Ammonium‐driven nitrification plays a key role in increasing Mn availability in calcareous soils     

Michael Dreyer  Merle Wichmann  Marie Rischen  Bruno M. Görlach  Annika Ehmke  Britta Pitann  Karl H. Mühling 《植物养料与土壤学杂志》2020,183(3):389-396

Background : Manganese deficiency often becomes a yield limiting factor, particularly on calcareous soils, even though the total soil manganese content is usually sufficient. Although it is known that acidifying N fertilizers can improve Mn availability, the reason of this effect is still unknown. Aim : Our aim was to investigate the effect of stabilized ammonium fertilizers as a tool to distinguish between physiological‐ and nitrification‐induced acidification. Method : Two pot experiments with Triticum aestivum L. and one soil incubation experiment using different nitrogen forms (CN = calcium nitrate, AN = ammonium nitrate, AS = ammonium sulfate, ATS = ammonium thiosulfate) with and without addition of nitrification inhibitors (DCD, Nitrapyrin, Piadin, DMPP) were conducted to examine the effect on Mn availability in the soil and Mn uptake by the plants at different development stages (EC 31 und 39). Results : With increasing fertilizer ${\mathrm{NH}}_4^{+}$ content a higher Mn concentration was detected: CN: 32 µg Mn g^?1 DM, AN: 39 µg Mn g^?1 DW, AS: 55 µg Mn g^?1 DM, ATS: 109 µg Mn g^?1 DM. The addition of a nitrification inhibitor resulted in a significantly lower rhizosphere pH compared to the non‐stabilized fertilizer. Surprisingly, the use of different nitrification inhibitors led to unchanged (CN, AN) or lower Mn concentrations of wheat. Especially in the ${\mathrm{NH}}_4^{+}$ treatments (AS and ATS), this negative effect was very evident (AS+DCD: 42 µg Mn g^?1 DM; ATS+DCD: 55 µg Mn g^?1 DM). Conclusions : Mn availability was enhanced by ongoing nitrification process rather than physiological acidification. Compared to other N forms, ammonium thiosulfate led to the highest Mn availability in bulk soil.  相似文献   

Rapid determination of polyphenols and vitamin C in plant-derived products   总被引：5，自引：0，他引：5  

Georgé S  Brat P  Alter P  Amiot MJ 《Journal of agricultural and food chemistry》2005,53(5):1370-1373

Polyphenols, widely spread in our diet by the consumption of plant food products, are commonly determined using Folin-Ciocalteu reagent that interacts with other different reducing nonphenolic substances and leads to an overestimation of polyphenol content. In this paper we report an optimized Folin-Ciocalteu method to specifically determine the contents of total polyphenols and vitamin C. After the optimal conditions for the colorimetric assay were set, solid-phase extraction (Oasis HLB (hydrophilic-lipophilic balance)) was carried out to eliminate the water-soluble reducing interferences including vitamin C. Colorimetric correction was thus performed by subtracting interfering substances contained in the water washing extract from the raw extract. Moreover, vitamin C present in the water washing extract can be destroyed by heating and thus colorimetrically deduced. This procedure was set up with synthetic solutions and validated on different extracts from fruit products.  相似文献   

Evaluation of isoflavone aglycon and glycoside distribution in soy plants and soybeans by fast column high-performance liquid chromatography coupled with a diode-array detector     

Klejdus B  Mikelová R  Petrlová J  Potesil D  Adam V  Stiborová M  Hodek P  Vacek J  Kizek R  Kubán V 《Journal of agricultural and food chemistry》2005,53(15):5848-5852

An ultrafast HPLC/UV-vis DAD method working at 254 nm was applied for the determination of isoflavone aglycons and glycosides (genistin, genistein, daidzein, daidzin, glycitin, glycitein, ononin, formononetin, sissotrin, and biochanin A) in roots, stems, leaves, and soy pods of soy plants and in soybeans of five varieties (Korada, Quito, Rita, OAC Erin, and OAC Vison). An Atlantis dC18 ultrafast RP chromatographic column (20 mm x 2.1 mm, 3 microm particle size) was applied for separation of the isoflavone aglycons and glycosides. A flow rate of the mobile phase (0.1% (v/v) acetic acid, pH 3.75-solvent A and methanol-solvent B) was 0.35 mL min(-1), and the column temperature was 36 degrees C. A linear gradient profile from 13 up to 22% B (v/v) from zero to 2.5 min, up to 30% B to 3.21 min, up to 35% B to 4 min, up to 40% B to 4.5 min, up to 50% B to 5.14 min, and followed by negative gradient up to 13% B to 7.71 min was used. The absolute limits of detection per sample injection (5 microL) were the highest for biochanin A (166.2 fmol) and the lowest for genistin (17.0 fmol), respectively. An accelerated solvent extraction (ASE) in combination with sonication was applied for isolation of biologically active compounds. A solid-phase extraction procedure was used to purify the extracts in the case of analysis of soy plants parts. The recoveries of 96-106% were obtained for the different concentrations of the isoflavone aglycons and glycosides and the different matrixes (overall RSDs 2-9%). The highest isoflavone concentrations were found in roots (12.5 microg g(-1) dry weight), while the amounts were about 3-1100 microg g(-1) fresh weight in different varieties of soybeans.  相似文献   

Total folate content and retention in rosehips (Rosa ssp.) after drying     

Strålsjö L  Alklint C  Olsson ME  Sjöholm I 《Journal of agricultural and food chemistry》2003,51(15):4291-4295

Folate concentrations in rosehips and commercial rosehip products and factors affecting folate retention during drying were investigated. On the basis of the raw material studied during 3 years, rosehips were shown to be a rich folate source, 400-600 microg/100 g based on dry matter and 160-185 microg/100 g based on the fresh weight (edible part). Rosehips are not often consumed fresh; therefore, drying to produce stable semimanufactures is a crucial step. The degradation of folate was shown to be dependent on the drying time until the water activity was below 0.75. The required drying time was reduced by cutting the rosehips in slices and to some extent also by increasing the temperature. Retention of folate and ascorbic acid was affected by the same factors, and high content of ascorbic acid could provide a possible protection for folate degradation.  相似文献   

Seasonal and phenological variations of the essential oil from the narrow endemic species Artemisia molinieri and its biological activities     

Masotti V  Juteau F  Bessière JM  Viano J 《Journal of agricultural and food chemistry》2003,51(24):7115-7121

The volatile components of the aerial parts of Artemisia molinieri, an endemic wormwood of southern France, were analyzed by GC and GC-MS. Among the 69 compounds identified, major components were ascaridole (19-76%), alpha-terpinene (traces-36%), p-cymene (1-17%), 1,8-cineole (0.3-8%), and germacrene D (0.6-15%). Quantitative variations have been characterized following the season, the phenological cycle, and the aging of the plants. Bioassays have been performed on a sample of essential oil, which has shown a strong inhibition of the growth of both tested yeasts (Candida albicans and Saccharomyces cerevisiae var. chevalieri) and minor activity on both tested Gram-negative bacteria (Escherichia coli and Enterococcus hirae). The oils have shown interesting antioxidant activities on the basis of alpha-tocopherol as reference compound, up to 400-1200%.  相似文献   

A class of potent antimalarials and their specific accumulation in infected erythrocytes     

Wengelnik K  Vidal V  Ancelin ML  Cathiard AM  Morgat JL  Kocken CH  Calas M  Herrera S  Thomas AW  Vial HJ 《Science (New York, N.Y.)》2002,295(5558):1311-1314

During asexual development within erythrocytes, malaria parasites synthesize considerable amounts of membrane. This activity provides an attractive target for chemotherapy because it is absent from mature erythrocytes. We found that compounds that inhibit phosphatidylcholine biosynthesis de novo from choline were potent antimalarial drugs. The lead compound, G25, potently inhibited in vitro growth of the human malaria parasites Plasmodium falciparum and P. vivax and was 1000-fold less toxic to mammalian cell lines. A radioactive derivative specifically accumulated in infected erythrocytes to levels several hundredfold higher than in the surrounding medium, and very low dose G25 therapy completely cured monkeys infected with P. falciparum and P. cynomolgi.  相似文献   

Induction of T helper type 2 immunity by a point mutation in the LAT adaptor     

Aguado E  Richelme S  Nuñez-Cruz S  Miazek A  Mura AM  Richelme M  Guo XJ  Sainty D  He HT  Malissen B  Malissen M 《Science (New York, N.Y.)》2002,296(5575):2036-2040

The transmembrane protein LAT (linker for activation of T cells) couples the T cell receptor (TCR) to downstream signaling effectors. Mice homozygous for a mutation of a single LAT tyrosine residue showed impeded T cell development. However, later they accumulated polyclonal helper T (TH) cells that chronically produced type 2 cytokines in large amounts. This exaggerated TH2 differentiation caused tissue eosinophilia and massive maturation of plasma cells secreting to immunoglobulins of the E and G1 isotypes. This paradoxical phenotype establishes an unanticipated inhibitory function for LAT that is critical for the differentiation and homeostasis of TH cells.  相似文献   

Regulation of bone mass in mice by the lipoxygenase gene Alox15     

Klein RF  Allard J  Avnur Z  Nikolcheva T  Rotstein D  Carlos AS  Shea M  Waters RV  Belknap JK  Peltz G  Orwoll ES 《Science (New York, N.Y.)》2004,303(5655):229-232

The development of osteoporosis involves the interaction of multiple environmental and genetic factors. Through combined genetic and genomic approaches, we identified the lipoxygenase gene Alox15 as a negative regulator of peak bone mineral density in mice. Crossbreeding experiments with Alox15 knockout mice confirmed that 12/15-lipoxygenase plays a role in skeletal development. Pharmacologic inhibitors of this enzyme improved bone density and strength in two rodent models of osteoporosis. These results suggest that drugs targeting the 12/15-lipoxygenase pathway merit investigation as a therapy for osteoporosis.  相似文献   

RNA secondary structure repression of a muscle-specific exon in HeLa cell nuclear extracts   总被引：44，自引：0，他引：44  

B Clouet d'Orval  Y d'Aubenton Carafa  P Sirand-Pugnet  M Gallego  E Brody  J Marie 《Science (New York, N.Y.)》1991,252(5014):1823-1828

The chicken beta-tropomyosin pre-messenger RNA (pre-mRNA) is spliced in a tissue-specific manner to yield messenger RNA's (mRNA's) coding for different isoforms of this protein. Exons 6A and 6B are spliced in a mutually exclusive manner; exon 6B was included in skeletal muscle, whereas exon 6A was preferred in all other tissues. The distal portion of the intron upstream of exon 6B was shown to form stable double-stranded regions with part of the intron downstream of exon 6B and with sequences in exon 6B. This structure repressed splicing of exon 6B to exon 7 in a HeLa cell extract. Derepression of splicing occurred on disruption of this structure and repression followed when the structure was re-formed, even if the structure was formed between two different RNA molecules. Repression leads to inhibition of formation of spliceosomes. Disrupting either of the two double-stranded regions could lead to derepression, whereas re-forming the helices by suppressor mutations reestablished repression. These results support a simple model of tissue-specific splicing in this region of the pre-mRNA.  相似文献   

Capping by branching: a new ribozyme makes tiny lariats     

Pyle AM 《Science (New York, N.Y.)》2005,309(5740):1530-1531

The number of naturally occurring RNA enzymes has just been expanded by the discovery of a new branching ribozyme. But this ribozyme has unexpected relatives: group I introns.  相似文献