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Marsilea.pptx
- 1. MARSILEA 1
- 2. Classification of marsilea Division :pterophyta Class: leptosporangiopsida Order:Marisileales Family:Marsieaceae Genus:Marsilea
- 3. EXTERNAL MORPHOLOGY OF SPOROPHYTE • Sporophyte is creeping in the mud & possess root, rhizome and leaves • Rhizome is horizontal structure with fairly long internodes. From the rhizome, leaves and roots are given out from the nodes. • The roots are adventitious, given out from the nodes from the underside of rhizome. They absorb minerals, salt and water, and anchor sporophyte in the mud. • The leaves are alternately produced from nodes on rhizome and are arranged in distichous manner. • Each mature leaf shows a long petiole with four leaflets at the tip. The leaflets are actually one pair is placed a little higher than the other in opposite decussate manner. • Each leaflet shows very minute petiole (sub-sessile). The leaflet is obovate in shape with entire or serrate margin, rounded apex and dichotomously venation. 3
- 4. EXTERNAL MORPHOLOGY OF SPOROPHYTE 4
- 5. INTERNAL MORPHOLOGY OF SPOROPHYTE exarch xylem. 5 T.S. OF ROOT: • Epidermis • Cortex: Outer aeparenchymatous cortex, middle parenchymatous cortex & inner cortex sclerenchymatous. • Stele: Endodermis, pericycle, radial vascular bundles with diarch &
- 6. INTERNAL MORPHOLOGY OF SPOROPHYTE T.S. OF RHIZOME: • Epidermis • Cortex: parenchymatous with a ring Outer cortex of air chambers (aerenchymatous), inner parenchymatous cortex with sclerenchymatous patch. • Stele: Amphiphloic centre and can parenchymatous submerged plants) siphonostele. • Pith: Present in the be (in or sclerenchymatous (terrestrial plants) 5
- 7. INTERNAL MORPHOLOGY OF SPOROPHYTE T.S. OF PETIOLE: • Epidermis • Cortex: Outer cortex parenchymatous, Middle cortex aerenchymatous (septate), inner cortex parenchymatous. • Stele: Protostele (plectostelic). Xylem consists of two plates with metaxylem in the centre & protoxylem towards the periphery. 7
- 8. INTERNAL MORPHOLOGY OF SPOROPHYTE 8 T.S. OF LEAFLET: • Upper epidermis • Mesophyll: Isobilateral (in the submerged species), dorsiventral with aerenchyama (in terrestrial species) • Vascular bundles: Concentric vascular bundles arranged in parallel series. • Lower epidermis
- 9. REPRODUCTION • Vegetative: Tubers • Asexual: Heterosporous (Microspores, megaspores), microsporangia & megasporangia in sporocarps 9
- 10. 10 SPOROCARP External morphology of sporocarp • Young sporocarps – Soft and green • Mature sporocarps – Dark brown desiccation 20 to 25 years). and hard (Withstand • Sporocarp = Pedicel or stalk + Body, Pt. of attachment = Raphe. • Distal end of raphe – 1 or 2 teeth-like projections known as horns. • Sporocarp wall – Hard, thick, resistant. Differentiated into 3 layers – Outer (epidermis with sunken stomata), middle (thick walled palisade) and inner (thin walled palisade).
- 11. SPOROCARP Vascular supply of sporocarp • V.L.S. – Single vascular strand enters the sporocarp near the lower horn and continues forward along the upper side forming a midrib (dorsal bundle). • From midrib, the lateral branches (lateral bundles) arise & pass to both sides. • Placental bundle develops from the point of forking of lateral bundle which enters into the receptacle bearing sporangia and dichotomises. • Sporocarp - Bivalved structure with closed network of vascular system. • Fertile sporophyll with marginal sori. Developed from 2 folded pinnae. • Sori – Gradate type, megasporangia in upper rows, microsporangia in lower rows and leptosporangiate type of sporangial development. 11
- 12. SPOROCARP - Internal structure V.L.S. (Vertical Longitudinal Section) • Section vertically sporocarp is cut but the is cut longitudinally. V.T.S. (Vertical Transverse Section) • Section is cut vertically but the sporocarp is cut transversely. H.L.S. (Horizontal Longitudinal Section) horizontally the sporocarp • Section is cut but is cut longitudinally. 12
- 13. SPOROCARP - Internal structure Vertical longitudinal section (V.L.S.) • Many sori arranged in vertical rows. • Either megasporangia or microsporangia are visible. • Each sorus is surrounded by an indusium. • The development of sori is of gradate type. • The gelatinous mucilage ring is more prominent in dorsal side. 13
- 14. SPOROCARP - Internal structure and ventral sides. 14 Horizontal Longitudinal Section (H.L.S.) • Each sorus transversely • Sorus is an is cut elongated structure, covered by a delicate indusium. • Sori are of gradate type, in basipetal pattern. • Sorus consists of a row of megasporangia at top and two rows of microsporangia on either sides. • Mucilage ring is present in two masses on dorsal
- 15. SPOROCARP - Internal structure Vertical transverse section (V.T.S.) • Two sori opposite to each other. • Each sorus shows many megasporangia in the middle while 1-2 microsporangia at the ends. • The mucilage ring is present only on the dorsal side. 15
- 16. 16 SPORANGIUM – Structure & Dehiscence Structure • Each micro or megasporngium, consists of a single layered jacket enclosing spore mother cells. • At maturity, the spore mother cells undergo meiosis followed by few mitosis to produce 32-64 spores. • In microsporangium, all spores survive while in megasporangium, only one spore survives and becomes a very large megaspore. Dehiscence • During dehiscence, sporocarp imbibes water and the gelatinous ring swells, expands and pushes out of the split sporocarp. • It also pulls the sori and the sori come out in a row. • Indusium gelatinise and liberate the sporangia. • Later the sporangial walls also gelatinise and the spores are liberated in the surrounding water.
- 17. 17 GAMETOPHYTE – Male Microspore and male gametophyte • Microspore – Yellowish, spherical haploid with a triradiate ridge & consists of uninucleate cytoplasm is surrounded by spore wall. • Spore wall – 2 layered – endosporium & exosporium. • Spore absorbs water and increase considerably in size. • Nucleus divides to form a small prothalial cell & large apical cell. • Apical cell divides to form two antheridial initials. • Antheridial initial – few jacket cells externally & one spermatogenous cell internally. • Spermatogenous cell forms 16 androcytes which represent one antheridium. • At this stage, prothalial cell and jacket disintegrate and two groups of androcytes remain free but within the microspore. • Each androcyte now develops into multiciliated, coiled spermatozoid with vesicle at one end. • Thus, development of male gametophyte is endosporic.
- 19. 19 GAMETOPHYTE – Female Megaspore and female gametophyte • Mature megaspore is elliptical with a short papilla at one end. • Spore wall – 2 layered – endosporium & exosporium. • Papilla is surrounded only by endosporium. • Nucleus is located in the apical papilla and is surrounded by a dense cytoplasm. • The rest of the spore is filled with watery cytoplasm & food. • Megaspore germinates to give rise to female gametophyte. The development is endosporic. • Apical nucleus is divided into unequal nuclei. One nucleus remains in the dense cytoplasm while the larger one migrates to watery cytoplasm. • Transverse wall is formed at the base of the papilla separating the upper small cell and lower larger cell called prothalial cell. • Prothalial cell do not divide further and acts as nutritive cell. • Upper cell soon develops an archegonium with a short neck and venter. The neck has single neck canal cell surrounded by jacket made up of two tiers of four cells each. • Venter contains a venter canal cell. At maturity, megaspore absorbs water, the tip of the megaspore splits in tri-radiate fissure and the archegonium is exposed. • Female gametophyte is surrounded by a gelatinous mass & a funnel shaped opening at the top.
- 20. GAMETOPHYTE – Fertilization 20 • During fertilization, spermatozoids or male gametes are liberated from ruptured male gametophyte and are attracted by the chemical substances present in the gelatinous mass. • Movement of spermatozoids under the influence of chemical substances is called chemotaxis. • Spermatozoids swarm around and enter the gelatinous matrix of the female gametophyte. Only one spermatozoid enters the open neck and fertilizes the egg to form diploid zygote. SPOROPHYTE – Development • Zygote develops into embryo. Embryo shows cotyledons and roots developed from upper half of the embryo while stem and foot developed from lower half of embryo. • The cotyledon comes out from calyptra. The rhizoids are developed at first on the root. Very soon the embryo settles in the mud and