Corolla biology. The structure of a plant flower

The corolla forms the inner circle of a double perianth and usually differs from the calyx in larger sizes and in a different, mostly bright color. It is usually the most conspicuous, conspicuous part of the flower, and in the hostel, when talking about flowers, they usually mean the corolla. The petals that form it can be free, not fused - separate-petal corolla - or grow together with each other over a greater or lesser extent - jointly - or cleavage whisk. In separate-petalled corollas in some plants (carnation, etc.), the lower part of the petals narrows and rather sharply separates from the upper, expanded one; the first is called a nail, the second is called a plate. In interpetal corollas, the fused part of the petals is distinguished - the tube, the non-fused part is the limb and the place where the tubule passes into the limb - the pharynx (Fig. 281). By the number of lobules, lobes or teeth of the corolla, one can often (but not always) judge the number of petals that formed it. Joint-petaled corollas developed from separate-petaled corollas during the evolution of plants.

1 - petal: n- nail, pl- plate; 2 - spliced ​​corolla: t- whisk tube from- bend, h- yawn.

In the pharynx of the corolla or at the point of transition of the nail into the plate, there are sometimes various outgrowths of petals in the form of scales, denticles, tubules, etc., which, when large, form their so-called corolla or crown. Such a corolla is especially well developed in some daffodils in the throat of their simple corolla-shaped perianth. Petals, or corolla lobes, can be split, notched, serrated, etc.

If several planes of symmetry can be drawn through the rim (Fig. 282, 2 ), it is called regular or actinomorphic (polysymmetric - see p. 228), such as cruciferous, clove, primrose. In the right corolla, all the petals are

of the same size and shape or, if they are different, alternate correctly. A rim through which only one plane of symmetry can be drawn (Fig. 282, 1 ), are called irregular or zygomorphic (monosymmetric, see p. 228), as, for example, in moths, labiates, toadflax, snapdragon, veronica, etc. Its petals are not the same in shape, size. In the vast majority of zygomorphic corollas, the plane of symmetry divides the corolla into right and left halves, in a few (corydalis, fumes) - into upper and lower (transversely zygomorphic). If not a single plane of symmetry can be drawn through the rim, it is also called irregular, asymmetric (Fig. 282, 3 ); such corollas are found in a few plants, for example, in the tropical family of Cannes (in them, however, the entire corolla perianth is asymmetric), in valerian. Zygomorphic and asymmetric corollas developed in most cases in the process of flower evolution later than actinomorphic ones and are more specialized, better adapted to body shapes and habits of insects visiting flowers and producing cross-pollination (Fig. 307 and 308)

1 - zygomorphic; 2 - actinomorphic; 3 - asymmetrical flower.

If on a plant with zygomorphic corollas an apical flower develops, ending with an axis, then its corolla is correct, actinomorphic, and in this case is called peloric. Such flowers are sometimes formed in toadflax, sage, foxglove, etc. It is suggested that their actinomorphism depends on the uniform action of gravity on them due to their apical, not lateral position.

It is customary to speak of regular and irregular, or zygomorphic, flowers, judging by the corolla. Very often the symmetry of the corolla coincides with the symmetry of the whole flower, but there are discrepancies, for example, in Solanaceae, where the corolla is actinomorphic, and the whole flower is zygomorphic, and these two concepts should be distinguished.

The color of the corolla most often depends on anthocyanins dissolved in cell sap(see page 72). Yellow colors are also due to soluble anthochlores (dahlias, poppies, etc.) or, as already indicated, chromoplasts. There is no white pigment in flowers, and their white color depends on the absence of any pigments and the reflection of all light rays. There is no black pigment either, and the so-called black colors of flowers are very condensed dark purple, dark red, etc.

The velvety of the petals depends on the small papillae located on the epidermal cells.

The role of the corolla in flowers is partly to protect the more essential parts of the flower, the androecium and gynoecium, but mainly to attract insects that promote cross-pollination. During

In the evolution of the flower, the corolla developed, as already indicated, in a few plants, probably from the apical leaves, and in the majority from stamens that have lost anthers.

The corolla (Fig. 1) consists of petals - modified leaves, painted in various colors, and sometimes reflecting all the rays of the spectrum and having White color. In the latter case, the petal parenchyma is especially rich in air-filled intercellular spaces. The different bright color of the corolla depends on: 1) anthocyanin pigment, which is sometimes red, sometimes blue, sometimes blue or purple, depending on the acidity of the lash juice (lungwort, bruise); 2) yellow pigments of cell sap, giving a yellow color (toadflax); 3) chromoplasts having a red, orange or yellow color (nasturtium).

Fig.1. Whisk shapes:
1 - four-petal cruciferous plant; 2 - funnel bindweed; 3 - tubular sunflower; 4 - reed dandelion; 5 - two-lipped clasps; 6 - wheel-shaped potato: 7 - bell-shaped bell; 8 - with catchment spurs; 9-10 - the correct five-petal buttercup; 11 - wrong five-petal pansies; 12 - moth pea; 13 - components of the moth corolla: p - sail, c-c - oars, l - boat. Proper beaters- 1, 2, 3, 6, 7, 8, 9, 10. Incorrect - 4, 5, 11, 12, 13.

Corolla happens cleavage(pumpkin, tomato, bindweed) when the petals grow together, and free-petal(buttercup, poppy, cabbage) when the petals are freely separated from each other. Each petal of the corolla consists of a claw (narrow part of the petal) and a limb (wider part), developed to a greater or lesser extent. Such a structure is clearly visible on the flower of a clove or cruciferous plant (Fig. 1, - 1).

At the base of the corolla on the nail or on the receptacle, a nectary is often placed, sometimes covered with scales (buttercup, radish), which secretes sweet juice to attract insects. The aroma of flowers depends on the essential volatile oils produced by the petals. Thus, the main role of the corolla - attracting pollinators - is performed by bright color, aroma and the presence of nectar.

The forms of corollas and flowers are extremely diverse (Fig. 1). There are regular corollas and pollen (actinomorphic), through which you can mentally draw more than one plane of symmetry (flowers of cabbage, beets, onions, etc.), and irregular corollas and flowers (zygomorphic), through which you can draw only one plane of symmetry (flowers peas, sage, etc.). If not a single plane of symmetry can be drawn through the corolla and the flower, the flower is called asymmetric (cannes).

Diverse in nature different forms perianths, sometimes bizarre, developed in accordance with the diverse insects that produce pollination, and in tropical plants and in accordance with the forms of birds (hummingbirds).

Sometimes the perianth is either completely absent, or is in its infancy; in such cases, its role is played by scales, hairs, bristles, etc. (cereals, sedges, willows).

All corollas are also divided into correct, or actinomorphic (corolla actinomorpha) and wrong, or zygomorphic (corolla zygomorpha). Actinomorph corolla is also called multisymmetric, since several planes of symmetry can be drawn through it. Zygomorphic corolla unisymmetric, since only one axis of symmetry passes through it.

The shape of the rim is very diverse, among others, the following forms of rims are distinguished:

• tubular whisk, formed during the fusion of petals almost along its entire length (annual sunflower);
• bell-shaped corolla, for the most part fused into a tube, and then divided into several petals (Rapunzel bell);
• funnel-shaped corolla, similar to bell-shaped, at the base the petals are fused into a tube, and then diverging in different directions (common tobacco);
• wheel whisk, the petals of which have a small part fused into a tube, pharynx, and a noticeable free part, bent almost in the same plane, called limb(Veronica oak);
• reed corolla, close to tubular, however, it has a limb of fused petals, extending to the side in the form of a tongue (common chicory);

• two-lipped corolla, with a limb consisting of two unequal parts - lips(Larberry zelenchukova);
• moth whisk, an interpetal zygomorphic corolla, 5 petals of which have their own names and differ in size and shape (horned loon);
• spurred corolla, one or more petals of which have a cavity of various lengths, called a spur (one and a half foot angrekum);
• cruciform corolla, actinomorphic separate-petal corolla, four petals of which are bent in one plane, forming a “cross” (field yarutka);
• cap whisk, calyptra, the petals of which grow together at the ends, and are free at the base (Amur grapes).

Functions

The main function of the corolla is to protect the generative organs of the flower during flowering. In most plant species, the corolla is the most visible part of the flower and also serves to attract pollinating insects necessary for cross-pollination.

Corolla in flower formula

In the flower formula, the characteristic of the corolla is placed after indicating the structure of the calyx and is indicated by the letters Co or C, next to which the number of petals is indicated, for example: Co 5 - a corolla of 5 free petals. The number of petals in the corolla corolla is taken in brackets, for example: Co (5) .

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Literature

• Beketov A.N. Corolla, in botany // Encyclopedic Dictionary of Brockhaus and Efron: in 86 volumes (82 volumes and 4 additional). - St. Petersburg. , 1890-1907.
• Biology. Modern Illustrated Encyclopedia. Ch. ed. A. P. Gorkin; Moscow: Rosmen, 2006.

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An excerpt characterizing the Corolla

I was very ashamed to feel like a complete bum, but the desire to know more was a hundred times stronger than any shame, so I hid my pride as deep as possible and carefully asked:
– And what about all these amazing “realities” that we are now seeing here? 'Cause it's someone else's concrete life and you don't create them the same way you create all your worlds?
- Oh no! - again, the baby was delighted with the opportunity to explain something to me. - Of course not! It's just the past in which all these people once lived, and I'm just taking you and me there.
- And Harold? How does he see all this?
Oh, it's easy for him! He's just like me, dead, so he can move wherever he wants. After all, he no longer has a physical body, so his essence knows no obstacles here and can walk wherever she wants ... just like me ... - the little girl finished sadly.
I sadly thought that what was for her was just “ simple transfer into the past”, for me, apparently, for a long time it will be “a mystery behind seven locks” ... But Stella, as if having heard my thoughts, immediately hurried to reassure me:
- You'll see, it's very simple! You just have to try.
- And these "keys", don't they ever repeat with others? I decided to continue my questions.
- No, but sometimes something else happens ... - for some reason, smiling funny, the baby answered. - At the beginning, that’s exactly how I got caught, for which I was very much “beaten” ... Oh, it was so stupid! ..
- But as? I asked very interested.
Stella replied cheerfully:
- Oh, that was very funny! - and after a little thought, she added, - but it’s also dangerous ... I searched all the “floors” for the past incarnation of my grandmother, and instead of her, along her “thread”, a completely different entity came, which somehow managed to “copy” my grandmother’s “ flower” (apparently also a “key”!) and, as soon as I managed to be glad that I had finally found it, this unfamiliar entity mercilessly hit me in the chest. Yes, so much so that my soul almost flew away! ..
"But how did you get rid of her?" I was surprised.
- Well, to be honest, I didn’t get rid of it ... - the girl was embarrassed. - I just called my grandmother ...
What do you call "floors"? I still couldn't calm down.
– Well, these are different “worlds” where the spirits of the dead live... In the most beautiful and highest, those who were good live... and, probably, the strongest too.
- People like you? I asked smiling.
– Oh, no, of course! I must have gotten here by mistake. - The girl said sincerely. – Do you know what is the most interesting? From this "floor" we can walk everywhere, but from the others no one can get here ... Is it really interesting? ..
Yes, it was very strange and very exciting for my “hungry” brain, and I really wanted to know more! gave me something (like, for example, my “star friends”), and therefore, even such a simple childish explanation already made me unusually happy and made me delve even more furiously into my experiments, conclusions and mistakes ... as usual, finding in everything that happens even more incomprehensible. My problem was that I could do or create “unusual” very easily, but the whole trouble was that I also wanted to understand how I create it all ... Namely, this is what I have not been very successful with yet ...
What about the rest of the floors? Do you know how many there are? They are completely different, unlike this one? .. - unable to stop, I impatiently bombarded Stella with questions.

A flower is a conspicuous, often beautiful, important part of flowering plants. Flowers can be large and small, brightly colored and green, odorous and odorless, single or collected together from many small flowers into one common inflorescence.

A flower is a modified shortened shoot that serves for seed reproduction. The flower usually ends on the main or side shoot. Like any shoot, a flower develops from a bud.

flower structure

The flower is a reproductive organ angiosperms, consisting of a shortened stem (flower axis), on which the flower cover (perianth), stamens and pistils, consisting of one or more carpels, are located.

The axis of the flower is called receptacle. The receptacle, growing, takes different shape flat, concave, convex, hemispherical, cone-shaped, elongated, columnar. The receptacle at the bottom passes into the pedicel, connecting the flower with the stem or peduncle.

Flowers that do not have a pedicel are called sessile. On the pedicel of many plants there are two or one small leaves - bracts.

flower cover - perianth- can be divided into a cup and a corolla.

Cup forms the outer circle of the perianth, its leaves are usually relatively small sizes, Green colour. Distinguish between separate and joint-leaved calyx. Usually it performs the function of protecting the inner parts of the flower until the bud opens. In some cases, the calyx falls off when the flower blooms, most often it remains during flowering.

The parts of the flower located around the stamens and pistil are called the perianth.

The inner leaves are the petals that make up the corolla. The outer leaves - sepals - form a calyx. The perianth, consisting of a calyx and a corolla, is called double. Perianth, which is not subdivided into corolla and calyx, and all the leaves of the flower are more or less the same - simple.

Corolla- the inner part of the perianth, differs from the calyx in bright color and larger size. The color of the petals is due to the presence of chromoplasts. Distinguish separately - and joint-petal corollas. The first consists of individual petals. In interpetal corollas, a tube and a limb perpendicular to it are distinguished, having a certain number of teeth or vanes of the corolla.

Flowers are symmetrical and asymmetrical. There are flowers that do not have a perianth, they are called naked.

Symmetrical (actinomorphic)- if many axes of symmetry can be drawn through the whisk.

Asymmetrical (zygomorphic)- if only one axis of symmetry can be drawn.

Double flowers have an abnormally increased number of petals. In most cases, they result from the splitting of the petals.

Stamen- part of a flower, which is a kind of specialized structure, which forms microspores and pollen. It consists of a filament, through which it is attached to the receptacle, and an anther containing pollen. The number of stamens in a flower is a systematic feature. Stamens are distinguished by the method of attachment to the receptacle, by the shape, size, structure of the stamen filaments, connective and anther. The collection of stamens in a flower is called the androecium.

filament- the sterile part of the stamen, bearing an anther on its top. The filament can be straight, curved, twisted, winding, broken. In shape - hairy, cone-shaped, cylindrical, flattened, club-shaped. By the nature of the surface - naked, pubescent, hairy, with glands. In some plants, it is short or does not develop at all.

Anther located at the top of the staminate filament and attached to it by a ligament. It consists of two halves connected by a link. Each half of the anther has two cavities (pollen sacs, chambers, or nests) in which pollen develops.

As a rule, the anther is four-celled, but sometimes the partition between the nests in each half is destroyed, and the anther becomes two-celled. In some plants, the anther is even single-celled. It is very rare to see trinity. According to the type of attachment to the filament, the anthers are fixed, mobile and swinging.

Anthers contain pollen or pollen grains.

The structure of the pollen grain

The dust grains formed in the anthers of the stamens are small grains, they are called pollen grains. The largest ones reach 0.5 mm in diameter, but usually they are much smaller. Under the microscope, you can see that the dust particles different plants are not at all the same. They differ in size and shape.

The surface of the dust grain is covered with various protrusions, tubercles. Getting on the stigma of the pistil, pollen grains are held with the help of outgrowths and a sticky liquid released on the stigma.

The nests of the young anther contain special diploid cells. As a result of meiotic division, four haploid spores are formed from each cell, which are called microspores for their very small size. Here, in the cavity of the pollen sac, microspores turn into pollen grains.

This happens as follows: the microspore nucleus is divided mitotically into two nuclei - vegetative and generative. Around the nuclei, areas of the cytoplasm are concentrated and two cells are formed - vegetative and generative. On the surface of the cytoplasmic membrane of the microspore, a very strong shell is formed from the contents of the pollen sac, insoluble in acids and alkalis. Thus, each pollen grain consists of vegetative and generative cells and is covered with two shells. Many pollen grains make up the pollen of a plant. Pollen matures in the anthers by the time the flower opens.

pollen germination

The beginning of pollen germination is associated with mitotic division, as a result of which a small reproductive cell is formed (sperms develop from it) and a large vegetative cell (a pollen tube develops from it).

After the pollen in one way or another gets on the stigma, its germination begins. The sticky and uneven surface of the stigma helps to retain pollen. In addition, the stigma releases a special substance (enzyme) that acts on the pollen, stimulating its germination.

The pollen swells, and the restraining influence of the exine ( outer layer shell of the pollen grain) causes the contents of the pollen cell to break one of the pores, through which the intina (the inner, poreless shell of the pollen grain) protrudes outward in the form of a narrow pollen tube. The contents of the pollen cell pass into the pollen tube.

Under the epidermis of the stigma is loose tissue into which the pollen tube penetrates. It continues to grow, passing either through a special conductive channel between the mucilaginous cells, or tortuously along the intercellular spaces of the conductive tissue of the column. At the same time, a significant number of pollen tubes usually advance simultaneously in the column, and the “success” of one or another tube depends on the individual growth rate.

Two sperm and one vegetative nucleus pass into the pollen tube. If the formation of spermatozoa in the pollen has not yet occurred, then the generative cell passes into the pollen tube, and here, by its division, sperm cells are formed. The vegetative nucleus is often located in front, at the growing end of the tube, and sperm cells are successively located behind it. In the pollen tube, the cytoplasm is in constant motion.

Pollen is rich in nutrients. These substances, especially carbohydrates (sugar, starch, pentosans) are intensively consumed during pollen germination. In addition to carbohydrates chemical composition pollen includes proteins, fats, ash and an extensive group of enzymes. Pollen contains a high content of phosphorus. Substances are in the pollen in a mobile state. Pollen easily transfers low temperatures up to - 20Сº and even lower, for a long time. High temperatures quickly reduce germination.

Pestle

The pistil is the part of the flower that forms the fruit. It arises from the carpel (a leaf-like structure that carries the ovules) after the fusion of the edges of the latter. It can be simple if it is composed of one carpel, and complex if it is composed of several simple pistils fused together by the side walls. In some plants, the pistils are underdeveloped and are represented only by rudiments. The pistil is divided into ovary, style and stigma.

Ovary- the lower part of the pistil, in which the seed germs are located.

Having entered the ovary, the pollen tube grows further and enters the ovule in most cases through the pollen inlet (micropyle). Infiltrating into embryo sac, the end of the pollen tube bursts, and the contents pour out onto one of the synergids, which darkens and quickly collapses. The vegetative nucleus is usually destroyed before the pollen tube penetrates the embryo sac.

Flowers right and wrong

The tepals (simple and double) can be arranged so that several planes of symmetry can be drawn through it. Such flowers are called correct. Flowers through which one plane of symmetry can be drawn are called irregular.

Flowers bisexual and dioecious

Most plants have flowers that have both stamens and pistils. These are bisexual flowers. But in some plants, some flowers have only pistils - pistillate flowers, while others have only stamens - staminate flowers. Such flowers are called dioecious.

Plants monoecious and dioecious

Plants that develop both pistillate and staminate flowers are called monoecious. Dioecious plants - staminate flowers on one plant, and pistillate - on another.

There are species in which bisexual and unisexual flowers can be found on the same plant. These are the so-called polygamous (polygamous) plants.

inflorescences

Flowers are formed on shoots. Very rarely they are located alone. More often, flowers are collected in conspicuous groups called inflorescences. The beginning of the study of inflorescences was laid by Linnaeus. But for him, the inflorescence was not a type of branching, but a way of flowering.

In inflorescences, the main and lateral axes are distinguished (sessile or on pedicels), then such inflorescences are called simple. If the flowers are on the lateral axes, then these are complex inflorescences.

Inflorescence type	Inflorescence scheme	Peculiarities	Example
Simple inflorescences
Brush		Separate lateral flowers sit on an elongated main axis and at the same time have their own pedicels, approximately equal in length	Bird cherry, lily of the valley, cabbage
Ear		The main axis is more or less elongated, but the flowers are without stalks, i.e. sedentary.	Plantain, orchid
cob		It differs from the ear in a fleshy thickened axis.	Corn, calla
Basket		The flowers are always sessile and sit on a strongly thickened and widened end of a shortened axis, which has a concave, flat or convex appearance. In this case, the inflorescence outside has a so-called wrapper, consisting of one or many consecutive rows of bracts, free or fused.	Chamomile, dandelion, aster, sunflower, cornflower
Head		The main axis is greatly shortened, the lateral flowers are sessile or almost sessile, closely spaced to each other.	Clover, scabiosa
Umbrella		The main axle is shortened; lateral flowers come out, as it were, from one place, sit on legs of different lengths, located in the same plane or dome-shaped.	Primula, onion, cherry
Shield		It differs from the brush in that the lower flowers have long stalks, so that as a result the flowers are located almost in the same plane.	Pear, spirea
Complex inflorescences
Complex brush or panicle		Lateral branching axes depart from the main axis, on which flowers or simple inflorescences are located.	Lilac, oats
complex umbrella		Simple inflorescences depart from the shortened main axis.	Carrot, parsley
Complex spike		Individual spikelets are located on the main axis.	Rye, wheat, barley, wheatgrass

The biological significance of inflorescences

The biological significance of inflorescences is that small, often inconspicuous flowers, collected together, become noticeable, give the largest number pollen and better attract insects that carry pollen from flower to flower.

Pollination

In order for fertilization to occur, the pollen needs to land on the stigma of the pistil.

The process of transferring pollen from the stamens to the stigma is called pollination. There are two main types of pollination: self-pollination and cross pollination.

self pollination

During self-pollination, pollen from a stamen falls on the stigma of the pistil of the same flower. This is how wheat, rice, oats, barley, peas, beans, and cotton are pollinated. Self-pollination in plants most often occurs in a flower that has not yet opened, that is, in a bud, when the flower opens, it is already completed.

During self-pollination, germ cells formed on the same plant merge and, therefore, have the same hereditary characteristics. This is why the offspring resulting from the process of self-pollination are very similar to the parent plant.

cross pollination

With cross-pollination, the recombination of the hereditary traits of the paternal and maternal organisms occurs, and the resulting offspring can acquire new properties that the parents did not have. Such offspring are more viable. In nature, cross-pollination is much more common than self-pollination.

Cross-pollination is carried out with the help of various external factors.

Anemophilia(wind pollination). In anemophilous plants, the flowers are small, often collected in inflorescences, a lot of pollen is formed, it is dry, small, and when the anther opens, it is thrown out with force. The light pollen of these plants can be carried by the wind over distances of up to several hundred kilometers.

The anthers are located on long thin filaments. The stigmas of the pistil are wide or long, pinnate and protrude from the flowers. Anemophilia is characteristic of almost all grasses, sedges.

Entomophily(carrying pollen by insects). The adaptation of plants to entomophily is the smell, color and size of flowers, sticky pollen with outgrowths. Most flowers are bisexual, but maturation of pollen and pistils does not occur simultaneously, or the height of the stigmas is greater or less than the height of the anthers, which serves as protection against self-pollination.

In the flowers of insect pollinated plants there are areas that secrete a sweet fragrant solution. These areas are called nectaries. Nectaries may be in different places flower and have different shapes. Insects, having flown up to the flower, are drawn to nectaries and anthers, and during the meal they get dirty with pollen. When an insect moves to another flower, the pollen grains carried by it stick to the stigmas.

When pollinated by insects, less pollen is wasted, and therefore the plant saves substances by producing less pollen. Pollen grains do not need to stay in the air for long and can therefore be heavy.

Insects can pollinate sparsely located flowers and flowers in calm places - in the forest thicket or thick grass.

Typically, each plant species is pollinated by several species of insects, and each pollinating insect species serves several plant species. But there are some types of plants whose flowers are pollinated by insects of only one species. In such cases, the mutual correspondence between the modes of life and the structure of flowers and insects is so complete that it seems miraculous.

Ornithophilia(pollination by birds). It is typical for some tropical plants with brightly colored flowers, abundant secretions of nectar, and a strong elastic structure.

hydrophilia(pollination with water). Observed in aquatic plants. The pollen and stigma of these plants most often have a filamentous shape.

bestiality(pollination by animals). These plants are characterized by large flower sizes, abundant secretion of nectar containing mucus, mass production of pollen during pollination. bats- flowering at night.

Fertilization

The pollen grain falls on the stigma of the pistil and is attached to it due to the structural features of the shell, as well as the sticky sugary secretions of the stigma, to which the pollen adheres. The pollen grain swells and germinates into a long, very thin pollen tube. The pollen tube is formed as a result of division of a vegetative cell. First, this tube grows between the cells of the stigma, then the style, and finally grows into the cavity of the ovary.

The generative cell of the pollen grain moves into the pollen tube, divides and forms two male gametes (sperms). When the pollen tube enters the embryo sac through the pollen passage, one of the sperm fuses with the egg. Fertilization occurs and a zygote is formed.

The second sperm fuses with the nucleus of the large central cell of the embryo sac. Thus, in flowering plants, two fusions occur during fertilization: the first sperm fuses with the egg, the second with the large central cell. This process was discovered in 1898 by the Russian botanist, academician S.G. Navashin and called it double fertilization. Double fertilization is typical only for flowering plants.

The zygote formed by the fusion of gametes divides into two cells. Each of the resulting cells divides again, and so on. As a result of multiple cell divisions, a multicellular embryo of a new plant develops.

The central cell also divides, forming endosperm cells, in which reserves accumulate nutrients. They are necessary for the nutrition and development of the embryo. The seed coat develops from the integument of the ovule. After fertilization, a seed develops from the ovule, consisting of a peel, an embryo, and a supply of nutrients.

After fertilization, nutrients flow to the ovary, and it gradually turns into a ripe fruit. The pericarp, which protects the seeds from adverse effects, develops from the walls of the ovary. In some plants, other parts of the flower also take part in the formation of the fruit.

Spore formation

Simultaneously with the formation of pollen in the stamens, the formation of a large diploid cell occurs in the ovule. This cell divides meiotically and gives rise to four haploid spores, which are called macrospores because they are larger in size than microspores.

Of the four formed macrospores, three die off, and the fourth begins to grow and gradually turns into an embryo sac.

Embryo sac formation

As a result of threefold mitotic division of the nucleus in the cavity of the embryo sac, eight nuclei are formed, which are clothed with cytoplasm. Cells without membranes are formed, which are arranged in a certain order. At one pole of the embryo sac, an egg apparatus is formed, consisting of an egg and two auxiliary cells. At the opposite pole there are three cells (antipodes). One nucleus migrates from each pole to the center of the embryo sac (polar nuclei). Sometimes the polar nuclei fuse and form the diploid central nucleus of the embryo sac. The embryo sac in which nuclear differentiation has occurred is considered mature and can accept sperm.

By the time the pollen and the embryo sac have matured, the flower opens.

The structure of the ovule

The ovules develop on inner sides walls of the ovary and, like all parts of the plant, are made up of cells. The number of ovules in the ovaries of different plants is different. In wheat, barley, rye, cherries, the ovary contains only one ovule, in cotton - several dozen, and in poppy their number reaches several thousand.

Each ovule is covered with a covering. At the top of the ovule there is a narrow channel - the pollen entrance. It leads to the tissue that occupies the central part of the ovule. In this tissue, as a result of cell division, an embryo sac is formed. Opposite the pollen entrance, there is an egg in it, and the central part is occupied by a large central cell.

Development of angiosperms (flowering) plants

Formation of seed and fruit

During the formation of a seed and a fetus, one of the sperm fuses with the egg, forming a diploid zygote. Subsequently, the zygote divides many times, and as a result, a multicellular embryo of the plant develops. The central cell, which has merged with the second sperm, also divides many times, but the second embryo does not appear. A special tissue is formed - the endosperm. The endosperm cells accumulate reserves of nutrients necessary for the development of the embryo. The integuments of the ovule grow and turn into a seed coat.

Thus, as a result of double fertilization, a seed is formed, which consists of an embryo, a storage tissue (endosperm) and a seed coat. From the wall of the ovary, the wall of the fruit, called the pericarp, is formed.

sexual reproduction

Sexual reproduction of angiosperms is associated with a flower. Its most important parts are stamens and pistils. They undergo complex processes associated with sexual reproduction.

In flowering plants, the male gametes (sperm) are very small, while the female gametes (ovules) are much larger.

In the anthers of the stamen, cell division occurs, resulting in the formation of pollen grains. Each pollen grain of angiosperms consists of vegetative and generative cells. The pollen grain is covered with two shells. The outer shell, as a rule, is uneven, with spines, warts, outgrowths in the form of a mesh. This helps the pollen grains to stick to the stigma of the pistil. The pollen of the plant, ripening in the anthers, by the time the flower opens, consists of many pollen grains.

flower formula

Formulas are used to conditionally express the structure of flowers. To draw up a flower formula, the following notation is used:

	A simple perianth, consisting of sepals or petals alone, its parts are called tepals.
H	Calyx composed of sepals
L	Corolla, composed of petals
T	Stamen
P	Pestle
1,2,3...	The number of flower elements is indicated by numbers
,	The same parts of a flower, differing in shape
()	fused parts of a flower
+	Arrangement of elements in two circles
_	Upper or lower ovary - a dash above or below the number that shows the number of pistils
	wrong flower
*	right flower
♂	Unisexual staminate flower
♀	unisexual pistillate flower
	Bisexual
∞	Number of flower parts greater than 12

Cherry blossom formula example:

*H 5 L 5 T ∞ P 1

flower diagram

The structure of a flower can be expressed not only by a formula, but also by a diagram - a schematic representation of a flower on a plane perpendicular to the axis of the flower.

Draw up a cross-sectional diagram of unopened flower buds. The diagram gives a more complete picture of the structure of a flower than a formula, since it also shows mutual arrangement its parts, which cannot be shown in the formula.

Hello, friends!
Today I continue the conversation about the whisk. I have prepared mine for you. original review this question.

With all the variety of types of corollas, they can be divided into two groups according to the principle of fusion of petals. Corollas with loose petals(colza, wild rose, mallow) and corollas with petals fused to varying degrees - sympetalous.

Evolutionary corollas appear later, on the basis of corollas with free petals. They have many interesting forms, which we will consider below.

Asymmetric corollas

Among the interpetal corollas, we can also see different symmetry and distinguish groups of regular (actinomorphic) and irregular (zygomorphic) flowers. How easy and fun it is to learn to distinguish between them in the game with a mirror, read HERE.

It is noteworthy that the petals can grow together not only at the base, but also at the tops, forming a cap (calyptra). For example, in the flowers of grapes, eucalyptus. When the bud opens, the cap falls off.Although more often the fusion occurs at the level of the nails of the petals, at the base.

The structure of the corolla

A typical spice-petaled corolla resembles a gramophone trumpet.
Petals fused at the base to form a tube (see diagram below). The tube can be wide, like bluebells, or narrow, like lilac flowers; short, like periwinkle flowers, or long, like fragrant tobacco flowers.

The wide part of the corolla corolla - limb. The limb can be pronounced, like in phlox flowers, or not pronounced, like in the middle tubular sunflower flowers.

In the limb, the petals can grow together as a whole, like bindweed flowers, or be free, like periwinkle flowers. The limb can be shifted to the side, as in the reed marginal white chamomile flowers, which are often mistakenly called petals.

periwinkle flowers

The place of transition of the bend into the tube we call the pharynx. The pharynx can be wide, like a lamb, sage, or narrow, like a lilac flower.

The combination of features of the tube, throat and limb, allows us to distinguish several types among the corollas.

For example, flowers with a long narrow tube, a narrow throat and a wide wheel-shaped limb have NAIL-SHAPED corolla corollas. In this description, you can recognize the lilac flower.

Finding frame for the classification of streaked corollas

A little about the history of the idea. Among foreign blogs, the idea of ​​using find frames is popular. For example, for clouds. You could see similar frames in Tatyana Pirozhenko's blog "It's interesting".

You can use this frame finder for anything. Pretty handy for playing. I decided to apply this principle finder frames for convenience in the classification of biological objects, in particular, corollas. The idea was slightly adapted to the needs of a young naturalist in the style of fairy fairies.

Fairies give such a frame for young explorers. To download a picture, click on it - the image will open in full size. Print the frame on thick paper, make an empty window inside and laminate for durability.

You can take the frame with you for a walk and classify whisks in real time. We can turn the frame into a field notebook. On the laminated surface, you can write with a marker, marking the finds, and then erase the inscriptions. You can stick stickers on the frame on the back side, and make notes and sketches on them with a simple pencil. The stickers are then easily transferred to the naturalist's stationary diary.

Tasks for the research diary

Fairies give their tasks to young researchers.

1 . Go botanically hunting in a garden or park with a finder frame. Mark the found types of whisks with checkboxes. Determine which corollas turned out to be more?

2. Make a photo compilation of your finds. If conditions allow, you can make a thematic herbarium.

3. In the process of research, there may be flowers of a different shape, not indicated in the schemes of the frame. The frame shows the most popular types of whisk, but there are others in nature. Photograph and draw such whisks. Measure their size. Describe the features of the structure of their tube, pharynx and limb. Long or short, wide or narrow, complete or partial fusion. Find the types of framed corollas that the flower looks like.

Eucalyptus corolla biomodeling

Fairies offer to do biomodelling. I have had a thread-grass idle for a long time. I finally figured out where to use it! And also, I propose to combine biomodeling with phytotherapy, since we will be doing eucalyptus flowers.

Eucalyptus has an unusual corolla. The beauty of its flowers is not due to the petals, but thanks to the stamens. Stamens, by the way, can be of different colors - yellow, white, red, pink. And the petals grow together with their tops, forming a heroic helmet-cap. We already know that this type of fused corolla is called calyptra.

1. Studying the smell of eucalyptus

I propose to introduce the child to the smell of eucalyptus. If the child does not have allergies, eucalyptus essential oil can be used. It's good to ignite aroma lamp with eucalyptus oil for atmosphere. For a sick child, this procedure will be curative, and for a healthy child - preventive. If eucalyptus oils could not be found, then there are Pinosol nasal drops, which include eucalyptus and mint oils.

2. We study the leaves of eucalyptus

In addition, eucalyptus leaves can be bought at the pharmacy. If there is no aromatic oil, you can smell the dried eucalyptus leaf. The smell is quite pronounced. You may be lucky to find whole eucalyptus leaves in the box. Or put together a puzzle. Pay attention to their shape. You can circle them in a research diary, or stick them.

One can envy the Black Sea coast, where there are eucalyptus alleys, and,of course the Australians. You can walk to the eucalyptus trees and watch the trees live.

Eucalyptus leaves are like silver crescents.

To determine the shape of the leaves, we use the classifier simple leaves, which many of my regular readers already have, especially those who have become the owner of the book. But individual tables can also be downloaded for free HERE -.

3. Modeling a Eucalyptus Flower

materials: packaging from under shoe covers, chenille wire, green cocktail tube, thread-grass, cotton pad, scissors, pen.

3.1 Make a hole in the bottom of the package in the center with scissors so that you can insert the wire.

3.2 We circle the bottom of the packaging of shoe covers on a cotton pad with a pen. Cut a circle around the diameter of the bottom, make a hole in the center. Let's put the liner on the bottom.