Explain the steps involved in the formation of root nodule.

Steps involved in the formation of root nodule :
* Nodule Formation involves a sequence of multiple interactions between Rhizobium and roots of the host plant.
* Rhizobium attracted by sugars and Amino acids released by the host legume.
* Rhizobium multiply and colonise the surrounding of roots and attached to root hair cells of epidermis.
* The root hairs curl and the bacteria invade the root hair.
* After infection thread is produced and enter into cortex of root.
* Then bacteria released from infection thread and enter into cortex.
* Endodermis and pericycle cells differentiate to form swollen structures known as Nodules.