Pteridophyta Updated PDF

Plant Diversity Pteridophytes Dr. N. P. Dissanayake Department Of Botany  Plant diversity ranges enormously from unicellular bacteria to seed bearing plants like Giant redwood in California. Bacteria, algae, fungi, bryophytes and pteridophytes are all cryptogams (do not...

Plant Diversity Pteridophytes Dr. N. P. Dissanayake Department Of Botany  Plant diversity ranges enormously from unicellular bacteria to seed bearing plants like Giant redwood in California. Bacteria, algae, fungi, bryophytes and pteridophytes are all cryptogams (do not produce seeds). Pteridophytes are "spore bearing vascular plants or vascular cryptogams as they have a developed vascular system.  The term Pteridophytes is derived from two words "Pteron meaning feather" and "phyton meaning plant". Thus Pteridophytes are the plants with feather like leaves.  So Pteridophytes are vascular plants that disperses spores as they have neither flowers nor seeds. They also referred to as "cryptogams" due to their hidden reproduction.  Division Pteridophyta Vascular cryptogams (plants having a vascular system, reproduce by spores and do not produce seeds). Pteridophyta is being represented by primitive living vascular plants like selaginella and fossil vascular plants like Rhynia. Most of the living members are - terrestrial - but prefer to grow in cool shady places - some in aquatic conditions.  Main differences between bryophytes and pteridophytes. - Sporophyte is dominant in pteridophytes and Arial (Body) gametophyte is dominant in bryophytes. - Completely independent sporophyte in pteridophytes but in bryophytes it is dependent on the gametophyte. - In both pteridophyta and bryophyta, gametophyte requires water for external fertilization.  How different are gymnosperms from bryophytes and Pteridophytes? The key difference between these three groups is the habitat where they are grown. Bryophytes are adapted to grow in amphibious environments; Pteridophytes are adapted to terrestrial environments which are a moist and shady while, Gymnosperms are fully adapted to terrestrial environments.  General characters of pteridophyta It has roots, leaves and stems. Developed vascular system present. Independent sporophyte which is the dominant plant. Gametophyte has a very short life period which can overcome the drought period. ∙ Spores produce in sporangia or in sporophylls. In some species sporangia are produced in specialized bodies called sporocarps. -Leaves – 2 types, mega and microphylls. - Microphylls - Simple, small & sessile (petioles and stipules are absent). - Megaphylls- Large, petiolate (petioles and stipules are present). - 2 types of life cycles, homosporous or heterosporous. ( All spores are in same type – Homosporous Heterosporous – Two types of spores as micro spores & mega spores  Vascular system varies from Protostele to dictyostele (stele sums up the vascular system, associated tissues and the pith Deposition of some substances over the aerial surface of the plant to protect the plant from excessive evaporation. Epidermal cells with chlorophyll, spongy parenchyma and palisade layer can be seen. Sometimes there may be a cuticle. On the basis of the development of sporangia, pteridophyta can be catagorised into two types as Eusporangiate and Leptosporangiate.  Shows circinate vernation. Spores have a very thick outer covering which is resistant to drought period. When the leaves are absent, stem can synthesize food using sun light. Gametophytes require water for external fertilization but it has a very short life period.  Pteridophyta shows some similarities with gymnosperms also. - Sporophyte differentiated into roots,stems and leaves. - Regular alternation of gametophytic and sporophytic generation - Young leaves show circinate vernation. In the vascular system, - Vessels are absent in both. (except order Gnetales in gymnosperms). - Phloem lacks companion cells in both.  The Spatial Arrangement of Vascular Bundles and the Theory of Steles The spatial arrangement of vascular bundles is explained by the theory of steles. Stele means sums up the vascular system, associated tissues and the enclosed pith. The theory of steles says that the primary plant body of roots and shoots is constructed according to the same principle, since both contain a central pillar (stele) that is embedded into primary bark.  It does not deal with secondary growth. Different types of steles, - Protostele - Plectostele - Siphonostele - Dictyostele The pattern of steles can be regarded as a conservative feature, whose complexity increased in the course of evolution.  Protostele - simple, unbranched, centrally located axial strand of xylem present. - No pith. - Found in primitive vascular plants like Rhynia, young fern shoots etc. Phloem Xylem  Plectostele - Interconnected regions of xylem are collectively surrounded by a mass of phloem. - Eg: Club mosses (Lycopodiopsida)  Siphonostele - represents the prototype of the vascular systems of ferns - Further developed in vascular (seed) plants. - Composed of several axial vascular bundles that are arranged within the stem in the shape of a tube with enclosed pith. - Two types of life cycles.. Homosporous. Heterosporous 1) Homospory - Homosporous (Isospory) plants produce bisexual gametophytes. - Life cycle of Homosporous plant..........  2) Heterospory - The male gametophyte produces sperm, and is associated with smaller or microspores. - The female gametophyte is associated with the larger or megaspores. - Heterospory is considered by botanists as a significant step toward the development of the seed. - A generalized heterosporous life cycle....  A fairly complete, and the present accepted system of classification of vascular cryptogams that is based on Smith (1955), Bold (1957), Benson (1957), Zimmermann (1959) , Cronquist (1960), and Takhatajan (1964) can be outlined as below. Classification of division pteridophyta Four sub divisions/ Phyla - Psilophyta - Lycophyta - Sphenophyta - Pterophyta or Filicophyta  According to Pteridophyte Phylogeny Group in 2016, (PPG I), Pteridophytes consist of two separate but related classes named as Class Lycopodiopsida and Class Polypodiopsida.  PPG I. A first classification, PPG I, was produced in 2016, covering only extant (living) pteridophytes. The classification was rank-based, using the ranks of class, subclass, order, suborder, family, subfamily and genus.  It has been recognized two pteridophyte classes: Lycopodiopsida (lycophytes) and Polypodiopsida (ferns). These are distinct lineages within the tracheophyte tree of life, with ferns resolved as more closely related to seed plants than to lycophytes.  Class Lycopodiopsida consist of three orders as Lycopodiales, Isoetales and Selaginellales while Class Polypodiopsida consist of four Subclasses as Equisetidae, Ophioglossidae, Marattiidae and Polypodidae.  Within Lycopodiopsida, further recognize three orders (Lycopodiales, Isoëtales, and Selaginellales). Order Lycopodiales includes one family and 16 genera, whereas orders Isoëtales and Selaginellales each contain a single monogeneric family.  Class Lycopodiopsida Order Lycopodiales- Lycopodium cernuum Huperzia phlegmaria Order Selaginellales- Selaginella sp. Order Isoetales Isoetes sp.  Class Polypodiopsida Subclasses Equisetidae Order Equisetales – Genus Equisetum sp.  Subclass Ophioglossidae – Order Psilotales Psilotum nudum Order Ophioglossales Ophioglossum sp. Helminthostachys sp.  Subclass Marattiidae – Order Marattiales Marattia sp. Angiopteris sp.  Subclass Polypodidae – Order Osmundales Osmunda sp. Order Schizaeales Lygodium sp. Order Gleicheniales Gleichenia sp.  Order Salviniales Salvinia sp. Marsilea sp. Order Polypodiales Nephrolepis sp. Acrostichum sp. Adiantum sp. Davallia sp.  When we consider the previous classification on all pteridophytes (extinct and extant) consists of 04 phyla.  Psilophyta The plant body is a rootless sporophyte that differentiates into a subterranean rhizome and an aerial erect shoot. 2. Branching is dichotomous in both subterranean rhizome and aerial shoot. 3. Rhizoids borne on the rhizome absorb water and nutrients from the soil. 4. Leaves often absent or if present, they are spirally arranged scale like ( e.g. Psilotum) or leaf-like appendages (e.g. Tmesipteris  5. The vascular tissue is of primitive type i.e., simple, cylindrical protostele with annular or spiral tracheids. 6. Secondary growth is absent. 7. Sporangia are borne at the apex of the aerial shoots. They are either solitary (e.g., Rhynia) or in groups and terminal in position. There was nothing like that of sporophyll. 8. Sporangia always bearing the same type of spores i.e., they are homosporous  9. The gametophyte is known only in Psilotum and Tmesipteris (living genera) 10. The gametophyte is cylindrical or branched, subterranean and colourless. 11. Sex organs are partially embedded in the prothallus. 12. Antherozoids are spirally coiled and multi- flagellated.  Phylum Psilophyta Class Psilotopsida Order Psilophytales - All members are extinct and their fossils have been recorded. Eg. Rhynia. Order Psilotales Family Psilotaceae Genus Psilotum According to the Pteridophyte phylogeny group, Subclass Ophioglossidae – Order Psilotales Psilotum nudum Order Ophioglossales Ophioglossum sp. Helminthostachys sp.  Subclass Ophioglossidae – Order Psilotales Psilotum nudum  Eg: Psilotum nudum & Psilotum complanatum. Psilotum nudum Psilotum complanatum  Distribution-Tropical and sub tropical. Roots are absent and unicellular rhizoids are present. (to absorb water). Erect stem which is dichotomously branched, growing on the ground. Some times may grow as an epiphyte. Very small scale like leaves on aerial branches. Spirally arranged. No true leaves. Aerial stem has a thick cuticle or cutinized epidermis and sunken stomata.  Sporangia at the tips and also on the other places of the aerial shoots. Sporangia are thick walled and homosporous. 3 sporangia are get together to form a synangium. Life cycle homosporous Dichotomous rhizome with rhizoids. Generally contains mycorhizal fungus.  Lycophyta 1.The plant body is sporophytic (Sporophyte is dominant) and can be differentiated into root, stem and leaves.. 2. The leaves are small (microphyllous), simple with a single mid vein. They are usually spirally arranged, sometimes in opposite or even in whorls. 3. In some cases the leaves are ligulate (e.g., Selaginella, Isoetes). The ligule is present at the base of each leaf. 4. The vascular tissue may be either in the form of plectostele, siphonostele or sometimes even polystele. Leaf gaps are absent.  5. Sporophylls are loosely arranged or aggregated to form strobilus or cones. 6. Some members are homosporous ( e.g. Lycopodium) while others are heterosporous (e.g. Selaginella). 7. Antherozoids are biflagellate or multi-flagellate. 8. Secondary growth does not take place except in Isoetes  Phylum Lycophyta Characteristic features … - Sporophyte is dominant. Stems, roots and leaves present. - Leaves are microphyllous. Arrangement is generally spiral. In some cases, may be opposite or whorled. - Steles may be proto or siphonostelic. - Fertile leaves (sporophylls) produce single sporangium on the upper surface.  Most of the sporophylls are borne on strobili. Life cycle – Homosporous or heterosporous. Eg : Lycopodium - homosporous Selaginella - heterosporous Class Lycopsida( 5 orders) - Lepidodendrales (E) - Isoetales Strobili - Lepidocarpales (E) - Lycopodiales - Selaginellales  Order Lycopodiales Genera – Lycopodium (present in Sri Lanka) Phyloglossum (not present in Sri Lanka). Restricted to temperate countries. Eligulate leaves. Lycopodium annotinum L.  Lycopodium Eligulate leaves, microphyllous. Occupy in widely different habitats. Sporophylls and foliages may or may not be similar (in shape and size). Stem is covered with sharp and pointed leaves. Moss like appearance and club shaped strobili. (club mosses). L. selago and L. phlegmaria – lack of specialization of the sporophylls.(similar to vegetative leaves).  L. cernuum and L. clavatum sporophylls and foliages are different. Homosporous. One sporangium in one sporophyll. Spores release and germinate few days after it shed. Some times it may remain for 3- 8 years. Gametophyte takes long time for developing sex organs.  Gametophyte is partly sub terrestrial (green and photosynthetic or colourless and dependent upon a mycorrhizal association for their development). Gametophyte is very small compared to the sporophyte. Sex organs are borne on the upper surface of the gametophyte. Nutrition is by endophytic mycorrhiza in the lower portion of the gametophyte. L.S.Lycopodium strobilus  Order Selaginellales Family Selaginellaceae Genus Selaginella (only the living genera). Mostly confined to the tropics and sub tropics. Herbaceous sporophyte with ligulate leaves. Heterosporous. Sporophylls are aggregated to form strobili. Selaginella flabellata L.S. Selaginella strobilus  Order Lepidodendrales (E) Genus Lepidodendron Unbranched stem. Upper region shows dichotomous branching. Branches are covered with long grass like leaves. Sporophylls are aggregated in to a cone. Ligulate and microphyllous. Sporangium is incompletely septate. Heterosporous. Life cycle is similar to Selaginella. Lepidodendron  Order Isoetales Genus Isoetes Isoetes, commonly known as the quillworts, is the only extant genus of plants in the family Isoetaceae, which is in the class of lycopods. There are currently 192 recognized species, with a cosmopolitan distribution but with the individual species often scarce to rare. Most quillworts grow submerged in fresh water all or part of the year.  Isoetes is commonly called 'Quill wort' due to the quill (a large feather)-like structure of the leaves. The plant body consists of a condensed, lobed corm or axis that bears a tuft of roots at the base and long feathery leaves on the top.  Submerged species of Isoetes have evergreen leaves whereas wetland species are often deciduous, losing their leaves over the non- growing seasons. Isoetes plants also have unusual stems. They are short and swollen and grow underground.  Submerged species of Isoetes have evergreen leaves whereas wetland species are often deciduous, losing their leaves over the non- growing seasons. Isoetes plants also have unusual stems. They are short and swollen and grow underground.  Quillworts are herbaceous, spore-bearing plants with grassy spikelike leaves. The spirally arranged quill-like leaves are divided into vertical rows of cavities that are connected to one central conducting strand. The leaves rise from a cormlike or tuberlike base, with roots below.  One of the common quillworts is Isoetes lacustris. Small grass like plant. Resemble to spring onion. Majority of them are lived in water or swamp areas. Stem is like a corm. Roots are dichotomously branched. Spores are produced at the base of the leaves. Macro and micro sporangia are present.(Inner micro sporophylls and outer mega sporophylls.)  A large saclike round-to-oblong sporangium is sunk into a pit on the inner surface of each leaf base, where a small thin structure known as a ligule also occurs. The terrestrial species tend to grow in seasonally wet habitats, and the plants die back to the corm when the soil dries. Quillworts have different ways to spread their spores based on the environment.  Isoetes are heterosporous--spores are of two distinct sizes, microspores and megaspores. Outside of heterospory, a distinguishing feature of Isoetes (and Selaginella) from other pteridophytes, is that their gametophytes grow inside the spores. This means that the gametophytes never leave the protection of the spore that disperses them, cracking the perispore (the outer layer of the spore) just enough to allow the passage of gametes. Isoetes Isoëtes lacustris  A number of quillworts are listed as endangered species by the International Union for Conservation of Nature’s (IUCN) Red List of Threatened Species, largely due to habitat loss, water pollution, and small population sizes.  Class Polypodiopsida Subclasses Equisetidae Order Equisetales – Genus Equisetum sp.  Phylum Sphenophyta Genus Equisetum (Horse tail). Only the living genus today. Distributed throughout the world. 20-30 spp are known. Some species are in marshy conditions. Sporophyte is differentiated into stems, leaves and roots. Stem is always ribbed or ridged (longitudinally furrowed).. Leaves are microphyllous. Arrange in whorls on the stem and branches at each node.  Perennial herb with branched, underground horizontal rhizome and an erect aerial stem. (Both shows nodes and internodes). Stele proto or siphanostelic. (without leaf gaps). Living species are homosporous and extinct types are heterosporous.  How Sphenophyta differs from other Pteridophyta Leaves never arranged alternatively. Whorled arrangement at each node. Ridging of the stem is very characteristic. No sporophylls. Sporangia are born in a cone on Sporangiophores. Aerial branches are 2 types. Sterile (green) and fertile (colourless, unbranched with a single strobilus at its terminal end). Equisetum palustre T.S stem Equisetum  Sclerenchyma is found at the ridges and parenchyma is at the grooves. Opposite to the grooves, there are large cavities called vallecular canals which contain air. Proto xylem may be disintegrated forming carinal canals. Those are usually water filled. Above structure is applied only to the inter nodal region. Near the node it is very complicated. Pith cavity is also supplied air.  Each sporangiophore is a stalked peltate structure bearing 5- 10 sporangia. Sporangia are thick walled. Spores develop into prothalli. Antherozoids are multiflagellated. Spores of Equisetum  Subclass Polypodidae – Order Osmundales Osmunda sp. Order Schizaeales Lygodium sp. Order Gleicheniales Gleichenia sp.  Phylum Filicophyta (Pterophyta) Most advanced group of the Pteridophyta. Stele – protostelic, siphonostelic or dictyostelic. Sporangia born in large numbers on the lower (abaxial) surface of the leaf. In a few we found marginal tassels. Spores develop into small, green, free living gametophytes. Frequently heart shaped. Sex organs are restricted to ventral surface.  Small root like rhizoids can be seen on the lower side of the gametophyte.(G) Produces the sex cells (egg + sperm) that give rise to a fern sporophyte (S) Sporophyte is differentiated into roots,stems and spirally arranged leaves. Leaves are megaphyllous. Most of them have compound leaves (fronds).  Antherozoids are multi flagellated. 3 orders in this phylum as Ophioglossales (most primitive), Marattiales and Filicales (most advanced).  Order Ophioglossales Ophioglossum sp. Helminthostachys sp.  Order Ophioglossales No any early fossil records. Widely distributed in tropics. Horizontal rhizome. No circinate vernation. Stipules are present. Fertile branches give rise to spikes. Sporangium is embedded in the stalk in Ophioglossum. Ophioglossum Botrychium sp.  Pinnately compound leaves and branched spike in Botrychium. Found in montane forests in Sri Lanka. Gametophyte of Botrychium  Helminthostachys sp. Flower like spike is produced  Sporangium is not embedded in the stalk in Helminthostachys. But it is also a spike. Clusters of sporangia in 2 rows. Compound leaves. Cluster of sporangia of Helminthostachys  Subclass Marattiidae – Order Marattiales Marattia sp. Angiopteris sp.  Order Marattiales 2 genera Marattia and Angiopteris. Stem is short and unbranched. Large compound leaves Circinate vernation is present. Fertile leaves and sterile branches are not distinguished as separate branches.  Sporangia are in groups as leaf sori. Indusium is absent. 0-30 sporangia in one sori. Marattia and Angiopteris plants are morphologically very similar. But sporangia are laterally fused to form synangium in Marattia. Marattia sp. Angiopteris sp. Angiopteris frond Marattia forming synangium.  Subclass Polypodidae – Order Osmundales Osmunda sp. Order Schizaeales Lygodium sp. Order Gleicheniales Gleichenia sp.  Order Filicales Most advanced group of pterophyta. Most advanced characteristic features can be seen. Main character is the nature of the sori. (Strobilus is the primitive character.) 3 types of sori in Filicales. Simple, gradate and mixed sori. So grouped as simplices, gradatae & mixtae.  Arrangement of sori in Filicales A sorus in which all the spoprangia appear, grow and mature at the same time is called simple sorus. A sorus in which the centre is occupied by oldest sporangium and the successive younger sporangia are present towards the base is called gradate sorus. The sporangia of different ages are present in a sorus without any definite arrangement is called mixed sorus. Simple sori All the sporangia are at the same stage of development. Eg. Gleichenia, Osmunda Gradate sori The oldest sporangia are at the top of the receptacle with successively young sporangia. Cyathea, Marsilea, Salvinia Mixed sori sporangia of different stages are mixed. (unordered manner). Fern sporangium  Family Gleicheniaceae Genus Gleichenia Creeping dichotomous rhizome. Mostly grows in open habitats. Sori are along the side veins. No inducium. Sorus contains 7-8 sporangia. Primitive feature. Gleichenia sori  Gleichenia Often seen growing under waterfalls, in swamps, under cliffs and in tall open forest and in open habitats. Prefers high humidity and good levels of sunshine and moisture. Sporangia with oblique annuli and organized in simple sori  Family Osmundaceae. Genus Osmunda (Royal fern) Two types of leaves as fertile pinnate and large sterile leaves. Form small number of spores. No inducium. Primitive type of sporangium. Osmunda simple sori  Family Schizaeaceae 3 Genera Schizaea, Anaemia and Lygodium In schizaea, unbranched short stem which forms roots. Linear vegetative leaves and fertile leaves. Schizaea elegans  Marginal sporangia in Lygodium (finger like projections). Can see in open habitats. These are also primitive types of pterophyta. Anemia True Indusium Eg: Asplenium False Indusium Eg: Adiantum sp  Family Cyatheaceae Genus Cyathea (Tree fern) Normally ferns have short stems but this has a long stem. So it is called tree fern. Very large, terrestrial ferns, the rhizomes trunk like and upright; indument of hairs or scales; sori indusiate. Sorus has a cup shaped true inducium. Cyathea Capensis Cyathea fulva  Cyathea leaf sori spores mostly tetrahedral, nonperisporial  Family Hymenophyllaceae Genus Hymenophyllum (Filmy fern) Leaves are very thin. Veins are very clear. Sorus arrange at the end of the veins. Inducium is a part of the leaf. Hymenthophyllum caudiculatum Hymenophyllum tunbrigense  Family: Salviniaceae Genus Salvinia Floating aquatics with small, rounded sporangia contained in saclike indusia; leaves sessile; heterosporous. Salvinia sporocarps Family Marsiliaceae Genus Marsilia (water fern) Marsilea quadrifolia L - Aquatics with long, usually rooted rhizomes - leaves long-petioled with 2 or 4 terminal leaflets, or none - sporangia contained in sporocarps (nutlike receptacles) along petiole; heterosporous Marsilea sporocarps  Family Azollaceae Genus Azolla Sporangia are also borne on special structures called sporocarps.  Family Polypodiaceae Genera Drynaria, Acrostichum, Asplenium, Adiantum, Pteris, Pyrrosia ,Blechnum. Acrostichum grows in or near mangrove ecosystem. (Sori all over the lower surface of the leaves.) Drynaria and Drymoglossum grow as an epiphytes. They have dimorphic leaves.  Drynaria sp. Epiphytic or lithophytic fern. Fronds are in two types. Green and sterile