Question

Thallus:

The thallus is made of long, cylindrical well branched filaments. The filament is aseptate, coenocytic structure. The thallus is attached to substratum by means of branched rhizoids or branched holdfast called the haptera. The thallus of V. mayyanadensis is differentiated in subterranean branched rhizoidal system and an erect aerial system. The filaments are rough, interwoven and appear as dark green felt like structure.

Some species like V. debaryana show calcium carbonate incrustations. The branching may be lateral or dichotomous. The filaments are non-septate, the protoplasm with many nuclei is continuous along the entire length of thallus thus the coenocytic Vaucheria thallus makes siphonaceous structure (Fig. 1A, B). The septa formation occurs only during reproduction or in Gongrosira condition or for sealing of an injury.



The thallus structure is differentiated into cell wall and protoplasm. The cell wall of thallus is thin, weak and non-elastic. The cell wall is made of two layers, the outer layer is pectic and the inner layer is cellulosic. Inner to the cell wall there is thick layer of protoplasm. A very large central vacuole filled with cell sap runs from one end of the filament to another forming a continuous canal or siphon.​

Answer 1

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