Question

Azolla has a symbiotic relationship with
A. Chlorella
B. Anabaena
C. Nostoc
D. Tolypothrix

Answer 1

Hint: Azolla maintains a symbiotic relationship with Anabaena. They work together and benefit each other. Azolla fern procures a safe environment for Cyanobacteria and in return, it gets nitrogen fixed by Anabaena. When Azolla dies, the nitrate fertilizer is released into the environment, where it becomes available to other plants.

Complete answer:
> Option A - Chlorella
Chlorella is a genus. It consists of single-celled green algae belonging to the division Chlorophyta. Its structure is spherical, about 2 to 10 μm in diameter, and is without flagella. It appears green because it comprises green photosynthetic pigments- chlorophyll-a and -b in its chloroplast.

> Option B - Anabaena
Anabaena is a genus. It comprises of filamentous cyanobacteria that exist as plankton. They possess nitrogen-fixing abilities, and they form symbiotic relationships with certain plants, like the mosquito fern.

> Option C - Nostoc
Nostoc is a genus of cyanobacteria. It is found in various environments forming colonies of filaments of moniliform cells in a gelatinous sheath. The name Nostoc was given by Paracelsus. Nostoc can originate in soil, on moist rocks, at the bottom of lakes and springs, and rarely in marine habitats.

> Option D - Tolypothrix is a genus of cyanobacteria. It exists in small tufts either floating in torpid water or attached to plants and rocks.

Hence, the correct answer is option (B).

Note: Azolla is a genus of seven species of aquatic ferns belonging to the family Salviniaceae. They are extremely reduced in form and specialized. Therefore, they look nothing like other typical ferns and possess more resemblance to duckweed or some mosses. One of just two fern species for which a reference genome has been published is known as Azolla filiculoides.