How do pollination and fertilization occur in flowering plants? What develops in flowering plants from the wall of the ovary? What is an ovary
The variety of flowering plants is surprisingly large. To understand this diversity, botanists combine all types of plants into groups, which in turn are combined into larger groups. To establish such groups of plants, signs of their similarities and differences are used, by which one can judge the degree of relatedness of plants to each other.
Flowering plants have a more perfect structure than the structure of other groups. Only in angiosperms flowers are formed, and in flowers - pistils. The ovules are located in the ovaries of the pistils. Flowering of different angiosperms differ in size, shape, color, structure; the flowers of some angiosperms are adapted for pollination by the wind, others for pollination by insects. But with any method of pollination, pollen grains fall on the stigmas of pistils, where pollen tubes are formed.
Pollen tubes with sperm grow to the ovules and grow into them, where fertilization occurs, which is characteristic only for flowering plants. At the same time, an embryo is formed from the zygote that arises from the fusion of gametes. The largest cell, after merging with the second sperm, grows, divides, and endosperm is formed, which stores nutrients for the embryo. Seeds develop from the ovules, and the pericarp develops from the wall of the ovary. 
So, seeds in flowering plants develop inside the fruit. Therefore, flowering plants are called angiosperms. Currently, angiosperms dominate among the plants that inhabit the land of the Earth.
Consider plants that bloom in autumn, for example, pansies, or tricolor violet. This plant, like most others, has organs:
roots and shoots. A shoot is a stem with leaves and buds located on it. Modified underground shoots are rhizomes, tubers and bulbs. Flowers may develop on the shoots. In their place, fruits with seeds ripen. Plants that bloom at least once in their lives are called flowering plants.
The same organs of flowering plants can be outwardly very diverse.
A flower is a modified shoot, in the place of which a fruit with seeds or with one seed ripens.
flower structure
Consider the structure of a flower. The flower develops on a pedicel expanding in the receptacle; all other parts of the flower are formed on it.
The brightly colored corolla consists of petals. Below the corolla is a cup of green leaves - sepals. The corolla and calyx are perianths that protect the interior of the flower from damage and may attract pollinating insects.
The main parts of a flower are the pistil and stamens. The stamen consists of a thin filament and anther, in which pollen is produced. In the pistil, a wide lower part is distinguished - the ovary, a narrow style and a stigma. The fruit develops from the ovary. In some plants, other parts of the flower, such as the receptacle, also take part in the formation of the fruit. Only a few plants have single flowers. In most, the flowers are collected in inflorescences.
In summer and autumn on plants ripen different in shape and color. 
fruits. Fruits are formed from ovaries. The overgrown and modified walls of the ovary, which has become a fruit, are called the pericarp. Inside the fruit are seeds. According to the number of seeds, the fruits are divided into single-seeded and multi-seeded.
There are juicy and dry fruits. Ripe juicy fruits have juicy pulp in the pericarp. Ripe dry fruits do not have pulp.
Seeds of plants are distinguished by shape and size. The seed consists of a peel (shell), an embryo and contains a reserve nutrients. In the embryo, the embryonic root, stalk, bud with leaves are distinguished.
Plants that have one cotyledon in the embryo of the seed are called monocots. 
In dicot plants, as the name suggests, the seed has two cotyledons. The supply of nutrients can be found in the cotyledons or in a special storage tissue - the endosperm. A new plant develops from the embryo of a seed. The seed is the germ of the future plant.
Plants differ from each other in the color and shape of stems, leaves, flowers and fruits, life expectancy and other features. But no matter how different flowering plants are, each of them can be attributed to one of three groups: trees, shrubs and herbs.
Trees are usually large plants with perennial woody stems. Each tree has a trunk, branches, tree branches form their crowns. Everyone knows birch, aspen, linden, maple, ash. Among the trees there are real giants, such as eucalyptus trees, reaching a height of more than 100 meters.
Shrubs differ from trees in that their trunk begins almost at the very surface of the soil and is difficult to recognize among the branches. Therefore, shrubs do not have one trunk, like trees, but several stems extending from a common base. Shrubs are widespread: hazel-hazel, lilac, honeysuckle, elderberry.
Herbs, or herbaceous plants, have, as a rule, green succulent stems; they are almost always lower than trees and shrubs. But a banana, for example, reaches a height of 7 meters, and some hogweeds are taller than a person. There are tiny herbaceous plants. Duckweed lives on the surface of reservoirs; the size of each plant is a few millimeters.
Trees and shrubs - perennials. For example, some oaks live for more than a thousand years. Herbs include both perennials, annuals and biennials.
Of the perennial herbs, lily of the valley, dandelion, coltsfoot, and nettle are well known. Aboveground parts of most of these herbaceous plants die off in autumn. In the spring, they develop anew, since in the soil under the snow these plants retain roots and other underground organs with buds.
Annual plants, such as violets, quinoa, levkoy, radishes, buckwheat, oats, wheat, develop from seeds in spring, bloom, form fruits with seeds, and then die.
Biennial plants live for almost two years. In beets, radishes, cabbage, usually only roots, stems and leaves develop in the first year. In the second year, these plants develop new shoots, bloom and produce fruits with seeds, and die off by autumn.
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All-Russian Olympiad for schoolchildren
2015-2016 academic year
school stage
Biology, grade 11
Tasks
Maximum score - 90.5
Part I You are offered test tasks that require you to select only one answer
out of four possible. The maximum number of points that can be scored is 30
(1 point for each test task). The answer index you think is the most
complete and correct, indicate in the answer matrix.
1. In flowering plants, the following develops from the wall of the ovary:
a) an embryo;
b) seed coat;
c) endosperm;
d) pericarp.
2. Algae, which, thanks to their pigments, are most adapted to photosynthesis at great depths:
a) green
b) red;
c) brown;
d) golden.
3. Functions of the root cap in plants:
a) ensuring the growth of the root in length;
b) holding water and solutions of mineral substances;
c) protection of the root tip from damage;
d) absorption of water and solutions of mineral substances.
4. Name the type of fruit in potatoes:
a) tuber;
b) berry;
c) a box
d) a seed.
5. Which plant has a fibrous root system:
a) beets;
b) sunflower;
c) tulip;
d) peas.
6. Same-sex flowers are typical for:
a) pumpkins
b) wheat;
c) peas;
d) rye.
7. What set of chromosomes is in the endosperm cells in the wheat seed?
a) haploid; b) diploid; c) triploid; d) polyploid.
8. Spike inflorescence is typical for:
a) dill; b) plantain; c) lily of the valley; d) gladiolus.
9 Bacteria are the causative agents of:
a) scabies; b) hepatitis; c) cholera; d) malaria.
10. Which of the formations by origin is not a derivative of the skin epidermis:
a) whalebone b) rhinoceros horn; c) pangolin scales; d) cat vibrissae
a) bull tapeworm; b) roundworm; c) pork tapeworm; d) echinococcus.
12. Which of the following organisms exhibits positive phototaxis:
a) chlorella; b) malarial plasmodium; c) euglena d) amoeba-proteus.
13. To insects with complete transformation relate:
a) orthoptera, diptera; b) hemiptera, homoptera; c) Coleoptera, Lepidoptera; d) Hymenoptera, dragonflies.
14. Roundworms differ from flatworms by the presence of:
A) nervous system; b) anus; c) cuticles; d) excretory system.
15. The figure shows the skeleton of a vertebrate.
In its structure it is impossible to find:
a) the cranium;
b) chest;
c) cervical vertebrae;
d) ribs.
16. Malaria is caused by:
a) amoeba; b) trypanosomes; c) plasmodia; d) ciliates.
17. The intestine is absent in:
a) liver fluke; b) a wide ribbon; c) pinworms; d) roundworm.
18. Human erythrocytes are destroyed in:
a) thymus b) yellow bone marrow c) liver d) pancreas.
19. Of the listed enzymes in the small intestine does not function:
a) chymotrypsin; b) lipase; c) pepsin; d) pancreatic amylase
20. Therapeutic serum is:
a) an antibody preparation b) weakened bacteria c) a suspension of leukocytes d) an antibiotic solution.
21. Cartilaginous semirings form the basis of the skeleton:
a) trachea b) esophagus c) larynx d) bronchioles.
22. The composition of the anterior roots of the spinal cord includes axons:
a) conducting impulses from the brain b) motor neurons c) sensory neurons d) intercalary neurons.
23. The unpaired bone of the skull is:
a) maxillary b) occipital c) parietal d) temporal.
24. The human respiratory center is located in:
a) bark hemispheres b) diencephalon c) medulla oblongata d) cervical segments of the spinal cord.
25. Mucus covering the walls of the stomach:
a) inactivates saliva enzymes b) softens food c) promotes the conversion of pepsinogen into pepsin d) prevents self-digestion of the stomach walls.
26. The first stage of embryonic development is called:
a) neurula; b) blastula; c) crushing; d) gastrula.
27. Examples of homologous organs are:
a) the dorsal fin of a shark and a dolphin;
b) digging limb of a mole and a bear;
c) the pectoral fin of a perch and a human hand;
d) tortoise shell and snail shell.
28. According to the results of genetic analysis by the wild ancestor of the domestic cat
are at least five representatives of one of the subspecies:
a) European cat;
b) forest cat;
c) reed cat;
d) a Chinese cat.
29. In ecosystems of great depths of the ocean, there are necessarily:
a) animals, microorganisms; b) plants, microorganisms; c) plants, animals, microorganisms; d) plants and animals.
30. Interactions of individuals in a population, between populations are called:
a) abiotic factors; b) biotic factors; V) anthropogenic factors;
d) evolutionary factors.
31. The divergence of daughter chromatids to the poles occurs in meiosis in:
a) prophase I;
b) metaphase II;
c) anaphase I;
d) anaphase II.
32. What happens in an ecosystem if there are no decomposers in it or their activity is poorly expressed:
a) nothing happens
b) there is an accumulation of organic matter;
c) the number of producers decreases,
d) the number of consumers increases.
33. When crossing a red cat with a tortoiseshell cat in offspring:
a) all kittens will be black;
b) half of the kittens will be red;
c) all cats will be red;
d) all cats will be black.
34. In the body of animals, an oxygen molecule does not bind to:
a) myoglobin;
b) hemoglobin;
c) cytochrome c;
d) cytochrome a3.
35. Of the listed ecosystems, the lowest production per square meter have:
a) meadow;
b) taiga;
c) tropical forest;
d) open ocean.
Part II. You are offered test tasks with one answer option out of four possible, but requiring a preliminary multiple choice. The maximum number of points that can be scored is 20 (2 points for each test task). The index of the answer that you consider the most complete and correct, indicate in the answer matrix.
1. Mushrooms with animals bring together signs:
1) the only posterior flagellum in motile cells;
2) autotrophic type of nutrition;
3) store glycogen;
4) the ability to unlimited growth;
5) the presence of chitin.
a) 1, 2, 3;
b) 1, 2, 4;
c) 1, 3, 5;
d) 2, 3, 4;
e) 2, 3, 5.
2. The following compounds are involved in the regulation of blood sugar levels:
1) glucagon;
2) insulin;
3) prolactin;
4) testosterone;
5) estradiol.
a) only 1, 2;
b) only 1, 5;
c) only 2, 3;
d) only 2, 4;
e) 1, 2, 3.
3. The processes of plastic exchange include:
1) ATP synthesis;
2) photosynthesis;
3) protein synthesis;
4) glycolysis;
5) synthesis of nucleotides.
a) 1, 2, 3;
b) 2, 3, 4;
c) 2, 3, 5;
d) 2, 4, 5;
e) 3, 4, 5.
4. Indicators of biological regression are:
1) reduced life expectancy;
2) increase in embryonic mortality;
3) decrease in species diversity;
4) reduced fertility;
5) size reduction.
a) only 3;
b) only 1, 3;
c) only 1, 2, 3;
d) only 2, 3, 5;
e) 1, 2, 3, 4.
5. From the Central American Center of Origin (according to N.I. Vavilov)
cultivated plants occur:
1) wheat;
2) corn;
3) rice;
4) soy;
5) sunflower.
a) only 1, 3;
b) only 1, 5;
c) only 2, 5;
d) only 1, 2, 5;
e) 2, 3, 5.
6. Remote hybridization in animals is difficult due to:
1) a different set of genes in different types;
2) a different set of chromosomes in different species;
3) tissue incompatibility of different types;
4) different conditions species habitats;
5) different mating behavior of species.
a) only 1, 3;
b) only 1, 5;
c) only 2, 5;
d) only 1, 3, 4;
e) 2, 4, 5.
7. In eukaryotes, transcription occurs in:
1) core;
2) the Golgi apparatus;
3) mitochondria;
4) plastids;
5) lysosomes.
a) 1, 2, 3;
b) 1, 2, 4;
c) 1, 2, 5;
d) 1, 3, 4;
e) 1, 3, 5.
8. One codon of messenger RNA can encode:
1) one amino acid;
2) two amino acids;
3) three amino acids
4) four amino acids;
5) not a single amino acid.
a) only 1, 2;
b) only 1, 3;
c) only 1, 4;
d) only 1, 5;
e) 1, 2, 5.
9. Of the listed processes in mitochondria, the following occurs:
1) protein synthesis;
2) DNA synthesis;
3) synthesis of fatty acids;
4) ATP synthesis;
5) oxidation of fatty acids.
a) only 3;
b) only 2, 4;
c) only 1, 3, 4;
d) only 1, 4, 5;
e) 1, 2, 4, 5.
10. Lipids are part of :
1) ribosome;
2) mitochondria;
3) chromatin;
4) nucleolus;
5) Golgi apparatus.
a) 1, 2;
b) 1.5;
c) 2, 3;
d) 2, 4;
e) 2, 5.
Part 3 You are offered test tasks in the form of judgments, with each of which you must either agree or reject. In the response matrix, indicate the answer option "yes" or "no". The maximum number of points that can be scored is 20 (1 point for each test task).
1. The bulk of pine wood is made up of vessels and mechanical fibers.
2. The products of photosynthesis move down the sieve tubes.
3. In the vein of the leaf, the phloem is located below, and the xylem is above.
4. Oxygen is released by all green plants.
5. Plant roots can carry out photosynthesis.
6. Cockroach blood is colorless because it does not contain hemoglobin.
7. All ciliates have contractile vacuoles.
8. Kamchatka crab is a hermit crab, which is characterized by a weak development of the abdominal region.
9. Lungfish - an extinct group of fish from which terrestrial vertebrates originated.
10. characteristic feature mammal is live birth.
11. The main organ that, under the influence of the hormone insulin, provides a decrease in the level of glucose in human blood is the liver.
12. Oxygen and carbon dioxide are transported by blood only due to binding to hemoglobin and transfer as part of the hemoglobin-gas molecule complex.
13. The liver is able to quickly and without serious consequences regenerate up to 70% of its volume removed during surgery.
14. The basis of biological membranes is a double layer of phospholipids.
15. The largest molecules in living organisms are muscle proteins.
16. The products of the dark stage of photosynthesis are glucose and oxygen.
17. Compounds indispensable for the human body include amino acids and nitrogenous bases.
18. In terrestrial ecosystems, the highest density of plant biomass is found in tropical forests.
19. The absence of intestines in tapeworms indicates a biological regression of this group of animals.
20. Mitochondria and lysosomes appeared in eukaryotic cells as a result of symbiosis.
Part 4 You are offered test tasks that require compliance. The maximum number of points that can be scored is 15.5. Complete the answer matrices as required by the assignments.
( max . 3.5 points)
Before you is a section of the stem of a plant. Correlate the main structures of the conducting beam (A-Zh) with their designations in the figure (1-7).
A - the main parenchyma; B - sieve tubes; B, companion cells;
G - spiral vessel; D - sclerenchyma; E - porous vessel;
G - ringed vessel.
Notation
1
2
3
4
5
6
7
structures
2. ( max . 4 points)
The figure shows representatives of the fauna of the forest floor and upper soil horizons.
Establish a correspondence between organisms (1-8) and taxa to which they belong (A–E): A) Centipedes; B) arachnids; B) the simplest; D) crustaceans; D) insects.
organisms
1
2
3
4
5
6
7
8
taxa
3. ( max . 3 points)
Which of the following structures are indicated in the figure by numbers 1 - 5?
A - bladder, B – kidney; B - kidney cortex; D - medulla of the kidney; D - renal pelvis; E - ureter.
number
1
2
3
4
5
6
organ
4. ( max . 2.5 points)
For each product in the right column, find the corresponding substance in the left column.
A. Sucrose
1. Beef liver
B. Lipids
2. Beetroot
B. lactose
3. Fish oil
G. Glycogen
4. Pea grains
D. Protein
5. Milk
1
2
3
4
5
5. ( max . 2.5 points)
Many species of arthropods are closely related to man and his dwelling (1-5). Select from the list (A-E) the type of relationship that arises with the person.
1 - Housefly (Musca domestica)
2 – Bed bug(Cimex lectularius)
3 – Black(Blatta orientalis)And ginger(Blatella germanica)cockroaches
4 – Home spider(Tegenaria domestica)
5 – mosquitoes kindCulex (urban form– C. pipiens f. molestus)
A) proto-operation
B) commensalism
B) neutralism
D) symbiosis
1
2
3
4
5
Member of the subject-methodical commission: /Skorykh S.A./
Male sex cells - sperm - are formed in the dust particles of pollen that develop in the anthers of the stamens of the flower. Usually, pollen consists of many dust particles (pollen grains) connected in groups. In dust particles, sperm are formed - male germ cells.
Female reproductive cells - eggs - are formed in the ovules located in the ovary of the pistil of the flower (flowering plants have ovaries with one or more ovules). In order for seeds to develop from all the ovules, it is necessary to deliver sperm to each ovule to the eggs, since each egg is fertilized by a separate sperm.
The process of fertilization in plants is preceded by pollination. As soon as a speck of dust hits the stigma of the pistil (with the help of wind or insects), it begins to germinate. One of its walls stretches and forms a pollen tube. At the same time, two spermatozoa are formed in the dust grain. They move to the tip of the pollen tube. Moving through the tissues of the stigma and style, the pollen tube reaches the ovary and penetrates into the ovule.
By this time, in the ovule, in its middle part, one cell divides and greatly elongates, forming the so-called embryo sac. In it, at one end is an egg, and in the center is a cell with two nuclei, which soon merge, forming one - the central nucleus. Having penetrated the ovule, the pollen tube germinates into the embryo sac, and there one sperm merges (combines) with the egg, forming a zygote, from which the embryo of a new plant develops.
Another sperm that has entered the embryo sac fuses with the central nucleus. The resulting cell divides very quickly, and soon a nutrient tissue, the endosperm, is formed from it.
The fusion in the embryo sac of sperm - one with the egg and the other with the central nucleus is called double fertilization.
The process of double fertilization is a phenomenon peculiar only to flowering plants. Thanks to double fertilization, the embryo of a new plant receives a very valuable endosperm with nutrients.
There is another classification:
13. Structure and functions of a flower.
Flower - reproductive organ of angiosperms. The flower consists of a pedicel, receptacle, perianth, androecium and gynoecium.
Fertile parts of a flower (stamen, pistil).
Sterile parts of the flower (calyx, corolla, perianth).
flower functions.
A flower is a modified shortened shoot adapted for the reproduction of angiosperms (flowering) plants.
The exclusive role of the flower is due to the fact that it combines all the processes of asexual and sexual reproduction, while in the lower and many higher plants they are divided. In a bisexual flower, micro- and megasporogenesis, micro- and megagametogenesis, pollination, fertilization, and the formation of seeds and fruits are carried out. The peculiarities of the structure of the flower make it possible to carry out the listed functions with minimal expenditure of plastic substances and energy.
The central (main) parts of the flower. Most plants have one or more pistils in the center of the flower. Each pistil consists of three parts: ovary - expanded base; column - more or less elongated middle part; stigma - the top of the pistil. Inside the ovary are one or more ovules. Outside, the ovule is surrounded by integuments through which a narrow channel passes - the pollen entrance.
Around the pistil (or pistils) are stamens. Their number in a flower is different in flowering plants: in wild radish - 6, in clover - 10, in cherry - a lot (about 30). The stamen consists of two anthers and a filament. Pollen develops inside the anther. Individual dust grains are usually very small grains. They are called pollen grains. The largest pollen grains reach 0.5 mm in diameter.
Perianth. In most flowers, the pistils and stamens are surrounded by a perianth. In cherries, peas, buttercups, the perianth consists of a corolla (a set of petals) and a calyx (a set of sepals). Such a perianth is called double. In a tulip, lily, lily of the valley, all the leaves are the same. Such a perianth is called simple.
Flowers with double perianth
Flowers with simple perianth
The tepals may grow together or remain free. In the tulip and lily, the perianth is simple, separate-leaved, and in the lily of the valley, it is joint-leaved. Flowers with a double perianth may also have fused sepals and petals. Primrose flowers, for example, have a calyx and a corolla. Cherry ranunculus flowers have a single-leaved calyx and a single-petaled corolla. The bell has a separate-leaved calyx, and the corolla has a joint-petal.
The flowers of some plants do not have a developed perianth. For example, in willow flowers, it resembles scales.
Inflorescences and flowers of willow
flower formula. The structural features of the flower can be noted in abbreviated form in the form of a formula. The following abbreviations are used in its compilation:
Ok - leaves of a simple perianth,
H - sepals, L - petals, T - stamens, P - pistils.
The number of flower parts is indicated by numbers in the form of an index (Ch5 is 5 sepals), with large numbers flower parts use the sign ∞. In the case of fusion of parts with each other, the number indicating their number is enclosed in brackets (L (5) - the corolla consists of 5 fused petals). If the parts of the flower with the same name are located in several circles, then a + sign is placed between the numbers indicating their number in each circle (T5 + 5 - 10 stamens in the flower are located 5 in two circles). For example, the lily flower formula- Ok3+3T3+3P1, bell- CH5L(5)T5P1.
Receptacle. All parts of the flower (near the flower garden, stamens, pistils) are located on the receptacle - the overgrown axial part of the flower. Most flowers have a pedicel. She moves away from the stem and connects it to the flower. In some plants (wheat, clover, plantain), pedicels are not expressed. Such flowers are called sessile.
Flowers bisexual and unisexual. Usually in one flower there are both pistil (pistils) and stamens. Such flowers are called bisexual. Some plants (willow, poplar, corn) have only pistil or stamens in the flower. Such flowers are called unisexual - staminate or pistillate (Fig. 71).
Monoecious and dioecious plants. In birch, corn, cucumber, same-sex flowers (staminate and pistillate) are located on one plant. Such plants are called monoecious. In poplar, willow, sea buckthorn, stinging nettle, some plants have only staminate flowers, while others have pistillate ones. These are dioecious plants.
Fertilization
Female sex cell(gamete) is called egg. Pestle
Male sex cell(gamete) is called sperm. Stamen
Pollen composed of pollen grains. pollen grain
Vegetative
generative sperm
pollen tube The structure of the ovule: Chromosomes
First sperm double.
zygote.
Second sperm triple.
Endosperm
From the shells of the ovule seed coat is formed. From the walls of the ovary
double. Navashin S.G. In 1898. Thus, a fruit is formed, which consists of a seed and a pericarp.
The formation of the ovule.
A cavity appears in the middle of the primary tubercle, and ovules will form on its inner wall.
The ovules of angiosperms are similar in structure to those of gymnosperms, i.e. it is a megasporangium (nucellus), dressed in integuments, one of whose megaspores germinates into a female gametophyte. These ovules go through several stages of development. At first they are very tiny, in the form of a bulge of meristem cells. These are nucellus cells. Further, in the middle of the nucellus, one cell stands out in size - this is an archesporial cell, which subsequently divides by meiosis and 4 megaspores arise.
Nucellus by this time will increase in size and outside will be dressed (overgrown) with covers - integuments.
Of the 4 megaspores, only one will germinate into the female gametophyte, while the other 3 will be crushed and disappear (obliterate).
In the ovary, the formation of ovules takes place, the stigma catches and retains pollen grains on its surface, the style conducts male gametes to the ovules that arise during the germination of pollen grains.
By the time the development of the ovule is completed, the ovary becomes large, green, and on the cross section you can see that it consists of two structures: the walls of the ovary and the ovules.
The walls of the ovary are part of the green carpel and anatomically have a leaf structure, i.e. outer and inner epidermis, and between them green pulp - mesophyll cells.
Publication date: 2015-02-17; Read: 319 | Page copyright infringement
At angiosperms the reproductive organ is the flower. Consider the processes occurring in stamens and pistils.
The formation of pollen grains occurs in the stamens. The stamen consists of a filament and an anther. Each anther is formed by two halves, in which two pollen chambers develop - microsporangia. The nests contain special diploid microsporocidal cells.
Each microsporocid undergoes meiosis and produces four microspores. Inside the pollen nest, the microspore increases in size.
7. Ovules in plant flowers develop in A. stigma of pistil B
Its nucleus divides mitotically and two nuclei are formed: vegetative and generative. A strong cellulose shell with pores is formed on the surface of the former microspore. Pollen tubes grow through the pores. As a result of these processes, each microspore turns into a pollen grain (pollen) - a male gametophyte. A mature pollen grain consists of two (vegetative and generative) or three (vegetative and two sperm) cells.
The formation of the female gametophyte (embryo sac) occurs in the ovule, which is located inside the ovaries of the pistil.
The ovule is a modified megasporangium protected by integuments. At the top of it there is a narrow channel - the pollen entrance. Near the pollen entrance, a diploid cell begins to develop - a megasporocyte (macrosporocyte). It divides by meiosis and produces four haploid megaspores. Three megaspores are soon destroyed, the fourth most distant from the pollen entrance develops into the embryo sac.
The embryo sac is growing. Its nucleus divides three times by meiosis. As a result, eight daughter nuclei are formed. They are located in four groups in two groups: one is near the pollen entrance, the other is at the opposite pole.
Then, one nucleus departs from each pole to the center of the embryo sac - these are polar nuclei. They can merge to form one central core. At the pollen entrance there is one egg and two cells of the synergid.
At the opposite pole, there are antipodal cells, which are involved in the delivery of nutrients to the cells of the embryo sac, and then disappear. Such an eight-core embryo sac is a mature female gametophyte.
Pestle. In the center of the flower is one or more pistils, usually pitcher-shaped or bottle-shaped.
In most pistils, one can distinguish the ovary - the main lower expanded part, which is strongly narrowed at the top into a column, forming a stigma at the top.
Ovary- a slightly enlarged, sometimes swollen part of the pistil, in which the ovules are located (seeds are formed from them after fertilization). If the ovary is attached to the receptacle only by its base, the rest of it is free, then it is called top(potato, tomato).
bottom(cucumber, pumpkin).
sedentary(poppy).
The megasporophyll grows together at its edges, forming a moist chamber that protects the modified megasporangium - the ovule.
Pollen is perceived by the glandular surface of the suture at the site of fusion of the edges of the megasporophyll. The evolution of the pistil is associated with the formation of specialized parts - the stigma, style and ovary, with the formation of the pistil from several megasporophylls, with the appearance of the lower ovary.
carpel.
Gynoecium
The ovules in the flowers of plants develop in
The gynoecium is called: apocarpous monocarp, cenocarpous - carpels 2 or more, they coalesce into one pistil (onion, potato, poppy).
With a cenocarpous gynoecium, the ovary cavity can be divided into nests according to the number of carpels (Fig. 5).
placenta.
The placenta is located at the site of fusion of the edges of the carpels. There are angular, central (columnar) and parietal placentation.
pedicel.
nucellus, integuments.
micropyle. chalazoy(Fig. 6).
Rice. 6 The structure of the ovule with the embryo sac:
direct, reverse And bent.
Megasporogenesis- formation of haploid megaspores by meiotic division. At the micropylar end, a megaspore mother cell (usually one) is laid. As a result of meiosis of this diploid cell, four haploid megaspores are formed. Three of them die off, one (usually the lower one, located farther from the micropyle) grows into a female gametophyte.
The female gametophyte is the embryo sac, formed by three successive mitotic divisions.
After the first division of the haploid nucleus of the megaspore, two nuclei are formed. They diverge towards the poles of the elongating megaspore, a large vacuole appears between them.
These polar nuclei combine to form a diploid nucleus called central, or secondary, nucleus of the embryo sac.
One of the three cells will ovum, the other two are synergists(auxiliary cells).
antipodes.
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Pestle. In the center of the flower is one or more pistils, usually pitcher-shaped or bottle-shaped. In most pistils, one can distinguish the ovary - the main lower expanded part, which is strongly narrowed at the top into a column, forming a stigma at the top.
Ovary- a slightly enlarged, sometimes swollen part of the pistil, in which the ovules are located (seeds are formed from them after fertilization).
If the ovary is attached to the receptacle only by its base, the rest of it is free, then it is called top(potato, tomato).
If the ovary is immersed in the receptacle with which it fuses, then such an ovary is called bottom(cucumber, pumpkin).
The column departs from the top of the ovary. It ensures that the stigma is carried upwards to a position favorable for trapping pollen. The stigma serves to perceive pollen, releases substances that contribute to its germination (sugars, lipids, enzymes). In the absence of a column, the stigma is directly adjacent to the ovary, in which case it is called sedentary(poppy).
The origin of the pistil is associated with the evolution of megasporophylls of ancient gymnosperms.
The megasporophyll grows together at its edges, forming a moist chamber that protects the modified megasporangium - the ovule. Pollen is perceived by the glandular surface of the suture at the site of fusion of the edges of the megasporophyll. The evolution of the pistil is associated with the formation of specialized parts - the stigma, style and ovary, with the formation of the pistil from several megasporophylls, with the appearance of the lower ovary.
The megasporophyll of angiosperms is called carpel.
Gynoecium- a set of carpels (megasporophylls) of a flower.
The gynoecium is called: apocarpous when there are 2-3 or more carpels in a flower, each of them forms an independent pistil (buttercup, wild rose); monocarp, when there is one carpel in the flower, forming one pistil (pea); cenocarpous - carpels 2 or more, they coalesce into one pistil (onion, potato, poppy). With a cenocarpous gynoecium, the ovary cavity can be divided into nests according to the number of carpels (Fig.
Rice. 5 Types of gynoeciums: a - apocarpous of three carpels; b, c, d - cenocarpous of three carpels: 1 - carpel; 2 - placenta; 3 - ovule
The place of attachment of the ovules to the wall of the ovary is called placenta. The placenta is located at the site of fusion of the edges of the carpels. There are angular, central (columnar) and parietal placentation.
Ovule, formation of megaspores and embryo sac. The ovules develop on the inner wall of the ovary, on the placenta.
The ovule is attached to the placenta pedicel.
The ovule consists of the multicellular nucleus of the ovule, or nucellus, and the two coverings surrounding it, or integuments.
Above the top of the nucellus, the integuments do not grow together, a microscopic channel is formed - the pollen entrance, or micropyle. The part of the ovule opposite the micropyle, from where the integuments depart, is called chalazoy(Rice.
The structure and development of the ovule of plants
6 The structure of the ovule with the embryo sac:
1, 2 – inner and outer integuments; 3-ovum; 4 - embryo sac; 5 - nucellus; 6 – chalaza; 7-antipodes; 8 - secondary nucleus; 9 - synergides; 10 – funiculus; 11 - placenta; 12 - conducting beam; 13 - pollen entry (micropyle)
Ovules are of three types: direct, reverse And bent.
In the direct ovule, the nucellus is a direct continuation of the seed stalk (the families Buckwheat, Nettle, Pepper), in the reverse, the nucellus is located at an angle to the seed stalk (most common), but the latter remains straight. In bent ovules, a bend is observed in both the nucellus and the pedicels (Leguminous, Marevy, Cabbage).
In the ovary there can be the most diverse number of ovules: in cereals - one, in grapes - several, in cucumber, poppy - many.
Nucellus is a true homologue of megasporangium; integuments arose later in the first seed plants.
In the nucellus, the ovule sequentially occurs: megasporogenesis, the development of the female gametophyte - the embryo sac, double fertilization, the development of the embryo and endosperm.
Megasporogenesis- formation of haploid megaspores by meiotic division. At the micropylar end, a megaspore mother cell (usually one) is laid.
As a result of meiosis of this diploid cell, four haploid megaspores are formed. Three of them die off, one (usually the lower one, located farther from the micropyle) grows into a female gametophyte.
The female gametophyte is the embryo sac, formed by three successive mitotic divisions. After the first division of the haploid nucleus of the megaspore, two nuclei are formed. They diverge towards the poles of the elongating megaspore, a large vacuole appears between them.
Then one nucleus from each quadruple moves to the center of the cell. These polar nuclei combine to form a diploid nucleus called central, or secondary, nucleus of the embryo sac.
The central nucleus is clothed with cytoplasm and becomes the central cell of the embryo sac (sometimes the fusion of the polar nuclei occurs later). Near the micropylar end of the embryo sac, an egg apparatus is formed from three cells that have arisen from three nuclei, around which the cytoplasm is concentrated.
One of the three cells will ovum, the other two are synergists(auxiliary cells).
Three cells develop at the chalazal end of the embryo sac antipodes.
The resulting embryo sac with seven naked cells is now ready for the fertilization process.
The embryo sac is the most strongly reduced female gametophyte.
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FERTILIZATION IN FLOWERING PLANTS
Fertilization- this is the process of fusion of male and female germ cells (gametes).
Female sex cell(gamete) is called egg. The ovules are produced in the ovules of the ovary. Pestle is the female reproductive organ.
Male sex cell(gamete) is called sperm. Sperm are produced in the anthers of the stamens.
Stamen is the male reproductive organ.
The anthers of the stamens contain pollen.
Pollen composed of pollen grains. pollen grain- this is one stick. Pollen grain contains 2 cells - vegetative and generative.
Vegetative is the cell that forms the pollen tube.
generative is the cell that produces two sperm.
sperm are the male sex cells.
In the process of pollination, the pollen grain falls on the stigma of the pistil, germinates and forms a pollen tube. pollen tube moves through the stigma, style into the ovary. In the ovary of the pistil are ovules (seed rudiments). They will develop into seeds. The structure of the ovule: ovule membranes, embryo sac, main ovum with a double set of chromosomes, central ovum with a single set of chromosomes.
help urgently) please 1. ovules in flowering plants develop in ... a) stigma
Chromosomes contain genes and are responsible for the storage and transmission of hereditary information.
The pollen tube carries 2 spermatozoa to the ovules and germinates into the ovule through the pollen entrance. Sperm have a single set of chromosomes.
First sperm fertilizes the main egg and the chromosome set becomes double.
As a result, a fertilized egg is formed, which is called - zygote. From the main egg and the first sperm, the embryo of a new plant is formed.
The structure of the embryo of a new plant: germinal root, germinal stalk, germinal leaves and buds.
Second sperm fertilizes the central egg and the chromosome set becomes triple.
As a result, endosperm is formed. Endosperm is a supply of nutrients that are necessary for the germination of the seed germ.
From the shells of the ovule seed coat is formed.
From the walls of the ovary the pistil is formed pericarp.
This fertilization of two eggs by two sperm is called double. It was discovered by Russian scientists Navashin S.G. In 1898.
Thus, a fruit is formed, which consists of a seed and a pericarp.
