This document summarizes the distribution, systematic position, and life cycle of the cyanobacteria Nostoc and the charophyte alga Chara. Nostoc is a terrestrial or aquatic cyanobacteria that grows in gelatinous colonies of trichomes containing vegetative cells, heterocysts, and akinetes. It fixes atmospheric nitrogen and reproduces through hormogonia formation or budding. Chara is a submerged freshwater charophyte alga that attaches to substrates via rhizoids. It has a branched thallus with nodes bearing short branches, stipulodes, and longer axillary branches. It reproduces vegetatively through amylum stars and bulbils or

1. Distribution, systematic position and life
cycle of Nostoc and Chara
Sankrita Gaonkar
Assistant Professor in Botany
sankrita002@gmail.com

2. Contents
• Nostoc
• Chara
• References

3. Nostoc
Systematic position:
• Division: Cyanophyta
• Class: Cyanophyceae
• Order: Nostocales
• Family: Nostocaeae
• Genus: Nostoc

4. Distribution and features:
• Terrestrial and aquatic habitats
• Grows in large colonies of closely packed trichomes –
embedded in gelatinous material.
• Colour – olive green or blue-green
• Terrestrial – grows on damp soil
• Aquatic – free floating or lie at bottom attached to
submerged vegetation
• Fix atmospheric nitrogen – maintain soil ferility

5. • Structure
• Trichome – enclosed by mucilaginous sheath – filament
• Composed of numerous cells joined like string of beads
• Heterocyst – colourless, empty-looking, barrel shaped cells – slightly larger
and thicker than vegetative cells – intercalary or terminal
• Akinetes – resting bodies stored with food materials

6. Life cycle:
1. Heterocystous phase - a) motile hormogonia; b) non
motile hormogonia with terminal heterocysts and
enveloped in a hyaline sheath; c) aseriate colonies
formed by several divisions occurring in different
planes. At the beginning the colony is elongated, then
it becomes spherical and contains a coiled filament
formed by vegetative cells and heterocysts; d)
reproduction of the colony by hormogonia or budding.
Buddings are more frequent in cultures grown on solid
medium. The hormogonia also are formed by a
breaking of the colonial filament at the junction of the
heterocysts and are released by rupture or dissolution
of the colony sheath; e) vesicles of transparent
mucillage containing numerous isolated hetercysts
after the release of the hormogonia.
2. Sporogenous phase – light exposure – 2 to 4 celled
fragments, grow to form long trichomes without
heterocysts, trichomes break into fragments,
intercalary cells develop into spores, spores germinate
– form 2-3 celled germlings

7. Chara
Systematic position:
• Division: Charophyta
• Class: Charophyceae
• Order: Charales
• Family: Characeae
• Genus: Chara

8. Distribution and features:
• Submerged aquatic alga – attach to soft mud at the bottom
• Prefers fresh, hard and shallow water
• Species growing in water containing calcareous materials
become encrusted by calcium carbonate
• Thallus organization:
o Rhizoids – for attachment to the substratum
o Has upright branched axis – short nodes and long internodes
o Node:
1. Branchlets – short branches of limited growth (primary
laterals)
2. Long branches – branches of unlimited growth (axillary
branches)
3. Stipulodes – unicellular outgrowths arise from node

10. • Life cycle:
• Vegetative reproduction – amylum stars (star-shaped cell aggregation on
nodes), bulbils (rounded tuber-like structures on rhizoids)
• Sexual reproduction – oogamous - antheridia (globule), oogonia (nucule)

13. References
• Vashishta B.R., Sinha A.K. and Singh V.P. 2012. Botany for
degree students: Algae. S. Chand & company ltd.
• Fritsch, F.E.,(1956). The structure and reproduction of the
Algae; Volume I and II. Cambridge University Press.