Question

What is soredia?

Answer 1

Hint: A soredium can be defined as the structure containing algal cells enveloped by fungal filaments or hyphae that gives rise to a thallus under suitable conditions. Lichens without soredia may propagate by the mode of fragmentation of their thalli.

Complete answer:
A lichen, also known as lichenized fungus, comprises two organisms that are fungus and algae that function as a single unit. Lichens can be described as a symbiotic relationship between a fungus and algae.
The sexual reproduction in lichen takes place through sexual reproducing structures termed as either ascomycetes or basidiomycetes. The sexual propagules produced by ascomycetes are termed as ascospores, which are produced within microscopic organs called asci.The sexual propagules produced by basidiomycetes are termed as basidiospores, which are produced within microscopic organs called basidia.
The vegetative propagules in lichen occur via isidia and soredia. The former are small outgrowths of the thallus, length ranging up to a millimetre. It contains both fungal hyphae and photobiont cells. The broken off isidia can be transported by wind, water or animals to give rise to new thalli. Soredia can be described as small powdery granules whose length range from 20 and 100 micrometres in diameter. It contains few photobiont cells surrounded by fungal hyphae which can be dispersed by wind, water or animal.

Note:
Some of the symbiotic relationships observed in different animals are mutualism, commensalism, and parasitism. In case of mutualism both the organisms are benefited. In the case of commensalism one organism is benefited whereas the other organism is neither harmed nor benefited. In case of Parasitism one organism is termed as parasite which is benefited and other is termed as host which is harmed.