Question

The dominant photosynthetic phase in the life cycle of pteridophyte is equivalent to the
(a) Gametophytic phase of bryophyte
(b) Sporophytic phase of bryophyte
(c) Gametophytic phase of pteridophytes
(d) Gametophytic phase of gymnosperm

Answer 1

Hint: Pteridophytes are vascular plants that disperse spores. They produce neither flowers nor seeds. They have hidden reproduction presents. In pteridophytes, the gametophyte results in the sporophyte by the process of syngamy, and the sporophyte results in the gametophyte by the process of meiosis.

Complete answer
Pteridophytes exhibit a regular feature of alternation of generations. During sporogenesis, the reduction division results in the formation of haploid spores representing the first stage of the gametophyte generation followed by fertilization resulting in the formation of a zygote representing the first stage of sporophyte generation. The gametophyte takes part between meiosis and syngamy whereas the sporophyte takes part between syngamy and meiosis. The gametophyte is haploid (n) and the sporophyte is the diploid phase (2n). These two phases follow one another in regular succession resulting in the regular alternation of generation. While in the case of bryophytes the predominant phase in the life cycle of bryophytes is gametophyte. A gametophyte is a haploid multicellular organism which gets developed from the haploid sport that consists of one set of chromosomes. Thus they have the same haplo-diplontic life cycle but different dominant phases as gametophyte in bryophytes while sporophytes in pteridophytes.
The antherozoids (male gametes) are produced from antheridia in numbers. They are flagellated and can swim in the water. The oospheres (female gametes) are produced in flask-shaped archegonia singly. These are non-motile. The fusion between an egg cell and an antherozoid results in a zygote (diploid) having the combined nuclear material of the two gametes. The zygote undergoes mitotic divisions and develops into the sporophyte (diploid). The spore mother cells of the sporangia undergo meiosis resulting in non-motile spores (haploid). These spores undergo mitosis and result in gametophyte (haploid) thus completing the life cycle.

So, the correct answer is ‘Gametophytic phase of bryophyte’.

Note:
The term “Alternation of generation” was used by Hofmeister in 1851. The gametophytic phase is sexual and the sporophytic phase is asexual. The dominant phase of their life cycle is known to be the sporophytic phase.