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Why do nitrogen-fixing bacteria form nodules on the roots of legumes?
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ammonia
Ammonia and amines have a slightly flattened trigonal pyramidal shape with a lone pair of electrons above the nitrogen. In quaternary ammonium ions, this area is occupied by a fourth substituent.
Nitrogen-fixing bacteria, such as Rhizobium, form nodules on the roots of legumes to establish a mutually beneficial, symbiotic relationship.1
When these bacteria invade the root hairs of a host plant, they stimulate the plant to create root nodulesāspecialized structures where the bacteria and plant cells exist in intimate association. Within these nodules, the bacteria transform atmospheric nitrogen into ammonia. The host plant then utilizes this ammonia to support its own growth and development, while the plant provides the bacteria with a protected environment and nutrients. This process is a vital component of the nitrogen cycle, as it converts nitrogen into a form that is usable by plants.1