Pre-Fertilisation Structures and Events

Introduction

Both sexual reproduction and asexual reproduction occur in plants. Almost all flowering plants are sexually reproduced. Flowers are important because they include both male and female reproductive components, defined as androecium and gynoecium, respectively.

Fertilisation

Fertilisation in plants can be defined as the process of amphimixis that occurs as a result of pollination and germination. After carpal pollination, the male gametes (described as pollen) infused with feminine gametes (recognised as ovum) generate a diploid zygote through a physicochemical process. The entire process takes place in a zygote, which then develops into a seed. Male gametes are delivered into female reproductive organs by pollinators during the process (butterflies, honey bees, birds, flower beetles and bats,). As a result, an embryo develops throughout the development of a seed. Flowers are also the reproductive organs of angiosperms, and they reproduce in a unique way.

Pre fertilisation Structures and Events flowering plants

Pre fertilisation is the process which occurs before real fertilisation, that is the process that arises before gamete fusion.

There are two events which arises before the process of fertilisation:

1. Gametogenesis
2. Gamete transfer

Gametogenesis

The creation of gametes is referred to as gametogenesis. Inside the anther, male gametes are created. Microsporogenesis and micro gametogenesis are two of the phases. Megasporogenesis and megagametogenesis are the two processes involved in the formation of female gametes inside the ovules.

Structures

Microsporangium

The epidermis, middle layers, endothecium, and tapetum surround the Microsporangium (Pollen sac). This is where pollen grains are created. There have been four pollen sacs on the plant. A collection of compactly packed homogeneous tissues designated sporogenous tissues makes up a section of each sac.

Ovules

The development of female gametes takes place in ovules. These are found at the bottom of vase-like structure termed as a carpel, which has a style neck and a stigma opening at the top.

Pollen Grains

Pollen Grains come in a variety of sizes. It has two walls: an inner wall made of cellulose termed endospore, and an exterior wall made of sporopollenin.

Anther

The anther is a structure with two lobes. The sterile part’s strip is linked to the two lobes.

Stamen

The filament is the stalk of the stamen. The filament’s proximal end is attached to the thalamus, which is a flower petal.

Formation of Male Gametes

Microsporogenesis

Microsporogenesis is the first step in the production of pollen grains or microspores in the microsporangium, the pollen sac of the anther.

Meiosis produces four haploid microspores from diploid pollen mother cell.

A pollen particle emerges from each microspore.

Microgametogenesis

Micro gametogenesis is the formation of a male gametophyte from a pollen grain.

Mitosis occurs in pollen grains, resulting in the formation of two types of cells: smaller reproductive cells and big vegetative cells. This is where pollination takes place.

Two male gametes are produced by the generative cells, whereas pollen tubes are produced by the vegetative cells.

Formation of Female Gametes

Megasporogenesis

The megasporangium is where the megaspore develops. Megasporogenesis is the term for this process.

The nucellus, a structure inside the ovule, is where the process takes place.

Meiosis occurs in the diploid megasporocyte within the ovule, resulting in the formation of four haploid megaspores.

The megagametophyte develops from only one megaspore, whereas the other three dissolve.

Mega-gametogenesis

The functioning megaspore produces the female gamete. Megagametogenesis is the term for this process.

The megaspore passes through three rounds of mitosis and produces an embryo sac containing eight nuclei.

Initially, each chalaza and micropyle and end had four nuclei. One of them is from each pole fuses at the centre during fertilisation to generate a diploid nucleus.

Later, the three cells dissolve at the chalaza end of the chalaza.

One out of the three cells at the micropyle develops into the egg cell. The pollen tube is guided by substances secreted by the remaining two.

Pollination

Pollination is the transport of pollen grains from one powerful flower to the stigma of some other flower, which is the equal of reproduction. It could also occur in the same flower. In flowering plants, this strategy is the first step in sexual reproduction. Male gamete is found in the anthers of the floral portion, and pollen grains contain it.

Conclusion

Gametogenesis and gamete transference are pre-fertilisation phenomena. Gametogenesis is a biological method that entails the division and development of haploid precursor or diploid cells into mature haploid gametes. The transfer of gametes from male to female is known as gamete transfer. It is transmitted through fertilisation in plants and copulation in mammals.