Ammonia assimilation

Although the antibacterial and antifungal activities of bialaphos and phosphinothricin were not found to be usehil, the two agents were later used as biodegradeable, relatively nonselective, postemergent herbicides. Glutamine synthetase inhibition is toxic to plants because the enzyme is key to ammonia assimilation. There is some selectivity for individual plant species as shown by the LD for bialaphos ranging from 0.125 to 8.5 kg/ha (301—303). 

Ammonia assimilation is the process by which NH3 or NH4 is taken up by an organism to become part of its biomass in the form of organic nitrogen compounds. 

J. B. Cliquet and G. R. Stewart, Ammonia assimilation in Zea mays L. infected with a vcsicular-arbuscular mycorrhizal fungus Glomus fasciculaiiim. Plant Phy.s-iol. /0/ 865 (1993). 

L. J. Reitzer, Ammonia Assimilation and the Biosynthesis of Glutamine, Glutamate, Aspartate, Asparagine, L-alanine, and D-alanine. In Escherichia coll and Salmonella, Cellular and Molecular Biology F. C. Neidhardt, Ed. ASM Press Washington, DC, 1996 Vol. 1, pp 391 07. 

Jain, V., Garg, N., and Nainawatee, H.S., Effect of nod regulators on the ammonia assimilation enzymes of Rhizobium sp vigna and Rhizobium meliloti, Natl. Acad. Sci. Lett., 15, 345, 1992. 

A good overview of ammonia assimilation in bacterial systems and its regulation. 

Figure 10.5 Major processes involved in the biogeochemical cycling of N in estuaries and the coastal ocean (1) biological N2 fixation (2) ammonia assimilation (3) nitrification (4) assimilatory NC>3 reduction (5) ammonification or N remineralization (6) ammonium oxidation (speculative at this time) (7) denitrification and dissimilatory NO3 reduction to NH4+ and (8) assimilation of dissolved organic nitrogen (DON). (Modified from Libes, 1992.)...

Ammonia assimilation is where NH3 or NII4+ is taken up and incorporated into organisms as organic nitrogen molecules (Jaffe, 2000), as shown below in the case of NH4+ ... 

GS in plants is the key enzyme of the GS/GOGAT (glutamine synthetase/g1utamine 2-oxyg1utarate aminotransferase) pathway and thus plays a crucial role in ammonia assimilation/reassimilation (117. 118). GS inhibition by phosphinothricin causes accumulation of toxic levels of ammonia. Since ammonia production is increased by photorespiration and conversion of nitrite to ammonia (also light-dependent), nitrogen fertilizers and light act to promote phosphinothricin efficacy (119). 

Ammonia assimilation is the uptake of NH3 or NH4 by an organism into its biomass in the form of an organic nitrogen compound. For organisms that can directly assimilate reduced inorganic nitrogen, this is an efficient process to incorporate nitrogen into biomass. 

Figure 19. Biological transformation /N species. I-nitrogen fixation 2-ammonia assimilation 3-nitrification 4-assimilatory nitrate reduction 5-ammoniafication 6-denitrification.

Figure 2. Biological transformation of N species, /—nitrogen fixation, 2—ammonia assimilation. 3—nitrification, 4—assimilatory nitrate reduction, 5—ammoniaficatinn, 6—denitrification.

Ammonia assimilation The metabolic uptake of dissolved ammonia (NH3) by primary producers. 

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