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Pteridophyte - Simple and easy notes to study

Simple and easy notes to study
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Bsc botony (Botony)

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Academic year: 2022/2023
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PTERIDOPHYTES

Pteridophyta (Gr, Pteron = feather, phyton = plant), the name was originally given to those groups of plants which have well developed pinnate or frond like leaves. Pteridophytes are cryptogams (Gr. kruptos = hidden, and Gamos = wedded) which have well developed vascular tissue.

Therefore, these plants are also known as vascular cryptogams or snakes of plant kingdom. They are represented by about 400 living and fossil genera and some 10,500 species. Palaeobotanical studies reveal that these plants were dominant on the earth during the Devonian period and they were originated about 400 million years ago in the Silurian period of the Palaeozoic era.

GENERAL CHARACTERS OF PTERIDOPHYTES

i. Majority of the living Pteridophytes are terrestrial and prefer to grow in cool, moist and shady places (e., Ferns), some members are aquatic (e., Marsileci , Azolla ), xerophytic (e., Selaginella rupestris , Equisetum ) or epiphytic (e., Lycopodium squarrosum ) ii. Majority of the Pteridophytes are herbaceous but a few are perennial and tree like (e., Angiopteris ). Smallest Pteridophyte is Azolla (an aquatic fern) and largest is Cyathea (tree fern). iii. Plant body is sporophytic and can be differentiated into root, stem and leaves. iv. Roots are adventitious in nature with monopodial or dichotomous branching. Internally usually they are diarch. v. Stem is usually branched. Branching is monopodial or dichotomous. Branches do not arise in the axil of the leaves. In many Pteridophytes stem is represented by rhizome. vi. Leaves may be small, thin, scaly (microphyllous e., Equisetum ), simple and sessile (e., Selaginella ) or large and pinnately compound (megaphyllous e., Dryopteris , Adiantum ). vii. Vascular tissue is present in stem and root. It consists of xylem and phloem. Xylem consists of tracheids only and phloem has only sieve tubes.

viii. The steel is protostele (e., Rhynia , Lycopodium ), siphonostele (e., Equisetum ), dictyostele Adiantum ) or polycyclic (e., Angiopteris ). ix. Cambium is absent; hence, they do not show secondary growth.

REPRODUCTION IN PTERIDOPHYTES

i. Reproduction takes place by means of spores which are produced inside sporangia. ii. The development of the sporangium may be leptosporangiate (sporangium originates from a single cell) or eusporangiate (sporangium develops from a group of cells). iii. Sporangia may be borne either on stem or leaves. On the stem they may be terminal (e., Rhynia) or lateral (e., Lycopodium). On the leaves (sporophylls) they may be ventral, marginal (Pteris, Adiantum) or dorsal (e., Polypodiceae). In Equisetum the sporangia are borne on special structures called sporangiophores which constitute a cone. In Marsilea, Azolla, Salvinia sporangia are produced in sporocarps. iv. Spores on germination give rise to multicellular gametophytic bodies called prothalli (sing. prothallus). v. In homosporous Pteridophytes prothalli are monoecious (antheridia and archegonia develop on the same prothallus). In heterosporous species prothalli are always dioecious. Microspores on germination give rise to male prothalli and megaspores to the female prothalli. vi. Antheridia and archegonia are developed on prothalli. vii. Antheridium is surrounded by a single layered sterile jacket. viii. Archegonium consists of four vertical rows of neck cells, 1-2 neck canal cells, ventral canal cell and egg. ix. Antherozoids are unicellular, biflagellate (e., Selaginella) or multiflagellate (e., Equisetum and ferns) and motile. x. Antherozoids are attracted towards the neck of the archegonium chemotactically by certain substances like malic acid) present in the mucilaginous substance formed by the degeneration of neck canal cells and venter canal cell. xi. Water is essential for fertilization (zooidogamous). Therefore, Pteridophytes are also known as amphibians of the plant kingdom.

WATER Essential for Fertilization Not necessary

MICROSPORES AND MEGASPORES

Develop independently after being shed from their Sporangia

Microspores are shed for a short time from Microsporangia and the Megaspores are permanently retained within Megasporangia. POLLEN TUBE Absent Present OVULE Absent Present SEED Absent Present

GAMETOPHYTE Independent of the Sporophyte Dependent on the Sporophyte.

COMPARISON OF PTERIDOPHYTES WITH BRYOPHYTE

BASIS FOR COMPARISON BRYOPHYTES PTERIDOPHYTES

BODY DEFINITION Bryophytes has leafy or thalloid plant body.

In pteridophytes plant body in differentiated into roots, stems, and leaves.

VASCULATURE SYSTEM No vasculature system, which means xylem and phloem absent.

Proper vasculature is present which means xylem and phloem is present.

VASCULAR TISSUE Absent Present

PRESENCE OF ROOTS No roots, instead rhizoids are present helps in anchoring

Roots are present.

PRESENCE OF STEMS OR No true stems or leaves are True stem and leaves are

BASIS FOR COMPARISON BRYOPHYTES PTERIDOPHYTES

LEAVES present. present.

ARCHEGONIUM AND ITS FORMATION

Common exposure of archegonium, whose neck is formed of six rows of cells.

Partially embedded archegoninum and it's neck has only four rows of cells.

ANTHERIDIUM Stalked. Sessile.

DOMINATING PART Gametophyte is dominating. Sporophyte is dominating.

CELL TYPE It has haploid cells. It has diploid cells.

EXAMPLES Mosses, liverworts, hornworts. Spikemosses, clubmosses, ferns, quillworts.

SPOROPHYTIC PHASE Depends completely on gametophytic.

Saprophytic phase is an independent autotrophic.

DEVELOPMENT OF SPORANGIA IN PTERIDOPHYTES

On the basis of development, the sporangia in Pteridophytes are divided into two types. i. EUSPORANGIATE TYPE ii. LEPTOSPORANGIATE TYPE

i. Eusporangiate Type

Sl. No: EUSPORANGIATE TYPE LEPTOSPORANGIATE TYPE 01 Sporangium is massive Sporangium is small

02 Sporangium is formed from many initials

Sporangium formed from single initial

03

Sporangium tissue is derived from the inner daughter cell

Sporangium tissue is derived from the outer daughter cell

04 Wall is several cells thick Wall is only one cell thick

05 Examples:- Lycopodium, Selaginella, Equisetum

Examples:- Pteris, Polypodium, Marsilea

LIFE CYCLE PATTERNS IN PTERIDOPHYTES

Pteridophytes show heteromorphic alternation of generation. The main plant body is sporophytic and forms a dominant phase in the life cycle. Sporophytic plant body develops sporangia in which sporogenous tissue is formed. Sporogenous tissue divides meiotically to form haploid spores.

Majority of the Pteridophytes are homosporous e., Lycopodium, Pteris etc. Spores on germination produce monoecious gametophyte. Some Pteridophytes are heterosporous and produce two types of spores: microspores and megaspores.

Microspores on germination produce male gametophyte (prothallus) while megaspores on germination produce female gametophyte (prothallus). So, the prothalli are dioecious.

Antheridia and archegonia develop on the same prothallus (monoecious) or on different prothalli (dioecious). The male and female gametes fuse to form zygote which develops into sporophyte. Thus, the life cycle of a Pteridophyte consists of an alternate succession of sporophytic and gametophytic generations.

APOGAMY, APOSPORY AND PARTHENOGENESIS

Pteridophytes show heteromorphic alternation of generation. However, there are certain other modifications where the essential stages of life cycle are eliminated. These modifications are called apogamy, apospory and parthenogenesis. APOGAMY The formation of a sporophyte directly from the vegetative cells of the gametophyte without the act of syngamy or gametic union is called apogamy (Winkler, 1908). The term apogamy was first used by De Bary (1878). It was first reported in Pteris cretica by Farlow (1874). Later, apogamy has been described in many Pteridophytes e., Selaginella (Hieronymus, 1911, 1913), Marsilea (strasburger, 1907) etc. The apogamous embryo may develop from one or more cells of the gametophyte. The sporophytes, produced as a result of apogamy, possess the same number of chromosomes as the gametophyte. APOSPORY The formation of gametophyte from a sporophytic cell without meiosis is known as apospory. It was first discovered by Druery (1884) as a natural phenomenon in Athyrium filix- femina var. clarissima. Since then it has been reported in many Pteridophytes e., Tricohmanes (Bower, 1888), Pteris aquilina (Farlow, 889) Asplenium dimorphum (Goebel, 1905), Osmunda Javanica (Sarbadhikari, 1936), Tectaria trifoliata Steil. 1944) etc.

b clavatum is used in skin diseases. c. Equisetum arvense is used as diuretic (promoting urine discharge). d and frond bases of Dryopteris filix-mas are used as taenifuge. iv. SOME OTHER USES a. Several species of Lycopodium e., L. obscurum are used in Christmas wreaths and other decorations. It is commonly called as 8Christmas green9. b arvense is biological indicator (for the presence of gold in the soil). c. Equisetum deposit large amount of silica in their cell walls. So formerly, it was used in cleaning and polishing the metal pots. Therefore, the plant has been given the name 8scouring rushes9. d shoots of Dryopteris filix-mas are used as vegetables. e. Starchy paste of sporocarps of Marsilea drummondii is used in making cakes and is called 8nardoo f. Azolla is grown in the rice fields to maintain its fertility because it has the symbiotic association with the cyanobacteria (blue green algae) Nostoc.

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Pteridophyte - Simple and easy notes to study

Course: Bsc botony (Botony)

650 Documents
Students shared 650 documents in this course

University: University of Calicut

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PTERIDOPHYTES
Pteridophyta (Gr, Pteron = feather, phyton = plant), the name was originally given to
those groups of plants which have well developed pinnate or frond like leaves. Pteridophytes are
cryptogams (Gr. kruptos = hidden, and Gamos = wedded) which have well developed vascular
tissue.
Therefore, these plants are also known as vascular cryptogams or snakes of plant
kingdom. They are represented by about 400 living and fossil genera and some 10,500 species.
Palaeobotanical studies reveal that these plants were dominant on the earth during the Devonian
period and they were originated about 400 million years ago in the Silurian period of the
Palaeozoic era.
GENERAL CHARACTERS OF PTERIDOPHYTES
i. Majority of the living Pteridophytes are terrestrial and prefer to grow in cool, moist and
shady places (e.g., Ferns), some members are aquatic (e.g., Marsileci, Azolla), xerophytic
(e.g., Selaginella rupestris, Equisetum) or epiphytic (e.g., Lycopodium squarrosum)
ii. Majority of the Pteridophytes are herbaceous but a few are perennial and tree like (e.g.,
Angiopteris). Smallest Pteridophyte is Azolla (an aquatic fern) and largest is Cyathea
(tree fern).
iii. Plant body is sporophytic and can be differentiated into root, stem and leaves.
iv. Roots are adventitious in nature with monopodial or dichotomous branching. Internally
usually they are diarch.
v. Stem is usually branched. Branching is monopodial or dichotomous. Branches do not
arise in the axil of the leaves. In many Pteridophytes stem is represented by rhizome.
vi. Leaves may be small, thin, scaly (microphyllous e.g., Equisetum), simple and sessile
(e.g., Selaginella) or large and pinnately compound (megaphyllous e.g., Dryopteris,
Adiantum).
vii. Vascular tissue is present in stem and root. It consists of xylem and phloem. Xylem
consists of tracheids only and phloem has only sieve tubes.

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