This ppt has been made by Xanthophyceae also known as yellow green algae. It occupies second position in algae classification by F.E Fritsch. It is classified into four orders. It contain xanthophyll in large amount that gives it yellow colour, hence it is commonly know as yellow green algae.
4. INTRODUCTION
• Tribophyceae, after the common genus Tribonema.
• Yellow green algae.
• Related to Phaeophyceae
• Photosynthetic organisms
• Genera – 118, Species - 600
• Freshwater, marine waters, damp soil, or on tree trunks.
DID YOU KNOW ??
Xanthophyceae are "secondary
endosymbionts" -- they evolved from protists
that engulfed algae and assimilated their
chloroplasts
6. GENERAL CHARACTERS
• Occurrence : Mostly freshwater and a few marine representative
• Pigments : Chlorophyll, carotene and xanthophylls
• Pyrenoids : Usually absent
• Reserve food material : Chrysolaminarin, Oil and fat
• Cell wall : Rich in pectic compounds and composed of two equal pieces
overlapping at the edges.
• Structure : Eukaryotic unicellular motile to simple filamentous
• Flagella : Present, two unequal, situated anteriorly. Longer one tinsel and
shorter one whiplash
• Reproduction : Vegetative, Asexual and Sexual (Mainly Isogamous,
Anisogamy is rare, Oogamous in Vaucheria)
7. CLASSIFICATION
• Fritsch (1935) recognizes the following orders in the class Xanthophyceae:
• Order Heterochloridales
• Suborder Heterochlorineae
• Family Heterochloridaceae (e.g., Heterochloris)
• Suborder Heterocapsineae
• Family Heterocapsaceae (e.g., Chlorogloea)
• Suborder Heterodendrineae
• Family Mischococcaceae (e.g., Mischococcus)
• Suborder Heterorhizidineae
• Family Heterorhizidaceae (e.g., Rhizolekane)
Mischococcus
8. CLASSIFICATION
• Order Heterococcales
• Family Halosphaeraceae (e.g., Halosphaera)
• Family Myxochloridaceae (e.g., Myxochloris)
• Family Chlorobotrydaceae(e.g., Chlorobotrys)
• Family Chlorotheciaceae (e.g., Chlorothecium)
• Family Ophiocytiaceae (e.g., Ophiocytium)
• Order Heterotrichales
• Family Tribonemataceae (e.g., Tribonema)
• Family Heterocloniaceae (e.g., Heterodendron)
• Order Heterosiphonales
• Family Botrydiaceae (e.g., Botrydium)
Botrydium
Ophiocytium
Tribonema
10. RANGE OF THALLUS STRUCTURE
• Thallus structure includes motile, palmelloid, dendroids, filamentous and siphoneous
form.
The following are levels of organisation which can be found in Xanthophyceae :
• Unicellular flagellate (monadoid) - Chloromeson
• Amoeboid - Rhizochloris, Myxochloris
• Palmelloid- Gloechloris
• Coccoid - Chloridella, Botrydiopsis, Characiopsis, Ophiocytium
• Filamentous - Tribonema, Hetrodendron
• Siphonous- Botrydium, Vaucheria.
• They lack pseudo-parenchymatous or truly parenchymatous thalli.
12. CELL STRUCTURE
• The yellow green algal group is also known as the heterokonate because
there are two structurally different flagella (or sometimes one flagellum)
.
• Motile cells have a forwardly directed tinsel flagellum and a posteriorly
directed whiplash flagellum.
• The cell wall is composed of pectic substances and sometimes silica.
• The cellulose as a cell constituent of the cell wall is meager but the cell
wall in Botrydium is wholly of cellulose.
• The cell wall has tightly overlapping halves.
• In Tribonema, the cell wall is composed of ‘H’ shaped pieces which
overlap each other alternately.
• The number of chromatophores in a cell, depending upon the species,
varies from one to several.
13. CELL STRUCTURE
• Chromatophores usually lack pyrenoids but if present, are naked and
these do not serve for the storage of food.
• Yellow green algae has uniform, simple shape of the chloroplast, usually
discoid and parietal in position.
• The members of Xanthophyceae are both uninucleate and
multinucleate.
• The eyespot in motile cells is always in the chloroplast and the
chloroplasts are surrounded by two membranes of chloroplast
endoplasmic reticulum .
• The outer membrane of the chloroplast-endoplasmic reticulum complex
is usually continuous with the outer membrane of the nucleus.
• Mostly walls of non-motile cells are composed of two overlapping
18. VEGETATIVE REPRODUCTION
• For majority of xanthophyceae only vegetative reproduction is known which
occurs by;
• Vegetative cell division
• Algal cells divide mitotically to form 2 daughter cell ,eventually grows into an
independent organism.
• Filament fragmentation
• Thallus often breaks into small fragment, each fragment grow independently
to form new thallus.
• - mechanical pressure
• -dissolution of cell wall
• -difference in turgor pressure between adjoining cells.
Vaucheria
VEGETATIVE FILAMENT FROM ROCK
20. ASEXUAL REPRODUCTION
•Xanthophycean organisms multiply asexually by
zoospores, and aplanospores.
•Zoospores: motile naked structures with flagella.
•Zoospores are formed by a majority of the genera.
•The zoospores are biflagellate, with the forward
tinsel flagellum usually being four to six times longer
than the shorter whiplash flagellum.
21. • Aplanospores :
• non motile spores , each cell may form a single aplanospore
or its protoplast may divide to form many aplanospores.
• Akinetes :
• Vegetative cell develop into thick walled spore like structure
with abundant food reserve .
• Always have additional wall layers around the protoplast
which are fused with parent wall.
• They are resistant to unfavourable environmental condition.
23. SEXUAL REPRODUCTION
• Sexual reproduction is very rare.
• Isogamy is common.
• Isogamy : two gametes fuse to form zygote , they are
morphologically & physiologically similar.
• Anisogamy :takes place between morphologically &
physiologically different gametes.
• Isogamy & anisogamy – Botrydium.
• Oogamy : advanced type , large non motile egg fuses with small
motile sperm ,egg is formed within oogonium and sperm within
antheridium.
• Isogamy & oogamy – Vaucheria
24.
25. (a, b)Vaucheria borealis
(a) oogonium,
(b) antheridium and oogonium, scale bar
40 μm
(c–e)V. geminata (V aucher ) DC .:
(c) generative branch with central
antheridium and two oogonia, scale bar
40 μm
(d) generative branch with central
antheridium, scale bar 40 μm,
(e) generative branch with central
antheridium and two oogonia, scale bar
25 μm;
(f)V. woroniniana generative branch
with central antheridium and two
oogonia, scale bar 40 μm.
26. ECONOMIC IMPORTANCE
1. Contaminent of water :
• Xanthophyta are important contaminants of source of water or drinking
water supplies.
• These are able to change the quality of water but these are so small that
mostly scientists ignore their role which they play for water.
2. Treatment plants :
• Some species of xanthopyta are presumably in response to elevate
nutrients from fertilizers.
• Some species produce substantial biomass in wastewater treatment
suggests they may have promise for nutrients or heavy metal removal.
27. 3. Water supply :
• Health pertaining to algae in domestic water supplies have
historically been focused on taxa known produce toxins, taste and
odour problems.
• PCR method developed for detecting marine may prove useful in
future studies of water supplies.
4. Toxin production :
• Freshwater xanthophyta algae are not known to be toxin
producers, but marine species produce potent ichtyotoxins that
lead to massive fish kill during blooms.
28. 5. Stabilization process of excess mud :
Useful in the stabilization process of excess mud.
E.g. Vaucheria
6. Production of oxygen :
Due to its high content in chlorophyll and β-carotene, it is
highly useful in the production of oxygen.
7. As food :
Countries like Japan are consuming some forms of this algae.
E.g.Vaucheria
8. For recreational uses :
Vaucheria gives parrot green colour to gardens.
30. EVOLUTIONARY PERSPECTIVE
•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.
31. 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.
