THALLUS ORGANISATION OF CHLOROPHYCEAE.pptx

There exist a wide variety of thalli in algae, particularly in vegetative plant body
The different forms show a definite range.

1. Thallus organization on Chlorophyceae Rashmi M G 1 st year MSc. BOTANY MAHARANI’S SCIENCE COLLEGE FOR WOMEN MYSORE

2. INTRODUCTION TO ALGAE The algae was derived from a Latin word ‘alga’ meaning washed away plants on the sea shore or simply sea-weeds Algae are chlorophyll bearing thallophytes in which the sex organs are either unicellular or multicellular and not protected by sterile envelope In many unicellular forms, the entire cell acts as gamete If multicellular, the algae may produce many celled sex organs, and all cells of the sex organs produce gametes There is no sterile cell in the sex organs. However there are some exceptions That is the male sex organ (antheridium) of Chara is multicellular and surrounded by layer of sterile cells

3. Some commonly known algae Chara Diatoms Fucus Volvox Oedogonium Nitella Ectocarpus Sargassum Oscillatoria Chlorella Caulerpa Vaucheria Laminaria Polysiphonia Chlamydomonas Ulothrix

4. Phycology The study of algae is called algology or phycology The term phycology was derived from Greek word phycos meaning sea weeds The term algae was first introduced by Linnaeus in 1754 to include a group of cryptogamic plants, since then the term algae has been used in botany

5. Salient features of algae Algae generally live in aquatic or moist habitat The plant body is a unicellular or multicellular thallus which is never differentiated into root, stem and leaves Chlorophyll and other pigments are found in chromatophores present in the thallus, therefore algae are autotrophic in nutrition Starch is the common reserve food in algae

6. Salient features of algae The eukaryotic cells may be uninucleate or multinucleate. Algal cell wall is rich in cellulose. Some cells are motile due to the presence of flagella or cilia Primitive algae reproduce only by vegetative methods, but asexual and sexual reproduction are common in higher forms Asexual reproduction takes place by the formation of motile zoospores The sexual reproduction may be isogamous, anisogamous or oogamous type

7. Fritsch’s system F. E. FRITSCH the well known algologist of the great Britain has published the two volumes of books on STRUCTURE AND REPRODUCTION OF THE ALGAE IN 1935-45 and classified the algae based on pigmentation, details of flagella, storage food, presence or absence of true nucleus in cells, range of thallus structures, methods of reproduction and patterns of life cycle

8. Fritsch’s system He divided algae into 11 different classes CHLOROPHYCEAE XANTHOPHYCEAE CHRYSOPHYCEAE BACILLARIOPHYCEAE CRYPTOPHYCEAE DINOPHYCEAE CHLOROMONADIAE EUGLENEAE PHAEOPHYCEAE RHODOPHYCEAE MYXOPHYCEAE

9. CHLOROPHYCEAE The members of Chlorophyceae are otherwise called green algae This class includes 9orders:- Volvocales Chlorococcales Ulothrichales Cladophorales Chaetophorales Oedogoniales Conjugales Siphonales Charales

10. Chlorophyceae These algae have grassy-green chromatophores which contain chlorophyll a, chlorophyll b, xanthophyll and carotenoids. Storage food- starch and oil Pyrenoids – present in the chromatophores surrounded by starch sheath Cell wall- cellulose Flagella -2 or 4 equal in length if motile Sexual reproduction- isogamy, anisogamy, oogamy Thallus- may be unicellular or multicellular; if multicellular, it may be filamentous or heterotrichous or siphonous or pseudo- parenchymatous Many species are haploid but some are diploid They are common in freshwater than in salt water Ex. Chlamydomonas, Volvox, Chlorella, Oedogonium, Caulerpa, Coleochaete etc

11. Thallus organization There exist a wide variety of thalli in algae, particularly in vegetative plant body The different forms show a definite range. On the other hand there are simple plants where the thallus body is microscopic and consists of only one single cell (Chlamydomonas) All the morphological structures and cytological, physiological, genetical and other vital and necessary activities go on regularly in that single cell only

12. Thallus organization Some of the algae are very large (sometimes 60m or more) and very complex type of plant body is some Chlorophyceae and many Phaeophyceae and Rhodophyceae that becomes completely a parenchymatous organization ( Ulva, Porphyra, Laminaria, Macrocystic, Nereocystis ) resembling superficially with that of an angiospermic plant There are intermediate stages also like colonial ( Volvox ) palmelloid ( Tetraspora ) dendroid ( Prasinocladus ) coccoid (chlorella) filamentous ( Spirogyra, Ulothrix, Oedogonium, Cladophora, Pithophora ) heterotrichous ( Fritschiella ) siphonous ( Vaucheria ) uniaxial ( B atrachospermum ) multiaxial ( Nemalion , Polysiphonia )

13. UNICELLULAR MOTILE FORMS Unicellular motile forms are found in all major groups except Phaeophyceae, Rhodophyceae, Bacillariophyceae and Myxophyceae The distinguishing features are the presence of a unicellular plant body bearing means of motility i.e. flagella The most common example is Chlamydomonas in which the biflagellate plant body is surrounded with a definite cell wall, enclosing a cup-shaped chloroplast, one or more pyrenoids,2 contractile vacuoles, an eyespot besides other cell organelles and a nucleus

14. UNICELLULAR NON MOTILE FORMS It is seen in algal groups of Chlorophyceae, Chrysophyceae,Cyanophyceae, Xanthophyceae, Bacillariophyceae and Rhodophyceae They posses unicellular plant body with no flagella. The most common example is Chlorella which possesses microscopic spherical cells, each with a nucleus and cup shaped chloroplast

15. MULTICELLULAR FLAGELLATED FORMS/ COLONIAL FORMS These are colonial members of algae whose cells bear the means of motility i.e. flagella Innumerable numbers of cells are present in the colony. A colony with definite number of cells and having a constant shape and size is called coenobium Multicellular motile forms are found in many genera of Chlorophyceae, Chrysophyceae, Dinophyceae The most common example of such forms is Volvox in which a definite number of cells (500-50000) are interconnected with each other with the help of protoplasmic connections The coenobium is hollow and spherical and contain a single layer of cells arranged on the periphery All cells are chlamydomonad in structure

16. MULTICELLULAR NON FLAGELLATE FORMS /NON FLAGELLATED COLONIES In this form the algae bear a definite number of cells and thus represent a coenobium The cells are non motile and do not have flagella or any other means of motility The cells of the net remain connected in the form of groups of 5/6 forming pentagonal or hexagonal structures . This is seen in Pediastrum This must have been developed by the aggregation of unicellular non-motile cells

17. PLAMELLOID FORMS In this form the algae in which non motile cells remain embedded in an amorphous gelatinous/ mucilaginous matrix The cells are aggregated within a common mucilaginous envelope. All the cells are quite independent of one another and fulfill all functions of an individual In Chlamydomonas the cells loose their flagella, undergo successive divisions and form 8/16 or more cells which simultaneously get surrounded by a mucilage On coming over of favorable conditions mucilage gets dissolved and all the cells are set free

18. FILAMENTOUS FORMS Many cells arranged one upon the other in a definite sequence, uniseriate row, constitute filament The filaments may be branched or unbranched in different algal members Unbranched filaments are found in algae like Spirogyra , Ulothrix , Oedogonium , Oscillatoria , Spirulina , Anabaena Branched filaments are found in Cladophora , bulbochaete etc

19. HETEROTRICHOUS FORMS Hetero means different and trichous denotes trichome or filament In this form the algal plant body is very much evolved and consists of more than one type of filaments and thus represents the heterotrichous habit It is one of the characteristic feature of Chaetophorales of Chlorophyceae Ex, Fritschiella tuberosa

20. SIPHONOUS FORM In this form the plant body enlarges without the formation of any septa Because of the presence of many nuclei, such an organization of plant body is a coenocyte A large central siphon-like vacuole is present in the thallus and thus the name siphonous Ex. Vaucheria

21. CONCLUSION A wide range of thallus are observed in algal groups which are developed and evolved to sustain in the external environment where they live All the morphological structures and cytological, physiological, genetical and other vital and necessary activities go on regularly in their forms Reference https://www.wikipedia.org/ https:// www.google.com/photos/ Diversity of microbes and cryptogams by O P SHARMA, MAC GRAW HILL EDUCATION