Unisexual and bisexual flowers are examples. unisexual flowers

Same-Sex Families I think that almost every homosexual dreams of marriage with his friend. Robin Maugham A same-sex family is impossible. This is a fucking thing. At this point, once passion, so you need one so that you love him until you lose consciousness. Where can you find this kind. And if he is,

Same-sex marriage

Same-sex marriage Not so long ago, same-sex marriage was banned in Germany. The first country to give them permission in 2001 was Holland. Every year everything more countries pass laws recognizing this form of family, including Belgium, Spain, Canada,

Same-sex relationships

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

See what "unisexual flowers" are in other dictionaries:

Flowers, in which there are stamens and no pistils (male, or staminate, flowers) or there are pistils and no stamens (female, or pistillate, flowers). According to the evant theory of the origin of the flower, O. c. arose in the process of evolution from bisexual as a result of ... ... Biological encyclopedic dictionary

SINGLE FLOWERS- flowers containing only stamens or carpels ...

Flowers are bisexual (with androecium and gynoecium) or unisexual (only with androecium or only with gynoecium). Same-sex flowers can either be on the same plant, like oak, birch, milkweed, corn (and then the plant as a whole ... ... Biological Encyclopedia

Flower "Flowers" redirects here. See also other meanings. Flower (Latin flos, Greek ανθοζ) organ seed propagation flowering (angiosperms) plants. The flower is a modified, shortened and limited in growth ... Wikipedia

PISTILE FLOWERS- same-sex flowers with only pistils (e.g. Zea mays L.) ... Glossary of botanical terms

Bisexual flowers, flowers in which there are both stamens and a pistil (or pistils). Among angiosperms, most species have O. c. Wed Single flowers... Great Soviet Encyclopedia

One of the five types of flowers of plants of the Compositae family (lat. Compositae). These are bisexual or unisexual flowers with a rather long corolla tube, from which the upper lip, consisting of two free teeth, and the lower lip extend, ... ... Wikipedia

Unisexual plant species are those in which flowers of both sexes are placed on the same tree or shrub, therefore they are also called bisexual species. Sometimes there are polygamous cultures that have male bisexual and same-sex flowers at the same time on a single individual.

Monoecious species, in which flowers of two sexes grow at once, are very common in nature.

Examples of monoecious plants

Hazel

watermelons

Hazel

birches

Corn

Walnuts

Cucurbits

Flowers of plants with monoeciousness

Monoeciousness is a special adaptation, which consists in the fact that flowers of both sexes live in the same "house". On the same tree or shrub, both staminate and pistillate inflorescences are found. Sometimes there are flowers in which the perianths are not quite formed. In this case, the pollen is well dispersed by the wind over long distances, and it is carried by bees, but their main advantage lies in the fact that they have a self-pollination mechanism (entomophily), and therefore do not depend on external factors. This happens when pollination occurs in one flower: pollen from one inflorescence falls on others. It is worth noting that in stressful situations for plants, they turn from monoecious. This phenomenon is observed in cannabis.

How does pollination of monoecious plants occur?

Different species with monoeciousness have their own characteristics of pollination. To do this, it is better to consider a few examples. So the walnut is considered a wind-pollinated tree. The fact is that bees sit only on male inflorescences, and female ones do not visit, so insects take almost no part in the pollination of flowers. walnut. This is also because male and female flowers do not bloom on the tree at the same time. In this regard, the inflorescences are pollinated due to the activity of the wind.

An interesting mechanism of pollination in hazel. This is a genus of shrubs and trees (in rare cases) in which the male flowers are in catkins, and the female flowers are in the middle of the buds, so they are not so easy to reach. Pollination occurs due to the wind.

Thus, in nature, the mechanism of monoeciousness is most often encountered, when both male and female flowers grow on the same plant. So plants have a much better chance of pollination. First, bees do not need to fly long distances to deliver pollen from male flowers to female flowers. Secondly, if insects take a weak part in the pollination process, then the wind will always scatter pollen, and it will fall from male flowers to female flowers, which will subsequently ensure the appearance of fruits.

bisexual called a flower in which there are both pistils and stamens (androecium and gynoecium). Sometimes the terms are also applied to the bisexual flower. perfect or monoecious flower.

A flower that has only stamens (androecium) or only pistils (gynoecium) is called gay. Unisexual flowers with stamens staminate, or men's flowers; accordingly, flowers only with pistils - pistillate, or female flowers.

Male and female same-sex flowers can grow on the same plant, then the plant is called monoecious, or bisexual, for example: oak, birch, spurge, corn. In this case, pollination can occur between flowers within the same plant.

If male and female flowers grow on different plants, then we are dealing with dioecious plant. A dioecious plant with staminate flowers is called male , and with women - feminine plant, for example: poplar, willow, hemp, nettle. For fertilization of dioecious species, the presence of at least two plants of different sexes is necessary - male and female.

A plant that has both bisexual and unisexual flowers is called polygamous, for example, such a neighborhood is found in the inflorescences of Compositae.

Flowers lacking spore-bearing organs are sterile, or asexual flowers, such as reed flowers in Compositae inflorescences.

An example of a polygamous plant: in the gerbera inflorescence in the photo there are male flowers (with yellow anthers), female flowers (with white pistils) and sterile reed flowers along the edge.

Flowers of cereals, sedge.

Flowers of cereals, sedge.

Cereal flowers are usually small and inconspicuous. They are adapted for wind pollination, and therefore lack a perianth, since they have no reason to attract insects. Cereal flowers are located on the lateral shoots of the spikelet and consist of stamens and ovary With stigma branches . The flower is protected by the top and bottom lemmas . Two small colorless scales grow above the flowering scales - the so-called flower films , or lodiculae . During flowering, long stamens protrude beyond the scales, spreading pollen in the wind. Cereal flowers can be bisexual or unisexual, sometimes within the same inflorescence.

Sedge flowers are also small and inconspicuous, collected in various spikelets and sitting in the axils of bracts, called cover scales . The sedge flower itself consists of stamens and haviazi With stigma branches . Flowers are bisexual and unisexual, with and without perianth. The sedge perianth may consist of a set of scales, hairy or fringed bristles or silky hairs, and is more commonly present in bisexual or female flowers.

ANDROECIUM

(gr. "man's house"): set microsporophylls, stamens consisting of a filament with a divided into two halves anther containing four microsporangia (pollen sac). The stamens are arranged in one or two circles. Stamens are divided into free and fused.

Exist different types androecium, distinguished by the number of fused groups of stamens:

-unifraternal(stamens in one group, lupine, camellia),

-bifraternal(two groups of stamens),

-polyfraternal(several groups, magnolia, St. John's wort),

-fraternal(non-united stamens).

Also, stamens vary in length: equal, unequal, double-strength(out of four stamens, two are long), three-strong(out of six stamens, three are long), four-strong(out of six stamens, four are long).

Stamen comprises stamen tissue, at the upper end of which is anther, and the lower end is attached to the receptacle. The main tissue of the filament is parenchyma. Important processes take place in the anther - microsporogenesis(formation of microspores in microsporangia) and microgametogenesis(formation from microspores of the male gametophyte). The sterile stamen is called staminodes.

Fig.3 Stamen and anther development

Anther consists of homogeneous cells surrounded by the epidermis.

Diagram- This is a schematic projection of a flower on a plane in which the flower intersects across, perpendicular to its axis. Diagram design rule: inflorescence axis at the top, cover leaf at the bottom. Conventions diagrams: arcs indicate parts of the perianth, sepals - with a protrusion in the middle of the arc, petals - without a protrusion. The stamens are indicated in the form of a cross-section of the anther or filament. Gynoecium - in the form of a transverse section of the ovary. If individual members grow together, this is indicated on the diagram by arcs.

Androecium

Androecium is a collection of stamens in which microsporogenesis, microgametophytogenesis and the formation of male spores occur.

In ontogeny, stamens can be laid in the form of tubercles of a growth cone, as in acropetal(i.e. from the base to the top), and in basipetal(top to bottom) sequence. In the first case, the youngest stamens are located closer to the center of the flower, and the old ones are closer to its periphery, and in the second case, vice versa. The stamens may be free or grow together in various ways and to varying degrees. For example, in the tropical meliaceae family, all 10 stamens grow together with their filaments into a tube ( unifraternal androecium). In St. John's wort, the stamens grow together in bunches; for Compositae, anthers stick together. In many members of the legume family, 9 stamens grow together, and one remains free (the so-called bifraternal androecium).

Each stamen consists of a narrowed filiform or rarely ribbon-like or petaloid part - the stamen filament and usually an expanded part - the anther. Anther has two halves connected to each other liaison, which is a continuation of the filament. The connective is sometimes continued into the epiconnector, visible as a small protrusion above the anther.

The formation of the thread begins later than the anther, and its further elongation is carried out due to intercalary growth. The number of emerging tubercles is sometimes less than the number of stamens, later the tubercles split, and there can be quite a lot of stamens (mimosa). The length of the filaments varies from plant to plant. More often they are more or less equal in length to the perianth, but sometimes they are much shorter or many times longer than it, as, for example, in the well-known tropical medicinal plant kidney tea, or cat's whiskers, from the labiate family. On a transverse section through the filament, it can be seen that most of it consists of parenchymal tissue, and one vascular bundle passes in the center.

Each half of the anther carries two (rarely one) nests - microsporangia. Anther nests are sometimes called pollen sacs. In the mature anther, the partitions between the nests mostly disappear. Outside, the anther is covered with epidermis. Directly under the epidermis is a layer of cells of the so-called endothecium, with thickened cell walls. When the membranes of the endothecium dry out, the nests of the anther open. Deeper lie 1-3 layers of medium-sized thin-walled cells. The innermost layer lining the cavity of the pollen sacs is called tapetum. It is believed that the contents of its cells serve as food for developing mother cells. microspores(microsporocytes) and promotes their differentiation. Anther nests are usually filled with microspore mother cells, microspores, and mature pollen. Microspores are known to arise from microsporocytes as a result of meiosis, and microsporocytes themselves - from a few cells of archesporium (educational tissue that functions in the early stages of development of anther nests). The mature anther opens in various ways: longitudinal cracks, holes, valves, etc. At the same time, pollen spills out.

Signs of the structure, shape, position, number of stamens, as well as the type of androecium itself have great importance for taxonomy of flowering plants and knowledge of their phylogeny.

In some species, part of the stamens loses its original function, becomes sterile and turns into the so-called staminodes. Sometimes the anthers are transformed into nectaries - the secretory parts of the flower that secrete nectar. Petals, their parts, parts of the pistil, and even outgrowths of the receptacle can also turn into nectaries or osmophores. Nectaries have a variety of shapes, are usually located in the depths of the flower and are often distinguished by their shiny surface.

Gynoecium.

The collection of carpels of one flower, forming one or more pistils, is called gynoecium. carpels, or carpels, are structures believed to be related in origin to the leaf. However, functionally and morphologically, the carpels do not correspond to vegetative leaves, but to leaves bearing megasporangia, i.e., megasporophylls. Most morphologists believe that in the course of evolution from flat and open carpels, folded along ( conduplicatively) carpels. Then they grew together at the edges and formed a pistil with its most essential part - the ovary, which carries the ovules. Thus, a unique structure was formed, which is not found in any other groups of plants, resembling a closed vessel in which reliably protected ovules develop. The structure of the pistil is ideally suited for pollination and fertilization. In the ovules, which are in the ovary, the processes of megasporogenesis and megagametophytogenesis are carried out.

The pistil, or rather the ovary, acts as a wet chamber that protects the ovules from drying out. This made angiosperms virtually independent of moisture levels. environment and was one of the factors of their extensive development of arid territories. In addition, the pestle reliably covers the ovules from being eaten by insects and partly from temperature fluctuations.

A pistil formed from one carpel is called simple, from two or more fused carpels - complex. A simple pistil is usually unilocular; complex can be divided into nests or it can also be single-nested. Polynesting occurs either as a result of the fusion of carpels, or due to the formation of additional partitions - outgrowths of the walls of the ovary.

The stigma of the pistil is a structure unique and characteristic only for flowering plants, designed to receive pollen. It develops at the top of the style or directly on the ovary - a sessile stigma; less often (in archaic species) - along the fused edges of the carpel. The shape and size of the stigma are different in different types. The surface of the stigma is very often uneven, tuberculate and covered with a sticky liquid, which contributes to more effective fixation and trapping of pollen. In addition, the stigma surface bears a thin protein layer, the pellicle, which, interacting with pollen grain sporoderm proteins, ensures or prevents pollen tube germination.

The column consists of loose parenchymal tissue. It seems to lift the stigma up, which is necessary for some mechanisms of the pollination process. The morphology of the columns is quite diverse and serves as an important systematic feature. Many archaic families (especially from the magnoliid subclass) are characterized by the absence or weak development of the style. Styles are often undeveloped in many specialized wind-pollinated forms, for example, in many cereals. In large wind-pollinated flowers (in some species of lilies), the columns reach a considerable length, the stigma is carried high up, and thus pollination is facilitated. However, this significantly lengthens the path of the pollen tube.

The ovary is the most essential part of the pistil, bearing the ovules. It is varied in form and appearance, which is largely determined by the type of gynoecium.

The place of attachment of the ovules in the ovary is called placenta. The placenta usually looks like a small swelling, outgrowth or protrusion formed by the tissues of the ovary.

Depending on the features of the attachment of the ovules to the wall of the ovary, several types of placentation are distinguished.

wall, or parental, when the ovules are located inside the ovary along its walls or in places where the carpels are fused.

axial, or axial, when the ovules are located on the central column of the ovary, divided into nests according to the number of carpels.

free central placentation, when the ovules develop on a free central column that is not connected by partitions to the wall of the ovary.

basal, when the only ovule is located at the very base of a single-celled ovary.

Types of gynoeciums:

1. apocarpous - the carpels do not grow together, and each carpel forms a separate pistil (buttercup, rose)

a) monomeric - the gynoecium consists of 1 pistil, and it is formed by 1 carpel (pea, plum, cherry)

b) polymeric - there are many pistils, but each consists of one carpel

(buttercup, strawberry, wild rose)

1. cenocarpous - the pistil is formed from carpels fused together

a) syncarpous - carpels grow together with lateral surfaces, several rings (tulip) are formed. Several nests are formed inside the fruit.

b) paracarpous - the carpels grow together at the edges and form one ring (poppy), or the central chamber.

c) lysicarpous - the carpels grow together at the edges, forming one chamber or cavity, and a column protrudes from the bottom of the ovary, on which the ovule is located, and then the seeds (cloves).

13. Ovule - a relatively complex formation, consisting of a seed stalk (funicular), bearing a nucellus enclosed in one or two integuments. Depending on the species, from one to many ovules develop on the placenta. The developing ovule initially consists entirely of the nucellus, but soon one or two integumentary layers (integuments) appear with a small opening, a micropyle, at one end (Fig. 6).

Rice. 6. Scheme of the formation of the ovule and embryo sac.

1, 2, 3, 4 - development of the nucellus, isolation and meiosis of the archesporium cell, death of three megaspores; 5, 6, 7, 8 - development from the megaspore (remaining) of the female gametophyte - the embryo sac.

At an early stage of ovule development, a single diploid megasporocyte appears in the nucellus. It divides mitotically, producing four haploid megaspores, usually arranged in a linear tetrad. This completes megasporogenesis. Three megaspores are usually destroyed, and the fourth, furthest from the micropyle, develops into a female gametophyte.

The functional megaspore soon begins to increase due to the nucellus, and its nucleus divides mitotically three times. At the end of the third mitosis, eight daughter nuclei are located in four groups in two groups - near the micropylar end of the megagametophyte, as well as at the opposite, chalazal, end. One nucleus from each group migrates to the center of the eight-nuclear cell; they are called polar. The three nuclei remaining at the micropylar end form the egg apparatus, consisting of an egg and two synergic cells. At the chalazal end, cell membranes are also formed around the nuclei located here, and the so-called antipodal cells arise. The polar nuclei remain in the binuclear central cell. This eight-nuclear, seven-cell structure is the mature female gametophyte called the embryo sac.

Bisexual and unisexual flowers

Flowers are bisexual (with androecium and gynoecium) or unisexual (only with androecium or only with gynoecium). Same-sex flowers can be either on the same plant, like in oak, birch, milkweed, corn (and then the plant as a whole is bisexual), or on different plants, like in poplar, willow, hemp (then we have male and female plants). In this regard, two terms have long existed in the botanical literature - monoecious and dioecious. Since the time of Linnaeus, many botanists have applied these terms to the plants themselves and speak of dioecious and monoecious plants. If both bisexual and unisexual flowers are found on the plant, as in many Compositae, then they are said to be polygamous (from the Greek poly - many and gamos - marriage). However, starting with O. P. de Candoll, S. L. Zndlihor, D. Weptam, and J. D. Hooker, and ending with A. Engler, R. Wettgatein, A. B. Repdl, and J. Hutchinson, many authors use the terms "double" i. "monoecious" only to flowers, not whole plants. The disputes that sometimes arise as to which of these two uses of the terms is more correct are essentially meaningless. Cannabis or willow can just as easily be said to be dioecious or to have dioecious flowers. Depending on the context, one or the other use of these terms may be more convenient, and in no case will this cause misunderstanding.

There is every reason to believe that unisexual flowers arose from bisexual ones, and in unisexual flowers, dioecy is clearly later than monoecious. Since the second half of the last century, numerous studies on the comparative morphology and biology of pollination have led to the conclusion that unisexual flowers arose from bisexual ones as a result of underdevelopment or complete suppression of stamens in some cases, and carpels in others. In the same-sex flowers of many genera and entire families, reduced remains (rudiments) of stamens and carpels (the so-called staminodes and carpellodes) are often preserved. Such residual formations can be seen in the flowers of representatives of various families, including those of the plane tree, some mulberries, nettles and walnuts. The main biological reason for the transition of bisexual flowers to unisexual is more reliable cross-pollination, as pointed out by Charles Darwin.

After reading these lines, the reader may ask the question: is it possible to talk about the field of a flower, because a flower is part of a sporophyte, or asexual generation, and is thus devoid of sex? Some botanists think so, and instead of the terms "male", "female" and "bisexual", they prefer to use the terms "staminate", "pistillate" and "perfect" (perfect in the sense that there are both stamens and carpels). However, most botanists continue to use the terms bisexual and same-sex, male and female, and with good reason. Morphologically, the flower is undoubtedly part of the sporophyte, but functionally it is most directly related to the sexual process.

When we talk about male and female flowers, we mean their role in the preparation of sexual reproduction, and not belonging to the sexual generation (gametophyte). The thing is that the genetic and physiological differentiation between the male and female sexes also passes to the asexual generation, a certain sexualization of the sporophyte occurs. This is especially pronounced in dioecious plants (plants with dioecious flowers). Male and female cannabis plants are genetically and physiologically different, and it can even be said that male cannabis is no less masculine than male animals. With the same reason, the stamen can be considered a male structure, and the carpel - female.

Plant life: in 6 volumes. - M.: Enlightenment. Edited by A. L. Takhtadzhyan, Chief Editor Corresponding Member USSR Academy of Sciences, prof. A.A. Fedorov. 1974 .

See what "Bisexual and unisexual flowers" are in other dictionaries:

Flowers that have only stamens but no pistil(s) or only pistil(s) but no stamens. In the first case, the flowers are called staminate (male), in the second, pistillate (female). In many O. c. not… …

Bisexual flowers, flowers in which there are both stamens and a pistil (or pistils). Among angiosperms, most species have O. c. Wed Single flowers... Great Soviet Encyclopedia

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