Question

A filament of Nostoc without its mucilaginous sheath is called
A. Mycelium
B. Trichome
C. Hypha
D. Colony

Answer 1

Hint: The blue-green algae or cyanobacteria has the ability to fix the nitrogen of the environment and it can be found in both the terrestrial and the aquatic habitat. It can be seen in the gelatinous colonies and filaments are surrounded by the mucilage sheath.

Complete answer:
Nostoc is a genus of cyanobacteria in the family Nostocaceae. The blue green algae is mainly found in various environments that forms colonies which are composed of filaments of moniliform cells in a gelatin sheath. Nostoc are mostly found in moist rocks, soil, at the bottom of lakes and springs and sometimes in marine water. The name Nostoc was given by Paracelsus.
Cyanobacteria or blue-green algae are blue-green bacteria. Some of them are spherical, some are rod-shaped, while some of them are filamentous. A filament has a row of cells linearly arranged and is covered by mucilage sheath. Cyanobacteria use carbon dioxide and release oxygen during photosynthesis so that the environment becomes fresh for aquatic animals. Flagella is absent in cyanobacteria and many of them have the capacity to fix atmospheric nitrogen. Glycogen is the stored food in cyanobacteria.
A single chain-like filament of Nostoc is called trichome. It is a filament of Nostoc without mucilaginous sheath mostly found in many members of cyanobacteria. The thallus is the body of Nostoc that consists of many threads like structures known as filaments. Nostoc contains chlorophyll so it can prepare food of its own i.e., it’s an autotroph.
In a filament of single trichome consists of heterocyst. It is a thick-walled structure which is colorless. In this filament photosynthetic pigment is absent, so they do not play any role in the process of photosynthesis. These are the structures used for the purpose of reproduction and Nitrogen-fixation.
Trichome is a filament of Nostoc without its mucilaginous sheath.

So, option B is the correct answer.

Note: Mycelium is the thread-like structure of fungi which can be found in soil and other substrates. Hypha is the long, filament-like structure of the fungus and collectively called mycelium. A colony is composed of two or more groups of species that live together or are associated with each other.