Post Fertilisation Events

The origin of newborn plants remains a mystery. There’s a good chance you’ve heard that seeds can produce new plants. When a flower is successfully pollinated and fertilised, it eventually develops into a fruit, seed, etc. After fertilisation, the floral parts undergo a series of transformations, culminating in the development of the seed. The endosperm, embryo development, seed creation, and fruit development are all known as post-fertilisation modifications.

Endosperm

After fertilisation, but before the zygote begins to divide, the primary endosperm nucleus (PEN) differentiates into an endosperm. When two polar nuclei and one sperm nucleus fuse together, they form the main endosperm nucleus, which possesses 3n chromosomes. It is a nutrient and regulatory structure that provides nourishment to the embryo as it develops. Angiosperms have three distinct forms of endosperm, each with a distinct development mechanism. There are three types of endosperms, nuclear, cellular, and global.

The primary endosperm nucleus (PEN) separates into two without forming a wall in the nuclear type of endosperm. There will be no more free nuclei or cytoplasm in the endosperm after this initial division, leaving only two free nuclei. Later on, the nuclei might either remain open or be walled off.  The main endosperm nucleus (PEN) separates into two nuclei in this type of endosperm, which is followed by the creation of a wall. Walls are used to creating further divisions.

It is possible that the endosperms will be devoured by the growing embryo or they will remain in the mature seeds. Non-endospermic or exalbuminous seeds are the names given to seeds without endosperms. Peas, groundnuts, and beans are some examples. Endospermous or albuminous seeds refer to seeds that contain the endosperm. During seed germination, the endosperms of these seeds provide the embryo with the nutrients it needs. Coconut, Castor, and Paddy are just a few of the examples.

Ruminate endosperm is made up of endosperm that has surface irregularities and inconsistencies that make it difficult to digest. In this form of endosperm, the seed coat or endosperm is active. Passiflora endosperm rumination is caused by the uneven radial elongation of the seed coat layer.

Endosperm’s Functions

1.       Tissue that provides nourishment to the growing embryo is called the endometrium.
2.       Endosperm development is a critical step in most angiosperms’ zygote division.
3.       The particular method of embryo development is regulated by the endosperm.

Embryogenesis

The zygote divides transversely to produce higher and lower cells, referred to as terminal and basal, respectively. A four-celled proembryo is formed when the terminal cell divides vertically and the basal cell divides transversely. The terminal cell undergoes a second vertical division at an angle to the first one, creating a four-celled stage known as a quadrant. There are two tiers of four cells each in the stage known as the octant stage after a quadrant transverse division.

Seed

A seed is a fertilised ovule that has an embryo, endosperm, and a coat of protection. Wheat, maize, barley, and sunflower seeds are examples of endospermic seeds. (Beans, mangoes, orchids, and cucurbits)

Fruit

The walls of the ovary become the pericarp, or fruit walls when the ovule develops into a seed. Flowers typically lose their petals and produce only fruit from the ovary during this time (true fruits such as grapes and figs). A few fruits have other sections of the flower developing into a fruit as well, such as apples and strawberries (false fruits).

After Fertilisation Events

After fertilisation, the embryo undergoes mitotic division, resulting in a multicellular organism. Nutrition for the embryo is provided by the endosperm nucleus, which divides to form a mass of endosperm cells. After fertilisation, the flower undergoes a variety of transformations. This process results in the formation of a new plant that has diploid DNA.

1.       The ovary becomes a fruit, and the ovules develop into seeds.
2.       The testa and seed coat are formed by the integuments.
3.       Synergids and antipodal cells break apart.
4.       Petals and other fragments fall to the ground.

Fertilisation and Post-Fertilisation Events in Flowering Plant Reproduction

In plants, fertilisation occurs when the male and female gametes combine to form a zygote. Flowering plants have two male nuclei in the pollen grain, which fuse with an egg and the polar nuclei to produce a diploid zygote and a triploid endosperm, which is called double fertilisation.

A Flower’s Post-Fertilisation Evolution

1.       Many alterations to the flower’s structure take place after fertilisation.
2.       The ovary is transformed into a fruit.
3.       As a result, the ovule is transformed into a seed.
4.       The ovule’s integument develops into the seed’s covering as it matures.
5.       The petals and sepals of the corolla come off the calyx as the flower matures.

Conclusion:

Endosperm and embryo development, the maturation of ovules into seeds, and fruit development are the most critical post-fertilisation events in a flower. In animals, after the zygote is formed, post-fertilisation activities take place in sexual reproduction. Post-fertilisation in humans is defined as the period following fertilisation. Everything that happens after fertilisation or after the zygote is formed is referred to as a “post-fertilisation event” (PFE). Embryogenesis, or embryo development, is the main event at this stage.