Plants are photosynthetic living organisms related to eukaryotes. They have a cellular cellulose membrane, a reserve nutrient in the form of starch, are inactive or immobile and grow throughout their life.

The chlorophyll pigment they contain gives plants their green color. In the light of carbon dioxide and water, they create organic matter and release oxygen, thereby providing nutrition and respiration for all other living organisms. Plants also have a regenerating ability, they can restore vegetative organs.

The science that studies the structure and life of plants, their taxonomy, ecology and distribution is called botany(from the Greek. botane -grass, herbs and logos -teaching).

Plants make up the bulk of the biosphere, forming the green cover of the Earth. They live in various conditions - water, soil, ground-air environment, occupy the entire land of our planet, with the exception of the icy deserts of the Arctic and Antarctica.

Life forms of plants.Treescharacterized by the presence of a lignified stem - a trunk that persists throughout life. Shrubshave several small stems. For herbssucculent, green, non-lignified shoots are characteristic.

Life expectancy.Distinguish annual, biennial, perennialplants. Trees and shrubs are perennial plants, and grasses can be both perennial and annual and biennial.

The structure of plants.The body of plants is usually dissected into rootand the escape.Of the higher plants, flowering plants are the most highly organized, numerous and widespread. In addition to the root and shoot, they have flowers and fruits - organs that are absent in other plant groups. It is convenient to consider the structure of plants using the example of flowering plants. The vegetative organs of plants, the root and shoot, provide their nutrition, growth and asexual reproduction.

Figure: 62.Types of root systems: 1 - core; 2 - fibrous; 3 - cone-shaped root vegetable of parsley; 4 - beet root crop; 5 - dahlia root cones

With the help of (Fig. 62) the root, the plant is fixed in the soil. It also provides the flow of water and minerals and often serves as a place for the synthesis and storage of nutrients.

Roots begin to form in the bud. When the seed germinates from the embryonic root, the main root.After a while, numerous lateral roots.In a number of plants, stems and leaves form adventitious roots.

The collection of all roots is called root system.The root system can be pivot,with a well-developed main root (dandelion, radish, apple tree) or fibrous,formed by lateral and adventitious roots (barley, wheat, onion). The main root in such systems is poorly developed or completely absent.

A number of plants store nutrients in the roots (starch, sugar), for example, carrots, turnips, beets. Such modifications of the main root are called root crops.In dahlias, nutrients are deposited in thickened adventitious roots, they are called root tubers.Other root modifications are also found in nature: attachment roots(near lianas, ivy), aerial roots(monstera, orchid), stilted roots(in mangrove plants - banyan tree), respiratory roots(in marsh plants).

The root grows to the top, where the cells are educational tissue - the point of growth.She is protected root cap. Root hairssuck water with dissolved minerals in suction area.By conductive systemroot water and minerals go up to the stems and leaves, and downward move organic matter.

The escape Is a complex vegetative organ consisting of buds, stems and leaves. Along with vegetative ones, flowering plants have generative shoots on which flowers develop.

The shoot is formed from the embryonic seed bud. The development of perennial shoots from buds is clearly visible in spring.

By the location of the buds on the stem, they distinguish apicaland lateral kidneys.The apical bud ensures the growth of the shoot in length, and the lateral ones - its branching. The outside of the bud is covered with dense scales, often impregnated with resinous substances; inside there are a rudimentary shoot with a growth cone and leaves. In the axils of the rudimentary leaves, there are barely noticeable rudimentary buds. In the generative bud are the rudiments of flowers.

Stem - This is the axial part of the shoot, on which the leaves and buds are located. It performs a supporting function in the plant, ensures the movement of water and minerals from the root up to the leaves, organic matter down, from the leaves to the root.

Outwardly, the stems are very diverse: in corn, sunflower, birch - erect; in wheatgrass, Potentilla - creeping; in bindweed, hops - curly; peas, lianas, grapes - climbing.

The internal structure of the stem is different in monocotyledonous and dicotyledonous plants (Fig. 63).

Figure: 63.Internal structure of the stem. Cross section: 1 - corn stalk (vascular bundles are located throughout the stalk); 2 - linden branches

1. Have dicotyledonous plantthe stem is covered with skin on the outside - epidermis,in perennial lignified stems, the skin is replaced stopper.Under the cork there is a bast formed by sieve tubes that ensure the movement of organic matter along the stem. Bast mechanical fibers give the stem strength. Cork and bast form bark.

To the center of the bast is cambium - a single layer of cells of the educational tissue, providing the growth of the stem in thickness. Under it is located woodwith vessels and mechanical fibers. Water and mineral salts move through the vessels, and the fibers give the wood strength. With the growth of wood, tree rings,by which the age of the tree is determined.

In the center of the stem is core.It performs a storage function, organic matter is deposited in it.

2. Have monocotyledonous plantsthe stem is not divided into bark, wood, and pith; they lack a cambial ring. Conducting bundles, consisting of vessels and sieve tubes, are evenly distributed throughout the stem. For example, in cereals, the stem is a straw, it is hollow inside, and the conducting bundles are located along the periphery.

A number of plants have modified stems: thornsthe hawthorn, serving for protection; antennaefor grapes - for attachment to the support.

Sheet - It is an important vegetative organ of a plant that performs the main functions: photosynthesis, water evaporation and gas exchange.

In plants, several types of leaf arrangement are distinguished: another,when the leaves are arranged alternately one after another, opposite - the leaves are located opposite each other and whorled - three or more sheets extend from one node (Fig. 64).

Figure: 64.Leaf arrangement: 1 - alternate; 2 - opposite; 3 - whorled

The sheet consists of leaf bladeand petiole,sometimes stipules are present. Leaves without petiole are called sedentary.In some plants (cereals), petiolate leaves form a tube - a sheath, wrapping around the stem. Such leaves are called vaginal(fig. 65).

Figure: 65. Types of leaves (A): 1 - petiolate; 2 - sedentary; 3 - vaginal; leaf venation (B): 1 - parallel; 2 - arc; 3 - mesh

Leaves can be simple or complex. Simple sheethas one leaf blade, and complicated - several leaf blades located on one petiole (Fig. 66).

Figure: 66. Leaves are simple: 1 - linear; 2 - lanceolate; 3 - elliptical; 4 - ovoid; 5 - heart-shaped; 6 - rounded; 7 - arrow-shaped; complex: 8 - paired; 9 - pinnate; 10 - triple; 11 - finger complex

The forms of leaf blades are various. In simple leaves, leaf blades can be whole and dissected with various edges: dentate, serrate, crenate, wavy. Composite leaves can be paired and odd-pinnate, palmate, trifoliate.

The sheet plate contains the system veins,performing support and transport functions. Distinguish meshvenation (in most dicotyledonous plants), parallel(cereals, sedges) and arc(lily of the valley) (see fig. 65).

Internal structure of the sheet (Fig. 67). Outside the sheet is covered epidermis – skin,which protects the inner parts of the sheet, regulates gas exchange and evaporation of water. Skin cells are colorless. On the surface of the leaf, there may be outgrowths of skin cells in the form of hairs. Their functions are different. Some protect the plant from being eaten by animals, others from overheating. The leaves of some plants are covered with a waxy bloom, which is poorly permeable to moisture. This helps to reduce the loss of water from the leaf surface.

Figure: 67.Internal structure of the leaf: 1 - skin; 2 - stomata; 3 - columnar tissue; 4 - spongy tissue; 5 - leaf vein

On the underside of the leaf in most plants, the epidermis contains numerous stomata - holes formed by two guard cells. Gas exchange and water evaporation are carried out through them. During the day, the stomatal gap is open, and closes at night.

The inner part of the sheet is formed by the main assimilating tissue,providing the process of photosynthesis. It consists of two types of green cells - columnar,arranged vertically, and rounded, loosely located spongy.They contain a large amount of chloroplasts, which give the leaf green color. The pulp of the leaf is permeated with veins formed by conductive vessels and sieve tubes, as well as fibers that give strength. The organic substances synthesized in the leaf move along the veins to the stem and roots, and the flow of water and minerals flows back.

In our latitudes, there is a massive shedding of foliage every year - leaf fall.This phenomenon has an important adaptive value, it protects the plant from drying out, freezing, and prevents tree branches from breaking. In addition, with dead leaves, the plant is freed from unnecessary and harmful substances.

Many plants have modified leaves that perform specific functions. Pea antennae, clinging to the support, support the stem, nutrients are stored in the scaly leaves of onions, barberry spines protect it from being eaten, sundew traps lure and catch insects.

Most perennial herbaceous plants have modification of shoots,which have adapted to the performance of various functions (Fig. 68).

Figure: 68.Modifications of shoots: 1 - kupena rhizome; 2 - onion bulb; 3 - potato tuber

Rhizome - This is a modified underground shoot that serves as a root, as well as serving to store nutrients and vegetative propagation of plants. Unlike the root, the rhizome has scales - modified leaves and buds, it grows horizontally in the ground. Adventitious roots grow from it. The rhizome is found in lily of the valley, sedge, kupena, and creeping wheatgrass.

Strawberries form aboveground modified stolons - mustache,providing vegetative reproduction. When in contact with the ground, they take root with the help of adventitious roots and form a rosette of leaves.

Underground stolons - tubersin potatoes, these are also modified shoots. In the well-developed core of their strongly thickened stem, nutrients are stored. On the tubers you can see eyes - buds arranged in a spiral, from which aerial shoots develop.

Bulb -it is a shortened shoot with succulent leaves. The lower part - the bottom is a shortened stem from which the adventitious roots grow. The bulb is formed in many lily plants (tulips, lilies, daffodils).

Modified shoots are used for vegetative propagation of plants.

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The name of the body and its functions	Structural features
Vegetative organs of flowering plants For maintaining plant life: for nutrition, respiration, growth and development
The root is one of the main vegetative organs of higher plants. The primary root, formed during the development of the embryo, during germination in some plants, forever remains the longest and most noticeable in the root system. It turns into the main root, from which the lateral ones grow. The main tasks that it performs are the absorption of water and mineral salts from the soil, their transfer to the aboveground organs, as well as anchoring the plant itself in the soil. In some plants, the root serves as a repository of reserve nutrients. In root-sucking plants, vegetative propagation is carried out with the help of roots.
A shoot is an aboveground organ of a plant that arose as an adaptation to life in the air of land. The shoot consists of a stem, leaves and / or buds. The stem is adapted to the movement of substances through the plant and to retain the leaves and carry them out to the light, performs a supporting function. Leaves perform the most important functions of photosynthesis, transpiration and gas exchange. Thanks to the buds, the shoot can branch and create a shoot system, increasing the area of \u200b\u200bplant nutrition.
Reproductive organs of flowering plants For the formation of offspring
A flower is a reproductive organ of angiosperms, designed for the formation of spores and gametes, the process of fertilization, followed by the formation of seeds and fruits	a - pedicel; b - receptacle; in - a cup; d - whisk; d - staminate thread; e - anther; g - stigma; h - column; and - ovary; k - pistil.
New plants grow from seeds, similar to mothers	Seed - formed from the ovule after double fertilization. Each seed consists of an integument, an embryo and a supply of nutrients. The seed coat develops from the integument of the ovule and can be soft, leathery, filmy and hard (woody). The embryo is a plant in its infancy and consists of an embryonic root, stalk, cotyledons and buds. An embryo develops from a zygote formed as a result of the fusion of sperm with an egg.
The fruit is the reproductive organ of angiosperms, which provides seed reproduction of plants. It is designed to form, protect and spread seeds. The fruit develops from a flower.	The outer zone is called the exocarp or exocarp; middle - mezocarp or mesocarp; internal - intracarp or endocarp.

Vegetative propagation of plants. Methods of natural and artificial vegetative propagation of plants

Natural vegetative reproduction occurs with the help of the following organs:

1. Rosette of leaves, "whiskers".

2. Lines - aboveground leafy shoots with a leaf rosette at the end.

3. Rhizome - underground shoots bearing dormant buds.

4. Root shoots - shoots formed from dormant buds of plant roots.

5. Bulbs. Bulbous plants are divided into two groups: evergreen and deciduous, the latter, in turn, according to the location of the baby bulbs, are subdivided into underground, aerial - stem, located in the leaf axils, and in the form of inflorescences filled with bulbs.

6. Root tubers, or modified roots - repositories of nutrients. The root tubers themselves are unsuitable for reproduction, since they do not have dormant buds, like real tubers of stem origin. Therefore, they are separated with a piece of the root collar with one or two buds.

8. Stem tubers. Distinguish between stem tubers with limited growth, i.e., stopping growth at the end of the growing season, and stem tubers with continued growth in subsequent growing seasons.

TO artificial methods of vegetative reproduction include the following.

1. Dividing a bush is the easiest way. Usually, rhizome plants are propagated in this way, especially strongly bushy and forming a large number of aerial shoots coming from roots or rhizomes

2. Cuttings - a method of vegetative propagation by rooting certain parts of the plant. Cuttings can be root, leaf, stem. Stem cuttings are subdivided into lignified, semi-lignified and green.

3. Layers - rooted shoots that have developed on the mother plant.

Horizontal layering. Young branches are laid in shallow grooves, they are pinned and, as the shoots grow, they spud 2-4 times per season.

Air layering. In the place of the desired rooting, the leaves are cut off. Previously, the pot is cut along the length, adjusting the bottom hole to the diameter of the stem at the root. The trunk is wrapped in moss, a pot is attached to it with pegs, filled with light earth and watered. For better root formation, longitudinal cuts are made on the trunk. The pot can be replaced by wrapping the shoot with plastic wrap.

Vertical layering. If you cut a young tree, a strong growing stump will appear. When the shoots reach 8 - 10 cm in height, the first hilling is carried out (necessarily with nutritious soil for 2/3 - 3/4 of their length), the second - when the shoots are 15 - 18 cm long, the third, when their length reaches 45 - 50 cm. at the end of September, the land is removed, the rooted shoots are cut and planted in a nursery or in a permanent place.

4. Grafting consists in transferring part of one plant to another and splicing them, which allows you to preserve the varietal characteristics of the grafted plant. The plant or part of it to be grafted onto is called the stock, and the part to be grafted is called the scion. A graft can be a bud with a small piece of bark and wood (the so-called peephole, or scutellum) or a stalk, that is, a part of the shoot (branch) with all the buds on it.

Lecture 6. Reproduction of plants

Reproduction is an essential property of living organisms to reproduce their own kind. Thanks to reproduction, the continuity and continuity of life is ensured. There are two main forms of reproduction: asexual and sexual.

Asexual reproduction. Reproduction, in which one organism takes part, there is no formation and fusion of gametes, there is no fusion of genetic material in any form... This is the most ancient form of reproduction, widespread in all groups of plants, occurs by mitotic division or with the help of spores, a special form of asexual reproduction is vegetative reproduction.

Division ... Reproduction by division is characteristic of unicellular algae. Division occurs by mitosis, as a result of which individuals are formed that are genetically identical to each other and to the mother's body.

Reproduction by spores . Plant spores are reproductive, unicellular formations that serve to form new individuals... In most algae living in water, the spores are mobile, since they have flagella. Such disputes are called zoospores... In land plants and fungi, they do not have special adaptations for active movement. Spores are formed in the organs of asexual reproduction - sporangia or zoosporangia. In algae, almost any cell can become a sporangium; in higher plants, sporangia - a multicellular organ. In plants, spores are always haploid. If they arise on a diploid plant, then their formation is preceded by meiosis, if on a haploid plant, mitosis. The spores resulting from meiosis are genetically unequal; the organisms that develop from them are genetically unequal.

The plant on which spores form is called a sporophyte. If the spores are morphologically indistinguishable, then the plants that form them are called homosporous, heterosporous plants are plants that form spores, always differing in size and physiological characteristics. Microspores - smaller spores that form in microsporangia, grow out of them male gametophytes (plants that form male gametes ). Megaspores - larger spores that form in megasporangia, grow out of them female gametophytes ... Diversity is more common among higher plants (some lyes, ferns, all gymnosperms and angiosperms).

Reproduction by spores is of great biological importance - as a result of meiosis, a recombination of genetic material occurs, new combinations of gene alleles appear in disputes, which fall under the control of selection; usually in plants, spores are formed in huge quantities, which provides a high intensity of reproduction. Due to their small size and lightness, the spores are carried over long distances, ensuring the dispersal of plants; the dense spore shell serves as a reliable protection against adverse environmental conditions.

Vegetative propagation of plants - this is an increase in the number of individuals due to the separation of viable parts of the vegetative body and their subsequent regeneration (restoration to the whole organism). This breeding method is widespread in nature. Both algae and higher plants reproduce in a vegetative way.

Vegetative reproduction happens natural and artificial ... Thanks to natural vegetative reproduction in nature, there is a rapid increase in the number of individuals of the species, their dispersal and, as a result, success in the struggle for existence. Natural vegetative reproduction occurs in several ways: by fragmentation of the maternal individual into two or more daughter; destruction of areas of ground-creeping and lodging shoots (lyes, gymnosperms, flowering); with the help of special structures specially designed for vegetative propagation (tubers, bulbs, rhizomes, corms, axillary buds, adventitious buds on leaves or roots, brood baskets of bryophytes, etc.).

Artificial vegetative reproduction is carried out with human participation in the cultivation of cultivated plants. Artificial vegetative reproduction has a number of advantages over seed: it provides offspring that retain the characteristics of the parent organism, accelerates the generation of offspring, and allows you to get a large number of offspring. In addition, with the help of vegetative propagation, clones of those plants can be reproduced that form non-viable seeds or do not form them at all.

Vegetative propagation methods.Plants can be propagated by vegetative organs - by dividing the whole plant into parts, by aboveground and underground shoots, leaves, roots.

Fragmentation the division of an individual into two or more parts is called, each of which regenerates into a new individual (Fig. 34). Such reproduction is typical for filamentous and lamellar algae (scraps of filaments or parts of the thallus), some flowering plants (for example, Canadian Elodea). Only female specimens of Elodea came to Europe, unable to form seeds due to the lack of male plants, and fragmentation turned out to be the only way of reproduction.

Division of bushes. Currants, gooseberries, primroses, rhubarb reproduce well in parts of the bushes. The plant is dug up, divided into parts and planted separately from each other. The bushes are usually divided in spring or late summer.

Reproduction by aerial shoots.

Mustache ... In agricultural practice, strawberries and strawberries are propagated with a mustache. In the nodes of the whiskers, lateral buds and adventitious roots are formed. After the internodes dry up, the plants separate. In nature, plants such as creeping buttercup and saxifrage reproduce with a mustache.

Figure: Reproduction of currants by layering

Layers. Layers are areas of shoots that are specially pressed to the ground and covered with earth, and after the development of adventitious roots, they are separated from the mother plant (Fig. 36). For better rooting, the shoot can be cut. This disrupts the outflow of nutrients and their accumulation at the site of the incision, which creates favorable conditions for the formation of adventitious roots. Gooseberries, currants, grapes reproduce by layering.

Stem cuttings. The stem cutting is an aerial shoot site. Stem cuttings propagate grapes, currants, gooseberries, decorative species of spirea, red pepper, eggplant and others. For reproduction, cuttings are taken from 2-3 to 6-8 cm long, consisting of one internode and two nodes. At the top node, leaves are left (if the leaf blades are large, then they are cut by half). The cuttings are planted in special greenhouses, and after rooting, in open ground.

Figure: ... Propagation by cuttings

Graft (or transplantation) - artificial fusion of a part (cuttings, buds) of one plant with the shoot of another. A stalk or bud with an adjacent

a plot of bark and wood (eye) grafted onto another plant is called graft. Rootstock - a plant or a part thereof on which the vaccination was carried out. Grafting allows you to use the root system of the rootstock to preserve or reproduce a certain variety, replace a variety, obtain new varieties, accelerate fruiting, obtain frost-resistant plants, repair or rejuvenate old mature trees.

There are many methods of grafting, but all of them can be reduced to two main types: grafting by rapprochement, when the scion and the stock remain on their roots, grafting with a separated scion, when only the stock has roots.

The most common methods of vaccination are as follows (Fig. 38). Inoculation into cleft or semi-cleavage... It is used if the graft is thinner than the rootstock. The cross section of the rootstock is completely or partially divided and a scion is inserted into it, obliquely cut from both sides.

Bark grafting. The graft is also thinner than the rootstock. A horizontal cut is made on the rootstock under the stem node, the bark is incised in the vertical direction and its edges are carefully turned off. A cut in the form of a half-cone is made on the scion, inserted under the bark, clamped with bark lapels and tied.

Copulation... It is used if the scion and rootstock have the same thickness. On the scion and rootstock, make oblique cuts and combine them, ensuring a tight connection.

Budding... Inoculation of the bud-eye. A T-shaped incision is made on the stock, the edges of the bark are folded back, and a bud with a small piece of wood is inserted behind the bark and bandaged tightly.

Reproduction by underground shoots.

Tuber ... Potatoes and Jerusalem artichoke are the most famous of the agricultural plants propagated by tubers. They can be propagated by planting whole tubers or parts thereof with eye buds. Tubers, as a repository of nutrients, are formed in wild plants such as feeding, weekly.

Rhizome ... In agriculture, rhizomes are used to propagate rhubarb, mint, asparagus, bamboo, in decorative gardening - lily of the valley, iris and others. They multiply easily by dividing the rhizomes into parts, each of which must contain a vegetative bud.

A large number of rhizome plants, primarily cereals, live in forests, steppes, and meadows. Rhizomatous plants include wheatgrass, timothy, whiteus, kupena, oxalis, field horsetail and other wild plants. In many, the rhizomes branch, and when the old parts die off, new plants separate.

Bulb ... In agricultural practice, bulbs are propagated by onions, garlic, ornamental plants: tulips, daffodils, hyacinths and others. In nature, many plants reproduce by bulbs: tulips, goose onions, scrub, snowdrop, etc. Vegetative propagation of bulbous plants is carried out by overgrown adult bulbs, children, individual scales.

Corm ... The reserve nutrients of the corm are used up for flowering, but by the end of the season a new corm is formed. In addition, one or more corms may form - fleshy buds developing between the old and new corms. Corms include gladiolus, crocus.

Root tubers ... They are thickenings of lateral roots. In ornamental gardening, dahlias, sweet potatoes are propagated by root tubers. When breeding dahlias, it is necessary to take root tubers with the base of the stem bearing the buds, since the root tubers do not form buds. Root tubers are propagated by the spring cleaver, two-leaved lyubka.

Reproduction by root suckers. Root suckers are shoots arising from adventitious buds on the roots (Fig. 36). Root offspring reproduce plants that easily form adventitious buds on the roots: cherry, plum, raspberry, lilac, aspen, sow thistle, thistle field, etc.

Root cuttings. The root cutting is part of the root. They reproduce species, on the roots of which adventitious buds easily develop: horseradish, raspberries, cherries, roses. Root cuttings are harvested in autumn, less often in spring. To do this, use the lateral roots of the first order at the age of 2-3 years. The length of the cuttings is up to 10-15 cm, the diameter is 0.6-1.5 cm.The cuttings are planted in the soil to a depth of 2-3 cm.Many wild plants also propagate by cuttings: willow, poplar, aspen, dandelion

Reproduction by leaves.

Whole leaves. Many flowering plants are propagated by leaves, such as saintpaulias, begonias. It is enough to put the leaf in water, adventitious roots and adventitious buds appear, after a while the plant is transplanted into the soil.

Leafy cuttings. Sometimes even a part of a leaf is enough for vegetative propagation. A part of the leaf with a large vein is cut out from the royal begonia, the leaf of the sansevier can be cut into several leaf cuttings and put in water.

Accessory buds on the leaves, kids ... In bryophyllum, adventitious buds are formed on the leaves, similar to small plants. Falling, they become independent plants.

Tissue culture. Tissue culture is the growth of plant cell groats on artificial media. Plant cells have the property totipotency - a single cell can develop into a normal plant using certain phytohormones. The tissue culture method allows you to obtain clones some higher plants. Cloning - obtaining a set of individuals from one maternal vegetative way. Cloning is used for propagation of valuable plant varieties and for the improvement of planting material.

Sexual reproduction. Sexual reproduction is associated with the formation of a special type of cells by plants - gametes. The plant on which the formation of gametes occurs is called gametophyte... The process of gamete formation is called gametogenesis... It takes place in special organs - gametangia... In homosporous plants, the gametophyte is usually bisexual: it bears both female and male gametangia. In heterosporous plants, a gametophyte with male gametangia develops from microspores, and a gametophyte with female gametangia from megaspores. Gametes of plants are formed mitotically, meiosis occurs after the formation of a zygote ( zygotic reduction) - many algae, or during the formation of spores ( controversial reduction) - in diploid algae and higher plants. In animals, meiosis occurs during the formation of gametes ( gametic reduction).

Sexual reproduction has several advantages over asexual reproduction. Firstly, when gametes merge, an organism is formed with a unique double set of alleles of genes obtained from parents with different genotypes, an organism with a unique genotype is formed. As a result of selection, individuals will survive whose genotype allows them to adapt to the given environmental conditions, even if these conditions change.

Secondly, mutations that change genes are more often recessive and harmful in given environmental conditions. The diploid set of genes allows the emerging recessive alleles to be preserved due to the presence of dominant alleles of these genes. Each diploid organism contains hundreds, thousands of genes in a recessive state, as the sponge is saturated with water, and the genotype is saturated with them, they are passed on to the next generation and gradually spread throughout the population. A mutation will manifest itself if both gametes carry a given recessive allele of the gene, and by this time the environment may have changed, and this mutation may be useful. This is how mutations accumulate and spread.

Gametes are always haploid. When the male and female gametes merge, a diploid zygote is formed, from which a new organism develops. The process of gamete fusion is called fertilization... The essence of the sexual process is the same for all living organisms, and its forms are diverse. There are the following types of sexual process: hologamy, conjugation, isogamy, heterogamy and oogamy (Fig. 39).

Hologamia ... Hologamy is the fusion of haploid unicellular, externally indistinguishable organisms with each other. This type of sexual process is characteristic of some unicellular algae. In this case, not gametes merge, but whole organisms acting as gametes. The formed diploid zygote usually immediately divides meiotically ( zygotic reduction) and 4 daughter haploid unicellular organisms are formed.

Conjugation. A special form of the sexual process is conjugation, which is characteristic of some filamentous algae. Individual haploid cells of filamentous thalli located close to each other begin to form outgrowths. They grow towards each other, connect, the partitions dissolve at the junction, and the contents of one cell (male) pass into another (female). As a result of conjugation, a diploid zygote is formed.

Isogamy. With isogamy, gametes are morphologically similar to each other, that is, they are the same in shape and size, but physiologically they are of different quality. This sexual process is typical for many algae and some fungi. Isogamy occurs only in water, for movement in which the gametes are equipped with flagella. They are very similar to zoospores, but are smaller in size.

Heterogamy. With heterogamy, there is a fusion of mobile germ cells, similar in shape, but differing in size. The female gamete is several times larger than the male gamete and less mobile. Heterogamy is characteristic of the same groups of organisms as isogamy and also occurs in water.

Oogamy. It is characteristic of some algae and all higher plants. The female gamete - the ovum - is large and motionless. In lower plants, it is formed in unicellular gametangia - oogony, in higher plants (excluding angiosperms) - in multicellular archegonium... The male gamete (spermatozoon) is small and mobile; it is formed in fungi and algae in unicellular organisms, and in higher plants (excluding angiosperms) in multicellular gametangia - antheridia... Sperm cells can only move in water. Therefore, the availability of water is a prerequisite for fertilization in all plants, with the exception of seed. In most seed plants, male gametes have lost their flagella and are called sperm.

Key terms and concepts

1. Asexual reproduction. 2. Plant spores. 3. Zoospores. 4. Sporophyte. 5. Male and female gametophytes. 6. Microspores and megaspores. 7. Vegetative reproduction. 8. Graft. 9. Rootstock. 10. Gametangia. 11. Zygotic reduction. 12. Spore reduction. 13. Gametic reduction. 14. Hologamia. 15. Isogamy. 16. Heterogamy. 17. Oogamy. 18. Conjugation. 19. Oogonia. 20. Archegonia. 21. Antheridia. 22. Totipotency.

Essential Review Questions

1. Reproduction of plants by division.

2. Reproduction by spores.

3. Natural vegetative reproduction.

4. Reproduction by fragmentation and division of bushes.

5. Reproduction by aerial shoots (mustache, layering, stem cuttings).

6. The main methods and features of reproduction by grafting.

7. The main methods of reproduction by ground shoots.

8. The main methods of propagation by roots.

9. The main methods of plant propagation by leaves.

10. Reproduction by tissue culture.

11. Benefits of sexual reproduction.

12. Characteristics of the main types of sexual processes (chologamy, conjugation, isogamy, heterogamy, oogamy).

Vegetative propagation - one of the methods of asexual reproduction; the formation of daughter individuals from the multicellular vegetative organs of the mother's body (or parts of these organs). It is very common in nature. Thanks to vegetative propagation, plants quickly spread, capturing new territories. In some cases, seed propagation is difficult, and vegetative propagation is the only possible way. In addition, vegetative reproduction is actively used by humans in the reproduction of agricultural and ornamental plants, because it preserves valuable varietal characteristics.
VIDEO
1. Reproduction by the root.
1.1. Root offspring - raspberry, apple, mountain ash, poplar, lilac, cherry, etc. From the adventitious buds on the roots, shoots grow - root suckers. over time, the old areas of the roots are destroyed, and the offspring become independent plants.

1.2. Only those plants propagate by root cuttings. in which adventitious buds can form on the roots. A root cutting is a 15-25 cm long piece of root on which adventitious buds can form. On the cuttings planted in the soil, adventitious roots are formed, and aerial shoots develop from the buds. Dandelion, rose hips, garden raspberries.

1.3. Root tubers. Root tubers are modified underground roots with a supply of nutrients. Adventitious buds can develop on root tubers. dahlia.

2. Reproduction by leaf.

this is how some types of indoor plants are propagated - begonia, saintpaulia (violet), sansevier. The leaves are planted in wet sand, and adventitious buds and adventitious leaves develop on them. Sometimes even part of a leaf is enough.

3. Reproduction by aerial shoot.

3.1. Stem cuttings (this is a segment of a shoot with several buds) propagate currants, roses, poplar, willow and many other trees and shrubs. For this, cuttings 25-30 cm long are planted in well-prepared soil. By the fall, adventitious roots will grow on the cuttings, and then the cuttings are dug up and transplanted to a permanent place.

3.2. Currants, gooseberries, apple trees are propagated by layering, For this, the lower branches are bent to the ground and the bark is incised at the bend. By autumn, adventitious roots develop at the incision site, the shoot can be cut off from the mother plant and transplanted to a permanent place.

3.3. Reproduction by creeping shoots - "mustache" is characteristic of tenacious, meadow tea, strawberries, chlorophytum; adventitious roots are formed in the nodes of creeping shoots.

3.4. Reproduction by grafting in vivo is extremely rare. But it is very common in gardening. A bud-eye or stalk of a cultivated plant is spliced \u200b\u200bwith a wild-stalk (which has greater power, unpretentiousness and frost resistance). The eye or stalk of a cultivated plant is called the scion, and the wild is called the stock. this is how fruit trees are propagated - apple, pear, cherry, plum ...

Grafting by cuttings - copulation

Peephole grafting - budding

4. Reproduction by underground modified shoots.

4.1. Rhizome propagation is characteristic of a huge number of plants. many of them are vicious weeds. Nettle, wheatgrass, white-grass, yarrow, lily of the valley, windweed, orchids, etc.

4.2. Bulbs are typical for monocotyledonous plants - tulips, hyacinths, amaryllis, daffodils, etc. One bulb can form several small baby bulbs that can be transplanted.

4.3. Potatoes and Jerusalem artichoke are propagated by tubers. If there are not enough tubers, you can use the part of the tuber with an eye (bud).

5. Reproduction by tissue culture ... We live in the 21st century, and cell engineering comes to the rescue of agriculture. In special chambers on a nutrient medium, cells of plant educational tissues are grown, from which whole plants with signs are formed. identical to the characteristics of the parent. This method of reproduction allows you to get a large amount of planting material, which is important when introducing a new variety into culture. Potatoes, cloves, gerberas, orchids reproduce well by tissue culture

What trait allows you to distribute angiosperms by families? 1.number of cotyledons in a seed 2.structure

3.veination of leaves

4.type of root system

The epithelium is referred to as multilayer epithelial tissue ...

1.the outer layer of the skin

2.the walls of the stomach

3.intestinal walls

4.the walls of the airways

What organs provide vegetative propagation of plants? Choose 3 correct answers

3.Aboveground shoots

1. What organs provide vegetative propagation of plants? Please select

three correct answers out of six and write down the numbers under which they are indicated.
1) seeds
2) tubers
3) aerial shoots
4) flowers
5) fruits
6) roots

2. Establish a correspondence between the animal and the type of its postembryonic

development. To do this, select a position for each element of the first column
from the second column. Enter the numbers of the selected answers in the table.
ANIMAL TYPE OF DEVELOPMENT TYPE OF DEVELOPMENT

2) indirect

A) ordinary already

B) white hare
C) May beetle
D) gooseneck newt
D) brown bear

3, Arrange the processes of excretion from the body of fish in the correct order

harmful metabolic products dissolved in water, starting from the intake
blood to the kidneys. In the answer, write down the appropriate sequence
numbers.
1) removal of urine through the urethra
2) drainage of urine from the kidneys through the ureters
3) the flow of urine into the bladder
4) the passage of blood through the blood vessels of the kidneys
5) filtration by the kidneys of the fluid that entered it and the formation of urine

What organs provide vegetative propagation of plants? Choose three correct answers out of six and write down the numbers under which they are indicated. 1) seeds 2)

tubers 3) aerial shoots 4) flowers 5) fruits 6) roots Establish a correspondence between the animal and the type of its postembryonic development. To do this, select a position from the second column for each element of the first column. Enter the numbers of the selected answers in the table. ANIMAL TYPE OF DEVELOPMENT A) common snake B) white hare C) May beetle D) comb newt E) brown bear 1) direct 2) indirect