Question

Sexual reproduction in lichen thallus belongs to
A. Algal component only
B. Fungal component
C. Both algal and fungal components
D. Not understood yet

Answer 1

Hint: In lichens, there are 2 components, i.e., algal partner called phycobiont and fungal partner called mycobiont. Lichens are defined as fungi parasitizing algae. It is a symbiotic association between algae and fungi.

Complete answer:
Lichens grow in various habitats and can also grow in such habitats where other plants wouldn’t grow e.g., on bare rocks and in the arctic region.
There are some special structures associated with lichen thallus:
Breathing pores: Loosely arranged areas in the upper cortex known as breathing pores and they help in gaseous exchange.
Cyphellae: Loosely arranged areas in the lower cortex known as cyphellae. It also helps in gaseous exchange.
Cephalodia: These are rounded outgrowth on the upper cortex. They help in retaining the moisture.
Isidia: Elongated outgrowths on upper cortex. They increase the surface area of lichens.
Both asexual and sexual reproduction happens in the lichens.
Asexual reproduction: Asexual reproduction is done by the formation of pycnidiospores or pycniospores which are produced inside the pycnidium which is a flask shaped structure. Ostiole is a pore which is an opening of pycnidium. The pycniospores come out through Ostiole and come in contact with suitable algae to form a new lichen thalli.
Sexual reproduction: Sexual reproduction in lichen thallus belongs to the fungal component. Male sex organ is called spermatogonium and inside the spermatogonium the non-motile sperms or spermatia are produced. Female sex organ is called carpogonium which is having lower coiled portion called ascogonium and upper straight portion called trichogyne.
The sperms get attached to trichogyne and reach to ascogonium for fertilization. Diploid ascogenous hyphae arises from ascogonium. The terminal cell of ascogenous hyphae called ascus mother cell and reductional division occurs in ascus and 8 ascospores are formed. Ascospores are released from ascus to form new lichen thalli.

So the correct answer is option B.

Note: Ascogenous hyphae, ascus mother cells, ascospores and some sterile hyphae form a fruiting body called apothecium. Cyphellae are analogous to stomata of higher plants. Lichens show a very slow growth.