Vegetative propagation is manifested in the ability of plants to form new individuals from individual vegetative organs - roots, stems, leaves, or their modifications - tendrils, rhizomes, tubers, bulbs, etc., as well as their parts. Natural vegetative propagation is widespread in nature in many wild plants. Perennial grasses actively reproduce with the help of rhizomes, such as creeping wheatgrass, common grass, lily of the valley, coltsfoot; Strawberries, some types of cinquefoil and saxifrage reproduce by above-ground creeping shoots ╫ tendrils and lashes; Many lilies (lilies, alliums) reproduce by bulbs.
The biological feature of vegetative propagation is that the daughter plants mainly retain the properties and characteristics of the mother plant. In agricultural practice, plants are often artificially propagated vegetatively in order to preserve the purity of the variety (potatoes, dahlias, Jerusalem artichokes, many fruit trees and shrubs, etc.). Trees and shrubs can be propagated by layering. The essence of this method is to root the lower shoots before separating them from the mother plant. After the formation of roots, the cuttings can grow independently, developing into a normal plant (grapes, currants, gooseberries). Trees and shrubs can also be propagated using stem or root cuttings, i.e. parts of a shoot with several internodes (grapes, raspberries, willows, roses, etc.). In the practice of fruit growing, propagation by grafting is widely used, when part of one living plant is transplanted to another living plant on which it takes root. Some plants can reproduce by leaves or parts thereof (begonias). In floriculture, the so-called bush division is used to propagate perennial herbs (in daisies, phlox, primroses).
GENERATIVE ORGANS AND LIFE CYCLE OF FLOWERING PLANTS
FLOWER
The wide variety of flowers of angiosperms and their sharp difference from the corresponding organs of gymnosperms make it difficult to explain the origin of the flower.
There are several hypotheses about the origin of the flower. According to the most widespread and well-founded strobilar, or evanth, hypothesis, a flower is a modified shortened spore-bearing shoot, originally resembling a gymnosperm cone. During the process of metamorphosis, megasporophylls turned into carpels, and microsporophylls into stamens, which many researchers associate with the adaptation of angiosperms to pollination by insects. According to this hypothesis, the most ancient families are Magnoliaceae, Ranunculaceae, etc. According to another hypothesis, called pseudanthic, a flower is a modified inflorescence consisting of small heterosexual flowers that have undergone reduction, convergence and fusion; The most ancient are considered to be families with dioecious, inconspicuous flowers - willow, casuarinaceae, etc. These hypotheses, based on the idea of the formation of flowers from leafy shoots, are contrasted with various telomic hypotheses, according to which all parts of the flower can be derived from telomes, i.e. cylindrical shoot structures characteristic of rhinophytes.
Currently, most botanists consider a flower as a modified shortened shoot, all parts of which, except the receptacle, are leafy in nature.
A flower is a shortened, modified spore-bearing shoot that develops from a bud and is specifically designed for reproduction (formation of micro- and megaspores, pollination, fertilization, formation of seeds and fruits).
The flower consists of several parts. The peduncle connects the flower to the stem. Receptacle - the extended, shortened upper part of the peduncle to which all other parts of the flower are attached. The sepals make up the outer part of the perianth - the calyx. The petals form the inner part of the perianth ╫ corolla (sometimes in flowers there is no division of the perianth into a calyx and corolla, in this case the perianth is called simple). The collection of stamens forms the androecium. The collection of carpels (megasporophylls) forms the gynoecium, which is located in the center of the flower. The peduncle and receptacle are a modified stem of the shoot, and the sepals, petals, tepals, stamens and carpels fused into a pistil are modified leaves of the shoot. In some plant species there is no peduncle; the flower sits directly on the stem and is called sessile. The receptacle can be of different shapes: flat, convex, highly elongated, concave, etc.
Parts of a flower (perianth elements, stamens, pistils) can be arranged on the receptacle in a spiral (spiral arrangement) or in a circle (circular or cyclic arrangement). Sometimes the arrangement is mixed, or hemicyclic: parts of the perianth are arranged in a circle, and the stamens and pistils are arranged in a spiral.
The flower develops from a bud located in the axil of the leaf. Such a leaf is called covering. The leaves (usually modified) located on the peduncle, under the flower, are called bracts.
The calyx is septate or sphenofolate, depending on whether the sepals are free or fused. The calyx is usually green, but may have other colors. The sepals have different shapes (lanceolate, subulate, triangular, etc.). If the shape and size of the sepals of a flower are not the same, then the calyx is called irregular; if they are the same, it is called regular.
The corolla consists of free or fused petals and is accordingly called separate-petaled or sphenoletal. It is usually brightly colored. Petals can be of different shapes.
The perianth, consisting of a pronounced calyx and corolla, is called double (or complex). A perianth consisting of identical leaflets is called simple. The brightly colored simple perianth is called corolla-shaped, and the green one is called calyx-shaped. Some plant species do not have a perianth and the flowers are called glabrous.
The entire variety of flowers with respect to their symmetry can be reduced to the following three types: 1) regular, or actinomorphic, flower, through which several planes of symmetry can be drawn (representatives of the carnation, rosaceae families); 2) irregular, or zygomorphic, flower, through which only one plane of symmetry can be drawn (representatives of the legume, Lamiaceae, orchid families); 3) an asymmetrical flower through which no plane of symmetry can be drawn (representatives of the cannaceae and banana families).
The androecium consists of stamens, which are microsporophylls in nature. The stamen has a filament and an anther attached to it by means of a connective tissue. Each anther contains four pollen sockets in which pollen (microspores or pollen grains) develops.
Mature pollen grains in different species can be spherical, elliptical, or other types of shape. They are covered with two shells. The outer thick one is called exine, the inner soft one is called intina. Various projections, spines, and tubercles are formed on the exine in different species. In each microspore located inside the anther, the nucleus divides, forming two nuclei: vegetative and generative. This begins the development of the male gametophyte, and microspores turn into pollen. Subsequently, two sperm are formed from the generative nucleus, which are male gametes.
The gynoecium consists of one or more pistils. Each pistil is formed by one or more free (apocarpous gynoecium) or fused (coenocarpous gynoecium) carpels (megasporophylls). The formed pistil usually consists of a lower expanded part - the ovary, a middle cylindrical part - the style, and an upper expanded part - the stigma. When the style is absent and the stigma is located directly on the ovary, it is called sessile. The stigma can be of different shapes: capitate, bilobed, stellate, pinnately lobed, etc. One or many cavities called nests are formed in the ovary. They develop ovules (megasporangia), from which seeds develop after fertilization. The number of styles, stigma lobes, and ovary nests may indicate the number of carpels forming the pistil. The place where the ovule is attached to the ovary is called the placenta (or placenta).
A visual description of the structure of a flower is given by the formula and diagram of the flower. The formula reflects the structure of the flower using letters and numbers, the diagram reflects the structure of the flower using a drawing (projection of parts of the flower onto a plane, plan of the flower). The flower formula is composed as follows. A simple perianth is denoted by the Latin letter P, calyx ╫ K, corolla ╫ C, androecium (stamens) ╫ A, gynoecium, or carpels, ╫ G. The correct flower is indicated by an asterisk *, the wrong one ╫ by an arrow?. Each letter has a number at the bottom right indicating the number of members in a given circle of the flower. If there are many members and their number is indefinite, they put an infinity sign? If these parts of the flower are located not in one, but in two circles, then the member sign has two numbers connected by a “+” sign. When any parts of a flower grow together, the number indicating their number is enclosed in brackets. The superior ovary is marked with a line under the number indicating the number of carpels; inferior ovary ╫ line above the number. The flower diagram is drawn up as follows. A cross section of a flower is depicted in the form of a projection of all its parts on a plane. The fused members of any part of the flower in the diagram are connected by a dotted line or a solid thin line. The diagram shows not only the number of flower parts, but also their relative positions.
A mature ovule consists of an achene, one or two integuments (integuments) and an ovule nucleus (nucellus), which contains the embryo sac (female gametophyte). The integuments at the apex of the ovule have a narrow canal called the pollen duct (or micropyle).
The embryo sac develops in the nucellus. Inside the embryo sac there is an egg, two of its companion cells (synergids), two polar nuclei, and three antipodes (nuclei at the opposite pole of the embryo sac to the egg). Angiosperms lack archegonia. At a certain stage, the polar nuclei of the central cell merge, forming the diploid central (secondary) nucleus of the embryo sac. During the sexual process, double fertilization occurs - a process characteristic only of flowering plants, discovered by the Russian botanist S.G. Navashin in 1898. Moreover, after the penetration of two sperm of the male gametophyte into the embryo sac, not only the egg is fertilized, but also the central nucleus of the embryo sac. After fertilization, the embryo develops from the zygote, and the nutritious tissue, or endosperm, of the seed develops from the central cell with a triploid nucleus. Double fertilization promotes rapid development of the endosperm, which speeds up the entire process of seed formation.
INFLORESCENCE
The flowers can be single, completing the shoot, but more often they are collected in inflorescences. An inflorescence is a shoot or system of shoots bearing flowers. In inflorescences, flowers emerge from the axils of the covering leaves (bracts).
Inflorescences can be divided into two groups: monopodial (racemose, bothric) and sympodial (cymose). In monopodial inflorescences, the youngest flowers are in the center or apex of the inflorescence. In sympodial inflorescences, the first apical flower ends the main axis of the inflorescence, and further development of the inflorescence occurs due to the development of lateral axes of the first order, then the second, etc.
Monopodial inflorescences can be simple (flowers sit directly on the main axis of the inflorescences) or complex (flowers sit on the branches of the main axis of the inflorescences). Simple monopodial inflorescences include: raceme ╫ flowers are located on an elongated axis, have pedicels (cherry); spike ╫ similar to a raceme, but the flowers are sessile (plantain); cob ╫ an ear with a thick, fleshy axis (corn); head ╫ similar to a brush, but the main axis is very shortened, the flowers appear sessile (clover); scutellum ╫ similar to a raceme, but differs in that the lower flowers have long pedicels, as a result the flowers are located almost in the same plane (pear); basket ╫
the flowers are always sessile, located at the strongly thickened and widened end of the shortened axis of the inflorescence (representatives of the Asteraceae family); umbrella - the main axis of the inflorescence is greatly shortened, the lateral flowers sit on stalks of the same length (onion). Complex monopodial inflorescences include: complex spike ╫ elementary spikelets (wheat) sit on the main axis; panicle, or complex raceme, ╫ on the main axis, lateral branches develop at different heights, in turn branching and bearing flowers or small simple inflorescences (lilac); a complex umbrella ╫ differs from a simple one in that its axes end not in flowers, but in simple umbrellas (carrots); complex scutellum - the main axis is a scutellum, and the side axis is a basket (yarrow).
Sympodial inflorescences include: monochasia (divided into gyrus and whorl); dichasia, or fork, and pleiochasia, or false umbrella. Monochasium - the axis of each order gives only one branch with a flower. In a curl, all flowers are directed in one direction (forget-me-not). In the gyrus, the lateral axes with the flower extend alternately in two opposite directions (gladiolus). Dichasium - the axis of each order gives two branches. The blooming of the inflorescence begins with the apical flower, immediately below it there are two lateral flowers of the second order, and from the axils of the last two flowers of the third order arise, etc. (representatives of the clove family). Pleiochasium - from each axis bearing an apical flower, more than two branches emerge, outgrowing the main axis (euphorbia).
The biological significance of inflorescences is very great. The inflorescences make the flowers clearly visible from a long distance, which is important for pollinating insects. For wind-pollinated plants, inflorescences increase the likelihood of flowers being pollinated by a “cloud” of flying pollen.
The fruit is usually formed from the ovary of the pistil. The pericarp develops from the walls of the ovary, which consists of three layers: outer (exocarp), middle (mesocarp) and inner (endocarp). These three parts are not always well expressed.
Fruits can be simple, or true, formed from a single pistil in a flower, and complex, or composite, from several pistils of one flower (fruits of raspberries, blackberries, buttercups, etc.). If other parts of the flower (receptacle, perianth) take part in the formation of the fruit in addition to the pistil, the fruit is called false.
All real fruits, based on the structure of the pericarp, are divided into dry and juicy. Dry fruits have a dry, woody or leathery pericarp and are divided into opening-
unbreakable and unopenable. In addition to fruits that open in different ways, there are disintegrating fruits, represented by two groups: fractional fruits that disintegrate longitudinally in the plane of fusion of the carpels (umbelliferous), and articulated fruits that disintegrate transversely in planes perpendicular to the longitudinal axis of the carpels (some types of cruciferous plants, etc.). In juicy fruits, the entire pericarp or part of it is juicy or fleshy. Juicy fruits are divided into berries and drupes.
The variety of fruits is determined primarily by the structure of the pericarp, as well as the method of opening and the number of seeds. Among dry and juicy fruits, single-seeded and multi-seeded are distinguished.
DRY MULTI-SEEDED OPENING FRUITS: capsule ╫ single-locular or multi-locular fruit, formed from several carpels, opened with holes or cracks (poppy, henbane, cotton); leaflet ╫ single-locular fruit formed from one carpel, opened along the ventral suture (larkspur); a complex leaflet is a group of leaflets (marigold, bladderwort); bean - a single-locular fruit formed by one carpel, unlike a leaflet, opens along two seams - ventral and dorsal (representatives of the moth family); pod - an elongated bilocular fruit formed from two carpels, and between the valves there is a longitudinal septum (mustard); pod ╫ the same as a pod, but its length is no more than three times its width (shepherd's purse).
DRY SINGLE-SEED NON-OPENING FRUITS: caryopsis ╫ the seed grows tightly together with a thin membranous pericarp (rye, wheat); achene ╫ leathery pericarp, not fused with the seed; the achene is often equipped with a tuft or fly (dandelion); in the umbelliferous family, two-samples are formed; lionfish ╫ achene with a wing-like appendage (ash), diploid (maple); nut ╫ hard, woody pericarp (hazel); nut ╫ small nut (hemp); acorn ╫ is similar to a nut, but the pericarp is leathery and the lower part of the fruit is immersed in a cup-shaped plus (oak).
JUICY POLYSEED FRUITS: berry ╫ juicy endocarp and mesocarp, leathery exocarp (grapes, tomatoes); apple is a false fruit, in the formation of which, in addition to the ovary, a greatly expanded receptacle (apple tree, pear) takes part; pumpkin is a false fruit, the receptacle, the exocarp is hard, sometimes woody, the mesocarp and endocarp are juicy (watermelon, pumpkin); orange ╫ citrus fruit, soft-skinned exocarp, rich in essential oils, dry, spongy mesocarp, juicy endocarp (lemon, orange).
JUICY SINGLE-SEED FRUITS: drupe ╫ thin, leathery exocarp, juicy mesocarp, stony endocarp (cherry, plum); compound drupe ╫ a group of drupes formed from one flower (raspberry, blackberry).
The above classification of fruits is artificial, since it is based mainly on external morphological characteristics. There is also a morphogenetic classification of fruits based on the type of gynoecium from which the fruits develop.
Some plants develop infructescences. They are formed from an inflorescence as a result of the fusion of several fruits into one whole (fig, pineapple).
Seeds are specialized structures (organs) that arose in the process of evolution in seed plants (divisions of gymnosperms and angiosperms) and perform the functions of their reproduction and dispersal. Seeds are formed from ovules (ovules) after fertilization and are enclosed in flowering plants in single-seeded or multi-seeded fruits. Typically, a mature seed of a flowering plant consists of an embryo, endosperm, and seed coat.
The seed coat is usually multi-layered; its main function is to protect the embryo from excessive drying, mechanical damage and premature germination. Sometimes its structure facilitates the spread of seeds in the environment. There is a small hole in the peel - the seed entrance, which facilitates the penetration of water into the seed at the beginning of swelling. A scar is also visible on the peel - a trace from the seed stalk, with the help of which the seed is attached to the walls of the fruit.
Endosperm is a nutritious tissue consisting of triploid cells and arising from the central cell of the embryo sac during the process of double fertilization. The function of the endosperm is to provide nutrition to the embryo at the initial stages of its development during seed germination.
The embryo is the rudiment of a new plant and consists largely of educational tissues. Several structures are clearly visible in it. The embryonic shoot is represented by an embryonic stalk, which has a growth point at the top, and cotyledons (rudimentary leaves). The lower end of the shoot gradually passes into the embryonic root, usually represented only by educational tissue covered by the root cap.
The embryo of representatives of the dicotyledonous class of flowering plants usually has two cotyledons extending from the axis
escape on the sides. The growth point of the shoot is located between them and is the apical one. The cotyledons of dicotyledons are often large and fleshy (for example, in legumes, pumpkin, asteraceae) and contain reserves of nutrients, while the endosperm is almost invisible. In different groups of flowering plants, the ratio of the sizes of the endosperm and the cotyledons of the embryo varies greatly.
The embryo of representatives of the monocot class of flowering plants has only one cotyledon. It usually occupies an apical position, with the growth point shifted to the side. Representatives of the grass family, one of the most important economically, have a very unique seed structure and differ from most monocots. The embryo in the seed of a single-seeded fruit-caryopsis is adjacent to the endosperm on one side, and is not surrounded by it. As a result, the cotyledon occupies a lateral position and has the shape of a flat shield, the main function of which is the absorption of nutrients from the well-developed endosperm. The apical bud in cereals is quite well developed and has several leaf primordia.
Compared to other plant organs, which contain 70–95% water, seeds consist mainly of dry matter. They contain 10–15% water. The dry matter of the seed contains only 1.5-5% ash (mineral) substances, the rest is organic matter. Organic substances in the seed are represented by proteins, carbohydrates and fats. The ratio of these main groups of organic substances varies among different taxonomic groups of plants. For example, the seeds of legumes are very rich in protein (25-30% of the dry weight of the seed). Cereal seeds contain significantly less protein (about 10%), but starch makes up more than half of their dry weight. The seeds of legumes and cereals usually contain a negligible amount of fat, while in hemp and flax seeds the proportion of fat is about 30%, and in the seeds of certain varieties of sunflower it is more than 50%.
Seeds require certain conditions for germination. Since their tissues are severely dehydrated, the presence of water is necessary. Sufficient air access is also important, ensuring intensive respiration of germinating seeds. When they breathe, they emit not only carbon dioxide, but also a significant amount of heat. This determines the conditions for storing seeds in a thin layer in dry, well-ventilated areas: if seeds are stored in a thick layer, they can overheat, which will lead to the death of the embryos. For each type of plant there is a certain temperature below which the seeds cannot begin to germinate. For the germination of seeds of some plant species, it is beneficial
Variable temperatures are pleasant (barberry, celery). The seeds of many plants of the natural flora of temperate and cold zones can germinate only after exposure to low temperatures (stratification phenomenon). Sometimes seed germination is determined by the light regime. Seeds of a number of species can germinate only in the light (meadow bluegrass, carrots), while others can germinate only in the dark (some types of bells and speedwells). Seeds of many species are indifferent to light.
The germination of a seed is preceded by its swelling, a necessary process associated with the absorption of a large number of species and the watering of the seed tissue. This usually breaks the seed coat. Simultaneously with the absorption of water, active enzymatic activity begins, leading to the mobilization of reserve substances. The growth and development of the embryo, its transformation into a seedling (a young plant with the first green leaves), occurs due to the division and growth of its cells. - For growth, especially in the very first stages of development, the embryo uses nutrients stored in the seeds, i.e. . leads a heterotrophic lifestyle. It receives reserve substances in the form of sugars from cotyledons or endosperm as a result of starch hydrolysis.
The time for sowing seeds of various plants is determined by their relationship to the above environmental factors (especially soil moisture and temperature). For cultivated plants, favorable conditions for germination are created by humans as a result of loosening and moistening the soil. The depth of sowing seeds of agricultural crops depends on many factors: the size of the seeds, the physical properties of the soil (determining water, air and thermal regimes), as well as on the biological characteristics of the species (some species are characterized by above-ground germination, when the cotyledons of the seedlings are brought into the light, others - underground germination when the cotyledons remain in the upper soil horizon).
PRINCIPLES OF SYSTEMATICS AND NOMENCLATURE OF PLANTS
Basic concepts about systematic (taxonomic) categories. Systematics studies the biological diversity of organisms (see also section V, p. 322). The main goal of any systematic study is the classification of the existing (and previously existing) diversity of species. During the classification procedure, based on comparison and analysis of anatomical-morphological and ecological-biological characteristics and properties of organisms, related and evolutionary relationships are established
between groups of organisms ╫ taxa (i.e. subordination of systematic categories).
The highest taxonomic category in taxonomy is “kingdom”. Modern taxonomists distinguish from three to nine kingdoms of the organic world (see also p. 359). The most widely known systems are the American biologist R.H. Whittaker (who justified the identification of five kingdoms of living nature) and one of the largest domestic botanists, academician A.L. Takhtadzhyan, who identified four kingdoms of the organic world: Prokaryotes (see sections II, X), Fungi (see section II), Plants, Animals (see section III).
According to the ideas of A.L. Takhtadzhyan, the kingdom of Plants includes photosynthetic eukaryotic (for characteristics of eukaryotes, see section X, p. 420) organisms. According to other taxonomists, this kingdom should include only higher plants.
The main taxonomic category used in biological systematics is species. The specificity of each species is expressed morphologically (phenetically) and serves as a reflection of its genetic characteristics. Close species form genera, close genera form families, families form orders (orders in zoology), orders (orders) form classes, classes form divisions (types in zoology) and, finally, divisions (types) form the kingdoms of the organic world. Each plant thus belongs to a number of successively subordinate taxa. This is a hierarchical classification system. Any scientific name of a species (including a plant species) consists of two Latin words (it is binary). It includes the genus name and specific epithet, for example, black nightshade (Solanum nigrum). Each genus (including the genus Nightshade) contains a certain number of species that differ from each other in their morphology, biochemistry, ecology, role in vegetation and other properties. The founder of binary nomenclature is the outstanding Swedish naturalist Carl Linnaeus (1707–1778), who published his work “Species plantarum” (“Species of Plants”) in 1753 (see section V).
The meaning of international plant names. Binary Latin names of plants are accepted by the scientific community, understandable to specialists from different countries and enshrined in the International Codes of Nomenclature that regulate and define taxonomic rules. Scientific publications should use international nomenclature rather than local plant names.
The position of the above-mentioned species (Black Nightshade) in the modern classification system is as follows:
╒ Kingdom Plantae ╫ Plants.
╒ Department Angiospermae, or Magnoliophyta, ╫ Angiosperms, or Flowering plants.
╒ Class Dicotyledones ╫ Dicotyledons.
╒ Order Scrophulariales ╫ Noricaceae.
╒ Family Solanaceae ╫ Solanaceae.
╒ Genus Solanum ╫ Nightshade.
╒ Species Solanum nigrum ╫ Black nightshade. Species name required
The abbreviation of Linnaeus's surname is ╫ Linnaeus).
According to the International Code of Botanical Nomenclature, there are rules for the formation of names for taxa of various ranks, which makes it possible to immediately distinguish their level. Thus, numerous names of departments have the ending -phyta. For example, the department Flowering plants is called Magnoliophyta, the department Green algae is called Chlorophyta, etc. The name of the orders ends in -ales. For example, the order Ranunculaceae ╫ Ranales, the order Ceramaceae ╫ Poales, etc., the name of the families has the ending -ceae. For example, the Rosaceae family ╫ Rosaceae, the Legume family ╫ Fabaceae, etc.
MAIN PLANT GROUPS
ALGAE DEPARTMENT
The concept of “algae” unites a fairly large group of mainly aquatic unicellular and multicellular organisms, very heterogeneous both in structure and origin, which arose and evolved independently of each other.
In this regard, in modern algology (the science of algae), this concept has only a biological meaning and has lost its significance as a taxonomic category (division, class). Many experts define algae as a heterogeneous group of predominantly aquatic organisms with oxygenic photosynthesis, whose body is not differentiated into multicellular organs, but is represented by a thallus or thallus, and which have unicellular reproductive organs. Both prokaryotic and eukaryotic organisms fit this definition, etc. therefore, the position of algae in the system of the organic world cannot be unambiguous. If we accept the previous definition, then they should be placed in several kingdoms of living nature: prokaryotic forms (blue-green algae, or cyanobacteria, and prochlorophytes) ╫ in the kingdom of Bacteria, eukaryotic forms ╫ in the kingdom of Protesta and the kingdom of Plants.
Algae are found in bodies of water of any type and in almost all habitable habitats on land - in the soil and on its surface, on stones and rocks, tree trunks. For example, trentepoly forms a brown coating on the bark of trees; yellow-green, green, diatoms, and blue-green algae predominate in the soil. There are about 35-40 thousand species of algae. Most freshwater algae are microscopic in size; the largest freshwater algae, Characeae, can reach 2 m in length. However, giant algae are found in the seas and oceans, for example, the brown algae macrocystis reaches a length of up to 60 m. In the aquatic environment, algae occupy a variety of niches. For example, microscopic algae (from a few thousandths of a millimeter to several millimeters) float freely in the water column. 1 cm3 of water contains up to 40,000,000 cells. In order not to sink to the bottom, some algae accumulate fat drops; others can develop various outgrowths on the cell walls that increase friction; others have flagella and can actively move through the water column. There are also algae attached to the soil at the bottom of reservoirs or to various objects.
Among algae there are unicellular, colonial and multicellular representatives. In many eukaryotic algae, the cell has features characteristic of a plant cell: the presence of a cell wall, a vacuole with cell sap and chloroplasts, called chromatophores, in which photosynthesis occurs. Chromatophores carry pigment systems, including chlorophylls (chlorophyll a is found in all photosynthetic algae and higher plants), carotenoids and phycobilins. Combinations of these pigments determine the color of algae thalli: for example, in red algae, the red color is due to the fact that green chlorophyll is masked by red and blue phycobilins. Some algae belonging to different divisions have lost photosynthetic pigments and completely switched to a heterotrophic mode of nutrition.
Algae propagation. The forms of algae reproduction are varied. Vegetative reproduction occurs by cell division in half (for example, in Euglena green), sections of colonies (for example, in colonial diatoms) and filaments (for example, in Spirogyra), and specialized structures (for example, nodules in Chara). Asexual reproduction is carried out by motile zoospores (Ulotrix, Chlamydomonas) and immobile aplanospores (Chlorella). Spores of asexual reproduction are formed in special cells called sporangia, and the individual on which sporangia are formed is called a sporophyte. Algae have sexual reproduction. The cells in which sex cells (gametes) are formed are called gametangia, and an individual
on which they are formed, ╫ gametophyte. During sexual reproduction, as a result of paired fusion of gametes, a zygote is formed, giving rise to new individuals. The main types of sexual process in algae are as follows: isogamy ╫ fusion of motile gametes of the same size and shape (ulotrix); heterogamy ╫ fusion of motile gametes of the same shape, but different sizes (some types of Chlamydomonas); oogamy is the fusion of a large, immobile female gamete (egg) with a small, motile sperm (seaweed). In algae, sexual reproduction without the formation of gametes also occurs - conjugation, when the protoplasts of two haploid vegetative cells merge to form a diploid zygote (spirogyra). The listed methods of reproduction are presented differently in different groups of algae. For example, the well-known unicellular non-motile alga Chlorella reproduces only asexually, and the seaweed Acetabularia reproduces only sexually; In the life cycle of kelp (seaweed) both asexual and sexual reproduction are represented, while green euglena reproduces only vegetatively.
Unicellular algae. Chlamydomonas is a single-celled, motile green algae of oval (or drop-shaped) shape that lives in puddles and other small fresh water bodies. Movement is carried out using two identical flagella at the anterior end of the cell. The cytoplasm is delimited from the external environment by a cell wall consisting of pectin substances. The cytoplasm contains the nucleus and contractile vacuoles. There is no vacuole with cell sap. Most of the cell is occupied by a cup-shaped chromatophore. The process of photosynthesis occurs in it and starch is deposited as a reserve substance. In reservoirs rich in organic matter, Chlamydomonas can also absorb ready-made organic substances (this is the basis for its use in wastewater treatment). In the anterior part of the chromatophore there is a red eye, which takes part in photoreception. Chlamydomonas reproduces asexually and sexually. During asexual reproduction, 4–8 biflagellate zoospores are formed in the cell, each of which, after release, grows into an adult. During sexual reproduction, gametes are formed under the membrane of the mother cell. As a result of pairwise fusion of gametes, a zygote is formed. It becomes covered with a shell and hibernates. In the spring, its nucleus undergoes a reduction division, and as a result, 4 young haploid chlamydomonas are formed.
Chlorella is well known among single-celled, non-motile green algae. It is found in fresh and salt waters, as well as in soil. Chlorella has a spherical shape. Under the dense cellulose shell there is cytoplasm, a nucleus and a large green chromatophore. Chlorella reproduces only asexually
by means of immobile aplanospores. It is characterized by a high reproduction rate and efficient photosynthesis. This has made chlorella one of the most convenient cultivation objects. Thanks to her, many of the secrets of photosynthesis were revealed.
Filamentous algae. These include, in particular, ulotrix and spirogyra. Ulothrix lives in marine and fresh waters, where it forms a green coating on underwater objects. Ulothrix has the appearance of non-branching filaments, which consist of short cells. Most of the cell is occupied by a vacuole with cell sap; in the cytoplasm there is a nucleus and a chromatophore in the form of a belt. Ulotrix reproduces vegetatively, asexually and sexually. During asexual reproduction, four-flagellate zoospores are formed in cells, which, after entering the water, float, then attach to underwater objects, begin to divide and form new threads. During sexual reproduction, biflagellate gametes are formed in cells. Having left the mother cell, they merge in water, forming a four-flagellate zygote, which, after a period of swimming, settles and becomes covered with a shell. The dormant period ends with the formation of 4 haploid zoospores, which, after entering the water, attach to the substrate and germinate into new filaments.
Spirogyra is common in fresh waters, where it forms accumulations of green mud. Spirogyra filaments are unbranched and consist of large cylindrical cells covered with a cellulose membrane and mucus. The center of the cell is occupied by a vacuole with cell sap, in which the nucleus is suspended on cytoplasmic filaments. The chromatophore looks like a spirally twisted ribbon. One cell can have several chromatophores. Reproduction in Spirogyra is vegetative and sexual. The sexual process is conjugation, in which the contents of the vegetative cells of two adjacent filaments merge. The resulting diploid zygote is covered with membranes and overwinters in this form. In spring, the nucleus undergoes a reduction division, three nuclei die off and only one new haploid strand grows.
Seaweed. Among seaweeds there are unicellular, colonial and multicellular forms. Multicellular representatives are mainly brown, red and green algae. Brown algae are only multicellular, predominantly macroscopic, have a yellow-brown color due to a large number of yellow and brown pigments. Brown algae are found to a depth of 40–100 (200) m, but the densest thickets are formed to a depth of 15 m. One of the most famous brown algae, kelp, or seaweed, is widespread in the northern hemisphere. Its thallus can reach a length of 20 m. Laminaria contains large quantities
amino acids methionine, iodine, carbohydrates, minerals and vitamins, surpassing many vegetables and fodder grasses in these indicators (this is the basis of its importance in human nutrition).
Red algae, OR purple algae, are overwhelmingly found in the seas. They got their name because of the color of the thallus: depending on the ratio of pigments, the color of the thallus varies from dark crimson, pink to bluish-green or yellow. The presence of phycoerythrin (a red pigment) makes it possible for red algae to live at great depths (these are the deepest sea algae), since it absorbs green rays of sunlight passing through the water column. Most red algae have multicellular thalli in the form of beautiful, complexly dissected plates, but some representatives may consist of a single cell or form colonies. In addition to cellulose, the cell wall of red algae contains agar and carrageenan. The cell wall can calcify, and then these algae resemble corals. Scarecrows play a prominent role in the life of the sea, often determining the nature of vegetation and dominating various communities. They serve as food for marine animals, participate in the processes of natural self-purification of waters, many of them are edible (for example, porphyry).
Among green macroscopic seaweeds, the most famous are algae from the genus Ulva (sea lettuce). The thallus of the ulva has the form of a plate that can reach 1.5 m in length. The population of many coastal countries consumes these algae as food.
The meaning of algae. Algae in reservoirs play the role of producers, as they are able to synthesize organic substances from inorganic ones. They also release large amounts of oxygen during photosynthesis. Algae thickets serve as feeding, sheltering and breeding places for many animals.
When favorable external conditions occur, the mass of some algae develops so strongly that it causes changes in the color of the water. This phenomenon is called "water blooming", and mention of it can be found in the messages of Pliny in 77 AD. Green blooms of water in ditches, puddles and pits are most often caused by either euglena or green algae. Algae can also cause blooms in seawater. For example, in recent years, great damage has been caused by “red tides” - “sea blooms” caused by an increase in the mass of a number of microscopic unicellular algae (dinoflagellates). Multiplying algae release substances that are toxic to animals and humans.
Algae is not only found in water. Terrestrial representatives are the “pioneers” of vegetation on rocks, sand and other barren places. They participate in the formation of soil structure and fertility. Organic substances secreted by algae, like the thalli themselves, serve as food for many soil organisms: bacteria, fungi, and invertebrate animals. Algae also take part in the formation of sedimentary rocks.
A number of seaweeds (about 160 species) are widely used as food (species of the genera Porphyra, Laminaria, Undaria, Ulva). A number of species (porphyry, kelp, etc.) are successfully cultivated. Laminaria, which is used in human nutrition, for livestock feed, is used in medicine, and is cultivated in Russia and the countries of Southeast Asia. In Japan since the end of the 17th century. Porphyra is cultivated, and today it is the most popular algae for mass cultivation in algae farms in Japan and South Korea. From one hectare of water surface it is possible to obtain from 25 to 100 tons of mass per year. All over the world, red algae is used to produce agar, which has gelling properties. It is used to make jelly, marshmallows, soufflés, many sweets and other products. Agar is used in microbiology to make nutrient media. Every year, 10,000 tons of agar are produced worldwide.
Brown algae is the only source of alginates. These alginic acid compounds improve the quality of food products and stabilize a variety of solutions and suspensions. Mostly brown algae (kelp, fucus, ascophyllum) are used to feed livestock. Fertilizers are also obtained from algae.
Some algae are used in medicine to treat a number of diseases. For example, in folk medicine, algae are used as anthelmintics, in the treatment of coughs, wounds, gout, goiter (some algae contain in their thalli
a large amount of iodine), etc. Antiviral compounds are obtained from red algae that block the attachment of viruses to the cell membrane. In recent years, preparations from brown algae have been used to remove radionuclides.
Algae are used as indicator organisms in determining the condition of water bodies; They are also used in the process of wastewater treatment (Chlamydomonas).
Algae serve as good model objects for scientific research. Chlorella can be called a “veteran” of space biology: experiments were carried out with it on spaceships to use it for air regeneration and recycling of organic matter in closed life support systems. Acetabularia, for example, is used in studying the relationship between the nucleus and the cytoplasm in a living cell, since this unicellular and for most of its life cycle mononuclear algae is characterized by rapid regeneration and the exceptional vitality of its giant nucleus. An excellent object for biophysical and physiological research is charophyte algae, on the large cells of whose internodes the processes of membrane permeability, cytoplasmic movements, and complex electrical phenomena are studied.
DEPARTMENT BRYOUS, OR MOSSES
Bryophytes are evergreen, autotrophic, mostly perennial plants. The department includes about 25,000 species, is known from the Carboniferous and apparently originates from ancient green algae.
The body of bryophytes is either a thallus (thallus) pressed to the substrate, or a stalk with leaves; there are no roots, there are only rhizoids. Plant sizes range from 1 mm to several tens of centimeters. Bryophytes have a relatively simple internal organization. Assimilative tissue is developed in their body, but conductive, mechanical, storage and integumentary tissues are weakly expressed in comparison with other higher plants.
Unlike all other divisions of higher plants, the vegetative body of bryophytes is represented by a gametophyte (sexual generation), which dominates their life cycle; The sporophyte (asexual generation) occupies a subordinate position in mosses, developing on the gametophyte.
On the gametophyte of bryophytes, multicellular specialized organs of sexual reproduction develop - male (antheridia) and female (archegonia). A large number of biflagellate spermatozoa are formed in the antheridia. Each archegonia produces one egg. In damp weather (during rain), sperm, moving in the water, penetrate the egg, finding
archegonium located inside. One of them merges with her, producing fertilization. From a fertilized egg (zygote) a sporophyte grows, i.e. asexual generation, represented by a box sitting on a stalk. In the sporangium, a multicellular specialized organ of asexual reproduction located inside the capsule, haploid spores are formed as a result of reduction division.
When a spore germinates, a protonema appears - a thin branched thread (less often a plate). Numerous buds are formed on it, giving rise to leafy shoots of the gametophyte or thalli in the form of a plate.
Gametophytes of bryophytes are capable of vegetative reproduction, and their development for a long time can occur without the formation of a sporophyte.
Bryophytes are divided into 3 classes: Anthocerotes, Liverworts and Leaf mosses.
There are about 300 species in the class Anthocerotidae. They are distributed mainly in tropical and warm temperate regions of the globe. In our country, only the genus Antoceros is found, which includes 3–4 species. The gametophyte of anthocerotes is a thallus (thallus). In the genus Antoceros, the thallus is rosette-shaped, 1–3 cm in diameter, less often leaf-shaped, dark green, tightly adjacent to the soil. The capsules (sporogony) are numerous, slightly curved, bristle-like. They give anthocerote mosses a distinctive appearance.
There are over 6 thousand species in the class Liverworts. Liverworts are widespread, but in general their role in vegetation is much less compared to green and sphagnum mosses (see below). Unlike other bryophytes, in most liverworts the protonema is poorly developed and short-lived. The gametophyte has the form of either a thallus or a leafy plant. The structure of the gametophyte in liver mosses is very diverse, the sporophyte is of the same type. One of the most common liverworts in our flora, growing in swamps and forests at the site of fires, is the common marchantia. The body of Marchantia is represented by a thallus in the form of a dark green plate. The plant is dioecious. On some individuals archegonia are formed, on others - antheridia. Archegonia develop on a special stand, the top of which resembles a multi-rayed star. The male stand with antheridia looks like a flat disk.
The subclass Jungermanniaceae contains both thallus and leafy plants. Most species have recumbent dorsoventral shoots. The shape of the leaves and their attachment to the stem are varied, the shape of the box is from spherical to cylindrical, it usually opens with 4 leaves.
The class Leafy mosses includes 3 subclasses: sphagnum, andreic and brie mosses.
The subclass Sphagnum mosses is represented by one family, Sphagnaceae, with a single genus, Sphagnum. In our country there are 42 species of this subclass. Sphagnum mosses are widespread mainly in temperate and cold regions of the Northern Hemisphere, where they form a continuous cover in swamps and humid forests. The stems of sphagnum mosses are erect, with fascicle-shaped leafy branches. At the top, the branches are shortened and gathered into a rather dense head. The leaves are single-layered and have two types of cells: chlorophyll-bearing and aquiferous (hyaline). Chlorophyll-bearing cells containing chloroplasts are narrow and worm-shaped. They are located between wide, colorless aquifer cells, devoid of cellular contents. Thanks to its many water-bearing cells, sphagnum can quickly absorb and retain large amounts of water for a long time (almost 40 times its dry weight). Antheridia and archegonia are formed in the upper part of the stems. After fertilization of the egg, a capsule grows from the archegonium.
The subclass of Brie, or Green, mosses is represented in our country by approximately 2 thousand species. Green mosses are most often perennial, mostly green plants with a height of 1 mm to 50 cm. They are widespread and form a continuous cover in swamps, coniferous forests, meadows, mountains and tundras. Green mosses are characterized by a well-developed, often filamentous, branching protonema. Green mosses are very diverse in the structure of their vegetative organs.
The most important characteristics of plants of this subclass are reflected, for example, in the moss Kukushkin flax, widespread in damp coniferous forests and along the outskirts of swamps. The stem of this moss is erect, unbranched, reaches a height of 30–40 cm and is densely covered with linear-lanceolate leaves. Kukushkin flax is a dioecious plant. Archegonia are formed at the top of the stems of some plants, and antheridia on others. After fertilization, a capsule develops from the zygote, sitting on a stalk. Spores ripen in the box. The spore, once on moist soil, germinates, giving rise to a filamentous protonema. Buds form on the protonema, from which stems with leaves grow.
The importance of mosses in nature is great. Representatives of bryophytes grow almost everywhere. The exception is saline deserts and habitats with moving substrate (wind-blown sands, screes, pebbles). No known marine bryophytes. Mosses are abundant in swamps and forests. They often dominate the ground cover of coniferous forests (spruce forests, pine forests, etc.). Mosses are widely represented in the vegetation of tundras and highlands;
The tundra zone and humid highlands are rightly called the “kingdom of mosses and lichens.”
The property of bryophytes to quickly absorb water and firmly retain it causes weak decomposition of the moss turf from below, leading to the formation of peat. Moss cover can contribute to waterlogging of areas. Sphagnum mosses have antibiotic properties and are used in medicine. They are peat formers, participating in the formation of a thick moss cover in raised bogs. Sphagnum peat is widely used as fuel and in agriculture.
Many green mosses form a continuous carpet in lowland bogs, where they form deposits of lowland peat rich in nutrients. Lowland peat is widely used in agriculture as fertilizer. Mosses can have an adverse effect on the life of some types of vascular plants: growing in a continuous dense carpet, they impede soil aeration, causing it to sour.
DEPARTMENT MOSSMODS, OR MOSSCOADS
Lycopods are one of the most ancient groups of plants. The first lycophytes were herbaceous plants. During the Carboniferous period, tree-like forms appeared, but they became extinct, and their remains formed coal deposits. Most of the lycophytes are now extinct. Only relatively numerous species of club mosses and selaginella have survived.
All modern representatives of lycophytes are perennial herbaceous, usually evergreen plants. Some of them resemble green mosses in appearance. The leaves of lycophytes are relatively small. Dichotomous (forked) branching is also characteristic of lycopods. At the top of the stems of many lycophytes, spikelets (strobilae) are formed, in which spores ripen.
Among the lycophytes there are homosporous and heterosporous plants. In the former, the spores do not differ morphologically; germinating, they form bisexual gametophytes; In heterosporous species, small spores give rise to male gametophytes bearing antheridia, and large ones to female gametophytes bearing archegonia. Bi- or multiflagellate spermatozoa are formed in antheridia, and eggs are formed in archegonia. After fertilization, a new asexual generation, the sporophyte, grows from the resulting zygote.
The section Mossaceae includes two classes: Mossaceae and Polusniformes. From the first we will consider the order Lycophytes, and from the second we will consider the order Selaginella, the representatives of which live at the present time.
The order Lycophytes is characterized by homosporousness. It is represented by one family ╫ Moss, the main genus of which is the genus Moss, numbering about 400 species. There are 14 species of mosses found in our country. Many club mosses are small herbaceous plants. Their leaves are relatively small. A midrib consisting of tracheids and parenchyma cells runs along the leaf.
Let's consider one of the types of clubmoss - clubmoss. This species is widespread in coniferous (usually pine) forests on poor soils. Moss is an evergreen perennial herbaceous plant with a creeping stem up to 1–3 m long. It produces ascending above-ground shoots up to 20 cm high, which end in spore-bearing spikelets. All shoots are densely covered with small subulate-shaped leaves. The spikelets contain kidney-shaped sporangia, in which a large number of identical small yellow spores are formed. After ripening, the spores fall to the soil. When they germinate, an outgrowth (gametophyte) is formed. The moss growth is perennial and looks like a small nodule (2╫5 mm in diameter) with rhizoids. It lacks chlorophyll (therefore colorless) and cannot feed on its own. Its development begins only after the fungal hyphae (endotrophic mycorrhiza) penetrate the body. On the upper surface of the prothallus, in the depths of its tissue, antheridia and archegonia are formed. Fertilization occurs in the presence of water. An embryo develops from a fertilized egg and grows into a perennial evergreen plant called a sporophyte. In lycophytes there is a clearly expressed change of generations. The development cycle is dominated by the sporophyte. Reduction division occurs in the sporangium during the formation of spores.
The stems and leaves of club mosses contain alkaloids and are used in medicine. The spores are used as a powder (lycopodium) for powders, as well as for sprinkling pills. To protect the reserves of club mosses, when collecting spores, it is necessary to carefully cut off only the spore-bearing spikelets.
The order Selaginellaceae, which belongs to the class Polushnikovae, is characterized by heterosporousness. It is represented by one family, Selaginellaceae. There are almost 700 species in the genus Selaginella, mostly native to tropical and subtropical regions. There are 8 species of this genus found in our country. Selaginella are very diverse in appearance. Most of them are small, usually creeping herbaceous plants. The leaves are simple, entire, small, up to 5 mm long. They reproduce mainly asexually, using spores.
Let's take a closer look at Selaginella selaginaceae. This plant has short creeping stems covered with elongated ovate leaves. At the top of the shoot, spore-bearing co-
gloss. The main difference between Selaginella and club mosses is that the spikelet contains two types of sporangia: the larger ones (megasporangia) contain 4 large spores (megaspores); smaller ones (microsporangia) contain numerous microspores. During germination, the microspore forms a highly reduced male prothallus, on which one antheridium develops. A female prothallus grows from the megaspore, on which a few archegonia develop. The movement of sperm requires water, so it occurs after rain or through dew. Over time, an adult selaginella plant grows from a fertilized egg.
Thus, in Selaginella two types of spores are formed - microspores and megaspores - and unisexual prothlae develop. Thalli, especially male ones, are greatly reduced, which is the main direction of the evolution of higher plants. This can be clearly seen in other departments of higher plants. Selaginella are little used by humans.
DEPARTMENT EAILS, OR HORSEtails
Equisetaceae are characterized by division into clearly defined internodes and nodes with whorled leaves.
Currently, horsetails are represented on Earth by a single class, Equisetaceae, which includes one order, Equisetaceae, and one family, Equisetaceae. The family has one genus, horsetail, which includes about 30 species, 17 of which are found in our flora (swamps, forests, meadows, arable lands, etc.).
The greatest development of horsetails occurred during the Carboniferous period. Then many of them were represented by large trees. Later the tree-like forms became extinct. The dead remains gave rise to coal deposits. Many herbaceous forms also became extinct.
Modern horsetails are perennial rhizomatous herbs with a stem length of up to several tens of centimeters. At the nodes of the stem there are whorls of branches. Small scale-like leaves grow together with sheaths into a tube; the function of photosynthesis is performed by green shoots. Some shoots end in a spore-bearing spikelet (strobilus), consisting of sporangia. Modern horsetails are homosporous plants.
The sexual generation (gametophyte) in modern horsetails is represented by unisexual or bisexual short-lived, very small green shoots several millimeters in size. Antheridia and archegonia are formed on them. Multiflagellate sperm develop in antheridia, and eggs develop in archegonia. Fertilization occurs in the presence of a drop-liquid medium (water), and a new asexual generation, the sporophyte, grows from the zygote.
The structure of horsetails and their life cycle can be considered using the example of Horsetail. This perennial rhizomatous plant grows in fields, meadows, and fallow lands. From the rhizome in early spring, pinkish-brown, short, straight shoots appear, at the top of which a spore-bearing spikelet is formed. On the axis of the spikelet there are sporophylls that look like hexagonal scutes. The sporophylls contain sporangia, which contain spores. Externally, all spores are the same: each has two appendages in the form of narrow ribbons called elater. Morphologically, the spores are the same, but the spores differ physiologically: some of them, when germinating, produce male shoots, others - female shoots. The male prothallus is a small green plate, divided into lobes and attached to the soil by rhizoids. Antheridia containing multiflagellate spermatozoa develop at the ends of the lobes. The female prothallus is larger and bears archegonia. Fertilization occurs in the presence of moisture. A perennial sporophyte develops from the zygote. In the spring, green vegetative shoots, devoid of spikelets, develop from the rhizomes of horsetail.
Other types of horsetail have only one type of shoot. It is both spore-bearing and assimilative. The practical value of horsetails is small; they are used, in particular, in phytomedicine as a medicine.
DEPARTMENT FERNES, OR FERNES
Ferns are ancient plants. A significant part of them have now become extinct. Nowadays, ferns far exceed in the number of species all other groups of modern spore-bearing vascular plants: more than 12 thousand species are known. There are about 100 species of ferns in the flora of Russia.
Representatives of this department are very diverse in appearance, life forms, and living conditions. Among them there are many herbaceous perennial plants, and there are also trees. Tropical tree ferns are up to 25 m tall, and the trunk diameter reaches 50 cm. Among the herbaceous species there are very small plants, several millimeters in size.
Unlike lycophytes and horsetails, pteridophytes are characterized by “large leaves”. The “leaves” of ferns are of stem origin and are called “fronds”. Their origin is confirmed by apical growth. The sizes of frond ferns range from a few millimeters to many tens of centimeters. Their shape and structure are varied. The fronds of many ferns combine the functions of photosynthesis and sporulation. In some species (for example, the ostrich) it happens
two types of fronds: photosynthetic and spore-bearing. The leaves of the fronds are quite often feathery, often dissected many times.
Most forest ferns of temperate regions have fleshy rhizomes that form new rosettes of fronds every year, which usually prevail in weight and size over the stem in ferns.
Almost all ferns, with the exception of aquatic ones, are homosporous plants. Sporangia are often located on the lower surface of fronds and are collected in groups called sori. Fern spores give rise to free-living bisexual growths (gametophytes) bearing antheridia and archegonia. For fertilization, the presence of droplet-liquid water is necessary, in which multiflagellate sperm can move. A sporophyte develops from a fertilized egg. As the sporophyte grows, it becomes independent and the gametophyte dies.
The fern division is divided into 7 classes. Of these, 4 classes are represented exclusively by fossil forms, which differed in appearance from typical ferns.
Let's take a closer look at the male shield plant, which, in terms of its general structure and development cycle, is typical of ferns. It forms a thick creeping rhizome, at the end of which a rosette of large, twice pinnately dissected leaves appears annually. Young leaves are snail-shaped at the end and grow from the top (like a stem). Adventitious roots extend from the rhizomes. Round sori are formed on the lower surface of the fronds in summer. Identical spores are formed inside the sporangium. Male shield fern is a typically homosporous fern. Once on the ground, the spore germinates and a shoot is formed. It is a heart-shaped green plate about 1 cm in size. Archegonia and antheridia are formed on the lower surface of the prothallus. Helically twisted multiflagellate spermatozoa develop in the antheridia. Fertilization occurs in the presence of water. A perennial large sporophyte gradually grows from a fertilized egg.
Aquatic ferns are heterosporous plants. This is a small group. An example is Salvinia floating, which belongs to the order Salviniaceae. This is a small plant that floats on water. Male and female gametophytes develop respectively from micro- and megaspores, which are formed in micro- and megasporangia. The male gametophyte, developing from a microspore, is greatly reduced. The female gametophyte develops inside a megaspore and is multicellular. After fertilization, a perennial sporophyte develops. The process of spore germination, fertilization and sporophyte development occur in water.
The practical importance of ferns is small. The young leaves of some herbaceous plants, as well as the core of tree ferns, are eaten. Some ferns are medicinal plants.
Related information.
Reproduction and its meaning. Reproduction methods. The ability to reproduce or self-reproduce is one of the mandatory and most important properties of living organisms. Reproduction supports the long-term existence of the species and ensures continuity between parents and their offspring over many generations. It leads to an increase in the number of individuals of the species and contributes to its dispersal. In plants, the vast majority of which lead an attached lifestyle, dispersal during the process of reproduction is the only way to occupy a large habitat area.
There are two types of reproduction: asexual and sexual. IN asexual reproduction Only one parent is involved and divides, buds, or spores. When sexual reproduction individuals of a new generation appear with the participation of two organisms - maternal and paternal. Asexual reproduction occurs in two forms: vegetative and actually asexual. Reproduction using vegetative organs (in plants) and body parts (in animals) is called vegetative. Vegetative propagation is based on the ability of organisms to restore (regenerate) missing parts. This method of reproduction is widespread in nature, but is most varied in plants, especially flowering plants. When unicellular bacteria, algae, and protozoa divide by mitosis, two daughter organisms are formed. In unicellular algae, fungi and lichens, reproduction is carried out respectively by fragments of filaments, spores and fragments of thalli. An example of vegetative propagation is budding, which is characteristic of yeast and fungi. If the daughter individuals do not separate from the mother, colonies may form. In flowering plants in nature, new individuals can arise from vegetative organs: stem (cacti, duckweed, elodea), leaf (gloxinia), root (raspberry, gooseberry, sow thistle, dandelion), rhizome (wheatgrass), tendrils (strawberry), etc. Actually asexual Reproduction is characterized by the fact that for the reproduction of offspring, specialized cells are formed - spores, each of which germinates and gives rise to a new organism. Sporulation occurs in protozoa, fungi, algae, mosses, mosses, horsetails and ferns. In gymnosperms and angiosperms, spores are not directly involved in the reproduction process.
With any form of asexual reproduction - by body parts or spores, an increase in the number of individuals of a given species is observed without increasing their genetic diversity: all individuals are an exact copy of the maternal organism. This feature is used by humans to obtain homogeneous offspring with good characteristics in fruit, ornamental and other groups of plants.
Vegetative propagation in angiosperms it is divided into natural and artificial. Natural vegetative propagation is very widespread. Most often it occurs with the help of rhizomes, bulbs, corms, roots, and tendrils. Artificial vegetative propagation carried out with human intervention. TO artificial Vegetative propagation of flowering plants is used if the plant does not produce seeds, produces low-quality seeds, or if it is necessary to preserve the genetic purity of the variety. Highly decorative plant varieties obtained by hybridization are usually propagated vegetatively, since during seed propagation, splitting of individuals is observed and the variety loses its qualities.
Under natural conditions and in culture, plants often reproduce using the same organs. This property of plants is widely used in the practice of plant growing, forestry and, especially, horticulture.
Very often propagation occurs using cuttings. Cutting- this is a segment of any vegetative organ of a plant capable of restoring missing organs. Segments of shoots 20-30 cm long with one to three leaves, in the axils of which axillary buds develop, are called stem cuttings. Under natural conditions, such cuttings can easily propagate willow, poplar, and in cultivation - geranium, currant, rose, etc.
Root cuttings- sections of lateral roots 10-20 cm long - harvested in the fall and stored in sand, planted in a greenhouse in the spring. Used for propagation of cherries, apples, and raspberries.
The leaf that forms the root is also used as leaf cutting. Begonia, Uzumbara violet, and gloxinia are propagated by leaf cuttings.
When artificially propagated, cuttings are separated from plants and rooted in water, sand or a light earthen mixture. Some plants take root easily, others find it difficult. Plant cuttings should be covered with glass to create increased air humidity, periodically sprayed and ventilated. When propagating with large leaf blades, part of the leaf blade must be removed.
In nature, vegetative reproduction occurs root shoots. This is how cherry, aspen, plum, lilac, and bird cherry reproduce.
Reproduction layering It is also used for growing currants, grapes, azaleas and other plants. To do this, one- or two-year-old shoots of the plant are tilted into a specially dug ditch, pinned and covered with earth so that the end of the shoot remains on the soil surface. Rooting goes better if you make an incision in the bark under the bud. The flow of nutrients to the cuts stimulates the formation of adventitious roots. Rooted shoots are separated from the mother plant and planted.
Plants are easily propagated by special creeping shoots - mustache(strawberries, cinquefoil, tenacious).
Vegetative propagation is widespread not only by typical organs or their parts, but also by modifications of the stem - rhizomes, bulbs, tubers.
Berry and ornamental plants are also propagated by dividing the bush into several parts, each of them is planted in a new place.
A special method of vegetative propagation is graft. Graft- splicing of a bud or cutting of one plant with the stem of another growing in the soil. The cutting or bud is called the scion, and the plant with the root is called the rootstock.
Grafting a bud with a piece of wood is called budding. In this case, a T-shaped cut with a length of
2-3 cm, horizontal - no more than 1 cm. Then the edges of the bark are carefully folded back, and a peephole cut with a piece of wood is inserted under the bark. The peephole is pressed tightly against the wood with bark flaps. The grafting site is tied with a washcloth, leaving the bud open. After fusion, the stem of the rootstock above the eye is removed. Budding is carried out in summer and spring.
Less commonly used copulation- grafting a one-year-old cutting with several buds. In this case, the scion and rootstock should be the same thickness. They make identical oblique cuts. The scion is applied to the rootstock so that their tissues coincide (the matching of the cambium is especially important) and carefully tied with a washcloth. If the thickness of the scion and rootstock is different, grafting is done into the cleft, behind the bark, into the butt, etc.
The importance of vegetative propagation. Vegetative propagation of plants is of great importance in agriculture. It makes it possible to quickly obtain a large amount of planting material, propagate plants that do not form seeds, and preserve the characteristics of the variety. Since vegetative propagation involves mitotic division of somatic cells, the offspring receives the same set of chromosomes and completely retains the characteristics of the mother plants.
Sexual reproduction differs significantly from asexual in that in this case the genotype of the offspring arises as a result of the recombination of genes belonging to both parents. This increases the ability of organisms to adapt to changing environmental conditions. Sexual reproduction is characterized by the presence of a sexual process, one of the most important stages of which is the fusion of germ cells, or gametes, specialized haploid cells covered with a plasma membrane. Gametes differ in structure and physiological properties and are divided into male (motile - sperm, immobile - sperm) and female (eggs). Unlike spores, one gamete, with the exception of cases of parthenogenesis, cannot give rise to a new individual. This is preceded by the process of fusion of two germ cells - fertilization, which results in the formation of a zygote. Subsequently, the embryo of a new organism develops from the zygote.
The formation of germ cells in algae, many fungi and higher spore plants occurs by meiosis in special organs of sexual reproduction: eggs - in oogonia or archegonia; spermatozoa and spermatozoa - in antheridia.
The process of fertilization consists of the fusion of female and male gametes to form a zygote. The zygote has a double set of chromosomes. In angiosperms, double fertilization occurs within the flower.
Flower It is a shortened, unbranched, modified shoot with limited growth, which serves for the formation of spores and gametes, for the sexual process, after which the seed and fruit are formed.
Flowers are formed on the main and lateral stems and develop from buds located in the axils of the covering leaf. The stem part of the flower shoot is called the peduncle. It has limited growth and a peculiar growth point expanded upward, called the receptacle, from which all parts of the flower extend. On the receptacle, a perianth is formed, consisting of a calyx and corolla, as well as the floret and pistils themselves, which are modified leaves. In some flowers, individual parts may be missing.
Peduncle- the part of the stem that bears the flower, located between the receptacle and the bract. If it is not developed, then the flower is called sessile (flowers in a basket inflorescence). The pedicel sometimes develops one or two small apical leaves called bracts.
Receptacle- this is the expanded axial part of the flower, which is its shortened stem part. The remaining parts of the flower extend from it. The receptacle can be widened (strawberry), flat (peony), conical (raspberry), concave (cherry, plum).
Perianth make up the leaf parts of the flower, providing protection to the stamens and pistils. The perianth can be simple or double. The double perianth consists of a calyx and corolla, varying in color and size. If the integument of the flower is homogeneous and there is no differentiation into a calyx and corolla, then such a perianth is called simple. A simple perianth with green leaves is called calyx-shaped (nettle, hemp), a brightly colored simple perianth is called corolla-shaped (tulip, lily of the valley). Flowers that do not have a perianth are called coverless, or naked (willow, sedge).
Rice. 26. Flower structure diagram:
1 – boot in cross section, 2 – boot in longitudinal section,
3 – pollen on the stigma, 4 – style, 5 – ovary walls, 6 – ovary nest, 7 – embryo sac, 8 – receptacle, 9 – sepal, 10 – corolla petal, 11 – ovum, 12 – central nucleus, 13 – antipodes, 14 – synergids.
Cup. The outer modified leaves of a flower are called sepals - together they make up the calyx. It can be dioecious (free sepals) or fused-leaved (sepals fused); the arrangement of sepals can be spiral or circular. The sepals can be arranged in two circles - then the lower tier is called the undercup. In most representatives of Asteraceae and Umbelliferae, the calyx is poorly developed or absent. The function of the calyx is to protect the remaining parts of the flower from adverse influences (temperature, moisture, pests).
Whisk. It consists of petals arranged in a spiral or circle. The petals are usually larger than the sepals and have different colors. The corolla can be separate-petaled or fused-petaled (the sepals are fused). The petaled corollas are varied: in shape they can be spike-shaped (potato), bell-shaped (bell-shaped), reed-shaped (chicory), two-lipped (lamella), etc. The corolla can be regular, having at least two planes of symmetry; irregular, having one plane of symmetry; and asymmetrical, through which no axis of symmetry can be drawn. Regular corollas have apple, cherry, etc. flowers, irregular corollas have toadflax and pea flowers, and asymmetrical corollas have canna flowers.
The main function of the corolla is to attract insects that promote cross-pollination and protect the stamens and pistils from unfavorable conditions.
Androecium- a collection of stamens in a flower. Their number ranges from one to several hundred. They are located on the receptacle or in a spiral or in a circle (in one or two circles). In most flowers, the stamen consists of a filament and an anther. The two halves of the anther are connected to each other using a connector. The anthers can be fixedly attached to the thread, and in some plants (cereals) they are swaying. Each anther contains two pairs of pollen nests in which pollen develops. Stamens can be fused with filaments (in legumes), anthers (in Asteraceae), filaments and anthers (in pumpkin plants). Stamens arise from the tubercles of the growth cone of the flowering shoot. Initially, the anther is formed, and then the filament. One vascular bundle goes along the filament to the connective tissue. Differentiation of tissues in the anther occurs as follows. The epidermis is formed from the outer layer of educational tissue, and the archisporium emerges from the inner layer, giving rise to mother cells of microspores.
Archisporium cells divide repeatedly by mitosis and give rise to mother cells of microspores, which divide by meiosis, and from each four mononuclear haploid microspores are formed, interconnected. Pollen or pollen grains are formed from microspores. The pollen grain has two shells: the inner - thin - intina and the outer - thick, often cutinized - exine, nucleus and cytoplasm. The exine has non-thickened areas - pores and thickened areas in the form of tubercles.
During the formation of a pollen grain from a microspore, the nucleus and cytoplasm divide by mitosis (without cytokinesis) to form two nuclei (cells). The larger cell is called vegetative (from which the pollen tube subsequently develops), the smaller one is called generative. The nucleus of the generative cell in some plants is divided in the pollen nest (later in other plants) by mitosis, and two cells are formed - sperm, which are male reproductive cells - involved in fertilization. A similar two-celled or three-celled germinated microspore is a male gametophyte. It represents the pollen grain or pollen needed for pollination. The color of pollen is different: white, red, yellow. Shape - spherical, triangular, elliptical, rod-shaped, etc.
There is one or more in a flower pestles, each pistil develops from one or more carpels. The collection of carpels is called gynoecium. The pistil usually consists of a stigma, style and ovary. A thin cylindrical column rises above the ovary, bearing a stigma at the upper end (acting as a pollen-collecting apparatus). Some plants do not have a style, and then the stigma sits directly on the ovary, in which case it is called sessile. The style, raising the stigma, promotes better pollination and the passage of pollen tubes during pollen germination.
Ovary- an enlarged, sometimes swollen part of the pistil in which the ovules are located.
There are three types of ovaries in flowers: upper, lower and semi-lower. The superior ovary is located freely on the receptacle and is formed only by carpels. The inferior ovary results from the fusion of the bases of the calyx, corolla and androecium with the ovary, with the perianth extending from the apex of the ovary. The semiinferior ovary is rare. It is fused with the perianth and stamens only by its lower part, while the upper part remains free. The ovary can contain from one to several thousand ovules. The ovule, or megosporangium, develops on the inner wall of the ovary, consists of a nucellus (ovule nucleus), one or two integuments (integuments), and a hole remains between the integuments - the pollen passage (micropyle). Megaspores are formed in the ovule. The archisporial nucellus cell, or mother cell, divides by meiosis to form a tetrad of haploid megaspores. Of the four, only one develops, and three are reduced (disappear). The remaining megaspore begins to germinate. When a megaspore germinates, its nucleus is successively divided by mitosis. The resulting two nuclei diverge towards the poles, and a large vacuole forms between them in the cytoplasm. Each nucleus then divides twice more, so that four haploid nuclei are formed at the poles of the embryo sac. From each pole of four nuclei, one extends into the central part of the embryo sac. Here these two nuclei merge into one diploid one, which is called the secondary or central nucleus of the embryo sac, it has a diploid set of chromosomes and becomes the central cell of the embryo sac.
Three nuclei, together with the cytoplasm at the micropylar end, form the egg apparatus. One of the cells more distant from the pollen passage is the egg.
(i.e. female gamete). The other two are called accessory cells or synergids.
Near the other opposite pole there are also three cells, called antipodes. Thus, an embryo sac with seven nuclei appears, ready for the fertilization process (sometimes the number of nuclei may be different) (Fig. 26).
Bisexual and unisexual flowers. If a flower has both stamens and pistil(s), it is called bisexual. About 75% of flowers are bisexual. If a flower has only stamens or only pistils, then the flower is called same-sex. It will be male if it contains only stamens, and female if only pistils are present. Unisexual flowers may be distributed differently on plants. For example, in hemp and willow, some specimens have male flowers, while others have female flowers. Such plants are called dioecious. Cucumber and corn have both male and female flowers on the same plant. These plants are called monoecious. Polyecious plants are also found. On one individual you can find bisexual and unisexual flowers. They are called polygamous (maple, ash).
Flower formula. The structure of a flower can be shown in the form of a formula. To do this, use conventional signs to write down the formula of a flower. Each flower circle is indicated by a specific capital letter. Simple perianth - P (P), calyx - Ch (K, Ca), corolla - B (Co), stamens - T (A), pistil - P (G). The number of flower members in each circle is indicated by numbers, and if their number is more than 12, then by the infinity sign (∞). Their absence is indicated by - 0. If the members of the flower are fused, then the numbers are written in brackets (). The upper ovary is designated by a horizontal line under the number of carpels, and the lower ovary by a line above the number of carpels. An irregular corolla is shown with an arrow (), a correct one is shown with an asterisk (*), unisexual staminate flowers are marked with ♂, unisexual female flowers - ♀, bisexual flowers - ♂♀.
Potatoes: * Ca (5) Co (5) A 5 G (2)
Flower diagram. Flowers can be depicted by diagrams, which represent a schematic projection of the flower on a plane, perpendicular to its axis, intersecting the axis of the mother plant and the covering leaf. On diagrams, sepals are usually depicted as a bracket with a keel on the back, petals as a round bracket, stamens as a transverse section through the anther, and a gynoecium as a transverse section through the ovary. The fusion of parts of a flower is shown by their connection.
Rice. 27. Flower and its diagram.
In flowering plants, the process of fertilization is preceded by pollination. Pollination– transfer of pollen from the anther of the stamens to the stigma of the pistil. Once on the stigma of the pistil, the pollen grain begins to germinate. A long pollen tube develops from the vegetative cell, which grows through the tissues of the style to the ovary and ovule. Two sperm are formed from the generative cell. The pollen tube enters through the pollen duct and its nucleus is destroyed. The tip of the tube breaks and two sperm enter the embryo sac. Soon the synergids and antipodes die off. After this, one of the sperm fertilizes the egg. As a result, a diploid zygote is formed from which the seed embryo develops. The second sperm fuses with two polar nuclei to form a triploid cell. Nutrient tissue, the endosperm, develops from the triploid cell. Its nutrients are necessary for the development of the embryo.
This method of fertilization, in which one sperm merges with an egg, was discovered in 1898 by the Russian cytologist S.G. Navashin.
Thanks to double fertilization, the rapid formation and development of endosperm occurs and accelerates the formation of the ovule and seed. After fertilization, the ovule develops into a seed. And the ovary forms the fruit.
In angiosperms, the reproductive organ is the flower. Let's consider the processes occurring in stamens and pistils.
Scheme of fertilization in flowering plants:
1 - stigma of the pistil; 2 - sprouted pollen; 3- pollen tube;. 4 - egg; 5 - central cell; 6 - ovule; 7 - sperm.
The formation of pollen grains occurs in the stamens. The stamen consists of a filament and an anther. Each anther is formed in two halves, in which two pollen chambers, microsporangia, develop. The nests contain special diploid microsporocid cells. Each microsporocide undergoes meiosis and forms four microspores. Inside the pollen nest, the microspore increases in size. Its nucleus divides mitotically and two nuclei are formed: vegetative and generative. A durable cellulose shell with pores is formed on the surface of the former microspore. Pollen tubes subsequently grow through the pores. As a result of these processes, each microspore turns into a pollen grain (pollen) - a male gametophyte. A mature pollen grain consists of two (vegetative and generative) or three (vegetative and two sperm) cells.
The formation of the female gametophyte (embryo sac) occurs in the ovule, which is located inside the ovaries of the pistil. The ovule is a modified megasporangium protected by integument. At the top there is a narrow channel - a pollen passage. Near the pollen passage, a diploid cell begins to develop - a megasporocyte (macrosporocyte). It divides by mitosis and produces four haploid megaspores. Three megaspores are soon destroyed, the fourth, furthest from the pollen entrance, develops into an embryo sac. The embryo sac grows. Its nucleus divides three times by meiosis. As a result, eight daughter nuclei are formed. They are located in two groups of four: one near the pollen entrance, the other at the opposite pole. Then, one nucleus extends from each pole to the center of the embryo sac - these are polar nuclei. They can merge to form one central core. At the pollen entrance there is one egg cell and two synergid cells. At the opposite pole are antipodal cells, which participate in the delivery of nutrients to the cells of the embryo sac and then disappear. This eight-nucleate embryo sac is the mature female gametophyte.
Most plants produce flowers. How do flowering plants reproduce? “Vegetatively” - you will answer, and you will be right. However, the vegetative method of reproduction in such plants is not the only one.
Like all other plant organisms, the formula for sexual reproduction “gamete + gamete = zygote” is valid for them. This formula seems simple, but you already know that it hides very difficult stages in the life cycle of a plant.
Life cycle of flowering plants? What does their asexual generation look like - sporophyte, where to look for spores? Where is the gametophyte of a flowering plant? How and where do gametes fuse?
We need to find answers to these questions by analyzing the life of a flower plant. Let's use a drawing for this; it will help us, step by step, trace the stages of development of the familiar cherry.
In spring, flowers appear on the cherry trees. Let's look into a cherry blossom. We will see that in the center of the flower there is a pistil, similar to a cone. It is surrounded by stamens. Each stamen consists of a thin filament, at the end of which is an anther.
All events associated with both asexual and sexual reproduction of this plant take place in these flower organs. There are sporangia where cherry spores are formed. Cherry spores are of different sizes: large spores are formed in the pistil sporangia, and small ones are formed in the anther sporangia.
What is the structure of the pistil? Its upper expanded part is the stigma, the lower thickened part is the ovary, they are connected by a thin column.
Inside the ovary there is a cavity where two sporangia are located. In flowering plants they are called ovules. Four haploid cells are formed there - four spores.
But only one of these spores germinates: from its ovary a gametophyte is formed, consisting of only seven cells. And only one of these cells is a gamete. This is an egg, and the gametophyte on which it is formed is called the female gametophyte (germ sac).
What happens in the anther of a cherry blossom? Under a microscope it is clearly visible that there are many “sacs” in the anther. These are also sporangia. They produce small spores. Each spore produces a male gametophyte, consisting of only two cells surrounded by a durable membrane. It is called a pollen grain. There are many pollen grains in the anther.
The pollen sac opens and insects come to the aid of the plant. They transfer pollen from the anthers of one flower to the stigma of another. This is how cherry pollination occurs.
The stigma of the pistil secretes special sticky substances to which pollen grains stick.
What happens to the male gametophyte that lands on the stigma of the pistil? The “work” of the male gametophyte continues on the stigma. One of its two cells divides, forming two male gametes - two sperm.
It is known that for fertilization, male and female gametes must merge, and only then a zygote will appear. How can two gametes merge if one of them is on the stigma of the pistil and the other is in the ovary?
The second cell of the male gametophyte is “responsible” for the delivery of sperm to the ovary. This cell is called a “tube cell,” and its name is not accidental. The “tube cell” begins to grow through the pistil column. It actually forms a tube through which sperm travel. When the tube reaches the entrance to the embryo sac, it ruptures and sperm emerge. One of them fuses with the egg, forming a zygote.
What happens to the second sperm? In addition to the egg, the female gametophyte has another special cell - the central one. It differs from all others in that it contains two cores. The second sperm merges with it.
Thus, in the ovary of the pistil, two fertilizations occur at once: one sperm fuses with the egg, forming a zygote, the other sperm fuses with the central cell. This process is called double fertilization.
The embryo of the future plant develops from the zygote. What happens to the second fertilized cell? It gives rise to tissue, stores it, its name is endosperm. Due to the substances of the endosperm, the embryo will first grow. Integumentary tissue, the skin, is formed from the integument of the seed germ that surrounded the female gametophyte. This is how a seed is formed - a multicellular formation with the help of which the cherry reproduces.
What happens to the pestle at this time? The ovary grows, and from its tissues a fruit is formed, inside which the seed is hidden.
It is now obvious that the life cycle of a flowering plant is similar to the life cycle of a fern. It also contains asexual generations - a sporophyte plant with roots and shoots, and a sexual generation - male and female gametophytes.
However, unlike ferns, cherry gametophytes are not separate independent individuals, but are formed and live in the flowers of a sporophyte plant. The male gametophyte is in the pollen grains, and the female gametophyte (embryo sac) is in the ovary of the pistil. These gametophytes are microscopically small and are not capable of photosynthesis. The asexual generation (sporophyte) supplies the sexual generation (gametophytes) with what they need nutrients.
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Flowers are the most numerous group of flora. Most shrubs, trees and grasses are flowering plants. There are several ways to propagate flowers. Let's look at each of them.
How flowers reproduce through pollination
Pollination is the most common method of reproduction of flowering plants. Pollination mainly occurs with the help of insects, and specific types of insects are involved in the pollination of certain flowers. Thus, clover flowers are pollinated by bumblebees, and geranium flowers are pollinated by hoverflies.
The pollination process itself occurs as follows: flowers secrete nectar, which attracts insects with its aroma. While insects collect nectar, pollen grains stick to their legs, which are partially transferred by pollinators to other flowers. This is how reproduction occurs by pollination.
How does sexual reproduction occur in flowers?
After pollination, the flower withers and its petals fall off, and in this place a fruit with seeds appears. Ripe seeds are carried by wind, animals, birds and people. This is how seed or sexual reproduction of flowers occurs. Since seeds can ripen all year round, this method of propagation is the most optimal.
How does vegetative propagation of flowers occur?
This is the propagation method that gardeners prefer. To do this, they take any part of the plant: root, leaf or stem, which is deposited in a nutritious substrate, where it takes root. The most popular method for vegetative propagation is propagation by root suckers, since with it a positive result is almost always achieved.