Ferns are truly one of the most mysterious representatives of the plant world. They are associated with beautiful stories and legends. In our article, we will consider the fern development cycle, the life span diagram, and the characteristics of these plants.
Department Features
Representatives of ferns are represented by two life forms. Perennial grasses grow in temperate forests. Their aerial part consists only of leaves. And the shoot itself is modified in the rhizome and is located underground. Bunches of fibrous root system depart from it . In the zone of tropical rainforests, tree ferns are found. Their stem may be curly or erect. In any case, in these species it reaches several tens of meters.
Ferns belong to the group of higher spore plants, representatives of which are the first to come to land. In the process of evolution, they have formed real tissues and organs. This is what allowed these plants to develop a new habitat. The name of this systematic group is also associated with the fact that ferns form spores, which are cells of asexual reproduction.
Fern development cycle: description scheme
All ferns are characterized by a life cycle. This is the name of the period between two identical stages of development of generations. Typical of these plants is the developmental cycle of bracken fern. It can be represented in the form of steps presented in the table.
| Life cycle | Function |
| Asexual plant | Photosynthesis, spore formation, vegetative propagation, mineral nutrition, transpiration, plant fixing in the soil |
| Disputes | Asexual reproduction, gametophyte formation |
| Zarostok | Photosynthesis, plant fixation in the soil, the formation of germ cells - eggs and sperm |
| Gametes | Sexual reproduction of the plant |
| Embryo | Formation of the asexual generation - sporophyte |
Further, the fern development cycle is repeated. This process ensures the continued existence of all departments of higher spore plants. Now consider each stage in more detail.
Asexual plant
Acquaintance with the fern development cycle, the scheme of which is presented below, we will start with a sporophyte. This is the name of an adult leafy plant, which forms significant thickets in the forests of the temperate zone. On the surface, we can only see fern leaves. They come in two forms. Young leaves are spirally twisted; they are called vayi. They grow at their apex and reach considerable size. So there are lush and sprawling leaves of adult plants.
Sporophyte is the predominant generation of these plants. This is a significant difference in the development cycles of mosses and ferns. In the first, the main generation is the gametophyte. It has the appearance of a green leafy carpet and propagates using germ cells.
Where are the sporangia
The next stage of the fern development cycle is the maturation of asexual reproduction organs. They are called sporangia. These structures look like small brown tubercles located on the underside of leaves. Above they are additionally protected by membranous "bokers". Sporangia of ferns are grouped into groups called soruses.
In late summer, these structures darken. This means that sporangia are ripe. Then they open up, and thousands of small cells spill out into the earth. This is the debate. If there is enough moisture, they immediately begin to germinate.
What is a sprout
The result of the development of spores is a seedling. This is the individual of the sexual generation, which is the next link in the fern development cycle. For a long time, scientists did not even know about its existence. The thing is that the seedling has very small sizes - just a centimeter in diameter. Outwardly, it is a green plate of a heart-shaped shape. Growth develops on the soil to which it is attached with the help of rhizoids.
As the gametophyte develops, reproductive organs form on its lower side. Sex cells of two types mature in them: ova and sperm.
Fertilization conditions in the development cycle of bracken fern
The haploid set of chromosomes, which the gametophyte germ cells have, changes to double in the process of their fusion. Fertilization in ferns has its own characteristics. First, male and female germ cells on the same seedling mature at different times. Therefore, fusion of gametes is possible only between different plants. This type of fertilization is called cross fertilization.
The second feature of this process in ferns is the obligatory presence of water. The fact is that germ cells of spore plants cannot move independently. Therefore, the sperm can reach the egg only with the help of water. Thus, ferns, although they belong to the group of the first terrestrial plants, have not lost their connection with the previous habitat.
Further, a plant of asexual generation develops from a fertilized egg, spores mature on it, and the process repeats.
Life span
How long can the fern development cycle be repeated? It depends on the specific type of plant and its place of growth. So, in grassy forms of temperate latitudes, the leaves die off every season, and in the tropics they grow for several years. But due to the presence of an underground modification of the shoot, which is called the rhizome, the plant itself remains viable regardless of the season and climatic conditions. In many ways, this particular structural feature retained these ancient plants until the present stage of the development of the organic world.
The roots of ferns perform their functions on average about four years, after which they are replaced by new ones. But the escape can remain viable for up to 100 years.
So, we examined the developmental features of one of the departments of higher spore plants - fern-shaped. The following symptoms are characteristic of these plants:
- The appearance of these tissues (mechanical, conductive, integumentary) and vegetative organs (leaves, adnexal roots, modified underground shoot).
- Asexual reproduction is carried out using specialized cells - spores.
- In the cycle of fern development sporophyte prevails. This is an asexual generation with a leaf-stem structure.
- The gametophyte fern is called a seedling. It is a green plate of a heart-shaped form with a diameter of up to 1 cm. The seedling develops separately from the sporophyte and is not anatomically associated with it.
- In the life cycle, there is a consistent alternation of generations - sexual and asexual.