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1.
Sediment-related growth limitation of Elodea nuttallii as indicated by a fertilization experiment 总被引:4,自引:0,他引:4
1. A fertilization experiment was performed to identify the limiting nutrient for the growth of submerged vegetation in ditches of a peat-grassland system in the Netherlands, in which restoration measures involved ceasing fertilization, exporting nutrients by removal of above-ground plant mass and large-scale introduction of calcium-rich, nutrient-poor artesian water.
2. Growth of Elodea was significantly enhanced by enrichment with nitrogen alone, and by fertilization with nitrogen in combination with phosphorus, and by nitrogen in combination with phosphorus and potassium.
3. Plant tissue nutrient concentrations increased significantly, for nitrogen by enrichment with nitrogen alone, and with nitrogen in combination with phosphorus and potassium; for phosphorus by enrichment with phosphorus alone and with phosphorus in combination with nitrogen and potassium; tissue concentrations of potassium were not enhanced by any treatment.
4. The elemental ratios of treated plants indicated that nitrogen, rather than phosphorus, was limiting in all treatments, except in those involving nitrogen and NK enrichment (when phosphorus was limiting).
5. The efficiency with which plants used nutrients declined with increased supply of nitrogen and phosphorus, but was unchanged when potassium was increased. Efficiencies were similar to those of other aquatic macrophytes. 相似文献
2. Growth of Elodea was significantly enhanced by enrichment with nitrogen alone, and by fertilization with nitrogen in combination with phosphorus, and by nitrogen in combination with phosphorus and potassium.
3. Plant tissue nutrient concentrations increased significantly, for nitrogen by enrichment with nitrogen alone, and with nitrogen in combination with phosphorus and potassium; for phosphorus by enrichment with phosphorus alone and with phosphorus in combination with nitrogen and potassium; tissue concentrations of potassium were not enhanced by any treatment.
4. The elemental ratios of treated plants indicated that nitrogen, rather than phosphorus, was limiting in all treatments, except in those involving nitrogen and NK enrichment (when phosphorus was limiting).
5. The efficiency with which plants used nutrients declined with increased supply of nitrogen and phosphorus, but was unchanged when potassium was increased. Efficiencies were similar to those of other aquatic macrophytes. 相似文献
2.
E.P.H. BEST H. WOLTMAN & FH.H. JACOBS 《The Plant journal : for cell and molecular biology》2003,36(1):33-44
1. A fertilization experiment was performed to identify the limiting nutrient for the growth of submerged vegetation in ditches of a peat-grassland system in the Netherlands, in which restoration measures involved ceasing fertilization, exporting nutrients by removal of above-ground plant mass and large-scale introduction of calcium-rich, nutrient-poor artesian water.
2. Growth of Elodea was significantly enhanced by enrichment with nitrogen alone, and by fertilization with nitrogen in combination with phosphorus, and by nitrogen in combination with phosphorus and potassium.
3. Plant tissue nutrient concentrations increased significantly, for nitrogen by enrichment with nitrogen alone, and with nitrogen in combination with phosphorus and potassium; for phosphorus by enrichment with phosphorus alone and with phosphorus in combination with nitrogen and potassium; tissue concentrations of potassium were not enhanced by any treatment.
4. The elemental ratios of treated plants indicated that nitrogen, rather than phosphorus, was limiting in all treatments, except in those involving nitrogen and NK enrichment (when phosphorus was limiting).
5. The efficiency with which plants used nutrients declined with increased supply of nitrogen and phosphorus, but was unchanged when potassium was increased. Efficiencies were similar to those of other aquatic macrophytes. 相似文献
2. Growth of Elodea was significantly enhanced by enrichment with nitrogen alone, and by fertilization with nitrogen in combination with phosphorus, and by nitrogen in combination with phosphorus and potassium.
3. Plant tissue nutrient concentrations increased significantly, for nitrogen by enrichment with nitrogen alone, and with nitrogen in combination with phosphorus and potassium; for phosphorus by enrichment with phosphorus alone and with phosphorus in combination with nitrogen and potassium; tissue concentrations of potassium were not enhanced by any treatment.
4. The elemental ratios of treated plants indicated that nitrogen, rather than phosphorus, was limiting in all treatments, except in those involving nitrogen and NK enrichment (when phosphorus was limiting).
5. The efficiency with which plants used nutrients declined with increased supply of nitrogen and phosphorus, but was unchanged when potassium was increased. Efficiencies were similar to those of other aquatic macrophytes. 相似文献
3.
Dexterous manipulation relies on modulation of digit forces as a function of digit placement. However, little is known about the sense of position of the vertical distance between finger pads relative to each other. We quantified subjects'' ability to match perceived vertical distance between the thumb and index finger pads (dy) of the right hand (“reference” hand) using the same or opposite hand (“test” hand) after a 10-second delay without vision of the hands. The reference hand digits were passively placed non-collinearly so that the thumb was higher or lower than the index finger (dy = 30 or –30 mm, respectively) or collinearly (dy = 0 mm). Subjects reproduced reference hand dy by using a congruent or inverse test hand posture while exerting negligible digit forces onto a handle. We hypothesized that matching error (reference hand dy minus test hand dy) would be greater (a) for collinear than non-collinear dys, (b) when reference and test hand postures were not congruent, and (c) when subjects reproduced dy using the opposite hand. Our results confirmed our hypotheses. Under-estimation errors were produced when the postures of reference and test hand were not congruent, and when test hand was the opposite hand. These findings indicate that perceived finger pad distance is reproduced less accurately (1) with the opposite than the same hand and (2) when higher-level processing of the somatosensory feedback is required for non-congruent hand postures. We propose that erroneous sensing of finger pad distance, if not compensated for during contact and onset of manipulation, might lead to manipulation performance errors as digit forces have to be modulated to perceived digit placement. 相似文献
4.
Kai Hilpert Dirk FH Winkler Robert EW Hancock 《Biotechnology & genetic engineering reviews》2013,29(1):31-106
Spatial organization of metabolic enzymes may represent a general cellular mechanism to regulate metabolic flux. One recent example of this type of cellular phenomenon is the purinosome, a newly discovered multi-enzyme metabolic assembly that includes all of the enzymes within the de novo purine biosynthetic pathway. Our understanding of the components and regulation of purinosomes has significantly grown in recent years. This paper reviews the purine de novo biosynthesis pathway and its regulation, and presents the evidence supporting the purinosome assembly and disassembly processes under the control of G-protein-coupled receptor (GPCR) signaling. This paper also discusses the implications of purinosome and GPCR regulation in drug discovery. 相似文献
5.
Miriam YH Ueda Paulo G Alvarenga Juliana M Real Eloisa de Sá Moreira Aripuan? Watanabe Ana Maria Passos-Castilho Matheus Vescovi Yana Novis Vanderson Rocha Adriana Seber Jose SR Oliveira Celso A Rodrigues Celso FH Granato 《Memórias do Instituto Oswaldo Cruz》2015,110(4):461-467
Human herpesvirus 6 (HHV-6) may cause severe complications after haematopoietic stem
cell transplantation (HSCT). Monitoring this virus and providing precise, rapid and
early diagnosis of related clinical diseases, constitute essential measures to
improve outcomes. A prospective survey on the incidence and clinical features of
HHV-6 infections after HSCT has not yet been conducted in Brazilian patients and the
impact of this infection on HSCT outcome remains unclear. A rapid test based on
real-time quantitative polymerase chain reaction (qPCR) has been optimised to screen
and quantify clinical samples for HHV-6. The detection step was based on reaction
with TaqMan® hydrolysis probes. A set of previously described primers and
probes have been tested to evaluate efficiency, sensitivity and reproducibility. The
target efficiency range was 91.4% with linearity ranging from 10-106
copies/reaction and a limit of detection of five copies/reaction or 250 copies/mL of
plasma. The qPCR assay developed in the present study was simple, rapid and
sensitive, allowing the detection of a wide range of HHV-6 loads. In conclusion, this
test may be useful as a practical tool to help elucidate the clinical relevance of
HHV-6 infection and reactivation in different scenarios and to determine the need for
surveillance. 相似文献
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8.
Obesity is a major health problem. We investigated the effects of forskolin and rolipram in the diet of animals in which obesity had been induced. We used 50 female albino Wistar rats that were assigned randomly into five groups as follows: group 1, control; group 2, high fat diet; group 3, high fat diet + forskolin; group 4, high fat diet + rolipram; and group 5, high fat diet + rolipram + forskolin. The rats were fed for 10 weeks and rolipram and forskolin were administered during last two weeks. The animals were sacrificed and blood samples were obtained. Serum cAMP, cGMP and free fatty acids (FFA) levels were measured using ELISA assays. We also measured weight gain during the 10 week period. cAMP and FFA levels of groups 3, 4 and 5 were significantly higher than those of groups 1 and 2. We found no significant differences in serum cGMP levels among the groups. The weight gain in groups 3, 4 and 5 was significantly less than for group 2. We also found that the weight gain in group 5 was significantly less than in groups 3 and 4. We found that both forskolin and rolipram stimulated lipolysis and inhibited body weight increase by increasing cAMP levels. Also, combination therapy using the two agents may be more effective in preventing diet induced obesity than either agent alone. We found also that these agents did not effect cellular cGMP levels in diet induced obesity. 相似文献
9.
The hand is one of the most fascinating and sophisticated biological motor systems. The complex biomechanical and neural architecture of the hand poses challenging questions for understanding the control strategies that underlie the coordination of finger movements and forces required for a wide variety of behavioral tasks, ranging from multidigit grasping to the individuated movements of single digits. Hence, a number of experimental approaches, from studies of finger movement kinematics to the recording of electromyographic and cortical activities, have been used to extend our knowledge of neural control of the hand. Experimental evidence indicates that the simultaneous motion and force of the fingers are characterized by coordination patterns that reduce the number of independent degrees of freedom to be controlled. Peripheral and central constraints in the neuromuscular apparatus have been identified that may in part underlie these coordination patterns, simplifying the control of multi-digit grasping while placing certain limitations on individuation of finger movements. We review this evidence, with a particular emphasis on how these constraints extend through the neuromuscular system from the behavioral aspects of finger movements and forces to the control of the hand from the motor cortex. 相似文献
10.
Brazão V Caetano LC Filipin Mdel V Santello FH Toldo MP do Prado JC 《Experimental parasitology》2009,121(1):105-109
Zinc is an essential nutritional component required for normal development and maintenance of immune functions. The possible effects of zinc in upregulating the host immune response during the acute and chronic phases of experimental Chagas’ disease were evaluated. In young, infected and Zn-supplemented animals, higher concentrations of IFN-γ and NO were observed. During the chronic phase, decreased concentrations of NO and IFN-γ were found for older infected animals that received Zn supplementation. For young animals, hearts from Zn-supplemented groups displayed reduced inflammatory infiltrate, heart weight and number of amastigote burdens. For older, infected and Zn-supplemented animals amastigote nests were absent with reduced inflammatory cell infiltrate. This study identifies a potentially novel therapeutic approach that could control the parasite load during acute phase of disease, consequently preventing the deleterious, parasite-elicited responses observed during chronic phase. 相似文献