The term “Pteridophyta” is originated from Greek word- “Pteron” which means feather and “phyton” means plants i.e. the plants having feather like fronds. The pteridophytes formed a dominant part of earth’s vegetation about 282-230 million years ago during the Palaeozoic era. Late Palaeozoic era can be clearly regarded as the age of pteridophytes because during this period, pteridophytes were the dominant land plants on earth. There are about 12,000 species of pteridophytes across the world.
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Habitat of Pteridophytes
Pteridophytes were the first land vascular plants that are mostly found in the tropical and temperate climatic zones. Most of them are terrestrial, however there is an exception. Different habitats of pteridophytes are discussed as follows:
- Terrestrial: From fossils to the most advanced pteridophytes grows in terrestrial habitats. They prefer moist and shady places. Species that grows in terrestrial habitats are Ophioglossum sp., Lycopodium clavatum, Lycopodium cernum, Equisetum sp. etc. However there are some exceptions- Equisetum debile can grow in hydrophytic, mesophytic as well as xerophytic habitats. E. paulstris prefers swampy habitats. E. arvense grows in open grasslands.
- Aquatic pteridophytes: Most of the members of family Marsileaceae and Salviniaceae grow in aquatic and semi-aquatic regions. They are commonly known as aquatic ferns. Marsilea minuta, M. quadrifolia etc. are the common aquatic species.
- Xerophytic pteridophytes: Some species of Selaginella grows in pteridophytic region Examples are S. wightii, S. repanda, S. lepidophylla, etc.
Life Cycle of Pteridophytes
Sporophyte
The vascular cryptogams possess an independent sporophyte with a vascular system. It exhibits a great variation in form, size, and structure.
Except tree ferns, almost all the pteridophytes are herbaceous.
They may be dorsiventral or radial in symmetry and have dichotomously or laterally branched stems that bear microphyllous or megaphyllous leaves.
The roots are generally adventitious, primary root is short lived.
The sporophyte produces sporangia, which are specialized structures where spores are formed by meiosis. Sporangia can be located on the underside of leaves (as in ferns) or on specialized structures like strobili (in horsetails and club mosses). Sporangia may be aggregated into sori (clusters) in ferns, protected by structures called indusia in some species. Pteridophytes may be homosporous i.e. producing one kind of spore or heterosporous i.e. producing different types of spore.
Gametophyte
It is quite independent of the sporophyte and maybe autophytic or saprophytic. The homosporous pteridophytes generally have monoecious prothalli. These may be protrandrus or protogynous.
The prothalli in homosporous pteridophytes are green, simple and branched or colourless tuberous and saprophytic.
The heterosporous pteridophytes generally have dioecious prothalli.
The sex organs may be embedded or projecting. They resemble the bryophytes in structure. The archegonium consists of neck-canal cells, ventral canal cells, neck cells, and cover cells.
The antheridia may be either with stalk or without stalk. It has a single layer of sterile jacket enclosing a variable number of spermatozoids.
The zygote develops into an embryo within the archegonial venter and is surrounded by prothalli tissue. The development may be endoscopic, exoscopic or lateral.
Vascular bundles and stele in pteridophytes
Pteridophytes have a sophisticated vascular system composed of xylem and phloem. The xylem is responsible for the transport of water and minerals, whereas the phloem distributes organic nutrients.
The vascular bundles are seen for the first time in pteridophytes with variable arrangements in the position of xylem and phloem at the central part of stem.
The central vascular cylinder found in the roots, stems and leaves are called stele.
Types of stele found in pteridophytes
Different types of stele found in pteridophytes are as follows-
Protostele
It is the simplest and most primitive type of stele, consisting of a solid core of xylem surrounded by phloem.
Subtypes:
- Haplostele: A solid, cylindrical core of xylem with a surrounding layer of phloem. Found in some primitive pteridophytes like the whisk fern (Psilotum).
- Actinostele: A variation where the xylem core is star-shaped, with radiating arms of xylem surrounded by phloem. Found in some club mosses (Lycopodium).
Siphonostele
It is the type of stele with central pith surrounded by a ring of vascular tissue. It is more advanced than the protostele.
Subtypes:
- Ectophloic Siphonostele: Phloem is present only on the outside of the xylem ring. Found in some ferns.
- Amphiphloic Siphonostele: Phloem is present on both the inside and outside of the xylem ring. Found in most ferns, such as the bracken fern (Pteridium).
- Soleno-stele: A variant of the amphiphloic siphonostele where the vascular cylinder is continuous without leaf gaps.
Dictyostele
It is a type of siphonostele where the vascular cylinder is dissected by leaf gaps, resulting in a network (or net-like appearance) of vascular strands.
It is found in most advanced ferns, such as the maidenhair fern (Adiantum). The gaps are formed where leaves (fronds) are attached, allowing for more flexibility and efficiency in nutrient transport.
Plectostele
It is the stele where vascular bundles are scattered or irregularly arranged without central pith.
Subtype:
- Mixed Protostele: Contains both protoxylem and metaxylem in a central core surrounded by phloem, found in some ferns and horsetails (Equisetum).
Atactostele
Stele with scattered vascular bundles throughout the ground tissue.
Eustele
It is characterized by discrete vascular bundles arranged in a ring around the pith.
It represents a further evolutionary advancement and is a feature of seed plants. Although more common in seed plants, certain evolutionary transitions in pteridophytes exhibit eustele-like features, providing insights into the evolution of vascular plants.
Economic importance of pteridophytes
Pteridophytes are of high economic importance but it is considered to be of limited economic importance. The economic mportance of pteridophytes are discussed below-
Pteridophytes as food
Ferns are found to be good source of starch, and nutrients. Fresh uncurled fronds of ferns like Diplazium esculentum, Tectaria codunata, Diplazium kawakamii etc. are eaten as vegetable. Pith of Cyathea sp. are cooked and eaten by tribals in some parts of the world. Sporocarps of Marsilea drumondi (Australian swamp fern) are grounded into paste to prepare bread.
Pteridophytes as medicine
Pteridophytes like Lycopodium are used to cure stomach pain. Species like Pteridium aquilinium are used in the treatment of toothache; Selaginella flabellate is used to control fever and headache.
Leaves of Pteris ensiformis, Aspidium latifolium etc. are applied to boils and wounds. Hot fronds of Polystichum sp. are applied to swellings by tribals.
Pteris ensiformis is used to control menstruation whereas Lygodium dichotomum is used as contraceptive, the roots and stems being taken internally.
Dryopteris filix-mas (male fern): Used as an anthelmintic to expel parasitic worms.
Pteridophytes as horticultural items
Boston fern (Nephrolepis exaltata): It is commonly used in hanging baskets and as a houseplant.
Maidenhair fern (Adiantum sp.): Valued for its delicate, fan-shaped fronds and graceful appearance, often used in terrariums and shaded garden areas.
Staghorn fern (Platycerium sp.): Unique epiphytic fern, popular for mounting on boards and growing in hanging pots.
Bird’s Nest fern (Asplenium nidus): Features large, undivided fronds that form a rosette, commonly grown as a houseplant or in shaded outdoor gardens.
Japanese Painted fern (Athyrium niponicum): Known for its striking silver and burgundy foliage, used to add colour to shaded garden areas.
Pteridophytes as ritual items
The silver fern (Cyathea dealbata), known as ponga, is a national symbol of New Zealand and holds significant cultural importance for the Maori people. The unfurling frond (koru) symbolizes new life, growth, strength, and peace.
Ferns, such as the hapu’u fern (Cibotium glaucum), are considered sacred in Hawaiian culture. They are associated with Laka, the goddess of hula, and are used in hula rituals.
Various African cultures use ferns and other pteridophytes in traditional medicine and spiritual practices. These plants are believed to have protective properties and are used in rituals to ward off evil spirits and negative energies.
Pteridophytes as decorative items
Fern fronds, particularly those with unique shapes and textures, are used in floral arrangements and bouquets to provide a natural and earthy contrast to flowers. Ferns add a touch of greenery and can help fill out arrangements, providing a backdrop for colourful blooms during weddings, parties, and other celebrations.
Pteridophytes as biofertilizers
Azolla, a heterosporous water fern which contains endophytic cyanobacterium Anabena azollae is used as biofertilizer in rice fields. Azolla is also a heavy metal resistant plant and is beneficial for crops.
References
- Bajracharya.B.Gan., Bajracharya.Bashana., 2022. A comprehensive review on Nepalese wild vegetable food ferns. Heliyon. [ DOI: 10.1016/j.heliyon.2022.e.11637]
- Banks, H.P. (1968). “The early history of Land Plants” Yale Univ. Symp. On Evolution and Environments. New Haven Conn.
- Hait, G., Bhattacharya, K., & Ghosh, A. K. (2012). A textbook of Botany, Volume I.
- Kawasaki, T. (1970), Reproductive Biology of Pteridophyta. IV. Ibid., 63 : 153-169
- Kholia, B.S., 2014. Fern and Fern-allies of Sikkim part II. ix+291 pp. .Sikkim State Biodiversity Board and BSI.
- Kholia,B.S. 2010. Fern and Fern-Allies of Sikkim part I. pp.207. Sikkim State Biodiversity Board and BSI.
- Kholia,B.S., 2016. Traditional Uses of pteridophytes in Sikkim Himalayas. https://www.researchgate.net/publication/290441020.
- KU – Botany III – U I – 2. (n.d.). https://www.winsomepublication.in/p/ku-botany-iii-u-i-2.html
- Pteridophyta by B.R. Vashishta, A.K. Sinha, Adarsh Kumar (S.Chand & Company ltd)
- Sussex. IM.(1966). The origin and development of heterospory in vascular plants. Trends in plant Morphogenesis. 140-152.
- Types of stele – Pteridophytes. (n.d.). BrainKart. https://www.brainkart.com/article/Types-of-Stele—Pteridophytes_32882/