Characteristics of Bryophytes

Bryophytes are the most simplest and most primitive land plants. Name bryophyte is derived from two words; ‘Bryon’ = moss; ‘phyton’ = plant. At present the phylum Bryophyta includes  ~ 960 genera and ~ 24000 species. The present post discusses the Characteristics of Bryophytes highlighting its Habit, Thallus Diversity, Gametophytic and Sporophytic Generations and Life Cycle.

Habit and Habitat of Bryophytes

Ø  Byrophytes are cosmopolitan in distribution.
Ø  They are quite uncommon in marine environments.
Ø  Bryophytes are terrestrial plants but require water at every stages in their life cycle.
Ø  They grow usually in moist and shady places.
Ø  They fail to complete its life cycle in the absence of water.
Ø  Few bryophytes are truly aquatic and underwater forms(example Riccia fluitans).


Sphagnum moss (source wikipedia)

Ø  Peat moss (Sphagnum moss) grown in bogs and marshy areas.

Ø  Porella is an epiphytic bryophyte that grow on tree trunks.

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Ø  Radulla protensa is an epiphyllous bryophyte grow on the surface of leaves.

Ø  Tortula desortorum is a xerophytic bryophyte growing in deserts.

Ø  Bryophytes are fundamentally land plants.

Land Aadaptations of Bryophytes

§  Possess root like rhizoids to absorb water from soil.

§  Free surface of epidermis is coated with water proof waxy coating to prevent water lose and protect against desiccation.

§  They possess stomata like structures for gaseous exchange.

§  Possess multicellular sex organs surrounded by sterile jacket.

§  After fertilization the zygote is left inside the archegonium to provide nutrition for the sporophyte development.

§  These features helps bryophytes to live in land condition.


Riccia fluitans (source wikipedia)

Bryophytes the Amphibians of Plant Kingdom

Ø  Amphibians in the animal kingdom lives in water as well as in land.

Ø  Similarly bryophytes represented by liverworts, hornworts and mosses grow well in the areas between water and terrestrial habitats (amphibious zone).

Ø  Bryophytes are dependent on water to complete their life cycle.

Ø  Presence of water is required and essential for the:

§  Dehiscence of mature antheridia

§  Liberation of antherozoids form antheridia

§  Transfer of antherozoids form antheridia to archegonia

§  Opening of archegonial neck

§  Movement of flagellated antherozoids into the archegonial neck.

Ø  Life cycle of bryophytes will not complete in the absence of water.

Ø  Thus they are called as the amphibians of plant kingdom.

Anthoceros agrestis 060910c

Anthoceros (hornwort) (source wikipedia)

Gametophyte of Bryophyte

Ø  Life cycle consists of gametophytic and sporophytic phases (generations).

Ø  Gametophytic and sporophytic generations are physically connected.

Ø  Gametophytic and Sporophytic phases are Heteromorphic (morphologically distinct).

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Ø  Characteristic of gametophytic generation of Bryophyte:

@.   Gametophytic generation is more conspicuous phase in life cycle

@.    Gametophytic generation is long lived and prominent phase

@.    It is independent, green autotrophic phase

@.    Gametophytic plant is fleshy

@.    In lower forms gametophyte is undifferentiated and thalloid

@.    In higher forms, gametophyte is differentiated into root like, leaf like and stem like structures

Physcomitrella Sporophyt

Moss Capsule (source wikipedia)

Ø  Characteristics of sporophytic generation of Bryophyte:

@.    Sporophytic generation is less conspicuous phase in life cycle.

@.    Sporophytic generation is short lived.

@.    Sporophyte is completely dependent on gametophytic plant for nutrition.

@.    Usually differentiated into foot, seta and capsule.

Ø  In primitive forms (Riccia and Marchantia) gametophyte is undifferentiated, prostrate and thalloid.

Ø  In advanced forms (mosses) plant body is erect, differentiated into stem (axis), lateral appendages (leaves) and rhizoids.

Ø  True roots are absent in bryophytes.

Ø  Rhizoids are present, rhizoids helps in anchorage and absorption.

Ø  Rhizoids may be unicellular and un-branched to multicellular branched.

Ø  Sometimes multicellular scales may be present.

Ø  Scales helps to protect growing region of the thallus.

Ø  Plant body consists of parenchymatous cells only.

Ø  Thick walled and lignified cells are completely absent in all phases.

Ø  Vascular tissue are completely absent.

Ø  Plant body sometimes internally differentiated into photosynthetic and storage zone (labour division).

Ø  Xylem and phloem are absent

Reproduction of Bryophytes

Ø  They reproduce by vegetative and sexual reproduction.


Marchantia with Gemmae (source wikipedia)

Ø  Vegetative multiplication takes place by:

§  Death and decay of older parts

§  Fragmentation of thallus

§  Adventitious branches

§  Tuber formation

§  Production of gemmae on gemmae cups

Sexual Reproduction in Bryophytes

Ø  Sexual reproduction is oogamous type

Ø  Sex organs are multicellular

Characteristics of Bryophytes

Antheridia (LS) (source wikipedia)

Ø  Sex organs are more complex than thallophytes (algae, fungi and lichens).

Ø  Male sex organ is called antheridia.

Ø  Antheridia are stalked and globose.

Ø  They have one cell thick sterile jacket around it for protection.

Ø  Jacket surrounds a solid mass of fertile cells called antherocytes.

Ø  Antherocytes metamorphose into antherozoids.

Ø  Antherozoids are bi-flagellate and thus they are motile (can swim in water).


Archegonia (LS) (source wikipedia)

Ø  Female sex organ is called archegonia.

Ø  Archegonia is a flask shaped structure.

Ø  Archegonia have basal swollen venter and an elongated upper part called neck.

Ø  The ventre and neck are surrounded by one layer thick sterile jacket cells.

Ø  Four to six neck canals cells and one venter canal cell is present.

Fertilization in Bryophytes

Ø  Water is necessary for fertilization.

Ø  When antheridia matures, their sterile jacket disintegrate and liberate the motile anthropoids to the surrounding thin film of water.

Ø  When archegonia matures, the neck canal cells and venter canal cell disintegrate and forms a mucilage mass.

Ø  The cover cells of the archegonia opens and the mucilage ooze out through the pore into the thin film of water.

Ø  Antherozoids are attracted by chemicals present in the mucilage and move towards it by chemotaxis through the thin film of water.

Ø  Antherozoids enters into the archegonium through neck and venter.

Ø  Antherozoids fuse with egg to from a diploid zygote.

Sporophyte of Bryophytes

Mosses on a tombstone.jpg

Bryum Gametophyte & Sprophyte (source wikipedia)

Ø  Sporophyte develop from embryo.

Ø  Zygote is the first stage in the diploid sporophytic generation.

Ø  Zygote does not have any resting period.

Ø  Zygote mitotically divide immediately after fertilization.

Ø  Bryophyts shows exoscopic mode of embryo development.

Ø  First division of zygote is always transverse to produce two cells (outer cell and inner cell).

Ø  Outer cell give rise to embryo.

Ø  Embryo develops within the ventre of archegonium.


Archegonia (source wikipedia)

Ø  Sporophyte is simple structure without rhizoids stem or leaves.

Ø  Sporophyte is completely dependent on gametophyte for nourishment.

Ø  Sporophyte is s projecting structure in most of the forms, it project out from the gametophytic tissue.

Ø  Sporophyte is differentiated into foot, seta and capsule.

Ø  Sporogenous cells present in the capsule divide meiotically to produce haploid spores.

Ø  All spores are similar in shape and size (homosporous).

Ø  Sometimes elaters are present.

Ø  Elaters are hygroscopic and they helps in spore dispersal.

Ø  Spores are non-motile and they disperse exclusively by wind or water current.

Ø  Under favorable condition the spores germinate to form the gametophytic plant.

Ø  In lower forms, the germination of spores is by the formation of a germ tube which later divide to give rise the younger gametophyte (Riccia, Marchantia).

Ø  In advanced forms (mosses) spores germinate to form a filamentous branched  protonema.

Ø  From the protonema, many gametophytic plants arises.

Key questions

  1. What are bryophytes?
  2. What are the characteristics of bryophytes?
  3. Explain the life cycle of bryophytes.
  4. Explain the reproduction in bryophyte.
  5. Explain the structure of Antheridium and Archegonium of Bryophyta.
  6. Explain alternation of generation in bryophytes.
  7. What are the economic importance of bryophytes?
  8. What are the ecological importance of bryophytes?

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