3. Kingdom Plantae - part 02 - Bryophyta

 

3. Kingdom Plantae - part 02 - Bryophyta


Bryophyta (Bryon : moss ; phyton : plant) :
  • Bryophytes are mostly terrestrial plants. 
  • They are found in moist shady places. But they need water for fertilization and completion of their life cycle. Hence they are called ‘amphibious plants’. 
  • They include approximately 960 genera and about 25,000 species.
  • Life cycle of Bryophytes shows sporophytic and gametophytic stages.
  • Vegetative plant body is thalloid or leafy which represents gametophytic generation. 
  • Spore producing capsule represents sporophytic generation.
  • Bryophytes have root-like structures called rhizoids. 
  • Rhizoids are unicellular in liverworts while multicellular in mosses.
  • Rhizoids absorb water and minerals and also help in fixation of thallus on the substratum.
  • Bryophytes are divided into two groups :
  1. liverworts and 
  2. mosses.

1. Liverworts (Hepaticeae) :
  • These are lower members of Bryophyta.
  • These are primitive group of Bryophytes.
  • Gametophyte possesses flat plant body called thallus. 
  • The thallus is green, dorsiventral, prostrate with unicellular rhizoids.
  •  e.g. Riccia, Marchantia.
Hornworts (Anthocerotae) - 
  • These member possess flattened thallus. 
  • The thallus produces horny structures which are called sporophytes hence the name hornworts. e.g. Anthoceros.
2.  Mosses (Musci) :

  • These are advanced members of Bryophyta which possess erect plant body.
  • Gametophytic phase of the life cycle includes two stages namely-  
  1. protonema stage and 
  2. leafy stage. 
Protonema stage :
  • The protonema is prostrate green, branched and filamentous (it is also called juvenile gametophyte). 
  • It bears many buds. 
  • Leafy stage is produced from each bud. Thus protonema helps in the vegetative propagation. 
Leafy stage :

  • The leafy stage has erect, slender stem like (Cauloid) main axis bearing spiral leaf like structures (Phylloid). 
  • It is fixed in soil by multicellular branched rhizoids. 
  • This stage bears sex organs. 
  • Vegetative reproduction takes place by fragmentation and budding in secondary protonema.
  • e.g. Funaria,  olytrichum, Sphagnum , etc.

Economic importance -

  • Some mosses provide food for herbivorous mammals, birds, etc. 
  • Species of Sphagnum, a moss; provides peat used as fuel.
  • Mosses are also used as packing material for transport of living materials because they have significant water holding capacity. 
  • Just like lichens, mosses are the first living beings to grow on rocks. 
  • They decompose rocks to form soil and make them suitable for growth of higher plants. 
  • Dense layers of mosses help in prevention of soil erosion, thus act as soil binders.

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