What do the microorganisms such as Rhizobium and certain Blue Green Algae help in the fixation of?

The correct answer is Nitrogen.

Key Points

• Rhizobium is a symbiotic bacterium that forms nodules on the roots of leguminous plants and helps in the fixation of atmospheric nitrogen into ammonia.
• Blue-green algae (cyanobacteria) such as Anabaena and Nostoc also play a crucial role in nitrogen fixation, especially in aquatic ecosystems and rice paddies.
• Nitrogen fixation is the process of converting inert atmospheric nitrogen (N₂) into bioavailable forms such as ammonia (NH₃), which plants can absorb and use for growth.
• The process of biological nitrogen fixation contributes significantly to the nitrogen cycle, which is essential for maintaining soil fertility and agricultural productivity.
• These microorganisms form a mutualistic relationship with plants, where they provide nitrogen in exchange for carbohydrates and shelter.

Additional Information

• Nitrogen Cycle:
  • The nitrogen cycle is a biogeochemical cycle that describes the transformation and movement of nitrogen through the atmosphere, biosphere, and lithosphere.
  • Key processes include nitrogen fixation, nitrification, assimilation, ammonification, and denitrification.
• Biological Nitrogen Fixation:
  • It is carried out by prokaryotic organisms, including free-living bacteria (e.g., Azotobacter) and symbiotic bacteria (e.g., Rhizobium).
  • The enzyme nitrogenase is key to this process, as it catalyzes the conversion of atmospheric nitrogen to ammonia.
• Importance of Nitrogen for Plants:
  • Nitrogen is a critical component of chlorophyll, which is essential for photosynthesis.
  • It is also a part of amino acids, nucleic acids (DNA and RNA), and ATP, all of which are fundamental to plant growth and development.
• Symbiotic Relationships:
  • In the case of Rhizobium, the bacteria infect the plant roots and form nodules, where nitrogen fixation occurs in an oxygen-free environment.
  • Plants provide the bacteria with carbohydrates produced during photosynthesis, creating a mutually beneficial relationship.