The following events take place:

1. Rhizobium multiply and colonise arround the surrounding of the roots and get attached to the epidermal and root hair cells.

2. Now, the root hair cells curl and the bacteria enters the root hairs.

3. After entering the root hair an infection thread is formed.Which carries the bacteria to the cortex of the root.

4. In the cortex nodule formation starts taking place .

5. Here, the bacteria are released from the thread in the cells, which leads to differentiation of nitrogen fixing cells.

6. A vascular connection is established with the host for exchange of nutrients.

Leghaemoglobin is a red coloured pigment present in the root nodules of a legume.It is also considered as oxygen molecule scavenger because it combines with the oxygen molecule and helps in it’s removal. Thus helping enzyme nitrogenase in nitrogen fixation,which only works in absence of molecular