Question

The most common mode of reproduction in Spirogyra is
a. Conjugation
b. Aplanospore formation
c. Fragmentation
d. All the above

Answer 1

Hint: We must understand that spirogyra species are capable of reproducing both sexually and asexually. However, the most common mode of reproduction is vegetative or asexual reproduction.
The process of fragmentation which is the most common mode of reproduction takes place in asexual or vegetative reproduction. In sexual reproduction, the process of conjugation takes place.

Complete answer:
We would have noticed free-floating green algae in freshwater habitats such as ponds, lakes, etc., These organisms are known as Spirogyra. We commonly call these organisms “water silk or pond silk”. They have a filamentous and unbranched structure.

> Spirogyra Reproduction
Spirogyra can reproduce in three different ways, namely, vegetative, sexual, and asexual. Spirogyra has a haplontic life cycle i.e., free-living haploid gametophyte dominant stage and diploid zygote represents sporophyte.

> Vegetative reproduction – This mode of reproduction takes place by fragmentation. Vegetative reproduction is the most common and preferred form of reproduction under favorable conditions.
After fragmentation, vegetative filament develops into a new filament. Each fragment developed into a new filament after undergoing multiple division and elongation processes.

> Asexual reproduction – There are only a few species in which asexual reproduction takes place. In asexual reproduction, the formation of azygospores, akinetes, or aplanospores takes place.
Aplanospores are formed under unfavorable conditions.
Akinetes have thicker cell walls of cellulose and pectin as compared to aplanospores.
The other name of a zygospores is parthenos pores. These gametes failed to fuse during sexual reproduction and asexually develop into a new filament.

> Sexual reproduction – This type of reproduction takes place by the conjugation process. It is isogamous in nature that means gametes of males and females of similar size fuse together in sexual reproduction.

Hence, option C is the right answer.

NOTE: Approx. 400 species of spirogyra were found in nature. Spirogyra is photosynthetic and contributes to the carbon dioxide fixation. They increase the oxygen level in their habitat and most of the aquatic organisms feed on them.