Red pigment $(Leghaemoglobin)$ having affinity for oxygen is present in the roots of

Leghaemoglobin occurs in

Which of the following is not a symbiotic nitrogen-fixing bacterium?

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

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