Question

Independent alternation of generation is found in
A. Pteridophyta
B. Spermatophyta
C. Thallophyta
D. Bryophyta

Answer 1

Hint: Alteration of generation is defined as the alteration of asexual phase and sexual phase in the lifecycle of an organism. It is also known as Metagenesis.

Complete answer:
Pteridophytes are vascular plants that are xylem and phloem are present in it. In pteridophytes, vessels in xylem and companion cells in phloem are absent.
In pteridophytes the plant body is completely differentiated into root, stem and leaf. The dominant phase in the life cycle of pteridophytes is sporophytic phase. Their life cycle is diplo-haplontic type.
The unique character of the life cycle of pteridophytes is: independent alternation of generation that is sporophyte and gametophyte are independent of each other.
The gametophytic phase in pteridophytes is represented by prothallus. Prothallus is made up of thallus and rhizoids. It is non-vascular.

So the correct option is(A) Pteridophyta.

Additional Information:
1. Pteridophyte plant is sporophyte (plant body is diploid).
2. Most of the pteridophytes are homosporous i.e. during reproduction only one type of spores are formed. Exception - Some pteridophytes are heterosporous i.e. during reproduction, two types of spores are produced i.e. microspores and megaspores.
3. Formation of spores takes place in sporangia. Sporangia are formed at the abaxial (base of leaf) surface of leaves.
4. The leaves on which sporangia are formed are called sporophylls (reproductive leaves) and normal photosynthetic leaves are called trophophylls (vegetative leaves). Groups of sporangia are called sorus (Plural-sori). Sori are found on sporophylls.
5. Spore mother cells are present in sporangia. Spores are formed by meiosis in spore mother cells and these spores start the gametophytic generation.

Note: Photosynthetic sporophyte is the unique character of pteridophyta.
Spore germination is exosporic in pteridophyta.
As compared to bryophytes, Pteridophytes are more adapted terrestrial plants because vascular tissue is present in pteridophytes. They have roots, stems and leaves.
Pteridophytes are not completely successful Terrestrial plants because they need water for fertilization so their growth is limited in the cool, shady and moist places.