Theory:

These constitute the final events of the process of reproduction. They are as follows:
  • After the fertilization stage the parts of the flower other than the ovary are shed off.
  • In plants like tomato, peas and brinjal the sepals are found to exist in a shriveled form.
Tomato_fruit_and_flower.png
Sepals retained back in a tomato fruit
  • After triple fusion, the primary endosperm nucleus develops into an endosperm (the nutritive tissue).
724px-Coconut_layers.svg.png
  • This endosperm serves as nourishment for the developing embryo.
  • After the formation of the endosperm and the zygote, the synergids and antipodal cells degenerate.
  • The ovule develops into the seed.
  • Ovary grows in size to form fruit.
  • The wall of the ovary becomes the wall of the fruit.
  • The integuments of the ovule develop into the seed coat.
diagram415321280.png
Structure of fruit and seed
 
A video explaining the events of post fertilization
Significance of fertilization:
  • The process of fertilization stimulates the ovary to develop into a fruit.
  • It also leads to the development of new characters from two different organisms.
Reference:
https://commons.wikimedia.org/wiki/File:Coconut_layers.svg
https://letstalkscience.ca/educational-resources/backgrounders/life-cycle-a-tomato-plant