The organ of sexual reproduction of angiosperms is a flower. Flower- a modified, shortened, unbranched shoot, intended for the formation of spores and gametes and the sexual process, culminating in the formation of seeds and fruit.
Flower structure
A flower is distinguished by a peduncle, a receptacle, a perianth, stamens and pistils. Some flowers may be missing some parts.
The flowers of most plant species have both stamens and pistils. Such flowers are called bisexual(cherry, peas). Flowers that have only pistils are called pistillate (feminine). Flowers that have only stamens are called staminate (male). Depending on the distribution of unisexual flowers on plants, there are: monoecious plants- plants in which both female and male flowers are located on the same specimens (cucumber, corn, oak); dioecious plants- plants in which some specimens have female flowers, and others have male flowers (stinging nettle, hemp, sea buckthorn); polyhomous plants- plants in which both bisexual and unisexual flowers are found on the same specimens in various quantitative ratios (buckwheat, some types of ash, maple).
Peduncle- internode under the flower. Flowers without pedicels are called sessile (flowers in the inflorescence are a basket of sunflower, aster, dandelion).
Receptacle- a shortened stem part of the flower. All other parts of the flower are located on it.
Perianth- the sterile part of the flower, its cover. The perianth can be simple (not differentiated into a calyx and corolla, formed by a set of homogeneous leaves of the same size and color) and double (differentiated into a calyx and a corolla, differing from each other in size and color. A simple perianth can be corolla-shaped (formed by brightly colored leaves ) or calyx (formed by green leaves) Flowers without a perianth (willow, poplar) are called glabrous.
Cup- the outer part of the double perianth, is a collection of sepals - modified bracts. Sepals are usually small and green in color. They are similar to ordinary leaves, but simpler in structure.
Distinguish: a separate-leaved calyx - a calyx formed by free (non-accrete) sepals (cabbage, buttercup); spliced calyx - a calyx formed by partially or completely accreted sepals (potatoes, tobacco, peas).
Corolla- the inner, usually colored part of the double perianth. It is a collection of petals, often brightly colored. The number of corolla petals may vary. The petals can be more or less the same (buttercup, apple tree) or differ in size and shape (violet, peas). As a result, the corolla can be correct, irregular, or asymmetrical. The corolla, as well as the calyx, can be separate-petalled and spliced. The split-petal corolla consists of loose, non-accrete petals. The petal corolla consists of petals accreted to one degree or another. The main function of the corolla is to attract pollinators.
Androecium
Androecium- a set of stamens of one flower. The number of stamens in a flower is from one (orchid) to several hundred (some cacti). In most plants, the stamen consists of a filament and an anther. Filament- the lower, usually narrowed, sterile part of the stamen. The lower end of the filament extends from the receptacle, and the upper end bears the anther. Usually filaments are thin, long, rounded in cross section. Anther- the upper expanded fertile part of the stamen. The boot consists of two halves connected by a binder. Each half has two pollen nests (microsporangia), in which microspores are formed, and subsequently dust particles. The binder is a continuation of the filament, through which nutrients enter the anther.
Microsporogenesis
Microsporogenesis is the process of formation of microspores in microsporangia (anther nests). Microspores are formed from mother cells - microsporocytes with a diploid set of chromosomes. As a result of meiosis, each mother cell forms four haploid microspores. Microspores quickly separate from each other.
Microgametogenesis
Microgametogenesis- the process of formation of male germ cells (sperm) occurs in the pollen grain, which is the male gametophyte of angiosperms. The development of the male gametophyte also occurs in the nests of the anthers of the stamens and is reduced to one mitotic division of the microspore and the formation of the shells of the pollen grain. The shell of a pollen grain consists of two layers: intine (inner, thin) and exine (outer, thick). Each pollen grain contains two haploid cells: vegetative and generative. From the generative (spermagenic), two sperm are further formed. From the vegetative (siphonogenic) pollen tube is subsequently formed.
Gynoecium
Gynoecium- a set of pistils of one flower. Usually, three parts are distinguished in the pistil: the ovary, the column and the stigma.
Ovary- closed, lower, hollow part of the pistil, which carries and protects the ovules. The ovary is: upper, lower, semi-lower. The ovary can contain from one (wheat, cherry) to several thousand (poppy) ovules. The walls of the ovary perform the function of protecting the ovules from adverse environmental factors (drying, temperature fluctuations, eating by insects, etc.). Inside the ovary (in the ovules), megasporogenesis and megagametogenesis occur, they take part in the formation of the pericarp.
Column- the middle, more or less elongated, sterile part of the pistil, usually extending from the apex of the ovary, connects the ovary and stigma.
Stigma- the upper, widened part of the pistil, intended for the perception of pollen. The stigma can be of various shapes (two-lobed, stellate, pinnate, etc.) and size, depending on the characteristics of pollination. In the absence of a column, the stigma is called sedentary.
Ovule consists of nucellus (nucleus) - the central part, which is a megasporangium, two integuments - integuments, which, when closed, form a narrow channel - micropyle, or pollen duct, through which the pollen tube penetrates to the embryo sac. The ovule attaches to the placenta with the help of the seed stalk. The place of attachment of the ovule to the seedling is called ribbed... The part of the ovule opposite the micropyle, where the nucellus and integuments merge, is called chalazoi.
In the ovule, megasporogenesis, megagametogenesis and fertilization take place. After fertilization (less often without fertilization), a seed is formed from the ovule.
Megasporogenesis
The process of forming megaspores is called megasporogenesis... It occurs in the ovule nucellus. After the inception of the ovule and the formation of nucellus in the micropyle, one archesporial (sporogenic) cell begins to grow - megasporocyte, or the mother cell of megaspores.
The mother cell of megaspores has a diploid set of chromosomes. In most angiosperms, four haploid megaspores are formed from it by meiosis. Of these, only one (usually the lower, facing the chalaza, less often the upper, facing the micropyle) gives rise to female gametophyte- the embryo sac. The rest of the megaspores die off.
Megagametogenesis
The formation of female germ cells takes place in the embryo sac. The formation of the female gametophyte begins with the proliferation of the megaspore, which is further divided three times by mitosis. As a result, eight cells are formed, which are located as follows: three - at one pole of the embryo sac (micropilar), three - at the other (hadazal), two - in the center. The remaining two merge in the center of the cell, forming a diploid central cell embryonic sac. One of the three cells located at the micropilar pole is large and ovum... Two adjacent cells are auxiliary and are called synergides... A group of three cells located at the opposite, chalazal pole is called antipode... Thus, the formed female gametophyte includes six haploid cells (egg, two synergistic cells, three antipode cells) and one diploid cell.
Angiosperms or flowering plants are the most numerous division of the plant kingdom. What plants are hidden under these terms? The most important thing is simple and clear.
235 thousand species of such plants are distributed throughout the planet.
Most of the representatives of this department are in tropical forests.
The flower is the main distinguishing feature of angiosperms. It can be of different shapes and types. They are responsible for reproduction. It is in flowers that important processes of pollination, fertilization, the emergence and growth of the fetus take place.
Flowering seeds are of two types. A single lobe seed is a trait of the monocotyledonous class. Seeds with two lobes form the dicotyledonous class.
Seeds are monocotyledonous and dicotyledonous. The main differences between these classes are:
- by the structure of the roots (fibrous root system of monocotyledons versus rod-dicotyledons);
- on the formation of cambium (it is not formed in monocots);
- by the structure of the flower (simple perianth versus double perianth in dicots);
- by the structure of the embryo (the number of embryo cotyledons laid the foundation for the name of the class).
Signs of angiosperms
Plants have common features of structure, development and reproduction.
Angiosperms differ in their appearance. The most important distinguishing features:
- flowers of various structures;
- there is a pistil that develops into a fruit;
- the pistil has stigmas that trap pollen;
- the seeds are protected by the fruit;
- plants have vessels (trachea).
Structure and reproduction
A flowering plant consists of a root and a shoot. A shoot is a stem, leaves, buds. Flowers grow from the buds.
The structure of organs in flowering plants reaches the greatest complexity. The process of sexual reproduction of angiosperms begins with pollination.
Pollen is transferred from the stamens to the pistil.
Pollination is cross-pollination and self-pollination. Violets and peanuts are able to pollinate in an unopened flower of the same plant.
Most self-pollinating flowering plants are pollinated within a single plant.
Angiosperms are pollinated in two ways. The second type of pollination is cross-pollination. Pollen is transferred from the stamens of the male plants to the pistils of the female. Plants pollinated in this way are more viable because of the exchange of genes.
Flowering plants in the course of long evolution have developed various adaptations for effective pollination. Pollen is transported by insects - biotic. Wind and water can also become pollinators. This is called abiotic pollination.
With artificial pollination, a person carries pollen.
Angiosperms are distinguished by double fertilization.
It consists of several stages:
- pollen cells attach to the stigma of the pistil;
- developing and germinating, they turn into a pollen tube that grows into an ovary;
- sperm is released from the pollen tube and grows together with the ovum of the ovary;
- another sperm connects to the nucleus of the central cell of the embryo;
- as a result of fertilization, a zygote is formed.
The zygote divides and turns into an embryo, the central cell turns into an endosperm with a supply of nutrients.
Nutrients flow to the ovary, and a ripe fruit is formed. The pericarp protects the seeds.
For flowering plants, vegetative propagation is also possible, that is, with the help of roots, shoots or leaves.
Examples of life forms of angiosperms
The life forms of flowering plants are diverse: annual and perennial grasses, shrubs and semi-shrubs, lianas, trees, shrubs and semi-shrubs.
Trees are distinguished by the presence of a trunk and tallness.
The life forms of flowering plants are varied. In shrubs, the trunk is not pronounced and hardly noticeable among the system of branches (examples: currants, lilacs, acacia, raspberries).
All of them have leaves, consisting of leaf blades. A large area of leaf plates accelerates all the main processes of plants: photosynthesis, moisture evaporation, respiration. The efficiency of these processes is increased.
When unfavorable conditions (drought or low temperatures) occur, the leaves fall off. The leaf fall process allows the plant to survive in an unfavorable period.
Shrubs are small in size, they are found in tundra conditions, in swamps and high in the mountains (examples: bearberry, northern linnea, winter lover, all marsh berries).
Half-shrubs and half-shrubs renew their shoots every year (examples: veronica, cinquefoil, thyme).
Grasses that bear fruit for several years (perennial) are divided into types according to the shape of the roots:
- taproot (legumes, alfalfa);
- brush-root (initial, plantain);
- short-rhizome (fescue, bluegrass, fine bent grass);
- long-rhizome (zubovka, reed grass);
- tuberous (daffodils, tulips);
- bulbous (hyacinth, garlic).
Annual herbs (peas, dill) bear fruit once in a lifetime.
Surprisingly, dill is also an angiosperm. Another group is aquatic angiosperms. They are: coastal, semi-submerged, floating and underwater.
Protected plant species
Despite the high adaptability and wide distribution, there are species of flowering plants that need protection.
The Red Book of Russia contains about 500 species of plants that will soon disappear. Among them there are 23 types of cereals: several varieties of feather grass, bluegrass, wheatgrass, etc. Oaks, maples and other trees also need protection and protection.
New ways of preserving endangered plant species are now being developed. There are several ways of protection:
- arrangement of sanctuaries, reserves and nature protection zones;
- cultural breeding of endangered species;
- restriction or termination of harvesting valuable plant species.
Botanical parks and arboretums perform not only an environmental function, but also an educational one. In such places, you can get more information about protected plants and develop new ways to protect rare and endangered species.
The value of angiosperms in nature and human life
All of these plants play a central role in shaping life on earth.
Most crops belong to this department.
Flowering plants are used in industry, pharmaceuticals, medicine and animal husbandry. The beauty of flowering plants is a source of inspiration for creativity, a beneficial effect on the nervous system.
The organ of sexual reproduction of angiosperms is a flower. Flower- a modified, shortened, unbranched shoot, intended for the formation of spores and gametes and the sexual process, culminating in the formation of seeds and fruit.
A flower is distinguished by a peduncle, a receptacle, a perianth, stamens and pistils. Some flowers may be missing some parts.
The flowers of most plant species have both stamens and pistils. Such flowers are called bisexual(cherry, peas). Flowers that have only pistils are called pistillate (feminine). Flowers that have only stamens are called staminate (male). Depending on the distribution of unisexual flowers on plants, there are: monoecious plants- plants in which both female and male flowers are located on the same specimens (cucumber, corn, oak); dioecious plants- plants in which some specimens have female flowers, and others have male flowers (stinging nettle, hemp, sea buckthorn); polyhomous plants- plants in which both bisexual and unisexual flowers are found on the same specimens in various quantitative ratios (buckwheat, some types of ash, maple).
Peduncle- internode under the flower. Flowers without pedicels are called sessile (flowers in the inflorescence are a basket of sunflower, aster, dandelion).
Receptacle- a shortened stem part of the flower. All other parts of the flower are located on it.
Perianth- the sterile part of the flower, its cover. The perianth can be simple (not differentiated into a calyx and corolla, formed by a set of homogeneous leaves of the same size and color) and double (differentiated into a calyx and a corolla, differing from each other in size and color. A simple perianth can be corolla-shaped (formed by brightly colored leaves ) or calyx (formed by green leaves) Flowers without a perianth (willow, poplar) are called glabrous.
Cup- the outer part of the double perianth, is a collection of sepals - modified bracts. Sepals are usually small and green in color. They are similar to ordinary leaves, but simpler in structure.
Distinguish: a separate-leaved calyx - a calyx formed by free (non-accrete) sepals (cabbage, buttercup); spliced calyx - a calyx formed by partially or completely accreted sepals (potatoes, tobacco, peas).
Corolla- the inner, usually colored part of the double perianth. It is a collection of petals, often brightly colored. The number of corolla petals may vary. The petals can be more or less the same (buttercup, apple tree) or differ in size and shape (violet, peas). As a result, the corolla can be correct, irregular, or asymmetrical. The corolla, as well as the calyx, can be separate-petalled and spliced. The split-petal corolla consists of loose, non-accrete petals. The petal corolla consists of petals accreted to one degree or another. The main function of the corolla is to attract pollinators.
Androecium
Androecium- a set of stamens of one flower. The number of stamens in a flower is from one (orchid) to several hundred (some cacti). In most plants, the stamen consists of a filament and an anther. Filament- the lower, usually narrowed, sterile part of the stamen. The lower end of the filament extends from the receptacle, and the upper end bears the anther. Usually filaments are thin, long, rounded in cross section. Anther- the upper expanded fertile part of the stamen. The boot consists of two halves connected by a binder. Each half has two pollen nests (microsporangia), in which microspores are formed, and subsequently dust particles. The binder is a continuation of the filament, through which nutrients enter the anther.
Microsporogenesis
Microsporogenesis is the process of formation of microspores in microsporangia (anther nests). Microspores are formed from mother cells - microsporocytes with a diploid set of chromosomes. As a result of meiosis, each mother cell forms four haploid microspores. Microspores quickly separate from each other.
Microgametogenesis
Microgametogenesis- the process of formation of male germ cells (sperm) occurs in the pollen grain, which is the male gametophyte of angiosperms. The development of the male gametophyte also occurs in the nests of the anthers of the stamens and is reduced to one mitotic division of the microspore and the formation of the shells of the pollen grain. The shell of a pollen grain consists of two layers: intine (inner, thin) and exine (outer, thick). Each pollen grain contains two haploid cells: vegetative and generative. From the generative (spermagenic), two sperm are further formed. From the vegetative (siphonogenic) pollen tube is subsequently formed.
Gynoecium
Gynoecium- a set of pistils of one flower. Usually, three parts are distinguished in the pistil: the ovary, the column and the stigma.
Ovary- closed, lower, hollow part of the pistil, which carries and protects the ovules. The ovary is: upper, lower, semi-lower. The ovary can contain from one (wheat, cherry) to several thousand (poppy) ovules. The walls of the ovary perform the function of protecting the ovules from adverse environmental factors (drying, temperature fluctuations, eating by insects, etc.). Inside the ovary (in the ovules), megasporogenesis and megagametogenesis occur, they take part in the formation of the pericarp.
Column- the middle, more or less elongated, sterile part of the pistil, usually extending from the apex of the ovary, connects the ovary and stigma.
Stigma- the upper, widened part of the pistil, intended for the perception of pollen. The stigma can be of various shapes (two-lobed, stellate, pinnate, etc.) and size, depending on the characteristics of pollination. In the absence of a column, the stigma is called sedentary.
Ovule consists of nucellus (nucleus) - the central part, which is a megasporangium, two integuments - integuments, which, when closed, form a narrow channel - micropyle, or pollen duct, through which the pollen tube penetrates to the embryo sac. The ovule attaches to the placenta with the help of the seed stalk. The place of attachment of the ovule to the seedling is called ribbed... The part of the ovule opposite the micropyle, where the nucellus and integuments merge, is called chalazoi.
In the ovule, megasporogenesis, megagametogenesis and fertilization take place. After fertilization (less often without fertilization), a seed is formed from the ovule.
Megasporogenesis
The process of forming megaspores is called megasporogenesis... It occurs in the ovule nucellus. After the inception of the ovule and the formation of nucellus in the micropyle, one archesporial (sporogenic) cell begins to grow - megasporocyte, or the mother cell of megaspores.
The mother cell of megaspores has a diploid set of chromosomes. In most angiosperms, four haploid megaspores are formed from it by meiosis. Of these, only one (usually the lower, facing the chalaza, less often the upper, facing the micropyle) gives rise to female gametophyte- the embryo sac. The rest of the megaspores die off.
Megagametogenesis
The formation of female germ cells takes place in the embryo sac. The formation of the female gametophyte begins with the proliferation of the megaspore, which is further divided three times by mitosis. As a result, eight cells are formed, which are located as follows: three - at one pole of the embryo sac (micropilar), three - at the other (hadazal), two - in the center. The remaining two merge in the center of the cell, forming a diploid central cell embryonic sac. One of the three cells located at the micropilar pole is large and ovum... Two adjacent cells are auxiliary and are called synergides... A group of three cells located at the opposite, chalazal pole is called antipode... Thus, the formed female gametophyte includes six haploid cells (egg, two synergistic cells, three antipode cells) and one diploid cell.
Fertilization. Seed and Fruit Formation
The fertilization process is preceded by pollination- transfer of pollen from the pollen sacs of the stamens to the stigmas of the pistils. Once on the stigma of the pistil, under the influence of substances secreted by the pistil, pollen begins to germinate: a pollen tube is formed, which penetrates into the tissue of the stigma. The tip of the pollen tube secretes substances that soften the tissue of the stigma and column. A siphonogenic cell takes part in the formation of a pollen tube. As the pollen tube grows, a sperm cell passes into it, which divides by mitosis to form two sperm (in some plants, a sperm cell gives rise to two sperm even before pollen germination). The pollen tube moves along the pistil column and grows into the embryo sac, usually through the micropyle. After penetration into the embryonic sac, the tip of the pollen tube breaks and the sperm enter. One of the sperm fuses with the egg, forming a diploid zygote. The second sperm merges with the central cell of the embryo sac, forming a triploid cell, from which the endosperm (nutrient tissue) of the seed is further formed, which provides nutrition to the embryo. Synergies and antipodes degenerate. The above process is called double fertilization... Double fertilization in flowering plants was discovered in 1898 by the Russian botanist S.G. Navashin.
After double fertilization, the seed embryo is formed from the egg, the endosperm is formed from the central nucleus of the embryo sac, the seed coat is from the integuments, the seed is from the entire ovule, and the pericarp is from the walls of the ovary. In general, a fruit with seeds is formed from the ovary of the pistil.
Go to lectures number 14"Reproduction of organisms"
Go to lectures No. 16"Ontogenesis of sexually reproducing multicellular animals"
105. Let us explain where the name of double fertilization in flowering plants came from.
In flowering plants, two fusions occur during fertilization: the first of the sperm fuses with the ovum and a zygote is formed, the second with a large central cell and the endosperm is formed.
106. Let us sign the elements of the development cycle of a flowering plant, indicated in the figure by numbers.
1.adult plant
2.flower
3.pollen grain
4. ovary
5.ripe fruit
6.ripe fruit with seeds
7.seed
8. young plant.
107. Let us connect the parts of the flower with the fruits formed from them.
108. Let's write the methods of pollination indicated in the figure.
1. Self-pollination.
2. cross-pollination.
109. Let us explain why cross-pollination is more common than self-pollination.
Cross-pollination provides a variety of traits in offspring, as different organisms multiply, and not one (as with self-pollination). It is more beneficial in terms of evolution. That is why, in nature, numerous mechanisms have developed in plants that prevent self-pollination. There are also a large number of pollen carriers (animals, wind, humans).
110. Let's fill in the table.
111. Let's distribute wind-pollinated and insect-pollinated plants.
Wind-pollinated: birch, oak, hazel, rye, corn, alder.
Insects: linden, apple, clover, wild rose, fragrant tobacco, snapdragon.
112. Let's designate the sequence of actions for artificial pollination.
The flower is a modified shoot bearing sepals, petals, stamens, pistils.
Division occurs in the anthers of the stamens. As a result, numerous cells are formed that mature into pollen. Pollen grains are derived from spores. They are covered with a two-layer shell. The outer shell is uneven, with outgrowths that help the pollen grains to adhere to the stigma of the pistil. Vegetative and generative cells are located under the membrane (see Fig. 1). It is the male angiosperm gametophyte.
Rice. 1. Pollen cells
The ovules (see Fig. 2) develop on the inner side of the ovary walls. Their number depends on the species of the plant.
Rice. 2. Ovules
An embryo sac is formed in the ovule (see Fig. 3) - the female gametophyte of flowering plants. Opposite the micropyle is the ovum, and in the center is the central cell.
Rice. 3. Embryo sac
The pollen grain gets on the stigma of the pistil and attaches to it, thanks to the peculiarity of the structure of the shell and the sticky sugary secretions of the stigma.
The pollen grain swells and germinates, forming a pollen tube - a derivative of the vegetative cell. The tube grows into the ovary cavity. In the pollen tube, the generative cell is divided into 2 sperm. When the pollen tube penetrates through the micropyle into the cavity of the embryonic sac, one of the sperm merges with the egg. Fertilization occurs and a zygote is formed. The second sperm is fused with the nucleus of the central cell.
Fertilization is the process of fusion of 2 germ cells to form a zygote.
This process is called double fertilization and is characteristic only of flowering plants.
The zygote begins to divide, as a result of which a multicellular plant embryo is formed. The central cell divides to form the endosperm. The seed coat is formed from the ovule shells. Nutrients flow to the ovary, gradually it becomes a ripe fruit. The walls of the ovary give rise to a pericarp, which protects the seeds from negative influences. In some plants, sepals and receptacles take part in the formation of the fruit.
Pollination is the process of transferring pollen from the anther of the stamen to the stigma of the pistil.
Pollination:
- Self-pollination - pollen from the stamen enters the stigma of the pistil of the same flower (rice, wheat, peas, beans). It can still occur in the bud. There is no combination of hereditary information, so the diversity of offspring is small.
- Cross-pollination - pollen from the stamen of one flower is transferred to the stigma of the pistil of another flower (corn, cucumber, watermelon, poplar, willow). High variety of offspring. But pollen is unlikely to get on the stigma of the pistil. Such plants have developed adaptations against self-pollination: pistils and stamens ripen at different times, stamens are shorter than pistils (heterostyly) (see Fig. 4), some plants are dioecious.
Rice. 4. Pistils of corn
Some plants (orchids) are characterized by mixed pollination.
Zoophilia is the pollination of a plant by animals. Flowers or inflorescences are large, bright, visible for pollination. May be labeled in the ultraviolet spectrum, which is visible to insects. In the presence of nectar and a strong aroma (fragrant tobacco). Pollen grains are large, pollen sticky, therefore it sticks to insects (see Fig. 5), feathers of birds, wool of mammals.
Rice. 5. Pollen on a honey bee
There are flowers that are pollinated by only one species of animals, so snapdragons and clovers are pollinated by bumblebees (see Fig. 6).
Rice. 6. Snapdragon
Kigelia is pollinated only by bats. Angrecum orchid one and a half feet is pollinated only by the predicted hawk moth (see Fig. 7).
Rice. 7. Foretold hawk maker
Anemophilia - wind pollination of plants (poplar, alder, oak, hazel, rye). The flowers are small, inconspicuous. The pollen is fine, light, dry. Anthers are located on long hanging filaments. Plants grow in large clusters (hazel (see Fig. 8)).
Rice. 8. Hazel flowers
The trees bloom in the spring, before the leaves open.
Some plants can be pollinated in both ways: insects and wind (plantain).
Artificial pollination is man-made pollination. It occurs for the purpose of hybridization, obtaining new varieties, increasing crop yields.
The pollen is transferred with a soft dry brush or a piece of rubber worn over a wire. The flowers of some self-pollinated plants are prepared in advance. To do this, open the bud and remove the stamens. Some buds are put on special caps. This prevents accidental pollination. When the flowers bloom, pre-prepared pollen is applied to the stigmas of the pistils.
Bibliography
- Biology. Bacteria, fungi, plants. 6th grade: textbook. for general education. institutions / V.V. Beekeeper. - 14th ed., Stereotype. - M .: Bustard, 2011 .-- 304 p .: ill.
- Tikhonova E.T., Romanova N.I. Biology, 6. - M .: Russian word.
- Isaeva T.A., Romanova N.I. Biology, 6. - M .: Russian word.
- Betonolog.ru ().
- Activestudy.info ().
- Lotoskay.ucoz.ru ().
Homework
- Biology. Bacteria, fungi, plants. 6th grade: textbook. for general education. institutions / V.V. Beekeeper. - 14th ed., Stereotype. - M .: Bustard, 2011 .-- 304 p .: ill. - With. 215, tasks and question 7, 9 ().
- How do the ovule and pollen grain work?
- Describe the process of double fertilization.
- * Think about what type of angiosperm pollination came about first. Which type of pollination is the most perfect? Why?
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