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

Which of the following is responsible for nitrogen fixation in an aquatic fern?

Identify the $A$ to $D$ correctly in the given diagram of root nodule development and choose the correct option accordingly.

In which of the following are root nodules found?

$A$: Bacteria enter only the polyploid cells of the root cortex.
$R$: These cells provide cytokinins to bacteria,which promote bacterial cell division.

Root nodules for nitrogen fixation of a non-leguminous tree possess