Question

Beijerinck (1888) discovered
(a) Nitrogen fixation
(b) Bacillus radicicola
(c) Nodule formation in legumes
(d) Both B and C

Answer 1

Hint: The microbe Beijernicka which is a free-living aerobic nitrogen-fixing bacteria found in soil is named after the scientist Beijerinck due to his exemplary work in the field of microbes and how they help in fertilizing the soil.

Complete Answer:
The process of biological nitrogen fixation was discovered by the Dutch microbiologist Martinus Beijerinck along with the German agronomist Hermann Hellriegel. He was awarded the Leeuwenhoek Medal by the Dutch Royal Academy of Sciences for this discovery. Biological nitrogen fixation is termed the process by which atmospheric nitrogen is converted into ammonia by living organisms. This is very vital for plant growth as plants cannot absorb nitrogen from the air and are dependent on these microbes for supplying nitrogen to them via soil. Some plants even make symbiotic relationships with nitrogen- fixing organisms such as leguminous plants.

Additional information: Let us look in detail at how symbiotic biological nitrogen fixation in leguminous plants takes place.
- Rhizobium bacteria come near susceptible root hair and start diving.
- This results in infection of the root hair causing it to become curled.
- Through this infection thread, the bacteria reach the inner cortex where they get modified into rod- shaped bacteroides and divide.
- This rapid division leads to the formation of nodules.
- The bacteria have an enzyme known as nitrogenase which converts nitrogen into ammonia.
- This nodule is provided with food and water in exchange for fixing nitrogen.
So, the correct option is ‘(a) Nitrogen fixation’.

Note:
- Beijerinck is the scientist who termed the virus as “contagium vivum fluidum”.
- Other nitrogen-fixing bacteria include cyanobacteria such as Nostoc and Anabaena, Rhodospirillum, Azotobacter, etc.
- The microbe Frankia performs symbiotic nitrogen fixation for non- leguminous plants such as Alnus.