Presentation1

This ppt explains the organisation in thallus of algae in breif.

1. RANGE OF THALLUS ORGANISATION IN ALGAE MADE BY UJALA YADAV

2. What are algae? DEFINITION : The autotrophs which are non vascular and non embryonic and having no cellular differentiation at tissue or organ level. Term algae is derived from Latin word alga which means sea weeds . THALLUS: They do not consist true roots, stems and leaves and thus their body is called thallus bodied Leave in moist places They are water dwellers Non jacketed reproductive organ Simple forms reproduce by vegetative ,asexual and sexual mode Advance forms reproduce only by sexual mode.

3. THIS IS HOW ALGAE LOOKS

4. NOW WE WILL STUDY ABOUT THALLUS OF ALGAE IN DETAILS.

5. UNICELLULAR MOTILE [FLAGELLOID] FORMS unicellular motile forms are simplest type of thallus in algae. Flagella are found for locomotion in Unicellular motile forms. Flagellated unicelled structures are distinctive of certain classes e.g., Euglenineae, Cryptophyceae , Chrysophyceae and Dinophyceae . Flagellated vegetative cells are absent in Cyanophyceae, Phaeophyceae, Rhodophyceae, Bacillariophyceae. Body may be spherical, oblong or pear-shaped and sometimes elongated and approximately circular in cross-section. E.g.. Chlamydomonas,Chlorogonium,OchromonasChromulina

6. Unicellular Non-motile (Protococcoidal) Forms Do not possess flagella, eyespot etc., meant for locomotion. (e.g., Chlorella, Chlorococcus). Show many morphological variations e.g., Bacillariophyceae (Diatoms), in many Chlorophyceae (Chlorellti, Cosmarium) Cyanophyceae (Synechococcus), and in some forms of Xanthophyceae, Dinophyceae and Rhodophyceae (Porpliyridium). Spherical or elongated cells e.g., Microcystis, Cylindrocystis, Pinnularia (Bacillariophyceae); Triangular cells e.g., Tetragonidium (Cryptophyceae) and Triceratium (Bacillariophyceae). The epiphytic or attached forms have a basal disc.

7. Colonial Forms A further evolution of the unicellular types from occasional and indefinite type of colony like structures. Here varying numbers of unicells aggregate together indifferent ways, often within a mucous envelope. Colonial forms are seen among Chlorophyceae , Chrysophyceae, Bacillariophyceae ,Dinophyceae, Xanthophyceae etc. The colony may be : (a) motile or (b) non-motile.

8. Motile Colonial Forms Motile flagellated cells aggregate together to form motile colonies. Colonies vary in shape and size and in the number of cells. The movement of the colony is effected by the conjoint and uniform flagellar action by all the cells. In Chlorophyceae, the colony is made up of Chlamydomonas like cells and the cells are arranged just below the mucilaginous surface. The colonies are either “plate-like” ( e.g., Gonium ) or spherical ( e.g., Volvox ).

9. cells may be connected by cytoplasmic strands, ( e.g.. Volvox ). In the majority of cases all the individual cells are alike, a few forms have some larger cells for reproductive functions; Rest of the cells being purely vegetative ( e.g., Volvox ) Mostly they are coenobia (sing., coenobium ) i.e., colonies composed of definite number of cells arranged in a defined manner.

10. Non-Motile Colony Aggregations of non-motile cells in the form of a colony (non-motile) common only in Chlorophyceae. cells are, more or less, fused together (e.g., Hydrodictyon). It may be plate like e.g.. Scenedesmus or net-like as in Hydrodictyon.

11. Branched Filaments Branchedfilamentousstructuresmaybeputintothreecategories: (i)Simple, (ii)Heterotrichous (iii)Pseudoparenchymatous. Theyareputaccordingtotheshapeandnatureofthethalli,aresultofdifferenttypesofcellbehaviourconcerninggrowthanddivision

12. Non Motile- Palmelloid : their shape and size is not definite the cells remain irregularly aggregated within a common mucilaginous matrix, but they are independent and function as individuals. In some palmelloid forms it is a temporary phase (e.g. Chlamydomonas), whereas in others it is a permanent feature (e.g., Tetraspora)

13. Non Motile- Dendroid The colony appears like a microscopic tree. The number, shape and size of cells is indefinite mucilaginous thread is present at the base of each cell. Threads of different cells are united to form a branched structure (e.g., Ecballocystis).

14. Filamentous Forms A further development would involve a more closely knit structure, i.e., the division of the single cell into many daughter cells with septa between the divided cells and common lateral walls derived from the mother cell. If the plane of cell division is transverse to the long axis of the thallus i.e., elongation followed by division, a filamentous type of construction would be formed. This type of multicellular thallus organization is seen in the filamentous types, common to most of the algae. Under the filamentous habit several types are possible. Filaments may be branched or un-branched.

15. Un-branched Filaments They are either free-living e.g., Spirogyra attached, at least initially e.g., Oedogonium aggregated in colonies e.g., Nostoc In many Cyanophyceae it consists merely of a row of cells connected closely (e.g., Oscillatoria). In the simpler forms e.g., Ulothrix, Spirogyra, there is no division of labour. The cells are all alike, structurally and functionally, may take part in growth and cell division and in reproduction. The cells of filaments may be uninucleate (e.g., Spirogyra) or multinucleate (e.g., Cladophora).

16. Branched Simple Simple branched filament with single row of cells and a basa lattaching ceil, hold fast or hapteron is common with many types e.g. Ulothrix , Oedogonium. In many, the branches arise immediately below the cross walls growth and divisions are restricted to the end-cells of the branches e.g., Cladophora. Simple branched filaments are also seen in Xanthophyceae ,Chrysophyceae. A peculiar form of branching, known as „false‟-branching is observed in Cyanophyceae e.g.,Scytonema.

17. Heterotrichous Most highly evolved type of plant-body, showing a good amount of division of labour, is characteristic of the Chaetophorales among Chlorophyceae, in many Phaeophyceae, Rhodophyceae, in some Chrysophyceae and Dinophyceae ( e.g., Dinoclonium ). The plant-body consists of two distinct parts: (1) A basal or prostrate creeping system and (2) An erect or upright system. The prostrate system is attached to some substratum, grows apically and gives rise to numerous photosynthetic and rhizoidal filaments. Rhizoidal filaments sometimes penetrate the substratum (e.g., Fritschiella). The erect system develops from the prostrate system and is composed of one or more and usually branched photosynthetic filaments.

18. Pseudoparenchymatous forms The term “pseudo = false” Plant body gives the appearance of parenchymatous construction. Parenchyma is a tissue composed of thin walled closely associated cells which has arisen by the division of a common parent cell. Where as the pseudoparenchymatous structure is a secondary development, close association of cells is a result of interweaving of filaments. Two types are recognised in the construction . The body may have (1) A single colourless central axial filament (uniaxialconstruction) eg., Batrachospermum (2) Many filaments (multi-axial) around which photosynthetic filaments are supported eg., Polysiphonia.

19. Siphonaceous Forms In a number of algae, belonging to Siphonales e.g., in Vaucheria, Botrydium, the growth of the plant body takes place without the usual cross-wall formation except during formation of reproductive organs .Thus a ‘tube’ –like multinucleate structure, or a coenocyte, is produced. Structure is multinucleate or coenocyte cell by some and as acellular by others. It contains a central vacuole with chloroplasts and nuclei in the peripheral cytoplasm. Anchored by branching rhizoids (e.g., Bo trydium).

20. Parenchymatous Forms Modification of the filamentous habit, with cell division in more than one plane. Depending upon the nature of cell division, the parenchymatous thalli maybe ‘leaf-like’ or foliose, tubular or highly developed structure. Flat, foliose or tubular thalli are formed by the division of the cells two or three planes. Common examples of flat and foliose structures in Viva (Chlorophyceae), Punctaria (Phaeophyceae) and Porphyra (Rhodophyceae).

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