Post Fertilization: Events and Changes in Plant

The process of development of endosperm and embryo followed by the formation of fruit after fertilisation is called post fertilization. A series of events takes place to form seeds, including four different processes such as development of endosperm and embryo followed by the maturation of ovules into seeds and a fruit is developed from the ovary of female gametes. Now let's first understand the definition of post fertilization, events of post fertilization and its types.

Keyterms: Fertilization, Embryo, Endosperm, Seed, Fruit, Gamete, Ovule, Zygote, Diploid zygote, Nutrition

Also Read: Reproductive Health

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Definition of Post Fertilization

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Post fertilization is defined as a series of events that occurs to form a fruit from the plants. In this process, after the fertilization of plants, an embryo division takes place mitotically to produce a multicellular embryo. The endosperm in zygote breaks to form a mass of endosperm cells and give nutrition to the developing embryo. There are different kinds of changes that occur in the flower after its fertilization. The diploid zygote forms a plant followed by the ovary which transforms into a fruit and the ovules in a seed.

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Events of Post Fertilization

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There are series of events that happen in the development of plants after their fertilization process to form a fruit from a diploid zygote. Below we have described about the four different developmental steps that occurs during post fertilization:

• Development of an Endosperm
• Development of an Embryo
• Development of a Seed
• Formation of a Fruit

Development of an Endosperm

The development of the endosperm happens before the embryo development . The essential endosperm cell partitions over and again to frame a triploid endosperm tissue. 

• In most cases, the primary endosperm nucleus goes through progressive atomic divisions without cytokinesis, to bring about free atomic endosperm.
• Consequently, the formation of cell wall begins from the periphery and the endosperm turns out to be totally cell, like in rice, maize, coconut, sunflower, etc

Endosperm Functions

Below we have given two major objectives of endosperm. 

• The endosperm tissues have the storage of food materials and are used for the metabolic support of the developing embryo.
• The endosperm likewise helps in the development of embryos before the seed germination, the endosperm is used by the seed.

Development of an Embryo

The embryo development process is called embryogeny and it starts developing at the micropylar end of the embryo sac in the zygote. The zygote starts their division after the formation of endosperm and its nutrition for the development is given by endosperm. The zygote leads to the formation of a pro embryo, the globular, heart-molded and mature organism. The stages for the formation of embryogeny is almost same in both the plants dicot and monocot, regardless of their structure.

Monocot Embryo

• The monocot Embryo has only a single cotyledon toward one side which is known as scutellum. 
• In the lower side, the embryonal axis has a radical and root cap enclosed in an undivided coleorhiza. 
• Some of the embryonal axis over the scutellum is the epicotyl. It has a shoot peak and a couple of leaf primordia encased in an empty foliar structure called coleoptile like grass, banana, bamboo, palm etc.

Dicot Embryo

• The dicotyledonous embryo plant comprises one embryonal axis and two cotyledons. 
• The embryonal axis part above the cotyledon terminates the plumule or stem tip and is called epicotyl.
• The rounded part below the cotyledon level terminates in the radicle or root tip and is known as hypocotyl.
• The root tip of the hypocotyl end and the cover of the tip id are called root caps such as in apple, mango, raddish, rose, etc.

Development of a Seed

The double fertilization in the angiosperms of plants leads to the development of ovule into a seed. These seeds are developed within the fruits. Mainly the seeds consist of three parts which are seed coat, cotyledon and the embryo axis. 

• The seed coat is typically double layered developed by the integuments. The inner end of the integuments creates an inner layer of seed coat called tegmen and the outer integuments develops the outer layer of seed called as testa.
• The cotyledons are typically thick and enlarged with food materials. They are mostly one to two in number and rich in storing food material. 
• The little opening found on the seed coat is called micropyle which works with the entry of water and oxygen into the seed.

Formation of a Fruit

After the cell division and separation in the ovary, it is changed into fruit because of stimuli received from fertilization just as developing seed. The ovary wall forms into the wall of a fruit known as pericarp which might be fleshy like in guava, tomato, cucumber or might be weathered and dry like pea, bean, mustard. Pericarp ensures that the seeds are protected and helps in seed dispersal. After following all the events mostly two types of fruits are formed:

• True Fruit: The food that comes from the plant ovary and is associated with the non-capillary part is called true Fruit such as mango, tomato, guava etc.
• False Fruit: The fruit which comes from other accessory floral parts instead of ovary is called a false fruit like cashew nut, strawberry, apple etc.

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Things to Remember

• The endosperm is a triploid primary nucleus which forms a nutritive tissue.
• The endosperm might endure or become completely digested during embryogenesis; the seeds having extensive measures of endosperm tissue are called albuminous seeds.
• Dormancy is a general metabolic activity in which an embryo slows down and in return the seeds germinated into plants.
• The food reserves in the seeds helps in the growth of seed to become nutritionally independent.

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