Nature of Association of Lichen - Symbiosis and Helotism

Lichens are organisms formed by the symbiotic association between algae and fungi that form a unique morphology distinct from both partner. The fungal partner is called mycobiont. The algal partner is called phycobiont.
Lichen Thallus structure
Two views regarding the nature of association in lichen
1. Symbiosis: De Bary (1879) termed this association as symbiosis where both partners are benefitted
Advantages for algal partner or phycobiont:
  • Algae get mechanical protection by fungal hyphal network
  • Fungus absorbs more water and nutrients from the substratum, thus promoting algal growth
Advantages for fungal partner or mycobiont:
  • Fungus gets nutrition from algae as algae is photosynthetic
2. Helotism: Crombic (1885) termed this association as ‘helotism’ a master- slave relationship where algae act as a slave for the fungal master.
  • Algae act as a slave and prepare food for the fungal master
  • In some association, fungi produce haustoria like projections which penetrate the algae
  • Algal sexual reproduction is inhibited by fungal association and adopted a slow growth under fungal influence.
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