Frankia form symbiotic association with

A free-living nitrogen-fixing cyanobacterium which can also form symbiotic association with the water fern Azolla is :

A free-living nitrogen-fixing cyanobacterium which can also form symbiotic association with the water fern Azolla is :

A free-living nitrogen-fixing cyanobacterium which can also form symbiotic association with the water fern Azolla is :

A free living nitrogen fixing cyanobacterium which can also form symbiotic association with the water fern Azolla is:

A free living nitrogen fixing cyanobacterium which can also form symbiotic association with the water fern Azolla ………….. .