The department is mossy: features of structure and vital activity, signs, nutrition, reproduction, general characteristics and significance. Representatives of the department are mossy

The bryophyte department is also called real mosses or bryophytes. All species are united in approximately 700 genera, which in turn constitute about 120 families.

Bryophyte: general characteristic

Representatives of the department are mostly small plants with a length of no more than 50 mm. The only exceptions are water mosses, which can reach up to 50 cm in length, and epiphytes, which are even longer.

The department refers to the higher plant taxon . The bryophyte branch has about 25 thousand species.

Previously, to this department, besides leaf-stalk mosses, hepatic mosses and anthocerot mosses were also included. However, at the moment, these taxa are independent departments. Often, speaking of the combined characteristics of these three departments, resort to the use of the informal collective term bryophytes (Bryophytes).

Plants of the department, like other representatives of bryophytes, have a certain feature associated with the course of the life cycle: the predominance of a haploid gametophyte over a diploid sporophyte.

History

The characteristic of the mossy department proves that mosses, like the rest spore, evolved from psilophytes (rhinophytes), which are ancient extinct terrestrial plants. Sporophyte of mosses is considered the final result of the process of reduction of ancestral branched sporophytes.

However, there is another hypothesis, according to which it is assumed that the mosses, together with the mosses and rhinophytes, originated from an even more ancient group of plants. The earliest paleontological finds date from the end of the Devonian - the beginning of the Carboniferous.

Biological Description

The bryophyte department is distinguished by the fact that its representatives do not have flowers, roots, a conducting system. For them, reproduction is characterized by spores maturing in the sporophyte sporangium.

The haploid gametophyte, which predominates in the life cycle, is a perennial green plant, often having leaf-like lateral processes and root-like outgrowths (rhizoids). In comparison with other groups of higher plants, representatives of the moss-like branch have a simpler structure. Among the majority of species that have a stem and leaves, there is also a minority that has thalli and thalli.

But the leaves and stems of mosses are not real, in scientific language they are called caulidia and phyllidia. Phyllidia bessherechenkovye, located on the stalk in a spiral. They have a single plate. The vein is not always available

The sporophyte has no ability to take root, and it is located directly on the gametophyte. Sporophyte is represented by three components: a capsule (sporangia), with spores developing in it; Leg (sporophora) on which the capsule is located; Stop, which provides physiological interaction with the gametophyte.

The mosses have a number of characteristics that distinguish them from all higher plants. This lack of roots, which is compensated by the presence of a large number of rhizoids. With their help, the plant and attached to the substrate, and also performs a partial absorption of moisture. Basically, the process of water absorption is carried out in the lower part of the plant.

There are assimilation, conducting, storing and covering cloth. But in moss-like there are no real vessels and mechanical tissue, whereas all higher plants have.

Distribution area

Because of its unpretentiousness, mosses are common on all continents, even in Antarctica, and often grow in extreme conditions.

As a rule, mosses grow in dense clusters. Shaded places, often in the immediate vicinity of the reservoir, are ideal conditions for mosses. But they can also grow on open dry plots.

The department of moss-like species includes such species that live in freshwater reservoirs. But there are no marine inhabitants among them, although there are several species that settle on the rocks in the coastal strip.

Department of bryophytes: value

In nature:

• Are participants in the creation of special biocenoses, especially where they practically completely cover the land (tundra);
• The moss cover accumulates and retains radioactive substances;
• The ability to absorb and retain a large amount of moisture causes participation in the process of regulating the water balance of landscapes.

In people's activities:

• Contribute to waterlogging of soils, therefore they decrease the effectiveness of agricultural land;
• Carry out the process of uniform transfer of surface runoff of water into the underground, which protects the soil from corrosion;
• Some species of sphagnum mosses are used in medicine as a bandage;
• Sphagnum mosses are a source of peat formation.

Classification

Symptoms of the department are mossy, in spite of their generality, nevertheless allow to classify representatives of the department into several isolated groups.

The most numerous group of plants that make up the department is the real class (leafy mosses). It includes subclasses of green, sphagnous and andreean mosses.

Green mosses

The habitats for green mosses are soil, tree trunks, rocks and roofs of houses, but are best planted in damp forests, in which they form a continuous carpet.

These plants, which are part of the department are mossy, are quite numerous. The most typical representative is Kukushkin flax. The stems of it are erect unbranched, they are densely covered with narrow linear-lanceolate leaves. The formation of archegonies and antheridium occurs at the tips of the stems of individuals, usually growing close to each other. In the antheridia, the formation of two-glutinal spermatozoa occurs, in archegons - one fixed egg.

In the presence of a large amount of moisture (rain or heavy dew) fertilization begins. Water is compulsory, since spermatozoa swim to archeonium along it. When the zygote is formed, a sporophyte begins to develop from it. It is in itself unviable, like all plants that are part of the bryophyte department. The sporophyte is fed by a female gametophyte.

The capsule contains sporangia. There occurs the formation of haploid spores. Having matured, the spores fall asleep. The wind carries them. If the conditions are favorable, the spores will germinate and give rise to a protoneme that looks like a green branched filament.

Sphagnum mosses

Sphagnum mosses (350 species) are another group of plants that constitute a class of real mosses, a branch of moss. The general characteristics and significance of these mosses have a number of characteristics. Sphagnum is the only genus of this subclass.

They are characterized by the absence of rhizoids, because of which the flow of water with dissolved mineral substances occurs directly to the cells of the leaf and stem. On the stalk of the gametophyte are whorls of branches, on which, in turn, leaves are located. They constitute an outlet located at the top of the main axis.

The leaves of sphagnum mosses do not have an average vein. They have two types of cells: living - assimilating (long and narrow, with chloroplasts), and dead (without protoplast, thickened on the walls, have pores). The second type of cells is in the stem. This anatomical structure of the stem and sphagnum leaf allows it to absorb and retain so much water that its mass can exceed the mass of the plant by a factor of 30. It is because of this, the soil on which grow sphagnum mosses, gradually experiencing an excess of moisture and waterlogged.

So diverse is the bryophyte. The reproduction of sphagnum mosses is typical, with the only difference from other representatives of the department, that antheridia and archegonia can be formed not only on neighboring individuals, but also on the same plant.

A feature of sphagnum mosses is the continuous growth of the stem by the apex and the withering of the lower part. But the dead parts do not rot completely, because the overmoistened soil contains little oxygen, which is necessary for the development of soil microorganisms that decompose plant remains.

After a long period of time, a large amount of organic matter is accumulated in the form of peat. The formation of peat is a very slow process: 1 cm in about 10 years, 1 m in a thousand years.

Andreevye mosses

Green and sphagnum mosses are the most numerous in the number of species of the group of plants that make up the bryophyte section. The general characteristic and value of the other group, in spite of its small number, make it possible to separate it into a separate taxonomic unit. A subclass of andreev mosses is represented by one family and one genus of andrea. The range of their distribution is the temperate and cold regions of both hemispheres. They grow in the mountains on rocks and rocks.

The gametophyte begins to develop further inside the dispute. First, the cells begin to be divided, and then the shells of the spore break. In single-leaf leaves, cells are uniform. The leaves grow for a long time, forming hygroscopic hairs. There are no conductive bundles in the stems.

Sporogony is represented by a capsule and haustorium. The capsule does not have a lid. When the spores are cracked, spores get to the outside through the cracks located between the 4 leaflets.

So, a large group of higher spore plants, in number inferior only to flowering plants - this department is mossy. The peculiarities of the structure and vital activity of these representatives of the plant kingdom make it possible to call them amphibians, since they usually live on land (except for aquatic mosses), but can reproduce only in the presence of water.