What are the steps involved in formation of a root nodule?
Nodule formation tales place into root of host plant in association with rhizobium . Firstly the rhizobia get multiplies and form a colonies near the root of host plant and surrounds the root , then it get attached to the epidermal cell and root hair cells . Then , root hair get curled and bacteria get penetrate into the curled root hair . The infection thread is produced carrying a bacteria till the cortex of root , the initiation of nodule formation takes place at cortex region of the root , in cortex region the bacteria get released from the infection thread and start differentiating into specialised nitrogen fixing cells . In this nodule formation takes place , the nodule have direct vascular connection with host plant for exchange of nutrients and other essential elements. The nodule that form in to the root of host plant contain many biochemical components such as nitrogenase and leg haemoglobin , nitrogenase mainly help to reduce the atmospheric nitrogen in to ammonia due to the presence of Mo-Fe protein which catalyse the reaction , ammonia is the first stable product of the nitrogen fixation . As nitrogenase is highly sensitive to molecular oxygen hence it needs a anaerobic conditions , to provide the anaerobic condition to nitrogenase , leg – haemoglobin is present also known as oxygen scavenger , it assure to provide the anaerobic condition to enzyme nitrogenase. Nitrogenase (when non – operational) lives in aerobic condition ,but during nitrogen fixation event they became anaerobic .
