Ferns are distributed virtually throughout the globe, from deserts to swamps, rice fields and brackish ponds. They are most diverse in tropical rainforests. There they are represented by both tree-like forms (up to 25m in height) and herbaceous and epiphytic forms (growing on tree trunks and branches). There are species of ferns only a few millimeters long.

The structure of ferns

The common fern plant we see is the asexual generation, or sporophyte. In almost all ferns it is perennial, although there are a few species that have an annual sporophyte. Ferns have adventitious roots (only in some species they are reduced).

Ferns - photo

The foliage, as a rule, prevails in weight and size over the stem. Stems can be erect (trunks), creeping or climbing (rhizomes); often branch. Our forest ferns (ostrich, bracken, male fern) have a well-developed rhizome with numerous adventitious roots extending from it. Only large pinnately dissected leaves - fronds - are located above the ground.

The young leaf is curled in a snail-like manner; as it grows, it straightens out. In some species, leaf development occurs within three years. The leaves of ferns grow from their apex like stems, indicating their origin from the stem. In other groups of plants, leaves grow from the base.

In size, they can range from several millimeters to three or more meters in length, and in most species they perform two functions - photosynthesis and sporulation.

Fern propagation

On the underside of the leaf there are usually brown tubercles - sori with sporangia located in them, covered on top with a thin film. In sporangia, as a result of meiosis, haploid spores are formed, with the help of which fern reproduction occurs.

From a forest fern spore that finds itself in favorable conditions, a haploid prothallus develops, a gametophyte, a small green heart-shaped plate, up to 1 cm in diameter. The shoot grows in shaded, moist places and is attached to the soil with the help of rhizoids. Antheridia and archegonia develop on the underside of the gametophyte.

The “conquest” of land by ferns turned out to be incomplete, since the gametophyte generation can only exist with an abundance of moisture and shade, and an aquatic environment is necessary for the fusion of gametes.

Horsetails - structure

Horsetails are represented mainly by fossil forms. They arose during the Devonian and flourished in the Carboniferous period, reaching a wide variety of forms - up to giants 13 m high.

Modern horsetails number about 32 species and are represented by small forms - no more than 40 cm in height. They are found from the tropics to the polar regions, with the exception of Australia, and can live in both wet and dry areas. Some species have silicon deposits in the epidermis, which gives them a rough appearance.

Reproduction and development of horsetails

The sporophyte of horsetails consists of a horizontally branched underground stem - a rhizome, from which thin, branching roots and articulated aboveground stems extend. Some lateral branches of the rhizome are capable of forming small tubers with a supply of nutrients.

The stem contains numerous vascular bundles arranged in a ring around the central cavity. On the stems, as well as on the rhizome, nodes are clearly visible, giving them a segmented structure.

A whorl of secondary branches extends from each node. The leaves are small, wedge-shaped, also arranged in whorls, covering the stem in the form of a tube. Photosynthesis occurs in the stem.

In addition to assimilating stems, horsetail also has unbranched, spore-bearing shoots of brown color, at the ends of which sporangia develop, collected in spikelets. Spores form in them. After the spores spill out, the shoots die off and are replaced by green branching (vegetative, summer) shoots.

Moss mosses - structure

Moss mosses were widespread in the late Devonian and Carboniferous periods. Many of them were tall tree-like plants. At present, a small number of species (about 400) have been preserved compared to the past - all of these are small plants - up to 30 cm in height. In our latitudes they are found in coniferous forests, less often in swampy meadows. The bulk of club mosses are inhabitants of the tropics.

Our common species is the club moss. It has a stem creeping along the ground, from which needle-branched side shoots extend vertically upward. Its leaves are thin, flat, arranged in a spiral, densely covering the stem and side branches. The growth of club mosses occurs only at the growing point, since there is no cambium in the stem.

Reproduction of club mosses

At the top of the stem there are special leaves - sporophylls, collected in a strobile. Outwardly, it resembles a pine cone.

A germinating spore produces a germ (gametophyte), which lives and develops in the ground for 12-20 years. It has no chlorophyll and feeds on fungi (mycorrhiza). The change of sexual and asexual generations in horsetails and mosses occurs in exactly the same way as in ferns.

Fossil ferns formed thick layers of coal. Hard coal is used as fuel and raw material in various industries. Gasoline, kerosene, flammable gas, various dyes, varnishes, plastics, aromatics, medicinal substances, etc. are obtained from it.

The meaning of ferns, horsetails and mosses

Modern pteridophytes play a significant role in the formation of plant landscapes on Earth. In addition, people use horsetails as a diuretic and as an indicator of soil acidity. Due to the rigidity of the stems, associated with silicon deposits in the cell walls, horsetails were used for polishing furniture and cleaning dishes.

Moss moss spores are used in medicine as a powder, and male shield spores are used as an anthelmintic. They are used to treat tobacco addiction, alcoholism and eye diseases. Some species of fern-like plants are bred as ornamental plants (adiantum, asplenium, nephrolepis).

Since the gametophyte of club mosses develops very slowly (12-20 years), these plants should be protected.

Introduction

Division Equiformes ( Sphenophyta, or equisetophyta), in the past diverse not only at the species, but also at the generic and family levels, now includes a single genus Equisetum. It contains only about 30 species, the history of which can be traced back to the beginning of the Cretaceous period. Some of them like from the tropics, reach 8 m in height and 4 cm in diameter. But most species are small in size - up to 30 cm in height and 0.5–2 cm in diameter. Horsetails are vascular plants capable of sexual reproduction through spores produced in sporangia at the ends of stems. The cell walls of horsetails contain granules of silica, which they accumulate from the soil solution, which gives their stems rigidity and vertical stability.

Horsetails have long been used in folk medicine as a hemostatic and diuretic. Some species, such as wintering horsetail ( Equisetum hiemale), whose epidermis is particularly rich in silica, were used to polish walls.

Horsetails are distributed almost throughout the globe - from the tropics to the polar latitudes. Their ecology is also diverse - from water-filled swamps to dry sands and rocks (Fig. 1).

Rice. 1. Ecological extremes of horsetails: A – on a rocky substrate; B – in the swamp

External structure

All modern horsetails are herbaceous perennials. They have an erect aboveground stem and a developed network of underground rhizomes. The stems and rhizomes are divided into nodes and internodes; therefore, horsetails are often called arthropods (Fig. 2). Outwardly, they vaguely resemble bamboo. The stem nodes are surrounded by reduced scale-like leaves called microphylls and whorls of branches (Fig. 3). The leaves do not have a photosynthetic function and are brown in color. But the cells of the stem and branches are rich in chlorophyll. The stems have monopodial branching and are hollow inside. At the top of the horsetail stem, spore-bearing organs are formed - strobili (Fig. 4). Aboveground shoots of horsetails die off for the winter. However, among horsetails there are also evergreen species, for example, wintering horsetail - Equisetum hiemale).

Rice. 3. Nodes of horsetail stems with whorls of twigs (A) and reduced leaves (B)

Rice. 5. Vegetative propagation of horsetail: A – appearance; B – view under a microscope

Like other plants, horsetails are capable of vegetative propagation. It is carried out through young shoots formed in the nodes of the rhizomes or in the lower nodes of the stem (Fig. 5).
Rhizomes can also form in the internodes of the stems if for some reason they come into contact with the ground.

Anatomy

At the top of the stem there is an apical meristem, which carries out apical growth. Like other vascular plants, the leaves and twigs of horsetails are formed from the apical meristem. In addition, the intercalary meristem provides intercalary growth at plant nodes. From it, cells are formed that grow the stem not only in height, but also radially (Fig. 6). Therefore, it never has a strictly cylindrical shape - the diameter of the nodes is always slightly less than the diameter of the internodes (Fig. 7).

A cross section of the internode shows that it has a large central cavity surrounded by a cortex, into which numerous bundles of vessels are inscribed (Fig. 8). In the node, on the contrary, there is no central cavity, and its anatomical structure is similar to the structure of the stems of other vascular plants (Fig. 9). Sclerenchyma cells are rich in lignin. Chlorenchyma cells contain chlorophyll. Epidermal cells have a thick cutinized membrane. Its surface is rough due to silica granules. They are arranged in regular rows so that ridges and grooves are formed between them. Stomata are located in the grooves (Fig. 10). Their structure is similar to the structure of the stomata of other vascular plants.

Rice. 8. Anatomical structure of the internode

Rice. 10. Stomata on a cross section of the epidermis

Bundles of vessels are located under siliceous ridges. They consist of phloem and xylem (Fig. 11, 12). A stele with such a structure is called eustela.

Generative organs

At the top of the vegetative shoots of horsetails there are sporangia collected in strobili (Fig. 4).

Rice. 13. Mature horsetail strobilus: A – appearance; B – longitudinal section

Individual sporangia are relatively large and elongated. They are collected on corymbose sporangiophores, or sporophylls (Fig. 13). Each sporophyll contains 5–10 sporangia on the inner side - sacs with spores (Fig. 14). Since horsetail spores are the same size and bisexual shoots grow from them, they are classified as homosporous plants. The spores have a spherical shape and are surrounded at the equator by elaters - special hygroscopic threads (Fig. 15). On a hot summer day, with low air humidity, the spore elaters in the opened sporangia are in a curled state. However, as soon as the air humidity rises slightly (for example, after rain), the elaters straighten and catapult the spores out. Once on moist soil, the spores germinate (Fig. 16).

The prothallus growing from the spore is haploid. It has rhizoids and is capable of photosynthesis. Over time, female (archegonia) and male (antheridia) reproductive organs appear on the prothallus. After fertilization of the egg located in the archegonium, a young sporophyte grows from the zygote, giving rise to a new articular plant.

What are the structural and reproductive features of horsetails (horsetails)?

Horsetails are perennial herbaceous plants with a segmented structure. The shoots are divided into nodes and internodes. The leaves are reduced to whole small blades. The function of photosynthesis is performed by the stem. Silica accumulates in the cells of horsetails, which makes the stem stiff. Horsetails reproduce by spores that form in spore-bearing spikelets. Spore-bearing spikelets are formed either on special spore-bearing shoots (in horsetail) or on the tops of vegetative shoots (meadow horsetail, wintering horsetail). The sporiferous spikelet consists of an axis on which sporangiophores are located. The sporangiophore consists of a stalk on which there is a hexagonal plate. On the underside of the plate there are sporangia. Spores are formed in sporangia. In dry weather, the spores spill out. A gametophyte (prothallus) is formed from the spore. It contains antheridia with sperm and archegonia with eggs. After fertilization, a zygote is formed, and from it an embryo and a new plant develop.

Date of__________

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 board

During the classes

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 (emosporous - club moss, heterosporous - selyaginella).

The importance of lycophytes (decorative, medicinal, pyrotechnics, production of resins, plastics, formation of 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 are the organs of asexual reproduction of a 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 the external structure of Horsetail and Moss clubmoss, enter the data into 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 club moss from the section Mocopods.

What questions do you have?

6. Homework.
Read §____ page ____

Work in the dictionary (intercalary growth, node, internode).

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 with 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 the chemical composition of plants of both groups and finding possibilities for their use is the main task of 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 the chemical elements of plant parts changes. 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.