Types of sporangia and spores submitted by shreyasi dey.roll no 08, 2nd semester, nbu
- 1. TYPES OF SPORANGIA AND SPORES IN PTTERIDOPHYTES Submitted & Presented by- Shreyasi Dey Roll No.08, 2nd Semester Department-Botany, N.B.U
- 2. BRIEF HIGHLIGHTS • Sporangium-the spore case • Orientation • Variety through modification • Evolution through Variation • Principal types of sporangium • KEY Features • Development pattern • Affinities of Protoleptosporangium • Gender of sporangium • Spores variety • Gender Inequality • Spore- The unit of Reproduction
- 3. SPORANGIUM-The Spore Case • Vascular cryptogams are an assemblage of seedless vascular plants that have successfully invaded the land and reproduce by means of spores. • It is an enclosure in which spores are formed • Can be composed of a single cell or can be multicellular • Most primitive sporangial types are stalk less, or sessile. If a stalk is present at all, it is merely a slightly raised multicellular area at the base of the sporangial capsule. • The trend in sporangial evolution is evidently from solitary large capsules to increasingly elaborate groupings of smaller sporangia.
- 4. ORIENTATION • The leaves in most of filicophyta serve a dual purpose of photosynthesis and reproduction. • In the common ferns like Adiantum, Pteris ,Dryopteris any leaf or leaflet can bear sori on its under surface. • There is no distinction between fertile and sterile leaves • There are however some ferns that exhibit segregation of photosynthetic and reproductive function. • Their position vary in different groups, viz. • Cauline –Psilotum, Rhynia; Adaxial Leaf surface- Lycopodium, Selaginella; Leaf axil- Ophioglossum
- 5. VARIETYTHROUGHMODIFICATION SYANANGIUM: a group of FUSED sporangia in which spores develop SPIKE: sporangia borne on an outgrowth-The fertile SPIKE projecting from the adaxial leaf surface. Sporangia found on the margins of spike SPOROPHYLL: sporangia containing fertile leaves STROBILUS: sporophylls grouped in definite areas SORUS: sporangia are aggregated in clusters. Sporangia and especially sori have traditionally provided the most important characters for fern classification. SPOROCARP: sporangia present within specialized structure. Mostly oval or bean shaped biconvex, flattened structure. It is green and soft when it is young but at maturity it becomes very hard and brown in colour.
- 6. EVOLUTUON THROUGH VARIATION Simple Sorus All sporangia originate and mature at the same time All sporangia are at the same stage of development Example- Osmunda, Ophioglossum Gradatae Sorus Sporangia develop over a period of time Mature sporangia at Center and the younger ones at peripheral sides Example-Marsilea, Cythea MixedSorus • Mature and Immature sporangia of Different ages are arranged in Irregular Fashion • Exampe- Pteris, Adiantum
- 7. PRINCIPAL TYPES OF SPORANGIUM • On the basis of sporangial development they are classified as 3 types. • The Advanced Leptosporangium and Primitive Eusporangium • The Transition type- Protoleptosporangium intermediate between the EUSPORANGIAUM and LEPTOSPORANGIUM • But they should in no case can be regarded as phylogenetic links between them. They have a long evolutionary history and were represented in the Permian, the living members of this type can be regarded as LIVING FOSSILS.
- 8. KEY FEATURES Eusporangium 1. Several cells are concerned in its initiation 2. Mature sporangium has a short and thick stalk 3. Sporogenous cells are sometimes cubical 4. Annulus is less developed and is present on only one side of the sporangium 5. Number of spores is comparatively large 6. Presence of cholorophyll in the spores is sometimes observed. Leptosporangium 1. Conical shape of sporangial initial 2. Wall is one or two layered 3. Tapetum orogiantes from the outermost sporogenous cells 4. Presence of a thin walled Stomium 5. The spore case itself is few celled, and the outer wall is only one cell thick at maturity. 6. The number of spores produced usually only 128, 64, or 32, most commonly 64. 7. Most leptosporangia have a bow or annulus made up of strongly modified, thickened cells
- 9. DEVELOPMENT PATTERN Sporangium develops from GROUP of superficial cells. These cells divide periclinally into primary wall layers and inner primary sporogenous cells. The outer wall layers form the wall of the sporangium while inner sporogenous cells divide meiotically and form spores Arises from a SINGLE superficial cell Divides transversely to form an outer and inner cell. While inner cell forms the stalk, the entire sporangium develops from outer cell. Sporogenous tissue divides meiotically to give rise to HAPLOID spores
- 10. AFFINITIES OF PROTOLEPTOSPORANGIUM Similarities with Eusporangium • 1. Large number of spores are produced .Sporangia massive and not arranged in distinct sori. • 2. Structure and development of the archegonium • 3. Antheridia large in size and have many wall cells and produce many spermatozoids • 4. Internal structure of the petiole. Presence of stipule like expansions at the base of petiole Similarities with Leptosporangium • 1. Origin of tapetum from the archesporial cells • 2. Presence of a primitive type of annulus in the sporangia • 3. Presence of a thin walled tapetum • 4. Wall of archegonium is single layered • 5. Antheridia and archegoinia are of projecting type • 6. The prothallus lack endophytic fungus and is of cordate type • 7. Embryo development is of prone type i.e the first division of zygote is vertical
- 11. GENDER OF THE SPORANGIUM • Depending on the gender of spore content, Sporangium is 2 types- • Microsporangium and Megasporangium a) Microsporangium- it is the producer of microspores which are small spores, numerous in number and give rise to male gametophyte b) Megasporangium- produces big spore called megaspores, fewer in number and give rise to female gametophyte • Depending on the type of spores, Sporangium is – • either Homosporous or Heterosporous a) Homosporous-all spores are alike. • In homosporous Pteridophytes prothalli are monoecious a) Heterosporous- micro and megaspores are produced separately. • In heterosporous species prothalli are always dioecious.
- 12. SPORES VARIETY Depending on the presence of chlorophyll- Green/Chlorophyllous and Non green/Non chlorophyllous Green Spores • First, they exhibit a clear tendency to a quick germination, which is in mean of 1.5 days. • Second, their germination ability is very rapidly lost, with a mean viability of around 48 days. • Green spores, in a state of active respiration with a higher water content and with chlorophyll present in an active state, can germinate almost immediately after sowing. • Do not enter into a period of dormancy characteristic of non-green spores. • The constant physiological activity of the green spore utilizes the storage compounds in an apparently short period of time. • As the storage compounds are totally used up, the spores become non-viable. Water loss may also play a part in reducing the length of viability in green spores. Non-Green Spores • Great majority of ferns have non-green spores, i.e., which are without evident chloroplasts at the time of dissemination. These spores do possess proplastids. • The length of time between sowing and germination in non- green spores is variable, from four to six days or even to 210 days • Must absorb additional water and produce chloroplastids from proplastids before germinating. • This difference in activity would account for the differences in germination rate • In contrast to green spores, non-green spores remain viable for extremely long periods, up to 48 years in Asplenium. • The absolute record to date of spore viability is reported within the heterosporous genus Marsilea: megaspores obtained from 100-year-old sporocarps of M. oligospora germinated forming rhizoids and archegonia (Johnson 1985).
- 13. GENDER INEQUALITY • The gender of a pteridophyte is based on the spore • Microspore ensures the Male plant body as after fertilisation it produces the Male Gametophyte only • On the other hand Megaspore is the Female spore which gives rise to Female Gametophyte • DEVELOPMENT PATTERN
- 14. SPORES : THE UNIT OF REPRODUCTION
- 15. THANK YOU