Environmentally induced changes in amino acid composition in the grain of durum wheat grown under different water and temperature regimes in a Mediterranean environment

Amino acid composition is an important feature in determining the nutritional value of wheat grain for human and animal diets. Environmental conditions are known to influence protein quantity as well as grain production and, in turn, amino acid composition. In this study, grain yield, protein content, and amino acid composition were determined in 10 durum wheat genotypes under three water and temperature regimes in a Mediterranean environment. The highest value for grain-protein content (15.7%) was found in the warmer and driest environment and the lowest (12.8%) in the irrigated environment. Although amino acid composition showed significant variation for all genotypes, with the exception of arginine and cysteine, major changes in amino acid composition were caused by environmental conditions and in particular by water availability and temperature during the grain-filling period, which significantly altered the duration of grain development. The amino acids with the highest percentage of variation between environments were tyrosine (26.4%), lysine (23.7%), methionine (20.3%), threonine (19.3%), and valine (15.6%), whereas phenylalanine (5.1%), glycine (6.4%), and aspartic acid (6.8%) showed the least variation between environments. Whereas the content of glutamine, phenylalanine, and proline increased with the decrease in grain-filling duration, the remaining amino acids tended to diminish, presumably because high temperature and drought favored the deposition of gliadins (proteins particularly rich in glutamine and proline), to the detriment of albumins and globulins (proteins especially rich in threonine, lysine, methionine, valine, and histidine). Despite the negative correlations found between the percentage of protein and its content in essential amino acids, the results indicate that reductions in lysine per unit of food were not very pronounced (0.32 to 0.29 g/100 g of flour) with increases of up 22.7% in grain-protein content, whereas threonine did not change and valine even slightly increased.     

Free amino acids of tronchuda cabbage (Brassica oleracea L. Var. costata DC): influence of leaf position (internal or external) and collection time

The free amino acid profile of 18 samples of tronchuda cabbage ( Brassica oleracea L. var. costata DC) leaves, harvested at three different months, was determined by HPLC/UV-vis. The tronchuda cabbage leaves total free amino acid content varied from 3.3 to 14.4 g/kg fresh weight. Generally, arginine was the major compound, followed by proline, threonine, glutamine, cysteine, and glutamic acid. This study indicates that free amino acids are not similarly distributed: in external leaves, proline and arginine were the major free amino acids, while in internal ones, arginine was the main free amino acid, followed by threonine, glutamine, and cysteine. Significant differences were observed for valine, proline, arginine, leucine, cysteine, lysine, histidine, and tyrosine contents. The levels of some free amino acids were significantly affected by the collection period. In external leaves, this occurred with glutamic acid, serine, valine, leucine, cysteine, and ornithine contents, while in internal leaves, it occurred with aspartic acid, arginine, and total contents.     

Changes in the free amino acid composition with maturity of the noble cultivar of Vitis rotundifolia Michx. grape

The changes in amino acid composition that occur with maturity of the Noble cultivar of the Vitis rotundifolia Michx. (muscadine) grape were determined by HPLC. Eighteen amino acids were identified. Histidine was the most prominent amino acid followed by alanine. The concentrations of most of the major amino acids (alanine, glycine, histidine, valine, isoleucine, aspartic acid, and serine) were highest at verasion. Glutamine and threonine contents dropped sharply after fruit set, while those of arginine and proline increased gradually with maturity and ripening. Tyrosine content increased gradually with maturity and ripening following a slight drop after fruit set. In ripe grapes, seeds contained most of the amino acids in mature grapes (50%) followed by the pulp (23%), the juice (15%), and the skin (11%). Alanine, histidine, and arginine were the principal amino acids identified in the juice. Alanine, histidine, arginine, valine, glutamine, aspartic acid, proline, serine, and threonine accounted for about 90% of the amino acids in the pulp. In seeds, alanine, proline, asparagine, and histidine accounted for over 55% of the amino acids, while alanine and histidine were found to be the predominant free amino acids in the skin. The profile indicates some differences in the changes in amino acid composition with berry maturity and relative amounts of amino acids present in muscadine compared to those in nonmuscadine grape species.     

青海黑青稞营养及活性成分分析与评价

为明确青海不同品种黑青稞的营养及化学成分含量,筛选优异种质资源,本研究开展了12种黑青稞营养及化学成分分析与评价。结果表明,参试黑青稞蛋白、总淀粉、直链淀粉、粗脂肪、粗纤维、灰分、β-葡聚糖含量在部分品种间存在显著差异(P<0.05),黑青稞具有较高含量的蛋白质(12.19%~14.07%)、纤维(2.13%~3.64%)、直链淀粉(18.96%~25.94%)和β-葡聚糖(3.91%~7.50%);参试黑青稞中Ca、K、Zn含量存在品种间显著差异(P<0.05),其余测定的矿物质含量存在部分品种间显著差异(P<0.05),其中K(581.42 mg·100g^-1)、Mg(171.90 mg·100g^-1)、Ca(90.28 mg·100g^-1)、Na(17.33 mg·100g^-1)含量较高;参试黑青稞蛋白中总必需氨基酸含量平均值为319.90 mg·g^-1(接近WHO/FAO推荐值360 mg·g^-1),第一限制性氨基酸为赖氨酸,第二限制性氨基酸为甲硫氨酸和胱氨酸,第三限制性氨基酸为苏氨酸;参试部分黑青稞品种的总酚、游离酚、结合酚、总黄酮、游离黄酮、结合黄酮及花色苷含量存在显著差异(P<0.05);主成分筛选出950、Z536、Z533黑青稞综合品质较优,聚类分析将12个黑青稞品种分为4类,第1类蛋白质、多酚、黄酮、β-葡聚糖含量较高;第2类花色苷、氨基酸含量较高;第3类纤维含量较高;第4类淀粉含量较高。本研究结果为黑青稞营养功能品质评价及加工利用奠定了基础,也为特异青稞资源的筛选提供了参考。     

Furosine: a suitable marker for assessing the freshness of royal jelly

Fifteen commercial samples of royal jelly, consisting of 10 imported samples, and 5 samples of known origin obtained freshly harvested from beekeepers, were analyzed for protein, lysine, and furosine content. In addition, a commercial sample of royal jelly, at the beginning of its commercial shelf life, was stored for 10 months both at 4 degrees C and at room temperature in order to assess the development of the Maillard reaction (furosine) and relative nutritional damage (blocked lysine). The commercial royal jelly products contained different amounts of furosine, ranging from 37.1 to 113.3 mg/100 g protein, evidence of different storage times and conditions. The average furosine content of the royal jelly samples of known origin and harvesting was significantly lower than that of the imported samples (41.7 versus 73.6 mg/100 g protein, respectively). With regard to shelf life, furosine content increased significantly from 72.0 mg/100 g protein to 500.8 mg/100 g protein after 10 months of storage at room temperature, while it increased to a much lower level (100.5 mg/100 g protein) when the royal jelly was stored at 4 degrees C. However, nutritional damage, expressed as blocked lysine (calculated indirectly from the furosine content), was minor or negligible, 11.9 and 2.3% of total lysine, in samples stored at room temperature and at 4 degrees C, respectively. Lysine was determined by an innovative procedure based on high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The results showed that furosine is a suitable index for assessing the quality and freshness of royal jelly.     

Comparative study on free amino acid composition of wild edible mushroom species

A comparative study on the amino acid composition of 11 wild edible mushroom species (Suillus bellini, Suillus luteus, Suillus granulatus, Tricholomopsis rutilans, Hygrophorus agathosmus, Amanita rubescens, Russula cyanoxantha, Boletus edulis, Tricholoma equestre, Fistulina hepatica, and Cantharellus cibarius) was developed. To define the qualitative and quantitative profiles, a derivatization procedure with dabsyl chloride was performed, followed by HPLC-UV-vis analysis. Twenty free amino acids (aspartic acid, glutamic acid, asparagine, glutamine, serine, threonine, glycine, alanine, valine, proline, arginine, isoleucine, leucine, tryptophan, phenylalanine, cysteine, ornithine, lysine, histidine, and tyrosine) were determined. B. edulis and T. equestre were revealed to be the most nutritional species, whereas F. hepatica was the poorest. The different species exhibited distinct free amino acid profiles. The quantification of the identified compounds indicated that, in a general way, alanine was the major amino acid. The results show that the analyzed mushroom species possess moderate amino acid contents, which may be relevant from a nutritional point of view because these compounds are indispensable for human health. A combination of different mushroom species in the diet would offer good amounts of amino acids and a great diversity of palatable sensations.     

Biochemical and microbial changes during the storage of minimally processed cantaloupe

The effect of storage time on pH, titratable acidity, degrees Brix, organic acids, sugars, amino acids, and color of minimally processed cantaloupe melon (Cucumis melo L. var. reticulatus Naud. cv. Mission) was determined at 4 degrees C and 20 degrees C. Changes in most of the biochemical parameters with storage time were relatively slow at the lower temperature. At 20 degrees C, a 17% loss in soluble solids and a 2-fold increase in acidity occurred after 2 days. Organic acid content also increased considerably with time at this temperature as a result of the production of lactic acid. Oxalic, citric, malic, and succinic acids were the organic acids, and glucose, fructose, and sucrose were the sugars present in the freshly cut cantaloupe. Malic acid concentration decreased concurrently with lactic acid production indicating the possible involvement of anaerobic malo-lactic fermentation along with sugar utilization by lactic acid bacteria. The effect of storage on microbial growth was determined at 4, 10, and 20 degrees C. Gram-negative stained rods grew at a slower rate at 4 degrees C and 10 degrees C than the Gram-positive mesophilic bacteria that dominated microorganism growth at 20 degrees C. Eighteen amino acids were identified in fresh cantaloupe: aspartic acid, glutamic acid, asparagine, serine, glutamine, glycine, histidine, arginine, threonine, alanine, proline, tyrosine, valine, methionine, isoleucine, leucine, phenyl alanine, and lysine. The dominant amino acids were aspartic acid, glutamic acid, arginine, and alanine. Total amino acid content decreased rapidly at 20 degrees C, but only a slight decrease occurred at 4 degrees C after prolonged storage. Changes in lightness (L), chroma, and hue at both temperatures indicate the absence of browning reactions. The results indicate the potential use of lactic acid and lactic acid bacteria as quality control markers in minimally processed fruits.     

江河源区高寒嵩草草甸土壤氨基酸成分和含量特征分析

通过高效液相色谱技术分析了青海省果洛州达日县窝赛乡原生嵩草草甸、严重退化草地及人工草地三类植被土壤中各种氨基酸成分及含量。结果表明:(1)三种类型土壤中都检测出19种常见氨基酸:精氨酸、天冬氨酸、丝氨酸、谷氨酸、苏氨酸、丙氨酸、甘氨酸、氨基丁酸、脯氨酸、蛋氨酸、缬氨酸、苯丙氨酸、异亮氨酸、亮氨酸、胱氨酸、组氨酸、鸟氨酸、赖氨酸、酪氨酸;(2)测定结果表明原生嵩草草甸土壤的氨基酸总量显著高于人工恢复重建草地和严重退化土壤氨基酸,而后两者之间差异不显著。原生高寒草地的土壤(6316.28μgg-1)严重退化草地土壤(2977.10μgg-1)人工恢复重建草地土壤(2975.90μgg-1)。(3)原生高寒草地土壤氨基酸总体呈现下降趋势:5月氨基酸含量最高,随后6月7月的显著下降,8月稍微有所回升,9月氨基酸含量到达最低;严重退化草地土壤与人工恢复重建草地土壤氨基酸含量季节变化相似,氨基酸总量在6月份到达最高点,随后7月8月显著下降,9月份稍微有所回升。     

蚕豆根系分泌物中氨基酸含量与枯萎病的关系

通过田间试验研究不同品种蚕豆枯萎病病情指数的差异,并通过水培试验鉴定蚕豆根系分泌物中氨基酸组分并测定氨基酸的含量,分析各氨基酸组分与蚕豆枯萎病病情指数的相关性。结果表明:根系分泌物中氨基酸总量随着蚕豆枯萎病抗性的降低而升高。感病品种和中抗品种中检出15种氨基酸,而抗病品种中检出14种,组氨酸只存在于中抗品种中,脯氨酸仅在感病品种中检测到,3个蚕豆品种根系分泌物中均未检出精氨酸。丝氨酸(Ser)、蛋氨酸(Met)和赖氨酸(Lys)与枯萎病病指呈负相关关系,以Ser的相关系数最高,其他13种氨基酸含量与蚕豆枯萎病的病情指数呈正相关。蚕豆根系分泌物中Ser、Met和Lys含量及Ser/Gly、Ser/Ala比值高能抑制枯萎病的发生与发展,而天门冬氨酸(Asp)、苏氨酸(Thr)、甘氨酸(Gly)、丙氨酸(Ala)、缬氨酸(Val)、酪氨酸(Tyr)、苯丙氨酸(Phe)含量高时能促进枯萎病的发生。不同蚕豆品种根系分泌的氨基酸含量与组分的差异是影响蚕豆对枯萎病抗性差异的重要原因之一。     

Rapid gastric fluid digestion and biochemical characterization of engineered proteins enriched in essential amino acids.

The barley high lysine (BHL) proteins are nutritionally enhanced derivatives of barley chymotrypsin inhibitor-2 (CI-2). A compactly folded new CI-2 derivative, BHL9, was engineered with the highest content of threonine, tryptophan, and isoleucine yet achieved in this protein family (15.1, 9.4, and 12.1 wt %, respectively). BHL9 had an unfolding midpoint of 5.5 M guanidinium chloride, significantly greater than values for wild type (3.9 M) or for the previously most stable BHL protein, BHL8 (3.6 M). BHL9 and all other derivatives were digested within 15 s in simulated gastric fluid (SGF), suggesting nutritional availability upon ingestion. Denaturation of the proteins in SGF minus pepsin was revealed by changes in their fluorescence emission spectra and/or far UV circular dichroism spectra. The proteins lack homology to known allergens. Significantly, the BHL8 and BHL9 proteins were stable to proteases at pH 7.5 or 8.0, attesting to their potential for high expression in plants.     

Effect of peduncle‐perfused nitrogen,sucrose, and growth regulators on barley and wheat amino acid composition

Abstract

Nitrogen (N) or growth regulator application to small grain cereals near anthesis has been demonstrated to alter grain fill and grain yield, the protein yield and nutritional quality may also be modified by these management factors. The objective of this study was to determine whether delivery of N, growth regulator, or sucrose solutions into greenhouse‐grown barley (Hordeurn vulgare L. cv. Leger) or wheat (Triticum aestivum L. cv. Katepwa), plants through peduncle perfusion altered the amino acid composition of the grain. The following treatments were tested: N (25 and 50 mM), chlormequat (30 μM), ethephon (15 μM), N + chlormequat, N + ethephon, detillering + N, sucrose (250 mM), distilled water check, and non‐perfused check. Perfusion lasted 30 d beginning 5 to 8 d after spike emergence. Addition of N via peduncle perfusion increased protein concentrations and concentrations of all amino acids in both barley and wheat when expressed in terms of grain dry matter. Protein yield and lysine content were also increased. However, the increase in essential amino acids such as lysine, methionine, threonine, isoleucine, arginine, and leucine was relatively small, and the proportions of these amino acids in the grain protein were actually reduced. The sucrose treatment only affected wheat, increasing lysine concentration and decreasing the total protein concentration. Growth regulators used in this study did not alter protein yield or amino acid composition in either crop.     

Total and reactive lysine contents in selected cereal-based food products

The aim of the study was to determine and compare reactive and total lysine contents in a range of breakfast cereal products. Crude fiber, fat, ash, and crude protein contents of 20 breakfast cereal products ranged from 4 to 38, 14 to 144, 7 to 32, and 52 to 253 g/kg, respectively. The concentrations of glutamic acid (18.7-32.1 g/100 g protein) and proline (4.7-10.8 g/100 g protein) were high while those of the amino acids methionine (1.2-2.0 g/100 g protein) and histidine (1.2-3.3 g/100 g protein) were relatively low. There was a strong relationship between reactive lysine determined using the guanidination and fluorodinitrobenzene methods (R = 0.99). The total lysine content, determined after conventional acid hydrolysis, ranged from 0.8 to 3.7 g/100 g protein, while the reactive lysine content (guanidination) ranged from 0.4 to 2.8 g/100 g protein. Reactive lysine was 20-54% lower than total lysine in the cereal products. The large differences between total and reactive lysine suggest a considerable loss of lysine in the breakfast cereals tested.     

Variations in Amino Acid and Protein Contents of Wheat During Milling and Northern‐Style Steamed Breadmaking

To determine the variations of amino acid and protein during milling and steamed breadmaking, two types of wheat cultivars belonging to soft and hard wheat types were used. The results showed that losses occurred in 17 amino acids during milling. The mean loss of threonine (18.0%) was the highest, which was followed by proline (15.5%), methionine (15.1%), and histidine (15.1%). The losses of tyrosine and lysine were the lowest (8.1 and 9.7%, respectively). Losses were also found for 17 amino acids during steamed breadmaking. The highest loss was observed in alanine (17.1%), with tyrosine (12.5%) close behind, and leucine (4.3%) exhibiting the lowest loss. The mean protein contents for whole‐wheat meal, flour, and steamed bread prepared from the test materials were 15.25, 14.27, and 14.33%, respectively. This meant that protein content decreased during milling; however, a slight increase was observed during steamed breadmaking. Amino acid scores of lysine in whole‐wheat meal, flour, and steamed bread prepared from the test materials were 45.4, 41.0, and 38.2, respectively. The general trend in the variations of protein and amino acids was similar in the two wheat cultivars tested.     

青藏高原青稞赖氨酸含量空间分布及其与环境因子的关系

青藏高原是地球上生态环境最复杂的地区,也是大麦的起源中心之一。为探究裸大麦(青稞)赖氨酸含量的空间分布规律及与环境因子的关系,利用农学和地理学相结合的方法,在青稞主种植区选取了83个样点数据,通过逐步回归分析法和随机森林回归分析法建立数学模型。结果表明,在地理水平方向上,形成了藏中和藏东2个青稞赖氨酸含量高值区;在地理垂直方向上,赖氨酸含量在海拔2 700 m以下和4 200 m以上分别形成2个高峰区;影响青稞赖氨酸含量的环境因素从大到小依次是土壤全氮含量年均日照时数年均降水量年均相对湿度8月平均降水量。由此可见,青稞赖氨酸含量高值分布区位于喜马拉雅山脉、冈底斯-念青唐古拉山脉、喀喇昆仑山脉交汇的高山峡谷地带,是生态环境最复杂地区,是西藏野生大麦群体发现地之一。环境对青稞赖氨酸含量有重要影响,其中最主要环境因素是土壤全氮含量、年均日照时数、年均降水量。本研究结果为青藏高原青稞育种、栽培和加工提供了科学依据。     

施用钾肥和有机肥对小麦产量、品质的影响

利用布置在河北玉田县的一个钾肥定位试验,研究了在施用氮磷化肥的基础上,施用钾肥和有机肥对小麦子粒产量、17种氨基酸、粗蛋白和粗淀粉含量的影响。结果表明,施用钾肥明显提高了小麦子粒产量,同时提高了天门冬氨酸、蛋氨酸、酪氨酸和赖氨酸的含量;施用有机肥明显提高了蛋氨酸、赖氨酸和脯氨酸的含量;钾肥和有机肥配合施用明显提高了产量、天门冬氨酸、蛋氨酸、酪氨酸和赖氨酸的含量,对上述氨基酸的提高幅度均在10%以上。施用钾肥和(或)有机肥提高了小麦子粒的氨基酸总量、粗蛋白含量,但降低了粗淀粉含量。     

Retention of essential amino acids during extrusion of protein and reducing sugars

This research investigates the retention of essential amino acid profiles of products during the extrusion of proteins and reducing sugars. Animal proteins (egg and milk protein at 10 and 30% levels) and reducing sugars (fructose and galactose at 0, 2, and 8% levels), with pregelatinized wheat flour, were extruded at 110 and 125 degrees C product temperatures and feed moistures of 19 and 23.5% for egg protein and 13.75 and 16% for milk protein. The nutritional property analyzed was essential amino acid retention, and sugar retention was also considered to understand the relationship of sugars with retention of amino acids. Lysine showed the lowest retention (up to 40%) of all the essential amino acids. Retention of other essential amino acids varied from 80 to 100% in most situations. Apart from lysine, tryptophan, threonine, and methionine were found to be significantly changed ( P < 0.05) with processing conditions. Increased protein and sugar levels resulted in a significant degradation of lysine. Greater lysine retention was found at a lower temperature and higher feed moisture. Results of sugar retention also showed similar patterns. The products made from fructose had greater lysine retention than products made from galactose with any type of protein. The outcomes of this research suggested that the combination of milk protein and fructose at a lower temperature and higher feed moisture is most favorable for developing high-protein extruded products.     

Improving nutritional quality of maize proteins by expressing sense and antisense zein genes

The predominant proteins in maize grain are a family of alcohol-soluble prolamin storage proteins called zeins. They account for >50% of total seed proteins but are deficient in several essential amino acids. As a result, the corn grain is considered to be nutritionally poor for monogastric animals with respect to key essential amino acids, most notably lysine, tryptophan, and methionine. Thus, corn mutants with reduced levels of zeins, such as opaque-2 (o2), have been demonstrated to possess grain with improved nutritional quality characteristics. The o2 mutant has a superior amino acid composition and has been used through conventional breeding to develop Quality Protein Maize (QPM) for human and animal consumption in developing countries. With the understanding of molecular genetics of zeins and progress in biotechnology, an alternative approach to zein reduction is explored here. Through the targeted reduction of the 19-kDa alpha-zeins, increased levels of lysine, tryptophan, and methionine have been engineered in grain of transgenic hybrids. Currently, the agronomic properties and nutritional values of these transgenic lines are being evaluated.     

Staling Effects When Adding Low Amounts of Normal and Heat‐Treated Barley Flour to a Wheat Bread

The properties of a white wheat bread could be changed by adding normal or heat‐treated barley flour in small amounts (2 and 4%) to a white wheat bread recipe. Differences regarding gelatinization as well as retrogradation properties were found when analyzing the two flours in model systems. The heat‐treated flour was fully gelatinized due to prior time, temperature, and pressure treatment and could therefore absorb larger amounts of water than the other flours. In gelatinized model systems with 40% flour (dwb), the heat‐treated barley flour contained less retrograded amylopectin as compared with normal barley flour after storage for up to 14 days, whereas no differences were found with 20% flour (dwb). However, stored breads showed an increased retrogradation of amylopectin (as measured by differential scanning calorimetry [DSC]) when 2% pretreated barley flour was added as compared with addition of 2% normal barley flour. On the other hand, there were no significant differences at the 4% level. Addition of either of the barley flours resulted in less firm breads during storage as compared with the control breads. Increased water absorption in barley flour and thus increased water content in the breads or different water‐binding capacities of the flour blends could explain these results. The present study indicated that water had a stronger influence on bread firmness than the retrogradation of amylopectin. This conclusion was based on breads with pretreated barley flour being less firm than breads with normal barley flour, although the retrogradation, as determined by DSC, was higher.     

Free amino acids in unhardened and cold‐hardened winter wheat crowns

The free amino acids proline and glutamic acid increased in the crown of winter wheat in all treatments when exposed to cold‐hardening. Glutamine also increased except when 90–80 N‐P fertilizer was applied. The increase of proline and glutamic acid was enhanced with the application of P but counteracted by N. This enhancement was smaller with glutamine. The decrease of threonine, tyrosine, phenylalanine, lysine and α‐aminobutyric acid with cold‐hardening was not counteracted by application of N and P. However, isoleucine in cold‐hardened winter wheat increased with the application of 180–0 fertilizer and aspartic acid increased when P was added. The increase in alanine with cold‐hardening was enhanced by P alone but counteracted by N‐P treatments. The marked increase in proline during cold‐hardening could be useful in the detection of cold‐hardiness in winter wheats.     

氨基酸部分替代硝态氮对小白菜生长、硝酸盐累积及大量元素含量的影响

A hydroponic experiment was carried out to determine the influence of replacing 20% of nitrate-N in nutrient solutions with 20 individual amino acids on growth, nitrate accumulation, and concentrations of nitrogen （N）, phosphorus （P）, and potassium （K） in pak-choi （Brassica chinensis L.） shoots. When 20% of nitrate-N was replaced with arginine （Arg） compared to the full nitrate treatment, pak-choi shoot fresh and dry weights increased significantly （P ≤ 0.05）, but when 20% of nitrate-N was replaced with alanine （Ala）, valine （Val）, leucine （Leu）, isoleucine （Ile）, proline （Pro）, phenylalanine （Phe）, methionine （Met）, aspartic acid （Asp）, glutamic acid （Glu）, lysine （Lys）, glycine （Gly）, serine （Ser）, threonine （Thr）, cysteine （Cys）, and tyrosine （Tyr）, shoot fresh and dry weights decreased significantly （P ≤ 0.05）. After replacing 20% of nitrate-N with asparagine （Asn） and glutamine （Gin）, shoot fresh and dry weights were unaffected. Compared to the full nitrate treatment, amino acid replacement treatments, except for Cys, Gly, histidine （His）, and Arg, significantly reduced （P ≤0.05） nitrate concentrations in plant shoots. Except for Cys, Leu, Pro, and Met, total N concentrations in plant tissues of the other amino acid treatments significantly increased （P ≤ 0.05）. Amino acids also affected total P and K concentrations, but the effects differed depending on individual amino acids. To improve pak-choi shoot quality, Gln and Asn, due to their insignificant effects on pak-choi growth, their significant reduction in nitrate concentrations, and their increase in macroelement content in plants, may be used to partially replace nitrate-N.