Question

In Rhizopus, if conjugation fails, gametangia behave as zygophore. It is called as:
A. Conidia
B. Parthenospore
C. Gametangia
D. Sporangiospore

Answer 1

Hint:- One positive mycelium comes into contact with another negative mycelium during conjugation in the Rhizopus. It stimulates the development of zygophores called specialised hyphae.

Complete solution: The fungal genus Rhizopus poses a set of inconsistencies and wonders, as the bane of fruit growers and managers of produce, but the recipient of high praise from Japanese chefs and vegetarians worldwide. These fungal colonies in the Zygomycetes (or Zygomycota) division, named because of their rhizome-like creeping stolons, can spread rapidly via airborne spores or through root-like rhizoids. Sexual reproduction occurs by means of gametangial copulation under unfavourable conditions. The gametangia look similar, but equal or unequal in size, and they give rise to zygospore by conjugation. So, Gametangia acts like zygophores when conjugation fails. It is referred to as parthenospore. The common wall at the point of their touch dissolves after maturation of the gametangia and the protoplast of both the gametangia unites to form zygospore. The nuclei of opposite gametangia fuse together to eventually degenerate to form diploid (2n) nuclei and unpaired nuclei.

Hence, Option B i.e., Parthenospore is the right answer.

Additional Information:
When two mycelia of compatible strain come close to each other when heterothallic species are cultivated, the mycelia generates small outgrowth, called progametangia. In near contact, the apical area of the two progametangia occurs. Every progametangium's nuclei and cytoplasm push more and more toward the apical region that swells with dense protoplasm. It vacuolates the rear area. The apical region, which is called the gametangium, is divided by a septum, and the basal region is called the suspensor. The undifferentiated protoplast of the gametangium multi-nucleate is called aplanogamete or coenogamete.

Note:-
A thick-walled resting spore from an unfertilized gamete that grows parthenogenetically. There are certain algae forming parthenos pores, e.g. Protosiphon and mushrooms, e.g. Muscae of the entomophthora. They can give rise to more gametes or a person with a haploid.