OSMUNDA .............................pptx

Osmunda

1. OSMUNDA PROTOLEPTOSPORANGIOPSIDA Osmundaceae

2. Both living and fossil forms Members intermediate between eusporangiopsida and leptosporangiopsida

3. Resemblance with eusporangiate ferns Eusporangiate development of sporangia Massive sporangia wiyh large number of spores Antheridia has many wall layers and produce many antherozoids Prothallus - thick, massive and long lived Indistinct endodermis, presence of mucilage canals near vascular bundles Presence of stipule at the base of petiole

4. Resemblance with leptosporangiate ferns Tapetum originate from archesporial cells Primitive type annulus Thin walled stomium Sporangial wall single layered Projecting type antheridia and archegonia Prothalus lack endophytic fungus and is of cordate type Prone type embryo development- first division of zygote vertical

5. Osmunda Wide distribution- tropical and temperate 12-14 sps In India- 5 sps- O.regalis , O.claytoniana , O.javanica , O. japonica, O.cinnamomea Grows in higher altitudes usually Prefer shaded and cool habitats Very much restricted in distribution- in isolated patches

6. Morphology Medium sized ferns A few- O.cinnamomea - 2-3 meters Rhizome- wholly subterranean, upright, short, stumpy, sparingly branched- dichotomous Rhizome is profusely beset with older leaf bases which are sclerenchymatous - additional strength to rhizome- are arranged in close spirals- on entire surface Near the base of leaves- adventitious roots arise from rhizome Roots- hard and rough, black or brown, profusely branched and has brown root hairs below their tips Rhizome with leaf bases and tufts of roots- may reach a foot or so in diameter

7. Circinate vernation present Leaves pinnately compound- unipinnate or bipinnate , length- 2-3 meters in some sps Leaf base flattened to form stipule like expansion Leaflets leathery, variously incised Older lower leaflets – larger in size and gradually become smaller towards the distal end- to give a conical appearance Young leaves covered with unbranched multicellular hairs which fall off at maturity Leaves arranged in close spirals and form a basket shaped crown at the top of rhizome

8. Leaves- monomorhic /dimorphic Monomorphic -( O.regalis , O.claytoniana ) only one type of leaves with dimorphic pinnae - some pinnule sterile others fertile- segregation of photosynthetic and fertile functions in the same leaf Dimorphic- ( O.cinnamomea , O.japonica )two types of leaves- sterile leaves and fertile leaves. Fertle leaves- no green lamina- have only sporangia directly borne on the branches of rachis

9. Anatomy Rhizome- No definite epidermis Outer cortex- several layers of thick walled cells, outer boundary is irregular due to persistent leaf bases Cells are dead and black coloured Numerous leaf traces present here Leaf base vascular bundles are also seen Gives mechanical strength

10. Inner cortex- few layered, thin walled cells fille with starch grains Some leaf traces are also present Leaf trace bundle- C shaped, has its own endodermis and 2-3 layered pericycle Phloem completely surrounds the central xylem strand Xylem- horse shoe shaped Protoxylem in the concave side as small masses

11. Endodermis- Next to inner cortex- endodermis- has distinct casparian strips Endodermis- completely surround the stelar region- uninterrupted Pericycle - 2-3 layerd , parenchymatous next to endodermis

12. Stele – has many C- shaped xylem bundles surrounded by a continuos ring of phloem elements Protoxylem lies in the concavity of the xylem bundle Number of xylem strands varies in different sps Pith- conspicuous- parenchymatous or a few sclerenchyma strands may be present Stele- is said to be dictyoxylic as it can not completely fulfill the conditions of a dictyostele

13. Petiole Epidermis- single layered parenchymatous Has simple multicellular hairs when young Few layered sclerenchymatous hypodermis Cortex- broad, parenchymatous Vascular bundle single, horse shoe/ C shaped Has a central xylem core surrounded by phloem on all sides Protoxylem groups- several along the concave side Metaxylem forms major part of the xylem tissue Many mucilage canals present towards the concave side of the vascular bundle

14. Leaflet Has upper and lower epidermis- parenchymatous Stomata- on lower epidermis Mesophyll undifferentiated- has thin walled parenchyma cells with intercellular spaces of varying dimensions Cell contain chloroplast Single concentric vascular bundle is present

15. Root Endogenous in origin from rhizome Distinct epidermis in young roots Later it is replace dby outermost layer of cortex- exodermis Next to epidermis- a few layered hypodermis of thick walled small cells Rest of the cortex- parenchymatous Endodermis- distinct Pericycle - 2 layered and thin walled Stele- usually diarch / in some triarch

16. Root - osmunda

17. Two xylem bundles meet at the centre Protoxylem - exarch No pith Phloem- as two patches on either side of the xylem masses

18. Reproduction Sporophyte- homosporous Fertile pinna arise as branches of the rachis Clusters of sporangia are borne on these thinned out leaflets- known as tassels of sporangia. In some sps- lower parts of pinna – fertile and distal parts sterile and photosynthetic In some. Sterile pinna bear sporangia along the margins In O.claytoniana , fertile pinna restricted to the middle of the leaf Pinna bear many sporangial clusters- known as tassels A sporangial tassel corresponds to a section of the leaflet Sporangia- naked- not covered by indusia or hairs

19. In O.claytoniana , an abnormal condition was seen for the sporangia in one study Some sterile pinnae were seen to possess sporangia as sori on their abaxial surface- may be a transition zone between sterile and fertile pinnae

20. Sporangia A mature sporangium – massive, short stalked and pyriform structure Stalk is many celled and varies in length Capsule has- single layered jacket cells Tapetum - 3 layered- do not disorganise to form plasmodial fluid But in O.claytoniana , tapetum is plasmodial Tapetal layer is derived from primary archesporial cell Spore mother cells undergo meiosis to form 128-512 haploid spores

21. Mature sporangium develops a transverse group of thick walled cells on one side- annulus A vertical row of thin walled cells opposite the annulus represents the line of dehiscence As the annulus dries and shrinks, sporangial wall is pulled apart along the line of dehiscence to liberate the spores

22. Sporangial development Sporangia appear as a small protuberance on the fertlie pinna In each such protuberance, a single sporangial initial becomes distinct by its larger size, distinct nucleus and abundance of cytoplasm Sorangial initial divides into an outer smaller cell (primary jacket cell) and inner larger cell(primary archesporial cell) primary archesporial cell divides to form 3 peripheral cells enclosing a central primary sporogenous cell The 3 peripheral cells divide periclinally and anticlinally to form the tapetal layers In some sps the inner layer of tapetum is derived from the primary sporogenous cell

23. Sporangial stalk is derived from the surrounding cells partially or fully – so the devpt cannot be traced to a single cell as in leptosporangiate ferns- so it is named as protoleptosporangiate development

24. Gametophytic generation Starts with haploid spores Spores- spherical, has adistinct triradiate mark Spore wall- outer exine - thick ornamented Inner- intine - thin Has a central distinct nucleus surrounded by cytoplasm and numerous chloroplasts Remain viable for one week

25. Spore germination Spore absorbes water, exine ruptures along the triradiate mark, intine comes out as a small conical papilla It divides by transverse wall into primary rhizoidal cell and large prothallial cell Rhizoidal cell forms the first rhizoid Prothallial cell has numerous chloroplast It grows exactly opposite the first rhizoid- bipolar germination In some prothallial cell divides by a few transverse walls to form a green filament The terminal cell of the filament divides by two intersecting oblique walls to form a triangular apical cell with two cutting faces

26. The lower cells of the filament divide longitudinally apical cell cuts off cells to its right and left sides in an alternate walls, then each by vertical wall to form an outer cell and inner cell Inner cells divide by horizontal walls which add to the thickness of the midrib Outer cells divide rapidly, overgrow the apical cell giving the prothallus a heart-shaped appearance Apical cell may remain functional for a longer period and cut off cells laterally and also to the dorsal and ventral sides Finally an elongate heart shaped prothallus with a distinct cushion below the notch is formed Mature prothallus - 3-6 cms long Dark green with a prominent midrib

27. Mature prothallus - elongated, unbranched, dorsiventral , green and cordate Length 2-3 cm Has a distinct midrib Midrib- thick and cishioned below the notch Rhizoids- arise from ventral side, usually unicellular Monoecious and protandrous , flat, ribbon like and has smooth/ slightly wavy margin Sometimes- prothallus may be unisexual

28. Sex organs Antheridia- projecting type Terminal/marginal/ even ventral in posotion Large and globular Stalk may or may not present Has a single layered jacket. Jacket cells contain chloroplast A triangular opercular cell is present, which will open to liberate the male gametes. Spermatozoids- minute, coiled and multiciliate structure Has two coils- posterior coil slightly broader than anterior one

29. Archegonium - produced on ventral side of prothallus Has a projecting neck from the median cushion Neck has 4 vertical rows of cells, each row 6 cells in height Neck encloses a single binucleate neck canal cell Venter is embedded in the prothallus tissue, has a single ventral canal cell and egg

30. Fertilization Usual process, neck canal cell and ventral canal cell disorganise and become mucilaginous It absorbes water swells up and forces the apical tier of cells apart, making a passage for the sperms to enter and fertilization occurs and zygote (2n) is formed

31. Embryogeny Dipoid zygote is established It secretes a thick wall to form the oospore inside the venter It divides by a vertcal wall to form 2 equal cells They divide by another vertical wall right angle to the first vertical wall to form quadrant stage the epibasl half form leaf and stem Hypobasal half form foot and root. No suspensor- so the development is exoscopic .

32. Quadrants divide to form octant by another transverse wall formation Further divisions are irregular Root initial forms the primary root, foot is haustorial Young leaf appears as a conical protuberance on one side Stem apex appears on one side of the leaf apex and grows into an underground stem after the primary root and leaf have established

33. Apogamy – from the prothallus the sporophyte develop as a vegetative outgrowth in some sps In O.javanica from the sporophytic tissue production of antheridia has been reported Economic importance- root and stem fibres used for orchid cultivation As ornamentals- for beauty of the foliage Young leaves used as vegetable by some people