Pteridophyta - Definition, Characteristics, Classification, Uses

Pteridophyta is a division of the kingdom Plantae that consists of plants that dominated the planet before the evolutionary appearance of seed-producing plants. Pteridophytes lack both flower and seed and reproduce mainly with the help of spores. Pteridophytes are the first group of plants that have evolved to show the vascular system.

The Plant Kingdom

All the eukaryotic, autotrophic, multicellular organisms are placed in this kingdom. They are mostly autotrophic but some exceptions like venus flytrap, pitcher plant, etc. show heterotrophic mode of nutrition too. These organisms have the characteristics feature of the cell wall, cell organelles like plastids whose type chloroplast consists of chlorophyll pigment that is capable of trapping the sun's light energy to perform photosynthesis.

Classification of Plant Kingdom

The kingdom Plantae is further classified into two sub-kingdoms based on their capability to produce seeds; Cryptogamae or the seedless plants and Phanerogamae or the seed-bearing plants. The sub-kingdom Cryptogamae consists of three divisions i.e. Thallophyta, Bryophyta, and Pteridophyta whereas the sub-kingdom Phanerogamae consists of division Spermatophyta which has two sub-divisions; Gymnospermae, and Angiospermae.

What are Pteridophytes?

Pteridophytes (Greek. pteron=feather, and phyton=plant) constitute one of the most primitive seedless vascular plants that reproduce using spores and have neither flowers, fruits nor seeds. Ernst Hackel called these groups of plants pteridophytes because of their pinnate or feather-like fronds. It is also known as the "Botanical Snakes" or "Snakes of the plant kingdom" and sometimes they are also known as "amphibians of the plant kingdom" because they depend on water for fertilization just like bryophytes while living on land.

Characteristics of Pteridophyta

Following are some of the general characteristics of the division Pteridophyta;

1. They are found mainly in shady or damp places.
2. The plant body is made up of roots, stems, and leaves.
3. They have well developed vascular system(xylem and phloem) for the conduction of water and other essential substances, from one part of the plant body to another.
4. These plants have no flowers and do not produce seeds.
5. Multicellular sex organs are present.
6. A fertilized egg develops into an embryo.
7. Water is essential for fertilization i.e. transfer of gamete.
8. They show a typical heteromorphic alternation of generations.
9. They show much variation in their form, size, and habit.
10. They range from small annual plants to large tree-like perennials.

Reproduction in Pteridophytes

Pteridophytes have a dominant sporophytic (diploid) phase that undergoes meiosis to produce spores and then comes a gametophytic (haploid) phase that undergoes mitosis to produce gametes. The gametophyte of pteridophyte bears the male sex organ called the antheridia and the female sex organ called the archegonia. Transferring the male gamete (antherozoids) to the female archegonia is achieved with the help of water. The male and female gametes then fuse to form the zygote which develops into the sporophyte that further undergoes meiosis to form the similar kind of spores (homospory).

👁 Reproduction-of-Pteridophytes

Life Cycle of Pteridophytes

Pteridophytes show an alternation of generation life cycle in which dominant diploid sporophytic generation takes up most of their life span whereas the haploid gametophytic generation is short-lived. Their life cycle is haplodiplontic in which the prophase and diplophase are almost equally balanced. Both the generations are independent of each other and are free-living. The diploid generation produces the spores whereas the haploid generation produces the gametes. These spores travel to different places and then in moist and damp place germinates into independent gametophytes called the prothallus which bears the male anthredia and female archegonia that forms the sperm and egg respectively. The sperm and egg fuse to form the zygote that develops into a multicellular sporophyte.

👁 Life-Cycle-of-Pteridophytes

Classification of Pteridophytes

Pteridophytes are mainly classified into four classes; Psilopsida, Lycopsida, Sphenopsida, and Pteropsida.

Psilopsida

Following are some of the characteristics of Psilopsida;

1. They are the most primitive class of pteridophytes that are now fossils.
2. Their stems were photosynthetic and were branched dichotomously.
3. They lack leaves but have rhizoids.
4. They have homosporous sporophytes.
5. Example: Psilotum, etc.

Lycopsida

Following are some of the characteristics of Lycopsida;

1. They are commonly known as the "club moss".
2. The body is well divided into root, stem, and leaves.
3. Leaves are very small so are called Microphyllous having a single unbranched mid-rib.
4. The sporophylls form clumps called strobili.
5. Examples: Lycopodium, Selaginella, etc.

Sphenopsida

Following are some of the characteristics of Sphenopsida:

1. They are commonly known as "horsetail".
2. They have nodes and internodes in their body.
3. Leaves are microphyllous and grow in whorls.
4. At the apex of the fertile branches, the sporangia forms compact cones.
5. Example: Equisetum, etc.

Pteropsida

Following are some of the characteristics of Pteropsida:

1. They are commonly called "ferns".
2. The body is divided into well-developed stems, roots, and leaves.
3. The leaves are large i.e. megaphyllous.
4. On the ventral surface of the sporophylls, the clumps of sporangia are formed which is called the sori.
5. Example: Dryopteris, Pteridium, etc.

Affinities of Pteridophytes

Pteridophytes occupy an intermediate position between bryophytes and higher vascular plants(gymnosperms and angiosperms).

Resemblances of Ptreridophytes with Bryophytes

Following are some of the characteristics that connect Bryophytes to Pteridophytes;

1. Both show heteromorphic alternation of generation i.e. haploid gametophyte in one generation and a diploid sporophyte in another generation.
2. The sexual reproduction in both groups is oogamous and the male and female reproductive structures are known as antheridia and archegonia.
3. Water is essential for the opening of mature sex organs and fertilization in both groups.
4. Certain pteridophytes are homosporous like bryophytes.

Differences between Bryophytes and Pteridophytes

Following are some of the differences between Bryophytes and Pteridophytes;

1. The plant body of pteridophytes is differentiated into root, stem, and leaves, whereas in bryophytes it is thalloid or foliose i.e. without distinct root, stem, and leaves.
2. Vegetative reproduction is more common in bryophytes than in pteridophytes.
3. Bryophytes are always homosporous, whereas many pteridophytes show heterospory.

Resemblances of Pteridophytes with Gymnosperms

Following are some of the characteristics that connect Pteridophytes with Gymnosperms;

1. The plant body in both groups is sporophytic, differentiated into root, stem, and leaves.
2. The vascular system is well developed in both groups, made up of xylem and phloem.
3. Like gymnosperms, many pteridophytes show heterosporous conditions.
4. Antherozoids of some gymnosperms are ciliated like those of pteridophytes.

Differences between Pteridophytes and Gymnosperms

Following are some of the differences between Pteridophytes and Gymnosperms;

1. Pteridophytes usually occur in moist and shaded places, whereas gymnosperms grow in xerophytic habitats.
2. Gymnosperms have tap roots but in pteridophytes, the tap root is ephemeral and is soon replaced by adventitious roots.
3. The archegonium in pteridophytes has neck canal cells but they are absent in gymnosperms.

Economic Importance of Pteridophytes

Following are some of the common uses of Pteridophytes;

• Pteridophytes are economically very important as dry fronds of many ferns are used as cattle feed.
• Pteridophytes are also used in medicine Lycopodium is used to treat skin diseases, and Dryopteris for the preparation of anthelminthic medicines.
• Pteridium aquilinum is the most widely used pteridophyte as a source of human food.
• Ferns are grown for their ornamental values.
• Selaginella helps in soil conservation.