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

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

6. 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,Ochromonas
Chromulina

7. 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

8. 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.

9. 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.,

10.  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.,

11. 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.

12. Branched Filaments
 Branchedfilamentousstructuresmaybeputint
othreecategories:
 (i)Simple,
 (ii)Heterotrichous
 (iii)Pseudoparenchymatous.
 Theyareputaccordingtotheshapeandnatureo
fthethalli,aresultofdifferenttypesofcellbeh
aviourconcerninggrowthanddivision

13. 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

14. 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).

15. 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.

16. 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.

17. 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

18. 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

19. 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

20. 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.

21. 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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