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Triticum Aestivum L.): Effects on the Distribution of Protein Sub-Fractions, Amino Acids, and Starch Characteristics
Published in Megh R. Goyal, Susmitha S. Nambuthiri, Richard Koech, Technological Interventions in Management of Irrigated Agriculture, 2018
Divya Jain, Bavita Asthir, Deepak Kumar Verma
The N in asparagine and glutamine can be transferred into a wide variety of amino acids, nucleic acid, ureides (R–CO–NH–CO–NH2 or R–CO–NH–CO–NH–CO–R) and polyamines.9,52 Key reactions in the metabolism of glutamate are the transfer of the α-amino group to a range of 2-oxo acid acceptors to form amino acids. The reversible reactions are carried out by pyridoxal phosphate-containing enzymes termed aminotransferases also known as transaminases, which can exhibit wide preferences for both the amino acid and oxo-acid substrates. Thus, nitrogen assimilation is a vital process controlling plant growth and development through inorganic nitrogen which is assimilated into amino acids. GOT and GPT might play an important role in the synthesis of amino acids and proteins.84 Lopes et al.96 studied the wheat nitrogen metabolism during grain filling, comparative roles of glumes, flag leaf, and grains in all three organs and no decrease in transaminase was detected. In literature, activity of GOT and GPT drastically appear to play a significant role in the de novo synthesis of amino acids and to facilitate the transfer of C from amino acids into carbohydrates.
Algal Photosynthesis and Physiology
Published in Stephen P. Slocombe, John R. Benemann, Microalgal Production, 2017
John A. Raven and John Beardall
Nitrogen assimilation can be energetically costly. Additional energy cost is incurred if the redox state of the nutrient element differs between the form supplied and the form that is assimilated during growth. Thus, for nitrate reduction to ammonium in the light, the reduction of each nitrate requires four NAD(P)H that, with 4.5 photons needed per NADP+ reduced, requires 18 photons. This means 2.72 additional photons per carbon dioxide in addition to those needed for carbon assimilation into carbohydrate (an increase of 30%). Further photon costs are incurred if nitrate is reduced in the dark as NAD(P)H is then derived from respiration of organic C.
Nutrient processes and modeling in urban stormwater ponds and constructed wetlands
Published in Canadian Water Resources Journal / Revue canadienne des ressources hydriques, 2019
Brendan Troitsky, David Z. Zhu, Mark Loewen, Bert van Duin, Khizar Mahmood
Macrophytes and phytoplankton are able to assimilate nitrogen in both NH4+ and NO3- forms, with different preference across various species; species traditionally found in wetlands with limited nitrification often prefer NH4+, whereas high NH4+ inhibits growth in many other species (Lee et al. 2009). The anaerobic conditions in hydric soil limit the oxygen intensive nitrification process, resulting in many naturally occurring wetland species displaying a preference to NH4+; this is supported by a correlation of decreased ammonia removal with greater pond depth, as traditional wetland macrophytes will have limited available habitat in these cases (Lee et al. 2009; Koch et al. 2014). Wetland macrophyte species are often adapted to intermittent flooding and anoxic conditions (Marsalek et al. 2008). This means that when selecting macrophytes to populate a stormwater pond, nitrogen type preference should be considered alongside traditional factors such as invasiveness, yield, and growing patterns (Uusi-Kämppä et al. 1996; Lee et al. 2009). The nitrogen uptake of plants is also affected by pH, temperature, sunlight, water levels, the availability of other nutrients and trace minerals, and soil moisture for shoreline macrophytes, among other factors (Glass and Siddiqi 1995; von Wirén et al. 1997; Crawford and Glass 1998). Rapid growth, high nutrient storage, high standing structure, and dense growth patterns are all ideal characteristics for maximizing nitrogen assimilation (Reddy and D'angelo 1997). Macrophytes are also seasonally active, assimilating nutrients for growth during the spring and summer, but, if they are not harvested or consumed before fall, much of the nutrients will be returned to the system as litter (Uusi-Kämppä et al. 1996; Fisher and Acreman 2004; Jefferson et al. 2017). Potential nitrogen removal rates can be effectively measured by standing stock, which relates to the amount of the plant available for harvest without removing the entire plant (Vymazal 1995). Typical aboveground N standing stock values range greatly, but have been reported to range from 0.6–72 g N m−2 (Johnston 1991), 2–64 g N m−2 (Vymazal 1999), 22–88 g N m−2 (Vymazal 1995), 2–29 g N m−2 (Mitsch and Gosselink 2000). It is important to note that root uptake for nutrients typically consists of dissolved phosphorus and nitrogen, so some sedimentated forms will not be immediately available for uptake (Carignan 1982; Vymazal et al. 1998; Cedergreen and Madsen 2002). Plant assimilation may only account for around 5% of nitrogen removal under typical conditions, however, with ideal growing conditions, low total loading, and regular harvesting, this can increase significantly (Hammer 1992).