Question

Microbes which act as biofertilisers are

Answer 1

Introduction of biofertilisers
Biofertilisers include the fertilisers of biological origin including microorganisms that enrich the nutrient content of the soil and increase plant growth. It include:

• Cyanobacteria
• Free living nitrogen fixing bacteria
• Symbiotic nitrogen fixing bacteria

\(Rhizobium\)
\(Rhizobium\) is a symbiotic nitrogen fixing bacteria which can fix atmospheric nitrogen into compounds that can be uptaken and utilised by the plants. Hence, it fosters the growth and development of the plants by improving the nutrient status of the soil and is a component of biofertiliser. However, \(Rhizobium\) is not a free-living bacteria. Hence, the option is incorrect.

\(Azospirillum\)
\(Azospirillum\) is a free-living nitrogen fixing bacteria which can fix atmospheric nitrogen into compounds that can be uptaken and utilised by the plants. It enriches the soil and enhances the growth and development of plants and can be considered as a biofertiliser.

\(Glomus\)
\(Glomus\) is an arbuscular mycorrhizal (AM) fungal genus which forms symbiotic association with the plant roots. These fungi take phosphorus from the soil and pass it to the plant, enhancing plant growth and development.

\(Azotobacter\)
\(Azotobacter \) is a free-living nitrogen fixing bacteria which can fix atmospheric nitrogen into compounds that can be uptaken and utilised by the plants. It can be considered as biofertiliser as it enriches the soil and enhances plant growth and development. However, it is not a root nodule bacteria forming a symbiotic association. Hence, the given statement is incorrect.
Final answer
(B) Free living nitrogen fixing bacteria-\(Azospirillum\)