Question

The family onagraceae is marked out by which type of embryo sac?
A. Peperomia
B. Plumbago
C. Polygonum
D. Oenothera

Answer 1

In plants, the ovule is a structure that contains the nucleus, integument, and female gametophyte and encloses the reproductive cells of females.
“The female gametophyte, often known as the embryo sac, is an oval structure found in the ovule of flowering plants”. When the haploid megaspore nucleus divides, an embryo sac is said to form. It has two haploid nuclei as well as six haploid cells without cell walls.
The haploid nuclei can sometimes merge to form a single cell (endosperm motor cell). One male nucleus and one egg nucleus join during fertilisation to form a zygote, which leads to the development of the embryo.

Complete answer:
Option A: In all of its genera except Trapa, the Onagraceae family is distinguished by the presence of a unique monosporic four-nucleate Onagrad-type of embryo-sac. The micropylar megaspore of the tetrad produces such an embryo sac. The megaspores at the lowest three chalazal ends do not dissolve.
The mature embryo sac in oenothera is arranged in an egg apparatus with an uninucleate centre cell, which is referred to as the oenothera type. The tetrad's micropylar megaspore produces this embryo sac during two nuclear divisions. As a result, four nuclei are formed in the shape of two synergids, an egg, and a polar nucleus.
So, option A is correct.
Option B: In oenothera, the mature embryo sac is arranged in an egg apparatus with an uninucleate centre cell, known as the oenothera type. During two nuclear divisions, the micropylar megaspore of the tetrad creates this embryo sac.
So, option B is incorrect.
Option C: The mature embryo sac in oenothera is arranged in an egg apparatus with an uninucleate centre cell, which is referred to as the oenothera type. This embryo sac is formed by the tetrad's micropylar megaspore during two nuclear divisions.
So, option C is not correct.
Option D: The mature embryo sac in oenothera is arranged in an egg apparatus with an uninucleate centre cell, which is referred to as the oenothera type. The tetrad's micropylar megaspore produces this embryo sac during two nuclear divisions.
So, option D is also correct.

Therefore, both option A and D are correct.

Note:
There are two stages to the creation of the embryo sac:
Megasporogenesis occurs in the first stage, when a single diploid mother cell undergoes meiosis, resulting in the formation of a haploid megaspore tetrad.
Three of these dissolve, while one survives and develops into the embryo sac.
Next stage: Megagametogenesis is the second stage, in which the embryo sac is generated by mitosis of a functioning haploid megaspore, resulting in an $8$-nucleate, $7$-celled gametophyte.
Out of all eight nuclei, the polar nuclei travel to the centre to join and form a single diploid cell at that site. The triploid endosperm is formed when this single diploid cell unites with the sperm.