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

Mark the correct sequence of steps for the development of root nodules in legumes:
$a.$ Formation of infection thread.
$b.$ Division of cortical and pericyclic cells.
$c.$ Curling of root hairs.
$d.$ Leghaemoglobin synthesis.

Identify the following process from the diagram.

Leghemoglobin is found in which one of the following organisms?

What is the function of leghemoglobin?

Which of the following is a recently discovered Gram-positive,non-leguminous,nitrogen-fixing bacterium?