Free Amino acid-N Research Articles

Comparison of nitrogen transformation dynamics in non-irradiated and irradiated alfalfa and red clover during ensiling.

ObjectiveTo study the contribution of plant enzyme and microbial activities on protein degradation in silage, this study evaluated the nitrogen transformation dynamics during ensiling of non- and irradiated alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.).MethodsAlfalfa and red clover silages were prepared and equally divided into two groups. One group was exposed to γ-irradiation at a recommended dosage (25 Gky). Therefore, four types of silages were produced: i) non-irradiated alfalfa silage; ii) irradiated alfalfa silage; iii) non-irradiated red clover silage; and iv) irradiated red clover silage. These silages were opened for fermentation quality and nitrogen components analyses after 1, 4, 8, and 30 days, respectively.ResultsThe γ-irradiation successfully suppressed microbial activity, indicated by high pH and no apparent increases in fermentation end products in irradiated silages. All nitrogen components, except for peptide-N, increased throughout the ensiling process. Proteolysis less occurred in red clover silages compared with alfalfa silages, indicated by smaller (p<0.05) increment in peptide-N and free amino acid N (FAA-N) during early stage of ensiling. The γ-irradiation treatment increased (p<0.05) peptide-N and FAA-N in alfalfa silage at day 1, whereas not in red clover silage; these two nitrogen components were higher (p<0.05) between day 4 and day 30 in non-irradiated silages than the irradiated silages. The ammonia nitrogen and non-protein nitrogen were highest in non-irradiated alfalfa silage and lowest in irradiated red clover silage after ensiling.ConclusionThe result of this study indicate that red clover and alfalfa are two forages varying in their nitrogen transformation patterns, especially during early stages of ensiling. Microbial activity plays a certain role in the proteolysis and seems little affected by the presence of polyphenol oxidase in red clover compared with alfalfaa.

Dissolved organic nitrogen distribution in differently fertilized paddy soil profiles: Implications for its potential loss

Dissolved organic nitrogen (DON) is recognized as an important nitrogen (N) pool in soil N cycling, but its role in the N cycling of paddy soils, which are intensively fertilized, is not fully predicted. In this study, we investigated DON in flooded layer and soil solution along soil profiles with suction cups in fertilized paddy fields. The DON concentration showed a relative decrease in the deeper layer of paddy soil, while free amino acid N (FAA-N) exhibited a drastic increase along with nutrient profiles of soil. In the upper layer (0–20 cm), DON accounted for 54–64% of total dissolved N (TDN), but this value increased up to 63–97% in the deeper layer (40–60 cm). Low concentrations (9.6–15.0 μg L−1) of FAA-N and low percentage of FAA-N/DON (0.1–0.2%) were observed in the upper layer, but higher concentrations (111–307 μg L−1) and increased percentage (8–36%) were examined in the deeper layer. The high percentage of DON/TDN indicated that DON was the predominant N pool in the deeper layer. Concentrations of DON were significantly and positively correlated with organic matter, total N, and electrical conductivity (EC), while negatively related to soil pH. Additionally, capillary porosity, air porosity, bulk density and particle density were also found to be significantly associated with DON. We suggest the DON and FAA in the paddy field could be an important source for N leaching, which is most strongly related with soil nutrient profiles and physical properties. It is estimated that a total loss of 4.0 kg N ha−1 yr−1 is potentially linked to DON in the paddy field, which implied that ca. 3.35% of the applied N fertilizers could be lost via DON.

Transformation and Transport Mechanism of Nitrogenous Compounds in a Biochar “Preparation–Returning to the Field” Process Studied by Employing an Isotope Tracer Method

Due to biochar’s excellent physical and chemical properties, such as rich void ration and large specific surface area, it could improve soil by conserving water and fertilizer and providing breeding grounds for soil microorganisms. Therefore, it has been attracting researchers’ interests for its potential as a soil amendment. In this work, elemental analysis-stable isotope ratio mass spectrometry (EA-IRMS) and X-ray photoelectron spectroscopy (XPS) were conjointly employed to investigate the migration and transformation mechanism of biochar nitrogenous compounds in the “preparation–returning” process. EA-IRMS data indicated that during the preparation process the nitrogen retention rate in biochar first dropped sharply (300–400 °C), then became stable (400–500 °C), and finally decreased slowly (500–800 °C) with increasing pyrolysis temperature. After returning biochar to soil, the measurable total nitrogen in biochar that migrated to soil and plants displayed a nitrogen mass distribution rate in the order of biochar after returning (88.40–90.42%) > soil (8.81–10.07%) > plants (0.77–1.53%). In addition, the pyrolysis temperature was negatively related to the nitrogen mass distribution rate in biochar, soil, and wheat. On the other hand, the pyrolysis atmosphere had little effect on the nitrogen retention rate in biochar before returning and the nitrogen mass distribution rate in biochar after returning to the field. XPS results suggested that alkaloid-N, free amino acid-N, protein-N, and NH4+-N in wheat straw were gradually transformed into pyridine-N, amino-N, pyrrole-N, quaternary-N, NH4+-N, NO2–-N, and NO3–-N in biochar during the biomass pyrolysis process. Biochar produced at 300 °C was in a transition stage that included all nitrogenous compounds present in wheat straw as well as biochar produced at the lower temperatures (≤500 °C). At higher temperatures, inorganic nitrogen species were more abundant and displayed higher contents. For pyrolysis temperatures ≤500 °C, biochars prepared under both N2 and CO2 atmospheres comprised similar nitrogenous compounds and contents. Moreover, the changes in nitrogenous compounds and nitrogen release patterns during the process of returning biochar to the field were not significantly different.

Influence of pyrolysis conditions on nitrogen speciation in a biochar ‘preparation-application’ process

To investigate biochar nitrogen conversion in a ‘preparation-application’ system and the response of its transportation in plants, biochar samples were produced from rice straw at different pyrolysis temperatures (400 °C and 800 °C) and atmospheres (N2 and CO2). Subsequently, biochar was synthesized under CO2 atmosphere to explore its nitrogen nutrient characteristics and further improve the chemical and physical properties of soil. Nitrogen speciation of the biochar and plant root samples were evaluated by X-ray photoelectron spectroscopy. Research has shown that organic nitrogen such as protein-N, free amino acid-N, and alkaloid-N in rice straw is converted into organic (nitrile-N, pyridine-N, amino-N, and pyrrole-N) and inorganic (NH4+-N, NO2−-N, and NO3−-N) species in biochar during the biomass pyrolysis process. In turn, biochar nitrogen is transported to plants as protein-N, free amino acid-N, alkaloid-N, NH4+-N, NO2−-N, and NO3−-N. Comprehensive consideration of the biochar quality and preparation cost indicated the lower pyrolysis temperature (400 °C) under CO2 atmosphere as the best conditions for biochar preparation.

Apparent digestibility, rumen fermentation and nitrogen balance in Tibetan and fine-wool sheep offered forage-concentrate diets differing in nitrogen concentration

SUMMARYA comparative study of the effect of dietary nitrogen (N) content [Low: 11·0; Medium-Low (MLow): 16·7; Medium-High (Mhigh): 23·1; High: 29·2 N g/kg dry matter (DM)] on apparent digestibilities, rumen fermentation and N balance was conducted in coarse wool Tibetan sheep and Gansu Alpine fine-wool sheep at Wushaoling in the northeast of the Qinghai-Tibetan Plateau. It was hypothesized that responses would differ between breeds and that responses would favour Tibetan over fine-wool sheep at low N intakes. Eight wethers [four Tibetan sheep and four fine-wool sheep, 20–24 months old; body weight ± standard deviation was 52 ± 3·2 kg] were used in two concurrent 4 × 4 Latin square designs. Dry matter, organic matter, neutral detergent fibre and acid detergent fibre digestibilities were higher in Tibetan than fine-wool sheep when fed the Low, MLow and High N diets while N retention was higher when the animals were fed the Low and MLow N diets. Tibetan sheep had a higher rumen pH than fine-wool sheep; however, total volatile fatty acids were similar between breeds. Molar proportions of acetate were higher but propionate and butyrate lower in Tibetan than fine-wool sheep. In addition, Tibetan sheep had higher concentrations of ruminal free amino acid-N and soluble protein-N than fine-wool sheep. Plasma and saliva urea-N concentrations were higher in Tibetan than fine-wool sheep when supplied with the Low N diet. It was concluded that Tibetan sheep were better able to cope with low N feed than fine-wool sheep because of the higher N retention and higher DM and fibre digestibilities with Low and MLow diets.

Influences of dietary nitrogen and non-fiber carbohydrate levels on apparent digestibility, rumen fermentation and nitrogen utilization in growing yaks fed low quality forage based-diet

The effects of dietary N and non-fiber carbohydrate (NFC) levels on nutrient digestibility, ruminal fermentation, and nitrogen utilization were investigated in growing yaks. Four diets (N content: 1.43%, 1.97%, 2.45% and 2.90% of DM basis; ratio of dietary NFC and RDP: 5.9, 3.2, 2.2 and 1.6) were offered to four yaks in a 4×4 Latin square design. Dietary N and NFC did not affect the gastrointestinal tract digestibility of DM, organic matter (OM), NFC, NDF, or ADF (P>0.05). Ruminal pH value, molar proportion of butyrate, and ratio of acetate to propionate were not affected by the diets (P>0.05); whereas, molar proportions of acetate, propionate, iso-butyrate, iso-valerate, valerate, and total VFA concentration in rumen fluid increased linearly (P<0.01) with increase in dietary N and decrease in dietary NFC. Except for ruminal NH3-N and soluble protein N, free amino acid-N and peptide-N maintained constantly within the sampling time (from 0 to 8h of post feeding; P>0.05). The increment of N intake linearly increased the N retention (P=0.003), but no difference (P>0.05) was observed in the ratio of N retention to the gastrointestinal trace absorbed N after dietary N reached to 2.45% of DM. Microbial N supply had linear and quadric (P<0.001) responses to the dietary N, and the highest microbial N synthesis efficiency was observed when the yaks were fed with 1.97% N diet in which ratio of NFC to RDP was 3.2, and dietary NFC and RDP were 20.2% and 6.7% of DM, respectively. Total purine derivatives excretion and microbial purine N:total N had a quadric (P<0.05) response to the dietary N. Results of the current experiment suggest that maximizing N utilization and microbial efficiency were obtained when the yaks were fed a diet with an optimal dietary ratio of NFC to RDP.

Effects of ammonium on growth, nitrogen and carbohydrate metabolism of Potamogeton maackianus A. Benn.

Growth, nitrogen and carbohydrate metabolism in relation to eutrophication were studied for a submerged plant Potamogeton maackianus, a species common in East Asian shallow lakes. The plants were grown in six NH4+-N concentrations (0.05, 0.50, 1.00, 3.50, 5.00 and 10.00 mg/L) for six days. NH4+-N levels in excess of 0.50 mg/L inhibited the plant growth. The relationships between external NH4+-N availability and total nitrogen (TN), protein-N, free amino acid-N (FAA-N) and NH4+-N in plant tissues, respectively, conformed to a logarithmic model suggesting that a feedback inhibition mechanism may exist for ammonium uptake. The response of starch to NH4+-N was fitted with a negative, logarithmic curve. Detailed analysis revealed that the influx NH4+-N had been efficiently incorporated into organic-N and eventually stored as protein at the expense of starch accumulation. These data suggest that this species may be able to tolerate high levels of ammonium when dissolved oxygen is sufficient.

Foliar Urea Application in the Fall Affects Both Nitrogen and Carbon Storage in Young `Concord' Grapevines Grown under a Wide Range of Nitrogen Supply

One-year-old `Concord' grapevines (Vitis labruscana Bailey) were fertigated with 0, 5, 10, 15, or 20 mm N in a modified Hoagland's solution for 8 weeks during summer. Half of the vines fertigated at each N concentration were sprayed with 3% foliar urea twice in late September while the rest served as controls. Four vines from each treatment combination were destructively sampled during dormancy to determine the levels and forms of N and carbohydrates. Nitrogen fertigation during the summer did not significantly alter vine N concentration whereas foliar urea application in the fall significantly increased vine N concentration. In response to foliar urea application, concentrations of both free amino acid-N and protein-N increased, but the ratio of protein-N to free amino acid-N decreased. Arginine was the most abundant amino acid in free amino acids and proteins, and its concentration was linearly correlated with vine N concentration. Concentrations of total nonstructural carbohydrates (TNC) decreased slightly in response to N supply from fertigation. Foliar urea application in the fall significantly decreased TNC concentration at each N fertigation level. Starch, glucose, and fructose decreased in response to foliar urea applications, but sucrose concentration remained unaffected. Approximately 60% of the carbon decrease in TNC caused by foliar urea application was recovered in proteins and free amino acids. We conclude that free amino acids account for a larger proportion of the N in vines sprayed with foliar urea compared with the unsprayed vines, but proteins remain as the main form of N storage. In response to foliar urea application, part of the carbon from TNC is incorporated into proteins and free amino acids, leading to a decrease in the carbon stored in TNC and an increase in the carbon stored in proteins and free amino acids.

Foliar Urea Application in the Fall Affects Both Nitrogen and Carbon Storage in Young `Concord' Grapevines Grown Under a Wide Range of Nitrogen Supply

One-year-old `Concord' vines were fertigated with 0, 5, 10, 15, or 20 mm N in a modified Hoagland's solution for 8 weeks during summer. Half of the vines fertigated at each N concentration were sprayed with 3% foliar urea twice in late September while the rest served as controls. Four vines from each treatment combination were destructively sampled during dormancy to determine the levels and forms of N and carbohydrates. Nitrogen fertigation during the summer only slightly increased vine N concentration whereas foliar urea application in the fall significantly increased vine N concentration. In response to foliar urea application, concentrations of both free amino acid-N and protein-N increased, but the ratio of protein N to amino acid N decreased. Arginine was the most abundant amino acid in free amino acids and proteins, and its concentration was linearly correlated with vine N concentration. Concentrations of total non-structural carbohydrates (TNC) decreased slightly in response to N supply from fertigation. Foliar urea application in the fall significantly decreased TNC concentration at each N fertigation level. Starch, glucose and fructose decreased in response to foliar urea applications, but sucrose concentration remained unaffected. Approximately 60% of the carbon decrease in TNC caused by foliar urea application was recovered in proteins and free amino acids. We conclude that free amino acids account for a larger proportion of the N in vines sprayed with foliar urea, but proteins remain as the main form of N storage. In response to foliar urea application, part of the carbon from TNC is incorporated into proteins and free amino acids, leading to a decrease in the carbon stored in TNC and an increase in the carbon stored in proteins and free amino acids.

Free and Total Amino Acid Composition of Edible Parts of Beans, Kale, Spinach, Cauliflower and Potatoes as Influenced by Nitrogen Fertilisation and Phosphorus and Potassium Deficiency

Vegetables were grown in pots at widely differing nutrient levels, which greatly affected dry matter (DM) yields and total-N concentrations in all crops. Nitrate-N contents were low and little affected in cauliflower and potatoes, and highest, and strongly affected, in spinach and kale. The sum of free amino acid-N as percentage of total-N of bean pods, kale, spinach, cauliflower curds and potato tubers varied between 12 and 27%, 10 and 21%, 5 and 12%, 7 and 36% and 34 and 56%, respectively. In beans and potatoes asparagine was the dominant free amino compound (29–55% and 33–59% free amino-N as percentage of total free amino-N, respectively), whereas in kale, spinach and cauliflower free glutamine was dominant (17–52%, 31–48% and 14–54%, respectively). Free essential amino acids were generally found in very low concentrations, especially cysteine (which can partly replace essential methionine in nutrition), tryptophan and phenylalanine. With some exceptions in beans, the concentrations of all total amino acids in DM increased linearly with increasing total-N content, and with correlation coefficients very close to 1·00 in most cases. P- and K-deficiency affected free and total amino acid composition mainly through their effects on total-N content but had some specific effect on arginine concentrations. Generally, chemical scores of the crude protein decreased with increasing N content of DM, which was mainly due to low contents of S-amino acids.

Free and Total Amino Acid Composition of Edible Parts of Beans, Kale, Spinach, Cauliflower and Potatoes as Influenced by Nitrogen Fertilisation and Phosphorus and Potassium Deficiency

Vegetables were grown in pots at widely differing nutrient levels, which greatly affected dry matter (DM) yields and total-N concentrations in all crops. Nitrate-N contents were low and little affected in cauliflower and potatoes, and highest, and strongly affected, in spinach and kale. The sum of free amino acid-N as percentage of total-N of bean pods, kale, spinach, cauliflower curds and potato tubers varied between 12 and 27%, 10 and 21%, 5 and 12%, 7 and 36% and 34 and 56%, respectively. In beans and potatoes asparagine was the dominant free amino compound (29–55% and 33–59% free amino-N as percentage of total free amino-N, respectively), whereas in kale, spinach and cauliflower free glutamine was dominant (17–52%, 31–48% and 14–54%, respectively). Free essential amino acids were generally found in very low concentrations, especially cysteine (which can partly replace essential methionine in nutrition), tryptophan and phenylalanine. With some exceptions in beans, the concentrations of all total amino acids in DM increased linearly with increasing total-N content, and with correlation coefficients very close to 1·00 in most cases. P- and K-deficiency affected free and total amino acid composition mainly through their effects on total-N content but had some specific effect on arginine concentrations. Generally, chemical scores of the crude protein decreased with increasing N content of DM, which was mainly due to low contents of S-amino acids.

8種の魚類筋肉エキス中の含窒成分の分布

In order to determine the distribution of nitrogenous constituents in the fish muscle extracts as completely as possible, free and combined amino acids, trimethylamine oxide (TMAO), trimethylamine, creatine, creatinine, and nucleotides were analyzed in 8 species of fish, red sea bream, stone flounder, flathead flounder, flounder, puffer, angler, common mackerel, and jack mackerel.In all species tested, the sum of the nitrogen in these constituents amounted to nearly 90% or more of the total extractive nitrogen. The distribution pattern of nitrogen among these constituents, however, varied considerably from species to species, except for nucleotides which were fairly constant. Free amino acid-N was 7-45% of the total extractive nitrogen, creatine-N 29-58%, and TMAO-N 2-23%.These results are discussed in reference to those reported previously by other authors.