Note on Bryophyta

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Bryophyta

Bryophyta
source:www.kullabs.com
fig:Bryophyta

The term Bryophyta was first coined by Robert Brawn in 1864. Bryophytes are the simple and primitive group of the moist terrestrial plant. These members are commonly called amphibian plants because water is essential for fertilization. This group is placed between algae and Pteridophyta. Member of bryophyte represents about 25,000 species. 653 species are also found in Nepal. Bryophyta includes three different categories of plants i.e. liverworts, hornworts, and mosses.

General characteristics of Bryophyta

  • Bryophytes are commonly found in moist, shady, damp and cool places such as moist rocks, moist walls, moist soil surface and wooden logs.
  • In the primitive group of bryophytes, the vegetative plant body is green and leafy thallus is present. Type of thallus is prostrate, dorsoventrally flattened and dichotomously branched. But in the advanced member of bryophyte vegetative plant body is aerial, erect and differentiated into rhizoids, axis, and leaves.
  • True rot is absent but for anchorage and absorption they bear unicellular or multicellular rhizoids.
  • Conducting tissue or xylem and phloem are absent.
  • They reproduce by vegetative and sexual methods. Vegetative multiplication is by fragmentation, tuber formation, adventitious branches, and gemma cup. Sexual reproduction is by monogamous type. The male reproductive organ is antheridium and female reproductive organ is archegonium.
  • Male gametes are biflagellate and motile.
  • Water is essential for fertilization.
  • Reproductive organs are multicellular and jacketed.
  • Fusion product of male and female gametes is a diploid zygote. It develops sporophyte.
  • They show distinct alternation of generation and embryo stage is present.

Alternation of generation in Bryophyta

In the life cycle of bryophytes, gametophyte and sporophyte generation are regularly alternate with each other to complete life cycle. Such a phenomenon is called alternation of generation. Gametophyte phase is dominant, independent, autotrop[hic and haploid. It reproduces by male and female gamete formation. Fusion product of male and female gamete is a diploid zygote. A zygote is the mother cell of sporophyte generation. It develops sporophyte. Sporophyte phase is reduced, diploid and depend on the gametophyte. It reproduces by haploid spore formation. Germination of haploid spore again gives rise to young gametophyte.

Classification of Bryophyta

Bryophyta is divided into three classes on the basis of gametophytic, thallus and sporophytic generation. They are:

  • Hepaticopsida
  • Anthocerotopsia
  • Bryopsida
Hepaticopsida Anthocerotopsida Bryopsida
Member of Hepaticopsida is also called liverworts because its gametophytic thallus is liver like.

Member of Anthocerotopsida is commonly called hornworts so its sporophytic phase is elongated, cylindrical and horn-like.

Member of Bryopsida is commonly called moss because its gametophytic plant body is aerial, erect and differentiated into underground rhizoids and leaf axis.
Ventral surface of the thallus bears unicellular rhizoids and multicellular scales. Rhizoids are smooth and tuberculate. Ventral surface of the thallus bears unicellular smooth rhizoid. Tuberculate rhizoids and scales are absent.

Rhizoids are multicellular and branched.

Reproductive organ develops at the terminal position.

Reproductive organ is embed in the dorsal surface of the thallus.

Reproductive organ develops at the tip of the branches.
Sporophyte may be simple or differentiated into food, seta, and capsule. Sporophyte is differentiated into food, and capsule. Seta is highly reduced. Sporophyte is differentiated into food, seta, and capsule.
The capsule contains single layer epidermis and stomata are absent. Capsule contains multilayer epidermis and stomata are present. Capsule contains multilayer epidermis and hypodermis. Stomata are present in the epidermal layer.
Centrally located columella is absent. Eg; Marchantia Centrally located columella is present. Eg; Anthoceros Centrally located columella is present. Eg; Funari

  • Bryophytes are commonly found in moist, shady, damp and cool places such as moist rocks, moist walls, moist soil surface and wooden logs.
  • Conducting tissue or xylem and phloem are absent.
  • Water is essential for fertilization.
  • Reproductive organs are multicellular and jacketed.
  • Fusion product of male and female gametes is a diploid zygote. It develops sporophyte.
  • They show distinct alternation of generation and embryo stage is present.
  • Bryophyta is divided into three classes on the basis of gametophytic, thallus and sporophytic generation.
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