Question

Reproduction in Spirogyra is:
A. Asexual
B. Conjugation
C. Both A and B
D. None of the above

Answer 1

Spirogyra is a filamentous charophyte green alga in the Zygnematales order, so called because of the helical or spiral structure of the chloroplasts. Spirogyra can be found in a variety of freshwater environments, and there are over $400$ species worldwide. It has a width of $10$ to $100$ metres and can grow to a length of several centimetres. The cell wall, nucleus, pyrenoid, and spiral chloroplasts of Spirogyra are all present. Spirogyra is capable of both sexual and asexual reproduction.

Complete explanation:
Option A: It reproduces asexually by fragmentation. The vegetative filament disintegrates into smaller pieces. Each fragment develops into a longer filament.
So, option A is incorrect.
Option B: Conjugation is a sexual reproduction process in which cells from two filaments lying side by side are joined by outgrowths called conjugation tubes. This helps the contents of one cell to fully enter and fuse with the contents of another cell.
So, option B alone is incorrect.
Option C: Both sexual and asexual reproduction occurs in Spirogyra species. The filaments are simply fragmented during asexual, or vegetative, reproduction. Conjugation is a sexual reproduction process in which cells from two filaments lying side by side are joined by outgrowths called conjugation tubes.
So, option C is correct.
Option D: Both sexual and asexual reproduction occurs in Spirogyra species. However, vegetative or asexual reproduction is the most common mode of reproduction. Asexual reproduction and sexual reproduction both involve fragmentation, which is the most common mode of reproduction.
So, option D is incorrect.

Hence, Option C is the correct answer.

Note:
In Spirogyra species, both sexual and asexual reproduction are possible. The most popular mode of reproduction, however, is vegetative or asexual reproduction. Both asexual and sexual reproduction, which is the most common form of reproduction, require fragmentation.
There are two types of sexual reproduction in Spirogyra.
Scalariform: It occurs between the cells of two filaments of opposing strains. At the time of conjugation two opposite strains are drawn toward each other and lie parallel in close contact under the traditional sheath of mucilage.
Lateral conjugation: In homothallic Spirogyra species, lateral conjugation occurs between cells of the same filament. It happens in two ways.
a) Indirect lateral conjugation b) Direct lateral conjugation.