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 option is A is true but R is false.

Step-by-step Explanation:

1. Analysis of Assertion (A):
Assertion (A) states that a typical unfertilized, angiosperm embryo sac at maturity is 8-nucleate and 7-celled.
During megasporogenesis and megagametogenesis, a single functional megaspore undergoes three successive mitotic divisions of the nucleus. These divisions are strictly free-nuclear (meaning they are not immediately followed by cell wall formation), resulting in an 8-nucleate stage.
Subsequently, cell walls are laid down leading to the organization of the typical female gametophyte or embryo sac:
- Three cells are grouped together at the micropylar end and constitute the egg apparatus (consisting of two synergids and one egg cell).
- Three cells are grouped at the chalazal end and are called the antipodals.
- The remaining two nuclei, called polar nuclei, are situated in the large central cell just below the egg apparatus.
Thus, the mature embryo sac has 7 cells (3 antipodals, 3 cells of the egg apparatus, and 1 central cell) but contains 8 nuclei (3 in antipodals, 3 in the egg apparatus, and 2 polar nuclei inside the central cell).
Therefore, Assertion (A) is true.

2. Analysis of Reason (R):
Reason (R) states that the egg apparatus has 2 polar nuclei.
As described above, the egg apparatus consists of three cells: one egg cell and two synergids. The two polar nuclei are actually located in the large central cell, not in the egg apparatus.
Therefore, Reason (R) is false.

Conclusion:
Since Assertion (A) is true and Reason (R) is false, the correct choice is "A is true but R is false."