Nostoc

NOSTOC

Object: Study of external features of Nostoc 
Work Procedure

Place a part of colony on the slide, press it little by another slide so that it spreads flat, stain in safranin and mount in glycerine.

Comments on Nostoc

1. Thallus is colonial. Young colonies are microscopic, spherical and solid. 

2. Mature colonies become irregular and hollow.

3. Colonial envelope encloses many filaments. These are much twisted, curved and entangled with each other.

4. Each filament has diffluent gelatinous sheaths.

Nostoc. A vegetative filament

5. The trichomes are unbranched. Each trichome is made of cells of uniform size and shape except those called heterocyst which occur throughout.

6. Structure of a cell is typically cyanophycean. It has a centrally located centroplasm, nucleus being altogether absent. Peripheral cytoplasm shows diffused pigments. A few shining cyanophycean granules are also present in this region.

7. Heterocysts are intercalary. These are double walled, pale yellow coloured with two shining polar granules, one each near the neighbouring cell on either side. Heterocysts are much of the same size of slightly bigger than the vegetative cells.

8. A few cells, mostly in chains between two consectutive heterocysts become modified into akinetes. These are the organs of perennation. Akinetes germinate into a new filament.

Object Study the akinetes of Nostoc
Work Procedure

Press a piece of mature colony to spread the filaments. Stain in safranin, mount in glycerine and study.

Comments on Nostoc

1. Akinetes are developed only in a mature colony. These occur in large number, in series between two heterocysts. Usually all vegetative cells between two successive heterocysts develop into akinetes.

 2. Akinetes are thick walled, sometimes ornamented, rich in food reserves and cyanophycean granules. 

3. Akinetes are liberated due to decay of colonial sheath. These germinate to form a new thallus.

Nostoc. heterocyst with akinetes in chains

Classification and identification:

Sub-division-Algae. (1) Thallus simple, (2) Presence of chlorophyll, (3) Cell wall of cellulose.

Class-Myxophyceae. (1) Chromatophore not organised, pigments diffused, blue-green, (2) Photosynthetic reserve of cyanophycean starch, (3) True nucleus absent. Order-Nostocales. (1) Thallus with trichomes, unbranched or branching false, (2) Hormogones, heterocysts,

exospores and endospores generally present. Family Nostocaceae. (1) Trichomes simple, unbranched, uniseriate and approximately of the same diameter throughout, (2) Heterocysts and akinetes present,

(3) Trichomes not differentiated.

Genus-Nostoc. 

(1) Trichomes much twisted into a mass of definite form with a firm colonial envelope,

(2) Heterocysts intercalary and single.

Hints for collection:

It commonly occurs in abundance after the first few rains. It is terrestrial as well as aquatic. It is collected from water pools, paddy fields, waterlogged soil, moist rocks, stagnant water, etc. It is known to occur as epiphyte on aquatic weeds and endophytically inside Cycas coralloid roots, Azolla-a fern, Blasia and Anthoceros bryophytes and form lichens in association with fungal partners members.

Nostoc Structure

Nostoc ar filiform and unbranching. varied filaments ar found in an exceedingly gelatinlike mass as a colony. The colonies is also as massive as Associate in Nursing egg. The filament consists of a series of cells, that seem like a bead. they're referred to as trichomes

Cells ar oval, spherical or cylindrical.

Some of the cells within the filament ar differentiated, they're referred to as heterocyst. they're sites for organic process. enzyme accelerator fixes chemical element

Each filament is roofed in an exceedingly gummy sheath, that may be a protecting layer. It absorbs and retains water. The gelatinlike sheath is formed from polysaccharides and conjointly contains proteins

Colonies ar of various shapes, sizes and colors. they're largely dark-green or bluish-green in color and even have red-brown or chromatic color

Extracellular pigments also are found, e.g. nostocine, scytonemin. These pigments together with some amino acids defend the cells from UV radiation

Each cell incorporates a thick plasma membrane created from peptidoglycan

The protoplasm of a cell is differentiated into outer colored thanks to peripherally organized plastid and inner clear protoplasm

Cells have numerous pigments. Cells contain chlorophyl (green pigment). pigment (blue) and pigment (red) also are gift

Inner protoplasm contains early nucleus or a nuclear body, desoxyribonucleic acid is while not histones

Nostoc replica

Nostoc reproduce vegetatively or asexually by reproductive structure formation.

The vegetative replica is by fragmentation. tiny colonies will grow connected to an oversized colony and later kind separated colonies.

Hormogonia ar short and free filaments. they're shaped once a filament breaks. It retains the gelatinlike sheath. New trichomes ar developed within the colony.

Asexual reproduction is by the formation of resting spores referred to as akinetes. a number of the cells become thick-walled thanks to accumulation of food. they'll stand up to unfavourable conditions for several years. underneath favourable conditions, they germinate to make a brand new filament.

Nostoc conjointly reproduce by heterocysts. Heterocysts break away the filament. They divide and germinate into a brand new filament.

Ecological Importance of Nostoc

Nostoc ar vital for his or her nitrogen-fixing ability. they're employed in paddy fields and also are wont to increase the nutrient worth of soil

They ar wealthy in proteins and antioxidant and are used as a delicacy in numerous Asian countries, e.g. N. flagelliforme, N. commune, etc.

N. muscorum has been shown to accumulate polyhydroxy butyrate, that may be a precursor of plastic. it's going to have helpful application within the trade

Cyanobacteria will convert CO2 to biofuels. blue-green algae have shown to provide chemical element

They can be used for bioremediation of waste material and degrade environmental pollutants

Various species, e.g. N. muscorum, N. commune, N. insulare, etc. extracts have shown medication or antiviral activity and should be employed in future to arrange medication