Pteridophyta: Definition, Life Cycle, Classification, Characteristics and Example

Pteridophyta Overview 

Pteridophyta, also known as ferns and their allies, are an ancient group of vascular plants that dominated the Earth's flora during the Carboniferous period. With over 12,000 species, they exhibit a wide range of sizes and morphologies, from tiny epiphytes to tree ferns that reach 20 meters in height. In this article, we will explore the characteristics, classification, and importance of Pteridophytes.

What are Pteridophyta

Pteridophytes were the first terrestrial vascular plants. Carolus Linnaeus classified them as cryptogamae. Pteridophytes are between bryophytes and spermatophytes. They do not produce flowers or seeds, so they are also known as Cryptogams. There are over 12,000 Pteridophyte species on the planet. Pteridophytes is derived from the Greek words pteron, which means "feather," and python, which means "plants." 

Characteristics of Pteridophyta

Pteridophyta, also known as ferns, are a group of plants that are characterized by their unique features. Here are some of the main characteristics of Pteridophyta:

1. Vascular plants: Pteridophyta are vascular plants, meaning they have specialized tissues that transport water, nutrients, and other materials throughout the plant.
2. Sporophyte dominant: The fern life cycle is dominated by the sporophyte stage, which is the diploid phase of the plant's life cycle.
3. Alternation of generations: Pteridophyta exhibit an alternation of generations life cycle, meaning they alternate between a haploid gametophyte stage and a diploid sporophyte stage.
4. Leaves: Pteridophyta have leaves, which are called fronds. The fronds are typically large and divided into many small leaflets. They also have specialized structures called sori that contain the spores.
5. Spores: Pteridophyta reproduce through spores, which are produced in the sori. The spores are released into the environment and can grow into a gametophyte plant.
6. Water-dependent reproduction: Pteridophyta reproduction is dependent on water because the sperm cells need water to swim to the egg cells for fertilization.
7. Habitat: Pteridophyta are found in a variety of habitats, including moist forests, swamps, and even deserts.
8. Diversity: Pteridophyta is a diverse group of plants, with over 12,000 known species. They range in size from tiny, delicate plants to large, tree-like species.

Classification of Pteridophyta

Pteridophyta can be divided into four major groups based on their reproductive structures and other characteristics:

 Psilopsida

• This group consists of only one living species, Psilotum nudum, which lacks true leaves and roots.
• They are the most primitive.
• The stem is photosynthetic and dichotomously branched.
• Rhizoids are present.
• Leaves are mostly absent.
• The sporophyte is homosporous synangium.
• Examples- Psilotum and Tmesipteris.

Lycopsida

• This group includes club mosses and spike mosses, which are small, herbaceous plants with scale-like leaves.
• They are commonly known as club moss.
• Well-differentiated plant body with adventitious root, stem, rhizophores and leaves.
• The sporophyte is homosporous or heterosporous.
• Examples- Selaginella, Lycopodium.

Sphenopsida

• This group includes horsetails, which have jointed stems and scale-like leaves arranged in whorls.
• Commonly known as horsetail.
• Well-differentiated plant body with roots arising from nodes of the underground rhizome, stem and scaly leaves.
• Homosporous, sporangia are borne on strobili.
• Examples- Equisetum.

Pteropsida

• This group includes ferns, which have true leaves, roots, and stems, and are the most diverse and well-known group of pteridophytes.
• Commonly known as a fern.
• Well-differentiated plant body with roots, stem and leaves.
• The sporophyte is homosporous or heterosporous.
• Antherozoids are multiflagellate.
• Examples- Pteris, Dryopteris, Adiantum

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Life Cycle of Pteridophyta

Pteridophytes exhibit an alternation of generations in their life cycle, which is similar to that of seed-bearing plants. However, unlike mosses and seed plants, both the haploid gametophyte and diploid sporophyte generations of pteridophytes are independent and free-living. The sexuality of pteridophyta gametophytes can be classified in the following ways:

• Dioicous: Each individual gametophyte is either male, producing antheridia and sperm, or female, producing archegonia and egg cells.
• Monoicous: Each individual gametophyte can produce both antheridia and archegonia and can function as both male and female.
• Protandrous: The antheridia mature before the archegonia.
• Protogynous: The archegonia mature before the antheridia.

Some examples of Pteridophyta include ferns, horsetails, and clubmosses.

Pteridophyta: Sporophyte Generation

1. This is the dominant and longer phase than the gametophyte generation.
2. The plant produces spores, which are carried away by the wind to distant locations.
3. Spore mother cells produce spores via meiosis.
4. The spores produced by most plants are similar. Such plants are known as homosporous. Lycopodium, for example.
5. Some plants are heterosporous because they produce two types of spores: microspores and macrospores. As an example, consider Selaginella.
6. Male antheridia are produced by microspores, and female archegonia are produced by megaspores.
7. These spores germinate into small independent gametophytes known as prothallus under favorable conditions.

Pteridophyta: Gametophyte Generation

1. The prothallus (gametophyte) can only grow in moist, cool, shady conditions. Their growth is restricted to a few areas.
2. Gametophytes are multicellular and photosynthetic organisms.
3. They have both male and female sex organs.
4. The male sex organ is referred to as antheridia, while the female sex organ is referred to as archegonia. 
5. The sperm in antheridia fuses with the egg in archegonia, resulting in the formation of a zygote.
6. The zygote eventually develops into a multicellular sporophyte.
7. Thus, the Pteridophyte's life cycle is completed.

Pteridophyta Examples

Following are some important examples of Pteridophyta:

1. Whisk Fern
2. Dicksonia
3. Selaginella
4. Lycopodium
5. Equisetum
6. Pteris
7. Dryopteris
8. Adiantum
9. Man fern
10. Silver fern

Also Read:  Living Things Definition and Scope of Microbiology.

Pteridophyta Uses

Pteridophytes have a range of uses and applications in various fields. Here are some examples of their uses:

1. Ornamental plants: Many species of ferns are cultivated for their attractive foliage and are used as ornamental plants in gardens, parks, and indoor spaces.
2. Medicinal purposes:Some Pteridophytes have been used in traditional medicine to treat various ailments. For example, the fern Polypodium leucotomos has been used to treat skin conditions such as psoriasis and eczema.
3. Food:Some Pteridophytes are edible and have been used as food in some cultures. For example, fiddleheads, which are the young shoots of certain ferns, are a delicacy in some parts of the world.
4. Soil stabilization:The extensive root systems of Pteridophytes help to stabilize soil and prevent erosion.
5. Ecological indicators:Pteridophytes can be used as indicators of the health of an ecosystem, as some species are sensitive to pollution or changes in environmental conditions.
6. Fossil fuels:Some Pteridophytes, such as coal-forming horsetails (Equisetum), have contributed to the formation of fossil fuels over millions of years.

Overall, pteridophytes have a range of uses and are important components of many ecosystems.

Pteridophyta Things to Remember

Pteridophyta is a diverse group of vascular plants that includes ferns, horsetails, and clubmosses. Here are some important things to remember about Pteridophyta:

1. Life cycle: Pteridophytes have a typical alternation of generations life cycle. The sporophyte (diploid) is the dominant phase and produces spores through meiosis. The spores develop into the gametophyte (haploid) phase, which produces gametes through mitosis. The gametes fertilize to form a zygote, which develops into a new sporophyte.
2. Vascular tissue: Pteridophytes have well-developed vascular tissue that allows them to transport water and nutrients throughout the plant. The vascular tissue consists of xylem, which transports water and minerals from the roots to the leaves, and phloem, which transports sugars and other organic compounds from the leaves to the rest of the plant.
3. Leaves: Pteridophytes have leaves that are typically called fronds. The fronds are often divided into smaller leaflets, which can be further divided into smaller segments. The leaves are usually green and photosynthetic, but some species have modified leaves that serve other functions, such as protection or reproduction.
4. Reproduction: Pteridophytes reproduce through spores rather than seeds. The spores are produced in structures called sporangia, which are usually located on the undersides of the fronds. The spores are dispersed by wind or water and develop into gametophytes.
5. Habitat: Pteridophytes are found in a variety of habitats, including forests, wetlands, and deserts. They are often found in moist environments because they require water for fertilization and spore dispersal.
6. Importance: Pteridophytes have several important ecological and economic roles. They are important food sources for animals such as deer and elk. They also play a key role in nutrient cycling and soil formation. Some species are used for medicinal purposes, while others are cultivated for their ornamental value.

Conclusion

Pteridophyta are a diverse and ancient group of vascular plants that have played an important role in the Earth's history. With over 12,000 species, they exhibit a wide range of morphologies and are found in many different ecosystems. They are important components of many ecosystems and have several practical uses for humans. Understanding and preserving these plants is important for maintaining the diversity of life on Earth.