Question

Describe symbiotic nitrogen fixation with the help of a diagram.

Answer 1

When the nitrogen-fixing bacteria live in symbiotic relationships with the host then it is called symbiotic nitrogen fixation. It is used by plants such as legumes for fixing atmospheric nitrogen gas to ammonia. It is established broadly in nature and has very low economic and environmental costs.

Complete answer:
The biological nitrogen fixation process that converts atmospheric nitrogen into the nitrogenous compounds of living organisms is called symbiotic nitrogen fixation. For example – Rhizobium, Frankia, etc. Most of the microorganisms partner themselves with host plants to fix nitrogen symbiotically. By the process of photosynthesis, plants provide sugars that are utilized by nitrogen-fixing microorganisms for producing energy that is necessary for nitrogen fixation.

The common example of symbiotic nitrogen fixation is Azolla’s symbiosis with a cyanobacterium Anabaena azollae. In this process, specialized cells are called heterocyst formed by the particular amount of nitrogen that is fixed by cyanobacteria. In wetlands of Southeast Asia, this type of symbiosis has been used for the last 1000 years as a biofertilizer.

The most crucial symbiotic relationship takes place between legumes and Rhizobium and Bradyrhizobium bacteria. This symbiotic association is common in the worldwide ecology. Some examples of legumes that are used in symbiotic nitrogen fixation are alfalfa, beans, clover, lupines, peanuts, etc.

In the symbiotic relationship, the supply of nitrogen by bacteria directly takes place in the legume and it indirectly provides nitrogen to the adjacent grass plants.

Note: Prokaryotes can fix nitrogen very easily and efficiently by the process of symbiotic nitrogen fixation. Thus, most plants are there that provide nutrients to one another by making a symbiotic relationship. In this way nutrient requirements of every plant complete. The plants will get the benefit and prevent them from getting dead.