Question

A teacher was explaining about a constant physical contact involving almost equal physiological interdependence in two different thalloid forms. He was trying to explain, which one of the following?

• A. Operation of heterothallism
• B. Mycorrhizal association
• C. Establishment of heterothallism
• D. Advent of lichen formation

Answer 1

Answer: (D)

The teacher was explaining the advent of lichen formation. A lichen is made up of a simple photosynthesising organism, usually green algae or cyanobacteria, surrounded by filaments of a fungus. Generally, most of lichens bulk is made of interwoven fungal filaments, although in filamentous and gelatinous lichens this is not the case. The fungus is called as a mycobiont. The photosynthesizing organism is called as a photobiont. Algal photobionts are called as phycobionts. Cyanobacteria photobionts are called as cyanobionts. The part of a lichen that is not involved in reproduction, the "body" or vegetative tissue" of a lichen, is called as the thallus. The thallus form is very different from any form, where the fungus or alga are growing separately. The thallus is made up of filaments of the fungus called as hyphae. The filaments grow by branching then rejoining to create a mesh, which is called being. The mesh of fungal filaments may be dense or loose.

Thus, the correct answer is option D.