Botany. Higher and lower plants. Preparing for the Unified State Exam - botany Preparing for the Unified State Exam on the topic of plants

Plants are eukaryotic photosynthetic autotrophic organisms. The plant kingdom has about 500 thousand species.

The listed differences between plants and animals are not absolute. Features of animal organization are often found in lower plants, which correspond to the early stages of evolutionary development. For example, the ability for both autotrophic and heterotrophic nutrition (green euglena). More highly organized plants differ quite clearly from animals.
Plants are divided into lower and higher. U lower plants the body (thallus or thallus) is not divided into tissues and organs. These include Red Algae (Purple Algae), True Algae and Lichens. U higher plants the body is divided into organs (root, stem, leaf) formed by differentiated tissues. Higher plants include Bryophytes, Mocophytes, Horsetails, Ferns, Gymnosperms and Angiosperms (Flowers). The first four divisions are dispersed by spores ( spore ), the last two - using seeds ( seed ).
Plant propagation. All higher plants are characterized by alternation in the life cycle of sexual and asexual reproduction and the associated alternation of generations (development phases) - haploid (n) (gametophyte) and diploid (2n) (sporophyte). On sporophyte sac-like formations appear - sporangia (organs of asexual reproduction), in which, as a result, sporogenesis accompanied by meiotic division, haploid cells are formed disputes . From the spores develops gametophyte . Special reproductive structures are formed on it - gametangia (organs of sexual reproduction) in which they are formed gametes .
The male genital organs where sperm are formed are called antheridia , the female genital organs where eggs are formed are called archegonia . If both archegonia and antheridia develop on a gametophyte, it is called bisexual , if only antheridia, then male , if only archegonia, then female. When gametes fuse, it is formed zygote . A sporophyte develops from a zygote.

Department Angiosperms (Flowering)

Angiosperms- evolutionarily the youngest and most numerous group of plants. The department includes about 250 thousand species. Angiosperms grow in all climatic zones, make up the bulk of plant matter in the biosphere and are the most important producers (producers) of organic matter on land.
The dominant role of flowering plants is due to a number of progressive features:

1. Appearance flower- an organ that combines the functions of asexual reproduction (spore formation) and sexual reproduction (seed formation).
2. Formation within a flower ovaries, which contains the ovules (ovules) and protects them from adverse environmental influences.
3. Formation from the ovary fetus: the seeds are located inside the fruit and are therefore protected (covered) by the pericarp. In addition, the fruit allows the use of various agents for seed dispersal (insects, birds, bats, as well as air and water flows).
4. Double fertilization, as a result of which a diploid embryo and a triploid (and not haploid, as in gymnosperms) endosperm are formed.
5. Maximum gametophyte reduction. The male gametophyte - pollen grain - consists of two cells: vegetative and generative, which divides to form two sperm. The female gametophyte consists of eight embryo sac cells, one of which becomes the egg.
6. Reproduction and seeds, And vegetative organs.
7. Complication and high degree of differentiation of organs and tissues. In particular, the most perfect conducting system: The xylem is represented by vessels, not tracheids; in the phloem, sieve tubes have a segmented structure, and satellite cells appear.
8. Rapid growth and development processes in annual forms.
9. Big variety of life forms: trees, shrubs, shrubs, subshrubs, perennial herbs, annual herbs, etc.
10. Can form complex multi-tiered communities due to the wide variety of life forms.

The importance of angiosperms in human life is difficult to overestimate. Almost everything cultivated plants belong to this department. Angiosperm wood is used in industry, construction, paper making, furniture, etc. Many flowering plants used in medicine.

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Gymnosperms - very ancient plants. The remains of their fossils are found in the layers of the Devonian period of the Paleozoic era. Currently, gymnosperms are mainly trees (up to 100 m in height), shrubs, tree-like vines and even epiphytes. Herbs are represented by only one reliably known species - Williamsoniella (from the bennite family).

Coulter's pine Ginkgo biloba Cycad averted

Branching of gymnosperms is mainly monopodial ; wood consists almost entirely of tracheid , there are no vessels (with the exception of pressure vessels). Most gymnosperms have needle-shaped (needles) or scale-like leaves; a few have large, often dissected leaves, similar to fronds of ferns or palm leaves. These are predominantly evergreen, mono-, di- or polyecious plants. The roots (main and lateral) have the usual structure for trees and shrubs, with mycorrhiza. Adventitious roots are very rare (among primitive representatives).

A distinctive feature of all gymnosperms is the presence ovules (ovules) and seed formation. The ovules are located openly on megasporophylls or at the ends of stems, which is why the plants are called gymnosperms. Openly lying seeds develop from the ovule. The ovule is a megasporangium surrounded by an integument. Seeds always contain nutritious tissue - endosperm; during germination, the cotyledons are brought to the surface and perform the functions of leaves.

Seed ferns- completely extinct plants that existed from the late Devonian to the early Cretaceous. These were tree-like plants or vines that had large leaves, similar to fronds of ferns, and adventitious roots. In addition to assimilating leaves, they had spore-bearing leaves; some had microsporangia and megasporangia with ovules. Seed ferns are a transitional group from ferns to seed plants. Apparently, other seed plants originated from them. The remains of seed ferns play a large role in the formation of coal in the territories of Russia, Western Europe and North America.

Heyday of conifers falls in the Jurassic period. This is the largest and most widespread group among modern gymnosperms. Conifers are evergreen plants, with the exception of larch and metasequoia. They are represented mainly by trees with a height of 10-15 to 100 m, tree-like stylates, and shrubs with monopodial branching. Needle-shaped (needles) or cone-shaped leaves are arranged on the stem in a spiral (single) or collected in bunches, scale-shaped leaves are opposite.

Conifers have a powerfully developed secondary xylem (wood), consisting of 90-95% tracheids. The bark and pith are poorly developed. The embryonic primary root usually turns into a powerful tap root and functions throughout life. Two forms of roots often develop: usually elongated and highly branched and shortened. It is the latter that are essentially mycorrhiza. Root hairs are localized in a narrow zone. Many conifers have resin passages in their bark, wood and leaves containing essential oil, resins, balms.

Conifers are monoecious plants, less often dioecious. For example, pine is a monoecious plant, male and female bumps are formed on one plant. Typically, it reaches a height of 50 m and lives up to 400 years. Sporulation occurs in the 30-40th year of life, but it can happen earlier.

Sporophylls are collected in cones of two types, which differ sharply from each other: men's represented by paniculate “inflorescences”, women's - single. A male cone, having an ellipsoidal shape, 4-5 cm long, 3-4 cm in diameter, is formed in the axil of the scales at the site of a shortened shoot and is a shoot with a well-developed axis (rod), on which there are spirally locatedmicrosporophylls- reduced spore-bearing leaves. They can be considered as homologs of angiosperm stamens. Microsporangia (anthers) are formed on the microsporophylls on the lower side.

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

Inside is a microsporangium on a male cone ( A ) is formed by autumn a large number of mother cells microspores . In the spring, they divide reductionally and form haploid microspores (four haploid microspores are formed from each diploid mother cell). Microspore ( IN ) is dressed in two shells and carries two air bags. Germination of microspores occurs in microsporangium with the subsequent development of a reduced gametophyte: the microspore nucleus divides mitotically (twice: the first two cells disappear and two nuclei are formed again) with the formation of an antheridial cell in which male cells gametes - sperm , and vegetative, with the help of which male gametes are delivered to the egg; pollen tube develops G ) due to the enzymatic growth of the vegetative cell. In gymnosperms, the organ of sexual reproduction, the antheridium, has already disappeared. The microspore covers remain the pollen covers. After the pollen ripens, the microsporangia open and the pollen spills out. Air sacs facilitate the transfer of pollen by wind. Further development of the male gametophyte occurs after pollination on the female cones inside the ovule.

Young ovule consists of nucellus and integument. Nucellus is essentially an ovule. In the middle part of the nucellus, one large megaspore cell (megaspore mother cell) separates, which divides meiotically and forms four haploid megaspores; three of them degenerate, and the remaining one divides repeatedly mitotically, forming a multicellular female gametophyte (called endosperm). From the two outer cells (near the micropyle) two highly reduced archegonia are formed, in which only egg. Fertilization occurs 20 months after the formation of the ovule.

After pollination of the scales of the female cone ( B ) close, and the male gametophyte continues its development on the megasporangium. When the male gametophyte grows towards the archegonium, the vegetative cell develops into a pollen tube, and the antheridial cell forms two cells: a stalk cell and a spermagen cell. They move into the pollen tube and reach the archegonium along it. Two sperm cells (male gametes lacking flagella) are formed from the nucleus of the spermogenic cell immediately before fertilization. Upon reaching the archegonium, the vegetative nucleus is destroyed, and one of the sperm fuses with the egg, and the other dies. From a fertilized egg - zygote (2n) the embryo develops (D ), surrounded by haploid endosperm, formed from the haploid female gametophyte and covered by the integument of the ovule.

This is how the seed is formed (E) gymnosperms - a diploid embryo, nourished by the primary haploid endosperm, protected by a skin (2n - ovule integument). Scots pine seeds ripen in the second year after pollination, and the following spring the scales separate and the seeds spill out.

The embryo consists of a suspension, a root, a stalk and cotyledons. Seed germination occurs under favorable conditions with the onset of spring in the temperate climate zone.

Conifers form natural landscapes - taiga over vast areas of continents. Their importance in the life of nature and in human economic activity is great. Being the most important component of biogeocenoses, they have enormous water protection and anti-erosion significance. Coniferous plants provide the bulk of construction wood and are the source material for the diversified forestry industry. Viscose, silk, cellulose, staples, balsams and resins, pine wool and camphor, alcohol and acetic acid, tanning extracts, etc. are obtained from conifers, as well as food products and vitamins. The seeds of some araucaria, cedar, and Siberian pine contain up to 79% oil, close to Provençal and almond oil. For the medical industry, conifers serve as raw materials for obtaining not only vitamins, but also the drug pinobin (an antispasmodic agent). Many types of conifers are used in folk medicine for the treatment of tuberculosis, nervous disorders, kidney diseases, bladder diseases, hemorrhoids, deafness and as an antileprotic agent.

The needles and young shoots of some conifers are an indispensable winter food for moose; wood grouse eat needles, and seeds Siberian cedar- many animals and birds (as well as seeds of other conifers). Juniper cones are food for black grouse. Yew wood is used to make expensive crafts and in the furniture industry; it is almost not susceptible to insects.

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Department Bryophytes. General characteristics.

• Modern bryophytes are represented by approximately 25 thousand species.

• Bryophytes - the only one in history flora line of evolution associated with the regressive development of the sporophyte. They represent a dead-end or blind branch of plant development.

• The vast majority are low-growing perennial plants ranging in size from 1 mm to several centimeters, less often up to 60 cm or more. The body of some bryophytes is a thallus or divided into stems and leaves. Characteristic sign- lack of roots. Absorption of water and attachment to the substrate is carried out by rhizoids, which are outgrowths of the epidermis.

• Representatives of the department mostly inhabit wet habitats, as they are poorly adapted to life on land.

• There is a regular alternation of sexual and asexual generations.

Asexual and sexual reproduction Bryophytes.

The development cycle is dominated by the haploid gametophyte. This is a specific feature of bryophytes compared to other higher plants. The gametophyte and sporophyte are one plant. The asexual generation (sporophyte) is the so-called sporogon (a small box with spores and a stalk, the lower part of which is turned into a sucker embedded in the body of the gametophyte). The sporophyte lacks independence and is completely dependent on the gametophyte.

The development of the sexual generation (gametophyte) begins from the moment of spore germination. First of all, a branched filamentous or lamellar formation develops protonema or preteen, on which the buds are formed. Stems with reproductive organs sprout from the buds. Genitals– gametangia (female – archegonia and male – antheridia ) multicellular. Large immobile eggs mature in archegonia, and independently moving spermatozoa mature in antheridia. During rain or heavy dew, the antheridia open and release numerous sperm, which, moving in drops of water covering the low tufts of the bryophytes, can reach the archegonium. The fusion of gametes and the further development of the zygote occurs inside the archegonium. At the top of the gametophyte stem, the zygote, over a period of several months to two years, gives rise to a sporophyte, ending in a capsule with spores. After the sporogon ripens, the capsule opens or falls off, and the spores spill out. The development cycle repeats. Spore formation is preceded by meiosis. Therefore, the spores, protonema and gametophyte are haploid. Only the zygote is diploid.

Classification of Bryophytes.

The bryophyte department is divided into three classes: anthocerotes, liverworts and phyllophytes. Leafy mosses are the largest class. It is divided into three subclasses: sphagnum mosses with one genus Sphagnum, andrea mosses and brie mosses (the largest subclass).

Sphagnums: brown deceptive protruding Magellan Andrey Skalnaya

Brie mosses. Polytrichum vulgaris or “cuckoo flax”

This is a species that forms sods in coniferous forests, meadows, swamps, where it takes part in the formation of peat deposits. “Kukushkin flax” is the tallest moss. Its stem reaches a height of 50 cm. It grows in large cushion-shaped sods. The stem is densely covered with leaves. The plant spores abundantly. The box is located on a long stalk, covered on top with an easily falling cap with thin, downward-pointing hairs that resemble linen yarn. Due to the formation of dense turf, Polytrichum vulgaris promotes surface accumulation of moisture and waterlogging of habitats.

Life cycle of Polytrichum vulgaris.

Subclass Sphagnum. Sphagnum mosses.

The Sphagnum subclass includes the only genus Sphagnum, which unites about 300 species. Species of the genus Sphagnum are large, soft, whitish-green, brown or reddish mosses. Most often these are plants of wet habitats, usually forming cushion-shaped turfs. Stem without rhizoids. At the top of the stem the branches are collected into a head. Sporophytes are red or brown almost spherical boxes that rise to pseudopod , which is part of the gametophyte and reaches 3 mm in length.

The anatomical structure of the branches is similar to the structure of the stem, however, in the place where the leaves are attached to the branches, in almost all species, peculiar water-collecting retort-shaped cells are formed. The leaves are single-layered and consist of two types of cells: chlorophyll-bearing and colorless dead aquifer. Green cells are narrow, dead - have pores and thickened walls; they fill easily with water. The water-holding capacity of sphagnum mosses is approximately 20 times its dry weight (for comparison, cotton wool can only absorb 4-6 times its own weight in water). Due to their excellent absorbent properties, these mosses have been used in Europe since the 1880s. as a dressing material for wounds and abscesses, but since the First World War they have been almost completely replaced in this sense by cotton, probably due to the more neat appearance of products made from it. Gardeners mix peat moss into soil to increase its water-holding capacity and acidity.

The life cycle of Sphagnum is similar to that of Polytrichum.

Representatives of this genus form extensive peat bogs. According to the most conservative estimates, peat bogs cover at least 1% of the land. Growing annually with the upper part of the shoot, the lower stem dies and “peats” (accumulates and becomes compacted). Thus, over many years, huge deposits of peat are formed. The process of peat formation occurs due to stagnant waterlogging, lack of oxygen and the creation of an acidic environment (pH) by sphagnum mosses

Meaning of Bryophytes.

Bryophytes are distributed everywhere except seas and highly saline soils, but everywhere they prefer the most moist habitats. They are especially widely represented in the tundra; their annual growth is insignificant: from 1-2 mm to several centimeters, but the total result is a rather significant increase in moss tufts. Mosses – perennial species, are usually not eaten by animals and decompose very slowly. Mosses are capable of accumulating many substances, including radioactive ones, absorbing moisture and holding it relatively firmly, which is why mosses play a special role in nature, primarily in regulating its water balance. Developing intensively, mosses worsen the productivity of agricultural lands, causing them to become waterlogged. But at the same time, they contribute to the transfer of surface water flow into underground water, protecting soils from erosion.

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Botany- science that studies the plant kingdom (Greek. nerd- grass, plant).

The ancient Greek scientist Theophrastus (III century BC), a student of Aristotle, created a system of botanical concepts, systematizing and summarizing all the knowledge of farmers and doctors known at that time with his own theoretical conclusions. It is Theophrastus who is considered the father of botany.

Modern botany- science of morphology, anatomy, physiology, ecology and taxonomy of plants

Signs of the Plant Kingdom

• eukaryotes;
• autotrophs (photosynthesis process);
• osmotrophic type of nutrition: the ability of cells to absorb only low molecular weight substances;
• unlimited growth;
• sedentary lifestyle;
• reserve substance - starch (accumulates in plastids during photosynthesis);

Features of the structure of a plant cell (Fig. 1):

• cell wall made of cellulose
  The presence of a cell wall prevents the penetration of food particles and large molecules into the cell, so plant cells absorb only low-molecular substances (osmotrophic type of nutrition). Plants absorb from environment water and carbon dioxide, for which the cell membrane is permeable, as well as mineral salts, for which cell membrane there are channels and carriers.
• plastids (chloroplasts, chromoplasts, leucoplasts);
• large central vacuole
  Bubble containing cell sap surrounded by a membrane - tonoplast. The tonoplast has a system of regulated transporters that transport various substances into the vacuole, maintaining the desired salt concentration and acidity in the cytoplasm. In addition, the vacuole provides the necessary osmotic pressure in the cell, which leads to the appearance turgor- tension on the cell wall, which maintains the shape of the plant. The vacuole also serves as a site for storing nutrients and storing metabolic waste.
• There are no centrioles in plant cell centers.

Rice. 1. Plant cell

plant classification

The main ranks of plant taxa are distributed according to principle of hierarchy(subordination): larger taxa unite smaller ones.

For example:

Plant Kingdom

department Angiosperms

class Dicotyledons

family Asteraceae

genus Chamomile

type Chamomile

Life form- external appearance of the plant.

The main life forms: tree, bush, shrub and grass.

Tree- a perennial plant with a large woody trunk.

Bush- a plant with numerous medium-sized lignified trunks that live no more than 10 years.

shrub- a low-growing perennial plant with lignified trunks, up to 40 cm high.

Herbs- grassy green shoots that die off annually. In spring, biennial and perennial grasses grow new shoots from wintering buds.

higher and lower plants

Different groups of plants differ significantly in structure.

Lower plants do not have organs or tissues. Their body is thallus, or thallus. Lower plants include algae. Most of them live in aquatic environment. Under these conditions, they receive nutrition by absorbing substances over the entire surface of the body. All or most of the cells of these plants are exposed to light and are capable of photosynthesis. Therefore they have no need to fast movement substances throughout the body. The cells of these plants in most cases have the same structure.

Other photosynthetic organisms are also found in the aquatic environment. These are primarily cyanobacteria, which are sometimes called blue-green algae. These are prokaryotic organisms that are not plants.

Higher plants that live in water are often called algae. In these cases, the term "algae" is used in an ecological rather than a systematic sense.

Higher plants have functionally different organs formed by specialized cells. Basically, they live on land. They receive water and mineral nutrition from the soil, and to carry out photosynthesis they must rise above its surface, so for such plants it is necessary to move substances between parts of the body (conductive tissue) and mechanical support and support for the ground-air environment (mechanical and integumentary tissue).

The presence of specialized cells, tissues and organs allowed them to reach large sizes and master a wide range of habitats. Many representatives of higher plants returned to the water for the second time. In fresh water bodies they make up the bulk of aquatic vegetation.

A flower is a shortened, modified shoot of angiosperms, specialized for the formation of spores and gametes, as well as for the sexual process, which results in the development of a fruit with seeds.

Let's start classifying the parts of the flower. The flower consists of:

• The stem part, in which stands out:
• Pedicel - branching of the stem on which the flower is located
• Receptacle - the expanded upper part of the peduncle, from which sepals, petals, stamens, and pistils extend
• Leaf part, which is divided into:
• Sepals - modified leaves that make up the calyx of a leaf
• Petals - internal modified leaves that make up the corolla of the leaf

Note that in botany there is such a thing as perianth: this is the name given to the outer part of the flower surrounding the reproductive organs. Typically, the perianth consists of an outer ring of sepals (calyx) and an inner ring of petals (corolla).

• Generative part, including:
• Stamens are the male reproductive organ of a flower, consisting of a filament and an anther, in the nests of which pollen is formed. Each pollen grain contains 2 haploid cells: vegetative and generative.
• The pistil, the main part of the flower located in the center, is the female reproductive organ.

It consists of the ovary - the lower thickened part of the pistil, from which the fruit is subsequently formed, the style - the central part of the pistil between the ovary and the stigma, and the stigma itself - the wide upper part of the pistil, which receives pollen.

Ovules are formed in the ovary of the pistil, which after pollination and fertilization form seeds. There are flowers with an upper ovary - potatoes, peas, radishes, cloves, and flowers with a lower ovary - in cucumbers, bells, sunflowers. The superior ovary is free and easy to separate from the flower. It is much more difficult to isolate the lower ovary without damaging the flower, since it grows together with the stamens, perianth leaves, and even with the receptacle (in cucumber).

Particularly note the presence of nectaries (honey cakes) in the flower. They attract pollinating insects by secreting nectar - a sugary juice with a characteristic odor. When trying to collect nectar, insects shake the generative part of the flower, scattering pollen on themselves, on the stigma (due to which pollination occurs) and on other parts of the flower. The insects themselves serve as pollinators, transferring pollen from one flower to another on their body and limbs.

Perianth

Together, the sepals and petals make up the perianth. The perianth of the flower is double and simple. A double perianth includes a calyx and a corolla, found in apple trees, peas, and potatoes. If the perianth is not divided into a calyx and corolla, then it is called simple. A simple perianth consists of leaflets, characteristic of onions, oaks, birches, tulips and lilies of the valley. Some plants have no perianth, their flowers are called “naked”: poplar, willow.

Cup

The calyx is the outer part of the perianth formed by the sepals. The structure of the calyx varies from plant to plant. Highlight:

• Separate calyx - consists of sepals separated from each other: in wild radishes, strawberries
• Composite calyx - sepals are fused together: in cloves, peas

whisk

The corolla is the inner part of the double perianth formed by the petals and is usually brightly colored. The structure of the corolla may be different. The whisk can be:

• Free-petalled - the petals of the corolla are separated from each other
• Spinopetalous - the petals of the corolla grow together

In the future, as we study the families of angiosperms, we will study flower formulas. Remember now that if any parts of the flower grow together, then in the flower formula their number is taken in brackets.

Flower symmetry

Based on the symmetry features of the flower, they are divided into:

• Regular (actinomorphic), through which many planes of symmetry can be drawn. Regular flowers are found in carnations, lilies, and cucumbers. In the formula, such flowers are indicated by *
• Irregular (zygomorphic), such flowers have only one plane of symmetry. Flowers of this type are found in peas, sage, and snapdragons. In the formula, such a flower is indicated by the sign

Bisexual flowers have both stamens and pistils in one flower. However, there are plants in which the stamens and pistils are located on different flowers. Such plants have either stamens (staminate flowers) - male flowers, or pistils (pistillate flowers) - female flowers. Depending on the arrangement of male and female flowers, these plants are divided into:

• Monoecious - they have both male and female flowers located on the same plant: corn, birch, pumpkin.
• Dioecious - have both female and male flowers located on different plants: poplar, hemp, willow.

I will share my own association so that you can successfully remember these concepts. Imagine that a large number of guests came to visit wealthy owners. The rich owners built two houses on the property, and they have the opportunity to separate all the guests, so that the men separate from the women and go to different houses("dioecious plants"). If the hosts were less wealthy, then they only had one house, so both male and female guests would have to look for a place to stay overnight in the same house (“monoecious plants”).

Ovule

Also called ovule. It is a multicellular organ formed in the ovary from which the seed develops. The tissues of the ovary form a protrusion (outgrowth) called the placenta, which attaches the ovule inside the ovary. The ovule communicates with the placenta using the peduncle.

The process of megasporogenesis occurs in the ovule, which we will dwell on in more detail:

Pollination

Pollination is the process of transferring pollen from the anthers to the stigma (in flowering plants) or to the ovule (in gymnosperms). In the study of any topic, classification is an important aspect. There are two types of pollination:

Fertilization

Fertilization is the fusion of a sperm, sperm (male reproductive cell) with an egg, ovum (female reproductive cell), leading to the formation of a zygote. In one way or another, pollen (pollen grain) ends up on the stigma. The vegetative cell begins to grow into the pistil tissue, dissolving them and forming a pollen tube. Two sperm are formed from the generative cell.

The pollen tube grows into the embryo sac, allowing the sperm to reach the egg. Next, a unique phenomenon occurs in flowering plants, discovered by S.G. Navashin - double fertilization. As you remember, two sperm were formed from the generative cell. The essence of double fertilization is that one of the sperm fuses with the egg (fertilizes it) to form a zygote (diploid), from which the embryo develops. The second sperm fuses with the central cell (this cell is already diploid at the time of fusion) to form endosperm (triploid) - a reserve nutrient.

After fertilization, seeds are formed from the ovules over time. The seed coat is formed from the integument of the ovule (from the Latin integumentum - cover, cover). The pericarp is formed from the walls of the pistil ovary.

Inflorescences

Flowers, especially in insect-pollinated plants, are rarely arranged singly. Most often, flowers form clusters - inflorescences. An inflorescence is a part of the annual shoot of a plant, bearing flowers and modified bracts, in the axils of which the flowers or inflorescences are located.

We will also study this section using classification. Inflorescences are divided into:

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Let us first define the main factors that characterize the organisms of this kingdom.

Features of cellular structure:

1.Presence of chloroplasts in a cell.
This organelle determines everything in the plant body: physiological processes and life cycles, and environmental role.

2. Vacuoles.

3. Cell wall(spare nutrient- carbohydrates (most often starch or cellulose)) - additional shell, thickening of the cell membrane. The main role is protective and a small supply of substance.

Plant Physiology

Breath: oxygen, like all other living organisms.
Nutrition: as we mentioned above, plants - autotrophs - produce their own food.

When you read school textbooks, you get the impression that plants need nothing more than light, water and carbon dioxide.

If you talk to gardeners, your hair will stand on end - some plants need more fertilized soil, others - less, alkaline, acidic, sandy...

It turns out that the plants do not feed on air or water...

Plants need nutrients and they get them from the soil.

These are both organic and inorganic (mineral) substances.

Growth and development

Another one distinguishing feature plants, common with fungi, but absent in animals - growth throughout life.

Reproduction:
1. sexual - with the help of gametes (sex cells);
2. asexual, vegetative - with the help of body parts;
3. asexual, using spores (only in spore-bearing plants).

Plant taxonomy

Plant departments:

Algae Department

It doesn’t matter whether the algae is unicellular or multicellular - no tissues, no organs!

Department of spore plants

They are already classified as higher, because both tissues and organs are available. By name and development - reproduction occurs with alternating generations - asexual (spore) and sexual (gametophyte).

There are no flowers, no fruits, no seeds.

Seed plants department

Complex structure and propagation by seeds.
Gymnosperms- reproductive organ - cone.
Angiosperms- reproductive organs - flower and fruit.

The evolution of plants went exactly this way - from protozoa to angiosperms: