Gynoecium- a collection of carpels in a flower that form one or more pistils.
Carpels- These are megasporophylls that bear ovules.
Nucellus- This is the central part of the carpel, which is homologous to the megasporangium. A pistil arose from one or more carpels due to the closure and fusion of their edges.
A journey from pollen - from anthers to stigma
Each stamen consists of a fillet and anther. Pollen grains are formed in the anthers, which interfere with reproduction. Each fireplace consists of a stigma, stylet and ovary. The ovary produces eggs that interfere with reproduction. In flowering plants, the anthers open when mature and release pollen grains that must reach the plant stigma of the same species so that reproduction can occur. Pollen grains may fall directly into the stigma of the same flower, or be carried by insects or wind and reach the stigma of other flowers of the same species, which are sometimes found over long distances.
The structure of the pistil. Pestle - the most essential part of the flower from which the fruit is formed. The shape of the pistil resembles a closed vessel in which the ovules develop. It usually consists of three parts: stigma, style and ovary (Fig. 9).
Stigma- this is the expanded part at the top of the style, which is designed to trap and germinate pollen. The shape and size of the stigma are varied and are usually adapted to the type of pollination. The surface of the stigma is often uneven, lumpy, and coated with a sticky liquid, which helps trap pollen more efficiently. In addition to the sticky surface, the stigma may have branched lobes and catching hairs.
The transport of pollen grains from the anther to the stigma is called pollination. Insect-pollinated flowers have characteristics that attract them, such as brightly colored petals, perfume, and nectar from which the insects feed. Pollen produced by flowers is usually sticky so that it easily clings to animals.
Wind-pollinated flowers are generally small, with downward aspect, without bright color and odorless. There are also other pollinating agents, although less frequent than wind and insects, which are birds, as well as water for aquatic plants. After pollination, fertilization can occur and seeds and fruits are formed.
Rice. 9. General form gynoecium:
A– simple gynoecium (shag); B– simple gynoecium (poppy); IN– complex gynoecium (susak); 1 – stigma; 2 – column; 3 – ovary
Column- a thin cylindrical sterile part of the pistil, usually extending from the apex of the ovary. It connects the ovary and stigma. The style lifts the stigma upward, which is sometimes necessary during pollination. In a number of plants the style is not developed, therefore stigma called sedentary(poppy). The absence of styles is often observed in wind-pollinated plants (cereals). In large insect-pollinated flowers (lilies), the styles are very long, the stigma is carried high up, which facilitates pollination. However, this significantly lengthens the path of the pollen tube.
Growing Seeds and Fruits After pollination, pollen grains are stored in a stigma, which has a viscous and sweet liquid. Each grain of pollen will develop a tube - the pollen tube - which flows down the stylet until it reaches the ovary and enters the egg cell.
Ova of animals and ova of plants. While in animals the ovum represents the female gametes, in plants it is the structure in which the female gametes are found. When two male gametes, formed in the pollen tube and carried by it, reach the egg, one of them unites with female gametes, leading to the appearance of an egg or zygote, and other fuses with a cell that is located in the central zone of the egg, forming the parent cell of reserve substances. After this double fertilization, the egg or zygote gives rise to the embryo, and the mother cell of the reserve substances forms the reserve substances.
Ovary- This is the closed lower expanded hollow part of the pistil that carries the ovules. The ovary cavity is single-locular or divided into several nests (see Fig. 9).
Below are the types of ovary according to the nature of fusion with other parts of the flower (Fig. 10).
1. Upper the ovary is freely located on the receptacle, without merging with other parts of the flower (buttercup, spirea, pea). Flowers that have superior ovary, called subpistillate.
The embryo and storage substances involved in the tegument make up the seeds. In some plants, the flower also produces a fruit - fruiting. During this process, some flower pieces such as petals and stamens wither and fall off. The ovary develops the pericarp, a fleshy structure that, together with the seeds, makes up the fruit. In addition to protecting the seeds, fruits contribute to their dispersal, that is, spreading them throughout different places. In fact, when the fruit is consumed by humans or other animals, the seeds included in it are either discarded or removed in feces, which can occur over long distances from where the fruit was found.
In some pink flowers (rosehip, plum, cherry, etc.) the ovary is free, but is located deep in the flower, at the bottom of the hypanthium. This ovary is also superior, but such a flower is called peripestial.
2. Lower The ovary is completely fused with other parts of the flower, so it cannot be isolated without disturbing the integrity of the flower. Such flowers are called suprapistal, since parts of the flower are located above the ovary. Most often, the lower ovary is formed as a result of fusion of the gynoecium with the floral tube (currant, apple tree, gooseberry, pear, rowan), less often it is formed as a result of fusion of the gynoecium with the receptacle (pumpkin, cactus).
Scattered on the soil, if the seeds germinate, they will give rise to a new plant. To develop a new plant, it is necessary that, firstly, seeds are spread on the soil. This process is called propagation. In many cases, dispersal is by wind because the seeds are very light and have hairs or membranes that make them easier to transport.
Some seeds are spread by animals who carry them to their hair or who ingest the fleshy and juicy fruits that contain them, releasing the seeds intact in their feces. Water also plays very important role in the dispersal of certain seeds which, when they float, are transported to other places.
3. Semi-lower the ovary fuses with parts of the flower up to half of the ovary (elderberry, honeysuckle). Flowers with this type of ovary are called semi-suprapistic.
Rice. 10. Types of ovary:
1 – top; 2 – semi-lower; 3 – lower; 4 – upper, surrounded by walls of hypanthium;
After seed propagation, when it is in good condition and has favorable conditions environment- the emergence of adequate air, humidity and temperature - germination, i.e. the embryo develops due to reserve substances, which leads to the appearance of a new plant.
Reproduction of mosses and fruits
Non-flowering plants, such as mosses and ferns, do not produce seeds and have a different reproductive process than flowering plants. IN certain time years, these plants produce specialized cells for reproduction - spores. In fruits, spores occur in sporangia, which are grouped in the serum located on the underside of the leaves. In mosses, spores form in capsules.
A– hypanthium wall
The ovary acts as a moist chamber that protects the ovules from drying out, temperature fluctuations, and being eaten by insects. In the ovules, which are in the ovary, the processes of megasporogenesis and megagametogenesis take place.
The place in the ovary to which the ovule is attached is called placenta . The placenta usually looks like a small swelling or outgrowth, formed by tissues ovaries
Once the spores are released, they are easily spread by the wind because they are very light. If they find favorable conditions, they germinate. In the fetus, the egg or zygote resulting from fertilization gives rise to a new plant where spores are produced; in moss the egg or zygote forms a capsule where spores are produced.
A flower is a modified branch formed by modified leaves, forming concentric rings around a central axis of support. A typical monoid flower has three types of organs. Supporting organs? organs that support the flower such as.
The location of the placentas in the ovary is called placentation . The following main types of placentation are distinguished:
1) laminal – attachment of ovules occurs throughout inner surface ovary or in certain places, but not along abdominal suture; characteristic of primitive flowering plants (magnolia, lotus, susak, hornwort);
The set of protective organs is called the perianth. A flower without perianto is considered naked. Its function is to protect the flower when pressed. They say that a flower without sepals is aseptic. In this case, the perianth is said to be undifferentiated. A flower without petals is said to pinch it. If the entire perianth is equal and similar to the petals, it is called petal. Also in this case, the perianth is designated undifferentiated. The male fertile leaves form the outermost ring, while the female fertile leaves the inner one.
2) sutural (marginal) – ovules are located along the edges of the carpels in two rows along the ventral suture. It happens (Fig. 11):
– central-corner- ovules are attached to internal corners in the center of the ovary, formed as a result of the fusion of the lateral sides of the carpels (apple tree, onion, lily);
– central-axial (columnar)– placentas are located on an axis (column), which is located in the center of a single-locular ovary (cloves);
Stamens are modified leaves or sporophiles because they support sporangia. After fertilization, the walls of the ovary form the fetus. The carpel passes through a narrow zone, the stylet, and ends in an enlarged zone that receives pollen grains called the stigma. Typically the stigma is higher than the anthers to discourage selfing. A flower presenting four concentric rings is considered complete, while a flower lacking one of the rings, be it a fertile or sterile ring, is considered incomplete.
– wall (parietal)– the ovules are located on the inner walls of the ovary along the sutures where the carpels grow together (violet, willow, orchid).
Rice. 11.Types of marginal placentation:
1 – central-angular; 2 – central-axial; 3 – wall
If a flower has radial symmetry, it is called actinomorphic, while flowers with bilateral symmetry are called zygomorphs. Flowers grouped in sets form inflorescences. Examples of inflorescences are daisies and sunflowers. Each of these colors? consists of numerous small flowers arranged in a wide base, representing a single peduncle.
Structure of male sporophiles
In the stamen, the most important area in terms of reproduction is the anther. The anther presents longitudinal grooves that divide it into two lobes or lobes, each of which contains two pollen sacs. The anther has three layers of cells with very different functions.
at the very top of the receptacle is the last part of the flower
– carpels, the totality of which is called the gynoecium. Each carpel has a lower expanded part - the ovary, above it - a more or less long style (sometimes it is absent), in the upper part of which there is a flat, or round, or feathery stigma. The formation of ovules occurs in the ovary, the stigma catches and retains pollen grains on its surface,
Epidermal cell layer - just like the entire plant body, the anther is surrounded by protective cells; Mechanical layer? located just below the epidermal cells. The cells of this layer, large and very regular in outline, have a very thick cell wall. As the anther matures, these cells lose water, causing the anther to rupture and subsequently release the spores inside. The rupture always occurs in the same zone of the anther, among the pollen sacs, which are already predetermined. The mechanism of spore release can be seen to be due to a mechanism similar to that which exists in fruit sporangia.
the style carries male gametes, which arise during the germination of pollen grains, to the ovules. A flower may have one or more carpels, which, like the stamens, can be free or fused, and
fusion of carpels can be complete or partial (only by ovaries, and the styles are free). In such cases, it is customary to use the following terms: polynomial apocarpous gynoecium, i.e. there are many carpels and they are free; gynoecium coenocarpous – carpels fused, with different numbers members - three-five-or polynomial (tulip, apple, poppy flowers).
Nutrient layer? the designation of these cells already reveals their important function, because through them are the cells that will be the source of nutrition for the spores. This layer can only be seen in young anthers where spores have not been released, as it is not functional in a mature anther.
The pollen sacs are male sporangia or microsporangia, and inside the spores are the mother cells that, through meiosis, give rise to spores. Since the spores are called pollen grains or microspores, in this case the cells that give rise to them are the mother cells of the pollen grains.
Note. In practice and everyday life, the gynoecium is usually called a pistil.
70. The shape of the receptacle and the position of the ovary in the flower. Anatomical structure of the ovary.
Receptacle- the upper expanded part of the peduncle, the axial part of the flower; All other parts of the flower (sepals, petals, stamens, pistils) depart from it. The receptacle is of stem origin - unlike the rest of the flower, which is of leaf origin.
While still enclosed in the anthers, the pollen grains begin their germination, suffering mitosis followed by cytokinesis, resulting in a cell with two nuclei: a germination nucleus and a vegetative nucleus. To release pollen grains, the disappearance of anthers occurs in the already expected fracture zones, and spores can be transported to the female sporophyte through the wind? anemophilous pollination? or insects? entomophilous pollination.
Structure of female sporophiles
Carpons consist of three main zones: ovary, stylet and stigma. Since each carp has only one ovary, which in turn contains only one cavity, it is clear that the lily, like many other plants, has three molten fruits.
The receptacle is usually somewhat wider than the peduncle and its shape can be different: in the simplest case it has the shape of a cone or a hemispherical head. The pistil, which is laid higher than other organs, is attached to the apex of the receptacle. The ovary of such a pistil, although usually hidden at the bottom of the flower, is called superior ovary.
These tags surround the nucella, the main tissue of the egg, but not completely because they leave an opening called the micropyle. Inside, the nucleo differentiates into a mother cell of the embryo sac or a macropospore-mother cell. This cell will undergo meiosis, resulting in four cells.
Of these, three degenerate and the rest are female spores or embryo sac. Germination of the embryo sac begins with three successive mitoses, always without cytokinesis, producing eight haploid nuclei. Synergids also protect the oosphere, functioning in this regard like the archgones of non-ansyspermic plants.
A further complication of the flower structure may consist in the fact that the goblet-shaped receptacle, closely fitting the ovary, fuses with its walls. The ovary is located under the flower, forming one whole with the receptacle, in this case we are talking about inferior ovary.
At semiinferior ovary the flowers grow together with it until about half of the ovary.
At the opposite pole of the egg are three antipodal cells, the function of which is still unknown, although they are capable of producing hormones, and in the center are two polar nuclei that eventually combine to form a diploid nucleus called a mesocyst.
A spore that germinates in this way corresponds to the female gametophyte: a germinated embryo sac or macroprotalo. Germinated pollen grains are released from the anther and carried to the stigma of a flower of the same species through a process called pollination.
The flower is divided into parts which... Cup: Leaves are produced, usually green and called sepals. Corolla: formed by modified leaves, colored and called petals. Stamens: These are modified leaves formed by the binder, anther and fillet. Therefore, since the anther is part of the stamens and the set of stamens and androger, it means that the androcenic part of the flower is responsible for the production of pollen. Soon after the flower is fertilized, the sepals, petals, stamens, stigma and stele dry out and fall off.
Ovary The pistil is formed from the primary tubercle of the conical formation of the flower.
The ovary is the most essential part of the pistil, bearing the ovules.
The ovary contains reliably protected ovules. After fertilization, the ovary turns into a fruit, inside which are the seeds that have developed from the ovules. The place where the ovules are attached to the ovary is called the placenta.
The ovary can be single or multilocular (in the latter case it is divided into nests by partitions; sometimes the nests are separated by false partitions).
71. Variations in flower morphology of different system groups (perianth, androecium, gynoecium, receptacle, types of flowers). Variations in the structure of the flower go back to one type, whose structure is close to the strobili of gymnosperms. The flower of the original type is radially symmetrical, with an elongated stem-like receptacle, on which it is arranged indefinitely in a spiral big number
The elements of the perianth, androecium and apocarpous gynoecium are not fused with each other. In many magnoliids, the flower has evolved and has a hemicyclic, less often cyclic, structure with a certain small number of perianth and gynoecium elements. Distinguish different types
flowers:
Dioecious (unisexual) - only stamens (male flowers) or only pistils (female flowers)
Monoecious - and wives. And husband. Flowers on one plant (cucumber, hazel, birch...)
If same-sex colors develop on different individuals, then dioecious (nettle, sea buckthorn...) Varies perianth
from single to double. The perianth is the sterile part of the flower that protects the more delicate stamens and pistils. The perianth elements are called tepals, or perianth segments. U simple perianth, all leaflets are the same; at double
Variations of structure androecium(set of stamens):
The number of stamens in one flower varies widely among different angiosperms, from one (orchids) to several hundred (mimosas). Often the stamens located in the same flower have a different structure (in the shape or length of the stamen filaments).
Stamens can be free or fused. Based on the number of groups of fused stamens, different types of androecium are distinguished: monofraternal, if the stamens grow together into one group (lupine, camellia); difraternal, if the stamens grow together into two groups; polygamous, if numerous stamens grow together into several groups; fraternal - the stamens remain unfused.
Carpels (gynoecium): The collection of carpels of one flower forming one or more pistils is called the gynoecium.
During the evolution of carpels, from flat and open carpels, longitudinally folded (conduplicate) carpels emerged, which then fused at the edges and formed a pistil. The pistil occupies the central part of the flower.
(according to lecture) Types of gynoecium:
monomerous-monocarp (from 1 carpel)
polynomial-apocarpous (from several free carpels)
syncarpous (several carpels fused with walls, central-angular placentation).
polynomial-coenocarpous - fused non-free
paracarpous - the same, but the walls of the carpels are not preserved. Placentation is wall.
Lysocarpous - differs from paracarpous by columnar (central) placentation.
Pseudomonocarpous (arises from a complex pistil reduced in the process of evolution with a single-locular ovary and a single ovule).
Receptacle may have different sizes and shapes. In some plants, as a result of the fusion of the receptacle (torus), lower parts Between the integument and the androecium, a special structure is formed - the hypanthium. The shape of the hypanthium can be varied and sometimes participate in the formation of the fetus.