Explain in detail about the symbiotic nitrogen fixation with nodulation.

Explanation

i. Nitrogen fixation with nodulation : Rhizobium bacterium is found in leguminous plants and fix atmospheric nitrogen. This kind of symbiotic association is beneficial for both the bacterium and plant. Root nodules are formed due to bacerial infection. Rhizobium enters into the host cell proliferates, it remains separated from the host cytoplasm by a membrane.
Stages of Roots nodule formation :
1. Legume plants secretes phenolics which attracts Rhizobium.
2. Rhizobium reaches the rhizosphere and enters into the roots hair, infects the roots hair and leads to curling of root hairs.
3. Infection thread grows inwards and separates the infected tissue from normal tissue.

4. A membrane bound bacterium is formed inside the nodule and is called bacteroid.
5. Cytokinin form bacteria and auxin from host plant promotes cell division and leads to nodule formation.