Ferns are seen by each of us. These herbaceous plants are widespread in the temperate climate zone. And what kind of fern growth does it have? You will find the answer to this question in our article.
General characteristics of the department
Fern-shaped are representatives of higher spore plants. These are the first land plants, which are characterized by the following features:
- the appearance of these tissues and organs;
- grassy life forms;
- reproduction using asexual reproduction cells - spores;
- alternation of generations in the life cycle.
Of the modern species, except for ferns, mosses, crowns and horsetails belong to this systematic group. In all these plants, the sexual and asexual generation is distinguished by the method of reproduction and morphological features. So, fern sporophyte is a leaf-stem plant. This is a sexless generation. But the gametophyte, a fern growth, has a completely different shape.
Life cycle features
A plant of an asexual generation of ferns consists of a root and shoot. On the surface we can only see complex leaves. The shoot itself is modified and developed underground. It is called a rhizome. Outwardly, this structure really resembles an underground organ. But the rhizome is an escape, because it consists of internodes, nodes and kidneys.
On the underside of fern leaves with the naked eye, small brown tubercles can be seen. These are sporangia in which asexual reproduction cells form. When ripe, they fall into moist soil. There they germinate, forming a fern sprout. This structure has a completely different look - a flat plate of green color. The dimensions of the seedling are very small - only a few millimeters. Therefore, it is very difficult to distinguish them in the dense cover of the plant thickets.
What type of fern sprout has
Despite the microscopic dimensions, the structure and functions of this stage of plant development are quite complex. In the photo, the fern overgrowth clearly shows that it develops separately from the plant of asexual generation. Mostly it has a heart shape with wavy edges. In the middle, this plate is massive. The edges are thinner, single-layer, slightly translucent.
The fern growth has the form of a heart-shaped plate, in the lower part of which thick bunches of rhizoids are formed. From these roots, these structures are distinguished by the absence of tissue. They consist of cells that combine anatomically, but each of them functions separately. Rhizoids perform the function of gametophyte attachment to the substrate.
Important for the development of sporophyte is that the cells of the sprout contain chlorophyll. This provides the process of photosynthesis and the presence of the necessary organic substances for the formation of plants of asexual reproduction, which has a more impressive size.
Gametophyte development
Fern spores develop only in moist soil. Their distribution occurs with the help of water, wind, insects and birds. As a result of spore germination, a plate is formed. In cross section, its size barely reaches 3 mm. The growth of fern is attached to the ground with the help of rhizoids, which also provides additional plant nutrition.
On the underside of this structure are the genitals - gametangia. These structures also have microscopic dimensions, which are even hard to imagine. They are of two types. Male are called anteridia. Sperm cells mature in them. These are germ cells that have flagella. But sperm movement is possible only in the presence of water. Therefore, the presence of moisture is a prerequisite for the implementation of the fertilization process in all spore plants. Female genitals are called archegonia. They form fixed eggs.
Ferns are characterized by cross-fertilization. This is due to the fact that the maturation of anteridia and archegonia occurs at different times. Therefore, gamete fusion usually occurs between different seedlings.
Sporophyte
From a fertilized egg, a plant of asexual generation develops, which prevails in the life cycle of fern-shaped. It is called a sporophyte. If the fern sprout looks like a plate, then the asexual generation is a herbaceous plant. It has an underground modified shoot - rhizome. From the vegetative buds located on it, leaves develop. They come in two forms. Young leaves are called vayi. They are spirally twisted and are by nature pre-runs. Mature leaves of ferns are complex, spreading.
There is another significant difference between the sexual and asexual generation of ferns. The fern growth has rhizoids, and the sporophyte has accessory roots.
Ancient species
Modern fern-shaped plants are characterized by sufficient species diversity. Of all the disputed, this group is the largest. This is due to their more perfect structure. At the present stage, there are more than 10 thousand species.
But the ancient ferns had a completely different appearance. They especially reached their heyday during the Carboniferous period. At that time, tree-like ferns reached up to 40 meters in height. The width of their trunks was also impressive. She was 2 meters.
The appearance of these plants on the planet dates from the Paleozoic era. During evolution, they evolved from the first terrestrial plants - rhinophytes. That was 400 million years ago. Ancient ferns became extinct due to climate change. They are the basis of a valuable fuel mineral - coal.
So, in our article, we found out what kind of fern growth the gametophyte has. This is a thin microscopic plate of green color. It represents the sexual generation of ferns. Growth develops separately from plants of asexual generation, is capable of photosynthesis, has rhizoids. On it, the organs of sexual reproduction develop, in which gametes are formed. As a result of their merger and the further development of the zygote, a fern sporophyte is formed, which has a leaf-stem structure.