The free-living nitrogen-fixing cyanobacterium that forms a symbiotic association with the aquatic fern Azolla is ............. .

What will happen if $Rhizobium$ bacteria are introduced into a wheat field?

Rhizobium lives symbiotically with root nodules and fixes atmospheric nitrogen. It provides nitrogenous compounds to the host and in turn takes food from the host. This food taken by the bacterium is:

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.

Which of the following is a symbiotic nitrogen fixer?

Assertion : Leguminous plants are nitrogen fixers.
Reason : Leguminous plants have $Rhizobium$ in their root nodules.