Plants play a very important role in nature, as they are capable of photosynthesis. This is a process in which a plant receives nutrients from carbon dioxide, water and solar energy for itself and releases oxygen into the atmosphere. Therefore, it is thanks to plants that animals and we can exist on Earth.

plant classification

Everything is divided into ten departments:

• Brown algae.
• Green algae.
• Blue-green algae.
• Red algae.
• Bryophytes.
• Ferns.
• Horsetail.
• Lycopsoid.
• Angiosperms.
• Gymnosperms.

Among these plants, depending on the complexity of the structure, two groups can be distinguished:

• lower;
• higher.

The lower ones include all sections of algae, since they lack tissue differentiation. The body has no organs. It is called thallus.

Higher plants, depending on the method of reproduction, can be divided into:

• spore;
• seed.

The spores include ferns, lycopsids, bryophytes, horsetails.

Classification of gymnosperms

The next taxon that stands out in all divisions of the kingdom "Plants" is the class. Gymnosperms are divided into four classes:

1. Oppressive.
2. Ginkgo.
3. Cycads (Cicadas).
4. Coniferous.

We will talk about the representatives and features of each class later. And now the common features of all gymnosperms, their physiology and biology will be considered.

Gymnosperms: plant structure

This section belongs to higher plants. This means that their body consists of organs that are built from different types of tissues.

Organs of gymnosperms

Depending on the location of organs, they can be divided into underground and terrestrial. Given their functions and structure, vegetative and generative organs can be distinguished.

Vegetative organs: structure and functions

This group of organs includes the underground root system and the ground shoot.

The root system consists of many roots, among which one main and many lateral roots can be distinguished. In addition, the plant may have additional roots.

The root has the following functions:

• Anchoring the plant in the soil.
• Absorption of water with micro and macro elements dissolved in it.
• Transportation of water and minerals dissolved in it to ground organs.
• Sometimes - the storage of nutrients.

Escape is also an organ system. It consists of a stem, leaves and buds.

Functions of the escape organs:

• Stem: supporting and transport functions, providing a connection between roots and leaves.
• Leaves: photosynthesis, respiration, gas exchange, temperature regulation.
• Buds: new shoots are formed from them.

Generative organs of gymnosperms

Generative organs are those that ensure the reproduction of an organism. In angiosperms, it is a flower. But the plants of the department "Gymnosperms" for the most part have such generative organs as cones. The most striking visual examples are spruce and pine cones.

Cone structure

It is a modified shoot covered with scales. There are male and female cones in which male and female sex cells (gametes) are formed, respectively.

Male and female pine cones as an example can be seen in the photo below.

There are such representatives of gymnosperms in which both male and female plants are on the same plant. They are called singletons. There are also dioecious gymnosperms. They have male and female cones on different species. However, the plants of the department "Gymnosperms" are mostly monoecious.

On the scales of female cones there are two ovules, on which female gametes are formed - eggs.

On the scales of male cones are pollen sacs. They form pollen, which contains sperm - male germ cells.

How a pine tree grows from a cone

Pollination of female cones occurs with the help of wind.

After fertilization, seeds develop from the ovules, which are located on the scales of female cones. From them, then, new representatives of the gymnosperms are formed.

What tissues are organs made of?

There are such types of plant tissues:

• Integumentary. These tissues perform a protective function. They are divided into epidermis, cork and crust. The epidermis covers all parts of plants. It has stomata for gas exchange. It can also be covered with an additional protective layer of wax. The cork is formed on the trunk, roots, branches and bud scales. The crust is an integumentary tissue consisting of dead cells with stiff shells. It consists of the bark of gymnosperms.
• Mechanical. This tissue provides strength to the stem. It is divided into collenchyma and sclerenchyma. The first is represented by living cells with thickened membranes. Sclerenchyma, on the other hand, consists of dead cells with stiffened membranes. Mechanical fibers are part of the gymnosperms contained in the stems.
• Main fabric. It is she who forms the basis of all organs. The most important type of basic tissue is assimilation. It forms the basis of the leaves. The cells of this tissue contain a large number of chloroplasts. This is where photosynthesis takes place. Also in the organs of gymnosperms there is such a type of main tissue as storage. Nutrients, resins, etc. are collected in it.
• Conductive fabric. Divided into xylem and phloem. Xylem is also called wood, and phloem is also called bast. They are found in the trunk and branches of the plant. The xylem of gymnosperms consists of vessels. It provides transportation of water with substances dissolved in it from the root to the leaves. The phloem of gymnosperms is represented by sieve tubes. The bast is designed to transport substances from the leaves to the root.
• Educational fabrics. All other gymnosperm tissues are formed from them, from which all organs are then built. They are divided into apical, lateral and intercalary. Apical are located at the top of the shoot, as well as at the tip of the root. Lateral educational tissues are also called cambium. It is located in the trunk of a tree between wood and bast. Interstitial educational tissues are located at the base of the internodes. There are also wound educational tissues that occur at the site of injury.

Gymnosperms: examples

When we already know how the plants of this department are arranged, let's look at their diversity. Next, representatives of the various classes that are included in the "Gymnosperms" department will be described.

Class "Gnetovye"

1. Family "Velvichia".
2. Family "Gnetovye".
3. Family "Conifers".

Let's look at the brightest representatives of these three groups of plants.

So, Velvichia is amazing.

This is the only representative of the Velvichi family. This representative of gymnosperms grows in the Namib Desert, as well as in other deserts of South West Africa. The plant has a short but thick trunk. Its height is up to 0.5 m, and its diameter reaches 1.2 m. Since this species lives in the desert, it has a long main root that goes 3 m deep. The leaves that grow from the trunk of velvichia are a real miracle. Unlike the leaves of all other plants on Earth, they never fall off. They constantly grow at the base, but periodically die off at the ends. Constantly renewing in this way, these leaves live as long as the velvichia itself (specimens that have lived for more than 2 thousand years are known).

The gnet family contains approximately 40 species. These are mainly shrubs, lianas, less often - trees. They grow in the tropical forests of Asia, Oceania, Central Africa. In their appearance, the gnetovye are more reminiscent of representatives of this family are melinjo, broad-leaved gnetum, ribbed gnetum, etc.

The coniferous family includes 67 plant species. In terms of life form, these are shrubs and semi-shrubs. They grow in Asia, the Mediterranean and South America. Members of this family have scaly leaves. Examples of conifers include American ephedra, horsetail ephedra, cone-bearing ephedra, green ephedra, etc.

Ginkgo class

This group includes one family. Ginkgo biloba is the only member of this family. This is a tall tree (up to 30 meters) with large fan-shaped leaves. This is what appeared on Earth 125 million years ago! Ginkgo extracts are often used in medicine to treat vascular diseases, including atherosclerosis.

Class "cycads"

They grow in Asia, Indonesia, Australia, Oceania, Madagascar.

These plants look like palm trees. Their height ranges from 2 to 15 meters. The trunk is usually thick and short when compared to the thickness. So, in a drooping cycad, its diameter reaches 100 cm, while its height is 300 cm.

Class "Coniferous"

This is perhaps the most famous class of gymnosperms. It is also the most numerous.

This class consists of one order - "Pine". Previously, there were three more orders on Earth, but their representatives died out.

The order mentioned above consists of seven families:

1. Capitate yew.
2. Yew.
3. Sciadopitisaceae.
4. Podocarps.
5. Araucariaceae.
6. Pine.
7. Cypress.

The capitate family includes 20 representatives. These are evergreen shrubs and trees. The needles are located in a spiral. They differ from yews in that their cones mature much longer, and they also have larger seeds.

The yew family includes about 30 species of shrubs and trees. All plants in this family are dioecious. Examples of representatives of this family include the Pacific yew, Florida, Canadian, European yews, etc.

The Sciadopitisaceae family includes evergreen trees that are often used as ornamental trees.

Examples of representatives of the podocarp family include dacridium, phyllocladus, podocarp, etc. They grow in humid areas: in New Zealand and New Caledonia.

The Araucariaceae family includes about 40 species. Representatives of this family existed on Earth already during the Jurassic and Cretaceous periods. Examples include the southern dammara, the Brazilian wollemia noble, etc.

The pine family includes such well-known trees as spruce, pine, cedar, larch, hemlock, fir, etc. All plants in this family grow in the Northern Hemisphere in temperate climates. Gymnosperms of this family are often used by humans in medicine and other industries due to their resins and essential oils.

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Gymnosperms are seed plants. Unlike angiosperms, they do not form flowers and fruits, and their seeds lie “naked” on the inner sides of the cone scales. The cone is a modified shoot with scaly leaves.

Conifers are characterized by special leaves, which are called needles. They are needle-like, covered with a cuticle, and the stomata are deeply embedded in the leaf tissue. All this serves as a device to reduce evaporation. On average, each needle lives for several years.

The stem tissues of gymnosperms are better differentiated than those of ferns. There is bark and wood, but the core is weakly expressed, and the conductive tissue consists of tracheids. Gymnosperms have developed cambium and secondary wood, so their trunks reach significant sizes.

Coniferous trees have resin canals in their trunks. These are intercellular cavities into which resins and essential oils are secreted by the cells lining them. These substances prevent the penetration of insects and bacteria.

Unlike higher plant spores, higher seed plants (gymnosperms and angiosperms) in the process of evolution went further onto land. Their breeding process is not dependent on the presence of water. So the pollen of gymnosperms is carried by the wind, and fertilization occurs with the help of a pollen tube.

Pine

Pine is widespread in the Northern Hemisphere, especially in temperate climates. This tree is undemanding to the soil, but demanding to light (it is light-loving). Pine can be found not only in coniferous forests, but also in swamps, rocks, sands. At the same time, depending on the growing conditions, the pine looks different. So in the forest of a pine, the main root develops strongly, it goes deeper. In open areas, lateral roots develop, occupying a large area near the surface. Pine trees growing in the forest are taller than those growing in open areas, they reach a height of about 40 meters. However, in the forest near the pines, the lower branches die off due to lack of light. Pine growing in open areas has a more spreading shape, its branches begin at the bottom of the trunk.

The lifespan of a pine tree is about 300 years.

Pine breeding

Male and female cones are formed on pine shoots in spring.

Male cones are collected in clusters resembling inflorescences, have a yellowish-green color and grow at the base of the shoots. In a group, the male cones are close to each other. On the underside of each scale, 2 pollen sacs develop. They produce pollen. The pollen of gymnosperms is haploid, that is, it has a single set of chromosomes. Pine pollen has two air sacs. It is a device for carrying pollen by wind.

Female pine cones are larger, have a reddish color, grow individually, not in groups. Female cones grow at the tops of the shoots. On each scale of the cone, 2 ovules develop. Ovules called differently ovules.

Pollination occurs in late spring or early summer. Pollen spills out of the male cones and is carried by the wind. At the same time, some of the pollen grains fall on the scales of female cones. After that, the scales close and stick together with resin.

After pollination, the female cone grows and becomes woody. In this case, fertilization does not occur. Only a year later, the pollen germinates and gives rise to the male gametophyte. One cell is called vegetative, it develops into a pollen tube. Another cell is called generative, two spermatozoa are formed from it. The pollen is called microspore .

The ovule is macrospore, which develops into a female gametophyte consisting of an egg and an endosperm.

One of the sperm fertilizes the egg through the pollen tube, resulting in the formation of a zygote. Later, an embryo develops from it, having a root, a stalk, several cotyledons and a kidney. The seed is formed from the ovule.

By the end of seed ripening, pine cones become dark brown. Seeds ripen only by the fall of next year. In winter, the scales of the cones diverge and the seeds fall out of them.

Pine seeds have pterygoid processes. Because of this, they are easily carried by the wind over long distances.

Spruce

Unlike pine, spruce is a shade-tolerant plant. Its crown grows from the very bottom of the trunk and has a pyramidal shape. Therefore, spruce forests are dark, grasses almost do not grow in them due to lack of light near the surface of the earth.

Spruce grows on fertile soils, in places with sufficient moisture.

The root system of spruce is located closer to the soil surface and is less developed than that of pine. Therefore, spruces cannot stand strong winds that can pull entire spruce plantings out of the soil.

If in pines each needle lives for several years, then in spruces they live up to 9 years. Spruce needles are arranged singly.

Cones ate larger than those of pine. Reach 15 cm in length. In addition, one year passes from the beginning of the appearance of the cone to its maturation.

Spruces live up to 500 years.

The value of conifers

Where there are many coniferous and mixed forests, their role in the formation of oxygen and organic matter is essential.

Delaying the melting of snow, coniferous forests enrich the soil with moisture.

Pine emits special volatile substances with antibacterial properties - phytoncides.

The importance of conifers in human life is also great. Since ancient times, people have used their wood as a building material. Ships were made from pine wood. Sequoia wood (mahogany) is used as a finishing material. Larch wood is resistant to decay. Paper is made from spruce wood.

Conifers are used in the chemical industry. So turpentine, plastics, rosin, varnishes, alcohols are obtained from them.

The seeds of the Siberian cedar pine look like nuts. They are eaten and oil is made from them.

Juniper cones look like berries. They are used as medicine.

Among the conifers there are ornamental plants.

Division Gymnosperms (Pinophyta or Gymnospermae)

seed plants

followed the line of further development of the sporophyte and reduction of the gametophyte. For seed plants, the most important evolutionary acquisition is internal fertilization. The gametophytes of these plants are sharply reduced. The female gametophyte and the gametes (ovules) formed by it do not leave the megasporangium and remain on the mother plant (sporophyte). The extremely reduced male gametophyte is embedded in a pollen grain. It is very important that the process of fertilization now does not depend on the presence of a drop-liquid aqueous medium. .

The unit of reproduction in seed plants, as the name suggests, is the seed. Seeds, unlike spores, have not only a fully formed embryo of the future sporophyte, but also reserve nutrients necessary at the first stages of its development. Dense shells protect the seed from adverse natural factors that are detrimental to most spores.

Thus, the successful conquest of land by seed plants is largely due to two aromorphoses (morphophysiological progressive changes in organisms) - the emergence of a seed and a pollen tube, which determined the reduction of the sexual generation (haploid gametophyte) with further improvement of the asexual generation (diploid sporophyte).

1. Department structure: There are about 700 species of modern gymnosperms. Department includes , two of which have died out, and of the remaining ones, the most numerous group is conifers (Pinopsida) - 50 genera, 550 species.

The heyday of conifers falls on the Jurassic period. Conifers - evergreens, with the exception of larch and metasequoia. Of these, pines - 90 species, probably the most famous.

2. Spreading : Gymnosperms are very ancient plants. The remains of their fossils are found in the layers of the Devonian period of the Paleozoic era (350 million years ago). At present, despite the relatively small number of species, gymnosperms are widespread, especially in the northern hemisphere, where they form large areas of coniferous forests called taiga. In the vast expanses of Northern Eurasia and North America, they form forests, often represented by the dominance of one species. The largest number of species of pine, fir, spruce and larch is concentrated near the Pacific coast, especially in China. In the southern hemisphere, conifers are most abundant in the temperate regions of New Zealand, Australia, and South America.

3. life forms : The sporophyte dominates, the asexual generation is a leafy plant. At present, gymnosperms are predominantly trees, shrubs, tree-like vines, and even epiphytes with monopodial branching. Herbs were represented by only one authentically known species - Williamsoniella (from bennitaceae). Among conifers there are giants of the plant world. For example, evergreen sequoia (California, USA) reaches 117 m in height with a trunk thickness of 11 m; mammoth tree - trunk thickness up to 12 m and age up to 4000 years; swamp cypress - trunk thickness up to 16 m. The longevity record was set by a long-lived pine found in Eastern Nevada (USA), its age is approximately 4900 years.

4. Root system : The embryonic primary turns, as a rule, into a powerful rod and functions throughout life. Two forms of roots often develop: usually elongated and strongly branched-shortened. It is the latter that are mycorrhiza. Root hairs are localized in a narrow zone. Adventitious roots are very rare (in primitive representatives).

5. Leaves: in gymnosperms they vary greatly in number, size and structure. The shape of the leaves can be needle-shaped (juniper, spruce, pine, larch), scaly (thuja, cypress). Needle leaves can be arranged in whorls one by one (spruce) or two to eight (pines), arranged in a spiral on the stem, scaly - opposite. What we see in a pine tree, in the form of a bunch of needles surrounded by scaly leaves, are shortened and (brachyblasts). In the structure of the leaves, a number of adaptations are observed to reduce evaporation: the shape of the leaf, a thick cuticle, submerged stomata, which are sealed with resin in the cold season. Most gymnosperms are evergreens. Pine needles are replaced after 3-4 years (the exception is deciduous larch). But in spinous pine (Pinus longaeva) it can maintain photosynthetic activity up to 45 years! Conifers have a powerfully developed secondary xylem (wood), consisting of 90-95% of tracheids. The bark and pith are poorly developed. Many conifers in the bark, wood and leaves have resin passages containing essential oils, resins, balms.

6. Sporangia : Specialized organs on which sporangia develop are cones, consisting of an axis and scales. On the scales of the female cone above(photo 1) megasporangia are ovules, and they contain an egg. On the scales of the male cone (microsporophylls - reduced spore-bearing leaves, which can be considered as homologues of angiosperm stamens) from below(photo 2) - microsporangia - anthers, and pollen grains in them. Conifers - monoecious plants (less often dioecious). For example, pine is a monoecious plant, male and female cones are formed on the same plant. In a typical case, it reaches a height of 50 m and lives up to 400 years. Sporulation occurs in the 30-40th year of life, but it happens earlier. Sporophylls are collected in cones of two types, which differ sharply from each other: males are represented by paniculate "inflorescences", females are single.

The male cone, which has an elliptical shape 4-5 cm long, 3-4 cm in diameter, is formed in the axil of the scale in place of a shortened a and is a well-developed axis (rod), on which microsporophylls are spirally arranged - reduced spore-bearing leaves. They can be considered as homologues of angiosperm stamens. Microsporangia (anthers) are formed on microsporophylls from the underside.

Female cones are formed on the tops of young ovs, they are larger and more complex. On the main axis, in the axils of the covering scales, thick scales are formed with two ovules on the upper side. These scales are called seed. A female cone is a group of metamorphosed shortened lateral ovaries located on a common axis.

a) Inside the microsporangium on the male cone, a large number of microsporocytes, the mother cells of microspores, are formed by autumn (2). In spring, they divide reductively and form haploid microspores (four haploid microspores are formed from each diploid mother cell). Each microspore is dressed in a shell - sporoderm, which consists of an external exine, which is a special persistent high-molecular substance - sporopollinin and can not only withstand extreme temperature and chemical influences, but can also be preserved for millions of years in geological sediments. Very often this shell bears special outgrowths and sculptural thickenings. The inner shell of intin is a thin film of cellulose and pectin, covering the contents of the microspore. The shells lag behind each other and thus form two air bags. The number of microspores produced on one plant is very high.

b) A young pine ovule consists of a nucellus and one integument. Nucellus is essentially the ovule. In the middle part of the ovule (nucellus), one large megaspore mother cell separates, which (remember) divides meiotically and forms four haploid megaspores; three of them degenerate, and the remaining one divides repeatedly mitotically, without cytokinesis. The nuclei are located in the wall layer, and then there is a free formation of cells. This is how it is formed multicellular female gametophyte(called the primary endosperm in gymnosperms). That. the formation of the female gametophyte from the megaspore occurs on the sporophyte itself.

9. Antheridia:

Germination of microspores occurs in the microsporangium with the subsequent development of a reduced gametophyte. Microspore integuments remain integuments pollen is the male gametophyte. First, 2 prothallial cells are separated. After the first division, the prothallial cells are pushed back to the wall of the pollen grain and destroyed. The remaining cell is divided into vegetative and antheridial. After maturation of the pollen, the microsporangia open and the pollen spills out. Air sacs facilitate the transport of pollen by wind. Further development of the male gametophyte occurs after pollination on female cones inside the ovule. Thus, the male gametophytes of pine are already completely devoid of antheridia.

10. archegonia

In a female cone inside the ovule on a multicellular female gametophyte, two outer cells (near the pollen inlet) form two strongly reduced archegonia in which only the eggs are well developed. Above them are small cells of the cervix and the abdominal tubular cell, which is destroyed shortly before fertilization.

11. Fertilization.

Fertilization can occur only 20 months after the formation of the ovule. Fertilization is preceded by pollination - the transfer of pollen by wind through the air to the ovules. Fertilization in a pine tree not associated with droplet medium- the sperm is delivered to the egg by pollen tube. During pollination, pollen falls on the ovules located openly on the female cone and sticks to the pollen inlet due to the sticky liquid secreted by it, and then through the pollen inlet (micropyle), when the liquid evaporates, it is drawn into the pollen chamber. The cone turns green, the scales grow together, become stiff. The pollen remains dormant until the following summer, when it begins to germinate. The exine bursts, and the intine surrounds the pollen tube formed from the vegetative cell of the pollen grain, which brings the sperm to the archegonium, where one of them merges with the egg. This happens as follows: after pollination, the scales of the female cone close, turn green, coalesce, become woody, and the male gametophyte continues its development on megasporangia. When the male gametophyte germinates in the direction of the archegonium, the vegetative cell develops into a pollen tube, and the antheridial cell forms two cells: a stalk cell and a spermatogenic cell. They move into the pollen tube and reach the archegonium through it. From the nucleus of the spermatogenic cell, immediately before fertilization, male gametes are formed, devoid of flagella. Upon reaching the egg, the pollen tube is destroyed, and one of the sperm merges with the egg, and the other with the remains of the vegetative cell and the stalk cell, die.

12. Embryo: From a fertilized egg - a zygote (2n), an embryo develops, equipped with a nourishing haploid tissue of the female gametophyte (n) (endosperm), surrounded by the cover of the ovule (2 n) - SEED.

The pine embryo consists of a suspension (the formation with which the embryo is attached to the shell of the embryo sac), root, hypocotyl, 3-15 cotyledons and apical meristems (root and oval).

13. reproduction

In plants, there are two main methods of reproduction - sexual and asexual. One type of asexual reproduction is sporulation. During spore formation, a specialized cell, a spore, is released from the composition of the mother's organism, which serves for the reproduction and settlement of plants. The spore germinates without first fusing with any other cell. In all higher plants, spores are formed as a result of meiosis, i.e. have a haploid set of chromosomes. Distinguish micro- and megaspores, developing, respectively, in micro- and megasporangia. In seed plants, micro- and megaspores have lost the function of settling, but their formation remains a necessary stage in the reproduction cycle. One of the general patterns inherent in plant reproduction is the change in their life cycle of asexual and sexual generations, i.e. alternation of generations.

Summing up what has been said, it should be noted once again that pine cones are laid at the beginning of winter, pollination occurs in the spring, fertilization - the next year. The maturation of female cones and seed abscission is completed during the next autumn. Hence, the life cycle of the female pine cone spans three growing seasons. Seed germination occurs under favorable conditions with the onset of spring in the temperate zone.

14. Meaning

1) Conifers form natural landscapes - taiga in vast expanses of continents. Their importance in the life of nature and in human economic activity is great.

2) Being the most important component of biogeocenoses, they are of great water protection and anti-erosion significance.

3) Coniferous plants provide the bulk of construction wood and are the source material for the diversified forestry industry.

4) Viscose, silk, cellulose, staple, balsams and resins, pine wool and camphor, alcohol and acetic acid, rosin and turpentine, tannin extracts, etc., as well as food products and vitamins are obtained from conifers.

5) The seeds of some araucaria, cedar, Siberian pine contain up to 79% oil, close to Provence and almond.

6) For the medical industry, conifers serve as a raw material for obtaining not only vitamins, but also the drug pinobine (antispasmodic). Coniferous extracts are used for therapeutic baths.

7) Many types of conifers are used in folk medicine for the treatment of tuberculosis, nervous disorders, diseases of the kidneys, bladder, hemorrhoids, deafness, and as an anti-leprosy remedy.

8) Needles and young and some conifers are an indispensable winter food for elks, capercaillie feed on needles, and many animals and birds feed on Siberian cedar seeds (as well as seeds of other conifers). Juniper cone berries - food for black grouse. Yew wood is used for the manufacture of expensive crafts and in the furniture industry, it is almost not affected by insects.

Gymnosperms called plants that form seeds, but do not form flowers and fruits. The seeds lie open and are only sometimes covered with scales. Gymnosperms evolved from primary. Currently, this group includes only about 700 species of trees and shrubs. The department of plants includes the departments: cycads, ginkgos, conifers, ephedras. Conifers are the most widespread. Almost all of them are trees. Conifers have a well-defined trunk, the leaves of most conifers are hard, needle-like (needles) and do not fall off; are replaced almost throughout life. The structure of gymnosperms has characteristic features. Among the gymnosperms, there are a large number of tree forms, sometimes having a large, well-defined trunk. Conifers have the longest lifespan. In the stem, on a transverse section, a thin bark, well-developed wood (conductor tissue) and a poorly expressed core, consisting of loose parenchymal (basic) tissue, are distinguished. In old trunks, the core is barely noticeable. The wood of gymnosperms is simpler than that of flowering plants, it consists mainly of tracheids - dead spindle-shaped cells with thick membranes that perform a conductive and supporting function.

Parenchyma in wood there is very little or it is completely absent. In many species, there is very little or no bark and wood in the bark. Many species in the bark and wood have resin channels filled with resin, essential oils and other substances. Evaporation of these substances creates the characteristic aroma of coniferous forest.

The leaves of most conifers are hard, needle-like (needles) and do not fall off during the unfavorable season. They are covered with a thick cuticle - a layer of a special substance released.

The stomata are embedded in the tissue, which reduces the evaporation of water: the replacement of needles occurs gradually throughout the life of the plant.

Reproduction of conifers on the example of pine

It is a bisexual, wind-pollinated plant. On young stems, two types of cones are formed - shortened: male and female. Male cones are located at the base of young shoots, have an axis to which scales are attached. On the underside of the scales there are two pollen sacs; microspores (male spores) with a single haploid set of chromosomes are formed in them. Male gametophytes are formed from microspores - pollen grains that carry germ cells - sperm.

Small reddish female cones sit on the tops of young shoots. The scales of female cones fuse in pairs, and develop between them. A megaspore (female spore) is formed there. As a result of its repeated division, a female gametophyte is formed - an egg and an endosperm, which subsequently nourishes the embryo. Pollen brought by the wind falls on the scales of female cones. The pollen grain germinates, the sperm reaches the egg through the pollen tube and merges with it - fertilization occurs. Connecting, sperm and egg form a cell with a double (diploid) set of chromosomes - a zygote. This is the first cell of the sporophyte. From the seven germ, a seed develops with a supply of nutrients, which is dressed in protective shells. In the second year after the formation of the female cone and the transfer of microspores to it, the seeds spill out and are carried by the wind.

- the basis of the vegetation cover of a number of natural zones. 90% of forests are represented by different types of gymnosperms. Birds feed on seeds, wood is used in the economy.

The so-called ship pines, which have a long straight trunk, were used in shipbuilding in former times. The entire sailing fleet was built mainly from pine. Many coniferous and now an excellent building material. In addition, paper, cardboard, turpentine and many other products valuable to humans are obtained from pine. The core of the cycads is eaten.