Class 11 Biology Plant Kingdom Bryophytes

Bryophytes

  • Bryophytes include various mosses and liverworts, commonly grow in moist shaded areas in the hills.
  • Bryophytes are also called amphibians of the plant kingdom because these plants can live in soil but are dependent on water for sexual reproduction.
  • Plant body is thallus-like and prostrate or erect, and attached to the substratum by unicellular or multicellular rhizoids.
  • They lack true roots, stem or leaves and may possess root-like, leaf-like or stem-like structures.
  • The main plant body of the bryophyte is haploid, produces gametes, and hence is called a gametophyte.
  • The male sex organ is called antheridium, which produce biflagellate antherozoids and the female sex organ called archegonium is flask-shaped, produces a single egg.
  • The antherozoids are released into water where they come in contact with archegonium and fuses with the egg to produce the zygote.
  • Zygotes produce a multicellular body called a sporophyte, which is not free-living but attached to the photosynthetic gametophyte and derives nourishment from it.
  • Some cells of the sporophyte undergo reduction division to produce haploid spores, which germinate to produce gametophyte.
  • The bryophytes are divided into liverworts and mosses.

Liverworts

  • The liverworts grow usually in moist, shady habitats.
  • The plant body of a liverwort is thalloid, the thallus is dorsiventral and closely appressed to the substrate.
  • Asexual reproduction in liverworts takes place by fragmentation of thalli, or by the formation of specialized structures called
  • Gemmae are green, multicellular, asexual buds, which develop in small receptacles called gemma cups located on the thalli.
  • The sporophyte is differentiated into a foot, seta, and capsule.
  • After meiosis, spores are produced within the capsule, the spores germinate to form free-living gametophytes.

Class_11_Biology_Plant_Kingdom_Liverworts

Fig. Liverworts

Mosses

  • The predominant stage of the life cycle of a moss is the gametophyte which consists of two stages:
  1. Protonema stage, which develops directly from a spore.
  2. Leafy stage, which develops from the secondary protonema as a lateral bud.
  • They are attached to the soil through multicellular and branched rhizoids.
  • Vegetative reproduction in mosses is by fragmentation and budding in the secondary protonema.
  • In sexual reproduction, the sex organs antheridia and archegonia produce zygote which develops into a sporophyte, consisting of a foot, seta and capsule.

 Examples of mosses are Funaria, Polytrichum.

Class_11_Biology_Plant_Kingdom_Moss

Fig. Moss

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