Members of the bean family are particularly important for crop rotation because:

The bacteria found in the root nodules of the family $Leguminosae$ are:

The nitrogen-fixing symbiotic organism present in $Azolla$ is:

What are the conditions necessary for fixation of atmospheric nitrogen by $Rhizobium$? What is their role in $N_2$-fixation?

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.

Arrange the stages of root nodule formation in the correct sequence:
$I-$ Infection thread is produced.
$II-$ Bacteria are carried to the cortex of the root.
$III-$ Bacteria attach to the root hair.
$IV-$ Bacteria are released from the thread into the cells.
$V-$ Differentiation into nitrogen-fixing cells occurs.