The Importance of itrogen in the Growth and Development of Plants
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Nitrogen is the most important nutrient required for growth and development of plants. Earth’s atmosphere contains about 78% nitrogen gas but majority of this remains unavailable to the plants. An important feature of our planet ecosystem is the nitrogen cycle, by which nitrogen is converted into different several other forms. The process of conversion involves both biological and non biological processes. Nitrogen cycle consists of nitrogen fixation, assimilation, mineralization, nitrification and denitrification (Postgate 1998). The process of conversion of molecular nitrogen to ammonia is known as nitrogen fixation.
Biological nitrogen fixation is the mechanism of reduction of atmospheric nitrogen to a metabolically active form exclusively by microorganisms. Biological nitrogen-fixation (BNF) involves the enzymatic reduction of N2 to ammonia (NH3-). Conversion of N2 to ammonia is catalyzed by a metalloenzyme called nitrogenase. Reaction has a high activation energy because molecular N2 is an unreactive gas with a triple bond between the two N2 atoms. Therefore, N2 reduction requires at least 8 electrons and 16 ATP moles, 4 ATPs per pair of electrons.
N2 + 8H+ + 8e¯ + 16 ATP = 2NH3 + H2 + 16 ADP + 16 P
Three genetically distinct nitrogenase systems have been found in diazotrophs, namely Nif, Vnf and Anf in which the active-site central metals are Mo, V, and Fe, respectively (Zhao et al 2006). The enzyme contains two components that are named according to their metal