🌿 Notes on Bryophyta 🌿

Term ‘Bryophyta’ was proposed by Robert Braun.
The study of Bryophytes is known as Bryology.
Father of Bryology is generally considered to be Hedwig, but some scientists credit Cavers.
Father of Indian Bryology is Prof. Shiv Ram Kashyap.

General Features

Bryophytes are the first land plants.
They are believed to have originated from aquatic plants and transitioned to land via water.
- This is supported by some features similar to aquatic plants, such as the presence of air canals.
Known as amphibians of the plant kingdom because they live in soil but need water to complete their life cycle (for sexual reproduction).
Not considered successful land plants due to:
- Absence of vascular tissue.
- Need for water for fertilization.
Water conduction occurs via parenchyma or Hadrom tissue (e.g., in Sphagnum).
- Hadrom is a dead tissue.
The plant body is dominantly haploid.
Plant body is more differentiated than algae: Multicellular, thalloid, and parenchymatous.
Roots are absent; Rhizoids (unicelled / multicelled) are present.
Bryophytes are sciophytes (prefer to grow in moist (wet) and shady places).
Vegetative reproduction is very common through:
- Fragmentation
- Tubers
- Gemmae (found inside gemma cup)
- Buds
- Adventitious branches

Habitat of Some Important Bryophytes

Found in water (Aquatic):
- Riccia flutains
- Riccia abuensis
- Ricciocarpus natans
- Riella
- Fontinalis
Epiphytic (grow on other plants):
- Dendroceros
Saprophytes (Non-photosynthetic):
- Buxbaumia
- Cryptothallus

Life Cycle of Bryophytes

The plant is the gametophyte and is haploid.
Sex organs are formed on the gametophyte.
Sex organs are multicellular and jacketed.
Male sex organ: Antheridium.
Female sex organ: Archegonium (Bryophytes are the 1st Archegoniate plants).
Male gametes are motile and called antherozoids.
- Antherozoids are comma shaped and biflagellate.
Female gamete is called egg.

💧 Notes on Fertilization, Sporophyte, and Life Cycle in Bryophyta 🌿

Fertilization and Zygote

Fertilization occurs by zoodiogamy: the motile male gamete reaches and fertilizes the female gamete (egg).
- Water is essential for this process.
Result of fertilization is a diploid zygote.
The zygote initiates the sporophytic generation (a diploid stage).
Zygote develops inside the archegonium and divides by mitosis to produce an embryo.
- Bryophytes are considered the first embryophytes (plants that form an embryo).
The embryo develops into a sporophyte, which is parasitic over the gametophyte (may be partial parasite as in mosses).

Sporophyte (Sporogonium)

The sporophyte is also called sporogonium.
It is composed of three parts: capsule, seta, and foot.
It produces meiospores (haploid spores) inside the capsule (after meiosis in spore mother cells).
The sporophyte remains attached to the gametophyte.
All bryophytes produce only one type of spore (Homosporous).

Development of Sporophyte

First division in zygote is transverse.
Second division is vertical.
Third division is also vertical but at right angle to second division, forming an eight-celled embryo.
A periclinal division takes place in the eight-celled embryo, resulting in a 16-celled embryo arranged in two layers:
- Outer 8 cells – Called Amphithecium.
- Inner 8 cells – Called Endothecium.
Endothecium cells divide to form sporogenous cells.
Some sporogenous cells become sterile and are called nurse cells (2n).
Remaining sporogenous cells function as spore mother cells.
Meiosis occurs in spore mother cells, resulting in haploid spores.
Nurse cells provide nutrition to spore mother cells and spores.

Spore Germination

Germination of spores can be direct or indirect.

Direct Germination

Occurs in Liverworts and Hornworts.
Each spore forms a gametophyte after germination (i.e., each spore forms one thallus).

Indirect Germination

Occurs in Mosses.
A multicellular filament is formed after spore germination, known as protonema.
Buds are formed on every cell of the protonema.
Each bud develops into a gametophyte plant.
Indirect germination is best for survival.
Mosses are gregarious in nature (they appear in groups).

Importance of Bryophyta

Sexual reproduction is of the oogamous type.
Life cycle is haplo-diplontic type.
Unique Character: The sporophyte is dependent on the gametophyte (either completely or partially).

🍽️ Ecological and Economic Importance of Bryophyta 🌿

Food: Some moss plants are used as food for herbaceous animals and birds.
Fuel: Sphagnum is used as peat coal.
Packing material: Sphagnum peat has a high water-holding capacity, making it useful as packing material for living material.
Ecological importance:
- Bryophytes play an important role in plant succession on bare rocks/soil (lithosere).
- Moss with lichen are the first colonizers on rocks.
- They decompose rocks to aid the growth of higher plants.
- They prevent soil erosion by forming a mat on the soil.

📊 Classification of Bryophyta

Bryophyta is divided into three classes:

(A) Hepaticopsida (Liverworts)
(B) Anthoceropsida (Hornworts)
(C) Bryopsida or Musci (Mosses)

(A) Hepaticopsida (Liverworts) 🍃

Named Liverworts because all bryophytes in this class have a shape like a liver.
Plant body is thallus-like.
Rhizoids and scales are present on the thallus.
- Rhizoids are unicellular, unbranched.
- Scales are multicellular.
Rhizoids are mostly on the ventral surface, while scales are on the margin and apical notch.
Thallus has two distinct zones: photosynthetic and storage zone.
Asexual reproduction occurs by:
- Fragmentation.
- Specialized structures called gemmae (e.g., in Marchantia).
Gemmae are: ‘8’ shaped, stalked, green, and multicellular asexual buds.
- They develop in small receptacles called gemma cups on the dorsal surface of the thallus.
In Marchantia, specific structures called Archegoniophore (bears archegonia) and Antheridiophore (bears antheridium) are found, on which sex organs are located in groups.
The sporophyte of liverworts is completely dependent on the gametophyte for food, water, and habitat.
The sporophyte is typically made up of foot, seta, and capsule.
- Exception: In Riccia, the sporophyte is made up of only capsule (simplest sporophyte in Bryophytes).
In this class, the formation of spores and nurse cells takes place by the cells of the endothecium.
The cells of the amphithecium form only the wall of the sporophyte.
- Amphithecium = Wall of sporophyte
- Endothecium = Sporogenous cells = Spore mother cells + Nurse cells
Elaters are present in the sporophyte of some members (e.g., Marchantia).
- In Marchantia, nurse cells are modified into elaters.
- Elaters are diploid, hygroscopic structures with spiral thickening bands which help in spore dispersal.
Examples: Riccia, Marchantia, Cryptothallus, Riella, Pellia, Porella (Leafy thallus with two rows of leafy appendages on a stem-like structure).
Note: In Bryophytes, the sporophyte of Riccia is the simplest.

🌿 Anthoceropsida (Hornworts) 🌿

The plant body is thallus-like.
Scales are absent, but rhizoids are present on the ventral surface.
Rhizoids are unicellular and unbranched.
Thallus is undifferentiated (i.e., no photosynthetic and storage zones).
Specific feature: Presence of one chloroplast and one pyrenoid in each cell (an algal character).
The sporophyte is divided into foot and capsule.
In place of a seta, a special meristematic zone is present.
- This meristem’s activity allows the sporophyte to grow rapidly, resembling an animal’s horn (hence, Hornworts).
The sporophyte is not completely dependent on the gametophyte; it is a semiparasite.
- It is photosynthetic (can manufacture its own food).
- It depends on the gametophyte only for water and habitat.
In hornworts, the cells of the amphithecium form the wall of the sporophyte and spores.
The cells of the endothecium form only elaters.
- Amphithecium = Wall of sporophyte and Spores
- Endothecium = Elaters
Since spore-forming cells and elater-forming cells are separate, the elaters are called pseudoelaters.
- Pseudoelaters are structurally and functionally similar to true elaters but do not have thickening bands.
Examples: Notothylus, Anthoceros.
Anthoceros shows algae-like characters:
- Archegonia jacketless.
- Only one chloroplast per cell (characteristic of green algae).
- Presence of pyrenoids (starch storing granule) in the chloroplast (an algal character).
Anthoceros shows ancestral characters, leading to bryophytes also being termed synthetic archaegoniatae.

🌱 Bryopsida or Musci (Mosses) 🌱

All Mosses are included in this class.
The plant body is composed of stem, leaves, and rhizoids.
The Rhizoids are multicellular and branched.
These rhizoids have oblique septa.

💡 Point to be Remembered 💡

The presence of leaves in the gametophyte is a unique character of Moss.
Sex organs are produced at the apex of the leafy shoots of the gametophyte.
The sporophyte of moss is the highly developed in bryophyta, while the sporophyte of liverworts (specifically Riccia) is the simplest.
The sporophyte of mosses is also a semiparasite like that of Hornworts (i.e., it is photosynthetic).
The sporophyte absorbs water from the gametophyte with the help of the foot.
The capsule is the fertile part of the sporophyte (spore formation takes place here).
The foot and seta are the sterile parts of the sporophyte.

🌱 Bryopsida (Mosses) – Continued Features 🌿

Cells of endothecium form spores. (This point seems to be a general reference to sporogenesis, but contextually for Bryopsida, see point 10 below).
In Bryopsida, cells of amphithecium form the wall of the sporophyte.
Elaters and nurse cells are absent in Bryopsida.
- They have advanced methods of spore dispersal from the capsule, such as the annulus, peristomial teeth, and operculum (e.g., in Funaria).
Endothecium develops Spores.

🧬 Evolutionary Note

In Riccia, the sporophyte is made up of only capsule (i.e., the whole sporophyte is fertile).
During evolution, there occurred gradual sterilization of the sporophyte: a gradual reduction of the fertile part (spore-producing) and gradual development of the sterile part (foot, seta, capsule wall).
Evolutionary Series (Increasing Complexity/Sterilization):

Riccia→Marchantia→Porella→Anthoceros→Sphagnum→Funaria→Polytrichum

📝 Common Names of Bryophytes

Funaria: Rope moss or Cord moss
Andria: Granite moss
Polytrichum: Hair cap moss
Fontinalis: Brook moss
Dawsonia: Australian moss
- The highest bryophyte (grows up to 5 cm).
Buxbaumia: Saprophytic moss (Photosynthesis absent).

💧 Sphagnum (Sphagnum Moss)

This bryophyte has several descriptive masses/uses:

Bog mass: Likes to grow on acidic bog (Quaking bog).
Peat moss: A fossil fuel obtained from the bog.
- Peat formation takes place by the fossilization of Sphagnum.
- Sphagnum grows in acidic bog, where the low number of bacteria prevents the complete degradation of dead cells. Hence, it remains in the form of a fossil (peat).
Absorbent cotton: Sphagnum can absorb a very high amount of water.
- Used as a form of absorbent cotton in Europe (e.g., used during World War).
Carpet moss or Turf moss: It spreads like a carpet on a bog, making the underlying swamp difficult to see.

Practice Questions

Q1. Assertion (A): Bryophytes are called amphibians of the plant kingdom.
Reason (R): Water is essential for the fertilization process in bryophytes.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Answer: (a)

Q2. Assertion (A): In bryophytes, the dominant phase is sporophyte.
Reason (R): The sporophyte is free-living and independent.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Answer: (d) (Gametophyte is dominant; sporophyte is dependent on gametophyte)

Q3. Assertion (A): Marchantia reproduces asexually by gemmae.
Reason (R): Gemmae are multicellular, green, asexual reproductive bodies that develop inside gemma cups.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Answer: (a)

Q4. Assertion (A): Anthoceros sporophyte has a columella.
Reason (R): The presence of columella is a feature common between Anthocerotopsida and mosses.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Answer: (a)

Q5. Assertion (A): Funaria shows alternation of generations.
Reason (R): Gametophyte is haploid, sporophyte is diploid.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Answer: (a)

Q6. Assertion (A): In Sphagnum, peat is formed.
Reason (R): Dead remains of Sphagnum accumulate in bogs and get compressed into peat.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Answer: (a)

Q7. Assertion (A): Liverwort sporophyte is more elaborate than moss sporophyte.
Reason (R): Moss sporophyte has foot, seta and capsule, while liverwort sporophyte lacks differentiation.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Answer: (d) (Moss sporophyte is more elaborate)

Q8. Assertion (A): Bryophyte sporophyte is parasitic on gametophyte.
Reason (R): Sporophyte depends on gametophyte for anchorage, nourishment and water.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Answer: (a)

Q9. Assertion (A): Elaters help in spore dispersal in Marchantia.
Reason (R): Elaters are hygroscopic structures associated with the capsule wall.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Answer: (a)

Q10. Assertion (A): Protonema is the first stage of gametophyte in mosses.
Reason (R): Protonema develops from the spore and is filamentous, green and branched.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not the correct explanation of A
(c) A is true but R is false
(d) A is false but R is true
Answer: (a)

Q11. Which of the following statements about bryophytes are correct?
I. They are the first land plants.
II. They lack vascular tissues.
III. They show embryo development inside archegonium.
IV. Sporophyte is independent of gametophyte.