What develops from the walls of the ovary. Angiosperms. Fertilization in flowering plants
Fertilization is the process of fusion of male and female reproductive cells (gametes).
Female reproductive cell(gamete) is called egg. The eggs are formed in the ovules of the ovary of the pistil. Pestle- This is the female reproductive organ.
Male reproductive cell(gamete) is called sperm. Sperm are produced in the anthers of the stamens. Stamen- This male organ reproduction.
The anthers of the stamens contain pollen.
Pollen consists of pollen grains. Pollen grain- this is one saw blade. A pollen grain contains 2 cells - vegetative and generative.
Vegetative is the cell that forms the pollen tube.
Generative- This is a cell that forms two sperm. Sperm- These are male reproductive cells.
During the process of pollination, the pollen grain lands on the stigma of the pistil, germinates and forms a pollen tube. Pollen tube moves through the stigma, style into the ovary. The ovary of the pistil contains the ovules (seed buds). From them the seed will develop. Structure of the ovule: ovule shell, embryo sac, main egg cell with a double set of chromosomes, central egg cell with a single set of chromosomes. Chromosomes contain genes and are responsible for storing and transmitting hereditary information.
The pollen tube carries 2 sperm to the ovules and grows 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. The embryo of a new plant is formed from the main egg and the first sperm. The structure of the embryo of a new plant: embryonic root, embryonic stalk, embryonic leaves and buds.
Second sperm fertilizes the central egg and the chromosome set becomes triple.
As a result, endosperm is formed. Endosperm- this is a reserve nutrients, which are necessary for the germination of the seed embryo.
From the shells of the ovule the seed coat is formed. From the walls of the ovary The pistil forms a pericarp.
This fertilization of two eggs by two sperm is called double. It was discovered by a Russian scientist Navashin S.G. In 1898. Thus, a fruit is formed, which consists of a seed and a pericarp.
The ovary is the empty lower thickened part of the pistil - the female reproductive organ of plants.
It provides protection and fertilization of the ovules (ovules) from which seeds are formed.
The pistil is located in the flower and consists of a stigma that traps pollen, a style that carries pollen inside, and an ovary where the seeds develop. After fertilization, a fetus is formed from it.
In the central part of the ovule (nucellus) there are eggs; in the case of pollination, they are fertilized and seeds develop from them. In the same place, an embryo sac is formed, from which they will feed.
Functions of the ovary
- Inside the ovary, the process of fertilization and seed maturation takes place;
- Protects ovules from external harmful factors environment (temperature changes, drought, eating by insects, rain, etc.);
- Supports required level moisture;
- Provides nutrition to seeds;
- It is the basis of the future fetus.
Types of ovary
According to the number of nests, that is, existing cavities separated by partitions in which the seeds are located, the ovary can be single- or multi-locular.
I - single-locular ovary, II - two-locular ovary, III - five-locular ovary. In all pictures: 1 - wall of the ovary; 2 - socket; a - ovules, 4 - seed carrier.
Another classification of ovaries is based on their location in relation to the receptacle.
The receptacle is the lower part of the flower, that is, its base, on which the petals, sepals, stamens and pistils are located.
According to the type of location, the ovary can be:
- Upper or free - located above the receptacle. It does not grow together with other parts of the flower; the flower is called subpistillate (cereals, ranunculaceae, legumes, etc.);
- The lower one is under the receptacle, the flower is attached to the top of the ovary, therefore it is called suprapistal (Asteraceae, cactaceae, orchids, etc.);
- Semi-inferior - grows together with the flower, but not at the very top; the flower is called semi-pistillate (saxifrage).
Formation of fruits from the ovary
Fruits, depending on the type of formation from the ovary, are divided into several types: 1. Real - formed only by the ovary. Divided into:
- Simple, formed by one pestle (cherry, plum, bird cherry, acacia beans);
- Complex, formed by several fused pistils (raspberries, blackberries)
- Fractional fruits are formed by a multilocular ovary with partitions (forget-me-not, basil, lavender, thyme, etc.);
2. False - formed with the participation of other parts of the flower such as the receptacle and perianth, including petals and sepals.
Please note
It is easy to distinguish false ones from real ones by the remains of parts of the flower (apples, pears).
Causes of damage to the ovary
Damage to the ovary can lead to a lack of further seeds and even fruits. The causes of damage may be:
- Late spring frosts during flowering, during which flowers and set fruits fall off. If the ovaries are partially damaged, then deformed, small, or unsuitable fruits develop from them;
- The absence or small number of pollinators, while some of the flowers remain unfertilized and are therefore discarded;
- Poor soil and lack of watering, when the plant does not have enough substances to grow all the ovaries that appear. In this case, it is necessary to add complex mineral and organic fertilizers and provide watering during drought;
- Pests (codling moth, apple sawfly, flower beetle, etc.). To get rid of them, you do not need to resort to artificial insect repellents, since they will also have a detrimental effect on pollinating insects. It is better to spray the plants with decoctions of herbs that repel pests (nettle, dandelion, garlic, wormwood, etc.)
- Leaf diseases. Healthy leaves are necessary to provide the plant with the necessary substances; without them, the ripening of fruits and seeds is impossible;
- Overload with the number of fruits: with a large number of ovaries formed, the plant cannot feed them all, so it discards some. Timely thinning of flowers will help to avoid this process.
The variety of flowering plants is amazingly 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 relationship between plants.
Flowering plants have a more advanced structure than other groups. Only angiosperms produce flowers, and flowers produce pistils. The ovaries of the pistils contain the ovules. Flowering plants of different angiosperms differ in size, shape, color, and structure; The flowers of some angiosperms are adapted to pollination by wind, while others are adapted to pollination by insects. But with any method of pollination, pollen grains fall on the stigmas of the 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 of flowering plants. In this case, an embryo is formed from the zygote resulting from the fusion of gametes. The largest cell, after merging with the second sperm, grows, divides, and an 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, the seeds of flowering plants develop inside the fruit. That's why flowering plants called angiosperms. Currently, angiosperms dominate among the plants inhabiting the Earth's land.
Consider plants that bloom in the fall, e.g. 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 can develop on the shoots. In their place, fruits with seeds ripen. Plants that bloom at least once in their life are called flowering plants.
The same organs of flowering plants can be very diverse in appearance.
A flower is a modified shoot, in the place of which a fruit with seeds or with one seed ripens.
Flower structure
Let's look at the structure of a flower. The flower develops on a peduncle that expands into the receptacle; All other parts of the flower are formed on it.
The brightly colored corolla consists of petals. Below the corolla there is a cup of green leaves - sepals. The corolla and calyx are the perianth that protects the internal parts of the flower from damage and can attract pollinating insects.
The main parts of a flower are the pistil and stamens. The stamen consists of a thin filament and an anther, which produces pollen. The pistil has a wide lower part - 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 flowers that are solitary. Most flowers are collected in inflorescences.
In summer and autumn, plants ripen in different shapes and colors. 
fruits Fruits are formed from ovaries. The enlarged and modified walls of the ovary, which has become a fruit, are called the pericarp. There are seeds inside the fruit. Based on the number of seeds, fruits are divided into single-seeded and multi-seeded.
There are juicy and dry fruits. Ripe, juicy fruits contain juicy pulp within the pericarp. Ripe dry fruits have no pulp.
Plant seeds are distinguished by shape and size. The seed consists of a peel (hull), an embryo and contains a supply of nutrients. The embryo is divided into a germinal root, a stalk, a bud with leaves.
Plants that have one cotyledon in the seed embryo are called monocots. 
In dicotyledonous plants, as the name suggests, the seed has two cotyledons. The supply of nutrients can be located in the cotyledons or in a special storage tissue - the endosperm. From the embryo of the seed, a new plant develops. A seed is the germ of a future plant.
Plants differ from each other in the color and shape of stems, leaves, flowers and fruits, life expectancy and other characteristics. But no matter how different flowering plants are, each of them can be classified into one of three groups: trees, shrubs and herbs.
Trees are usually large plants with perennial woody stems. Each tree has a trunk, branches, and tree branches form their crowns. Everyone is familiar with birch, aspen, linden, maple, and 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 trunks extending from a common base. Shrubs are widespread: hazel, lilac, honeysuckle, elderberry.
Herbs, or herbaceous plants, usually have green, succulent stems; they are almost always lower than trees and bushes. 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 several millimeters.
Trees and shrubs - perennials. For example, some oak trees live for more than a thousand years. Among the herbs there are both perennial, annual and biennial.
Among the perennial herbs, lily of the valley, dandelion, coltsfoot, and nettle are well known. The aboveground parts of most of these herbaceous plants die off in autumn. In the spring, they develop anew, since these plants retain roots and other underground organs with buds in the soil under the snow.
Annual plants, such as violets, quinoa, gillyflower, radishes, buckwheat, oats, wheat, develop from seeds in the spring, bloom, form fruits with seeds and then die.
Biennial plants live for almost two years. In beets, radishes, and cabbage, only roots, stems and leaves usually 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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Fertilization
Female reproductive cell(gamete) is called egg. Pestle
Male reproductive cell(gamete) is called sperm. Stamen
Pollen consists of pollen grains. Pollen grain
Vegetative
Generative Sperm
Pollen tube Structure of the ovule: Chromosomes
First sperm double.
zygote.
Second sperm triple.
Endosperm
From the shells of the ovule the 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.
Ovule formation.
A cavity appears in the middle of the primary tubercle, and on inner wall its ovules will form.
The ovules of angiosperms are similar in structure to those of gymnosperms, i.e. this is a megasporangium (nucellus), covered with integuments, one of the megaspores of which grows into the 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. Then, in the middle of the nucellus, one cell stands out in size - this is the appearance of an archesporial cell, which will subsequently divide by meiosis and 4 megaspores will arise.
By this time, the nucellus will increase in size and will be covered (overgrown) with integuments on the outside.
Of the 4 megaspores, only one will germinate into a female gametophyte, and the other 3 will be crushed and disappear (obliterate).
In the ovary, the formation of ovules occurs, the stigma catches and retains pollen grains on its surface, and the style conducts male gametes that arise during the germination of pollen grains to the ovules.
By the time the development of the ovule is complete, the ovary becomes large, green, and on a 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 the structure of a leaf, i.e. outer and inner epidermis, and between them green pulp - mesophyll cells.
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In angiosperms, the reproductive organ is the flower. Let's 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 in two halves, in which two pollen chambers, microsporangia, develop. The nests contain special diploid microsporocid cells.
Each microsporocid undergoes meiosis and forms four microspores. Inside the pollen nest, the microspore increases in size.
7. Ovules in plant flowers develop in A. stigma B
Its nucleus divides mitotically and two nuclei are formed: vegetative and generative. A durable cellulose shell with pores is formed on the surface of the former microspore. Pollen tubes subsequently 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 integument. At the top there is a narrow channel - a pollen passage. Near the pollen passage, 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, furthest from the pollen entrance, develops into an embryo sac.
The embryo sac grows. Its nucleus divides three times by meiosis. As a result, eight daughter nuclei are formed. They are located in two groups of four: one near the pollen entrance, the other at the opposite pole.
Then, one nucleus extends 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 cell and two synergid cells.
At the opposite pole are antipodal cells, which participate in the delivery of nutrients to the cells of the embryo sac and then disappear. This eight-nucleate embryo sac is the mature female gametophyte.
Pestle. In the center of the flower there is one or more pistils, usually pitcher- or bottle-shaped.
In most pistils, one can distinguish the ovary - the main lower expanded part, which at the top is strongly narrowed into a column that forms a stigma at the top.
Ovary- a slightly enlarged, sometimes swollen part of the pistil in which the ovules are located (from which seeds are formed after fertilization). If the ovary is attached to the receptacle only by its base, the rest of it being free, then it is called top(potatoes, tomato).
bottom(cucumber, pumpkin).
sedentary(poppy).
The megasporophyll fuses with its edges, forming a moist chamber that protects the modified megasporangium - the ovule.
Pollen is received 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 - stigma, style and ovary, with the formation of a pistil from several megasporophylls, and with the appearance of the lower ovary.
carpel.
Gynoecium
Ovules in plant flowers develop in
The gynoecium is called: apocarpous, monocarpous, coenocarpous – there are 2 or more carpels, they grow together into one pistil (onion, potato, poppy).
With a coenocarpous 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 wall placentations.
seed stalk.
Nucellus, integuments.
micropyle. chalaza(Fig. 6).
Rice. 6 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 mother cell of megaspores (usually one) is laid. Meiosis of this diploid cell produces four haploid megaspores. Three of them die, one (usually the lower one, located further from the micropyle) grows into the female gametophyte.
The female gametophyte, the embryo sac, is formed through three successive mitotic divisions.
After the first division of the haploid nucleus of the megaspore, two nuclei are formed. They diverge to the poles of the elongating megaspore, and 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 be egg, the other two are synergids(auxiliary cells).
antipodes.
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Pestle. In the center of the flower there is one or more pistils, usually pitcher- or bottle-shaped. In most pistils, one can distinguish the ovary - the main lower expanded part, which at the top is strongly narrowed into a column that forms a stigma at the top.
Ovary- a slightly enlarged, sometimes swollen part of the pistil in which the ovules are located (from which seeds are formed after fertilization).
If the ovary is attached to the receptacle only by its base, the rest of it being free, then it is called top(potatoes, tomato).
If the ovary is immersed in the receptacle with which it grows together, then such an ovary is called bottom(cucumber, pumpkin).
The style extends from the apex of the ovary. It ensures that the stigma is carried upward to a position favorable for pollen capture. The stigma serves to perceive pollen and secretes substances that promote its germination (sugars, lipids, enzymes). In the absence of a style, 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 fuses with its edges, forming a moist chamber that protects the modified megasporangium - the ovule. Pollen is received 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 - stigma, style and ovary, with the formation of a pistil from several megasporophylls, and with the appearance of the lower ovary.
The megasporophyll of angiosperms is called carpel.
Gynoecium– a collection of carpels (megasporophylls) of a flower.
The gynoecium is called: apocarpous, when a flower has 2-3 carpels or more, each of them forms an independent pistil (buttercup, rose hip); monocarpous, when a flower has one carpel, forming one pistil (pea); coenocarpous – there are 2 or more carpels, they grow together into one pistil (onion, potato, poppy). With a coenocarpous gynoecium, the ovary cavity can be divided into nests according to the number of carpels (Fig.
Rice. 5 Types of gynoecium: a – apocarpous of three carpels; b, c, d – coenocarpous of three carpels: 1 – carpel; 2 – placenta; 3 – ovule
The place where the ovules attach 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 wall placentations.
Ovule, formation of megaspores and embryo sac. Ovules develop on the inner wall of the ovary, on the placenta.
The ovule attaches to the placenta seed stalk.
The ovule consists of a multicellular ovule nucleus, or Nucellus, and the two covers surrounding it, or integuments.
Above the apex of the nucellus, the integuments do not grow together, a microscopic channel is formed - a pollen passage, or micropyle. The part of the ovule opposite the micropyle, from which the integuments arise, is called chalaza(Rice.
Structure and development of plant ovule
6 Structure of the ovule with the embryo sac:
1, 2 – internal and external integuments; 3–ovule; 4– embryo sac; 5 – nucellus; 6– chalaza; 7–antipodes; 8 – secondary core; 9– synergids; 10– funiculus; 11 – placenta; 12 – conductive bundle; 13– pollen passage (micropyle)
There are three types of ovules: direct, reverse And bent.
In the direct ovule, the nucellus is a direct continuation of the achene (of the Buckwheat, Nettle, and Pepper families), in the reverse ovule, the nucellus is located at an angle to the achene (most common), but the latter remains straight. In bent ovules, bending of both the nucellus and the peduncle is observed (legumes, chenopods, cabbages).
The ovary can have a very diverse number of ovules: cereals have one, grapes have several, cucumbers and poppies have many.
Nucellus is a true homolog of megasporangium; integuments arose later in the first seed plants.
In the nucellus of the ovule, the following occur sequentially: megasporogenesis, development of the female gametophyte - the embryo sac, double fertilization, development of the embryo and endosperm.
Megasporogenesis– formation of haploid megaspores by meiotic division. At the micropylar end, a mother cell of megaspores (usually one) is laid.
Meiosis of this diploid cell produces four haploid megaspores. Three of them die, one (usually the lower one, located further from the micropyle) grows into the female gametophyte.
The female gametophyte, the embryo sac, is formed through three successive mitotic divisions. After the first division of the haploid nucleus of the megaspore, two nuclei are formed. They diverge to the poles of the elongating megaspore, and 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 polar nuclei occurs later). Near the micropylar end of the embryo sac, an egg apparatus is formed from three cells arising from three nuclei, around which the cytoplasm is concentrated.
One of the three cells will be egg, the other two are synergids(auxiliary cells).
Three cells appear 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 highly reduced female gametophyte.
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FERTILIZATION IN FLOWERING PLANTS
Fertilization is the process of fusion of male and female reproductive cells (gametes).
Female reproductive cell(gamete) is called egg. The eggs are formed in the ovules of the ovary of the pistil. Pestle- This is the female reproductive organ.
Male reproductive cell(gamete) is called sperm. Sperm are produced in the anthers of the stamens.
Stamen- This is the male reproductive organ.
The anthers of the stamens contain pollen.
Pollen consists of pollen grains. Pollen grain- this is one saw blade. A pollen grain contains 2 cells - vegetative and generative.
Vegetative is the cell that forms the pollen tube.
Generative is a cell that produces two sperm.
Sperm- These are male reproductive cells.
During the process of pollination, the pollen grain lands on the stigma of the pistil, germinates and forms a pollen tube. Pollen tube moves through the stigma, style into the ovary. The ovary of the pistil contains the ovules (seed buds). From them the seed will develop. Structure of the ovule: ovule shell, embryo sac, main egg cell with a double set of chromosomes, central egg cell 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 storing and transmitting hereditary information.
The pollen tube carries 2 sperm to the ovules and grows 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. The embryo of a new plant is formed from the main egg and the first sperm.
The structure of the embryo of a new plant: embryonic root, embryonic stalk, embryonic leaves and buds.
Second sperm fertilizes the central egg and the chromosome set becomes triple.
As a result, endosperm is formed. Endosperm- this is a supply of nutrients that are necessary for the germination of the seed embryo.
From the shells of the ovule the seed coat is formed.
From the walls of the ovary The pistil forms a pericarp.
This fertilization of two eggs by two sperm is called double. It was discovered by a Russian scientist Navashin S.G. In 1898.
Thus, a fruit is formed, which consists of a seed and a pericarp.
Male reproductive cells - sperm - are formed in pollen grains, which develop in the anthers of flower stamens. Typically, pollen consists of many grains of dust (pollen grains) connected in groups. Sperm - male reproductive cells - are formed in dust particles.
Female reproductive cells - eggs - are formed in the ovules located in the ovary of the pistil of a flower (flowering plants have ovaries with one or more ovules). In order for seeds to develop from all ovules, sperm must be delivered 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 lands on the stigma of the pistil (either by wind or insects), it begins to germinate. One of its walls extends and forms a pollen tube. At the same time, two sperm are formed in a speck of dust. 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. It contains an egg at one end, and in the center there is a cell with two nuclei, which soon merge to form one - the central nucleus. Having penetrated the ovule, the pollen tube grows into the embryo sac, and there one sperm fuses (joins) with the egg, forming a zygote, from which the embryo of a new plant develops.
Another sperm that enters the embryo sac fuses with the central nucleus. The resulting cell divides very quickly, and soon nutritious tissue - endosperm - is formed from it.
The fusion of sperm in the embryo sac, one with the egg and the other with the central nucleus, is called double fertilization.
The process of double fertilization is a phenomenon characteristic only of flowering plants. Thanks to double fertilization, the embryo of a new plant receives very valuable endosperm with nutrients.
There is also this classification:
13. Structure and functions of a flower.
Flower - organ seed propagation angiosperms. A flower consists of a peduncle, receptacle, perianth, androecium and gynoecium.
Fertile parts of a flower (stamen, pistil).
Sterile parts of the flower (calyx, corolla, perianth).
Functions of a flower.
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 lower and many higher plants they are disunited. In a bisexual flower, micro- and megasporogenesis, micro- and megagametogenesis, pollination, fertilization, and the formation of seeds and fruits take place. The structural features of the flower allow the above functions to be carried out with minimal costs 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: the ovary - an expanded base; column - more or less elongated middle part; stigma - the upper part of the pistil. One or more ovules are located inside the ovary. Outside, the ovule is surrounded by integuments through which a narrow channel passes - the pollen passage.
The stamens are located around the pistil (or pistils). Their number in a flower varies among flowering plants: in wild radish - 6, in clover - 10, in cherry - many (about 30). The stamen consists of two anthers and a filament. Pollen develops inside the anther. Individual dust particles 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 perianth. In cherries, peas, and buttercups, the perianth consists of a corolla (a set of petals) and a calyx (a set of sepals). This type of perianth is called double. A tulip, lily, or lily of the valley has all the same leaves. Such a perianth is called simple.
Flowers with double perianth
Flowers with a simple perianth
The tepals may grow together or remain free. The tulip and lily have a simple, separate-leaved perianth, while the lily of the valley has a compound-leaved perianth. In flowers with a double perianth, both sepals and petals can also grow together. Primrose flowers, for example, have a fused calyx and a fused corolla. Cherry buttercup flowers have a separate-leaved calyx and a separate-petalled corolla. The bell has a septate calyx and a fused-petalled corolla.
The flowers of some plants do not have a developed perianth. For example, in willow flowers it resembles scales.
Willow inflorescences and flowers
Flower formula. The structural features of a flower can be noted briefly in the form of a formula. When compiling it, the following abbreviations are used:
Ok - tepals of a simple perianth,
H - sepals, L - petals, T - stamens, P - pistils.
The number of parts of a flower is indicated by numbers in the form of an index (H5 is 5 sepals), with large number flower parts use the sign ∞. If the parts grow together, the number indicating their number is placed in brackets (L(5) - the corolla consists of 5 fused petals). If the parts of the flower of the same name are arranged in several circles, then a + sign is placed between the numbers indicating their number in each circle (T5+5 - 10 stamens in a flower are arranged 5 in two circles). For example, the formula of the lily flower- Ok3+3T3+3P1, bell- Ch5L(5)T5P1.
Receptacle. All parts of the flower (near the flower bed, stamens, pistils) are located on the receptacle - the overgrown axial part of the flower. Most flowers have a pedicel. It extends from the stem and connects it to the flower. In some plants (wheat, clover, plantain) the pedicels are not pronounced. Such flowers are called sessile.
Flowers are bisexual and unisexual. Usually one flower contains both pistil(s) 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, and cucumber, unisexual flowers (staminate and pistillate) are located on the same plant. Such plants are called monoecious. In poplar, willow, sea buckthorn, and stinging nettle, some plants have only staminate flowers, while others have pistillate flowers. These are dioecious plants.
