SXConline
Bio Diversity
Nostoc
Objectives: (i).To know the vegetative structure

                   (ii). To know the reproductive structures and mode of reproduction

 

Requirements:

Apparatus: Slide, Cover slip, needle, compound microscope etc.

Material: Nostoc Sp.

 

Chemicals: Safranin and glycerin

 

Visual Observation:-

            Nostoc was a colonial filamentous alga found in the form of bluish green small ball in its natural habitat. It was slippery and shiny structure also called moonspit or star jelly.

 

Microscopic Observation:-

            The filament was multicellular, unbranched and made by uniceriate rows of cells. Three different types of cells were observed.

Vegetative Cell: They were thin walled and numerous

Heterocyst: They were mostly intercalary, slightly larger and with polar nodules

Akinetes: Thick walled with abundant reserve food materials and found in chain or singly.

            The filament was ensheated by mucilaginous sheath, the cell contents were not clear. Nostoc reproduces by formation of akinetes. During Adverse condition, the vegetative cell secretes thick wall, accumulates reserve food materials and change into resting spore called akinete. Onset of favourable condition, it develops into new filament.

            Heterocyst also reproduces by forming endospore and hormogonium and helps in nitrogen fixation.

 

Classification and Identification

Kingdom         : Plantae                      (cell wall present)

Sub Kingdom  :Cryptogams    (non flowering)

Division           :Thallophyta    (thallus body, no tissue differentiation, no embryo formation)

Sub Division   :Algae              (aquatic or semi-aquatic autotrophic thallophytes,  carbohydrate is reserve food)

Class                :Cyanophyceal                        (blue green, prokaryotic, no sexual reproduction, cyanophycean starch)

Genus              : Nostoc sp.                  (uniseriate, unbranched filament, heterocyst, intercalary, asexual reproduction by akinete and hormogonium)

View the Figure for this Practical