Question

Which cyanobacterium lives in association with the water fern Azolla and is widely used in paddy fields?

Options

• Azospirillum

• Rhizobium

• Anabaena

• Frankia

Answer 1

Anabaena is a nitrogen-fixing cyanobacterium that forms a symbiotic association with the water fern Azolla. This Azolla–Anabaena symbiosis is widely used in paddy fields because it significantly increases rice yield by enriching the paddy field soil with biologically fixed nitrogen.