Fertilization which is known as syngamy or impregnation is the combined state of gametes to give rise to a new individual organism or offspring to initiate its development process. There are several processes of fertilization which includes insemination or pollination which occurs before the fusion of gametes which are also sometimes called as fertilization. This cycle of fertilization and development of new individuals is known as sexual reproduction. Aristotle gave the idea of formation of new individuals through fusion of male and female fluids, which form and function and emerge gradually, in a presence of mode coined by him known as epigenetic. Let us know more about what post fertilization events are and take a deep dive into it.
Endosperm
Endosperm is a type of tissue, which is present inside the seeds of flowering plants during the time of fertilization. They reserve food materials which are filled in the cells of endosperm tissue which provides a nutritional element to the developing embryo which is in the form of starch. The endospermic development is classified into three types which are as follows: –
- Nuclear endosperm formation- it’s the process where the primary nucleus of an endosperm undergoes a nuclear division in a repeated process to produce a free nucleus without the wall formation.
- Cellular endosperm formation- during the nuclear division, the formation of cell walls occurs which leads to the formation of cellular endosperm formation.
- Helobial endosperm formation – it’s a type of endosperm formation which is intermediate between cellular and nuclear type of endosperm formation.
During maturation of seed, the developing embryo may either use the endosperm completely or it will be used by the seed during germination.
Embryogenic
Embryogenic can be defined as the process of growth and development for an embryo to form a zygote in the flowering plants. The development stages are the same for both the monocot and dicot plants.
In dicotyledonous plants, the embryonal axis and two cotyledons are present. Two parts of the embryonal axis are as follows:-
- Epicotyl: it’s located above cotyledon level
- Hypocotyl: it’s located below the cotyledon level
In a monocotyledonous plant, the embryo consists of only one cotyledon. Cotyledon can be termed as scutellum in the grass family. Root cap of grass is covered with an undifferentiated sheath which is known as coleorhiza. The portion of the embryonic axis, which is situated above the scutellum is called epicotyl. The epicotyl consist of shoot apex and coleoptiles.
Post Fertilization Events in Humans
There are several events which occur before and after the fertilization process in humans. It casts an impact on the entire process. It includes all the processes which have stages starting from the formation of zygote and the major event in this stage is embryogenesis. It also includes the formation of early embryonic development, establishing multi- cellularity, formation of blastula and lastly the formation of embryonic germ layer.
Gastrulation is one of the events which occurs in humans post the fusion of male and female gametes. It’s a highly coordinated cell and tissue movement where the cells of the blastula undergo a dramatic rearrangement. During this process, the cells get a multi layers body plan along with specified new positions of the organism. In the early stages of development, the embryo forms a disc-like structure which consists of 3 layers. These layers are ectoderm, mesoderm and endoderm.
The cleavage occurs post fertilization which is a series of mitotic division resulting in formation of smaller cells known as blastomeres. This rate of mitotic division slows down which then the blastomeres undergo movements where they change the position relative to one another. Once the three germ layers are formed post gastrulation , the cells interact with one another and rearrange themselves to form tissues and organs. The complete process is known as organogenesis.
At a very early stage in development of the embryo, the embryo acquires a three layered disc form called “The embryonic disc”.
Conclusion
Hence, fertilization is defined as the fusion of male and female gamete in order to form a diploid zygote and as well as in humans the same process of formation of zygote occurs and the major event is the stage known as embryogenesis.
We can conclude the post fertilization events occur differently in plants and animals. After fertilization the zygote, primary endosperm nucleus, ovary and ovule undergoes a series of changes to form a new organism.