The various steps in a sequence during root nodule formation in legumes are:
- Multiplication and colonisation of Rhizobia at root surroundings.
- Attachment of Rhizobia to epidermal cells or root hairs of root.
- Curling of root hairs.
- Infection thread formation which carries the bacteria into the cortical cells.
- Initiation of root nodule formation in root cortical cells.
- Release of bacteria from infection thread into root cortical cells.
- Differentiation of Rhizobia and cortical cells as specialised nitrogen fixing cells.
- Establishment of vasculature between the root and nodule.