$A$ nitrogen-fixing bacterium that forms a loose association with the roots of crop plants is

We find that $Rhizobium$ forms nodules on the roots of leguminous plants. Also,$Frankia$,another microbe,forms nitrogen-fixing nodules on the roots of the non-leguminous plant $Alnus$. Can we artificially induce the property of nitrogen fixation in a plant,whether leguminous or non-leguminous?

Bacteria which convert the nitrogen of the air to nitrogenous compounds are called

Name the most crucial enzyme found in root nodules for $N_2$ fixation. Does it require a special pink-coloured pigment for its functioning? Elaborate.

For nitrogen fixation,the useful pigment is

Oxygen carrier red coloured Hemoprotein is sensitive for