How does pollination and fertilization take place in flowering plants? What does flowering plants develop from the wall of the ovary?

Flowering plants are numerous anda diverse group that dominates most terrestrial ecosystems. From the main flowering plants cultivated by man, its existence depends. But that flowering plants appear, they must go through the stage of pollination and fertilization. How this happens, read this article.

Pollination

This process is carried out by transferring pollen fromstamens on the pistil. How does pollination and fertilization take place 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 pestle takes place in the same flower. So pollinated peas or tulips. When cross pollination pollen of a flower of one plant is transferred to the pestle of another. Polluted plants are most often insects, in rare cases - by wind (sedge and birch), birds and water.

As a result of pollination, insects formbright, well-noticeable flowers with a pleasant smell and nectaries, which produce a sweet liquid. Still such plants form a lot of pollen. It is a food for insects. They attract a bright color or the smell of flowers. When insects extract the nectar, they touch the surface of pollen grains that adhere to their bodies, and when they fly to a flower of another plant, remain on the pestle. So pollination occurs by insects. Many flowering plants are pollinated only by certain insects: sweet-smelling tobacco - a night butterfly, a creeping clover - a bee, and a meadow - a bumblebee.

Plants with cross pollination are betterare adapted to changing environmental conditions. But the process of pollination in this case depends on a number of factors. Self-pollination does not depend on anything. For him, weather conditions and the absence of intermediaries are not terrible.

Fertilization

The pollen grains, getting on the stigma of the pistil, beginsgradually germinate. A long pollen tube develops from the vegetative cell. Growing up, it reaches the level of the ovary, and then the ovule. Simultaneously, a pair of spermatozoa is formed, which penetrates into the pollen tube. She, in turn, gets into the ovule through the pollen man. Then the tube at the tip is torn and releases male spermatozoa, which are immediately sent to the embryonic membrane, it is called a sac. Here, eggs develop.

Further fertilization of the oocyte occurssperm, and the formation of a zygote, from which begins to form a small embryo of a completely new plant organism. At the same time, the second sperm merges 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 the supplies of the necessary substances for the normal development of the embryo of the future plant. Here are the organs of sexual reproduction of flowering plants.

When one sperm with an ovum, and another, withpolar nuclei, merge into one, this process is called double fertilization. It is peculiar only to flowering and is a unique feature of angiosperms. The fertilized ovule grows into a seed. As a result, the pestle is growing. In flowering plants, the fetus develops from the ovary wall.

Reproduction

Any plant, reaching a certain size andafter passing through the corresponding 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 between sexual and asexual reproduction, which occurs with the participation of one individual. When plants develop specialized cells - spores, organisms begin to multiply.

This is characteristic of moss, algae, ferns,placenta and horsetail. 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 in a favorable environment, quickly sprout and begin to form daughter plants, the properties of which do not differ from the parent.

During sexual reproduction, female and male sexualcells merge, resulting in the formation of daughter organisms, qualitatively different from the parent. Parental organisms of the female and masculine parts are already taking part here.

The structure and development of ovum plants

In the composition of ovule the main role is played bymacrosporangia. It is there that a single mother cell is laid, from which macrospores are formed. Three pieces begin to die, and, eventually, are destroyed. The fourth macrospora is feminine, lengthens and its core is divided. Then, the daughter nuclei move to different poles of an elongated cell. Each formed nucleus is 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 of the nuclei one of them follows the center of the embryo sac. There they merge, resulting in the formation of a secondary nucleus -diploid.

Then, in the embryo sac, in the cytoplasm, betweennuclei are formed septa 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 there are antipode cells, there are three of them. So, in the bag now six haploid cells and one diploid, with a secondary nucleus. It is in the center of the embryo sac.

What is the ovary?

It is called the lower thickened part of the pistil withclosed inside the cavity in which the ovules are located. Pollen gets from the stigma of the pistil into the ovule, which is protected from unfavorable conditions by an internal moist cavity. In the ovule, development of female reproductive cells - oocytes - takes place.

Flowering plants from the wall of the ovary develops fruit with seeds. Ovary of flowers is many-cavity and one-cavity. In the first case, it is divided into nests by partitions, and in the second - no. The ovary of flowering plants is also divided into one-seeded and many-seeded. It depends on the number of ovules in it: the plum, for example, has one, and the poppy has a lot.

What are the ovaries?

Types of ovaries of flowering plants can be:

• Upper. To the flower bud, it is attached freely, without fusing with other sections in the flower. The walls of the ovary are formed from carpels. In flowering plants, the fetus develops from the ovary wall. Examples are the buttercup and cereal plants. These flowers are called sub-tipical or near-bumpy.
• The lower ovary is always under the flower head. It is formed with the participation of other parts of the flower: the base of the sepals and the stamens with petals, which in many colors are attached to the top of the ovary. Flowering plants from the ovary wall develop a fruit. An example are Compositae, cactus and orchid plants. The flower is called suprugular.

• A semi-low ovary. Its top does not integrate with other parts, so it is free. Flowers of this type are called semi-nomadic. These are the types of ovaries of flowering plants.

Flowering plants

They are the most progressive groupplants, numbering two hundred and fifty thousand species, distributed throughout the planet Earth. The smallest plant is duckweed, whose diameter is equal to one millimeter. She lives in the water. The largest flowering plants are trees that reach a height of one hundred meters or more.

The appearance of flowering plants is due todevelopment of a special organ of reproduction - a flower. In some plants it is colored in bright colors, others - it smells wonderful. Flowers are small and unattractive in plants similar to grass. Despite the huge variety of flowering plants, they all fit harmoniously into our life: decorate gardens and parks, give joy to communicate with them.

The structure of the flower

The flower is a complex system of organs,providing reproduction of plants with seeds. Its appearance caused the widespread distribution of angiosperms (flowering) plants on the Earth. The flower performs many functions. With his participation, stamens with pollen grains, pistils with ovules are formed. It plays a major role in pollination, fertilization, the formation of seeds and fruits.

The flower is shortened, modified,limited in growth shoot, bearing perianth, pistils and stamens. All angiosperms have similar in structure and different in form flowers. This is how adaptation to pollination takes place in various ways.

The flower may end up in the main or lateralstems, the bare part of which under the flower is called the pedicel. It is strongly shortened or completely absent in the flowers of the sedentary. The peduncle passes into the peduncle, which is elongated, convex, concave, or flat. On it are placed all the parts of the flower. This is sepals with petals, stamens with a pistil, in the lower part of which an ovary is formed, in which are the ovules or ovules. A flower with such an ovary is concave. If the ovary forms at the top of the pistil, the flower will be convex or flat.