What is Nitrogen fixation? Explain two …

Our atmosphere has 78% of nitrogen but this atmospheric nitrogen cannot be utilised directly by plants or animals. It has to be first converted into nitrogen compounds. This process of converting nitrogen gas of atmosphere into compounds of nitrogen is called nitrogen fixation. The nitrogen gas of atmosphere can be fixed by

1. Certain nitrogen fixing bacteria present in the soil.
2. By Rhizobium bacteria present in the root nodules of leguminous plants
3. By blue-green algae
4. By lightning

The nitrogen fixing Rhizobium bacteria live in the root nodules of leguminous plants like peas, beans, etc. and show symbiotic relationship. When lightning takes place in the sky during thunderstorm, a high temperature is produced in the atmosphere and nitrogen gas combines with oxygen to form nitrogen compounds.