Introduction of Bryophytes

Nonvascular plants, called bryophytes, don’t have xylem and phloem. These plants have a wide range of habitats, from bare rocks under the scorching sun to frozen alpine slopes. These include mosses and liverworts, as well as hornworts. These plants need external water, often in the form dew or rain. They prefer to grow in damp, dark environments that provide moisture. Reproductive activities require water. Most mosses have water-conducting cells, called hydroids, in the stems. Some even have food-conducting cells, called leptoids. These cells aren’t as efficient as xylem or phloem, and bryophytes tend to be shorter than xylem. Plants are very soft and flexible due to the lack of vascular tissues.

The alternation of generations in nonvascular plants is represented by the gametophyte, which is the visible form of the sporophyte. The tips of the sporophyte-producing gametophyte generations are where the sporophyte generation produces spores. The sporophyte is a long, thin stalk with a cap at the top. Although all bryophytes have similar life cycles, and their chromosome numbers and habituation are similar, they are classified into three distinct groups according to the differences in their structure and reproduction.

Bryophytes definition

Bryophytes plants are plants that can be found growing in damp and shaded areas. These plants are unique because they can live on soil and bare rocks. They are an integral part of plant succession on bare rock. They exhibit alternation of generations and are known by a unique name. They are known as the amphibians in the plant kingdom. They can only reproduce in a terrestrial environment.

Why are bryophytes called amphibians of plants?

Bryophytes, also known as “amphibians in the plant kingdom”, are terrestrial plants that require water to complete the life cycle.

Characteristics of bryophytes

• The bryophyte plant body is gametophyte. It is not divided into root, stem or leaf-like structures.
• They are mostly primitive land dwellers. Some are aquatic (Riella and Ricciocarpus).
• The gametophyte, a prominent and long-lasting phase of the life cycle, is conspicuous. Hornworts and liverworts have thalloid forms. The Mosses have leaf-like, stem-like structures. Liverworts thallus is a plant that grows on the ground, and is attached to the substratum via rhizoids. There are two types of rhizoids: smooth walled or pegged. Multicellular scales can also be found. Moss has a plant body that is upright with a central axis and leaf-like expansions. There are multicellular rhizoids.
• Vascular tissue such as xylem or phloem is absent completely, thus the ‘Non-vascular cryptogams’.
• In Anthoceros, vegetative reproduction is achieved by the formation and maintenance of adventitious buds (Ricciafluitans). Tubers are formed from these buds. Some forms form small, detachable brood bodies or branches. They aid in vegetative reproduction like in Bryopteris. Gemmae, which are Marchantia’s propagative organs, aid in reproduction.
• Oogamous reproduction is a form of sexual reproduction. Antheridia, Archegonia and other multicellular organisms are protected by a protective cover.
• Antheridia produces biflagellate Antherozoids, which swim in thin water films and reach the archegonium to fuse with the egg and form diploid zygote.
• Fertilization requires water.
• The zygote, the first cell in the sporophyte-generation, is the first. It undergoes mitotic differentiation to create a multicellular, undifferentiated embryo. Exoscopic embryogeny (the embryogeny of an embryo is when the first division of the Zygote is transverse, and the embryo’s apex develops from the outer cells) The embryo divides, giving rise to sporophyte.
• Gametophyte is the only thing that can sustain the sporophyte.
• It can be divided into three distinct parts: seta, foot, and capsule. The basal portion of the foot is found in the gametophyte. It supplies water and nutrients to the sporophyte. The meiotic division of diploid spore mother cell cells in the capsule region results in haploidspores. Homosporous Bryophytes can be found. Some sporophytes have elaters that help disperse spores. The spores germinate and produce gametophyte.
• The sporophytic phase is made up of the embryo, zygote and sporogonium. Gametophytic phase refers to the green, long-living haploid phase. It alternates with diploid sporophyte.

Classification Of Bryophytes

The latest classification of Bryophyta divides it into three classes.

1. Hepaticopsida (Liverworts)
2. Anthocerotopsida (Hornworts)
3. Bryopsida (Mosses)

1. Hepaticopsida (Liverworts)

These are the lower forms of Bryophytes. They are simpler in structure than mosses, and they prefer to be found in damp and shaded areas. They possess an undifferentiated, thallus. The protonernal stage of the thallus is absent. Sporophyte can be very short-lived and is quite simple. Some people have no seta or foot. Example Riccia.

Order of Hepaticopsida (Liverworts)

Hepaticopsida can be further divided into four orders:

• Marchantiales (e.g. Riccia, Marchantia)
• Sphaerocarpales (e.g. Sphaerocarpos)
• Calobryales (e.g. Calobryum)
• Jungermanniales (e.g. Pellia)

Characteristics of Hepaticopsida (Liverworts)

The following are the main characteristics of the hepaticopsida class:

• The gametophyte plant can be either thalloid- or foliose.
• Foliose leaves have no midrib or dorsiventral.
• Thalloid is dorsiventral and lobed, with dichotomously branching.
• Many chloroplasts are found in each cell of the thallus, but none contain pyrenoids.
• Rhizoids can be unicellular, branched or aseptate.
• In gametophytic tissues, sex organs are dorsally embedded.
• Only capsule (in Riccia), or foot, seta, and capsule (in Marchantia), make up the sporophyte
• The capsule does not contain the columella
• Endothecium is the source of sporogenous tissue.

Reproduction of Hepaticopsida (Liverworts)

• Asexual reproduction: Asexual reproduction is achieved by either fragmentation or the formation of gemmae. Gemma cups contain gemma. Gemmae are multicellular, green-colored asexual buds. After being detached from its parent, the gemma cup becomes a new plant.
• Sexual reproduction: Antheridium (male) and archegonium may both be present on different thalli. They each produce sperm or eggs. The zygote is created after fertilization. After the zygote is formed, it becomes a diploid Sporophyte. A few cells of this sporophyte undergo meiosis in order to produce haploidspores. These spores become haploid gametophytes which are free-living, photosynthetic and photosynthesisable.

2. Anthocerotopsida (Hornworts)

This class contains around 300 species. They are also known as hornworts.

Order of Anthocerotopsida (Hornworts)

It only has one order, namely.

• Anthocerotales. Examples: Anthoceros, Megaceros, Notothylas.

Characteristics of Anthocerotopsida (Hornworts)

• The gametophytic body of the Anthocerotopsida is a flat, dorsiventral, simple, thalloid with no internal differentiation
• Rhizoids have smooth-walled walls
• Each cell contains one chloroplast that is equipped with a pyrenoid.
• The thallus contains dorsally embedded sexual organs
• The sporophyte can be divided into capsule, meristematic area and foot
• Amphithecium is the source of sporogenous tissue.
• The capsule contains pseudoelaters
• The capsule contains the columella, which is derived from endothecium.

Reproduction of Anthocerotopsida (Hornworts)

• Asexual reproduction: Vegetative reproduction is achieved by the fragmentation of the thallus or by tubers that are formed under unfavorable conditions.
• Sexual reproduction: They reproduce by way of waterborne sperm which travels from antheridium into archegonium. The sporophyte is formed from a fertilized egg. The sporophyte splits in half lengthwise to release the spores that turn into a gametophyte.

3. Bryopsida (Mosses)

This is the largest group of Bryophyta, with approximately 1400 species. They are also known as mosses. Examples: Funaria, Polytrichum, Sphagnum.

Order of Bryopsida (Mosses)

Bryopsida can be further divided into five orders:

• Bryales
• Andreales
• Sphagnales
• Polytrichales
• Buxbaumiales

Characteristics of Bryopsida (Mosses)

• The gametophyte can be divided into protonema or foliose.
• Foliose is composed of stem and leaves with no midrib.
• Rhizoids have multicellular structures and an oblique septa.
• The stem bears the sexual organs
• Absent are the Elaters
• The sporophyte can be divided into seta, foot and capsule.
• Endothecium is the source of sporogenous tissue.
• Columella is available
• The lid is removed to dehisce the capsule

Reproduction of Bryopsida (Mosses)

• Asexual reproduction: This is the budding and fragmentation secondary protonemas.
• Sexual reproduction: Antheridia, archegonia and spermatozoa are found at the apical portion of leafy shoots. Sporophyte, which is more distinct than liverworts, is produced after fertilization. The spores are what form the gametophyte.

Characteristics of the gametophytes of the three groups of bryophytes

	Liverworts	Mosses	Hornworts
Structure	Thalloid or foliose	Foliose	Thalloid
Symmetry	Dorsiventral or radial	Radial	Dorsiventral
Rhizoids	Unicellular	Pluricellular	Unicellular
Chloroplasts/cell	Many	Many	One
Protonemata	Reduced	Present	Absent
Gametangia (antheridia and archegonia)	Superficial	Superficial	Immersed

Characteristics of the sporophytes of the three groups of bryophytes

	Liverworts	Mosses	Hornworts
Stomata	Absent	Present	Present
Structure	Small, without chlorophyll	Large, with chlorophyll	Large, with chlorophyll
Persistence	Ephemeral	Persistent	Persistent
Growth	Defined	Defined	Continuous
Seta	Present	Present	Absent
Capsule form	Simple	Differentiated (operculum, peristome)	Elongated
Maturation of spores	Simultaneous	Simultaneous	Gradual
Dispersion of spores	Elaters	Peristome teeth	Pseudo-elaters
Columella	Absent	Present	Present
Dehiscence	Longitudinal or irregular	Transverse	Longitudinal

Bryophytes reproduction/Life Cycle of Bryophytes

The reproduction of a bryophyte is both sexual and asexual. Asexual reproduction occurs via fragmentation or gemmae formation. Their sexual reproduction is done via two types of spores, archaegonia and anthrezoids.

A. Asexual Reproduction of Bryophytes

Bryophytes may only experience asexual reproduction, or they might not be able to fertilize because of loss of functional sexuality.

• Vegetative reproduction: Gemmae, which are easily dispersed reproductive structures that allow for vegetative reproduction, are used. Gemmae can be a single or a cluster of cells with undifferentiated growth. When a gemma separates from its parent plant, it can form a new vegetative structure.
• Fragmentation: Bryophytes can also reproduce via fragmentation, which is another method of asexual reproduction. Water, wind, and animal movement are key factors in the spore dispersal process and fragmentation.

B. Sexual Reproduction of Bryophytes

It is divided into two phases, which are described below.

1. Gametophyte Stage

This stage occurs when bryophytes’ dormantspores form a germ tube. The protonema is a green, filiform compound that spores develop. After several maturation stages, the protonema develops rhizoids, and then aerial filaments.

The cells are stimulated by red light and kinetin, which promotes the growth of shoots. These shoots then enlarge and transform into mature gametophytes. Gametophytes then develop a specialized reproductive system (gametangia), which is located at the top of the main shoot and holds the gametes (eggs) and sperms.

The male and female gametangiums (antheridium and archegonium) are separated by the leafy gametophyte. The male archegonium contains one egg or archaegonia and the male antheridia are produced from the upper branches.

Anthrezoids from the male gametangiums of different plants are lowered to the archaegonium by water droplets before fertilization. A bryophyte gametangia are protected by a non-reproductive layer. This is an unusual feature that is not present in algal gametangia.

2. Sporophyte Stage

It starts with the fusion between a biflagellate and an archegonium sperm. The process is known as fertilization.

A biflagellate’s sperm is transported to the archegonium by a water film on the plant’s surface. After repeated mitotic divisions, a diploid zygote within the archegonium becomes a multicellular diploid embryo. The gametophyte provides nutrients such as sugars and minerals to an embryonic sporophyte.

A sporophyte embryonic differentiates into three distinct structures: foot, stalk, or capsule. The young sporophyte’s base is the foot. The stalk is a thin filament that attaches the sporangium to the foot cell.

A spore capsule is a tightly sealed cap (calyptra), which contains a layer of sterile protection cells surrounding an embryonic sporophyte at one end of the foot. The spore capsule contains a sporangium pouch that houses the heterospores. These are sexual dispersal units. To form spores (haploid), meiotic cells divide the spore-producing cells.

The foot cell absorbs the nutrients from the gametophyte, and then conducts them to spores via a seta or long stalk. A spore capsule is composed of a layer consisting of sterile cells as well as a layer that absorbs water from the surrounding.

Hydrogroscopic movement within the spore capsule causes the spores to flicker upward and outward. The spore capsule can burst when the spores reach maturity. As dormantspores, spores can move freely in their environment. Once the protonema germinates from a dormantspore, bryophytes continue their life cycle.

Bryophytes examples

Around 20,000 species of plants make up the Bryophytes. The three main categories of bryophytes can be categorized as liverworts, moses, and hornworts. These are some of the most common examples:

• Liverworts Examples:
  • Marchantia
  • Riccia
  • Pellia
  • Porella
  • Sphaerocarpos
  • Calobryum
• Mosses Examples:
  • Funaria
  • Polytrichum
  • sphagnum
• Hornworts Examples:
  • Anthoceros
  • Notothylas
  • Megaceros

Ecological Importance of Bryophytes

• They make the rock more suitable for higher plant growth. Soil formation is made possible by the acid secreted from lichens and the death and decay of mosses.
• Bryophytes are densely cultivated and act as soil binders
• Bog succession is a key role played by mosses. The landscape can be transformed from open soil to climax forests by the addition of mosses. Because of the presence of water, humus and mosses, the thick mat of mosses provides a suitable substrate for hydrophilic seed germination. The mesophytic process begins when the hydrophilic plants and dead mosses become a solid soil.
• They reduce the impact of falling rain on soil and prevent it from causing soil erosion
• Their water holding capacity reduces run-off water
• They aid in the recycling of nutrients
• They are a rock-builder. Some mosses (Bryum), along with alga, form limestone-like deposits around plants that are found in shallow calcium bicarbonate rich water or lakes. The plants produce insoluble calcium carbonate by decomposing bicarbonate ions. The mineral deposit covers several hundred square feet and continues to grow.

Importance of Bryophytes

1. Medicinal uses:

• Because of its high absorptive powers and antiseptic properties, sphagnum is often used in surgical dressings. It can be used to replace cotton bandages for treating boils or discharging wounds.
• Marchantia has been used for the treatment of pulmonary tuberculosis, liver affliction and other ailments.
• In the treatment of eye infections and acute hemorhage, dried sphagnum can be used to make a decoction.
• Peat-tar, which is an antiseptic, can be used as a preservative. Skin disease is treated with Sphagnol (a peat-tar distillate).
• The gall bladder and kidney stones can be removed by polytrichium species
• Certain bryophytes with antibiotic properties can be extracted with antibiotic substances.

2. Peat formation

Peat moss is another name for sphagnum. Slowing down the process of decaying creates peat. Peat is a dark-colored substance that results from the gradual compression and carbonization of partially decomposed vegetative material in bogs.

• It’s used to fuel vehicles
• Lower layers of peat make coal.
• Also, peat is used to produce ethyl alcohol and ammonium sulfurate, ammonia, dyes, paraffin, and tannins, among other things.
• It improves the soil texture in horticulture.

3. In research

Research in genetics uses liverworts and mosses. Liverworts are the key to understanding how plants determine sex.

4. Packing material

Dry mosses are a great packing material for fragile goods such as glassware and bulbs. Transshipment of cuttings or seedlings, as they are water-retentive.

5. Food

Some mosses are food for birds, herbaceous mammals and other mammals.

6. As Indicator plants

Bryophytes can be found in specific areas and used to indicate acidity or basicity of the soil. E.g. Polytrichum indicated the acidity of the soil, Tortella species grow well in the soil rich in lime or other bases and occur as calcicoles

7. In seedbeds

It is widely used for its water retention and in nurseries, seedbeds, nursery, and root cuttings. Sphagnum can also be used to maintain the high soil acidity needed by certain plants.

8. Formation of stone

Travertine rocks are widely used as a building material.

What are the Similarities between Bryophytes, algae, and vascular plants?

All vascular plants, green algae, and bryophytes have chlorophyll A and B. The chloroplast structures of all three are very similar. Bryophytes, like land plants and green algae, also produce starch in the plastids. They also contain cellulose in their walls. Different adaptations in bryophytes allow plants to colonize Earth’s terrestrial environment. A waxy cuticle may cover the soft tissues of plants to prevent them from becoming dry in terrestrial environments. Stomata in hornworts or mosses provide gas exchange between the atmosphere, and an internal intercellular space. Gametangia was created to provide additional protection for the gametes, the zygote, and the developing sporophyte. Bryophytes, vascular plants (embryophytes), also exhibit embryonic development that isn’t seen in green alga. Although bryophytes don’t have vascularized tissue, their organs are specialized to perform specific functions. This is similar to the functions of stems and leaves in vascular land plants.

Water is essential for bryophytes’ survival and reproduction. A thin layer of water on the plant’s surface is necessary, as with ferns or lycophytes. This allows for the movement of flagellated sperm among gametophytes and fertilization of an eggs.

FAQ

Q1. when do bryophytes (including mosses, liverworts and hornworts) first appear in the fossil record?

The first bryophytes (liverworts) probably appeared in the Ordovician period, about 450 million years ago. However, because they lack of lignin and other resistant structures, bryophyte fossil formation is improbable and the fossil record is poor.

Q2. mosses are classified as bryophytes. which best describes mosses?

• Mosses are seedless plants.
• Mosses bear fruit and flowers. 
• Mosses bear flowers, but no fruit. 
• Mosses have one cotyledon in a seed.

ANS: Mosses are seedless plants.

Q3. which of these statements is true of bryophytes

• A. In bryophytes , zygote dose not undergo reduction division immediately.
• B. Leafy members having leaf-like appendages in two rows on the stem-like structures are not observed in liverworts .
• C. Leafy stage of mosses develops from the primary protonema as a lateral bud .
• D. The sporophyte of mosses is less elaborate than that of liverworts .

Ans: A. In bryophytes , zygote dose not undergo reduction division immediately.

Q4. which of the following is true of the life cycle of bryophytes?

1. Dominant, diploid , multicellular sporophyte alters dominant with multicellular gametophytes.
2. Dominant , haploid multicellular gametophyte Which alternates with diploid sporophyte .
3. The plant body shows diplomatic life cycle.
4. The plant body shows haplontic life cycle .

Ans: Dominant , haploid multicellular gametophyte Which alternates with diploid sporophyte .

Q5. oak trees are an example of what group? ferns bryophytes gymnosperms angiosperms

Oaks, maples and dogwoods are examples of deciduous trees. Some angiosperms that hold their leaves include rhododendron, live oak, and sweetbay magnolia.

Q6. when did bryophytes first appear?

The first bryophytes (liverworts) most likely appeared in the Ordovician period, about 450 million years ago. Because of the lack of lignin and other resistant structures, the likelihood of bryophytes forming fossils is rather small.

Q7. how are water and nutrients transported through bryophytes?

The members of Bryophytes are nonvascular plants. They carry out the transport of water and nutrients via diffusion process. Lack of vascular tissues, the members of Bryophytes absorb water and nutrients at the surface and transport the materials from cell to cell.

Q8. why are bryophytes considered incompletely liberated from their ancestral aquatic habitat?

Grow at moist places and require moisture for reproduction.

Explanation:

• The bryophytes are the amphibians of the plant Kingdom. They grow at the most places and compulsorly require water or moisture for the fertilisation.
• The motile male gametes move to the destination by the help of flagella, simiilar to the quatic plants.
• So, it is considered that the Bryophtes have not completely relieved from the aquatic nature of their ancestors. Thank You

Q9. how are gametes produced by bryophytes?

The gametes of bryophytes are produced by Meiosis process.

Q10. how old are bryophytes?

Bryophytes are the oldest lineage of all land plants and are believed to be the closest remaining link between land and aquatic plants. Their soft tissue makes fossil records bleak but the oldest evidence that has so far been found can be dated back to almost 500 million years ago.

Q11. how are the bryophytes and seedless vascular plants alike?

Both bryophtes (the mosses) and seedless vascular plants (mostly ferns) rely on water fertilization, do not have complex xylem and phloem, do not have complex gametophytes, and simple root like systems instead of the roots you see in other vascular groups.

Q12. how many species of bryophytes are there?

There are around 20,000 species of Bryophytes.

Q13. what is the significance of sporopollenin in bryophytes?

Sporopollenin is one of the most inert biological polymers. It is the outer covering or protective wall of plants and pollen grains. Now, example of bryophytes are mosses, hornworts, and liverworts. As they do not have vascular tissues, sporopollenin serves as their protection.

Q14. what are bryophytes?

Bryophytes are a group of plant species that reproduce via spores rather than flowers or seeds. Most bryophytes are found in damp environments and consist of three types of non-vascular land plants: the mosses, hornworts, and liverworts.

Q15. bryophytes are known as nonvascular plants. what makes them nonvascular?

Bryophytes are members of embryophytes (land plants). They are non-vascular plants that do not have vascular tissues (xylem and phloem) for the conduction of food, water and minerals, even if present in some, they are not well-developed. They are cryptograms as their reproductive structures are hidden, seeds are absent.

Q16. why are bryophytes small?

Bryophytes are small because they lack vascular tissue and depend on water as a medium for their sperm transfer.

Q17. which of the following characteristics is common to bryophytes and to seedless vascular plants?

Both bryophtes (the mosses) and seedless vascular plants (mostly ferns) rely on water fertilization, do not have complex xylem and phloem, do not have complex gametophytes, and simple root like systems instead of the roots you see in other vascular groups.

Q18. when did bryophytes evolve?

Between 510 – 630 million years ago, however, land plants evolved from aquatic plants, specifically green algae. Molecular phylogenetic studies conclude that bryophytes are the earliest diverging lineages of the extant land plants.

Q19. which of the following structures represents the sporophyte stage of the bryophytes?

A. protonema

B. antheridia

C. capsule

Ans: C. capsule

Q20. the aquatic ancestry of bryophytes is most clearly demonstrated by what character?

The aquatic ancestry of bridal fights is most clearly demonstrated by the use of flagellating motile sperm.

Q21. where does meiosis take place in bryophytes?

Meiosis takes place in the tiny sprorophyte stage of bryophytes, which are attached to and dependent on the much larger gametophyte stage. The sporophytes create spores by meiosis, which disperse by wind and water to form new gametophytes. Fertilized eggs in gametophytes form sporophytes at the site of fertilization.

Q22. what is one evolutionary advantage pteridophytes have over bryophytes?

Pteridophytes have a vascular system, unlike bryophytes. Tissue cells are joined into tubes that transport water and nutrients through the plant body. This system is beneficial to the pteridophytes by easily enabling them to transport the necessary nutrients.

Q23. which group name translates as “naked seeds”? gymnosperm angiosperm mushrooms bryophytes?

Gymnosperms. Gymnosperms are plants with naked seeds. There are about 650 living species of gymnosperm plants.

Q24. how is the mechanism for spore dispersal in ferns similar to that of bryophytes?

Moisture causes changes in cell (elater or annulus) shape to release spores.

Q25. How are ferns more advanced than bryophytes?

Because ferns and fern allies posses true vascular tissues, they can grow to be much larger and thicker than the bryophytes.

Q26. how is the reproduction of bryophytes similar to that of ferns?

They’re Both Nonflowering Plants

To reproduce sexually, mosses and ferns produce sperm and eggs. The motile sperm must be able to swim through water to reach and fertilize the eggs, which is why most mosses and ferns live in damp habitats.

Q27. in bryophytes, how does the sperm reach the egg?

Bryophytes also need a moist environment to reproduce. Their flagellated sperm must swim through water to reach the egg. So mosses and liverworts are restricted to moist habitats.

Q28. where are bryophytes found?

Bryophytes are regarded as transitional between aquatic plants like algae and higher land plants like trees. They are extremely dependent upon water for their survival and reproduction and are therefore typically found in moist areas like creeks and forests.

Q29. why must bryophytes live in moist environments?

Bryophytes also need a moist environment to reproduce. Their flagellated sperm must swim through water to reach the egg. So mosses and liverworts are restricted to moist habitats.

Q30. how are bryophytes and seedless vascular plants alike?

Both bryophtes (the mosses) and seedless vascular plants (mostly ferns) rely on water fertilization, do not have complex xylem and phloem, do not have complex gametophytes, and simple root like systems instead of the roots you see in other vascular groups.

References

• https://biologyreader.com/life-cycle-of-bryophytes.html
• https://byjus.com/neet/classification-of-bryophytes/
• https://www.toppr.com/guides/biology/plant-kingdom/bryophytes/
• https://www.plantscience4u.com/2014/01/characteristics-of-bryophytes.html
• https://en.wikipedia.org/wiki/Bryophyte