Marchantia
- 1. Morphology, Anatomy & Reproduction: Marchantia By Akum Paul Singh Roll no.2084
- 2. Systematic Position ā¢ Kingdom-Plantae ā¢ Division-Bryophyta ā¢ Class-Hepaticopsida ā¢ Order-Marchantiales ā¢ Family-Marchantiaceae ā¢ Genus-Marchantia
- 3. Habitat and Distribution ā¢ Genus has about 65 species ā¢ Grows best in cool, moist and shady places ā¢ Marchantia polymorpha grows as a pioneer in burnt forest soil Distribution in India: ā¢ 11 species occur in India mainly in western Himalayas ā¢ M.polymorpha occurs at high altitudes in Himalayas on moist river banks and rocks ā¢ M.palmate occurs in Kashmir, Kumaon, South India, Bengal and Assam ā¢ M.simlana occurs in Himachal Pradesh ā¢ M.nepalensis in Punjab and in Garhwal & Kumaon hills
- 4. Gametophyte Morphology ā¢ Plant body is prostrate, dorsiventral and dichotomously branched
- 5. Dorsal Surface: ā¢ A shallow groove marked by the presence of a distinct midrib in each branch ā¢ Many polygonal areas which demarcate the outline of underlying air chambers ā¢ Each polygonal area has a pore in its centre called air pore ā¢ Gemma cups are present along the midrib ā¢ Each branch has a growing point situated at the apex in a groove called apical notch
- 6. ā¢ Ventral Surfaceā ļ¼ Bears rhizoids and scales along midrib
- 7. Rhizoids ā¢ Unicellular and colourless ā¢ Two types i. Smooth walled- Inner walls are smooth ii. Tuberculate- Inner walls show papilla like outgrowths ā¢ Functionā Anchorage and absorption of water and minerals Optical Section
- 8. Scales ā¢ Multicellular(one cell in thickness) and violet coloured due to presence of anthocyanin pigments ā¢ Arranged in 2 rows on either side of mid-rib ā¢ Two types i. Appendiculateā these have an apical sub-rotund appendage and from inner row of scales ii. Ligulateā these are small, without appendage and form outer row of scales ā¢ FunctionāProtection of growing point and retention of water by capillary action Appendage Appendiculate Scale Ligulate scale
- 9. Anatomy Air Pores ļ±A cross-section of thallus shows shows 3 distinct regions: (i) Epidermal region (ii) Photosynthetic region (iii) Storage region ļ Barrel shaped ļ Each pore has 4-8 superimposed tiers of cells Epidermal Region ā¢ Includes upper and lower epidermis ā¢ Upper epidermis forms protective covering over photosynthetic region ā¢ Has many air pores that open internally into air chambers ā¢ Lower epidermis forms lowermost layer of thallus ā¢ Cells of lower epidermis give rise to rhizoids ļ Each tier consist of a ring of 4-5 cells ļ The cells of lowermost tier project inward giving the pore a star-shaped appearance ļ Half of tiers project outward and half project inward ļ The pores have comparatively wide pore passage in the middle than on margins ļ These are analogous to stomata but they cannot control the pore size like stomata
- 10. Anatomy Photosynthetic region ā¢ Lies below upper epidermis ā¢ It consists of large air chambers separated by single layered partition wall ā¢ Uniform in shape and are arranged in a horizontal row ā¢ Many photosynthetic filaments arise from foot of each chamber ā¢ The filaments are made of chloroplast containing cells
- 11. Storage region ā¢ Lies below photosynthetic region ā¢ Compact zone of several layers of polygonal parenchymatous cells ā¢ Cells devoid of chloroplast and no intercellular spaces in between ā¢ Cells contain starch and protein granules ā¢ Mucilage and oil containing cells are also present ā¢ Storage region thick in the centre and tapers towards the margins ā¢ Cells of midrib region are elongated and with reticulate thickenings Anatomy
- 12. Reproduction Vegetative reproduction: By progressive death and decay ā¢ Mature cells are present at posterior end and are short-lived ā¢ New cells are regularly formed by apical cell ā¢ Death and decay therefore naturally starts from the posterior end ā¢ As the process of decay reaches the point of dichotomy, two apical parts of thallus separate ā¢ Each grows into a new plant
- 13. Reproduction By adventitious branches ā¢ Some species possess adventitious branches on ventral surface ā¢ On separation these grow into new thalli
- 14. Reproduction By Gemma ā¢ Gemma cups(2mm X 3mm) are cupules present on dorsal surface along midrib region ā¢ Margins are hyaline, lobed, spiny or entire ā¢ From floor of gemma cup many small, stalked, discoid & biconvex gemma arise ā¢ Gemma is constricted in middle and 2 notches possess a row of apical cells ā¢ Gemma contains chloroplast containing cells and rhizoidal cells ā¢ Some mucilage hairs also arise from gemma cupās floor which imbibe water and help in deispersal of gemmae ā¢ Gemmae on coming in contact with ground start germinating immediately
- 15. Sexual Reproduction ā¢ Marchantia is a heterothallic or dioecious plant ā¢ Male thallus bears antheridiophores and female thallus bears archegoniophores ā¢ They arise from distal end of thallus from growing point and after their formation growth of thallus ceases
- 16. Antheridiophore ā¢ It has 1-3cm long stalk that bears 8 lobed peltate disc ā¢ Inner structure similar to that of thallus with upper epidermis(having air pores), air chambers(having photosynthetic filaments) ā¢ Antheridial chambers alternate with air chambers ā¢ Each antheridial chamber contains a single antheridium and opens externally by a pore called ostiole. ā¢ On each lobe antheridia arise acropetally ā¢ Antheridiophore has 2 longitudinal grooves which contain rhizoids and scales
- 17. Antheridium ā¢ A mature antheridium is globular or oval with multicellular stalk ā¢ Body of antheridium has a single layered sterile jacket enclosing androcytes which eventually metamorphose into antherozoids ā¢ The antherozoid is a minute biflagellate structure Dehiscence of antheridium: ā¢ Water enters the antheridial chamber through ostiole ā¢ Some cells at the distal end disintegrate when they come in contact with water and hence antheridium ruptures ā¢ Antherozoids come out of ostiole like smoke column and spread on surface of antheridial disc
- 18. Archegoniophore ā¢ It has slightly longer stalk(2-5cm) and a terminal disc which is 8 lobed ā¢ Archegonia are borne on dorsal surface in acropetal succession ā¢ Internal structure is similar to thallus with upper epidermis having air pores and underlying air chambers
- 19. Archegonium ā¢ The archegonium is a stalked flask shaped structure with a basal swollen venter and an elongated neck ā¢ Venter is surrounded by 1 celled thick sterile jacket and contains a large egg cell and relatively small venter canal cell ā¢ The neck consist of 6 vertical rows of cells called neck cells which enclose 4-8 neck canal cells ā¢ Tip of neck has a rosette of 4 cover cells
- 20. Fertilization ā¢ Water is essential for fertilization ā¢ Archegonia are placed upright on archegonial disc ā¢ Venter canal and neck canal cells degenerate to form a mucilaginous substance which imbibes water and results in sparation of cover cells by pressure ā¢ Antherozoid present on surface of antheridial disc are splashed by rain drops on to the surface of archegonial disc ā¢ They are attracted chemotactically towards the neck of archegonium ā¢ Antherozoids enter archegonium and only one fuses with egg leading to formation of zygote
- 21. Post fertilization events (Inversion of Archegonia) ā¢ After fertilization, archegoniophore elongates accompanied by rapid growth of central part of archegonial disc that leads to inversion of archegonia ā¢ The arrangement of archegonia is also reversed from acropetal to basipetal ā¢ This process of inversion is accompanied by development of one cell thick tissue called perichaetium or involucre on both sides of each archegonial row ā¢ Also long, green, finger-like projections arise from margins of disc known as Rays
- 22. Sporophyte ā¢ Zygote develops to form sporophyte ā¢ It is differentiated into foot, seta and capsule ā¢ Foot-It is basal bulbous part which anchors and provides nutrition to sporophyte ā¢ Seta-It is short stalk that connects foot to capsule ā¢ Capsule-It is yellow coloured oval structure and has a single layered jacket ā¢ In young sporophyte, capsule encloses sporogenous mass which differentiate into spore mother cells and elater mother cells
- 23. Sporophyte ā¢ Spore mother cells give rise to spore tetrad by meiosis and elater mother cells give rise to elaters which are diploid and sterile ā¢ During the development of sporophyte from zygote, the venter wall cells give rise to 2-3 layered protective covering of sporophyte called calyptra ā¢ The basal cells of archegonium give rise to one celled thick collar like outgrowth outside the calyptra called Perigynium or Pseudoperianth ā¢ Towards maturity of sporophyte, the seta elongates and pushes the mature capsule out through calyptra, perigynium and perichaetium
- 24. Dehiscence of sporophyte ā¢ Single layered capsule wall splits into a no. of longitudinal valves which extend from apex towards the middle of capsule ā¢ The valves are rolled back due to annular thickenings in jacket cells ā¢ Jerky movement of elaters due to their hygroscopic nature leads to loosening up of spore mass and scattering of spores in air
- 25. Germination of Spores ā¢ Spores are viable for about a year ā¢ Under favourable conditions they absorb moisture from substratum and increase in size ā¢ Chloroplasts reappear at this stage ā¢ Spore undergoes repeated divisions to form 6-8 celled filamentous structure with a rhizoid at one end ā¢ The apical cell cuts off derivatives on lateral sides and finally give rise to gametophyte
- 26. References ļ¼P.C. Vashistha Bryophytes S. Chand, Delhi, India ļ¼A Textbook of Botany-- Singh, Pande and Jain ļ¼Bendre and KumarāPractical Botany Vol.1 ļ¼en.wikipedia.org/wiki/Marchantia ļ¼www.google.co.in/marchantiaimages
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