The process of Azolla Anabaena symbiosis

Azolla is a genus of its own family called Azollaceae. It is a floating water fern of worldwide distribution. At present, they exist 6 Azolla sp. in nature.  

• The mature plant ranges from 0.5­0-0.7 cm in diameter with simple individual roots, producing a rhizome up to 40 cm or more with a root bundle of 15 cm or more.  
• Azolla consists of a floating branched rhizome with small, alternate, adventitious, overlapping, bi­lobed leaves and simple roots that hang down into the water.  
• The upper lobes of the leaf are green, i.e., chlorophyllous, and perform photosynthetic activities, and the lower lobe is achlorophyllous, colorless, transparent, and remains in contact with water.  
• It produces itself mostly vegetatively, although sexual reproduction is also present. Anabaena The N2 fixing BGA, Anabaena is almost invariably present in the special cavity on the dorsal lobe of each fern leaf.   

Azolla anabaena symbiosis

• In symbiosis, Anabaena fixes N2 on the leaf of Azolla, and it supplies all of the N2 needs of the host plant. Azolla takes the necessary nitrogen from the Anabaena and reproduces.  
• Again, Anabaena takes up all other nutrients from Azolla except N2. Thus Azolla and Anabaena are benefited from each other. This symbiotic relation between Azolla and Anabaena is known as Azolla­ Anabaena symbiosis.