Question

Which of the following pairs has haploid structures?
A. Nucellus and antipodal cells.
B. Antipodal cells and egg cells.
C. Antipodal cells and megaspore mother cells.
D. Nucellus and primary endosperm nucleus.

Answer 1

Hint: Haploid cells, like gametes, have only one set of chromosomes (n), rather than two sets (2n). They are created through a process known as meiosis. The meiotic division divides the megaspore mother cell into four spores. Three haploid cells degenerate, with one surviving to form the embryo sac.
Step by step solution:
Angiosperm male gametophytes are reduced to three cells: one vegetative cell and two male gametes. The division that produces the gametes can occur either before or after the pollen grain disperses, during the development of the pollen tube. Apart from an opening (micropyle) at one end, the female sporangium has one or two coats or integuments; the sporangium with an integument is known as the ovule. The female gametophyte, recognized as the embryo sac in this group, advances from the parent spore while it is still in the sporangium. Three cell divisions produce eight nuclei, three located at each end and two in the centre. The cytoplasm then cleaves, resulting in three cells at each pole, abandoning two nuclei in a large central cell. The egg apparatus is formed by three cells at the micropylar pole (end toward the micropyle). Two of these cells, known as synergids, correspond to archegonium neck cells, while the third is an egg cell. In specific genera, the three cells at the opposite pole, known as the antipodals, play a role in embryo nutrition.
Three of the antipodal cells are haploid. The antipodal cells are found in the embryo sac at the opposite end of the micropyle.
The egg cell is at the opposite end of the embryo sac, flanked by two synergid cells. Egg cells are haploid as well.
As a result, both egg cells and antipodal cells have haploid chromosomes.
Hence, The correct option is B.

Note: The nucellus is the central and most important part of a plant ovule, enclosing the female gametophyte. Its nature of ploidy is diploid (2n). The primary endosperm nucleus, also known as the secondary nucleus, is created by the fusion of two polar nuclei in the embryo sac of a seed plant prior to fertilization. It is naturally diploid (2n). The megaspore mother cell is naturally diploid. It goes through meiosis to produce four haploid cells known as megaspores.