General Characters & Classification of Bryophytes General Characters
The word bryophyte is the collective term for mosses, hornworts and liverworts Bryology is the study of bryophytes. Includes the simplest and most primitive land plants. Plants lack true vascular system, hence called non-vascular plants . Terrestrial but need water to complete life- cycle, hence called amphibians of plant kingdom . Mostly, grow on shady damp places. General Characters Gametophytic Plant Body Dominant plant body is gametophytic (n). Thalloid plant body i.e. not differentiated into true roots, stem and leaves. Or leafy shoots are present. Plants are green and possess chloroplasts. Roots are absent, replaced by unicellular or multicellular rhizoids. Vascular tissue completely absent. Structure: Gametophyte
Gametophore – leafy Moss structure or thick, gametophore conspicuous part
Leafy Liverwort
Thallose liverwort General Characters Reproduction Always oogamous Male gamete is small and motile, female gamete is large and non-motile. Male reproductive organs are antheridia and female are archegonia . Both are multicellular and jacketed. Antheridia are differentiated into stalk, and body. Archegonia are stalked and differentiated into venter and neck. Antheridium
Archegonium General Characters Sporophyte Represents diploid zygote, the first cell of sporophytic generation. Totally dependant on gametophyte. In most, differentiated into foot, seta and capsule The sporophyte produce haploid spores. The spores fall on suitable substratum & germinate to produce gametophytic plant body. Sporophyte
Moss
Liverwort Hornwort General Characters
Young gametophyte
The haploid spores represent first cells of gametophyte. Spore fall on suitable medium and germinate to produce gametophytic plant body. General Characters
Life cycle : 2 phases The haploid gametophytic generation (The gametophyte). The diploid sporophytic generation (The sporophyte). General Characters Alternation of generation Classification of Bryophytes
* Division HEPATICOPSIDA - the Liverworts
* Division ANTHOCEROTOPSIDA - the Hornworts * Division BRYOPSIDA - the Mosses Three groups Mosses Hornworts
Leafy liverwort Classification of Bryophytes 1. Hepaticopsida – the liverworts The Four Classes of Hepaticopsida
* Calobryales * Jungermanniales * Marchantiales * Metzgeriales Classification of Bryophytes
1. Hepaticopsida – the liverworts • So-called because the thallus of many liverworts resembles the lobes of a liver; ending “wort” means “herb”. •Liverworts lack conducting elements (cuticle & stomata) •The gametophyte can be “thallose” or “leafy” (Jungermanniales) • The thallus usually has some internal differentiation in the form of photosynthetic cells, air chambers and storage tissues •The sporophyte is compact, without or a short seta •The capsule (sporangium) has a single-layered wall Classification of Bryophytes
2. Anthocerotopsida – the hornworts
• So-called because many hornworts have elongated horn- like structure, which is the sporophyte . •The gametophyte may be as rosette or ribbon-like thallus •Many hornworts develop internal mucilage -filled cavities invaded by photosynthetic cyanobacteria , especially species of Nostoc. •Such colonies of bacteria growing inside the thallus give the hornwort a distinctive blue-green color. •The horn-shaped sporophyte grows from an archegonium embedded deep in the gametophyte. Classification of Bryophytes
2. Anthocerotopsida – the hornworts
• In mature sporophyte, a multicellular outer layer, a central rod-like columella running up the center, and a layer of tissue in between that produces spores and pseudo -elaters are present.
• The pseudo-elaters are multi-cellular, unlike the elaters of liverworts . They have helical thickenings that change shape in response to drying out; they twist and thereby help to disperse the spores. Classification of Bryophytes
3. Bryopsida– the mosses • It is the largest class of mosses , containing 95% of all moss species . • The gametophyte is differentiated into prostrate protonema and erect radial leafy shoot , persistant leaves spirally arranged on stem, rhizoid with muticellualr oblique septa. • Sporogonium is differentiated into foot, seta and capsule . Classification of Bryophytes
3. Bryopsida– the mosses • The most important characteristic of the Bryopsida is the architecture of the ring of teeth (peristome) surrounding the mouth of the sporophyte capsule . • Bryopsida are the only mosses that have an arthrodontous peristome, i.e., a peristome in which the teeth are structured by articulated cell wall remnants. Classification of Bryophytes 2. Bryopsida – the mosses
* Sphanidae * Andreaeidae * Bryidae