Question

Nostoc fixes nitrogen in the symbiotic association of the following.

1. Alnus

2. Gunnera

3. Anthoceros

4. Casuarina

The correct combination is

• A. $1$ and $2$
• B. $1$ and $3$
• C. $1$ and $4$
• D. $2$ and $3$

Answer 1

The correct option is D $2$ and $3$

The atmospheric nitrogen is not available to plants. There are some nitrogen-fixing bacteria which converts atmospheric nitrogen into ammonia which is readily available to plants. Nostoc is a Cyanobacterium. It has the ability to fix atmospheric nitrogen. It fixes nitrogen in the symbiotic association with the plans like Gunnera and Anthoceros.

Thus, the correct answer is '2 and 3.'