If a wheat field is inoculated with $Rhizobium$,what will be the effect on the soil?

The anaerobic condition for nitrogen fixation is maintained by ..........

Which steps are associated with nodule formation?

Symbiotic nitrogen fixation in non-leguminous plants is carried out by

Identify $A$ and $B$ in the figure.

We find that $Rhizobium$ forms nodules on the roots of leguminous plants. Also,$Frankia$,another microbe,forms nitrogen-fixing nodules on the roots of the non-leguminous plant $Alnus$. Is it necessary for a microbe to be in close association with a plant to provide mineral nutrition? Explain with the help of one example.