Effects of combined nitrogen on anapleurotic carbon assimilation and bleeding sap composition in Phaseolus vulgaris L.

Dwarf french beans, Phaseolus vulgaris L., were grown with or without inoculation with rhizobia (strain 3644), and with or without a combined nitrogen source (nitrate or ammonium ions). The distribution of radioactivity into products of dark ¹⁴CO₂ assimilation was studied in roots or nodules from these plants. A detailed study was also made of the distribution and rates of excretion of nitrogen in xylem bleeding sap in 28 day old plants grown on the various sources of nitrogen. Whereas detached nodules accumulated radioactive glycine, serine and glutamate when incubated with ¹⁴CO₂, bleeding sap from plants root fed ¹⁴CO₂ contained low levels of radioactivity in these compounds but higher levels in allantoin. Chemical analysis showed allantoin to be the major compound transported in the xylem of nodulated plants, whether or not they were fed on combined nitrogen. In contrast uninoculated plants accumulated mainly amino acids in the bleeding sap, the amount and chemical composition of which depended on the combined nitrogen source.Abbreviations PEP phosphoenol pyruvate - OAA oxaloacetate     

Seasonal changes in the free amino acids of oat and barley phloem sap in relation to plant growth stage and growth of Rhopalosiphum padi

The concentrations and composition of free amino acids in phloem sap from two cultivars of oats and barley, both susceptible to the aphid Rhopalosiphum padi, were determined by means of high performance liquid chromatography. Sap was collected from excised aphid stylets at three developmental stages (seedlings, tillering plants and plants undergoing stem elongation) from plants given or not given fertiliser and grown outdoors. In connection, the growth of individual R. padi nymphs was estimated at the same phenological stages on plants grown in the greenhouse. The content of free amino acids was consistently higher in seedlings than in plants at the early tillering stage. Only in seedlings did the addition of fertiliser increase amino acid levels. Barley phloem sap contained more free amino acids than that of oats when fertiliser was added and at later developmental stages. Phloem sap of oats and barley showed similar patterns in their composition of free amino acids at the seedling stage, but as the plants grew older the patterns became increasingly different. Plants given fertiliser had higher amounts of dicarboxylic amino acids (glutamic and aspartic acid) than unfertilised plants. The concentrations of γ-amino butyric acid, glycine, histidine, and methionine were very low in all treatments. The relative growth rates of R. padi nymphs were low when amino acid content was low and vice versa. The results are discussed in relation to host plant suitability and plant resistance mechanisms.     

Transport and Partitioning of CO(2) Fixed by Root Nodules of Ureide and Amide Producing Legumes

Nodulated and denodulated roots of adzuki bean (Vigna angularis), soybean (Glycine max), and alfalfa (Medicago sativa) were exposed to ¹⁴CO₂ to investigate the contribution of nodule CO₂ fixation to assimilation and transport of fixed nitrogen. The distribution of radioactivity in xylem sap and partitioning of carbon fixed by nodules to the whole plant were measured. Radioactivity in the xylem sap of nodulated soybean and adzuki bean was located primarily (70 to 87%) in the acid fraction while the basic (amino acid) fraction contained 10 to 22%. In contrast, radioactivity in the xylem sap of nodulated alfalfa was primarily in amino acids with about 20% in organic acids. Total ureide concentration was 8.1, 4.7, and 0.0 micromoles per milliliter xylem sap for soybean, adzuki bean, and alfalfa, respectively. While the major nitrogen transport products in soybeans and adzuki beans are ureides, this class of metabolites contained less than 20% of the total radioactivity. When nodules of plants were removed, radioactivity in xylem sap decreased by 90% or more. Pulse-chase experiments indicated that CO₂ fixed by nodules was rapidly transported to shoots and incorporated into acid stable constituents. The data are consistent with a role for nodule CO₂ fixation providing carbon for the assimilation and transport of fixed nitrogen in amide-based legumes. In contrast, CO₂ fixation by nodules of ureide transporting legumes appears to contribute little to assimilation and transport of fixed nitrogen.     

淹涝胁迫对水稻生育后期的生理特性和产量性状的影响

比较研究了水稻（湘中灿３号）在生育后期（孕穗期和乳熟期）进行没顶淹水胁拓处理后几个相关的生理指标和生长发育、产量的形态指标。研究结果显示水稻受淹后完全伸展叶片净光合速率降低,叶绿素含量在孕穗期明显降低,但在乳熟期只有少量下降。电导率明显增加,细胞膜透性增大,脯氨酸含量增加。奶系伤流量和,根系活力降低经与中群伤流液中的主要基酸如Ａｌａ,ＯＰｒｏ,Ｐｈｅ的含量增加,根系伤流量减少,根系活力降低,伤流液     

GROWTH AND METABOLISM OF THE EMBRYO AND ATTACHED SEEDLING OF THE VIVIPAROUS MANGROVE,RHIZOPHORA MANGLE

Fruits of Rhizophora mangle were collected at various stages of development, separated into fruit wall, testa, and embryo or seedling. Wet weight, dry weight, and percent water content was determined for each. All parts of the fruit showed a similar growth pattern with a period of rapid exponential growth during the first 100 days, followed by a period of slower growth after the radicle-hypocotyl axis emerged through the fruit wall. In the final 45 days of seedling attachment the fruit wall and testa did not grow, and seedling growth rate was further reduced. Water content of the fruit wall was constant at 65 % throughout development; that of the testa decreased uniformly from 60 to 54%; embryo water content was uniformly 80%. In the germinated seedling, water content declined progressively to 58 % by the time detachment occurred. Growth of isolated seedlings in sterile culture was not responsive to inhibition by abscisic acid or to stimulation by benzyl adenine, and these hormones had no effect on incorporation of ³H-amino acids into protein or of ³H-uridine into RNA. These results are interpreted in relation to a theory which proposes that development of water stress in the seed is the signal for the inception of dormancy.     

Effects of applied nitrogen upon aspects of nitrogen metabolism and transport in developing nodulated winged bean plants

Nodulated winged bean [Psophocarpus tetragonolobus (L.) DC., cv. UPS 122] were grown under constant environmental conditions and supplied with mineral nutrient solution in which nitrogen was absent or was present as nitrate (12 mg N week^-1 plant^-1). Nitrate treatment dramatically promoted plant growth, increased fruit weight 1.6 fold, was necessary for tuberisation and enhanced nodulation. The in vitro accumulation of ¹⁴C into asparagine and aspartate components of excised nodules supplied with exogenous ¹⁴CO₂ and [¹⁴C]-D-glucose was greater for nitrate-treated plants, whilst accumulation into ureides was reduced by nitrate treatment. Levels of amino acids in xylem sap were greater for plants supplied with a complete nutrient solution, than those grown without applied nitrate, particularly for asparagine, glutamine and proline. Xylem ureide levels were greater for plants grown in the absence of supplementary nitrate. Nitrogen accumulated in leaf, stem and petiole, and root nodule tissues for utilisation during fruit development; peak nitrogen levels and time of anthesis were retarded for plants grown without applied nitrate. The shoot ureide content increased during fruiting, coincident with decreases in the total nitrogen content, indicating that ureide pools are not utilised during the early reproductive phase. However ureide reserves, particularly allantoin, were utilised during the later stages of pod fill. Enzyme activity which metabolised asparagine was found throughout the plant and was identified as K⁺-dependent asparaginase (EC 3.5.1.1) and an aminotransferase. Apart from temporal differences in developmental profiles of enzyme activity, the activity of these enzymes and of allantoinase (EC 3.5.2.5) in developing tissues were similar for both treatments. The main differences were greater asparaginase and asparagine:pyruvate aminotransferase activities in root tissues and fruit of nitrate-supplied plants; allantoinase activity in the primary roots of plants grown without nitrate decreased during development, whilst activity in developing tubers (nitrate-supplied plants) increased.     

Amino acid composition of vascular sap of maize ear peduncle

The amino acid composition of the vascular sap of a high lysine maize mutant was determined during kernel development. With the exception of proline and cystine, all amino acids that occur in the endosperm were found in the vascular sap of the ear peduncle. Glutamine is the major amino acid transported to the endosperm varying from 30.6 to 20.6 μmol at 7 and 42 days after pollination, respectively. Aspartic acid, the second most important nitrogen form translocated to the seeds, was ca 10 μmol% during kernel filling. Glutamine and arginine content decreased with maturity, while valine, methionine, isoleucine, leucine, tyrosine and phenylalanine increased with kernel development. The remaining N forms were constant during endosperm growth.     

苹果果实香气产生过程中氨基酸和脂肪酸含量及一些相关酶活性的变化

研究了苹果果实成熟期间香气和乙烯的产生动态,以及游离氨基酸、游离脂肪酸含量和脂氧合酶(LOX)、醇-酰基转移酶(AAT)活性的变化.结果表明,果实香气物质是随着乙烯释放的增加而产生和增加的.在此过程中,异亮氨酸大量积累.游离脂肪酸在果实香气很少时呈增加趋势;随着香气产生的增多而迅速下降;乙烯高峰过后又有增加.脂氧合酶活性随着果实成熟而提高,其活性在乙烯释放达到高峰时达到最大值,之后迅速下降.醇-酰基转移酶活性在果实开始产生香气时迅速增加,之后保持较高活性.     

Rhizobium strain effects on yield and bleeding sap amino compounds in Pisum sativum

Bleeding sap composition, dry matter production and nitrogen distribution in pea ( Pisum sativum L. cv. 'Bodil') grown with and without nitrate and nodulated with either Rhizobium leguminosarum strain 128c53 or strain 1044 were compared. Nitrate increased the total dry matter production of both symbioses, but decreased both the proportions of below-ground dry matter to total dry matter production and nodule dry matter to total below-ground dry matter production. The total dry matter yield and N-accumulation was greater in the symbiosis with strain 1044, whereas the accumulation of N in the roots plus nodules relative to the total N-accumulation was greater with strain 128c53 due to a higher production of nodule tissue. The root bleeding sap of the symbiosis with the greater yield (strain 1044) contained high levels of asparagine and aspartic acid. In the 128c53 symbiosis, glutamine plus bomoserine accounted for a higher percentage of the organic solutes transporting newly assimilated nitrogen from the root system than in the association with 1044. The Rhizobium strain effect on amino compound composition of the bleeding sap may indicate an influence of the bacteroids on either the N-assimilatory enzyme system in the plant cytosol, or on the pools of the Krebs cycle intermediates or related compounds in the nodules.     

Studies on the Nitrogen Metabolism in Tobacco Plants. A.

The nitrogenous compounds of tobacco saps have been studied both qualitatively and quantitatively and the following results were obtained.

(1) Nitrate nitrogen accounts for 40 to 70% of the total nitrogen and the rest is composed mostly of amino and alkaloid nitrogen.

(2) Amides and basic amino acids compose a large part of the amino and amide nitrogen. Among the amino acids and amides of the tobacco saps glutamine is the highest in the content and asparagine, lysine, leucine and serine follow glutamine.

(3) Topping procedure increased remarkably the alkaloid contents in the sap but decreased the amino acid nitrogen as compared with those of the untopped plant sap.     

Role of antioxidative system during the development and senescence of cucumber fruit

The oxidative processes and antioxidative system in cucumber (Cucumis sativus L.) fruit were determined during development and senescence. Four distinct developmental stages could be delineated during fruit maturation: immature (3–8 d after anthesis, DAA), mature (9–16 DAA), breaker (17–22 DAA), and yellow (35–40 DAA). The electrolyte leakage, malondialdehyde content, superoxide anion production rate, and hydrogen peroxide content increased continuously during fruit development and senescence. Superoxide dismutase and peroxidase activities consistently increased during fruit maturation, and the catalase activity displayed a single peak at the mature stage. Ascorbate peroxidase and glutathione reductase activities declined during fruit development, but both were activated in yellow fruit. Monodehydroascorbate reductase activity declined and dehydroascorbate reductase (DHAR) activity increased during fruit growth. DHAR was repressed in yellow fruit. Ascorbate dramatically accumulated and its redox state increased, whereas glutathione was degraded and its redox state declined, with fruit maturation.     

Nodule growth and activity may be regulated by a feedback mechanism involving phloem nitrogen*

We present a mechanism of regulation of growth and activity of legume root nodules which is consistent with published experimental observations. The concentration of reduced nitrogen compounds, probably amino acids, flowing into the nodules from the phloem, is sensed by the nodules; growth and activity of the nodules is adjusted accordingly. In many legumes this response may involve changes in the oxygen diffusion resistance of the nodule cortex. A straightforward feedback mechanism in which nodule activity is lowered when reduced N in the phloem is high and increased when it is low is envisaged. Almost all import into nodules is via the phloem sap originating in the lower leaves. As a plant develops, these mature leaves no longer utilize nitrogen delivered in the xylem and so export it in the phloem. In plants with an adequate nitrogen supply (from nodules or combined nitrogen in soil), a high concentration of nitrogen containing compounds in the phloem from the lower leaves may inhibit nodule growth as well as activity. This suggestion is an alternative to the hypotheses of carbohydrate deprivation or nitrate inhibition which are commonly used to explain the effects of combined nitrogen on nodule growth and activity.     

Metabolic profiling of strawberry (Fragaria x ananassa Duch.) during fruit development and maturation

Strawberry (Fragaria × ananassa Duch), a fruit of economic and nutritional importance, is also a model species for fleshy fruits and genomics in Rosaceae. Strawberry fruit quality at different harvest stages is a function of the fruit's metabolite content, which results from physiological changes during fruit growth and ripening. In order to investigate strawberry fruit development, untargeted (GC-MS) and targeted (HPLC) metabolic profiling analyses were conducted. Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were employed to explore the non-polar and polar metabolite profiles from fruit samples at seven developmental stages. Different cluster patterns and a broad range of metabolites that exerted influence on cluster formation of metabolite profiles were observed. Significant changes in metabolite levels were found in both fruits turning red and fruits over-ripening in comparison with red-ripening fruits. The levels of free amino acids decreased gradually before the red-ripening stage, but increased significantly in the over-ripening stage. Metabolite correlation and network analysis revealed the interdependencies of individual metabolites and metabolic pathways. Activities of several metabolic pathways, including ester biosynthesis, the tricarboxylic acid cycle, the shikimate pathway, and amino acid metabolism, shifted during fruit growth and ripening. These results not only confirmed published metabolic data but also revealed new insights into strawberry fruit composition and metabolite changes, thus demonstrating the value of metabolomics as a functional genomics tool in characterizing the mechanism of fruit quality formation, a key developmental stage in most economically important fruit crops.     

性腺发育不同阶段野生瓯江凤鲚肌肉营养成分的分析与评价

研究旨在针对不同性腺发育阶段(Ⅰ期、Ⅱ期、Ⅲ期、Ⅳ期、Ⅴ期)野生瓯江凤鲚(Coiliamystus)性腺发育情况和肌肉营养成分进行分析与评价。研究表明:在雌、雄野生瓯江凤鲚性腺从Ⅰ期发育至Ⅴ期的过程中,成熟系数呈现上升趋势,凤鲚卵巢的GSI值是精巢GSI值的5倍。在卵巢发育Ⅰ—Ⅴ期,粗脂肪含量显著下降,粗蛋白和水分显著上升(P<0.05);在精巢发育Ⅰ—Ⅴ期,粗脂肪含量显著上升,粗蛋白和水分显著下降(P<0.05),灰分含量先升后降,说明野生瓯江凤鲚在卵巢发育过程中脂肪为主要供能物质。雌凤鲚肌肉在卵巢发育Ⅰ—Ⅴ期显著上升(P<0.05),雄凤鲚肌肉氨基酸含量在精巢发育Ⅰ—Ⅴ期显著下降(P<0.05)。但各性腺发育阶段氨基酸组成相对稳定,雌、雄鱼肌肉总必需氨基酸/总氨基酸分别为(37.88±0.32)%—(41.66±0.44)%和(40.30±0.69)%—(40.94±0.29)%。依据氨基酸评分(AAS)和化学评分(CS)标准,不同性腺发育阶段的野生瓯江雌、雄凤鲚肌肉中第一限制性氨基酸均为色氨酸,第二限制性氨基酸均为甲硫氨酸(Met)和胱氨酸(Cys)。在卵...     

Carbon Metabolism, Nitrogen Assimilation, and Seed Yield of Cowpea (Vigna unquiculata L. Walp.) Grown in an Adverse Temperature Regime

When grown in an environment known not to favour the productionof large seed yields (warm days-cool nights; 33–19 °C),non-nodulated plants of cowpea cv. K 2809 supplied with abundantinorganic nitrogen not only assimilated N more rapidly but alsoproduced larger total dry weights and seed yields than plantsdependent on Rhizobium CB 756. Remobilization of nitrogen fromvegetative organs started sooner in nitrate-dependent than innodulated plants and contributed 69 and 47%, respectively, tothe N content of mature fruits. Plants dependent on nodulesrelied more on current assimilation of nitrogen during the laterstages of fruit growth than those given inorganic N; they alsoutilized a larger proportion of shoot-derived photosynthatesin growth of organs below ground and in the respiratory activitiesof both nodules and supporting roots. Although nitrate-dependentplants developed larger shoot systems than those relying onnodules, the distribution of carbon and nitrogen to leaves decreasedmarkedly as branches extended during early reproductive growth.The respiration of roots on nodulated plants became more efficientduring the later stages of fruit growth whereas the populationof secondary nodules present at this stage of development respiredless efficiently (mg C consumed per mg N assimilated) than theprimary nodules present earlier during development.     

Changes in γ-Methyleneglutamic acid, γ-Methyleneglutamine and other amino acids and amides during fruit growth of Tribulus terrestris

Abstract

Distribution and metabolism of γ-methyleneglutamic acid, γ-methyleneglutamine and other amino acids and amides has been studied during fruit growth of Tribulus terrestris. The largest concentration of free amino acids and amides has been observed in fruit stage 1. The marked decline in the amount of γ-methyleneglutamic acid and γ-methyleneglutamine after fruit stage 1 may indicate their rapid utilization along with asparagine and glutamine during fruit growth. In leaf and in different fruit growth stages, γ-methyleneglutamic acid dominated over γ-methyleneglutamine.     

IAA, ABA, polyamines and free amino acids associated with zygotic embryo development of Ocotea catharinensis

The aim of this work was to study morphological and biochemical aspects during zygotic embryogenesis in O. catharinensis, by measuring changes in the endogenous concentrations of proteins, amino acids, polyamines (PAs), indole-3-acetic acid (IAA) and abscisic acid (ABA). Buffer-soluble and insoluble protein contents were determined by spectrometry, and amino acids, PAs, IAA and ABA concentrations were determined by high performance liquid chromatography. Total amino acid accumulation, predominantly asparagine, occurred when the embryo showed completely developed cotyledons, with posterior reduction in the mature embryo. This decrease in total amino acid concentration in the mature embryo may result from their use in storage␣as well as for LEA protein synthesis. Free putrescine (Put) concentration decreased, while free spermine (Spm) increased during embryo development. This suggest a role for Put in the initial phases of embryogenesis when high rates of cell division occur, while elevated concentration of Spm are essential from the middle to the end of embryo development, when growth is mainly due to cell elongation. An IAA peak in zygotic embryos occurred during initial development, suggesting a link between growth and cellular division as well as with the establishment of bilateral symmetry. ABA concentration declined during initial stages of development then increased at the mature embryo stage, suggesting a possible relationship with dormancy and recalcitrance characteristics. Our results show that changes in the phytohormones (IAA, ABA and PAs) concentrations in combination with amino acids are likely important factors determining the developmental stages of O.␣catharinensis zygotic embryos.     

Nitrogen Nutrition and Xylem Sap Composition of Peanut (Arachis hypogaea L. cv Virginia Bunch)

The principal forms of amino nitrogen transported in xylem were studied in nodulated and non-nodulated peanut (Arachis hypogaea L.). In symbiotic plants, asparagine and the nonprotein amino acid, 4-methyleneglutamine, were identified as the major components of xylem exudate collected from root systems decapitated below the lowest nodule or above the nodulated zone. Sap bleeding from detached nodules carried 80% of its nitrogen as asparagine and less than 1% as 4-methyleneglutamine. Pulse-feeding nodulated roots with ¹⁵N₂ gas showed asparagine to be the principal nitrogen product exported from N₂-fixing nodules. Maintaining root systems in an N₂-deficient (argon:oxygen, 80:20, v/v) atmosphere for 3 days greatly depleted asparagine levels in nodules. 4-Methyleneglutamine represented 73% of the total amino nitrogen in the xylem sap of non-nodulated plants grown on nitrogen-free nutrients, but relative levels of this compound decreased and asparagine increased when nitrate was supplied. The presence of 4-methyleneglutamine in xylem exudate did not appear to be associated with either N₂ fixation or nitrate assimilation, and an origin from cotyledon nitrogen was suggested from study of changes in amount of the compound in tissue amino acid pools and in root bleeding xylem sap following germination. Changes in xylem sap composition were studied in nodulated plants receiving a range of levels of ¹⁵N-nitrate, and a ¹⁵N dilution technique was used to determine the proportions of accumulated plant nitrogen derived from N₂ or fed nitrate. The abundance of asparagine in xylem sap and the ratio of asparagine:nitrate fell, while the ratio of nitrate:total amino acid rose as plants derived less of their organic nitrogen from N₂. Assays based on xylem sap composition are suggested as a means of determining the relative extents to which N₂ and nitrate are being used in peanuts.