Development of male gametophyte

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The gametophyte is a phenomenon that occurs throughout the life cycle of all plants and some algae. It is a phase of the alternation of generation that occurs every so often. Sporophyte, or the multicellular diploid generation, and Gametophyte, or the haploid generation, are two of the alternating phases of the life cycle. When cells participate in a diploid generation, they each have two sets of chromosomes, which is referred to as “2n” in genetics. The term “haploid” refers to a cell that contains only one set of chromosomes, which is represented by the letter “n.” The primary goal of the gametophyte process is the production of gametes, which are haploid reproductive cells such as eggs and sperm, in the organism. A simple mitosis occurs during the haploid gametophyte phase, in which the male and female reproductive organs of the gametophyte organs create gametes (Mitosis is a process of cell-division without reducing the chromosome sets).

Asexual reproduction in flowering plants occurs through a fairly basic procedure when compared to the sporophyte’s development system. Despite the fact that it appears to carry the genetic information for a regular plant, all it accomplishes is extrude a tube that grows in length for several millimeters in length before dying. This growth causes the generative nucleus in the tube, which is already in late interphase or early prophase of mitosis, to divide. This division occurs during the course of the tube’s development. Many species’ pollen has already experienced this division in the pollen grain prior to anthesis, indicating that this division has already occurred. It appears that the only synthetic processes taking on in the pollen tube are those involving the synthesis of tube wall polysaccharides and the synthesis of membranes, both of which are unlikely. All other normal sporophyte developmental processes are suppressed as a result of this condition.

Male Gametophyte Structure

• Floral reproduction is the primary site of sexual reproduction in plants. The calyx, the corolla, the androecium, and the gynoecium are the most important parts of the flower.

• An individual stamen is a flower’s male reproductive organ, represented by a single stamen. It is composed of two components: the anther and the filament.

• The anther is the knob-like fertile component of the stamen that is found at the base of the flower.

• The filament is long and narrow, and it is made of nylon.

• Each anther is tetrasporangiate because it has four lobes, each of which contains a microsporangium or a pollen sac.

• In the form of pollen sacs, microsporangia mature and become filled with pollen grains, resulting in the formation of pollen grains.

• The male gametophyte is represented by the pollen grains, which are haploid and uninucleate.
• They are typically spherical in shape (25-50 micrometers in diameter).

• Each pollen particle is made up of two layers of the wall (sporoderm).

• The exine is a hard outer layer composed of sporopollenin that protects the body from the elements (one of the most resistant organic materials).

• Sporopollenin is not affected by high temperatures, enzymes, strong acids and alkalis, or any other environmental factors. As a result, it contributes to the fossilisation of pollen grains.

• It possesses conspicuous apertures known as germ pores, which are absent in the presence of sporopollenin. Germ pores release pollen tubes into the environment. Cellulose and pectin make up the intine, which is the thin and continuous inner wall of the cell membrane.

• The pollen grain’s cytoplasm is surrounded by a membrane known as the plasma membrane.

• Each mature pollen cell in angiosperm is made up of two cells: the vegetative cell and the generative cell, which work together to produce pollen.

• Dietary reserves and a large irregularly shaped nucleus characterise the vegetative cell, which is larger and contains more food.

• The generative cell is a tiny cell that floats in the cytoplasm of the vegetative cell and contributes to its growth. It has a spindle-shaped form and a thick cytoplasm and nucleus inside.

• The spleen grains are discharged at a 2-celled stage in the bulk of angiosperms, which accounts for more than 60% of all plants on the planet.

Male Gametophyte: Pollen Grain

Microspore mother cells are transformed into pollen grains, which is the first gametophytic structure to be produced. During the germination process, which occurs prior to pollination, the pollen grain develops into a male gametophyte that reproduces.

Pollen mother cell (PMC) performs meiosis within the microsporangium, resulting in the formation of four microspores, which eventually mature into pollen grains and form pollen grains. The inner layer, known as the tapetum, provides nourishment for the developing microspores.

Pollen grains are made up of two cells: a vegetative cell and a generative cell, which are both present in the flower. Once the microsporangium has reached maturity, it bursts open, releasing the pollen from the anther into the air.

The pollen grain consists of two layers.

The exine is the term used to describe the thick outer layer of skin.

Intine is the name given to the inner thin covering of pollen that protects it from being damaged.

The development of a male gametophyte can be divided into two stages: 

Pre-pollination development and post-pollination development are two stages of development.

Development of Male Gametophyte

A large central vacuole formation causes the nucleus to be pushed to one side, after which the nucleus undergoes mitosis, giving rise to two daughter nuclei. Precocious germination is a type of germination that occurs in the pollen sac and is characterised by the presence of a large central vacuole formation that causes the nucleus to be pushed to one side.

The small cell that forms is known as the generative cell, and the larger cell is known as the vegetative cell, which contains sufficient cytoplasm to serve as a food reserve for the development of the male gametophyte, while the generative cell forms at the mid-section of the pollen grain, and the vegetative cell is known as the reproductive cell. During this stage, the pollen grains land on the stigma, where they continue to develop further.

The pollen grains that fall on the stigma stimulate nutrition absorption through the germ pore on the stigma, which causes the vegetative cell to enlarge as a result of the pollen grains falling on the stigma. The enlargement causes the intine to travel out of the pollen tube through the germ pore, which is necessary for the creation of the pollen tube. 

The pollen tube is reached by the nuclei of the vegetative and generative cells traveling together. At this stage, the generative cell divides to generate two haploids, which are the non-motile and unicellular male gametes, which are then divided again. As a result of the deeper insertion of the tube, the size of the developing male gametophyte is reduced, and the gametophyte obtains its sustenance from the tissues of the style.

Conclusion

The flower is the plant’s reproductive organ, and it is responsible for fertilisation. The plant will not be able to reproduce if the blossom is not present. Pollination is the transmission of pollen from one plant to another by pollinators such as insects, wind, or other modes of transportation. In flowering plants, the male gametophyte (or pollen grain) is critical for plant fertility and crop production, since it is responsible for the formation and distribution of male gametes to the embryo sac, which allows for double fertilisation to take place.