In damp forests and swampy meadows, green moss - cuckoo flax - is often found. Its stems grow very densely, forming green carpets and hummocks.

Let's look at one cuckoo flax plant. It has a thin stem growing vertically upward. The stem is densely planted with green narrow leaves. When examining a moss leaf under a microscope, chlorophyll grains are visible in the cells of its pulp. Moss has no roots. Instead of roots, the underground part of the stem has thin thread-like outgrowths. They are called rhizoids. With the help of rhizoids, moss absorbs water and solutions of mineral salts from the soil.

Moss feeds in the same way as other green plants. It receives water and solutions of mineral salts from the soil, and absorbs carbon dioxide from the air. Organic matter is formed from carbon dioxide and water in chlorophyll grains.

Moss differs sharply from bacteria, algae, fungi and lichens in that its body has a stem and leaves. But moss has no real roots.

Living conditions of moss. Mosses are very unpretentious plants. They can withstand severe frosts and strong heating from the sun. When unfavorable conditions occur (cold, dry), they stop growing, but remain alive. When the rains fall and the weather warms up again, the mosses quickly come to life. Due to their hardiness, they often grow where other plants cannot exist. Following lichens, they settle on rocks, on tree trunks, on the walls and roofs of old houses. Under favorable conditions, for example, in humid northern coniferous forests, mosses cover the soil with a continuous green carpet. At the same time, they crowd out other plants, sometimes destroying entire forests, forming swamps in their place.

Moss reproduces by spores. In summer, at the end of the cuckoo flax stalk you can see a long thin stalk with a brown box at the top, inside of which there are tiny spores. The top of the box is covered with a special felt cap that protects it from drying out. When the spores mature, the cap falls off, the lid of the box falls off, and the spores begin to spill out.

Once on moist soil, the spores soon germinate and form thin branching threads. Buds form on these threads, giving rise to moss stems with leaves. The above-mentioned threads resemble in their structure filamentous green algae. This similarity of moss in the initial stages of its development with algae indicates a distant relationship between ancient algae and mosses. In the adult state, mosses have a more complex structure compared to algae, since they have a stem and leaves. Moss differs from flowering plants in that it does not have roots, flowers and does not form seeds; it reproduces by spores.

Sphagnum moss is also called white moss because it turns white after drying.

Sphagnum leaves contain living cells containing chlorophyll grains. Between the living cells are dead cells that have holes. When dry, dead cells are filled with air. Therefore, dried sphagnum moss is white. When it rains, these cells absorb enormous amounts of water. At the same time, the weight of the moss increases by 30 - 40 times.

Peat is formed from moss. Vast areas of peat bogs in the north of Russia, in the east (in Siberia and the Urals), in the west, and also in some other regions are called peat moss, or sphagnum.

Usually sphagnum covers the entire peat bog with a continuous thick carpet. Moss stalks grow from their tops. The lower parts of the stems are devoid of rhizoids. They gradually die off. Dead parts decompose slowly with little access to oxygen. Over time, huge reserves of half-decomposed parts of sphagnum and other bog plants accumulate in a peat bog. This is how peat is formed. Peat reserves in Russia are huge. Swamps make up about 7% of the country's total area. Peat is one of the sources of fuel for industry. Peat is also used to fertilize fields. Peat acquires especially great value as a fertilizer after it is used as bedding for livestock, since it absorbs liquid waste well.

Thus, moss is a more highly developed plant than algae and fungi: it has a stem and leaves. But moss has no real roots. They are replaced by rhizoids. Mosses reproduce by spores. Mosses are unpretentious plants. They often settle on rocks, following lichens. Peat deposits formed by peat moss - sphagnum - are of great economic importance.

MHI.

SYSTEMATICS :

Kingdom - Plants

Sub-kingdom – Higher spores

Department – Bryophytesabout 25,000 species

Class – Anthocerotaceaeabout 300 species

Class – Hepaticabout 10,000 species

Class – Leafy (true mosses)about 15,000 species

Orders of leaf stems:▪ shaving (green)about 14,000 species

▪ sphagnum (white)over 300 species

▪ andreceae (black) about 120 species

COVERING TISSUE less developed than in vascular plants. Often theyless specialized and contain chloroplasts . In most bryophytes● stomata do not have guard cells ● Rhizoids

CONDUCTIVE FABRICS absent or poorly developed (hydroids) MECHANICAL FABRICS .

● (sexual)

The concept of SPOROPHYTE and GAMETOPHYTE .

● Gametophyte – a haploid plant, which is the sexual stage of development. Male and female reproductive organs, gametangia, are formed on gametophytes. Antheridia are male reproductive organs, archegonia are female.

● Gametophytic stage of development (sexual) is the stage in the life cycle of a plant from spore to zygote.

● Sporophyte – this is the diploid (asexual) stage of plant development . Sporangia with spores develop on sporophytes.

● Sporophytic stage lasts from the moment the zygote is formed until the spores begin to mature.

● GAMETOPHYTE Bryophytes are, as a rule, low-growing plants, rarely reaching several tens of centimeters in length.

On the gametophyteThere are organs of sexual reproduction - antheridia (male) and archegonia (female).

Antheridia - representsingle-layer sac-like formations filled with sperm cells .

Archegonia - female genital organsbottle-shaped in which the egg is placed .

Among bryophytes you can find both monoecious and dioecious species. In monoecious plants, both archegonia and antheridia develop on the same plant, while in dioecious plants they develop on different plants, and in this regard, male and female individuals are distinguished

▪ boxes (sporangia), in which spores develop through meiosis.

▪ legs on which the box is located;

▪ feet , providing a physiological connection with the gametophyte.

● INTERNAL ORGANIZATION OF THE SPOROPHYTE relatively simple. On a cross section one can distinguishepidermis , parenchymal tissue Andconductive cord , consisting ofhydroids - dead cells devoid of protoplast (function - transport of water and minerals), andleptoids - living cells surrounding hydroids (function – transport of photosynthesis products).

DEVELOPMENT CYCLE .

In order for the sperm to reach the egg andfertilization has occurredwater is needed.

Once in the aquatic environment, the biflagellate sperm moves to the archegonium, enters its neck and penetrates the abdomen through the tubule, where it occursfertilization eggs and zygote formation . After thatthe zygote divides and the archegonium develops inside diploid embryo . Thenembryo grows and turns into sporophyte (sporogon) .

The internal contents of the capsule of a maturing sporophyte are represented by sporogenic tissue -archesporium . TOArchesporium's entrances are diploid, but as each cell maturesexposed meiotic division and gives rise 4 haploid spores .

Controversy , having found favorable conditions,sprout . During germination, sporesis formed protonema - juvenile stage in gametophyte development. Protonemacan be either lamellar or filamentous . As further developmentmature gametophytes are formed on which the reproductive organs (gametangia) develop , and the cycle thus closes.

VEGETATIVE REPRODUCTION – pieces of thallus or stem with leaves . Liver mosses formorgans of vegetative reproduction : brood bodies, buds, adventitious shoots, nodules .

GREEN MOSSES (breeve) .

Stem and leaves contain mechanical tissues .

Rhizoids green mossesmulticellular , .

CUKUSHKINA FLAX .

(before50 cm ) . Stems not branched Rhizoids consist of one rowmany cells . Thisdioecious plant .

On a male plant male genital organs - antheridia . At the topfemale plants are developingfemale genital organs - archegonia . FERTILIZATION PROCESS zygote . From a zygote after a few monthssprouts diploid sporophyte . .

disputes . gametophyte protonema . On protonemeare formed kidneys , from which they growadult moss plants .

SPHAGNUM MOSS .

Sphagnum refersto the order of white mosses :

▪ at the top of the stem twigs collectedto the head , ( apical branches );

▪ below branches are locatedhorizontally spaced ( protruding branches );

▪ more belowlong branches hanging branches ).

● Stems do not have rhizoids .

● Leaves . .

Chlorophyll-bearing cells . Theyhyaline cells filled with water . . Thanks to them, sphagnum.

acidifies water to a pH below 4 .

At the top of the stemsantheridia and archegonia .

FEATURES OF BRYOSYPHS .

● Bryophyteslive in places with high humidity (forests, swamps).

● Peat bogs play an important ecological role in nature. , where most European rivers have their sources.

General characteristics of higher spore plants

Higher plants that reproduce by spores are collectively called -higher spore plants. TO These include mosses, ferns, horsetails and mosses.

Higher spores lead a terrestrial lifestyle. Vegetative organs (root and shoot) are developed.

Life cycle consists of alternating generations: sporophyte and gametophyte.Sporophyte well developed (with the exception of bryophytes, where the gametophyte predominates). Multicellular sporangia develop on it, in which spores are formed after meiosis. The spores germinate into the gametophyte.Gametophyte lives for a short time. Multicellular reproductive organs develop on it: male -antheridia , women's -archegonia .

Fertilization occurs only in the presence of water.

According to the location of the genital organs, they are distinguishedbisexual (both male and female on the same plant) andsame-sex (on different plants) plants.

It is believed that seed plants come from higher spore plants.

GENERAL CHARACTERISTICS .

MOchophytes are commonin wet habitats ( in forests, swamps, tundras, along the banks of streams. Among them there are species livingin freshwater bodies . There are no sea inhabitants.

● BRYOSYPHS LIVE ON a wide variety of substrates:soil, rocks, stones, tree trunks, on the surface of leaves of other higher plants.

Most bryophytesare shade-loving .

In lower mosses there is no division of the body into stem and leaves . The body isthallus - a flat leaf-shaped blade attached to the soil by rhizoids - outgrowths of the epidermis.

In higher mosses the body is divided into stem and small leaves . All bryophytes lack roots .

COVERING TISSUE poorly developed. In most bryophytes● stomata do not have guard cells . They cannot finely regulate gas exchange.● Rhizoids Mosses absorb water poorly, so mosses absorb it over the entire surface of their body.

CONDUCTIVE FABRICS absent or poorly developed . Most bryophytes do not have vascular tissues.

MECHANICAL FABRICS most bryophytes lack .

● The most characteristic feature of bryophytes , sharply distinguishing them from all other higher plants, ispredominance in the development cycle of the haploid generation – gametophyte (sexual) and weaker development of the diploid generation - sporophyte (asexual).

GREEN MOSSES (breeve) .

Green mosses are the only representatives of bryophytes whose gametophyteshave relatively well-developed conducting tissues , resembling xylem and phloem of vascular plants.

Stem and leaves contain mechanical tissues .

Rhizoids green mossesmulticellular , but they absorb water relatively poorly . Therefore, green mosses, as well as other classes of mosses,absorb water over the entire surface of the body .

Structure, reproduction and development cycle CUKUSHKINA FLAX .

This is a large perennial plant (before50 cm ) . Stems not branched , are densely covered with leaves and have rhizoids.Rhizoids consist of one rowmany cells . Thisdioecious plant .

On a male plant among the upper leaves, developmale genital organs - antheridia . At the topfemale plants are developingfemale genital organs - archegonia .

FERTILIZATION PROCESS occurs during rainy weather. Spermatozoa swim to the archegonia. One of them penetrates the archegonium andfuses with the egg to form zygote . From a zygote after a few monthssprouts diploid sporophyte – a box with a long stem (sporogon) . It develops on female specimens .

Inside the capsule, as a result of meiosis, haploid cells are formed. disputes . The sexual generation develops from spores - gametophyte . First, a thin branchy green thread grows -protonema . On protonemeare formed kidneys , from which they growadult moss plants .

SPHAGNUM MOSS , peat formation and its significance .

Sphagnum refersto the order of white mosses . It is called white because of its faint green color.There are 3 types of branches on the stem of sphagnum :

▪ at the top of the stem twigs collectedto the head , ( apical branches );

▪ below branches are locatedhorizontally spaced ( protruding branches );

▪ more belowlong branches hang down along the stem (hanging branches ).

● Stems do not have rhizoids .

● Leaves consist of a single layer of cells, do not have a midrib . Two types of cells: chlorophyll-bearing and aquifer-bearing (hyaline) .

Chlorophyll-bearing cells – narrow, contain chloroplasts . Theysandwiched between wide colorless hyaline cells filled with water . Aquifer cells account for 2/3 of the leaf surface . Thanks to them, sphagnumabsorbs 37 times its dry weight in moisture . As a result of this unique hygroscopicity, sphagnumswamps the soil on which it grows .

The growth of the stems is carried out by the top, the lower parts gradually die off and sink to the bottom . During the growth process, sphagnum not only waterlogs the soil, but alsoacidifies water to a pH below 4 .

In an acidic environment without access to oxygen, dead stems of sphagnum and other plants do not completely decompose, but form layers of semi-decomposed remains in the form of peat.

At the top of the stemssexual reproductive organs are formed - antheridia and archegonia .

Green mosses are widespread throughout the globe, but they take the greatest part in the composition of vegetation in temperate and cold regions, forming tundra swamps and swampy taiga forests over vast areas. Their ecological range is quite wide, as they can live in water, on exposed rocks, on trees, and even in deserts and steppes. However, most species are confined to shady, damp habitats.

The development of the gametophyte of green mosses begins with the germination of spores. The spores of all green mosses are microscopically small and contain chloroplasts and oil droplets. Spore division begins with the formation of an outgrowth, i.e. The first cell of the young gametophyte is covered only with thin intine and therefore is entirely dependent on the external environment. Protonema is divided into green chloronema and underground colorless rhizonema (Fig. 27). The size, shape, and lifespan of the protonema vary significantly among different moss species. In some species, the branching protonema can occupy an area of ​​up to 1 sq.m and live for several months. In species with annual small gametophytes, the protonema is well developed and can exist for several years.

Basically, the dimensions of the protonema are measured in several centimeters, and the life expectancy is from several days to several weeks.

In a number of species, due to the characteristics of their habitat, the protonema has acquired features of high specialization. Thus, in the European species Schistostega pennata, which lives in caves, dark rock crevices, and tree hollows, the protonema glows with a greenish phosphorescent light. It has creeping green threads, from which vertical threads extend, ending in a single-layer horizontal plate. Each cell of this plate has the shape of a biconvex lens; the upper part is spherical-convex, and the lower part is funnel-shaped, containing 4-6 chloroplasts. The upper surface of the cell, refracting weak solar rays, focuses them on the lower side of the cell. Chloroplasts partially absorb these concentrated rays and partially reflect them, causing a greenish glow.

The protonema of the Javan epiphytic moss Ephemeropsis tjibodensis has a very unique structure; it has light green threads spreading along the leaf of another plant, with short, abundantly branching dark green photosynthetic threads extending upward from them. Along with them, there are long, non-branching hygroscopic threads that absorb atmospheric moisture, and short colorless threads that perform the function of attachment. In most mosses, several buds appear on the protonema, forming leafy shoots, i.e. protonema performs the function of vegetative propagation.

An extensive subclass of green mosses unites about 14 thousand species, which are characterized by different life forms, sizes, and life expectancies. There are few, but very unique species of annual mosses, having negligible sizes up to 1 mm (Fig. 28). Species of the genus Phascum have a short shoot with a rosette of 610 leaves. In ephemerum (Ephemerum), 5-7 leaves develop on a shortened shoot, performing only the function of protecting the genital organs, and the green protonema branches abundantly and can live for two seasons or more. The gametophyte of Buxbaumia has undergone an even greater reduction: the male gametophyte consists of a microscopic antheridium, covered with a single single-layer colorless leaf, looking like a bivalve shell; the female gametophyte has a shoot less than 1 mm long with 5-7 ovoid single-layer green leaves.

The largest mosses reach a length of 20-30 cm, these include cuckoo flax (Polytrichum), fontinalis (Fontinalis). Some Australian species of the genus Dawsonia reach a length of 50 cm and, as a rule, form dense turf. Mosses have the most diverse type of branching, and young shoots arise not in the leaf axil, but under the leaf, detached from its base. Some species have long thick rhizomes, abundantly covered with rhizoids (Fig. 29). The lateral branches in some species grow indefinitely, while in others they have limited growth. The arrangement of lateral branches can be alternate, whorled, multi-tiered. The nature of branching is influenced by the placement of the genital organs (apical, lateral). Rare mosses do not branch, for example cuckoo flax (Fig. 30). Abundantly branching rhizoids appear on the shoots in large numbers, which are characterized by the presence of beveled partitions. In some species, rhizoids densely cover the stems in the form of felt; sometimes, intertwining with each other, they form thick, durable cords.

Tests

620-1. The accumulation of which group of plants contributes to waterlogging of the soil?
A) lycophytes
B) horsetails
B) bryophytes
D) fern-like

Answer

620-2. A stem with leaves in the process of evolution first appeared in
A) algae
B) bryophytes
B) horsetails
D) fern-like

Answer

620-3. Mosses represent a dead-end branch in the evolution of plants, since
A) more highly organized ferns evolved from them
B) they did not give rise to more highly organized plants
C) more highly organized horsetails evolved from them
D) they originated from unicellular algae

Answer

620-4. What characteristic is characteristic of mosses?
A) adventitious roots develop from the stem
B) spores are formed in a capsule
C) they have no escape
D) pollination precedes fertilization

Answer

620-5. In mosses it develops from spores
A) a box on a leg
B) seed
B) green thread
D) outgrowth

Answer

620-6. The adaptability of sphagnum moss to life in conditions of excessive moisture is manifested in the presence
A) rhizomes with adventitious roots
B) cells with chloroplasts
B) dead cells
D) rhizoids

Answer

620-7. Representatives of which division of the Plant kingdom are shown in the picture?

Answer

620-8. What plants belong to the Bryophytes department?
A) living on land and reproducing by seeds
B) leafy, rootless, reproducing by spores
B) all plants in wet habitats
D) all herbaceous plants

Answer

620-9) What adaptations to absorbing large amounts of water appeared in the process of evolution in mosses?
A) rhizoids - outgrowths on the stem
B) large dead cells
B) spore capsules
D) cells of thin integumentary tissue

Answer

620-10. In green mosses, unlike algae,
A) cells have large and small nuclei
B) fertilization occurs in the presence of water
C) the thallus is divided into tissues and organs
D) sexual and asexual reproduction occurs

Answer

620-11. To which division of higher plants does the plant shown in the figure belong?

A) Angiosperms
B) Gymnosperms
B) Ferns
D) Bryophytes

Answer

620-12. By what characteristics are bryophytes distinguished from other plants?
A) in the process of their development there is an alternation of generations
B) reproduce by spores
B) have leaves, stem and rhizoids
D) capable of photosynthesis

Answer

620-13. Ferns, unlike green mosses, have
A) rhizoids
B) roots
B) leaves
D) stems

Answer

620-14. Cuckoo flax develops from the spores of green moss
A) a prothallus in the form of a green plate
B) pre-teen in the form of green threads
B) plants with leaves
D) seeds of the future plant

Answer

620-15. Of the higher plants there are no roots
A) Tsvetkov
B) Conifers
B) Mkhov
D) Ferns

Answer

620-16. Ferns are much more widespread on Earth than mosses, since they
A) have a developed root system and reproduce more efficiently
B) appeared earlier in the course of evolution and managed to adapt better
C) are widely grown by humans for their needs
D) are successfully spread by various animals

Answer

620-17. Mosses have the simplest structure among higher plants, since
A) they have no roots
B) their stem is unbranched, with narrow leaves
C) they form organic substances from inorganic ones
D) they have air cells

Answer

620-18. Why do mosses represent a dead-end branch in plant evolution?
A) they have not mastered the ground-air habitat
B) they came from algae
C) they have no roots and reproduce by spores
D) they did not give rise to more highly organized plants

Answer

620-19. A representative of which division of the Plant kingdom is shown in the figure?

A) Ferns
B) Gymnosperms
B) Moss-moss
D) Bryophytes

Answer

620-20. Which group of organisms includes green plants that have no roots, reproduce by spores, and whose life cycle is dominated by the sexual generation?
A) bryophytes
B) ferns
B) gymnosperms
D) lycophytes