Short Notes on Bryophytes - Pteridophytes - Gymnosperms

Short Notes on Bryophytes - Pteridophytes - Gymnosperms

BRYOLOGY

·         Famous Indian Bryologist: DK Singh

·   Hepaticae: Each cell in the thallus contains many chloroplasts; the chloroplasts are without pyrenoids.

·         Anthocerotae: Each cell of the thallus possesses a single large chloroplast with a pyrenoid.

·         In Moss, primary protonema is haploid and gametophytic

·         diploid in moss plant- Spore mother cell

·         Elators and pseudoelators in the capsules of bryophyte are meant for Spore dispersal

·         sporangia of mosses? Sporocytes undergo meiosis to produce spores

·         When moss spore germinate they form  Protonema , then a leafy gametophyte

·         The sporophyte contains pseudoelators in Anthoceros

·         Funaria:  The conducting tissues do not consists Xylem and Phloem tissues in

·         class “Metzgeriidae” belongs Jungermanniopsida

·         Riccia: bryophyte, the sporophyte at maturity has reduced to the sporangia.

·       Liverworts and mosses grow on soil, on dampy soil, on rocks, and on tree trunks and also in water

·         Pteridophytes and bryophytes common characters :multicellular sex organs with sterile jacket cells

Porella-  xerophytic bryophyte

Marchantia, the liverwort is characterized by

·         Female organs are known as archegonia and are protected by the thin surrounding perichaetum

·         Antheridia are enclosed by a protective layer of cells called the perigonium

·         Male gametes are produced in numerous and multiflagellate

·         The sporophyte hangs down from the underside of the archegonium.

Anthoceros

·         Bryophyte with Nostoc clony can be seen in the thallus : Anthoceros

·         Pseudo-elaters are present in Anthoceros

Funaria:

·         can produce an embryo during sexual reproduction

·         The spore dispersal mechanism of Funaria-  Peristomial teeth

Sphagnum

·         most primitive water conducting structures known as hydroids are found in  Sphagnum

·         Bryophyte is known for its capacity to hold water and as a source of peat: Sphagnum

PTERIDOLOGY

·         In the prothallus of the fern plant , The nuclei of all cells including sex organs and gametes have monoploid number

·         The protostele of Lycopodium species shows variations with respect to its shape and arrangement of vascular tissue such as actinostele, plectostele, mixed protostels and plectosteles.

·         Dehiscence of sporangia takes place by a vertical splitting in Selaginella

Classification of Pteridophyte

·         Pteridophytes with endosporic gametophytes will be heterosporic

·         In megaphyllous pteridophytes emergence of leaf traces leaves gaps in the stele.

SS

·         Stelar types in Pteridophytes has leaf traces: Dictyostele

·         Telome theory of Zimmermann

·         Telome concept has been used in understanding the origin and evolution of the major groups of pteridophytes.

·         Overtopping -> Reduction -> Plantation -> Syngenesis or webbing ->Curvation.

·         series led to the evolution of megaphyllous leaves:

·         Over topping - planation – syngenesis

·         Gametes are prouced in Prothallus

·         Vascular bundle in which xylem surrounds phloem is termed as Amphivasal.

·         Antherozoids are spirally coiled and multi- flagellated- Psilotopsida

·         Spores may be homosporous or heterosporous - Lycopsida

·         Gametophytes are exosporic and green -  Sphenopsida

·         Tree fern-Cyathea

Rhynia:  Rhynia has apical sporangium ,  Rhynia is a single-species genus of Devonian vascular plants , Rhynia gwynne-vaughanii was the sporophyte generation of a vascular plant.

·         Haplostele, actinostele, plectostele, medullated protostele alone are protosteles

Isoetes

·         A pteridophyte with the structures, velum and foramen.

·         Prismatic tissue - Isoetes

Selaginella

·         Heterospous pteridophyte

·         Male gametes in Selaginella are biflagellate.

Rhynia

·         Fossil pteridophyte Rhynia major belong to Psilophytales.

·         Rhynia belongs to devonian

·         is a pteridophyte without the differentiation into true leaves and roots

Salvinia

·         is a rootless Pteridophyte.

·         The archegonia are deeply sunk in the apical cushion. They have a very short neck, an egg cell, a venter canal cell and a two nucleate neck canal cell.

Equisetum

·         Pteridophyte with elators

·         Peltate disc is the characteristic feature of strobilus from the pteridophyta member

·         siphonostele having a single phloem ring external to the xylem is called as ectophloic siphonostele.

·         Vallecular canals and Carinal canals are the characteristic features of Equisetum

Marsilea

·         In the mature sporocarp of Marsilea, inner parenchymatous zone cells gelatinise and form a gelatinous ring which helps in the dehiscence of the sporocarp at maturity.

Osmunda

·         The maturity of sporangia within a sorus is varied. where, the sorus type

·         is a simple i.e., all the sporangia develop simultaneously

·         Tassel -  Osmunda

Azolla


·         It is an aquatic fern

·         It hosts symbiotic nitrogen fixing blue-green alga

Its vascular cylinder is siphonostelic

·         Sporocarp - Azolla

GYMNOSPERMS

ü  Heterosporous - microspores and megaspores, are typically produced in male ones or ovulate cones, respectively.

ü  Cycads and Ginkgo have motile sperm that swim directly to the egg inside the ovule, whereas conifers and gnetophytes have sperm with no flagella that are conveyed to the egg along a pollen tube.

ü  The mature seed comprises the embryo, the endosperm which is haploid, serves as food supplier with a seed coat.

·         Heterosporous

·         Generally xylem vessels are absent

·         In gymnosperms the endosperm is haploid

·         Softwood are wood of gymnosperm.

·         Largest ovules are found in Gymnosperms

·         Manoxylic wood with large amount of parenchyma

·         The general pollination mechanism in gymnosperms is: Anemophily

·         Pollination in gymnosperms occurs by wind.

·         A protective covering in gymnosperms, which morphologically is equivalent to ovuliferous scale, develops next to the integument: Epimatium

Pinus:

·         Gymnosperm with winged pollen

·         Winged seeds are present

·         The seed known by the name ‘Chilgoza’, that is used as a dry fruit Pinus gerardiana

Welwitschia mirabilis: monotypic gymnosperm genus

·         a plant with a thick, short stem less than 45 cm above the soil and a pair of large leathery leaves about two meters long in the south coast of the walvis Bay in South Africa.

Gnetum-  which is a woody climber - Gnetum ula

Ginkgo

·         Ginkgo biloba the only living fossil representative of Gymnosperm

Cedrus

·         Deodar wood, the strongest coniferous wood is obtained from  Cedrus

 

Extra:

·         Gymnosperms is a profusely branching shrub:  Ephedra distachya

Economic Importance of Gymnosperms

·         An anticancer drug obtained from Gymnosperm is Taxol

·         Ramenta - Pteris

·         Terminal Sporangium- Rhynia

·         Pycnoxylic wood -Pinus

·         Ovules at the tip of a stalk - Ginkgo

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