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Algae (Sargassam , Porphyra , and Diatoms)

microbiology Notes
8. Jun 2018
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Algae (Sargassam , Porphyra , and Diatoms)

  1. Structure and reproduction of Sargassum, Porphyra, Diatoms PRESENTED BY Vivek kumar M.sc MICROBIOLOGY Bangalore university
  2. SARGASSUM
  3. INTRODUCTION • Sargassum is a marine algae which popularly called as the Gulf Weed. • The Sargassum plant is macroscopic and more or less bushy in habit. • Most of the species occur in tropical or temperate zones attached along the rocky shores. Some species occur along the Indian coast(East and West) and that of the Australian sea and also in Japan. • Name of some common Indian Sargassum Sp. Is- a) S. tennerimum b) S. carpophyllum c) S. Duplication d) S. Plagiophyllum e) S. ilicifolium f) S. mycosystum
  4. Taxonomic Position • Division- Phaeophyta • Class- Cylospore • Order- Fucales • Family- Sargassaceae • Genus- Sargassum • Species- cinereum
  5. Structure • Organisation • Sargassum is a diploid sporophyte. • It has a main axis of approximately 30 cm long or more. • It bears richly branched Primary lateral. This primary lateral has unlimited growth and also called as long shoot. • The long shoot bears numerous secondary laterals of limited growth. • Of the latter the latter the basal one is usually most conspicuous. It is shaped like a leaf. • The basal member or members of auxiliary branch system are swollen into stalked and rounded structures called air bladders. This air bladders contained the same gases as the at the atmosphere and helps the plant to keep floating upon the surface of water. • The subsequent members of the auxiliary branched system may be cylindrical or flattened. They are called the receptacles. The receptacles are formed when the plant became fertile. • The receptacles are stud with fertile, flask-shaped conceptacles.
  6. Structure of a Sargassum peron. ab- air bladder; rc- receptacles bearing conceptacles; ax- auxiliary branch; lb- lateral branch; md-midrib; l- bearing lateral Structure of Sargassum longifolium A part of thallus showing laterals and receptacles
  7. Basal portion of the plant of Sargassum enerve. ab- air bludder; abr- auxillary branch; bl- basal lateral; l- lateral branch; ma- main axis; hf- holdfast
  8. Structure of the thallus • Meristoderm- It is a peripheral layer of columnar cells without any air spaces between them. It contains three layers of cells – Palaside layer, hypodermal layer and cutical. • Cortex- Within the hypodermal layer there is cortex consisting of thick-walled polygonal cells. • Medulla- the central zone is called as Medulla. The cells of this region is loosely arranged. They are narrow and elongated. The outer cells of the medulla have thick walls where as the inner cells have thin walls.
  9. Sargassum Sp. T.S. Thallus cu-cuticle; cort- cortex; hy- hypodermis; m-medulla; p- palsied layer.
  10. Reproduction • Reproduction of Sargassum takes place by two methods- • Vegetative method • Sexual method • Vegetative method- This process is done fragmentation. The older parts die and decay separating the younger parts. The latter continue to grow and finally developed to full-fledge Sargassum plant. • S. natans and S. hystrix multiply exclusively by this method.
  11. • Sexual Reproduction- It is the usual method of reproduction and is oogamous. • The sex organs produced in flask-shaped cavities called the conceptacles borne on the sporophyte plant. • Development of conceptacles. • Development of sex organs. For male it is called as Antheridia whereas in female it is called Oogonium. • Fertilisation. • Germination of Zygote.
  12. Oogonium of Sargassum Sp. with attached to conceptacle mst- Oogonia attached to the conceptacle wall long gelatinous stalks; ov-ovum; ow-oogonial wall.
  13. Germination of Sargsssum Sp.
  14. PORPHYRA
  15. Introduction • Porphyra, popularly known as “nori” in Japan, “laver” in the United Kingdom, the United States, and Canada, “purple laver” in Britain and Ireland, “karengo” in New Zealand, “kim” in Korea, and “zicai” in China. • It is a common marine red algae found in the intertidal zone on the rocky seashore. • It occurs on both the coasts, Atlantic and Pacific of North America. • Some species grow attached to the rocks (Lithophytes) and others are epiphytic. • Porphyra is primarily used as food in the Japanese delicacy “sushi,” which consists of roasted blades, fish, rice, and other ingredients
  16. Taxonomic position • Division- Rhodophyta • Class- Rhodophyceae • Sub-class- Bangiodeae • Order- Bangiales • Family- Bangiaceae • Genus- Porphyra • Species- umbilicus
  17. STRUCTURE • Thallus structure • The plant body is a plate or sheet like parenchymatous blade apparently resembling that of a marine algae ulva. • The margin of the blade can be smooth wavy to greatly convoluted. • The thallus is often unbranched and attached to the substratum by a small, basal disc cushion-like holdfast. • Depending on the species the blade like thallus one to two cells thick. Frequently it is one cell layer thick.
  18. • Cell structure • The cells are elongated. • They are cubical or ellipsoid in form and lie embedded perpendicular to the thallus surface in the tough gelatinous matrix derived from the cell walls. • The outer walls of the cells are strongly thickened and covered with cuticle. The cells are uninucleate. Each cell has a single large axile stellate chromatophore(Pigment containing cells) with a centrally located pyrenoid. • In certain species there are two chromatophore in each cell. • The nucleus lies adjacent to the chromatophore but between the adjacent cells. • The growth is intercalary. • It takes place by the division of cells at intervals irrespective of their position.
  19. Reproduction • Porphyra have two method of reproduction • Sexual method • Asexual method
  20. Asexual method • It takes place by means of asexual spores formed by direct transformation of vegetative cells. • These are known as the neutral spores.
  21. Sexual reproduction • In sexual reproduction method male and female sex organs are formed. • Most of the species are dioecious(“double house”) and monoecious(“Single House”). • The male sex organ is called as Spermatangia. • The female sex organ is called as Carpogonia. • Both are formed from a single vegetative cell.
  22. • Formation of Spermatangia • They are formed by repeated division of a vegetative cell • A vegetative cell of the male thallus divides in three planes. • The first wall is parallel to the surface. • The daughter cell undergo two vertical divisions. • Further transverse divisions results in a mass of 32-128 small colourless cells called as Spermatangia. • The liberated naked uninucleate protoplast of each spermatangia is called as spermatagnium. It is a non motile male gamate.
  23. • Formation of Carpogonia • The carpogonia is formed by slight modification in the vegetative cell of female thallus. • The swallon cell undergoes no division. Its protoplast functions directly as an egg. • Fertilisation • The carpogonium extends to the thallus surface one or both the ends by giving out a small papillate outgrowth which is considered as rudimentary trichogyne. • In those sp which don’t have trichogyne, a narrow process occurs containing a thin stream of cytoplasm. • It establishes a connection between spermatium and carpogonium. • Then the spermatatial nucleus migrates through it into the carpogonium to fuse with egg nucleus. • After entering the protoplast divides through meiosis and makes 8-32 uninucleate haploid meiospore known as carpospores. • These carpospores are then released and germinated and produced amoeboid cell and matured to new species.
  24. DIATOMS
  25. ITRODUCTION • The term diatomin is used for the mixture of chlorophyll and carotenoids, particularly carotene and several brown xanthophylls pigments. • It is a large group of algae consisting of 200 genera and over 10,000 species, out of which 92 genera and about 569 species are reported from India. • The diatoms are the most beautiful microscopic algae due to their structure and sculpturing of their walls. • They occur in various habitats like fresh water, saline water and also in terrestrial condition on or within the soil. • Sometimes they also occur as epiphytes along with algae, on the leaf of forest trees, mostly in tropical rain forests. • Depending on the mode of nutrition they may be photosynthetic autotrophs or heterotrophs.
  26. Class. Bacillariophyceae Order. Centrales i. Discoideae. e.g., Melosira. ii. Solenoideae. e.g., Corethron iii. Biddulphioideae e.g., Biddulphia iv. Rutilarioideae e.g., Rutilaria Order. Pennales i. Araphideae 1. Fragilarioideae e.g., Synedra. ii. Raphidioideae 2. Eunotioideae e.g., Eunotia. iii. Monoraphideae 3. Achnanthoideae e.g., Cocconeis iv. Biraphideae 4. Naviculoideae e.g., Navicula. 5. Epithemioideae e.g., Epiyhemia. 6. Nitzschioideae e.g., Bacillaria. 7. Surirelloideae e.g., Surirella.
  27. Plant Body Structure of Diatoms • Plant body is unicellular, generally moves singly. The cells are of different shapes like round, oval, elongated, rod-shaped, triangular, disc-shaped etc. • Sometimes they become aggregated and get embedded in a gelatinous matrix, but they do not behave like multicellular orga- nisms. • In colonial form the cells may be present as uniseriate row (e.g., Melosira), like a branched body (e.g., Licmophora flabellate) or other forms also.
  28. Cell Structure of Diatoms • The cell consists of cell wall and protoplast. • The cells are covered by a siliceous wall, the frustule. • It consists of two overlapping halves, the theca. The upper one is epitheca and lower one is hypotheca. • Both the theca consist of two portions: • (a) Valve — the upper flattened top and • (b) Connecting band or cingulum (pl. cingula) — the incurved region.
  29. • The common region of the connecting bands, where both the theca remain fitted together, is the girdle. • When the diatoms are observed from the valve side i.e., valve side is uppermost, called the valve view, but when viewed from the connecting band, it is the girdle view. • Depending on symmetry, the cells are divided into two orders: 1. Pennales (bilaterally symmetry) 2. Centrales (radially symmetry).
  30. • In some pinnate diatoms (Cybella cistula, Pinnularia viridis etc.) an elongated slit is present on their valves, called raphe. • The raphe is interrupted at its midpoint by thickening of the wall called central nodule. • Similar thickening is also present at the ends called polar nodules. • Some members like Tabellaria fenestrate etc. of the order Pennales, do not have raphe, called pseudoraphe. • The cell wall is mainly made up of pectic substances, impregnated with silica. The content of silica varies from 1% to about 50% on the basis of dry weight of the cell.
  31. Protoplast: • The entire content present inside the cell wall is the protoplast. • The cell membrane encloses a large central vacuole surrounded by cytoplasm. • The cytoplasm contains single nucleus, mitochondria, golgi bodies and chloroplasts. • The chloroplasts may be of different shapes like stellate, H-shaped, discoid etc. In some species the chloroplasts contain pyrenoids. • The photosynthetic pigments are chlorophyll a, c1 and c2, β-carotene, fucoxanthin, diatoxanthin and diadinoxanthin. The latter two are pre- sent in small quantity. (The golden-brown colour of diatom cells is due to the presence of xanthophylls like fucoxanthin, diatoxanthin and diadinoxanthin. • The reserve food of diatoms is chrysolami- narin and oil droplets (they do not store in the form of starch).
  32. Locomotion: • All diatoms with raphe are motile. • Most of the members of the order Pennales contain raphe and perform gliding movement. • The gliding movement is caused by the circulation of cytoplasm within the raphe by the release of mucilage. • The rate of movement varies from 02-25 µm/sec. • The locomotion is affected by temperature, light etc.
  33. Reproduction • Reproduction of diatoms occur in two ways • Vegetative Reproduction • Sexual Reproduction
  34. Vegetative Reproduction • Vegetative reproduction performs with the help of cell division. It takes place usually at midnight or in the early morning. • During cell division the protoplast of the cell enlarges slightly. • Then the protoplast undergoes mitotic division and gets separated along the longitudinal axis through the median line. • Now both the theca i.e., epitheca and hypotheca of mother cell behave as epitheca of the daughter cells. • Thus new silicious valves are deposited towards the naked sides of the protoplast and always behave as hypotheca of the daughter cells.
  35. Sexual Reproduction • The pattern of sexual reproduction differs in both orders — • Pennales • Centrales. • During this process, auxospore is formed in both the groups.
  36. Auxospore Formation in Pennales • It takes place through gametic union, autogamy and parthenogenesis. • These are the types- 1. Production of one auxospores by two conjugating cells. 2. Production of Two Auxospores by Two Conjugating Cells. E.g. Cymbella lanceolata, Gomphomema parvulum etc. 3. Production of One Auxospore by Autogamy. 4. Production of Auxospore by Parthenogenesis. 5. Production of Auxospore by Oogamy. E.g. Rhabdonema adriaticum
  37. Production of one auxospores by two conjugating cells.
  38. Production of Two Auxospores by Two Conjugating Cells.
  39. Production of One Auxospore by Autogamy. • In this process the diploid nucleus undergoes first meiotic division. Thus two haploid nuclei are formed. The two nuclei in the protoplast come side by side, fuse together and form diploid (2n) nucleus. This is called autogamous pairing. • The protoplast along with diploid (2n) nucleus comes out from the parent frustule and behaves as an auxospore. • This is found in Amphora normani.
  40. Production of Auxospore by Parthenogenesis.
  41. Production of Auxospore by Oogamy. In this process the nucleus (2n) of female cell which behaves as oogonium, undergoes meiosis and forms four nuclei. The protoplast is also divided into two unequal parts, each containing two nuclei. The lower half is larger and behaves as functional ovum and the upper smaller one as non-functional ovum. The functional ovum contains one functional nucleus and one non- functional nucleus, which gradually degenerates at maturity.
  42. • The male cell (2n) behaves as antheridium, also undergoes meiosis and forms four nuclei. The protoplast also divides into two parts. Thus two microgametes are formed. Each of which contains two nuclei, of which one is functional and other is non-functional. The microgametes are naked, globular and non-flagellate. • After coming out, the male gamete fertilizes the egg and forms the zygote (2n). Later it functions as an auxospore and forms new individual of normal size. It is found in Rhabdonema adriaticum.
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