Question

An angiospermic plant has 24 chromosomes in its mesophyll cells. The number of present in synergid, pollen grain, nuclleus and endosperm will be respectively

• A. 8, 8, 12, 36
• B. 12, 12, 12, 36
• C. 12, 12, 12, 72
• D. 12, 12, 24, 36

Answer 1

The correct option is D 12, 12, 24, 36

An angiospermic plant has 24 chromosomes in its mesophyll cells which are diploid.
In flowering plants, the pollen grain is the male gametophyte and the embryo sac is the female gametophyte.
The pollen grain contains 2 male gametes which are haploid. So they will have 12 chromosomes.
The diploid nucellus (24 chromosomes ) and the integuments surround the embryo sac.
The mature embryo sac has seven nuclei. Six nuclei are haploid - three antipodal cells, two synergids and the ovum. So the synergid has 12 chromosomes. After pollination the pollen tube enters the embryo sac through the synergid.
The pollen tube releases the two male gametes into the cytoplasm of the synergid. One of the male gamete towards the egg cell and fuses with its nucleus thus completing the syngamy.
The other male gamete moves towards the two polar nuclei located in the central cell and fuses with them to produce a triploid primary endosperm nucleus. So the endosperm has 36 chromosomes.