Pteridophytes
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Pteridophytes are vascular plants and have leaves (known as fronds), roots and sometimes true stems, and tree ferns have full trunks. Examples include ferns, horsetails and club-mosses. Fronds in the largest species of ferns can reach some six metres in length! Many ferns from tropical rain forests are epiphytes, which means they only grow on other plant species; their water comes from the damp air or from rainfall running down branches and tree trunks. There are also some purely aquatic ferns such as water fern or water velvet (Salvinia molesta) and mosquito ferns (Azolla species). Pteridophytes do not have seeds or flowers either, instead they also reproduce via spores. There are around 13,000 species of Pteridophytes.
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Pteridophytes
- 1. Gajendra C V Research scholar Department of tree breeding Forest college and research institute, Mettupalayam
- 2. Pteridophytes • Seedless vascular plants – Vascular cryptogams • In Gk Pteron means. Feather , phyton means plants (Feather like fronds / leaves) • Reproduce by means of spores • First land plants • Botanical amphibians : Bryophytes • Botanical snakes or snakes of plant kingdom: Pteridophytes • Dominant plants during carboniferous period : Age of Pteridophytes
- 3. Status of Pteridophytes – India • 500 species of ferns and 100 species of fern allies (other than the order of fillicales) are on record from India • Pteridophytic flora of India comprises of 67 families, 191 genera and more than 1000 species including 47 endemic Indian ferns, and 414 species of pteridophytes (219 at risk, of which 160 critically EN, 82 NT, 113 rare) constituting 41-43 % of the total number of 950 -1000 pteridophytes of india. (Vineet and Satyanarayana, 2015)
- 4. • A W Eichler
- 5. Further Pteridophytes Classified into 4 classes Psilophyta Psilopsida Psilotum and Rhynia Lycophyta Lycospisda (Lycopodinae) Lycopodium Arthrophyta Sphenopsida (Equisetinae) Equisetum Filicophyta Pteropsida (Filicinae) Ferns Pteridophyta
- 6. 1. Psilotum 2. Rhynia 3. Lycopodium 4. Equisetum 5. Ferns
- 7. Salient Features of Pteridophytes • Life cycle is heterologous diplohaplontic type • Sporophyte is the dominant plant body while gametophyte is a small, simple called as prothallus • Sporophyte has true roots, stem and leaves • In xylem, trachea (vessels) absent and, in phloem companion cells absent • Spores develop in sporangia are homosporous or heterosporous • Sporangia are produced in groups (sori) on sporophylls
- 8. Contd., • Young leaves of sporophyte show circinate vernation • Gametophyte develops small sessile antheridia and partially embedded archegonia with 4- rowed neck • Sex organs multi-cellular and jacketed • Embryonic stage present
- 9. Pictorial representation of Pteridophytes A. Azolla, B. Selaginella, C. Marsilea, D. Lycopodium, E. Equisetum, F. Adiantum
- 10. • Division: Filicophyta • Classs: Pterospsida • Sub-class: Leptosporangiate • Order: Filicales • Family: Polypodiaceae • Genus: Dryopteris
- 11. • Among 7600 spp. of ferns the dryopteris has 150 spp. • Male shield fern (Dryopteris filixmax) is world wide in distribution • They flourish in shade and humid conditions
- 12. External features – Dryopteris spp. • It is a perennial herb • It survives during unfavourable conditions (underground rhizome) • The rhizome bears a numerous aerial leaves which are bipinnate compound • The younger leaves show circinate coiling like watchspring • The older leaves are termed as fronds • The lower part of rachis is covered by brown coloured scale like structures called raments • The leaves show open furcate venation
- 13. Internal structure – Dryopteris spp. Rhizome: differentiated into epidermis, cortex and stele 1. Epidermis : Single layered 2. Cortex: differentiated into outer (Sclerenchymatous) and inner (Parenchymatous) cortex 3. Stele : Dictyostele, meristeles (concentric type of Vascular Bundle) Meristele is also known as hadrocentric becoz every meristele is enclosed by one or two layerd pericycle and endodermis Epidermis Cortex Stele
- 14. Internal structure – contd., Rachis : Rachis of ferns has dictyostele but the meristeles have typical horse shoe shaped arrangement Root: The fern plant show Central stele
- 15. Reproduction – Dryopteris spp. • Ferns have Diplohaplontic life cycle (Diploid and Haploid phase) • They are homomorphus • The sporophytic fern plant bears only one type of sporophylls • The sporophylls of diff. spp. Show the variation in the arrangement of sori on their sporophylls A. Kangaroo Fern frond B. Soft Tree fern frond C. Maidenhair Fern Clumped sori Open indusa Curled over @margin
- 16. Contd. • The sori appear reniform due to the kidney shaped protective thin and membranous covering called indusium • There is a single layered thick ring like structure consisting of annulus and stomium • The sporangium contains 16 spore mother cells which after reduction division produces 64 haploids • Dehiscence of the capsule – Catapult mechanism Kidney shape
- 17. Gametophyte • Spore of the fern germinates when suitable substratum and temperature and moisture conditions are ideal • It grows into a small green, flat, heart shaped dorsiventral thallus which is known as Prothallus – Antheridia and Archegonia
- 18. Chemotactic movement (mallic acid is rich @ archegonial tip) Fig: Dryopteris Archegonium at the time of fertilization Zygote (2n)
- 19. Sporophyte • The oospore divides transversely and vertically to form a total of 8 cell, which divide separately to form the embryo • While one half of the embryo gives rise to foot and stem the other half gives rise to root and cotyledon The Sporophyte continues to grow while the Gametophyte dies Very small heart-shaped non-vascular gametophyte with rhizoids. Sporophyte sprouting up.
- 20. 1. Sporophyte creates and releases haploid sporesAdult Sporophyte . . . . Ground
- 21. 2. Haploid spores land in the soil Ground Fern gametophytes are called a prothallus Let’s zoom in 3. From the haploid spores, gametophyte grows in the soil
- 22. 4) Sperm swim through water from the male parts (antheridium) to the female parts (archegonia)…zygote created eggegg egg zygo te zygo te zygo te
- 23. 5. Diploid sporophyte grows from the zygote Sporophyte Fiddlehead Ground . 6.Fiddlehead uncurls….fronds open up
- 24. Summing up
- 27. Let’s think…….. 1. What affects where ferns will grow? Factors of locality i.e., Edaphic, Climatic topographic and Biotic factors 2. Why do ferns grow in some places and not others, and why do some species thrive where others don't? Ferns are having a very successful niche plants: they are well adapted to particular environmental niches - soil moisture, humidity, light, etc. For example, in our region, the Mother Spleen wort fern always grows near waterfalls and in Evergreen forests, Bracket fern is found on grounds with high moisture content and litter fall
- 28. References • http://www.home.aone.net.au/~byzantium/ferns/about .html • A text book of botany by A C Dutta • Botany by V. Verma