Introduction to Bryophyta

Botany Department,

Brahmanand PG College,

►Bryophyta (Greek Bryon = Moss, phyton =plants) is a group of simplest and primitiveplants of the class Embryophyta.

►The group is represented by about 960 generaand 24,000 species.

►They represented by the swamps and the areaswhere water and land meet. It may well becalled the amphibious zone. Inhabiting theamphibious zone are the mosses , liverworts andhornworts which collectively constitute of nonvascular land plant called the bryophytes.

►They require water for fertilization this group istherefore regarded as plant amphibians.

► In India most of the species of bryophytes areconfined to Northern and Southern Himalayasand the Nilgiri hills.

►Most of the bryophytes are land dwellers whichinhibit damp shaded and humid localities. A fewof them , however live in or float on water(e.g.,Riccia fluitans, Ricciocarpus natans, Riella).

►Many masses and almost all species ofDendroces grow as epiphytes on the stem of theplant of tropical rain forest.

►Buxbaumia minakate, B. aphylla andCryptothallus mirabilis are saprophytic speciesof bryophytes.

► Some bryophytes thrive on dry rocks with scanty soil and moisture (e.g., Porella platyphylla)

►Gametophytic and sporophytic phases are presentin the life cycle of bryophytes and both thesesphases are morphologically distinct(Heteromorphic).

►Bryophytes are leafy or thalloid green plants andthey lacks true roots, stem and leaves.

► In primitive form (Riccia & Marchantia) thegametophytes is prostrate and thalloid but inmosses the plant body is erect.

►The gametophytic phase is a more conspicuous,long lived independent , where the sporophyticphase is short lived and completely dependentupon the gametophyte.

► In primitive form (Riccia and Marchantia) thegametophytes is prostrate and thalloid but inmosses the plant body is erect.

►The function of anchorage and absorption isperformed by filamentous structures know asrhizoids.

►Rhizoids are either unicellular and unbranched(Hepaticopsida and Anthocerotopsida) ormultcellular branched (Bryopsida).

► Some member of bryophytes (marchantiales)also have multicellular scale in addition torhizoids which protect the growing region ofthallus and help in absorption of water.

►Bryophytes lack the vascular tissue (xylem andphloem).

►They reproduce by vegetative and sexualmethods.

►Vegetative multiplication takes place by decayand death of the older parts of the thallus, byadventitious branches or by special structure liketubers, gemmae etc.

► Sexual reproduction is oogamous type , the sexorgan are multicellular and jacketed.

►The male sex organ know as antheridia arestalked, globose or somewhat elliptical. It hassolid mass of fertile cell, the androcytes. Theandrocytes metamorphoses in to motilebiflagellated antherozoids.

►Antheridia have an outer sterile one cell thicklayer of jacket.

►The female sex organ know as archegonium is aflask shaped structure having a basal swollenventer and somewhat more slender elongatedupper part, the neck.

►The venter and neck are surrounded by a jacketof sterile cells.

►Water is necessary for fertilization.

►The fertilized egg is retained with in the venterof the archegonium.

►The zygote undergoes repeated division to forman undifferentiated, multicellular structure calledthe embryo.

►The development of embryo is exoscopic.

►The venter wall enlarges with developingembryo to form protective, multicellular envelop,the calyptra.

►The embryo by further division anddifferentiation produces a relatively small sporeproducing structure which is not independent. Itis called sporogonium (sporophyte).

► Rhizoids, leaves and stem are absent insporophyte.

► Sporophyte is a projecting structure,differentiated into foot, seta and capsule.The sporogenous cells present in the capsuleform haploid spores after reduction division.

►Morphologically the meiospores in a givenspecies are of one kind .Thus the bryophytes ingeneral are described as homosporous.

►The spores are non motile and they disseminate

exclusively by wind.

►Under favorable condition, the spore either forma filamentous germ tube which divides to giverise to young gametophyte (Riccia, Marchantia)or form a protonema.

► Protonema bears buds which develop into erectgametophores.

►The occurrence of heterologous type ofalternation of generation is a constant feature ofthe life cycle of bryophytes.

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