Given below are two statements:

One is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): A typical unfertilized, angiosperm embryo sac at maturity is 8 nucleate and 7-celled.
Reason(R): The egg apparatus has 2 polar nuclei. In the light of the above statements, choose the correct answer from the options given below: 

The correct answer is A is true but R is false.

Concept:

• In angiosperms, the process of megasporogenesis leads to the formation of an embryo sac. The embryo sac is the female gametophyte and plays a critical role in sexual reproduction in flowering plants.
• The mature embryo sac in a typical angiosperm is known as the Polygonum type and consists of 8 nuclei arranged into 7 cells. This structure includes synergids, an egg cell, polar nuclei, and antipodal cells.
  • Antipodal cells - There are 3 of these uninucleate cells present at the chalazal end that degenerate after fertilization.
  • Central cell - It is centrally located covering most of the embryo sac and contains 2 polar nuclei.
  • Egg cell - It is the female gamete that undergoes fusion with a male gamete.
  • Synergid cells - There are 2 synergid cells at the micropylar end with the filiform apparatus at their base.

Explanation:

Assertion (A): A typical unfertilized angiosperm embryo sac at maturity is 8-nucleate and 7-celled.

• This statement is correct. The mature embryo sac contains the following:
  • 3 antipodal cells at the chalazal end.
  • 2 synergids and 1 egg cell at the micropylar end, collectively called the egg apparatus.
  • 2 polar nuclei in the central cell.
• Although there are 8 nuclei in total, the polar nuclei remain in a single central cell, making the structure 7-celled.

Reason (R): The egg apparatus has 2 polar nuclei.

• This statement is incorrect. The egg apparatus consists of the egg cell and 2 synergids, located at the micropylar end of the embryo sac.
• In contrast, the 2 polar nuclei are located in the central cell of the embryo sac and are not part of the egg apparatus.