Which of the following characteristics of mature embryo sac are correct?
A. Eight nuclei and one synergid cell
B. Eight nuclei and two synergid cells
C. Three antipodal cells at micropylar end
D. Three antipodal cells at chalazal end
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → B and D only
The embryo sac is the female gametophyte. At maturity it is 8-nucleate but 7-celled. At the micropylar end is the egg apparatus: one egg cell and two synergids. At the chalazal end are three antipodal cells. The large central cell in the middle has two polar nuclei, so it holds two of the eight nuclei.
A. Eight nuclei and one synergid cell — Incorrect. The egg apparatus has two synergids, not one.
B. Eight nuclei and two synergid cells — Correct. The embryo sac has eight nuclei, and two of its cells are synergids.
C. Three antipodal cells at micropylar end — Incorrect. The micropylar end holds the egg apparatus. The antipodals are at the opposite end.
D. Three antipodal cells at chalazal end — Correct. The three antipodals lie at the chalazal end.
NCERT Extract:
The Pistil, Megasporangium (ovule) and Embryo Sac – “… There is a characteristic distribution of the cells within the embryo sac. Three cells are grouped together at the micropylar end and constitute the egg apparatus. The egg apparatus, in turn, consists of two synergids and one egg cell. The synergids have special cellular thickenings at the micropylar tip called filiform apparatus, which play an important role in guiding the pollen tubes into the synergid. Three cells are at the chalazal end and are called the antipodals. The large central cell, as mentioned earlier, has two polar nuclei. Thus, a typical angiosperm embryo sac, at maturity, though 8-nucleate is 7-celled.”