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Oedogonium is unbranched filamentous alga of Chlorophyceae. In which caps are formed over cells after, ach cell division. The sexual reproduction is advanced oogamous type. The antheridia can be formed on, ormal filaments or on special dwarf nannandrous filaments. Depending upon the antheridium types,, Dedogonium can be nannandrous and macrandrous types., 4. Oedogonium, Class, Chlorophyceae, :, Praclant s, Order, Oedogoniales, :, dreamt, Family :, Oedogoniaceae, Oedogonium, Apical cell, Genus :, Order: Oedogoniales, The crder oedogoniales is represented by a single family, Chains of, antheridia, Cell wall, freshwater forms. These are found in permanent water bodies like, tsir, Nucleus, ponds, tanks and lakes. Oedogoniales, algae have filamentous, thallus with distinct polarity. The cell division is characteristic. The, Сар, reproduction takes place by vegetative, asexual and sexual methods., The motile reproductive structures are multiflagellate., Oogonium, Egg, 4.2 Occurrence of Oedogonium, The genus Oedogonium (Gr., Oedos-swelling, gonos- repro-, ductive bodies) comprises about 400 species. Common Indian, species are O.tenuis, O.elegans, 0.oblongellum and, O.cardiacum. Oedogonium is freshwater alga commonly found in, stagnant water like in small ditches, ponds, pools and lakes attached, to the leaves and stem of other plants i.e., plants are epiphytic. The, young filaments may also be found attached on other algae like, Cladophora, or on mature Oedogonium. Some species of, Oedogonium are terrestrial, found growing on moist soil, e.g.,, Suffultory cell, Vegetative cell, ashant sir, O.terrestris and O.randhawe. Young filaments are found, attached but mature filaments are free floating., 4.3 Thallus, The Oedogonium thallus is green, multicellular, unbranched, filaments made up of cylindrical cells (Fig. 8). The cells are, differentiated in following three types:, Holdfast, 1. The lower most basal cells or holdfast, 2. Intercalary cells, Pras, eart sir, 3. Apical cell, 1. Holdfast: The lower most basal cells or holdfast is club-shaped., Fig. 8: Oedogonium: Thallus Structure-, A Filament of a Homothallic Species, The, upper part of this cell is generally broad and round and the lower end of the cell is multi-lobed, disc-like, or finger-shaped (Fig. 8) which attaches the filament to substratum. It's colourless due to absence of, shande, shandir, shan

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2. Intercalary Cells : The cells between the apical cell and holdfast are called intercalary cells which, dor acuminate. In some species the apical cell, chloroplast or may possess poorly developed chloroplasts. Hence, it is unable to synthesize food for itself,, is modified, giving rise to narrow hair like structure, e.g., in O.ciliate. The apical cell possess chlorophyll, constitute the major part of the filaments. All intercalary cells are identical and possess chlorophyll., Hence are photosynthetic in nature. Some intercalary cells have cap like structure at their apical end and, Chloroplast, In flowing waters the holdfast persists and in terrestrial forms it may give out rhizoid like growth., are called cap cells (Fig. 8). The caps are formed at the, indicate how many time that cell has divided.-, caps, hak, and is photosynthetic in nature., 4.4 Structure of Cell, The cells are generally long and cylindrical. The cell walls are thick, rigid and rough. Cell walls are differentiated, into three layers. The outermost layer is made of chitin, the middle layer of pectin and inner most layer is made, of cellulose. The outermost chitin layer prevents dissolving away of pectin layer.,, The protoplast consists of a thin plasma membrane, cytoplasm, central vacuole, reticulate chloroplast with, pyrenoids and a single nucleus. The peripheral protoplast is called primordial utricle. The protoplast forms a, thin layer between the central vacuole and innermost cellulosic cell wall. The cell contains a central vacuole which, possess cell cap. The cell cap contains all type of secretions, excretions and inorganic compounds., The single nucleus present in cell is biscuit shaped or biconvex, it lies in the centre of the cell internal to, chloroplast. In some species the nucleus may be eccentric i.e., away from the centre. The nucleus possess 1-2, nucleoli, the chromo- somes are thread like or elongated. (Fig. 9 A-B), The single chloroplast forms a, reticulum which extends from, pole to pole, parallel to the long, axis of the cell. Many pyrenoids, are present at the intersection of, che chloroplast reticulum. The, Function of the pyrenoids is to, -Сар-, Lard sir, Cell wall, dreamstisin, tore starch over its surface., Pyrenoid, However, the excess starch is, ccumulated, -Nucleus, between, hloroplast lamellae., the, Chloroplast, he protoplasm also contains,, mitochondria, Golgi bodies,, ndoplasmic reticulum and, ell organelle., Praant sir, A, rowth, cowth In Oedogonium takes, ace by the, ercalary cells. However, in some cases the apical cell may also divide to increase the length of, bu Prasica, Fig. 9 (A-B): Oedogonlum: Cell Structure; (A) Young Cell, (B) Mature Cell, division of, chant sm, chant, hant, ants, by, hant sir

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by, 4.5 Reproduction, n Oedogonium reproduction takes place by vegetative, asexual and, by, methods., 4.5.1 Vegetative Reproduction, The vegetative multiplication takes place by fragmentation and akinete formation., A Fragmentation : When a filament of Oedogonium breaks into fragments,, each fragment is capable of forming new thallus. The fragmentation may, t su, vit so, sir, Vegetative, occur due to any of the following reasons:, (i) Mechanical injury, (ii) Drying up of some intercalary cells., (iii) Disintegration of intercalary cells after the formation of sporangia, (iv) Accidental breaking of the filaments under favourable conditions,, Akinetes, these fragments develop into new thalli., Akinete Formation : Akinetes are the modified vegetative cells which, become round or oyal, reddish-brown and thick walled. These cells contain, starch as the reserve food material and reddish-orange oil. The akinetes are, formed in unfavourable season and are formed in chains. After liberation the, Fig. 10: Oedogonium :, A Row of Akinetes, deant sir, akinetes germinate into new filaments in favourable season. (Fig. 10), 4.5.2 Asexual Reproduction, The asexual reproduction takes place by means of zoospores. (Fig. 11), 1. Formation of Zoospore (Fig. 11 A-C) : Generally, the newly formed cap cell i.e., a recently divided cell, as zoosporangium. The, zoosporangia are not formed in series, one sterile cell is always present, between two nearby zoosporangia. Each zoosporangium contains only one zoospore. The cell which is going, to function as zoosporangium gets filled with abundant food reserves. The contents of the cell contract slightly, from the cell wall., The central vacuole disappears, chloroplast frees itself from one end of the cell and become conical. A small, hyaline area develops on one side of the protoplast which eventually becomes the anterior end of the, 2oospore. At the base of this hyaline area, a ring of basal granules appears and from each granule a single, flagellum arises. The basalgranules remain connected with each other by fibrous strands. Thus, a ring of, flagella (About 30 flagella) appear at sub apical end below the hyaline area of zoospore., 2., Structure of Zoospore: The mature zoospore is an oval, spherical or pear-shaped structure. The, apical part of zoospore is hyaline and the rest is green due to presence of chlorophyll. The chloroplast is, ring-shaped with few pyrenoids embedded in it. The zoospore also contains eye-spot at one end and a, few contractile vacuoles. At maturity of the zoospore the wall of zooporangium splits near the cap region,, the adjacent cell moves apart and a passage is formed for the liberation of zoospore (Fig. 11 D). The, zoospore come out in a delicate mucilaginous vesicle, which soon gets dissolved and zoospores become, free. A ring of flagella about 30 and 120 in O.cardiacum is found at the base of hyaline region, this kind, of flagellation is called stephanokontic type., ant sir, chant s, shant sir, shant sir, by P

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ldfast. The upper part divides repeatedly to make new, It takes place with the help of male and female gametes. The male gametes known as antherozoids are, by, ant sir, by, Prash si, by, Receding, Contents, Vesicle, Zoospore, Prashte, shant sir, Prui, by, dashant si, Empty, zoosporangium-, Zoospore, ant sir, Fig. 11: Stages in Asexual Reproduction in Oedogonium, (A-C), Formation of Zoospore,, H, ushant, F, (D) Liberation of Zoospore, (F-I), Zoospore and its Germination, 3. Germination of Zoospore (Fig. 11 F-1) : After liberation the zoospores swims for an hour or more., E, Then it settles and attaches to a solid substratum with its hyaline flagellated end, soon it becomes, deflagellated and, lower part. The lower part elongates to develop holdfast. The upper part divides, filament. The terminal cell forms the apical cell., ENshart sir, cant sin, ongates considerably. A transverse septum separates the basal hyaline part and the, 4.5.3 Sexual Reproduction, The sexual reproduction in Oedogonium is of advanced oogam- ous type (Fig 12). Sexual reproduction ses, in when the water is alkaline and deficient in nitrogen, in presence of sufficient light and CO2. It is mor, common in forms growing in stagnant water than those growing in running water.., to make new, formed in antheridium. The female gametes called eggs are formed in oogonium. The genus Oedo to as, rasher, physiologically., as well, by Prashant sir