Nostoc Structure and Reproduction

Nostoc belongs to the group Cyanophyta of the kingdom Monera. It is blue-green algae. Nostoc is common as terrestrial and subaerial cyanobacteria. It is widely distributed in alkaline soils, moist rocks, water ponds, streams, and lakes, etc. Nostoc colony forms a jelly-like mass. Many filaments are embedded in this mass. The individual filament is called a trichome. The trichome is unbranched and it appears to the bead-like structure.

Thallus Structure of Nostoc

The body of Nostoc is called a thallus. It is a simple body and consists of many threads like structures, called filament. Each filament is composed of many rounded cells that are arranged in a chain-like manner or in beaded form. All the cells are similar. The whole filament is covered by a gelatinous sheath.nostoc

In the filament, some cells are larger in size and thick-walled, called heterocysts. These cells perform two functions, reproduction and Nitrogen Fixation. In Nitrogen fixation, Nitrogen is converted into simpler Nitrogen compounds, which are used by the plant.

Trichomes are unbranched and appear beaded. Individual cells are mostly spherical but sometimes barrel-shaped or cylindrical. All cells in the trichome are mostly similar in structure but at intervals are found slightly large, round, light yellowish thick-walled cells called heterocysts. Trichomes mostly break near heterocyst and form hormogonia and thus help in fragmentation.

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Structure of a cell of Nostoc

Each cell of Nostoc is rounded in shape. It is covered by an outer cell wall. The protoplasm of the cell consists of two parts:


It is the outer colored part along the cell wall, which contains blue-green pigments (Phycocyanin). It also prepares food material due to the presence of Chlorophyll pigments.chromoplasm (Structure of a cell of Nostoc)


It is the inner colorless part of the cell, which contains stored food granules. It also acts as a nucleus. The cell does not contain a true nucleus. The central body performs the function of the nucleus. It has no nuclear membrane or nucleolus, so it is called an incipient nucleus. i.e.(Incomplete nucleus).

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Reproduction in Nostoc

Sexual reproduction is absent in Nostoc. In Nostoc, the reproduction takes place by the following methods:

1.      By Hormogonia OR by Fragmentation

Hormogonia are formed by Fragmentation. The filament breaks at different points and each broken filament is called hormogonia. The filament breaks due to the decay and death of ordinary cells. Heterocyst may form the breaking point. Each hormogonium grows into a new filament by repeated cell division.hormogonia

2.      By Arthrospores OR by Akinetes Formation

During unfavorable conditions, some cells of filament become enlarge and they are covered by a thick wall, they are called Akinetes or Arthrospores or Resting Spores. They also store food materials. They germinate during favorable conditions into new filaments.akinetes formation

3.      By Heterocyst

At the time of reproduction, the heterocysts are separated from the Nostoc filament. These heterocysts are changed into normal reproductive cells. By the process of cell division, it is converted into a new filament.

Nutrition in Nostoc

Nostoc contains chlorophyll, so it can manufacture its own food i.e. it is Autotroph in nature.

Importance of Cyanobacteria

  • Cyanobacteria (Blue, Green Algae) use carbon dioxide and release oxygen during photosynthesis, so the environment becomes fresh and is used by aquatic animals.
  • They take part in Nitrogen Fixation.
Nostoc commune
Nostoc diagram
Nostoc reproduction
Photosynthetic Bacteria
Algae Genus

FAQ’s (Frequently Asked Questions)

Is nostoc harmful to humans?

no, nostoc is not considered harmful and poisonous to human beings. Nostoc commune does not cause harm and can be used for land reclamation sites, other cyanobacteria in this commune and genus grow large mats slippery safety concern and greenhouse walk-ways.

What is the use of nostoc?

it is used for nitrogen fixation for the environment which is necessary for all the organisms for the building blocks of life such as amino acids, proteins, etc.

What are the characteristics of nostoc?

nostoc has the following characteristics:

  • they are filamentous species
  • they also have complex life cycles involving cellular differentiation.
  • consist of cylindrical or spherical vegetative cells with intercalary heterocysts.
  • large specialized nitrogen-fixing cells developing in mature trichomes.

Is nostoc a bacteria or algae?

Nostoc is a cyanobacterium of blue-green algae, microscopic, single-celled organisms that contain no cell nucleus.

What is the importance of nostoc?

is an important component of extreme terrestrial habitats in the Arctic and Antarctic.

How do I get rid of Nostoc algae?

you can get rid of nostoc by adopting the following steps:

  1. do not overfertilize
  2. by improving the drainage
  3. do not overwater
  4. by moss and algae herbicide

How does nostoc reproduce?

they can reproduce asexually through spore formation called akinetes.

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