Textile- a group of cells that are structurally and functionally interconnected with each other, similar in origin, structure and performing certain functions in the body.
Tissues arose in higher plants in connection with their access to land and reached the greatest specialization at angiosperms, in which up to 80 species are distinguished. The most important plant tissues:
Educational,
Integumentary,
Conductive,
Mechanical
Basic.
Fabrics can be simple and complex. Plain fabricsconsist of one type of cell (for example, collenchyma, meristem), andcomplex- from cells of different structure, performing, in addition to the main and additional functions(epidermis, xylem, phloem, etc.).
Educational fabrics, or meristems, are embryonic tissues. Thanks to their long-lasting ability to divide (some cells divide throughout life), meristems participate in the formation of all permanent tissues and thereby form the plant, and also determine its long-term growth.
The cells of educational tissue are thin-walled, multifaceted, tightly closed, with dense cytoplasm, a large nucleus and very small vacuoles. They are capable of dividing in different directions.
According to the origin of meristems, there are primary and secondary. The primary meristem is the embryo of the seed, and in an adult plant it remains at the tip of the roots and tips of the shoots, which makes it possible for them to grow in length. Further growth of the root and stem in diameter (secondary growth) is ensured secondary meristems- cambium and phellogen. Based on their location in the plant body, apical (apical), lateral (lateral), intercalary (intercalary) and wound (traumatic) meristems are distinguished.
Integumentary tissues located on the surface of all plant organs. They perform a mainly protective function - they protect plants from mechanical damage, penetration of microorganisms, sudden temperature fluctuations, excessive evaporation, etc. Depending on their origin, three groups of integumentary tissues are distinguished - epidermis, periderm and crust.
Epidermis (epidermis, skin)- primary cover tissue, located on the surface of leaves and young green shoots (Fig. 8.1). It consists of a single layer of living, tightly packed cells that do not have chloroplasts. The cell membranes are usually tortuous, which ensures their strong closure. The outer surface of the cells of this tissue is often covered with a cuticle or waxy coating, which is an additional protective device. The epidermis of leaves and green stems contains stomata that regulate transpiration and gas exchange in the plant.
Periderm- secondary integumentary tissue of stems and roots, replacing the epidermis in perennial (less often annual) plants (Fig. 8.2.). Its formation is associated with the activity of the secondary meristem - phellogen (cork cambium), the cells of which divide and differentiate in the centrifugal direction (outward) into the cork (phellema), and in the centripetal direction (inward) - into a layer of living parenchyma cells (phelloderm). Cork, phellogen and phelloderm make up the periderm.
Rice. 8.1. Leaf epidermis of various plants: a-chlorophytum; 6 - common ivy: in - fragrant geranium; G - white mulberry; 1- epidermal cells; 2 - stomatal guard cells; 3 - stomatal fissure.
Figure 8.2. Periderm of elderberry stem (a - cross section of a shoot, b - lentils): I-performing fabric; 2 - remnants of the epidermis; 3 -cork (phellema); 4 - phellogen; 5 - phelloderm.
The cells of the cork are impregnated with a fat-like substance - suberin - and do not allow water and air to pass through, so the contents of the cell die and it fills with air. The multilayer cork forms a kind of stem cover that reliably protects the plant from adverse influences. environment. For gas exchange and transpiration of living tissues lying under the plug, the latter has special formations - lentils; These are gaps in the plug filled with loosely arranged cells.
Crust formed in trees and shrubs to replace cork. In the deeper tissues of the cortex, new areas of phellogen are laid down, forming new layers of cork. As a result, the outer tissues are isolated from the central part of the stem, deformed and die. On the surface of the stem, a complex of dead tissues gradually forms, consisting of several layers of cork and dead sections of bark. A thick crust lasts longer reliable protection for a plant than a cork.
Conductive fabrics ensure the movement of water and nutrients dissolved in it throughout the plant. There are two types of conductive tissue - xylem (wood) and phloem (bast).
Xylem- this is the main water-conducting tissue of higher vascular plants, ensuring the movement of water with minerals dissolved in it from the roots to the leaves and other parts of the plant (ascending current). It also performs a supporting function. The xylem consists of tracheids and tracheae (vessels) (Fig. 8.3), wood parenchyma and mechanical tissue.
Tracheids They are narrow, highly elongated dead cells with pointed ends and lignified membranes. The penetration of solutions from one tracheid into another occurs by filtration through pores - recesses covered with a membrane. Liquid flows through the tracheids slowly, since the pore membrane prevents the movement of water. Tracheids are found in all higher plants, and in most horsetails, clubmosses, ferns and gymnosperms they serve as the only conducting element of the xylem. U covered seed plants Along with tracheids there are vessels.
Figure 8.3. Elements of xylem (a) and phloem (6): 1-5 - ringed, spiral, scalariform and porous (4, 5) trachea, respectively; 6 - ringed and porous tracheids; 7 - sieve tube with companion cell.
Trachea (vessels)- these are hollow tubes consisting of individual segments located one above the other. In the segments, through holes are formed on the transverse walls - perforations, or these walls are completely destroyed, due to which the speed of the flow of solutions through the vessels increases many times over. The shells of the vessels are impregnated with lignin and give the stem additional strength. Depending on the nature of the thickening of the membranes, tracheas are distinguished as ringed, spiral, scalariform, etc. (see Fig. 8.3).
Phloem conducts organic matter, synthesized in the leaves, to all plant organs (downward current). Like xylem, it is a complex tissue and consists of sieve tubes with companion cells (see Fig. 8.3), parenchyma and mechanical tissue. Sieve tubes are formed by living cells located one above the other. Their transverse walls are pierced with small holes, forming a kind of sieve. The cells of the sieve tubes are devoid of nuclei, but contain cytoplasm in the central part, strands of which pass through through holes in the transverse partitions into neighboring cells. Sieve tubes, like vessels, stretch along the entire length of the plant. Companion cells are connected to the segments of the sieve tubes by numerous plasmodesmata and, apparently, perform some of the functions lost by the sieve tubes (enzyme synthesis, ATP formation).
Xylem and phloem are in close interaction with each other and form special complex groups in plant organs - vascular bundles.
Mechanical fabrics ensure the strength of plant organs. They form a frame that supports all plant organs, resisting their fracture, compression, and rupture. The main characteristics of the structure of mechanical tissues, ensuring their strength and elasticity, are the powerful thickening and lignification of their membranes, close closure between cells, and the absence of perforations in the cell walls.
Mechanical tissues are most developed in the stem, where they are represented by bast and wood fibers. In roots, mechanical tissue is concentrated in the center of the organ.
Depending on the shape of the cells, their structure, physiological state and the method of thickening of cell membranes, two types of mechanical tissue are distinguished: collenchyma and sclerenchyma (Fig. 8.4).
Rice. 8.4. Mechanical fabrics: a -angular collenchyma; 6- sclerenchyma; V -- sclereids from cherry plum fruits: 1 - cytoplasm, 2-thickened cell wall, 3 - pore tubules.
Collenchyma is represented by living parenchyma cells with unevenly thickened membranes, making them especially well adapted for strengthening young growing organs. Being primary, collenchyma cells easily stretch and practically do not interfere with the elongation of the part of the plant in which they are located. Collenchyma is usually located in separate strands or a continuous cylinder under the epidermis of the young stem and leaf petioles, and also borders the veins in dicotyledonous leaves. Sometimes collenchyma contains chloroplasts.
Sclerenchyma consists of elongated cells with uniformly thickened, often lignified shells, the contents of which die in the early stages. The membranes of sclerenchyma cells have high strength, close to the strength of steel. This tissue is widely represented in the vegetative organs of land plants and forms their axial support.
There are two types of sclerenchyma cells: fibers and sclereids. Fibers- these are long thin cells, usually collected in strands or bundles (for example, bast or wood fibers). Sclereids - these are round, dead cells with very thick, lignified membranes. They form the seed coat, nut shells, seeds of cherries, plums, and apricots; they give the flesh of pears their characteristic coarse character.
Main fabric, or parenchyma, consists of living, usually thin-walled cells that form the basis of organs (hence the name tissue). It houses mechanical, conductive and other permanent tissues. The main tissue performs a number of functions, and therefore they distinguish between assimilation (chlorenchyma), storage, pneumatic (aerenchyma) and aquiferous parenchyma (Fig. 8.5).
Figure 8.5. Parenchymal tissues: 1-3 - chlorophyll-bearing (columnar, spongy and folded, respectively); 4-storage (cells with starch grains); 5 - pneumatic, or aerenchyma.
Cells assimilation tissues contain chloroplasts and perform the function of photosynthesis. The bulk of this tissue is concentrated in the leaves, a smaller part in young green stems.
In cells storing proteins, carbohydrates and other substances are deposited in the parenchyma. It is well developed in the stems of woody plants, in roots, tubers, bulbs, fruits and seeds. Plants of desert habitats (cacti) and salt marshes have aquifer parenchyma, which serves to accumulate water (for example, large specimens of cacti from the genus Carnegia contain up to 2-3 thousand liters of water in their tissues). Aquatic and marsh plants develop a special type of basic tissue - pneumatic parenchyma, or aerenchyma. Aerenchyma cells form large air-bearing intercellular spaces, through which air is delivered to those parts of the plant whose connection with the atmosphere is difficult
Onion scales under a microscope
Biology test Department Angiosperms for 7th grade students. The test includes 2 options, each option consists of 3 parts (Part A, Part B, Part C). Part A has 7 tasks, Part B has 4 tasks, Part C has 1 task.
1 option
A1. The generative organ of angiosperms is
1) root
2) stem
3) flower
4) leaf
A2. One of the essential features of angiosperms, which is unique to this group of plants, is
1) presence of flowers
2) propagation by seeds
3) soil nutrition
4) carrying out photosynthesis in the light
A3. Vessels in flowering plants are formed by tissue cells
1) cover
2) conductive
3) storage
4) mechanical
A4. A modified shoot of a flowering plant is
1) seed
2) sheet
3) flower
4) stem
A5. The ovules of flowering plants are located in
1) sepals
2) pistil ovary
3) corolla petal
4) anther stamen
A6. Develops from the fertilized egg of flowering plants
1) filament
2) seed embryo
3) stigma
4) sperm
A7. After double fertilization in flowering plants, the ovule develops
1) seed
2) fruit
3) flower
4) inflorescence
B1.
A. The root system of flowering plants includes the main, lateral and adventitious roots.
B. Leaves on tropical flowering plants persist throughout the life of the plant.
1) Only A is correct
2) Only B is correct
3) Both judgments are correct
4) Both judgments are incorrect
B2. Choose three true statements. Traits of monocots
1) one cotyledon per seed
2) parallel veining of leaves
3) reticulate venation of leaves
4) rod root system
5) fibrous root system
6) five-membered flower
B3. Establish a correspondence between the family of flowering plants and its class.
Flowering plant family
A. Cereals
B. Rosaceae
B. Legumes
G. Liliaceae
D. Solanaceae
1. Monocots
2. Dicotyledons
B4. Establish the sequence of stages of evolution in the plant world
B1. Drawing assignment.
1) Cereals
2) Legumes
3) Liliaceae
4) Cruciferous
1) reticulate venation
2) parallel venation
3) compound sheet
4) round shape
1) single flowers
2) presence of inflorescence
3) bright corolla
4) juicy fruits
Option 2
A1. The ovule of angiosperms is located
1) on back side sheet
2) under the bark of the stem
3) in the ovary of the pistil
4) at the top of the shoot
A2. The thickness of a tree trunk in flowering plants is determined by the functioning
1) bark
2) bast
3) cambium
4) cores
A3. As a result of the division of cambium cells in the stem, the formation of
1) bast
2) peel
3) cores
4) tree rings
A4. The main parts of a flower include
1) pestle
2) whisk
3) cup
4) receptacle
A5. A flower that contains a pistil and a stamen is called
1) pistillate
2) staminate
3) same-sex
4) bisexual
A6. Sperm cells, which are formed from
1) pollen grain
2) stigma
3) corolla petals
4) filament
A7. A 7. In the seeds of flowering plants, the endosperm is
1) embryo
2) cover
3) water supply
4) supply of nutrients
B1. Are the following statements true?
A. A poplar shoot consists of a stem, leaves and buds.
B. Self-pollination occurs between two flowers of plants of the same species.
1) Only A is correct
2) Only B is correct
3) Both judgments are correct
4) Both judgments are incorrect
B2. Choose three true statements. Signs of dicotyledonous plants
1) arc venation of leaves
2) reticulate venation of leaves
3) two cotyledons in the seed
4) fibrous root system
5) tap root system
6) the number of flower parts is a multiple of three
B3. Establish a correspondence between the type of plant and the class to which it belongs.
Type of flowering plant
A. Homemade apple tree
B. Potatoes
B. Rye
G. Leek
D. White cabbage
1. Monocots
2. Dicotyledons
B4. Establish the sequence of stages of evolution in the plant world.
1) Ferns
2) Multicellular algae
3) Psilophytes (the first land plants)
4) Flowering plants
5) Unicellular algae
6) Gymnosperms
B1. Drawing assignment
A. What family does the flowering plant shown in the picture belong to?
1) Cereals
2) Legumes
3) Rosaceae
4) Compositae
B. The structural feature of the leaves of this plant
1) arc venation
2) parallel venation
3) reticulate venation
4) needle shape
B. Characteristics of the generative organs of this plant
1) the number of flower parts is a multiple of three
2) the number of flower parts is a multiple of five
3) simple perianth
4) the rim is missing
Answers to the biology test Department Angiosperms
1 option
A1. 3
A2. 1
A3. 2
A4. 3
A5. 2
A6. 2
A7. 1
B1. 1
B2. 125
B3. 12212
B4. 32514
IN 1. 122
Option 2
A1. 3
A2. 3
A3. 4
A4. 1
A5. 4
A6. 1
A7. 4
B1. 1
B2. 235
B3. 22112
B4. 523164
IN 1. 332
Department Angiosperms (Flowering) plants
OPTION 1
For each task, choose one correct answer from the four proposed.
A1. The generative organ of angiosperms is
2) stem
3) flower
A2. One of the essential features of angiosperms, which is unique to this group of plants, is
1) presence of flowers
2) propagation by seeds
3) soil nutrition
4) carrying out photosynthesis in the light
AZ. Vessels in flowering plants are formed by tissue cells
1) cover
2) conductive
3) storage
4) mechanical
A4. A modified shoot of a flowering plant is
3) flower
4) stem
A5. The ovules of flowering plants are located in
1) sepals
2) pistil ovary
3) corolla petal
4) anther stamen
A6. Develops from the fertilized egg of flowering plants
1) filament
2) seed embryo
3) stigma
4) sperm
A7. After double fertilization in flowering plants, the ovule develops
1) seed
4) inflorescence
B1.
A. The root system of flowering plants includes the main, lateral and adventitious roots.
B. Leaves on tropical flowering plants persist throughout the life of the plant.
1) Only A is correct
2) Only B is correct
3) Both judgments are correct
4) Both judgments are incorrect
B2. Choose three true statements. Traits of monocots
1) one cotyledon per seed
2) parallel veining of leaves
3) reticulate venation of leaves
4) tap root system
5) fibrous root system
6) five-membered flower
BZ. Establish a correspondence between the family of flowering plants and its class.
PLANT FAMILY
A, Cereals
B. Rosaceae
B. Legumes
G. Liliaceae
D. Solanaceae
FLOWER CLASS
1) Monocots
2) Dicotyledons
B4.
2) Psilophytes (the first land plants)
3) Algae
4) Flowering plants
5) Ferns
Answer: 3, 2, 5, 1, 4.
IN 1. Assignment to work with picture 3.
A. Which family does the flowering plant shown in Figure 3 belong to?
1) Cereals
2) Legumes
3) Liliaceae
4) Cruciferous
B.
1) reticulate venation
2) parallel venation
3) compound sheet
4) round shape
IN.
1) single flowers
2) presence of inflorescence
3) bright corolla
4) juicy fruits
OPTION 2
A1. The ovule of angiosperms is located
1) on the reverse side of the sheet
2) under the bark of the stem
3) in the ovary of the pistil
4) at the top of the shoot
A2. The thickness of a tree trunk in flowering plants is determined by the functioning
3) cambium
4) cores
AZ. As a result of the division of cambium cells in the stem, the formation of
3) cores
4) tree rings
A4. The main parts of a flower include
1) pestle
3) cup
4) receptacle
A5. A flower that contains a pistil and a stamen is called
1) pistillate
2) staminate
3) same-sex
4) bisexual
A6. Spermine, which is formed from
1) pollen grain
2) stigma
3) corolla petals
4) filament
A7. In the seeds of flowering plants, the endosperm is
1) embryo
3) water supply
4) supply of nutrients
B1. Are the following statements true?
A. A poplar shoot consists of a stem, leaves and buds.
B. Self-pollination occurs between two flowers of plants of the same species.
1) Only A is correct
2) Only B is correct
3) Both judgments are correct
4) Both judgments are incorrect
B2. Choose three true statements. Signs of dicotyledonous plants
1) arc venation of leaves
2) reticulate venation of leaves
3) two cotyledons in the seed
4) fibrous root system
5) tap root system
6) the number of flower parts is a multiple of three
BZ. Establish a correspondence between the type of plant and the class to which it belongs.
PLANT TYPE
A. Homemade apple tree
B. Potatoes
B. Rye
G. Leek
D. White cabbage
FLOWER CLASS
1) Monocots
2) Dicotyledons
Write down the corresponding numbers in the table.
B4. Establish the sequence of stages of evolution in the plant world.
1) Ferns
2) Multicellular algae
3) Psilophytes (the first land plants)
4) Flowering plants
Answer: 5, 2, 3, 1, 6, 4.
IN 1. Assignment to work with picture 4.
A. What family does the flowering plant shown in the picture belong to?
1) Cereals
2) Legumes
3) Rosaceae
4) Compositae
B. Features of the structure of the leaves of this plant
1) arc venation
2) parallel venation
3) reticulate venation
4) needle shape
IN. Characteristics of the generative organs of this plant
1) the number of flower parts is a multiple of three
2) the number of flower parts is a multiple of five
3) simple perianth
4) the rim is missing
OPTION 1
A1. Propagated by seeds
3. fern
A2. Fertilization does not depend on the availability of water
4. ferns
A3. Trunks coniferous trees produce
4.agar-agar
A4. The generative organ of the pine tree is
B 1.Are the following statements true?
A. Only female cones ripen on pine shoots.
B. Seeds in cones lie openly on the scales.
1. Only A is correct
2. Only B is correct
3. Both judgments are correct
4. Both judgments are wrong
B2. Choose three true statements. The seed of a gymnosperm plant contains
1. embryo
3. prothallus
4. endosperm
5. durable covers
BZ. Establish a correspondence between the feature of life activity and the organ of the gymnosperm plant that carries it out.
FEATURE OF LIFE ACTIVITIES
A. Provides soil nutrition
B. Provides photosynthesis
B. Strengthens the plant in the soil
D. Forms cones
D. Carries out the evaporation of water
2. Root
| A | B | IN | G | d |
OPTION 2
For each task, choose one correct answer from the four proposed.
A1. Unlike spores, seeds contain, in addition to the embryo,
2) stem
3) water supply
4) supply of nutrients
A2. Trees and shrubs predominate among life forms
1) chlorophyll
2) chitin
3) cuticle
4) carotene
A4. The pine ovule develops in
3) female bump
4) male bump
A. A speck of dust, or pollen grain, ripens in the male cones.
B. In many coniferous plants, water is involved in the pollination process.
1. Only A is correct
2. Only B is correct
3. Both judgments are correct
4. Both judgments are wrong
B2. Choose three true statements. Devices that reduce water evaporation from leaves are
1. needle-shaped needles
2. dense layer of cuticle
3. green color cells
4. presence of conductive tissues in leaves
5. small number of stomata on the skin
6. presence of chlorophyll in cells
BZ. Establish a correspondence between the propagation feature and the group of plants.
REPRODUCTION FEATURES OF A GROUP OF PLANTS
A. They reproduce by spores 1. Ferns
B.Gametes develop on the prothallus
D. Pollen is produced in the cone
Write down the corresponding numbers in the table.
| A | B | IN | G |
OPTION 1 For each task, choose one correct answer from the four proposed.
A1. The generative organ of angiosperms is
2. stem
A2. One of the essential features of angiosperms, which is unique to this group of plants, is
1. presence of flowers
2. propagation by seeds
3. soil nutrition
4. carrying out photosynthesis in the light
A3. Vessels in flowering plants are formed by tissue cells
1. coverslip
2. conductive
3. storage
4. mechanical
A4. A modified shoot of a flowering plant is
4. stem
A5.The ovules of flowering plants are located in
1. sepals
2. pistil ovary
3. corolla petal
4. anther stamen
A6. Develops from the fertilized egg of flowering plants
1. filament
2. seed embryo
3. stigma
4. sperm
A7. After double fertilization in flowering plants, the ovule develops
4. inflorescence
B1. Are the following statements true?
A. The root system of flowering plants includes the main, lateral and adventitious roots.
B. Leaves on tropical flowering plants persist throughout the life of the plant.
1. Only A is correct
2. Only B is correct
3. Both judgments are correct
4. Both judgments are wrong
B2. Choose three true statements. Traits of monocots
1. one cotyledon per seed
2. parallel veining of leaves
3. reticulated leaf venation
4. tap root system
5. fibrous root system
6. five-membered flower
BZ. Establish a correspondence between the family of flowering plants I and its class.
FAMILY OF FLOWERING PLANTS
1. Monocots
2. Dicotyledons
A. Cereals
B. Rosaceae
B. Legumes
G. Liliaceae
D. Solanaceae
Write down the corresponding numbers in the table.
| A | B | IN | G | d |
B4. Establish the sequence of stages of evolution in the plant world.
2. Psilophytes (the first land plants)
3.Algae
4. Flowering plants
5. Ferns
IN 1. Assignment to work with picture 3.
A.Which family does the flowering plant shown in Figure 3 belong to?
1) Cereals
2) Legumes
3) Liliaceae
4) Cruciferous
1) reticulate venation
2) parallel venation
3) compound sheet
4) round shape
B. Characteristics of the generative organs of this plant
1) single flowers
2) presence of inflorescence
3) bright corolla
4) juicy fruits
OPTION 2
For each task, choose one correct answer from the four proposed.
A1. The ovule of angiosperms is located
1) on the back of the leaf 3) in the ovary of the pistil
2) under the bark of the stem 4) at the top of the shoot
A2. The thickness of a tree trunk in flowering plants is determined by the functioning
1) bark 3) cambium
2) bast 4) core
A3. As a result of the division of cambium cells in the stem, the formation of
1) bast 3) core
2) skins 4) growth rings
A4. The main parts of a flower include
1) pestle 3) calyx
2) corolla 4) receptacle
A5. A flower that contains a pistil and a stamen is called
1) pistillate 3) unisexual
2) staminate 4) bisexual
A6. Sperm cells, which are formed from
1) pollen grain
2) stigma
3) corolla petals
4) filament
A7. In the seeds of flowering plants, the endosperm is
1. embryo
3. water supply
4. supply of nutrients
B1. Are the following statements true?
A. A poplar shoot consists of a stem, leaves and buds. B. Self-pollination occurs between two flowers of plants of the same species.
1.Only A is correct
2.Only B is correct
3.Both judgments are correct
4.Both judgments are incorrect
B2. Choose three true statements. Signs of dicotyledonous plants
1. arcuate leaf venation
2.reticulate venation of leaves
3.two cotyledons per seed
4. fibrous root system
5. tap root system
6.the number of flower parts is a multiple of three
BZ. Establish a correspondence between the type of plant and the class to which it belongs.
TYPE OF FLOWERING PLANT A. Apple tree B. Potato C. Rye D. Leek E. White cabbage
CLASS 1. Monocots
2.Dicotyledons
Part 3. Kingdom of Plants
Write down the corresponding numbers in the table.
| A | B | IN | G | D |
| - |
B4. Establish the sequence of stages of evolution in plants.
1) Ferns
2) Multicellular algae
3) Psilophytes (the first land plants)
4) Flowering plants
IN 1. Drawing assignment
A. What family does the flowering plant shown in the picture belong to?
1) Cereals
2) Legumes
3) Rosaceae
4) Compositae
B. The structural feature of the leaves of this plant
1. arc venation
2) parallel venation
3) reticulate venation
4) needle shape
B. Characteristics of the generative organs of this plant
1) the number of flower parts is a multiple of three
2) the number of flower parts is a multiple of five
3) simple perianth
4) the rim is missing
Distinctive features of angiosperms
In terms of time of appearance on Earth, angiosperms (flowering, pistillate) are the youngest and at the same time the most highly organized group of plants. In the process of evolution, representatives of this department appeared later than others, but they very quickly took a dominant position on the globe.
The most characteristic distinctive feature Angiosperms are characterized by the presence of a unique organ - a flower, which is absent in representatives of other plant divisions. This is why angiosperms are often called flowering plants. Their ovule is hidden, it develops inside the pistil, in its ovary, which is why angiosperms are also called pistillates. Pollen in angiosperms is captured not by ovules, as in gymnosperms, but by a special formation - the stigma, which ends at the pistil.
After fertilization of the egg, a seed is formed from the ovule, and the ovary grows into a fruit. Consequently, the seeds of angiosperms develop in fruits, which is why this plant division is called angiosperms.
Angiosperms(Angiospermae), or flowering(Magnoliophyta) - a division of the most advanced higher plants that have flowers. Previously included in the department of seed plants along with gymnosperms. Unlike the latter, the ovules of flowering plants are enclosed in an ovary formed by fused carpels.
The flower is the generative organ of angiosperms. It consists of a peduncle and a receptacle. The latter contains the perianth (simple or double), androecium (collection of stamens) and gynoecium (collection of carpels). Each stamen consists of a thin filament and an expanded anther in which sperm mature. The carpel of flowering plants is represented by a pistil, which consists of a massive ovary and a long style, the apical expanded part of which is called the stigma.
Angiosperms have vegetative organs that provide mechanical support, transport, photosynthesis, gas exchange, and nutrient storage, and generative organs involved in sexual reproduction. Internal structure tissues are the most complex of all plants; phloem sieve elements are surrounded by companion cells; Almost all representatives of angiosperms have xylem vessels.
The male gametes contained inside the pollen grains land on the stigma and germinate. Flowering gametophytes are extremely simplified and miniature, which significantly reduces the duration of the reproduction cycle. They are formed as a result of a minimum number of mitoses (three in the female gametophyte and two in the male). One of the features of sexual reproduction is double fertilization, when one of the sperm fuses with the egg, forming a zygote, and the second fuses with the polar nuclei, forming the endosperm, which serves as a supply of nutrients. The seeds of flowering plants are enclosed in the fruit (hence their second name - angiosperms).
The first flowering plants appeared at the beginning of the Cretaceous period about 135 million years ago (or even at the end of the Jurassic period). The question of the ancestor of angiosperms currently remains open; the extinct Bennettites are closest to them, however, it is more likely that, together with the Bennettites, the angiosperms separated from one of the groups of seed ferns. The first flowering plants were apparently evergreen trees with primitive flowers lacking petals; Their xylem still had no vessels.
In the middle of the Cretaceous period, in just a few million years, angiosperms conquered the land. One of the most important conditions The rapid spread of angiosperms was due to their unusually high evolutionary plasticity. As a result of adaptive radiation caused by environmental and genetic factors (in particular, aneupolydy and polyploidization), a huge amount of various types angiosperms belonging to a wide variety of ecosystems. By the mid-Cretaceous period, most modern families had formed. The evolution of terrestrial mammals, birds and, especially, insects is closely related to flowering plants. The latter play exclusively important role in the evolution of a flower, carrying out pollination: bright color, aroma, edible pollen or nectar - all these are means of attracting insects.
Flowering plants are distributed throughout the world, from the Arctic to the Antarctic. Their taxonomy is based on the structure of the flower and inflorescence, pollen grains, seeds, and the anatomy of xylem and phloem. Almost 250 thousand species of angiosperms are divided into two classes: dicotyledons and monocotyledons, differing primarily in the number of cotyledons in the embryo, leaf and flower structure.
Flowering plants are one of the key components of the biosphere: they produce organic matter, bind carbon dioxide and release molecular oxygen into the atmosphere; most pasture food chains begin with them. Many flowering plants are used by humans for cooking, building homes, making various household materials, and for medicinal purposes.
Angiosperms - the largest type of plants, which includes more than half of all known species - are characterized by a number of clear, sharply delimiting characteristics. Most characteristic of them is the presence of a pistil formed by one or more carpels (macro- and megasporophylls), fused with their edges, so that in the lower part of the pistil a closed hollow container is formed - the ovary, in which ovules (macro- and megasporangia) develop. After fertilization, the ovary grows into a fruit, inside of which there are seeds (or one seed) developed from the ovules. In addition, angiosperms are characterized by: an eight-core, or derived from it, embryo sac, double fertilization, triploid endosperm, formed only after fertilization, a stigma at the pistil that catches pollen, and for the vast majority, a more or less typical flower with a perianth. Among the anatomical features, angiosperms are characterized by the presence of true vessels (tracheas), while in gymnosperms only tracheites are developed, and vessels are extremely rare.
Due to the large number of common characters, it is necessary to assume a monophyletic origin of angiosperms from some more primitive group of gymnosperms. The earliest and very fragmentary fossil remains of angiosperms (pollen, wood) are known from the Jurassic geological period. From the Lower Cretaceous deposits, a few reliable remains of angiosperms are also known, and in the deposits of the mid-Cretaceous period they are found in large quantities and in a significant variety of forms, which all belong to many different living families and even genera.
Various groups of lower plants in the system were indicated as the putative ancestors of angiosperms - keithoniaceae, seed ferns, bennettites, and oppressed ferns. Caytoniaceae had an ovary and a stigma, but in them the ovary was formed differently than in angiosperms; they did not even have the semblance of flowers, their sporophylls are simple and, probably, they represent a blind branch of evolution. Bennettites had bisexual peculiar “flowers”, but did not have pistils, and their seeds were only hidden between sterile scales, and were not inside the fruits formed by megasporophylls. Seed ferns had no flowers and no angiosperms.
The theory of the origin of angiosperms from oppressive plants suggests that the most primitive angiosperms had small unisexual flowers without a perianth or with an inconspicuous perianth. But for a number of reasons, large, bisexual flowers are currently considered more primitive flowers. Therefore, it can be assumed that the ancestors of modern angiosperms were some extinct, very primitive gymnosperms with bisexual cone-type flowers (strobili), in which free (not fused with each other) tepals of a homogeneous perianth, microsporophylls ( stamens) and megasporophylls (carpels). In the gymnosperm system, this group must have stood somewhere between the seed ferns and the more specialized Bennettites and cycads.
Angiosperm undoubtedly represented big advantage in the sense of protecting ovules and developing seeds from any adverse external influences and, first of all, from dry air. But it is still difficult to explain the rapid powerful development angiosperms and their displacement of archegonial plants that previously dominated the earth. Russian botanist M.I. Golenkin expressed (in 1927) an interesting hypothesis about the reasons for the victory of angiosperms in the struggle for existence. He suggests that in the middle of the Cretaceous period, for some general cosmogonic reasons, a sharp change in lighting and air humidity occurred throughout the Earth. Thick clouds that previously constantly shrouded the Earth dissipated and gave access to bright sun rays, and therefore the dryness of the air sharply increased. The vast majority of higher archegonial plants of that time, not adapted and unable to adapt to bright light and dry air, began to die out or sharply reduced their areas of distribution (except for conifers, the most xerophytic).
On the contrary, angiosperms, which previously had a very limited distribution and were represented by a small number of forms, have developed the ability to tolerate bright light well. sunlight and dry air. This circumstance, as well as their extreme evolutionary plasticity, the ability to produce a wide variety of adaptations to various external conditions and determined the rapid, victorious spread of angiosperms throughout the Earth and the displacement of previously dominant groups of higher archegonial plants.
The victory of the angiosperms led to changes in the animal population of the Earth; it should have especially affected the rapid evolution of insects, mammals and birds that feed on insects, then predators and frugivores. In turn, in the angiosperms, countless adaptive changes in form, chemistry and function gradually arose in the process of evolution in connection with their complex and diverse relationships with the animal world. The victory of the angiosperms was a turning point, a profound revolution in the destinies of the entire animal population of the Earth.
Various assumptions have been made regarding the location of the original origin of angiosperms. Some believe that they first appeared on a hypothetical tropical continent located between America, Asia and Australia and subsequently sank into the waters of the Pacific Ocean. Others consider the region of the modern Arctic land to be their cradle, while others consider the mountains of the subtropical and warm temperate zone of the northern hemisphere. Most botanists now believe that the primordial angiosperms were woody plants with short trunks that branched monopodially into a few thick branches. From them larger sympodially branching trees with numerous thick and thin branches have already developed. From woody forms to different time and different phylogenetic lines, shrubs, subshrubs and herbaceous forms developed, first perennial, then in various genera due to specific climate and habitat conditions - biennials and annuals.
Due to the great plasticity of angiosperms, they have developed a huge diversity in the process of evolution. vegetative organs, especially in the leaves, numerous metamorphoses, as well as endless variety in flowers and fruits. Complexity and variety chemical composition and physiological reactions are also very characteristic of them.
The evolution of the flower, on the structure of which the taxonomy of angiosperms is mainly based, generally speaking and schematically, proceeded from flowers with a long receptacle (like a cone) from bisexual, actinomorphic with a spiral arrangement of free (unfused) and not fixed in the number of members, with the superior ovary and numerous ovules - to flowers that are cyclic, zygomorphic, dioecious, with a strictly fixed number of more or less fused members on a flat receptacle, with a lower single-locular ovary and few or one ovule. This evolution of the angiosperm flower occurred in their different evolutionary series independently of each other.
Angiosperms are widespread almost to the extreme limits of vegetation and determine the character of landscapes everywhere except coniferous forests, peat bogs and some types of tundra.
In human life and economic activity, the role of angiosperms is immeasurably greater than that of other groups of plants. Food, clothing, fodder for livestock, aromatics, narcotics, medicinal substances, tannins, rubber and gutta-percha, cork and much more are obtained from angiosperms; material for housing, fuel, ornamental materials, and paper are also largely supplied by angiosperms.
Angiosperms are divided into two classes - dicotyledons and monocotyledons. Dicotyledons are characterized by: two cotyledons in the seed, open vascular bundles (with cambium), preservation of the main root throughout life (in individuals born from seeds), pinnate and reticulate venation of leaves, 5-4-2-membered type of flowers. Monocots are characterized by opposite characters: one cotyledon per seed, closed vascular bundles (without cambium), early death of the main root and development of an adventitious root system, parallel or arcuate venation, three-membered type of flowers. Individual characteristics of one group can also be found in representatives of another group, so the entire set of characteristics is important.
The department of flowering plants includes two classes: dicotyledons and monocotyledons.
The most significant feature is the structure of the seed. But one sign is not enough to determine whether a plant belongs to a particular class. It is necessary to know all the signs of this plant.
The dicotyledonous class is the most numerous; it includes about 80% of angiosperm species, which are grouped into 325 families. Families of flowering plants are classified mainly on the basis of the structure of the flower and fruit.
The monocot class includes about 25% of flowering plants. These are mostly herbs. Only a few families contain arboreal forms, and even those live mainly in the tropics. The most simply organized group of monocots lives in reservoirs and swamps. This includes arrowhead, chastuha, and pondweed. But among monocots there are many species that have reached high level organizations such as cereals.
A typical family of the monocot class is the Liliaceae family. The predominant plants of this family are perennial herbs, which have well-developed rhizomes or bulbs, lanceolate or linear leaves with arcuate or parallel venation. Many of the lilies are ephemeral or ephemeroid - have a short growing season.
Lily flowers are large, of various colors, solitary or collected in a raceme. The perianth is simple, corolla-shaped, consists of six fused or free leaflets arranged in two circles. There are six stamens, also arranged in two circles, one pistil (of three fused carpels). The fruit of lilies is a berry or capsule.
Among the lilies there are many ornamental plants (lilies, tulips), food plants (onions, garlic), medicinal plants (lily of the valley, aloe, rosemary), etc.
The largest family in the monocot class is the cereals. There are over 10 thousand types of cereals. They are distributed throughout to the globe. This is a prosperous family that has reached a high level of organization.
Almost all cereals are herbaceous perennials, less often annuals. They form the basis of the herbage of many plant communities: meadows, steppes, etc. Bamboo is known among woody grasses. Plants of this family can be recognized by their hollow stem - a straw with nodes and internodes. The knots are filled with loose tissue. Cereal stems grow in length as a result of cell division in internodes. This type of growth is called intercalary.
Cereals can also be recognized by their leaves: they are narrow, long, and have parallel veins. The leaf has a wide base in the form of a tube - a vagina. It protects the delicate cells of the internodes from damage, due to the division of which the stem grows.
Cereals are also characterized by a fibrous root system. Thus, cereals can be distinguished from plants of other families by the structural features of their vegetative organs (leaves, roots and stems).
The flowers of cereals are small, dim, and collected in spikelets. From many spikelets, inflorescences are formed: a complex spike, a panicle, etc. Each spikelet has from 1 to 10 or more flowers. The cereal flower has three stamens and one pistil, but it does not have a calyx or corolla. Most cereals are wind-pollinated plants. Cereals have a typical fruit for this family - a caryopsis, rich in proteins and starch.
Cereals reproduce by seeds, as well as vegetatively using rhizomes and rooted shoots.
Cereals form the basis of human and farm animal nutrition. These include the most important feed and food cultivated plants. Wild cereals constitute the main feed for livestock. In the tropics, bamboo thickets form and sugar cane. Sugar cane is specially grown on plantations and sugar, rum, alcohol and molasses are obtained from it. Cereals are also used for paper production, textile, chemical and construction industries.
IN modern era As environmental conditions deteriorate, some species of cereals have become endangered. 23 species of grasses are listed in the Red Book: stone-loving feather grass, finely pubescent feather grass, evasive feather grass, multi-colored bluegrass, wheatgrass, leafy feather grass, etc.
Monocots(lat. Liliopsida, lat. Monocotyledones, English monocots) - a class of angiosperms, or flowering plants, the largest family of which is the Orchids, distinguished by extremely complex, beautiful flowers. In second place in terms of the number of species is the economically very important family Cereals.
Traditional Latin name for this group of plants is Monocotyledones, although in Lately, for example in the Cronquist system ( Cronquist) their official name -- Liliopsida (liliopsids). Because monocots-- a group of rank higher than family, the choice of name is not limited in any way. Article 16 of the ICBN allows both a descriptive name and a name derived from the type gender of the group.
Traditional name monocots, Monocotyledones or Monocotyledoneae, comes from the fact that the embryos of most members of the group have only one cotyledon, in contrast to dicotyledons, which usually have two. From a diagnostic point of view, determining the number of cotyledons is not easy in an accessible way, nor a reliable distinctive characteristic of the plant. The distinction between monocots and dicotyledons was first used in plant taxonomy back in early XVIII century by the English naturalist J. Ray.
However, monocots have more obvious distinctive features. The embryonic root usually soon stops growing and is replaced by adventitious roots. Stem vascular bundles are closed, scattered throughout the entire cross section of the stem; There is no cambium, so thickening of the stems like dicotyledons or gymnosperms is not observed. Stems rarely branch. Leaves for the most part stem-embracing, always without stipules, usually narrow and arcuate. Flowers are usually constructed according to the triple type: a perianth of two three-membered circles, stamens also 3 + 3, carpels 3, less often, instead of the number 3, the numbers 2 or 4 are observed in the flower.
Monocots are a monophyletic group that arose at the dawn of the history of the development of angiosperms. The oldest fossil plants that can be classified as monocots date back to the beginning of the Cretaceous period.
The APG II scientific classification system developed by the APG Group. Angiosperm Phylogeny Group), defines monocots as one of two largest groups among angiosperms. The second group is “eudicots” ( eudicots), according to established tradition, is sometimes called “paleodicots” ( palaeodicots). Among monocots, ten orders and two families are distinguished, which have not yet been definitively assigned to any of the orders. These orders are distributed as follows:
Major monocots
Family Petrosaviaceae ( Petrosaviaceae) / en:Petrosaviaceae
· Order Aeroceae ( Acorales) / en:Acorales
· Order Partiscolates ( Alismatales) / en:Alismatales
· Order Asparagusaceae ( Asparagales) / en:Asparagales
· Order Dioscoreaceae ( Dioscoreales) / en:Dioscoreales
· Order Liliaceae ( Liliales) / en:Liliales
· Order Pandanaceae ( Pandanales) / en:Pandanales
· Family ( Dasypogonaceae) / en:Dasypogonaceae
Order Palmaceae ( Arecales) / en: Arecales
· Order Commelinaceae ( Commelinales) / en:Commelinales
· Order Ceramaceae ( Poales) / en:Poales
· Order Gingeraceae ( Zingiberales) / en: Zingiberales
A more traditional classification is the system of Cronquist (1981), according to which all monocots were divided into five subclasses with the following orders:
Alismatids ( Alismatidae)
Order Alismatales
· Order Hydrocharitales
Order Najadales
Order Triuridales
Arecides ( Arecidae)
· Order of Palm Trees (Arecales)
Order Cyclanthales
Order Pandanaceae (Pandanales)
· Order Arales
Commelinoceae ( Commelinidae)
Order Commelinales
Order Eriocaulales
Order Restiales
Order Juncales (Juncales)
Order Sedges (Cyperales)
Order Hydatellales
Order Cattails (Typhales)
Ginger ( Zingiberidae)
Order Bromeliads (Bromeliales)
· Order Zingiberales
Liliids ( Liliidae)
· Order Liliales
Order Orchidaceae (Orchidales)
The class Dicotyledons belongs to the department Tsvetkov (Anthophyta), or Angiosperms ( Magnoliophyta, or Angiospermae) plants. This class is much more diverse and larger in volume than the second class from this department -- Monocots (Monocotiledonae or Liliopsida). From total number Dicotyledons account for about 80% of flowering plants.
Class Dicotyledons characterized the presence of the following characteristics that distinguish it from Monocots:
1. Embryo with two cotyledons.
2. The main root is well developed and persists throughout life, so the taproot (less often fibrous) root system predominates.
3. The stem is capable of secondary thickening due to the presence of cambium; conductive bundles are open.
4. The leaves are varied in shape and dissection, have palmate or pinnate veining, and the shape of the edge of the leaf blade can be different.
5. Flowers are acyclic, semicyclic and cyclic. The number of members of each circle is a multiple of 5, rarely 2, even less often 3.
The class Dicotyledons include about 200,000 species, 10,000 births, about 300 families(depending on the accepted classification). These are herbaceous and woody plants.
Taxonomy Since the 18th century, many botanists, both domestic and foreign, have been studying flowering plants. They all made invaluable contributions to modern construction phylogenetic (natural) system of flowering plants. However, there is still no generally accepted system for classifying angiosperms.
The most controversial question is which groups of angiosperms are closest to the ancient ancestral forms. In the systems of well-known botanists and phylogeneticists A. Engler and R. Wettstein, families with single-integumented and unintegued, inconspicuous, anemophilous flowers (willow, birch, etc.) are taken as the most primitive groups. In more modern systems As a primitive group, families with well-developed polynomial, separate-leaved, entomophilous flowers, the so-called polycarpids (families Magnoliaceae, ranunculaceae and etc.). Families with single-covered flowers are considered secondary simplified. Such systems are the systems of botanists N. A. Bush, A. A. Grossheim, A. L. Taxtadzhyan, Hutchinson (England), etc. One of the latest systems, which takes into account the largest number of characteristics, is the system of A. L. Takhtadzhyan ( 1970).
According to A.L. Takhtadzhyan, the class Dicotyledons includes 7 subclasses: Magnoliidae, Ranunculidae, Hamamelididae, Caryophyllidae, Dilleniidae, Rosidae and Asteridae. Within each subclass, its families are combined into orders. The entire class Dicotyledons includes 71 orders. The former cover the most primitive families, the latter - phylogenetically more advanced.
Basic orders Dicotyledonous class:
Subclass Choripetalae: order Magnoliales, order Ranunculales, order Papaverales, order Capparales, order Rosales, order Fabales, order Malvales, order Geraniums (Geraniales), order Terebinthales, order Umbellales, order Centrospermae, order Polygonales, order Fagales.
Subclass Sympetalae: order Scrophulariales, order Cucurbitales, order Asterales.
Literature
· Plant life. In 6 volumes. T. 6. Flowering plants. / Ed. A.L. Takhtajyan. - M.: Education, 1982. - 543 p., ill., 34 p. ill.
· Forest encyclopedia: In 2 volumes, volume 2/Ch. ed. Vorobyov G.I.; Ed. Col.: Anuchin N.A., Atrokhin V.G., Vinogradov V.N. and others - M.: Sov. Encyclopedia, 1986.-631 pp., ill.
