Bryophyta – Definition, Classification & Characteristics

Bryophyta, the division of green plants, refers to embryophytes, which are terrestrial plants, particularly non-vascular ones. Bryophyta has a relatively basic structure and is made up of individuals that are often shorter than 20 cm. Bryophyta lack roots, however, they do contain rhizoids, which are long cells or cell filaments that adhere to the substrate.

Many bryophytes have a leaf-like structure composed of a few cell layers through which they do photosynthesis. Because they lack roots to absorb water, they must obtain it from aerial structures, which is why they prefer moist and gloomy environments, such as marshes. Because bryophyte vascular tissue is not separated into xylem and phloem, liquids pass via core elongated cells. The main generation of bryophytes is made up of haploid gametophytes. Antheridia, which generate male germinal cells, and archegonia, which create egg cells, grow on the top of some of the leaflets. The male gamete floats in the water droplets, propelled by two flagella. The sporophyte develops on the gametophyte, and meiosis occurs in the capsule of a mature sporophyte. When the capsule opens, a ring of teeth surrounds it. When the atmosphere is dry, the teeth stay bent towards the newly created spores.

Define Bryophyta

Bryophyta is non-vascular plants consisting of three divisions, namely the mosses, liverworts, and hornworts. They are seedless plants and do not produce flowers or seeds, and true roots are also not present in these plants.

Bryophyta originated from two Greek words “Bryon” which means leaf and “Phyton”which means plant body.

What are the Main Characteristics of Bryophytes?

The Bryophyta shows the following characteristics:

Habitat and Habit

They are terrestrial, but they grow in moist and shady places. Few are truly aquatic and underwater. Example: Riccia fluitans. They also grow in marshy areas example: Sphagnum moss. Some bryophytes are also found in the desert and dry environment like Tortula desortorum.

Plant Body

The main plant body is gametophytic and haploid. It is differentiated into root-like rhizomes, leaf-like appendages, and short stem-like erect structure in mosses (Bryopsida).

Vascular Tissue

Bryophytes are non-vascular plants, and they lack specialized tissues for the transportation of water and dissolved food. Instead, the substances can move through the plant body by osmosis and diffusion from surface moisture.

Reproduction

Reproduction in Bryophyta is mainly Vegetative, Asexual, and Sexual.

A. Vegetative reproduction takes place by:
a. Death and decay of older parts.
b. Adventitious branches.
c. Formation of the tuber.

B. Asexual reproduction in bryophytes:
a. Fragmentation of thallus. 
b. Formation of gemmae inside Gemma cups.      

C. Sexual reproduction in bryophytes:
a. Sexual reproduction is an oogamous type.
b. The sporophytes (diploid generations) are partially parasitic on the gametophytes.
c. Sporophytes are more elaborated in mosses (Bryopsida) than liverworts (Hepaticopsida).
d. They have multicellular sex organs in their gametophytes.
e. Sex organs have a sterile jacket layer outside.
f. Male sex organ is called antheridium, and the female sex organ is called archegonium.
g. Antheridium has a surrounding sterile jacket layer. The sperm mother cell or antherozoid mother cell is at the center.
h. Antherozoids are bi-flagellated and motile. They swim to reach the egg cell.
i. Archegonium also has a surrounding sterile jacket layer and is flask-shaped. There is a tubular neck and a swollen venter. Venter has ventral canal cells and a central egg. The neck encloses sterile neck canal cells.
j. Egg cells are non-motile and much larger.
k. Water is essential for fertilization.
l. Fertilization forms zygote inside archegonium.
m. Zygote undergoes mitosis and forms diploid sporophytic generation.
n. Sporophyte has a foot, seta, anda capsule.
o. Foot and seta are much reduced in liverworts and elaborated in mosses.
p. Capsule bears the spore mother cells.
q. Meiosis takes place in spore mother cells and forms haploid spores. This is called Sporic meiosis.
r. All Bryophytes are homosporous.
s. Spores are dispersed by wind.
t. In certain mosses, like Funaria, spores on germination form juvenile gametophyte or the protonema.
u. Protonema shows buds and can propagate via fragmentation.
v. Protonema matures into adult moss.

Fig: Female and Male Thallus of Marchantia

Bryophyta Classification

The Bryophyta are classified into three classes: Hepaticopsida (Liverworts), Anthocerotopsida (Hornworts), Bryopsida (Mosses).

Fig: Flowchart of Classification of Bryophyta

Hepaticopsida (Liverworts)

a. The vegetative plant body of gametophyte is usually dorsiventral and is either thalloid or less commonly foliose.
b. Septa is absent in rhizoids.
c. The sporophyte is parasitic on the gametophyte. Seta is absent in Riccia.
d. Sex organs are dorsally present in gametophytic tissue and are produced from a single superficial cell.
e. Reproduction takes place by sexual and asexual methods.
f. Marchantia produces specialized structures, called gemma, for asexual reproduction.
g. Examples: Riccia, Marchantia, Pellia, Porella, etc.

Anthocerotopsida (Hornworts)

a. The gametophyte is flat, dorsiventral, lobed, thalloid.
b. Smooth walled rhizoids are present.
c. One Large chloroplast with central pyrenoid is present in each cell.
d. Reproduction takes place by vegetative and sexual methods.
e. Examples: Anthoceros, Megaceros, Notothylas, etc.

Bryopsida (Mosses)

a. Thegametophytic plant body is differentiated into prostrate protonema and erect leafy gametophore.
b. Multicellular rhizoids with oblique septa are present.
c. The sporophytic plant body is divided into foot, seta, and capsule.
d. Sex organs are present apically on the stem.
e. Reproduction takes place by asexual and sexual methods. 
f. Examples: Funaria, Polytrichum, Sphagnum, etc.

Bryophyta Life Cycle

1. The bryophyta shows an alternation of two morphologically distinct phases: the haploid gametophytic phase and the diploid sporophytic phase.
2. The gametophytic phase in bryophytes is dominant, independent, photosynthetic, and haploid.
3. The gametophyte carries gametes.
4. The last phase of gametophytic generation is represented by male and female gametes.
5. Haploid male and female gametes unite to form a diploid zygote(2n).
6. The diploid zygote represents the first phase of sporophytic generation.
7. Sporophyte is totally or partially dependent on the gametophyte for nutrition.
8. Sporogenous tissue is divided meiotically to form haploid spores.
9. Haploid gametophyte is produced by the germination of spores.
10. Bryophyta shows a haplo-diplontic life cycle.

Fig: Life Cycle in Bryophyta

What are the Examples of Bryophyta?

The examples of Bryophyta are:

1. Polytrichum
2. Funaria
3. Sphagnum
4. Marchantia
5. Anthoceros
6. Riccia

Fig: Examples of Bryophyta

Importance of Bryophyta

The importance of Bryophyta is:

1. It prevents soil erosion along the streams by holding water.
2. Decaying of death mosses help in soil conditioning.
3. Few mosses in association with green algae perform as rock builders. 
4. Peat mosses make the soil of banks solid ground, which helps in vegetation, e.g., Sphagnum.
5. Dried mosses are used as packing material.
6. They are used as preservative agents to absorb moisture, which helps preserve food and dead bodies.
7. In industrial use, peat mosses are used to make moss carpets, coir pots, hanging wire baskets.
8. Bryophyta has medicinal use. Examples: Marchantia, Polymorpha, Riccia, Anthoceros.
9. Food for many animals.

Bryophyta Affinities

Affinity with Thallophyta

a. Presence of filamentous protonema in Funaria.
b. Predominant gametophytic generation.

Affinity with Pteridophyta

a. Presence of multicellular antheridia and archegonia.
b. Biflagellated motile sperms.
c. Sporic meiosis and haplo-diplontic life cycle.

Difference Between Bryophyta and Thallophyta

The difference between Bryophyte and Thallophyta are:

Summary

Bryophyta are the ‘amphibian plants’ which form a small group. They are non-vascular plants, and the body is differentiated into root-like, stem-like and leaf-like structures. They are haploid and show alternation of generations in which the diploid phase is short and parasitic to the haploid generation. They grow in a moist and shady environment. Some mosses, like Sphagnum,are extremely important for packaging, fuel, etc.

Frequently Asked Questions on Bryophyta (FAQs) on Bryophyta

Q.1. Give two differences between Bryophyta and Thallophyta.
Ans: The two differences between Bryophyta and Thallophyta are:

Q.2. What are \(3\) types of Bryophytes?
Ans: The \(3\) types of Bryophytes are Liverworts, Hornworts and Mosses.

Q.3. What are the main characteristics of Bryophytes?
Ans:
1. The main plant body is gametophytic and haploid. It is differentiated into root-like rhizomes, leaf-like appendages, and short stem-like erect structure in mosses (Bryopsida). In liverworts, they may be dorsiventrally flattened.
2. The sporophytic generation is partially parasitic on the gametophyte.

Q.4. What type of sporophyte is found in Bryophytes?
Ans: The sporophyte is the diploid generation in the life cycle of bryophytes. This is partially parasitic on the gametophytes. This is represented by a foot, seta and a capsule. This is much elaborated in mosses as compared to liverworts.

Q.5. Do Bryophytes have swimming sperms?
Ans: Yes, bryophytes have swimming sperms.

Q.6. What is peat?
Ans: Sphagnum grows in acidic marshes. The old dead bodies are carbonised to form peat. Peat is dried, compressed and cut out into blocks that are used as fuel, manure.

Q.7. Where are Bryophytes found?
Ans: Bryophytes can be found in moist and shady places. Few are truly aquatic and underwater examples: Riccia fluitans. They also grow in marshy areas, for example, Sphagnum moss. Some bryophytes are also found in the desert and dry environments like Tortula desortorum.