General features of higher plants. Higher plants - definition, characteristics and signs

general characteristics. Higher plants include mosses, club mosses, horsetails, ferns, gymnosperms, angiosperms (flowering). Unlike lower plants, higher plants have well-differentiated tissues and organs. All higher male and female reproductive organs multicellular. Ontogeny in higher plants is divided into embryonic and postembryonic periods.
Higher plants, according to a very important feature - the structure of the female genital organs - are divided into two large groups: archegonial and pistillate. The first of them includes, for example, the departments Bryophytes, Lycopsids, Horsetails, Ferns, Gymnosperms and unites more than 50 thousand species. All representatives of this group have a female genital organ - archegonium. The second group - pistillates, is represented by one department - Angiosperms, or Tsvetkovy (about 250 thousand species), the female genital organ of which is the pistil.
Tissues of higher plants. Tissue is a collection of cells that are similar in morphological and physiological characteristics and perform certain functions. In the process of evolution, the most perfect tissues were formed in flowering plants.
Educational fabrics represented by young, rapidly dividing cells. Localized in the kidneys and the zone of reproduction of the roots. They provide the growth of plant organs in length and thickness, the formation of tissues.
Integumentary tissues(skin, cork, rind) are formed either by living, densely packed cells (skin) covering leaves, green stems and all parts of the flower, or by several layers of dead cells covering thick stems and tree trunks. Protect organs.
Conductive tissues form vessels, sieve tubes and conducting vascular fibrous bundles. Vessels are hollow tubes with woody walls. They form a wood-xylemma that runs along the root, stem and leaf veins. Provide an upward flow of water and minerals. Sieve tubes form a vertical row of living cells with sieve-like transverse partitions. A bast is formed - a phloem located along the root, stem, leaf veins. Carry out the transport of organic substances from the leaves to other organs and tissues. Conductive vascular-fibrous bundles form separate strands (herbs) or a continuous array (woody forms).
mechanical fabrics (fibers) consist of long, lignified, dead cells located around vascular-fibrous bundles. They act as the backbone of the plant.
Main fabrics subdivided into assimilation and storage. Assimilation tissues are represented by cells that form the columnar and spongy tissue of the leaf. They form the pulp of the leaf and stem, carry out photosynthesis and gas exchange. Storage tissues are formed by cells filled with starch, protein, oil drops, etc.
To excretory tissues lactic vessels, or lactiferous vessels, whose cells secrete milky juice.

Lower plants (Tallobionta) are a group of independent divisions that differ from one another in a complex of characteristics, vital properties and origin, and at the same time are characterized by the presence of common features that allow these divisions to be combined into one category - lower plants.

characteristic feature representatives of lower plants is the lack of dismemberment of their body into roots, stems and leaves, which is characteristic of higher - leafy plants. The body of lower plants, not divided into separate organs, is called thallus, or thallus, therefore lower plants are often called thallus, or thallus. Thallus is unicellular and multicellular, has a different size (from a few micrometers to 30 m, as, for example, in brown algae). Lower plants have underdeveloped cell differentiation, they lack vascular bundles. The female reproductive organ is an oogonium, usually unicellular.

According to the method of nutrition, representatives of lower plants are divided into 2 sharply different groups: heterotrophic and autotrophic plants. Some representatives of lower plants (most bacteria, slime molds and fungi) do not contain chlorophyll and, therefore, are incapable of photosynthesis; these plants feed on ready-made organic substances - heterotrophically. The remaining representatives of the department of lower plants have chlorophyll and, therefore, are able to photosynthesize, that is, they feed autotrophically (algae and lichens).

Most representatives of lower plants are also characterized by a wide geographical distribution in a wide variety of conditions.

Higher plants (Embryobionta) differ from the lower ones in the complex structure of the body, which is divided into a stem, a leaf, and, in the vast majority, a root. A characteristic feature of higher plants is also a terrestrial way of life. These are usually land plants, they develop in the air. In the process of long evolution, higher plants developed many different adaptations to the terrestrial way of life; simultaneously with the differentiation of organs, the anatomical structure also became more complicated. Therefore, higher plants are otherwise called leafy, or cormophytes.

There are several theories about the origin of higher plants. At present, it is believed that higher plants were of monophyletic origin, that is, they descended from one common ancestor. Such an ancestor of higher plants was algae, but which ones have not yet been precisely established. It is most likely that higher plants originated from extinct forms of brown algae.

The emergence of plants on land was carried out gradually. The first land plants also had a thallus structure. Gradually, thallus forms became more complex, acquired a dismemberment of the body and formed leaf-stem forms.

The "conquest" of land was a grandiose event in the life of plants. The winners were those plants that have adapted to new habitat conditions due to the development of specialized organs: 1) leaves, with the help of which photosynthesis is carried out; 2) stems on which leaves are formed and through which the connection between leaves and roots is carried out in the movement of nutrients; 3) roots located in the soil in which they were fixed and from which they absorbed nutrients; 4) reproductive organs - seeds, in more highly organized higher plants, as well as flowers and fruits (in angiosperms).

The presence of aquatic forms in existing flowering plants (duckweed, water lily, etc.). is a secondary phenomenon.

Representatives of higher plants are multicellular organisms. They have a variety of specialized tissues, including a well-defined conducting system, mechanical and integumentary tissues, which developed and improved as higher plants evolved.

The sexual process became more complicated, multicellular genital organs appeared - archegonia, in which the egg cell develops, and antheridia (numerous spermatozoa are formed in them).

Archegonium has a flask-like shape, its lower expanded part is called the abdomen, an egg develops in it; the upper narrow part is called the neck. By the time of fertilization, the neck of the archegonium is mucilaginous inside, which contributes to the penetration of the sperm to the egg. Therefore, in most plants, the ovum is protected by the archegonium. Antheridium is an oval-shaped organ with an opening for the exit of mature spermatozoa.

In the process of evolution, there was a gradual reduction of the genital organs in higher plants, and angiosperms, being the most highly organized, no longer have either antheridia or archegonia.

Gradually there were significant changes in the structure of male gametes. Motile spermatozoa with flagella, which are inherent in lower and spore higher plants, are replaced in more perfect higher plants (gymnosperms and angiosperms) by spermatozoa that do not have flagella. Sperm have lost the ability to move in water. And if in more ancient higher plants, such as mosses, club mosses, horsetails and ferns, there is still a dependence of the sexual process on the aquatic environment, then for more highly organized ones (the vast majority of gymnosperms and all angiosperms) the complete independence of sexual reproduction from drip-liquid water is characteristic . In these groups of plants, male gametes - sperm - move to the egg with the help of a pollen tube.

In higher plants, a rhythmic change of generation is well expressed: sexual (gametophyte) and asexual (sporophyte).

For most higher plants, the alternation of generations is characterized by the dominance of the sporophyte over the gametophyte. Only bryophytes are an exception, since their gametophyte reaches a greater development, while the sporophyte, on the contrary, is significantly reduced.

Highly organized higher plants are characterized by the presence of a new organ - a seed with an embryo, which appeared as a result of historical development.

The first terrestrial plants are considered extinct psilophytes, which had a conducting system, integumentary tissues and were already sufficiently adapted to a terrestrial lifestyle.

Higher plants are represented by a huge variety and occupy a dominant position on land. There are over 300 thousand species of higher plants, the largest number of which belongs to the angiosperms (flowering) department.

All higher plants according to the nature of reproduction are conditionally divided into 2 large groups: higher spore and seed plants. The higher spore plants include 5 divisions: 1) bryophytes; 2) psilophyte-like; 3) lycopsform; 4) horsetail; 5) fern-like.

A characteristic distinguishing feature of seed plants is the presence of a seed, which is absent in the previously considered plants. Seed plants reproduce and spread mainly by seeds, this is their main difference from higher spore plants, which reproduce by spores.

From point of view evolutionary development seed formation in plants is a progressive adaptation in the struggle for existence in comparison with reproduction by spores. The spore is a single cell, and the seed, unlike the spore, is a multicellular formation. The seed carries the embryo, which has in its infancy all the organs of the plant: root, stem, leaves. In addition, the embryo is provided with a supply of nutrients that it needs during germination and during the first time of the existence of its seedling. Thus, the appearance of seeds in plants contributed to their settlement in drier places.

The process of fertilization in seed plants is not associated with aquatic environment: male gametes (sperm) have lost their mobility and are transferred to the female gamete (ovum) by a pollen tube, which was a great advantage for seed plants in their struggle for the "conquest" of land. With the appearance of seeds in seed plants, there was an even greater decrease in the sexual generation (gametophyte), and, conversely, the asexual generation (sporophyte) was more developed. The sporophyte - the plant itself - in seed plants often reaches large sizes - a pine, oak tree, etc., while the gametophyte is a microscopically small formation.

This group of plants combines 2 departments of higher plants: gymnosperms and angiosperms, which differ significantly from each other both in morphological characteristics and in physiological characteristics.

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-terrestrial habitat, the general structure of higher plants has developed, which is expressed in their morphological division into a leaf-stem shoot and root system and in the complex anatomical structure of their organs. In higher plants that have adapted to life on land, there are special organs for absorbing mineral solutions from the substrate - 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 end apparatuses - the root hair and the green cell of the leaf, and from the supporting tissue that ensures the stable position of the plant in the soil and in the air. The stem, by its branching and leaf arrangement, provides the best placement of leaves in space, which achieves the most complete use of light energy, and root branching - 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 higher form the sexual process - oogamy and a two-phase development cycle, characterized by the alternation of two interdependent generations: the gametophyte, which carries the genital organs with gametes, and the sporophyte, which carries sporangia with spores. From the zygote, only the sporophyte develops, and from the spore, the gametophyte develops. 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 differences 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 features: 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); phragmoplast and cell wall formation cell division(not in all higher plants). Both for most algae and for higher plants, the alternation of generations is characteristic: a diploid sporophyte and a haploid gametophyte.

The main differences between higher and lower plants:

Habitat: the lower ones have water, the higher ones have mostly dry land.

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

Presence in higher plants vegetative organs- 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 an integumentary tissue - the epidermis, which performs protective functions.

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

Reproductive organs: in most lower plants - unicellular, in higher plants - 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 rhinophytes, primitive in structure. Once in a new air environment for them, rhinophytes gradually adapted to an unusual environment and over many millions of years gave a huge variety of terrestrial plants of various sizes and complexity of structure.

One of the key events in the early stage of plant emergence on dry land was the appearance of spores with hard shells that allow them to endure arid conditions. The spores of higher plants can be spread by wind.

Higher plants have various fabrics(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 an integumentary tissue - the epidermis and a water-insoluble cuticle or cork formed during secondary thickening. The thickening of the cell wall and its impregnation with lignin (gives rigidity to the cellulose backbone of the cell membrane) gave higher plants mechanical stability.

Higher plants (almost all) have multicellular organs of sexual reproduction. The reproductive organs of higher plants are formed on 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 (i.e., 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, since it is capable of sexual reproduction and forms gametes in the multicellular organs of sexual reproduction - antheridia (male mobile gametes are formed - spermatozoa) and archegonia (a female immobile gamete is formed - egg). When the cell matures, the archegonium opens at the top and fertilization occurs (the fusion of one spermatozoon with the 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 latter give rise to a new gametophyte generation.

One of these two generations always prevails over the other, and it 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.

3. Evolution of gametangia and life cycles of higher plants. Works by V. Hofmeister. Biological and evolutionary significance of heterosporia
Higher plants probably inherited their life cycle - the alternation of sporophyte and gametophyte - from their algal ancestors. As is known, algae exhibit very different relationships between the diploid and haploid phases of the life cycle. But in the algal ancestor of higher plants, the diploid phase was probably more developed than the haploid one. In this regard, of great interest is the fact that of the most ancient and most primitive higher plants of the extinct group of rhinophytes, only sporophytes have been reliably preserved in the fossil state. Most likely this can be explained by the fact that their gametophytes were more tender and less developed. This is also true of the vast majority of living plants. The only exceptions are bryophytes, in which the gametophyte prevails over the sporophyte.

The evolution of the life cycle of higher plants proceeded in two opposite directions. In bryophytes, it was directed towards an increase in the independence of the gametophyte and its gradual morphological division, the loss of independence of the sporophyte and its morphological simplification. The gametophyte became an independent, completely autotrophic phase of the life cycle of bryophytes, while the sporophyte was reduced to the level of an organ of the gametophyte. In all other higher plants, the sporophyte became an independent phase of the life cycle, and the gametophyte in them gradually decreased and simplified during evolution. The maximum reduction of the gametophyte is associated with the division of the sexes. Miniaturization and simplification of unisexual gametophytes occurred at a very accelerated pace. Gametophytes lost chlorophyll very quickly, and development was increasingly carried out at the expense of nutrients accumulated by the sporophyte.

The greatest reduction of the gametophyte is observed in seed plants. It is striking that both among the lower and higher plants, all large and complex organisms are sporophytes (kelp, fucus, lepidodendrons, sigillaria, calamites, tree ferns, gymnosperms and woody angiosperms).

Thus, everywhere around us, whether in the field or in the garden, in the forest, in the steppe or in the meadow, we see only sporophytes exclusively or almost exclusively. And only with difficulty and usually after a long search, we will find tiny gametophytes of ferns, club mosses and horsetails on moist soil. Moreover, the gametophytes of many club mosses are subterranean and therefore extremely difficult to detect. And only liverworts and mosses are noticeable by their gametophytes, on which much weaker, simplified sporophytes develop, usually ending with one apical sporangium. And to consider the gametophyte of any of the numerous flowering plants, as well as the gametophytes of conifers or other gymnosperms, is possible only under a microscope.

Works by V. Hofmeister.

Hofmeister received the most significant results in the field of comparative plant morphology. Described the development of the ovule and embryo sac (1849), the processes of fertilization and development of the embryo in many angiosperms. In 1851, his work Comparative Studies of Growth, Development, and Fruiting in Higher Myophogamous Plants and Seed Formation in Coniferous Trees was published, the result of Hofmeister's research on the comparative embryology of archegonial plants (from bryophytes to ferns and conifers). In it, he reported on his discovery - the presence of alternation of generations in these plants, asexual and sexual, established family ties between spore and seed plants. These works, carried out 10 years before the appearance of Charles Darwin's teachings, were of great importance for the development of Darwinism. Hofmeister is the author of a number of works on plant physiology, devoted mainly to the study of the processes of water and nutrients intake through the roots.

Biological and evolutionary significance of heterosporia

Heterosporia - heterosporous, spore formation different sizes in some higher plants (for example, aquatic ferns, Selaginella, etc.). Large spores - megaspores, or macrospores - produce female plants (growths) during germination, small - microspores - male. In angiosperms, a microspore (dust speck), germinating, gives a male outgrowth - a pollen tube with a vegetative nucleus and two sperm; the megaspore, which is formed in the ovule, germinates into the female outgrowth - the embryo sac.

Biological meaning:

—The desire to separate the sexes, i.e. dioeciousness:

- division in time: protandria (mosses) - first developed on the gametophyte. male and then female. floor. gametes.

—protogyny

- Physiological heterogeneity.

The evolutionary significance of heterosporia led to the emergence of the seed, and this allowed the seed. rast. completely lose dependence on external. environment and dominance. on the globe.

Read also:

The difference between higher plants and algae.

Higher plants are inhabitants of the ground-air environment, which is fundamentally different from the water.

The ground-air environment differs sharply from the water gas composition. These media also differ from each other in terms of humidity, temperature, density, specific gravity, and in the ability to change the strength and spectral composition of sunlight. The ecological conditions of the ground-air environment caused changes in the morphological and anatomical structure of the vegetative and reproductive organs of higher plants during a long process of evolution. This led to the development of adaptations in higher plants for a terrestrial lifestyle.

Higher plants, germ plants (Embryobionta, Embryophyta, from the Greek Embryon - embryo and phyton - plant), coppice, leaf-stem (Cormophyta, from Greek Kormos - stem, phyton - plant), talom plants (Telomophyta, Telomobionta, thalom - aboveground axial cylindrical organ of ancient higher plants and phyta - plant) differ from lower plants (Thallophyta, from Greek thallos - thallus, thallus and phyton - plant). Higher plants are complex differentiated multicellular organisms adapted to life in the terrestrial environment (with the exception of a few obviously secondary forms) with the correct alternation of two generations - sexual (gametophyte) and asexual (sporophyte). The organs of higher plants have a complex anatomical structure. The conducting system of the first terrestrial plants is represented by special tracheid cells, phloem elements, and in later groups by vessels and sieve-like tubes. Conductive elements are grouped into regular combinations - vascular fibrous bundles. Higher plants have a central cylinder-stele. At first, the central cylinder is simple - pratastela (from the Greek Protos - simple, stela - column, column). Then more complex steles arise: actynastela (from the Greek. Actis - beam), plectastel (from the Greek. Plectos - woven, twisted), siphonastel (from the Greek. Siphon - tube), artrastela (from lat. Arthrus - segmented), dyktyyastela ( from Greek diktyon - network), eustela (from Greek eu - real), ataktastela (from Greek atactos - chaotic) - the elements of the central cylinder of the meristel on the cross section of the stem are evenly located in its main parenchyma. The scheme of marked evolution of stelae is shown in Figure 1.

Higher plants have a complex musculoskeletal apparatus. Under the conditions of terrestrial life, highly developed mechanical tissues arise in higher plants. Sexual organs of higher plants - gametangia and sparangia Multicellular (or gametangia are reduced). In perfect higher plants, they are called anteridyav (male) and archigoniav (female). The zygote of higher plants develops into a typical squamous embryo. The reproductive organs of higher plants probably originated from multi-chambered gametangia of the type of modern hetaphorophic green algae. A characteristic feature of higher plants is the alternation of generations in the development cycle - gametaphyte (sexual) and sparaphyte (asexual) and the corresponding change in nuclear phases (haploid and diploid). The transition from the haploid nuclear phase to the diploid one occurs when the egg is fertilized by sperm or sperm. The transition from the diploid nuclear phase to the haploid one occurs during the formation of spores from a paragenous tissue - archespores by meiosis from a reduction in the number of chromosomes. A diagram of the general life cycle of a spore vascular plant is shown in Figure 2.

Origin of higher plants. The ancestors of higher plants were probably some kind of seaweed, in which, in connection with the transition to land, to a new environment, special adaptations were developed for water supply, for protecting gametangia from drying out and for ensuring the sexual process. An opinion is also expressed about the origin of higher plants from green schmatlet algae with heteratrychal thalomes of the type of modern hetaphorans with multichambered gametangia. Such algae had an isomorphic alternation of generations in the development cycle. The origin of higher plants is also associated with a group of streptaphyte algae, close to Kaleahetaev or choral. Precise fossil remains of higher plants (rhinite, harney, harneyaphyton, sporaganites, psilafite, etc.) are known from the Silurian (435-400 million years ago). From the moment they landed, higher plants developed in two main directions and formed two large evolutionary branches - haploid and diploid. The haploid branch of the evolution of higher plants is represented by the department of bryophytes (Bryophyta). In the development cycle of mosses, the gametaphyte, the sexual generation (the plant itself) predominates, while the sparaphyte is reduced and presented to the sparagons in the form of a box on a stem. The development of bryophytes proceeded from thalom forms to listaceous ones. The second evolutionary branch of higher plants with a predominance of sparaphyte in the development cycle is represented by the rest of the divisions of higher plants. Sparafit in terrestrial conditions turned out to be more adapted and lively. This group of higher plants with a predominance of sparaphyte in the development cycle has achieved the greatest success in conquering the land. Sparaphyte reaches large sizes, has a complex internal and external structure, the gametaphyte of this group of higher plants, on the contrary, has suffered reduction.

In more primitive higher plants - horsetail, moss, paparacepodobnye and others, some phases of development depend on water, without which the active movement of spermatozoa is impossible. Significant moisture in the substrate, the atmosphere is necessary for the existence of gametaphytes. In seed plants, as the most highly organized plants, adaptation to a terrestrial way of life was expressed in the independence of the sexual process of reproduction from a drop-liquid medium. The scheme of evolutionary changes in plants in the direction of increasing the size of the asexual (2n) and reducing the sexual (n) generations is shown in Figure 3.

Gradually went the improvement of higher plants, their adaptation to a variety of environmental conditions of life on Earth. Currently, there are more than 300 thousand species of higher plants. They dominate the Earth, inhabit it from the Arctic regions to the equator, from the humid tropics to dry deserts. Higher plants form various types of vegetation - forests, meadows, swamps, fill reservoirs. Many of them reach gigantic sizes (sequoias - up to 110 m and more); others are small, a few millimeters (duckweeds, some pistachios, mosses). Despite the great variety of appearance, higher plants retain a certain unity in structure. Higher plants are divided into 9 departments: ryniaphyta, zosterafilafity, bryophytes, dera-western, psilotopadobny, horsetail, paparacepodobny, gymnosperms and angiosperms (flowering). They are relatively easily linked with each other, which indicates the unity of their origin.

Description of higher plants. Their origin and characteristics

Place of higher plants in organic world

Modern science of the organic world divides living organisms into two kingdoms: pre-nuclear organisms (Procariota) and nuclear organisms (Eucariota). The super-kingdom of pre-nuclear organisms is represented by one kingdom - shotguns (Mychota) with two sub-kingdoms: bacteria (Bacteriobionta) and cyanothea, or blue-green algae (Cyanobionta).

The super-kingdom of nuclear organisms includes three kingdoms: animals (Animalia), mushrooms (Mycetalia, Fungi, or Mycota) and plants ( Vegetabilia, or plantae).

The animal kingdom is divided into two sub-kingdoms: protozoa (Protozoa) and multicellular animals (Metazoa).

The fungal kingdom is divided into two sub-kingdoms: lower mushrooms (Myxobionta) and higher mushrooms (Mycobionta).

The plant kingdom includes three sub-kingdoms: scarlet (Rhodobionta), true algae (Phycobionta) and higher plants (Embryobionta).

Thus, the subject of taxonomy of higher plants are higher plants that are part of the sub-kingdom of higher plants, the kingdom of plants, the super-kingdom of nuclear organisms.

General characteristics of higher plants and their difference from algae

Higher plants are inhabitants of the ground-air environment, which is fundamentally different from the aquatic environment.

Cells of higher plants:

a, b - meristematic cells; c - starch-bearing cell from the storage parenchyma; d - epidermal cell; e - binuclear cell of the secretory layer of the pollen nest; e - cell of the assimilation tissue of the leaf with chloroplasts; g - segment of the sieve tube with a companion cell; h - stony cell; and - a segment of the vessel.

Higher plants are leafy plants, many have roots. According to these signs in Latin they are called Cormophyta(from the Greek kormos - trunk, stem, phyton - plant) unlike algae - Thallophyta(from Greek thallos - thallus, thallus, phyton - plant).

The organs of higher plants have a complex structure. Their conducting system is represented by special cells - tracheids, as well as vessels, sieve tubes. Conductive elements are grouped into regular combinations - vascular fibrous bundles. Higher plants have a central cylinder - a stele.

At first, the central cylinder is simple - protostele (from the Greek protos - simple, stela - column, pillar). Then more complex steles appear: actinostele (from Greek actis - beam), plectostele (from Greek plectos - twist, twist), siphonostela (from Greek siphon - tube), artrostele (from Greek arthrus - jointed), dictiostele ( from Greek diktyon - network), eustela (from Greek eu - real), ataktostele (from Greek ataktos - disorderly).

Higher plants have a complex system integumentary tissues (epidermis, periderm, crust), a complex stomatal apparatus appears. Under the conditions of land-air life, highly developed mechanical tissues appear in higher plants.

The sexual organs of higher plants - multicellular antheridia (male) and archegonia (female) - probably originated from multicellular gametangia in algae such as dictyota and ectocorpus (from brown algae).

A characteristic feature of higher plants is the alternation of generations in the development cycle - the gametophyte (sexual) isporophyte (asexual) and the corresponding change of nuclear favs (haploid and diploid). The transition from the haploid nuclear phase to the diploid one occurs when the egg is fertilized by a sperm or sperm. Conversely, the transition from the diploid nuclear phase to the haploid one occurs when spores are formed from the sporogenous tissue - archesporium by meiosis with a reduction in the number of chromosomes.

Origin of higher plants

The haploid branch of the evolution of higher plants is represented by the mossy division ( Bryophyta)

In simpler forms (spore plants), the gametophyte still has an independent existence and is represented by an autotrophic or symbiotrophic outgrowth ( Lycopodiophyta, Equisetophyta, Polypodiophyta), and in heterosporous representatives of these departments, it is significantly simplified, reduced. In more organized - seed plants - the gametophyte has lost its independent way of life and develops on a sporophyte, while in angiosperms (flowering) it is reduced to a few cells.

Higher plants probably evolved from some kind of algae. This is evidenced by the fact that in the geological history of the plant world, higher plants were preceded by algae. The following facts testify in favor of this assumption: the similarity of the most ancient extinct group of higher plants - rhinophytes - with algae, a very similar nature of their branching; similarity in the alternation of generations of higher plants and many algae; the presence of flagella and the ability to swim independently in the male germ cells of many higher plants; similarity in structure and function of chloroplasts.

It is assumed that higher plants most likely originated from green algae, freshwater or brackish. They had multicellular gametangia, isomorphic alternation of generations in the development cycle.

The first land plants found in the fossil state were rhinophytes (rhinia, hornea, horneophyton, sporogonites, psilophyte, etc.).

After reaching land, higher plants developed in two main directions and formed two large evolutionary branches - haploid and diploid.

The haploid branch of the evolution of higher plants is represented by the bryophyte department. (Bryophyta). In the development cycle of mosses, the gametophyte, the sexual generation (the plant itself), predominates, while the sporophyte, the asexual generation, is reduced and is represented by a sporogon in the form of a box on a leg. The development of bryophytes went in the direction of increasing the independence of the gametophyte and its gradual morphological division, the loss of independence of the sporophyte and its morphological taming. The gametophyte became an independent, completely autotrophic phase of the life cycle of bryophytes, while the sporophyte was reduced to the level of an organ of the gametophyte.

Mosses, as representatives of the haploid branch of the evolution of higher plants, turned out to be less viable and adapted to the conditions of life on Earth. Their distribution is associated with the presence of free drop-liquid water, which is necessary not only for growth processes, but also for the sexual process. This explains their ecological confinement to places where there is constant or periodic moisture.

The second evolutionary branch of higher plants is represented by all other higher plants.

The sporophyte under terrestrial conditions turned out to be more viable and adapted to various environmental conditions. This group of plants conquered land more successfully. Their sporophyte often has a large size, a complex internal and external structure. The gametophyte, on the contrary, has undergone simplification, reduction.

In simpler forms (spore plants), the gametophyte still has an independent existence and is represented by an autotrophic or symbiotrophic outgrowth. (Lycopodiophyta, Equisetophyta, Polypodiophyta), and in heterosporous representatives of these departments, it is significantly simplified, reduced.

In more organized - seed plants - the gametophyte has lost its independent way of life and develops on a sporophyte, while in angiosperms (flowering) it is reduced to a few cells.

Under the new conditions, there was a gradual complication of terrestrial plants with a predominance of the sporophyte in the development cycle. They gave rise to a number of independent groups (divisions) of plants adapted to the diverse conditions of life on land.

Currently, higher plants number over 300,000 species. They dominate the Earth, inhabit it from the Arctic territories to the equator, from the humid tropics to dry deserts. They form various types of vegetation - forests, meadows, swamps, fill reservoirs. Many of them reach gigantic sizes (sequoiadendron - 132 m with a girth of 35 m, giant eucalyptus - 152 m (Flindt, 1992), rootless wolfia - 0.1-0.15 cm (Guide to plants of Belarus, 1999).

Despite the huge variety of appearance and internal structure All higher plants retain a certain unity in structure. Higher plants are divided into 9 divisions. However, they are relatively easily linked with each other, which indicates the unity of the origin of higher plants.

Publication date: 2015-02-17; Read: 2096 | Page copyright infringement

studopedia.org - Studopedia.Org - 2014-2018. (0.001 s) ...

General characteristics of the subkingdom of higher plants. Specify the main departments in Russian. and lat. language. Describe the origin and main progressive features.

Includes the following currently existing departments: bryophytes ( Bryophyta), Lycopsoid ( Lycopodiophyta), psilotoid ( Psilotophyta), horsetail ( Equisetophyta), ferns ( Polypodiophyta).

Spore plants appeared at the end of the Silurian period, more than 400 million years ago. The first representatives of spores were small in size and had a simple structure, but already in primitive plants, differentiation into elementary organs was observed. The improvement of the organs corresponded to the complication of the internal structure and ontogenesis. In the life cycle, there is an alternation of sexual and asexual methods of reproduction and the alternation of generations associated with this. The asexual generation is represented diploid sporophyte, sexual - haploid gametophyte.

On the sporophyte formed sporangia within which, as a result of meiotic division, haploid spores are formed. These are small, unicellular formations devoid of flagella. Plants in which all spores are the same are called equally spore. In more highly organized groups, there are two types of spores: microspores(formed in microsporangia), megaspores (formed in megasporangia). These are heterogeneous plants. During germination, spores form gametophyte.

The complete life cycle (from zygote to zygote) consists of gametophyte(period from spore to zygote) and sporophyte(period from zygote to spore formation). In club mosses, horsetails and ferns these phases are, as it were, separate physiologically independent organisms. mosses the gametophyte is an independent phase of the life cycle, and the sporophyte is reduced to its original organ - sporogon(sporophyte lives on gametophyte).

On the gametophyte organs of sexual reproduction develop: archegonia and antheridia. AT archegonia, similar to a flask, eggs are formed, and in saccular antheridia- spermatozoa. In isosporous plants, the gametophytes are bisexual; in heterosporous plants, they are unisexual. Fertilization occurs only in the presence of water. When gametes merge, a new cell is formed - a zygote with a double set of chromosomes (2n).

Mosses. Give a general description (classification in Russian and Latin, dominant generation, structural features of the gametophyte and sporophyte, habitat, role in the formation of vegetation).

Specify representatives (in Russian and Latin), value.

The gametophyte dominates the life cycle. The sporophyte does not exist on its own, it develops and is always located on the gametophyte. The sporophyte is a box in which the sporangium develops, on a stem that connects it to the gametophyte. Mosses reproduce by spores, they can also reproduce vegetatively - separate sections body. The department is divided into three class: Anthocerotes, liver mosses and leafy mosses. gametophyte has dark green thallus, dichotomously branched. Above and below the thallus is covered with epidermis, with numerous stomata. The thallus is attached to the substrate rhizoids. The thalli are dioecious, the organs of sexual reproduction develop on special vertical branches-supports. Male gametophytes have eight-lobed stands, on the upper side of which are antheridia. On female gametophytes, stands with stellate discs, on the underside of the rays, asterisks are located (neck down) archegonia. In the presence of water, sperm cells move, enter the archegonium and merge with the egg. After fertilization, the zygote develops sporogon. Inside the box, as a result of meiosis, spores are formed. Under favorable conditions, the spores germinate, from which a protonema develops in the form of a small thread, from the apical cell of which the marchantia thallus develops.

Club mosses. Give a general description (classification in Russian and Latin, dominant generation, structural features of the gametophyte and sporophyte, habitat, role in the formation of vegetation). Specify representatives (in Russian and Latin), value.

Creeping shoots of the club-shaped club reach up to 25 cm in height and more than 3 m in length. The stems are covered with spirally arranged lanceolate-linear small leaves. At the end of summer, two spore-bearing spikelets usually form on the side shoots. Each spikelet consists of an axis and small thin sporophylls- modified leaves, at the base of which are kidney-shaped sporangia. In sporangia after reduction cell division sporogenous tissue are formed of the same size, dressed in a thick yellow shell, haploid disputes. They germinate after a dormant period in 3-8 years into bisexual growths, which represent the sexual generation and live saprotrophic in the soil, in the form of a nodule. Rhizoids extend from the lower surface. Through them, fungal hyphae grow into the growth, forming mycorrhiza. In symbiosis with the fungus, which provides nutrition, a sprout lives, devoid of chlorophyll and incapable of photosynthesis. The growths are perennial, develop very slowly, only after 6-15 years archegonia and antheridia form on them. Fertilization takes place in the presence of water. After fertilization of the egg by a biflagellated spermatozoon, a zygote is formed, which, without a dormant period, germinates into an embryo that develops into an adult plant. In official medicine, mosquito spores were used as baby powder and sprinkles for pills. Sheep shoots are used to treat patients suffering from chronic alcoholism.

Horsetails. Give a general description (classification in Russian and Latin, dominant generation, structural features of the gametophyte and sporophyte, habitat, role in the formation of vegetation). Specify representatives (in Russian and Latin), value.

In all species of horsetail, the stems have an articulated structure with a pronounced alternation of nodes and internodes. The leaves are reduced to scales and arranged in whorls at the nodes. At horsetail(Equisetum arvense) lateral branches of the rhizome serve as a place of deposition of reserve substances, as well as organs of vegetative reproduction. In spring, spikelets are formed on ordinary or special spore-bearing stems, consisting of an axis that bears special structures that look like hexagonal shields ( sporangiophores). The latter bear 6-8 sporangia. Inside the sporangia, spores are formed, dressed in a thick shell, equipped with hygroscopic ribbon-like outgrowths - elaters. Thanks to elaters spores cling together in lumps, flakes.

The growths look like a small long-lobed green plate with rhizoids on the lower surface. Male growths are smaller than female ones and carry antheridia along the edges of the lobes with polyflagellated spermatozoa. Archegonia develop on female growths in the middle part. Fertilization occurs in the presence of water. The zygote develops into a new plant, the sporophyte.

Vegetative shoots of horsetail (E. arvense) in official medicine they are used: as a diuretic for edema due to heart failure; with diseases of the bladder and urinary tract; as a hemostatic agent for uterine bleeding; with some forms of tuberculosis.

ferns. Give a general description (classification in Russian and Latin, dominant generation, structural features of the gametophyte and sporophyte, habitat, role in the formation of vegetation). Specify representatives (in Russian and Latin), value.

Adventitious roots and large leaves depart from the rhizome ( fronds), having a stem origin and long-term growing top. Among the currently existing ferns, there are both isosporous, so heterosporous. In mid-summer, clusters of sporangia appear as brown warts on the underside of green leaves ( sori). The sori of many ferns are covered on top with a kind of veil - by induction. Sporangia are formed on a special outgrowth of a leaf ( placenta). Spores, When ripe, they are carried by air current and germinate under favorable conditions, forming a heart-shaped green multicellular plate ( sprout), attached to the soil by rhizoids. The growth is a sexual generation of ferns (gametophyte). On the underside of the growth, antheridia (with spermatozoa) and archegonia (with eggs) are formed. In the presence of water, sperm enter the archegonium and fertilize the eggs. An embryo develops from a zygote, which has all the main organs (root, stem, leaf and a special organ - a leg that attaches it to the growth) From rhizomes male fern(Dryopteris filix-mas), get a thick extract, which is an effective antihelminthic (tapeworms).

Give a general description of seed plants (classification in Russian and Latin, main differences from higher spore plants). Describe the structure of the ovule and seed. Specify the differences between a seed and a spore, the evolutionary significance of a seed.

By appearance, in structure and biological characteristics, higher plants are very diverse. The living higher plants are mosses, club mosses, horsetails, ferns, gymnosperms and angiosperms (flowering) plants. Total number their species exceeds 285 thousand.

In contrast to the "lower plants", the 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 include 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; strong development got mechanical.

A characteristic feature of higher plants is the correct change of generations (gametophyte and sporophyte) in the cycle of their development. 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 haploid, the sporophyte is diploid.

In mosses, the gametophyte dominates the life cycle, while the sporophyte occupies a subordinate position and lives on the gametophyte. Club mosses, horsetails and ferns are characterized by the biological independence of both the sporophyte and the gametophyte, but the sporophyte prevails 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.

Departments of higher plants

Higher plants are usually divided into 9 divisions, two of which are united only by extinct forms - rhinophytes, zosterophyllophytes; seven departments are represented by living plants - moss-like, lycopsid, psilot-like, horsetail, fern-like, gymnosperms and.

Department of Rhyniophyta (Rhyniophyta)

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

It is believed that rhinophytes are the original ancestral group from which mossy, lycopsid, horsetail and fern-like descended.

Department of Zosterophyllophyta (Zosterophyllophyta)

This division includes a small group of plants that existed in the Early and Middle Devonian. They had much in common with rhinophytes. Perhaps the plants of this group lived in water. Like rhinophytes, they had no leaves, their above-ground shoots branched dichotomously. Sporangia of zosterophyllophytes, which had a spherical or bean-shaped shape, were located laterally on short stalks, which is their difference from rhinophytes.

Division Bryophytes (Bryophyta)

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

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

Unlike all other divisions of higher plants, the vegetative body of moss 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, the genital organs develop - male (anteridia) and female (archegonia). formed in the antheridium big number biflagellated spermatozoa. Each archegonium produces one egg. In the wet (during rain), spermatozoa, moving into, penetrate to the egg, which is 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 box sitting on a leg. Spores are formed in the box.

When the 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.

Bryophyte gametophytes are capable of vegetative reproduction, and their development cycle for a long time can occur without the formation of a sporophyte.

Bryophytes combine 3 classes: Anthocerotes, liverworts and Leafy mosses.

AT class Anthocerota(Antocerotae) there are about 300 species. They are found mainly in tropical and warm temperate regions. 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. Capsules (sporogony) numerous, slightly curved, bristle-shaped. They give anthocerot mosses a peculiar appearance.

AT class Liverworts(Heraticae) there are over 6 thousand species. The liverworts are widespread. Unlike other bryophytes, in most liverworts the protonema is poorly developed and short-lived. The gametophyte has a thallus or leafy plant shape. The structure of the gametophyte in liver mosses is very diverse, while the sporophyte is of the same type.

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

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

In the subclass Jungermanniidae (Jungermanniidae) there are both thallus and leafy plants. Most Jungermannii 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 valves.

To class Leafy mosses(Musci) include 3 subclasses: Sphagnum, andreevy and bry mosses; of these, we consider two subclasses: Sphagnum and Brie.

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

The stems of sphagnum mosses are erect, with tufted leafy branches. At the top, the branches are shortened and collected in a rather dense head.

The leaves are single-layered, have two types of cells - chlorophyll-bearing and aquiferous (hyaline). Chlorophyll-bearing cells are narrow, worm-shaped, they contain chloroplasts. They are located between wide, colorless aquifers, devoid of cellular content. Due to the many aquifers, 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 pod grows from the archegonium.

The subclass Brie, or Green mosses (Bryidae) is represented in your country by about 2 thousand species. Green mosses are most often perennial plants from 1 mm to 50 cm high. Their color is usually green. They are widespread and form a continuous cover in swamps, coniferous forests, meadows, and mountains in the tundra.

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

As an example, reflecting the most important features of plants of this subclass, consider the cuckoo flax moss (Polytrichum commune), which is widespread in moist coniferous forests and along the edges of marshes. 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. At the top of the stems of some plants, archegonia are formed, on others - antheridia. After fertilization, a pod develops from the zygote, sitting on a leg. Spores ripen in the box. The spore germinates on moist soil, giving rise to a filamentous protonema. Buds are formed on the protonema, from which they grow with leaves.

The value of mosses in nature is great. Representatives of bryophytes grow almost everywhere. The exception is saline, habitats with a moving substrate; marine mosses are unknown. Mosses are abundant in swamps and forests. They often dominate the ground cover of coniferous forests (spruce, 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 hold it firmly causes the peat of the moss turf from below, its weak decomposition. Moss cover can contribute to waterlogging of territories. Sphagnum mosses have antibiotic properties and are used in medicine. Participating in the formation of the moss cover on raised bogs, they are peat formers. Sphagnum peat is widely used as a fuel and in agriculture.

Many green mosses form a solid carpet in lowland marshes, where they form deposits of nutrient-rich lowland peat. Lowland peat is widely used in agriculture as a fertilizer. Mosses also have a negative meaning. Growing in a continuous dense carpet, they make it difficult to aerate the soil, causing it to become acidic. This adversely affects the life of many plants. The role of liverworts in the vegetation cover is generally much less than that of sphagnum and green mosses.

Division Lycopodiophyta (Lycopodiophyta)

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

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

Among the lycopsids, there are equally spore and heterosporous plants. In isospores, spores are morphologically indistinguishable; during their germination, bisexual gametophytes are formed; in heterosporous, small spores give rise to male gametophytes bearing antheridia, and large ones give rise to female gametophytes bearing archegonia. In antheridia, two- or multi-flagellated spermatozoa are formed, in archegonia - eggs. After fertilization, a new generation grows from the resulting zygote - the sporophyte.

The Lycopsid department includes two classes: Lycopsids and Half-moss. From the class of Plaunovs, consider the order of the Plaunovs and from the class of the Polushnikovs, the order of the Selaginellas, whose representatives live at the present time.

Order Lycopsidae(Lycopodiales) is characterized by uniform sporulation. It is represented by one family - Lycopodiaceae. This family includes the genus Lycopodium, which has about 400 species. In our country, there are 14 species of club mosses.

Many clubs are small herbaceous plants. Their leaves are relatively small. A median vein runs along the leaf, consisting of tracheids and parenchymal cells.

Consider one of the types of club moss - club-shaped club (Lycopodium clavatum). This species is widespread, found in coniferous (often pine) forests on poor soils. Clubmoss 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 leaves. Spikelets contain kidney-shaped sporangia, in which a large number of identical small yellow spores are formed.

Spores after maturation fall to the ground. When they germinate, a seedling (gametophyte) is formed. The overgrowth of club moss is perennial, has the appearance of a small nodule (2-5 mm in diameter) with rhizoids. It is colorless, devoid of chlorophyll and cannot feed on its own. Its development begins only after penetration into the body of the hyphae of the fungus (endotrophic mycorrhiza).

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

In club mosses, there is a clearly pronounced change of generations. The sporophyte predominates in the development cycle. 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. Spores are used as a powder for powders, as well as for sprinkling pills. To protect the stocks of club mosses, it is necessary to carefully cut off only spore-bearing spikelets when harvesting spores.

Order Selaginella(Selaginellales), belonging to the Polushnikovye class, is characterized by heterogeneity. It is represented by one family Selaginellaceae (Selaginellaceae). In the genus Selaginella (Selaginella) there are almost 700 species, mainly growing in tropical and subtropical areas. There are 8 species of this genus 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 by spores is the main mode of reproduction for Selaginella.

Let's take a closer look Selaginella selagiformis(Selaginella selaginoides). This plant has short creeping stems covered with elongated ovate leaves. At the top of the shoot, spore-bearing spikelets are formed. The main difference between Selaginella and club mosses is that in the same spikelet there are 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 strongly reduced male outgrowth, on which one antheridium develops. A female growth grows from the megaspore, on which a few archegonia develop. The movement of spermatozoa occurs in water after rain or dew. A fertilized egg eventually grows into an adult plant.

Thus, two types of spores are formed in Selaginella - microspores and megaspores - and unisexual growths develop. The sprouts, especially male ones, are strongly reduced, which is the main direction in the evolution of higher plants. This is well seen in other departments of higher plants. Selaginella are little used by humans.

Division Psilotoid (Psilotophyta)

The Psilotoid department includes 12 species. It includes two genera: psilot (Psilotum) and tmesipteris (Tmesipteris). Representatives of these genera are distributed outside our country in the tropics and subtropics. They are simply arranged and resemble rhinophytes. In their structure, extremely primitive features have been preserved, which testify to their very ancient origin.

The sporophyte of the psilot has no roots or leaves. It consists of a dichotomously branching aerial part with small scaly outgrowths and a branched system of rhizomes with numerous rhizoids.

Psylot is an equisporous plant. Spores are produced in sporangia located at the ends of short lateral branches. An underground gametophyte grows from the spore, on the surface of which antheridia and archegonia are located. Sperm are polyflagellated and require water to reach the egg.

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

Department Horsetail (Equisetophyta)

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

Currently, horsetails are represented on Earth by one class Equisetopsida, including one order Equisetales and one family Equisetales. In this family, there is only one genus - 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 tree forms became extinct. Their dead remains gave rise to coal deposits. Many herbaceous forms also died out.

Modern horsetails are perennial rhizomatous herbs with stems up to several tens of centimeters high. At the nodes of the stem there are whorls of branches. Small scaly 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 isosporous plants.

The sexual generation (gametophyte) in modern horsetails is represented by unisexual or bisexual, short-lived, very small, green growths a few millimeters in size. They form antheridia and archegonia. In the antheridium, polyflagellated spermatozoa develop, and in the archegonium, eggs develop. Fertilization occurs in the presence of drip liquid water, 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, fallows. From the rhizome in early spring pinkish-brown, short, straight shoots appear, at the top of which a spore-bearing spikelet is formed. On the axis of the spikelet are sporophylls, which look like hexagonal shields. 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. Morphologically, the spores are the same, but differ physiologically. Some of them, germinating, give male growths, others - female.

The male growth is a small green plate, dissected into lobes and attached to the soil by rhizoids. At the ends of the lobes, antheridia develop, containing multi-flagellated spermatozoa. The female growth is larger, it bears archegonia. Fertilization occurs in the presence of moisture. The zygote develops into a perennial sporophyte. Dogs from the rhizomes of the horsetail develop green vegetative shoots, devoid of spikelets.

Other species of horsetail have only one type of shoot. It is both spore-bearing and assimilating at the same time. Practical value horsetail is small.

Division Ferns (Polypodiophyta)

Ferns are ancient plants. Most of them are now extinct. Today, ferns far outnumber all other groups of modern spore-bearing vascular plants in terms of number of species; 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, living conditions. Many of them are herbaceous perennials, there are also trees. Tropical tree ferns are up to 25 m tall, and the trunk diameter reaches 50 cm. Among herbaceous species there are very small plants a few millimeters in size.

Unlike lycopsids and horsetails, ferns are characterized by "large-leaved". The "leaves" of ferns are of stem origin and are called "fronds". Their origin is confirmed by apical growth.

The size of fern wai ranges 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. In some species (for example, the ostrich) there are two types of wai - photosynthetic and spore-bearing. Wai blades are quite often pinnate, often repeatedly dissected.

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

Almost all ferns, with the exception of aquatic ones, are equisporous plants. Their sporangia are often located on the lower surface of the wai 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 drop-liquid water is necessary, in which polyflagellated spermatozoa can move.

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

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

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

Rounded sori form on the lower surface of the fronds in summer. Inside the sporangium, identical spores are formed. The male shield is a typically equisporous fern. Once on, the spore germinates, and a sprout is formed. It is a heart-shaped green plate about 1 cm in size. Archegonia and antheridia form on the lower surface of the growth. In the antheridia, spirally twisted polyflagellated spermatozoa develop. Fertilization occurs in the presence of water. From a fertilized egg, a perennial large sporophyte gradually grows.

Water ferns are heterosporous plants. This is a small group. An example is Salvinia floating (Salvinia natans), belonging to the order of Salvinia (Salviniales). This is a small floating plant.

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

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

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

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

Further evolution of higher plants took the path of ensuring the independence of sexual reproduction from the presence of water.

This possibility was realized in seed plants. Here the general direction of the evolutionary development of the sporophyte 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 vegetation cover, since the sporophyte embryo is already inside it and it contains a significant supply of 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 the development of the embryo take place. All this ensures the independence of fertilization from drop-liquid water.

In the process of development, the ovule turns into a seed. The seed contains an embryo - a young, rudimentary, very small sporophyte. It has a root, a kidney and embryonic leaves (cotyledons). An adequate 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, rarely deciduous trees or shrubs, rarely lianas. The leaves of gymnosperms vary greatly in shape, size, morphological and anatomical features. So, in shape, the leaves are scaly, needle-shaped, pinnate, double-pinnate, etc.

Gymnosperms are heterospore plants. Microspores are formed in microsporangia located on microsporophylls, and megaspores - 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 Gymnosperms division includes 6 classes, with the classes Seed ferns (Pteridospermae) and Bennettites (Bennettitopsida) completely extinct. The currently living gymnosperms, numbering about 700 species, belong to the classes Cycads (Cycadopsida), Gnetovs (Gnetopsida), Ginkgos (Ginkgoopsida) and Conifers (Pinoposida).

Class Seed ferns reached its greatest development in the Carboniferous period. These plants completely died out in the Triassic period. They were represented by trees and creepers. Their treelike forms resembled modern tree ferns. Unlike modern ferns, they reproduced through seeds.

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

Primitive groups of gymnosperms, which are characterized by true strobili, or cones (bennettites, cycads), originated from seed ferns.

Class Bennettite- 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, resembling in structure the flower of modern angiosperms. Microsporophylls in in large numbers located along the periphery of the strobilus, and reduced megasporophylls - in the center of the strobilus. Each megasporophyll had one ovule. In the seeds of Bennettiaceae, there was an embryo that filled the entire seed.

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

Class Cycads- 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 that look like palm trees. Their leaves are large, hard, evergreen. In most cycads, sporophylls are collected in strobili (cones), which form at the end of the trunk among the leaves. Cycads are dioecious plants. Male and female strobili are formed on different individuals.

One of typical representatives class - 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 pinnate leaves up to 2 m long. In male specimens, male strobiles 50-70 cm long are formed.

Microspores spill out of microsporangia and are transferred by a meter to the ovule, where the male outgrowth develops further.

Megasporophylls in all species of the genus Cycad are located in a small number at the top of the stem, alternating with vegetative leaves. Megasporophylls pinnate, smaller than vegetative leaves, yellow or reddish. In the lower part of the megasporophyll, on its branches, are megasporangia (ovules). They are large, up to 5-6 cm long.

In the center of the ovule there is a multicellular tissue - the endosperm (a modified female growth), in the upper part of it two archegonia with large eggs are formed. Fertilization is carried out by motile spermatozoa that have numerous flagella. A fertilized egg develops into an embryo. It has all the parts inherent in an adult plant: the first leaves (cotyledons) and the rudimentary stem (subcotyledon), passing 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 class Gnetovye representatives of three genera: Ephedra (Ephedra), Welwitschia (Welwitschia) and Gnetum (Gnetum).

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

In the genus Ephedra, there are 40 species that grow in arid and desert regions of the globe. Most species are low, strongly branched shrubs resembling horsetails.

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

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

The genus Gnetum has about 30 species. They grow in tropical rainforests. These are small trees, shrubs and vines. They have broad leathery leaves arranged oppositely. Plants are dioecious. Microstrobili are catkin-shaped, compound. On the axis of the megastrobil, which looks like an elongated catkin, ovules (megasporangia) are located. After fertilization, an embryo develops that has two cotyledons. The ovules turn into bright pink seeds.

The only modern representative the Ginkgo class 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, a fan-shaped plate, usually bilobed at the top. Ginkgo is a dioecious plant. Microstrobili are catkin-shaped. Ovules (usually two) develop on megastrobiles. Inside each ovule, two archegonia are formed. Spermatozoa are mobile. One of them fertilizes the egg. From the ovule, a seed is formed, which in its structure resembles the fruit of a plum. The outer layer of the shell covering the seed is juicy, under it are 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: Cordaite (Cordaitales) and Coniferous (Pinidae). Cordaites are long-extinct plants. They reached their greatest development in the Carboniferous period. Cordaites were large trees with a monopodial branching stem and a high crown. Between the leaves on the branches were reproductive organs - complex catkin-shaped collections of strobiles.

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

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

Coniferous strobili are exclusively dioecious. Plants are monoecious, rarely dioecious. The shape and size of the strobili vary greatly.

The main features of the life cycle of conifers can be seen in the example of Scotch pine (Pinus sylvestris). This is a slender tree, reaching a height of 40 m. At the ends of the pine branches 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 - form. On the axis of the male cone 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 eventually turns into a pollen grain that has two cells: vegetative and generative (two male gametes, sperm, develop from the latter). The pollen grain (pollen) leaves the microsporangium (anther). Mature pine pollen has two shells: outer - exine, inner - intine. The exine forms two air sacs that facilitate the transport of pollen by the wind.

Megastrobili are called female cones. They are collected 1-3 at the ends of young shoots. Each cone is an axis, from which scales of two types extend in all directions: barren (covering) and seed. On each seed scale with inside two ovules are produced. In the center of the ovule, the endosperm or outgrowth (female gametophyte) develops. 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, advancing towards the archegonium. Two sperm travel down the pollen tube towards the egg. The tip of the pollen tube, which reaches the egg, breaks and releases the sperm. One of the sperm fuses with the egg and the other dies. As a result of fertilization, a diploid zygote is formed, and an embryo arises from it.

The mature embryo consists of a pendant, a primary root, a stalk, and cotyledons. Education suspension - 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 diverge and the seeds spill out. The mature seed has a transparent wing.

The subclass Conifers includes seven orders, two of which are extinct. Currently, there are the following: Araucariaceae, Nogoplodnikovye, 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. Scotch pine is widespread in our country, the needles of which are collected in pairs. In the Asian part of the country, Siberian pine (the so-called "Siberian cedar") is quite widespread, in which the needles are collected in bunches of five. Siberian pine provides valuable wood and edible seeds - pine nuts.

The genus Spruce includes about 50 species that live in the Northern Hemisphere. These are tall slender trees. For firs, it is characteristic pyramidal shape crowns. The needles are tetrahedral, pointed at the end. In our country, two species are most common: European spruce (Picea abies) and Siberian spruce (Picea obovata).

The genus Fir has 40 species living in the Northern Hemisphere. These are large tall trees. Outwardly similar 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 genus Larch is represented by 15 species that live in the Northern Hemisphere. These are large straight-stemmed trees that shed their needles for the winter. Larch needles are soft, flat. They are located in bunches on short shoots and singly on elongated shoots. Siberian larch (Larix sibirica) and Dahurian larch (Larix dahurica) are the most common in our country.

Order Cypress(Cupressales) is represented by two families. The Taxodiaceae family currently includes 10 genera and 14 species. Modern taxodium - large trees, rarely shrubs. Among them, mention should be made of the sequoiadendron (Sequojadendron giganteum), or "mammoth tree" - one of the largest and longest-lived plants in the world. Also interesting is the two-row taxodium, or "marsh cypress" (Taxodium distichum). It grows along the banks of rivers and in the swamps of southeastern North America. In this tree, horizontal roots form vertical outgrowths of a conical or bottle-shaped shape - 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 scaly or needle-shaped, small, arranged oppositely or in whorls of three, rarely four.

Quite a few species contain the genera Cypress and Juniper (respectively 20 and 55 species). Cypress species are monoecious evergreen trees with a pyramidal or spreading crown, less often shrubs. In culture, the pyramidal evergreen cypress is best known. The genus Juniper is represented by small evergreen trees or shrubs, sometimes creeping. Leaves are needle-shaped or scaly. In junipers, after fertilization, the scales of megasporophylls become fleshy, grow together, forming the so-called "cone". Junipers are widespread. They are photophilous, drought-resistant, frost-resistant and undemanding to soil conditions.

Yew Order(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 is berry, or common (Taxus baccata), which has flat needles. This tree has a hard and heavy wood, almost indestructible. The seeds are surrounded by a bright red fleshy roof, which makes them look like berries. Yew berry - most shade tree from all conifers.

Does everyone know which plants are called higher? This species has its own characteristics. To date, higher plants include:

• Club mosses.
• ferns.
• Horsetails.
• Gymnosperms.
• Angiosperms.

There are more than 285 species of such plants. They are distinguished by a much higher organization. Their bodies contain a shoot and a root (except for mosses).

Characteristics

Higher plants live on earth. This place of residence is different from the aquatic environment.

Characteristics of higher plants:

• The body is made up of tissues and organs.
• With the help of vegetative organs, nutrition and metabolic functions are carried out.
• Gymnosperms and angiosperms reproduce using seeds.

Most of the higher plants have roots, stems and leaves. Their organs are complex. This species has cells (tracheids), vessels, and their integumentary tissues form a complex system.

The main feature of higher plants is that they pass from the haploid phase to the diploid one, and vice versa.

Origin of higher plants

All signs of higher plants indicate that they may have evolved from algae. Extinct representatives belonging to the highest group have a very great resemblance to algae. They have a similar alternation of generations and many other characteristics.

There is a theory that higher plants appeared from or freshwater. The rhinophytes arose first. When the plants moved to land, they began to develop rapidly. Mosses were not as viable, as they need water in the form of drops to exist. Because of this, they appear in places where there is high humidity.

To date, plants have spread throughout the planet. They can be seen in the desert, the tropics and in cold areas. They form forests, swamps, meadows.

Despite the fact that when thinking about which plants are called higher, one can name thousands of options, but still they can be combined into some groups.

mosses

When figuring out which plants are called higher, we must not forget about mosses. In nature, there are about 10,000 of their species. Outwardly, this is a small plant, its length does not exceed 5 cm.

Mosses do not bloom, they do not have a root, a conducting system. Reproduction occurs with the help of spores. The haploid gametophyte dominates the moss life cycle. This is a plant that lives for several years, it may have outgrowths that look like roots. But the moss sporophyte does not live long, it dries out, has only a leg, a box where spores mature. The structure of these representatives of wildlife is simple, they do not know how to take root.

Mosses play such a role in nature:

• They create a special biocenosis.
• The cover of moss absorbs radioactive substances, retains them.
• Regulate the water balance of landscapes due to the fact that they absorb water.
• They protect the soil from erosion, which allows you to evenly transfer the flow of water.
• Some types of mosses are used for medicines.
• With the help, peat is formed.

Lycian plants

In addition to mosses, there are other higher plants. The examples may be different, but they are all somewhat similar to each other. For example, mosses resemble mosses, but their evolution is more advanced, since they are vascular species. They consist of stems that have covered small leaves. They have roots and vascular tissue through which nutrition occurs. By the presence of these components, club mosses are very similar to ferns.

In the tropics, epiphytic club mosses are isolated. They hang from the trees, giving the appearance of a fringe. Such plants have the same spores.

Some club plants are listed in the Red Book.

psilotoid plants

This type of plant lives for more than one year. This includes 2 genera of representatives of the tropics. They have erect stems similar to a rhizome. But they have no real roots. The conducting system is located in the stem, consists of phloem, xylem. But water does not enter the leaf-like appendages of plants.

Photosynthesis occurs in the stems, spores are formed on the branches, turning them into cylindrical branches.

Ferns

What plants are called higher still? These include ferns, which are part of the vascular department. They are herbaceous and woody.

The composition of the body of a fern includes:

• Petiole.
• Leaf plates.
• Roots and shoots.

Fern leaves were called fronds. The stem is usually short, it is developed. From the buds of the rhizome, fronds grow. They reach large sizes, perform sporulation, photosynthesis.

The sporophyte and gametophyte alternate in the life cycle. There are some theories that say that ferns evolved from club mosses. Although there are scientists who believe that many higher plants appeared from psilophytes.

Many types of ferns are food for animals, and some are poisonous. Despite this, such plants are used in medicine.

horsetail

Horsetails also belong to the higher plants. They consist of segments and nodes, which distinguishes them from other plants of a higher species. Horsetail representatives resemble some conifers and algae.

This is a kind of representative of wildlife. They have vegetative characteristics similar to cereals. The length of the stems can be several centimeters, and sometimes grows up to several meters.

Gymnosperms

Gymnosperms are also isolated from higher plants. There are only a few varieties today. Despite this, various scientists argued that angiosperms originated from gymnosperms. This is evidenced by various plant remains found. DNA studies were carried out, after which some scientists deduced theories that this species belongs to a monophyletic group. They are also divided into many classes and departments.

Angiosperms

These plants are also called flowering plants. They are considered to be of the highest order. They differ from other representatives in the presence of a flower that serves for reproduction. They have a feature - double fertilization.

The flower attracts pollinating agents. The walls of the ovary grow, change, turn into a fetus. This happens if fertilization has occurred.

So, there are different higher plants. Examples of them can be listed for a long time, but they were all disbanded into certain groups.