Uncategories Topic: Reproduction in Bryophytes – Marchantia, Anthoceros, and Sphagnum
Topic: Reproduction in Bryophytes – Marchantia, Anthoceros, and Sphagnum

Topic: Reproduction in Bryophytes – Marchantia, Anthoceros, and Sphagnum



1. Reproductive Mechanisms

(A) Marchantia

  • Vegetative (Asexual) Reproduction

    • Fragmentation: Thallus breaks into pieces; each grows into a new plant.

    • Gemmae Cups: Specialized cup-like structures on dorsal surface. Each gemma is a small green disc; when rainwater splashes, gemmae are dispersed → new thalli.

  • Sexual Reproduction

    • Oogamous type (male gametes small, motile; female gametes large, non-motile).

    • Male and female sex organs develop on special stalked structures – antheridiophore (male) and archegoniophore (female).

(B) Anthoceros

  • Vegetative Reproduction

    • Fragmentation of thallus.

    • Perennating tubers may form under adverse conditions.

  • Sexual Reproduction

    • Oogamous.

    • Sex organs are sunken in the thallus.

    • Antheridia develop in chambers; archegonia are embedded in the tissue.

(C) Sphagnum

  • Vegetative Reproduction

    • Fragmentation.

    • Formation of innovation branches – when detached, they grow independently.

  • Sexual Reproduction

    • Oogamous.

    • Male and female sex organs develop at tips of special branches.

2. Male and Female Reproductive Organs

(A) Marchantia

  • Antheridium

    • Stalked, club-shaped, borne on disc of antheridiophore.

    • Produces biflagellate antherozoids (male gametes).

  • Archegonium

    • Flask-shaped structure borne on radiating rays of archegoniophore.

    • Consists of neck, venter, and egg.

(B) Anthoceros

  • Antheridium

    • Sunken in the dorsal side of thallus in chambers.

    • Globose, stalked, produces motile sperm.

  • Archegonium

    • Embedded in the thallus tissue.

    • No stalk; egg lies deep inside.

(C) Sphagnum

  • Antheridium

    • Globose, terminal, on special male branches.

  • Archegonium

    • Found at tips of female branches.

    • Surrounded by a cluster of leaves (perichaetial leaves).

(Diagram suggestion: Draw separate labelled diagrams of antheridium & archegonium of Marchantia, Anthoceros, Sphagnum.)

3. Fertilization

  • Marchantia:
    Rainwater helps sperm swim from antheridiophore to archegoniophore. Sperm enters archegonium through neck canal, fuses with egg → diploid zygote.

  • Anthoceros:
    Mucilage-filled cavities in thallus allow sperm to swim. Fusion of gametes takes place inside archegonium → zygote formed.

  • Sphagnum:
    Water is essential; sperm swims through rainwater to archegonium. Fertilization inside venter produces zygote.

Role of Water: In all bryophytes, water acts as a medium for motile sperm to reach the egg.

4. Sporophyte Development

  • Marchantia:
    Zygote divides → embryo → differentiates into foot, seta, and capsule. Capsule contains spores + elaters (help in spore dispersal).

  • Anthoceros:
    Zygote develops into embryo inside archegonium. Sporophyte consists of foot + capsule (no seta). Capsule grows continuously from base, contains columella and spores.

  • Sphagnum:
    Zygote → embryo → sporophyte with foot + pseudopodium + capsule. Capsule develops operculum and columella.

5. Structure of the Sporophyte

  • Marchantia Sporophyte:

    • Foot (absorbs food from gametophyte).

    • Seta (elongated stalk).

    • Capsule (contains spores + elaters).

  • Anthoceros Sporophyte:

    • Foot + capsule only.

    • Capsule long, cylindrical, with central columella and pseudoelaters.

    • Continuous growth at base (unique feature).

  • Sphagnum Sporophyte:

    • Foot, pseudopodium (support), and capsule.

    • Capsule has operculum and columella.

    • Spores released by explosive opening.

(Diagram suggestion: Draw labelled sporophytes of each genus.)

Differences:

  • Marchantia → seta present, capsule with elaters.

  • Anthoceros → no seta, capsule with columella.

  • Sphagnum → pseudopodium, capsule with explosive dehiscence.

6. Gametophyte Development (Life Cycle)

  • Spore Germination: Each haploid spore germinates into protonema.

  • Protonema:

    • Marchantia: Germ tube forms a young thallus.

    • Anthoceros: Simple filamentous protonema → lobed thallus.

    • Sphagnum: Thalloid protonema → leafy gametophyte.

  • Mature Gametophyte: Develops sex organs → fertilization → zygote → sporophyte.

(Diagram suggestion: Draw life cycle of each showing alternation of generations.)

Comparative Points

Feature Marchantia Anthoceros Sphagnum
Vegetative Propagation Gemmae cups Fragmentation, tubers Innovation branches
Sporophyte Foot, seta, capsule (elaters) Foot + capsule (columella, no seta) Foot, pseudopodium, capsule (operculum)
Protonema Simple germ tube Filamentous Thalloid type
Spore Dispersal By elaters By pseudoelaters Explosive operculum

Conclusion

Bryophytes like Marchantia, Anthoceros, and Sphagnum show a distinct alternation of generations, with a dominant gametophyte and dependent sporophyte. Though they share similarities in reproduction, each genus exhibits unique features such as gemmae in Marchantia, columella in Anthoceros, and explosive capsules in Sphagnum. Water is essential in their life cycle for fertilization, highlighting their adaptation to moist habitats.

Just a example 


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