The fern is a perennial plant that is widely used to decorate flowerbeds and gardens. The most common type of fern for these purposes is Adiantum stop-like, which enchants the view with its original leaf shape in something similar to a light openwork cloud. Ferns love shade or penumbra, high humidity, and are still considered to be quite cold-resistant plants.
Fern life cycle
The development cycle of a fern includes two generations, which differ sharply from each other - asexual and sexual. An interesting fact is that we usually call the fern just asexual generation, which is called the sporophyte. And from the huge number of spores that are formed on the leaves of fern, only a very small number of them falls into favorable conditions for them, and then they give new life to young plants.
Moisture, heat and light are considered favorable factors for spores.
Of these same spores, small plants develop in a variety of shapes and sizes, called gametophytes. After the formation of these same plants - gametophytes - they form genitals - male (antheridia) and female (archegonia). Fertilization of a plant occurs only at high air humidity and the presence of water on the surface of a small plant, because gametophyte spermatozoa can only travel through water from antheridium to archegonia. The development of the sporophyte begins after fertilization.
Spore breeding is a very laborious process and an ordinary grower is unlikely to master it, so more often resort to vegetative propagation, which implies the division of overgrown bushes, rhizomes, processes and buds.
Some species of ferns reproduce vegetatively, i.e. excretory buds on the leaves of the plant, and in general the developmental cycle of a fern is quite interesting and requires special study from those interested in this plant.
Sexual reproduction by spores
Sexual reproduction by spores is characteristic of those species of ferns, which have only one growth point and do not form additional sockets. In this case, resort to sprouting spores.
This process is very similar to the germination of seeds, with the only difference: the size of the dispute is much smaller than the seed, because they need special care.
Collect spores from adult plants. In order to collect spores from a cultivated plant, it is necessary to cut off the leaf of a fern, on which traces of brown dust are clearly visible. The cut sheet must be placed in a paper bag. Then the package is placed in a warm dry place for a day. Periodically the package needs to be shaken.
In order for spores to grow well, it is necessary to choose the right soil mixture. Ideal for this is a mixture of peat, sand and leafy ground.
Be sure to add crushed charcoal. It should be remembered that all components must be mixed in equal quantities. The prepared soil mixture is poured into shallow pots, lightly tamped, moistened and spores are sprinkled over the surface of the earth. Before laying out the spores, you can sprinkle the ground with a very thin layer of crushed bricks.
From the soil surface to the edges of the pot should remain about 1 cm. In order for the spores to sprout quickly, we must create favorable conditions, i.e. temperatures around 25 degrees and high humidity. To do this, you need to cover the pots with glass and put in a pan with soft water. This design is placed in a warm place, periodically moistened through a spray bottle.
Approximately in a month the surface of the soil will be covered with a green carpet similar to moss. These are those outgrowths from which the leaves will later grow. Glass is not removed until small leaves appear from the outgrowths. In order to dive the plants in separate pots, it is necessary to give the leaves a little time to adapt. Grown up plants dive into pots with peat ground.
Vegetative breeding method
Vegetative breeding method is more acceptable for gardeners. The easiest way to divide the fern bush into several parts. These parts are landing material. There are certain types of ferns that breed by buds that form at the edges of the leaves.
For growing at home, the most suitable are the asplenium viviparous and onion-bearing. The division of the bushes or rhizomes is usually propagated by adiant, nephrolepisis, leaflets, pteris and pelleas.
When the vegetative method of reproduction by dividing it is necessary to pay attention to the growth points. Fern division is best done in spring in cool weather. After young plants are planted, they must be watered and sprayed more often.
Now, knowing the life cycle of a fern, you can grow this amazing plant.
Ferns are seedless vascular plants. They are arranged easier than vascular, forming seeds. The size of ferns can be from very small room to large tree forms. They are often used for decorative gardening at home. In addition, the leaves have the ability to clean the air and moisten it. In nature, are more common in areas with tropical climates. Prefer moist soil and air. They need a small amount of sunlight. In adverse conditions, ferns cease to multiply.
Most gametophyte ferns are not visible in nature. Typical specimens are about 1 cm in diameter, flat in the shape of a heart in green. Sporophyte is a large, familiar plant. There are thousands of different types of ferns. They differ in the shape and size of the stems and leaves.
All representatives of this species have:
- leaves that are called "fronds".
Usually the leaves are upright in the form of a fan, feathery, the color is from light to dark green. Stems are not developed, inferior in size and mass of foliage. In addition, the sporophyte plant has a sorus, which is a bundle of sporangia — special organs in which petty disputes develop. Sorus covers induzii, resembling an umbrella.
It should be noted that gametophyte and sporophyte play an equally important role in the developmental cycle of a fern. However, in terms of evolutionary development, gametophyte is a more primitive form.
The life cycle of a fern includes the sexual and asexual stages and is different from the life cycle of other plants. They do not bloom to reproduce, but do it sexually from spores. Spores are formed on the sporophyte and are asexual. Sleeping and germinating in favorable conditions, they form a gametophyte. It forms the male genital organs with motile spermatozoa and female genitals with fixed eggs. After fertilization, a new sporophyte develops from the egg, which continues the life cycle.
Fern spores are green and contain chlorophyll. They are short-lived, the viability is maintained from several days to several months depending on the environment. The conditions should allow disputes to fertilize, then allow sporangia to develop. As the latter grows, the environment must meet the requirements of the plant, which are quite different. Only if all the conditions are met, the fern development will be completed and its life cycle will not be interrupted.
The main stages of the life cycle of a fern occur in the following sequence:
- spore formation
- gametophyte development,
- the formation of eggs and sperm,
- fertilization (zygote),
- embryo formation,
- new plant.
Spores are formed in the sporangia of adult plants on the back of the leaf. When the spores are ripe enough, the induction dries out, the capsules open and the spores dissipate around the plant. They are spread by water, as well as by wind, birds and insects. Getting into moist soil rich in nutrients, the spore germinates. A gametophyte appears - a small plant (2-3 mm in diameter). Although this is not a full-fledged fern, but a completely independent and self-sufficient specimen capable of photosynthesis. The gametophyte is attached to the soil using rhizoids, which simultaneously provide the plant with nutrition.
Microscopically small genitals develop on its surface:
- 1 Male organs, or antheridia, produce numerous motile sperm. They are equipped with flagella and can move in water for short distances. It is for this reason that a moist environment is necessary for successful fertilization.
- 2 Female organs, or archegonias. An egg cell is embedded in each archegonium, which chemically attracts sperm to itself, and fertilization takes place.
Often, the egg cell and sperm of one plant mature at different times, which stimulates cross-pollination and improves the genetic strength of plants. Antheridia and archegonia most often develop on the same plant. Only in some species of ferns are plants haloed.
A fertilized egg contains a double set of chromosomes. It is repeatedly divided miotically, turning into an embryo. The life of a sporophyte begins, which at first depends on the gametophyte, but quickly develops its own roots and becomes independent. After this, the gametophyte fades and perishes.
Sporophyte generation in ferns is more durable compared to gametophytes. This is due to a more complex structural organization. Sporophyte has:
- vascular conduction system
- supporting fabrics, often associated with a conductive system,
- tissue specialization in the form of stems, roots and leaves.
Mature sporophyte produces specialized organs - sporangia, producing disputes. Some sporangia are combined into sori. Spores consist of a single cell surrounded by a strong cell wall and have a single set of chromosomes. Spores are produced in large quantities and are fixed. After rupture of the wall of sporangia, they get enough sleep and can spread over long distances with the help of wind or water. Getting into a favorable environment, spores germinate and give the next generation of gametophytes, completing the life cycle.
In its development, the plant goes through several stages. More clearly and accessiblely, this process demonstrates the scheme of the life cycle of a fern.
In addition to the gametophyte-sporophyte cycle, some species of ferns also have a vegetative propagation method. This method is beneficial when adverse conditions arise for the development of a gametophyte. In this case, the plants form vegetative buds or onions, which produce new roots. Rooting, they give rise to a new plant. Onions are formed in the leaf axils or in any other place of the leaf blade.
For gardeners, the vegetative propagation method is the most convenient and acceptable. Ferns can be transplanted by dividing a bush, rhizome or by cuttings. Species that have a single point of growth and do not form other rosettes can be propagated only by sowing spores.
Ferns grow in wild forests and form beautiful bushes with wide leaves. Many gardeners and landscape designers planted such a plant on plots and flower beds. The fern is demanding care and in order to get a healthy and attractive plant, you need to follow a few rules.
Description and life cycle
A fern is a perennial herb that belongs to the fern family. The form of its growth depends on the species and can be in the form of a bush tree or grass. Fern belongs to the oldest plants on the planet, the occurrence of which archeologists attribute to the Paleozoic era. In the modern world, representatives of this family can be found on any continent of the planet, mainly they grow in a tropical climate.
In nature, a fern can reach 2 meters in height and grow 3 meters in diameter. Of the vast number of genera and species, only a small percentage is grown at home. Basically, all these ferns have lush foliage and form an ornamental and dense bush. But they use it not only as a decorative ornament, the leaves of the plant are a good air purifier, as well as a humidifier.
The development cycle of a fern is divided into two types of sex and asexual.
Most often you can find asexual representatives of this plant. Their reproduction occurs with the help of spores, which are formed on the leaves, so this is the name. In ferns of the second type, male and female plant organs are formed. Such a process occurs only in an environment with high humidity.
Popular types of fern:
- Fern bracken. This type can be attributed to the most popular. It forms a shrub up to 150 cm in height. The leaves are large, spreading, flat, feather, painted green. Bracken fern is a poisonous plant, but the percentage of toxins is so low that the leaves are used as food after cooking and after several days of soaking.
- Thai fern This is a room type of plant that is grown in aquariums to maintain the required percentage of moisture. Plant height does not exceed 30 cm. The leaves are arranged alternately, have an elongated shape, pinnate, painted in a bright green tone. This look is very whimsical, therefore its maintenance obliges to quivering leaving. Temperature fluctuations or unsuitable water can cause disease and death of the plant.
- Male fern. Large shrub with long double-pinnate leaves. The rhizome is thick, goes deep into the ground, a thick rosette of leaves is formed on it. The height of the plant does not exceed 120 cm. The leaves are painted in a dark green tone, in the first year they grow upwards, and after a while under the weight they bend in an arc. This type of fern is used for medicinal purposes.
Fern breeding takes place with the help of spores, division and rooted shoots. At home, spore reproduction is practically not used, since it is a rather long and laborious process.
Some species form bulbs that divide when transplanting. Other species can be rooted using a leaf, the end of which is buried in the same pot and, after rooting, is separated from the parent plant.
The development cycle of gymnosperms on the example of Scots pine
In the life cycle of Scots pine and all gymnosperms, adult tall plants are represented by a sporophyte — a diploid (2n) generation. Pine refers to the woody plant life form, which develops from a seed germ and consists of the root - the root system and the shoot - the above-ground system of vegetative shoots: trunk, branches, leaves and generative shoots of male and female cones.
The root system of Scots pine is rod-shaped, up to 20–30 m long, formed by the main root branched to the side. Pine roots can enter into symbiosis (mutually beneficial coexistence) with the mycelium (body) of fungi, such as oil, creating mycorrhiza (fungus root). Hyphae (outgrowths of the mycelium) twist the roots of pine from the tips to the suction zone and penetrate into it, connecting to the conductive beams. Absorbing organic matter from the plant, the fungus supplies water with minerals to the plant.
The lignified vertical stem of a pine tree - the trunk, reaches a height of up to 30-40 m, has a well-shaped system of lateral branches developed in the upper part - elongated shoots. The elongated shoots are covered with sessile, spirally arranged brown scale-like leaves. Elongated shoots end with ovate, conical, brown buds, covered with resin. In the axils of scale-like leaflets, shortened shoots develop, of which two leaves grow, needles. A pair of leaves of Scots pine, 3–8 cm long, 1.5–2 mm thick, at the base covered with a vagina, functions (lives) for 3-5 years and falls together with a shortened shoot.
Male cones - spore-bearing spikelets (strobila), are formed in the spring at the base of young elongated shoots. They are assembled on a common axis. Each individual lump is 8–12 mm long, yellow or pink in color, consists of a short rod (axis) on which reduced sporiferous leaves, microsporophylls, are spirally located. On the lower side of the microsporophylls are located two microsporangia. In microsporangia - pollen chambers, as a result of meiosis (reduction division), haploid cells are formed from diploid cells of the sporogenous tissue. microspores. The microspore cell has a double shell: external, thick -exineand internal, thin -intinu. In two places, exine does not grow together with the intina, forming bulges - air sacs. A cell microspore after some time after formation forms mitosis twice, forming four haploid cells: vegetative, generative (antiridial) and two protalial cells. Проталиальные клетки являются резервными, поэтому отставая через некоторое время в росте, отдают свой ресурс на развитие генеративной и вегетативной клеток, быстро дегенерируют и исчезают.Thus, a four-cell male gametophyte is formed surrounded by a microspore double envelope - pollen.
Female cones appear on the tops of elongated shoots singly or in groups of 2-3, with a length of 3-7 cm, conical, symmetrical. They consist of a rod (axis) on which megasporophylls are spirally arranged - female sporiferous leaves. Each megasporofill includes a small surface covering on top and a large seed scale under it. On the upper side of the seed scales, at its base, there are two seed germs, covered with cover scales. The seed germ is a magasporogenous tissue - nucelus, covered with an integumentary tissue - intigument. At the top of the seed germ of the cone facing the axis, an opening remains in the intigument - the polynate (micropyle).
In the spring (May), after maturation (full formation) of pollen, microsporangia, in which it is contained, burst. Pollen is introduced by air currents (wind) between the scales of the female cones, which at that time were widely disclosed and access to seed germs was open. The process of pollen ingress on the micropyle of seed germs is called pollination. Flying between the integumentary and seed scales, pollen is glued to a sticky substance that is released from the micropyle. After some time, as a result of the drying out of this substance, the pollen delays through the polntus entrance to the nucelus. After pollination, the micropile grows over, the scales of the female cone close, and the whole cone is sealed outside (filled in) with resin. After a vegetative cell of pollen hits a nucelus, a pollen tube grows into it. The generative cell goes inside the vegetative cell and moves in its apical part. For the next 13 months, the pollen tube slowly grows into the nucelus, in the direction of the future female gametophyte, which will be formed later.
One month after pollination, one cell of the nucelus, the archesporial cell, is divided by meiosis, forming four haploid megaspores. Three of them degenerate, and the fourth megaspore that is the most distant from mycropyle begins to grow. Its development in the megagametophyte (female gametophyte, or endosperm) begins six months after pollination and requires another six months to complete its formation. During this time, the megaspore cell by mitotic division increases the number of its nuclei to about 2000 pieces. At 13 months after pollination, cytokinesis occurs in the megaspore - the separation of a multinucleated cell by cell walls, which localize the nuclei in individual cells. The haploid tissue formed is called endosperm. At 13-15 months after pollination, closer to the micropyle, two or three reduced archegonies with egg cells in the middle are formed from endosperm cells. The endosperm with two archegonies is a female gametophyte (outgrowth).
By the time of completion of the formation of the female gametophyte and the penetration of the pollen tube into it, the generative cell, in the middle of the vegetative cell (pollen tube), is divided into two daughter cells - sterilecage (leg-cage) andspermatogeniccell (body cell). After which the spermatogenic cell divides into twosperm. A vegetative cell with two sperm in the middle is a fully developed male gametophyte. Having penetrated into archegonia and reaching the egg cell, the vegetative cell (pollen tube) bursts, and one of the sperm fuses with the egg, forming a zygote, the other sperm dies (degenerates). The process of fertilization occurs approximately 13-15 months after pollination. Usually fertilized and begin to develop into embryos fertilized eggs (zygotes) of all archaegia (polyembryology), however, as a rule, only one embryo is formed completely. At the early stage of embryogenesis from a zygote by cell division, a pre-nucleus is formed, which forms four four-tiered columns of cells in the basal part of the arhegonium. All four apical (apical) cells of the columns (ie, the ovule most distant from the micropylar end) begin to develop into embryos. At the same time, the four cells of the next row — the suspensor cells (under the weight) —have strongly drawn out and push four unformed embryos into the depths of the female gametophyte. But only one of the embryos develops completely.
During embryogenesis, the integument is transformed into the seed coat (peel). Seeds of Scots pine black, with a diameter of 4-5 mm, membranous pterygoid protuberance of the seed coat, 12-20 mm long. Formed within 6 months and fully matured in November-December, 18-21 months after pollination. When ripe, female cones become dull from gray-light brown to gray-green, open (open their scales widely) from February to April and soon fall off.
Stages of fern development
The life cycle of a fern is all the stages, phases and stages that a plant goes through, starting with its appearance and the birth of the first leaf, and ending with the appearance of a new, ready-to-breed specimen. Such a cycle is closed and is divided into two types or types. Ferns breeding happens:
These two types are very different from each other. At the same time, the fern itself, in the form in which we know it, is called just the generation that has developed in a sexless way. This generation is called sporophyte.
For the birth of a young fern on the back of the leaves of the parent (or fatherly, as you like) plants should appear spores, which will begin to develop there. This is perhaps the most important phase of the life cycle of a fern, because without it, no development will just happen.
These disputes are in a kind of “bag”, which will burst after maturation, as a result of which the disputes will simply scatter in different directions. Life will be given only to those who fall into good and suitable conditions for them - in a damp, warm, dry and wind-blown place, which happens infrequently. Only in this case, the dispute will turn out plants.
In favorable conditions, small plants, like small hearts (gametophytes), develop from spores, on which male and female cells appear later (they are also called genitals).
Gametophytes have small thin rootlets, with which they hook on the soil, where they develop. This is the genital fern generation. The male organs are called antheridia, and the female cells are called archegonia.
Spermatozoa can move exclusively in the aquatic environment, on land they quickly die, so fertilization is possible only in the case of high humidity. The sprout has such a form that accumulates water falling on it from the outside - dew or rainwater. Spermatozoa move along it.
If fertilization did occur, a new cell called a zygote appears, and a sporophyte begins to develop from it. The sporophyte is the germ of the asexual generation of ferns.
The sporophyte has a leg, with which it receives nutrients. And only then, as it develops, the first leaf appears, from which the growth of the new fern begins.
Since fertilization and further development will not occur without water, it can be said that despite the fact that the life cycle of ferns passes all its stages on the surface of the earth, these plants are not completely removed from the habitat in which life originally originated water.
Schematically, the life cycle of a fern can be represented as follows:
- adult fern, capable of breeding,
- the presence of spores on the inside of a fern leaf,
- full maturation of the bags with spores, after which the spores fall out and fly away,
- in the event of a dispute in the necessary and suitable conditions for life, it is fixed in place and germinates,
- a small appendix is formed from the spores, which is attached to the place of growth by the roots-threads (such threads are called rhizoids),
- female and male reproductive cells appear on the appendix, while the female reproductive organs contain an egg cell, and the male reproductive organs contain sperm cells,
- on water formed on germ processes as a result of both dew and rain, sperm move to the ovum,
- sperms get inside the egg and fertilize it,
- in such an egg cell (it is called a zygote), a young leaf (sporophyte) is born and emerges from it,
- From this young leaf, a new fern appears, on which later on spores will ripen for later reproduction.
How to propagate the fern spores
The fern is a very interesting and original plant, so there is nothing surprising in the fact that it is being tried to propagate at home.
Dispute propagation is a rather complicated process, and mastering it is not so easy. Therefore, most often flower growers simply divide the fern bush into several parts with rhizomes and buds, and sit in suitable shady areas of their garden.
But not all ferns reproduce vegetatively. Some species of these plants have only one growth point, and no additional buds are formed on them.
For reproduction of this type of fern, it is necessary to germinate spores; to multiply it in another way simply will not work. After spore germination, the life cycle of a fern will be completed completely, and a new plant will be obtained from it.
The fern spore is germinated as follows:
- when they see that brownish bulges have formed on the leaf of an adult fern (these are bags with spores), they cut off this leaf and put it in a bag. The package should be paper, not cellophane,
- A package with a sheet for a day is placed in some warm place. at the same time the package should be shaken periodically,
- after the spores have matured and have fallen out, they need to be pulled out of the bag and poured onto a prepared nutrient mixture, which consists of peat, sand, coal and crushed greens,
- the container with the mixture, in which the pores will sprout, is placed in a moist and warm place (at least 25 degrees), periodically sprinkling onto the surface with warm water from a spray bottle and in no case allowing it to dry out. For better effect and less evaporation, the container with spores can be covered with glass.
After the first sprouts have appeared, it is necessary to monitor the irrigation even more closely, since the humidity at this time is a necessary component of the development of the plant. Fertilization will not occur without water, and all the work will go down the drain. And to grow a fern out of controversy is really work.
When a new young fern appears, the life cycle begins again, including the sexual and asexual generation.
At the same time, the sexual generation is the smallest process that is formed from spores and lives for very short periods. But the young fern that emerged from it, which grows for many years (some species live to 100 years) - this is exactly the strongest asexual generation.
However, a strong asexual generation is impossible to obtain, bypassing the stage of sexual reproduction.
Fern is an unusual plant. A great many beautiful legends are associated with its appearance. According to one of them, the plant originated from the goddess of love - Venus, who once dropped her hair, from which the fern grew.
The most famous legend is the legend of fern flowering. It says that if on the night of Ivan Kupala you see a flower of a plant, a mystery will be revealed to the person how to find the treasure. However, when studying it, it becomes clear that the legend cannot be translated into reality, since the life cycle of a fern does not have a flowering stage.
Higher and lower groups of plants
Plants are divided into higher and lower groups. They differ in their habitat. Higher plants "came out" on land and spend their life cycle on earth. These plants include ferns. In terrestrial plants there is a clear separation of the root, stem and leaf.
However, it cannot be said unequivocally that ferns have completely moved away from aquatic habitats, since the free-living gametophyte participates in their reproduction process and the spermatozoa necessary for the fertilization process can exist only in the aquatic environment.
Representatives of the fern squad spread throughout the world. They have a different appearance of leaves, ecologically unpretentious, while more like wet soil.
The fern has a root system, a stem and leaves. He has no seeds. On the inside of the sheet, below, are the spores in the sporangia sacs. Fern leaves are called "fronds", they do not look like the leaves of other plants. They look as if several branches were laid in one plane and attached to the stem. Their color can vary from light green to dark green.
The fern, not counting the root system, consists of a frond, a sorus, and an induction, where the sorus is a bundle of sporangia, and the induzia is a growth resembling an umbrella that closes the sorus.
The main stages of fern development
From the sporangia, when disputes ripen in them, they begin to fly out. The sporangia themselves are wonderfully adapted for this. When the disputes have ripened in them, the sporangia cracking in a special way, and often, even more and turn inside out. Disputes from this spill out and fly to the wind. The spores are very light and by air they can, like dust, fly away a considerable distance from the fern, from the frontier where they originated.
From the dispute, when they fall on wet soil, the next generation begins to form. Let us recall, alternately, the sexual generation should grow out of the dispute. It is completely unlike asexual. Remember the compliment that the old woman Shapoklyak gave the crocodile to Gena? She said: "It is good that you are green and flat." This is how one can characterize the sexual generation of the fern - a tiny green plate about the size of a claw, a little bit like a heart.
The main thing that this small, flat, green heart has is not on the upper side, but on the lower side. From the bottom of the gametophyte - this green flat heart - thin threads depart. These are not roots - these are rhizoids, those rhizoids that can be heard in algae or bryophytes. Have gametophyte (genital ferns), there are no real roots. It is attached to the soil by rhizoids - the same attachment organs that ancient plants had - its ancestors.
We will see here more important parts, for example, small sacs in which eggs must ripen, because before us is the sexual generation. We have to find where the sex cells are formed. So, eggs mature not far from the cutout, which makes our plate look like a heart. Near, but closer to the edge, there are other bags. In these bags, which go along the edge, ripen sperm. And here, it is clear why the gametophyte has such a structure and why it is so flat.
After the rain, the water flows under a thin plate and remains there for some time. A humid environment is formed in which the sperm from their sacs swim to the oocytes. So, we have a gametophyte. This gametophyte - bisexual, that is, it is hermaphroditic, and under it forms a moist environment in which the sperm cell crosses the ovum through this water film. This means that fertilization takes place and, where eggs have just been, zygotes are already being formed, that is, fertilized eggs, the first cells of a new future organism.
- A sporophyte, a new asexual generation, always grows out of zygotes, in alternation of generations. That closed the life cycle of a fern. After fertilization from zygotes, we can again go to a large fern - to the asexual generation, with which we started.
- Note that in bryophytes, the long-lived and relatively large, is the sexual generation, the gametophyte, and the mossy sporophyte is small and parasitic on the gametophyte. In ferns, the opposite is true: asexual generation is large and long-lived. And the sexual generation of ferns is tiny, small and dies quickly enough.
- We can say that ferns in the development of generations, unlike mosses, have relied on asexual generation. It is precisely this, as the scientists say, that which dominates, dominates, that is, long-lived and does not die off for a long time. And the sexual generation lives a very short life and, one might even say, it is necessary only to carry out fertilization.
Stages of the life cycle of a fern
For the emergence of a new young sprout requires several stages. The life cycle of a fern is a combination of all phases, starting from the birth of life and ending with the phase of maturity, when the plant is already able to give rise to a new life. The cycle is closed.
The stages of the life cycle of a fern are arranged in the following sequence:
- Gametophyte (outgrowth).
- Ovum, sperm.
- Young plant.
When all stages are completed, a young plant, having developed and strengthened, will be able to repeat this cycle for the birth of the next generation.
Бесполая и половая стадии в процессе размножения
Папоротник – результат бесполого поколения. Рассмотрим последовательность жизненного цикла папоротника.
Для того чтобы начать новую жизнь, у взрослого растения должны появиться на обратной стороне листа споровые мешочки, в которых будет проходить созревание спор. When the spores are ripe, the bag will burst and spores will fall out of it. Under the action of the wind, they will spread in different directions and will sprout on contact with favorable soil. This stage is very important, because without it the plant could not exist. As a result, an outgrowth will appear - the gametophyte - the sexual generation of a fern. His form is like a heart. This heart has thin threads below - rhizoids, which are attached to the soil. The seed of a fern is oboepoly, with small sacs located on it: in some eggs, in others, spermatozoa. Fertilization takes place with the help of water.
Since the seedlings are very small and have such a peculiar shape, this contributes to the slow drainage of rainwater and its retention below. Due to this, spermatozoa can swim up to the eggs and fertilize them. As a result, a new cell appears - a zygote, from which the sporophyte embryo is formed - the result of a new asexual generation. This embryo consists of haustoria, which by its appearance resembles a leg growing into the outgrowth, and at first consumes from it the substances necessary for its growth. After some time, the first leaf of the embryo appears, which is the beginning of the development of the fern.
Thus, in the life cycle of a fern, asexual generation prevails, which gives life to a new large and long-lived plant, and the sexual generation is small and quickly dying off. However, it is necessary for fertilization.
Schematically presented life cycle
At its reproduction, the plant goes through several stages. For clarity and better memorization, a schematic accompaniment of this issue is recommended. Consider the existing life cycle of a fern, the scheme of which is presented below:
1. Adult plant that can give new life.
2. On the leaves of the fern spores appear.
3. Mature bags of spores.
4. The bag burst, disputes fall out.
5. In the favorable soil of the dispute is strengthened and germinates.
6. An embryo is formed, which is attached to the ground with the help of strands-rhizoid.
7. On the embryo there are female and male cells: archegonia and antheridia:
- The female genital organs contain an egg.
- Male genitals contain sperm.
- Fertilization is possible only in a drop of rain.
- Spermatozoa swim up to the eggs and penetrate, fertilization occurs.
8. A fertilized egg zygote appears. A sporophyte is formed from a zygote - a young leaf.
9. Begins its development of a new young plant.
The diagram clearly shows the closed life cycle.
The role of ferns in human life is not too great. Various forms of nephrolepis are common indoor ornamental plants. The fronds of some of the shield workers are widely used as the green component of floristic compositions. Trunks of tree ferns are used as building material in the tropics, and in Hawaii their starchy core is eaten.