Bryophytes

Bryophytes also called Amphibians of the plant kingdom. They include mosses and liverworts which grow commonly in the moist shaded area in the hills. They show haplo-diplontic life cycle.

  • These are called Amphibians of the plant kingdom because they can live on soil but for sexual reproduction, they depend on water.
  • The embryophytes without vascular tissues.
  • Mostly occur in damp, humid, and shaded areas.

Body organization

  • Thallus-like, prostrate or erect, found attached with substratum by unicellular or multicellular rhizoids.
  • Lack of true root, stem, or leaves.
  • The main plant body is free-living gametophyte (dominant phase), Bryophytes plant body is haploid.

Reproduction

Gamet production takes place, so it called gametophyte. sex organs are multicellular.

  1. Vegetative Reproduction: Very common and occurs through fragmentation, tubers, gammae, buds, and adventitious branches.
  2. Sexual Reproduction:
  • Antheridium– Male sex organ- single, coiled, biflagellate antherozoids or spermatozoid produced by them.
  • Archegonium– A female sex organ- is flask-shaped and swollen base called a venter and upper elongated neck, produces a single egg.
  • Antherozoid released into the water and there it comes in contact with archegonium.
  • An antherozoid fuses with eggs to produce a zygote and a multicellular body is produced by them which is called the sporophyte. Sporophytes get attached to the photosynthetic gametophyte and get nourishment from it.
  • Some cell of the sporophyte follow reduction division i.e. meiosis and produces haploid spores. By the germination of these spores, gametophyte produced.

Alternation of Generation

The bryophytes show heteromorphic or heterologous alternation of generation in their life cycle, i.e. haplo-diplontic life-cycle. They also exhibit the phenomenon of apospory and apogamy.

  • Apospory: The process by which gametophyte develops from the vegetative cells of the sporophyte.
  • Apogamy: Sporophyte develops from gametophyte without gamete union.

life cycle showing alternation of generation in Bryophytes

Economic importance of Bryophytes

  • In general, Bryophytes are of little economic importance. Some mosses provide food for herbaceous mammals, birds, and other animals.
  • Sphagnum species of moss, provide peat which is used as fuel and packing material for trans shipment of living materials because they have the capacity to hold water. 

Ecological importance

  • Mosses along with lichens are the first organisms to colonize rocks and for this are of great ecological importance.
  • they decompose rocks and make substrate suitable for higher plants’ growth.
  • Mosses also prevent soil erosion forming dense mats on the soil which reduces the impact of rainfall on the soil.
Classification of Bryophytes 

The bryophytes divided as

  1. Hepaticopsida- Liverworts
  2. Anthocerotopsida- Hornworts
  3. Bryopsida- Mosses.

Examples of bryophytes

The Liverworts

Habitat: These grow in moist, shady habitats like banks of streams, marshy areas, damp soil, the bark of trees, and also in deep woods.

Plant body: The body of a bryophyte plant is thalloid. The thallus is dorsiventral and closely appressed to the substrate. Example- Marchantia.

reproduction

  • Asexual reproduction by fragmentation of thalli, or bay the formation of a specialized structure called gemmae.
    • these are green in colour, multicellular, asexual buds that develop in small receptacles called gemma cups and is located on thalli.
    • The gemmae get detached from the parent body and germinate into new individuals.
  • Sexual reproduction– during sexual reproduction both male and female sex organs are produced either on the same and different thalli.
    • Sporophyte gets differentiated into a foot, seta, and capsule- e.g. Marchantia. (only capsule- Riccia)
    • Spores are produced within the capsule after meiosis and germinate forming free-living gametophyte.
  • Example: Riccia, Marchantia, Porella, Pellia, Sphaerocarpus etc.
The Hornworts
  • Thalloid, aseptate Zhizoids gametophyte is found.
  • Sex organs present on the dorsal surface of the thallus.
  • Sporophyte differentiated into foot, short-meristem attic region, and capsule.
  • Example of hornworts: Anthoceros, Notothylus, Megaceros, etc.
The Mosses 

The prime stage of a moss’s life cycle is gametophytic which contains two stages:

  1. Protonema stage: developed by a spore directly. It is green, creeping, branches, and filamentous stage.
  2. leafy stage: Developed by secondary protonema as a lateral bus and consisting of upright, slender axes bearing arranged leaves, attached to the soil through multicellular and branched rhizoids. Sex organs born by this stage.

Reproduction

  • Vegetative reproduction by fragmentation and budding during secondary protonema.
  • Sexual reproduction as the sex organs antheridia and archegonia are produced at leafy shoots.
    • The zygote develops into a sporophyte after fertilization.
    • Sporophytes consist of a foot, seta, and capsule, which contains spores.
    • spores are formed after the meiosis.
  • Some common examples of mosses: Funaria, Polytrichum, and Sphagnum.

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