Question

Azolla is used as a biofertilizer because it
A) Multiplies very fast to produce massive biomass
B) Has association of nitrogen-fixing Rhizobium
C) Has association of nitrogen-fixing cyanobacteria
D) Has association of mycorrhiza

Answer 1

Hint: Azolla is a small fern which lives in symbiosis with Anabaena. It is referred as Anabaena azollae which is named as Nostocaceae.

Complete answer:
Biofertilizers are microbe-containing compounds that help to promote plant and tree growth by increasing the supply of vital nutrients to plants. It contains living species that include mycorrhizal fungi, bacteria, and blue-green algae. Biofertilizers are eco-friendly and cost effective.
Now, let us find the solution from the options-
- One of the essential nitrogen-fixing symbiotic bacteria is rhizobium. But Azolla does live with bacteria Rhizobium as symbiosis.
- Azolla is an aquatic fern which lives in symbiosis with cyanobacteria and can be used as a biofertilizer. Cyanobacteria exist in a symbiotic relationship with their roots. As a consequence, about three times more atmospheric nitrogen than legumes can be fixed by Azolla-Anabaena. Typical amounts for legumes are 400 kg of nitrogen per hectare per year, compared to 1100 kg of nitrogen per hectare per year for Azolla-Anabaena.
- Mycorrhiza is a symbiosis between a fungus and a plant.

Thus, the correct answer is option (C) Has association of nitrogen-fixing cyanobacteria.

Note: Mycorrhizal fungi preferentially extract minerals from the plant's organic matter, whereas cyanobacteria are distinguished by nitrogen fixation properties. The fixation of nitrogen is characterised as a process by which di-nitrogen molecules are converted into nitrogen compounds.