Q.The nitrogen is present in the atmosphere in huge amount but higher plants fail to utilize it. Why?

Step 1. Atmospheric nitrogen exists as the molecule N2, in which two nitrogen atoms are joined by an unusually strong triple covalent bond.

Step 2. Breaking this triple bond requires a large amount of energy and a specific catalyst; in biology, that catalyst is the enzyme nitrogenase, which reduces N2 to ammonia using ATP, electrons and a hydrogen donor, but only under anaerobic conditions.

Step 3. Higher plants do not possess the nitrogenase enzyme themselves, so despite living surrounded by an atmosphere that is roughly 78% nitrogen, they have no biochemical route to split N2 and use it directly. …

Explain the chemical barrier (the N2 triple bond) and the biochemical barrier ( …

• Stating only that N2 is 'unreactive' without identifying the specific triple-bond and missing-enzyme reasons. …