🌿 Introduction

Bryophytes are the first land plants in evolution that show adaptation to terrestrial life but still depend on water for reproduction. They are often called the amphibians of the plant kingdom because they can live in soil but depend on water for sexual reproduction.

They usually grow in moist, shaded areas in the hills.

They represent the transition between aquatic algae and terrestrial vascular plants (pteridophytes).

🌱 General Characteristics

  • Body is more differentiated than algae, typically thallus-like and prostrate or erect.
  • Attached to the substratum by unicellular or multicellular rhizoids.
  • They lack true roots, stems, or leaves but may possess root-like, leaf-like, or stem-like structures.
  • The main plant body is haploid (n) and is called the gametophyte. It produces gametes.
  • The sporophyte (diploid, 2n) is attached to the photosynthetic gametophyte and derives nourishment from it. It is short-lived and produces haploid spores via meiosis.

General Characteristics can be summarized into following:

  • Habitat: Damp, shady, and moist places.
  • Body Structure: Thallus-like; lacks true roots, stems, and leaves (has rhizoids).
  • Vascular Tissue: Absent.
  • Reproduction: Alternation of generations with dominant gametophyte and dependent sporophyte.
  • Need for Water: Water is required for motile male gametes to reach the female organ.

🔁Reproduction

  • The main plant body (gametophyte) produces gametes.
  • Sex organs are multicellular. The male sex organ is the antheridium (produces biflagellate antherozoids), and the female sex organ is the archegonium (flask-shaped, produces a single egg).
  • Antherozoids are released into water and swim to the archegonium.
  • Fusion of antherozoid with the egg produces a zygote (2n).
  • The zygote develops into a multicellular sporophyte, which is not free-living but attached to the gametophyte.
  • The sporophyte undergoes meiosis to produce haploid spores.
  • These spores germinate to produce a new gametophyte.

Economic Importance

  • Some mosses provide food for herbaceous mammals, birds, etc.
  • Sphagnum (a moss) provides peat, used as fuel and as packing material for trans-shipment of living material due to its water-holding capacity.
  • They are ecologically important as pioneer colonizers of bare rocks, along with lichens. They decompose rocks, making the substrate suitable for higher plants.
  • Mosses form dense mats on the soil, reducing the impact of falling rain and preventing soil erosion.

🔁 Alternation of Generations

  • Gametophyte: Haploid, independent, photosynthetic plant body.
  • Sporophyte: Diploid, dependent on gametophyte, produces spores through meiosis.

🧩 Classification of Bryophytes

Bryophytes are classified into three main groups:

Group Common Name Examples Distinguishing Feature
Liverworts Hepatics Marchantia, Riccia Dorsiventrally flattened thallus
Mosses Musci Funaria, Polytrichum Leafy gametophyte, upright growth
Hornworts Anthocerotes Anthoceros Sporophyte with horn-like structure

🌿 1️⃣ Liverworts (Hepaticopsida)

  • Habitat: Grow usually in moist, shady habitats like banks of streams, marshy ground, damp soil, bark of trees, and deep in the woods.
  • Structure: The plant body is a thalloid structure (e.g., Marchantia), dorsiventral and closely appressed to the substrate. Leafy members have tiny leaf-like appendages in two rows on stem-like structures.
  • Reproduction:
  • Asexual: By fragmentation or by formation of specialised structures called gemmae. Gemmae are green, multicellular, asexual buds developed in small receptacles called gemma cups on the thalli. Gemmae detach and germinate to form new individuals.
  • Sexual: Male and female sex organs are produced either on the same or different thalli. The sporophyte is differentiated into a foot, seta, and capsule. After meiosis, spores are produced within the capsule and germinate to form free-living gametophytes.
  • Example: Marchantia.

🌾 2️⃣ Mosses (Bryopsida)

  • Life Cycle: The predominant stage is the gametophyte which is leafy and upright, consists of two stages:
  1. Protonema stage: Develops directly from a spore. It is a creeping, green, branched, and frequently filamentous stage.
  2. Leafy stage: Develops from the secondary protonema as a lateral bud. Consists of upright, slender axes bearing spirally arranged leaves. Attached to soil through multicellular, branched rhizoids. This stage bears the sex organs.
  • Reproduction:
  • Vegetative: By fragmentation and budding in the secondary protonema.
  • Sexual: Antheridia and archegonia are produced at the apex of the leafy shoots. After fertilisation, the zygote develops into a sporophyte, consisting of a foot, seta, and capsule. The sporophyte in mosses is more elaborate than in liverworts. The capsule contains spores formed after meiosis. Mosses have an elaborate mechanism of spore dispersal.
  • Examples: Funaria, Polytrichum, Sphagnum.

🍃 3️⃣ Hornworts (Anthocerotopsida)

  • Sporophyte is elongated and horn-like, grows continuously.
  • Each cell has one chloroplast.
  • Example: Anthoceros.

🌎 Ecological Importance

Role Example
Soil formation and binding Mosses trap soil and moisture
Water retention Sphagnum stores water, used as packing material
Habitat for microorganisms Moss beds shelter microfauna
Peat formation Partially decomposed Sphagnum forms peat (used as fuel)

🧠 Summary

  • Bryophytes are non-vascular, small plants dependent on water for reproduction.
  • Gametophyte is dominant and photosynthetic.
  • Classified as liverworts, mosses, and hornworts.
  • Play vital ecological roles in soil formation and moisture retention.

💡 Solved Examples

Q1. Why are bryophytes called amphibians of the plant kingdom?
A1. Because they live on land but need water for sexual reproduction.

Q2. What are gemmae?
A2. Small, multicellular asexual reproductive bodies formed in gemma cups in Marchantia.

Q3. Name the dominant generation in bryophytes.
A3. Gametophyte is dominant and independent.

Q4. What is peat?
A4. Partially decomposed moss (Sphagnum) that accumulates in bogs and used as fuel.

Q5. Give one ecological importance of mosses.
A5. Mosses help in soil formation and moisture conservation.