life cycle of spiragyra?

Answer 1

Spirogyra is a genus of filamentous green alga of the order Zygnematales. It is commonly found in freshwater areas. Spirogyra is a photosynthetic, eukaryotic cell.

Spirogyra reproduces by conjugation, sexually by exchanging DNA between cells. Certain filaments in a loose parallel bundle of Spirogyra assume the female role, and others the male. The cells of adjacent filaments develop tubular extensions which grow towards one another and eventually fuse to form a continuous tube between the cells. Meanwhile the contents of each cell have formed a round sphere. The spheres from the male filament squeeze their way down the connecting tubes to fuse with a sphere of the female cell in the other filament. The result of this sexual union is the formation of a zygote (zygospore) within the chambers of the female filament. After a dormant period, the zygotes undergo meiosis and germinate, resulting in new filaments.

Answer 2

Spirogyra is a filamentous green alga which is common in freshwater habitats. It has the appearance of very fine bright dark-green filaments moving gently with the currents in the water, and is slimy to the touch when attempts are made to collect it. The slime serves to deter creatures which otherwise attatch themselves to underwater plants, so Spirogyra under the microscope is usually spotless
A field of Spirogyra filaments. Their appearance is not quite typical in that the nuclei are unusually prominent, and the characteristic spiral chloroplasts are so fine and tightly wound that close examination is needed to confirm the identification. In any case the possession of spiral chloroplasts is sufficient to positively identify Spirogyra to genus.
Darkfield, x120.
The central portion of a cell of Spirogyra showing the nucleus and giving an insight into the way the spiral chloroplast contacts with the wall of the cell. The filament in the background provides another view.
Brightfield. x1000.
Central portion of a Spirogyra cell showing nucleus and chloroplasts.
Brightfield, x1000.
This filament of Spirogyra is about to break into two filaments. The wall of each cell (centre of picture) has developed an inward indentation at the junction between the cells. Increase in pressure in each cell will cause the indentation to pop out, forcing separation of the filaments, and leaving them with highly convex ends.
Brightfield. x1000.
Two filaments of Spirogyra, the lower one clearly showing the nucleus. This picture also gives a good insight into the way the chloroplasts line the wall of the cell.
Brightfield. x1000.