Ferns, horsetails, mosses. General characteristics, reproduction and significance for humans. Mosses and horsetails Asexual reproduction of horsetails
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Horsetail cabbage soup(Equisetum) are perennial herbaceous plants that grow in wet fields and meadows, swamps and damp forests. Although they differ in appearance from ferns and mosses, they are similar to them in many ways. Horsetails, like ferns, are spore plants. Currently, horsetails do not play a major role in the formation of vegetation cover. Although horsetails often form thickets in places where other plants cannot exist.
The species diversity of horsetails is small - about 30 species. In forests on moist soil, horsetail with highly branched drooping lateral branches is often found. Overwintering horsetail grows on sandy soils and in ravines; marsh horsetail and riverine horsetail grow in wetlands, along the banks of rivers and lakes (Fig. 88).
Horsetail
A typical representative is horsetail (Fig. 87). This is a perennial weed that grows in fields and arable lands. In the soil there is a branched rhizome with adventitious roots and buds, from which above-ground shoots develop every year. When cultivating the soil, pieces of horsetail rhizome do not die, and an independent plant grows from each. Therefore, this weed is very difficult to control.
Structure
Horsetails have unique articulated stems. Leaves are located at the joints. The stem is impregnated with silica, which gives it greater strength.
Under favorable conditions, horsetail spores, like ferns, germinate into small plants, unlike leafy plants. Organs of sexual reproduction are formed on them, in which germ cells mature. In the presence of dripping water, fertilization occurs. A young horsetail plant with a rhizome is formed from the egg.
After the formation of spores, the spring shoots die, and green summer shoots grow from the rhizome, similar to small pine trees (see Fig. 87).
The stems of wintering horsetail contain a significant amount of silica - a hard, well-polishing substance. Therefore, its stems are especially tough and durable. They have long been used for cleaning metal utensils and instead of sandpaper.
Shoots of some horsetails (for example, horsetail) are used in folk medicine as a diuretic and astringent.
Theory for preparation for block No. 4 of the Unified State Exam in biology: with system and diversity of the organic world.
Moss moss
Moss-moss- one of the most ancient divisions of higher spore plants. Currently, they are represented by a relatively small number of genera and species, the participation of which in the vegetation cover is usually insignificant. Perennial herbaceous plants, usually evergreen, resembling green mosses in appearance. They are found mainly in forests, especially coniferous ones.
There are about 400 species, but only 14 are common in Russia (club-shaped moss, ram-moss, double-edged moss, etc.).
The structure of mosses
Lycopods are characterized by the presence of shoots with spirally, less often oppositely and whorled leaves. The underground parts of the shoots of some lycophytes have the appearance of a typical rhizome with modified leaves and adventitious roots, while in others they form a peculiar organ bearing spirally arranged roots and called a rhizophore (rhizophore). Roots of lycophytes are adventitious.
Nutrition and reproduction of mosses
Sporophylls may be similar to ordinary vegetative leaves, sometimes different from them. Among the lycophytes there are equi- and heterosporous plants. Homosporous gametophytes are underground or semi-underground, fleshy, 2-20 mm long. They are bisexual, saprophytic or semi-saprophytic, and mature within 1-15 years. Gametophytes of heterosporous unisexuals, non-green, usually develop within several weeks due to the nutrients contained in the spore, and upon maturity do not protrude or protrude slightly outside the spore shell. The reproductive organs are represented by antheridia and archegonia: in the former, bi- or multiflagellate sperm develop, and in archegonia, eggs develop. Fertilization occurs in the presence of drip-liquid water, and a sporophyte grows from the zygote.
Sporophyte club moss is a perennial evergreen plant. The stem is creeping, branched, produces vertical branched shoots about 25 cm high, densely covered with leaves that look like elongated pointed scales. Vertical shoots end in spore-bearing spikelets or apical buds. On the shaft of the spore-bearing spikelet there are sporophylls with sporangia on the upper side. The spores are identical, contain up to 50% non-drying oil, and germinate very slowly. The gametophyte develops in the soil in symbiosis with a fungus (mycorrhiza), which, receiving carbohydrates, amino acids and phytohormones from the vascular plant, makes water and minerals, especially phosphorus compounds, available for absorption and absorption by the plant. In addition, the fungus provides the plant with a larger absorption surface, which is especially important when it grows in poor soil. The gametophyte develops over 12-20 years, has rhizoids, and does not have chloroplasts. However, in some species it develops on the soil surface, then chloroplasts appear in its cells.
Gametophyte bisexual, resembles an onion in shape, acquires a saucer-shaped shape as it develops, and bears numerous antheridia and archegonia. Mature antheridia are almost completely immersed in the gametophyte tissue or slightly protrude above its surface. The archegonium consists of a narrow abdomen immersed in the tissue of the gametophyte and a long or short neck protruding above its surface. Antheridia usually mature before archegonia. The zygote germinates without a dormant period and gives rise to an embryo. Vegetatively propagated by parts of the stem and rhizome. Some club mosses also have specialized organs for vegetative reproduction: brood nodules on the roots, brood bulbs or buds on the tops of shoots.
Development cycle of clubmoss: A - sporophyte; B - gametophyte; 1 - creeping shoot with adventitious roots; 2 - ascending shoots; 3 - stalk of spore-bearing spikelets; 4 - leaves: ascending shoot (a) and stalks of spore-bearing spikelets (b); 5 - spore-bearing spikelets; 6 - sporolists: view from the ventral (c) and dorsal (d) sides; 7 - sporangia; 8 - disputes; 9 - germinating spore; 10 - archegonium; 11 - antheridium; 12 - fertilization; 13 - fertilized egg; 14 - development of a new sporophyte on the gametophyte.
Equisetaceae (Horsetails)
The living species are exclusively herbaceous plants ranging in height from a few centimeters to several meters.
In all types of horsetail, the stems have a regular alternation of nodes and internodes.
The leaves are reduced to scales and arranged in whorls at the nodes. Lateral branches are also formed here.
The underground part of horsetails is represented by a highly developed rhizome, in the nodes of which adventitious roots are formed. In some species (horsetail), the lateral branches of the rhizome turn into tubers, which serve as a place for deposition of reserve products, as well as organs of vegetative propagation.
The structure of horsetails
Horsetails are herbaceous plants with annual above-ground shoots. A small number of species are evergreen. The size of horsetail stems varies greatly: there are dwarf plants with a stem 5-15 cm high and a diameter of 0.5-1 mm and plants with a stem several meters long (in the polychaete horsetail the stem reaches a length of 9 m). Tropical forest horsetails reach a height of 12 m. The underground part is a rhizome, creeping, branched, in which nutrients can be deposited (tubers are formed) and which serves as an organ of vegetative propagation. Aboveground shoots grow at the top. Summer shoots are vegetative, branched, assimilating, consist of segments, with well-developed internodes. Whorled and also dissected branches branch off from the nodes. The leaves are inconspicuous and grow together into toothed sheaths that cover the lower part of the internode. Silica is often deposited in the epidermal cells of the stem, so horsetails are a poor food.
Spring shoots are spore-bearing, non-assimilating, unbranched, and spore-bearing spikelets are formed at their apex. After the spores mature, the shoots die. The spores are spherical, with four springy ribbons, greenish, germinate into shoots, unisexual - male or female. There are cases when antheridia and archegonia appear on the same prothallus. From the fertilized egg, a pre-adult grows, and then an adult horsetail.
Horsetails often make up a significant percentage of grasslands in meadows and wetlands; common in acidic soil. Most often, we have horsetail, meadow horsetail, marsh horsetail, marsh horsetail and forest horsetail.
Horsetails reproduce sexually. The sexual generation is the gametophyte (prothallus). Antheridia and archegonia are formed on gametophytes. Multiflagellate sperm develop in antheridia, and eggs develop in archegonia. Fertilization occurs in the presence of drip-liquid water, and a sporophyte grows from the zygote without a rest period.
The development cycle of horsetail is dominated by sporophyte- an adult, perennial plant consisting of rhizomes, fixed in the soil adventitious roots. In spring, it grows from the buds of the rhizome onto the soil surface. spore-bearing, chlorophyll-free vertical the escape(stem) with a whorled arrangement of reduced (small) leaves, ending in a spore-bearing spikelet ( strobile). The spore-bearing spikelet itself in its structure has axis, on which umbrella-shaped spore-bearing leaves (scutellums on stalks) are located - sporophylls. On the lower side of the sporophylls, facing the strobilus axis, there are from 5 to 10 sporangia. In sporangia as a result of reduction division meiosis cells sporogenous tissue(2n) haploid, morphologically identical, but different sexes are formed disputes(male and bisexual). The spore shells have special outgrowths - elaters, which are twisted spirally around the spores when wet, and unfold when dry. This allows the spores to cling to each other and spread in groups. After the spores ripen, the spore-bearing leaves of the strobile open, the sporangia burst and the spores are carried by the wind. Due to the content of chloroplasts in the spores, they quickly (within 3 weeks) lose their germination capacity. Once on moist muddy soil, groups of spores germinate into chlorophyll-bearing gametophytes in the form of lobed plates fixed in the substrate rhizoids. Gametophytes reach sexual maturity 3-5 weeks after germination. On male gametophytes, smaller in size, are formed antheridia- male gametangia, in which multiflagellates are formed spermatozoa. On bisexual gametophytes, more dissected in shape, archegonia(female gametangia) develop before antheridia, which increases the likelihood of cross-fertilization. For sperm to reach the eggs located in the archegonia, it is necessary water. On one gametophyte, several eggs can be fertilized at once, from which they further develop embryos, there are young sporophytes. The embryos are attached with their feet to the abdomen of the archegonium and receive from the gametophyte the necessary nutrients for development, forming a rudimentary root, stem and bud. After formation, the embryonic root begins to grow, is fixed in the soil, and the young sporophyte is detached from the gametophyte, which dies after some time. After sporulation spring(spore-bearing) shoots die and green rhizomes grow from the buds assimilation shoots. Assimilation shoots have a vertical stem with a whorled arrangement on it lateral branches And leaves underneath them. They perform the function of forming organic compounds during photosynthesis and accumulating them in the rhizome. At the end of the growing season, the assimilation shoots die off, leaving a rhizome that overwinters in the soil.
Rice. 34. Scheme of the life cycle of horsetail
Rice. 35. Life cycle of horsetail
Moss - department of higher spore plants, represented by 1200 species. They are characterized by the presence of a developed conducting system, a root-shoot type of structure of sporophytes and a thallus structure of gametophytes, asexual reproduction by spores and vegetative reproduction by above-ground shoots.
Vegetative propagation of field horsetail occurs due to the rhizome, which makes it a malicious weed that is very difficult to get rid of. Old sections of rhizomes die off and the initially single mother plant breaks up into several new ones.
Asexual reproduction
Spore-bearing or spring shoots (Fig. 14 - 1) of horsetail, pinkish-brown, appear in early spring, unbranched. They are often eaten by people in Asia and North America.
At their top a spore-bearing spikelet is formed (Fig. 14 - 1 spike), on the axis of which there are sporophylls bearing sporangia with spores. After sporulation, spring shoots die. Sporiferous spikelets of horsetails appear one at a time at the top of the main shoot. In most species of horsetails, the shoot bearing the spikelet is green and assimilative. But in horsetail, the spore-bearing shoot does not take part in photosynthesis.
The horsetail spikelet consists of numerous sporophylls - sporangiophores (Fig. 14 - 2), collected by whorls of its axis. Sporophylls consist of a stalk (Fig. 14 - 2n) and a shield disk located at its apex (Fig. 14 - 2w), usually having a hexagonal shape. On the side of the disc, around the stalk, there are 5–13 sac-like sporangia (Fig. 14 - 2c), in the mature state covered with a single-layer wall. The sporophylls in the spikelet are tightly packed together. By the time the sporangia mature, the axis of the spikelet expands somewhat (there is meristematic tissue at the base of all internodes) and the whorls of sporophylls move apart. A large number of identical spores are formed in the sporangia, since horsetail is a homosporous plant. The spore (Fig. 14 - 3), in addition to two shells, endo- and exosporium, is also covered with a third – outer shell – episporium. The outer shell is not solid, but consists of two spirally twisted ribbons (springs, elater), expanding spatulate at 4 ends and attached to the spore in one place. Springs (elaters) gradually unwind in dry weather (Fig. 14 - 4), fully untwisted elaters (Fig. 14 - 5) of different spores cling to each other, which facilitates the spread of spores in groups, heaps (Fig. 14 - 6). In damp weather, the spores are swirled around.
The sporangia are opened by a longitudinal crack; after the whorls of sporophylls move apart, the spores spill out. Once on the ground, the spores germinate into a shoot, which is the horsetail gametophyte.
Sexual reproduction
The prothallus of a horsetail has the appearance of a green, repeatedly dissected plate 0.1–0.9 cm in size. Antheridia and archegonia arise either on the same prothallus or on different prothalluses, despite the fact that the spores are morphologically identical. Many species of horsetails have a physiological diversity.
Horsetail spores, united in groups due to adhesion by springs, when they fall on the soil, find themselves in unequally favorable conditions of lighting, water supply, etc. (for example, the top and bottom spores in a pile). When sprouting, some of them form smaller male growths (Fig. 14 – 7) with antheridia (Fig. 14 – 7an), others, larger ones, form female growths (Fig. 14 – 10) with archegonia (Fig. 14 – 10a) . This phenomenon can be considered as a well-known echo of the morphological heterosporousness of the ancestors of horsetails, especially since in some species the physiological heterosporousness is constant and is not related to the conditions of development of the shoots.
And for horsetail, the following has been experimentally established: by watering the growths on which antheridia have begun to develop with a nutrient solution, it is possible to achieve an increase in their size and the development of archegonia on them.
Antheridia of horsetail (Fig. 14 – 8) are immersed in the tissue of the prothallus. In each of them, over 200 multiflagellate sperm develop (Fig. 14 – 9). Archegonia (Fig. 14 – 11), only the neck rises above the prothallus. Fertilization takes place in damp weather. The fertilized egg gives rise to the embryo (Fig. 14 – 12). Horsetails do not form a pendulum. The embryo is initially hidden in the tissue of the germ. It consists of a stalk (Fig. 14 - 12n), a rudimentary root (Fig. 14 - 12k), 2-3 first leaves (Fig. 14 - 12pl) and a stem in the form of a growing point (Fig. 14 - 12ch). By breaking through the tissue of the shoot, the root becomes stronger in the ground, and the plant begins to live independently. Several embryos often appear on one shoot.
Horsetail as a medicinal plant has been known since ancient times. An infusion of the herb is used as a diuretic for edema due to circulatory failure, as well as for inflammatory diseases of the bladder and urinary tract, pleurisy, tuberculosis, dysentery, and as a hemostatic agent for dysentery. Internal use of horsetail, as a poisonous plant, requires caution, that is, the dosage must be strictly observed.
Among the higher spore plants, which include mosses, mosses, ferns and horsetails, the latter have several features in their external and internal structure. The horsetail plant looks like a small Christmas tree with hard side stems. Interestingly, animals do not eat either it or other types of horsetails. This is explained by the fact that plant tissues are impregnated with silicon compounds. The systematic position of the Horsetail genus indicates the fact that their reproduction occurs with the help of spores. Our article will focus on the structure of horsetail, as well as consideration of its use in medical practice as a medicine.
What is alternation of generations?
In the life cycle of a plant, two life forms change cyclically: asexual and sexual generations. The first is represented by a perennial herbaceous plant, the second has the appearance of green plates with a dissected surface with numerous threads. The reproductive organs develop on them: female - archegonia and male - antheridia. The maturation of eggs and sperm, as well as the process of fertilization itself, occurs only in the presence of water. So, to imagine what horsetails are, you must remember that plants exist in two different forms - gametophyte and sporophyte.
External structure
As we said earlier, the asexual generation of horsetail is a plant that has above-ground and underground parts. Thus, the rhizome provides support and promotes vegetative propagation. A large number of adventitious roots extending from it absorb water and minerals from the soil. The rhizome has a large number of thickenings - nodules. It grows deep into the ground. It should be noted that horsetails are indicators of soil acidification. What are soil indicators? These are plants that require a certain concentration of soil solution for normal functioning. In our example, this is an excess amount of hydrogen ions, that is, high acidity of the soil. As it turned out, plants of the Horsetail genus do not live on neutral or alkaline soils, so their favorite places to grow are biocenoses of swampy areas and river floodplains. The most common type of horsetail is horsetail. It is its branches that are harvested as medicinal plant raw materials. Also found are forest horsetail, meadow horsetail (has a triangular stem), and swamp horsetail with a pentagonal stem shape and black edges at the stem nodes. In addition, this species is also highly poisonous.
Vegetative organs
Let's continue to look at the appearance and properties of horsetail. In addition to the rhizome, the vegetative parts of the plant body include stems, leaves and sporangia. They form a sporophyte - an asexual generation, whose task is to carry out the process of photosynthesis and the formation of reproductive organs - spore-bearing spikelets. The main ground shoot grows from the rhizome; it branches and is divided by nodes, from which lateral branches diverge in the form of a whorl. There are no leaves with a clearly defined leaf blade; they are reduced to colorless scales that grow from the nodes. Therefore, the function of photosynthesis in horsetails is performed by stems containing chlorophyll. Let's continue to study higher spore plants - horsetails. What are spring and summer forms of shoots? It turns out that the axial organ of the plant is ribbed, impregnated with silicon compounds and has a clear differentiation. Thus, spring shoots are light pink in color, incapable of branching and devoid of green pigment and leaves. At their tops, sporangia are formed in the form of hard shields resembling spikelets containing haploid spores. Summer shoots are the main and subsidiary stems, which are bright green. They are capable of branching and, thanks to chlorophyll, carry out the synthesis of organic substances: proteins, carbohydrates and fats, and also provide the release of oxygen.
Sporangia and spores
Like other representatives of higher spore plants - mosses, mosses and ferns, horsetails develop organs on the sporophyte plant in which the maturation of asexual reproduction cells - haploid spores - occurs. Spikelets - sporangia of horsetails, have the form of special structures collected together, called sporangiophores. They are derivatives of lateral stems and look like rings, closely pressed to each other. Spores are formed through the process of meiosis and are haploid cells of the same type. Therefore, the question of what horsetails are from the point of view of the structure of their asexual generation - the sporophyte - can be answered as follows: these are homosporous plants. In addition, the spores are equipped with special springs - elaters, which serve as a device for their better distribution. Subsequently, once on moist soil, the spores germinate and unisexual shoots appear, on which male or female genital organs develop separately.
Gametophyte and fertilization process
Haploid spore cells under favorable environmental conditions (sufficient humidity and absence of direct sunlight) begin to form green lamellar structures with filamentous processes along the edges. This is how a growth is formed. Which genital organs, male or female, will form on it will depend on the light and ambient temperature. On the underside of the shoot there are rhizoids that attach it to the soil surface. Antheridia are male reproductive organs that ensure the development of sperm, and archegonia contain eggs. Fertilization occurs in the presence of water. From the resulting zygote, an embryo develops, which subsequently gives rise to the development of the sporophyte - an asexual generation of horsetail, the medicinal properties of which have been known to man for quite a long time. Next we will look at them in more detail.
Application in medicine
One of the most common species, horsetail, is an effective diuretic and hemostatic herbal preparation obtained from the stems. If the functioning of the kidneys and heart is impaired, accompanied by fluid retention in the tissues and the appearance of severe edema, use a decoction prepared in the proportion: 20 g of raw material per 200 g of water. The diuretic effect is explained by the presence of saponin in horsetail shoots and the high content of potassium ions. In addition to them, plant materials contain vitamin C, carotene, equisetrin, calcium and iron ions. Horsetail decoction is used for uterine bleeding, in the treatment of pleurisy, and for inflammatory processes in the ureters and bladder. Pharmacological raw materials can be purchased in pharmacies in the form of an extract, brewing bags or briquettes.
Horsetail: properties and contraindications
The presence in the vegetative parts of horsetail of a large number of microelements, for example, copper, boron, molybdenum, has a positive effect on metabolism in the human body. However, the high concentration of alkaloids, glycosides and saponin determines not only the astringent, anti-inflammatory and diuretic properties of the plant, but can also cause a number of negative symptoms. For example: diarrhea, nausea, heaviness and pain in the epigastric region. Horsetail extract should be used with caution in the treatment of patients with gastric and duodenal ulcers. A prerequisite for taking medications is not only a strict dosage - no more than half a glass, but also the frequency of use (no more than 3 times a day), as well as compliance with the main rule - using a decoction or extract an hour after meals.
The role of horsetails in ecosystems
What is the significance of horsetails in nature? Giant extinct species of tree-like higher spore plants: horsetails, mosses and ferns, which lived in the Carboniferous period of the Paleozoic era, caused the formation of coal reserves in the bowels of the earth. Modern species of plants of the genus Horsetails are much smaller and distributed in different climatic zones, especially in floodplain meadows and swamps, as well as in coniferous forests. As we said earlier, horsetails thrive on acidic soils; many species, for example, horsetail, clog crops and pastures for domestic animals, since they are inedible for them. In everyday life, the hard branches of horsetail, containing silicic acid and its salts, were previously used as an abrasive for cleaning heavily soiled kitchen utensils.
In our article we examined the properties, structure and significance of horsetails in nature and human life.