what is nodule formation

Nodules are the structures seen on the roots of leguminous plants formed due to adherence of Rhizobium sp. Legumes release various nutrients from their roots, which trigger the production of nod factors by the bacteria. When the nod factor is sensed by the root, a number of biochemical and morphological changes happen: cell division is triggered in the root to create the nodule, and the root hair growth is redirected to wind around the bacteria multiple times until it fully encapsulates 1 or more bacteria. The bacteria encapsulated divide multiple times, forming a microcolony. From this microcolony, the bacteria enter the developing nodule through a structure called an infection thread, which grows through the root hair into the basal part of the epidermis cell, and onwards into the root cortex; they are then surrounded by a plant-derived membrane and differentiate into bacteroids that fix nitrogen 

Rhizobia normally live in the soil, but when there is limited soil nitrogen, <a data-push="true" data-track="Sneak:clicked_mentioned_key_term" href="https://www.boundless.com/microbiology/definition/legume/">legumes</a> release flavonoids which signal to rhizobia that the plant is seeking <a data-push="true" data-track="Sneak:clicked_mentioned_key_term" href="https://www.boundless.com/microbiology/definition/symbiotic/">symbiotic</a> <a data-push="true" data-track="Sneak:clicked_mentioned_key_term" href="https://www.boundless.com/microbiology/definition/bacterium/">bacteria</a>.When exposed to flavonoids, the Rhizobia release <a data-push="true" data-track="Sneak:clicked_mentioned_key_term" href="https://www.boundless.com/microbiology/definition/nodulation-factor/">nodulation factor</a>, which stimulates the plant to create deformed root hairs. Rhizobia then form an "<a data-push="true" data-track="Sneak:clicked_mentioned_key_term" href="https://www.boundless.com/microbiology/definition/infection/">infection</a> thread" which allows them to enter the root cells through the root hairs.Once the rhizobia are inside the root cells, the root cells divide rapidly, forming a nodule.The rhizobia create ammonia from nitrogen in the air, which is used by the plant to create <a data-push="true" data-track="Sneak:clicked_mentioned_key_term" href="https://www.boundless.com/microbiology/definition/amino-acid/">amino acids</a> and <a data-push="true" data-track="Sneak:clicked_mentioned_key_term" href="https://www.boundless.com/microbiology/definition/nucleotide/">nucleotides</a>. The plant provides the bacteria with sugars.




 

The rhizobia resides inside the root and divides to form nodule.This rhizobia forms ammonia which helps to form nucleotides and amino acids in plants.

Once the rhizobia are inside the root cells, the root cells divide rapidly, forming a nodule. The rhizobia create ammonia from nitrogen in the air, which is used by the plant to create amino acids and nucleotides. The plant provides the bacteria with sugars