Question

Which one of the following is regarded as a biofertilizer?
A. An association between pteridophytes and cyanobacteria Anabaena.
B. An association between gymnosperms and Nostoc.
C. An association between legume and Rhizobium.
D. All of the above

Answer 1

Hint: Biofertilizer is a substance that contains live microbes, which when comes in association with higher plants increases the availability or supply of essential nutrients to them. It can be through many processes such as fixation of atmospheric nitrogen,

Complete answer: Anabaena lives in a symbiotic association with pteridophytes such as Azolla. The association has the potential to be used as a biofertilizer and can be used as a substitute for the chemically synthesized nitrogen compounds, which could potentially damage the soil. The main application of this happens in rice fields.
Nostoc, which is also a cyanobacterium, has the ability to fix the nitrogen present in the atmosphere to ammonia which can be easily absorbed by the plants. When the colonies of Nostoc were isolated and applied to growing plants such as many gymnosperms, it can accelerate its growth and promote leaf production. It is thus a sustainable biofertilizer.
Rhizobium exists in a symbiotic relationship with many leguminous plants. And they fix atmosphere nitrogen and provide the nutrients for the growth and development of the associated plants. The application of these as a biofertilizer is shown to produce an increase in the uptake of nitrogen. And also reduce the expenses and the pollution chances caused by the usage of chemical fertilizers. Thus, from the above options, all the associations are found to have the potential to be used as biofertilizers.
Hence, the correct answer to the question is D, “all of the above”.

Note: A new method of eco-friendly pest control is done by utilizing the natural prey-predator mechanism so that the adverse effects caused due to chemical pesticides and weedicides can be minimized. This method is known as biological pest control. It now functions as an important part of the Integrated Pest Management Programme.