Pre Fertilisation Events

The fusion (or fertilisation) of male and female gametes is a characteristic of sexual reproduction. Pre fertilisation, fertilisation, and post fertilisation are the three steps of the development of successive zygote events and embryogenesis, respectively.

All pre fertilisation sexual events, including gametogenesis and gamete transfer, are included in the term ‘pre fertilisation events’. The process of male and female haploid gametes forming is referred to as gametogenesis. In certain algae, the male and female gametes look so similar that it is impossible to tell them apart. They are known as homogametic as a result of this (isogametes). However, the gametes produced in most sex-reproducing organisms are of physically distinct types (heterogametes). The male gamete is known as an antherozoid or sperm in these animals, whereas the female gamete is known as an egg or ovum.

Sexual Reproduction in Plants

The fusing of gametes from two separate individuals is the most common method of sexual reproduction in living creatures. Male and female reproductive organs can be found in the same plant (bisexual) or different plants (heterosexual) (not the same sex). Homothallic and monoecious names are used to describe both states in fungi and plants, while heterothallic and dioecious terms are used to characterise homosexuality.

The male flower of flowering plants is known as a staminate. It contains the female pistillate, or pistils, as well as the stamens. Both male and female flowers may be present in a single (monoecious) or dioecious blooming plant (separate individuals). Cucurbits and coconut are two more monoecious plants. Papaya and palm are dioecious plants. Earthworms, sponges, tapeworms, and leech worms are examples of bisexual animals with male and female reproductive organs.

Gametogenesis

Male and female gametes are the only two forms of gametes found in nature. Although the parent plant from which they are generated may be haploid or diploid, gametes are haploid.

The mitotic division is used to produce gametes from haploid parents. The chromosomes from the parent are evenly segregated to generate two gamete cells, which is known as an equational division. Monera, fungi, algae, and bryophytes have haploid bodies and undergo mitotic division. The parental body is diploid in diploid organisms such as pteridophytes, gymnosperms, angiosperms, and the majority of the human species. Meiosis cell division is required when a diploid organism must produce a haploid gamete. Meiosis division is also called reductional division, in which the number of chromosomes is divided into four haploid gametes. 

In diploid structures, specialised cells called meiocytes (gamete mother cells) are responsible for meiosis. Only one set of chromosomes is inserted into each gamete at the end of meiosis.

Gamete Transfer

For fertilisation to take place, the haploid gametes that have developed must be transported to the female half of the flower at this stage. The male gamete in most species is motile, while the female is erect. The only exceptions are a few fungi and algae, which have both forms of gametes. A medium through which male gametes can move is required. Water is the medium in which gamete transfer happens in a few basic plants, such as algae, bryophytes, and pteridophytes. Many male gametes, on the other hand, do not reach female gametes. The amount of male gametes produced is a few thousand times more than the number of female gametes generated to compensate for the loss of male gametes during travel.

Pollen grains contain male gametes, and ovaries contain an egg in angiosperms. Pollen grains formed in anthers must therefore be transferred to the stigma before fertilisation can occur. Because anthers and stigma are close together in bisexual, self-reproducing plants like peas, the transfer of pollen grains to stigma is a simple procedure. Pollen grains come into contact with the stigma quickly after they are shed.

Pollination, a unique technique that promotes the transport of pollen grains to the stigma, is used in pollinated plants (including dioecious plants). Pollen grains grow from the stalks, and pollen tubes take the male gametes to the entrance, where they are released near the egg. Pollinators, or mediators, are the ones who make pollination happen. Entomophily refers to pollination by bees, whereas anemophily refers to pollen transfer by the wind.

Conclusion

Fertilisation is the process of fusion of gametes of both males and females. Any events that occur before the fertilisation process are part of the pre fertilisation process. Two significant events that occur are gametogenesis and gamete transfer. The formation of haploid gametes in the body of diploid or haploid parents is called gametogenesis, while the transfer of these gametes to the female part of the plant is called gamete transfer.