Cyanophyta

CYANOPHYTA
PRESENTED BY-
DR. SANGEETA DAS
ASSISTANT PROFESSOR
DEPARTMENT OF BOTANY

CYANOPHYTA EXAMPLES
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CYANOPHYTA EXAMPLES

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CYANOPHYTA-G. Characters

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CYANOPHYTA
ALSO
KNOWN AS
??

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CYANOPHYTA
SIMILARITIES BETWEEN CYANOBACTERIA AND BACTERIA:

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CYANOPHYTA
DISTRIBUTION:
 It is a primitive group of algae consisting of 150 genera and about
2,000 species all over the world.
 In India, this group is represented by 98 genera and 833 species.

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CYANOPHYTA
 ECOLOGY & OCCURRENCE:

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 ECOLOGY & OCCURRENCE:
CYANOPHYTA

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 What is a thallus?
CYANOPHYTA-Range of Thallus Organization

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 The thallus may be of unicellular or colonial forms:
 1. Unicellular Form:
 In unicellular form, the cells may be oval or spherical. Common members
are Gloeocapsa, Chroococcus and Synechococcus.

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 2. Colonial Form:
 In most of the members the cells after division remain attached by their
cell wall or remain together in a common gelatinous matrix, called a
colony.
 The colonies may be of two types:
 a. Non- filamentous, and
 b. Filamentous.

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 a. Non-Filamentous Type:
 The cells of this type divide either alternately or in three planes, thereby they
form
 Spherical (Gomphosphaera, Coelosphaerum),
 Cubical (Eucapsis alpine, Merismopedia) or
 Irregular (Microcystis).
Eucapsis Microcystis

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 b. Filamentous Type:
 By the repeated cell division in one plane, single row of cells are formed,
known as trichome e.g., Oscillatoria, Spirulina, Arthospora etc.
 The trichome when covered by mucilaginous sheath is called a filament.
 The filament may contain single trichome (Oscillatoria, Lyngbya) or several
trichomes (Hydrocoleus, Microcoleus).

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CYANOPHYTA
 The trichomes may be
 Unbranched (Oscillatoria, Lyngbya),
 Branched (Mastigocladus limilosus, and
 Falsely branched (Scytonema and Tolypothrix).
Oscillatoria Mastigocladus Scytonema

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CYANOPHYTA-Cell structure

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 Cyanobacterial cells are larger and more
elaborate than bacteria.
 Cell structure is typically prokaryotic— one
envelope organisation with peptidoglycan wall,
naked DNA, 70S ribosomes and absence of
membrane bound structures.
 The cell wall is four layered with peptidoglycan
present in the second layer. The outer part of
the protoplast contains a number of photosyn-
thetic thylakoids. It is called chromoplasm.
The thylakoids lie freely in the cytoplasm.
Their membranes contain chlorophyll a,
carotenes and xanthophyll’s. Chlorophyll b is
absent.
CYANOPHYTA-Cell structure

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CYANOPHYTA-Reproduction
 They reproduce by both vegetative and asexual methods.
 Sexual reproduction is absent.

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Vegetative Reproduction:
1) Binary fission – dividing in two 2) Fragmentation of colonies

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Vegetative Reproduction:
3) Hormogonia formation (Nostoc) 4) Hormospores formation (Westiella)

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Asexual Reproduction:
Different types of spores are produced.
1) Akinetes (Anabaena)

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2) Endospores (Dermocarpa) 3) Exospores (Chamaesiphon)

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2) Nannocytes (Aphanothece): They may divide into many parts without
any change in shape.

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CYANOPHYTA-NOSTOC
 SYSTEMATIC POSITION:
Phylum: Cyanobacteria
Class: Cyanophyceae
Order: Nostocales
Family: Nostocaceae
Genus: Nostoc

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 Nostoc are filamentous and
unbranched.
 Numerous filaments are found in a
gelatinous mass as a colony.
 The filament consists of a chain of
cells, which appear like a bead.
They are called trichomes
 Cells are oval, spherical or
cylindrical.
 Some of the cells in the filament are
differentiated, they are called
heterocyst. They are sites for
nitrogen fixation. Nitrogenase
enzyme fixes nitrogen.
NOSTOC-MORPHOLOGY

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 Each filament is covered in a
mucilaginous sheath, which is a
protective layer. It absorbs and
retains water.
 The gelatinous sheath is made up of
polysaccharides and also contains
proteins
 Colonies are of different shapes,
sizes and colours.
 They are mostly greenish or bluish-
green in colour and also have red-
brown or yellow-green colour.
NOSTOC-MORPHOLOGY

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 Nostoc reproduce vegetatively or asexually by spore
formation.
 The vegetative reproduction is by fragmentation.
Small colonies can grow attached to a large colony
and later form separated colonies.
 Hormogonia are short and free filaments. They are
formed when a filament breaks. It retains the
gelatinous sheath. New trichomes are developed
inside the colony.
 Asexual reproduction is by the formation of resting
spores known as akinetes.
 Nostoc also reproduce by heterocysts.
NOSTOC-REPRODUCTION

Cyanophyta

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