Bryophytes are small non-vascular plants without true roots, stems and leaves. They may possess root-like (rhizoids), stem-like( axis) and leaves like (phylloid) structure. The body of bryophytes is very small and ranges from a few mm to many cm. They are most simple, primitive land plants primarily including mosses, liverworts and hornworts.
Bryophytes lacks specialised vascular system for conducting nutrients, water, and minerals throughout the plant body. Bryophytes are most commonly grow in damp and shady places. They typically need a moist environment for active growth and reproduction; however, some bryophytes can adapt to survive in dry conditions by developing specialized features.
Bryophytes have successfully adapted to both land and aquatic environments. However, they are not fully considered adapted to land conditions because they depend on water for sexual reproduction. Due to their complete reliance on water to complete their life cycle, they are often referred to as the amphibians of the plant kingdom.
Characteristics of Bryophytes
- A small group of primitive land dwellers that possess a small, leafy, or thalloid green plant body.
- The main plant body is haploid and produces gametes called gametophyte.
- The dominant phase of bryophytes is gametophyte on which sporophyte is dependent for nutrition.
- The plant body of bryophytes is thallus-like and prostrate or erect, and attached to the substratum by branched or unbranched unicellular or multi cellular root-like structure, the rhizoids.
- The thalloid plant body is not differentiated into true roots, stems and leaves. It may possess root-like, leaf-like and stem-like structures.
- Bryophytes lack vascular tissue (xylem and pholem) and hence called non vascular plant.
- Sexual reproduction in bryophytes is oogamous type.
- The sex organs are jacketed and multicellular.
- Male sex organ is antheridium and produce biflagellate
- Antherozoid and both the flagella are of whiplash type.
- Flask shaped archegonium produces a single egg.
- The antherozoids are released into water where they come in contact with archegonium. An antherozoid fuses with the egg to produce a zygote that develop into multicellular body called a sporophyte.
- The sporophyte dependent on gametophyte for its nutrition.
- Sporophyte differentiated into foot, seta and capsule.
- Sporophyte undergo meiosis to produce haploid spores. These spores germinate to give rise gametophyte.
Classification of Bryophytes
Bryophytes are classified into three distinct phyla: Mosses (phylum Bryophyta), liverworts (phylum Hepatophyta), and hornworts (phylum Anthocerophyta).
Mosses
Mosses, members of the Bryophyta phylum, constitute a diverse and ecologically significant group of approximately 12,000 recognized species. These small, non-vascular plants typically form dense colonies or patches, exhibiting a distinctive growth habit that sets them apart from vascular plants.
Unlike their vascular counterparts, mosses lack true roots, stems, and leaves. Instead, they possess minute, filamentous structures known as rhizoids, which facilitate nutrient and water absorption. The upright, stem-like axis, bearing leaf-like structures, is a defining characteristic of mosses, differentiating them from other non-vascular plants such as liverworts and hornworts. The life cycle of mosses is particularly noteworthy, as it involves a complex alternation of generations. Unlike seed plants, mosses reproduce via spores rather than seeds. Common examples of mosses are Funaria, Polytrichum and Sphagnum.
Liverworts
Liverworts belonging to phylum Hepatophyta consist of about 9000 species of nonvascular plants. Their dominant generation is the gametophyte, but the gametophytes of some liverworts differ from those of mosses. The plant body of a liverworts is thalloid that is not differentiated into leaves, stems, or roots. Liverworts predominantly inhabit moist, shaded environments, including stream banks, marshy areas, damp soil, tree bark. Like other members of the bryophyte group, liverworts are small, often unnoticeable plants that thrive primarily in moist surroundings. Common examples are Marchantia polymorpha and Riccia.
Hornworts
Hornworts, a small group of approximately 200 species of bryophytes, belong to the phylum Anthocerophyta. Their gametophytic form resembles that of thalloid liverworts, yet they possess unique structural and developmental features. These hardy plants thrive in undisturbed environments, such as fallow fields and roadside verges, where they can survive in marginal habitats. Hornworts may or may not be closely related to other bryophytes. For instance, their cellular structure, particularly the presence of a single large chloroplast in each cell, resembles certain algal cells more than plant cells. Conversely, mosses and liverworts possess numerous disc-shaped chloroplasts within each cell. Example of hornworts are Anthoceros natans.
