BryophytaBryophyta General Characters The word bryophyte is the collective term for mosses,...

Bryophyta

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.

Gametophytic Plant Body

Dominant plant body is gametophytic (n).

Thalloid plant body i.e. not differentiated into true roots, stem and leaves.

Sometimes leafy shoots are present.

Plants are green and possess chloroplasts.

Roots are absent, replaced by unicellular or multicellular rhizoids.

Vascular tissue completely absent.

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 and germinate to produce gametophytic plant body.

Plant Body

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.

Classification of Bryophytes

HEPATICOPSIDA - the Liverworts

ANTHOCEROTOPSIDA - the Hornworts

BRYOPSIDA - the Mosses

1. Hepaticopsida – the liverworts So-called because the thallus of many liverworts

resembles the lobes of a liver; ending “wort” means “herb”.

The gametophyte can be “thallose” or “leafy”.

The thallus usually has some internal differentiation in the form of photosynthetic cells, air chambers and storage tissues.

Liverworts lack conducting elements (cuticle & stomata).

The sporophyte is compact, without or a short seta.

The capsule (sporangium) has a single-layered wall.

Riccia

Hepaticopsida

Marchantiae

Marchantiales Sphaerocarpales Monocleales

Jungermaniae

Calobryales Jungermaniales Metzgeriales

Takakiales

Subclasses

Orders Orders

2. Anthocerotopsida – the hornworts

So-called because many hornworts have elongated hornlike structure, which is the sporophyte.

Hornworts

Anthoceros

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. 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.

Anthocerotopsida – General Characters

Anthocerotophyta (Division)

Leiosporocerotopsida

Leiosporocerotales

Anthocerotopsida

Anthocerotales Notothyladales

Order Orders

3. Bryopsida – the mosses Mosses are mostly-terrestrial and found in a range of habitats,

although moist and shady habitats are more common. Mosses are often epiphytes.

The dominant phase of the moss life cycle is the gametophyte (haploid).

The plant is called a thallus, they may be erect or prostrate (axis along the ground).

Mosses have radial symmetry, in that a cut down the long axis of an individual gives two similar halves.

The gametophyte has a stem like axis with spirally arranged leaves, which are known as phyllids. Mosses attach to their substrate with multicellular rhizoids.

Moss leaves are variable in shape. Leaves usually consist of a single cell layer and are traversed by a midrib that is always more than one cell in thickness. The phyllids of mosses such as Mnium may be a single cell thick, but with a midrib with hydroids and leptoids. Polytrichum have a pad of cells and filamentous strands of photosynthetic cells. The margins of the leaves are often toothed, the teeth pointed or rounded.

It lacks xylem and phloem. The plant body may have conducting tissue.

The xylem-like water-and-mineral-conducting tissue is called hydroid. The phloem-like sugar-and-amino-acid-conducting tissue is called leptoid.

All mosses have a sporic (diplohaplontic) life cycle that is oogamous.

It has only three orders:

(i) Bryales (ii) Andriales (iii) Sphagnales

Plant body (Mosses)