Govt. Exams
Entrance Exams
A microspore undergoes mitosis to form the male gametophyte (2-celled or 3-celled pollen grain consisting of generative and vegetative cells). The pollen grain itself is the male gametophyte.
In typical monosporic development, the megaspore mother cell produces four megaspores through meiosis, but only one (usually the chalazal megaspore) survives and develops into the female gametophyte. The other three degenerate.
The primary endosperm nucleus is formed by the fusion of one sperm cell with the two polar nuclei (or secondary nucleus), making it triploid.
Meiosis reduces ploidy from diploid (2n) to haploid (n), while fertilization restores diploid (2n) condition.
Synergids guide the pollen tube towards the egg apparatus and help in pollen tube entry through the filiform apparatus.
Pollen grain (male gametophyte) and embryo sac (female gametophyte) represent the gametophytic phase in angiosperms.
Endosperm is triploid (3n), formed by fusion of one sperm nucleus (n) with two polar nuclei (2n).
Pollination is part of sexual reproduction, not vegetative propagation. It involves transfer of pollen.
After meiosis produces microspores, one mitotic division produces a two-celled pollen grain (mature male gametophyte).
The functional megaspore undergoes mitotic divisions to develop into the embryo sac (female gametophyte).
