â¢ Planktonic plant = Sargassum. Out of these, 7 nuclei degenerate and the remaining one functions as an egg (Fig. 3.121A). The sex organs are produced 3.119B). Sexual It is very common in Africa, South America, Australia etc. Vegetative reproduction: Vegetative propagation takes place by fragmentation of the thalli. The asexual reproduction takes place by the formation of biflagellate zompores. by means of spores. Grafting, layering, and micropropagation are some methods used for artificial asexual reproduction. The new plant is genetically identical to the parent plant from which the stock has been taken. The macroalgae genus Sargassum adopts a heteromorphic life history (distinct sexual haploid and asexual diploid stages) and oogamous fertilisation (union of mobile male and immobile female gametes) . The cells are meristema- tic in nature. The anterior Oogonium produces one egg and the antheridium produces 64 biflagellate sperms. It however remains attached to its original position by means of a The spores germinate The plant body is diploid (2n), erect and branched thallus (Fig. Asexual reproduction occurs by forming a specific type of spores. In India it is found in Porbandar, Bombay, Okha, Lakshadweep Island etc. It serves the function of anchorage, photosynthesis, storage, conduction and support. Disclaimer Copyright, Share Your Knowledge layer. Asexual reproduction. Asexual, or vegetative, reproduction occurs by simple fragmentation of the filaments. Thus The cells are smaller in size than meristoderm. Oogonia This layer possibly helps in conduction. Our mission is to provide an online platform to help students to share notes in Biology. The three wall layers are outer Each such Mutations have been known to exist, however, and sea-faring scholars have recorded individual sargassum fiends reaching masses of truly enormous size, up to Colossal. The mature oogonia come out of the conceptacle through the ostiole, but still they remain attached with the conceptacle base by a long gelatinous stalk formed by the exochite. 3.119D). are the various mechanisms of asexual reproduction. Fragmentation is a type of ___ for drift algae, like Sargassum. egg begins its germination while surrounded by the gelatinous sheath the conceptacles are found 3.118) single superficial cell on the receptacular branch becomes enlarged and functions as conceptacle initial (Fig. The uppeer or antheridial of the antheidium get divided into 64 haploid protoplasts. anterior flagella. by the gelatinized wall of the oogonia and are held in position just The diploid (2n) nucleus undergoes first meiotic (Fig. Reproduction The mode of reproduction is both sexual and asexual. It generally takes place by the following method: derived from the oogonial wall and still attached to the interior The main axis i.e., stem is vertically elongated and differentiated into nodes and internodes. while the functional haploid nucleus enlarges and becomes centrally In West Africa, a part of Atlantic Ocean becomes densely occupied by Sargassum and the region is called as ‘Sargasso sea’. wall and a single ovum or oosphere. Share Your PPT File. The thallus is differentiated into a basal holdfast and an expanded, leafy, cylindrical main axis. Asexually reproducing plants thrive well in stable environments. This layer can store food material. in sea water. Explain genic balance mechanism of sex determination. becomes mucilaginous. Thus it shows a typical example of diplontic life cycle. It is of oogamous type and takes place by the union of antherozoid and egg, developed in antheridia and oogonia respectively. This cell is larger in size with dense protoplasm than the other surrounding cells. Vegetative reproduction takes place by fragmentation. attach themselves to the gelatinous sheath of the ovm by mean of their It breaks its connection from the paraphysis Reproduction in Sargassum: It reproduces by both vegetative and sexual means. the sperm penentrate the mucilaginous covering and fuses with the The main axis is generally of 10 to 50 cm in length. The conceptacles bear sex organs. 3.121C). 3.121 B), but later they fuse together and form the zygote (Fig. Calculation of incidence of asexual vs. sexual dispersal is difficult as comparison with known asexually vs. sexually propagated populations of other Sargassum species within the same distribution range is needed. and a number of oil droplets. Asexual reproduction is either by biflagellate zoospores or by non-flagellate tetraspores developed in sporangia. These are flask-shaped with many sterile unbranched filaments, the paraphyses developed from the base. In this process, some cells or protoplasm of few cells of the plant divide to create a small-sized structure, the spore. At maturity the antheridium is detached from the stalk and comes out from the conceptacle through ostiole. placed. During development (Fig. Asexual reproduction is by fission, budding, fragmentation or by zoospores (motile spores). An ecological demographic study was conducted from January to December 2009 at Changshan Island on the northern side of Shandong Peninsula, China. Zygote germinates directly and produces a new sporophytic (2n) plant. reproduction : The reproduction is oogamous and involves the fusion and an upper oogonial cell. The uninucleate bodies metamorphose into pyriform, haploid biflagellate antherozoids (Fig. The medulla i.e., the inner layer consists of narrow, thick walled elongated cells. This is a dioecious species producing separate male and female colonies. Asexual reproduction is absent. Some of the cells of this layer function as an oogonial initials (Fig. The zygote is diploid (2n) and on germination it develops sporophytic (2n) plant of Sargassum. After coming out, the wall of sporangium gets gelatinised and the antherozoids are liberated. reproduction : FRagmentation is the only known method of reproduction The lower rhizoids which 3.120B). The former type refers to reproduction in which a new organism is generated from a single parent. Many antherozoids get attached with the egg by their anterior flagella and their posterior ones help in swimming (Fig. climate Sargassum muticum has been shown to grow year round, but it will still lose its branches (Norton, 1976; Arenas & Fernández, 2000; and Britton-Simmons, 2004). Share Your Word File Phytoplankton â¢ Diatoms â¢ Silica impregnated, porous cell wall â Frustule - 2 halves â¢ Asexual and sexual reproduction â¢ Very rapid division = bloom. Or they may be diploid formed in manycellod plurilocular sporangia. The stalk cell again undergoes transverse division and forms upper antheridial cell and lower stalk cell. The wall of the mature antheridium ovum or oosphere. It bears long shoots of unlimited growth (primary laterals), leaves (secondary laterals), air bladders and receptacles. Both stem and leaves are differentiated into epidermis, cortex and medulla. Here's a list of organisms able to asexually reproduce. The thallus breaks into fragments due to mechanical injury or death and decay of older parts. The diploid nucleus outside the ostiole by means of mucilaginous stalk. is a pear shaped biflagellate structure of pale brown colour. : A large number of antheridia develop in each male conceptacle. Due to its unlimited growth, the primary laterals are also called long shoots. The oogonial initial undergoes transverse division and forms lower small stalk cell and upper large oogonial cell (Fig. When two or more separate multicellular algae stages occurs in succession during the life cycle, we call this: alternation of generations. In sterile conceptacle it only develops sterile hairs, the paraphyses, but in fertile conceptacle it develops either antheridia or oogonia and also paraphyses in some regions. It produces the typical thallus. Pelagic Sargassum - âGulf weedâ Class PhaeophyceaePelagic Brown Alga Drift alga Two holopelagic species, co-occur Occur in warm waters of Atlantic Ocean Asexual reproduction - fragmentation which is the only known method of vegetative reproduction in the free floating species of Sargassum. In addition to vegetative reproduction by fragmentation of the thallus most brown algae reproduce both by asexual and sexual means. of the conceptace by means of mucilage stalk. These zoospores may be haploid produced in one-celled unilocular sporangia. The asexual reproduction is absent. Vegetative 10. flagella are inserted laterally. The cells of the wall have many chromatophores. 3.120C), then mitotic divisions and 8 nuclei are formed. Fertlization The antherozoids and eggs i.e., the gametes, represent only the haploid (n) stage. The antheridia are developed from the inner fertile layer of the antheridial conceptacle (Fig. Asexual reproduction is absent. It swelling breaks The plant body Sargassum is â¦ Internally the antheridium contains initially a On both surfaces of the leaf there are many sterile conceptacles, the cryptostomata or cryptoblasts (Fig. The first antheridium Each one divides by a transverse wall into two cells. 13. Chromatophore is reduced The genus Sargassum (Spanish sargazo, seaweed) is represented by about 150 species, out of which 1 6 species are found in India. Features 6. also termed as microsprangia and megasporangia.
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