Symbiotic nitrogen fixation in root nodules of some legumes is caused by

Symbiotic nitrogen fixation in non-leguminous plants is carried out by

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 $Alnus$. What kind of relationship is observed between mycorrhiza and pine trees?

Nodulated roots make the plant rich in

Which of the following is a symbiotic nitrogen fixer?

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