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A distinctive feature of angiosperms is the presence. Progressive features of angiosperms. The most important distinguishing features

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

The most characteristic distinguishing feature of angiosperms is the presence in them of a peculiar organ - a flower, which is absent in representatives of other plant divisions. Therefore, angiosperms are also more often called flowering plants. Their ovule is hidden, it develops inside the pistil, in its ovary, therefore angiosperms are called otherwise pistillate. Pollen in angiosperms is not captured by the ovules, as in gymnosperms, but by a special formation - the stigma, which ends in the pistil. After fertilization of the egg, a seed is formed from the ovule, and the ovary grows into a fetus. Therefore, seeds in angiosperms develop in fruits, therefore this department of plants is called angiosperms.

Angiospermae (Angiospermae), or flowering (Magnoliophyta) - a department of the most perfect higher plants that have a flower. Previously, they were included in the division of seed plants together with gymnosperms. In contrast to the latter, ovules of flowering plants are enclosed in an ovary formed by accrete carpels.

The flower is the generative organ of angiosperms. It consists of a peduncle and a receptacle. On the latter, there is a perianth (simple or double), androecium (a set of stamens) and a gynoecium (a set 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 column, the apical expanded part of which is called the stigma.

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

The male gametes contained inside the pollen grains enter the stigma and germinate. Flowering gametophytes are extremely simplified and miniature, which significantly reduces the duration of the breeding cycle. They are formed as a result of the minimum number of 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 other with the polar nuclei, forming the endosperm, which serves as a supply of nutrients. The seeds of flowering plants are enclosed in a 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 closest to them are the extinct bennettites, 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 devoid of petals; their xylem still had no vessels.

In the middle of the Cretaceous, in just a few million years, the conquest of land by angiosperms takes place. 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, aneupolydia and polyploidization), a huge amount of different types angiosperms included in a wide variety of ecosystems. By the middle of the Cretaceous period, most modern families were 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 found all over the world, from the Arctic to the Antarctic. Their taxonomy is based on the structure of the flower and inflorescence, pollen grains, seed, anatomy of the xylem and phloem. Almost 250 thousand species of angiosperms are divided into two classes: dicotyledonous and monocotyledonous, differing primarily in the number of cotyledons in embryos, 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 of the pasture food chains begin with them. Many flowering plants are used by humans for cooking, building houses, making various household materials, and for medical purposes.

Angiosperms, the largest type of plants, to which more than half of all known species belong, are characterized by a number of clear, sharply demarcated characters. Most characteristic of them is the presence of a pistil formed by one or several carpels (macro- and megasporophylls), fused with their edges, so that a closed hollow container is formed in the lower part of the pistil - an ovary in which ovules (macro- and megasporangia) develop. After fertilization, the ovary grows into a fruit, inside which there are seeds developed from the ovules (or one seed). In addition, angiosperms are characterized by: an eight-core, or a derivative of it, an embryonic sac, double fertilization, a tripled 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. Of the anatomical signs, angiosperms are characterized by the presence of real vessels (trachea), while gymnosperms have developed only tracheitis, and vessels are extremely rare.

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

As the alleged ancestors of angiosperms, various groups of lower plants in the system were indicated - keytonia, seed ferns, bennettites, oppressive ones. The Keytoniaceae had an ovary, a stigma, but their ovary was formed differently than that of angiosperms; they did not even have the likeness of flowers, their sporophylls are simple and, probably, they represent a blind branch of evolution. The Bennettites had bisexual peculiar "flowers", but there were no pistils, and their seeds were only hidden between sterile scales, and were not inside the fruits formed by megasporophylls. The seed ferns had no flowers, no angiosperms.

The theory of the origin of angiosperms from oppression suggests that the most primitive angiosperms had small unisexual flowers without a perianth or with a nondescript 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 kind of extinct, very primitive gymnosperms with bisexual flowers such as cones (strobilae), in which free (non-accrete with each other) leaves of a uniform perianth, microsporophylls ( stamens) and megasporophylls (carpels). In the gymnosperm system, this group had to stand somewhere between the seed ferns and the more specialized bennettites and cycads.

The angiosperms undoubtedly represented a great advantage in the sense of protecting the ovules and developing seeds from any unfavorable external influences, and primarily from dry air. But angiosperms alone are still difficult to explain 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. The thick clouds that had previously enveloped the Earth permanently scattered and gave access to bright sunlight, and therefore, the dryness of the air increased sharply. 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 ones).

On the contrary, angiosperms, which had previously had a very limited distribution and representation in a small number of forms, developed the ability to tolerate bright sunlight and dry air. This circumstance, as well as their extraordinary evolutionary plasticity, their ability to develop a variety of adaptations to various external conditions, led to the rapid victorious spread of angiosperms throughout the Earth and the displacement of the previously dominant groups of higher archegonial plants.

The victory of the angiosperms brought about changes in the animal population of the Earth; especially it should have affected the rapid evolution of insects, mammals and birds that feed on insects, then predatory and fruit-eating. In turn, in the process of evolution, the angiosperms also gradually developed innumerable adaptive changes in form, chemistry and functions in connection with their complex and varied relationships with the animal world. The victory of the angiosperms was a turning point, a deep revolution in the fate of the entire animal population of the Earth.

On the question of the place of the initial origin of angiosperms, various assumptions were made. Some believe that they first appeared on a hypothetical tropical continent located between America, Asia and Australia and subsequently plunged into the waters. The Pacific... Others consider the cradle of their area of the modern Arctic land, others - the mountains of the subtropical and moderately warm zone of the northern hemisphere. Most botanists now believe that the primary angiosperms were woody plants with low trunks, monopodially branched into a few thick branches. They have already developed larger sympodially branching trees with numerous thick and thin branches. Shrubs, semi-shrubs and herbaceous forms, at first perennial, then in different genera due to the specific conditions of climate and habitat - biennials and annuals, developed from arboreal forms at different times and in different phylogenetic lines.

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

The evolution of the flower, on the structure of which the taxonomy of angiosperms is mainly based, generally speaking and schematically, proceeded in them from flowers with a long receptacle (like a cone) from bisexual, actinomorphic with a spiral arrangement of free (non-accrete) and not fixed in the number of members, with upper ovary and numerous ovules - to cyclical, zygomorphic, dioecious flowers, with a strictly fixed number of more or less fused members on a flat receptacle, with a lower unilocular ovary and few or one ovule. This evolution of the flower of angiosperms took place in different evolutionary series of them independently of each other.

Angiosperms are widespread almost to the extreme limits of vegetation and determine the nature of landscapes everywhere, except for 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, aromatic, narcotic, medicinal, tannins, rubber and gutta-percha, cork and much more are obtained from angiosperms; materials for dwellings, fuels, ornamental materials, paper are also largely supplied by angiosperms.

Angiosperms are divided into two classes - dicotyledonous and monocotyledonous. Dicotyledons are characterized by: two cotyledons in the seed, open vascular bundles (with cambium), preservation throughout life of the main root (in individuals born from seeds), pinnate and reticulate leaf venation, 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 the adventitious root system, parallel or arcuate venation, three-membered type of flowers. Individual signs of one group can also be found in representatives of another group, therefore the whole set of signs is important.

The department of flowering plants unites two classes: dicotyledonous and monocotyledonous. The most essential feature is the structure of the seed. But one trait is not enough to determine the belonging of a plant 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 united in 325 families. Families of flowering plants are distinguished mainly on the basis of the structure of the flower and fruit.

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

A typical family of the class of monocots is the lily family. The plants of this family are dominated by perennial grasses with well-developed rhizomes or bulbs, lanceolate or linear leaves with arched or parallel venation. Many of the lily ephemera or ephemeroids have a short growing season. Liliaceae flowers are large, of various colors, solitary or collected in a brush. The perianth is simple, corolla-shaped, consists of six fused or loose leaves arranged in two circles. Six stamens, also located in two circles, one pistil (of three accrete carpels). The fruit of the liliaceae is a berry or a capsule. Among liliaceae, there are many ornamental plants (lilies, tulips), food (onions, garlic), medicinal (lily of the valley, aloe, medicinal), etc.

The largest family in the class of monocots is cereals. There are over 10 thousand types of cereals. They are distributed throughout the globe. They are a thriving family with 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. Bamboos are known from woody grasses. Plants of this family can be recognized by a hollow stem - a straw with nodes and internodes. The knots are filled with loose fabric. Stems of cereals grow in length as a result of cell division in internodes. This growth is called intercalary growth.

Cereals can also be recognized by their leaves: they are narrow, long, with parallel venation. The leaf has a wide tube-like base - the vagina. It protects from damage the delicate cells of the internodes, due to the division of which the stem grows. For cereals, a fibrous root system is also characteristic. Thus, cereals can be distinguished from plants of other families by the structural features of the vegetative organs (leaves, roots, and stem).

Flowers in cereals are small, dim, collected in spikelets. Inflorescences are formed from a multitude of spikelets: a complex spike, a panicle, etc. Each spikelet contains from 1 to 10 or more flowers. The cereal flower has three stamens and one pistil, but it lacks a calyx and corolla. Most cereals are wind-pollinated plants. Cereals have a fruit typical for this family - a caryopsis, rich in proteins and starch. Cereals reproduce by seeds, as well as vegetatively with the help of rhizomes and rooting shoots.

Cereals form the basis of human and farm animal nutrition. These include the most important forage and food crops. Wild grains are the main feed for livestock. In the tropics, bamboo and sugarcane thickets form. Sugarcane is specially grown on the plantations, and sugar, rum, alcohol and molasses are obtained from it. Cereals are also used for the production of paper, in the textile, chemical and construction industries. In the modern era, when environmental conditions are deteriorating, some types of cereals are threatened with extinction. 23 types of cereals are listed in the Red Book: stone-loving feather grass, fine feather grass, evading feather grass, multicolored bluegrass, leaf grass feather grass, etc.

Distinctive features of angiosperms

After fertilization of the egg, a seed is formed from the ovule, and the ovary grows into a fetus. Therefore, seeds in angiosperms develop in fruits, therefore this department of plants is called angiosperms.

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

In the middle of the Cretaceous, in just a few million years, the conquest of land by angiosperms takes place. 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, aneupolydia and polyploidization), a huge number of different species of angiosperms have been formed, belonging to a wide variety of ecosystems. By the middle of the Cretaceous period, most modern families were 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.

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

Angiosperms (flowering) plants

Angiosperms- the most perfect and most numerous group of the modern plant world. Flowering plants evolved from a group of extinct algae that gave rise to seed ferns. Thus, gymnosperms and angiosperms are parallel branches of evolution that have a common ancestor, but then evolved independently of each other. The remains of the first flowering plants are found in the Early Cretaceous sediments. Since the end of the Cretaceous period of the Mesozoic era, the Earth begins to dominate angiosperms, which have acquired a number of advantages over other higher plants, including gymnosperms. The same period accounts for the greatest distribution of insects, birds and mammals, which are interconnected by food chains, adaptations for reproduction and habitation in the same environmental conditions. The life forms of angiosperms are represented by trees, shrubs or grasses, which determines their greatest ecological plasticity and distribution on land in all natural areas and in water basins. Their main vegetative organs are the root, stem and leaf, which have numerous modifications, the most specialized in structure and function. Angiosperms, like gymnosperms, reproduce using seeds, but their seeds are protected pericarp, which contributes to their better preservation and distribution. And the appearance flower - an organ of seed reproduction, which (as a whole) gives a new generation (reproduction), puts this department of plants in the position of the most highly organized representatives of the plant kingdom.
The morphological diversity of flowering plants is very great. The structure of the vegetative and generative organs in them reaches the greatest complexity, the tissues are characterized by a high degree of specialization.
Flowering plants are the only group of plants capable of forming complex multi-tiered communities.
The angiosperms department is divided into two classes - dicotyledonous and monocotyledonous.
^ DISTINCTIVE FEATURES OF POTATO-SEED:

1. The presence of a flower. 2. The presence of an ovary and a fruit that preserves ovules and seeds.
3. Pollination by wind, insects, water, birds. 4. The female outgrowth is an eight-core embryo sac without archegonia. 5. Male outgrowth - pollen grain (pollen),
consisting of two cells - vegetative and generative.
6. Double fertilization: one sperm fertilizes the egg, the other - the secondary (central) nucleus of the embryo sac. 7. Double fertilization ends with the following transformations: from the ovary, a fruit is formed, from the ovule (ovule) - a seed, from a zygote - an embryo of a seed (diploid), from a fertilized secondary nucleus - a secondary endosperm.
8. Endosperm is represented by a tissue with a triploid set of chromosomes. It is formed simultaneously with the embryo of the seed; reserve nutrients (proteins, carbohydrates, fats) are deposited in it. 9. During germination, as soon as water enters the seed, its swelling begins, reserve substances pass into soluble forms available for absorption by the embryo. Some of the endosperm storage substances are broken down by respiratory enzymes. Which frees up the energy (in the form of ATP) necessary for the growth of the embryo.
10. The triploidity of the endosperm cell nuclei carrying hereditary information of the maternal and paternal organisms increases the adaptability of the young plant to various environmental conditions. 11. A sporophyte grows from the seed embryo (demon
hollow diploid generation), which can be represented by a different life form - grass (annual or perennial), shrub, tree, liana. Any life form of a plant has basic organs - root, stem, leaves and their modifications, as well as flowers, seeds, fruits.
Monocotyledonous class .

The name of the class "monocots" is due to the fact that there is one cotyledon in the embryo of the seed. Monocots differ significantly from dicots in the following ways:

1) a fibrous root system, the root has a primary structure (there is no cambium in it);

2) the leaves are mostly simple, whole-edged with arcuate or parallel venation;

3) the conducting bundles in the stem are closed, scattered, but throughout the entire thickness of the stem.
Cereals family (over 6 thousand species). Family biology: herbaceous plants (except for bamboo). The stems are simple, sometimes branched, cylindrical or flattened, separated by nodes, while in most plants they are hollow in internodes, filled with tissue only in the nodes. Such a stem is called a straw. Leaves are linear or lanceolate, with a sheath at the base. At the place of transition of the vagina into the lamina, there is an outgrowth-tongue, the shape of which is a sign when determining cereals. The flowers are yellowish-green, small, collected in inflorescences of spikelets, which form an ear, brush, panicle. At the base of each spikelet are attached two spikelet scales that cover the spikelet. There are 2-5 flowers in a spikelet. The perianth consists of two floral scales, two membranes. The bisexual flower contains three stamens and a pistil with two feathery stigmas. In some cases, there are 1-6 spikelet and flower scales, 2-6, rarely 40 stamens. The fruit is a weevil (nut or berry). Economic value: 1. Wheat, rye, barley, oats, corn, rice, sorghum, mogar, sugarcane - grain, industrial crops (get sugar, alcohol "beer). 2. Fescue, bluegrass, timothy are forage grasses. 3. Reed, bamboo. The stems are used in construction, to produce paper, as fuel. Cereals are widely used for fixing sands, slopes, in decorative floriculture. 4. Wheatgrass creeping, wild oat, bristle grass, barnyard - weeds. Liliaceae family (about 2800 species). Family biology: one-, two- and perennial grasses, shrubs, shrubs into trees. Perennial grasses are characterized by the presence of bulbs or rhizomes. Flowers are bisexual, less often unisexual. The perianth is generally corolla-shaped, sometimes calyx-shaped, of loose or incompletely accrete leaves. The number of stamens corresponds to the number of perianth leaves. One pistil. The fruit is a three-celled capsule or berry. Economic value: 1. Onions, garlic, asparagus - vegetable crops. 2. Lily of the valley, aloe, hellebore - raw material for medicines. 3. Lily, lily of the valley, tulip, hyacinth are decorative crops.

Class dicotyledonous

A systematic feature of dicotyledons is the presence of two cotyledons in the embryo.

Distinctive features of dicotyledons are as follows:

1) the root system is pivotal, with developed lateral roots;

2) the root and stem have a secondary structure, there is a cambium;

3) open-type vascular-fibrous bundles of the stem are arranged concentrically;

4) leaves, both simple and complex;
5) flowers of five- and four-membered type;

6) endosperm in ripe seeds is well expressed in a number of species: nightshade, umbrella, etc. But in legumes, Compositae, etc. others (for example, peas, beans, sunflowers, are poorly developed or completely absent, and reserve nutrients are located directly in the cotyledons of the embryo.
"Family Rosaceae (about 3 thousand species). Family biology: common in countries with subtropical and temperate climates. They are very diverse in the structure of the flower, inflorescences, fruits and leaves. A characteristic feature is the peculiar structure of the gynoecium and receptacle. The latter tends to grow. In some plant species, the parts of the flower that surround the pistil grow together at the bases and form a fleshy bowl with the intergrown receptacle - hypanthium. Flowers with a double five-membered perianth, many stamens, they are located in a circle (their number is a multiple of 5), one or more pistil. The ovary is superior, inferior or middle. Fruits - drupes, nuts, often false or composite. Insect pollinated plants. Economic value: 1. Rosehip. Fruits contain a lot of vitamin C, 1-8% sugar, up to 2% starch, 1-5% nitrogenous substances. The roots are rich in tannins. They are used in food (pharmaceuticals) and perfumery industries. 2. Roses, raspberries, strawberries, apple trees, pears, rowans, plums, cherries, apricots, peaches, almonds are decorative crops used in the food, perfumery, and pharmaceutical industries.
Legumes family (about 12 thousand species). Family biology; stems are erect, curly, creeping. Compound leaves with stipules. The structure of the flower is typical: a calyx of 5 sepals (3 + 2), a corolla of 5 petals (the posterior one is a sail, two lateral ones are inserted, the two lower ones “fused together in the upper part are a boat). 10 stamens (9 of them grow together and form an unclosed tube). One pistil. The ovary is superior, unilocular. The fruit is a bean. Pollinated by insects. The economic value of the representatives of the family (astragalus, camel thorn - shrub, vetch, peas, clover, alfalfa, beans, soybeans, lupine): food, fodder, melliferous, ornamental plants. Thanks to nodule bacteria, siderites (food and forage qualities are reduced due to the concentration of glycosides and alkaloids), play a significant role in the formation of the vegetation cover.
Solanaceae family (about 2200 species). Family biology: herbs, less often shrubs, shrubs. The leaves are alternate, without stipules, simple, with a whole or dissected plate. Flowers are correct or incorrect. Corolla with spice-petal, tubular. 5 stamens are attached to the corolla tubule. One pistil with an upper two-celled ovary, which contains numerous seed buds . The flowers are bisexual. Insect pollinated plants. Fetus- berry or box. Most nightshades contain poisonous alkaloids, which are used in small doses to obtain medicines. Economic value: 1. Nightshade (black nightshade). Citric acid and drugs are obtained from the leaves, and tobacco oil is obtained from tobacco seeds. 2. Potatoes, eggplants, tomatoes, peppers. Used in Food Industry... Z. Belladonna (belladonna), scopolia, dope, black henbane - medicinal plants.
Family Cruciferous (about 2 thousand species). Family biology: one-, two-, perennial grasses, shrubs with alternate leaves, sometimes collected in a basal rosette. The flowers are bisexual, collected in racemose inflorescences. The perianth is double, four-membered. Sepals and petals are arranged crosswise. Stamens6 , 4 of them are longer, 2 are shorter. One pistil. The fruit is a pod or pod. The seeds contain 15 - 49.5% oil. Economic value: 1. Wild radish, shepherd's purse, field mustard, jaundice - weeds. 2. Cabbage, radish, turnip, turnip - garden crops. 3. Mustard, rapeseed - oilseeds. 4. Levkoy, night beauty, mattiola - ornamental plants.
Family Asteraceae (near 15 thousand species). Family biology: annual and perennial herbaceous plants, shrubs, shrubs, small trees. Leaves are alternate or opposite, without stipules. A typical sign is a basket inflorescence. Separate flowers are located on the flat or convex bottom of the basket. The basket has a common wrap, consisting of modified apical leaves. Typical flowers are bisexual, with a lower ovary, to which a modified calyx is attached, the corolla is ligulate, tubular, funnel-shaped; coloring white, blue, yellow, blue and others. There are unisexual flowers (male or female), the extreme flowers are often sterile. There are 5 stamens; they grow together with dust particles into a tube through which a column carrying a stigma passes. The fruit is a common achene with a hairy tuft, or filmy crown.
Cross-pollination or self-pollination. Economic value: 1. Salad, chicory, artichoke - food crops. 2. Sunflower is an oilseed crop. 3. Jerusalem artichoke is a forage crop.

4. Dandelion, wormwood, string, yarrow, chamomile are medicinal plants. 5 ..- Dahlias, marigolds, chrysanthemums: - ornamental plants, 6. Euphorbia sow thistle, cornflower, blue, creeping bitterness - weeds.

Angiosperms, or flowering, plants currently dominate the plant world of the globe. This is the most large group, in which there are more than 390 families, about 13,000 genera and 240,000 species. Flowering plants are found in all climatic zones - from rainforest to the tundra. They occupy a significant place in human life, since most cultural products ( vegetables, fruit trees, cereals) belong to angiosperms.

A distinctive feature of angiosperms is the presence of a fruit, flower and seed. They differ from gymnosperms in that the ovules are enclosed in a more or less closed cavity of the ovary, which is why they got this name.

Flowering plants include trees, shrubs and grasses. Currently, the number of herbaceous plant species significantly exceeds the number of tree and shrub species. Angiosperm leaves are quite varied in shape and size. They are both simple and complex.

The flower is a complex system of organs and serves for the formation of fruits and seeds. It is located in the stem. The part of the stem under the flower, usually devoid of leaves, is called pedicel, which passes into the shortened axis of the flower - the receptacle. Parts of the flower are located on the receptacle: pistil, stamens, petals, sepals. The collection of sepals is called by a cup... It consists of several sepals, usually green in color. Sepals may grow together or not at all.

The main function of the petals is to attract insects and promote successful pollination. The set of petals is called a corolla, the size, structure and color of which are very diverse. In many flowering plants, corollas are poorly developed or absent altogether. The corolla can be free-petaled or spliced, when the petals grow together at the edges.

Sepals and petals together make up the perianth. It is double, if it consists of a calyx and corollas, and simple, when the petals are absent or when there is no clear distinction between sepals and petals.
On the receptacle, stamens are located inward from the perianth. The stamen consists of a filament and an anther; pollen matures inside. The inner part of the receptacle is occupied by a pistil, which consists of an ovary, a column, and a stigma.
Flowers are bisexual, when they contain stamens and a pistil, and unisexual, when they have either only stamens or only a pistil. Plants on which unisexual flowers grow are called monoecious . Dioecious are those species in which plants of the same species have only male flowers, others only female. These include willow, nettles, sorrel, sandpipes, cat legs. There are also three-house species.

The order and course of flowering plants are varied. Usually, flowers appear already on leafy shoots, but often in many plants in the spring, flowers first bloom, and then leaves. The main thing in fertilization is the ingress of pollen on the stigma of the corresponding flower. There are two types of pollination - self-pollination and cross-pollination. There are many self-pollinators among cultivated plants ( peas, oats, etc..). Cross-pollination is carried out by insects and wind.

After fertilization has occurred, the flower enters a new phase of development, which ends with the formation of the fruit. Fruits are varied in shape, color, they can be juicy or dry.
Flowering plants are classified into two classes: monocotyledonous and dicotyledonous.
The monocotyledonous class has about 65 families, 3000 genera and 60,000 species. Although in all these parameters they are inferior to dicotyledons, their role is extremely great, since many cultivated plants, in particular cereals, are monocotyledons.

^ Liliaceae family
Mostly perennial herbaceous plants, often with bulbs and rhizomes. They have a corolla-shaped perianth with free or accrete leaflets located in two circles. Stamens - 6, ovary - upper, consisting of three carpels. The fruit is a capsule or berry. In the alpine and lowland tundra, in swamps, along the banks of mountain rivers and lakes, a small plant grows - Tofieldia tiny ... It is a small plant with a branched root. The basal leaves are leathery, slightly curved, located in the same plane with the edge to the stem. The flowers are small, white, collected in a simple brush. Tepals are concave, obtuse.
In damp meadows, on the swampy edges of the forest, along the banks of mountain rivers and lakes, a rather large plant is found - Lobel's cheremitsa. Its life span is 50 years or more, flowering occurs in the 20-30th year. One plant can produce about 5000 seeds. This is medicinal plant, in folk medicine known for a long time, used for the preparation of analgesic ointments and disinfectants. Very poisonous.

In wet meadows, on rocky and sandy shoals of rivers and streams, you can often find Siberian onion - a valuable food and medicinal plant. Its leaves retain their nutritional qualities, but only until flowering, after which they become coarse. Onions are a common food seasoning, they contain vitamins and microelements. The bow has medicinal properties... All parts of plants contain an odorous substance from a mixture of sulphurous allyls with a characteristic onion smell, have phytoncidal and antiseptic properties.

^ Orchid family
The largest in the plant world. There are 800 genera and 30,000 species. There are 19 species in the Murmansk region. Our northern orchids are small perennial herbaceous plants that are well adapted to insect infestation. Some of them have medicinal properties ( spotted fingerweed, mosquito kokushnik).

^ Family Cereals
A very extensive family, which includes perennials, biennials and annuals, mainly grasses. There are about 500 genera and over 6000 species. A significant place is occupied by food and fodder views. On the Kola Peninsula widespread meandering pike, fragrant alpine spikelet, alpine timothy, field grass, fescue and others.

The class of dicotyledons in the number of species, genera and families significantly exceeds the class of monocotyledons. This is a class of flowering plants characterized by the presence of two cotyledons in the embryo of the seed. In the stems of such plants there is a cambium, which promotes the growth of the stem in thickness. The leaves of these plants have pinnate or finger venation. Dicotyledonous plants are distinguished by their diversity, they can synthesize more complex substances. This class contains about 10,000 genera and 180,000 species.

^ Family Cruciferous
The species composition of cruciferous plants is very diverse. Species from the genera play a significant role in the vegetation cover. grits, core ... Has a certain value spoon grass... Ornamental flower plants include representatives of the genus rezuha ... In our region, the alpine crusher grows. It is a very polymorphic family. Certain types of cruciferous plants have nutritional value.

^ Family Rosaceae
It unites over 120 genera and 2000 species. Many species are rich in vitamins, sugars, organic acids and essential oils. There are 11 genera and 52 species in the Murmansk region. These are trees, shrubs, grasses. Many of them are valuable food (chaffinch Gorodkov, bird cherry, cloudberry, stoneberry, raspberry, wild strawberry, prince), medicinal (meadowsweet or meadowsweet, erect cinquefoil, burnet) and decorative(alpine cuff, dryads point and eight-petal, cotoneaster) plants.

Dryad - the legendary flower of the North. It has 8 petals, a creeping woody stem, from which peculiar leaves emerge in bunches: oblong and wavy along the edge. From above they are dark green, and from below they are lined with an eider feather.

Kulgan (erect cinquefoil). The flower resembles an ancient Maltese cross: four notched petals form a symmetrical figure, which is unusual for a member of the Rosaceae family, the characteristic feature of which is the presence of 5 petals. Meadowsweet ... The flower consists of five small petals and unusually long stamens, so the inflorescence looks fluffy.
Rowan ... Rowan ordinary - deciduous tree (up to 15 m tall) or shrub. Natural habitats - in the undergrowth of coniferous, small-leaved and broad-leaved forests, along the valleys of rivers and streams, it enters the plain and mountain tundra. In our region, the appearance of the first leaves of mountain ash is observed in mid-May, early June. In Russia, specially bred fruit and ornamental forms of mountain ash are cultivated. The common mountain ash is resistant to air pollution, therefore, it is often used for landscaping industrial centers, in particular, on the Kola Peninsula.

^ Legumes family
By the number of species (12,000), it is one of the largest families. Legumes are capable of accumulating nitrogenous substances in the roots, and green mass and seeds are rich in proteins. The green fruits and mature seeds of legumes are edible. In the Murmansk region, only herbaceous plants grow from legumes. In total, there are 35 species, 11 genera in the region, and most of the legumes are invasive.
Creeping clover has a good ability to regrow. Refers to moisture-loving plants, grows well even with waterlogging. Good honey plant.
Widespread in the region sharp-edged boatman. It is a perennial herb with a powerful root with pinnate leaves. Flowers are collected in dense multi-flowered capitate inflorescences. Coloring from pale yellow to blue. The shark-tundra is a typical mountain tundra and tundra plant. It is well eaten by deer.

^ Family Willow
Dioecious trees and shrubs. Leaves are whole, with petioles. The inflorescence is an earring, the flower is with a small bracts. The perianth is reduced or absent at all. There are from 2 to 5 or more stamens. The ovary is superior, the column is short. Reverse ovules. The fruit is an upper paracarinous capsule. Seeds with white hairs fly.
Willow. Large, polymorphic, difficult to identify genus. A plant with leaves with two stipules. It usually blooms before the leaves open. Bracts pubescent, sometimes densely hairy. At the base of the flowers are nectaries. In the Murmansk region, 50 species are registered, from trees to dwarf shrubs. Willow is a light-loving plant. The most common species are goat willow, shaggy, gray; from dwarf ones - reticular, polar.

^ The Vodyanikov family
Small, outstretched, evergreen shrubs with narrow leaves, the edges of which are curled inward. The flowers are dioecious, dark red. Berry-shaped juicy fruit (crowberry bisexual). Vodyanik (or crowberry) is widespread. Many animals feed on its berries. People also eat it.

^ Family Heather
The Far North is characterized by arctous (translated from the Sami "thunder-berry"). The plant is remarkable for its phenological characteristic: it begins the circumpolar spring. Berries are black. They are eaten by tundra partridges.
Cowberry - evergreen undersized (height up to 30 cm) shrub with leathery glossy leaves. It grows in tundra, coniferous and mixed forests, on swamp ridges. Lingonberry blooms in our region from mid-June. Mass flowering occurs in early July. The first berries ripen in mid-August, mass ripeness occurs in September. Almost every year in September, lingonberries have a secondary flowering, but in this case, of course, there are no berries. Lingonberry is a medicinal plant. The leaves are used as a diuretic and astringent.

Blueberry myrtle - deciduous shrub (10 - 40 cm tall). Blueberry shoots are not round, but with sharp edges, which are gradually lost with age .: In our region, the leaves on blueberries begin to bloom in May, soon after the snow melts. The medicinal properties of the plant are well known. Dried berries are used for gastric diseases, leaves for diabetes. Leaves were previously used for tanning leather. Cranberry. A creeping shrub with aerial stems, rising flowering branches, leathery wintering ovoid leaves, with pink flowers. The berries are large, globular or pear-shaped, red in color, overwintering. Blossoms in July; bears fruit in August-September. Occurs in the south-west of the region, in swamps, forests and meadows, on sphagnum mosses. They are harvested in large quantities in autumn and spring, kept fresh for a long time, goes to the preparation of jelly, fruit drinks.

Heather. The life span of a plant is 40 days. Where the heather bushes die off, his relative, the bearberry, settles. In the curtain of bearberry, shoots of heather always appear. She gradually gives way to him. Bearberry exhibits exceptional fire resistance.

^ Family Lipoids
It is quite rich in plant species with a pleasant smell and medicinal properties. We have thyme, which because of its smell has the name Bogorodskaya grass. The biology of its reproduction is interesting. Tymyan seeds spread over short distances - 60 cm.For 100 years, the Bogorodskaya grass has advanced only 900 m forward.

^ Birch family
This family includes woody and shrub plants, among which birch, alder, and hazel are well known.
Birch trees - deciduous trees (up to 20 m and more), but there are forms not with one, but with several trunks, giving the general appearance of the plant the appearance of a bush, there are also shrub forms. In some places, birches form indigenous forests, but are usually present as an admixture in coniferous and mixed forests. : Birch is a wind-pollinated plant. Male inflorescences begin to form in early summer, by winter they are almost fully developed. Leaves, buds, young branches are used in medicine to treat various diseases.

^ Dogwood family
In the Murmansk region, only one species is found - the Swedish deren Derain Swedish - a semi-shrub with a perennial underground woody rhizome. Its rhizome, strongly branching, grows under the soil surface, and annually produces herbaceous aerial shoots up to 30 cm in height in spring, which die off in autumn. In our region, it is found in forests, birch crooked forests, tundra, and is common on the sea coast. Derain is not used directly by humans. It is of interest as a decorative perennial.

Gymnosperms (Gymnospermae) - the most ancient and still thriving group of seed plants, occupying an intermediate position between ferns and flowering plants... Previously, researchers have allocated all seed plants that do not form flowers in a separate department or even in the class of the department of seed plants (Spermatophyta). Currently, many scientists are inclined to divide the group of gymnosperms into several independent divisions.

All gymnosperms are trees or shrubs, often reaching enormous sizes. Some gymnosperms are highly branched and bear many small (often scale-like) leaves. Others are weakly branched and have large feathery leaves. Most gymnosperms in xylem there are no vessels, and in phloem- companion cells. On the other hand, the tissues of gymnosperms are more complex than those of ferns.

Scots pine structure

All gymnosperms are heterogeneous plants; microsporophylls and macrosporophylls vary greatly in shape, size and structure. In the most primitive seed ferns, they grew freely on ordinary shoots; in all other gymnosperms, they are located on shortened shoots - strobilae, as a rule, dioecious. Microspores in seed plants develop in the pollen sac and are called pollen grains or dust grains. They are transferred to the female gametophyte, as a rule, with the help of the wind, germinating inward after entering the megasporangium. Inside the megasporangium, called the ovule, a megaspore develops; after fertilization by the male gamete, the ovule turns into a seed. The female gametophyte, of course, to a very large extent depends on the parent plant, but to a much greater extent than the gametophyte of the fern, it is resistant to dehydration. The nutrient reserve surrounding the seed is used by the zygote during germination; the seeds can remain dormant until conditions are favorable. Fruits are not formed, but the seed can develop various adaptations that facilitate their spread.

Gymnosperms are known from the upper devonian... IN Carboniferous and perm there are representatives of most orders, and on Mesozoic their heyday falls.

The oldest seed plants are Progymnospermophyta. They combined the evolutionarily advanced structure of the stem with primitive lateral shoots, not much different from the shoots of psilophytes. Instead of true leaves, they developed forked leafless twigs. Progymnosperms, apparently, were still propagated by spores, but were already on the way to seed formation.

Seed ferns (Pteridospermophyta or Lyginodendrophyta), which are now classified as an independent division, were much more complex in structure. These were tree-like plants, the appearance and structure of the leaves resembled real ferns, but propagated with the help of seeds. The development of the embryo, most likely, took place after the seed fell to the ground. The large stems of the seed ferns contained a secondary xylem; feathery leaves differed from real ferns only in the structure of the epidermis, stomata, and petioles. Sometimes seed ferns are referred to as sagovnikov.

Division Gymnosperms

general characteristics. The first gymnosperms appeared at the end of the Devonian period about 350 million years ago; they probably descended from the ancient ferns that became extinct at the beginning of the Carboniferous period. In the Mesozoic era - the era of mountain building, the rise of the continents and desiccation of the climate - gymnosperms reached their prime, but already from the middle of the Cretaceous period they lost their dominant position to angiosperms.

The department of modern gymnosperms has more than 700 species. Despite the relatively small number of species, gymnosperms have conquered almost the entire globe. In the temperate latitudes of the Northern Hemisphere, they form coniferous forests called taiga over vast areas.

Modern gymnosperms are represented mainly by trees, much less often by shrubs and very rarely by lianas; there are no herbaceous plants among them. The leaves of gymnosperms differ significantly from other groups of plants, not only in shape and size, but also in morphology and anatomy. In most species, they are needle-shaped (needles) or scaly; in some representatives they are large (for example, in velvichia surprising their length reaches 2-3 m), pinnately dissected, bilobate, etc. The leaves are arranged singly, two or more in bunches.

The vast majority of gymnosperms are evergreen, mono- or dioecious plants with a well-developed stem and root system formed by the main and lateral roots. They are settled by seeds, which are formed from ovules. The ovules are glabrous (hence the name of the department), located on megasporophylls or on seed scales collected in female cones.

In the cycle of development of gymnosperms, there is a sequential change of two generations - sporophyte and gametophyte with sporophyte dominance. Gametophytes are highly reduced, and male gametophytes of holo- and angiosperms do not have antheridia, which sharply differ from all heterogeneous seedless plants.

Gymnosperms include six classes, two of which have completely disappeared, and the rest are represented by living plants. The best preserved and most numerous group of gymnosperms is the class Conifers, numbering at least 560 species that form forests in vast areas of Northern Eurasia and North America. The largest number of species of pine, spruce, and larch is found off the coast of the Pacific Ocean.

Class Conifers. All conifers are evergreen, less often deciduous (for example, larch) trees or shrubs with needle or scaly (for example, cypress) leaves. The needle-shaped leaves (needles) are dense, leathery and tough, covered with a thick cuticle layer. The stomata are immersed in wax-filled depressions. All these features of the structure of leaves provide a good adaptation of conifers to growth in both arid and cold habitats.

In conifers, erect trunks covered with scaly bark. In the cross section of the stem, well-developed wood and less developed bark and pith are clearly visible. The xylem of conifers is 90-95% formed by tracheids. Coniferous cones dioecious; plants are more often monoecious, less often dioecious.

The most widespread representatives of conifers in Belarus and Russia are Scots pine and Norway spruce, or European spruce. Their structure, reproduction, alternation of generations in the development cycle reflects characteristics all conifers.

^ Scotch pine - a single-house plant (Fig. 9.3). In May, bunches of greenish-yellow male cones 4-6 mm long and 3-4 mm in diameter are formed at the base of young pine shoots. On the axis of such a cone there are multilayer scaly leaves, or microsporophylls. On the lower surface of microsporophylls there are two microsporangia - pollen sac, in which pollen is formed. Each pollen grain is equipped with two air sacs, which makes it easier to carry pollen by the wind. In the pollen grain there are two cells, one of which subsequently, when it hits the ovule, forms a pollen tube, the other, after division, forms two sperm.

Rice. 9.3. Scots pine development cycle: a - branch with cones; b- a female bump in the context; c - seed scales with ovules; G - cutaway ovule; d-male cone in the context; e - pollen; f - seed scales with seeds; 1 - male bump; 2 - young female bump; 3- bump with seeds; 4 - a bump after a rash of seeds; 5 - pollen inlet; 6 - cover; 7 - pollen tube with sperm; eight - archegonium with ovum; nine - endosperm.

On other shoots of the same plant, reddish female cones are formed. On their main axis are small transparent covering scales, in the axils of which there are large thick, subsequently lignified scales. On the upper side of these scales there are two ovules, each of which develops female gametophyte - endosperm with two archegonia with a large egg in each of them. At the apex of the ovule, outside protected by the integument, there is a hole - the pollen passage, or micropyle.

In late spring or early summer, ripe pollen is carried by the wind and falls on the ovule. Through the micropyle, the pollen is drawn into the ovule, where it grows into the pollen tube, which penetrates to the archegonia. The two sperm formed by this time pass through the pollen tube to the archegonia. Then one of the sperm fuses with the egg, and the other dies off. From a fertilized egg (zygote), the embryo of the seed is formed, and the ovule turns into a seed. Pine seeds ripen in the second year, spill out of the cones and, picked up by animals or the wind, are carried over considerable distances.

In terms of their importance in the biosphere and their role in human economic activity, conifers rank second after angiosperms, far exceeding all other groups of higher plants.

They help to solve huge water protection and landscape problems, serve as the most important source of wood, raw materials for obtaining rosin, turpentine, alcohol, balsams, essential oils for the perfumery industry, medicinal and other valuable substances. Some conifers are cultivated as decorative ones (fir, thuja, cypress, cedar, etc.). The seeds of a number of pines (Siberian, Korean, Italian) are used for food, and oil is also obtained from them.

Representatives of other classes of gymnosperms (cycad, oppressive, ginkgo) are much less common and less known than conifers. However, almost all types of cycads are decorative and are widely popular with gardeners in many countries. Evergreen leafless low shrubs of ephedra (class oppressive) serve as a source of raw materials for obtaining the ephedrine alkaloid, which is used as a means of stimulating the central nervous system, as well as in the treatment of allergic diseases.

In the middle of the Cretaceous, in just a few million years, the conquest of land by angiosperms takes place. 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, aneupolydia and polyploidization), a huge number of different species of angiosperms have been formed, belonging to a wide variety of ecosystems. By the middle of the Cretaceous period, most modern families were 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.

Angiosperms, or flowering plants, are the division of higher plants that formed in the second half of the Mesozoic and quickly took a dominant position in the vegetation cover of the Earth.

Signs of angiosperms

Remark 1

The most characteristic features of angiosperms are the presence of a flower and a fruit.

From the ovary of a flower, a fruit develops, in the middle of which there is one or many seeds. Since the seeds are protected by the pericarp, which forms from the walls of the ovary, the name of the department arose - Angiosperms.

Among other signs inherent in flowering plants, the following should be distinguished:

double fertilization, as a result of which an embryo is formed and a special nutritious tissue develops - triploid endosperm;
even greater than in gymnosperms, reduction of male and female gametophytes and their accelerated development;
diverse anatomical structure;
the presence of real vessels (trachea) in the wood;
high ability to vegetative propagation due to the presence of a variety of modifications of vegetative organs.

Reproduction of angiosperms

A characteristic feature of angiosperms is the presence of an eight-core (eight-celled) embryo sac, in which double fertilization occurs - a process that is not exactly repeated in any of the other parts of the plant kingdom. Due to double fertilization, an embryo develops from one zygote, and a triploid (secondary) endosperm from the other. In gymnosperms, the endosperm (female germ) is primary. The sexual generation (gametophyte) of angiosperms was reduced even more in comparison with gymnosperms.

The male germ usually consists of only $ 3 $ cells, of which $ 2 $ are gametes, which means it is simplified to a minimum. The female germ is represented by the $ 8 $ -cellular embryo sac.

Flowers in most angiosperms have a perianth, single or double, often brightly colored, stamens and pistil or pistils. Most angiosperms are pollinated by insects (entomophilia), as well as by wind (anemophilia) or water (hydrophilia), less often (in the tropics) by birds (ornithophilia).

Remark 2

Double fertilization is the main feature of angiosperms.

For sexual reproduction, flowering plants do not need water, and immobile male reproductive cells - sperm, located in the stamens of the flower, are delivered to the female ovum located in the pistil. Each particle of pollen that gets on the stigma of the pistil contains two sperm. One of them fertilizes the egg (fertilization itself), and the other - the central cell (its secondary nucleus) of the embryo sac. An embryo is formed from a fertilized egg, and an endosperm with a supply of nutrients for the embryo is formed from the central cell.

The angiosperms are the most highly organized and most abundant group among higher plants and have about $ 250 thousand species, which are combined into approximately $ 10 \ 000 $ genera and $ 300 $ families. They are the most common on the globe and are the most important from a practical (economic) point of view. Therefore, the taxonomy of angiosperms, the issue of their evolution and development are not only of great theoretical, but also very important practical importance.

Flowering plants are of great economic importance as food, fodder, technical, medicinal, melliferous and ornamental plants.

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