Chlorophyta

About 20,000 species.
Eukaryotic cell and contain all the membrane bound organelles.
Thallus is green due to the presence of green pigment chlorophyll.
Chlorophyll is contained in chloroplast.
Pyrenoids embedded in chloroplast.
Cytoplasm contains vacuoles.
Motile cell of primitive forms contains eye spot or stigma.
Reserve carbohydrates are in the form of starch.
Cell wall invariably contains cellulose.
Produce motile reproductive bodies generally with two or four flagella.
Most are aquatic but some are subarial.
Several species of ulvales and siphonales are marine.
Some strains of chlorella are thermophilic.
Species of chlamydomonas and some chlorococcales occur in snow.
Coloechaete nitellarum is endophytic.
Cephaleuros is parasitic – cause ‘red rust of tea’.
Live epizoically on or endozoically within the bodies of lower animals – chlorella is found in hydra; chlorella beneath the scales of fish; characium on the antennae of mosquito.
Green algae in assosciation with the fungi constitute lichens.

1. CHLOROPHYTA ALEN SHAJI P1914015

2. INTRODUCTION About 20,000 species. Eukaryotic cell and contain all the membrane bound organells . Thallus is green due to the presence of green pigment chlorophyll . Chlorophyll is contained in chloroplast . Pyrenoids embedded in chloroplast. Cytoplasm contains vacuoles . Motile cell of primitive forms contains eye spot or stigma . Reserve carbohydrates are in the form of starch . Cell wall invariably contains cellulose . Produce motile reproductive bodies generally with two or four flagella .

3. OCCURENCE Most are aquatic but some are subarial . Several species of ulvales and siphonales are marine . Some strains of chlorella are thermophilic . Species of chlamydomonas and some chlorococcales occur in snow . Coloechaete nitellarum is endophytic . Cephaleuros is parasitic – cause ‘red rust of tea’. Live epizoically on or endozoically within the bodies of lower animals – chlorella is found in hydra; chlorella beneath the scales of fish; characium on the antennae of mosquito. Green algae in assosciation with the fungi constitute lichens .

4. THALLUS ORGANIZATION UNICELLULAR THALLUS A] MOTILE UNICELLULAR THALLUS eg ; Chlamydomonas

5. B] NON MOTILE UNICELLULAR THALLUS eg ; Chlorococcum

6. 2. COLONIAL THALLUS A] MOTILE COLONIAL THALLUS eg ; Volvox , Pandorina

7. B] NON MOTILE COLONIAL THALLUS eg ; Pediastrum , Hydrodictyon

8. 3. SIPHONOUS OR COENOCYTIC THALLUS eg ; Characium , Acetabularia

9. 4. MULTICELLULAR FILAMENTOUS THALLUS A] SIMPLE FILAMENT eg ; Spirogyra, Ulothrix , Oedogonium

10. B] BRANCHED FILAMENT eg ; Bulbochaete , Chaetophora , Cladophora

11. C] FOLIACEOUS THALLUS eg ; Ulva D] MASSIVE PARENCHYMA TOUS THALLUS

12. E] HETEROTRICHOUS FILAMENT eg ; Stigeoclonium , Fritschiella , Coleochaete , Draparnaldia , Draparnaldiopsis

13. CELL STRUCTURE Protoplast is bounded by a thin plasma membrane and shows an advance over the cyanophyta in the presence of a definite nucleus , a distinct cytoplasm , one or more membrane limited chloroplasts, mitochondria, dictyosomes , endoplasmic reticulum , and frequently a sap cavity . Cell wall is stable. Inner layer of cell wall is composed of cellulose which occurs in the form of microfibrillar units.[ excptn ; callose in siphonales ] Outer layer of cell wall is made of pectose . In spirogyra ; outermost portion of pectose changes into pectin and it dissolves in water to form gelatinous sheath which is slimy and it envelops the entire filament.

14. In ulothrix , oedogonium , cladophora ; an insoluble substance impregnates into the external portion of the pectose layer and prevents dissolving away of pectose . In chlorogonium , haematococcus ; cell wall is composed of hemicellulose . Cell wall of some marine caulerpales [old name siphonales ] are impregnated with lime. In desmids ; deposition of iron compounds has been reported on cell walls. Protoplast containing plasma membrane contains three layers; middle lipid layer is sandwiched between the two protein layers. Vacuoles are present; function as osmoregulatory organelles , absent in motile forms of volvocales and non motile forms of chlorococcales . Big central vacoule is traversed by a number of cytoplasmic strands that shoot out from the lining layer of cytoplasm refered to as the primordial utricle .

15. Large central vacoule is boundedby a definite plasma membrane known as the tonoplast . Plasmodesmata are present in volvox , eudorina . Mitochondria, golgi bodies [ dictyosomes ], ribosomes , endoplasmic reticulum, chloroplasts are present.

16. CHLOROPLAST Pigment containg bodies in green algae and charophyta are called chloroplasts and but in all other algal divisions except euglenophyta , they are referred to as chromatophores . Plastids which contain both chlorophyll a and chlorophyll b are usually termed as chloroplasts . Plastids which contain chlorophyll a but not chlorophyll b and have carotenoids in excess over chlorophyll are known as chromatophores . Green pigments- chlorophyll a and chlorophyll b . Yellow pigments- carotene and xanthophyll . Green colouration of members of chlorophyta is due to the presence of excess of chlorophyll in the chloroplasts. Beta carotene is commonly found in green algae.

17. Sacsdb A] large cup shaped chloroplasts- volvacales . B] single; collar shaped chloroplasts- ulothrix . C] discoid chloroplast- siphonales . D] parietal, girdle shaped with incised margins and more or less reticulate- draparnaldiopsis . E] band like chloroplast- debarya . F] parietal ribbon shaped, spirally wound chloroplast- conjugales . G] two parietal plates with a nucleus in between a pair of axial stellate bodies- conjugales . H] an axial plate- conjugales .

18. Complex structure among eukaryotic algae. Double membrane envelope limits the chloroplasts. Matrix within is often full of lamellar structure and is thus greately reduced. Number of thylakoids in the stack varies within a wide range. Usually , 2-20 discs in a band or stack. In nitella ; 40-100 thylakoids in a single stack.

19. Thylakoids in the stacks assosciate and dissociate in various ways giving a grana like appearance . Stacks are well defined with discs closely appressed together. Some of the bands extend for a considerable distance. Discs in the stacks may often shift from one stack to another.

20. In some green algae; the discs appear to be randomly arranged with little suggestion of regular stacks . Discs come together and separate in an irregular manner. Chloroplast matrix contains starch grains besides the ribosomes and osmiophilic globules. In some green algae; the pyrenoid is a region of dense matrix material in the chloroplast. Pyrenoids contains fibrils which are tight packed. In spirogyra and cosmarium lundelii ; pyrenoid is transversed by single discs which may be continous with the chloroplast bands. In some green algae; pyrenoid lacs discs. Pyrenoid has around it a sheath of starch grains which seperates it from the chloroplast matrix.

21. CHLOROPLAST OF CHLOROPHYTA

22. FLAGELLA OF CHLOROPHYTA

23. Fine protoplasmic whiplike threads called flagella helps in locomotion . Usually there are two or four flagella of equal lengths [ isokontic ]. Inserted at the anterior or apical end of the motile cells. In oedogoniales ; motile cells have a ring of flagella. Flagella in green algae have a smooth surface and are called whiplas or acronematic . Flagellum is an extremely fine, hyaline emergence of the cytoplasm . Usually there is a single granule at the base of each flagellum known as the blepharoplast or basal body . Each flagellum consists of a thin axial filament of axoneme surrounded by a cytoplasmic membrane or sheath which is an extension of the cell or plasma membrane. Naked portion of the axoneme is called the end piece . Axoneme constists of 11 fibrils; two are in centre and known as the axial or central fibrils .

24. SIMILARITIES OF THE CELL STRUCTURE OF A GREEN ALGAE WITH HIGHER PLANTS 1] Presence of chlorophyll a and chlorophyll b as the principal pigments. 2] Accessory pigments [xanthophylls and carotenes] are the same in both. 3] Starch as the principal food reserve. 4] Components of cell such as the cytoplasm, nucleus, cell membranes, and chloroplasts have basically the same structure as those of the higher plants.

25. VEGETATIVE REPRODUCTION 1] CELL DIVISION Also called as fission . In unicellular forms ; it is a method of reproduction. In multicellular forms ; it leads to growth. Division of the cell is preceeded by the division of the nucleus which is mitotic and it is followed by the cleavage of the cytoplasm which begins by a median constriction at the periphery.

26. 2] FRAGMENTATION Breaking up of multicellular Filamentous thallus into one or many celled segments of living Cells. Due to the formation of mitospores or gametes or external forces in certain parts of the filament followed by the breaking up of empty cells.

27. 3] AKINETES They are one celled specially modified resting vegetative structures. Akinetes enable plant to tide over unfavourable conditions. On favourable conditions; each akinete may germinate directly to a new individual.

28. ASEXUAL REPRODUCTION 1] ZOOSPORE FORMATION Developed in zoosporangia. Zoospore is tiny, naked mass of protoplast containing a single Nucleus, an eye spot and one or more chloroplasts. Flagella are isokont . Inserted at the anterior end. Function as locomotory Organs.

29. STRUCTURE OF ZOOSPORE

30. On favourable conditions develops into a new plant resembling the parent.

31. 2] APLANOSPORE FORMATION Non motile asexual spores- aplanospores . Aplanospore identical to parent cell- autospores . Thick walled apalnospores - hypnospores .

32. SEXUAL REPRODUCTION 1] ISOGAMY

33. ISOGAMOUS SEXUAL REPRODUCTION IN HETEROTHALLIC SPECIES OF CHLAMYDOMONAS

34. 2] ANISOGAMY

35. 3] OOGAMY

36. GERMINATION OF ZYGOSPORE Resting stage- zygospores . Zygotic meiosis. Meiospores . Incipient or primitive sporophyte . Intermediate meiosis. Diploid filament or sporophyte .

37. ALTERNATION OF GENERATION 1] HAPLONTIC LIFE CYCLE OF SPIROGYRA

38. 2] HAPLONTIC LIFE CYCLE OF ULOTHRIX

39. 3] ISOMORPHIC OR HOMOLOGOUS DIPLOHAPLONTIC LIFE CYCLE IN CLADOPHORA

40. CLASSIFICATION There are four classes in the chlorophyta ; 1] PRASINOPHYCEAE 2] CHAROPHYCEAE 3] ULVOPHYCEAE 4] CHLOROPHYCEAE

41. PRASINOPHYCE Primitive green algae. Some of which gave rise to the other classes in the chlorophyta . Scaly or naked flagellates with interzonal spindles that are persistant during cytokinesis . CHAROPHYCEAE Two flagella attached in a lateral position in the cell. Scales common outside of motile cells. Motile cells asymmetrical . Eyespots usually not present . Predominantly freshwater . Sexual reproduction involves the formation of a dormant zygote. Meiosis occurs when the zygote germinates.

42. ULVOPHYCEAE Flagella attached at anterior end of cell . Motile cells have near radial symmetry externally. Eyespots common. Predominantly marine. No dormant zygotes. Alternation of generations common. CHLOROPHYCEAE Flagella attached at anterior end of cell. Eyespots common. Predominantly freshwater. Zygote undergoes a dormant period . Meiosis occurs when the zygote germinates .

43. TETRASPORINE LINE OF DEVELOPMENT OF THALLUS IN GREEN ALGAE

44. SALIENT FEATURES They are grass green in colour owing to the preponderance of chlorophyll a and chlorophyll b over carotene and xanthophyll . Pigments are located in the green plastids known as chloroplasts. Reserve carbohydrate food is stored as starch. Chloroplast normally contain the pyrenoids . Cell has a well defined nucleus and in the higher forms a central sap cavity in addition. Majority produce motile reproductive cells. Flagella are isokontic and inserted at the anterior end.

45. Sexual reproduction ranges from isogamy to oogamy . Sex organs are always unicellular. Zygote generally is the only diploid structure in the life cycle. Plant body is unicellular or multicellular .

46. REFERENCES Lee RE, PHYCOLOGY, Cambridge University Press.

47. THANK YOU GOD