Effect of nitrogen nutrition on the free amino acid composition in tobacco plant

Nitrogen nutrition has great influences not only on the growth, but also on leaf quality of tobacco. There have been many reports on the nitrogen nutrition of tobacco, in which various nitrogen constituents such as amino acids and related compounds have been analyzed. But definite conclusions were often hard to be drawn out, since sometimes the work was limited by the failure of finding suitable chemical techniques. The recent development of paper chromatographic methods, however, has made possible to detect the individual amino acids, and has provided a new approach to the study of nitrogen nutrition of tobacco. Using the paper chromatographic techniques, the effects of nitrogen form, the effect of sulfur nutrition and excess of chlorine on free amino acid composition of tobacco leaf have been reported by the authors (1). The next step of the work presented here was undertaken for the quantitative study of the effect of nitrogen nutrition on free amino acid content of tobacco cultured for commercial purpose employing the amino acids estimation method developed by MOORE and STEIN (2) (3).     

钼、氮肥配合施用对冬小麦子粒蛋白质及其氨基酸组成的影响

盆栽试验结果表明 ,施钼和缺钼时 ,氮肥对冬小麦的增产率分别为 319.9%和 174.0% ;冬小麦子粒中蛋白氮、清蛋白氮、醇溶蛋白氮含量 ,面粉蛋白质氨基酸总量及其氨基酸组分的含量以及谷氨酸、脯氨酸的比例等随氮肥水平提高而增加 ;但冬小麦面粉中游离天门冬氨酸和苏氨酸的含量和比例降低 ,游离氨基酸含量在缺钼时提高了 38.3% ,施钼时则下降了 37.1%。在高、低氮肥水平下施钼 ,冬小麦子粒中蛋白质含量没有明显影响 ,但分子量小的蛋白质含量及其占总量的比例下降 ,清蛋白比例分别下降 14.5、6.6个百分点 ;而大分子量蛋白质含量和比例均提高。在不同施氮水平下缺钼冬小麦子粒中游离氨基酸含量比施钼分别高 48.0%和 15.26% ,且亲水性氨基酸比例增加。缺钼冬小麦子粒中低分子量蛋白质、游离氨基酸以及亲水性氨基酸的增加 ,可能是诱发缺钼冬小麦子粒低休眠度以及出现收获前萌芽的重要原因。     

Influence of glyphosate on amino acid composition of Egyptian broomrape

The parasitic plant broomrape is entirely dependent on its host for reduced carbon and nitrogen and is also susceptible to inhibition by glyphosate that is translocated to the parasite through a host. Studies were conducted to examine the effect of broomrape parasitism on amino acid concentrations of two hosts: common vetch that is tolerant of low levels of glyphosate and oilseed rape that has been genetically engineered for glyphosate resistance. The influence of glyphosate on the amino acid content of broomrape and the two hosts was also examined. Amino acid concentrations in leaves and roots of parasitized common vetch plants were generally similar to those of the corresponding tissues of nonparasitized plants. Amino acid concentrations in broomrape were lower than those of the parasitized common vetch root. For common vetch, glyphosate applied at rates that selectively inhibited broomrape growth did not alter individual amino acid concentrations in the leaves, but generally increased amino acid levels at 0.18 kg ha-1. Glyphosate application also increased the amino acid concentrations, with the exception of arginine, of broomrape growing on common vetch and did not generally influence concentrations in leaves or roots of common vetch. In oilseed rape, parasitization by broomrape generally led to higher amino acid concentrations in leaves but lower concentrations in roots of parasitized plants. Broomrape had higher amino acid concentrations than roots of the parasitized oilseed rape. Glyphosate applied at 0.25 and 0.5 kg ha-1 generally increased the amino acid concentrations in oilseed rape leaves, but the 0.75 kg ha-1 application caused the amino acid concentrations to decrease compared to those of untreated plants. In oilseed rape root the general trend was an increase in the concentration of amino acids at the two highest rates of glyphosate. Individual amino acid concentrations in broomrape attachments growing on oilseed rape were generally increased following glyphosate application of 0.25 kg ha-1. These results indicate that low rates of glyphosate alter amino acid profiles in both host and broomrape and raise questions about the regulation of amino acid metabolism in the parasite.     

Effects of conservation treatment and cooking on the chemical composition and antioxidant activity of Portuguese wild edible mushrooms

The effects of processing and cooking practices on the chemical composition and antioxidant activity of Portuguese wild edible mushroom species (Lactarius deliciosus, Macrolepiota mastoidea, Macrolepiota procera, and Sarcodon imbricatus) were investigated. Dried, frozen, and cooked samples were analyzed for proximate constituents (moisture, fat, crude protein, ash, and carbohydrates) and nutritional value. Fatty acid and sugar profiles were also obtained by gas-liquid chromatography/flame ionization detection and high-performance liquid chromatography/refraction index, respectively. The antioxidant properties were evaluated by several biochemical assays: 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity, reducing power, inhibition of beta-carotene bleaching, and inhibition of lipid peroxidation in brain tissue using thiobarbituric acid reactive substances. Results of this study show that mushroom species and processing and cooking practices are all effective determinants for either chemical composition or antioxidant properties. Cooked samples proved to have lower nutrient concentrations and lower antioxidant activities than either dried or frozen samples. In what concerns fatty acids and sugar individual profiles, only cooking proved to be relevant: The cooked samples presented higher monounsaturated fatty acid and lower polyunsaturated fatty acid and sugars contents.     

Modeling protein functional properties from amino acid composition

Physicochemical and functional properties of proteins were modeled as a function of the contributions of each of the 20 coded amino acids to three (z-scores) or five (extended z-scores) amino acid principal properties using partial least squares regression. The five term models were in all cases stronger in both fit and prediction than the three term models, indicating that useful information is contained in the fourth and fifth property scores. Models predicting protein hydrophobicity (R = 0.932), viscosity (R = 0.737), and foam capacity (R = 0.880) from amino acid composition rather than sequence were obtained. It is likely that additional functional and physicochemical properties of proteins can be modeled in this way.     

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.     

Chemical composition of some wild peanut species (Arachis L.) seeds

Oil, protein, ash, and carbohydrate contents, iodine value, and fatty acid and sterol compositions were studied in seeds of Arachis trinitensis, A. chiquitana, A. kempff-mercadoi, A. diogoi, A. benensis, A. appressipila, A. valida, A. kretschmeri, A. helodes, A. kuhlmannii, A. williamsii, A. sylvestris, A. matiensis, A. pintoi, A. hoehnei, A. villosa, and A. stenosperma. Oil content was greatest in A.stenosperma (mean value = 51.8%). The protein level was higher in A. sylvestris (30.1%) and A. villosa (29.5%). Mean value of oleic acid varied between 30.6% (A. matiensis) and 46.8% (Arachis villosa), and linoleic acid oscillated between 34.1% (A. villosa) and 47.4% (A. appressipila). The better oleic-to-linoleic (O/L) ratio was exhibited by A. villosa (1.38). Some species showed higher concentration of behenic acid. The greatest level of this fatty acid was found in A. matiensis (6.2%). Iodine value was lower in A. valida (99.2). The sterol composition in the different peanut species showed higher concentration of beta-sitosterol (mean values oscillated between 55.7 and 60.2%) followed by campesterol (12.4-16. 5%), stigmasterol (9.7-13.3%), and Delta(5)-avenasterol (9.7-13.4%). The chemical quality and stability of oils (iodine value and O/L ratio) from wild peanut studied in this work are not better than those of cultivated peanut.     

Plant capture of free amino acids is maximized under high soil amino acid concentrations

Free amino acids (AA's) represent a significant source of available N for some plants and soil microorganisms. It can be expected, however, that significant competition will exist between plants and microorganisms for this organic N resource. Our study indicated that microbial capture and utilization of glycine was very rapid at a range of soil solution concentrations (0.1 μM to 10 mM) indicating that significant competition will exist between roots and soil microorganisms. Plant capture of free AA's was maximal at high soil solution concentrations where microbial utilization was slowest. Our results suggest that plant capture of soil dissolved organic N may primarily occur in organic rich patches in soil where concentrations of free AA's are high.     

Antioxidant activity and phenolic composition of wild, edible, and medicinal fennel from different Mediterranean countries

Fennel (Foeniculum vulgare Mill.) is a typical aromatic plant of the Mediterranean area, long used as a medicinal and spice herb. Fennel is also well-known for its essential oil, which has been extensively studied for many years owing to its commercial importance. In this work, the antioxidant activity and the total phenolic and flavonoid contents, as well as the quantitative determination of individual flavonoids and phenolic acids of wild, edible, and medicinal fennel from different Mediterranean countries, have been determined. The antioxidant activity was measured as the free radical (DPPH), hydroxyl radical, and superoxide anion scavenging activities. Wild fennel was found to exhibit a radical scavenging activity, as well as a total phenolic and total flavonoid content, higher than those of both medicinal and edible fennels.     

Comparative effectiveness of several d‐amino acid oxidases

Abstract

Inherent complexity and instability of enzyme preparations make deceptively‐simple enzymic methods more vulnerable to error than methods using pure stable chemicals. Hence, four D‐amino acid oxidase (DAAO) preparations from three commercial sources were compared for enzymatic effectiveness. Per unit of claimed activity, the four DAAO enzyme preparations differed by <2 to >100 fold in apparent ability to oxidize “reactive”; ¹⁴C‐D‐methionine and “unreactive”; ¹⁴C‐D‐lysine in pure solution. The data illustrate how use of such differing preparations on less‐pure soil or plant extracts, which may contain unknown amounts of enzyme‐inhibiting or ‐inactivating components, would produce confounding results and permit erroneous conclusions. Implications are that users of commercially available DAAO preparations must acquire large enough lots of homogenous enzyme to establish effectiveness on the most resistant substrates of interest and still have enough for all experimental assays where direct relative comparisons are required.     

Soil amino acid composition quantified by acid hydrolysis and anion chromatography-pulsed amperometry

Soil organic N accounts for 95-98% of the total soil N content with amino acids (AAs) and amino sugars (ASs) identified as the major soil organic N compounds, but traditional 6 M HCl with reflux or sealed digestions for 24 h and various detection systems have accounted for only 30-40% of soil total N content as AA-N. This study compared traditional HCl extraction methodology with methanesulfonic acid (MSA) hydrolysis and nonderivatized AA and AS quantification by ion chromatography with pulsed amperometric detection for determination of the AA composition of plant litter and soils. MSA (4 M) gave AA-N recovery comparable to or better than 6 M HCl for plant AA digestions (16 h, 121 degrees C, 104 kPa). Use of 4 M MSA (0.5-1.5 h, 136 degrees C, 112 kPa) increased the total recovery of organic N as AAs, ASs, and NH(4)(+) by 46% from soils (n = 22) compared with 6 M HCl (12 h, 110 degrees C, reflux) with a MSA recovery rate of 85.6% of the total N content (n = 22 soils). The shorter MSA soil digestions (0.5-1.5 h) suggested that the majority of soil organic N was not present as protein forms found in plant litter analysis (16 h of digestion). MSA ion chromatographic analysis for soil AA/AS composition is a robust nonderivatization method requiring little sample preparation that can distinguish between small changes in soil AA composition during one growing season due to vegetation and tillage managements.     

Antioxidant characterization of some Sicilian edible wild greens

Epidemiological studies have demonstrated that many antioxidants and the total antioxidant capacity (TAC) of the diet may protect against cancers and cardiovascular disease. Common fruits and vegetables are good sources of antioxidants, although in some Mediterranean areas traditional wild greens are responsible for a significant percentage of total dietary antioxidant intake. In the European Prospective Investigation into Cancer and Nutrition cohort of Ragusa (Sicily), a high number of subjects were found to frequently eat wild greens, including Sinapis incana and Sinapis nigra, Diplotaxis erucoides, Cichorium intybus, Asparagus acutifolius, and Borrago officinalis. On the basis of these observations, detailed characterization of single antioxidant components (i.e., polyphenols, carotenoids, chlorophylls, and ascorbic acid) and the TAC of these edible wild traditional plants was performed. The wild plants examined were found to be very rich in antioxidants, such as flavonoids and carotenoids, with high TAC values, suggesting that the importance of these vegetables, not only in the traditional but even in the contemporary diet, needs to be emphasized.     

Plant species affect the concentration of free sugars and free amino acids in different types of soil

Substantial amounts of low molecular weight organic compounds (LMWs) such as sugars and amino acids are transferred from plant roots into soil. These substances are released due to decomposition processes or leaching (exudation). Afterwards they can be metabolized by soil microorganisms into different compounds, or they can be partially re‐absorbed by the plants. The aim of this study was to clarify the influence of five wild plant species on the composition and pool sizes of LMWs extractable from three different soils. Four of the five species caused significant changes in soil LMW pools. In Chernozem, the sugar concentrations of soil with plants were up to 60 % higher than those of the bulk reference soil, and amino acids increased by as much as 207 %. The relative abundance of free amino acids in roots did not correlate with the relative abundance of amino acids in soil after six weeks of plant growth. The relative abundance of soil amino acids, that increased after plant growth, was strongly dependent on the type of soil and on the plant species present. We suggest that rather than rhizodeposition being dependent on soil type, it reflects differential microbial metabolization of amino acids in the respective soils.     

Discriminating significance of the free amino acid profile in almond seeds

Known statistical techniques have been applied to the free amino acid composition of 107 samples from 10 different almond cultivars (Marcona, Desmayo-Largueta, Guara, Tuono, Ferragnes, Masbovera, Non Pareil, Titan, Texas, and Primorskyi) cultivated in seven different locations and growing conditions. It is concluded that free amino acid composition can constitute a basis for classifying and typifying these cultivars into five groups: (1) Marcona and Texas, (2) Ferragnes and Masbovera (and probably Primorskyi), (3) Tuono and Guara, (4) Non Pareil (and probably Titan), and (5) an isolated cultivar (Desmayo Largueta). As a result, an easy decision tree is proposed to discriminate the cultivar of an almond flour, as used in confectionery, if it consists of a single cultivar.     

Soil amino acid composition across a boreal forest successional sequence

Soil amino acids are important sources of organic nitrogen for plant nutrition, yet few studies have examined which amino acids are most prevalent in the soil. In this study, we examined the composition, concentration, and seasonal patterns of soil amino acids across a primary successional sequence encompassing a natural gradient of plant productivity and soil physicochemical characteristics. Soil was collected from five stages (willow, alder, balsam poplar, white spruce, and black spruce) of the floodplain successional sequence on the Tanana River in interior Alaska. Water-extractable amino acid composition and concentration were determined by HPLC. Irrespective of successional stage, the amino acid pool was dominated by glutamic acid, glutamine, aspartic acid, asparagine, alanine, and histidine. These six amino acids accounted for approximately 80% of the total amino acid pool. Amino acid concentrations were an order of magnitude higher in coniferous-dominated late successional stages than in early deciduous-dominated stages. The composition and concentration of amino acids were generally constant throughout the growing season. The similar amino acid composition across the successional sequence suggests that amino acids originate from a common source or through similar biochemical processes. These results demonstrate that amino acids are important components of the biogeochemical diversity of nitrogen forms in boreal forests.     

Basic composition and amino acid contents of mushrooms cultivated in Finland

The basic composition (moisture, total carbohydrates, dietary fiber, crude fat, ash, nitrogen, and protein) and amino acid contents were determined in the cultivated mushrooms Agaricus bisporus/white, Agaricus bisporus/brown, Lentinula edodes, and Pleurotus ostreatus. In addition, nitrogen-to-protein conversion factors were calculated for each species by dividing the sums of amino acid residues with total (Kjeldahl) nitrogen contents. The dry matter contents of mushrooms varied from 7.7% to 8.4%. The dry matter of mushrooms contained large amounts of carbohydrates, from 4.5 (A. bisporus/white) to 5.8 g/100 g fresh weight (L. edodes). L. edodes proved to be an especially good source of dietary fiber (3.3 g/100 g fresh weight); the other mushrooms contained 1.5-2.4 g/100 g fresh weight. Crude fat, ash, and protein (based on amino acid analysis) contents of the mushrooms varied 0.31-0.35, 0.49-0.78, and 1.8-2.09 g/100 g fresh weight, respectively. Mushrooms proved to be good sources of almost all essential amino acids when compared with common vegetables. The mean nitrogen-to-protein conversion factor analyzed in the present study was 4.7 +/- 0.21. When using this factor, a very good estimation of protein contents could be obtained for the main species of mushrooms cultivated in Finland.