Question

Which of the following is the pair of biofertilizers?
(a) Azolla and BGA
(b) Nostoc and legume
(c) Rhizobium and grasses
(d) Salmonella and E. coli

Answer 1

Hint: Biofertilizers are fertilizers that contain living organisms and are applied to plants to promote growth through metabolic activities of the microbial and other living things involved. Apart from the correct option, the microorganisms mentioned here are not inherently used as biofertilizers.

Complete answer:
Biofertilizers are substances that contain living organisms and they are applied to the plant just like chemical fertilizers, but here, the organisms colonize the part of the plant, such as the rhizosphere to promote growth by increasing the availability of nutrients or metabolizing substances from the surrounding environment and providing them to the plant.
- Azolla and blue green algae (BGA) are biofertilizers used in rice fields. They provide nitrogen to the plant and are used as an alternative to biofertilizers.
- The blue green algae Anabaena has a symbiotic relationship with the water fern Azolla to produce and supply nitrogen to the host plants.

Additional Information: - Nostoc is a BGA that is used for increasing nitrogen levels in paddy fields. Legumes have a symbiotic relationship with Rhizobium bacteria.
- Rhizobium species nodulate the roots of legumes and form a symbiotic relationship, fixing nitrogen from the environment to the plant.
- Salmonella and E. coli are not biofertilizers in nature and can be actually pathogenic to the human body.

So, the correct answer is ‘(a) Azolla and BGA’.

Note:
Apart from increasing the crop yield by providing nitrogen to deprived areas, biofertilizers also provide protection to the plant from soil-borne diseases.
- Biofertilizers are also known as bioeffectors.
- The microorganisms that are used in biofertilizers are scientifically known as Plant Growth Promoting Rhizobacteria or PGPRs.