Download Bryophytes

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 lifecycle, 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
structure or thick,
conspicuous part
Moss
gametophore
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
Leafy liverwort
Hornworts
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 hornlike 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