Adapted and modified from Merrill and Watt This recommendation is made with the knowledge that there is no official Association of Analytical Communities AOAC  method for amino acid determination in foods.
Elemental Nitrogen, Ammonical and organic form of Nitrogen: Ammonical form of N2 is available in soil in the form of urea or NH4 in free-state. Urea, if present, is first split into NH4 and CO2, and NH4 is then utilized directly by metabolic pathways by higher plants.
But recent studies indicate that urea can be directly used up by metabolic pathways in certain plants. It should be remembered here, that free ammonia is the only utilizable form of N2 that can be directly incorporated into amino acids. Whatever may be the source of nitrogen, first it has to be converted to NH3 and fixed into amino acid.
It can be converted or transferred to other forms by various pathways that operate in living systems. Different plants use different pathways to different levels. Soy bean plants moves a large amount of malate to the roots where they convert it to alkali while the potassium recirculates; www.
The same are absorbed by the root system and utilized directly. Thus the decaying organic matter acts as the rich source of organic nitrogen that can be utilized by not only higher plants but also by micro-organisms.
And nitrites are also found but in small quantities. These forms are available as ions and the same are easily absorbed by the roots or cellular surfaces from its surrounding soil solution. The absorption of NO3 or NO2 ions is not by just diffusion process, but it is facilitated by specific carriers.
Nitrite and nitrate ions; www. Under normal conditions, nitrite is never accumulated in the soil in sufficient quantities and it is toxic to plants and to other microbes. But more of nitrate reductive activity is found in leaves than in roots. However, the mechanism of nitrate and nitrite reduction is performed by different enzymes while NO3 is reduced by nitrate reductase enzymes and the NO2 is reduced by nitrite reductases.
This enzyme has been isolated and purified from various sources like Aspergillus, bacteria, chlorella, blue green algae, alfa alfa and other higher plants. The enzyme is associated with 2 cofactors i. FAD and two molybdenum ions. The former is available in non chlorophyllous tissues and the latter is found in chloroplast containing leaves.
With the addition of NO3 as the substrate, the amount of this enzyme increases many fold. However, the induction requires light without which the enzyme induction is not possible to the fullest extent. The nitrate induced enzyme synthesis can be inhibited by the inhibitors of transcription and translation like actinomycin D and cycloheximide respectively, which indicates that NO3 acts as an inducer of nitrate reductase gene expression.
How light modulates the gene expression is not yet clear. Furthermore, phytohormones, particularly cytokinin also induces nitrate reductase synthesis denovo even in the absence of light and NO3. The mechanism of denovo synthesis of nitrate reductase, though not clear, it is fully accepted that the nitrate reductase is an inducible enzyme.
A model for the control of nitrate uptake by leaf-generated signals during rapid vegetative growth left and rapid pod fill right Ismande and Touraine, During vegetative growth leftnitrate ions are rapidly absorbed by the root and transported via the xylem to the leaf.
In the leaf, nitrate reduction produces organic acids OA and amino acids AA. Most of the newly formed OA are translocated to the root where a carboxyl group is released in exchange for a nitrate ion, whereas the newly assimilated N is incorporated primarily into leaf N compounds protein Ismande and Touraine, Expression of genes that encode nitrogen metabolic enzymes only occurs upon nitrogen catabolite derepression and simultaneous induction by a pathway-specific metabolite.
The repressing metabolite appears to be glutamine, although the nature of the factor with which it interacts is unknown. NIT-2 is a sequence-specific DNA-binding protein with a single zinc finger that acts globally to activate the expression of many structural genes that encode enzymes of nitrogen metabolism.
NMR is a negative-acting regulatory protein that is required to establish nitrogen repression, and it appears to act by binding directly to NIT-2 to inhibit its function.
NIT-4 is a pathway-specific positive-acting regulatory factor that has a zinc cluster DNA-binding motif. Other specific positive-acting factors are required to express genes encoding enzymes for other nitrogen pathways.
URC signifies uricase, for which the structural gene has not yet been identified in Neurospora. Original figure from G.Sample Scientific Research Paper Just as animals around the world have evolved to better survive in their environments, botanical life everywhere has also been forced to grow and adapt to their habitats.
Note: ① Wall thickness in the pipeline parameters is the estimated average wall thickness of the entire pipeline; ② in the section from “No. 1 Valve Chamber-Terminal Station”, nitrogen displacement is performed in two-stage pressure regulation.
The next step is nitrogen reduction. This process reduces nitrate back into the amino group (ammonium). This allows the plant to absorb the ammonium ions.
Acknowledgements The original draft of Nitrate and nitrite in drinking-water, Background document for development of WHO Guidelines for Drinking-water Quality, was prepared by G.J.A. Speijers. It has been updated and revised by Mr J.K.
Fawell of the United Kingdom. Essay Nitrogen was isolated by the British physician Daniel Rutherford in and recognized as an elemental gas by the French chemist Antoine Laurent Lavoisier about Properties Nitrogen is a colorless, odorless, tasteless, nontoxic gas.
We Welcome you to submitting your article for our Special Anniversary Reviewing Promotion and you are automatically qualified for a raffle draw conducted by Google Scholar, Scopus, Science Web, Elsevier, Thomson Reuters, funded by the International Monetary Fund (IMF).