Pteridophytes PDF

1 Major paper 3 PTERIDOPHYTES General characteristics: Pteridophytes, often referred to as ferns and their relatives, are a diverse group of vascular plants that have a range of un...

1 Major paper 3 PTERIDOPHYTES General characteristics: Pteridophytes, often referred to as ferns and their relatives, are a diverse group of vascular plants that have a range of unique characteristics. Here’s a summary of their general features: 1. Vascular Tissue  Xylem: Carries water and minerals from the roots to the rest of the plant. Unlike angiosperms, pteridophytes lack vessels and have a simpler xylem structure.  Phloem: Transports the products of photosynthesis (mainly sugars) from the leaves to other parts of the plant. 2. Reproductive Cycle  Alternation of Generations: Pteridophytes have a life cycle that includes two distinct phases: o Sporophyte: The dominant, diploid phase, which is the familiar fern plant. It is generally large and photosynthetic. o Gametophyte: The smaller, haploid phase known as the prothallus. It is usually a tiny, heart-shaped structure that produces gametes (sperm and eggs).  Spore Production: The sporophyte produces spores via meiosis in specialized structures called sporangia. Spores are usually released in clusters called sori on the underside of the fronds. 3. Spores  Sporangia: Structures where spores are produced. They can be found in various arrangements: o Sori: Clusters of sporangia, often covered by an indusium (a protective layer). o Strobili: Cone-like structures in some species, where sporangia are aggregated.  Germination: Spores germinate to form the gametophyte (prothallus) under suitable conditions, which then produces gametes. 4. Leaves (Fronds)  Structure: Fronds can be simple or highly divided into smaller leaflets called pinnae. They may be pinnate (feather-like) or pinnatifid (deeply lobed).  Growth: Fronds emerge from the fiddlehead stage (a coiled, young frond) and expand as they mature. 1 2 5. Rhizomes  Function: Underground or creeping stems that anchor the plant and store nutrients. They often produce new shoots and roots.  Structure: Typically horizontal, growing parallel to the soil surface. 6. Reproduction  Asexual Reproduction: Many pteridophytes can reproduce asexually through vegetative means, such as producing new individuals from rhizomes or by budding.  Sexual Reproduction: Involves the fusion of sperm and egg cells produced by the gametophyte stage, leading to the formation of a new sporophyte. 7. Habitat  Diversity: Pteridophytes are found in a wide range of environments, from tropical rainforests and temperate woodlands to rocky outcrops and arid regions.  Epiphytic Forms: Some species grow on other plants, using them merely for support without deriving nutrients from them. 8. Growth Forms  Terrestrial: Many pteridophytes grow directly in the soil.  Epiphytic: Some grow on trees or other plants, particularly in tropical regions.  Aquatic: Some species are adapted to living in aquatic environments. 9. Ecological Role  Soil Formation: Their decaying fronds contribute to soil development and nutrient cycling.  Habitat: Provide shelter and food for various microorganisms and small animals.  Pioneer Species: Some pteridophytes can colonize bare or disturbed soils, aiding in ecological succession. 10. Diversity and Classification  Major Groups: Pteridophytes are broadly classified into three main groups: o Ferns (Filicopsida): The largest group, with diverse forms and sizes. o Club Mosses (Lycopsida): Small, evergreen plants with scale-like leaves. o Horsetails (Equisetopsida): Plants with jointed stems and a brush-like appearance. Understanding these characteristics provides insight into the evolutionary significance and ecological roles of pteridophytes, showcasing their adaptability and diversity. 2  3 CLASSIFICATION OF PTERIDOPHYTES Pteridophytes are classified into several groups based on their evolutionary relationships and morphological characteristics. The classification is generally based on three main classes, with further subdivisions into orders, families, and genera. Here’s a detailed breakdown: 1. Class Lycopsida (Club Mosses) 2. Class Filicopsida (Ferns)  Characteristics: These are small, often evergreen  Characteristics: Ferns are the most diverse group of plants with simple, scale-like leaves. They have a pteridophytes. They typically have large, divided fronds distinctive appearance, often resembling mosses but and are widely recognized for their lush, green foliage. are actually more closely related to ferns.  Reproductive Structures: They produce spores in  Reproductive Structures: They produce spores in structures called sori, which are usually found on the cone-like structures called strobili or sporophylls. underside of the fronds. Some ferns have elaborate  Orders and Families: methods of spore dispersal.  Orders and Families:  Order Lycopodiales o Family Lycopodiaceae: Includes  Order Polypodiales genera like Lycopodium and Huperzia. o Family Polypodiaceae: Includes genera Members typically have creeping like Polypodium and Dryopteris. This is one of the largest families of ferns with rhizomes and erect, dichotomously various habitats and growth forms. branching stems.  Order Gleicheniales  Order Selaginellales o Family Gleicheniaceae: Includes genera o Family Selaginellaceae: Includes like Gleichenia. Members often have genera like Selaginella. Members often highly divided fronds and are typically have branching stems and are found in tropical regions. sometimes referred to as "spike  Order Cyatheales mosses." o Family Cyatheaceae: Includes tree ferns  Order Isoetales such as Cyathea and Dicksonia. These o Family Isoetaceae: Includes genera ferns can grow to be quite large, with a like Isoetes. These are aquatic or semi- trunk-like base and large, arching fronds. aquatic plants with tuber-like stems and  Order Ophioglossales thick, fleshy leaves. o Family Ophioglossaceae: Includes genera like Ophioglossum (adder’s tongue fern) and Botrychium (grape fern). These ferns are often smaller and have a simple, non-dissected frond with 3. Class Equisetopsida (Horsetails) a distinctive sporophyll.  Characteristics: Known for their jointed stems and whorled leaves, horsetails have a distinctive, brush-like appearance. They are often found in moist, marshy areas.  Reproductive Structures: They produce spores in cone-like structures called strobili, and they have a unique structure known as the sporangiophore.  Orders and Families: o Order Equisetales 3  Family Equisetaceae: Includes the genus Equisetum. Horsetails are the only living members of this order and family, characterized by their segmented stems and reduced leaves. 4 PSILOTUM Taxonomic position  Division: Psilophyta  Class: Psilotopsida  Order: Psilotales  Family: Psilotaceae  Genus: Psilotum General characteristics  Commonly known as Whisk fern.  Represented by only two species P.nudum and P.flaccidum.  P.nudum is distributed throughout the tropics and subtropics. It is found in Florida, Hawaii,New Zealand etc and in India it is found in Assam, Bengal,Kulu etc.  P.nudum is an erect, slender,shrubby plant found in the crevices of rocks but sometimes it occur as epiphyte also. Attains to a height of 25cm.  It is cultivated in green houses and Botanical gardens.  P.flaccidum is found in Mexico, Jamaica and some pacific islands.It is a rare species and a pendulous epiphyte which can grow up to 90cm in length.  Psilotum species occur as epiphytes generally on trees, on the trunks of coconut trees or at the vase of trees.  P.flaccidum differs from P.nudum in possessing flattened stem. Morphology Plant body is sporophytic and consists of subterranean rhizome and an erect aerial shoot. RHIZOME  Rhizome is cylindrical, irregularly, extensively and dichotomously branched, prostrate.  It is brown in colour and lack roots.  Rhizoids are present instead of roots which helps in absorption and anchorage.  Often associated with the rhizome,there will be an intracellular mycorrhizal fungus whose hyphae enter through the rhizoids and reach the cortex.  Sometimes the tips of immature rhizoids give rise to gemmae which helps in vegetative propagation.  The branches of rhizome, which are near the surface and also exposed to light,ultimately turn into aerial shoots. 4  5 AERIAL SHOOT  Aerial shoots are slender,green, upright, ridged and dichotomously branched.  In terrestrial forms, they grow upright and in epiphytes, the hangs down from the host plant.  The basal part of aerial shoot is usually smooth and cylindrical. But their distal part is longitudinally ribbed in P.nudum and flat in P.flaccidum.  The aerial shoots of P.nudum are short (15- 20cm) while those of P.flaccidum are long (upto 90cm).  In the absence of true leaves, green aerial shoots function as photosynthetic organs. APPENDAGES  Aerial shoots are devoid of true leaves. They bear small,scale like appendages which are devoid of vascular traces and stomata.  In P.nudum,they are arranged spirally or maybe irregularly distributed.  In P.flaccidum they are arranged in subopposite pairs.  The appendages are absent on rhizome and at the extreme basal part of the aerial shoots.  In the terminal part of the shoots,fertile appendages can be seen. In the axils of these fertile appendages, trilobite sporangia called synangia can be seen. ANATOMY AERIAL SHOOT Transverse section of the aerial shoot is irregular in outline due to the presence of ridges and grooves. It consist of three parts namely Epidermis, Cortex and Stele. 1. EPIDERMIS  well-developed single layered epidermis.  Cells are elongated and protected by thick cuticle.  Sunken stomata present. It shows the xerophytic feature.  The stomata are without subsidiary cells,a situation comparable to gymnosperms.  2. CORTEX  A well-developed cortex is present which is differentiated into three zones. Outer cortex middle cortex inner cortex  Made up of 2 to 5 layers of  Made up of 4 to 5 layers  Broadest zone. thin walled, elongated, of closely packed, thick  Consist of thin walled chlorophyll containing walled, parenchymatous cells cells. sclerenchymatous cells. with no intercellular  5 Intercellular spaces  Provides mechanical spaces. present. support  Cells rich in starch  This zone is photosynthetic reserves 6 3. STELE  In the rhizome, it is a protostele with central core of xylem completely surrounded by phloem.The xylem core is not starshaped or lobed.There is no pith.  In the transit zone between rhizome and aerial shoot,the xylem becomes lobed and as many as ten lobes can be counted. The protoxylem occupies the tips of the lobes. The phloem occurs in between the lobes and forms irregular patches. Here the stele is actinostelic protostele. There is no pith.  In the middle of aerial shoot, the number of xylem lobes are reduced to 5 or 7 and pith appears in the centre. Here it changes from protostele to siphonostele. RHIZOME The anatomy of rhizome is somewhat similar to aerial shoot. very small rhizomes of less than 1mm diameter is without any vascular tissues and is uniformly parenchymatous. The stele gets differentiated in some larger rhizomes. The following structures can be observed in rhizomes with a diameter of more than 2mm. ★ Epidermis:single layered, uninterrupted, made up of thin walled cells. ★ Cortex:well developed and differentiated into three regions. ★ Outer cortex:contain many hyphae of endophytic mycorrhizal fungus. ★ Middle cortex:consist of parenchymatous cells storing starch. ★ Inner cortex:two to four layered,cells are brown in colour due to deposition of phlobaphene which is compound formed as result of oxidation and condensation of tannins. APPENDAGES  The anatomy of appendage is simple.It consist of Epidermis and Mesophyll.  Epidermis: single layered, cutinized, stomata absent.  Mesophyll: consist of chlorophyllcontaining parenchymatous cells  No differentiation into palisade and spongy tissues.  More intercellular spaces in Psilotum nudum than Psilotum flaccidum.  In the absence of stomata and vascular traces,the leaves are not photosynthetic in function.Cuticle Epidermis Mesophyll.Fig: T.S of Leaf of Psilotum spp. 6  7 REPRODUCTION The sporophytic plant reproduces vegetatively and also by spores. VEGETATIVE REPRODUCTION (ASEXUAL REP)  Vegetative reproduction takes place by means of ovoid, minute,one cell thick,multicellular outgrowths developing on the rhizome. These outgrowths are called gemmae.Gemmae cells contain starch.  They undergo germination and produce new sporophytes which in turn produce new gemmae and repeat the cycle.  Germination of sporophytic gemmae occur when they remain attached to the parent plant and also after falling to an ideal substratum.  Gemmae like structures also develop on the gametophyte also. They are structurally similar to those occuring on the sporophyte. They germinate and produce new prothalli to repeat the cycle.  Vegetative reproduction also takes place by the death of the older parts of the rhizome. The younger parts of rhizome separate from the dead rhizome and grow as independent plants. REPRODUCTION BY SPORES (SEXUAL REP)  Reproduction by spores occur when the sporophytic plant attains maturity.  Spores are produced within the trilobite sporangia called synangia which is formed by the fusion of 2 or more sporangia.  A synangium develop on a small fertile appendage, subtended by a forked bract.  They together constitute of sporangium complex. STRUCTURE OF SYNANGIUM DEVELOPMENT OF SPORANGIUM  Synangium is a trilocular (three chambered)  Development of sporangium is of eusporangiate spore bearing structure in Psilotum. type.  It is considered as a fusion product of three  Early stages of the sporangial development indicate sporangia. that each of the three sporangia of a group develops  Location: axils of fertile appendages on the from a single epidermal cell of the sporangiophore. aerial shoot.  This initial cell divides periclinally to form outer  Wall is 3 to 4 layered. primary jacket cell and an inner primary archesporial  Thick outer wall forms the epidermis. cell.  Inner wall separates the three chambers.  The jacket cell undergoes repeated anticlinal and  Each locule is filled with large numbers of periclinal divisions to form 4 to 5 cells thick jacket bean shaped spores and they are of layer. The outermost layer becomes the epidermis. homosporous type.  The primary archesporial cell divides repeatedly to  Synangium splits along the three longitudinal form sporogenous cells which differentiate into lines of dehiscence thereby releasing spores. sporogenous tissue.  Psilotum differ from most of the other pteridophytes because neither its outermost sporogenous cells nor innermost jacket cells develop into tapetum. 7  8 SPORES IN PSILOTUM  Spores are homosporus.  Mature spores are kidney shaped.(average 0.065- 0.032mm)  The two curved ends of the mature spores are joined by a narrow slit.On either side of the slit,thick,Smooth, border called lip is present.  Outer coat of the spore is exine and inner coat is called the intine. DEVELOPMENT & STRUCTURE OF GAMETOPHYTE  The spore germination is a slow process which takes 3-4months.  The germinating spore absorbs water and swells.as a result, the turgor pressure inside increases, the exine opens along the median slit. All the inner contents, covered by the thin membrane of intine, project out in the form of a conical mound.  With the formation of transverse wall,a basal large spherical cell is separated from the upper extruded cell. The basal cell remains covered by the portions of the ruptured outer wall.  The upper cell divides by two intersecting oblique divisions to form and apical cell.  This apical cell leads to the formation of the prothallus  This results in the formation of prothallus provided with rhizoids. Prothallus represents the gametophyte.  The prothallus is simple, irregularly dichotomising, cylindrical, subterraneous measuring 0.5 to 2mm in diameter and upto 18mm in length. It is pale yellow to dark brown in color and covered with hair like rhizoids. Over the entire surface of the prothallus, antheridia and archegonia are scattered without any definite arrangement.  The prothalli are penetrated by an endophytic fungus in their early stages of development, which provides nutrients to the prothallus. Thus the prothallus is saprophytic. It usually lacks vascular tissue. SEX ORGANS The gametophyte is monoecious with male and female sex organs,they are scattered over the surface of the gametophyte. ANTHERIDIUM ARCHEGONIUM  It is the male sex organ.  It is the female sex organ.  In Psilotum it is projected out or emergent.  It is usually embedded in the prothallus  Mature antheridium is a semi spherical and consist of projecting neck. structure.  The neck consist of generally six tiers of  It is surrounded by a well defined jacket four cells each,2 neck canal nuclei and which is single layered and one cell thick. venter region encloses one venter canal  The jacket encloses a mass of spirally coiled cell and an egg cell. and multiflagellate antherozoids which are  2 cover cells are present at the tip of the unicellular, uninucleate and mutlciliate in neck region. Psilotum.  The jacket 8 contains only one opercular cell.  They are liberated through a passage formed by the disintegration of the opercular cell.  9 FERTILIZATION  Fertilization takes place with the help of water.  Antherozoids are attracted chemotactically towards the archegonium. A chemical substance comes out from the open archegonium, it functions as a sperm attractor, contains large amount of organic and inorganic compounds, especially malic acid and fumaric acid.  The neck canal nuclei and venter canal nuclei disintegrate to form a free passage for the entry of  antherozoids.   During fertilization  antherozoids swim down along this canal and fuses with the egg to form a diploid zygote. DEVELOPMENT OF SPOROPHYTE  Zygote isthe first cell of sporophytic generation.  It enlarges in size and completely fills the venter cavity.  It divides to form an outer epibasal cell and an inner hypobasal cell.  The epibasal cell undergo repeated division to form shoot LIFE CYCLE OF PSILOTUM and hypobasal cell form the foot.  This type of embryogeny in which the shoot forming cell is directed towards the neck of the archegonium is called exoscopic embryogeny.  After the formation of epibasal and hypobasal cells, both of them undergo longitudinal division to form four cells.  Further divisions are irregular (Holloway, 1939)  Some of the cells of the foot undergo transverse division to form finger like rows of cells.  These finger like structures penetrate into the gametophytic tissue.  With the help of some regular divisions of the epibasal cell, a three sided apical cell is formed.  A typical rhizome is soon formed which is infected by an endophytic mycorrhizal fungus.  Then the rhizome branches dichotomously. Some of these branches turn upward and develop to aerial shoots and thus a new sporophytic plant is formed. LIFE CYCLE  The plant body of Psilotum is a diploid sporophyte. Synangium is the trilobite sporangia which bears the spores.  Inside the Synangium, the diploid SMC undergo meiosis to form haploid spores.  They germinate to form the haploid prothallus (monoecious ). Antheridium produces antherozoids and archegonium produces egg  Fertilization occurs and a diploid zygote is formed. 9  The zygote develop into embryo which later form the mature plant body, diploid sporophyte and the cycle is repeated.  10 SELAGINELLA Systematic position general characteristics  spike moss or club moss  About 700 species of selaginella are distributed in the  Division: Lycopodiophyta tropical and temperature areas.  Class: Lycopodiopsida  Most of the selaginella species grow in damp shady  order: Selaginellales areas.  family: Selaginellaceae  Some species are xerophytes. e.g: S. lepidophylla, S.  genus : Selaginella rupestris MORPHOLOGY OF SELAGINELLA  Some are epiphytic eg: s.oregana Plant body is differentiated into:  Common species S. rupestris S. megaphylla S. kraussiana S. bryopteris  Root  Stem ROOT  Leaves  The root is adventitious grow from the tip of rhizophore or directly  Ligules from the stem.  Rhizophore  Root are arise endogenously and branched dichotomously.  Aerial root contain cap. (in epiphyte).  Root hair is present. STEM LEAVES LIGULES  Stem is green, herbaceous,  Leaves are microphyllous  On the upper surface a dichotomously branched, erect with a single unbranched small, membranous, or prostrate with erect branches. midrib. tongue like or leaf like  Stem is covered with leaves.  On the upper surface a small, outgrowth called ligule  They are also pseudomonopodia membranous, tongue like present on the adaxial (false growth from one point). outgrowth called ligule is side of the leaf.  The shoot apex consists of a present.  A mature ligule has a single apical cell in most cases.  The leaves are dorsiventral. prominent basal portion called the glossopodium.  Definite function of the RHIZOPHORE ligule is unknown.  It is a colourless, leafless, unbranched and cylindrical structure.  This structure arises from the prostrate axis at the point of dichotomy and elongates downward.  free end of rhizophore touches the soil it develops a tuft of adventitious roots. 10  Root cap is absent. It develops adventitious root at its tip.  11 ANATOMY OF SELAGINELLA STEM ANATOMY LEAF ANATOMY  Epidermis is without hair and stomata. It is  Epidermis single layered on the lower and surrounded by a cuticle. upper side stoma is present.  Epidermis is followed by a well defined cortex  Stomata present on the upper surface region. It is parenchymatous or is differentiated.Epidermis contain chloroplast. into outer sclerenchymatous and inner  Mesophyll is uniformly formed either all of parenchymatous regions. spongy or all palisade like elongated cells with  Stele is generally protostelic, where xylem is air spaces surrounded by phloem cells. The number of steles  Simple vascular bundle at the center. varies in different species.  Central portion is separated from cortex by a LIGULES ANATOMY cavity having air spaces  The ligule arise from several short rows of  Endodermis :the cortex and central tissue is superficial cells. connected by radially elongated cells called  Fully developed ligule consists of a distinct and trabeculae. hemispherical basal region where cells are  Stele is surrounded by a pericycle that is single large and thin walled and contain vacuolated layered. Pith is generally absent. cytoplasam this region is glossopodium.  Glossopodium surrounded by a sheath called ROOT ANATOMY glossopodium sheath.  Outermost layer is epidermis (large single layer), covered by cuticle.  Root hairs are present and arise from some epidermal cells.  Lower region of the epidermis, wide zone of cortex is present  Outer hypodermis (have sclerenchyma cells)  Inner parenchyma cells.  Endodermis layer is present (inconspicuous)  Single layered pericycle is present just below the endodermis.  Xylem is surrounded by phloem RHIZOPHORE ANATOMY  Outermost layer is epidermis. It is of thick walled and single layer cells.  Root hairs are absent. REPRODUCTION  Just below the epidermis there is cortex region  Hypodermis (thick walled) few layered. 11  Thin walled parenchymatous region  After cortex region endodermis layer around the pericycle.  Thin walled pericycle is present around the vascular tissue.  12 REPRODUCTION 1. Vegetative rep. fragmentation tubers  Fragmentation These appear towards the end of Under humid conditions in  Resting buds the growing season. The tubers S.rupestris,branches of the stem  Tubers may be aerial, developing at the develop some roots. These branches 2. Sexual rep. tips of underground branches (e.g., later disjoin from the parent plant S. chrysocaulos) (e.g., S. and develop into separate individual chrysorrhizos). Under favourable plants. conditions tubers germinate into a new plant. Resting buds The resting buds develop at the tip of some aerial branches. They pass the unfavourable conditions and develop rhizophore in the favourable conditions. Sexual reproduction by spores f  Selaginella is a sporophytic plant and reproduce sexually.  Selaginella is a heterosporous i.e., produce two different types of spores- megaspores and microspores.  These spores are produced in megasporangia and microsporangia, respectively which, in turn, are produced on fertile leaves known as megasporophylls and microsporophylls respectively.  Usually both these structures are grouped together to form a compact structure known as strobilus which is usually a terminal structure. sporangia  Mature sporangia is a stalked structure consist short stalk and capsule.  Stalk is multicellular and multiseriate,megasporophyll capsule is 2 layered wall called jacket.  Two types of sporangia:  Megasporangia(large and pale)  Microsporangia (small, slightly elongated. Structure of sporangia Sexual reproduction (gametophyte)  Microsporangia: they are small, stalked, oval and  Microspores and macrospores develop varying in shapes, into male and female gametophyte.  Mega sporangia: they are stalked and 4 lobes, larger  Germination is precocoious ( within the in size and present at base of strobilus, spores are of walls of sporangia). larger size.  Male gametophyte is released at 13 celled stage while female gametophyte 1. Both consist of 2 layered sporangial wall surrounding the comes at various stages, depending upon tapetum and sporogenous tissue. the species. 2. Tapetum is developed from innermost layer of sporangial wall. 3.Both differ 12in their size, location, and number of spores 4. To release spore, both sporangia form vertical cleft in wall.  13 Microspore (future male gametophyte) Megaspores (future female gametophyte) The microspores are very minute in size and The megaspores are much bigger in size than the microspores range in diameter from 0.015 to 0.05 mm. Soon and range in diameter from 1.5-5 mm. When they are in tetrad after separation from the tetrad they will be the spores have a triadiate shape but become sub- spherical triradiate but gradually assume a sub-spherical on separation. The wall of the megaspore is very thick and shape. The spore wall is two- layered. The outer consists of a sculptured exine, a middle mesospore and a thin exine (exospore) is very thick and is sculptured. intine. The inner inline (endospore) is thin and delicate. The cytoplasm consists of reserve food in the form of oil The spore consists of reserve food material in the globules and nitrogenous material. The amount of nitrogenges form of oil globules and nitrogenous material. material present is considerably less in comparison with the microspore. Chemical analysis of the stored food in megaspores of Selaginella reveals that they have 48% fats, 0.43% nitrogenous matter and 1.26% mineral material. Fertilization:  Water is necessary to carry out the process of fertilization. The swimming antherozoids reach the egg through the neck of archegonium and the nucleus of antherozoid fuses with the egg nucleus thus forming a zygotic nucleus.  The fertilized egg secretes a wall around it forming a diploid structure known as zygote or oospore (2x).  Thus the gametophytic generation ends and the initial stage of sporophytic generation is formed.  In some species e.g. S. intermedia the egg develops into embryo without fertilization. This phenomenon is known as parthenogenesis. 13  14 EQUISETUM CLASSIFICATION GENERAL CHARACTERISTICS  Horsetails are commonly found in wet or damp environments,  Division: Pteridophyta such as riverbanks, marshes, and floodplains. Some species are  Class: Equisetopsida adapted to dry habitats.  Order: Equisetales  Family: Equisetaceae  They are often perennial, with underground rhizomes from  Genus: Equisetum which the above-ground stems arise  The main feature of Equisetum is its jointed, ribbed, and often hollow stems. These stems are typically green and photosynthetic. They are segmented by nodes and internodes, with the nodes bearing whorls of branches or leaves.  Equisetum reproduces through spores rather than seeds. The spores are produced in structures called strobili (or cones) located at the tips of the stems or branches.  These are spore-producing structures that appear as cone-like or spike-like formations at the tips of the fertile stems. They contain sporangia where spores are produced. MORPHOLOGY stem leaves  Jointed Stems: The primary feature of  Leaf Arrangement: The leaves are small, scale-like, Equisetum is its jointed, ribbed stems. and arranged in whorls at each node. They are typically These stems are typically green and serve reduced in size and do not play a major role in as the main photosynthetic organs of the photosynthesis. plant. They are segmented by nodes and  Leaf Structure: The leaves are fused into a sheath internodes. around the stem at each node. They are generally non-  Nodes and Internodes: The stem is photosynthetic in most species, with the stem handling divided into segments by nodes (the points the photosynthesis where leaves or branches arise) and reproductive structures internodes (the sections between nodes). Internodes are usually hollow, while nodes  Strobili (Cones): The reproductive structures, or strobili, are solid. are cone-like or spike-like structures located at the tips  Silica Content: The stems contain high of the fertile stems or branches. They contain sporangia levels of silica, which gives them a rough where spores are produced. texture and contributes to their abrasive quality. rhizomes Underground Rhizomes: Equisetum plants have a system of underground rhizomes (horizontal, subterranean stems) from which the above-ground stems arise. Rhizomes serve as a means of vegetative reproduction14and help the plant spread. Me watching you read mere mehnat ke notes  15 ANANTOMY Stem anatomy leaf anatomy  Epidermis: The outermost layer of the stem is  Leaf Arrangement: The leaves of Equisetum are covered by an epidermis, which may have a small, scale-like, and arranged in whorls around the waxy cuticle to reduce water loss. nodes. They are usually not photosynthetic but serve  Cortex: Beneath the epidermis is the cortex, more for structural support. which contains collenchyma (supportive tissue)  Leaf Structure: Each leaf is fused into a sheath that and sometimes sclerenchyma (more rigid encircles the stem at the node. These leaf sheaths are support tissue). In Equisetum, the cortex can be generally simple and do not have a complex internal relatively thick and provides structural support. structure.  Vascular System: Equisetum has a unique vascular arrangement. The vascular bundles are rhizomes scattered throughout the stem, and there are no distinct vascular cylinders or central pith as  Structure: Equisetum plants have an extensive found in many other plants. The vascular underground rhizome system. Rhizomes are bundles consist of xylem (water-conducting horizontal, underground stems that store nutrients tissue) and phloem (nutrient-conducting tissue) and help the plant spread vegetatively. and are arranged in a circular pattern in the  Function: The rhizomes allow for asexual stem's cross-section. reproduction and the establishment of new shoots, reproductive structures contributing to the plant's ability to colonize and spread in its habitat.  Strobili (Cones): Equisetum reproduces via spores, and the reproductive structures are called strobili or cones. These structures are located at the tips of fertile stems or branches.  Sporangia: Within the strobili, sporangia (spore-producing organs) are present. They release spores that are dispersed for reproduction.  REPRODUCTION Sex Organs of Equisetum i. Antheridium: In monoecious species, antheridia develop later than archegonia. They are of two types - projecting type and embedded type. Antheridia first appear on the lobes of the gametophyte. The periclinal division of the superficial antheridial initial gives rise to jacket initial and an androgonial cell. The jacket initial divides anticlinally to form a single-layered jacket. The repeated divisions of androgonial cells form numerous cells which, on metamorphosis, produce spermatids/antherozoids. The antherozoids escape through a pore created by the separation of the apical jacket cell. The apical part of the antherozoid is spirally coiled, whereas 15 the lower part is, to some extent, expanded.  16 ii. Archegonium:  Any superficial cell in the marginal meristem acts as an archegonial initial which undergoes periclinal division to form a primary cover cell and an inner central cell. The cover cell, by two vertical divisions at right angle to each other, forms a neck. The central cell divides transversely to form a primary neck canal cell and a venter cell.  Two neck canal cells are produced from the primary neck canal cell. While,the venter cell, by a transverse division, forms the ventral canal cell and an egg.At maturity, an archegonium has a projecting neck comprising of three to four tiers of neck cells arranged in four rows, two neck canal cells of unequal size, a ventral canal cell, and an egg at the base of the embedded venter. Fertilization:  Water is essential for fertilization. The gametophyte must be covered with a thin layer of water in which the motile antherozoides swim to the archegonia. The neck canal cells and ventral canal cell of the archegonia disintegrate to form a passage for the entry of antherozoids.  Many antherozoids pass through the canal of the archegonium but only one of them fuses with the egg. Thus diploid zygote is formed. Generally more than one archegonia are fertilized in a prothallus. Embryo (The New Sporophyte):  The embryo is the mother cell of the next sporophytic generation. Unlike most pteridophytes, several sporophytes develop on the same prothallus. The first division of the zygote is transverse. This results in an upper epibasal cell and lower hypobasal cell. The embryo is therefore exoscopic (where the apical cell is duacted outward. No suspensor is formed in Equisetum.  The epibasal and hypobasal cells then divide at right angles to the oogonial wall, and as a result a tour-celled quadrant stage is established. All the four cells of the quadrant are of different size and shape.  The four-celled embryo undergoes subsequent divisions and the future  shoot apex originate from the largest cell and leaf initials from the remai- ning cells of one quadrant of the epibasal hemisphere. 16  17 TELOME THEORY It was first proposed by zimmermann in 1930 and elaborated 1965. According to this theory, all muscular plants evolved from a simple, leafless, rootless, dichotomously branched, sterile and fortile anis. called telomer which originated from Medially symmetrical and dichotomously branched algal ancestor. The other plants develop leaf, root and sporangia by modification and differentiation in telomes. zimmermann termed the internal terminal portion of plants having single rib as telome. The internodes below it as mesosome. The telome may be fertile having single terminal sporangium or sterile without sporangia According to this theory, the organs leaves, root, sporangia & have evolved from 2 the simplest and earliest vascular plants by progressive differentiation called elementary process. Process of Telome Theory overtopping planation  Overtopping  One of the twodichotomising  Plnation Rearrangement branches outgrows the other of telomes and mesomes  Planation and become larger and from a three dimensional  Syngenesis mechanically stronger pattern to a single plane.  Reduction  Larger branch forms - Axis  Curvation  Overtopped branch forms - lateral branches Syngenesis reduction curvation Telomes and mesomes fuse  Activity of terminal  The fertile Telomes become tangentially. meristem of each telome curved or bend downwards supressed resulting into  Two sub processes Parenchymatous tissueis developed in much shorter branches  Incurvation -downward shifting between Known as webbing process Responsible for - of the sporangia from terminal In stem of Selaginella polystelic  ➤ Microphyllous leaves of or ventral surface of the leaf in condition due to – simple lycopsida and Sphenopsida Pteropsida parenchymous webbing Needle like leaves of  Recurvation -downward conifers bending of the sporangia occurs along with the sporangial stalks in Sphenopsida 17  18 Origin of leaves origin of sporophylls origins of roots Acc. To zimmermann telome theory Acc. To zimmermann there are 3 divisions The roots originated from the microphyllus leaves in lycophyta underground creeping  Origin of sporophylls in lycophyta branches. originated by the process of reduction & megaphyllus leaves of  Origin of sporophylls in sphenophyta fern originated by combined process  Origin of sporophylls in flycophyta of overtopping,planation,syngenesis. Merits of telome theory demerits of telome theory  describes the origin and evolution  Does not explain how a telome-like characteristic body has of sporophytes of land plants been developed [Bower (1935)]  Structure of the sporophytes of the  Telome theory does not explain the whorled or spiral most primitive known plants is arrangement of sporangia [Thomas (1950)] defined  For origin of Lycopsida, it is somewhat hypothetical [Andrews  The exact relationship between the (1960)] root, stem and leaves  Does not provide an acceptable origin of all leafy structures  Connects the living and fossil  It does not explain the derivation of the dictyostelic condition plants. [Stewart (1964)] Apogamy and apospory These are two mechanisms related to the reproduction of plants, particularly in ferns and some other non-flowering plants. They are forms of asexual reproduction, where the plant can reproduce without the typical processes of fertilization. Here's a detailed look at each: Apogamy Apospory Definition: Apogamy is a type of asexual reproduction in Definition: Apospory is a form of asexual reproduction which a plant reproduces without fertilization. where a gametophyte develops from somatic cells of the Specifically, it occurs when a sporophyte (the diploid sporophyte without the need for meiosis. It involves the stage of the plant) develops directly from a gametophyte formation of a new gametophyte directly from the tissues of (the haploid stage) without the fusion of gametes. the sporophyte generation. Mechanism: Mechanism: 1. Gametophyte Stage: In plants that reproduce via 1. Sporophyte Tissue: In apospory, cells of the apogamy, the gametophyte (haploid stage) is sporophyte (diploid stage) undergo mitosis rather usually a small, independent plant. In ferns, this than meiosis. These cells develop into a new stage is often referred to as a prothallus. gametophyte. 2. Sporophyte Development: Instead of 2. Gametophyte Formation: The newly formed undergoing fertilization (where sperm fertilizes gametophyte is genetically identical to the the egg), a sporophyte develops directly from the sporophyte from which it originated. This process gametophyte. This can occur when a cell in the skips the reduction division typically involved in gametophyte undergoes mitosis to produce a gametophyte development, leading to a gametophyte sporophyte without the typical fertilization that is genetically identical to the parent sporophyte. process. 3. Resulting Plants: The new gametophyte then goes 18 Plant: The resulting sporophyte is 3. Resulting through the usual process of growing and potentially genetically identical to the gametophyte. This producing sporophytes, completing the life cycle. means that the new plant is essentially a clone of the original gametophyte.  19 STELAR EVOLUTION The stele (=Greek word meaning pillar or column) is defined as a central vascular cylinder, with or without pith. Endodermis is the boundary between cortex and stele. The central cylinder or core of vascular tissue, consisting of xylem, phloem, pericycle and sometimes mudullary rays and pith, is technically called the stele. The concept of the stele as the fundamental unit of vascular system was put forward by Van Tieghem and Douliot (1886) who proposed and developed Stelar theory. The stele of stem was connected with that of leaf by a vascular connection known as leaf trace. Types of stele in pteridophytes :The stele in pteridophytes can be differentiated into two major groups. 1. Protostele Siphonostele It is the most simplest and primitive type of stele. In. Siphonostele: Medullated protostele is called siphonostele. It protostele, the vascular bundle is a concentric solid is characteristic of Filicophyta. This is the modification of mass and the central core of xylem is surrounded by a protostele. During the development the siphonostele the layer of phloem and finally surrounded by a layer of central core of xylem is replaced by parenchymatous cells so that definite pith surrounded by xylem appears in the centre. pericycle Evolution of the stelar system It is now generally clear that the simplest type of stele is protostele. It is fundamental type for the vascular plants in general and the pteridophyta in general and all the other types of stele have been derived from it in the course of evolutionary specialization. As far as known all pteridophytes in the initial (sporeling) stage start with protostelic stem. When the shoot grows accompanying an increase in size, there is internal differentiation of the stele. The first step is appearance of parenchyma, scattered in the xylem core and finally a central parenchymatous medulla or pith is developed in the protostele. Such type of stele is called Siphonostele. The method by which medullation came about in a protostele and formed a siphonostele is a debated question and explained by two hypotheses viz. Extra-stelar and Intra-stelar origin of pith. In its simplest form the siphonostele has no leaf gaps e.g. Selaginella and known as cladosiphonic siphonostele in contrast with phyllosiphonic condition with leaf gaps. Siphonosteles which are perforated by scattered leaf gaps are known as Solenostele and a siphonostele with more overlapping gaps is known as dissected siphonostele or dictyostele. The final elaboration of the stellar organization in pteridophytes consists in the development of a number of separate steles. Such a stele is known as Polycyclostele. Another modification of siphonostele is the Eustele in which the vascular system consists of collateral vascular bundles 19  20 Economic importance of Pteridophytes Pteridophytes, which include ferns, horsetails, and clubmosses, play several important roles in various economic sectors. While they might not be as widely recognized as flowering plants, their contributions to industry, horticulture, and other areas are significant. Here’s a detailed look at their economic importance: 1. Horticulture and Landscaping 2. Traditional Medicine  Ornamental Plants: Many ferns and other pteridophytes Herbal Remedies: In many cultures, pteridophytes are popular as ornamental plants due to their unique foliage have been used in traditional medicine. For and aesthetic appeal. They are commonly used in gardens, example: indoor plants, and landscaping designs. Examples include Boston ferns (Nephrolepis exaltata), maidenhair ferns  Horsetails (Equisetum spp.): Known for (Adiantum spp.), and bird’s nest ferns (Asplenium spp.). their high silica content, horsetails are used  Ground Cover: Certain ferns are used as ground cover in herbal medicine for their potential plants because of their ability to thrive in shaded or low- benefits in bone health and connective light conditions where other plants might struggle. This tissue repair. makes them valuable for erosion control and soil  Ferns (e.g., Pteridium aquilinum): Some stabilization in shaded garden areas. ferns have been used in traditional remedies for digestive issues and other ailments. 3.Industrial Applications 4. Cultural and Aesthetic Value  Soil Stabilization and Erosion Control: The extensive root  Crafts and Decorations: Some systems of some pteridophytes help stabilize soil, making them useful pteridophytes are used in crafts and in preventing erosion in areas prone to soil loss, such as construction decorations. Fern fronds are often used sites or degraded land. in floral arrangements and as part of traditional art forms, such as pressed  Bioindicators: Pteridophytes are used as bioindicators for plant art. environmental monitoring. Their sensitivity to pollutants and changes in environmental conditions makes them useful for assessing ecosystem health. 5.Agriculture 6.Ecological Importance Soil Fertility: Certain pteridophytes, like ferns, contribute Biodiversity: Pteridophytes contribute to the biodiversity of various to soil fertility by adding organic matter when they ecosystems. Their presence supports a range of other organisms, decompose. Their role in nutrient cycling helps maintain including insects, fungi, and other plants, which can be important soil health, which can indirectly benefit agricultural for ecosystem stability and productivity. productivity. In summary, pteridophytes have a diverse range of economic roles, from horticulture and medicine to industrial and ecological applications. Their contributions, while sometimes overlooked, are significant in supporting both human needs and environmental health. 20