Question

From the examples of alternation of generations in plants, identify:
Stages at which mitosis is seen in haploid cells in them.

Answer 1

Part 1: Mitosis in haplontic life cycle
The main plant body of the bryophyte and some algae is haploid gametophyte. It produces gametes by mitosis.

Part 2: Mitosis in haplo-diplontic life cycle
Bryophytes and pteridophytes have multicellular gametophytes. Hence, the haploid spore formed in the sporophyte undergoes mitosis to give rise to the gametophyte (protonema stage in mosses develops directly from a spore).
The sex organs in bryophytes are multicellular and haploid. They produce haploid male gametes, antherozoids and female gametes, eggs, by mitotic division.
Development of haploid gametophyte from haploid spore in pteridophyte needs mitosis in haploid cells.

Part 3: Mitosis in diplontic life cycle
Diplontic plants such as gymnosperms and angiosperms undergo mitosis in the haploid gametophyte formed due to meiosis of gamete mother cell. In gymnosperms, the megaspore (haploid) develops into multicellular gametophyte by mitosis.
Specifically, in case of angiosperms, haploid microspore undergoes mitosis to form male gametes while the haploid megaspore undergoes mitosis to form seven-celled eight-nucleate embryo sac.