Xanthophyta by sohail riaz hashmi

introduction
general account
evolution
classification

1. XANTHOPHYTA Yellow green algae

2. Presented by: Sohail Hashmi Presented to: Dr Umair Ahmed Awan

3. CONTENTS 01 02 03 Introduction Genral account Evolution Classification 04

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 (unequ al) Life cycle is mostly haplontic

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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 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 Unicellular motile form e.g Chloramoeba,heterochloris Palmelloid forms e.g Chlorosaccus,chlorogolea . Dendroid forms e.g Mischococcus Rhizopodial forms e.g Stipitococcus Coccoid form e.g Chlorobotrys

18. 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

19. 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

20. Thank you