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Which one of the following pairs of plant structures has haploid number of chromosomes?
A
Nucellus and antipodal cells
B
Egg nucleus and secondary nucleus
C
Megaspore mother cell and antipodal cells
D
Egg cell and antipodal cells
Detailed Solution
The megaspore mother cell (2n) undergoes meiosis to form four haploid megaspores, one of which develops into the embryo sac (female gametophyte).
All the cells of the embryo sac are formed by mitosis of the haploid functional megaspore, so the egg cell, the synergids and the antipodal cells are all haploid (n).
So the egg cell and the antipodal cells both have the haploid number of chromosomes.
The nucellus is the diploid (2n) tissue of the ovule, belonging to the parent sporophyte.
The megaspore mother cell is diploid (2n).
The secondary nucleus is formed by the fusion of the two haploid polar nuclei, so it is diploid (2n).
Every other pair contains at least one diploid structure, so the correct pair is egg cell and antipodal cells.
All the cells of the embryo sac are formed by mitosis of the haploid functional megaspore, so the egg cell, the synergids and the antipodal cells are all haploid (n).
So the egg cell and the antipodal cells both have the haploid number of chromosomes.
The nucellus is the diploid (2n) tissue of the ovule, belonging to the parent sporophyte.
The megaspore mother cell is diploid (2n).
The secondary nucleus is formed by the fusion of the two haploid polar nuclei, so it is diploid (2n).
Every other pair contains at least one diploid structure, so the correct pair is egg cell and antipodal cells.