Hello,

1.Nodules are specialized organs found in roots of the plants

They are developed by host plant, mostly legumes in which symbiotic microorganism reduces N2 to ammonium

2.They are the extra lobes of certain plants like peas And beans in which nitrogen fixing bacteria are found

Under , nitrogen limiting conditions , capable plants forms symbiotic relationship with a host specific strain known as rhizobia

3.Bacteria in these nodules convert atmospheric nitrogen into nitrates which is utilized by plants to synthesize proteins and other materials

FORMATION OF ROOT NODULES :

• Rhizobia divides & form colonies and get attached to the root hairs & epidermal cells
• Root hairs get curled and are invaded by bacteria
• This is followed by a infection thread Formation. It carries the bacteria into the cortex of the root.
• The bacteria get modified into rod shaped bacteroides
• So , the cells in the cortex and pericycle undergoes division, leading to the formation of root nodules
• The nodules get connected with vascular tissues of the roots for nutrient exchange

Hope it helps