Download Oscillatoriales ( Harmogonales) Family 3 :Nostocaceae Genus :Nostoc

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Algae
are a very large and diverse group of eukaryotic organisms
simple, typically autotrophic organisms, ranging from unicellular genera
such as Chlorella to multicellular forms such as the giant kelp that grow
to 65 meters in length . All true algae therefore have a nucleus enclosed
within a membrane and plastids bound in one or more membranes.
Algae exhibit a wide range of reproductive strategies, from simple,
asexual cell division to complex forms of sexual reproduction.
Algae lack the various structures that characterize land plants, such as
the leaf-like phyallids of bryophytes, rhizoids in nonvascular plants, and
the roots, leaves, and other organs that are found in tracheophytes
(vascular plants).
Distinctive character of Algae :
1- The algae are chlorophyll bearing organism with a thallus like
plant body .
2- Thalli (singular : thallus) lack vascular tissue and epidermis with
stomata .
3- There is no embryo formation after gametic union .
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Prokaryotic Algae (Cyanophyta ) ***
Cyanophyta can be found in almost every terrestrial and aquatic
habitat—oceans, fresh water, damp soil, temporarily moistened rocks in
deserts. Cyanophyta include unicellular and colonial species. Colonies
may form filaments, sheets Some filamentous colonies show the ability
to differentiate into several different cell types: vegetative cells, the
normal, photosynthetic cells that are formed under favorable growing
conditions; akinetes, the climate-resistant spores that may form when
environmental conditions become harsh; and thick-walled heterocysts .
Prokaryotic Algea (Cyanophyta )
Pigment : chlorophyll a, Biliprotein ( phycoerythrin &phycocyanin).
Food reserves : Cyanophycin starch & cyanophycin protein .
Division : Cyanophyta .
Order 1 :Chroococcales
Family 1 : Chroococcaceae
Genus : Chroococcus
Merismopedia
Family 2 : Microcystaceae
Genus : Gloeocapsa
Microcystis
Order 2 : Oscillatoriales ( Harmogonales)
Family1 : Oscillatoriaceae
Genus :Oscillatoria
Family2 : Rivulariaceae
Genus : Rivularia
Gloeotrichia
Family 3 :Nostocaceae
Genus :Nostoc
Anabaena
Chroococcus
Division : Cyanophyta
Order 1 :Chroococcales
Family 1 : Chroococcaceae
Genus : Chroococcus
a unicellular organism, cells are ovoid or rod-shaped ,usually found in
colonies of two, four, or eight cells with a transparent protective
covering sheath containing photosynthetic pigments. Chroococcus is an
autotrophic organism able to survive almost without any freshwater or
oxygen source (Carboni) , it uses an extensive quantity of atmospheric
carbon for photosynthetic processes, creating free oxygen to be used by
other organisms .. It produces oxygen and adenosine triphosphate (ATP)
through photosynthetic methods using sunlight as the catalyst.
Merismopedia
Division : Cyanophyta
Order 1 :Chroococcales
Family 1 : Chroococcaceae
Genus : Merismopedia
found common in several varieties of water habitats fresh and salt
water. They grows as unicellular organisms in colonial form, reproducing
in two fission planes to form plate-like colonies consisting of up to 4000
cells with ovoid or spherical shape that arranged in rows and flats ,
forming rectangular colonies held together by a mucilaginous matrix this
form called (( palmelloid)) .
Gloeocapsa
Division : Cyanophyta
Order 1 :Chroococcales
Family 2 : Microcystaceae
Genus : Gloeocapsa
The cells secrete individual gelatinous sheaths , the cell rounded , They
are also known as glow caps, a term derived from the yellowish given off
by the cap. It is responsible for the black/dark green stains that form on
roofs. These black stains are the algae themselves in mass amounts
covering the surface of the roof shingles . Some species of this genus are
halophiles and hence found in hypersaline lakes and other high salinity
environments .
Microcystis
Division : Cyanophyta
Order 1 :Chroococcales
Family 2 : Microcystaceae
Genus : Microcystis
The cells are usually organized into colonies (large colonies) may be
viewed with the naked eye that begin in a spherical shape, but losing
their coherence to become perforated or irregularly shaped over time .
produce two groups of toxin, neurotoxins and peptide hepatotoxins .
Oscillatoria
Division : Cyanophyta
Order 2 : Oscillatoriales ( Harmogonales)
Family1 : Oscillatoriaceae
Genus :Oscillatoria
 It is a genus of filamentous cyanophyta , some of it cells are
broader than longer , where is other the reverse is true ,
Oscillatoria forms long filaments of cells which can break into
fragments called harmogonia , longer filament, Breaks usually
occur where dead cells
 There is no differentiation among the component cells of trichome
except the apical cell .
 Have no mucilage sheath , It is reproduces by fragmentation .
Gloeotrichia
Division : Cyanophyta
Order 2 : Oscillatoriales ( Harmogonales)
Family2 : Rivulariaceae
Genus : Gloeotrichia
* it is taper from basal to apex (hair like)
* the mucilage sheath envelopes body to end of akinete.
*the body differentiated into 3 types of cells :
1-basal heterocyst
2- elongated akinete
Rivularia
Division : Cyanophyta
Order 2 : Oscillatoriales ( Harmogonales)
Family2 : Rivulariaceae
Genus : Rivularia
3-vegetative cell.
 the filaments (trichomes) are tapered from wider at the base to
narrower at the tip.
 The sheath envelopes whole body .
 Akinetes are lacking .
Nostoc
Division : Cyanophyta
Order 2 : Oscillatoriales ( Harmogonales)
Family 3 :Nostocaceae
Genus :Nostoc
 It forms colonies composed of unbranched filaments of
moniliform cells in a gelatinous sheath .
 It may also grow symbiotically within the tissues of plants
providing nitrogen to its host through the action of terminally
differentiated cells heterocysts .
 The body differentiated into 3 types of cells : heterocyst , akinete ,
vegetative cell .
Anabaena
Division : Cyanophyta
Order 2 : Oscillatoriales ( Harmogonales)
Family 3 :Nostocacea
Genus : Anabaena
 It is unbranched filamentous .
 The body differentiated into 3 types of cells : heterocyst , akinete ,
vegetative cell .
 Anabaena differ from Nostoc in vegetative cell , are being dram or
cylindrical shape , while small spherical in Nostoc .
 The tow genus used in rice field because of (N2) fixation .