Ferns are an ancient group of higher spore plants that played a crucial role in the formation of coal on the planet. These are the first true leafy organisms. The structure of the fern, the features of its life cycle and distribution in nature will be considered in our article.
Structural Features of Ferns
As a rule, ferns grow in the forests of the temperate climatic zone. Their body consists of a modified shoot located underground - rhizomes. Above ground, only leaves are visible. This is the external structure of the fern. The diagram below illustrates the nature of the leaf arrangement. It clearly shows that additional ones are attached to the main axis, and leaf blades are directly attached to them.
The underground structure of the fern is also represented by a system of subordinate roots that extend in a bundle from a modified shoot.
But the fossil forms of fern-like do not resemble their modern relatives. Along with herbs, these were small shrubs and giant trees, reaching a height of several tens of meters.
Life cycle
The external structure of the fern periodically changes. How is this possible? The thing is that throughout the life of ferns there is a process of alternation of generations: sexual (gametophyte) and asexual (sporophyte). They differ in the method of reproduction, development, and a number of significant morphological features.
Sporophyte
The asexual generation of fern is a green leafy plant. We are used to seeing him in the forests. In this form, a fern (the photo below shows a sporophyte) exists the predominant part of its life cycle. On the underside of the leaves of the plant are sporangia - asexual reproductive organs. They are collected in specialized structures - soruses. They contain asexual reproduction cells called spores.
Gametophyte
Once in the soil and sprouting, spores give rise to the sexual generation. Such a gametophyte determines completely different traits and structure of the fern. It has the appearance of a flat green plate, which over time takes the form of a heart. Gametophyte is attached to the soil with the help of rhizoids. These filamentary formations resemble plant roots in appearance and function, but do not form tissues. The sexual generation of ferns is bisexual. The process of fusion of gametes is possible only in the presence of water. As a result, a zygote is formed - a fertilized egg. Developing, it gives rise to the embryo, and then to the adult plant. at first, the young sporophyte is not capable of photosynthesis, so its nutrition is due to the green plate of the sexual generation. As the ability to photosynthesis develops and arises, an adult leafy plant begins to function separately.
Variety of ferns
Currently, taxonomists comprise about 10 thousand species of representatives of this department. Among aquatic ferns, salvinia is the most common. This plant floats on the surface of the water and in appearance is very similar to algae. Together with Marsilia and Azolla, Salvinia floating represents a group of heterogeneous ferns. These are typical aquatic plants.
However, in the vast majority of cases, fern (photo shows a perennial plant) is a inhabitant of forests. And most of them are representatives of a group of equals. The most common of these are the common bracken, female coomber, male thyroid, and millipede ordinary. It is about such species of fern that a beautiful ancient legend still exists. If you can find the night on the holiday of Ivan Kupala to find this flowering plant in the forest, then you can acquire amazing abilities. For example, understand the language of any living creature. This beautiful legend arose because no one had ever seen a fern flower. Our ancestors did not know that this is simply impossible, since spore plants do not form flowers and fruits.
In tropical forests, several species of tree ferns are found. Like all higher spore plants, they prefer moisture, and therefore grow along streams and rivers. Very often in these places thickets of tropical ferns form real jungle.
The value of fern-like
It is the external structure of the fern and its features that have now made this plant one of the most popular decorative cultures. It is widely used for landscaping various landscapes and territories. And lovers of indoor plants have long looked after various types of ferns for landscaping houses, apartments and various rooms.
In nature, these plants are an integral part of many ecosystems, significantly increasing their biomass.
However, the greatest importance of ferns lies in the formation of a very important mineral - coal. In antiquity, all spore plants were giant trees. From their dead trunks under conditions of high pressure and lack of oxygen, coal was formed. Paleontologists still find fossilized remains of ancient spore plants in the strata of this substance.
Great importance of ferns in medicine. For example, the rhizomes of the male thyroid have a very strong anthelmintic effect. But the adiantum (hair venus) causes a gag reflex, while not irritating the mucous membranes. It acts as a laxative and diuretic. The Strawberry bush has long been used as an antidote to snakebites. In Tibetan medicine, the millipede Virgin is widely used. Pain killers and cold medicines are made from it.
The structure of the fern is the most complex and progressive among all higher spore plants. In his life cycle sporophyte prevails. Modern ferns are most often represented by grassy life forms that occupy an important niche in diverse ecosystems.