1
Which of the following is a true pair of biofertilizers?
- Nostoc and legume
- Rhizobium and grasses
- Salmonella and E. coli
- Azolla and BGA
Answer
(4) Azolla and BGA
Solution
As per NCERT, biofertilisers are organisms that enrich the nutrient quality of the soil; the main sources are bacteria, fungi and cyanobacteria.
∵ Cyanobacteria (blue-green algae, BGA) such as Anabaena, Nostoc and Oscillatoria fix atmospheric nitrogen in paddy fields.
∵ Azolla, a water fern, carries the nitrogen-fixing cyanobacterium Anabaena and is used as a biofertiliser for rice.
⇒ A legume and grasses are plants, while Salmonella and E. coli are not biofertilisers.
∴ Azolla and BGA is the true pair.
Answer: (4)
AIPMT 2001