Question:
Most abundant gas in our atmosphere that plants cannot utilize directly in its atmospheric form and is captured by certain bacteria that live symbiotically in the nodules of roots
Most abundant gas in our atmosphere that plants cannot utilize directly in its atmospheric form and is captured by certain bacteria that live symbiotically in the nodules of roots
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Always remember that dinitrogen (\(N_2\)) is chemically inert under standard biological conditions because of its triple bond. Only specialized diazotrophic bacteria and cyanobacteria can fix it biologically.
Updated On: Jul 24, 2026
- Oxygen
- Nitrogen
- Neon
- Hydrogen
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The Correct Option is B
Solution and Explanation
Step 1: Understanding the Concept:
This question focuses on the composition of the Earth's atmosphere and the biological mechanisms through which gaseous elements are fixed into bioavailable forms for plant nutrition.
Step 2: Detailed Explanation:
Let us analyze the atmospheric gases and their utilization by plants:
The Earth's atmosphere consists of approximately 78% nitrogen (\(N_2\)), 21% oxygen (\(O_2\)), 0.9% argon, 0.04% carbon dioxide, and trace amounts of other gases like neon and hydrogen.
Therefore, nitrogen is the most abundant gas in our atmosphere.
Although nitrogen is highly abundant, plants cannot absorb or utilize atmospheric dinitrogen (\(N_2\)) directly. This is because the two nitrogen atoms in an \(N_2\) molecule are joined by an extremely strong triple covalent bond (\(N \equiv N\)), which requires a high amount of activation energy to break.
Certain prokaryotic microorganisms possess the specialized enzyme complex known as nitrogenase, which can reduce atmospheric nitrogen to ammonia (\(NH_3\)), a form that plants can readily assimilate.
Many of these nitrogen-fixing bacteria, such as those in the genus Rhizobium, live in a mutualistic, symbiotic relationship inside the specialized root nodules of leguminous plants.
In this symbiosis, the host plant provides carbohydrates and a protected anaerobic environment, while the bacteria provide fixed nitrogen to the plant.
Thus, the gas in question is nitrogen.
Step 2: Final Answer:
The correct option is (B), representing Nitrogen.
This question focuses on the composition of the Earth's atmosphere and the biological mechanisms through which gaseous elements are fixed into bioavailable forms for plant nutrition.
Step 2: Detailed Explanation:
Let us analyze the atmospheric gases and their utilization by plants:
The Earth's atmosphere consists of approximately 78% nitrogen (\(N_2\)), 21% oxygen (\(O_2\)), 0.9% argon, 0.04% carbon dioxide, and trace amounts of other gases like neon and hydrogen.
Therefore, nitrogen is the most abundant gas in our atmosphere.
Although nitrogen is highly abundant, plants cannot absorb or utilize atmospheric dinitrogen (\(N_2\)) directly. This is because the two nitrogen atoms in an \(N_2\) molecule are joined by an extremely strong triple covalent bond (\(N \equiv N\)), which requires a high amount of activation energy to break.
Certain prokaryotic microorganisms possess the specialized enzyme complex known as nitrogenase, which can reduce atmospheric nitrogen to ammonia (\(NH_3\)), a form that plants can readily assimilate.
Many of these nitrogen-fixing bacteria, such as those in the genus Rhizobium, live in a mutualistic, symbiotic relationship inside the specialized root nodules of leguminous plants.
In this symbiosis, the host plant provides carbohydrates and a protected anaerobic environment, while the bacteria provide fixed nitrogen to the plant.
Thus, the gas in question is nitrogen.
Step 2: Final Answer:
The correct option is (B), representing Nitrogen.
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