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1.
Vitamin B12-deficiency may induce specific symptoms as neurological alterations and unspecific symptoms such as anaemia and growth retardation. In this study, maternal vitamin B12 deficiency from end of gestation to weaning was evaluated in mouse dams, which was provoked by feeding a vitamin B12-deficient diet. The animals were divided into two groups (control and deficient). The control group received the vitamin B12-deficient diet supplemented with commercial vitamin B12. Compared to the control, the vitamin B12-deficient dams and their offspring showed a significant decrease of body weight (by 20 and 39%, respectively), serum vitamin B12 concentration (by 61 and 67%, respectively), haematological values as haematocrit (25 and 26%, respectively), and IgA producer cells (by 36 and 54%, respectively). In both, vitamin B12-deficient mouse dams and their offspring, histological alterations of small intestine were observed, whereas growth retardation occurred in the offspring only. This experimental murine model allows assessing the incidence of maternal cobalamin deficiency in offspring and would be useful for evaluating novel adjuncts such as functional foods to prevent vitamin B12 deficiency.  相似文献   

2.
Partial purification of gibberellin oxidases from spinach leaves   总被引:3,自引:1,他引:2       下载免费PDF全文
Four enzyme activities catalyzing the following oxidative steps in the gibberellin (GA) biosynthetic pathway have been extracted from spinach (Spinacia oleracea L.) leaves after exposure to 8 long days: GA12 → GA53 → GA44 → GA19 → GA20. Two of these, GA53 oxidase and GA19 oxidase, were separable from the other two, GA44 oxidase and GA12 13-hydroxylase, by anion exchange high performance liquid chromatography (HPLC). Apparent molecular weights of the four enzymes as determined by gel filtration HPLC are: GA12 13-hydroxylase, 28,400; GA53 oxidase, 42,500; GA44 oxidase, 38,100; GA19 oxidase, 39,500. GA44 oxidase was purified approximately 100-fold in 0.3% yield by a combination of ammonium sulfate fractionation, anion exchange HPLC, phenyl-Sepharose chromatography and gel filtration HPLC.  相似文献   

3.
The maximum yield of lytic enzyme was obtained from shake flask cultures of Streptomyces globisporus 1829 which were grown at 30°DC for 48 hr in a medium containing 2% dextrin, 0.5% soybean meal, 0.2% polypeptone, 0.5% Na2HP04. 12H20, 0.1% KH2P04, 0.1% MgS04·7H20, 1.0% NaCI and 0.02% CaCl2, pH 7.5. The activity of successively transferred substrains of St. globisporus 1829 gradually decreased. However, a mutant strain obtained by ultra-violet irradiation has been shown not to have lost any lytic activity for 2 years. The enzyme exhibited maximum activity at 60°C in the pH range of 6 to 6.5 and was lytic against the intact cells of Streptococci, Lactobacilli and Bacilli but inert against the intact cells of Staphylococcus aureus and Micrococcus lysodeikticus.  相似文献   

4.
Epicuticular waxes from whole plants of Agropyron dasystachyum var. psammophylum, A. riparium and A. elongatum contain hydrocarbons (5–8 %), long chain esters (12–15%) and free acids (2–5%). The major esters are C34C56 esters derived from C16C30 acids and alcohols (1-hexacosanol is the major alcohol) but C31, C33 and C35 esters (3–11%) are also present. The latter esters are C18 and C20 acid esters of C13 and C15 2-alkanols. A. dasystachyum wax contains 2% free alcohols, that of A. riparium contains 17% and that of A. elongatum 11% (1-hexacosanol is the major alcohol in each). Diesters (2%), C8C12 diols esterified by (E)-2-alkenoic acids, are present in A. riparium wax. Hentriacontane-14,16-dione is present: 29% in A. dasystachyum wax and 32% in A. riparium wax, but only 5% in A. elongatum wax. 25-Oxohentriacontane-14,16-dione forms 14% of A. dasystachyum wax and 27% of A. elongatum wax but the oxo β-diketones of A. riparium wax (5%) consist of both 10-oxo- and 25-oxohentriacontane-14,16-diones in the ratio 4:1. Hydroxy β-diketones of the waxes are 25- and 26-hydroxyhentriacontane-14,16-diones; in A. dasystachyum (20%) the ratio is 3:1, in A. elongatum (20%) the ratio is 9:1 but in A. riparium (5%) it is ca 1:2. The configuration of the hydroxyl group in the 26-hydroxy β-diketone is opposite to that in the 25-hydroxy derivative. The unusual composition of the oxygenated β-diketones of A. riparium confirms that this species should be regarded as separate from A. dasystachyum. Wax from A. elongatum also contains 4-hydroxy-25-oxohentriacontane-14,16-dione (4%) and an unusual oxo-β-ketol, 18-hydroxy-7,16-hentriacontanedione (2%), both these components are probably derived biosynthetically from the 25-oxo β-diketone which is the major component of this wax. Syntheses of racemic 18-hydroxy-7,16-hentriacontanedione and of a model β-ketol, 12-hydroxy-10-pentacosanone, are described.  相似文献   

5.
Photosynthesis controls of CO2 efflux from maize rhizosphere   总被引:4,自引:0,他引:4  
The effects of different shading periods of maize plants on rhizosphere respiration and soil organic matter decomposition were investigated by using a 13C natural abundance and 14C pulse labeling simultaneously. 13C was a tracer for total C assimilated by maize during the whole growth period, and 14C was a tracer for recently assimilated C. CO2 efflux from bare soil was 4 times less than the total CO2 efflux from planted soil under normal lighting. Comparing to the normal lighting control (12/12 h day/night), eight days with reduced photosynthesis (12/36 h day/night period) and strongly reduced photosynthesis (12/84 h day/night period) resulted in 39% and 68% decrease of the total CO2 efflux from soil, respectively. The analysis of 13C natural abundance showed that root-derived CO2 efflux accounted for 82%, 68% and 56% of total CO2 efflux from the planted soil with normal, prolonged and strongly prolonged night periods, respectively. Clear diurnal dynamics of the total CO2 efflux from soil with normal day-night period as well as its strong reduction by prolonged night period indicated tight coupling with plant photosynthetic activity. The light-on events after prolonged dark periods led to increases of root-derived and therefore of total CO2 efflux from soil. Any factor affecting photosynthesis, or substrate supply to roots and rhizosphere microorganisms, is an important determinant of root-derived CO2 efflux, and thereby, total CO2 efflux from soils. 14C labeling of plants before the first light treatment did not show any significant differences in the 14CO2 respired in the rhizosphere between different dark periods because the assimilate level in the plants was high. Second labeling, conducted after prolonged night phases, showed higher contribution of recently assimilated C (14C) to the root-derived CO2 efflux by shaded plants. Results from 13C natural abundance showed that the cultivation of maize on Chromic Luvisol decreased soil organic matter (SOM) mineralization compared to unplanted soil (negative priming effect). A more important finding is the observed tight coupling of the negative rhizosphere effect on SOM decomposition with photosynthesis.  相似文献   

6.
Vitamin B12 production in fermentation of Propionibacterium shermanii and Propionibacterium arl AKU 1251 in whey permeate medium has been studied. The observed results and simulated expected values obtained by fitting statistical equations to the recorded data showed that 24 h old inoculum, 5 mg iron l?1 and 4% whey lactose were optimal for vitamin B12 biosynthesis in both strains when fermentation was carried out under anerobic (84 h) and aerobic (84 h) conditions at 30°C. The supplementation of whey medium with 0.5% (NH4)2HPO4 enhanced further the metabolite yield; however, the preference for a mixed carbon source (lactose + d-glucose or lactose + d-fructose) at different levels varied in the strains under study. P. shermanii, under optimal cultural conditions, was found to be a better strain than Propionibacterium arl AKU, 1251 in fermenting whey lactose for product (vitamin B12) formation.  相似文献   

7.
A Gram-negative, facultatively anaerobic, non-motile and rod-shaped bacterial strain, designated SMK1-12T, was isolated from a tidal flat sediment on the western coast of Korea. Phylogenetic analyses based on 16S rRNA and gyrB gene sequences showed that strain SMK1-12T belonged to the genus Shewanella, clustering with the type strain of Shewanella amazonensis. Strain SMK1-12T exhibited the highest 16S rRNA gene sequence similarity value (97.0 %) and the highest gyrB sequence similarity value (87.8 %) to S. amazonensis SB2BT, respectively. Strain SMK1-12T contained simultaneously both menaquinones and ubiquinones; the predominant menaquinone was MK-7 and the predominant ubiquinones were Q-7 and Q-8. The major fatty acids (>10 % of the total fatty acids) detected in strain SMK1-12T were the MIDI system summed feature 3 (iso-C15:0 2-OH and/or C16:1 ω7c), iso-C15:0, C17:1 ω8c and C16:0. The DNA G+C content of strain SMK1-12T was 58.0 mol% and its mean DNA–DNA relatedness value with S. amazonensis ATCC 700329T was 15 ± 4.6 %. Differential phenotypic properties, together with the phylogenetic and genetic distinctiveness, revealed that strain SMK1-12T is distinguishable from recognized Shewanella species. On the basis of the data presented, strain SMK1-12T is considered to represent a novel Shewanella species, for which the name Shewanella litorisediminis sp. nov. is proposed. The type strain is SMK1-12T (=KCTC 23961T = CCUG 62411T).  相似文献   

8.
Strain BS12T, a Gram-negative motile bacterium, was isolated from soil in South Korea and characterized to determine its taxonomic position. Phylogenetic analyses based on the 16S rRNA gene sequence revealed that the strain belonged to the family Alcaligenaceae in the class Betaproteobacteria. The highest degree of sequence similarities of strain BS12T were found with Pigmentiphaga litoralis JSM 061001T (98.3%), Pigmentiphaga daeguensis K110T (98.2%), and Pigmentiphaga kullae K24T (98.1%). Chemotaxonomic data revealed that strain BS12T possessed ubiquinone-8, which is common in the family Alcaligenaceae, and the predominant fatty acids were C16:0, C17:0 cyclo, summed feature 3 (C16:1 ω6c/ω7c), and summed feature 8 (C18:1 ω6c/ω7c). The major polar lipids of strain BS12T were phosphatidylethanolamine and phosphatidylglycerol. Based on these data, BS12T (=KCTC 23577T =JCM 17666T =KEMB 9004-082T) should be classified as a type strain of a novel species, for which the name Pigmentiphaga soli sp. nov. is proposed.  相似文献   

9.
Jiang  Hui-Ning  Yun  Shuai-Ting  Wang  Bao-Xun  Zhang  Ming-Jing  Ma  Yu  Zhou  Yan-Xia 《Antonie van Leeuwenhoek》2022,115(6):773-782

A Gram-stain-positive, orange-pigmented, rod-shaped and flagellated bacterial strain T12T was isolated from wetland soil in Kunyu Mountain Wetland in Yantai, China. The strain was able to grow at 15–40 °C (optimum 37 °C), at 0.0–9.0% NaCl (optimum 2%, w/v) and at pH 5.5–9.0 (optimum 8.5). A phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain T12T is a member of the family Planococcaceae, sharing 97.6% and 97.1% sequence similarity with the type strains of Jeotgalibacillus salarius and Jeotgalibacillus marinus, respectively. Genome-based analyses revealed a genome size of 3,506,682 bp and a DNA G?+?C content of 43.7%. Besides, the genome sequence led to 55.0–74.6% average amino acid identity values and 67.8–74.7% average nucleotide identity values between strain T12T and the current closest relatives. Digital DNA-DNA hybridization of strain T12T with the type strains of Jeotgalibacillus proteolyticus and J. marinus demonstrated 19.0% and 20.3% relatedness, respectively. The chemotaxonomic analysis showed that the sole quinone was MK-7. The predominant cellular fatty acids were iso-C15:0, anteiso-C15:0, C16:1ω7c alcohol and iso-C14:0. The polar lipids consisted of an unidentified aminolipid, phosphatidylglycerol, diphosphatidylglycerol and two unidentified phospholipids. Based on the polyphasic characterization, strain T12T is considered to represent a novel species, for which the name Jeotgalibacillus aurantiacus sp. nov. is proposed. The type strain is T12T (=?KCTC 43296 T?=?MCCC 1K07171T).

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10.
Interactions between delipidated Ca2+-ATPase from sarcoplasmic reticulum and four nonionic detergents—dodecyl octaoxyethyleneglycol monoether (C12E8), Triton X-100, Brij 58, and Brij 35—were characterized with respect to activation of ATPase activity, binding, and solubilization. C12E8 and Triton X-100 activated the delipidated ATPase to at least 80% of the original activity at the critical micelle concentrations (CMCs), whereas Brij 58 and Brij 35 activated no more than 10% of the original activity. The inability of Brij 58 and Brij 35 to activate the delipidated enzyme was probably a result of reduced binding of these detergents below the CMCs; both detergents exhibited a sixteenfold reduction in binding at the CMC compared with C12E8. The two Brij detergents were also unable to solubilize the delipidated enzyme and form monomers, as determined by sedimentation experiments. Thus the reduced binding levels of these detergents may result from an inability to overcome protein/protein interactions in the delipidated preparation. However, the Brij detergents were capable of solubilizing active enzyme from membrane vesicles, although with lower efficiency than C12E8 and Triton X-100. These results suggest that Brij 58 and 35 may be useful for solubilization of membrane proteins without disrupting protein/protein interactions, while Triton X-100 and C12E8 are more useful when bulk solubilization is the goal.  相似文献   

11.
A Gram-stain negative, strictly aerobic, motile by gliding, rod-shaped and yellow pigmented strain THG-G12T was isolated from soil of a bamboo field in Seoul, Republic of Korea. Strain THG-G12T was observed to grow well at 20–28 °C and pH 7.0–7.5 in the absence of NaCl on nutrient agar. Based on 16S rRNA gene sequence comparisons, strain THG-G12T was found to be most closely related to Pedobacter ginsengisoli Gsoil 104T (97.5 % sequence similarity), Pedobacter steynii WB2.3-45T (97.4 %), Pedobacter metabolipauper WB2.3-71T (97.2 %), Pedobacter nyackensis NWG-II14T (97.2 %), Pedobacter caeni LMG 22862T (97.1 %) and Pedobacter duraquae WB2.1-25T (97.0 %), but DNA relatedness between strain THG-G12T and its phylogenetically closest neighbours was below 9.5 %. The G+C content of the genomic DNA was determined to be 39.9 mol%. The only isoprenoid quinone detected in strain THG-G12T was menaquinone-7 (MK-7). The major component in the polyamine pattern was sym-homospermidine. The major polar lipids were found to be phosphatidylethanolamine, unidentified phosphoglycolipids, unidentified aminophosphoglycolipids, unidentified aminolipids and unidentified lipids. Strain THG-G12T showed the presence of two ceramide phosphorylethanolamines (CerPE-2′ and CerPE-2″), dihydrosphingosines and an unidentified ceramide as the major ceramide. The major fatty acids were identified as summed feature 3 (as defined by the MIDI system; C16:1 ω7c and/or C16:1 ω6c) and iso-C15:0. These data support the affiliation of strain THG-G12T to the genus Pedobacter. The results of physiological and biochemical tests enabled strain THG-G12T to be differentiated genotypically and phenotypically from the recognized species of the genus Pedobacter. Therefore, the novel isolate represents a novel species, for which the name Pedobacter seoulensis sp. nov. is proposed, with THG-G12T as the type strain (=KACC 17529T =JCM 19363T).  相似文献   

12.
A strictly anaerobic, homoacetogenic, Gram-positive, non spore-forming bacterium, designated strain SR12T(T=type strain), was isolated from an anaerobic methanogenic digestor fed with olive mill wastewater. Yeast extract was required for growth but could also be used as sole carbon and energy source. Strain SR12Tutilized a few carbohydrates (glucose, fructose and sucrose), organic compounds (lactate, crotonate, formate and betaine), alcohols (methanol), the methoxyl group of some methoxylated aromatic compounds, and H2+CO2. The end-products of carbohydrate fermentation were acetate, formate, butyrate, H2and CO2. End-products from lactate and methoxylated aromatic compounds were acetate and butyrate. Strain SR12Twas non-motile, formed aggregates, had a G+C content of 55 mol % and grew optimally at 35°C and pH 7.2 on a medium containing glucose. Phylogenetically, strain SR12Twas related toEubacterium barkeri, E. callanderi, andE. limosumwithE. barkerias the closest relative (similarity of 98%) with which it bears little phenotypic similarity or DNA homology (60%). On the basis of its phenotypic, genotypic, and phylogenetic characteristics, we propose to designate strain SR12TasEubacterium aggreganssp. nov. The type strain is SR12T(=DSM 12183).  相似文献   

13.
A previously unknown pathway for the biosynthesis of 12α-hydroxylated gibberellins was found in a cell-free system from Cucurbita maxima endosperm. The microsome fraction converts the gibberellin precursor GA12-aldehyde simultaneously to GA12 and 12α-hydroxy-GA12-aldehyde. The ratio of these products is pH-dependent: above pH 6.5, the production of GA12 is favoured, whilst below pH 6.5, 12α-hydroxy-GA12-aldehyde is the predominant product. 12α-Hydroxy-GA12-aldehyde is converted further by soluble enzymes to 12α-hydroxy-GA14, 12α-hydroxy-GA15, 12α-hydroxy-GA37 and several unidentified products. This conversion is optimal between pH 6.0 and 6.5 in contrast to the previously known conversion of GA12-aldehyde to GA43 by soluble enzymes, which is optimal at pH 7.5. GA58, a major 12α-hydroxylated endogenous constituent of C. maxima endosperm, was not obtained when 12α-hydroxy-GA12-aldehyde was used as a substrate, but it was obtained together with GA4 when GA9 was incubated with a preparation containing both microsomal and soluble enzymes.  相似文献   

14.
Strains BSK12Z-3T and BSK12Z-4, two Gram-stain-positive, aerobic, non-spore-forming strains, were isolated from Shankou Mangrove Nature Reserve, Guangxi Zhuang Autonomous Region, China. The diagnostic diamino acid in the cell-wall peptidoglycan of strain BSK12Z-3T was LL-diaminopimelic acid and MK-8(H4) was the predominant menaquinone. The polar lipids comprised diphosphatidylglycerol (DPG), phosphatidylglycerol (PG) and phospholipid (PL). The major fatty acids was iso-C16:0. Phylogenetic analysis based on 16S rRNA gene sequences suggested that the two strains fell within the genus Nocardioides, appearing most closely related to Nocardioides ginkgobilobae KCTC 39594T (97.5–97.6 % sequence similarity) and Nocardioides marinus DSM 18248T (97.4–97.6 %). Genome-based phylogenetic analysis confirmed that strains BSK12Z-3T and BSK12Z-4 formed a distinct phylogenetic cluster within the genus Nocardioides. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values of strains BSK12Z-3T, BSK12Z-4 with their most related species N. marinus DSM18248T were within the ranges of 77.2–77.3 % and 21.3–21.4 %, respectively, clearly indicated that strains BSK12Z-3T, BSK12Z-4 represented novel species. Strains BSK12Z-3T and BSK12Z-4 exhibited 99.9 % 16S rRNA gene sequence similarity. The ANI and dDDH values between the two strains were 97.8 % and 81.1 %, respectively, suggesting that they belong to the same species. However, DNA fingerprinting discriminated that they were not from one clonal origin. Based on phylogenomic and phylogenetic analyses coupled with phenotypic and chemotaxonomic characterizatons, strains BSK12Z-3T and BSK12Z-4 could be classified as a novel species of the genus Nocardioides, for which the name Nocardioides bruguierae sp. nov., is proposed. The type strain is BSK12Z-3T (=CGMCC 4.7709T = JCM 34554T).  相似文献   

15.
亲和层析纯化肌质网Ca2+-ATP酶   总被引:1,自引:1,他引:0  
建立了一种亲和层析纯化肌质网Ca2+-ATP酶的方法.用非离子型去污剂C12E8 溶解肌质网,再通过反应红-120琼脂糖亲和层析柱使肌质网Ca2+-ATP酶纯度从粗品中的65%提高到99%,并具有较高ATP水解活性.经SDS-聚丙烯酰胺凝胶电泳检测,为电泳纯.  相似文献   

16.
A novel Ca2+ binding protein, named caligulin, was extracted from the heat-treated 100 000 × g supernatant of bovine brain and purified to electrophoretic homogeneity. The apparent Mr of caligulin determined on sodium dodecyl sulfate polyacrylamide gels was 24 000. Analysis by gel filtration chromatography indicated an apparent Mr of 33 000, suggesting a monomeric protein. Amino acid composition data demonstrated the presence of 25% acidic residues, 12% basic residues and 10% leucine. In the presence of 1 mM MgCl2 and 0.15 M KCl, caligulin bound 1 mol Ca2+/mol protein with half-maximal binding at about 0.2 μM Ca2+.  相似文献   

17.
Gibberellin (GA) biosynthetic pathways from GA12-aldehyde, GA12 and GA53 were investigated in cell-free systems from developing embryos of Cucurbita maxima L. Gibberellin A12-aldehyde and GA12 were converted to GA25, putative 12α-hydroxyGA25, GA13 and GA39 as main products. Minor products were GA4, GA34 and, when GA12 was the substrate, putative 12α-hydroxyGA12. The intermediates GA15 and GA24 accumulated at low protein concentrations. The influence of various factors on GA12 metabolism was examined. At low 2-oxoglutarate and ascorbate concentrations, or at acid pH, 3β-hydroxylated products predominated, whereas with increasing 2-oxoglutarate and ascorbate concentrations, or at neutral pH, the yield of 12α-hydroxylated GAs increased. Gibberellin A53 was metabolised mainly to the C20-GAs GA44, GA19, GA17, GA23 and GA28, with the C19-GAs GA20, GA1 and GA8 as minor products. Only C19-GAs were 2β-hydroxylated, which is a main characteristic of the embryo systems. In addition to GA13, GA25, GA39, GA43, GA49, GA58, GA74, 12α-hydroxyGA25 and GA39 3-isovalerate, which were known previously from embryos of C. maxima, GA1, GA4, GA17, GA28, GA37, GA38, GA48, GA85, 12α-hydroxyGA37 and putative 12α-hydroxyGA43 were identified as endogenous components by full-scan capillary gas chromatography-mass spectrometry and Kovats retention indices. Evidence for putative 2β-hydroxyGA28 and GA23 was also obtained but it was less conclusive because of contamination.  相似文献   

18.
Vibrio species are well known as motile, mostly oxidase-positive, facultative anaerobic Gram-negative bacteria. They are abundant in aquatic environments and are a common cause of human infections including diarrhea, soft tissue diseases, and bacteremia. Here, two Gram-negative bacteria, designated M12-1144T and M12-1181, were isolated from human clinical specimens and identified using a polyphasic taxonomic approach. Phylogenetic study based on 16S rRNA gene sequence analysis revealed that the isolates belong to the genus Vibrio, and are closely related to Vibrio metschnikovii KCTC 32284T (98.3%) and Vibrio cincinnatiensis KCTC 2733T (97.8%). The major fatty acids were summed feature 3 (C16:1 ω7c/C16:1 ω6c, 38.0%), C16:0 (23.0%), and summed feature 8 (C18:1 ω7c or C18:1 ω6c, 19.3%) and major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, and phosphatidylethanolamine. The G + C content of the genomic DNA was determined to be 44.1 mol%. DNA–DNA relatedness between the two newly isolated strains and V. metschnikovii KCTC 32284T and V. cincinnatiensis KCTC 2733T was between 42.6 to 47.5%. The similarities of genome-to-genome distance between M12-1144T and related species ranged from 18.4-54.8%. Based on these results, a new species of the genus Vibrio, Vibrio injenensis is proposed. The type strain is M12-1144 T(=KCTC 32233T =JCM 30011T).  相似文献   

19.
Nitrate reduction in roots and shoots and exchange of reduced N between organs were quantitatively estimated in intact 13-d-old seedlings of two-row barley (Hordeum vulgare L. cv. Daisengold) using the 15N-incorporation model (A. Gojon et al. (1986) Plant Physiol. 82, 254–260), except that NH + 4 was replaced by NO - 2 . N-depleted seedlings were exposed to media containing both nitrate (1.8 mM) and nitrite (0.2 mM) under a light-dark cycle of 12:12 h at 20°C; the media contained different amounts of 15N labeling. Experiments were started either immediately after the beginning (expt. 1) or immediately prior to the end (expt. 2) of the light period, and plants were sampled subsequently at each light-dark transition throughout 36 h. The plants effectively utilized 15NO - 3 and accumulated it as reduced 15N, predominantly in the shoots. Accumulation of reduced 15N in both experiments was nearly the same at the end of the experiment but the accumulation pattern in roots and shoots during each 12-h period differed greatly depending on time and the light conditions. In expt. 1, the roots accounted for 31% (light), 58% (dark), and 9% (light) of nitrate reduction by the whole plants, while in expt. 2 the contributions of the root were 82% (dark), 20% (light), and 29% (dark), during each of the three 12-h periods. Xylem transport of nitrate drastically decreased in the dark, but that of reduced N rather increased. The downward translocation of reduced 15N increased while nitrate reduction in the root decreased, whereas upward translocation decreased while nitrate reduction in the shoot increased. We conclude that the cycling of reduced N through the plant is important for N feeding of each organ, and that the transport system of reduced N by way of xylem and phloem, as well as nitrate reduction by root and shoot, can be modulated in response to the relative magnitude of reduced-N demands by the root and shoot, with the one or the other predominating under different circumstances.Symbols Anl accumulation of reduced 15N from 15NO - 3 in 14NO - 3 -fed roots of divided root system - Ar accumulation in root of reduced 15N from 15NO - 3 - As accumulation in shoot of reduced 15N from 15NO - 3 - Rr 15NO - 3 reduction in root - Rs 15NO - 3 reduction in shoot - Tp translocation to root of shoot-reduced 15N from 15NO - 3 in phloem - Tx translocation to shoot of root-reduced 15N from 15NO - 3 in xylem  相似文献   

20.
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