Xanthophyta: Yellow Green Algae Pigments and Classification
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Xanthophyta: Yellow Green Algae Pigments and Classification
- 2. Presented by: Sohail Hashmi Presented to: Dr Umair Ahmed Awan
- 4. SECTION 1 introduction and genral account
- 5. INTRODUCTION • Yellow-green algae or the Xanthophyceae are an important group of algae • Most live in fresh water, but some are found in marine and soil habitats • They vary from single celled flagellates to simple colonial and filamentous forms • Oil and fats are usual reserve food products • The division includes 375 species and 75 genera
- 6. Characteristics of Class Xanthophyceae (Yellow Green Algae) • Mostly fresh water and unicellular • Cells are eukaryotic with silica and pectin in the cell wall • Chief pigments include chlorophyll a and e, beta carotene, neoxanthin and violaxanthin • Reserve food includes chrysolaminarin and oils,Starch and pyrenoids absent • Sexual reproduction is isogamous, anisogamous or oogamous • Zoospore formation is common • Male gametes are flagellate • Flagella are heterokont (unequal) • Life cycle is mostly haplontic
- 7. C l i c k h e r e t o a d d t o t h e t i t l e
- 8. Pigments • Xanthophyte chloroplasts contain the photosynthetic pigments • chlorophyll a • chlorophyll c • β-carotene • carotenoid diadinoxanthin • Unlike other heterokonts, their chloroplasts do not contain fucoxanthin, which accounts for their lighter colour • Their storage polysaccharide is chrysolaminarin • Xanthophyte cell walls are produced of cellulose and hemicellulose
- 9. Classification • The species now placed in the Xanthophyceae were formerly included in the Chlorophyceae • In 1899, Lüther created the group Heterokontae for green algae with unequal flagella • Pascher (1914) included the Heterokontae in the Chrysophyta • In 1930, Allorge renamed the group as Xanthophyceae Vaucheria
- 10. Classification • Xanthophyceae have been divided into the following four orders in some classification systems: • Order Botrydiales • Asterosiphon • Botrydium
- 11. Order Mischococcales • Botrydiopsis • Botryochloris • Bumilleriopsis • Chlorellidium • Mischococcus • Monodus • Ophiocytium • Pleurochloris
- 12. Order Tribonematales Pascher • Bumilleria • Heterococcus • Heterothrix • Tribonema • Order Vaucheriales • Vaucheria
- 13. Lüther system of classification • Classification according to Lüther (1899) Class Heterokontae Order Chloromonadales Order Confervales Classification according to Pascher Heterokontae Heterochloridales Heterocapsales
- 14. Evolutionary perspective • Three major evolutionary lines can be traced among the Xanthophyta I. One line may have developed from an unicellular motile ancestry giving rise to non-motile unicells which may be solitary or colonial II. Another tendency is to produce a tubular, or siphonaceous form III. While the third one is leading to the formation of multicellular filamentous type
- 15. Reproduction 1. Vegetative reproduction • the reproduction in filamentous form oocur by fragmentation • unicellular forms divided by simple division
- 16. Asexual reproduction • They form one or more zoospores in each cell.Zoospores are biflagellated.The flagella have unequal length.The longer flagella is tinsel type and shorter flagellum is whiplash type • aplanospores are also produced in some bacteria • Sexual reproduction • sexual reproduction is rare in this group.sexual reproduction is oogamous or sometimes isogamous type • in case of oogamous antheridia and oogonia are produced
- 17. examples i. Unicellular motile form e.g Chloramoeba,heterochloris ii. Palmelloid forms e.g Chlorosaccus,chlorogolea. iii. Dendroid forms e.g Mischococcus iv. Rhizopodial forms e.g Stipitococcus v. Coccoid form e.g Chlorobotrys
- 19. Thallus • The plant body is bladder like unicellular,coenocytic and yellowish green • It is differentiated into underground rhizoidal portion and an aerial vesicular portion • The thallus is surrounded by a tough cellulose cell wall .Just inner to the cell wall is present a layer of cytplasm which surrounds a large central vacuole • Starch formation is totally absent
- 20. Vaucheria • One example of a relatively common Xanthophyta is the class Vaucheria that gathers approximately 70 species • whose structure consists of several tubular filaments, sharing its nuclei and chloroplasts without septa • They live mainly in freshwater, although some species are found in seawater spreading along the bottom like a carpet
- 23. Thank you