Appearance higher plants marked a new era in the life of the planet. Their occurrence is associated with geological changes in the structure of continents and the need to adapt to the characteristics of life outside of water.

The diversity of living conditions on Earth contributes to the formation of many forms of existence of living organisms.

Higher plants - definition, structure, characteristics and characteristics

Multicellular terrestrial plants that are capable of using light in the process of life, possessing developed organs and tissues, and characterized by alternating types of reproduction are called higher.

Development took place in an effort to adapt to terrestrial existence.

The result was transformations in the structure:

• roots that absorb water and minerals, as well as strengthening the plant in the soil;
• leaves capable of synthesizing organic substances from inorganic ones;
• stems - conduct organic matter and water.

Land plants are characterized by alternation of generations and autotrophic nutrition.

Origin of higher spore plants

The theory states that the ancestors of land plants - streptophyta, were forced due to geological changes to adapt to other living conditions. What was important was that only the fittest algae survived.

Transitional forms developed protective film- cutin deposited on the surface. Film formation in large quantities interfered with gas exchange, causing the plant to die. In organisms whose cutin was formed moderately, an epidermis with stomata was formed - a complex tissue that protects against drying out and also does not interfere with gas exchange.

The appearance of the epidermis prevented the absorption of water throughout the body, thereby promoting the formation of single-cell filaments - rhizoids. The result of the development process was the formation of a more complex system - roots.

Lighting on land significantly exceeds the same indicator in water, due to this the number and size of photosynthetic organs - leaves - have increased significantly. The distribution of substances formed during photosynthesis and water absorbed by the roots is carried out by the conducting organ - the stem.

The rapid increase in species and the spread of higher organisms is explained by the development of vegetative organs and changes in the reproductive system, which, under terrestrial conditions, must have reliable protection.

The reproductive multicellular organs of land plants - gametangia and sporangia - have a shell of living cells that protects the spores from drying out.

How do higher plants differ from lower ones?

Let's list the main ones:

1. The tissues and organs that make up plants have a complex multicellular structure.
2. The habitat is mostly dry land.
3. During development, there is an alternation of generations - gametophyte and sporophyte.
4. The spore is protected by a hard multicellular membrane.

Divisions of higher plants

According to the classification, the subkingdom of higher plants includes 9 divisions.

Representatives of the first three divisions completely died out. The remaining six make up living organisms.

Rhiniophytes

The first higher plants that gave rise to other divisions are Rhiniophytes or Rhiniaceae. They are characterized by a primitive herbaceous appearance, reaching a height of 60 cm. They had the simplest structure. There were no real leaves and roots; instead of roots there was a rivomoid organ, from which rivoids extended downwards, and stems extended upwards.

Photosynthesis was carried out by a stem that branched mainly into two shoots. Sporangia attached to the axes, and spores developed within them.

The presence of integumentary tissues, as well as stomata, indicates that representatives of the department grew on land. The most ancient representative of the department is considered to be Cooksonia.

Zosterophyllophytes

They have much in common with rhinophytes. Some scientists believe that Zosterophyllophytes gave rise to the Lycophytes. They differ in that they had an erect stem covered with a thick layer of cuticle.

Sporangia, collected in spike-shaped formations, have a short stalk, as well as identical spores. A representative is Goslinglia, it has no roots, and the stems have branches with twisted tops.

Bryophytes

A peculiarity is the predominance of the haploid phase (sexual generation); the diploid phase is poorly developed. For the sexual process of mosses, a moist environment is required, so they must grow in low-lying, swampy places, which is facilitated by their small size.

The main differences between bryophytes and other divisions:

• low lighting is sufficient for the formation of organic matter;
• water is absorbed throughout the body;
• the ability to grow on nutrient-poor soils and assume a state of suspended animation for a long period. All this ensures competitiveness in comparison with other representatives of departments.

Bryophytes are divided into three classes:

1. Hepatic class. Gametophytes are characterized by a dorsinventral structure. The leaves are always single-layered, the rhizoids are unicellular. They grow in the tropics, entangling the soil, trunks, and leaves of trees in a continuous carpet. These include small Blassia (Blassia pusilla).
2. Class Antocerotaceae. At the edges of the rosette-shaped lamellar thalli there are meristematic cells that form lobes that overlap each other and give the thallus a curly appearance. The most common is the genus Antoceros.
3. Moss class. They are characterized by the presence of leafy shoots of radial symmetry. Rhizoids are located on leaves and stems - always multicellular. Most mosses grow in northern and temperate latitudes. A prominent representative is sphagnum; their types differ not only in structure, but also in their association with natural conditions.

Moss-moss

Herbaceous forms of lycophytes can still be found today. They have shoots with small leaves and roots.

The leaves are a single leaf blade with an expanded base in the form of a pad. They are divided into two classes - Moss-moss and Half-moss.

Psilotoides

Psilotophyta are represented by only one family - Psilotaceae. There are no roots, so they often grow on other trees. They can be found both on soils rich in organic matter and on the rocks of tropical forests. Water must be involved in the fertilization process.

One of the representatives is Psilot naked - a decorative fern. It got its name due to the lack of leaves. Grows at the base of palm trunks or humus soils. Reproduces by spores.

Horsetails

The department is divided into two classes - Sphenophyllaceae and Equisetaceae.

A prominent representative is horsetail, a perennial herbaceous plant with roots. Serves as an indicator of acidic soils.

The stems are divided into internodes, from which underdeveloped, dark, clove-like leaves emerge. The spores are located in the spore-bearing spikelet. Reproduction occurs when high humidity: rain or heavy dew.

Ferns

Perennial herbaceous, less common tree plants. They are characterized by macrophyllia - powerfully developed leaves of relatively short length. Their large leaves(fronds) can be whole or strongly dissected, twisted like a snail in the bud.

In most ferns, leaves perform two functions - photosynthesis and sporulation. They are distributed throughout the globe, but the maximum diversity of species is found in the tropics.

The department has five classes: Cladoxyleaaceae, Zygopteriaceae, Uzhovniaceae, Marattiaceae, and Polypodiaceae.

Gymnosperms

Modern biology includes four classes: Cycadaceae, Ginkgoaceae, Conifers and Gnetaceae. In ancient times, they included two more, already extinct, classes: Seed ferns and Bennettitaceae.

Reproduction of gymnosperms is carried out by seeds - multicellular organs containing the embryo rudiment, endosperm and multilayered skin. They are the most highly organized department in their morphological characteristics, approaching the angiosperm department.

Pine Kokha (Crimea)

Typical representatives of our country are spruce and pine.

Conclusion

The subkingdom of higher plants has come a long way in the process of its evolution. In the most developed representatives you can see a flower, a seed, a fruit. All changes in the body occurred in order to gain a foothold on land: the appearance of roots, leaves, and the improvement of the method of reproduction.

Only higher plants are capable of producing organic matter from inorganic matter.

, lycosperms, gymnosperms and angiosperms).

Higher plants in some classification systems are considered as a taxon of subkingdom rank.

The wide variety of conditions for the existence of terrestrial life explains the extraordinary richness of plant forms. But despite the diversity of appearance, all higher plants are characterized by one type of sexual process (oogamy) and two variants of one type of change of nuclear phases, or “change of generations” (heteromorphic development cycles with a predominance of either sporophyte or gametophyte). In all cases, both “generations” - hematophyte and sporophyte - differ morphologically, cytologically and biologically. In the evolution of almost all departments of higher plants (with the exception of bryophytes), the sporophyte predominates in the development cycles.

Mosses

Among higher plants, Bryophytes have the most primitive structure ( Bryophyta sensu lato) - they lack a root (they have rhizoids), and Marchantiaceae, Anthoceroteceae and some Jungermannia mosses do not have a division into leaf and stem - they are thallous, like algae or lichens. The stomatal apparatus is extremely primitive, the conducting system is not developed, the conducting functions are performed by the parenchyma.

Vascular spores

Seed plants

An important evolutionary breakthrough of plants on the path to conquering land was the appearance of the seed and the shell of the pollen grain. Due to the fact that from now on the gametophyte (now consisting of only a few cells) began to be completely contained within the moisture-retaining shell, plants were able to develop desert and cold areas.

In some gymnosperms and in almost all flowering plants, vessels and sieve tubes appear in the conducting structures - hollow conducting elements consisting of the walls of dead cells, due to which their conducting systems act extremely efficiently.

Notes

Literature

• Elenevsky A. G. Botany. Systematics of higher, or terrestrial, plants: textbook. for students higher ped. textbook institutions / A. G. Elenevsky, M. P. Solovyova, V. N. Tikhomirov. - Ed. 4th, rev. - M.: Publishing center "Academy", 2006. - 464 p. - 3000 copies.- ISBN 5-7695-2141-4

- UDC 596(075.8)

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2010. See what “Higher plants” are in other dictionaries: Embryonic plants (Embryobionta, Embryophyta), shoots, leafy plants (Cormophyta, Cormobionta), telome plants (Telomophyta, Telomobionta), one of the two subkingdoms of the plant kingdom. Unlike lower plants

V. r. complex... ... Biological encyclopedic dictionary- (telome plants) subkingdom flora

. Unlike lower plants, the body of higher plants is divided into specialized organs: leaves, stem and root. Over 300 thousand species. Divisions: rhiniophytes, bryophytes, psilotoides; lycophytes,... ...

Big Encyclopedic Dictionary Modern encyclopedia Higher plants

- HIGHER PLANTS, subkingdom of the plant world. Unlike lower plants, the body of higher plants is divided into specialized organs: leaves, stem and root. Over 300 thousand species. Higher plants include mosses, ferns, gymnosperms,... ... Illustrated Encyclopedic Dictionary

- (telome plants), subkingdom of the plant world. Unlike lower plants, the body of a higher plant is divided into specialized organs: leaves, stem and root. Over 300 thousand species. Divisions: rhiniophytes, mossy, psilotoides;... ... encyclopedic Dictionary

Embryonic plants (Embryobionta, Embryophyta), shoot plants (Cormophyta, Cormobionta), telome plants (Telomophyta, Telomobionta), one of two subkingdoms of the plant world. Unites at least 300 thousand plant species... ...- ▲ plant having a stem; higher plants, shoot plants, cormophytes are divided into vegetative organs and a well-defined stele (frame, stem); the body is made up of different plant tissues... Ideographic Dictionary of the Russian Language

Embryonic plants (Embryobionta, Embryophyta), shoot plants (Cormophyta, Cormobionta), telome plants (Telomophyta, Telomobionta), one of two subkingdoms of the plant world. Unites at least 300 thousand plant species... ...- plants whose body is differentiated into organs and tissues, with multicellular organs of asexual and sexual reproduction and a relatively well-defined embryo. There are higher spores (divisions: Bryophyta - Bryophyta, Psilote - ... ... Anatomy and morphology of plants

- (telome plants), the sub-kingdom grows. peace. Unlike lower plants, the body of V. r. divided into specialists. organs leaves, stem and root. Over 300 thousand species. Divisions: rhinophytes, mossy, psilotoid, lycophytes, horsetail,... ... Natural science. encyclopedic Dictionary

The plant kingdom amazes with its greatness and diversity. Wherever we go, no matter what corner of the planet we find ourselves in, we can find representatives of the plant world everywhere. Even the ice of the Arctic is no exception for their habitat. What is this plant kingdom? The types of its representatives are diverse and numerous. What is general characteristics plant kingdom? How can they be classified? Let's try to figure it out.

General characteristics of the plant kingdom

All living organisms can be divided into four kingdoms: plants, animals, fungi and bacteria.

The characteristics of the plant kingdom are as follows:

• are eukaryotes, that is, plant cells contain nuclei;
• are autotrophs, that is, they form organic substances from inorganic substances during photosynthesis using the energy of sunlight;
• lead a relatively sedentary lifestyle;
• unlimited growth throughout life;
• contain plastids and cell walls made of cellulose;
• starch is used as a reserve nutrient;
• presence of chlorophyll.

Botanical classification of plants

The plant kingdom is divided into two subkingdoms:

• lower plants;
• higher plants.

Subkingdom "lower plants"

This subkingdom includes algae - the simplest in structure and the most ancient plants. However, the world of algae is very diverse and numerous.

Most of them live in or on the water. But there are algae that grow in the soil, on trees, on rocks and even in ice.

The body of algae is a thallus or thallus, which has neither roots nor shoots. Algae do not have organs or various tissues; they absorb substances (water and mineral salts) over the entire surface of the body.

The subkingdom “lower plants” consists of eleven divisions of algae.

Significance for humans: release oxygen; are eaten; used to produce agar-agar; are used as fertilizers.

Subkingdom "higher plants"

Higher plants include organisms that have well-defined tissues, organs (vegetative: root and shoot, generative) and individual development (ontogenesis) which are divided into embryonic (embryonic) and postembryonic (post-embryonic) periods.

Higher plants are divided into two groups: spore plants and seed plants.

Spore-bearing plants spread through spores. Reproduction requires water. Seed plants spread by seeds. Water is not needed for reproduction.

Spore plants are divided into the following sections:

• bryophytes;
• lycophytes;
• horsetails;
• fern-like.

Seeds are divided into the following sections:

• angiosperms;
• gymnosperms.

Let's look at them in more detail.

Department "bryophytes"

Bryophytes are low-growing herbaceous plants, the body of which is divided into a stem and leaves; they have a kind of roots - rhizoids, the function of which is to absorb water and anchor the plant in the soil. Besides photosynthetic and ground tissue, mosses have no other tissues. Most mosses are perennial plants and grow only in moist areas. Bryophytes are the most ancient and simplest group. At the same time, they are quite diverse and numerous and are second only to angiosperms in the number of species. There are about 25 thousand of their species.

Bryophytes are divided into two classes - liver and phyllophytes.

Liverworts are the most ancient mosses. Their body is a branched flat thallus. They live mainly in the tropics. Representatives of liverworts: mosses Merchantia and Riccia.

Leafy mosses have shoots that consist of stems and leaves. A typical representative is cuckoo flax moss.

In mosses, sexual and asexual reproduction is possible. Asexual can be either vegetative, when the plant reproduces by parts of stems, thallus or leaves, or spore-bearing. During sexual reproduction in bryophytes, special organs are formed in which immobile eggs and motile sperm mature. Sperm move through the water to the eggs and fertilize them. Then a capsule with spores grows on the plant, which, after maturation, scatter and spread over long distances.

Mosses prefer damp places, but they grow in deserts, on rocks, and in tundras, but they are not found in the seas and on highly saline soils, in shifting sands and glaciers.

Importance for humans: peat is widely used as fuel and fertilizer, as well as for the production of wax, paraffin, paints, paper, and in construction it is used as a heat-insulating material.

Divisions "mocophytes", "tail-like" and "fern-like"

These three divisions of spore plants have similar structure and reproduction, most of them grow in shady and moist places. Woody forms of these plants are very rare.

Ferns, club mosses and horsetails are ancient plants. 350 million years ago they were large trees, they were the forests on the planet, in addition, they are the sources of coal deposits at the present time.

The few plant species of the fern, horsetail and lycophyte divisions that have survived to this day can be called living fossils.

Externally different types mosses, horsetails and ferns are different from each other. But they are similar internal structure and reproduction. They are more complex in structure than bryophytes (they have more tissue in their structure), but simpler than seed plants. They belong to spore plants, since they all form spores. Both sexual and asexual reproduction are also possible for them.

The most ancient representatives of these orders are club mosses. Nowadays, club moss can be found in coniferous forests.

Horsetails are found in the Northern Hemisphere; now they are represented only by herbs. Horsetails can be found in forests, swamps and meadows. A representative of the horsetails is horsetail, which usually grows in acidic soils.

Ferns are a fairly large group (about 12 thousand species). Among them there are both grasses and trees. They grow almost everywhere. Representatives of ferns are ostrich and bracken.

Significance for humans: ancient pteridophytes gave us deposits of coal, which is used as fuel and valuable chemical raw materials; some species are used for food, used in medicine, and used as fertilizers.

Department "angiosperms" (or "flowering")

Flowering plants are the most numerous and highly organized group of plants. There are more than 300 thousand species. This group makes up the bulk of the planet's vegetation. Almost all representatives of the plant world that surround us in everyday life, both wild and garden plants, are representatives of angiosperms. Among them you can find all life forms: trees, shrubs and herbs.

The main difference between angiosperms is that their seeds are covered with a fruit formed from the ovary of the pistil. The fruit protects the seed and promotes its distribution. Angiosperms produce flowers, the organ of sexual reproduction. They are characterized by double fertilization.

Flowering plants dominate the vegetation cover as the most adapted to modern living conditions on our planet.

Value for humans: used for food; release oxygen into environment; used as building materials and fuel; used in the medical, food, and perfume industries.

Department "gymnosperms"

Gymnosperms are represented by trees and shrubs. There are no herbs among them. Most gymnosperms have leaves in the form of needles (needles). Among gymnosperms, a large group of conifers stands out.

About 150 million years ago conifers dominated the planet's vegetation.

Significance for humans: form coniferous forests; release large amounts of oxygen; used as fuel, building materials, shipbuilding, and furniture manufacturing; used in medicine and in the food industry.

Diversity of flora, plant names

The above classification continues; departments are divided into classes, classes into orders, followed by families, then genera and, finally, plant species.

The plant kingdom is huge and diverse, so it is customary to use botanical names for plants that have a double name. The first word in the name means the genus of plants, and the second means the species. This is what the taxonomy of the well-known chamomile will look like:

Kingdom: plants.
Department: flowering.
Class: dicotyledonous.
Order: astroflora.
Family: Asteraceae.
Genus: chamomile.
Type: chamomile.

Classification of plants according to their life forms, description of plants

The plant kingdom is also classified according to life forms, that is, according to the external appearance of the plant organism.

• Trees are perennial plants with lignified aerial parts and a distinct single trunk.
• Shrubs are also perennial plants with lignified aerial parts, but, unlike trees, they do not have a clearly defined one trunk, and branching begins near the ground and several equal trunks are formed.
• Shrubs are similar to shrubs, but are low-growing - no higher than 50 cm.
• Subshrubs are similar to shrubs, but differ in that only the lower parts of the shoots are lignified, and the upper parts die off.
• Lianas are plants with clinging, climbing and climbing stems.
• Succulents are perennial plants with leaves or stems that store water.
• Herbs are plants with green, succulent and non-woody shoots.

Wild and cultivated plants

Humans have also contributed to the diversity of the plant world, and today plants can also be divided into wild and cultivated.

Wild - plants in nature that grow, develop and spread without human help.

Cultivated plants come from wild plants, but are obtained through selection, hybridization or genetic engineering. These are all garden plants.

In appearance, structure and biological characteristics, higher plants are very diverse. Higher plants living today are mosses, mosses, horsetails, ferns, gymnosperms and angiosperms (flowering) plants. The total number of their species exceeds 285 thousand.

Unlike “lower plants,” higher ones are characterized by a number of features of a higher organization. Their body is divided into organs: shoot and root (with the exception of bryophytes). These organs contain many different tissues.

Higher plants have a well-developed conducting system, represented by xylem (tracheids or vessels) and phloem (sieve tubes with accompanying cells). Along with the conducting system, there is a complex system of integumentary tissues, a complex stomatal apparatus; Mechanical ones have received strong development.

Characteristic higher plants - the correct change of generations (gametophyte and sporophyte) in their development cycle. The gametophyte - the sexual generation on which antheridia and archegonia are formed - is replaced by the asexual generation of the sporophyte, on which sporangia with spores are formed. The gametophyte is always a haploid plant, the sporophyte is always diploid.

In bryophytes, the gametophyte dominates life cycle, and the sporophyte occupies a subordinate position and lives on the gametophyte. Mosses, horsetails and ferns are characterized by the biological independence of both the sporophyte and the gametophyte, but the sporophyte predominates in the life cycle, and the gametophyte is reduced to varying degrees. In the most highly organized higher plants (gymnosperms, angiosperms) the greatest reduction of the gametophyte is observed.

Divisions of higher plants

Higher plants are usually divided into 9 divisions, two of which combine only extinct forms - rhinophytes, zosterophyllophytes; seven divisions are represented by living plants - bryophytes, lycophytes, psilotoides, horsetails, pteridophytes, gymnosperms, etc.

Division Rhyniophyta

Rhiniophytes (psilophytes) became extinct in the Middle Devonian. These first higher plants had a very simple structure. They reproduced by spores and had dichotomously branching bodies with apical sporangia. There was no differentiation into roots, stems and leaves.

It is believed that rhiniophytes are the original ancestral group from which the bryophytes, lycophytes, horsetails and pteridophytes descended.

Division Zosterophyllophyta

This department includes a small group of plants that existed in the Early and Middle Devonian. They had much in common with rhyniophytes. Perhaps the plants of this group lived in water. Like rhiniophytes, they did not have leaves, their aboveground shoots branched dichotomously. Sporangia of zosterophyllophytes, which had a spherical or bean-shaped shape, were located laterally on short stalks, this is their difference from rhinophytes.

Division Bryophyta

Bryophytes are evergreen, autotrophic, mostly perennial plants. They number about 25,000 species and have been known since the Carboniferous. This group of higher plants apparently descends from ancient green algae.

The body of bryophytes is either a thallus (thallus) pressed to the substrate, or a stalk with leaves; there are no roots, there are only rhizoids. These are small plants, their sizes range from 1 mm to several tens of centimeters. Bryophytes have a relatively simple internal organization. Their body contains assimilation tissue, but conductive, mechanical, storage and integumentary tissues are weakly expressed in comparison with other higher plants.

Unlike all other divisions of higher plants, the vegetative body of bryophytes is represented by the gametophyte, which dominates in their life cycle, while the sporophyte occupies a subordinate position, developing on the gametophyte.

On the gametophyte of bryophytes, reproductive organs develop - male (antheridia) and female (archegonia). A large number of biflagellate spermatozoa are formed in the antheridia. Each archegonia produces one egg. In wet conditions (during rain), sperm, moving into, penetrate the egg located inside the archegonium. One of them merges with her, producing fertilization. From a fertilized egg (zygote) a sporophyte grows, that is, an asexual generation represented by a capsule sitting on a stalk. Spores form in the box.

When a spore germinates, a protonema appears - a thin branched thread (less often a plate). Numerous buds are formed on the protonema, giving rise to gametophytes - leafy shoots or thalli in the form of a plate.

Gametophytes of bryophytes are capable of vegetative propagation, and their development cycle long time can occur without sporophyte formation.

Bryophytes combine 3 classes: Anthocerotaceae, Liverworts And Leaf mosses.

IN class Anthocerotidae(Antocerotae) there are about 300 species. They are distributed mainly in tropical and warm temperate regions of the globe. In our country, only the genus Antoceros is found, represented by 3-4 species.

The gametophyte of anthocerotes is a thallus (thallus). In species of the genus Anthoceros, the thallus is rosette-shaped, 1-3 cm in diameter, less often leaf-shaped, dark green, tightly adjacent to the soil. The capsules (sporogony) are numerous, slightly curved, bristle-like. They give anthocerote mosses a distinctive appearance.

IN class Liverworts(Heraticae) there are over 6 thousand species. Liverworts are widespread. Unlike other bryophytes, in most liverworts the protonema is poorly developed and short-lived. The gametophyte has a thalliform or leaf-stem form. The structure of the gametophyte in hepatic mosses is very diverse, but the sporophyte is of the same type.

As an example, we can consider a representative of the Marchantiidae subclass - Marchantia polymorpha. This is one of the most common liverworts in our flora (in swamps and forests at fire sites). The body of Marchantia is represented by a thallus in the form of a dark green plate.

Marchantia is a dioecious plant. On some specimens archegonia are formed, on others - antheridia. Archegonia develop on a special stand, the top of which resembles a multi-rayed star. The male stand with antheridia looks like a flat disk.

The subclass Jungermanniidae contains both thallus and leafy plants. Most Jungermanniaceae have recumbent dorsoventral shoots. The shape and their attachment to the stem are varied, the shape of the box is from spherical to cylindrical, it usually opens with 4 doors.

TO class Leafy mosses(Musci) include 3 subclasses: Sphagnum, andreic and brie mosses; Of these, we will consider two subclasses: Sphagnum and Briaceae.

The subclass Sphagnidae is represented by one family, Sphagnaceae, with a single genus, Sphagnum. There are 42 species found in our country. Sphagnum mosses are widespread in temperate and cold regions of the Northern Hemisphere, forming a continuous cover in swamps and humid forests.

The stems of sphagnum mosses are erect, with fascicle-shaped leafy branches. At the top, the branches are shortened and gathered into a rather dense head.

The leaves are single-layered and have two types of cells - chlorophyll-bearing and aquiferous (hyaline). Chlorophyll-bearing cells are narrow, worm-shaped, and contain chloroplasts. They are located between wide, colorless aquifer cells, devoid of cellular contents. Thanks to its many water-bearing cells, sphagnum can quickly absorb large amounts of water (almost 40 times its dry weight).

Antheridia and archegonia are formed in the upper part of the stems. After fertilization of the egg, a capsule grows from the archegonium.

The Bryidae subclass is represented in your country by approximately 2 thousand species. Green mosses are most often perennial plants with a height of 1 mm to 50 cm. Their color is usually green. They are widespread and form a continuous cover in swamps, coniferous forests, meadows, mountains and tundras.

Green mosses are characterized by a well-developed, often filamentous, branching protonema. Green mosses are very diverse in the structure of their vegetative organs.

As an example reflecting the most important characteristics of plants of this subclass, consider the cuckoo flax moss (Polytrichum commune), widespread in damp coniferous forests and along the edges of swamps. The stem of this moss is erect, unbranched, reaches a height of 30-40 cm. It is densely covered with linear-lanceolate leaves.

Kukushkin flax is a dioecious plant. Archegonia are formed at the top of the stems of some plants, and antheridia on others. After fertilization, a capsule develops from the zygote, sitting on a stalk. Spores ripen in the box. The spore, once on moist soil, germinates, giving rise to a filamentous protonema. Buds form on the protonema, from which they grow into leaves.

The importance of mosses in nature is great. Representatives of bryophytes grow almost everywhere. The exception is saline habitats with moving substrate; marine bryophytes are unknown. Mosses are abundant in swamps and forests. They often dominate the ground cover of coniferous forests (spruce forests, pine forests, etc.). Mosses are abundant in the tundra, high in the mountains. The tundra zone and humid highlands are rightly called the kingdom of mosses and lichens.

The property of bryophytes to quickly absorb water and firmly retain it causes the moss turf to become peaty from below and weakly decompose it. Moss cover can contribute to waterlogging of areas. Sphagnum mosses have antibiotic properties and are used in medicine. Participating in the formation of moss cover in raised bogs, they are peat formers. Sphagnum peat is widely used as fuel and in agriculture.

Many green mosses form a continuous carpet in lowland bogs, where they form deposits of lowland peat rich in nutrients. Lowland peat is widely used in agriculture as fertilizer. Mosses also have a negative meaning. Growing in a continuous dense carpet, they impede soil aeration, causing it to sour. This adversely affects the life of many plants. The role of liverworts in the vegetation cover is generally much less than the role of sphagnum and green mosses.

Division Lycopodiophyta

Lycopods are one of the most ancient groups of plants. The first lycophytes were herbaceous plants. During the Carboniferous period, tree-like species appeared, but they died out, and their remains formed coal deposits. Most of the lycophytes are now extinct. Only a few species of club mosses and selaginella have survived.

All modern representatives of lycophytes are perennial herbaceous, usually evergreen plants. Some of them resemble green mosses in appearance. The leaves of lycophytes are relatively small, this is typical for this group of plants. Dichotomous (forked) branching is also characteristic of lycopods. At the top of the stems of many lycophytes, spikelets (strobilae) are formed, in which spores ripen.

Among the lycophytes there are homosporous and heterosporous plants. In homosporous species, the spores do not differ morphologically; during their germination, bisexual gametophytes are formed; In heterosporous species, small spores give rise to male gametophytes bearing antheridia, and large spores give rise to female gametophytes bearing archegonia. Bi- or multiflagellate spermatozoa are formed in antheridia, and eggs are formed in archegonia. After fertilization, a new generation grows from the resulting zygote - the sporophyte.

The section Mossaceae includes two classes: Mossaceae and Polusniformes. From the class Plaunovs we will consider the order Plaunovs and from the class Polushnikovs - the order Selaginella, representatives of which live at the present time.

Order Lycophytes(Lycopodiales) is characterized by homosporousness. It is represented by one family - Lycopodiaceae. This family includes the genus Lycopodium, which has about 400 species. There are 14 species of mosses found in our country.

Many mosses are small herbaceous plants. Their leaves are relatively small. A midrib consisting of tracheids and parenchyma cells runs along the leaf.

Let's consider one of the types of club moss - club moss (Lycopodium clavatum). This species is widespread and is found in coniferous (usually pine) forests on poor soils. Moss moss is an evergreen perennial herbaceous plant with a creeping stem up to 1-3 m long. On this stem, rising above-ground shoots up to 20 cm high are formed, ending in spore-bearing spikelets. All shoots are densely covered with small subulate-shaped leaves. The spikelets contain kidney-shaped sporangia, in which a large number of identical small yellow spores are formed.

After ripening, the spores fall to the soil. When they germinate, an outgrowth (gametophyte) is formed. The moss growth is perennial and looks like a small nodule (2-5 mm in diameter) with rhizoids. It is colorless, lacks chlorophyll and cannot feed on its own. Its development begins only after the fungal hyphae (endotrophic mycorrhiza) penetrate the body.

On the upper surface of the prothallus, in the depths of its tissue, antheridia and archegonia are formed. Fertilization occurs in the presence of water. From the fertilized egg, an embryo develops and grows into a perennial evergreen plant - sporophyte.

In lycophytes there is a clearly expressed change of generations. The development cycle is dominated by the sporophyte. Reduction division occurs in the sporangium during the formation of spores.

The stems and leaves of club mosses contain alkaloids that are used in medicine. The spores are used as a powder for powders, as well as for sprinkling pills. To protect the reserves of club mosses, when collecting spores, it is necessary to carefully cut off only the spore-bearing spikelets.

Order Selaginellaceae(Selaginellales), belonging to the class Polushnikovye, is characterized by heterosporousness. It is represented by one family, Selaginellaceae. There are almost 700 species in the genus Selaginella, mostly native to tropical and subtropical regions. There are 8 species of this genus found in our country. Selaginella are very diverse in appearance. Most of them are small, usually creeping herbaceous plants. The leaves are simple, entire, small, up to 5 mm long. Asexual reproduction via spores is the main method of reproduction of Selaginella.

Let's take a closer look Selaginella selaginoides(Selaginella selaginoides). This plant has short creeping stems covered with elongated ovate leaves. Spore-bearing spikelets are formed at the top of the shoot. The main difference between Selaginella and club mosses is that the same spikelet contains two types of sporangia. Some of them are larger (megasporangia) and contain 4 large spores (megaspores). Other sporangia are smaller (microsporangia) and contain numerous microspores.

During germination, the microspore forms a highly reduced male prothallus, on which one antheridium develops. A female prothallus grows from the megaspore, on which a few archegonia develop. The movement of sperm occurs in water after rain or dew. Over time, an adult plant grows from a fertilized egg.

Thus, in Selaginella two types of spores are formed - microspores and megaspores - and unisexual prothlae develop. Thalli, especially male ones, are greatly reduced, which is the main direction of the evolution of higher plants. This can be clearly seen in other departments of higher plants. Selaginella are little used by humans.

Division Psilotophyta

The Psilotidae department includes 12 species. It includes two genera: Psilotum and Tmesipteris. Representatives of these genera are distributed outside our country in the tropics and subtropics. They are simply arranged and resemble rhyniophytes. Their structure retains extremely primitive features, which indicate their very ancient origin.

The sporophyte psilota has no roots or leaves. It consists of a dichotomously branching aerial part with small scale-like outgrowths and a branched system of rhizomes with numerous rhizoids.

Psilot is a homosporous plant. Spores are formed in sporangia located at the ends of short lateral branches. An underground gametophyte grows from the spore, on the surface of which are located antheridia and archegonia. Sperm are multiflagellate and require water to reach the egg.

Tmesipteris is similar to psilot, differing from it in larger leaf-like appendages.

Division Equisetophyta

Equisetaceae are characterized by division into clearly defined internodes and nodes with whorled leaves.

Currently, horsetails are represented on Earth by one class Equisetopsida, which includes one order Equisetales and one family Equisetales. There is only one genus in this family - Horsetail (Equisetum), which includes about 30 species, 17 of which are found in our flora (in swamps, forests, meadows, arable lands, etc.).

Horsetails reached their greatest development in the Carboniferous period. Then many of them were represented by large trees. Later the tree-like forms became extinct. Their dead remains gave rise to coal deposits. Many herbaceous forms also became extinct.

Modern horsetails are perennial rhizomatous herbs with a stem up to several tens of centimeters high. At the nodes of the stem there are whorls of branches. Small scale-like leaves grow together with sheaths into a tube; the function of photosynthesis is performed by green shoots. Some shoots end in a spore-bearing spikelet (strobilus), consisting of sporangia. Modern horsetails are homosporous plants.

The sexual generation (gametophyte) in modern horsetails is represented by unisexual or bisexual short-lived, very small, green shoots several millimeters in size. Antheridia and archegonia are formed on them. Multiflagellate sperm develop in antheridia, and eggs develop in archegonia. Fertilization occurs in the presence of droplet-liquid water, and a new asexual generation grows from the zygote - the sporophyte.

The structure of horsetails and their life cycle can be considered using the example of horsetail (Equisetum arvense). This is a perennial rhizomatous plant that grows in fields, meadows, and fallow lands. From rhizome in early spring pinkish-brown, short, straight shoots appear, at the top of which a spore-bearing spikelet forms. On the axis of the spikelet there are sporophylls that look like hexagonal scutes. The sporophylls contain sporangia, which contain spores.

Outwardly, all disputes are the same. Each has two appendages in the form of narrow ribbons called elater. The spores are morphologically identical, but physiologically different. Some of them, when germinating, produce male shoots, others - female shoots.

The male prothallus is a small green plate, divided into lobes and attached to the soil by rhizoids. Antheridia containing polyflagellate spermatozoa develop at the ends of the lobes. The female prothallus is larger and bears archegonia. Fertilization occurs in the presence of moisture. A perennial sporophyte develops from the zygote. Green vegetative shoots, devoid of spikelets, develop from the rhizomes of horsetail.

Other types of horsetail have only one type of shoot. It is both spore-bearing and assimilative. The practical value of horsetails is small.

Division Fern-like (Polypodiophyta)

Ferns are ancient plants. A significant part of them have now become extinct. Nowadays, ferns far exceed in the number of species all other groups of modern spores. vascular plants; More than 12 thousand species are known. There are about 100 species from this group in our flora.

Representatives of this department are very diverse in appearance, life forms, and living conditions. Among them there are many herbaceous perennial plants, and there are also trees. Tropical tree ferns are up to 25 m tall, and the trunk diameter reaches 50 cm. Among the herbaceous species there are very small plants several millimeters in size.

Unlike lycophytes and horsetails, pteridophytes are characterized by “large leaves”. The “leaves” of ferns are of stem origin and are called “fronds”. Their origin is confirmed by apical growth.

The sizes of fronds of ferns range from a few millimeters to 30 cm. Their shape and structure are varied. The fronds of many ferns combine the functions of photosynthesis and sporulation. Some species (for example, ostrich) have two types of fronds - photosynthetic and spore-bearing. The leaves of the fronds are quite often feathery, often dissected many times.

Most forest ferns of temperate regions have fleshy rhizomes that form new rosettes of fronds every year, which usually prevail in weight and size over the stem in ferns.

Almost all ferns, with the exception of aquatic ones, are homosporous plants. Their sporangia are often located on the lower surface of the fronds and are collected in groups - sori. Fern spores give rise to free-living bisexual growths (gametophytes) bearing antheridia and archegonia. For fertilization, the presence of droplet-liquid water is necessary, in which multiflagellate sperm can move.

A sporophyte develops from a fertilized egg. As the sporophyte grows, it becomes independent and the gametophyte dies.

The Fern division is divided into 7 classes. Of these, 4 classes are represented exclusively by fossil forms, which differed in appearance from typical ferns.

Let's take a closer look at the male shield fern (Dryopteris filix-mas), which, in terms of its general structure and development cycle, is typical of ferns. It forms a thick creeping rhizome, at the end of which a rosette of large, doubly pinnately dissected “leaves” appears annually. Young leaves are snail-shaped at the end and grow from the top (like a stem). Adventitious roots extend from the rhizomes.

Round sori are formed on the lower surface of the fronds in summer. Identical spores are formed inside the sporangium. Male shield fern is a typically homosporous fern. Once on, the spore germinates and a shoot is formed. It is a heart-shaped green plate about 1 cm in size. Archegonia and antheridia are formed on the lower surface of the prothallus. Helically twisted multiflagellate spermatozoa develop in the antheridia. Fertilization occurs in the presence of water. A perennial large sporophyte gradually grows from a fertilized egg.

Aquatic ferns are heterosporous plants. This is a small group. An example is the floating salvinia (Salvinia natans), which belongs to the order Salviniales. This is a small plant that floats on water.

Male and female gametophytes develop from micro- and megaspores, which are formed in micro- and megasporangia. The male gametophyte, developing from a microspore, is greatly reduced.

The female gametophyte develops inside a megaspore and is multicellular. After fertilization, a perennial sporophyte develops. The process of spore germination, fertilization and sporophyte development occur in water.

The practical importance of ferns is small. The young leaves of some herbaceous plants, as well as the core of tree ferns, are eaten. Some ferns are medicinal plants.

In ferns, horsetails and mosses, sexual reproduction can occur only in the presence of water at the time of fertilization.

The further evolution of higher plants followed the path of ensuring the independence of sexual reproduction from the availability of water.

This possibility was realized in seed plants. Here the general direction of the evolutionary development of the sporophytic line continues - the progressive development of the sporophyte and the further reduction of the gametophyte. The sporophyte reaches its most complex structure in angiosperms.

Among higher plants, only two divisions are characterized by the presence of a seed: gymnosperms and angiosperms. The seed determined the dominance of seed plants in the modern plant cover, since inside it there is already a sporophyte embryo and it contains a significant reserve nutrients.

Seed plants are heterosporous. They produce microspores, which give rise to the male gametophyte, and megaspores, which give rise to the female gametophyte.

Megaspores of seed plants develop in special formations - ovules (ovules), which are modified megasporangia. The megaspore remains permanently enclosed within the megasporangium. In the megasporangium, the development of the female gametophyte, the process of fertilization and embryo development occur. All this ensures the independence of fertilization from drop-liquid water.

During development, the ovule turns into a seed. The seed contains an embryo - a young, embryonic, very small sporophyte. It has a root, a bud and embryonic leaves (cotyledons). A sufficient supply of nutrients in the seed ensures the first stages of embryo development. Thus, seeds provide more reliable plant dispersal than spores.

Division Gymnosperms (Pinophyta, or Gymnospermae)

Gymnosperms are evergreen, less often deciduous trees or shrubs, and rarely lianas. The leaves of gymnosperms vary greatly in shape, size, morphological and anatomical features. Thus, the shape of the leaves can be scale-like, needle-like, pinnate, double-pinnate, etc.

Gymnosperms belong to heterosporous plants. Microspores are formed in microsporangia located on microsporophylls, and megaspores are formed in megasporangia formed on megasporophylls. Micro- and megasporophylls attached to the axis are a shortened spore-bearing shoot (strobilus, or cone). The structure of strobili in gymnosperms is varied.

The Gymnosperm department includes 6 classes, and the classes Seed ferns (Pteridospermae) and Bennettites (Bennettitopsida) are completely extinct. Today's living gymnosperms, numbering about 700 species, belong to the classes Cycadopsida, Gnetopsida, Ginkgopsida and Pinoposida.

Class Seed ferns reached its greatest development during the Carboniferous period. These plants became completely extinct in the Triassic period. They were represented by trees and vines. Their tree-like forms resembled modern tree ferns. Unlike modern ferns, they reproduced through seeds.

Seed ferns had large, mostly feathery leaves. Assimilating leaves differed sharply from spore-bearing leaves (sporophylls). The latter were of two types: microsporophylls and megasporophylls.

From seed ferns evolved primitive groups of gymnosperms, which are characterized by true strobili, or cones (Bennettiaceae, Cycadaceae).

Bennettite class- completely extinct plants. They were mainly represented by tree-like forms. Many of them had slender, tall trunks topped with large feathery leaves at the top.

Many Bennettites had bisexual strobili, reminiscent in structure of the flower of modern angiosperms. Microsporophylls were located in large numbers along the periphery of the strobilus, and reduced megasporophylls were located in the center of the strobilus. Each megasporophyll had one ovule. Bennettite seeds contained an embryo that filled the entire seed.

Bennettites are similar in appearance to cycads, and the two classes are thought to be descended from seed ferns.

Class Cycadaceae- a once widespread group of plants. Currently, this class includes about 120 species from 10 genera, found in tropical and subtropical regions of the globe. Cycads are tree-like plants similar to palm trees. Their leaves are large, hard, evergreen. In most cycads, sporophylls are collected in strobili (cones), which are formed at the end of the trunk among the leaves. Cycads are dioecious plants. Male and female strobili are formed on different individuals.

One of the typical representatives of the class is the drooping cycad (Cycas revoluta), widespread in East Asia. This is a tree with a columnar trunk up to 3 m high. At the top of the trunk there is a crown of feathery leaves up to 2 m long. In male specimens, male strobili 50-70 cm long are formed.

Microspores spill out from the microsporangium and are transferred by a meter to the ovule, where the male prothallus develops further.

Megasporophylls in all species of the cycad genus are located in small numbers at the apex of the stem, alternating with vegetative leaves. Megasporophylls are pinnate, differ from vegetative leaves in smaller size, and are yellow or reddish in color. In the lower part of the megasporophyll, on its branches, megasporangia (ovules) are located. They are large, up to 5-6 cm long.

In the center of the ovule there is multicellular tissue - endosperm (a modified female prothallus), in the upper part of which two archegonia with large eggs are formed. Fertilization is carried out by motile spermatozoa having numerous flagella. An embryo develops from a fertilized egg. It has all the parts inherent in an adult plant: the first leaves (cotyledons) and the rudimentary stem (subcotyledon), which turns into the root.

Thus, in cycads the sexual generation is greatly reduced. The male gametophyte is reduced to three cells, two of which are antheridium. The female gametophyte is a small formation located inside the macrosporangium on the sporophyte. The female gametophyte has lost the ability to exist independently.

TO Gnetovye class include representatives of three genera: Ephedra, Welwitschia and Gnetum.

The class is characterized by the following general characters: the presence of perianth-like integuments around microsporophylls and megasporophylls; dichasial branching of strobili assemblies; dicotyledonous embryos; the presence of vessels in the secondary xylem; absence of resin passages.

There are 40 species in the genus Ephedra, native to arid and desert regions of the globe. Most species are represented by low, highly branched shrubs, reminiscent of horsetails.

Ephedras are dioecious plants, less often monoecious. On male specimens microstrobiles are formed, on female specimens - megastrobiles. At the top of the megastrobilus there is an ovule, or ovule (megasporangium). An embryo develops from a fertilized egg, and a seed develops from an ovule, surrounded by a juicy, red-colored outer covering.

There is only one species in the genus Welwitschia - the amazing Welwitschia (Welwitschia mirabilis), which lives in the deserts of southwestern Africa. It has a rather long root and a short and thick stem. In the upper part, two opposite ribbon-like leaves extend from the stem, up to 2-3 m long, lying on the ground and growing throughout life. Velvichia is a dioecious plant. Micro- and megastrobiles, forming complex branched assemblies, appear directly above the bases of the leaves, as if in their axil. The mature embryo is surrounded by endosperm and has two cotyledons, a subcotyledon, a primary root and a stalk.

The genus Gnetum has about 30 species. They grow in tropical rainforests. This small trees, shrubs and vines. They have wide, leathery leaves arranged oppositely. Plants are dioecious. Microstrobili are catkin-shaped and complex. On the axis of the megastrobilus, which looks like an elongated earring, there are ovules (megasporangium). After fertilization, an embryo develops with two cotyledons. The ovules turn into bright pink seeds.

The only modern representative class Ginkgoidae is An ancient relict plant - ginkgo biloba (Ginrgo biloba). It is a deciduous tree, reaching a height of more than 30 m and having a trunk diameter of more than 3 m. Ginkgo leaves are petiolate, the blade is fan-shaped, usually bilobed at the apex. Ginkgo is a dioecious plant. Microstrobiles are catkin-shaped. Ovules (usually two in number) develop on megastrobiles. Two archegonia are formed inside each ovule. Spermatozoa are motile. One of them fertilizes the egg. A seed is formed from the ovule, which in its structure resembles a plum fruit. The outer layer of the shell covering the seed is juicy, underneath there is a hard stony shell and an inner thin layer. The embryo consists of a root, a stalk and two cotyledons.

Class Conifers includes two subclasses: Cordaitales and Conifers (Pinidae). Cordaites are long extinct plants. They reached their greatest development during the Carboniferous period. Cordaites were large trees with a monopodially branching stem and a high crown. Between the leaves on the branches there were reproductive organs - complex catkin-shaped collections of strobili.

Conifers are the most extensive and richest subclass among all gymnosperms. In terms of its importance in nature and in human life, this group ranks second after flowering plants. Currently, conifers number about 610 species belonging to 56 genera and 7 families. They form forests over vast areas of Northern Eurasia and North America, and are found in temperate regions of the Southern Hemisphere. In terms of their antiquity, conifers are superior to all living groups of seed plants; they have been known since the Carboniferous.

The anatomical structure of coniferous stems is quite uniform. Wood consists of 90-95% tracheids. The bark and wood of many coniferous species contain many horizontal and vertical resin ducts.

The strobili of conifers are exclusively dioecious. Plants are monoecious, less often dioecious. The strobiles vary greatly in shape and size.

The main features of the life cycle of conifers can be considered using the example of Scots pine (Pinus sylvestris). This is a slender tree, reaching a height of 40 m. At the ends of the pine branches there are buds that give rise to new shoots every year.

In spring, at the base of some young shoots, collections of greenish-yellow male cones - strobili - are formed. On the axis of the male cone there are microsporophylls, on the lower surface of each there are two microsporangia (pollen sacs). Microspores are formed inside the microsporangia after reduction division. The microspore begins to germinate inside the microsporangium and ultimately turns into a pollen grain that has two cells: vegetative and generative (from the latter, two male gametes - sperm) develop. The pollen grain (pollen) leaves the microsporangium (anther). Mature pine pollen has two shells: the outer one is exine, the inner one is intina. The exine forms two air sacs that facilitate the transfer of pollen by the wind.

Megastrobiles are called female cones. They are collected in groups of 1-3 at the ends of young shoots. Each cone represents an axis from which scales of two types extend in all directions: sterile (covering) and seed-bearing. On each seed scale, two ovules are formed on the inside. In the center of the ovule, the endosperm or prothallus develops (female gametophyte). It is formed from a megaspore, and its cells have a haploid set of chromosomes. In the upper part of the endosperm, two archegonia with large eggs are laid.

After the pollination process, the fertilization process begins. The period between pollination and fertilization lasts about a year. A long pollen tube grows from the pollen grain and moves towards the archegonium. Two sperm move along the pollen tube to the egg. The tip of the pollen tube, which reaches the egg, ruptures and releases sperm. One of the sperm fuses with the egg, and the other dies. As a result of fertilization, a diploid zygote is formed, and from it an embryo arises.

The mature embryo consists of a pendulum, a primary root, a stalk and cotyledons. Education pendant is one of distinctive features all conifers. In parallel with the development of the embryo, the integument of the ovule is transformed into the seed coat. The entire ovule turns into a seed. After the seeds ripen, the scales of the cones separate and the seeds spill out. A mature seed has a transparent wing.

The subclass Conifers includes seven orders, two of them are extinct. Currently, there are the following: Araucariaceae, Nogocarpaceae, Pine, Cypress and Yew. The last three orders are the most common.

Order Pine(Pinales) is represented by one family - Pine (Pinaceae). There are 11 genera and about 260 species in this family. The largest genera are Pine (Pinus), Spruce (Picea), Fir (Abies) and Larch (Larix).

The largest in this family is the genus Pine, which includes about 100 species. Scots pine, whose needles are collected in pairs, is widespread in our country. In the Asian part of the country, Siberian pine (the so-called “Siberian cedar”), whose needles are collected in bunches of five, is quite widespread. Siberian pine produces valuable wood and edible seeds - pine nuts.

The genus Spruce includes about 50 species living in the Northern Hemisphere. These are tall slender trees. Characteristic of spruces pyramidal shape crowns The needles are tetrahedral, pointed at the end. In our country, the two most common species are: Norway spruce (Picea abies) and Siberian spruce (Picea obovata).

The Fir genus includes 40 species living in the Northern Hemisphere. These are large tall trees. They are similar in appearance to spruce, but their needles are flat, soft, with two stripes of stomata on the underside. Siberian fir (Abies sibirica) is widespread in Russia. It grows mainly in the southern regions of Western Siberia and in the northeast of the European part of the country.

The Larch genus is represented by 15 species that live in the Northern Hemisphere. These are large, straight-trunked trees that shed their needles in the winter. Larch needles are soft and flat. They are located in bunches on short shoots and singly on elongated shoots. In our country, the most common species are Siberian larch (Larix sibirica) and Dahurian larch (Larix dahurica).

Order Cypress(Cupressales) is represented by two families. The Taxodiaceae family currently includes 10 genera and 14 species. Modern taxodiaceae are large trees, less often shrubs. Among them, we should mention the sequojadendron giganteum, or “mammoth tree” - one of the largest and longest-living plants in the world. Taxodium distichum is also interesting. It grows along river banks and swamps in southeastern North America. In this tree, horizontal roots form vertical outgrowths of a conical or bottle-shaped form - respiratory roots up to 0.5 m high.

The Cypress family (Cupressaceae) includes 19 genera and about 130 species, widely distributed in the Southern and Northern Hemispheres. Cypress - evergreen shrubs and trees. Their leaves are scale-like or needle-shaped, small, arranged oppositely or in whorls of three, rarely four.

The genera Cypress and Juniper contain quite a few species (20 and 55 species, respectively). Types of cypress are monoecious evergreen trees with a pyramidal or spreading crown, less often shrubs. In culture, the most famous is the evergreen pyramidal cypress. The Juniper genus is represented by small evergreen trees or shrubs, sometimes creeping. Leaves are needle-shaped or scale-shaped. In junipers, after fertilization, the scales of megasporophylls become fleshy and grow together, forming the so-called “coneberry.” Junipers are widespread. They are light-loving, drought-resistant, frost-resistant and undemanding to soil conditions.

Order Yew(Taxales) includes evergreen trees and shrubs from two families, 6 genera and 26 species. The most famous genus is Tiss; it is represented by 8 species. In our country, the most common yew, or common yew (Taxus baccata), has flat needles. This tree has hard and heavy wood that is almost resistant to rotting. The seeds are surrounded by a bright red, fleshy covering, which makes them look like berries. Yew berry is the most shade-tolerant tree of all conifers.

The higher ones include all terrestrial leafy plants that reproduce by spores or seeds. The modern plant cover of the Earth consists of higher plants, the common biological feature of which is autotrophic nutrition. In the process of long-term adaptive evolution of autotrophic plants in the air-ground habitat, the general structure of higher plants was developed, expressed in their morphological division into leaf-stem shoots and root system and in complex anatomical structure their organs. In higher plants, adapted to life on land, special organs for absorbing mineral solutions from the substrate arise - rhizoids (in the gametophyte) or root hairs (in the sporophyte). Assimilation carbon dioxide from the air is carried out by leaves, consisting mainly of chlorophyll-bearing cells. The protostele of the primary stem and root was formed from the conductive tissue that connects the two most important terminal apparatuses—the root hair and the green cell of the leaf—and from the supporting tissue that ensures the plant’s stable position in the soil and in the air. The stem, with its branching and leaf arrangement, ensures the best placement of leaves in space, which achieves the most complete use of light energy, and the branching of the root provides the effect of placing a huge suction surface of root hairs in a relatively small volume of soil. Primary higher plants inherited from their algae ancestors the highest form of the sexual process - oogamy and a two-phase development cycle, characterized by the alternation of two interdependent generations: the gametophyte, which carries reproductive organs with gametes, and the sporophyte, which carries sporangia with spores. Only the sporophyte develops from the zygote, and the gametophyte from the spore. At the early stages, two directions of evolution of higher plants appeared:

• 1) the gametophyte plays a predominant role in the life of the organism,
• 2) the predominant “adult” plant is the sporophyte.

Modern higher plants are divided into the following types:

• 1) Bryophytes,
• 2) Ferns,
• 3) Gymnosperms,
• 4)Angiosperms, or Flowering.

The most important similarities between higher and lower plants

The most common theory of the origin of higher plants associates them with green algae. This is explained by the fact that both algae and higher plants are characterized by the following characteristics: the main photosynthetic pigment is chlorophyll a; the main storage carbohydrate is starch, which is deposited in chloroplasts, and not in the cytoplasm, as in other photosynthetic eukaryotes; cellulose is an essential component of the cell wall; the presence of pyrenoids in the chloroplast matrix (not in all higher plants); formation of phragmoplast and cell wall during cell division (not in all higher plants). Both the majority of algae and higher plants are characterized by an alternation of generations: a diploid sporophyte and a haploid gametophyte.

The main differences between higher and lower plants:

Habitat: among the lower ones - water, among the higher ones - mainly land.

Development of various tissues in higher plants - conductive, mechanical, integumentary.

The presence of vegetative organs in higher plants - root, leaf and stem - division of functions between different parts of the body: root - fixation and water-mineral nutrition, leaf - photosynthesis, stem - transport of substances (ascending and descending currents).

Higher plants have integumentary tissue—the epidermis—that performs protective functions.

Enhanced mechanical stability of the stem of higher plants due to a thick cell wall impregnated with lignin (provides rigidity to the cellulose skeleton of the cell).

Reproductive organs: in most lower plants they are unicellular, in higher plants they are multicellular. The cell walls of higher plants more reliably protect developing gametes and spores from drying out.

Higher plants appeared on land in the Silurian period in the form of rhyniophytes, primitive in structure. Finding themselves in a new air environment, rhinophytes gradually adapted to the unusual environment and over the course of many millions of years gave rise to a huge variety of land plants of various sizes and structural complexity.

One of the key events in the early stage of plant emergence on land was the appearance of spores with durable shells that made it possible to tolerate arid conditions. Spores of higher plants can be spread by the wind.

Higher plants have different tissues (conductive, mechanical, integumentary) and vegetative organs(stem, root, leaf). The conductive system ensures the movement of water and organic matter in land conditions. The conducting system of higher plants consists of xylem and phloem. Higher plants have protection from drying out in the form of a covering tissue - the epidermis and a water-insoluble cuticle or a plug formed during secondary thickening. Thickening the cell wall and impregnating it with lignin (giving rigidity to the cellulose skeleton of the cell wall) gave higher plants mechanical stability.

Higher plants (almost all) have multicellular organs of sexual reproduction. The reproductive organs of higher plants are formed in different generations: on the gametophyte (antheridia and archegonia) and on the sporophyte (sporangia).

Alternation of generations is characteristic of all higher land plants. During the life cycle (that is, the cycle from the zygote of one generation to the zygote of the next generation), one type of organism is replaced by another.

The haploid generation is called a gametophyte because it is capable of sexual reproduction and forms gametes in the multicellular organs of sexual reproduction - antheridia (male motile gametes - sperm are formed) and archegonia (female immobile gametes - egg are formed). When the cell matures, the archegonium opens at the apex and fertilization occurs (fusion of one sperm with an egg). As a result, a diploid zygote is formed, from which a generation of diploid sporophyte grows. The sporophyte is capable of asexual reproduction with the formation of haploid spores. The successors give rise to a new gametophytic generation.

One of these two generations always predominates over the other and accounts for most of the life cycle. In the life cycle of mosses, the gametophyte predominates; in the cycle of holo- and angiosperms, the sporophyte predominates.