The largest mosses. The main types of mosses. What is moss? Structure, reproduction, types of mosses, their meaning and application
Bryophyte department- these are higher spore plants, the species diversity of which reaches 20 thousand. The study of mosses has been going on for many centuries, the scientists involved in their research were called bryologists, they founded a separate botanical branch dedicated to bryophytes - bryology. Briology - the science of mosses, studies the structure, reproduction and development of bryophytes (actually mosses, liverworts, anthocerotes).
General characteristics of mosses
Moss - general characteristics
Bryophytes are one of the oldest plants that inhabit our planet. The remains are found in fossils from the end of the Paleozoic era. The distribution of mosses is associated with a preference for a humid environment and shaded areas, so the majority inhabit the northern part of the Earth. Poorly take root in saline areas and deserts.
Bryophyte classes
Leafy mosses is the most numerous class. Plants are composed of stem, leaves and rhizoids.
Stem can grow vertically or horizontally, divided into bark and main tissue (contains water, starch, chloroplasts for photosynthesis).
Stem cells can produce filamentous processes - rhizoids, necessary for anchoring to the soil and absorbing water. They are often located at the base of the stem, but can cover it along its entire length.
Leaves simple, often attached to the stem at a right angle, in a spiral. Leaf blades are equipped with chloroplasts, in the center there is a vein (serves to carry nutrients).
Deciduous mosses can reproduce by stems, buds, branches, which give rise to the formation of solid carpets of mosses that cover the ground. The class of leafy plants includes sphagnum mosses (they have a variety of stem colors - light green, yellow, red), andreevy and bry mosses.
liverworts found on the coasts, swamps, rocky terrain. Distinctive features: leaves do not have a vein, dorsoventral structure, a special mechanism for opening the sporophyte.
The leaves are arranged in rows, have two lobes (the lower lobe is often wrapped and serves as a reservoir for water), rhizoidal processes are unicellular. During the rash of spores, the sporophyte box opens into separate valves, and elaters (spring formations) contribute to the dispersion of cells.
Reproduction can be carried out with the help of buds (vegetatively), which are formed at the upper pole of the leaves. Representatives of the class pella endievistnaya, milia anomalous, moss marchantia, etc.
Anthocerotus mosses inhabit the tropical zone. The multinuclear body (thallus) has a rosette shape, consists of the same type of cells. In the upper balls of cells are chromatophores (contain a dark green pigment). The lower part of the thallus gives rise to processes, rhizoids, the body itself forms cavities filled with a viscous fluid that maintains constant moisture.
On the surface of the thallus, under adverse conditions, tubers are formed that are resistant to low humidity; after a period of drought, a new generation is formed. Plants are monoecious, reproductive organs develop in the thickness of the thallus, the sporophyte stage is predominant. Anthocerotes include folioceros, anthoceros, notothilas, etc.
How do mosses reproduce?
There is an alternation of asexual and sexual reproduction in the life cycle of mosses. The asexual period begins with the formation of spores and their germination on moist soil (a pregrowth is formed, a thin thread that gives life to male and female individuals). There are two types of mosses:
monoecious- male and female reproductive organs are on the same plant.
Dioecious- Reproductive organs are located in different representatives of the sex.
After the spore germinates, the moss life cycle enters the sexual phase. The organs of sexual reproduction are antheridia (male) and archegonia (female). Representatives of males are weaker than females, smaller in size, after the formation of antheridia they die off.
Spermatozoa are formed on male plants, eggs on female plants, after their fusion a zygote is formed (located on the female, it feeds the immature sporophyte), which later develops into sporangium. After maturation of the sporangium, it opens, spores spill out of it - the asexual reproduction period of mosses begins again.
Reproduction of offspring is possible in a vegetative way, mosses form thalli (green branches), buds, tubers, which take root well on moist soil.
What is the importance of spores in the life of mosses?
Spores are the cells that mosses need to reproduce. Moss plants do not bloom, do not have roots, therefore, in order to continue the genus, they have formed a sporophyte with sporangia (the place where spores ripen).
The sporophyte has a short life cycle; after drying, the spores disperse around, and when they get on moist soil, they quickly take root. Under unfavorable conditions, they can persist for a long time without germinating, resistant to low and high temperatures, and prolonged droughts.
The value of mosses in nature and human life
Mosses are food for many invertebrates.
After dying, they give deposits of peat, which is necessary in the production of plastics, resins, carbolic acid, and is used as fuel or fertilizer.
Moss completely covers the ground in places of growth, which leads to the accumulation of moisture and waterlogging of the territory. Thus, the germination of other vegetation becomes impossible. At the same time, they prevent erosion, soil destruction by surface water and winds. When the mosses die off, they take part in the formation of the soil.
Able to grow in places of fires, persistent and hardy, they inhabit the territory of the tundra (the main vegetation background, since other plants cannot survive in such conditions).
In wartime, sphagnum moss was used as a dressing because of its bactericidal properties and ability to absorb moisture.
With the help of mosses, you can navigate the terrain: they do not like light, therefore they are located on the shady side of stones and trees. Moss points the man to the north.
In construction, it is used as an insulating, insulating material.
Moss is the oldest plant, over 400 million years old. To study this department of higher plants, a whole science called bryology has been singled out.
Many people have no idea what types of bryophytes are, and often do not distinguish between mosses and lichens. Meanwhile, this amazing representative of the flora plays an important role in the ecosystem and soil moisture, is used in medicine and is a source of peat deposits, from which people later get fuel. It is impossible to deny the great importance of the diversity of mosses in the life of people and nature. Moss, the pictures of which will be provided below, is striking in its variety of appearance.
Structure and distribution
Mossy plants are distinguished by the absence of flowers and root systems. Some species have rhizoids - processes that resemble roots. The leaves have a supply of chlorophyll and support vital functions. There is also a sporophyte, consisting of a stem and a box in which spores ripen, which serve for reproduction. The maximum stem height is 5 cm, with the exception of some aquatic mosses and epiphytes. It should be noted that reindeer moss, called reindeer moss and reaching 20 cm in height, does not belong to the bryophyte department.
Moss is an example of plants that use two modes of reproduction for greater survival: sexual and asexual. During the breeding season by spores, shoots may look flowering due to the appearance of flower-like green heads. Spores remain viable for decades, with the help of emerging threads, they are attached to the selected surface.
Mosses can be found in almost all corners of the planet. Most species prefer moist soil in swampy areas, shady places and tree trunks for growth. In the event of a dry period, bryophytes temporarily stop growing and fall into a state of suspended animation. Less commonly, rocks and stones can be observed as a habitat for spore plants. . These representatives of the flora cannot be found in the seas or in areas with saline soil, as they cannot tolerate salt.
Species diversity
The first representatives of the bryophyte department originated in the Carboniferous period long before the appearance of flowering plants and outwardly did not undergo any changes, retaining their original appearance to our times. At present, the number of moss species is about 20 thousand, including the division of liverworts and anthocerotophytes.
The following classes exist:
- Hepatic;
- Anthocerotes;
- Leafy (briev).
Subclasses can be distinguished from the list:
- Sphagnum (peat or white);
- Takakievye;
- Hypnic;
- Andreevs.
Liver and Anthocerota
More than 6,000 moss species belong to the liver class with the dominant life stage gametophyte. Liverworts are common in tropical areas and in moderately humid climates. They are characterized by a vegetative mode of reproduction. Jungermannian liverworts have stems and leaves, thallus - a flat thallus (thallus), located on the ground or floating on the water surface.
Of the most famous representatives of the class, one can single out the polymorphic marchantia, pellia, ciliated ptilidium, and buoyant richchia. The latter is often bred in aquariums.
Anthocerotes are characterized by the presence of a lamellar thallus or thallus. Like liverworts, anthocerotophytes are found mainly in the tropics. In conditions of excessive drought, tuberous thickenings appear on the thalli, thanks to which the plants can survive adverse conditions. Often live in symbiosis with blue algae.
Typical representatives: field antoceros, smooth and forked antoceros.
Brie or bryopsides
Leafy - one of the largest classes of mosses. Distributed throughout the world. There are both annual and perennial specimens. In height, they are both low, 5–10 mm each, and higher, reaching 15 cm. Difistium multi-leaved, for example, can be attributed to especially small mosses.
Known representatives of briopsids are cuckoo flax and fire-fighting fontinalis, which can often be found in the forests of Russia in northern and middle latitudes. Due to the abundance of flat leaves, the cuckoo flax resembles a small part of a coniferous branch growing upwards, but fontinalis is more like a tiny fern.
In the southern lands, there is a small-mouthed funaria and a wavy mnium - low plants with pointed leaves of green hues. Rhodobrium rosette, on the contrary, prefers to stay in the shade of coniferous forests.
Another example of briev - shiny hylocomium having leaves in the form of scales. It consists of several tiers due to the special branching and dense leafy cover.
sphagnum mosses
An example of the most famous subclass of bryophytes is sphagnum. There are more than 300 species, which are characterized by red, greenish-white or yellow color and relatively large size. Sphagnum grows in the tundra and forest lowlands with damp soil, forming a dense carpet due to the dense growth of leaves. If young shoots have rhizoids, then adult representatives of the species are completely devoid of root-like formations.
Popular representatives: swamp sphagnum, brown, hairy, Magellanic.
Peat, the source of which is sphagnum, is actively used in agriculture and industry to produce peat gas. The carbolic acid secreted by moss has found application in medicine due to its bactericidal properties.
Takakiev, Hypnum and Andreev
Bryophytes belonging to the class Takakiya are rather controversial plants. At first, bryologists attributed this class to liverworts due to the characteristic structure of gametophytes, however, after a detailed study of sporophytes, the plant was reclassified to leafy. Visually, takakia differs from other bryophytes. There are two types of takaki: takakia horn-leaved and lepidosiform. Habitats are the Far East, as well as the northwest of North America.
Representatives of the Hypnaceae species form a plant carpet on wet soils and rocks. Shoots are abundantly covered with leaves on all sides, hypnum mosses are spread mainly in the north. A well-known representative of the cypress hypnum species is also common in the forest belt; it can be found both in a dense grove and on rocky hills.
Bryophytes, belonging to the Andreev class, prefer cold terrain. Due to the peculiarities of the structure and the ability to take root in stone pores, they can grow on rocks and in stony soils. There are about 100 species of Andreev mosses. Examples: cold Andrew and Rocky Andrew.
aquarium moss
There are varieties of decorative mosses suitable for decorating aquariums. Bryophytes are loved by aquarists due to their high survival rate, unpretentiousness and slow growth. A large number of variations in appearance is another advantage in favor of bryophytes.
Common key moss, fontinalis, java moss, Riccia floating, Riccardia are examples of plants suitable for decorating an aquarium.
Mosses occupy a not always noticeable, but extremely important role in people's lives. In addition to applications in construction, medicine, industry and aquariums, bryophytes can become an object for collecting and numerous photographs. These creations of nature are truly amazing and beautiful.
moss species
Second only to angiosperms, or flowering plants, which indicates the important ecological role that these plants play in nature.
Bryophytes do not have roots, they have poorly developed integumentary and conductive tissues, and for reproduction they need drip liquid moisture. Therefore, they live mainly in places with high humidity - in swamps, under the forest canopy, on the shaded side of tree trunks, etc.
During rain and snowmelt mosses, like a sponge, they absorb moisture and then slowly release it to the rivers. Therefore, the drainage of raised bogs and deforestation, in which mosses live, leads to floods in the spring, during the melting of snow. At the same time, turbulent streams of water wash away the top fertile soil layer (this phenomenon is called water erosion of the soil). At the same time, in summer, the rivers fed by the water of raised bogs become shallow, and drought sets in.
Due to their unique ability to absorb moisture throughout the surface of the body, some species of bryophytes have adapted to life in conditions where root functions are ineffective - in very cold or very dry and stony soil. Bryophytes dominate not only in swamps, but also in the subpolar zone, preventing catastrophic thawing of permafrost, as well as on rocky mountain slopes. Bryophytes are the dominant plants of tropical mountain forests located at an altitude of more than 3000 m above sea level (the so-called mossy forests).
Some bryophytes have adapted to life on dry, sun-exposed mountain slopes, on hot rocks, and even in the desert. Such mosses can remain viable for years when dried, quickly becoming active when moistened (unlike most mosses, which die when dried for a day).
Classification and diversity of bryophytes
All are divided into 3 classes:
- Anthocerotes(Anthocerotopsida);
- liverworts(Hepaticopsida);
- Leafy or true mosses(Bryopsida, or Musci).
Leafy, or true mosses, can, in turn, be divided into 3 subclasses:
- brieves(or green) mosses (Bryidae);
- Sphagnum(or white) mosses (Sphagnidae);
- Andreevs(or black) mosses (Andreaeidae).
Class Anthocerota
Class Anthocerota(Anthocerotopsida) has over 300 species distributed mainly in the tropics and subtropics. Haploid ( n) the gametophyte of anthocerotes is a thallus, outwardly resembling a rosette or saucer of dark green color, in the center of which a bright green "candle" of diploid ( 2n) sporophyte (Fig. 1).
At the end of maturation, the “candle” spore cracks and the spores spill out onto the ground. It is interesting that sporophyte cells (“candles”) contain the usual small oval-shaped chloroplasts, similar to chloroplasts of vascular plants, and gametophyte cells (“rosettes”) contain large chloroplasts, inside which are pyrenoids, which further enhances the similarity of “rosettes” - gametophytes. with algae.
Rice. 1. Anthoceros: a) Anthoceros (Anthoceros laevis) - general view with mature sporangia; b) sporangium with spores; c) archegonium; d) antheridium (internally developing spermatozoa); 1 - abdomen archegonium (in the center of the egg); 2 - neck (inside cervical tubular cells)
The stomata in the epidermis of the Anthocerota sporophyte consist of two guard cells and are outwardly similar to the stomata of vascular plants. The sporophyte of Anthoceridae, in contrast to the sporophytes of other bryophytes, retains the ability to grow and photosynthesize for a long time; it has been shown that it can generally grow and feed on its own, without the help of a gametophyte. These features of Anthocerotes allow some scientists to see them as reduced vascular plants or even the lowest link in their evolution (i.e., to consider Anthocerotes as possible ancestors of the first vascular plants - rhinophytes).
Anthocerotes are very different from other bryophytes and, in general, from other terrestrial plants. Liverworts and leafy mosses differ much less from each other. It is possible that the origin of Anthocerotes and other bryophytes is different, and they should generally be considered as different divisions of the realm of the races of genius.
Cyanobacteria of the genus Nostoc ( Nostoc) that fix atmospheric nitrogen and supply nitrogen compounds to the host plant. However, slow-growing atocerota are weak competitors, so most species of this class are inhabitants of disturbed habitats (unsodden edges of arable lands, ditches, roads, river banks).
Class liverworts
Class liverworts(Hepaticopsida), or liver mosses, unites about 10,000 species.
The liverworts were named so due to the fact that their thallus resembles the liver with its outlines, therefore, in the Middle Ages, these mosses were considered an effective remedy for the treatment of its diseases.
Many liverworts are thallus (thallus) organisms. A typical representative of thallus liverworts is diverse.
However, most liverworts are not thallus, but leafy. The leaves of the liverworts, unlike the leaves of leafy mosses, are arranged not in spirals, but in 3-4 rows.
Rhizoids are unicellular. The protonema in most liverworts is poorly developed and short-lived.
Liverworts live on moist soil, on rocks, along river banks.
Vegetative reproduction is very well developed in liverworts.
Class leafy, or real mosses
Class deciduous, or real mosses (Bryopsida, or Musci) - this is the largest class of mosses, numbering about 25,000 species.
The deciduous class includes three subclasses:
- shaving;
- sphagnum;
- andrew mosses.
Brie mosses
Brie subclass(Bryidae), or green mosses, includes 14,000 species. In damp places, representatives of this group are ubiquitous: they settle on the soil, bark, tree trunks. Green mosses live in spruce and pine forests, swamps, mountain slopes, and often form a continuous cover in the tundra.
A typical representative of green mosses -, or polytrichum(Polytrichum commune) - Brie mosses of the polytrichous and dausonian families are the only representatives of mosses whose gametophytes have relatively well-developed conductive tissues resembling the xylem and phloem of primitive vascular plants. The leaves on the gametophytes of all briids are located but in a spiral. The upper side of the leaf is covered with columns of photosynthetic cells called assimilation plates. The integumentary tissue (epidermis), which protects the plant from drying out, is located only on the underside of the leaf. The stem and leaves of polytrichous also contain mechanical tissues, which are elongated cells resembling the sclereids of vascular plants. Mosses from the polytrich family are perennial, relatively large plants (for example, the height of the cuckoo flax stems sometimes reaches 40-50 cm), often forming extensive covers on the soil in forests, swamps and tundra.
Green moss rhizoids, unlike liverwort rhizoids, are multicellular, but absorb water relatively poorly. Therefore, green mosses, like other classes of mosses, absorb water with the entire surface of the body, primarily with leaves. So, cuckoo flax can absorb water 4-5 times more than the dry weight of its own body. In this regard, mosses often swamp the soil on which they grow.
A characteristic feature of the life cycle of green mosses is that their development begins with the formation of a special filamentous structure - protonemes, outwardly resembling a filamentous green algae. Interestingly, in some leafy mosses, the gametophyte does not develop at all. Protonema becomes the main life form of such mosses. The most famous of them is luminous moss. schistostega pinnate(Shistostega pennata), found in caves throughout southern Europe. It is with him that the appearance of legends about the treasures of the dwarves, disappearing at dawn, is connected.
Schistostega glows due to the concentration and subsequent reflection of light, as the eyes of cats “glow”. Special lenticular cells of moss first concentrate the light on the chloroplasts, and then the concentrated light, reflected from the back wall of the cell, passes through the chloroplasts a second time. This feature of the structure allows the Schistostega to live in the weak, diffused light of the caves.
In green mosses, as well as in liverworts, vegetative propagation is well developed.
sphagnum mosses
Subclass sphagnum(Sphegnidae), or white mosses, is represented by a single genus sphagnum(Sphagnum), including over 300 species. A characteristic feature of sphagnum is a branching stem: not individual leaves, but whorls of branches (sometimes 5 at a node) depart from the main stem of sphagnum, and a head of closely spaced branches forms at the top of the shoot.
The initial phase of sphagnum development is the formation of lamellar protonema from spores.
Sphagnum leaves contain special dead cells that serve as water containers. Large dead aquifers are surrounded by small photosynthetic cells (Fig. 2). When the sphagnum dries, the water from the aquifers evaporates and the sphagnum becomes whitish - hence the second name of sphagnum mosses - "white mosses". Due to the presence of water-bearing cells, some types of sphagnum absorb moisture 20-40 times their dry weight. Due to this unique ability, sphagnum waterlogs the soil on which it grows.
Sphagnum does not have rhizoids. As the plant grows, the lower parts of the stem die off and sink to the bottom. In the process of growth, sphagnum not only swamps the soil, but also acidifies the water to a pH below 4. In an acidic environment without oxygen, dead stems of sphagnum and other plants do not rot, but turn into peat.
Peat bogs are an interesting object for archaeologists and paleobotanists. In the acidic environment of peat bogs, spores of ancient plants, tree trunks, ancient tools, boats, building structures are perfectly preserved. So, recently in the UK, a wooden road was discovered in peat deposits, connecting two settlements of people of the Stone Age. The age of this building is 6000 years.
Rice. 2. Sphagnum moss: a) general view; 6) box; c) leaf cells under a microscope
Peat is an excellent and renewable fuel. Peat is mainly used in thermal power plants to generate electricity. In agriculture, peat is used as a fertilizer, as well as to retain moisture in the soil. In greenhouses, peat-humus pots are used for growing seedlings.
In medicine, sphagnum is used as an excellent dressing material and filler for various moisture-absorbing pads. Sphagnum, in comparison with conventional dressings, such as vaga, absorbs moisture 5-6 times more efficiently. In addition, unlike cotton wool, sphagnum has pronounced bactericidal properties.
An interesting feature of sphagnum is the spore dispersal mechanism.
The sporophyte of sphagnum is a round box, rising on a stand (pseudopod) from the tissues of the gametophyte. In humid weather, air enters the box through the stomata. When the box dries up, the stomata on its surface close, the air pressure inside rises, as a result, with a distinct pop, the lid breaks off and a cloud of spores rises above the box.
Peat bogs occupy about 1% of the Earth's area and play an important role in regulating the Earth's water balance. The supply of water from raised bogs feeds the rivers.
Andrew mosses
Subclass andreiaceae(Andreaeidae), or black mosses, unites about 120 species of black-green or red-brown rock mosses, characteristic of mountainous and arctic regions. Protonema - lamellar, thick-walled, multi-lobed.
The mechanism of spore dispersal is interesting. The box on the pseudopod from the tissues of the gametophyte cracks into 4 plates. In dry weather, due to the reduction of the central axis, it shrinks like a Christmas toy, and the spores pour out of the box through the opened cracks. In wet weather, the axis of the box lengthens and the slots close.
When flowering plants did not yet exist in nature, he was already pleasing to the eye ... dinosaurs.
The forest, covered, reminds us of primitive times. Its layer of only a few centimeters creates the feeling of a dense green carpet covering everything around.
Moss superstar: classes and types
The first mosses appeared on our planet over 400 million years ago, long before flowering plants. Like, these plants reproduce by spores. There are about 18,000 moss species grouped into three classes.liver mosses
The oldest of them - liver mosses. The most famous member of this group is blepharostomy hairy (Blepharostoma trichophyllum) with its characteristic flat, spreading shape. Most liverwort mosses have both stems and true leaves.Blepharostomy hairy most often grows on the soil, as well as on deadwood, stumps and stones along the banks of streams and rivers, forming dense or loose, mixed with other bryophytes, turfs and even whole carpets.
A large class is also bryophytes. They are all divided into orders according to the structure of their stems, leaves and the way they are fixed in the soil. Mosses form "pillows" from millimeters to several centimeters high, and sometimes cover vast areas with a dense lawn of living plants and their dead parts with a layer up to 1-3 m thick or more.
Anthocerotus mosses
The second no less extensive class - mosses, outwardly resembling "liverworts". They got their name from the Greek words anthos - flower and keros - horn, since the shape of the plants is a dark green lamellar rosette (thallus) with a diameter of 1-3 cm, tightly adjacent to the soil, and numerous horn-shaped outgrowths (sporogons) up to 2 -3 cmIt belongs to one of the most common species. In the forest, it can cover very large areas, but it also has a place in inhabited places, on the walls and roofs of houses. The picture clearly shows long stems with spore boxes.
moss cuckoo flax outwardly resembles a branch of coniferous plants. Its length can reach up to 15 cm, it is cuckoo flax that often lines the soil in the forest.
Wall tortula forms small pillows and grows on limestone stones, including on the walls of houses made of such material.
In some mosses, the spore boxes sometimes look like flowers, such as this one. juniper-like polytrichum.
Cirriphyllum hairy (Cirriphyllum piliferum) forms loose light green tufts. It prefers calcareous soil rich in nutrients. Cirriphyllum can be found in forests and bushes. However, he also has a place in the garden.
Hylocomium brilliant ( Hylocomium splendens) most often found in forests, although meadows, roadsides and quarries often give it shelter. In the process of growth, it forms cascades, consisting, as it were, of separate floors. 
Sphagnum hairy (Sphagnum capillifolium) grows primarily in swamps and wet forests. Plant height does not exceed 20 cm. This moss can be whitish-green, brown, reddish or yellow. 
Anthoceros smooth (Anthoceros laevis)- one of the few species from the genus Anthocerotus mosses that live in northern latitudes. This moss is often the first to appear on damp soil after weeding in beds, flower beds and especially furrows. 
Where do mosses live
On the rocks and mosses feel out of competition: after all, there is no place for flowering plants here. High humidity and regular rises of water in streams also contribute to the spread of "green and fluffy".
The persistence with which moss spreads through the garden is directly related to its ability not only to spore reproduction, but also to vegetative reproduction, especially in leafy species. So that from every patch of moss that falls from under the lawn mower blade, a full-fledged new plant can grow. Thanks to this property, you will be able to populate part of your site with “fluffy” inhabitants almost without difficulty:
- Moss is cut to 5-10 mm and these tiny pieces are scattered over the surface of pre-moistened soil.
- At the end of the process, the area should be covered with at least 10% moss trimmings.
- After that, everything is thoroughly pressed down and the first weeks are intensely moisturized. The earth before "sowing" can be replaced with sand or lava pebbles.
Most Creative ideas for using mosses in garden decor you will find in No. 1 of the magazine “Country. Style and lifestyle” for February-March 2016.
Question 1. What are rhizoids?
Rhizoids - filamentous formations from one or more single-row cells; serve to attach to the substrate and absorb water and nutrients from it. Available in mosses, lichens, some algae and fungi.
Question 2. Why are algae classified as lower plants?
Algae belong to the lower plants, because they have no roots, no stems, no leaves.
Question 3. What is a dispute?
Spores are microscopic rudiments of lower and higher plants that have different origins and serve for their reproduction and (or) preservation under adverse conditions. In biology, the concept of "dispute" is divided into:
* spores of bacteria that serve to wait out adverse conditions;
* spores of plants, sporozoans and fungi that serve for reproduction.
Laboratory work No. 10. The structure of moss.
1. Consider a moss plant. Determine the features of its external structure, find the stem and leaves.
Stem erect, not branched. The length of the stem is 12 cm, but can reach 30-40 cm. The stems are densely covered with leaves. At the top there is a box with spores. At the bottom of the stem there are outgrowths - rhizoids.
2. Determine the shape, location, size and color of the leaves. Examine the leaf under a microscope and draw it.
The leaves are concave dark green, have a petiole around the stem. Each leaf on its upper surface has assimilation plates and a large main vein. The leaf looks like a thick needle and miniature flax plants. The lower leaves on the stem develop in the form of scales.
3. Determine if the plant has a branched or unbranched stem.
Moss has an unbranched stem.
At the tops of male plants are the reproductive organs, in which mobile sex cells (gametes) - spermatozoa - develop.
In female plants, the genital organs are located at the tops with the female reproductive cell (gamete) - the egg.
On female plants, boxes develop on long legs, covered with hairy pointed caps. They look like a sitting cuckoo. Spores develop in the boxes. Spilling out and germinating, they form new moss plants.
5. Examine the spore box. What is the importance of spores in the life of mosses?
The plant produces numerous spores. Spilling out and germinating, they form new moss plants. From each spore, under favorable conditions, an shoot develops with a short lifespan, which looks like a box (sporangium) on a stalk.
6. Compare the structure of moss with the structure of algae. What are their similarities and differences?
Differences: algae do not have roots, their body is represented by a thallus. Mosses develop rhizoids. Algae live only in aquatic environments, mosses only live in humid environments. Mosses have stems and leaves, but algae do not.
Similarities: cells have plastids (chloroplasts, chromoplasts, leukoplasts), so they can carry out photosynthesis. Grows indefinitely throughout life. Motionless.
7. Write down your answers to the Questions.
Conclusion: mosses are more developed than algae. They may no longer be in water, but in a humid environment. Stems and leaves are already emerging.
Question 1. Why are mosses called higher spore plants?
Since the body of mosses is divided into stems and leaves, and they reproduce by spores, they are classified as higher spore plants.
Question 2. What is the structure of cuckoo flax?
Its slender brownish stems are covered with small dark green leaves and look like miniature flax plants.
Cuckoo flax has male and female plants. At the tops of male plants are the reproductive organs, in which mobile sex cells (gametes) develop - spermatozoa (from the Greek words "sperm" - seed, "zoon" - a living being and "eidos" - species). In female plants, the genital organs are located at the tops with the female reproductive cell (gamete) - the egg.
On female plants, boxes develop on long legs, covered with hairy pointed caps. They look like a sitting cuckoo. Hence the name of the moss - cuckoo flax. Spores develop in the boxes. Spilling out and germinating, they form new moss plants.
Question 3. How is sphagnum different from cuckoo flax?
Kukushkin flax - green moss, sphagnum - light green moss, peat. Cuckoo flax has rhizoids, sphagnum does not. In cuckoo flax, the stem does not branch, and in sphagnum there are branches of three types, in the leaves of cuckoo flax there are no dead cells, and in sphagnum there are a large number of them, these are air-bearing cells capable of absorbing moisture. Boxes with spores in cuckoo flax have a hairy cap and an elongated shape, in sphagnum they are without a cap and rounded. Cuckoo flax plants are male and female, while sphagnum plants are bisexual. Boxes with spores in cuckoo flax are located on the tops of female plants one by one, and in sphagnum 3-5.
Question 4. How is moss different from algae?
Mosses are more complexly organized than algae. Among the algae there is a large group of unicellular, all mosses are multicellular organisms. Most algae live in the aquatic environment, most mosses live on land, but with a high percentage of humidity. The body of moss is differentiated into organs; only in the most developed algae can one observe something similar to tissues. Mosses have external differences between males, females, between sexual and asexual generations. In algae, all individuals of the same species are the same. Mosses cannot reproduce vegetatively, but algae can. Mosses have stems and leaves, like all higher plants, and algae have thallus.
Question 5. What is the importance of mosses in nature and human life?
Mosses, settling in meadows, in forests, cover the soil with a continuous carpet, making it difficult for air to enter. This leads to acidification and waterlogging of the soil.
Leaf-stemmed, especially sphagnum, mosses cover swamps with a continuous carpet and, dying, form peat, which is widely used by man. Peat is used as a fuel, fertilizer and as a raw material for industry. Wood alcohol, carbolic acid, plastics, insulating tapes, resins and many other valuable materials are obtained from peat. Some animals eat moss.
Think
Why don't even the largest mosses reach sizes over 80 cm?
Mosses are not tall because in places where they grow there is very "poor" soil. Frosts and strong winds are rather unfavorable conditions for existence. Mosses do not have a conductive system and, as a result, have limited height growth.
Quests for the curious
1. Examine the leaves of sphagnum moss under a microscope. Note the structural features of the two types of cells of which they are composed.
There are two types of cells in leaf cells. Narrow green cells in which photosynthesis takes place (there is chlorophyll) are connected at the ends and form a mesh structure in which organic substances move. Between them are large transparent dead cells, of which only shells remain (they contain water).
2. Place some riccia in a jar of damp soil. Cover the jar with glass and place in a warm, bright place. Make sure the soil is constantly moist. Watch what happens with Riccia.
Riccia will begin to develop as favorable conditions (from moist and warm air, light). Floating Riccia does not have rhizoids, but it can form them on damp soil.
If you grow Riccia in water, if the temperature is lower than 20°C, the growth of Riccia slows down, but the appearance remains attractive. You also need to know that soft water is considered optimal for this plant, the hardness of which should not exceed 15 units, but if this figure is higher than 8, this already negatively affects growth. The acceptable pH level is 4-8.
