Anabaena azollae is endosymbiotic nitrogen fixing cyano bacterium of the floating pteridophytes Azolla. Azolla- Anabaena is used as a biofertilizers in the paddy fields for enriching the nitrogen in the fields. The Azolla is either incorporated in the soil or is grown along with the other crop in the field. The Anabaena azollae fixes the atmospheric nitrogen gas and combines it with the hydrogen which forms the ammonia. The process such as the nitrification and the ammonification make the nitrogen available for the rice plants.