The bryophytes are also called true mosses or bryophytes. All species are united in approximately 700 genera, which, in turn, comprise about 120 families.
Mossy Department: General Description
Representatives of the department are mainly small plants with a length of not more than 50 mm. The only exceptions are water mosses, which can reach 50 cm in length, and epiphytes, which are even longer.
Division refers to the taxon higher plants. The bryophyte division has about 25 thousand species.
Previously, besides leafy mosses, hepatic mosses and anthocerotic mosses were also assigned to this department. However, at the moment, these taxa are separate departments. Often, speaking about the combined features 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 prevalence of the haploid gametophyte over the diploid sporophyte.
History
The characteristic of the bryophyte division proves that mosses, like the other spore ones, evolved from psilophytes (rhinophytes), which are ancient extinct land plants. Moss sporophyte is considered the end result of the process of reduction of ancestral branched sporophytes.
However, there is another hypothesis, according to which it is believed that mosses, together with the plaoid and rhinophytes, came from an even more ancient group of plants. The earliest paleontological findings date back to the end of the Devonian - the beginning of Carboniferous.
Biological description
The mossy department is distinguished by the fact that its representatives do not have flowers, roots, or a conducting system. They are characterized by reproduction by spores ripening in sporophyte sporangia.
The prevailing haploid gametophyte in the life cycle is a perennial green plant, often having leaf-like lateral outgrowths and root-like outgrowths (rhizoids). Compared with other groups of higher plants, representatives of the bryophyte division have a simpler structure. Among most species that have a stem and leaves, there is a minority with thalli and thalli.
But the leaves and stems of mosses are fake, in the scientific language they are called caulidia and phyllidia. Phyllidiums are decailli, arranged on a stem in a spiral. They have a single plate. Vein is not in all cases
The sporophyte does not have the ability to take root, and it is located directly on the gametophyte. The sporophyte is represented by three components: a box (sporangia), with disputes developing in it; the leg (sporophore) on which the box is located; foot, providing physiological interaction with gametophyte.
Mosses have a number of characteristics that distinguish them from all higher plants. This is the absence of roots, which is compensated by the presence of a large number of rhizoids. With their help, the plant attaches to the substrate, and also partially absorbs moisture. Basically, the process of water absorption is carried out in the lower part of the plant.
There are assimilative, conductive, storage and integumentary tissues. But the bryophytes do not have real vessels and
mechanical tissue, while all higher plants have.
Distribution area
Due to their unpretentiousness, mosses are common on all continents, even in Antarctica, and often grow in extreme living conditions.
As a rule, mosses grow in dense clusters. Shaded areas, often in the immediate vicinity of a body of water, are ideal conditions for mosses. But they can grow in open dry areas.
The bryophytes division also includes species that live in freshwater bodies of water. But there are no marine inhabitants among them, although there are several species that settle on rocks in the coastal strip.
Mossy department: meaning
In nature:
- are participants in the creation of special biocenoses, especially where the earth is almost completely covered (tundra);
- 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 the activities of people:
- contribute to waterlogging soils, therefore, reduce the effectiveness of agricultural land;
- carry out the process of uniform transfer of surface runoff to underground, which protects the soil from corrosion;
- some types of sphagnum mosses are used in medicine as a dressing;
- Sphagnum mosses are a source of peat formation.
Classification
The signs of the department are mossy, despite their generality, nevertheless they allow us to classify the representatives of the department into several separate groups.
The largest group of plants included in the department is the real class (leafy mosses). It includes subclasses of green, sphagnum and andrey mosses.
Green mosses
The habitats for green mosses are soil, tree trunks, rocks and roofs of houses, but they grow best in moist forests in which they form a continuous carpet.
These plants, which are part of the bryophyte division, are quite numerous. The most typical representative can be called Kukushkin flax. Its stems are erect, unbranched, densely covered with narrow linear-lanceolate leaves. The formation of archegonies and anteridia is carried out at the tops of the stems of individuals, usually growing nearby. In anteridia, the formation of double-flagellated spermatozoa takes place, in archegonia - one fixed egg.
In the presence of a large amount of moisture (rain or heavy dew), fertilization begins. Water is required, as sperm swim to the archegony along it. When the zygote has formed, a sporophyte begins to develop from it. It itself is not viable, like all plants belonging to the bryophyte division. Sporophyte nutrition is carried out due to the female gametophyte.
The sporogonum box contains sporangia. The formation of haploid spores occurs there. Ripening, spores get enough sleep. They are carried by the wind. If the conditions are favorable, the spores will germinate and give rise to a protonema, which looks like a green branched thread.
Sphagnum Mosses
Sphagnum mosses (350 species) are another group of plants that make up the class of real mosses, the bryophyte division. The general characteristics and significance of these mosses have a number of features. Sphagnum is the only genus of this subclass.
They are characterized by the absence of rhizoids, which is why water with dissolved mineral substances flows directly to the leaf and stem cells. On the stem of the gametophyte are whorls of branches, on which, in turn, the leaves are located. They make up the outlet located at the top of the main axis.
Sphagnum moss leaves have no middle vein. They have two types of cells: living cells - assimilating (long and narrow, with chloroplasts), and dead cells (without protoplast, thickened on the walls, have pores). The second type of cells is in the stem. This anatomical structure of the stem and leaf of the sphagnum allows it to absorb and hold such an amount of water that its mass can exceed the mass of the plant by 30 times. It is because of this that the soil on which sphagnum mosses grow gradually experiences an excess of moisture and becomes swampy.
So diverse is the bryophyte division. Reproduction of sphagnum mosses is typical, with the only difference from other representatives of the department that anteridia and archegonia can form not only on neighboring individuals, but also on the same plant.
A feature of sphagnum mosses is the continuous growth of the stem with the apex and the death of the lower part. But the dead parts do not rot completely, because waterlogged soil contains little oxygen, which is necessary for the development of soil microorganisms that decompose plant debris.
After a long period of time, a large amount of organic matter accumulates in the form of peat. Peat formation is a very slow process: 1 cm in about 10 years, 1 m in a thousand years.
Andrew Mosses
Green and sphagnum mosses are the most numerous in the number of species groups of plants that make up the bryophyte division. The general characteristics and significance of another group, despite its small number, make it possible to distinguish it as a separate taxonomic unit. The Andrei Moss subclass is represented by one family and one genus of Andrea. The distribution area is the temperate and cold regions of both hemispheres. They grow in the mountains on rocks and stones.
The gametophyte begins to develop even inside the spores. First, the cells begin to divide, and then the spore shells are torn. In single-layer leaves, cells are homogeneous. Leaves grow apex for a long time, forming hygroscopic hairs. There are no conducting beams in the stems.
Sporogony is represented by a box and a haustorium. The box does not have a lid. When cracked, spores get out through cracks located between 4 wings.
So, an extensive group of higher spore plants, second in number to only flowering ones, is a bryophyte division. The structural and vital features of these representatives of the plant kingdom make it possible to call them amphibians, since they, as a rule, live on land (except for water mosses), and can multiply only in the presence of water.