Correct option is D
Correct Answer: (d)
Explanation: Nitrogen-fixing symbioses involve a prokaryotic partner such as cyanobacteria or bacteria interacting directly with an angiosperm host. Azolla is an aquatic fern (a pteridophyte), not an angiosperm, although it harbors the cyanobacterium Anabaena for nitrogen fixation. Rice does not directly form a nitrogen-fixing symbiosis with Azolla. Hence, this pair does not represent a prokaryote–angiosperm symbiotic nitrogen-fixing association.
Information Booster
· Symbiotic nitrogen fixation requires a prokaryotic nitrogen-fixing partner.
· Nostoc forms a unique intracellular symbiosis with the angiosperm Gunnera.
· Frankia establishes actinorhizal nodules in angiosperms like Casuarina.
· Bradyrhizobium forms root nodules in Parasponia, a non-legume angiosperm.
· True symbiosis involves direct metabolic integration between partners.
