Today we will look at the structure of the fern, its development cycle and talk about the diversity of the fern division. To understand in detail the life cycle of a fern, it is necessary to remember the structure of its main organs.
The underground part of the fern is represented by the rhizome. Roots extend from the rhizome. The aerial parts are represented by special leaves. It must be said that this plant has leaves that are not quite familiar to us. From the ordinary leaves of all plants that we can see outside the window, those plants that are flowering, fern leaves differ in some significant details:
- A fern leaf grows indefinitely.
- On the underside of the leaves there are spores in sporangial sacs.
On leaves familiar to us, for example, poplar, maple, some herbaceous plants like plantain, all flowering plants, we will never see any sporangia with spores on the lower part of the leaves. Therefore, before us, as they rightly believe scientists, not really leaves. Before us are special formations that are something between a branch and a leaf. Ferns are ancient plants. Their parts are not yet as perfect as those of flowering plants we are accustomed to.
The leaves of a fern are called fronds, which is why they get their special name because they are not exactly the same leaves as those of flowering plants. From the bottom of the frond and sporangia with spores are located. These sporangia look like a kind of small chandelier. The spore balls on thin stalks actually look like a ceiling light.
In addition, a special outgrowth serves for protection, which, just in case, like an umbrella, covers this bundle of sporangia. A bundle of sporangia is called a sorus, and an umbrella-shaped outgrowth that protects the sorus - a bundle of sporangia - is called indusia. If we see sporangia, it means that in the alternation of generations we have an asexual generation - a sporophyte. In gametophytes (the sexual generation), we would not see any sporangia.
It's time to move on to the fern development cycle
The main stages of fern development
From the sporangia, when spores mature in them, they begin to fly out. The sporangia themselves are surprisingly adapted for this. When the spores in them have already matured, the sporangia crack in a special way, and often even turn outward. This causes spores to spill out and fly in the wind. The spores are very light and they can fly through the air, like dust, to a considerable distance from the fern, from the frond where they formed.
The spores, when they fall on moist soil, begin to form the next generation. Let us remember that by alternation, the sexual generation should grow from the spores. It doesn't look asexual at all. Remember the compliment that old woman Shapoklyak gave the crocodile Gena? She said, "It's good that you're green and flat." This is how the sexual generation of a fern can be characterized - a tiny green plate about the size of a marigold, a little like a heart.
The main thing this small, flat, green heart has is not on the top side, but on the bottom. Thin threads extend from the underside of the gametophyte - this green flat heart. These are not roots - these are rhizoids, the same rhizoids that you hear about in algae or bryophytes. In the gametophyte ( sexual generation of ferns), there are no real roots. It is attached to the soil by rhizoids - the same attachment organs that were present in ancient plants - its ancestors.
We will also see here more important parts, for example, small sacs in which eggs must mature, because we are faced with the sexual generation. We must find where sex cells are formed here. So, eggs mature not far from the cutout that makes our record look like a heart. Nearby, but closer to the edge, there are other bags. Sperm mature in these sacs that run along the edge. And here, it’s clear why the gametophyte has such a structure and why it is so flat.
After rain, water flows under the thin plate and remains there for some time. A moist environment is formed in which sperm from their sacs swim to the eggs. So, we have a gametophyte. This gametophyte - bisexual, that is, it is hermaphroditic, and a moist environment is formed under it, in which the sperm swims through this film of water to the egg. This means that fertilization occurs and where there were just eggs, zygotes are already formed, that is, fertilized eggs, the first cells of a new future organism.
There are two stages in the life cycle of plants: sporophyte and gametophyte:
- quickly fit does disputes(by meiosis);
- the spore grows into a gametophyte (prothallus*);
- gameto fit does** gametes(by mitosis);
- After fertilization, a zygote is obtained, from which the sporophyte grows.
The zygote and sporophyte are diploid (2n). All others are haploid (spores, gametophyte and gametes - n).
Tasks
Select two cells in which the chromosome set is diploid. Write down the numbers under which they are indicated.
1) Cells of the fern prothallus
2) Moss capsule cells
3) Rye sperm
4) Horsetail spores
5) Linden cambium cells
Answer
1. Establish the sequence of stages of fern development, starting from the moment of spore germination. Write down the corresponding sequence of numbers.
4) development of a shoot with adventitious roots from the zygote
5) formation of a perennial plant (sporophyte)
Answer
2. Establish the sequence of stages of fern development, starting with spore germination. Write down the corresponding sequence of numbers.
1) formation of gametes
2) fertilization and formation of a zygote
3) development of an adult plant (sporophyte)
4) formation of a prothallus
Answer
3. Establish the correct sequence of the fern life cycle, starting with an adult plant. Write down the corresponding sequence of numbers.
1) Sporophyte
2) Outgrowth
3) Disputes
4) Zygote
5) Gametes
Answer
4. Determine the sequence of stages of fern development, starting with fertilization. Write down the numbers under which they are indicated.
1) development of the prothallus
2) fertilization
3) sporophyte development
4) formation of archegonia and antheridia
5) formation of sporangia
6) germination of spores
Answer
5. Establish the sequence of stages in the fern life cycle, starting with the formation of an adult plant. Write down the corresponding sequence of numbers.
1) formation of boxes on fronds
2) maturation of gametes
3) development of the prothallus
4) formation of a zygote
5) sporophyte formation
Answer
1. Establish the correct sequence in the changing stages in the moss development cycle, starting with the formation of spores. Write down the corresponding sequence of numbers.
1) sporophyte formation
2) formation of a green thread (protonema)
3) formation of an adult gametophyte
4) formation of dispute
5) fertilization
Answer
2. Establish the sequence of stages in the life cycle of sphagnum moss, starting with fertilization. Write down the corresponding sequence of numbers.
1) fertilization
2) development of a leafy plant
3) development of a pedunculated capsule
4) development of reproductive organs and gametes
5) development of disputes
6) germination of protonema
Answer
3. Establish the sequence of stages in the life cycle of green moss, starting with spore germination. Write down the corresponding sequence of numbers.
1) development of a leafy plant
2) maturation of spores in sporangia
3) spore germination and protonema formation
4) gamete formation and fertilization
5) formation of a young sporophyte from a zygote
Answer
4. Determine the sequence of processes occurring in the life cycle of the cuckoo flax moss, starting with the result of the fusion of gametes. Write down the corresponding sequence of numbers.
1) formation of protonema
2) formation of gametes
3) cell division of sporangium by meiosis
4) sporophyte development
5) formation of a zygote
Answer
Establish the sequence of stages of horsetail development, starting from the moment of spore germination. Write down the corresponding sequence of numbers.
1) fertilization on the germ
2) formation of gametes on the gametophyte
3) spore germination and germ formation
4) zygote mitosis and seedling development
5) formation of vegetative organs and a spore-bearing spikelet on the sporophyte
Answer
Establish a correspondence between the stage of development of the cuckoo flax moss and its ploidy: 1) Haploid, 2) Diploid. Write numbers 1 and 2 in the correct order.
A) Dispute
B) Protonema (green thread)
B) Leafy plant
D) Box
D) Gametes
E) Zygote
Answer
Establish the sequence of processes in the horsetail development cycle, starting with fertilization
1) development of an adult plant (sporophyte)
2) development of the prothallus
3) spore maturation
4) formation of male and female gametes
5) formation of a zygote
Answer
1. Choose three options. The process of fertilization in flowering plants is characterized by
1) flower formation
2) fusion of sperm with the central cell
3) formation of pollen grains
4) fusion of sperm and egg
5) formation of a zygote in the embryo sac
6) division of the zygote by meiosis
Answer
2. Select three options. How is fertilization characterized in angiosperms?
1) fusion of the nuclei of female and male gametes occurs
2) the egg is surrounded by a large number of sperm
3) the haploid nucleus of the gamete merges with the diploid central cell
4) mobile male gametes are involved in the process
5) the process can occur outside the body
6) occurs in the embryo sac of an adult organism
Answer
3. Choose three correct answers out of six and write down the numbers under which they are indicated. During the process of double fertilization in flowering plants,
1) formation of stamens
2) fusion of sperm and central nucleus
3) formation of pollen grains
4) fusion of sperm and egg
5) formation of a zygote
6) fetal formation
Answer
Establish a correspondence between the type of cell and the method of its formation: 1) mitosis, 2) meiosis. Write numbers 1 and 2 in the correct order.
A) moss spore
B) moss sperm
B) monkey sperm
D) sunflower egg
D) poppy microspores
E) fern archegonium cell
Answer
Establish a correspondence between the stage of fern development and its ploidy: 1) haploid, 2) diploid. Write numbers 1 and 2 in the correct order.
A) dispute
B) outgrowth
B) mature sporophyte
D) young sporophyte
D) gamete
Answer
Select the haploid stages of fern development. Identify two organisms that have a haploid set, and write down the numbers under which they are indicated.
1) sperm
2) sporangium
3) leaves
4) dispute
5) zygote
Answer
FLORAL
1. What chromosome set is characteristic of the cells of the seed embryo, seed endosperm, and barley leaves? Write down three numbers in the order specified in the task, without separators (spaces, commas, etc.).
Answer
2. What chromosome set is characteristic of the endosperm cells of seeds, the egg and the root of a flowering plant? Write down three numbers in the order specified in the task, without separators (spaces, commas, etc.).
Answer
3. What chromosome set is characteristic of the endosperm cells of the seed, sperm and cherry leaves? Write down three numbers in the order specified in the task, without separators (spaces, commas, etc.).
Answer
What chromosome set is characteristic of the vegetative, generative cells and sperm cells of the pollen grain of a flowering plant? Write down three numbers in the order specified in the task, without separators (spaces, commas, etc.).
Answer
What chromosome set is characteristic of pine pollen grain and sperm cells? Write two numbers in the order specified in the task, without separators (spaces, commas, etc.).
Answer
FERNES
What chromosome set is characteristic of fern spores and germ cells? Write two numbers in the order specified in the task, without separators (spaces, commas, etc.).
Answer
What chromosome set is characteristic of sporophyte cells and fern prothallus cells? Write two numbers in the order specified in the task, without separators (spaces, commas, etc.).
Answer
Horsetails, mosses
What chromosome set is characteristic of gametes (egg and sperm) and spores of horsetail? Write two numbers in the order specified in the task, without separators (spaces, commas, etc.).
Answer
MHI
1. What is the chromosome set in the cells of an adult plant and the spores of cuckoo flax? Write two numbers in the order specified in the task, without separators (spaces, commas, etc.).
Answer
2. What chromosome set is characteristic of the cells of an adult plant and sphagnum spores? Write two numbers in the order specified in the task, without separators (spaces, commas, etc.).
Answer
SEAWEED
In Chlamydomonas, the predominant generation is the gametophyte. Determine the chromosome set of Chlamydomonas spores and gametes. Write two numbers in the order specified in the task, without separators (spaces, commas, etc.).
Answer
In the green alga Ulothrix, the predominant generation is the gametophyte. What chromosome set do the cells of an adult organism and a sporophyte have? Write two numbers in the order specified in the task, without separators (spaces, commas, etc.).
Answer
ONE NUMBER
What chromosome set is characteristic of a macrospore, from which the eight-nucleate embryo sac and egg cell of a flowering plant are subsequently formed? In response, write down only the number.
Answer
There are 24 chromosomes in the somatic cell of a sporophyte of a flowering plant. How many chromosomes are there in a microspore of this plant? Write down only the number in your answer.
Answer
It is known that double fertilization occurs in angiosperms. One sperm fertilizes the egg, from which the embryo then develops, and the second sperm fertilizes the central cell, from which the triploid endosperm then develops. Using this information, select three statements from the text below that describe these characteristics of this organism. Write down the numbers under which they are indicated.
1) As a result of the first fertilization, a zygote is formed.
2) During the process of reproduction, the cell divides in half.
3) The offspring retains all the hereditary characteristics of the parent.
4) The central cell is diploid.
5) The embryo develops from a diploid zygote.
6) Parts of the plant participate in reproduction.
Answer
Select cells in which the set of chromosomes is haploid. Identify three true statements and write down the numbers under which they are indicated.
1) fern prothallus cells
2) moss capsule cells
3) linden cambium cells
4) rye sperm
5) wheat endosperm cells
6) horsetail spores
Answer
Consider the diagram of the ontogeny of leafy moss. Identify two stages of ontogenesis with a diploid set of chromosomes and write down the numbers under which they are indicated.
Answer
All but two of the terms below are used to describe the process of double fertilization in flowering plants shown in the figure. Identify two terms that “drop out” from the general list and write down the numbers under which they are indicated.
1) the pollen tube reaches the embryo sac
2) a vegetative cell and sperm participate in fertilization
3) micro and macrospores are formed from the mother cells of the spores
4) gametes - sperm and eggs - are formed as a result of meiosis of microspores
5) the egg is fertilized by one sperm, and the other sperm fertilizes the central cell.
Answer
Choose one, the most correct option. Sperm in plants are formed as a result of
1) mitosis
2) fertilization
3) meiosis
4) growth
Answer
Establish the sequence of plant development, starting with the spore. Write down the corresponding sequence of numbers.
1) gametophyte
2) fertilization
3) dispute
4) zygote
5) gametogenesis
6) sporophyte
Answer
Choose one, the most correct option. Which cell can form a pollen tube after pollination of flowering plants?
1) vegetative
2) central
3) generative
4) secondary
Answer
Establish a correspondence between the processes in life cycles and plant divisions: 1) Angiosperms, 2) Bryophytes. Write numbers 1 and 2 in the order corresponding to the letters.
A) participation of water in fertilization
B) formation of sporogon on the gametophyte
B) formation of megaspores in the ovule
D) formation of protonema
D) mitosis of the generative cell of the pollen grain
E) double fertilization
Answer
© D.V. Pozdnyakov, 2009-2019
I have always considered ferns to be very interesting plants, and in all the shady corners of my garden these oldest inhabitants of our planet, who appeared on Earth many centuries ago, grow.
The Far East and Northern China are considered the birthplace of all fern-like plants. But the most interesting thing about this plant is the process of its reproduction, which is called the life cycle of development.
In ancient times, huge tree ferns grew. Today there are very few such species left in nature; ferns have become shorter, more graceful, miniature and have practically turned into indoor and garden flowers. In nature, ferns reach two meters in height.
These unpretentious plants amaze with their beauty and diversity, and are often used in landscape design.
Ferns are also called bracken ferns because their wide, carved leaves resemble eagle wings.
At the same time, fern has many beneficial properties; it contains protein, is easily digestible and tones the body when consumed. Fern also has a beneficial effect on the nervous system.
In order to figure out what kind of plant it is, it is necessary to find out how it develops.
The fern grows very interestingly: its carved leaves stick out straight from the ground, without a stem or trunk (these leaves are called fronds), at first they resemble a snail in a shell, then, as they grow, they unfold and resemble ordinary hooks until they open completely .
There are no flowers on ferns, contrary to beautiful legends, and this plant reproduces with the help of spores.
Fern development stages
The life cycle of a fern is all the stages, phases and stages that the plant goes through, starting from its appearance and the birth of the first leaf, and ending with the appearance of a new specimen ready for reproduction. Such a cycle is closed and is divided into two types or types. Reproduction of ferns occurs:
- sexual;
- and asexual.
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 precisely the generation that has developed asexually. This generation is called sporophyte.
For the birth of a young fern, spores must appear on the back side of the leaves of the mother (or father, as you like) plant, which will begin to develop there. This is perhaps the most important phase of the fern's life cycle, because without it, no development will simply occur.
These spores are in a kind of “bag”, which will burst after ripening, as a result of which the spores will simply fly away in different directions. Life will be given only to those of them that find themselves in good and suitable conditions for them - in a moist, warm, dry and wind-free place, which does not happen often. Only in this case will the spores produce plants.
Under favorable conditions, small plant-like shoots develop from the spores, resembling small hearts (gametophytes), on which a little later male and female cells will appear (they are also called genitals).
Gametophytes have small thin roots-threads, with which they cling to the soil, where they develop. This is the sexual generation of the fern. Male organs are called antheridia, and female cells are called archegonia.
Spermatozoa can move exclusively in an aquatic environment; on land they quickly die, therefore fertilization is possible only in cases of high humidity. The sprout has a shape in which water falling on it from the outside - dew or rainwater - accumulates. Sperm move along it.
If fertilization does occur, a new cell called a “zygote” appears, and a sporophyte begins to develop from it. A sporophyte is the embryo of an asexual generation of ferns.
The sporophyte has a stalk with which it receives nutrients. And only then, as it develops, the first leaf appears, from which the growth of a new fern begins.
Since fertilization and further development will not occur without water, we can say that despite the fact that the life cycle of ferns takes place all its stages on the surface of the earth, these plants still have not completely moved away from the habitat in which life originally arose - water.
The life cycle of a fern can be schematically represented as follows:
- adult fern capable of reproduction;
- the presence of spores on the inside of a fern leaf;
- complete maturation of the spore sacs, after which the spores fall out and scatter;
- if the spore finds itself in the necessary and suitable conditions for life, it is fixed in place and germinates;
- a small shoot is formed from the spore, which is attached to the place of growth by root-threads (such threads are called rhizoids);
- female and male reproductive cells appear on the process, while the female genital organs contain an egg, and the male genitals contain sperm;
- through the water formed on the embryonic shoots as a result of either dew or just rain, sperm move to the egg;
- sperm enter the egg and fertilize it;
- in such an egg (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 spores will subsequently mature for subsequent reproduction.
How to propagate fern by spores
Fern is a very interesting and unique plant, so it is not surprising that people are trying to propagate it at home.
Reproduction by spores is a rather complex process, and it is not so easy to master. Therefore, most often, gardeners simply divide the fern bush into several parts with rhizomes and buds, and plant them in suitable shady places in their garden.
But not all ferns reproduce vegetatively. Some species of these plants have only one growing point, and no additional buds are formed on them.
To propagate this type of fern, you should germinate spores; there is simply no other way to propagate it. It is after the spore germinates that the life cycle of the fern will be completed completely, and a new plant will emerge from it.
Fern spores are germinated as follows:
- seeing that brownish bulges have formed on the leaf of an adult fern (these are sacs with spores), such a leaf is cut off and placed in a bag. The bag should be paper, not cellophane;
- The bag with the leaf is placed in some warm place for a day. in this case, the package must be shaken periodically;
- after the spores have matured and fallen out, they need to be taken out of the bag and poured onto a nutrient mixture prepared in advance, which consists of peat, sand, coal and chopped herbs;
- The container with the mixture in which the pores will grow is placed in a damp and warm place (at least 25 degrees), periodically spraying the surface with warm water from a spray bottle and under no circumstances allowing it to dry out. For better effect and less evaporation, containers with spores can be covered with glass.
After the first sprouts have appeared, watering must be monitored even more carefully, since humidity at this time is a necessary component of plant development. Without water, fertilization will not occur, and all work will go down the drain. But growing a fern from a spore is really hard work.
When a new young fern appears, the life cycle begins again, including sexual and asexual generations.
At the same time, the sexual generation is the same small process that is formed from spores and lives for a very short time. But the young fern that emerges from it, which grows for many years (some species live up to 100 years), is just that very strong asexual generation.
However, a strong asexual generation cannot be obtained without skipping the stage of sexual reproduction.
Ferns appeared on Earth many years ago. In ancient times, forests of tree ferns could be found. Today there are very few such large plants left. Ferns have become more decorative and indoor. They are beautiful and unpretentious, they can be used for landscape design. Plants are durable and interesting.
Legends about fern
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 shed her hair, from which the fern grew.
The most famous legend is the legend of the flowering fern. It says that if you see Ivan Kupala on the night of Ivan Kupala, a secret will be revealed to a person, how to find treasures. However, when studying it, it becomes clear that the legend cannot be translated into reality, since the life cycle of the fern does not have a flowering stage.
Higher and lower groups of plants
Plants are divided into higher and lower groups. They differ from each other in their habitat. Higher plants “came” to land and spend their life cycle on the ground. These plants include ferns. Earthly plants have a clear division into roots, stems and leaves.
However, it cannot be said unequivocally that ferns have completely moved away from the aquatic habitat, since a free-living gametophyte is involved in their reproduction process and the spermatozoa necessary for the fertilization process can only exist in an aquatic environment.
Appearance
Representatives of the order of ferns have spread throughout the world. They have a different appearance and are environmentally unpretentious, but they prefer moist soils.
A fern has a root system, stem and leaves. It has no seeds. On the inside of the leaf, at the bottom, there are spores in sacs called sporangia. Fern leaves are called fronds and are not like the leaves of other plants. They look as if several branches were placed 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, sorus and indusia, where the sorus is a bunch of sporangia, the indusia is an outgrowth resembling an umbrella that covers the sorus.
Life cycle of higher plants
Existing on Earth, each plant goes its own way. fern - movement from the origin of life to the full maturation of the plant, capable of giving new life. The cycle consists of two phases: asexual and sexual. These phases determine the sequence of generations, one occurs with the help of gametes - sexual, the second - with the help of spores - asexual.
By merging, the gametes form a diploid zygote, which gives rise to a new generation, asexual. In the asexual generation, reproduction occurs with the help of spores. Haploid spores give rise to the sexual generation. One generation always predominates over the other and makes up the majority of the plant's life cycle.
Stages of the Fern Life Cycle
Several stages are required for the appearance of a new young sprout. The life cycle of a fern is the totality of all phases, starting from the origin of life and ending with the maturity phase, when the plant is already capable of giving rise to a new life. The cycle is closed.
The stages of the fern life cycle are arranged in the following sequence:
- Spore.
- Gametophyte (thallus).
- Eggs, sperm.
- Zygote.
- Embryo.
- Young plant.
When all the stages are completed, having developed and strengthened, it will be able to repeat this cycle for the birth of the next generation.
Asexual and sexual stages in the process of reproduction
The fern is the result of an asexual generation. Consider the sequence of the fern life cycle.
In order to start a new life, an adult plant must have spore sacs on the back of the leaf, in which the spores will mature. When the spores are ripe, the sac will burst and spores will fall out onto the ground. Under the influence of the wind, they will spread in different directions and when they fall on favorable soil they will germinate. This stage is very important, because without it the plant would not be able to exist. As a result, a shoot will appear - a gametophyte - the sexual generation of the fern. Its shape is similar to a heart. This heart has thin threads at the bottom - rhizoids, with which it is attached to the soil. The fern prothallus is bisexual, with small sacs located on it: in some, eggs mature, in others, sperm. Fertilization occurs with the help of water.
Since the outgrowth is very small and has such a unique shape, this contributes to the slow flow of rainwater and its retention below. Thanks to this, sperm can swim to the eggs and fertilize them. As a result, a new cell appears - a zygote, from which a sporophyte embryo is formed - the result of a new asexual generation. This embryo consists of a haustorium, which in appearance resembles a stalk growing into the prothallus, and at first consumes from it the substances necessary for its growth. After some time, the first leaf of the embryo appears, which serves as the beginning of the development of the fern.
Thus, in the life cycle of a fern, the asexual generation predominates, which gives birth to a new large and long-lived plant, and the sexual generation is small and quickly dies. However, it is necessary for fertilization.
Fern propagation at home
Ferns are interesting and original plants. Therefore, they are often bred at home. In order for the fern's life cycle to complete and a new young plant to emerge, it is necessary to germinate the spore. A leaf of an adult fern, on which sacs with spores have appeared - brown tubercles, is cut off and placed in a paper bag. This package is kept for one day in a warm place, shaking occasionally.
While the spores ripen and fall out, a mixture is prepared for planting. They take a steamed mixture of peat, herbs, sand, and also add crushed charcoal, all this is taken in equal proportions. The prepared mixture is placed in shallow pots, pressed down and moistened.
Ripe and fallen spores are taken out of the bag and poured onto the prepared surface. Favorable conditions are created for their germination:
- Temperature: optimal 25 degrees Celsius.
- Maintains high humidity.
- Cover the pots with glass.
Water the pots with a spray bottle. When a seedling appears, special attention is paid to watering, since subsequent development of the plant is possible only in the presence of an aqueous environment in which fertilization of the egg will occur.
As soon as the first leaves appear, remove the glass. Then they are given a little time to adapt to the environment and dive into the ditches. When the leaves begin to grow a little, they are first kept in cold greenhouses and then planted in separate pots. In this way, new young plants are obtained, ready to grow and develop further.
Schematically represented life cycle
It 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 diagram of which is presented below:
1. An adult plant that can give new life.
2. Spores appear on fern leaves.
3. Spore sacs mature.
4. The sac bursts and the spores fall out.
5. In favorable soil, the spore strengthens and germinates.
6. A prothallus is formed, which is attached to the ground with the help of rhizoid threads.
7. The embryo contains female and male cells: archegonia and antheridia:
- The female genital organs contain an egg.
- The male genital organs contain sperm.
- Fertilization is possible only in a drop of rain.
- Sperm swim up to the eggs and penetrate inside, fertilization occurs.
8. A fertilized egg appears - a zygote. From the zygote a sporophyte is formed - a young leaf.
9. A new young plant begins to develop.
The diagram clearly shows the closed life cycle.
Economic importance
The role of ferns in human life is not too great. Various forms of nephrolepis are common indoor ornamental plants. The fronds of some shield plants are widely used as a green component of floral compositions. The trunks of tree ferns serve as building material in the tropics, and in Hawaii their starchy pith is used as food.
Conclusion
So, we studied the life cycle of this plant. You became aware, for example, at what stage of the life cycle of ferns the embryo appears. It is impossible for them to reproduce without water. They have spread throughout the world, choosing places with high humidity to live.
In total there are about 10 thousand varieties of ferns. They can be medicinal, decorative, or indoor.
When a new young plant is born, a life cycle begins, which includes sexual and asexual generations. The sexual generation is a seedling, it is very small and does not live long, and the young, strong, long-lived plant that appears is an asexual generation. The sporophyte phase predominates in the fern life cycle.
Thus, the main generation of fern is asexual, and it is impossible to reproduce without going through the sexual generation.
