Question

In Spirogyra, lateral conjugation takes place in the cells of
A. Same filament
B. Two filaments of same species
C. Two filaments of different species
D. Both A and B

Answer 1

A Spirogyra is a filamentous, charophyte, green algae belonging to order Zygnematales. It is named as Spirogyra because of the helical or spiral arrangements of chloroplasts found in them. It is found in shallow ponds, ditches, and large lakes. It is generally free-floating.

Complete answer: In Spirogyra , lateral conjugation takes place between two adjoining cells of the same filament, of which the upper cell functions as the male gametangium or male reproductive gamete and the lower cell as the female gametangium or female reproductive unit. The lower cell or the female cell increases in size, but the upper cell remains smaller in size. The content present in the male cell passes onto the female gamete and as a result of which, a zygospore or zygote is formed. Lateral conjugation occurs in monoecious species. It is of rare occurrence that involves the fusion of gametes from two adjacent cells of the same filament in monoecious species. It is of two types; Indirect and direct lateral conjugation.
a) Indirect lateral conjugation: Two outgrowths emerge on both sides of a transverse septum of two adjunct cells and after some growth, the two protuberances unite to form a conjugation tube. Of the two adjacent cells, one behaves as the male reproductive cell, while other as the female reproductive cell. The constituents from male gametes pass through the conjugation tube and enter into female gametes. By the fusion of male and female gametes, a zygospore is formed which is diploid.
b) Direct lateral conjugation: In this type of conjugation, the male gametangium after passing through an aperture in the transverse septum of gametangium, enters the female gametangium and fuses with the female gamete, and a diploid zygospore is formed.
Hence, the correct answer is option A.

Note: In spring, Spirogyra grows underwater, but when there is sufficient sunlight and warmth, it produces oxygen in large amounts. The filamentous masses come to the surface of the water and become visible as slimy green mats. Spirogyra has a cell wall, nucleus and spiral chloroplasts.