Which of the following is a non–symbiotic nitrogen fixing bacteria?
1.  Rhizobium
2.  Mycorrhiza
3.  Azotobacter
4.  Nitrosomonas

Anabaena is associated with Azolla's:
1.  Stem
2.  Leaves
3.  Roots
4.  Flowers

Nitrogen-fixing bacteria converts:
1. $N_2$ $\to$ $N{H}_3$
2. $N{H}_4^{+}$ $\to$ $Nitrates$
3. $N{O}_2$ $\to$ $N{O}_3$
4. $N{O}_3$ $\to$ $N_2$

An aquatic fern that is used to increase the yield of paddy crops:

1. Azolla

2. Salvinia

3. Marsilea

4. Isoetes

Enzyme first used for nitrogen fixation:
1.  Nitrogenase
2.  Nitroreductase
3.  Transferase
4.  Transaminase

Which aquatic fern performs nitrogen fixation:
1.  Azolla
2.  Nostoc
3.  Salvia
4.  Salvinia

If by radiation all nitrogenase enzymes are inactivated, then there will be no:
1. Fixation of atmospheric nitrogen
2. Conversion from nitrate to nitrite in legumes
3. Conversion from ammonium to nitrate in soil
4. Fixation of nitrogen in legumes

All of the following statements concerning the Actinomycetous filamentous soil bacterium Frankia are correct EXCEPT that Frankia: