Question

Auxospore formation is seen in
A. Nostoc
B. Yeast
C. Diatoms
D. Agaricus

Answer 1

Hint:- Spores are reproductive cells in plants; fungi, algae and other protists. They are generally one-celled and have the capability to form into a new organism. Spores do not need to fuse for reproduction to occur, and produce progeny.

Complete step-by-step solution:-
Nostoc, by spore formation, reproduces vegetatively or asexually. Vegetative reproduction is carried out by fragmentation. Small colonies may grow attached to a larger colony and form distinct colonies, later on.
As the nucleus divides, yeasts replicate asexually by a process known as budding. A bud is formed on the outer surface of the parent cell.
Agaricus reproduces itself by spores. On basidium, spores develop, which are offshoots located under the cap on the hymeneal gills. The name “Agaricus Bisporus” suggests that in the basidium two spores develop.
Auxospores are specialised cells present in some diatoms that are formed at key stages in their cell cycle or life history. In the growth processes, sexual reproduction or dormancy, auxospores usually play a role.
As successive mitotic cell divisions lead to a decrease in cell size, auxospores are involved in re-establishing the normal size of diatoms. This happens because one of the two valves that make up the frustule (a silica cell wall) is inherited by each daughter cell formed by cell division and then a smaller valve grows within it. Consequently, the average diatom cell size in a population is decreased by each division period. If its size becomes too small, an auxospore is formed by a dividing diatom cell to increase its cell size back to what is normal for vegetative cells.
Auxospores may also play a role in the sexual reproduction of diatoms and may be developed to form a diploid zygote after haploid gametes fuse. Lastly, diatoms may generate auxospores to serve as dormant phases, often referred to as "resting spores". These are used to survive periods of time that are unfavourable for development, such as winters or when nutrients are depleted.
So, the correct answer is option (C).

Note:- Diatoms are algae that are single-celled. They are the only organisms on the earth that have translucent, opaline silica consisting of cell walls. The cell walls of diatoms are ornamented by complex and striking silica patterns. Diatoms are photosynthesizing algae, having a silica skeleton (frustule) and are present in almost any aquatic environment, including fresh and coastal waters, soils, almost anywhere.