and central axial cylinder.
Cooking-absorbent fabric - risoderma performs the coating, supochny, as well as partially, reference function. Represented by one layer of epib cells.
The primary bark root is most powerful. It consists of an exoderma, mesoderma \u003d parenchyma of the primary bark and endoderma. The cells of the exoderma polygonal, firmly adjacent to each other, are located in several rows. Their cell walls are impregnated with suberin (testing) and lignin (webly). Suburin provides the impenetrability of water and gases. Lignin gives her strength. The water absorbed by ricoderma and mineral salts pass through the thin-walled cells of the exoderma \u003d bandwidth cells. They are located under root hairs. As the cells of the risoderma, the ectoderma can perform the coating function.
Mesoderma is located under the ectoderma and consists of living parenchymal cells. They perform a sparkling function, as well as the function of conducting water and dissolved in it salts from root hairs to the central axial cylinder.
The inner single-row layer of primary bark is represented by the endoderma. Endoderm with cappar belts and endoderm with horseshoe thickens.
Endoderma with cappar belts - the initial stage of the formation of the endoderma, in which only the radial walls of its cells are thickened due to the impregnation of their lignin and subverin.
In monocotional plants, in the cells of the endoderma there is a further impregnation of subverin cell walls. As a result of the unclean, only the outer cell wall remains. Among these cells, cells with thin cellulose shells are observed. These are bandwidths. They are usually located opposite the rays of the radial type beam.
It is believed that the endoderma is a hydraulic barrier, contributing to the promotion of minerals and water from the primary cortex to the central axial cylinder, and prevent them from the reverse current.
The central axial cylinder consists of a single-row pericycle and radial vascular fibrous beam. Pericycle is capable of meristematic activity. It forms side roots. Vascular fibrous beam is a conductive root system. At the root of dicotyledonous plants, the radial beam consists of 1 - 5 rays of xylems. At one-bedroom - from 6 and more xyleries. The cores have no roots.
At one-bedroom plants, the root structure during the life of the plant does not undergo significant changes.
For bombing plants At the border of the suction zone and the fortification zone (conduct), there is a transition from the primary secondary structure root. The process of secondary changes begins with the appearance of Cambia, under the primary flolam sites, inside it. Cambier arises from the weakly differentiated parenchyma of the central cylinder (stele).
Between the rays of the primary xylem from the cells of the pronambia (the side meristem) are formed cambia arches, closed on pericycle. Pericycle partially forms Cambier and Fellogen. Cambial sites arising from pericycles form only parenchymal cores of core rays. Cambia cells to the center are delayed by a secondary xylem, and the duct is secondary flolam. As a result of Cambia activities between the rays of the primary xylem, open collateral vascular fibrous beams are formed, the number of which is equal to the number of rays of primary xylems.
At the place of the pericycle, cork cambium (fellogen) is laid, which gives the beginning of the periderma - secondary coating fabric. Cork isolates the primary bark from the central axial cylinder. The bark dies and reset. Pedider becomes a coating cloth. And the root is actually represented by the central axial cylinder. In the very center of the axial cylinder, the rays of the primary xylema are preserved, the vascular fibrous beams are located between them. Fabric complex Outside from Cambia received the name of the secondary bark. So The root of the secondary structure consists of xylem, Cambia, secondary cortex and cork.
The absorption and transport of the root of water and minerals.
The absorption from the soil of water and delivery to the ground authorities is one of the most important functions of the root that arose in connection with the access to the land.
Water enters plants through risoderm, in the absorption zone, the surface of which is increased due to the presence of root hairs. In this zone, the root is formed by xylem, providing an upward current of water and minerals.
The plant absorbs water and mineral substances independently of each other, because These processes are based on various mechanisms of action. Water passes into the root cells passive, thanks to Osmozos. In the root hair there is a huge vacuol with cellular juice. Its osmotic potential and ensures the flow of water from the soil solution in the root hairs.
Mineral substances come in root cells mainly as a result of active transport. Their absorption contributes to the discharge of the root of various organic acids that translated inorganic connections to the form available to absorb.
At the root, the horizontal movement of water and minerals occurs in the following sequence: root hairs, cords of cortex parenchyma, endoderma, pericycle, axial cylinder parenchyma, root vessels. Horizontal vehicles of water and minerals takes three ways:
The path through apoplast (a system consisting of interclausers and cell walls). The main for the transport of water and ions of inorganic substances.
The path through the symplast (the system of protoplasts of the cells connected by means of plasmodes). Carries out the transport of mineral and organic substances.
The vacuolar path is the movement of vacuole in a vacuole through other components of adjacent cells (plasma membranes, cytoplasm, vacuolet tonoplast). Apply exclusively for water transport. For the root is insignificant.
In the root, the water moves along apoplast to the endoderma. Here, its further advancement is hampered by Kaspari's beliefs, so further water enters Stel in the simplast through the endoderma bandwidth. Such switching paths provides the regulation of the movement of water and mineral substances from the soil in the xylem. In Stele, water does not meet resistance and enters the Cweemera vessels.
Vertical vehicles of water goes along dead cells, so the movement of water is ensured by the root and leaves. The root supplies water into the vessels of the stem under pressure, called root. It arises 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 selection of the root of mineral and organic substances in the vessels. Its value is 1 - 3 atm.
Proof of the presence of root pressure is "Plant Plant" and Guttling.
"Plant Plant" is the release of fluid from the cut stem.
Guttling is the release of water in an intact plant through the tips of the leaves, when it is in a wet atmosphere or intensively absorbs water and mineral substances from the soil.
The upper power of water movement is the suction force of the leaves provided by transpiration. Transpiration - evaporation of water from the surface of the leaves. The sucking force of the leaves in the trees can reach 15-20 atm.
In the vessels of xylems, water moves in the form of continuous water yarns. Between the water molecules exist clutch (cohesion), which makes them move in each other. The adhesion of water molecules to the walls of vessels (adhesion) provides an upward capillary water current. The main driving force is transpiration.
For normal development, roots should be provided with moisture, fresh air access and necessary mineral salts. All this plants are obtained from the soil, which is the upper fertile layer of the Earth.
To increase the fertility of the soil, various fertilizers contribute to it. Putting fertilizers during plant growth is called feeding.
Allocate two main groups of fertilizers:
Mineral fertilizers: nitrogen (nitrate, urea, ammonium sulfate), phosphate (superphosphate), potash (potassium chloride, ash). Full fertilizers contain nitrogen, phosphorus and potassium.
Organic fertilizers - substances of organic origin (manure, bird litter, peat, humus).
Nitrogen fertilizers are well soluble in water, contribute to the growth of plants. They are brought into the soil before sowing. For ripening fruits, root growth, bulbs and tubers need phosphoric and potash fertilizers. Phosphoric fertilizers are poorly soluble in water. They are brought in autumn, along with manure. Phosphorus and potassium increase plant farmers.
Plants in greenhouses can be grown without soil, on an aquatic environment that contains all the elements, required plants. This method was called hydroponics.
There is also an aircraft culture method - when the root system is in the air and periodically irrigates the nutrient solution.
Root functions.The root is the main organ of the highest plant. The functions of the roots are as follows:
Soils are absorbed from soil and mineral salts dissolved in it, transports them up stalk, leaves and reproductive organs. The suction function is performed by root hairs (or mycorrhoids) located in the suction zone.
Due to great strength, the plant is fixed in the soil.
- In the interaction of water, the ions of mineral salts and photosynthesis products synthesize the products of primary and secondary metabolism.
- Under the action of root pressure and transpiration of the ions of the aqueous solutions of minerals and organic substances according to the vessels of xylems, the root are moving along the rising current into the stem and leaves.
- Nutrients (starch, inulin, etc.) are deposited in the root.
- The roots are carried out by biosynthesis of secondary metabolites (alkaloids, hormones and other BAV).
- Synthesized in the meristematic zones of roots Rights (gibberllinins, etc.) are necessary for the growth and development of the above-ground parts of the plant.
- Due to the roots, symbiosis is carried out with soil microorganisms - bacteria and mushrooms.
- Using the roots there is a vegetative reproduction of many plants.
10. Some roots perform the function of the respiratory body (Monster, Philodendron, etc.).
11. The roots of the row of plants perform the function of "wounded" roots (Ficus Banyan, Pandanus, etc.).
12. The root is capable of metamorphosis (thickening of the main root form "roots" in carrots, parsley, etc.; Thickening of side or pressing roots form root tubers in dahlia, earthy nuts, cleaning, etc., shortening the roots in bulbous plants).
Root - axial organ, usually cylindrical shape, with radial symmetry with geotropism. It grows until the top meristem is preserved, covered with root case. At the root, unlike escape, leaves are never formed, but, like escape, the root branches, forming root system.
The root system is a totality of the roots of one plant. The nature of the root system depends on the ratio of the growth of the main, lateral and apparent roots.
^ Types of roots and root systems.In the nucleation of the seed, all organs of the plant are in the infancy. Chief, or first, root develops from germ roof.The main root is located in the center of the entire root system, the stem serves as a continuation of the root, and together they constitute the first-order axis. The plot on the border between the main root and the stem is called root neck.This transition from the stem to the root is noticeable in different thickness of the stem and root: the stem is thicker than the root. Plot of stem from the root cervice to the first germinal leaves - cotyledons called saddletonal kneeor hypocotylene. The side roots of the next orders are departed from the main root to the parties. Such a root system is called santneva, many bipartite plants, it is capable of branching. A branched root system is a variety of a rod root system. The side branching of the root is characterized by the fact that new roots are laid at some distance from the tops and are formed endogenous - in the inner tissues of the preceding order of the parent root due to the activity of the pericycle. The more lateral roots from the main root, the larger the plant's facilities, therefore there are special agrotechnical techniques that enhance the ability of the main root to form lateral, for example, pinching or divethe main root on L / 3 of its lengths. After diving, some time the main root ceases to grow long, while the side roots grow intensively.
In dysfotrol plants, the main root, as a rule, is preserved all his life, a single-barbing germinal root dies rapidly, the main root does not develop, and from the foundation of escape is formed podidroots, which also have branches of the first, second, etc. orders. Such a root system is called bashed.Pressure roots, like the side, are laid endogenous. They can be formed on stems and leaves. The ability of plants to develop the apparent roots is widely used in crop production in vegetative reproduction of plants (reproduction of stomens and leaf cuttings). Overhead strong cuttings Wavy, poplar, maple, currant black, etc.; Sheet cuttings - violet Uzambar, or Satpolia, some types of begonias. Underground cuttings of modified shoots (rhizomes) multiply many medicinal plants, for example, the Lily of the Lily May, buying medicinal and others. Some plants form many apparent roots when the bottom of the stem (potatoes, cabbage, corn, etc.), thereby creating additional food.
At the highest disputes (plants, chests, ferns), the main root does not occur at all, they are formed only the apparent roots from the root. In many dicapotic grassy rhizome plants, the main root often deviates and prevails the system of the apparent roots, which depart from rhizomes (sick, nettle, buttercup and dr.).
At the depth of penetration into the soil, the first place belongs to the rod root system: the record depth of root penetration, according to some information, reaches 120 m! However, the urine root system, possessing the main surface location of the roots, contributes to the creation of the turf and warns the soil erosion.
The total length of the roots in the root system is different, some roots reach several dozen and even hundreds of kilometers. For example, wheat length of all root hairs reaches 20 km, and winter rye has a total length of the roots of the first, second and third orders of over 180 km, and with the addition of fourth-order roots - 623 km. Despite the fact that the root grows all his life, its growth is limited to the influence of the roots of other plants.
The degree of development of root systems on different soils in different natural zones. So, in the sandy deserts where deeply run groundwaterThe roots of some plants go to the depth of 40 m or more (Zlak Celine, Propis surrounding from the bean family, etc.). Plants-ephemera semi-deserts have surfacethe root system, which is adapted to the rapid absorption of the wounds of the moisture, is quite sufficient for the rapid passage of all phases of plant vegetation. On clay, poorly aerated subzoles of the Taiga Forest zone, the root system of plants by 90% is concentrated in the surface layer of the soil (10-15 cm), plants have "feed roots" (european spruce). For example, Saksaul has roots in different time Years use moisture different horizons.
Very important factor In the distribution of the root system - humidity. The direction of the roots goes to the side of greater humidity, but in water and in the overwhelmed soil roots are branched much weaker.
The degree of development of root systems, the depth of root penetration and other plastic characteristics of the root depend on external conditions and at the same time are hereditaryly fixed behind each plant plant.
^ The zone of the young root.In the young root distinguish: 1) the division zone, covered with a root case; 2) the zone of stretching cells, or growth zone; 3) suction zone, or root hairs zone; 4) Conductive zone.
^ Division zoneis the root tip, outside covered root caseprotecting the top, or apical, meriste. To the touch, the young tip of the root is slippery due to the secreted mucus cells. With the rise of the root in the length of the mucus reduces the friction of the tip of the root of the soil. According to the expression of Academician V.L. Komarov, root case "Root Earth", it protects the dividing cells of the meristem from mechanical damage, and also controls positive geotropismthe root itself, i.e. contributes to the growth of the root and penetrate it into the depths of the soil. The root case consists of living parenchymal cells in which starch grains are present. Under the case there is a division zone, or root rapid conepresented by primary educational fabric (meristem). As a result of the active division of the elite measure of the root, all other root zones and fabric are formed. The division zone of a young root is only 1 mm long. From other zones, it looks yellow.
^ Tensile zone,or growth zone,the length of several millimeters is externally transparent, consists of almost undetented, but stretching cells in the longitudinal direction. Cells increase in size, vacuoles appear in them. Cells are characterized by a high tour. In the stretch zone, the differentiation of primary conductive tissues occurs and constant root tissue begin to form.
Above the stretch zone is located suction zone.Its length is 5 - 20 mm. The zone of suction is represented by root hairs - epidermal cells have increased. Using root hairs, absorption of water soil and salts solutions. The numerous root hairs, the greater the suction surface of the root. By 1 mm at the surface of the root can be located about 400 root hairs. Root hairs are short-lived, live 10 - 20 days, after which they die. Root hair length different plants From 0.5 - 1.0 cm. Young root hairs are formed above the tensile zone, and die over the suction zone, so the zone of root hairs is constantly moving as the root and plant increases, it is possible to absorb water and dissolved in it nutrients from different soil horizons .
Above the suction zone begins zone holding, or side root zone.The water absorbed by the root and salts solutions are transported by wood vessels up to the above-ground parts of the plant.
There are no sharp limits between the root zones, and there is a gradual transition.
6. Root metamorphosis. Them biological significance. Mikoriza.Most plants in the same root system are clearly distinguished growth and suckingend. Lisplicity is usually more powerful, quickly lengthened and progress in the soil. The stretching zone is well pronounced, and apical meristems work vigorously. The sucking finishes arising in large quantities on the growth roots are lengthened slowly, and their apical meristems almost cease to work. The sucking ending seems to stop in the soil and intensively "sucking it."
W. wood plants distinguish fat skelette and semidentalroots on which short-lived root Mety. The root urges that continuously replace each other include growth and sucking endings.
If the roots perform special functions, their structure changes. Sharp, hereditary fixed modification of the organ caused by changing functions, is called metamorphosis. Channel modifications are very diverse.
The roots of many plants form symbiosis with gifs of soil fungi, called mikodism("Mribocornia"). Mikoriza is formed on sucking roots in the absorption zone. The mushroom component facilitates the roots of obtaining water and mineral elements from the soil, often gifs of mushrooms replace root hairs. In turn, the mushroom receives carbohydrates and other nutrients from plants. There are two main types of mycorrosis. Gifs etototrofnamycorrosis form a cover, enveloping the root outside. Extracticorosis is widespread in trees and shrubs. Endotrofnamycorridge is found mainly in herbaceous plants. Endomicuriza is located inside the root, the gifs are introduced into the cells of the cow parenchyma. Mycothrophic nutrition is very widespread. Some plants, such as orchid, cannot exist without symbiosis with mushrooms.
On the roots of legumes there are special formations - navalin which bacteria are inserted from the genus Rhizobium. These microorganisms are able to absorb the atmospheric molecular nitrogen by translating it into the associated state. Some of the substances synthesized in the fools are absorbed by plants, bacteria, in turn, use substances that are rooted. This symbiosis has great importance for agriculture. Bean plants thanks to an additional nitrogen source are rich in proteins. They give valuable food and fodder products and enrich the soil with nitrogen substances.
Very widespread painting Roots. They are usually thickened and strongly parenchymalized. Very thickened apparent roots called root cones, or cornklubnia(Georgin, some orchid). Many, more often than bilateral, plants with a rod root system occurs, an education that is called kornefloda. In the formation of root, the main root takes part, and bottom part Stem. The carrot almost all the root is compiled by the root, the turnip root forms only the lowest part of the root of the root ( fig. 4.12).
Corneflands of cultivated plants arose as a result of a long selection. In rootfolds, stocking parenchyma is strongly developed and mechanical fabrics disappeared. Carrots, parsley and other umbrella parenchym are strongly developed in the floem; Dips, radish and other cruciferous - in xylene. In Beckla, spare substances are postponed in a parenchyma formed by the activities of several addition layers of Cambia ( fig. 4.12.).
Many bully and rhizome plants are formed retracting, or contractual roots ( fig. 4.13, 1.). They can shorten and pull the escape into the soil on the optimal depth at the time of summer drought or winter frosts. Rooting roots have thickened bases with transverse wrinkles.
Respiratory Roots, or pneumatic phones (fig. 4.13, 2.) They are formed in some tropical woody plants living in conditions of lack of oxygen (taxodium, or swamp cypress; mangrove plants that live on the swampy shores of oceanic coasts). Pneumatophores grow vertically up and are thrown over the surface of the soil. Through the system of holes in these roots associated with Arenhima, the air enters underwater organs.
Some plants for maintaining escapes in the air formed additional reference Roots. They depart from the horizontal branches of the crown and, reaching the surface of the soil, intensively branched, turning into pillars supporting the crown of wood ( pillarsrainan roots) ( fig. 4.15, 2). Walkers Roots depart from the lower sections of the stem, giving stability stability. They are formed in plants of mangrove thickets, plant communities developing on flooded during the tide of the tropical banks of the oceans ( fig. 4.15, 3.), as well as in corn ( fig. 4.15, 1.). Ficus rubcoming formed sharkovidroots. Unlike pillars and wobble, they are not appreciated by origin, but by side roots.
Fig. 4.15. ^ Supported roots : 1 - wandering roots of corn; 2 - Banyan's pillars; 3 - wandering roots of rizoforlas ( etc- zone of the tide; from - Lock zone; il.- The surface of the orstive bottom).
Concept of shoot. Morphological disagreement of escape. Nodes and intermodines. Top shoot of escape. Building and activityConstruction. Escape is called the stem with the leaves and kidneys located on it.
Sections of the stems on which the leaves are developing, call nodes.
Sections of the stem between the two nearest nodes called interstices.
The angle between the sheet and the above intercourse called the sinus sheet.
In the sinus of the sheet formed a stubborn kidney. Escape consists of repetitive sites - metamers.
One metaode includes interstice, knot, sheet and stubby kidney. Escape is called a complex consisting of a stem and leaves. The primary escape is laid in the bud, where it is reprehension. The kidney consists of a germinal stalk - epicotyl, apical meristem and one or more leaf progroms (rigids of the leaves). When germinating seed, the skeleton is extended. From apical meristems develop new leafy countries, from leaf Primordiev develop leaves, and in sinuses of leaves Formed coinwood. This developmental algorithm during the formation of the shooting system of the plant may repeatedly repeat.
Formed escape distinguish the nodes - part of the escape, where the sheet is connected to the stem; Intezium - part of the escape between the nodes, is usually part of the stem; Leaf sinuses are an angle between the sheet and the ascending part of the stem.
Part of the escape are kidneys. This is, first of all, the top kidney representing the increasing cone escape. AT sinuses of leaves Seed plants are formed stress, or side kidneys. If they develop one over the other (honeysuckle, walnut, Robinia, etc.), then called serial. If the kidneys develop in the sinuses of the leaves nearby, about a friend (plum, cereals, etc.), then they are called collateral. The kidneys can form endogenously in the area of \u200b\u200bthe interdozy. These kidneys are called apparent.
The trees and shrubs of a cold and temperate climate are formed wintering, or resting kidneys, which are often called eye. From these kidneys, new shoots develop the next year. The outer leaves in these kidneys are usually converted to renal scales that protect the inner parts of the kidneys from damage.
Winter, or resting kidneys are formed and perennial herbs, on those organs that do not die for the winter, i.e. on rhizomes, at the base of stalks, etc. These kidneys are called the renewal kidney. Of these, the in the spring develops overhead shoots.
All of the above kidneys are called vegetative. Such kidneys consist of an apex, industrial assemblies, incharpasses of interstitial, leaf Primordiev, above which kidney countries can develop, and ridicule leaves.
From the kidneys that does not have renal priority, a simple or brown the escape. Branchy develops from kidney with kidney priority the escape.
In addition, seed plants have more generative kidneys. These are flowering kidneys and kidneys, giving rise to the bumps of gifted. They differ from vegetative appearance. In addition to the apex, stuffed interstitial and ridiculous units, such kidneys have a premium, which give the origin of the flower parts or parts of the cones. At the kidneys, which gives rise to inflorescences, flower landslides are formed.
Finally, there are so-called mixed kidneys, of which designer shoots with flowers.
The morphological characteristic of escape implies a description of the structure of nodes, interstitial, kidneys. Be sure to indicate the type of registration. For most plants, it is another - one sheet is located in the node, but may be opposed or mutual. Certain Type Lategories forms a leaf mosaic that allows you to best use space to ensure uniform sheet lighting.
With the growth process and the development of escape is connected and dividing leaves into three categories: lower leaves, middle leaves, Top, or riding leaves. In the morphological description of the leaves, the median leaves usually describe, but the full morphological description requires separate description all categories of leaves, because even middle leaves On one shoot there are differences. This phenomenon is called heterophillery or discrepancy.
Top growing escape - growth of escapes in length due to modification of the cone of the rise, investment and growth in its foundation of the infrack leaves. In the process of modification, the increasing cone increases in length, becomes complicated and changes its form.
Bud. This is a successful escape. It consists of a meristematic axis ending the increasing cone (primary stem), and leafy progrrdiyev (incharpasses), that is, from a series of infrack meta chambers. The discontinent leaves below are covered below the increasing cone. So the vegetative kidney is arranged. In the vegetative-reproductive kidney, the increasing cone is turned into a reservation flower or the infardation of inflorescence. Reproductive (floral) kidneys consist only of the rudimentary flower or inflorescences and do not have adaptation of photosynthetic leaves.
13. Metamorphized shoots.
The occurrence of them is often associated with the performance of the functions of the extension of spare products, transferring the unfavorable conditions of the year, vegetative reproduction.
Rhizome - This is a long-term underground escape with a horizontal, ascending or vertical growth direction that performs the functions of accumulation of spare products, renewal, vegetative reproduction. Rhizome has reduced leaves in the form of scales, kidneys, apparent roots. Spare products accumulate in the stem. The rise and branching occurs just like an ordinary escape. Rhizome is distinguished from the root by the presence of leaves and the absence of root case on the top. Rhizome can be long and thin (drink) or short and thick. Early from the top and stubble kidneys are formed overhead annual shoots. Old parts of the root gradually die away. Plants with horizontal long rhizomes forming many above-ground shoots, quickly occupy a large area, and if these are weeds (drinking), the fight against them is pretty difficult. Such plants are used to fix the sands (Colosnyak, Aristide). In Luragovychy, cereals with long horizontal rhizomes are called rhizable (wildfish, mintalist), and with short-bush (Timofeevka, Belous). Rhizomes are found mainly in perennial herbaceous plants, but sometimes shrubs (bearing) and shrub (lingonberry, blueberries).
Tuber - This is a thickened part of the escape, a compatibility of spare products. Tubers are overhead and underground.
Overhead tuber It is a thickening of the main (Kohlrabi) or side (tropical orchids) escape and carries normal leaves.
Underground tuber - Thickening hypocotylene (cyclamen) or short-lived underground escape - alarm (potatoes). The leaves on the underground club are reduced, in the sinuses there are kidneys, called eyes.
Overhead column - This is a short-lived creeping escape that serves to spread (seizure of the territory) and vegetative reproduction. It has long interstices and green leaves. At the nodes are formed apparent roots, and from the top kidney - a shortened escape (socket), which, after alarm, continues independent existence. Increases an overhead column sympodial. Overhead collines, lost the function of photosynthesis and performing mainly the function of vegetative reproduction, are sometimes called mustache (strawberries).
Bulb - This is a shortened stem (donation), carrying numerous, closely pinned leaves and apparent roots. At the top of the Donets there is a kidney. Many plants (onions, tulip, hyacinth, etc.) are formed from this kidney an overhead escape is formed, and a new bulb is formed from the side stubby kidney. Outdoor scales in most cases dry, film and perform protective function, internal - fleshy filled with spare products. On the shape of the bulbs there are spherical, egg-shaped, flattened, etc.
Corm Externally, it looks like a bulb, but all the leaf scales are dry, and spare foods are postponed in the stem part (saffron, gladiolus).
Spinys They have different origins - from escape (apple tree, pear, Turn, Hawthorn, Globyia, Citrus), Sheet (Barbaris) or its parts: Rakhis (Astragal), Hightails (White Acacia), Plate section (COMPACE). Spines are characteristic of plants of hot dry habitats.
Mustache They are formed from escape (grapes), sheet or its parts: Rakhis and several leaves (peas), plates (rank.), Highlights (Sassaparil). Serve to attach to the support.
Fillocladium - These are flat sheet shoots located in the sinuses of reduced leaves. Flowers are formed on them. There are predominantly arid habitats (iglitsa, phillantus) in plants. Cutting devices - modified leaves peculiar to insectivores. Surveys (Rosyanka, Mukholovka). They have the shape of aids, urnoches, bubbles or slamming and wrapped plates. Small insects, getting into them, die, dissolve using enzymes and are consumed by plants as mainly an additional source of mineral substances.
There are no leaves on the root, there are no chloroplasts in the root cells.
In addition to the main root, many plants have numerous appendage roots. The combination of all roots of the plant is called the root system. In the case when the main root is slightly expressed, and the apparent roots are expressed significantly, the root system is called urine. If the main root is expressed significantly, the root system is called a rod.
Some plants are delayed in the root of spare nutrients, such formations are called root crops.
The main functions of the root
- Reference (fixing the plant in the substrate);
- Suction, water and mineral substances;
- Supply of nutrients;
- Interaction with roots of other plants, mushrooms, microorganisms living in the soil (mycorrhosis, legumes of legumes).
- Synthesis of biologically active substances
Many plant roots perform special functions (air roots, roots of suction cups).
The origin of the root
The body of the first plants came out on land have not yet been dismembered on shoots and roots. It consisted of branches, some of which were raised vertically, while others pressed to the soil and absorbed water and nutrients. Despite the primitive structure, these plants were provided with water and nutrients, as they had small sizes and lived near the water.
In the course of further evolution, some branches began to delve into the soil and gave rise to roots adapted to more perfect soil nutrition. This was accompanied by a deep restructuring of their structure and the appearance of specialized tissues. The formation of the roots was a major evolutionary achievement, thanks to which the plants were able to master the dry soil and form major shoots raised up to the light. For example, the Mossoid real roots do not, their vegetative body small sizes - Up to 30 cm, MAY inhabit wet places. Purchase appears real roots, this leads to an increase in the size of the vegetative body and to the flourishing of this group in the coal period.
Modifications and specialization of roots
The roots of some buildings have a tendency to metamorphosis.
Root modifications:
- Korneflod - modified juicy root. The main root and lower part of the stem participate in the formation of the root. Most root plants are twilight.
- Root tubers (root cones) are formed as a result of thickening of lateral and apparent roots.
- Root-hooks - peculiar appendage roots. With these roots, the plant "sticks" to any support.
- Walker roots - Make the role of support.
- Air roots - Side roots grow down. Absorb rainwater and oxygen from the air. Many tropical plants are formed under high humidity.
- Mikoriza - The cohabitation of the roots of higher plants with gifs of mushrooms. With such a mutually beneficial cohabitation, called symbiosis, the plant receives water from the mushroom with nutrients dissolved in it, and the mushroom is organic substances. Mycorridge is characteristic of the roots of many higher plants, especially woody. Mushroom gifs that are tired of thick and shrub's root roots are performed by root hairs.
- Bacterial tongs on the roots of higher plants - The cohabitation of higher plants with nitrogen-fixing bacteria - are modified lateral roots, adapted to symbiosis with bacteria. Bacteria penetrate the root hairs inside the young roots and cause them to form the nodule. With such a symbiotic cohabitation of bacteria, the nitrogen contained in the air is translated into a mineral form available to plants. And plants, in turn, provide a special habitat with bacteria, in which there is no competition with other types of soil bacteria. Bacteria also use substances that are in the roots of the highest plant. More often than other bacterial tubers are formed on the roots of plants of the bean family. In connection with this feature, the seeds of legumes are rich in protein, and representatives of the family are widely used in crop rotation to enrich the soil by nitrogen.
- Flashing roots - rooted roots consist mainly from the basin of the main fabric (turnip, carrots, parsley).
- Respiratory roots - W. tropical plants - Perform an additional respiratory function.
Features of the structure of roots
The totality of the roots of one plant is called the root system.
The root systems include roots of various nature.
Distinguish:
- main root,
- side roots,
- putting roots.
The main root develops from the embryonic root. Side roots arise at any root as a side branch. Putting roots are formed by escape and its parts.
Types of root systems
In the rod root system, the main root is strongly developed and is well noticeable among other roots (characteristic of two-colon). In the urine root system on early stages Development The main root formed by the embryonic root, dies, and the root system is compiled by the apparel roots (characteristic of monocoons). The rod root system penetrates the soil usually deeper than the urine, but the urine root system is better than the adjacent ground particles, especially in its upper fertile layer. In the branched root system, equally developed main and several side roots prevail (from wood breeds, strawberries).
The zones of the young root end
Different parts of the root perform unequal functions and differ in appearance. These parts received the name of the zones.
The root tip is always covered with root case that protects gentle cells of the meristem. The case consists of living cells that are constantly updated. Cells of root case isolated mucus, it covers the surface of the young root. Due to the mucus, friction is reduced about the soil, its particles easily stick to the root endings and root hairs. In rare cases, roots are devoid of root case ( water plants). Under the case there is a division zone represented by educational fabric - meristem.
The cells of the division zone are thin-walled and filled with cytoplasm, there are no vacuoles. The division zone can be distinguished on a live root along yellowish color, its length is about 1 mm. Following the division zone, the stretching zone is located. It is also small in the length of only a few millimeters, it is distinguished by light color and, as it were, is transparent. The growth zone cells are no longer divided, but are able to stretch in the longitudinal direction, pushing the root end of the soil deploy. Within the growth zone, cells are separated on the tissue.
The end of the growth zone is well noticeable to the emergence of numerous root hairs. Root hairs are located in the suction zone, the function of which is understandable from its name. Its length from a few millimeters to several centimeters. In contrast to the growth zone, the sections of this zone are no longer shifted relative to the soil particles. The main mass of water and nutrients The young roots are absorbed using root hairs.
Root hairs appear in the form of small papillas - cell growth. After a certain time, the root hairs dies. The duration of his life does not exceed 10-20 days.
Above the suction zone, where the root hairs disappear, the zone of conduct begins. For this part of the root of water and solutions of mineral salts, absorbed by root hairs are transported in the above laying plants.
The anatomical structure of the root
In order to get acquainted with the absorption system and the movement of water along the root, it is necessary to consider the inner structure of the root. In the growth zone, the cells are beginning to be differentiated on the fabric and in the suction zone and conducting conductive tissues ensuring the rise of nutrient solutions into the above-ground part of the plant.
Already at the very beginning of the root growth zone, the mass of the cells is differentiated into three zones: risoderma, bark and axial cylinder.
Rizoderma - Cooking fabric, which is covered with young root ending outside. It contains root hairs and participates in suction processes. In the zone of suction ricoderma passively or actively absorbs the elements of mineral nutrition, spending energy in the latter case. In this regard, the risoderma cells are rich in mitochondria.
Velen, like the risoderma, refers to the primary coating fabrics and comes from the surface layer of the apical meristem of the root. It consists of hollow cells with thin, tracked shells.
- Size: 2 Mgabytes
- Number of slides: 36
Description of the presentation root and root systems 1. Functions and evolutionary slides
Root and root systems 1. Functions and evolutionary root occurrence. 2. The primary structure of the root. 3. Secondary root changes. 4. The formation of lateral and apparent roots. Root systems. 5. Specialization and modifications of roots.
The root is an axial organ with radial symmetry and vaguely increasingly increasingly due to the activities of the apical meristem. At the root, the leaves never occur, and the apical meristem is always covered with a cavering. The main function of the root is the absorption of water and mineral substances, i.e. providing soil nutrition of the plant. In addition to the named main function, the roots are performed by other functions: strengthen the plant in the soil, make it possible to vertical growth and shooting up; The roots occurs the secondary synthesis of various substances (amino acids, alkaloids, phythogormones, etc.); Spare substances can be laid in the roots; Roots interact with roots of other plants, soil microorganisms and mushrooms.
The roots arose from the body of rhinofitis, open on the surface of the soil. In the course of evolution, some branches of these bodies began to delve into the soil and gave rise to roots.
Roots are adapted to more perfect soil nutrition. The appearance of the roots was accompanied by a deep restructuring of their entire structure. They had specialized fabrics. The function of absorption of substances from the soil began to perform young finishes of the roots. They retain alive cells on the surface. These cells have formed the root fabric - risoderma in functionality.
The function of absorption of substances from the soil began to perform young finishes of the roots. They retain alive cells on the surface. These cells have formed the root fabric - risoderma in functionality. Next, in the process of evolution, an increase in the absorbing surface of the root took place due to the three factors: 1) the abundant branching and the formation of a large number of suction endings; 2) the constant increase in the roots and the movement of suction expirations into new parts of the soil; 3) the formation of root hairs.
Since the rise of the root occurs in dense soil, the top meristem should be protected. Protection of apical meristem from damage ensured the appearance of an root case. The appearance of the roots was caused by increasing climate dryness. The occurrence of a more dry climate has caused terrestrial plants the need to attach water and nutrients to the substrate and absorb from it. However, during the evolution, the structure of the root different species Plants changed less than that of the stem. This is due to the fact that in the soil environment, the conditions are more stable than in the air. Therefore, the root is considered a more "conservative" authority, although it appeared much later escape. Formation of roots - important aromorphosis of plants. Thanks to him, the plants were able to learn more dry soil and form large, rising up shoots.
Reaction of amindlasts of root case for gravity. The movement of Statolites plays an important role in creating gradients of phytogorms, providing a vertical growth of the root.
The structure of the root of wheat seedlings (Triticum Aestivum): A - Root structure diagram; B - differentiation of risoderma cells and exoderma. 1 is a zone of conduct, 2 - zone of suction, 3 - zone of stretching, 4 - zone of division, 5 - root hairs, 6 - root case.
Cross cut of the root (a - monocycle, b - bicycle rod)
The primary bark occurs from the periblex. Its main mass make up living parenchymal cells with thin shells. Between them, the system of interclausers stretched along the root axis is formed. The gases circulate (CO 2) for interclauders. Gases are necessary to maintain intensive metabolism in cortex cells and risoderma. The energetic metabolism in the cells of the cortex is necessary to perform a number of important functions: 1) cortex cells supply with risoderma with plastic substances and are involved in the absorption and conducting substances; 2) various substances transmitted to other fabrics are synthesized in the core; 3) spare substances accumulate in bark cells; 4) There are often gifs of mushrooms forming mikuriza.
Endoderma cells pass three stages of development. In the suction zone, the endoderma is in the first stage. In the middle of the radial walls of its cells, the cappar belts are formed. Kaspari's belts overlap the movement of substances through the cellular shells, that is, according to Apoplast. The second stage can be observed in the side root zone. At the same time S. inner The cell shell appears a thin suberinet plate. However, the endoderma is still free to pass solutions, since it remains separate throughputs with thin walls. The third stage of the seaside and the edge of the endoderma can be observed in the zone of monocotional roots. The internal and radial walls of its cells are very thickened. On transverse sections, such cells have a horseshoe-shaped form. There are no bandwidth cells. Tolstoyed endoderma protects conductive tissues and increases the strength of the root.
Caspari - waterproof barrier, forcing water to leave the apoplastic and rushing through the membranes of the endoderma cells in the symplast
The flow of water from the soil to the root: water can move around apoplast and the symplast until it reaches the endoderma. Further movement on Apoplast is impossible.
Different types of the structure of the central cylinder of the root (primary structure): A-diarch, b-triirchny, is a tetrarchnyh, polyarchnic. Types A-in Characteristic for dicotyledtles, Mr. Many monocoons. 1 - Plot of primary bark, 2 - primary Floem, 3 - Primary xylem.
4 stages of the root transition from the primary structure to secondary: 1) the appearance of Cambia between the primary flolam and xylem sections are distinguished; 2) the formation of fellogenesis pericycle; 3) discharge of the primary bark; 4) change of radial arrangement of conductive tissues collateral.
The transition from the primary structure of the root to the secondary 1-Purpose Floem, 2-Operating xylem, 3 - Cambier, 4 - pericycle, 5 - Endoderma, 6 - Mesoderma, 7 - Rizoderma, 8 - exoderma, 9-Real xylem, 10 - Secondary Floam , 11 - Secondary Cora, 12 - Fellogen, 13 - Fellem.
Scheme of primary differentiation of conductive tissues in the root of pea 1-CENTROSTROVITIVE DIFFERENCIATION OF XILEMA, 2 -EPIDERMA, 3-PERSONAL CORRA, 4 -Endoderma, 5-in-line differentiated elements of xylems, 6-shaped elements of xylems, 7 -Proof differentiated flolam elements, 9 -Pick Meristhem, 10-aknevial \u200b\u200bcase.
Secondary change in monocoa root. The overwhelming majority of single-rope plants The primary structure of the root retains until the end of life. However, at the same time, many elements of the root are appointed. Wood monocotional (palm trees, dragees, yukki) in the root cortex of parenchyma cells or from pericycles arises a layer of meristem. It forms rows of closed conductive beams. Following this, a new layer of educational fabric appears in the peripheral part of the parenchyma of the primary bark. This layer of the meristema gives the beginning of a new row of conductive beams. Thus, the root thickening occurs.
Pressure roots arise on different organs of plants - on stems, leaves and roots. The apparent roots arising on the stem are called the stelerroduks that have arisen on the root - root. Side and apparent roots have endogenous origin, i.e. they are laid in the inner tissues.
The locking of the side root begins with the division of pericycle cells. At the same time, a meristematic tubercle is formed on the surface of the stela. After a number of divisions of the cells of the meristematic tuberca, side root occurs. It has its own apical merysist and case. The descendant of the side root grows, breaks through the primary bark of the mother root and extends outside. Usually lateral roots arise against the elements of xylems. Therefore, they are located right longitudinal rows along the root. They arise in the absorption zone or somewhat higher. The locking of the side roots occurs both acroptal, i.e. from the base of the root to its top.
Pressure roots are usually laid in tissues capable of meristematic activity: in Pericycle, Cambia, Fellogene. Endogenous formation of lateral (and pressing) roots has an adaptive value. If the branch occurred in the apex, the progress of the root in the soil was difficult.
Dichotomous branching in the root system of the pladen of Maulanoid (Lycopodium Clavatum) 1 - isotomed dichotomous branching of the most thin roots
Mycorrhuses: A - Etototrophic Oak Mikoriza, B, B - Endotrofan Mikariza Yatryshnik. Nujna on the roots of Lupine