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RICHARD J. GREEN / SCIENCE PHOTO LIBRARY RICHARD J. GREEN / SCIENCE PHOTO LIBRARY
Spirogyra is a genus of filamentous green algae of the order Zygnematales. It owes its name to a chloroplast (the green part of the cell) that is wound into a spiral, a unique property of this genus which makes it easily to recognise. It is commonly found in freshwater areas. Spirogyra is a photosynthetic, eukaryotic cell with similar rectangular cells placed end to end. The cell wall is two layers, the outer one is of cellulose while the inner one is made up of pectin. The cytoplasm forms a thin lining in contact with the cell wall. The cytoplasm encloses a large central vacuole containing cell sap. Chloroplasts are embedded in the cytoplasm. The chloroplast is ribbon shaped and spirally arranged. Each chloroplast contains several pyrenoids, situated in the central vacuole. Spirogyra can reproduce both asexually and sexually. In asexual reproduction, fragmentation takes place, and spirogyra simply undergos mitosis to form new filaments. In sexual reproduction, different filaments line up side by side either partially or throughout their length. One cell each from opposite lined filaments give our tubular protuberances known as conjugation tubes.
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