Bryophyta

Bryophyta

Bryophytes are amphibians of the plant kingdom. They occur in damp, shady places.

  • Have a haplodiplontic life cycle.
  • Plant body is the gametophyte.
  • Sporophyte is parasitic on the gametophyte.
  • Plant body is a thallus i.e., not differentiated into root, stem & leaf.
  • Vegetative reproduction is by fragmentation, gemmae & tubers.
  • Highly specialized oogamous, sexual reproduction.
  • Male sex organ is antheridium which produces biflagellate antherozoids.
  • Archegonium (flask-shaped) is the female sex organ, which produces an egg.
  • Fertilization occurs with the help of water and movement of antherozoids towards the archegonia is chemotactic.
  • The zygote divides immediately to form the sporophyte that grows on the gametophyte.
  • Sporophyte is differentiated into foot, seta & capsule.
  • Capsule produces haploid spores.
  • Spores on dispersal germinate to form the new gametophytic plant.

 

Divided into 3 classes:
  • Hepaticopsida (liverworts): e.g., Riccia, Marchantia, Porella.
  • Anthoceropsida: e.g., Anthoceros.
  • Bryopsida (mosses): e.g., Funaria, Sphagnum, Polytrichum.

Marchantia

  • Dorsoventrally flattened thallus.
  • Unicellular rhizoids & multicellular scales present.
  • They are dioecious.
  • Sex organs develop in groups on long stalks i.e., antheridiophore & archegoniophore.
  • Haploid spores & diploid elaters are produced in the capsule.
  • Elaters are hygroscopic & help in dispersal of spores.

Funaria

  • They have a protonema stage and an erect stage.
  • Spores germinate to produce filamentous, branched protonema, that produces buds.
  • Buds form the erect stage.
  • The erect stage has a stem like axis, leaf-like phylloid & multicellular rhizoids.
  • They are monoecious & autoecious.
  • Antheridia & archegonia develop in groups along with paraphyses on the upper part of the stem, surrounded by leaves.
  • Sporophyte is semi-parasitic on gametophyte.
  • Capsule is an elaborate structure divided into lower apophysis, middle theca & upper operculum.
  • Apophysis is photosynthetic.
  • Spore sac present in theca, produces haploid spores.
  • Covering spore sac is the operculum & peristome teeth.
  • Peristome teeth are hygroscopic, present in 2 rows of 16 each. They help in dispersal of spores.

Economic importance:

  • Help in soil formation & prevent soil erosion.
  • Used as fodder for cattle.
  • Peat used as fuel is obtained from Sphagnum.
  • Due to their water retaining capacity, Sphagnum is used in preserving & transporting living materials

Read also Alternation of Generations

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