Spirogyra is a filamentous algae. It reproduces asexually by conjugation.
In spirogyra, sexual reproduction takes place by conjugation.
Sexual reproduction in Spirogyra is isogamous, i.e. male and female gametes of similar size fuse together in the sexual reproduction.
1. Asexual Reproduction in Spirogyra
Fragmentation under ideal condition of food, sunlight and water a mature filament of spirogyra simply breaks into pieces. Each fragment forms a new filament.
Fragmentation in Spirogyra
2. Sexual Reproduction in Spirogyra
There are two types of sexual reproduction in spirogyra. These are: lateral conjugation and scalariform conjugation.
(a) Scalariform Conjugation
In this, two filaments lie side by side, particularly or fully along their lengths. One cell from each filament produces tubular protuberances called conjugation tubes. These elongated and fuse to form conjugation canal. The mobile cytoplasm (male cytoplasm) moves through the canal and fuses with the cytoplasm of the other filament. The gametes in both fuses to form a zygospore. The zygospore germinates and forms a new filament.
Scalariform conjugation in spirogyra
(b) Lateral Conjugation
Conjugation occurs between two adjacent cells on the same filament. Two common adjoining cells near their common transverse wall produce protuberances called conjugation tubes, which further form conjugation canal upon contact. The male cytoplasm migrates through the conjugation canal, fuses with the female. This union produces a zygospore. Each zygospores germinates and forms a new filament.