Symmetrical florals. Asymmetrical, zygomorphic and actinomorphic flower: brief characteristics

A flower is a shortened shoot of a plant with modified leaves. This part is intended primarily for reproduction. The shape of y can be very different.

Main types of whisks

All currently existing ornamental crops can be divided into three large groups:

• with symmetrical flowers;
• with asymmetrical;
• with asymmetrical ones.

All these varieties are represented by a huge number of plants of various genera and families. by the way, is an important criterion for correct taxonomy.

Symmetrical rims

The first type of flowers in biology is called actinomorphic. All parts of the corollas of such plants are absolutely symmetrical. An actinomorphic flower is characterized primarily by the fact that at least two planes can be drawn through its axis. Such plants, of course, look very attractive. However, it is believed that they are not very well adapted for pollination by insects.

Variety of symmetrical rim shapes

A regular actinomorphic flower, among other things, can have a different number of petals. Sometimes they are located in one row, sometimes in several. Actually, the actinomorphic corollas themselves differ in such characteristics as:

• tube length;
• bend shape;
• bend size.

An actinomorphic flower can be:

1. Wheel-shaped. The tube of such corollas is small or practically absent. In this case, the bend is deployed practically in the same plane.
2. Funnel-shaped. These flowers have a very large tube. The bend of the corolla is small.
3. Tubular. The corollas of this group are characterized by a cylindrical tube and an erect short limb.
4. Bell-shaped. Such an actinomorphic flower has a cup-shaped spherical tube, gradually turning into an inconspicuous limb.
5. Kolpachkov. In such flowers, the petals grow together at the tips.

Asymmetrical flowers

Plants with corollas of this variety are quite common in nature. Biologists call such flowers zygomorphic. Only one plane can be drawn through the center of an asymmetrical rim.

Types of zygomorphic flowers

The corollas of this group have a special shape, which is often a morphological characteristic of the species (and sometimes even of the family). Their petals are most often fused. Zygomorphic flowers are found in nature:

1. Double lips. In such corollas, the limb consists of an upper and lower lip.
2. Reed. The fused petals extend from the corolla tube.
3. Spurred. The petals of such flowers form a full growth, which is called a spur.

Asymmetrical flowers

We found out what an actinomorphic and zygomorphic flower is. Asymmetrical rims are characterized, first of all, by the fact that not a single plane of symmetry can be drawn through their center. Such plants are not found very often in the wild. The vast majority of ornamental crops still have symmetrical or asymmetrical corollas.

Examples of actinomorphic flowers

The fact that symmetrical corollas are poorly pollinated by insects, according to biologists, is a sign of their low organization. But be that as it may, plants with actinomorphic flowers are most often found in nature. This group includes well-known meadow, wild and forest flowers, including:

• forget-me-nots (wheel-shaped);
• dope, tobacco (funnel-shaped);
• flowers (tubular);
• lilies of the valley (bell-shaped);
• wild grapes (cap).

In gardens, the vast majority of ornamental herbaceous and shrub crops also have symmetrical corollas. For example, peonies, daffodils, sunflowers, lilies, and mallows have actinomorphic flowers.

Among the shrub crops, this group includes rosehip, lilac, and spirea. The flowers of garden grapes are also actinomorphic.

Examples of plants with zygomorphic corollas

We found out which plants have regular, actinomorphic flowers. This group is the most common in nature. Zygomorphic plants are somewhat less common in fields and forests. Examples of such crops include:

• bilabial burrows;
• reed dandelion;
• spurred toadflax and columbine.

The decorative qualities of flowers in this group are usually not very high. Therefore, they are grown quite rarely for decorating streets and courtyards, as well as for making bouquets. But sometimes, of course, you can see such flowers in gardens and flower beds. For example, knitting peas (garden mouse peas) can be a good decoration for the site. This culture is often used in landscape design as a ground cover.

Examples of asymmetrical colors

Plants of this group, as already mentioned, are rare both in nature and in gardens. Their corollas look quite attractive and unusual, and therefore can be used in landscape design. Very striking representatives of the group of plants with asymmetrical flowers are, for example, the well-known cannas. Horse chestnut is also often used in landscape design.

Of course, plants of this group can also be found in the wild. The medicinal plant valerian, for example, has asymmetrical flowers.

the right flower

ACTINOMORPHIC FLOWER(from Greek Aktis- beam and morphe- shape), regular flower, has more than two planes of symmetry (symmetry is determined by the perianth, most often by the corolla). Characteristic of many families of dicotyledons and monocotyledons. Actinomorphic flowers can be separate-petaled (in Carnationaceae, Roseaceae, Umbellaceae) or sphenolate (in Borageaceae, Solanaceae, Campanaceaceae). They are often pollinated by insects, so sometimes actinomorphic flowers, like zygomorphic flowers, develop various adaptations for pollination by specialized pollinators (scales in the throat of various borage, a very long corolla tube in tobacco, datura and others).

Types of flower symmetry: 1 - actinomorphic flower, 2 - zygomorphic flower.

See also:

Zygomorphic flower

ZYGOMORPHIC FLOWER(from Greek zygon pair, yoke and morphe form), a flower whose perianth has one plane of symmetry. Usually this plane passes through the middle of the bract, the peduncle and the axis of the inflorescence, that is, it coincides with the median plane of the flower...

Flower

FLOWER(Latin flos, Greek anthos), the reproductive organ of angiosperms (flowering) plants. In a bisexual flower, micro- and megasporogenesis, micro- and megagametogenesis, pollination, fertilization, embryo development and the formation of a fruit with seeds occur...

Leaf arrangement

LEAF ARRANGEMENT, phyllotaxis ( phyllotaxis), the order in which leaves are placed on the stem, reflecting the symmetry in the structure of the shoot. Leaf arrangement depends primarily on the order in which leaf primordia are laid down on the growth cone and is usually a systematic feature. There are three main types of leaf arrangement...

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

A flower is a modified shortened shoot used for seed propagation. The main or side shoot usually ends in a flower. Like any shoot, a flower develops from a bud.

Flower structure

A flower is the reproductive organ of 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 on various shapes: flat, concave, convex, hemispherical, cone-shaped, elongated, columnar. The receptacle below turns into a peduncle, connecting the flower with the stem or peduncle.

Flowers without a peduncle are called sessile. On the peduncle of many plants there are two or one small leaves - bracts.

Cover of a flower - perianth- can be divided into a calyx and corolla.

Cup forms the outer circle of the perianth; its leaves are usually relatively small in size and green in color. There are separate and fused calyx. Usually it serves the function of protecting the internal parts of the flower until the bud opens. In some cases, the calyx falls off when the flower opens; most often it remains during flowering.

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

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

whisk- the inner part of the perianth, differs from the calyx in its bright color and larger size. The color of the petals is due to the presence of chromoplasts. There are separate and fused corollas. The first consists of individual petals. In fused-petal corollas, a tube is distinguished and a limb located perpendicular to it, which has a certain number of teeth or corolla blades.

Flowers can be symmetrical or 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 rim.

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

Double flowers have an abnormally increased number of petals. In most cases they occur as a result of petals splitting.

Stamen- part of a flower, which is a kind of specialized structure that 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 shape, size, structure of the stamen filaments, connective tissue and anther. The collection of stamens in a flower is called the androecium.

filament- the sterile part of the stamen, bearing an anther at its apex. The filament can be straight, curved, twisted, tortuous, or broken. Shape: hair-like, cone-shaped, cylindrical, flattened, club-shaped. The nature of the surface is bare, pubescent, hairy, with glands. In some plants it is short or does not develop at all.

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

As a rule, the anther is four-locular, but sometimes the partition between the nests in each half is destroyed, and the anther becomes two-locular. In some plants the anther is even single-lobed. Very rarely found with three nests. Based on the type of attachment to the filament, anthers are classified into immobile, movable, and oscillating anthers.

Anthers contain pollen or pollen grains.

Pollen grain structure

The dust particles 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 a microscope you can see that dust particles from different plants are not at all the same. They differ in size and shape.

The surface of the dust particle is covered with various protrusions and tubercles. Once on the stigma of the pistil, the pollen grains are held with the help of outgrowths and the sticky liquid secreted on the stigma.

The nests of young anthers contain special diploid cells. As a result of meiotic division, four haploid spores are formed from each cell, which are called microspores due to 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. Areas of cytoplasm are concentrated around the nuclei 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 membranes. Many pollen grains make up the pollen of a plant. Pollen matures in the anthers at 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 (sperm cells develop from it) and a large vegetative cell (the pollen tube develops from it).

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

The pollen swells, and the restraining influence of the exine (the outer layer of the pollen grain shell) causes the contents of the pollen cell to rupture 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 there is loose tissue into which the pollen tube penetrates. It continues to grow, passing either through a special conducting channel between mucus cells, or tortuously along the intercellular spaces of the conductive tissue of the column. In this case, usually a significant number of pollen tubes simultaneously advance in the style, 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 sperm cells in pollen has not yet occurred, then a generative cell passes into the pollen tube, and here, through its division, sperm cells are formed. The vegetative nucleus is often located in front, at the growing end of the tube, and sperm 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, the chemical composition of pollen includes proteins, fats, ash and a large group of enzymes. Pollen contains a high phosphorus content. Substances in pollen are in a mobile state. Pollen easily tolerates low temperatures down to -20Cº 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 bearing ovules) subsequently fusion of the edges of the latter. It can be simple if it is made up of one carpel, and complex if it is made up of several simple pistils fused together with 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, which contains the seed buds.

Having entered the ovary, the pollen tube grows further and enters the ovule in most cases through the pollen duct (micropyle). Invading the embryo sac, the end of the pollen tube bursts and the contents spill 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 regular and irregular

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

Flowers bisexual and dioecious

Most plants have flowers that contain 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.

Monoecious and dioecious plants

Plants that bear both pistillate and staminate flowers are called monoecious. Dioecious plants have staminate flowers on one plant and pistillate flowers 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 the shoots. Very rarely they are located alone. Much more often, flowers are collected in noticeable groups called inflorescences. The study of inflorescences began with Linnaeus. But for him, the inflorescence was not a type of branching, but a way of flowering.

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

Inflorescence type	Inflorescence diagram	Peculiarities	Example
Simple inflorescences
Brush		Individual 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 stalkless, i.e. sessile.	Plantain, orchis
cob		It differs from the ear by its thick, fleshy axis.	Corn, calligraphy
Basket		The flowers are always sessile and sit on the strongly thickened and widened end of the shortened axis, which has a concave, flat or convex appearance. In this case, the inflorescence on the outside has a so-called involucre, consisting of one or many successive rows of bract leaves, 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 axis is shortened; lateral flowers emerge as if from one place, sit on stalks of different lengths, located in the same plane or dome-shaped.	Primrose, onion, cherry
shield		It differs from the raceme in that the lower flowers have long pedicels, so that as a result the flowers are located almost in the same plane.	Pear, spirea
Complex inflorescences
Complex brush or whisk		Lateral branching axes extend from the main axis, on which flowers or simple inflorescences are located.	Lilac, oats
Complex umbrella		Simple inflorescences extend from the shortened main axis.	Carrots, parsley
Complex ear		Individual spikelets are located on the main axis.	Rye, wheat, barley, wheatgrass

Biological significance of inflorescences

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

Pollination

In order for fertilization to occur, pollen must land on the stigma.

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

Self-pollination

In self-pollination, pollen from the stamen ends up on the stigma 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 finished.

During self-pollination, sex cells formed on the same plant and, therefore, having the same hereditary characteristics merge. This is why the offspring produced by the process of self-pollination are very similar to the parent plant.

Cross pollination

During cross-pollination, a recombination of hereditary characteristics 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 occurs much more often 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 produced, it is dry, small, and when the anther opens, it is thrown out with force. Light pollen from 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, feathery and protrude from the flowers. Anemophily is characteristic of almost all grasses and sedges.

Entomophily(transfer of pollen by insects). Adaptations of plants to entomophily are the smell, color and size of flowers, sticky pollen with outgrowths. Most flowers are bisexual, but the 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.

The flowers of insect-pollinated plants have areas that secrete a sweet, aromatic solution. These areas are called nectaries. Nectaries can be located in different places of the flower and have different shapes. Insects, having flown up to a flower, are drawn to the nectaries and anthers and become dirty with pollen during their meal. When an insect moves to another flower, the pollen grains it carries stick to the stigmas.

When pollinated by insects, less pollen is wasted, and therefore the plant conserves nutrients 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 windless places - in the thicket of a forest or in thick grass.

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

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

Hydrophilia(pollination by water). Observed in aquatic plants. The pollen and stigma of these plants most often have a thread-like shape.

Bestiality(pollination by animals). These plants are characterized by large flower sizes, abundant secretion of nectar containing mucus, massive production of pollen, and, when pollinated by bats, flowering at night.

Fertilization

The pollen grain lands 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 sticks. The pollen grain swells and germinates, turning 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 (sperm). When the pollen tube penetrates the embryo sac through the pollen duct, one of the sperm fuses with the egg. Fertilization occurs and a zygote is formed.

The second sperm fuses with the nucleus by the large central cell of the embryo sac. Thus, in flowering plants, during fertilization, two fusions occur: 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 characteristic only of flowering plants.

The zygote formed by the fusion of gametes is divided into two cells. Each of the resulting cells divides again, etc. As a result of repeated cell divisions, a multicellular embryo of a new plant develops.

The central cell also divides, forming endosperm cells in which nutrient reserves accumulate. 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 influences, develops from the walls of the ovary. In some plants, other parts of the flower also take part in the formation of the fruit.

Education dispute

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

Formation of the embryo sac

As a result of threefold mitotic division of the nucleus, eight nuclei are formed in the cavity of the embryo sac, which are covered with cytoplasm. Cells deprived of 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 to form the diploid central nucleus of the embryo sac. The embryo sac in which nuclear differentiation has occurred is considered mature and can receive sperm.

By the time the pollen and embryo sac mature, the flower opens.

Structure of the ovule

Ovules develop on the inner sides of the walls of the ovary and, like all parts of the plant, consist of cells. The number of ovules in the ovaries of different plants varies. In wheat, barley, rye, and cherry, 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 canal - the pollen passage. 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 opening there is an egg cell, and the central part is occupied by a large central cell.

Development of angiosperms (flowering) plants

Formation of seed and fruit

When the seed and fruit are formed, one of the sperm fuses with the egg, forming a diploid zygote. Subsequently, the zygote divides many times, and as a result, a multicellular plant embryo develops. The central cell, fused with the second sperm, also divides many times, but the second embryo does not arise. A special tissue is formed - endosperm. The endosperm cells accumulate reserves of nutrients necessary for the development of the embryo. The integument of the ovule grows and turns into a seed coat.

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

Sexual reproduction

Sexual reproduction in angiosperms is associated with flowers. Its most important parts are the stamens and pistils. Complex processes associated with sexual reproduction occur in them.

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

In the anthers of the stamens, 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 coats. The outer shell, as a rule, is uneven, with spines, warts, and mesh-like outgrowths. This helps the pollen grains to stay on the stigma. The pollen of a plant, ripening in the anthers, consists of many pollen grains by the time the flower blooms.

Flower formula

Formulas are used to conditionally express the structure of flowers. To compile a flower formula, use the following notation:

Example of cherry blossom formula:

*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.

Make a diagram using cross sections of unopened flower buds. The diagram gives a more complete idea of ​​the structure of a flower than a formula, since it also shows the relative position of its parts, which cannot be shown in a formula.

A flower is a shortened, unbranched shoot with limited growth, in which the formation of spores, tentorium, processes of pollination, fertilization, and the formation of fruits and seeds occur. This is a special morphological structure inherent only to angiosperms.

Types of flower symmetry:

The relative position of flower parts. Identify the parts of a flower: pedicel, bracts, bracts. Types of receptacle.

Peduncle- the lower axial part of the flower can be well defined or greatly shortened, differentiated into three or two internodes and have two or one node. Can be represented by one internode.

Bracts- the first (usually two) leaves formed from the lower leaf tubercles of the flower bud.

Bracts(usually one) - leaflets formed from the second block of leaf tubercles from the bottom.

The receptacle can be: flat, convex, elongated, curved.

The arrangement of flower parts on the receptacle can be: cyclic, acyclic (spiral), hemicyclic (bottom in circles, top in a spiral).

Morphological structure of the perianth. Types of perianth. Designation of perianth elements in the flower formula. Parts of the corolla, calyx, simple perianth.

The perianth is the sterile part of the flower. It can be double or simple.

The double perianth is differentiated into two parts: a calyx and a corolla, the elements of which - sepals and petals - are sharply different from each other. Subchases are leaflets located on the receptacle under the calyx, and differ from the sepals in shape and size.

The simple perianth is not differentiated into a calyx and corolla. The elements of a simple perianth are called tepals.

Corolla parts: petals. The petaled corolla consists of: a tube, a limb, and a pharynx. The free corolla consists of: a plate and a marigold.

Calyx parts: sepals. If there are several circles of sepals, then the outer circle is the subcup.

Parts of a simple perianth: calyx or corolla.

The following notations are usually used: P- perianth, Ca(or K) - calyx, Co- whisk, A- androecium, G- gynoecium, - actinomorphic flower, - zygomorphic flower, - male flower, - female flower, () - accretion; a line under the number indicating the number of carpels, for example, - superior ovary, - inferior ovary.

Morphological definition of androecium. The structure of the stamen. Types of androecium. Designation of androecium elements in the flower formula.

Androecium- a set of stamens.

Structure of the stamen: filament, anther, connective tissue.

Types of androecium:

· Polygamous – stamens free A∞

· Monofraternal – fused stamens A(5)

· Bifraternal – 9 conjoined and 1 free A(9)+1

· Double-strength – out of 4, two are longerA2+2

· Four-strong A4+2

The generative (reproductive) organs of higher angiosperms include flowers and fruits.

The flower is a modified shortened spore-bearing shoot of limited growth, adapted for the formation of micro- and megaspores, gametes and for cross-pollination.

A flower consists of a stem part (pedicel, receptacle) and a leaf part (sepals, petals, stamens, pistils). The part of the shoot between the flower and the bract is called peduncle ( analogous to an internode). the peduncle is connected to the stem. Vascular-fibrous bundles pass through the peduncle to nourish the flower and give it a certain position in space.

If flowers do not have a pedicel and they are located directly on the stem, then the flower is called sedentary. Such flowers are characteristic of the Compositae family. For example, coltsfoot, dandelion, sunflower, sow thistle, thistle, daisies.

The peduncle ends with a receptacle, which serves to attach all other parts of the flower, connecting them into a single whole.

Overgrown receptacle called hypanthium. Hypanthium is characteristic of the Rosaceae family. The hypanthium can be saucer-shaped, goblet-shaped, or convex. The strawberry fruit is juicy, the red pulp is an overgrown hypanthium, the red pulp of the rose hip is a goblet receptacle - the hypanthium, the white core of the raspberry is the hypanthium.

Perianth represented by a calyx and corolla. If a flower has both a calyx and a corolla, then the perianth is called double. If the perianth consists only of a calyx or corolla, it is called simple.

Cup consists of sepals. The sepals come from ordinary leaves, so they look like green leaves in appearance and perform a protective function - they protect the bud from the outside. When the bud opens, the sepals fall off. They can participate in photosynthesis, and partly nourish the flower and even the fruit. In pear and apple trees, the sepals are retained at the top of the fruit.

Whisk called a set of petals. Their origin can be either leaf or modification of the stamens. Petals are flattened and overgrown sterile stamens. Their role: in entomophiles, the bright corolla serves to attract pollinating insects; in wind-pollinated plants, the corolla is modest. The petals are small, in the form of scales - cereals. Sedges have no corolla at all. A flower consists only of pistil and stamens.

The reproductive parts of a flower include the stamens and pistils.

Stamens. They are microsporophylls. The collection of stamens is called the androecium. (Andros is a man). The stamen consists of a filament and an anther. The filament gives a certain position to the anther, nourishes it, and pollen is formed in the anther. The anther consists of 4 nests (microsporangia). Stamens of the same flower may differ in shape or length of filaments. If all the stamens grow together, then such an androecium is called monofraternal. If one of the stamens is not fused with the others, then the androecium is bifraternal. If the stamens grow together into several groups - polybrotherous.

Carpels are megasporophylls. Typically, it consists of three parts - the ovary, the style and the stigma. Carpels are sometimes called carpels, indicating that they will develop into a fruit, or pistils. More often, the term pistil refers to the entire set of carpels located in one flower, i.e. gynoecium

Pestle consists of the lower expanded part - the ovary. The cavity formed by the fused carpel contains the ovules, and the wall forms the fruit. At the top of the pistil there is a stigma. In wind-pollinated plants, the stigma is sticky and feathery to better absorb pollen. Reception of pollen is a function of the stigma. Between the stigma and the ovary there is a column. The column can have a different angle of inclination and different lengths. Its role is to give a certain position to the stigma (coadaptation to pollination).

Some plants do not have a style. Such a stigma is called sessile (in cereals). Sem. Poagrass (Poagrass, wheatgrass, reed, timothy).

A flower may have several pistils. The number of carpels and pistils may not be the same. Usually in monocots the number of flower members is a multiple of 3. (3, 6, 9) lily of the valley - 6. In dicotyledons - the number of flower members is a multiple of 4, and more often - 5. Many stamens are considered if there are more than 10. An exception is the raven's eye (Paris quadrifolia ) of the Liliaceae family – 4 sepals, 4 petals.

Sometimes flowers do not have either pistils or stamens. Such flowers are called unisexual. Those. Unisexual - flowers that contain either only stamens or only pistils.

If unisexual flowers develop on the same plant, then such plants are called monoecious (birch, hazel).

If staminate and pistillate flowers grow on different individuals, then the plants are called dioecious. For example, all willows: willow = white willow, willow, sea buckthorn.

Flowers are asexual = sterile. Sterile flowers are needed to attract pollinators. Chamomile - yellow flowers - fertile, white - sterile, blue cornflower - funnel-shaped - sterile.

Flower symmetry. If only one plane of symmetry can be drawn through a flower, then these flowers are called zygomorphic. There are many of them: family. Legumes = Fabaceae – clover, alfalfa. Sem. Lamiaceae = Laminaceae: mint, lavender, sage, motherwort.

If two or more axes of symmetry can be drawn through a flower, then such flowers are called actinomorphic: ranunculus, all Rosaceae, lily of the valley, lungwort.

Flower parts can grow together. If the sepals are fused, then the calyx is called sphenolate, or fused-leaved. If the petals grow together, then the corolla is called fused-petal, or fusion-petal (lily of the valley).

If the perianth is more like a cup, then the perianth is simple, cup-shaped, for example, a mantle.

If the simple perianth is bright, similar to petals, then it is called simple corolla (tulip - 3 outer petals of the calyx, 3 inner ones - the corolla). Lily of the valley is a simple, corolla-shaped, fused-petalled perianth.

Position of the ovary. The ovary can be superior, inferior, or semi-inferior. Depending on the shape of the receptacle, the position of the ovary is distinguished - lower or upper.

Upper- this is an ovary when all the members of the flower (stamens, petals) are attached to the receptacle under the ovary. For example, tulip, lily of the valley, buttercup, strawberry, raspberry.

The lower one is the ovary, in which all the members of the flower are attached to the upper edge of the ovary. For example, Compositae: sunflower, daisies, cornflowers, pumpkin seeds: watermelons, melons, zucchini, squash.

Types and evolution of the gynoecium. Depending on how closely the carpels are connected to each other, two groups of gynoecium are distinguished: apocarpous, if the carpels are free, and coenocarpous, if the carpels are fused.

The ovary consists of 3 carpels that are not fused together (3 pistils). Where the edges of the carpels are fused, the ventral suture is distinguished. The ovule is located along it. Such a gynoecium is called an apocarpous gynoecium.

The next step in evolution is the formation of the gynoecium from fused carpels.

Syncarpous (fused gynoecium) biological benefit is that the ovules are more reliably protected from external influences. The gynoecium is three-locular - there are as many nests as there are carpels.

The paracarpous gynoecium has a cavity common to all carpels, formed due to the divergence of the sutures of the carpels. Single-nested.

Lysicarpous gynoecium arises as a result of the dissolution of the lateral walls of the carpels, because in this case, the marginal parts of the carpels with ovules are not affected, they form a central column with ovules. The gynoecium is unilocular. Characteristic of primroses.