Question

Azolla is used in cultivation of –
A. Maize
B. Sorghum
C. Wheat
D. Rice

Answer 1

Hint: Azolla is used as a bio-fertilizer and it provides nitrogen to the crops for their overall growth and development especially during initial phases of growth. Nitrogen is important for all crops as it is a major component of chlorophyll and thus enhances the process of photosynthesis in plants. It is mostly used to increase the yield on crop plants which serve as a major source of carbohydrates.

Step by step answer:Even though the air around us is majorly composed of nitrogen gas, the form in which nitrogen is present in the air is complex and cannot be utilized by plants as it is, directly from the atmosphere. Therefore, plants require some bacteria which can convert these complex forms of nitrogen to simpler forms that plants can absorb. The bacteria that fulfill this function are called ‘Nitrogen-fixing’ bacteria.
Azolla is a rapidly growing plant that is in a symbiotic relationship with a nitrogen-fixing bacteria called Cyanobacteria commonly called Blue-green algae. In this symbiotic relationship, both, the plant and the bacteria get some benefit comprising a successful symbiotic relationship. The plant Azolla provides habitat and protection to the bacteria and in exchange for that, the bacteria convert the incompatible form of nitrogen into a compatible form which can be utilized by plants. Nitrogen plays an important limiting factor in determining the yield of rice. It is a major component of chlorophyll, the rate of photosynthesis and the nutrient a particular crop produces depends on the amount of nitrogen available for the crop. And rice stands as one of the important staple crops feeding millions of people. Therefore to attain the maximum yield and maximum nutrient in the form of carbohydrates, Azolla is used in the cultivation of Rice as a biofertilizer.
So the answer is option D. Rice
Additional information: Azolla is an aquatic fern. It gets the maximum required nutrition from its symbiotic relationship with Cyanobacteria, it does not require soil to grow and usually grows in ponds, damp places, ditches, rice paddies, and fields. Azolla is also used to feed livestock as it is rich in protein.

Note: As Azolla serves as a green fertilizer for almost all staple crop plants, it is chiefly used in the cultivation of Rice. The primary reason being, paddies or rice fields are one of the few places Azolla thrives and grows and provides nitrogen to the growing Rice.