Lecture 6. Plant propagation

Reproduction is an integral property of living organisms to reproduce their own kind. Reproduction ensures continuity and continuity of life. 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 fission is characteristic of unicellular algae. Division occurs by mitosis, resulting in the formation of individuals that are genetically identical to each other and the maternal organism.

Reproduction by spores . Plant spores are reproductive, single-celled formations that serve to form new individuals.. Most algae living in water have motile spores because they have flagella. Such disputes are called zoospores. In terrestrial 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 can become 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, by mitosis. The spores formed as a result of meiosis are genetically unequal, and the organisms that develop from them are genetically unequal.

The plant on which spores are formed 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 are smaller spores that form in microsporangia, from which they grow male gametophytes (plants that produce male gametes ). Megaspores are larger spores formed in megasporangia, from which they grow female gametophytes . Heterosporousness is more common among higher plants (some mosses, ferns, all gymnosperms and angiosperms).

Reproduction by spores is of great biological importance - as a result of meiosis, recombination of genetic material occurs, in spores new combinations of gene alleles arise that come under the control of selection; Typically, plants produce spores in huge quantities, which ensures high reproduction rates. Due to their small size and lightness, spores are carried over long distances, ensuring the dispersal of plants; The dense spore shell serves as reliable protection from unfavorable 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 a whole organism). This method of reproduction is widespread in nature. Both algae and higher plants reproduce vegetatively.

Vegetative propagation occurs natural and artificial . Thanks to natural vegetative reproduction in nature, there is a rapid increase in the number of individuals of the species, their settlement and, as a result, success in the struggle for existence. Natural vegetative propagation occurs in several ways: fragmentation of the mother into two or more daughters; destruction of areas of ground-creeping and lodging shoots (moss mosses, gymnosperms, flowering plants); using special structures specifically designed for vegetative propagation (tubers, bulbs, rhizomes, corms, axillary buds, adventitious buds on leaves or roots, brood baskets of bryophytes, etc.).

Artificial vegetative propagation is carried out with human participation when growing cultivated plants. Artificial vegetative propagation has a number of advantages over seed propagation: it ensures the production of offspring that retain the characteristics of the parent organism, speeds up the production of offspring, and allows one to obtain a large number of offspring. In addition, using vegetative propagation, it is possible to reproduce clones of those plants that produce non-viable seeds or do not produce them at all.

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

Fragmentation called the division of an individual into two or several parts, 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), and some flowering plants (for example, Elodea canadensis). Only female specimens of Elodea came to Europe; they were unable to produce seeds due to the lack of male plants, and fragmentation turned out to be the only method of reproduction.

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

Reproduction by aboveground shoots.

Mustache . In agricultural practice, strawberries and strawberries are propagated with mustaches. At the nodes of the mustache, lateral buds and adventitious roots are formed. After the internodes dry out, the plants become isolated. In nature, plants such as creeping buttercup and saxifrage reproduce with tendrils.

Rice. Reproduction of currants by layering

Layerings. Layerings are sections 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, and grapes are propagated by layering.

Stem cuttings. A stem cutting is a section of an above-ground shoot. Grapes, currants, gooseberries, ornamental types of spirea, red peppers, eggplants and others are propagated by stem cuttings. For propagation, cuttings are taken from 2-3 to 6-8 cm long, consisting of one internode and two nodes. The leaves are left on the top node (if the leaf blades are large, then they are cut in half). The cuttings are planted in special greenhouses, and after rooting - in open ground.

Rice. . Propagation by cuttings

Graft (or transplantation) is the artificial merging of a part (cutting, bud) of one plant with a shoot of another. A cutting or bud with an adjacent

a piece of bark and wood (eye) grafted onto another plant is called scion. Rootstock– the plant or part thereof on which the grafting was carried out. Grafting allows you to use the root system of the rootstock to preserve or propagate 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 they can all be reduced to two main types: grafting by proximity, when the scion and rootstock remain on their roots, grafting by separated scion, when only the rootstock has roots.

The most common grafting methods are the following (Fig. 38). Grafting into cleft or half-split. Used if the scion is thinner than the rootstock. The cross section of the rootstock is completely or partially divided and a scion, obliquely cut on both sides, is inserted into it.

Bark grafting. The scion is also thinner than the rootstock. A horizontal cut is made on the rootstock under the stem node, the bark is cut vertically and its edges are carefully turned back. A half-cone-shaped cut is made on the scion, inserted under the bark, clamped with bark flaps and tied.

Copulation. It is used if the scion and rootstock have the same thickness. Oblique cuts are made on the scion and rootstock and combined, ensuring a tight connection.

Budding. Kidney-eye grafting. A T-shaped cut is made on the rootstock, 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 . Of the agricultural plants that reproduce by tubers, the most famous are potatoes and Jerusalem artichokes. They can be propagated by planting whole tubers or parts of them with buds and eyes. Tubers, as a storehouse of nutrients, are formed in such wild plants as syt, sedmichnik.

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

Forests, steppes, and meadows are home to a large number of rhizomatous plants, primarily cereals. Rhizomatous plants include wheatgrass, timothy, white grass, rosemary, wood sorrel, horsetail and other wild plants. Many rhizomes branch, and when the old parts die off, new plants separate.

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

Corm . The corm's reserve nutrients 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 that develop between the old and new corms. Corm plants include gladiolus and crocus.

Root tubers . They are thickenings of lateral roots. In ornamental gardening, dahlias and sweet potatoes are propagated from root tubers. When propagating dahlias, it is necessary to take root tubers with the base of the stem bearing buds, since root tubers do not form buds. Spring grass and Lyubka bifolia reproduce by root tubers.

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

Root cuttings. A root cutting is a part of a root. They propagate species whose roots easily develop adventitious buds: horseradish, raspberries, cherries, roses. Root cuttings are harvested in the fall, less often in the spring. To do this, use lateral roots of the first order at the age of 2-3 years. The length of the cutting 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 are also propagated by cuttings: willow, poplar, aspen, dandelion

Reproduction by leaves.

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

Leaf cuttings. Sometimes even part of a leaf is enough for vegetative propagation. In a royal begonia, a part of a leaf with a large vein is cut out; a sansevieria leaf can be cut into several leaf cuttings and placed in water.

Adventitious buds on leaves, children . Bryophyllum produces adventitious buds on its leaves that look like small plants. When they fall, they become independent plants.

Tissue culture. Tissue culture is the growth of plant cells in artificial media. Plant cells have the property totipotency– a single cell can develop into a normal plant using certain phytohormones. The tissue culture method makes it possible to obtain clones some higher plants. Cloning– obtaining a set of individuals from one mother by vegetative means. Cloning is used to propagate valuable plant varieties and to improve the health of planting material.

Sexual reproduction. Sexual reproduction is associated with the formation of a special type of cell by plants - gametes. The plant on which gametes are formed is called gametophyte. The process of gamete formation is called gametogenesis. It occurs 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. Plant gametes are formed mitotically, meiosis occurs after the formation of the zygote ( zygotic reduction) – many algae, or when spores form ( sporic reduction) – in diploid algae and higher plants. In animals, meiosis occurs during the formation of gametes ( gametic reduction).

Sexual reproduction has a number of advantages over asexual reproduction. Firstly, when gametes merge, an organism is formed with a unique double set of gene alleles received 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 given environmental conditions, even if these conditions change.

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

Gametes are always haploid. When male and female gametes fuse, 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 varied. The following types of sexual process are distinguished: hologamy, conjugation, isogamy, heterogamy and oogamy (Fig. 39).

Hologamia . Hologamy is the fusion of haploid single-celled, outwardly indistinguishable organisms with each other. This type of sexual process is characteristic of some unicellular algae. In this case, it is not gametes that fuse, but entire organisms that act as gametes. The resulting 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, 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 at the junction dissolve, 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, identical in shape and size, but physiologically they are of different quality. This sexual process is characteristic of many algae and some fungi. Isogamy occurs only in water, in which gametes are equipped with flagella for movement. They are very similar to zoospores, but are smaller in size.

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

Oogamy. Characteristic of some algae and all higher plants. The female gamete - the egg - is large and immobile. In lower plants it is formed in unicellular gametangia - oogonia, in higher plants (excluding angiosperms) - in multicellular archegonia. The male gamete (sperm) is small and mobile, formed in fungi and algae in unicellular gametangia, and in higher plants (excluding angiosperms) - in multicellular gametangia - antheridia. Sperm can only move in water. Therefore, the presence of water is a prerequisite for fertilization in all plants, with the exception of seed ones. 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 propagation. 8. Scion. 9. Rootstock. 10. Gametangia. 11. Zygotic reduction. 12. Sporic reduction. 13. Gametic reduction. 14. Hologamy. 15. Isogamy. 16. Heterogamy. 17. Oogamy. 18. Conjugation. 19. Oogonia. 20. Archegonia. 21. Antheridia. 22. Totipotency.

Basic review questions

1. Plant propagation by division.

2. Reproduction by spores.

3. Natural vegetative propagation.

4. Reproduction by fragmentation and division of bushes.

5. Reproduction by above-ground shoots (tendrils, layering, stem cuttings).

6. Basic methods and features of propagation by grafting.

7. Basic methods of propagation by underground shoots.

8. Basic methods of propagation by roots.

9. The main methods of plant propagation by leaves.

10. Reproduction by tissue culture.

11. Advantages of sexual reproduction.

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

There are several main ways to propagate plants: they can be sown in the ground (open or closed) with seeds or seedlings can be obtained from them, bulbs, tubers or rhizomes can be divided. There are also less common options - propagation of vegetables by cuttings, layering and grafting. Vegetative methods of plant propagation are those that involve parts of crops.

They are resorted to for a number of reasons:

• there are crops that do not produce seeds, for example garlic, horseradish, multi-tiered onions;
• some vegetables (potatoes, spicy varieties of onions), sown with seeds, form small productive organs in the first year - such as sets;
• gardeners cultivate plants that, when grown from seeds, produce strong splitting (as when sowing seeds collected from hybrids), for example rhubarb;
• There are crops that have very small seeds that are difficult to germinate, and it takes 70-90 days to grow seedlings. These include artichoke, rosemary, tarragon, etc. Therefore, it is simply more convenient to grow them using the vegetative method of propagating cultivated plants.

Different methods of propagating vegetable crops

In practice, propagation of vegetable crops by dividing bulbs is common. For example, a multi-bud onion forms a fairly large number of bulbs - 3-12 pieces, into which it can be divided and then planted in beds. You can divide the bulbs not only by the number of children, but also into parts - by the number of embryos. Using this method of plant propagation, cut off the upper part of the bulb “up to the shoulders”; on the cross section you will see the rudiments, into which you will need to disassemble the bulb. When they dry out a little in the air, plant them in the same way as sets (bulbs grown from seeds and having a diameter of 1.5-2.2 cm) or selections (bulbs with a diameter of 3-4 cm).

There is a rule that, if followed, will allow you to grow a good harvest of shallots, multi-tiered onions and garlic: before sowing the bulbs, calibrate them by size and plant them at a depth that is 3 times their height. Then the plants will develop equally and at the same time produce a harvest.

What other methods of plant propagation do gardeners use? Perennial crops, such as asparagus, rhubarb, lovage, mint, thyme, etc., reproduce by dividing the rhizomes. It contains a sufficient supply of nutrients to support the vital activity of young plants until they develop their own root system. Divide the rhizomes into parts in the fall or spring and immediately plant them in a garden bed where they will grow for several years.

Artichoke and lemon balm provide root shoots. But their root system is quite weak, so in order for it to take root after the separation of the daughter plant from the mother plant, it must be grown in a nursery.

Vegetable plants such as potatoes, Jerusalem artichoke and stachys are propagated by dividing the tubers, based on the biological characteristics of these crops. A tuber is a modified thickened shoot, so potatoes are not a root crop, like carrots or beets (their fruit is a thickened root), but a tuber crop. At its top there are buds - eyes, which are unevenly distributed throughout the tuber. With 12 eyes 6-7 pcs. will fall on the top third, on the middle third - 1-2 pieces, on the bottom third - 2-3 pieces. When cutting the tuber, make sure that there are several eyes for each part.

How else does a person propagate cultivated plants that have tubers? Potatoes can also be propagated by eyes and sprouts (layers). In the first case, cut out the eyes in the form of cones, and the tubers themselves can be used for food. Leave the eyes in the air for several hours so that they wilt a little, pour them into a box in a small layer and store at a temperature of 3-4 ° C. During planting, place 2-3 eyes in each hole. By providing optimal care, you will get a good potato harvest.

Using this method of propagating vegetable plants, potatoes must undergo vernalization to produce sprouts. To do this, leave the tubers in the light for about 30 days at a temperature of 16-17 ° C. After sprouts 10-15 cm long have formed on them, lay the potatoes in layers, alternating each of them with humus or peat. After 4-6 days, the root system will develop on the sprouts. Separate them from the tuber (try not to damage the eyes) and plant them in a plot (at a distance of 20 cm from each other, and there should be 50 cm between rows) or in a nursery for growing (this is how sweet potatoes are usually cultivated). Further care does not differ from the generally accepted one.

When practicing plant propagation in different ways, experienced gardeners use grafting. Reproduction by grafting is a method better known in fruit growing. It was first applied to vegetables by I.V. Michurin. Of course, grafting is not so common in vegetable growing, however, tomatoes can be grafted onto potatoes, sunflowers onto Jerusalem artichokes, cucumbers and melons onto pumpkins. This method is used to the greatest extent in breeding, but it is not found in the practice of amateur vegetable growing.

Method of propagating vegetable plants by cuttings

What other methods of plant propagation are there, and how to use them? Tomatoes can be propagated by cuttings, especially if the plants are very elongated or if there are not enough seeds. Cut off the top and shoots of the seedling and root. From such cuttings, completely conditioned bushes will grow. At the same time, the mother plant planted in the ground will also develop normally and bear fruit.

Using the method of propagating plants by cuttings is associated with one difficulty - maintaining viability until they develop a full-fledged root system. This can only be achieved if they are provided with heat, light and moisture, which is possible in a greenhouse. In the process of propagating various cultivated plants by cuttings, he will need boxes filled with perlite or vermiculite, that is, sterile, light and loose substrates that can create optimal conditions for a new root system. You can use compost, humus, and rotted sawdust pre-treated with fertilizers.

In addition to tomatoes, stem cuttings are used for potatoes, lovage, marjoram, and tarragon. It is important to choose the right cuttings, which should be neither too young (they do not give roots well) nor too old (they dry out, since a large amount of nutrients is used to maintain the developed vegetative organs - leaves). Therefore, choose healthy shoots, free from pests and diseases, that are just beginning to become lignified. To stimulate the formation of roots, use heteroauxin, for which dissolve 2 tablets in a glass of hot water, pour in water at room temperature, bringing the amount to 10 liters, and keep the cuttings in the liquid for 6 hours.

The survival rate of cuttings will increase if you soak them in a 0.005% sodium humate solution. To obtain a liquid of this concentration, dilute 10 g of the drug in 150 ml of water and leave for 1 day, then drain the solution, and pour 20 ml of sediment into 10 liters of water.

Cuttings come not only from stems, but also from roots. This is how artichokes, rosemary and horseradish are grown. For example, prepare horseradish cuttings 15-20 cm long in the fall and store them in the basement in the sand until the next season. Before planting, wipe them with a cloth, removing all the buds in the middle. And in artichoke, root cuttings are grouped around the mother plant; they can simply be separated with a knife and planted in a permanent place.

In higher plants, which include flower crops, the forms of vegetative propagation are most diverse: by dividing the bush, tubers, bulbs, corms, rhizomes, cuttings. Reproduction by layering, offspring and grafting is less commonly used. The latter method is used for tree crops of roses, which, as beautifully flowering plants, are used in flower decoration (parterres, mixborders, borders). Vaccinations are also used in cactus culture. Vegetative propagation is used for perennial plants.

Dividing the bush. Herbaceous perennial flower crops, in their life form, belong to perennial polycarpic plants, in which the bush grows over time, sometimes breaking up into separate parts (gelenium), and a weakening of flowering is observed. Such large individuals are divided into parts and planted, taking into account the time of initiation and formation of flowers in a particular species: the division of bushes must be carried out outside this period. Plants that bloom in spring and summer (peony, primrose) are divided in July-August, and those that bloom in autumn (asters, solidago, late phlox) are divided in spring. Depending on the growth rate of the bush, division is carried out at different time intervals: perennial asters can be divided every year; once every 2 years - soapwort, horned violet, Korean chrysanthemums; once every 3-4 years, divide most perennials - asters, astilbe, helenium, gaillardia, carnations, delphinium, elecampane, bells, rudbeckia, solidago, phlox, etc.; After 5-6 years, you can divide well-growing and flowering aquilegia, maquea, bergenia, iberis, lily of the valley, daylily, monarda, hosta, black cohosh, etc. Some plants react painfully to division and replanting - they are stunted in growth and often die. These include aconite, gypsophila, dicletra (dicentra), lupine, oriental poppy, hellebore, eremurus, and ash. It is advisable not to disturb these plants, divide and replant them very carefully.

The technology for dividing bushes (peony, dahlia, phlox) is usually given when describing specific crops.

Division of rhizomes. This method is used for crops that have plagiotropic rhizomes - iris, cannas, lily of the valley. The division of rhizomes of iris and lily of the valley is carried out without germination after flowering in September, and the division of heat-loving cannas, stored in winter in the storage of cannas, is carried out after germination in February-March in greenhouses. The technology for dividing rhizomes is usually given when describing the corresponding crops.

Reproduction by tubers and their division. Anemones, tuberous begonia, gloxinia, caladiums, and buttercups are propagated by tubers and their division. When dividing a tuber, it is necessary that each part has at least one eye (bud). The cuts are sprinkled with crushed coal. In winter, tubers are stored in dry, cool rooms.

Propagation by bulbs. This method is used for bulbous plants (tulip, hyacinth, narcissus, scylla, muscari, lilies, hazel grouse), in which, in addition to the large mother bulb, small daughter bulbs are formed underground. These bulbs are separated and grown into adult, flowering bulbs. Bulbous plants also have unique ways of propagating bulbs. Thus, hyacinth is characterized by a method of violating the integrity of its bottom in various ways (a cross-shaped incision, scraping the bottom, punching the bottom with a tube) to living tissues, after which, with an optimal combination of temperature and humidity, many baby bulbs are formed on the living tissues of the bottom. For narcissus, there is a method of propagation by segments with two scales (cutting option) on a piece of bottom - baby bulbs are formed at the base of the scales in a warm and moist substrate.

Some lilies (bulbous, tiger, sulfur-yellow, etc.) are characterized by the formation of aerial bulblets on the flowering stem, in the axils of the leaves. When planted in the ground in the fall, they produce flowering plants after 3-4 years.

Reproduction by corms and their division. This method is typical primarily for gladiolus, crocus, and freesia. During the period of growth and development, small corms are formed at the base of the new corm: (babies), which grow to an adult flowering individual.

The corm has buds that allow it to be divided into parts with 1-2 eyes and grown as a regular plant. This method allows you to get more corms and children, which is especially important for varieties that produce few children, but are very valuable for their decorative properties.

Propagation by cuttings. A cutting is a section of a stem with leaves or buds, a root with adventitious buds, or a leaf separated from the mother plant. The cuttings are respectively stem, root and leaf.

In ornamental herbaceous plants, the stem cuttings are herbaceous. Only roses and azaleas are propagated by semi-lignified (green) cuttings. Herbaceous cuttings are used to propagate phlox, chrysanthemums, carnations, peonies, carpet plants, hydrangea, pelargonium, as well as many evergreen (indoor) plants - tetrastigma, ganura, scindapsus, Kalanchoe, bellflower, zebrina, peperomia, etc. Such perennials can be propagated by herbaceous cuttings annuals, such as ageratum, salvia, petunia, etc. Tetrastigma, columna, aucuba, beloperona, codiaum, monstera, philodendron, etc. are propagated by semi-lignified stem cuttings.

Peonies can be propagated by root cuttings - its long thickened roots, which fall off when dividing the bush, are divided into parts and rooted in boxes in open ground in a semi-shaded place. This method is suitable for the roots of old plants that may have adventitious buds. The best time is spring; by autumn the roots can give rise to young shoots. For peony, this method is more productive. Dracaenas, arrowroots, and aralias can be propagated by root cuttings.

Many species are propagated by leaf cuttings. This is most often used in begonia, achimenes, Uzumbara violet, and sansevieria. Adventitious roots of leaves are formed mainly on the morphologically lower side of the leaf, in places where large veins branch; buds and then shoots appear on the upper side of the leaf. Propagation of lilies by leaf cuttings is propagation by scales of bulbs (scales are metamorphosed leaves) and the actual leaves located on the peduncle. For propagation, young upper stem leaves are taken. The greatest effect is obtained when planting leaves in greenhouses. Leaves and leaf scales are planted at half their length.

An option for propagation by leaf cuttings is the option of propagation by a leaf with an axillary bud, for example in phlox, aucuba, hydrangea, roses. In evergreen indoor crops, it is important to take into account the phase of plant development, since leaf cuttings taken from a plant in the active growth phase develop vegetative buds, and those taken from a plant ready for flowering develop flowering buds (Achimenes). Technologies for propagation by leaf cuttings, as a rule, are given for specific plants.

Reproduction by grafting. This method is typical, as mentioned above, for roses and lilacs, which are cultivated for cutting indoors. In this case, they can be conditionally classified as flower crops, and not as open ground shrubs. These plants are propagated using types of grafting such as budding and “bark cuttings.” Budding is carried out at a time when the bark is well separated - during the period of active sap flow in the spring (ascending current) and in August (descending current). As a rootstock (plant on which to graft) for roses in the Non-Black Earth Region, dog rose is used (for plants grown for open ground and for rose crops in the greenhouse) and Indian rose (for rose crops in the greenhouse). Eyes and cuttings are taken from varietal plants. When budding, a T-shaped incision is made on the rootstock into which a peephole is inserted. When grafting “by the cutting by the bark,” the cutting, whose lower, basal end is cut obliquely, is inserted into a longitudinal cut made on the bark of the rootstock. In this case, the rootstock should be somewhat thicker than the cuttings. When vegetative propagation, especially when cuttings, cuttings from plants are cut in different ways, depending on the biology of the plants. Thus, cuttings of remontant carnation are collected all year round, breaking out young shoots from the leaf axils. At the same time, they always keep in mind that the quality of cuttings taken in summer and winter will be different - summer cuttings are more powerful and heavier. In azaleas, especially in difficult-to-root varieties, cuttings are cut from plants up to six months old at the first pinching in order to form a bush. Chrysanthemum cuttings are cut from the mother plant, which is in a long day mode. Evergreen, so-called indoor plants, are cut from spring or in the active growth phase.

For all types of cuttings taken from a plant at any time and in any way, it is necessary to create especially favorable environmental conditions. The temperature of the substrate in the rooting zone, where the basal part of the cutting is placed, should be 4-5 0 C higher than the temperature above the substrate in order to ensure the flow of nutrients into the basal part and thereby improve root formation, and in the air to reduce the transpiration of cutting tissue. If the substrate temperature is insufficient, under-shelf heating is turned on, which is provided in all modern greenhouses. The substrate temperature for most crops should be in the range of 20-25 0 C, and the ambient air temperature - 18 - 20 0 C. To reduce transpiration, the cuttings are covered with a waterproof film, stretching it over the frame over the cuttings. The optimal ratio of the listed factors affecting the rooting of cuttings is created under conditions of so-called artificial fog. Artificial fog is produced using special spraying units equipped with nozzles that provide droplet spray of water jets. In the State Botanical Garden of the Russian Academy of Sciences, the installation of artificial fog provides a very fine, mist-droplet spray (particle size 146 - 360 microns) and can operate continuously or intermittently (20 seconds on, 1 minute break). With artificial fog, 100% illumination is maintained, which is very important for photosynthesis of cuttings. With the help of artificial fog, high rooting of cuttings in difficult-to-root species is achieved. In principle, easily rooted species do not need artificial fog, but it is used to speed up rooting and improve the quality of the resulting root system.

Vegetative propagation is of great practical importance, as it guarantees the production of offspring that fully retain the properties and characteristics of the mother plant; Flowering in a number of species occurs earlier than during seed propagation; Some plants here do not produce seeds (Japanese anemone, etc.).

Methods of vegetative propagation .

1) Reproduction by rhizomes. This method is used to propagate rhizomatous plants - irises, larkspur, chrysanthemums, lilies of the valley, goldenrod, etc. The rhizome is an underground stem; it has dormant buds that give rise to new shoots. Rhizomatous plants therefore grow very quickly, take root well after transplantation and develop well. The dug up bush is cut into pieces with a shovel or knife, or you can break it with your hands, trying to cause as little injury to the plant as possible. Each part of the bush should have 3-4 buds and its own roots. Plants that bloom in spring are best divided in autumn, those that bloom in summer and those that bloom in autumn are best divided into spring.

2) Reproduction by tubers. Tubers are of stem origin (modified stems) and root origin - modified roots. A distinctive feature of stem tubers from root ones is the presence of dormant buds on them, which allows them to be propagated by division (artichoke - tubers die off after a year; tuberous begonia, cyclamen - tubers live for several years). Root tubers that do not bear buds are separated from the part of the root collar where dormant buds (dahlias) are located.

3) Reproduction by bulbs and corms. Bulb plants are divided into 2 groups based on the structure of the bulbs: the first has scaly bulbs (lilies), the second has filmy bulbs (tulips, daffodils, hyacinths, etc.). In filmy and scaly bulbs, baby bulbs are formed from the axillary buds, with which plants reproduce. Lilies can also be propagated by bulb scales, and some species form aerial bulbs in the leaf axils.

Gladioli and crocuses reproduce by corms; they can be divided into parts, each of which should have 1-2 buds.

4) Reproduction by mustache(stem shoots growing horizontally and forming new rooting plants at the nodes) is typical for Indian strawberry, periwinkle, tenacious, fragrant violet, etc. Rooted specimens in spring or autumn are separated from the mother ones and planted in a new place.

5) Root suckers propagated by plants on the roots of which there are adventitious buds capable of developing into above-ground shoots (bindweed, dracaena, hops, etc.). The offspring are separated from the mother plant and planted.

6)Cuttings- one of the most common methods of plant propagation. Any part separated from a plant intended for vegetative propagation is called a cutting. Cuttings are divided into stem, root and leaf. Stem cuttings, in turn, are: green, harvested with immature wood and unformed leaves, intended for propagation of biennials, perennials, potted crops and certain types of shrubs; semi-lignified, characterized by formed leaves and incompletely ripened wood (roses, lilacs, indoor jasmine, fuchsia, etc.); lignified, characterized by durable, well-formed wood without leaves (willow, jasmine, spirea, etc.).

Most rhizomatous plants (peonies, phlox, irises, oriental poppy, etc.) are propagated by root and rhizomatous cuttings. In most cases, greenhouse plants (Rex begonia, gloxinia, sanseveria, echeveria, etc.) are propagated by leaf cuttings.

It is better to carry out cuttings in greenhouses, greenhouses or in a specially protected area with well-fertilized and treated soil. Planting is carried out in autumn or spring. The cuttings are covered for the winter. In the first year of plant life, flowers and inflorescences are plucked out, giving the opportunity to better develop vegetative organs.

7) Reproduction by grafting– transplanting a cutting or eye from one plant (scion) to another (rootstock). This method is used to propagate roses, azaleas, lemons, cacti, etc. For grafting to be successful, it is necessary to combine living cells capable of dividing, i.e. at least in some areas, the cambium (tissue between the phloem and the wood) of the scion should coincide with the cambium of the rootstock.

Vaccination should be carried out during the period when the scion buds are dormant. There are several methods of vaccination. They are quite widely described in the horticultural literature. The most commonly used method is budding (by eye). It is performed in the spring (with the germinating eye) and in the summer (July - August) with the dormant eye.

Reproduction is the property of organisms to increase their numbers in the process of producing offspring. Plants can reproduce organisms similar to themselves, ensuring continuity and continuity of life. However, the concepts of “reproduction” and “reproduction” are not completely identical in biological meaning. Reproduction is understood as the process of producing descendants identical (similar) to a given generation. In plants and fungi, reproduction often leads to the formation of descendants that are biologically different from the breeding generation, and reproduction itself occurs only after one or even several generations. In this case, in any case, each next generation of descendants is formed as a result of the reproduction of individuals of the previous generation. There are usually three main forms of reproduction: vegetative, asexual and sexual.

Vegetative propagation provides an increase in the number of individuals of a given species due to the separation of any viable parts of the vegetative body of the plant. With such reproduction, regeneration occurs - the restoration of the whole organism from its part. The ability for vegetative reproduction is very characteristic of plants and fungi at all levels of their organization. In animals, a similar form of reproduction occurs only in certain groups of lower organisms.

There are many different ways of vegetative propagation of fungi and plants: parts of the thallus, mycelium or parts of vegetative organs (roots, stems, leaves, buds). In unicellular organisms, it is carried out by dividing the original cell into two derivatives (daughter cells). Many filamentous and lamellar algae, fungal mycelium, and lichen thalli easily break down into parts, each of which can become an independent organism. Higher plants often reproduce by fragmenting the body into separate shoots. Individuals arising from one parent as a result of vegetative propagation form a clone.

In some gymnosperms and angiosperms, reproduction is by root suckers (aspen), creeping underground shoots and root shoots (sequoia Sequoia sempervirens), are more important than propagation by seeds.

Vegetative propagation is also carried out using brood buds. They can appear on a plant (ferns, flowering plants) in large numbers, and then fall from it like seeds (for example, in bryophyllum). Such formation of brood buds is often observed on the edges or veins of fronds of ferns. Sometimes brood buds can be modified into bulbs (for example, in catfish Dentaria and some lilies) or nodules of stem origin (in Polygonum viviparous Bistorta vivipara).

In agricultural practice, a whole series of various methods of artificial vegetative propagation of cultivated and semi-cultivated plants belonging to a wide variety of life forms has been developed. Many ornamental shrubs and perennial herbs reproduce by dividing the bush, rhizomes, and root suckers.

Many representatives of lilies Liliaceae artificially propagated by bulbs and corms, separating the daughter “babies” from the mother plants (onions, garlic, lilies, tulips, hyacinths, crocuses, gladioli). Forms of vegetative propagation using cuttings and grafting are especially common in gardening.

Cutting – This is a part of the vegetative organ that serves for artificial vegetative propagation. Cuttings can be stem or shoot (willow, poplar, currant, pelargonium), leaf (begonia, lily), root (dandelion, raspberry, cherry, aspen). A type of cutting is the propagation of trees and shrubs by layering. In this case, part of the shoot is first specially pressed to the soil for rooting, and only when this has occurred is the rooted layer cut off. Layerings are found in nature - in some conifers (lodging spruce, fir), linden, bird cherry and other species that can take root with branches lying on the ground. Many fruit, tree and herbaceous ornamental plants are propagated by cuttings in open ground and indoor culture. When cuttings, all the properties of the variety of the mother cultivated plant are preserved, which is very important, since during seed propagation many characteristics specially bred through selection may be lost.

Vaccination or transplantation , called the transplantation of part of one plant to another with their subsequent fusion. This method of vegetative propagation does not occur in nature. Grafting is very widespread in horticulture as one of the methods for obtaining new varieties or targeted changes in existing ones (the so-called “mentor method” proposed by I.V. Michurin). Grafting is also used for the purpose of propagating an existing variety for maximum preservation of all its qualities that can be lost during seed propagation: for the development of a powerful root system in the grafted plant, which has greater frost resistance, resistance to fungal diseases, for obtaining vegetative hybrids. This is the only way to reproduce varietal plants that do not produce seeds. There are more than 100 methods of vaccination.

Asexual reproduction of plants and fungi is carried out by spores, that is, specialized cells that serve for reproduction and dispersal ( rice. 6.1).

Rice. 6.1. Spores of some agaric fungi.

The number of spores produced by one plant or fungal organism can be very large. The spores are not differentiated sexually. In algae and fungi they are diploid or haploid. Spores of higher plants are always haploid. In some algae and many fungi, spores are equipped with undulipodia (flagella) and are motile - such spores are called zoospores .

Spores of land plants usually do not have adaptations for active movement and are protected from drying out by a hard cell wall, consisting of two layers - a thin, permeable inner layer (intina) and a thick, impermeable outer layer (exine) to water and gases.

The organism that produces spores is called a sporophyte, and the process of spore formation is called sporogenesis. In plants, spores are formed in sporangia (if zoospores, then in zoosporangia). Sporangium of algae (lower plants) is usually unicellular; the contents of this single cell divide, resulting in the formation of spores, which are released when the sporangium membrane is opened. In higher plants, the sporangium is a multicellular organ with a single or multilayer wall. Inside the multicellular sporangium, educational tissue is formed - archesporium (from the Greek "arche" - beginning), from which spores are subsequently formed. From archesporium cells, spores arise as a result of meiosis. On a haploid organism (some fungi), spores are formed as a result of mitotic division. Upon germination, such spores reproduce a new individual identical to the mother. In a diploid organism, spore formation is preceded by meiosis. From the spores formed as a result of meiosis, during germination, a haploid organism arises, which will reproduce sexually (due to the formation of gametes) - a gametophyte (thallus), not identical to the diploid maternal sporophyte.

In lower plants, mosses, and even in many modern higher vascular spore plants (horsetails, mosses, and ferns), all spores are identical in size and physiological characteristics. These are homosporous organisms. In many plants (some mosses, ferns, all gymnosperms and flowering plants), two types of spores are formed on the same individual or on different individuals of the same species, different in size and physiological characteristics. Such plants are called heterosporous (some club mosses and ferns, all gymnosperms and angiosperms). Relatively smaller spores (microspores) ( rice. 6.2) are formed in microsporangia, and larger ones (megaspores) – in megasporangium. Microspores, germinating, give rise to a unisexual male gametophyte (male), on which male genital organs arise - antheridia . During germination, megaspores form a female gametophyte (female specimen), bearing female reproductive organs - archegonia. Heterosporous evolutionarily arose in higher plants (some lycophytes and ferns, all gymnosperms and angiosperms).

Rice. 6.2. Microspores of flowering plants. A – magnolia, B – susak, C – juzgun, G – peony, D – buttercup, E – isod.

Sexual reproduction – This is a type of reproduction in which new individuals are formed as a result of the sexual process. For the sexual process, as a rule, two parent individuals are required, producing two physiologically different types of germ cells (gametes) with recombined parental chromosomes, which merge and form a zygote. A new daughter individual subsequently develops from the zygote

The organisms on which gametes are formed are called gametophytes, and the process of gamete formation is called gametogenesis. In most plants and fungi, gametes arise in special organs - gametangia. Gametes are always haploid. Gametophytes of homosporous plants are usually bisexual and form both male and female gametangia. In heterosporous plants, gametophytes with male gametangia usually grow from microspores, and gametophytes with female gametangia from megaspores.

Due to the fact that different plants are capable of producing different types of gametes in size and mobility, several types of sexual process are distinguished. In the simplest case, in some unicellular algae and fungi that lack a hard shell, entire unicellular organisms merge. This sexual process is called hologamy.

If the sexual process involves specialized sex cells - gametes, then this process is called gametogamy ( rice. 6.3). Gametes formed in gametangia can be morphologically of the same type, then they are called isogametes. Their pairwise fusion is based only on physiological differences, and a sexual process of this type is called isogamous. Isogamy occurs in some algae and in very few fungi. If the motile gametes differ in size (one is several times larger than the other), then the fusion of such gametes causes a heterogamous sexual process. In some fungi-like organisms (oomycetes), algae, and in all higher plants, the sexual process is oogamous. The female gamete (egg) in the oogamous form of the sexual process is immobile, lacks flagella (undulipodia), is large in size and has a large supply of nutrients. The male gamete (sperm) is small, mobile, with flagella (undulipodia), or without flagella (then it is called sperm); consists of a large nucleus and a very small amount of cytoplasm. The immobile egg cell is formed either in the gametangium, called oogonia (in algae and some fungi), or in the archegonium (higher plants, excluding flowering plants).

Oogonia (from the Greek “oon” - egg, “gone” - birth) usually consists of one cell, less often (in charophyte algae) it is multicellular. Archegonium (from the Greek “arche” - beginning) is the female reproductive organ of higher archegonial plants - mosses, mosses, horsetails, ferns and gymnosperms. This is always a multicellular formation, consisting of an expanded abdomen, in which the egg is placed, and an elongated neck. Above the egg is the ventral tubule cell. The outer cells of the archegonium are sterile and form a single-layer wall. Through the cervical canal, filled with mucus, sperm penetrate into the abdomen and one of them merges with the egg.

Spermatozoa in spore plants are formed in gametangia called antheridia. Antheridium (from the Greek “anteros” - flowering) is a unicellular (in most lower plants) or multicellular (in higher spore plants) male reproductive organ, which has a different (round or oval) shape in different systematic groups. Sperm matured in the antheridia can reach the egg only in the presence of dripping liquid water. Its presence is a prerequisite for the implementation of the fertilization process in all groups of plant organisms, excluding seed plants. In flowering plants, gametangia have been completely reduced, but sex cells (sperm and eggs) are formed and participate in the sexual process.

In addition to the typical sexual process, in which two gametes are necessarily involved, there is a special type of sexual process in which the embryo develops from an unfertilized egg. This phenomenon in plants is most often known as apomixis (from the Greek “apo” - from (without) and “mixis” - mixing). Apomixis is widespread in many angiosperms (some Rosaceae, Asteraceae), especially in a number of cultivated plants (beet, cotton, flax, tobacco).

Rice. 6.3. Various types of sexual reproduction in plants, algae and fungi (diagram). A – isogamy (characteristic of some algae); B – heterogamy (some algae); IN – oogamy (some algae, all higher plants); G – conjugation (some algae).

Sexual and asexual forms of reproduction have certain biological advantages. During sexual reproduction, a combination of the hereditary material of the parent forms is achieved. The individual formed during sexual reproduction is not genetically identical to any of its parents. The sexual process ensures the genetic variability of organisms from generation to generation, and sexual reproduction gives the species advantages that are realized through natural selection. With asexual reproduction, hereditary characteristics are transmitted without changes and can easily be fixed over a number of generations. However, most often plants alternate between sexual and asexual generations. With the alternation of generations, the gametophyte is naturally replaced by the sporophyte, which is then again replaced by the next gametophyte in the series of generations.

The gametophyte and sporophyte can be the same both morphologically and in life expectancy (isomorphic alternation of generations) (in many algae) or sharply different (heteromorphic alternation) (in some algae and all higher plants).

Thus, both forms of alternation of generations occur in different groups of algae. Higher plants are characterized only by heteromorphic alternation. Both generations develop either independently as independent individuals, or one generation “settles” on the other. Thus, in mosses, the sporophyte develops on the green gametophyte. In seed plants, the extremely reduced chlorophyll-free female gametophyte does not leave the sporophyte. In all higher plants, except mosses, the sporophyte predominates, and the gametophyte is less developed and short-lived. The alternation of generations is associated with a change in nuclear phases - haploid (n) and diploid (2n). This change is ensured due to meiosis, which occurs in all higher plants during sporogenesis, and the sexual process.

The diploid sporophyte of higher plants always produces haploid meiospores. From them a haploid gametophyte grows, producing haploid mitogametes (sex cells formed during mitosis). When gametes merge, the diploid number of chromosomes in the zygote is restored, from which a diploid sporophyte grows.