With asexual reproduction of plants, division of the parent individual and vegetative propagation.
Asexual reproduction widespread in all plant groups. In its simplest form, with this type of reproduction, the parent individual is divided into two parts, each of which develops into an independent organism. This method of reproduction, called fission, is found, as a rule, only in single-celled organisms. The cell divides by mitosis.
Many multicellular organisms are also capable of successfully reproducing by separating viable sections of the vegetative body, from which full-fledged daughter individuals are formed. This type of asexual reproduction in the plant world is often called vegetative. The ability for vegetative reproduction is very characteristic of plants and fungi at all levels of their organization, as well as for some lower groups of animals. Such reproduction is characterized by the restoration of the whole organism from its part, called regeneration.
Often, plants reproduce by scraps or parts of thallus, mycelium or parts of vegetative organs. Many filamentous and lamellar algae, fungal mycelia, and lichen thalli freely disintegrate into parts, each of which easily becomes an independent organism. Some flowering plants that live in water can also reproduce this way. An example of a plant that reproduces exclusively vegetatively in Europe is the dioecious Elodea canadensis, which came here from North America. At the same time, only female specimens were brought to Europe, unable to form seeds in the absence of male plants. Despite the lack of seed regeneration, this plant reproduces exceptionally quickly and quickly develops new habitats.
In agricultural practice, many methods of artificial vegetative propagation have been developed. cultivated plants belonging to a wide variety of life forms. Thus, many shrubs and perennial herbs reproduce by dividing the bush, rhizomes and root suckers. Onions, garlic, lilies, tulips, hyacinths, crocuses, gladioli, etc. successfully reproduce from bulbs and tuber bulbs, separating daughter bulbs, or “babies,” from the mother plants. In gardening, forms of vegetative propagation using cuttings and grafting are especially widespread.
A cutting is a segment of a vegetative organ used for artificial vegetative propagation. Cuttings can be stem or shoot, but some plants can also be propagated by leaf (begonia, lily) or root (raspberry) cuttings. 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 then cut off. Layerings are also found in nature, when the branches of fir, linden, bird cherry and other species that can take root in this way are lodged. Many fruit, tree and herbaceous plants are propagated by cuttings. ornamental plants in open and closed ground. When cuttings, all the properties of the mother cultivated plant are preserved, which is very important, since during seed propagation many characteristics specially selected through selection are easily lost.
Grafting is used very widely in gardening, when a cutting or just a vegetative bud of a plant with the necessary properties, the so-called scion, is fused with a more powerful and unpretentious plant or rootstock. Grafting allows you to quickly propagate valuable plants and ensure their accelerated development, while completely preserving necessary qualities. In this case, the grafted plant receives such valuable properties rootstock, such as frost resistance, resistance to fungal diseases and unpretentiousness to soil fertility. More than 100 vaccination methods have been developed. Many varietal plants that do not produce seeds reproduce exclusively by grafting.
Reproduction- this is the reproduction of similar organisms, an important property of living things. Sooner or later, organisms die: some from old age, others from disease, others become victims of predators. However, with the death of each organism, the life of species on Earth does not end. Thanks to reproduction, new generations of organisms appear to replace dying and dying individuals.
During reproduction, the number of individuals increases, and organisms settle in new places. Reproduction is associated with growth - an increase in mass and size and development - internal and external changes that occur from the moment of formation to the death of the organism.
A distinction is made between asexual and sexual reproduction. The most ancient and simplest method of reproduction is asexual. It is carried out by division, spores and vegetative organs. Only one organism participates in asexual reproduction. With this method of reproduction, the greatest similarity of the offspring with their parents is maintained.
Sexual reproduction involves male and female individuals, fertilization occurs - the fusion of male and female reproductive cells. Therefore, during sexual reproduction, each organism inherits the properties of both parents.
Plant propagation. Widely distributed in plants vegetative propagation. It occurs due to the separation of vegetative organs or their parts from the mother’s body and the development of new ones from them, daughter plants(Fig. 62). During vegetative propagation, a new individual is formed from a part of the body of the mother’s organism, so it inherits all its characteristics.
Rice. 62. Vegetative propagation of flowering plants
In flowering plants, vegetative propagation in nature occurs with the help of all organs on which buds are formed - future shoots. Vegetative propagation allows plants to quickly spread and occupy new areas.
Many weeds, for example, dandelion, wheatgrass, thistle, reproduce vegetatively. They are very difficult to fight. When you pull a dandelion out of the soil, you will likely leave behind part of the root from which a new plant will grow.
Some forest herbs reproduce using long rhizomes, since seed propagation is difficult for them due to the lack of pollinators, lack of light, etc. Such plants include lily of the valley.
Algae can multiply through sections of threads or separation of a part of the body at the point of attachment to the ground. In mosses and ferns, young shoots can grow and separate from each other.
Some plants: algae, mosses, ferns - reproduce using spores. A spore is a single cell with a thick shell that protects it from drying out and mechanical damage.
Usually there are a lot of disputes. They are very small and light, so they are carried by the wind over long distances. Of the huge number of spores, only a few end up in favorable conditions and germinate, giving rise to a new organism. A significant part of them die. Therefore, the formation of a large number of spores by plants or fungi is an adaptation to the survival and preservation of the species.
Answer the questions
- What is reproduction?
- What are the features of asexual reproduction?
- Why do many plants reproduce primarily asexually?
New concepts
Reproduction. Asexual reproduction. Vegetative propagation.
Think
Why are many cultivated plants propagated vegetatively?
My laboratory
Vegetative propagation is used in urban landscaping, in agriculture. For example, gooseberries, currants, phlox, and daisies are propagated by dividing the bush; strawberries - mustaches, potatoes - tubers.
Often, cuttings are used for propagation - part of a stem, leaf, or root that develops into a new shoot. Currants, tradescantia, and pelargonium are propagated by stem cuttings; root cuttings - rose hips, raspberries; leaf cuttings - begonia.
You can propagate by cuttings houseplants ficus, comus, etc. To do this, cut cuttings with 3-4 leaves. Cut off the two bottom sheets (explain why). Plant the cuttings in a box with soil covered with moistened sand, inclined at an angle of 45°. Cover the cuttings glass jar to reduce water evaporation. After two to three weeks, roots will form on the lower part of the cuttings planted in the soil. Transplant young plants into pots and care for them.
IN Lately wide application in the national economy, he received another method of vegetative propagation - from one cell or piece of tissue. This is the so-called tissue culture method (Fig. 63). It allows in a relatively short time to small areas, even in vitro, to obtain numerous offspring of a particular plant.
Rice. 63. Tissue culture method
Using the tissue culture method, it was possible to establish industrial production so rare and valuable medicinal plant like ginseng. If in natural conditions Only by the age of 50, the mass of ginseng root is about 50 g, then under artificial conditions this mass is obtained in about six to seven weeks.
Asexual reproduction is also typical for animals. In this case, the offspring are produced by one parent individual. Simplest form asexual reproduction of animals - division. It is characteristic of unicellular and some multicellular animals.
The asexual method of reproduction of freshwater hydra is budding. Under favorable conditions, buds form on the hydra’s body, which grow and after some time separate from the mother’s body, turning into young hydras (Fig. 64).
Rice. 64. Asexual reproduction of freshwater hydra by budding
REMEMBER
Question 1. How do plants reproduce?
All types of reproduction can be divided into two main groups - vegetative propagation and generative. About vegetative propagation, it is enough to say only that this is propagation by lateral shoots, buds, roots, tubers, that is, a young plant is separated from an adult plant. Generative reproduction is in turn divided into sexual, asexual and seed. Asexual reproduction, that is, reproduction by spores, is characteristic of ferns and mosses, as well as algae. Other higher plants reproduce sexually, that is, they have special organs in which fertilization and pollination occur, that is, the fusion of male and female reproductive cells. A type of sexual reproduction is seed reproduction, when a seed is formed, from which a new plant subsequently grows.
Question 2. What do you know about animal reproduction?
Multicellular animals reproduce primarily sexually, but there are groups (especially among lower invertebrates) that reproduce very successfully asexually.
Asexual reproduction of multicellular organisms is an increase in the number of individuals formed from somatic (non-reproductive) cells. Among animals, it is completely absent in primary cavity worms and mollusks. In arthropods and vertebrates, asexual reproduction can include polyembryony, that is, asexual reproduction at the stages of embryonic development.
Sexual reproduction in animals comes in several forms. Firstly, we can distinguish bisexual reproduction, which exists in the form of dioeciousness and hermaphroditism, and secondly, virgin reproduction, or parthenogenesis.
Question 1. What is reproduction?
Reproduction is the reproduction of similar organisms, an important property of living things.
Question 2. What are the features of asexual reproduction?
The most ancient and simplest method of reproduction is asexual. It is carried out by division, spores and vegetative organs. Only one organism participates in asexual reproduction. With this method of reproduction, the greatest similarity of the offspring with their parents is maintained.
Question 3. Why do many plants reproduce primarily asexually?
Vegetative propagation is widespread in plants. It occurs due to the separation of vegetative organs or their parts from the mother’s body and the development of new, daughter plants from them. During vegetative propagation, a new individual is formed from a part of the body of the mother’s organism, so it inherits all its characteristics.
1. Look at Figure 81 and make a plan for a story about the vegetative propagation of flowering plants. Choose examples.
1. Methods of vegetative propagation and their diversity
2. Reproduction in separate parts body
3. What plants reproduce vegetatively?
2. Using Internet sources, popular science magazines, books, textbook text, prepare a message on the topic “Reproduction using spores.”
Plant propagation is physiological process reproduction of similar organisms, ensuring the continuity of the existence of the species and its distribution in the environment.
Asexual reproduction in a number of plants (algae, mosses, ferns) is carried out using spores. A spore is a single cell, protected by a thick shell from drying out and mechanical damage. Spores are formed in special formations - sporangia. Being very light, the spores are carried far by the wind. Under favorable conditions, spores germinate and new organisms are formed from them. Plants usually produce a huge number of spores, but not all of them produce new plants. Many spores fall into unfavorable conditions and die.
In the process of evolution, about 400 million years ago, rhiniophytes arose from multicellular green algae - the first higher plants that reproduce by spores, which gave rise to all modern higher spore and seed plants. This is an extinct group of plants. IN life cycle higher spore plants, like some algae, alternate individuals of asexual and sexual generations, which reproduce, respectively, asexually and sexually. In a complete life cycle, which ensures the continuity of life of organisms, there is an alternation of gametophyte (sexual) and sporophyte (asexual generation). Organs of asexual reproduction are formed on the sporophyte, and organs of sexual reproduction are formed on the gametophyte.
Higher spore plants After reaching land, they underwent metamorphoses in two directions during evolution. This is how two large evolutionary groups were formed - haploid and diploid. The first branch includes mosses, in which the gametophyte is better developed, and the sporophyte occupies a subordinate position. The diploid branch includes ferns, horsetails and mosses. Their gametophyte is reduced and looks like a prothallus.
From the spores that form individuals of the asexual generation, individuals of the sexual generation grow. They have special male and female genital organs, in which male and female reproductive cells (gametes) develop - motile sperm and immobile eggs. For fertilization, the sperm must enter the external environment and fertilize the egg, which is located inside the female reproductive organ. Water is needed to move sperm. An embryo is formed from a fertilized egg. It germinates and turns into an asexual generation individual that reproduces by spores.
THINK!
Why are many cultivated plants propagated vegetatively?
During vegetative propagation, the properties of the mother plant are completely preserved. Neither pollination, nor pruning methods, fertilizers, etc. can affect this. Whereas sowing seeds from a cultivated plant gives a whole range of differences from the original plant.
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, no fusion occurs 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. U land plants and they don't have mushrooms special devices 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 sporangium is 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 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 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 makes it possible to obtain a large number of descendants. 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, unable to form seeds due to the lack male plants and the only way to reproduce was fragmentation.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 wild 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.
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Stem cuttings. A stem cutting is a section of an above-ground shoot. Grapes, currants, gooseberries are propagated by stem cuttings, decorative types spirea, red pepper, eggplant and others. 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.
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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. Vaccination allows you to use root system rootstock for preserving or propagating a certain variety, replacing a variety, obtaining new varieties, accelerating fruiting, obtaining frost-resistant plants, repairing or rejuvenating 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 away. 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, kupena, wood sorrel, horsetail and others 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 . Spares nutrients The corms 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 Propagated by leaves, for example Saintpaulia, begonia. 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).
Hologamy . 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. U lower plants 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 required condition for fertilization in all plants, with the exception of seed ones. 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).
Asexual reproduction is the reproduction of organisms in which there is no participation of another individual, and the reproduction of their own kind occurs by separating several or one cell from the maternal organism. A single parent individual takes part in this process. the cells completely correspond to the original mother.
Asexual reproduction is extremely simple. This is due to the fact that the organization of the structure of unicellular organisms is also relatively simple. Organisms with this method of reproduction reproduce their own kind very quickly. Under favorable conditions, the number of such cells doubles every hour. This process can continue indefinitely until a random change occurs, the so-called mutation.
In nature, such reproduction occurs in both plants and
Asexual reproduction of organisms
Simple division is observed in animals, for example, in ciliates, amoebas and some algae. First, the nucleus in the cell is divided in half through mitosis, and then a constriction is formed, and the parent is divided into two parts, which are daughter organisms.
In animals, asexual reproduction has been preserved only in some forms: sponges, coelenterates, and tunicates. In these organisms, a new individual is obtained as a result of budding or division, after which the part separated from the parent organism is completed to form the whole. In some cases, parts of the body have the ability to develop into a separate organism in animals. A whole hydra, for example, can develop from a two-hundredth part. With asexual reproduction, newly created individuals arise from several cells or one through mitotic divisions, receiving the same hereditary information that the cell of the mother’s body possessed.
Asexual plant reproduction
This method of reproduction is widespread in flora. There are a number of plants that reproduce well by tubers, layering, cuttings and even leaves, which makes it possible to use the vegetative organs of the parent plant to grow new organisms. This type of asexual reproduction is called vegetative, and it is characteristic of highly organized plants. An example of such reproduction can be considered one that occurs by whiskers, for example, in strawberries.
Sporulation is asexual reproduction that occurs in many plants, for example, algae, ferns, mosses, and fungi at some stage of development. In this case, special cells take part in the reproduction mechanism, often covered with a dense membrane, which protects them from adverse effects external environment: overheating, cold, drying out. As soon as favorable conditions arise, the spore shell bursts, the cell begins to divide repeatedly, giving life to a new organism.
Budding is a method of reproduction when separation occurs from the parent individual. small area body from which a daughter organism is later formed.
A set of individuals that descended from one common ancestor using this type of reproduction is called clones in biology.
Asexual propagation is widely used in agriculture in order to obtain plants with a set of necessary characteristics useful for human life. Strawberries are spread with long “mustaches” and shoots, and trees are spread with cuttings. Scientists are studying the mechanisms of reproduction to learn how to control them and manage their development. The necessary hereditary information is first multiplied, and then the necessary whole plant is grown from them.
