EVERYDAY SCIENCE

Detailed explanation-1: -Azolla is water fern which is also used as a biofertilizer. There are around 80, 000 symbiotic cyanobacteria present on its leaves. Symbiotic cyanobacteria Anabaena Azollae is responsible for nitrogen-fixation which increases the fertility of the soil and in turn enhances the yield.

Detailed explanation-2: -Azolla-Anabaena as a Biofertilizer for Rice Paddy Fields in the Po Valley, a Temperate Rice Area in Northern Italy.

Detailed explanation-3: -So the correct answer is ‘Nostoc’.

Detailed explanation-4: -Azolla grows rapidly – it doubles its biomass every few days. It is high in protein – up to 35 percent by mass. And it is one of the few plants that can fertilize itself – it grows in symbiosis with a photosynthetic bacterium that takes nitrogen from the atmosphere and shares it with the fern.

Detailed explanation-5: -In Asia, Azolla is the most commonly used green manure for rice crop, due to its high growth rate, nitrogen-fixing capacity and ability to scavenge nutrients from soil and water.