The amount of nitrogen in nature is fixed by .....

Nitrogenase enzyme is found in $Nostoc$ in the cell of:

Nodules with nitrogen-fixing bacteria are present in

Select the correct statements from the given:
$(a)$ Nitrogenase is a heterodimeric protein.
$(b)$ Root hairs curl by action of nitrogenase and plant 'nod factors'.
$(c)$ During symbiotic $N_2$ fixation,$ATP$ is provided by the legume plant.

Trace the events starting from the coming in contact of Rhizobium to a leguminous root till nodule formation. Add a note on the importance of leghemoglobin.

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.