Date__________
Class__________
Subject: Structure, reproduction and development of horsetails. The significance of horsetails in nature and human life.
Tasks: 1. To develop knowledge about the structural features and vital functions of horsetails.
2. Develop the concept of the diversity of the plant world using the example of horsetails.
3. Foster elements of environmental culture.
Lesson type: Combined
Equipment: interactive whiteboard
Lesson progress
1. org moment
2. Checking homework a) Frontal conversation with the class
The structure of the club moss.
List the extinct lycophytes (Lepidodendra, Sigillaria, Leuromea, Osteroxylon).
Describe modern lycophytes.
Why do lycophytes reproduce primarily vegetatively?
What groups are lycophytes divided into? Describe them, name their representatives (equisporous - club moss, heterosporous - selyaginella).
The value of lycophytes (decorative, medicinal, pyrotechnics, production of resins, plastics, education coal).
B) Cards: application
C) working with concepts
Define:
Sorus is a collection of sporangia.
A sporophyte is a plant that reproduces asexually.
Gametophyte is a plant that reproduces sexually.
Sporangia - organs asexual reproduction sporophyte.
Gametangia are the organs of sexual reproduction of the gametophyte.
A spore is a cell of asexual reproduction.
Gamete is a cell of sexual reproduction.
3. new topic:
In science, horsetails are called segmented because of the structure of the stem.
Appendix the structure of horsetail
Filling out the table
Compare external structure Horsetail and Moss clubmoss, enter the data in the table.
Table.
Questions
Horsetail
Moss clubmoss
Division of the body into organs
Types of shoots
Stem branching
6.) Conclusion: What is the difference between the external structure of Moss clubmoss and Horsetail?
Like the lycophytes, the ancient horsetails were represented by trees (calamites) or shrubs (cluneifolia). Modern species are exclusively herbaceous plants, represented by one genus - horsetail, and about 25 plant species.
Habitat: terrestrial. The body consists of a rhizome, the shoot is articulated, consisting of nodes and internodes. The nodes contain lateral branches and brown scaly leaves. Shoots of horsetails are spore-bearing (formed in spring) and bear sporangia at the tops, collected in strobili, brown in color; vegetative shoots are formed in summer, green, photosynthesis occurs in the stems.
Reproduction – sexual or asexual. Gametophytes of horsetails are green plates that live independently. The dominant generation is a sporophyte.
Horsetails are homosporous plants; spores are spread by the wind. They carry two springs - elaters, which interlock with each other.
Working with the textbook
Representatives: Horsetail - the most common type,Large horsetail – the largest, listed in the Red Book, found in the Carpathians,Horsetail , Horsetail , Horsetail .
Horsetail meaning:
Formation of coal
Silica stems are used for grinding metal and wood.
Horsetail is an indicator of acidic soils.
Horsetail is a medicinal plant.
Weeds.
Horsetail propagation
application
4. fastening:
Work in an individual notebook
5
. Summing up the lesson.
Today in the lesson we got acquainted with the features of horsetails using the example of Horsetail and compared it with the clubmoss club-shaped from the section Lycophytes.
What questions do you have?
6.
Homework.
Read §____ page ____
Work in the dictionary (intercalary growth, node, internode).
Lesson No. 36 (botany) 6th grade
Structure, reproduction and development of horsetails. The significance of horsetails in nature and human life.
Tasks: To develop knowledge about the structural features, reproduction and significance of horsetails. To form concepts about the complexity and development of plants.
LESSON PROGRESS:
1.Survey on the previous topic (in writing):
Performing a test followed by mutual verification. After testing, students grade using the proposed grading criteria.
1. The following does not belong to ferns: A) horsetail B) clubmoss C) sphagnum
2. Ferns include: A) cuckoo flax B) clubmoss C) riccia
3. The following features are characteristic of ferns:
A) presence of stem, leaves and root B) presence of stem and leaves C) presence of rhizoids and thallus
4. Vaii are called: A) shoots of ferns B) rhizomes of ferns C) dissected leaves of ferns
5. What develops in sporangia in ferns: A) seeds B) pollen C) spores
6. Water is necessary for ferns for: A) movement B) reproduction C) respiration
7. In what conditions do ferns grow: A) in damp and shady places B) in dry and sunny places C) in cold and damp places
8. Mosses, mosses, horsetails and ferns have similarities:
A) In conditions of reproduction. For sexual reproduction, the presence of water is necessary B) In the structure of the body. The body consists of roots, stems and leaves B) The presence of root-like structures. There are rhizoids D) In the methods of reproduction. Reproduce by seeds
9. The gametophyte of a fern is called: A) Prothallus B) Seedling C) Zygote D) Embryo
10.B life cycle fern predominates: A) Sporophyte B) Gametophyte
Test answers:
1 - B 4 - B 7 - A 10 - A
2 - B 5 - B 8 - A
3 - A 6 - B 9 - A “5” -10 correct answers; “4” - 9-8 correct answers; “3” -7-6 correct answers.
2. Learning new material:
(slide 1,2,3 presentation)
In modern flora There are just over 30 species of horsetails. All of them are perennial spore-bearing herbaceous plants that have a thin rhizome with nodules in which nutrients are deposited. The above-ground part of the stem reaches 0.5-1 m or more. A characteristic feature of horsetails is the division of the body into nodes and internodes. Horsetails have no leaves; they look like denticles, which, fused at the base, form a sheath covering the node. The leaves look like heavily modified lateral branches. Photosynthesis in horsetails occurs in the stem. The stem is ribbed and impregnated with silica. The stem has many cavities, some of them filled with air, others with water. This structure is determined by the habitats of horsetails: meadows, swamps, banks of reservoirs. . The underground stem (rhizome) is located at different depths. There are horizontal and vertical rhizomes. Horizontal rhizomes are thicker, with longer internodes than vertical ones. Tubers are formed on the rhizomes - a thickened and modified internode of the branch. The tuber cells are very large and filled with starch grains.
Reproduction and development of horsetails
(slide 4.5 of the presentation)
In spring, shoots grow on the rhizomes, at the tops of which there are spore-bearing spikelets. Spikelets contain sporangia in which spores are formed. After the sporangium opens, the spores spill out and are carried by the wind. From the spores, gametophytes (thallusts) develop in the form of plates with a diameter of several mm to 3 cm. On the underside of the gametophyte, colorless rhizoids up to 1 cm long appear, with the help of which it attaches to the soil and absorbs water with mineral salts dissolved in it. Horsetail reproduces vegetatively (using rhizomes and nodules), asexually and sexually, with alternating asexual (sporophyte) and sexual (gametophyte) generations. The sporophyte predominates in the life cycle of development. Horsetails are homosporous plants, but their gametophytes are dioecious, that is, from some externally identical spores male prothalluses with antheridia are formed, and from others - female prothalluses bearing archegonia. Spermatozoa are multiflagellate. Fertilization occurs in water. The most common are field, meadow, forest and marsh horsetails.
The importance of horsetails in nature and human life
Both in nature and in practical human activity, the role of horsetails is insignificant. Extinct horsetails of tree-like forms played an important role in the formation of coal throughout the world. Almost all of them are malicious weeds that are difficult to eradicate. In autumn and winter they serve as food for deer and wild boars. Young vegetative shoots of horsetail are used in medicine as a diuretic.
It is believed that horsetails evolved from rhyniophytes. Their development went in the direction of decreasing size. All horsetails, except horsetails, became extinct. They did not give rise to other groups of plants and represent a blind branch of development.
D.z. abstract
A prerequisite for their growth is increased soil moisture. Therefore, on the banks of reservoirs, in swamps, in damp meadows and in forests, club mosses, like horsetails, can predominate among other herbaceous vegetation. What is the significance of horsetails in human life and how did people learn to use this group of plants?
Features of horsetails
Modern species of this plant have very modest sizes. Growing in temperate latitudes of the northern hemisphere, horsetails reach a height of sixty centimeters to one meter. Varieties inhabiting regions with tropical climates are, of course, large in size.
Horsetails are difficult to confuse with others. Their shoots consist of internodes and nodes, due to which a peculiar stem consisting of segments grows. It is designed to perform the main function in the life of a plant - photosynthesis.
The underground part of horsetails also has a jointed structure. The rhizome easily breaks in the part where the nodes are located, giving the opportunity for the birth of young shoots. It is for this reason that horsetails quickly colonize areas where favorable conditions exist for their growth.
In addition to the vegetative one, they can spread by spores. The shoot on which they ripen appears only once - in the spring.
Silica accumulates in all cells of the plant body, due to which horsetails avoid mechanical damage. The plant is not eaten by insects, shellfish, or vertebrates. At first glance, it may seem that the importance of horsetails in human life is also small. But it turns out that this is not at all the case.
From the past of plants
The forests mainly consisted of giant club mosses, ferns and horsetail plants. It was thanks to them that the primary layers of soil began to form. This is a special formation, without which further life on the planet could not have its modern forms.
The importance of horsetails in human life and in nature is very great. These green giants at one time did the job of saturating the Earth's atmosphere with oxygen. The life of all creatures on the planet today depends on its sufficient content.
The importance of horsetails and mosses in human life can be understood if you know that coal is also a product of the vital activity of these plants. Deposits of valuable combustible substances were discovered precisely in those places where billions of years ago horsetails, mosses, and ferns, which in those distant times had not only herbaceous, but also tree-like forms, were rampant.
Horsetails in human life
The species of these plants, being representatives of modern fauna, are mainly defined by humans as weeds having poisonous properties. It is known that in pastures where horsetails are found, cases of poisoning of domestic animals by this plant are possible.
Its accidental use can be fatal. For this reason, hay meadows, where horsetail began to spread, gradually cease to be used for their intended purpose.
Today, the importance of horsetails in human life is quite important only in the field of pharmacology. The plant is used in the production of diuretics and hemostatic drugs. Traditional healers also find horsetail widely used.
Types of horsetails
The evolutionary path that horsetails have traveled is very long. It is a proven fact that this is one of the oldest plants on Earth. Today there are several of its species - meadow, field, forest, wintering, swamp, riverine. Only a small number of species can be added to this list.
Sometimes in modern classification all horsetails are divided into two groups. The first includes forest, riverine, meadow, swamp, and field. The second group includes branched, polychaete, reed, and wintering.
Modern research into the properties of horsetail
Studying chemical composition plants of both groups and the search for possibilities of their use is main task scientists. Research is carried out not only in the laboratory, but also through experiments and observations in nature.
It has now been proven that horsetails belonging to the second group have high feeding qualities. The same can be said about some types of plants of the first group. They are eaten by wild boars, deer, and horses.
It turns out that under the influence of certain temperatures the percentage and composition of chemical elements plant parts. In connection with the latest scientific data, there is a need to reconsider the meaning of horsetail in human life, since its use may become much wider in the near future.
Among the higher spore plants, which include mosses, mosses, ferns and horsetails, the latter have several features in external and internal structure. The horsetail plant looks like a small Christmas tree with hard side stems. Interestingly, animals do not eat either it or other types of horsetails. This is explained by the fact that plant tissue impregnated with silicon compounds. The systematic position of the Horsetail genus indicates the fact that their reproduction occurs with the help of spores. Our article will be devoted to the question of the structure of horsetail, as well as consideration of its use in medical practice as a medicine.
What is alternation of generations?
In the life cycle of a plant, two life forms change cyclically: asexual and sexual generations. The first is represented by perennial herbaceous plant, the second - has the appearance of green plates with a dissected surface with numerous threads. The reproductive organs develop on them: female - archegonia and male - antheridia. The maturation of eggs and sperm, as well as the process of fertilization itself, occurs only in the presence of water. So, to imagine what horsetails are, you must remember that plants exist in two different forms - gametophyte and sporophyte.
External structure
As we said earlier, the asexual generation of horsetail is a plant that has above-ground and underground parts. Thus, the rhizome provides support and contributes vegetative propagation. A large number of adventitious roots extending from it absorb water and minerals from the soil. The rhizome has a large number of thickenings - nodules. It grows deep into the ground. It should be noted that horsetails are indicators of soil acidification. What are soil indicators? These are plants that require a certain concentration of soil solution for normal functioning. In our example, this is an excess amount of hydrogen ions, that is, high acidity of the soil. As it turned out, plants of the Horsetail genus do not live on neutral or alkaline soils, so their favorite places to grow are biocenoses of swampy areas and river floodplains. The most common type of horsetail is horsetail. It is its branches that are harvested as medicinal plant raw materials. There is also horsetail, horsetail (has a triangular stem), horsetail with a pentagonal stem shape and black edges at the stem nodes. In addition, this species is also highly poisonous.
Vegetative organs
Let's continue to consider appearance and properties of horsetail. In addition to the rhizome, the vegetative parts of the plant body include stems, leaves and sporangia. They form a sporophyte - an asexual generation, whose task is to carry out the process of photosynthesis and the formation of reproductive organs - spore-bearing spikelets. The main ground shoot grows from the rhizome; it branches and is divided by nodes, from which lateral branches diverge in the form of a whorl. There are no leaves with a clearly defined leaf blade; they are reduced to colorless scales that grow from the nodes. Therefore, the function of photosynthesis in horsetails is performed by stems containing chlorophyll. Let's continue to study higher spore plants - horsetails. What are spring and summer forms of shoots? It turns out that the axial organ of the plant is ribbed, impregnated with silicon compounds and has a clear differentiation. Thus, spring shoots are light pink in color, incapable of branching and devoid of green pigment and leaves. At their tops sporangia are formed in the form of hard shields resembling spikelets containing haploid spores. Summer shoots are the main and subsidiary stems, which are bright green. They are capable of branching and, thanks to chlorophyll, carry out the synthesis of organic substances: proteins, carbohydrates and fats, and also provide the release of oxygen.
Sporangia and spores
Like other representatives of higher spore plants - mosses, mosses and ferns, horsetails develop organs on the sporophyte plant in which the maturation of asexual reproduction cells - haploid spores - occurs. Spikelets - sporangia of horsetails, have the form of special structures collected together, called sporangiophores. They are derivatives of lateral stems and look like rings, closely pressed to each other. Spores are formed through the process of meiosis and are haploid cells of the same type. Therefore, the question of what horsetails are from the point of view of the structure of their asexual generation - the sporophyte - can be answered as follows: these are homosporous plants. In addition, the spores are equipped with special springs - elaters, which serve as a device for their better distribution. Subsequently, once on moist soil, the spores germinate and unisexual shoots appear, on which male or female genital organs develop separately.
Gametophyte and fertilization process
Haploid spore cells in favorable conditions external environment(sufficient humidity and absence of direct sun rays) begin to form green lamellar structures with thread-like processes along the edges. This is how a growth is formed. Which genital organs, male or female, will form on it will depend on the light and temperature environment. On the underside of the shoot there are rhizoids that attach it to the soil surface. Antheridia are male genital organs that ensure the development of sperm, and archegonia contain eggs. Fertilization occurs in the presence of water. From the resulting zygote, an embryo develops, which subsequently gives rise to the development of the sporophyte - the asexual generation of horsetail, medicinal properties which have been known to man for quite a long time. Next we will look at them in more detail.
Application in medicine
One of the most common species, horsetail, is an effective diuretic and hemostatic herbal preparation obtained from the stems. If the functioning of the kidneys and heart is impaired, accompanied by fluid retention in the tissues and the appearance of severe edema, use a decoction prepared in the proportion: 20 g of raw material per 200 g of water. The diuretic effect is explained by the presence of saponin in horsetail shoots and the high content of potassium ions. In addition to them, plant materials contain vitamin C, carotene, equisetrin, calcium and iron ions. Horsetail decoction is used for uterine bleeding, in treatment of pleurisy, with inflammatory processes in the ureters and bladder. Pharmacological raw materials can be purchased in pharmacies in the form of an extract, brewing bags or briquettes.
Horsetail: properties and contraindications
Presence in vegetative parts of horsetail large quantity microelements, for example, copper, boron, molybdenum, have a positive effect on metabolism in the human body. However, the high concentration of alkaloids, glycosides and saponin determines not only the astringent, anti-inflammatory and diuretic properties of the plant, but can also cause a number of negative symptoms. For example: diarrhea, nausea, heaviness and pain in the epigastric region. Horsetail extract should be used with caution in therapy for patients peptic ulcer stomach and duodenum. A prerequisite for taking medications is not only a strict dosage - no more than half a glass, but also the frequency of use (no more than 3 times a day), as well as compliance with the main rule - using a decoction or extract an hour after meals.
The role of horsetails in ecosystems
What is the significance of horsetails in nature? Giant extinct species of tree-like higher spore plants: horsetails, mosses and ferns, which lived in the Carboniferous period of the Paleozoic era, caused the formation of coal reserves in the bowels of the earth. Modern species of plants of the genus Horsetails are much smaller and distributed in different climatic zones, especially in floodplain meadows and swamps, as well as in coniferous forests. As we said earlier, horsetails thrive on acidic soils; many species, for example, horsetail, clog crops and pastures for domestic animals, since they are inedible for them. In everyday life, the hard branches of horsetail, containing silicic acid and its salts, were previously used as an abrasive for cleaning heavily soiled kitchen utensils.
In our article we examined the properties, structure and significance of horsetails in nature and human life.