Question

Non-biological nitrogen fixation is -
A. Electrochemical and photochemical
B. Rhizobial
C. Cyanobacterial
D. None of the above

Answer 1

Hint:
The molecular dinitrogen is a comparatively nonreactive molecule that is metabolically useless to all but little microorganism is called Atmospheric nitrogen. It consists of two nitrogen atoms connected by a triple covalent bond, thus making the molecule extremely inert and nonreactive. The nitrogenase enzyme catalyzes the breaking of this bond and the joining of three hydrogen atoms to each nitrogen atom.

Complete answer:
Non-biological nitrogen fixation is obtained by lightning converting nitrogen and oxygen into nitrogen oxides. Nitrogen oxides may react with water to create nitrous acid or nitric acid, which goes down into the soil, where it makes nitrate, which growing plants can easily use.
The nitrate is more profuse in well-oxygenated, non-acidic soils, while ammonium is predominant in acidic or waterlogged soils. The erstwhile sources of available soil nitrogen may be amino acids from decomposing organic matter, animal excreta (urea), and chemical fertilizers that can be absorbed straight by the plants.

So the right option is "electrochemical and photochemical", Option (A).

Note: Cyanobacteria are oxygenic photosynthetic bacteria that are prevalent in marine, freshwater, and terrestrial environments, and most of them are able to fix atmospheric nitrogen.
The Rhizobium or Bradyrhizobium bacteria inhabit the host plant’s root system and make roots to form nodules to house the bacteria. The bacteria then start to fix the nitrogen necessary for the plant. Access to the fixed nitrogen allows the plant to make leaves fortified with nitrogen that can be recycled all over the plant. This allows the plant to amplify photosynthetic capacity, which ultimately yields nitrogen-rich seed.