Tag: nutrient cycles

Nitrification is an important process in nitrogen cycle in nature, which is brought about by nitrifying bacteria. In warm moist soils having a temperature of $30-35^0$C and neutral pH, ammonia gets oxidized to nitrite ($NO _2^-$) and then nitrate ($NO _3^-$) by the process of nitrification. 

The common Nitrogen fixer in the paddy field is Azospirillum. This is a soil and root bacteria. It is a nitrogen-fixing bacteria when added to the soil it multiplies and supplies 30-40Kg nitrogen per hectare per season. It also produces Indole acetic acid which helps in growth.

Some bacteria and cyanobacteria (blue-green algae) are able to fix nitrogen into usable forms of salts of nitrogen for plants.

Rhizobium and Cynobacteria are involved in nitrogen fixation. There are many more bacteria like Nitrobacter, Nitrosomanas etc involve in maintaining the balance of nitrogen gas in the atmosphere.

Rhizobium is a bacterium found in the root nodules of leguminous plants. It induces the formation of special structures called nodules inside which it fixes atmospheric nitrogen. It does this with the help of nitrogenase enzyme that converts of nitrogen to ammonium that is an important factor required for plant growth. In turn, the bacterium receives shelter from the plant. Thus the correct answer is option A.

The second step (oxidation of nitrite into nitrate) is done mainly by bacteria of the genus Nitrosomonas and Nitrobacter.

Oxidation of Ammonia to nitrite is performed by two groups of bacteria. Nitrosomonas and Nitrosocossus are examples of bacterias which perform the oxidation of ammonia to nitrite.

Anaerobic bacteria do not need oxygen. This is because they don't  use oxygen in any of their processes. Thus bacteria are poisoned by oxygen.

Nitrification is a process of conversion of ammonium salts to nitrites and nitrites to nitrates. The bacteria that carry out this process are called as nitrifying bacteria. Nitrosomonas, Nitrosospira, Nitrosococcus convert ammonia into nitrites. Nitrobacter, Nitrospina, Nitrococcus convert nitrites into nitrates.

Atmospheric carbon dioxide is used by plants to produced food. Due to industrialization, large amount of carbon dioxide is released in the atmosphere. This CO$ _2$ provides nutrient source to certain plants. However, excess amount of CO$ _2$ inhibits growth in plants. It inhibits nitrate assimilation in certain plants. It basically inhibits absorption of nitrogen.