Fertilization
Female sex cell(gamete) is called egg. Pestle
Male sex cell(gamete) is called sperm. Stamen
Pollen composed of pollen grains. pollen grain
Vegetative
generative sperm
pollen tube The structure of the ovule: Chromosomes
First sperm double.
zygote.
Second sperm triple.
Endosperm
From the shells of the ovule seed coat is formed. From the walls of the ovary
double. Navashin S.G. In 1898. Thus, a fruit is formed, which consists of a seed and a pericarp.
The formation of the ovule.
A cavity appears in the middle of the primary tubercle, and ovules will form on its inner wall.
The ovules of angiosperms are similar in structure to those of gymnosperms, i.e. it is a megasporangium (nucellus), dressed in integuments, one of whose megaspores germinates into a female gametophyte. These ovules go through several stages of development. At first they are very tiny, in the form of a bulge of meristem cells. These are nucellus cells. Further, in the middle of the nucellus, one cell stands out in size - this is an archesporial cell, which subsequently divides by meiosis and 4 megaspores arise.
Nucellus by this time will increase in size and outside will be dressed (overgrown) with covers - integuments.
Of the 4 megaspores, only one will germinate into the female gametophyte, while the other 3 will be crushed and disappear (obliterate).
In the ovary, the formation of ovules takes place, the stigma catches and retains pollen grains on its surface, the style conducts male gametes to the ovules that arise during the germination of pollen grains.
By the time the development of the ovule is completed, the ovary becomes large, green, and on the cross section you can see that it consists of two structures: the walls of the ovary and the ovules.
The walls of the ovary are part of the green carpel and anatomically have a leaf structure, i.e. outer and inner epidermis, and between them green pulp - mesophyll cells.
Publication date: 2015-02-17; Read: 319 | Page copyright infringement
In angiosperms, the reproductive organ is the flower. Consider the processes occurring in stamens and pistils.
The formation of pollen grains occurs in the stamens. The stamen consists of a filament and an anther. Each anther is formed by two halves, in which two pollen chambers develop - microsporangia. The nests contain special diploid microsporocidal cells.
Each microsporocid undergoes meiosis and produces four microspores. Inside the pollen nest, the microspore increases in size.
7. Ovules in plant flowers develop in A. stigma of pistil B
Its nucleus divides mitotically and two nuclei are formed: vegetative and generative. A strong cellulose shell with pores is formed on the surface of the former microspore. Pollen tubes grow through the pores. As a result of these processes, each microspore turns into a pollen grain (pollen) - a male gametophyte. A mature pollen grain consists of two (vegetative and generative) or three (vegetative and two sperm) cells.
The formation of the female gametophyte (embryo sac) occurs in the ovule, which is located inside the ovaries of the pistil.
The ovule is a modified megasporangium protected by integuments. At the top of it there is a narrow channel - the pollen entrance. Near the pollen entrance, a diploid cell begins to develop - a megasporocyte (macrosporocyte). It divides by meiosis and produces four haploid megaspores. Three megaspores are soon destroyed, the fourth most distant from the pollen entrance develops into the embryo sac.
The embryo sac is growing. Its nucleus divides three times by meiosis. As a result, eight daughter nuclei are formed. They are located in four groups in two groups: one is near the pollen entrance, the other is at the opposite pole.
Then, one nucleus departs from each pole to the center of the embryo sac - these are polar nuclei. They can merge to form one central core. At the pollen entrance there is one egg and two cells of the synergid.
At the opposite pole, there are antipodal cells, which are involved in the delivery of nutrients to the cells of the embryo sac, and then disappear. Such an eight-core embryo sac is a mature female gametophyte.
Pestle. In the center of the flower is one or more pistils, usually pitcher-shaped or bottle-shaped.
In most pistils, one can distinguish the ovary - the main lower expanded part, which is strongly narrowed at the top into a column, forming a stigma at the top.
Ovary- a slightly enlarged, sometimes swollen part of the pistil, in which the ovules are located (seeds are formed from them after fertilization). If the ovary is attached to the receptacle only by its base, the rest of it is free, then it is called top(potato, tomato).
bottom(cucumber, pumpkin).
sedentary(poppy).
The megasporophyll grows together at its edges, forming a moist chamber that protects the modified megasporangium - the ovule.
Pollen is perceived by the glandular surface of the suture at the site of fusion of the edges of the megasporophyll. The evolution of the pistil is associated with the formation of specialized parts - the stigma, style and ovary, with the formation of the pistil from several megasporophylls, with the appearance of the lower ovary.
carpel.
Gynoecium
The ovules in the flowers of plants develop in
The gynoecium is called: apocarpous monocarp, cenocarpous - carpels 2 or more, they coalesce into one pistil (onion, potato, poppy).
With a cenocarpous gynoecium, the ovary cavity can be divided into nests according to the number of carpels (Fig. 5).
placenta.
The placenta is located at the site of fusion of the edges of the carpels. There are angular, central (columnar) and parietal placentation.
pedicel.
nucellus, integuments.
micropyle. chalazoy(Fig. 6).
Rice. 6 The structure of the ovule with the embryo sac:
direct, reverse and bent.
Megasporogenesis- formation of haploid megaspores by meiotic division. At the micropylar end, a megaspore mother cell (usually one) is laid. As a result of meiosis of this diploid cell, four haploid megaspores are formed. Three of them die off, one (usually the lower one, located farther from the micropyle) grows into a female gametophyte.
The female gametophyte is the embryo sac, formed by three successive mitotic divisions.
After the first division of the haploid nucleus of the megaspore, two nuclei are formed. They diverge towards the poles of the elongating megaspore, a large vacuole appears between them.
These polar nuclei combine to form a diploid nucleus called central, or secondary, nucleus of the embryo sac.
One of the three cells will ovum, the other two are synergists(auxiliary cells).
antipodes.
Publication date: 2014-11-02; Read: 955 | Page copyright infringement
studopedia.org - Studopedia.Org - 2014-2018. (0.001 s) ...
Pestle. In the center of the flower is one or more pistils, usually pitcher-shaped or bottle-shaped. In most pistils, one can distinguish the ovary - the main lower expanded part, which is strongly narrowed at the top into a column, forming a stigma at the top.
Ovary- a slightly enlarged, sometimes swollen part of the pistil, in which the ovules are located (seeds are formed from them after fertilization).
If the ovary is attached to the receptacle only by its base, the rest of it is free, then it is called top(potato, tomato).
If the ovary is immersed in the receptacle with which it fuses, then such an ovary is called bottom(cucumber, pumpkin).
The column departs from the top of the ovary. It ensures that the stigma is carried upwards to a position favorable for trapping pollen. The stigma serves to perceive pollen, releases substances that contribute to its germination (sugars, lipids, enzymes). In the absence of a column, the stigma is directly adjacent to the ovary, in which case it is called sedentary(poppy).
The origin of the pistil is associated with the evolution of megasporophylls of ancient gymnosperms.
The megasporophyll grows together at its edges, forming a moist chamber that protects the modified megasporangium - the ovule. Pollen is perceived by the glandular surface of the suture at the site of fusion of the edges of the megasporophyll. The evolution of the pistil is associated with the formation of specialized parts - the stigma, style and ovary, with the formation of the pistil from several megasporophylls, with the appearance of the lower ovary.
The megasporophyll of angiosperms is called carpel.
Gynoecium- a set of carpels (megasporophylls) of a flower.
The gynoecium is called: apocarpous when there are 2-3 or more carpels in a flower, each of them forms an independent pistil (buttercup, wild rose); monocarp, when there is one carpel in the flower, forming one pistil (pea); cenocarpous - carpels 2 or more, they coalesce into one pistil (onion, potato, poppy). With a cenocarpous gynoecium, the ovary cavity can be divided into nests according to the number of carpels (Fig.
Rice. 5 Types of gynoeciums: a - apocarpous of three carpels; b, c, d - cenocarpous of three carpels: 1 - carpel; 2 - placenta; 3 - ovule
The place of attachment of the ovules to the wall of the ovary is called placenta. The placenta is located at the site of fusion of the edges of the carpels. There are angular, central (columnar) and parietal placentation.
Ovule, formation of megaspores and embryo sac. The ovules develop on the inner wall of the ovary, on the placenta.
The ovule is attached to the placenta pedicel.
The ovule consists of the multicellular nucleus of the ovule, or nucellus, and the two coverings surrounding it, or integuments.
Above the top of the nucellus, the integuments do not grow together, a microscopic channel is formed - the pollen entrance, or micropyle. The part of the ovule opposite the micropyle, from where the integuments depart, is called chalazoy(Rice.
The structure and development of the ovule of plants
6 The structure of the ovule with the embryo sac:
1, 2 – inner and outer integuments; 3-ovum; 4 - embryo sac; 5 - nucellus; 6 – chalaza; 7-antipodes; 8 - secondary nucleus; 9 - synergides; 10 – funiculus; 11 - placenta; 12 - conducting beam; 13 - pollen entry (micropyle)
Ovules are of three types: direct, reverse and bent.
In the direct ovule, the nucellus is a direct continuation of the seed stalk (the families Buckwheat, Nettle, Pepper), in the reverse, the nucellus is located at an angle to the peduncle (it is most common), but the latter remains straight. In bent ovules, a bend is observed in both the nucellus and the pedicels (Leguminous, Marevy, Cabbage).
In the ovary there can be the most diverse number of ovules: in cereals - one, in grapes - several, in cucumber, poppy - many.
Nucellus is a true homologue of megasporangium; integuments arose later in the first seed plants.
In the nucellus, the ovule sequentially occurs: megasporogenesis, the development of the female gametophyte - the embryo sac, double fertilization, the development of the embryo and endosperm.
Megasporogenesis- formation of haploid megaspores by meiotic division. At the micropylar end, a megaspore mother cell (usually one) is laid.
As a result of meiosis of this diploid cell, four haploid megaspores are formed. Three of them die off, one (usually the lower one, located farther from the micropyle) grows into a female gametophyte.
The female gametophyte is the embryo sac, formed by three successive mitotic divisions. After the first division of the haploid nucleus of the megaspore, two nuclei are formed. They diverge towards the poles of the elongating megaspore, a large vacuole appears between them.
Then one nucleus from each quadruple moves to the center of the cell. These polar nuclei combine to form a diploid nucleus called central, or secondary, nucleus of the embryo sac.
The central nucleus is clothed with cytoplasm and becomes the central cell of the embryo sac (sometimes the fusion of the polar nuclei occurs later). Near the micropylar end of the embryo sac, an egg apparatus is formed from three cells that have arisen from three nuclei, around which the cytoplasm is concentrated.
One of the three cells will ovum, the other two are synergists(auxiliary cells).
Three cells develop at the chalazal end of the embryo sac antipodes.
The resulting embryo sac with seven naked cells is now ready for the fertilization process.
The embryo sac is the most strongly reduced female gametophyte.
Previous12345678910111213141516Next
Publication date: 2014-11-02; Read: 954 | Page copyright infringement
studopedia.org - Studopedia.Org - 2014-2018. (0.001 s) ...
FERTILIZATION IN FLOWERING PLANTS
Fertilization- this is the process of fusion of male and female germ cells (gametes).
Female sex cell(gamete) is called egg. The ovules are produced in the ovules of the ovary. Pestle is the female reproductive organ.
Male sex cell(gamete) is called sperm. Sperm are produced in the anthers of the stamens.
Stamen is the male reproductive organ.
The anthers of the stamens contain pollen.
Pollen composed of pollen grains. pollen grain- this is one stick. Pollen grain contains 2 cells - vegetative and generative.
Vegetative is the cell that forms the pollen tube.
generative is the cell that produces two sperm.
sperm are the male sex cells.
In the process of pollination, the pollen grain falls on the stigma of the pistil, germinates and forms a pollen tube. pollen tube moves through the stigma, style into the ovary. In the ovary of the pistil are ovules (seed rudiments). They will develop into seeds. The structure of the ovule: ovule membranes, embryo sac, main ovum with a double set of chromosomes, central ovum with a single set of chromosomes.
help urgently) please 1. ovules in flowering plants develop in ... a) stigma
Chromosomes contain genes and are responsible for the storage and transmission of hereditary information.
The pollen tube carries 2 spermatozoa to the ovules and germinates into the ovule through the pollen entrance. Sperm have a single set of chromosomes.
First sperm fertilizes the main egg and the chromosome set becomes double.
As a result, a fertilized egg is formed, which is called - zygote. From the main egg and the first sperm, the embryo of a new plant is formed.
The structure of the embryo of a new plant: germinal root, germinal stalk, germinal leaves and buds.
Second sperm fertilizes the central egg and the chromosome set becomes triple.
As a result, endosperm is formed. Endosperm is a supply of nutrients that are necessary for the germination of the seed germ.
From the shells of the ovule seed coat is formed.
From the walls of the ovary the pistil is formed pericarp.
This fertilization of two eggs by two sperm is called double. It was discovered by Russian scientists Navashin S.G. In 1898.
Thus, a fruit is formed, which consists of a seed and a pericarp.
Flowering plants are a large and diverse group that dominates most terrestrial ecosystems. From the main flowering plants cultivated by man, his existence depends. But in order for flowering plants to appear, they must go through the stage of pollination and fertilization. How this happens, read this article.
Pollination
This process is carried out by the transfer of pollen from the stamens to the pistil. How do pollination and fertilization occur in flowering plants? This is done in two ways: self-pollination and cross-pollination. In the first case, the transfer of pollen grains to the pistil occurs in the same flower. This is how peas or tulips are pollinated. In cross-pollination, pollen from a flower of one plant is transferred to the pistil of another. most often by insects, in rare cases - by wind (sedge and birch), birds and water.
As a result of pollination by insects, bright, highly visible flowers with a pleasant smell and nectaries that produce a sweet liquid are formed. These plants also produce a lot of pollen. It is food for insects. They are attracted by the bright color or smell of the flowers. When insects extract nectar, they touch the surface of pollen grains that stick to their body, and when they fly to the flower of another plant, they remain on the pistil. This is how insect pollination works. Many are pollinated only by a certain insect: fragrant tobacco - by a night butterfly, creeping clover - by a bee, and meadow clover - by a bumblebee.
Cross-pollinated plants are better adapted to changing environmental conditions. But the process of pollination in this case depends on a number of factors. And self-pollination does not depend on anything. He is not afraid of weather conditions and the absence of intermediaries.
Fertilization
A grain of pollen, falling on the stigma of the pistil, begins to germinate gradually. A long pollen tube develops from the vegetative cell. Growing up, it reaches the level of the ovary, and then the ovule. At the same time, a pair of sperm is formed, which penetrates the pollen tube. She, in turn, enters the ovule through the pollen passage. Then the tube at the very tip breaks and releases the male sperm, which are immediately sent to the embryonic membrane, which is called the sac. This is where the eggs develop.
Next, the egg is fertilized with one sperm, and the formation of a zygote, from which a small embryo of a completely new organism of plant origin begins to form. At the same time, the second sperm fuses with the nucleus of the zygote or with the polar nuclei. As a result, a triploid cell is formed, from which the endosperm arises. It is called a nutrient tissue, which contains reserves of the necessary substances for the normal development of the embryo of a future plant. This is how the organs of sexual reproduction of flowering plants are represented.
When one sperm cell with an ovum, and the other with polar nuclei, merge together, this process is called It is peculiar only to flowering plants and is a unique feature of angiosperms. The fertilized ovule grows into a seed. As a result, the ovary of the pistil grows. In flowering plants, a fruit develops from the wall of the ovary.
reproduction
Any plant, reaching a certain size and having passed the appropriate stages of development, begins to reproduce organisms of a similar species. This is reproduction, which is a necessary property of life. All organisms thus prolong the existence of the species itself. Distinguish sexual and which occurs with the participation of one individual. When plants develop specialized cells - spores, organisms begin to multiply.
Mosses, algae, ferns, club mosses and horsetails. Spores are special small cells with a nucleus and cytoplasm, which are covered with a membrane. They are able to endure bad conditions for a long time. But, getting into a favorable environment, they quickly germinate and begin to form daughter plants, the properties of which do not differ from the mother ones.
During sexual reproduction, female and male germ cells merge, resulting in the formation of daughter organisms that are qualitatively different from the parent. Here the parental organisms of the feminine and masculine are already taking part.
The macrosporangium plays a dominant role in the composition of the ovule. It is in it that the laying of one mother cell occurs, from which macrospores are formed. Three things begin to die off, and eventually collapse. The fourth macrospore is feminine, elongates and its nucleus divides. Then the daughter nuclei move to different poles of the elongated cell. Each nucleus formed is further divided twice.
In cells located near different poles, four nuclei are formed. This is called the embryo sac, in which there are eight haploid nuclei. Further, from each four nuclei, one of them follows to the center of the embryonic sac. There they merge, as a result of which they form a secondary nucleus - diploid.
Then, in the embryo sac, in the cytoplasm, partitions are formed between the nuclei at the cellular level. There are seven cells in the bag. Near one of its poles is the egg apparatus, which includes a large egg and two auxiliary cells. At the other pole, antipodal cells are located, there are three in total. So, there are now six in the bag and one diploid, with a secondary nucleus. It is located in the center of the embryonic sac.
What is an ovary?
It is called the lower thickened part of the pistil with a cavity closed inside, in which the ovules are located. Pollen enters from the stigma of the pistil into the ovule, which is protected from adverse conditions by an internal moist cavity. In the ovule, the development of female germ cells - eggs.
What are the ties?
Types of ovaries of flowering plants are:
- Upper. It is attached freely to the receptacle, without growing together with other sections in the flower. The walls of the ovary are formed from the carpels. In flowering plants, a fruit develops from the wall of the ovary. An example is ranunculus and cereal plants. These flowers are called sub-pistillate or near-pistillate.
- The lower ovary is always under the receptacle. It is formed with the participation of other departments of the flower: the base of the sepals and stamens with petals, which in many flowers are attached to the top of the ovary. In flowering plants, a fruit develops from the wall of the ovary. Examples are Compositae, cactus and orchid plants. The flower is called an overspray.
- Semi-inferior ovary. Its top does not grow together with other parts, so it is free. Flowers of this type are called semi-pistillate. These types of ovaries of flowering plants are.
flowering plants
They are the most progressive group of plants, numbering two hundred and fifty thousand species distributed throughout the planet Earth. The smallest plant is duckweed, the diameter of which is one millimeter. She lives in the water. The largest flowering plants are trees reaching a height of one hundred meters or more.
The appearance of flowering plants occurs due to the development of a special reproductive organ - a flower. In some plants, it is painted in bright colors, in others it smells wonderful. The flowers are small and inconspicuous in grass-like plants. Despite the huge variety of flowering plants, they all harmoniously fit into our lives: they decorate gardens and parks, give the joy of communicating with them.
flower structure
A flower is a complex organ system that provides reproduction of plants by seeds. Its appearance led to the wide distribution of angiosperms (flowering) plants on Earth. The flower has many functions. With its participation, stamens with pollen grains, pistils with ovules are formed. It plays a major role in pollination, fertilization, seed and fruit formation.
The flower is a shortened, modified, growth-limited shoot bearing a perianth, pistils, and stamens. All have flowers similar in structure and different in shape. So there is an adaptation to pollination in various ways.
The flower may end in the main or lateral stems, the bare part of which, under the very flower, is called the pedicel. It is greatly shortened or completely absent in sessile flowers. The pedicel passes into the receptacle, which is elongated, convex, concave or flat. It contains all parts of the flower. These are sepals with petals, stamens with a pistil, in the lower part of which an ovary is formed, in which ovules or ovules are located. A flower with such an ovary has a concave receptacle. If the ovary forms at the top of the pistil, the receptacle will be convex or flat.
Fertilization- this is the process of fusion of male and female germ cells (gametes).
Female sex cell(gamete) is called egg. The ovules are produced in the ovules of the ovary. Pestle is the female reproductive organ.
Male sex cell(gamete) is called sperm. Sperm are produced in the anthers of the stamens. Stamen is the male reproductive organ.
The anthers of the stamens contain pollen.
Pollen composed of pollen grains. pollen grain- this is one stick. Pollen grain contains 2 cells - vegetative and generative.
Vegetative is the cell that forms the pollen tube.
generative is the cell that produces two sperm. sperm are the male sex cells.
In the process of pollination, the pollen grain falls on the stigma of the pistil, germinates and forms a pollen tube. pollen tube moves through the stigma, style into the ovary. In the ovary of the pistil are ovules (seed rudiments). They will develop into seeds. The structure of the ovule: ovule membranes, embryo sac, main ovum with a double set of chromosomes, central ovum with a single set of chromosomes. Chromosomes contain genes and are responsible for the storage and transmission of hereditary information.
The pollen tube carries 2 spermatozoa to the ovules and germinates into the ovule through the pollen entrance. Sperm have a single set of chromosomes.
First sperm fertilizes the main egg and the chromosome set becomes double.
As a result, a fertilized egg is formed, which is called - zygote. From the main egg and the first sperm, the embryo of a new plant is formed. The structure of the embryo of a new plant: germinal root, germinal stalk, germinal leaves and buds.
Second sperm fertilizes the central egg and the chromosome set becomes triple.
As a result, endosperm is formed. Endosperm is a supply of nutrients that are necessary for the germination of the seed germ.
From the shells of the ovule seed coat is formed. From the walls of the ovary the pistil is formed pericarp.
This fertilization of two eggs by two sperm is called double. It was discovered by Russian scientists Navashin S.G. In 1898. Thus, a fruit is formed, which consists of a seed and a pericarp.
The variety of flowering plants is surprisingly large. To understand this diversity, botanists combine all types of plants into groups, which in turn are combined into larger groups. To establish such groups of plants, signs of their similarities and differences are used, by which one can judge the degree of relatedness of plants to each other.
Flowering plants have a more perfect structure than the structure of other groups. Only in angiosperms flowers are formed, and in flowers - pistils. The ovules are located in the ovaries of the pistils. Flowering of different angiosperms differ in size, shape, color, structure; the flowers of some angiosperms are adapted for wind pollination, others for insect pollination. But with any method of pollination, pollen grains fall on the stigmas of pistils, where pollen tubes are formed.
Pollen tubes with sperm grow to the ovules and grow into them, where fertilization occurs, which is characteristic only for flowering plants. At the same time, an embryo is formed from the zygote that arises from the fusion of gametes. The largest cell, after merging with the second sperm, grows, divides, and endosperm is formed, which stores nutrients for the embryo. Seeds develop from the ovules, and the pericarp develops from the wall of the ovary. 
So, seeds in flowering plants develop inside the fruit. Therefore, flowering plants are called angiosperms. Currently, angiosperms dominate among the plants that inhabit the land of the Earth.
Consider plants that bloom in autumn, such as pansies, or violet tricolor. This plant, like most others, has organs:
roots and shoots. A shoot is a stem with leaves and buds located on it. Modified underground shoots are rhizomes, tubers and bulbs. Flowers may develop on the shoots. In their place, fruits with seeds ripen. Plants that bloom at least once in their lives are called flowering plants.
The same organs of flowering plants can be outwardly very diverse.
A flower is a modified shoot, in the place of which a fruit with seeds or with one seed ripens.
flower structure
Consider the structure of a flower. The flower develops on a pedicel expanding in the receptacle; all other parts of the flower are formed on it.
The brightly colored corolla consists of petals. Below the corolla is a cup of green leaves - sepals. The corolla and calyx are perianths that protect the interior of the flower from damage and may attract pollinating insects.
The main parts of a flower are the pistil and stamens. The stamen consists of a thin filament and anther, in which pollen is produced. In the pistil, a wide lower part is distinguished - the ovary, a narrow style and a stigma. The fruit develops from the ovary. In some plants, other parts of the flower, such as the receptacle, also take part in the formation of the fruit. Only a few plants have single flowers. In most, the flowers are collected in inflorescences.
In summer and autumn on plants ripen different in shape and color. 
fruits. Fruits are formed from ovaries. The overgrown and modified walls of the ovary, which has become a fruit, are called the pericarp. Inside the fruit are seeds. According to the number of seeds, the fruits are divided into single-seeded and multi-seeded.
There are juicy and dry fruits. Ripe juicy fruits have juicy pulp in the pericarp. Ripe dry fruits do not have pulp.
Seeds of plants are distinguished by shape and size. The seed consists of a peel (shell), an embryo and contains a supply of nutrients. In the embryo, the embryonic root, stalk, bud with leaves are distinguished.
Plants that have one cotyledon in the embryo of the seed are called monocots. 
In dicot plants, as the name suggests, the seed has two cotyledons. The supply of nutrients can be found in the cotyledons or in a special storage tissue - the endosperm. A new plant develops from the embryo of a seed. The seed is the germ of the future plant.
Plants differ from each other in the color and shape of stems, leaves, flowers and fruits, life expectancy and other features. But no matter how different flowering plants may be, each of them can be attributed to one of three groups: trees, shrubs and herbs.
Trees are usually large plants with perennial woody stems. Each tree has a trunk, branches, tree branches form their crowns. Everyone knows birch, aspen, linden, maple, ash. Among the trees there are real giants, such as eucalyptus trees, reaching a height of more than 100 meters.
Shrubs differ from trees in that their trunk begins almost at the very surface of the soil and is difficult to recognize among the branches. Therefore, shrubs do not have one trunk, like trees, but several stems extending from a common base. Shrubs are widespread: hazel-hazel, lilac, honeysuckle, elderberry.
Herbs, or herbaceous plants, have, as a rule, green succulent stems; they are almost always lower than trees and shrubs. But a banana, for example, reaches a height of 7 meters, and some hogweeds are taller than a person. There are tiny herbaceous plants. Duckweed lives on the surface of reservoirs; the size of each plant is a few millimeters.
Trees and shrubs are perennials. For example, some oaks live for more than a thousand years. Herbs include both perennials, annuals and biennials.
Of the perennial herbs, lily of the valley, dandelion, coltsfoot, and nettle are well known. The above-ground parts of most of these herbaceous plants die off in autumn. In the spring, they develop anew, since in the soil under the snow these plants retain roots and other underground organs with buds.
Annual plants, such as violets, quinoa, levkoy, radishes, buckwheat, oats, wheat, develop from seeds in spring, bloom, form fruits with seeds, and then die.
Biennial plants live for almost two years. In beets, radishes, cabbage, usually only roots, stems and leaves develop in the first year. In the second year, these plants develop new shoots, bloom and produce fruits with seeds, and die off by autumn.
Article rating:
