Higher plants representatives. What is the difference between lower plants and higher

They have well developed tissues and organs. Integumentary tissues (skin, cork, bark) protect against drying and freezing, provide gas exchange with the external environment. Mechanical tissues allow the stem to carry the leaves as high as possible so that they are not shaded by other plants. Through conductive tissues (bast and wood), water, salts (upward current) and organic substances (downward current) are transported.

The ground parts of higher plants (shoots) are in the atmosphere, and the underground parts (roots) are in the soil. Roots have adaptations for absorption of water and minerals from the soil. Thus, outgrowths of the cells of the integumentary tissue of the root - root hairs - significantly increase the surface of the roots. They absorb water due to the resulting root pressure and the evaporation of water from the leaves.

Plants reproduce asexually and sexually. In this case, the methods of reproduction alternate. During asexual reproduction, spores are formed. From the spores, the sexual generation grows, which produces germ cells - gametes. With the participation of gametes, sexual reproduction occurs. As a result of the fusion of male and female gametes (fertilization), a zygote is formed. It gives rise to an asexual generation, which again produces spores, and the life cycle is not interrupted. Higher plants are also characterized by such a type of asexual reproduction as vegetative, that is, reproduction by vegetative parts of the body.

Ground-air environment

In the process of evolution, the first terrestrial plants originated from algae, among which individuals that had hereditary changes corresponding to the new habitat were preserved by natural selection. Gradually, tissues and organs formed in plants. The emergence of plants on land is one of the greatest stages of evolution. It was prepared by changes in animate and inanimate nature: the appearance of soil and the appearance of an ozone screen that stood in the way of ultraviolet rays that were destructive to all living things.

Complication of the structure

Further evolution of higher plants under terrestrial conditions followed the path of differentiation of vegetative organs (the appearance of roots, leaves, more complex branching of the stem), the development of integumentary and mechanical tissues, the conducting system, and reproductive organs.

free floating plants

Some higher plants returned to their "historical homeland" - to the water. Their roots act as an anchor, and the metabolism with the environment is carried out through the entire surface of the body. A typical example is duckweed, an inhabitant of shallow water bodies. Its lamellar shoot floats on the surface of the water. The root has a length of 2-3 mm, in some species of duckweed it does not exist at all.

Modern classification higher plants reflects their diversity and the history of their appearance on Earth: material from the site

• seed plants.

mosses

Mosses are higher plants, have vegetative organs (stems, leaves), their reproduction is associated with water. The asexual generation is a box with spores, the sexual generation is moss shoots. Mosses play an environmental role in marsh ecosystems.

Ferns (Vascular spores)

Ferns have stems, leaves and roots, their reproduction is associated with water. Sexual generation - sprout, asexual - plant shoots.

Gymnosperms

Reproduction of gymnosperms is not associated with water. Ovules develop in female cones, pollen in male cones. Gymnosperms are the dominant species in coniferous forests.

Angiosperms (flowering)

Angiosperms have a flower and seeds hidden inside the fruit. As a result of double fertilization, the embryo and endosperm are formed.

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 residence is different from 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 distinguished. 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.

Plants have evolved since they landed, and their body has been divided into segments, each of which has its own function. But algae do not have such a division, and their body entirely consists of one type of tissue. That is why they are considered lower plants.

Outdated classification of lower plants

Until the middle of the 20th century, in addition to algae, the category of lower plants included organisms such as:

• bacteria;
• Lichens;
• Mushrooms.

However, with the development of technologies and research methods, it became clear that of all this, plants are only algae. Fungi and bacteria have been separated into separate kingdoms, and lichens are included in a separate category, because. This is a heterogeneous organism, which is a symbiosis of algae with a fungus or bacterium.

The difference between lower plants and higher

IN modern world scientists use the term "lower plants" rarely and only in relation to algae, as mentioned above. Since these organisms live in water, their entire body (thallus) consists of one type of tissue that performs all functions, such as:

• reproduction;
• Photosynthesis;
• Synthesis of nutrients from water.

The density of water allows them to stay on the surface or attach to the bottom, but not lose their shape.

With access to the surface, environmental conditions forced plants to take a different evolutionary path. For example, on land, water and useful material concentrated in the soil to which the plants are attached, but the rays of the sun do not seep there. Therefore, in higher plants, the roots specialized in the absorption of water and minerals, while the leaves, on the contrary, are engaged in photosynthesis. To withstand the wind, the stem became hard, and many plants developed vessels to connect the roots to the leaves.

Higher plants currently include:

• ferns;
• Gymnosperms;
• Angiosperms.

Of these types, mosses are the most primitive and are closest to algae. Their body is not divided into a large number of sections, so they are often called lower spore plants.

All plants of our planet are divided into two groups: lower and higher.

Lower plants do not have true tissues and organs and can be either unicellular or multicellular. Their body is called the thallus. Algae belong to the lower plants.

Higher plants have tissues (educational, conductive, integumentary, basic, mechanical) and organs (shoot and root). These include mosses, club mosses, horsetails, ferns - higher spore plants; and gymnosperms, angiosperms - higher seed plants.

In appearance, in their structure and biological characteristics, higher plants are very diverse. These, in addition to flowering and gymnosperms, also include ferns, horsetails, club mosses and mosses. The main difference between gymnosperms and higher spore plants is seed propagation. The number of species reaches 300 thousand, and, according to some botanists, at least 500 thousand.

general characteristics

Higher plants have developed many various devices and properties for life in a variety of land conditions. Angiosperms have reached the greatest development and adaptability to a terrestrial way of life.

Signs characteristic of higher plants:

• Differentiation into organs and tissues;
• conducting system consisting of xylem and phloem;
• correct generational change;
• organs of sexual reproduction: antheridia and archegonia;
• the body of plants is characterized by a leaf-stem structure.

Grounds for dividing plants into higher and lower

All representatives flora depending on the structure, they are divided into 2 groups - lower and higher.

The main criterion by which plants are classified as higher is the presence of a complex tissue structure. It is represented by conductive and mechanical tissues. Also hallmark is the presence of tracheas, tracheids and sieve tubes, which quickly deliver nutrients from the root to the leaves, inflorescences, stems.

The lower ones, in turn, have a primitive structure, consist of one cell, there are multicellular organisms, the body of which is called a thallus. They are devoid of roots, stems, and leaves.

Lack of muscle and nerve tissue

Higher plants are a group of living organisms that occupy a special place in nature. Representatives of the plant world are capable of photosynthesis, they convert the energy of sunlight into organic matter and oxygen. They get their food from the soil and their environment, so they don't have to move in search of food. Fertilization is carried out with the help of rodents, insects, wind, so their muscle and nervous tissue is not developed. Unlike animals that travel great distances to obtain food and search for favorable breeding grounds and raising offspring.

Significance in nature and human life

1. Oxygen enrichment of atmospheric air.
2. An integral part of food chains.
3. Used as building material, raw materials for the manufacture of paper, furniture, etc.
4. Application useful properties in medicine.
5. Production of natural fabrics (linen, cotton).
6. Purify the air from dust pollution.

Life cycle

Higher plants are characterized by the presence of a clearly pronounced alternation of two generations: sexual (gametophyte) and asexual (sporophyte). Their sporophyte gradually took a dominant position over the gametophyte. Only bryophytes are an exception, since their gametophyte reaches a greater development, while the sporophyte, on the contrary, is significantly reduced.

In the process of evolution, the sexual process became more complicated, multicellular genital organs developed, which well protect the egg from drying out. The female gamete, the ovum, is immobile. Gradually there were significant changes in the structure and physiology of male germ cells.

In more advanced types of higher plants (angiosperms), motile spermatozoa with flagella turned into spermatozoa without flagella, which lost the ability to move independently. And if in more ancient terrestrial representatives (mosses, club mosses, horsetails and ferns) there is still a dependence of the act of fertilization on the aquatic environment, then in more organized types (most gymnosperms and all angiosperms) there is already complete independence of sexual reproduction from drip-liquid water.

The sporophyte is an asexual diploid generation that produces asexual reproductive organs, the sporangia. In them, after reduction division, haploid spores are formed. They develop into a haploid gametophyte.

Origin

About 400 million years ago, the first forms of plants appeared, adapted to life on land. The exit from the water led to adaptive changes in the structure of individual species, which needed new structural elements to survive.

So the plant world left the limits of the aquatic environment and began to populate the expanses of land. Such "explorers" were rhinophytes, which grew near the shores of reservoirs.

This is a transitional form of life between lower plants (algae) and higher ones. In the structure of rhinophytes, there are many similarities with algae: real stems, leaves, and root system were not traced. They were attached to the soil with the help of rhizoids, through which they received nutrients and water. Rhinophytes had integumentary tissues that protected them from drying out. They reproduced by means of spores.

Rhiniophytes later modified and gave rise to the development of club mosses, horsetails, ferns, which already had stems, leaves, and roots. These were the ancestors of modern spore plants.

Why are mosses and flowering plants classified as higher spores?

Mosses are higher plants that have the most primitive structure. The root system is missing. They are distinguished from algae by the presence of rhizoids, the body is differentiated into organs and tissues. Mosses, like higher plants, reproduce by spores.

Flower representatives have a body divided into organs. Vegetative organs - a root with an escape, which provide growth and development. As well as reproductive organs - the fruit, seeds, flower, responsible for distribution.

Similarities and differences with algae

Differences:

1. Algae are not differentiated into organs and tissues, often the body is represented by one cell or their cluster. Higher plants are endowed with well-developed tissues, have roots, leaves, stems.
2. In algae, asexual reproduction predominates, by dividing the original mother cell. They also have vegetative and sexual divisions. Higher spore plants are characterized by a strict alternation of sexual and asexual generations.
3. What organelles are absent in cells of higher species, but characteristic of lower species? These are centrioles that are also present in animals.

Similarities:

1. Mode of nutrition - both groups of plants are photoautotrophs.
2. Cell structure: the presence of a cell wall, chlorophyll, nutrients.
3. Cannot actively move around life cycle two phases alternate sequentially: gametophyte and sporophyte.

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, a general structure higher plants, expressed in their morphological dismemberment into a leafy 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 the highest form of the sexual process - oogamy and a two-phase development cycle, characterized by the alternation of two interdependent generations: the gametophyte, which carries the reproductive 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. In 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); the formation of a phragmoplast and a cell wall during 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.

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

Higher plants have 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 emergence 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 life cycle. In the life cycle of mosses, the gametophyte predominates, in the holo- and angiosperms- 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 or almost exclusively only sporophytes. 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 was published Comparative studies of growth, development and fruiting in higher myogamous plants and seed formation in coniferous trees, 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 the teachings of Charles Darwin, had 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, the formation of spores of various 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 environments also differ in terms of humidity, temperature regime, density, specific gravity, according to the property to change the strength and spectral composition of sunlight. The ecological conditions of the ground-air environment appeared to cause changes in the morphological and anatomical structure of the vegetative and reproductive organs 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 algae, in which, in connection with the transition to land, in a new environment, special devices for water supply, for the protection of 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 on 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 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. Scheme evolutionary change 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 wide variety appearance higher plants retain a certain unity in structure. Higher plants are divided into 9 divisions: ryniaphytes, zosterafilafites, 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 independent way life and develops on the sporophyte, and 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. The sporophyte is often big sizes, 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 the disputed were small 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. IN 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. Fusion of gametes produces new cell– zygote with a double set of chromosomes (2n).

Mosses. Give general characteristics(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. IN favorable conditions spores germinate, protonema develops from them 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. From bottom surface rhizoids emerge. 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 during mature 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 for the deposition of reserve substances, as well as organs vegetative propagation. 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, under favorable conditions, germinate, 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 sperm) 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 agent (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.