General Characters of Algae
Posted on : 19-11-2017 Posted by : Admin

 

Introduction

Algae are Eukaryotic, autotrophic and usually aquatic thallophytes. As algae possess chlorophyll, they are photosynthetic in nature. The organization of their thallus is either unicellular or multicellular.

 

General chartacters of Algae

  1. They are usually aquatic. They occur both in marine and fresh water habitats.
  2. Some of the algae are also found as terrestrial, subterranean or epiphytic forms.
  3. The thallus of algae shows great degree of variation in size and form.
  4. The algal cell wall is made up of cellulose.
  5. They are unicellular or colonial or multicellular unbranched or branched filamentous forms or siphonous forms or heterotrichous forms.
  6. Algal cells have chloroplasts or chromatophores with photosynthetic pigments.
  7. These members show eukaryotic organization but one of the classes Cyanophyaceae has prokaryotic organization.
  8. Algae are autotrophic and synthesize their own food. Their main reserve food material is starch. However, different algae store different food material.
    • Phaeophyceae stores laminarin or mannitol.
    • Rhodophyceae stores floridean starch.
    • Bacillariophyceae and Xanthophyceae stores leucosin.
  9. Algae reproduce by vegetative, sexual and asexual methods.
  10. Sexual reproduction may be isogamous, physiologically anisogamous or oogamous type.
  11. Asexual reproduction takes place by zoospores, aplanospores, endospores, harmagonia and auxospores etc.
  12. Algae show progressive evolution in sexuality.
  13. The motile vegetative cells, zoospores and gametes of algae (except the class Rhodophyceae and Cyanophyacae) show a pair of flagella. Each flagellum shows 9+2 arrangement of fibrils. The flagella of algae are of two types namely acronematic and pantonematic.
  14. Algae exhibit haplontic life cycle or diplontic life cycle, haplodiplontic life cycle, haplobiontic life cycle and diplobiontic life cycle.
  15. The photosynthetic pigments of algae are of three types:

Photosynthetic pigments of Algae

Chlorophylls: They may be of five types. Namely, chlorophyll a, b, c, d, e

  • Chlorophyll a is present in all algal groups
  • Chlorophyll b is present in Chloropyceae
  • Chlorophyll c is present in Phaeophyceae
  • Chlorophyll d is present in Rhodophyceae
  • Chlorophyll e is present in zoospores of Vaucheria

Carotenoids: They are of two types. Namely Carotenes and Xanthophylls

  • β-Carotenes is present in all algal groups
  • Xanthophyll, Leutin is present in Chlorophyceae and
  • Another xanthophyll, Fucoxanthin is present in Bacillariophyceae and Phaeophyceae

Phycobilins: These are water soluble pigments. They are two types namely, Phycocyanin and Phycoerythrin.

  • Phycocyanin is predominant in Cyanophyceae
  • Phycoerythrin is predominant in Rhodophyceae


- Share with your friends! -