Symbiotic And Non Symbiotic Nitrogen Fixation

Definition Of Nitrogen Fixation

Nitrogen fixation is the process of converting atmospheric nitrogen, N₂, to a form that can be utilised by living organisms—for example, ammonia, NH₃. Nitrogen is an element critical to life. Nitrogen forms part of the composition of amino acids, proteins, DNA, and chlorophyll.

Without available nitrogen, plants can't grow, and the entire food web—animals and humans—would be disrupted. Nitrogen fixation may occur biologically with symbiotic bacteria like leguminous plants' Rhizobium or abiotically through natural occurrences like lighting and industrial processes, for example, the Haber-Bosch process.

Types Of Nitrogen Fixation

The types of nitrogen fixation are-

Biological Nitrogen Fixation

• In the nitrogen cycle, the process of fixation is of prime importance and needs to be understood about other processes like nitrification, assimilation, ammonification and denitrification, which provide a source of nitrogen and its recycling in the ecosystem.

Enzyme nitrogenase

• Catalyses reduction of atmospheric nitrogen (N₂) to ammonia (NH₃)
• Anaerobic conditions to enable nitrogen fixation to occur

Symbiotic Nitrogen Fixation

The symbiotic Nitrogen fixation is described below-

• The plants and nitrogen-fixing bacteria are in a mutual symbiotic relationship in which these.
• The bacteria enter the roots of the plants, and special structures developed as a response termed nodules that perform the reaction of nitrogen fixation

Types Of Symbiotic Nitrogen Fixation

The types of symbiotic nitrogen fixation are:

Legume-Rhizobium Symbiosis

Examples: Peas, beans, clover

Non-Legume Symbiosis

Examples: Alder trees with Frankia bacteria

Process Of Symbiotic Nitrogen Fixation

• Infection: It is a process where the infection by bacteria requires attachment and penetration of the root hair.

• Nodule formation: Plant cells increase and form nodules.

• Nitrogen fixation: Atmospheric nitrogen is reduced to ammonia under the influence of bacteria in the nodules.

Importance Of Symbiotic Nitrogen Fixation

• A better understanding and manipulation of nonsymbiotic nitrogen fixation can help in sustainable agriculture and hence global food security.

• The process avails the important plant diet from the process so that high crop plants are achieved, ensuring sustainable agriculture.

Non-Symbiotic Nitrogen Fixation

The free-living nitrogen-fixing bacteria and the cyanobacteria do not enter into any specific association with plants. They do free-living nitrogen-fixing.

They convert atmospheric nitrogen into a biologically available form because of their metabolic activities.

Types Of Non-Symbiotic Nitrogen Fixation

The different types of non-symbiotic nitrogen fixation are:

1. Free-Living Bacteria
2. Examples: Azotobacter, Clostridium
3. Cyanobacteria
4. Examples: Anabaena, Nostoc

Process Of Non-Symbiotic Nitrogen Fixation

• Activity of enzyme: The reaction needs to be carried out in the presence of the nitrogenase enzyme.

• Nitrogenase: It reduces atmospheric nitrogen (N₂) to ammonia (NH₃).

Importance Of Non-Symbiotic Nitrogen Fixation

The non-symbiotic nitrogen fixation is important in:

Contribution To The Nitrogen Cycle

This appears to be a significant ecological function performed within natural ecosystems because it maintains the balance of nitrogen by converting atmospheric nitrogen from its inert form to a plant-available form.

Role In Natural Ecosystems

The process helps in the maintenance of primary productivity and thus the perpetuation of the ecosystems due to the constant replenishment of nitrogen in its reduced forms.

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