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 discussed in our article.
Features of the structure of ferns
As a rule, ferns grow in the forests of the temperate climate zone. Their body consists of a modified shoot located underground - a rhizome. Only the leaves are visible above the ground. This is the external structure of the fern. The diagram below illustrates the nature of the leaf arrangement. It clearly shows that additional blades are alternately attached to the main axis, and leaf blades directly to them.
The underground structure of the fern is also represented by a system of adventitious roots, which extend from the modified shoot in a bundle.
But the fossil forms of ferns are not at all similar to their modernrelatives. 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 changes periodically. How is this possible? The thing is that during the life of ferns there is a process of alternation of generations: sexual (gametophyte) and asexual (sporophyte). They differ in the way of reproduction, development and a number of significant morphological features.
Sporophyte
The asexual generation of the fern is a green leafy plant. We are used to seeing him in the forests. In this form, the fern (the photo below shows a sporophyte) exists for the predominant part of its life cycle. On the underside of the leaves of the plant are sporangia - organs of asexual reproduction. They are collected in specialized structures - sori. They contain cells of asexual reproduction called spores.
Gametophyte
Getting into the soil and germinating, spores give rise to the sexual generation. Such a gametophyte determines completely different features and structure of the fern. It looks like a flat green plate, which over time takes the shape of a heart. The gametophyte is attached to the soil with the help of rhizoises. These filamentous 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 ofwater. 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 the process of photosynthesis, therefore its nutrition occurs due to the green plate of the sexual generation. With the development and emergence of the ability to photosynthesize, an adult leafy plant begins to function separately.
Variety of ferns
Currently, taxonomists have about 10 thousand species of representatives of this department. Among aquatic ferns, the most common is salvinia. This plant floats on the surface of the water and looks very much like algae. Together with Marsilia and Azolla, Salvinia floating represents a group of heterosporous ferns. These are typical aquatic plants.
However, in the vast majority of cases, the fern (the photo shows a perennial plant) is a forest dweller. And most of them are representatives of the equal-spore group. The most common of them are common bracken, female kochedyzhnik, male shield, common centipede. It is about these types of ferns that a beautiful ancient legend still exists. If you find this flowering plant in the forest on the night of Ivan Kupala's holiday, then you can acquire amazing abilities. For example, to understand the language of any living being. 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 formflowers and fruits.
There are several types of tree ferns in tropical forests. Like all higher spore plants, they prefer moisture, so they grow along streams and rivers. Very often in these places thickets of tropical ferns form a real jungle.
Meaning of ferns
It is the external structure of the fern and its features that have now made this plant one of the most popular ornamental crops. It is widely used for landscaping various landscapes and territories. Yes, and lovers of indoor plants have long looked after various types of ferns for landscaping houses, apartments and various premises.
In nature, these plants are an integral part of many ecosystems, significantly increasing their biomass.
However, the greatest value of ferns lies in the formation of a very important mineral - coal. In ancient times, 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 layers of this substance.
The significance of ferns is also great in medicine. For example, the rhizomes of the male thyroid gland have a very strong antihelminthic effect. But the maidenhair (hair venus) causes a gag reflex, while not irritating the mucous membranes. It works and howlaxative and diuretic. Wildflower has long been used as an antidote for snake bites. In Tibetan medicine, centipede virginiana is widely used. It is used to make painkillers and cold medicines.
The structure of the fern is the most complex and progressive among all higher spore plants. Its life cycle is dominated by the sporophyte. Modern ferns are most often represented by herbaceous life forms that occupy an important niche in a variety of ecosystems.
