Question

Describe the complete life cycle of non vascular plants (Bryophyta) and explain the process of alternation of generation in their sexual reproduction.Include but not limited to; gametophyte, sporophyte, zygote formation, diploid and haploid stages, and spore formation.

Answer 1

Answer :

Non-vascular plants are known as bryophytes. It is believed they originated from aquatic plants and they came to land through the water. They are known as the amphibians of the plant kingdom.

The life cycle of Bryophytes can be described as follows :

1. The main plant body of a bryophyte is haploid. It produces gametes and hence is called a gametophyte.
2. Sex organs are formed on the gametophyte. Sex organs are multicellular and jacketed in bryophytes.
3. Male sex organs are called Antheridium and female sex organs are called Archegonium
4. Archegonium is flask-shaped.
5. The male gametes of bryophytes are motile and are called antherozoids.
6. Antherozoids are usually comma-shaped and biflagellate
7. The female gamete is called egg
8. Fertilization is performed by zoidogamy i.e. male gametes swims into the water to reach the female gamete and fertilizes it. A diploid zygote is formed as a result of fertilization.
9. The zygote does not undergo Meiosis immediately.
10. Zygote initiates sporophytic generation, which is a diploid stage.
11. Zygote forms embryo and then sporophyte by mitosis.
12. The sporophyte of Bryophyta does not have root, stem, and leaves but has foot, seta, and capsule, It is known as sporogonium.
13. Some cells present in the capsule of the sporophyte function as spore mother cells. Spore mother cells undergo meiosis to form haploid spores.
14. The germination of spores can be direct or indirect.
15. In Direct germination, each spore forms a gametophyte i.e. each spore forms one thallus. For example Liverworts and Horn warts.
16. In Indirect germination, a multicellular filament is formed after the germination of spore. This filament is known as protonema. Now buds are formed on this protonema. Each bud develops and forms a gametophyte plant. This type of germination is best for the survival of the species. For example -Mosses.
17. Sexual reproduction in Bryophytes is oogamous type and the life cycle is Haplodiplontic type.
18. In Bryophyta, the unique character is that the sporophyte depends on the gametophyte.

Buds Gametophyte (2) Peatonema (n) Antheridin Axchegonia verwarts Hornwarts Antherozoids (12) cn) Germunalion Mosses Zygate (2n) Spares (n) Gametophytic Conexalion Sparophytic Generation Mitasis Sparic meiosk Embryo Can) Spare mother cells Spaxophyte Can) LIFE CYCLE OF BRYOPHYTA