A. A distinctive feature of angiosperms is the presence of... and... B. All angiosperms are divided into classes:... and... B. Angiosperms are the most widespread group of plants on Earth, since... D. C In the process of evolution, angiosperms acquired a number of important characters:... D. The female gametophyte in flowering plants is called... E. The male gametophyte in flowering plants is called...

A. The number of petals and sepals is a multiple of four or five B. Fibrous root system B. Tap root system D. The number of sepals and petals is a multiple of three E. Arc or parallel venation E. Reticulate venation G. Two cotyledons 3. One cotyledon

1. Rosehip is a plant of the lily family. 2. Gametophyte is the sexual generation of a plant. 3. Dicotyledonous plants have a fibrous root system, simple leaves with arcuate or parallel veins. 4. In the tropics, the rate of tree growth is determined by the alternation of dry and wet seasons. 5. Many temperate trees lose their leaves every fall, which is why they are called evergreens.

Distinctive features of angiosperms

In terms of time of appearance on Earth, angiosperms (flowering, pistillate) are the youngest and at the same time the most highly organized group of plants. In the process of evolution, representatives of this department appeared later than others, but they very quickly took a dominant position on globe.

The most characteristic distinctive feature of angiosperms is the presence of a peculiar organ - a flower, which is absent in representatives of other plant divisions. This is why angiosperms are often called flowering plants. Their ovule is hidden, it develops inside the pistil, in its ovary, which is why angiosperms are also called pistillates. Pollen in angiosperms is captured not by ovules, as in gymnosperms, but by a special formation - the stigma, which ends at the pistil.

After fertilization of the egg, a seed is formed from the ovule, and the ovary grows into a fruit. Consequently, the seeds of angiosperms develop in fruits, which is why this plant division is called angiosperms.

Angiosperms(Angiospermae), or flowering(Magnoliophyta) - a division of the most advanced higher plants that have flowers. Previously included in the department of seed plants along with gymnosperms. Unlike the latter, the ovules of flowering plants are enclosed in an ovary formed by fused carpels.

The flower is the generative organ of angiosperms. It consists of a peduncle and a receptacle. The latter contains the perianth (simple or double), androecium (collection of stamens) and gynoecium (collection of carpels). Each stamen consists of a thin filament and an expanded anther in which sperm mature. The carpel of flowering plants is represented by a pistil, which consists of a massive ovary and a long style, the apical expanded part of which is called the stigma.

Angiosperms have vegetative organs that provide mechanical support, transport, photosynthesis, gas exchange, and the storage of nutrients, and generative organs involved in sexual reproduction. Internal structure tissues are the most complex of all plants; phloem sieve elements are surrounded by companion cells; Almost all representatives of angiosperms have xylem vessels.

The male gametes contained inside the pollen grains land on the stigma and germinate. Flowering gametophytes are extremely simplified and miniature, which significantly reduces the duration of the reproduction cycle. They are formed as a result minimum quantity mitoses (three in the female gametophyte and two in the male). One of the features of sexual reproduction is double fertilization, when one of the sperm fuses with the egg, forming a zygote, and the second fuses with the polar nuclei, forming the endosperm, which serves as a supply of nutrients. The seeds of flowering plants are enclosed in the fruit (hence their second name - angiosperms).

The first flowering plants appeared at the beginning of the Cretaceous period about 135 million years ago (or even at the end of the Jurassic period). The question of the ancestor of angiosperms currently remains open; the extinct Bennettites are closest to them, however, it is more likely that, together with the Bennettites, the angiosperms separated from one of the groups of seed ferns. The first flowering plants were apparently evergreen trees with primitive flowers lacking petals; Their xylem still had no vessels.

In the middle of the Cretaceous period, in just a few million years, angiosperms conquered the land. One of the most important conditions for the rapid spread of angiosperms was their unusually high evolutionary plasticity. As a result of adaptive radiation caused by environmental and genetic factors (in particular, aneupolydy and polyploidization), a huge amount of various types angiosperms belonging to a wide variety of ecosystems. By the mid-Cretaceous period, most modern families had formed. The evolution of terrestrial mammals, birds and, especially, insects is closely related to flowering plants. The latter play an extremely important role in the evolution of the flower, carrying out pollination: bright color, aroma, edible pollen or nectar are all means of attracting insects.

Flowering plants are distributed throughout the world, from the Arctic to the Antarctic. Their taxonomy is based on the structure of the flower and inflorescence, pollen grains, seeds, and the anatomy of xylem and phloem. Almost 250 thousand species of angiosperms are divided into two classes: dicotyledons and monocotyledons, differing primarily in the number of cotyledons in the embryo, leaf and flower structure.

Flowering plants are one of the key components of the biosphere: they produce organic matter, bind carbon dioxide and release molecular oxygen into the atmosphere; most pasture food chains begin with them. Many flowering plants are used by humans for cooking, building homes, making various household materials, and for medicinal purposes.

Angiosperms - the largest type of plants, which includes more than half of all known species - are characterized by a number of clear, sharply delimiting characteristics. Most characteristic of them is the presence of a pistil formed by one or more carpels (macro- and megasporophylls), fused with their edges, so that in the lower part of the pistil a closed hollow container is formed - the ovary, in which ovules (macro- and megasporangia) develop. After fertilization, the ovary grows into a fruit, inside of which there are seeds (or one seed) developed from the ovules. In addition, angiosperms are characterized by: an eight-core, or derivative of it, embryo sac, double fertilization, triploid endosperm, formed only after fertilization, a stigma at the pistil that catches pollen, and for the vast majority, a more or less typical flower with a perianth. Among the anatomical features, angiosperms are characterized by the presence of true vessels (tracheas), while in gymnosperms only tracheites are developed, and vessels are extremely rare.

Due to the large number common features it is necessary to assume a monophyletic origin of angiosperms from some more primitive group of gymnosperms. The earliest and very fragmentary fossil remains of angiosperms (pollen, wood) are known from the Jurassic geological period. A few reliable remains of angiosperms are also known from the Lower Cretaceous deposits, and in the deposits of the mid-Cretaceous period they are found immediately in large quantities and in a considerable variety of forms, which all belong to many different living families and even genera.

Various groups of lower plants in the system were indicated as the putative ancestors of angiosperms - keithoniaceae, seed ferns, bennettites, and oppressed ferns. Caytoniaceae had an ovary and a stigma, but in them the ovary was formed differently than in angiosperms; they did not even have the semblance of flowers, their sporophylls are simple and, probably, they represent a blind branch of evolution. Bennettites had bisexual peculiar “flowers”, but did not have pistils, and their seeds were only hidden between sterile scales, and were not inside the fruits formed by megasporophylls. Seed ferns had no flowers and no angiosperms.

The theory of the origin of angiosperms from oppressive plants suggests that the most primitive angiosperms had small unisexual flowers without a perianth or with an inconspicuous perianth. But for a number of reasons, large, bisexual flowers are currently considered more primitive flowers. Therefore, it can be assumed that the ancestors of modern angiosperms were some extinct, very primitive gymnosperms with bisexual cone-type flowers (strobili), in which free (not fused with each other) tepals of a homogeneous perianth, microsporophylls ( stamens) and megasporophylls (carpels). In the gymnosperm system, this group must have stood somewhere between the seed ferns and the more specialized Bennettites and cycads.

Angiosperm undoubtedly represented a great advantage in the sense of protecting ovules and developing seeds from any adverse external influences, and primarily from dry air. But it is still difficult to explain by angiosperm alone the rapid powerful development of angiosperms and their displacement of the archegonial plants that previously dominated the earth. Russian botanist M.I. Golenkin expressed (in 1927) an interesting hypothesis about the reasons for the victory of angiosperms in the struggle for existence. He suggests that in the middle of the Cretaceous period, for some general cosmogonic reasons, a sharp change in lighting and air humidity occurred throughout the Earth. Thick clouds that previously constantly shrouded the Earth dissipated and gave access to bright sun rays, and therefore the dryness of the air sharply increased. The vast majority of higher archegonial plants of that time, not adapted and unable to adapt to bright light and dry air, began to die out or sharply reduced their areas of distribution (except for conifers, the most xerophytic).

On the contrary, angiosperms, which previously had a very limited distribution and were represented by a small number of forms, have developed the ability to tolerate bright sunlight and dry air well. This circumstance, as well as their extreme evolutionary plasticity, the ability to produce a wide variety of adaptations to various external conditions and determined the rapid, victorious spread of angiosperms throughout the Earth and the displacement of previously dominant groups of higher archegonial plants.

The victory of the angiosperms led to changes in the animal population of the Earth; it should have especially affected the rapid evolution of insects, mammals and birds that feed on insects, then predators and frugivores. In turn, in the angiosperms, countless adaptive changes in form, chemistry and function gradually arose in the process of evolution in connection with their complex and diverse relationships with the animal world. The victory of the angiosperms was a turning point, a profound revolution in the destinies of the entire animal population of the Earth.

Various assumptions have been made regarding the location of the original origin of angiosperms. Some believe that they first appeared on a hypothetical tropical continent located between America, Asia and Australia and subsequently sank into the waters Pacific Ocean. Others consider the region of the modern Arctic land to be their cradle, while others consider the mountains of the subtropical and warm temperate zone of the northern hemisphere. Most botanists now believe that the primordial angiosperms were woody plants with short trunks that branched monopodially into a few thick branches. From them larger sympodially branching trees with numerous thick and thin branches have already developed. From tree forms, at different times and in different phylogenetic lines, shrubs, subshrubs and herbaceous forms developed, first perennials, then in various genera due to specific climate and habitat conditions - biennials and annuals.

Due to the great plasticity of angiosperms, in the process of evolution they have developed a huge variety of vegetative organs, especially in leaves, numerous metamorphoses, as well as endless diversity in flowers and fruits. The complexity and diversity of chemical composition and physiological reactions is also very characteristic of them.

The evolution of the flower, on the structure of which the taxonomy of angiosperms is mainly based, speaking in general and schematically, proceeded from flowers with a long receptacle (like a cone) from bisexual, actinomorphic with a spiral arrangement of free (unfused) and not fixed in the number of members, with the superior ovary and numerous ovules - to flowers that are cyclic, zygomorphic, dioecious, with a strictly fixed number of more or less fused members on a flat receptacle, with a lower single-locular ovary and few or one ovule. This evolution of the angiosperm flower occurred in their different evolutionary series independently of each other.

Angiosperms are widespread almost to the extreme limits of vegetation and determine the character of landscapes everywhere except coniferous forests, peat bogs and some types of tundra.

In human life and economic activity, the role of angiosperms is immeasurably greater than that of other groups of plants. Food, clothing, fodder for livestock, aromatics, narcotics, medicinal substances, tannins, rubber and gutta-percha, cork and much more are obtained from angiosperms; material for housing, fuel, ornamental materials, and paper are also largely supplied by angiosperms.

Angiosperms are divided into two classes - dicotyledons and monocotyledons. Dicotyledons are characterized by: two cotyledons in the seed, open vascular bundles (with cambium), preservation of the main root throughout life (in individuals born from seeds), pinnate and reticulate venation of leaves, 5-4-2-membered type of flowers. Monocots are characterized by opposite characters: one cotyledon per seed, closed vascular bundles (without cambium), early death of the main root and development of an adventitious root system, parallel or arcuate venation, three-membered type of flowers. Individual characteristics of one group can also be found in representatives of another group, so the entire set of characteristics is important.

The department of flowering plants includes two classes: dicotyledons and monocotyledons.

Most essential feature- structure of the seed. But one sign is not enough to determine whether a plant belongs to a particular class. It is necessary to know all the signs of this plant.

The dicotyledonous class is the most numerous; it includes about 80% of angiosperm species, which are grouped into 325 families. Families of flowering plants are classified mainly on the basis of the structure of the flower and fruit.

The monocot class includes about 25% of flowering plants. These are mostly herbs. Only a few families contain arboreal forms, and even those live mainly in the tropics. The most simply organized group of monocots lives in reservoirs and swamps. This includes arrowhead, chastuha, and pondweed. But among monocots there are many species that have reached a high level of organization, for example cereals.

A typical family of the monocot class is the Liliaceae family. Among the plants of this family, perennial herbs predominate, with well-developed rhizomes or bulbs, lanceolate or linear shape leaves with arcuate or parallel veins. Many of the lilies are ephemeral or ephemeroid - have a short growing season.

Lily flowers are large, of various colors, solitary or collected in a raceme. The perianth is simple, corolla-shaped, consists of six fused or free leaflets arranged in two circles. There are six stamens, also arranged in two circles, one pistil (of three fused carpels). The fruit of lilies is a berry or capsule.

Among the lilies there are many ornamental plants (lilies, tulips), food plants (onions, garlic), medicinal plants (lily of the valley, aloe, rosemary), etc.

The largest family in the monocot class is the cereals. There are over 10 thousand types of cereals. They are distributed throughout the globe. This is a prosperous family that has reached a high level of organization.

Almost all cereals are herbaceous perennials, less often annuals. They form the basis of the herbage of many plant communities: meadows, steppes, etc. Bamboo is known among woody grasses. Plants of this family can be recognized by their hollow stem - a straw with nodes and internodes. The knots are filled with loose tissue. Cereal stems grow in length as a result of cell division in internodes. This type of growth is called intercalary.

Cereals can also be recognized by their leaves: they are narrow, long, and have parallel veins. The leaf has a wide base in the form of a tube - a vagina. It protects the delicate cells of the internodes from damage, due to the division of which the stem grows.

Cereals are also characterized by a fibrous root system. Thus, cereals can be distinguished from plants of other families by the structural features of their vegetative organs (leaves, roots and stems).

The flowers of cereals are small, dim, and collected in spikelets. From many spikelets, inflorescences are formed: a complex spike, a panicle, etc. Each spikelet has from 1 to 10 or more flowers. The cereal flower has three stamens and one pistil, but it does not have a calyx or corolla. Most cereals are wind-pollinated plants. Cereals have a typical fruit for this family - a grain, rich in proteins and starch.

Cereals reproduce by seeds, as well as vegetatively using rhizomes and rooted shoots.

Cereals form the basis of nutrition for humans and farm animals. These include the most important forage and food crops. Wild cereals constitute the main feed for livestock. In the tropics, bamboo and sugar cane form thickets. Sugar cane is specially grown on plantations and sugar, rum, alcohol and molasses are obtained from it. Cereals are also used for paper production, textile, chemical and construction industries.

In the modern era, when environmental conditions are deteriorating, some species of cereals have become endangered. 23 species of grasses are listed in the Red Book: stone-loving feather grass, finely pubescent feather grass, evasive feather grass, multi-colored bluegrass, wheatgrass, leafy feather grass, etc.

Monocots(lat. Liliopsida, lat. Monocotyledones, English monocots) - a class of angiosperms, or flowering plants, the largest family of which is the Orchids, distinguished by extremely complex, beautiful flowers. In second place in terms of the number of species is the economically very important family Cereals.

The traditional Latin name for this group of plants is Monocotyledones, although recently, for example in the Cronquist system ( Cronquist) their official name is Liliopsida (liliopsids). Because monocots-- a group of rank higher than family, the choice of name is not limited in any way. Article 16 of the ICBN allows both a descriptive name and a name derived from the type gender of the group.

Traditional name monocots, Monocotyledones or Monocotyledoneae, comes from the fact that the embryos of most members of the group have only one cotyledon, in contrast to dicotyledons, which usually have two. From a diagnostic point of view, determining the number of cotyledons is neither an easily accessible method nor a reliable distinguishing characteristic of a plant. The distinction between monocots and dicotyledons was first used in plant taxonomy at the beginning of the 18th century by the English naturalist J. Ray.

However, monocots have more obvious distinctive features. The embryonic root usually soon stops growing and is replaced by adventitious roots. Stem vascular bundles are closed, scattered throughout the entire cross section of the stem; There is no cambium, so thickening of the stems like dicotyledons or gymnosperms is not observed. Stems rarely branch. The leaves are mostly stalk-embracing, always without stipules, usually narrow and arcuate. Flowers are usually constructed according to the triple type: a perianth of two three-membered circles, stamens also 3 + 3, carpels 3, less often, instead of the number 3, the numbers 2 or 4 are observed in the flower.

Monocots are a monophyletic group that arose at the dawn of the history of the development of angiosperms. The oldest fossil plants that can be classified as monocots date back to the beginning of the Cretaceous period.

System scientific classification APG II, developed by the APG group Angiosperm Phylogeny Group), defines monocots as one of the two largest groups among angiosperms. The second group is “eudicots” ( eudicots), according to established tradition, is sometimes called “paleodicots” ( palaeodicots). Among monocots, ten orders and two families are distinguished, which have not yet been definitively assigned to any of the orders. These orders are distributed as follows:

Major monocots

Family Petrosaviaceae ( Petrosaviaceae) / en:Petrosaviaceae

· Order Aeroceae ( Acorales) / en: Acorales

· Order Partiscolates ( Alismatales) / en:Alismatales

· Order Asparagusaceae ( Asparagales) / en:Asparagales

· Order Dioscoreaceae ( Dioscoreales) / en:Dioscoreales

· Order Liliaceae ( Liliales) / en:Liliales

· Order Pandanaceae ( Pandanales) / en:Pandanales

· Family ( Dasypogonaceae) / en:Dasypogonaceae

Order Palmaceae ( Arecales) / en: Arecales

· Order Commelinaceae ( Commelinales) / en:Commelinales

· Order Ceramaceae ( Poales) / en:Poales

· Order Gingeraceae ( Zingiberales) / en:Zingiberales

A more traditional classification is the system of Cronquist (1981), according to which all monocots were divided into five subclasses with the following orders:

Alismatids ( Alismatidae)

Order Alismatales

· Order Hydrocharitales

Order Najadales

· Order Triuridales

Arecides ( Arecidae)

· Order of Palm Trees (Arecales)

Order Cyclanthales

Order Pandanaceae (Pandanales)

· Order Arales

Commelinoceae ( Commelinidae)

Order Commelinales

Order Eriocaulales

Order Restiales

· Order Juncales (Juncales)

Order Sedges (Cyperales)

Order Hydatellales

Order Cattails (Typhales)

Ginger ( Zingiberidae)

Order Bromeliads (Bromeliales)

· Order Zingiberales

Liliids ( Liliidae)

· Order Liliales

Order Orchidaceae (Orchidales)

The class Dicotyledons belongs to the department Tsvetkov (Anthophyta), or Angiosperms ( Magnoliophyta, or Angiospermae) plants. This class is much more diverse and larger in volume than the second class from this department -- Monocots (Monocotiledonae or Liliopsida). From total number Dicotyledons account for about 80% of flowering plants.

Class Dicotyledons characterized the presence of the following characteristics that distinguish it from Monocots:

1. Embryo with two cotyledons.

2. The main root is well developed and preserved throughout life, therefore the taproot (less often fibrous) root system predominates.

3. The stem is capable of secondary thickening due to the presence of cambium; conductive bundles are open.

4. The leaves are varied in shape and dissection, have palmate or pinnate venation, and the shape of the edge of the leaf blade can be different.

5. Flowers are acyclic, semicyclic and cyclic. The number of members of each circle is a multiple of 5, rarely 2, even less often 3.

The class Dicotyledons include about 200,000 species, 10,000 births, about 300 families(depending on the accepted classification). These are herbaceous and woody plants.

Taxonomy Since the 18th century, many botanists, both domestic and foreign, have been studying flowering plants. All of them made an invaluable contribution to the modern construction of the phylogenetic (natural) system of flowering plants. However, there is still no generally accepted system for classifying angiosperms.

The most controversial question is which groups of angiosperms are closest to the ancient ancestral forms. In the systems of famous botanists and phylogeneticists A. Engler and R. Wettstein, the most primitive groups are taken to be families with one-integument and one-integument, inconspicuous, anemophilous flowers (willow, birch, etc.). In more modern systems, families with well-developed polynomial, separate-leaved, entomophilous flowers, the so-called polycarpids (families Magnoliaceae, ranunculaceae etc.). Families with single-covered flowers are considered secondary simplified. Such systems are the systems of botanists N. A. Bush, A. A. Grossheim, A. L. Taxadzhyan, Hutchinson (England), etc. One of the latest systems that takes into account greatest number signs is the system of A. L. Takhtadzhyan (1970).

According to A.L. Takhtadzhyan, the class Dicotyledons includes 7 subclasses: Magnoliidae, Ranunculidae, Hamamelididae, Caryophyllidae, Dilleniidae, Rosidae and Asteridae. Within each subclass, its families are combined into orders. The entire class Dicotyledons includes 71 orders. The former cover the most primitive families, the latter - phylogenetically more advanced.

Basic orders Dicotyledonous class:

Subclass Choripetalae: order Magnoliales, order Ranunculales, order Papaverales, order Capparales, order Rosales, order Fabales, order Malvales, order Geraniums (Geraniales), order Terebinthales, order Umbellales, order Centrospermae, order Polygonales, order Fagales.

Subclass Sympetalae: order Scrophulariales, order Cucurbitales, order Asterales.

Literature

· Plant life. In 6 volumes. T. 6. Flowering plants. / Ed. A.L. Takhtajyan. - M.: Education, 1982. - 543 p., ill., 34 p. ill.

· Forest encyclopedia: In 2 volumes, volume 2/Ch. ed. Vorobyov G.I.; Ed. Col.: Anuchin N.A., Atrokhin V.G., Vinogradov V.N. and others - M.: Sov. Encyclopedia, 1986.-631 p., ill.

It is perhaps simply impossible to list all angiosperms. And it will be quite difficult to name the species that are most important in nature and human life. After all, these plants have long acquired great practical importance, and their representatives are known as food, industrial, ornamental and fodder crops. What characteristics does the Angiosperms department have? The general characteristics and significance of these plants will be discussed in our article. So let's get started.

Biology: department Angiosperms

All seed plants have a number of structural features that make them dominant on Earth. All of them arose in the process of evolution as a result of adaptation of organisms to changing conditions environment. The Angiosperms department, according to taxonomy, currently numbers more than two hundred and fifty thousand species. While their predecessors - the Gymnosperms department - are only eight hundred.

The main characteristics of the Angiosperms department:

Presence of a flower;

Formation of the fetus;

Development of the embryo inside the seed germ;

Double fertilization;

The presence of a seed surrounded by a pericarp.

Taken together, all these characteristics determine the advantages thanks to which representatives of the Angiosperms department were able to spread across the planet, mastering the conditions of different climatic zones and zones.

Holo- and Angiosperms: similarities and differences

But let's go back to basics. All seed plants are grouped into two divisions: Holosperms and Angiosperms. Specimens of the first systematic group are mainly represented by plants with a predominant woody life form, with a taproot system. The foliage is represented by thin leaves - needles. Thanks to them and the presence of resin passages, which prevent the process of excessive evaporation, these plants remain evergreen throughout all seasons. But the main feature of this section is the absence of flowers, and therefore fruits. Their seeds are located openly on the scales of the cones; they are not protected by anything. Therefore, the likelihood that they will germinate is not so great, since there are not enough nutrients for this.

The Angiosperms department unites plants that produce a flower and, accordingly, a fruit. Inside this, the seeds are reliably protected from any adverse environmental influences, warmed and provided with the necessary supply of nutrients.

Advantages

Angiosperms are a department of higher plants that have undoubted advantages. In addition to protecting the seed and creating favorable conditions for the development of the embryo, they also include the adaptation of seeds to dissemination. For example, maple fruits have special blades, thanks to which they are easily carried by the wind. And the poppy capsule itself cracks when ripe, spreading the seeds. The tasty fruits of fruit trees are distributed by animals that eat them and excrete undigested food debris over some distance. Gymnosperms do not have fruits. Their seeds are found in cones, which are not fruits at all. These are modified shoots that serve as a place for the formation and development of seeds. They have neither the supply of substances necessary for the development of the embryo, nor the devices for the dissemination of seeds and the settlement of plants.

Classification Features

The Angiosperms department is divided into two classes. The main feature of this division is the number of cotyledons in the seed embryo. The families of the Angiosperm department - Mono- and Dicotyledonous - have other characteristic features.

Division Angiosperms: general characteristics of Monocots

The Angiosperms department, class Monocots, includes more than 600 thousand species. The life forms in which it is represented are mainly grasses. In addition to one cotyledon in the seed embryo, representatives of this class are characterized by the presence simple leaves with parallel, and less often - with arc or pinnate type of venation. The cambium is the side of the stem and is absent in monocots. For this reason, they do not form powerful trunks. The monocot class includes several smaller systematic units - families.

Family Cereals

A characteristic feature of all cereal plants is the presence of a hollow stem. It's called a straw. Such a stem is formed due to the fact that the educational tissue is located in the nodes. Representatives of the family are wheat, rye, barley, corn, wheatgrass and other plants. One more characteristic feature cereal is an unusual flower in which the corolla is transformed into scales. The number of stamens varies from three to six, sometimes there are more. Such unusual flowers are collected in inflorescences - a panicle or a complex spike. The ovary is formed by two carpels. The sessile leaves of cereals, without petioles, consist of three parts: the sheath, the ligule and the plate itself.

All cereals are very valuable food crops. Most of them are used for making cereals, flour, and baking different types of bread. One of the representatives of cereal plants is sugar cane.

and Liliaceae

A characteristic feature of representatives of this family is the presence of an underground modification of the shoot - a bulb. It contains a supply of nutrients, thanks to which these plants remain viable throughout the entire unfavorable period. Chest and leeks are typical members of the family. But lily plants also form bulbs and sometimes rhizomes. Tulip, woodland, hyacinth, lily of the valley, hazel grouse... These plants are the first sign of spring. Before the onset of the dry period, they have time to grow and bloom. Then their aboveground part dies off, and the bulb underground remains viable throughout the entire period of existence of representatives of the Liliaceae family.

Class Dicotyledons: characteristic features

We continue to consider the Angiosperms department, the classes of which are well known to everyone. By the way, Dicotyledons are the most numerous of them. They have two cotyledons in the seed embryo, a taproot system, simple or compound leaves with pinnate, palmate or arcuate venation. In the stem of dicotyledons there is a cambium - a lateral educational tissue. It determines their growth in thickness. Therefore, such plants are characterized by the following life forms: herbs, shrubs and trees. The families that belong to this class are numerous. Therefore, we will consider only a few of them.

Family Rosaceae

These are as many as three thousand species of fruit crops. Apple, pear, apricot, plum, quince, cherry, peach - these are just some of their representatives. They can be easily distinguished from others by their characteristic features: a five-membered flower with many stamens and a double perianth. Inflorescences - raceme or corymb. And the main types of fruits are drupes and apples. These crops are eaten and preserved by humans, because they have valuable taste qualities.

Family Legumes

This systematic unit has another name - Moths. These plants wear it due to the structure of the flower, the petals of which different shapes and outwardly resemble a butterfly with folded wings. And they owe their first name to the type of fruit - the bean. It is dry and opens with two flaps along the seam. Each of them contains seeds. The family includes medicinal, oilseed, fodder, food and ornamental plants. Their typical representatives are soybeans, peas, beans, clover, licorice, acacia, peanuts and other plants.

Family Solanaceae

The most famous crops representing the Solanaceae family, in addition to the plant of the same name, are potatoes, tomato, eggplant, sweet peppers and tobacco. Their flowers are also five-membered, but the sepals and petals are fused, and the fruit types are berry or capsule. The greatest economic importance among them are vegetables and industrial crops, which include tobacco and shag. But the nightshade dope, henbane and belladonna are poisonous plants that can cause severe poisoning of the human body.

Brassica family

This systematic unit, so named because of its most typical representative, is also known as Cruciferous. The thing is that the flower has four petals located opposite each other. Outwardly, it resembles the shape of a cross. In addition to different types of cabbage, these include relis, turnip, radish, horseradish, mustard and rapeseed.

The importance of angiosperms in nature and human life

The Department of Flowering (Angiosperms) plants is, first of all, an integral part of almost all communities, a link in the food chain, the basis of green organic mass.

Among food crops, representatives of the families Cereals, Legumes, Rosaceae, and Cruciferae are of particular importance. Many plants are used to make medicines. These are licorice, marshmallow, valerian, tansy, St. John's wort, celandine. The fruits of flowering plants are rich in vitamins, especially C. These are strawberries, blueberries, viburnum, rose hips, garlic and onions.

No cultural landscape can be imagined without decorative flowering plants, among which the most common are roses, daffodils, dahlias, asters, petunias, daisies, lilies, tulips and others.

Many crops are honey-bearing. Their flowers have a pleasant aroma and sweet nectar, which attracts pollinated insects. Among such plants one can name different types of acacias, linden, and buckwheat.

But humans still have to fight with some flowering plants. These are malicious weeds: wheatgrass, quinoa, sow thistle, barnyard grass and others. There are also poisonous species. Yes, when misuse Celandine can cause severe convulsions, and Datura can cause hallucinations, lack of consciousness control and delirium.

The characteristics of the department Angiosperms indicate their high organization, which allowed them to take a leading position in the system flora.

angiosperms are characterized by a special generative organ - a flower, which has a complex organization and is a modified bisexual strobilus, homologous to the strobili of gymnosperms;

the main unit of dispersal is the seed (as in gymnosperms);

during pollination, various animals (insects, birds, bats, etc.), as well as air and water flows, are “used”;

there is a maximum reduction of gametophytes, while there are no archegonia and antheridia;

the process of sexual reproduction is accompanied by double fertilization, as a result of which a diploid zygote is formed and triploid nutritional tissue is formed - endosperm;

there is a fruit, which allows the use of various agents when dispersing seeds;

the conducting system is well formed; in the vast majority of cases, the xylem is represented by vessels rather than tracheids; phloem sieve elements are equipped with companion cells;

the photosynthetic apparatus is resistant to direct rays of light, which makes it possible to populate open, well-lit places;

there is a wide variety of life forms - there are woody, semi-woody species, grasses;

some are characterized by rapid development and growth processes (annual forms);

Unlike other groups, flowering plants can form complex multi-layered communities.

Thus, flowering plants are the most highly organized group in the plant world, possessing significant evolutionary plasticity and having great potential for adaptation to various environmental conditions.

	Dicotyledons	Monocots
The structure of the embryo	The embryo has two cotyledons	The embryo has one cotyledon
Leaf structure	The leaves are simple and compound. Venation is usually reticulate	The leaves are simple. Venation parallel or arcuate
Root system	Usually rod-shaped	Usually fibrous
Life forms	Woody, semi-woody and herbaceous forms
Flowers	Usually five-membered, less often four-membered	Usually three-membered, less often four-term

Mosses are classified as higher spore plants because mosses for the first time in the course of evolution appear organs: leaves, stems. But mosses do not have roots; the function of roots is performed by rhizoids.

Ferns are more highly organized plants, since they have real roots for the first time in the course of evolution. There are leaves (fronds), a stem, and they reproduce using spores.

Flowering plants (angiosperms) are the most highly organized group of plants, since in the course of evolution they have a flower - an organ of seed reproduction, a fruit in which the seed is covered with a pericarp.

The appearance of terrestrial, or higher, plants marked the beginning of a new era in the life of our planet. The development of land by plants was accompanied by the appearance of new, terrestrial forms of animals; The conjugate evolution of plants and animals led to a colossal diversity of life on earth and changed its appearance. The first reliable land plants, known only from spores, date from the beginning of the Silurian period. Land plants have been described from Upper Silurian and Lower Devonian deposits based on preserved macroremains or organ imprints. These first higher plants known to us are united in the group of rhinophytes. Despite the anatomical and morphological simplicity of the structure, these were already typical terrestrial plants. This is evidenced by the presence of cutinized epidermis with stomata, a developed water-conducting system consisting of tracheids, and the presence of multicellular sporangia with cutinized spores. Consequently, it can be assumed that the process of colonization of land by plants began much earlier - in the Cambrian or Ordovician. There were apparently several prerequisites for the appearance of land plants. Firstly, the independent course of evolution of the plant world prepared the emergence of new, more advanced forms. Secondly, due to photosynthesis of seaweed, the amount of oxygen in the earth's atmosphere increased; by the beginning of the Silurian period it had reached such a concentration that life on land was possible. Thirdly, at the beginning of the Paleozoic era, major mountain-building processes took place over vast areas of the earth, as a result of which the Scandinavian Mountains, Tien Shan Mountains, and Sayan Mountains arose. This caused the shallowing of many seas and the gradual appearance of land in place of former small bodies of water. If previously the algae that inhabited the littoral zone found themselves out of water only during certain short-term periods of their lives, then as the seas became shallower they moved on to a longer stay on land. This was obviously accompanied by massive death of algae; Only those few plants survived that were able to withstand the new living conditions. In the course of a long evolutionary process, new species arose, gradually forming typical land plants. Unfortunately, the paleontological record has not preserved intermediate forms. The new air-terrestrial habitat turned out to be extremely contradictory, fundamentally different from the original aquatic one. First of all, it was characterized by increased solar radiation, moisture deficiency and complex contrasts of the two-phase air-ground environment. It is quite possible to assume that in some transitional forms, in the process of metabolism, cutin could be produced, which was deposited on the surface of plants. This was the first stage in the formation of the epidermis. Excessive release of cutin inevitably led to the death of plants, since a continuous film of cutin interfered with gas exchange. Only those plants that secreted a moderate amount of cutin were able to form a complex specialized tissue - the epidermis with stomata, capable of both protecting the plant from drying out and carrying out gas exchange. Thus, the epidermis should be considered the most important tissue of land plants, without which the development of land is impossible. However, the emergence of the epidermis deprived land plants of the ability to absorb water over their entire surface, as occurs in algae. In the very first land plants, which were still small in size, water absorption was carried out with the help of rhizoids - unicellular or multicellular single-row threads. However, as the body size increased, the process of formation of complex specialized organs - roots with root hairs - took place. Apparently, the formation of roots, which began in the Upper Devonian period, occurred in different ways in different systematic groups of plants. Active absorption of water by rhizoids and roots stimulated the emergence and improvement of water-conducting tissue - xylem.

Division angiosperms, or flowering plants

Angiosperms (Angiospermae), or flowering plants (Anthephyta), according to the time of their appearance on Earth, are the youngest and at the same time the most highly organized group of plants. In the process of evolution, representatives of this department appeared later than others, but very quickly took a dominant position on the globe and supplanted many groups of plants that had previously appeared on Earth. Angiosperms began their victorious spread across the Earth in the Cretaceous period, when some groups of plants were already fully formed, while others were partially or completely extinct. The most characteristic distinctive feature of angiosperms is the presence of a peculiar organ - a flower, which is absent in other plants. This is why angiosperms are also called flowering plants. Their ovule is hidden, it develops inside the pistil, in its ovary, which is why angiosperms are also called pistillates. Pollen in angiosperms is captured not by ovules, as in gymnosperms, but by a special formation - the stigma, which ends at the pistil of a flower.

After fertilization of the egg, a seed is formed from the ovule, and the ovary grows into a fruit. Consequently, the seeds of angiosperms develop in fruits, which is why this plant division is called angiosperms.

In angiosperms, as well as in previous plant divisions, there is an alternation of two generations. Like most higher plants, the most developed and dominant in them is the asexual generation - the sporophyte, while the sexual generation in angiosperms is reduced even more than in gymnosperms.

Angiosperms are also characterized by the presence of double fertilization, which is absent in representatives of other divisions of the plant world. As a result of double fertilization, 2 zygotes are formed. One of them subsequently gives rise to the embryo, and the other to the endosperm - the nourishing tissue of the embryo. The endosperm of angiosperms, therefore, is a hybrid tissue that combines the hereditary characteristics of the maternal and paternal organism, while in gymnosperms the primary endosperm develops as a result of the germination of a megaspore, i.e., before the fertilization process and is haploid. The zygote that gives rise to the endosperm of angiosperms is triploid, since its formation involves 3 cells with a haploid number of chromosomes. The zygote that gives rise to the seed embryo (fertilized egg) is diploid.

The presence of double fertilization in all representatives of angiosperms is one of the proofs of their single, monophylithic origin.

Angiosperms are also the most plastic plants; they have exceptional adaptability to the most varied natural and historical conditions of the Earth; their representatives have a very wide geographical distribution; they grow in extremely diverse climatic conditions. As they are more adapted to environmental conditions, angiosperms are distinguished by a wide variety of forms of vegetative and reproductive organs - roots, leaves, flowers, fruits, seeds. They have a more complex and more advanced anatomical structure than representatives of the previously considered plant departments. The elements of the conductive system ensure the fastest movement of water and plastic substances throughout the plant, which contributes to a more energetic metabolism. They have well-developed true vessels - tracheae, and not tracheids, like gymnosperms (which is why angiosperms are often called vascular plants).

Angiosperms are infinitely diverse in size. Among them, very small plants are known - a few centimeters in size (duckweed) and giant plants reaching a height of more than 100 m (eucalyptus).