Families and names of medicinal plants. Angiosperms: general characteristics, examples, structure, reproduction

Currently, angiosperms, or flowering plants, dominate the vegetation on Earth. There are about 300 thousand species. Angiosperms are the most highly organized plants. They are represented by different life forms (trees, shrubs, grasses, etc.) with different life expectancies and inhabit most land habitats.

Angiosperms, or flowering plants, are a group that is in the status department according to modern classification.

Angiosperms differ from all other plants by the presence of:

• double fertilization,

  more perfect structure of the conduction system.

In addition to these main ones, there are other distinctive features.

Angiosperms produce seeds, unlike mosses and ferns, which produce spores. However, seeds are formed not only in angiosperms, but also in gymnosperms. The main difference between them is that gymnosperms lack an ovary, which protects the ovules, and a fruit, which serves as an organ for seed dispersal.

The acquisition of flowers and fruits in the process of evolution allowed angiosperms (flowering plants) to develop new methods of pollination of generative organs and new methods of seed dispersal. Pollination began to be carried out not only with the help of water (like mosses and ferns) and wind (like gymnosperms). Mostly angiosperms have adapted to pollination by a variety of insects. To do this, they have evolutionarily developed bright, fragrant, nectar-producing, clearly visible flowers and inflorescences. The presence of the fruit, in turn, allowed flowering plants to spread their seeds not only with the help of the wind, but also with the help of animals and birds, by self-dispersal and other methods.

Angiosperm seeds contain a large number of spare nutrients. They are contained either in parts of the embryo (usually in the cotyledons), where they flow from the endosperm during maturation, or remain in the endosperm. Endosperm is a special tissue of flowering plants, which is the result of double fertilization. After pollination, one sperm fertilizes the egg (a zygote is formed), and the second fertilizes the so-called central cell of the ovule. As a result, the central cell becomes triploid (3n, contains a triple set of chromosomes). Its division forms the endosperm, which contains a supply of nutrients for the plant embryo developing from the zygote.

These and other features together made it possible for angiosperms to colonize new habitats and better adapt to them. Flowering plants turned out to be a more progressive group of plants than ferns and gymnosperms.

In the plant kingdom, the most numerous and advanced group is the department of Angiosperms. In this article we will introduce you to the general characteristics and significance of representatives of these plants and tell you about their structural features.

Origin

It is known that angiosperms originated from a group of algae that have not survived to this day. It was they who founded the development of seed ferns, from which gymnosperms and angiosperms originated.

Angiosperms have another name - flowering plants, which they received due to the presence of the main reproductive organ - the flower.

The first remains of flowering representatives date back to the early Cretaceous deposits. In the second half of the Cretaceous period of the Mesozoic, angiosperms occupied a dominant position on the planet.

Main features

This type flora has a variety of forms: trees, bushes, grasses. They are widespread in all natural areas. Their structure consists of a root system, stem, leaf and flower, from which the fruit and seed are formed.

Rice. 1. Plant forms.

The presence of a pericarp around the seed, which ensures their preservation and distribution, is a feature of angiosperms. In addition, the main features of this department are:

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• the presence of a flower;
• the ovary and fruit retain ovules and seeds;
• can be pollinated by water, wind, birds and insects;
• the female prothallus is presented in the form of an eight-nucleate embryo sac;
• male - in the form of a pollen grain, which consists of two types of cells: vegetative and generative;
• double fertilization: sperm fertilize the egg and the nucleus of the embryo sac;
• The life cycle is a change of generations.

The development cycle of a fertilized flower continues with the following transformations: the ovary turns into a fruit, the ovule into a seed, the zygote into a seed embryo, the secondary nucleus into a secondary endosperm, which has a triploid set of chromosomes.

Rice. 2. Flowering plant.

The flowering plant division is divided into two classes: Monocots and Dicotyledons.

The name mono- and dicotyledons is due to the presence of the number of cotyledons.

The distinctive features of the classes can be studied in the following table:

Rice. 3. Characteristic signs monocots and dicotyledons.

Cereals

The stems (straws) are mostly simple, cylindrical, separated by nodes. The leaf is linear or lanceolate. The flower is collected in a spike in the form of small yellowish-green spikelets. Examples of angiosperms in this family are wheat, rye, oats, sugar cane, corn, bamboo and others.

Liliaceae

Perennial species have bulbs as roots. The flower is bisexual, the perianth is corolla-shaped from free (unfused) petals. The fruit is in the form of a berry or capsule. This family includes: onions, garlic, lilies of the valley, aloe, tulips, lilies and others.

Rosaceae

They have a special receptacle structure. The fruit is presented in the form of a nut or drupe. Pollinated by insects. Representatives: roses, strawberries, raspberries, plums, cherries, pears, apple trees and others.

Legumes

A special feature is the erect, curly stems. The structure of the leaves is complex; they have stipules. The flower consists of 5 sepals, the corolla has five petals. Bean-shaped fruit. Plants are pollinated by insects. Legumes include: peas, clover, soybeans, beans, alfalfa and others.

Solanaceae

The peculiarity of the structure is regular simple leaves with a whole or dissected plate. The corolla is tubular to which the stamens are attached. The fruit is represented by a berry or a capsule. Representatives: potatoes, nightshade, eggplant, tomatoes, peppers, dope.

Cruciferous

The flowers of the plants are presented in the form of racemose inflorescences. The sepals and petals are crosswise. There are 6 stamens: four long and two short. The fruit is in the form of a pod. Example: radish, cabbage, shepherd's purse, mustard, matthiola.

Compositae

A distinctive feature is the inflorescence of the basket, at the bottom of which there are small flowers. The fruit is an achene with a tuft or crown. Representatives: sunflower, asters, dandelion, chamomile, cornflower.

Flowering plants are used:

• in the food industry;
• in medicine and pharmacology;
• as technological and feed crops;
• V landscape design.

What have we learned?

Numerous representatives of the plant kingdom are angiosperms. Their peculiarity is the presence of a flower, which serves as a reproductive organ. Depending on the number of cotyledons in the embryo, flowering plants are divided into monocotyledons and dicotyledons. All of them are widely used in nutrition, treatment, and landscape design. We also studied in detail the properties of each family.

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Theory for preparation for block No. 4 of the Unified State Exam in biology: with system and diversity of the organic world.

general information

Flowering plants or Angiosperms- a department of higher plants, the distinctive feature of which is the presence of a flower as an organ of sexual reproduction and a closed container for the ovule.

Flowering plants evolved from a group of extinct algae that gave rise to seed ferns. Thus, gymnosperms and angiosperms are parallel branches of evolution, having a common ancestor, but then evolving independently of each other. Remains of the first flowering plants are found in Early Cretaceous sediments.

Starting from the end of the Cretaceous period of the Mesozoic era, angiosperms began to dominate the Earth, which acquired a number of advantages over others. higher plants, including gymnosperms. The same period accounts for the greatest distribution of insects, birds and mammals, which are interconnected by food chains, adaptations to reproduction and living in the same environmental conditions. The life forms of angiosperms are represented by trees, shrubs or herbs, which determines their greatest ecological plasticity and distribution on land in all natural zones and water basins. Their main vegetative organs- root, stem and leaf, which have numerous modifications and are the most specialized in structure and function.

Angiosperms, like gymnosperms, reproduce using seeds, but their seeds are protected by the pericarp, which contributes to their better preservation and distribution. And the appearance of a flower - an organ seed propagation, which (in general) gives rise to a new generation (reproduction), places this plant division in the position of the most highly organized representatives of the plant kingdom.

Distinctive features of angiosperms

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 prothallus is an eight-nucleate embryo sac without archegonia.
5. The male prothallus is a 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: a fruit is formed from the ovary, a seed is formed from the ovule (ovule), a seed is formed from the zygote (diploid), and a secondary endosperm is formed from the fertilized secondary nucleus.
8. The endosperm is represented by 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 turn into soluble forms available for absorption by the embryo. Some of the reserve substances of the endosperm are broken down by respiratory enzymes. which releases energy (in the form of ATP) necessary for the growth of the embryo.
10. The triploidity of the nuclei of endosperm cells, which carry hereditary information from the maternal and paternal organisms, increases the adaptability of the young plant to different conditions environment.

From the embryo of the seed grows a sporophyte (asexual diploid generation), which can be represented by various life forms - 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.

Angiosperms are represented by two classes - monocotyledons and dicotyledons.

Comparison of classes monocots and dicotyledons

Now let's look at each class separately.

Class Monocots

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

1. fibrous root system, the root has a primary structure (it lacks a cambium)
2. leaves are mostly simple, entire with arcuate or parallel veins
3. conducting bundles in the stem are closed, scattered throughout the entire thickness of the stem

Cereal family

Herbaceous plants (with the exception of bamboo). The stems are simple, sometimes branched, cylindrical or flattened, separated by nodes. Most plants are hollow at the internodes and filled with tissue only at the nodes. Such a stem is called a straw. The leaves are linear or lanceolate, with a sheath at the base. At the junction of the vagina and the plate there is a tongue-shaped outgrowth, the shape of which is a sign in identifying cereals. The flowers are yellowish-green, small, collected in inflorescences, spikelets that form a spike, raceme, panicle. At the base of each spikelet two glumes are attached, covering the spikelet. There are 2-5 flowers in a spikelet. The perianth consists of two floral scales, two films. The bisexual flower contains three stamens and a pistil with two feathery stigmas. In some cases, there are 1-6 spikelets and floral scales, 2-6, rarely 40 stamens. The fruit is a grain (nut or berry).

Economic importance

1. Wheat, rye, barley, oats, corn, rice, sorghum, mogar, sugar cane - grain, industrial crops (receive 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 to stabilize sand, slopes, and in decorative floriculture.
4. Creeping wheatgrass, wild oats, bristle grass, barnyard grass are weeds.

Lily family

One-, two- and perennial herbs, subshrubs, shrubs into trees. Perennial herbs are characterized by the presence of bulbs or rhizomes. The flowers are bisexual, less often unisexual. The perianth is mostly corolla-shaped, sometimes cup-shaped, consisting of free or incompletely fused leaves. The number of stamens corresponds to the number of perianth leaves. One pestle. The fruit is a three-lobed capsule or berry.

Economic importance

1. Onions, garlic, asparagus are vegetables.
2. Lily of the valley, aloe, hellebore are raw materials for medicines.
3. Lily, lily of the valley, tulip, hyacinth - ornamental crops.

Class dicotyledons

A systematic feature of dicotyledons is the presence of two cotyledons in the embryo. Distinctive features dicotyledons are as follows:

1. the root system is taprooted, with developed lateral roots;
2. the root and stem have a secondary structure, there is a cambium;
3. vascular-fibrous bundles of the stem open type, located concentrically;
4. leaves both simple and compound;
5. flowers of five- and four-membered type;
6. The endosperm in ripened seeds is well expressed in a number of species: Solanaceae, Apiaceae, etc. But in legumes, Asteraceae, 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

Distributed in countries with subtropical and temperate climate. Very diverse in the structure of the flower, inflorescences, fruits and leaves. Feature-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 are fused at their bases and form a fleshy cup, the hypanthium, with the fused receptacle. Flowers with a double five-membered perianth, many stamens, they are arranged in a circle (their number is a multiple of 5), one or several pistils. The ovary is superior, inferior or middle. The fruits are drupes, nuts, often false or mixed. Insect-pollinated plants.

Economic importance

1. Rose hip. The fruits contain a lot of vitamin C, 1-8% sugar, up to 2% starch, 1-5% nitrogenous substances. The roots are rich in tannins. Used in food ( medications) and perfume industry.
2. Roses (anthus, tea), raspberries, strawberries, apple, pear, rowan, plum, cherry, apricot, peach, almonds are ornamental crops used in the food, perfume, and pharmaceutical industries.

Legume family

Stems are erect, climbing, creeping. The leaves are compound with stipules. The structure of the flower is typical: a calyx of 5 sepals (3+2), a corolla of 5 petals (the back one is a sail, two lateral ones are a vela, two lower ones, fused at the top - a boat). There are 10 stamens (9 of them grow together and form an open tube). One pestle. The ovary is superior, unilocular. The fruit is a bean. Pollinated by insects.

Economic importance of representatives of the family (astragalus, camel thorn - subshrub, vetch, peas, clover, alfalfa, beans, soybeans, lupine): food, fodder, melliferous, ornamental plants. Thanks to nodule bacteria, green manure. Nutritional and feed quality is reduced due to the concentration of glycosides (glycyrrhizine, coumarin) and alkaloids (cytisine, sparteine). They play a significant role in the formation of vegetation cover.

Nightshade family

Herbs, less often subshrubs, shrubs. Leaves are alternate, without stipules. Simple, with a whole or dissected plate. Flowers are correct or incorrect. The corolla is fused-petalled, tubular. There are 5 stamens attached to the corolla tube. There is one pistil with an upper two-locular ovary, which contains numerous seed germs. The flowers are bisexual. Insect-pollinated plants. The fruit is a berry or capsule (rarely drupe-shaped). Most nightshades contain poisonous alkaloids, which are used in small doses to produce medicines.

Economic importance

1. Nightshade (black nightshade). It is obtained from the leaves citric acid, drugs, from tobacco seeds - tobacco oil.
2. Potatoes, eggplants, tomatoes, peppers. Used in the food industry.
3. Belladonna (belladonna), scopolia, datura, black henbane are medicinal plants.

Family Cruciferae

One-, two-, perennial herbs, subshrubs with alternate leaves, sometimes collected in a basal rosette. The flowers are bisexual, collected in racemes. The perianth is double, four-membered. Sepals and petals are arranged crosswise. There are 6 stamens, 4 of them are longer, 2 are shorter. One pestle. The fruit is a pod or pod. The seeds contain 15-49.5% oil.

Economic importance

1. Wild radish, shepherd's purse, field mustard, yellow grass are weeds.
2. Cabbage, radish, turnip, rutabaga are garden crops.
3. Mustard, pane - oilseeds.
4. Levkoy, night beauty, matthiol- ornamental plants.

Family Asteraceae

Annuals and perennials herbaceous plants, subshrubs, shrubs, small trees. Leaves are alternate or opposite, without stipules. A typical feature is the inflorescence basket. Individual flowers are located on the flat or convex bottom of the basket. The basket has a common involucre consisting of modified apical leaves. Typical flowers are bisexual, with a lower ovary, to which a modified calyx is attached, a corolla ligulate, tubular, funnel-shaped; the color is white, blue, yellow, blue, etc. Flowers are unisexual (male or female), the outer flowers are often sterile. There are 5 stamens, they grow together as dust particles into a tube through which passes a style bearing the stigma. The fruit is an ordinary achene with a hairy pappus, or membranous crown.

Economic importance

1. Lettuce, chicory, artichoke are food crops.
2. Sunflower is an oilseed crop.
3. Jerusalem artichoke is a fodder crop.
4. Dandelion, wormwood, string, yarrow, chamomile are medicinal plants.
5. Dahlias, marigolds, chrysanthemums - ornamental plants, 6. Euphorbia thistle, cornflower, blue, creeping bitterweed - weeds.

Comparative characteristics of families

Angiosperms (Magnoliophyta, or Angiospermae) are the largest division. There are at least 250 thousand species. Every year, about 2 thousand new species are described around the world. It is believed that 85% of the modern biological diversity of flowering plants has been identified. Currently, flowering plants dominate the vegetation cover of our planet and are the most important group of plants for humans. This is the “youngest” plant division on a geological time scale. Flowering plants appeared in the Jurassic period, and in the middle of the Cretaceous period they began to spread very quickly, revealing an exceptional ability for speciation.

The wide variety of flowering plants (angiosperms) is due to their high adaptability to a variety of environmental conditions. Flowering plants are characterized by the following features: the presence of organs such as pistil and fruit; seeds enclosed inside the fruit (hence the name of the department - Angiosperms); further reduction of male and female gametophytes; double fertilization; presence of real vessels in wood different types, as well as the presence of flowers.

The wide variety of flowers of angiosperms and their sharp difference from the corresponding organs of gymnosperms make it difficult to explain the origin of the flower. In this regard, there are several hypotheses.

According to the most widespread and well-founded strobilar, or evanth, hypothesis, a flower is a modified shortened spore-bearing shoot, originally resembling a gymnosperm cone. During the process of metamorphosis, megasporophylls turned into carpels, and microsporophylls into stamens, which many researchers associate with the adaptation of angiosperms to pollination by insects. According to this hypothesis, the most ancient families are Magnoliaceae, Ranunculaceae, etc.

According to another hypothesis, called pseudantic, a flower is a modified inflorescence consisting of small flowers of different sexes that have undergone reduction, convergence and fusion. According to this hypothesis, the most ancient families with dioecious, inconspicuous flowers are willow, casuarina, etc.

These hypotheses, based on the idea of ​​the formation of flowers from leafy shoots, are contrasted with various telome hypotheses, according to which all parts of the flower can be derived from telomes, i.e., cylindrical shoot structures characteristic of rhinophytes.

Currently, almost all botanists believe that phylogenetically a flower is a modified shortened shoot and its parts, except the receptacle, are leafy in nature.

A flower is a shortened, modified spore-bearing shoot that is specifically designed for reproduction (formation of micro- and megaspores, pollination, fertilization, formation of seeds and fruits). Like any shoot, it develops from a bud.

The flower consists of several parts. The peduncle connects the flower to the stem. Receptacle - expanded top part the pedicel to which all other parts of the flower are attached. The sepals make up the outer part of the perianth - the calyx. The petals make up the inner part of the perianth - the corolla (sometimes in flowers there is no division of the perianth into a calyx and corolla, in this case the perianth is called simple). The collection of stamens forms the androecium. The collection of carpels (megasporophylls) forms the gynoecium, which is located in the center of the flower. The peduncle and receptacle are the modified stem of the shoot, and the sepals, petals, tepals, stamens and carpels fused into a pistil are the modified leaves of the shoot. The flowers of some plant species do not have a peduncle; the flower sits directly on the stem and is called sessile. The receptacle can be of different shapes - flat, convex, highly elongated, concave.

Parts of a flower (perianth, stamens, pistils) can be arranged on the receptacle in a spiral (spiral arrangement) or in a circle (circular or cyclic arrangement). Sometimes there may be a mixed (hemicyclic) arrangement, when parts of the perianth are arranged in a circle, and the stamens and pistils are arranged in a spiral.

The flower develops from a bud located in the axil of the leaf. Such a leaf is called covering. The leaves (usually modified) located on the peduncle, under the flower, are called bracts.

The calyx consists of free or fused sepals and is accordingly called sepifolate or sphenofolate. The calyx is usually green, but may have other colors. Sepals come in various shapes (lanceolate, subulate, triangular, etc.). If the sepals of a flower have different shapes, then the calyx is called irregular; if the sepals are the same, it is called regular.

The corolla consists of free or fused petals and is accordingly called separate-petaled or sphenoletal. The corolla is usually brightly colored. Petals can be of different shapes.

Perianth, consisting of different appearance calyx and corolla, called double (or complex). A perianth consisting of identical leaflets is called simple. The brightly colored simple perianth is called corolla, and the green one is called calyx. Some plant species do not have a perianth and the flowers are called glabrous.

If a plane is drawn through the axis of the flower, passing through the pistil, receptacle and pedicel, it will cut the flower into two symmetrical parts. Such an imaginary plane is called a plane of symmetry. The whole variety of flowers with respect to their symmetry can be reduced to the following three types: 1) regular, or actinomorphic, flower, through which several planes of symmetry can be drawn; 2) irregular, or zygomorphic, flower, through which only one plane of symmetry can be drawn; 3) an asymmetrical flower, through which no plane of symmetry can be drawn.

The androecium consists of stamens, which are microsporophylls. The stamen has a filament and an anther, which is attached to the filament by means of a connective tissue. Each anther contains four pollen sockets in which pollen (microspores or pollen grains) develops.

Mature pollen grains different types have different shape: spherical, elliptical, etc. They are covered with two shells. The outer thick one is called exine, the inner soft one is called intina. Various projections, spines, and tubercles are formed on the exine in different species. In each microspore located inside the anther, the nucleus divides, forming two nuclei: vegetative and generative. With this, the development of the male gametophyte begins and microspores turn into pollen. Subsequently, two sperm are formed from the generative cell, which are male gametes.

The gynoecium consists of one or more pistils. Each pistil is formed by one or more fused carpels (megasporophylls). The formed pistil usually consists of a lower expanded part - the ovary, a middle cylindrical part - the style, and an upper expanded part - the stigma. When the style is absent and the stigma is located directly on the ovary, it is called sessile. The stigma may be different shapes: capitate, bilobed, stellate, pinnately lobed, etc. One or many cavities called nests are formed in the ovary, ovules (megasporangia) develop in them, from which seeds develop after fertilization. The number of styles, stigma lobes, and ovary nests may indicate the number of carpels forming the pistil. The place where the ovule is attached to the ovary is called the placenta (or placenta).

A mature ovule consists of an achene, one or two integuments (integuments) and an ovule nucleus (nucellus), which contains the embryo sac (female gametophyte). The integuments at the apex of the ovule have a narrow canal called the pollen duct (or micropyle).

The embryo sac develops in the nucellus. Inside the embryo sac there is an egg, two synergids, two polar nuclei, and three antipodes. Angiosperms lack archegonia. At a certain stage, the polar nuclei of the central cell merge, forming the diploid central (secondary) nucleus of the embryo sac. During the sexual process, double fertilization occurs, which is characteristic only of flowering plants. During this process, sperm fertilizes not only the egg, but also the central nucleus of the embryo sac. After fertilization, the embryo develops from the zygote, and the endosperm of the seed develops from the central cell with a triploid nucleus. Double fertilization promotes rapid development nutritional (endosperm), which occurs only after fertilization and accelerates the entire process of formation of the ovule and seed.

Flowering plants reproduce and spread by seeds. The seeds are enclosed in fruits, which protect them and often help them spread.

Flower formula and diagram

They provide a visual description of the structure of the flower. The formula reflects the structure of the flower using letters and numbers, the diagram - using a drawing (projection of parts of the flower onto a plane, plan of the flower).

The flower formula is composed as follows. A simple perianth is designated by the letter P (Perigonium), a calyx - K (Kalyx), a corolla - C (Corolla), androecium (stamens) - A (Androeceum), gynoecium, or carpels, - G (Gynoeceum). The correct flower is indicated by an asterisk *, the incorrect one - by an arrow. Each letter has a number at the bottom indicating the number of members of that part of the flower. If there are many members, an indefinite number, an infinity sign is placed. If these parts of the flower are located not in one, but in two circles, then two numbers are placed at the member sign, connected by a “+” sign. When any parts of a flower grow together, the number indicating their number is enclosed in brackets. The superior ovary is marked with a line under the number indicating the number of carpels; the lower ovary is a line above the number.

The flower diagram is drawn up as follows. A cross section of the flower is depicted in the form of a projection of all its parts onto a plane. The fused members of any part of the flower on the diagram are connected by a dotted line or a solid line thin line. The diagram shows not only the number of flower parts, but also their relative positions.

Types of inflorescences

Flowers can be single, completing the shoot. They are often collected in inflorescences. An inflorescence is a shoot or system of shoots that bears flowers. In inflorescences, flowers emerge from the axils of the covering leaves (bracts).

Inflorescences can be divided into two groups: monopodial (racemose, bothric, indeterminate) and sympodial (cymose, indeterminate). In monopodial inflorescences, the youngest flowers are in the center or apex of the inflorescence. In sympodial inflorescences, the first apical flower ends the main axis of the inflorescence and further development of the inflorescence occurs due to the development of lateral axes of the first order, then the second, etc.

Monopodial inflorescences can be simple (flowers sit directly on the main axis of the inflorescences) or complex (flowers sit on the branches of the main axis of the inflorescences).

Simple monopodial inflorescences include: raceme - the flowers are located on an elongated axis and have pedicels (cherry); spike - similar to a raceme, but the flowers are sessile (plantain); cob - an ear with a thick fleshy axis (corn); head - similar to a brush, but the main axis is very shortened, the flowers seem to be sessile (clover); scutellum - similar to a brush, but differs in that the lower flowers have long pedicels, as a result the flowers are located almost in the same plane (pear); basket - the flowers are always sessile, located at the strongly thickened and widened end of the shortened axis of the inflorescence (representatives of the Asteraceae family); umbrella - the main axis of the inflorescence is greatly shortened, the lateral flowers sit on stalks of the same length (onion).

Complex monopodial inflorescences include: complex spike - elementary spikelets (wheat) sit on the main axis; panicle, or complex brush - on the main axis on different heights lateral branches develop, in turn branching and bearing flowers or small simple inflorescences (lilac); complex umbrella - different from simple themes that its axes end not in flowers, but in simple umbrellas (carrots); complex shield - the main axis is a shield, and the side ones are baskets (yarrow).

Sympodial inflorescences include: monochasia (divided into gyrus and whorl); dichasia, or fork, and pleiochasia, or false umbrella. Monochasium - the axis of each order produces only one branch with a flower. In a curl, all flowers are directed in one direction (forget-me-not). In the gyrus, the lateral axes with the flower extend alternately in two opposite directions (gladiolus). Dichasium - the axis of each order gives two branches. The blooming of the inflorescence begins with the apical flower, and immediately below it there are two lateral flowers of the second order, and from the axils of the last two flowers of the third order arise, etc. (representatives of the Carnation family). Pleiochasia - from each axis bearing an apical flower, more than two branches emerge, outgrowing the main axis (euphorbia).

Fruit

The fruit is usually formed from the ovary of the pistil. The pericarp develops from the walls of the ovary, which consists of three layers: outer (exocarp), middle (mesocarp) and inner (endocarp). These three parts are not always well expressed.

Fruits can be simple, or true, formed from a single pistil in a flower, and complex, or composite, from several pistils of one flower (fruits of raspberries, blackberries, buttercups, etc.). If other parts of the flower (receptacle, perianth) take part in the formation of the fruit in addition to the pistil, the fruit is called false.

All real fruits, based on the structure of the pericarp, are divided into dry and juicy.

Dry fruits have a dry, woody or leathery pericarp and are classified as dehiscent or indehiscent.

In addition to dehiscence different ways fruits, there are disintegrating fruits, represented by two groups: fractional fruits, disintegrating longitudinally in the plane of fusion of the carpels (umbelliferous), and articulated fruits, disintegrating transversely in planes perpendicular to the longitudinal axis of the carpels (some types of cruciferous plants, etc.).

In juicy fruits, the entire pericarp or part of it is juicy or fleshy. Juicy fruits are divided into berries and drupes.

The variety of fruits is determined primarily by the structure of the pericarp, as well as the method of opening and the number of seeds. Among dry and juicy fruits, single-seeded and multi-seeded are distinguished.

Dry multi-seeded dehiscent fruits: capsule - a single-locular or multi-locular fruit, formed from several carpels, opened with holes or cracks (poppy, henbane, cotton); leaflet - a single-locular fruit formed from one carpel, opened along the ventral suture (larkspur); a complex leaflet is a group of leaflets (marigold, bladderwort); bean - a single-locular fruit formed by one carpel, unlike a leaflet, opens along two seams - ventral and dorsal (representatives of the Moth family); pod - an elongated bilocular fruit formed from two carpels, between the valves there is a longitudinal partition (mustard); pod - the same as a pod, but its length is no more than three times its width (shepherd's purse).

Dry single-seeded, indehiscent fruits: caryopsis - the seed grows tightly together with a thin filmy pericarp (rye, wheat); achene - leathery pericarp, not fused with the seed; the achene is often equipped with a tuft or fly (dandelion); in the Umbrella family, two-samples are formed; lionfish - achene with a wing-shaped appendage (ash), diploid (maple); nut - hard, woody pericarp (hazel); nut - a small nut (hemp); acorn - similar to a nut, but the lower part of the fruit is immersed in a cup-shaped plus (oak).

Juicy multi-seeded fruits: berries - juicy endocarp and mesocarp, leathery exocarp (grapes, tomatoes); apple is a false fruit, in the formation of which, in addition to the ovary, a greatly expanded receptacle (apple tree, pear) takes part; pumpkin is a false fruit, the receptacle takes part in its formation; the exocarp is hard, sometimes woody, the mesocarp and endocarp are juicy (watermelon, pumpkin); orange - citrus fruit; exocarp soft-skinned, rich essential oils, mesocarp is dry, spongy, endocarp is juicy (lemon, orange).

Juicy single-seeded fruits: drupe - thin, leathery exocarp, juicy mesocarp, stony endocarp (cherry, plum); compound drupe - a group of drupes formed from one flower (raspberry, blackberry).

The above classification of fruits is artificial, since it is based mainly on external morphological features. There is also a morphogenetic classification of fruits based on the type of gynoecium from which the fruits develop.

Some plants develop infructescences. They are formed from an inflorescence as a result of the fusion of several fruits into one whole (mulberry, fig).

Taxonomy of angiosperms

Angiosperms are the largest division of the plant kingdom, including more than 250 thousand plant species belonging to approximately 13,000 genera from more than 500 families. Currently, angiosperms dominate the vegetation cover of the globe, providing an example, as M.I. Golenkin puts it, of “winners in the struggle for existence.” The most ancient remains of flowering plants indicate that this group arose in the Jurassic period of the Mesozoic era. It is interesting that among the Jurassic remains of angiosperms, representatives of most modern families are known, which indicates a sudden mass appearance of the main phyla of this department in the Jurassic flora of the globe. The reasons for such a high rate of evolution (“a dizzying career”, according to Seward, or a “magnificent explosion”, according to Emberge) in the first stages of the formation of flowering plants are still unclear, despite the fact that this problem has long attracted and continues to attract the attention of many researchers (the great Charles Darwin called the origin of angiosperms a “disgusting mystery”).

As one of the main reasons for the dominance of flowering plants in the modern vegetation cover, their dominance in most types of modern ecosystems, it is not without reason that a number of specific morphological structures that arose in this group in the process of evolution and allowed it to gain advantages in the development of natural landscapes are considered. Of the most important evolutionary “acquisitions”, we first note the following: 1) a flower - a kind of specialized metamorphosed shortened spore-bearing shoot; 2) pistil, or carp - a structure formed by one or more carpels (essentially modified megasporophylls), fused edges and thereby forming a closed container, isolated from the external environment - the ovary, where the ovules are located. After fertilization, a seed develops from the ovule, and from the ovary - a formation specific to angiosperms - the fruit, 3) further reduction of male and female gametophytes (the male gametophyte is reduced to a pollen grain, consisting at the maturity stage of only two cells - vegetative and generative; the female gametophyte is reduced to an 8-nucleated embryo sac, one of the nuclei of which is the egg; archegonia were thus completely reduced in flowering plants.

In this article we accept the main provisions of the system of flowering plants developed by Academician A.L. Takhtadzhyan in 1987. As in most modern systems, angiosperms are distributed in this system among two classes - Dicotyledons and Monocots. The Dicotyledonous class is divided, in turn, into 8 subclasses, and the Monocot class into 4 subclasses.

Subclasses within dicotyledons and monocotyledons combine orders that have a common origin. Families are combined into orders using the same principle. In total, in the system of A. L. Takhtadzhyan there are 12 subclasses, 166 orders and 533 families.

general characteristics

The ovules of flowering plants are protected by the ovary. The ovary (ovarium) is the lower thickened part of the pistil of a flower with a closed cavity inside. Inside there are reliably protected ovules. Pollen, captured by the stigma, travels through the style to the ovules, where fertilization occurs. The internal moist cavity protects the ovules from drying out, temperature fluctuations and damage by insects. The fertilized ovary turns into a fruit, in which seeds develop from the ovules. The ovary cavity is often divided into nests by solid or separate partitions. Such an ovary is called multilocular, and an ovary without partitions is called unilocular.

Flower structure

The upper one is freely attached to the receptacle and does not grow together with other parts of the flower; its walls are formed exclusively by carpels, for example, in cereals and ranunculaceae. Such flowers are called subpistillate or circumpistillate. The lower one is located under the receptacle. Other parts of the flower take part in its formation: the bases of the sepals, stamens and petals, which are attached at its apex, for example, in Asteraceae, orchids, and cacti. In this case, the flower is called suprapistal. The semi-inferior one has a free apex, since it does not grow together at the very top with other parts of the flower, the receptacle or hypanthium, for example, in some saxifrages; such flowers are called semi-supapistal.

Flowering plants grow in different conditions

Habitats that are extreme in their conditions are inhabited by flowering plants, the structure of which differs in many respects from the typical one. Thus, deserts are characterized by thorny shrubs with small leathery leaves, as well as cacti and other succulents, i.e. species with fleshy green parts (in agaves, for example, these are leaves) that contain special water-storing tissue. Most cacti have no leaves at all, and the function of photosynthesis is performed by the stems - in this way it is possible to reduce moisture loss due to evaporation. In submerged flowering plants there is no need for xylem and it is usually absent: their stems are soft and their leaves are often filamentous or dissected into thin segments with a simplified anatomy. Sometimes the entire body of these plants is penetrated by a system of air-bearing cavities: gases involved in vital processes accumulate in them. Such air-bearing tissue (aerenchyma) is also characteristic of many plants, the lower part of which takes root under water, and the upper part floats on the surface or rises above it, for example, reeds and water lilies.

Life forms of angiosperms.

The life form of a plant does not remain constant, but can change as it grows and ages. The external environment plays the most important role in the formation of a life form. But this, of course, does not mean that the life form of any plant is infinitely plastic and depends only on the conditions directly acting at the moment. Each plant species reacts to external influences within the framework of its hereditarily fixed capabilities. Strawberries, for example, will not become a spreading tree even in the most favorable environment for growth and branching. Speaking of harmony with external environment, we mean that in the current life form each species exhibits traits of hereditary adaptation developed in the process of natural selection to a certain set of external factors.

Structure of a flowering plant

Leaves. Main part of nutrients organic matter on Earth it is formed in the leaves of flowering plants. Typically, a leaf consists of a flat leaf blade on a petiole, which is attached at its base to the stem. At the point of attachment there are two leaf-like outgrowths - stipules. However, each of these structures may be missing. The leaf blades of some flowering plants, for example many Lamiaceae and cruciferous plants, are sessile, i.e. arise directly from the stem without a petiole; in other species, all that remains of the leaves are their sheaths with plates reduced to thread-like structures (this can be observed in cereals). Inside the leaf there are relatively loosely packed cells rich in the green pigment - chlorophyll. Photosynthesis occurs in them. At the upper surface of the leaf, these cells are usually elongated and located side by side perpendicular to the surface: they form the so-called. palisade parenchyma. The underlying cells are less uniform in shape and are separated by air-filled intercellular spaces - this is the so-called. spongy parenchyma. Air exchange of internal leaf tissues with environment goes through small holes in the single-layer skin (epidermis) covering it: as a result, photosynthetic cells receive carbon dioxide, necessary for the formation of organic matter, and get rid of “production waste” - oxygen. The epidermis is usually covered on the outside with a waxy coating (cuticle) and is relatively impermeable to water and gases, and its cells are incapable of photosynthesis. Unfortunately, the leaf loses quite a lot of water through evaporation, which can sometimes threaten the existence of the entire plant. It is supplied with water through a system of internal veins, usually forming a dense branched network. The veins consist of vascular tissue cells that deliver water with mineral salts dissolved in it to the photosynthetic areas and carry organic matter from there to all parts of the plant. Since some cells of this conducting system are thick-walled, the veins simultaneously play the role of the skeleton of the leaf, supporting it in a straightened state and ensuring a normal supply of light and air to all its parts.

Stem. Through the conducting cells of the stem, water with mineral salts dissolved in it flows from the root to the veins of the leaf, which contain cells of the same type. In a young stem, this water-conducting system (xylem) usually forms a cylinder that begins underground, serving as a rigid support for leaves, flowers and fruits and capable of thickening and becoming lignified over time, turning into a powerful multi-meter trunk. Outside the xylem there is a similar cylinder - phloem, consisting of cells through which the transport of organic substances occurs. Phloem also extends into the leaf veins. The rest of the stem consists of soft fabric, sometimes photosynthetic, in which excess nutrients are often stored. central part The stem - the core - can collapse, and then a cavity remains in the stem in its place. Stems with leaves (as well as flowers and fruits, which are thought to be derived from the leaves) are called shoots.

Root. Root system anchors the plant in the substrate. The root also contains conducting tissues - xylem is closer to the center, phloem is further from the center. Large amounts of reserve substances can accumulate here, which is why some roots are very large. In addition to support and storage, the most important function of roots is absorption: water with salts dissolved in it must flow from the soil into the shoots and compensate for the costs and losses of the plant. Suction is carried out by the so-called. root hairs - numerous outgrowths of superficial root cells in a relatively narrow zone near its tip. It is the root hairs, penetrating between the smallest soil particles, that provide the enormous total absorbing surface of the underground part of the plant. The presence of a conductive, or vascular, system - characteristic all flowering plants, which in all other respects can vary greatly in their structure. Xylem and phloem in all flowering plants consist, in principle, of the same, more or less identically located elements. Anatomically, flowering plants are closest to conifers, cycads and other gymnosperms; a more distant evolutionary relationship connects them with pteridophytes.

Flower structure

A flower is a specialized shoot or, more likely, a system of shortened and closely spaced shoots, the parts of which form several concentric circles or spirals around the apex. On the outside there is usually a calyx of green sepals that cover the other parts of the flower in the unopened bud. As a rule, closer to the center there is a corolla of brightly colored and pleasantly smelling petals. Both of these circles form the so-called. perianth. Even closer to the center are the stamens, and, finally, directly in it - one or more pistils. These are the actual reproductive parts of the flower - male and female, respectively. Sometimes a flower lacks a calyx, corolla, entire perianth, stamens or pistils. For example, an individual cereal flower consists of three stamens and one pistil, surrounded by hard scales that, strictly speaking, cannot be called either petals or sepals. Oak trees have two types of flowers: some consist of stamens with sepals, others - only pistils. However, in any case, in order for a flower to take part in reproduction, it must have stamens or pistils; if neither one nor the other is present, it is sterile. However, in some species, sterile flowers serve to attract pollinators (for example, the marginal “petals” in sunflower inflorescences), and humans specifically breed “double” peonies, carnations and other flowering plants without stamens and pistils for decorative purposes.

Woody plants

Reproduction of angiosperms

Pollination

The reproductive part of the stamen is its head, the so-called. anther. It usually consists of four pollen sacs located side by side. When ripe, they open with longitudinal cracks or rounded pores and release pollen - many tiny, volatile or sticky pollen grains. Wind pollination. Wind-pollinated plants form huge quantities flying pollen: most of it is lost uselessly, and only individual pollen grains, accidentally landing on the stigma of a flower of a specimen of the same species, ensure reproduction. This method of pollination is characteristic of many trees (not only flowering trees, but also conifers), cereals, sedges and some well-known weeds, such as wormwood and ragweed. Their flying pollen can cause hay fever, which affects many people. Ambrosia, which blooms at the end of summer, is especially dangerous in this sense. Pollination by insects. Sticky pollen can simply fall from the anther onto the pistil, but more often it is carried from flower to flower by insects (birds and even small mammals sometimes also play the role of pollinators). The relationships between flowering plants and the animals that visit their flowers are very interesting, and it is difficult to explain their occurrence without resorting to the concept of “purpose”. As a result, you can often hear that insects “look” for very specific flowers, and those, in turn, “arrange” their stamens specifically for this particular guest. Be that as it may, insects are really attracted to pollinated flowers by their color and smell, which is not necessarily pleasant. Flies, for example, fly to the smell of carrion, spread by kirkazon and "skunk cabbage" (Symplocarpus stinking), and moths react to the bright whiteness of species blooming at dusk. Penetrating into a flower for food, the pollinator involuntarily shakes off pollen grains and some of this pollen can then just as “accidentally” be left on the stigma of the same or another flower, not necessarily even a flower of the same species. The food for such insects is either pollen itself, or, in most cases, nectar - a sweet liquid formed by structures of different origins - nectaries and accumulating in the depths of the corolla or in special tubular petals - spurs, for example in violets and larkspur. Typically, an insect-pollinated flower is designed in such a way that it is necessary to get to the nectar by touching the stamens, which in some cases are equipped with special mechanisms that respond to such a touch. For example, the walls of the anthers can be under pressure, like those of Kalmia: as soon as you touch them, they explode and shower the guest with pollen grains. Among such adaptations, the most surprising are those that ensure cross-pollination, i.e. the transfer of pollen to the pistil of a flower not from the same plant specimen (this is called self-pollination), but from another. Cross-pollination is beneficial because it increases the diversity of members of a species, and therefore the chances of survival of that taxonomic group as a whole. However, contrary to Darwin’s opinion, self-pollination also does not always lead to degradation, and many plants constantly use it. Some flowers do not open at all, and the pollen reaches the pistil without any external carrier. However, cross-pollination appears to be more widespread, even among wind-pollinated species: many of them have flowers that are either pistillate or staminate (unisexual), with some plants often being purely female and others purely male. Flower structure and pollination. In many flowers, the stamens mature earlier or later than the pistils, so that self-pollination is impossible, but the pollen can be transferred to another specimen of the same species, the pistils of which are quite ready to receive it. For example, in sage (Salvia), the anther of each stamen, strongly elongated and bent by a rocker, resembles a lever: getting into the corolla tube, the insect inevitably presses its head with its short arm - the long one lowers, touches the back of the insect and leaves a portion of pollen on it. In older flowers, the anthers are already empty, but the pistil arches so that its stigma is located exactly where the pollinator's back, stained with pollen, should appear. Tubular flowers of the same type of primrose are of two types: in some specimens the anthers are located above the mouth of the tube, and the stigma is located in the depths, in others - vice versa. Climbing headfirst into the tube for nectar, insects in the first case stain only their backs with pollen, and in the second case only their heads and then leave pollen, respectively, only on long or only on short pistils, i.e. already on other plants. Some violets on the same plant have some flowers that are clearly visible, capable only of cross-pollination, while others are small, indehiscent - only self-pollination is possible for them; the latter, by the way, are more prolific. Most complex mechanism, which ensures cross-pollination, has arisen in most orchid species. In the center of their flower is the so-called. a column of a single stamen fused with a pistil. Pollen grains are united into sac-like masses - pollinia. Each of them is located in a special recess and is equipped with a leg, the end of which is connected to a sticky disk (stick). The adhesive is attached to the insect that has visited the flower so precisely that the entire mass of pollen can only end up on the stigma of another flower of the same species.

Fertilization

The most complex part of a flower is the pistil. It consists of one or more carpels, on the walls of which there are seed primordia - ovules. The ovules are concentrated in the lower swollen part of the pistil, called the ovary, and its upper part forms a more or less extensive and sticky “landing area” for pollen - the stigma. Often it rises above the ovary on a rod-shaped column. Once on the stigma, the pollen grain receives water and nutrients from it and germinates into a pollen tube, which penetrates the ovary and, ultimately, the ovule. There it breaks through and releases two male gametes. One of them merges with the egg located in the ovule - fertilization occurs and a zygote appears, giving rise to a new plant. An embryo develops from the zygote, and from the tissues surrounding it, a supply of nutrients for it (in many cases this is endosperm) and a protective shell - the ovule turns into a seed. Thus, fertilization and seed development occur inside the ovary. It is to this structure that flowering plants, also called angiosperms, owe much of their evolutionary success. The embryo inside the seed can remain dormant for many weeks, months and even years: it is protected from external influences by the seed coat and supplied with a supply of food; at favorable conditions it will begin to grow, quickly increasing the size of its rudimentary structures due to internal reserves, and will turn into a seedling. This process is called seed germination. The sizes of seeds in flowering plants are very diverse - from microscopic in orchids to huge in coconut tree. One plant can produce colossal amounts of them: plantain and shepherd’s purse - more than five thousand per year, wormwood (Artemisia vulgaris) - more than a million. Some seeds are edible, some are poisonous, some are so hard that they cannot be cut with a knife. Their shape and color are very diverse, they can be smooth and wrinkled, sticky and hairy. The fact that seeds contain a supply of nutrients is widely used by humans. Wheat flour, castor oil or, for example, the sugar contained in sweet corn kernels - we get all this from the endosperm of the seeds. In other cases, reserve substances are located inside the embryo itself, in its fleshy edible cotyledons. This is the case, for example, with soybeans, peanuts, beans and peas, the seeds of which lack endosperm.

Life cycle of a flowering plant

The flower, a structure unique to this plant division, contains the reproductive organs that give rise to seeds and fruit: stamens and pistils. A series of divisions of certain cells they contain (megaspore and microspore mother cells), including the so-called. reduction division (meiosis) leads to the formation of sex cells (gametes) with half the number of chromosomes in each. For fertilization, the male gamete (sperm) from the pollen grain (more precisely, its nucleus) must merge with the female (ovum), which is located in the ovule, enclosed in the ovary of the pistil. To do this, a pollen tube grows through the pistil. During fertilization, a zygote appears with a normal (double) number of chromosomes for the species. After a series of divisions, an embryo is formed. The surrounding tissues differentiate into the outer protective seed coat and nutritional tissue (endosperm). In parallel, the ovary (sometimes together with neighboring structures) changes, turning into a fruit. After a period of dormancy, the seed germinates and the embryo develops into a new plant. The life cycle is completed.

The meaning of plants

The importance of plants in nature and human life. As we know, all people and animals breathe oxygen and emit carbon dioxide. The amount of carbon dioxide in the air also increases from burning fuel. Plants, in turn, absorb carbon dioxide from the air in the light and release oxygen. In addition, plants enrich the air with oxygen, reducing the amount of carbon dioxide. Due to the fact that oxygen is an essential component for the life of humans and animals, life on Earth would be impossible without green plants. To enrich cities and villages with oxygen - avenues, boulevards, streets, etc. landscaping. People plant trees and shrubs, develop parks, boulevards, flower beds, and lawns. In general, in any city on the planet they try to plant as many plants as possible, which are so necessary to preserve the health of the population. Given that plants absorb carbon dioxide, they also release oxygen and some gaseous substances into the air, which trap dust and destroy microbes harmful to health. Therefore, we must take care of protecting our plants, every leaf, and increase green spaces, or rather, do not forget to plant new plants, care for them, and protect them from damage. The importance of plants in the formation of organic substances in them also plays an important role. Green plants create organic substances, and people and animals receive them ready-made from green plants for their nutrition. People grow cultivated plants in order to further harvest fruits, vegetables, grains, etc. and eat them and store them for the winter. And for farm animals, grains and silage are collected, which are also necessary for the life of animals, because they contain nutritious organic substances. Animals could not exist without green plants, since they feed on ready-made organic substances that are formed in them. In large meadows you can also find a lot of useful organic matter, which is used as feed for livestock. To do this, cattle are driven out to pastures or grass is cut and hay is collected. But mowing must be done at the very beginning of the grasses flowering, because at this time the plants contain the most succulent nutrients. If mowing is done during flowering or fruiting, the grass becomes coarser, and its nutritional quality is significantly reduced. As a result, we can say that the importance of plants in nature and human life plays a very important role. Because green plants They provide people with food, raw materials for industry, and feed for farm animals.