Answer: The conversation process where nitrogen gas combines with hydrogen to form ammonium ions is known as THE ACTION OF THUNDERSTORMS while when air in the top layer of soil comes into contact with certain bacteria, nitrogen in the air is converted by NITROGEN- FIXING MICROORGANISMS.
Explanation:
About 79% of air is composed of gaseous nitrogen. However, only a few microorganism can make use of this nitrogen. The important sources of nitrogen for plants and most living organisms are the inorganic nitrogenous compounds in soil. In nature, nitrogen is constantly being removed from the soil and returned to it through the NITROGEN CYCLE
Conversation of gaseous Nitrogen into nitrogenous substances such as ammonium and amino-compouds are carried out by:
--> The action of thunderstorms, and
--> NITROGEN- fixing microorganisms.
During thunderstorms, Nitrogen reacts with oxygen to form nitric oxide. The nitric oxide is oxidizes to Nitrogen peroxide which dissolves in rainwater to form nitric and nitrous acid. When these acids enter the soil, they combine with mineral salts to form nitrates. The nitrates then, dissolve in soil water and are absorbed by the plants. These nitrates are converted into plant proteins and become part of the plant body.
Some microorganisms such as the Nitrogen fixing microorganisms are able to absorb nitrogen from the atmosphere and change it into amino-compouds and proteins. Examples of such microorganisms include:
--> the free living bacteria: these include the azotobacter and clostridium
--> the symbiotic bacteria: the rhizobium which is found in the root nodules of leguminous plants
