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N Status (n + status)
Selected AbstractsNitrogen fertilization effects on Myzus persicae aphid dynamics on peach: vegetative growth allocation or chemical defence?ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2010Marie-Hélène Sauge Abstract Plant nitrogen (N) fertilization is a common cropping practice that is expected to serve as a pest management tool. Its effects on the dynamics of the aphid Myzus persicae (Sulzer) (Hemiptera: Aphididae) were examined on young peach [Prunus persica (L.) Batsch (Rosaceae)] trees grown under five N treatments, ranging from N shortage to supra-optimal supply for growth. Aphid population increased over time at the three intermediate N levels. It remained stable at the lowest N level and decreased at the highest N level. Four weeks after the start of infestation, the number of aphids displayed a parabolic response to N level. The relationships between N status and parameters of plant vegetative growth (stem diameter) or biomass allocation (lateral-total leaf area and root-shoot ratio) were consistent with responses proposed by models of adaptive plasticity in resource allocation patterns. However, the variation in plant growth predicted aphid population dynamics only partially. Whereas aphid number was positively correlated with plant N status and vegetative growth up to the intermediate N level, it was negatively correlated with plant N status above this level, but not with vegetative growth. The concentrations of primary and secondary (plant defence-related) metabolites in the plant shoots were modified by N treatments: amino acids (main nutritional resource of aphids) and prunasin increased, whereas chlorogenic acid decreased with increasing N availability. Constitutive changes in plant chemistry in response to N fertilization could not directly explain the reduced aphid performance for the highest N level. Nevertheless, the indirect effect of N on the induction of plant defence compounds by aphid feeding warrants further investigation. The study focuses on the feasibility of handling N fertilization to control M. persicae in orchards, but findings may also be relevant for our understanding of the physiological relationships between the host's nutritional status and the requirements of the insect. [source] Assessment of the nitrogen status of grasslandGRASS & FORAGE SCIENCE, Issue 2 2004A. Farruggia Abstract Two types of diagnostics are used for N management in grasslands: diagnostics based on N concentration of shoots and diagnostics based on soil mineral N. The Nitrogen Nutrition Index (NNI) is an example of the first type. However, its evaluation requires the determination of shoot dry weight per unit area and, thus, constitutes a practical limit to its utilization in the context of farm studies. In order to simplify its evaluation, a method based on the N concentration of the upper sward layer (Nup) has been proposed. The objectives of this study were to test the relationship between NNI and Nup in the context of permanent grassland and to examine the relationship between Nup and soil mineral status. The study was conducted as two experiments, one on small cut-plots receiving contrasting rates of mineral N fertilization, and a second on plots of an existing field-scale lysimeter experiment. In each plot and at several dates, shoot biomass within quadrats was measured, N concentration was determined on the upper leaves and on the entire shoots, and mineral nitrogen of the soil below the vegetation sampled was determined. N concentration of the upper lamina layer of the canopy was linearly related to the NNI determined on the entire shoots. Therefore, determining N concentration in leaves at the top of canopy appears to be an alternative means to evaluate NNI without having to measure shoot biomass. The absence of an overall significant correlation between soil mineral N content and sward N index, observed over the two studies, indicates that each of these two indicators has to be considered specifically in relation to the objective of the diagnostic procedure. As sward N index may vary independently of soil mineral N content, the sward N indicator does not appear to be a suitable indicator for diagnosis of environmental risks related to nitrate leaching. However, soil mineral N content does not allow the prediction of sward N status and thus is not a suitable indicator of sward growth rate. Although soil mineral N content is an important environmental indicator for nitrate-leaching risks during potential drainage periods, it has a limited diagnosis value with respect to the herbage production function of grasslands. [source] Advanced-staged tonsillar squamous carcinoma: Organ preservation versus surgical management of the primary site,HEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 7 2006Haider Ali Shirazi MD Abstract Background. Our aim was to review our experience in the management of advanced tonsillar squamous cell carcinoma (SCC) and to compare treatment outcomes between patients treated with and without surgery to the primary site. Methods. The records of 74 patients with advanced-stage tonsillar SCC were reviewed. The median age at diagnosis was 58 years. Thirty-eight patients received definitive surgery to the primary site, and 36 were treated with an organ-preservation approach (OP) using radiotherapy ± chemotherapy. Results. No significant difference in overall survival (OS) or freedom from relapse (FFR) by treatment was found. T classification and N status were significant independent predictors on multivariate analysis for OS and FFR. Major late toxicity was noted in 10 patients in the surgical group and nine in the OP group. Conclusion. Patients treated with OP and primary surgery had comparable OS and FFR. T classification and N status were significant independent predictors for tumor relapse and survival. On the basis of these results, we favor organ-preservation therapy for patients with advanced-stage tonsillar SCC. © 2006 Wiley Periodicals, Inc. Head Neck, 2006 [source] Impact of nutrition support on treatment outcome in patients with locally advanced head and neck squamous cell cancer treated with definitive radiotherapy: A secondary analysis of RTOG trial 90-03,HEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 4 2006Rachel Rabinovitch MD Abstract Background. The aim was to evaluate the relationship between nutrition support (NS) on host toxicity and cancer outcome in patients with locally advanced head and neck squamous cell carcinoma (HNSCC) undergoing definitive radiotherapy (XRT). Methods. We performed a secondary analysis of Radiation Therapy Oncology Group (RTOG) 90-03, a prospective randomized trial evaluating four definitive XRT fractionation schedules in patients with locally advanced HNSCC, which prospectively collected data on NS delivered before treatment (BNS), during treatment (TNS), and after definitive XRT. NS data and pretreatment characteristics of the 1073 evaluable patients were analyzed against therapy toxicity and outcome. Results. Patients receiving BNS experienced significantly less weight loss by the end of treatment and less grade 3 to 4 mucositis than patients not receiving BNS. However, patients receiving BNS had a poorer 5-year actuarial locoregional control rate than patients receiving TNS or no NS (29%, 55%, and 57%, respectively, p < .0001) and a poorer 5-year overall survival rate (16%, 36%, and 49%, respectively, p < .0001). Patients receiving BNS were significantly more likely to have a higher T classification, N status, and overall American Joint Committee on Cancer (AJCC) stage and initial presentation with greater pretreatment weight loss, and a poorer Karnofsky Performance Status (KPS) than patients not receiving BNS. After adjusting for the impact of these prognostic factors through a recursive partition analysis, a multivariate analysis with a stratified Cox model found that BNS was still a highly significant independent prognostic factor for increased locoregional failure (hazards ratio [HR], 1.47; 95% confidence interval [CI], 1.21,1.79; p < .0001) and death (HR, 1.41; 95% CI, 1.19,1.67; p < .0001). Conclusion. In this study, the largest prospective evaluation of nutrition data in treated patients with cancer, BNS was associated with inferior treatment outcome in the patients with HNSCC undergoing XRT. These results should be considered hypothesis generating and encourage prospective clinical research and identification of the mechanisms underlying this finding. © 2005 Wiley Periodicals, Inc. Head Neck28: 287,296, 2006 [source] Definitive radiotherapy with interstitial implant boost for squamous cell carcinoma of the tongue baseHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 5 2005Omur Karakoyun-Celik MD Abstract Background. The purpose of this study was to examine the long-term outcome of a cohort of patients with unresected base of tongue carcinoma who received interstitial brachytherapy after comprehensive external beam radiation therapy. Methods. Between 1983 and 2000, 122 patients with primary or recurrent squamous cell carcinoma of the oropharynx or oral cavity received interstitial brachytherapy as part of their overall management. Forty patients had primary, unresected carcinoma of the base of tongue and are the subjects of this analysis. The median age was 54 years. Fifty-four percent had T3 or T4 disease, and 70% had clinical or radiographic lymphadenopathy. Twenty-four (60%) received two to three cycles of neoadjuvant chemotherapy. The oropharynx, bilateral neck, and supraclavicular fossae were comprehensively irradiated, and the tongue base received a median external beam dose of 61.2 Gy (50,72 Gy). The primary site was then boosted with an interstitial 192Iridium implant by use of a gold-button single-strand technique and three-dimensional treatment planning. The dose rate was prescribed at 0.4 to 0.5 Gy/hr. The median implant dose was 17.4 Gy (9.6,24 Gy) and adjusted to reach a total dose to the primary tumor of 80 Gy. N2 to 3 disease was managed by a planned neck dissection performed at the time of the implant. Results. The median follow-up for all patients was 56 months, and the overall survival rates were 62% at 5 years and 27% at 10 years. The actuarial primary site control was 78% at 5 years and 70% at 10 years. The overall survival and primary site control were independent of T classification, N status, or overall stage. Systemic therapy was associated with an improvement in overall survival (p = .04) and a trend toward increased primary site control with greater clinical response. There were seven documented late effects, the most frequent being grade 3 osteonecrosis (n = 2), grade 2 swallowing dysfunction (n = 2), trismus (n = 2), and chronic throat pain (n = 1). Conclusions. In an era of greatly improved dose distributions made possible by three-dimensional treatment planning and intensity-modulated radiation therapy, brachytherapy allows a highly conformal dose to be delivered in sites such as the oropharynx. If done properly, the procedure is safe and delivers a dose that is higher than what can be achieved by external beam radiation alone with the expected biologic advantages. The long-term data presented here support an approach of treating advanced tongue base lesions that includes interstitial brachytherapy as part of the overall management plan. This approach has led to a 78% rate of organ preservation at 5 years, with a 5% incidence of significant late morbidity (osteonecrosis) that has required medical management. © 2005 Wiley Periodicals, Inc. Head Neck27: XXX,XXX, 2005 [source] Putative Nitrogen Sensing Systems in Higher PlantsJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 8 2006Hon-Ming Lam Abstract Nitrogen (N) metabolism is essential for the biosynthesis of vital biomolecules. N status thus exerts profound effects on plant growth and development, and must be closely monitored. In bacteria and fungi, a few sophisticated N sensing systems have been extensively studied. In animals, the ability to receive amino acid signals has evolved to become an integral part of the nervous coordination system. In this review, we will summarize recent developments in the search for putative N sensing systems in higher plants based on homologous systems in bacteria, fungi, and animals. Apparently, although plants have separated and diversified from other organisms during the evolution process, striking similarities can be found in their N sensing systems compared with those of their counterparts; however, our understanding of these systems is still incomplete. Significant modifications of the N sensing systems (including cross-talk with other signal transduction pathways) in higher plants may be a strategy of adaptation to their unique mode of life. (Managing editor: Ping He) [source] Identification of a 150 bp cis -acting element of the AtNRT2.1 promoter involved in the regulation of gene expression by the N and C status of the plantPLANT CELL & ENVIRONMENT, Issue 11 2007THOMAS GIRIN ABSTRACT The Arabidopsis thaliana AtNRT2.1 gene, which encodes a NO3 - transporter involved in high-affinity uptake by the roots, is a molecular target of several mechanisms responsible for the regulation of root NO3 - acquisition by the N status of the plant. All levels of AtNRT2.1 expression (promoter activity, transcript level, protein accumulation, transport activity) are coordinately up-regulated in the presence of NO3 - , and repressed by downstream N metabolites. Transgenic plants expressing the GUS reporter gene under the control of upstream sequences of AtNRT2.1 have been studied to identify elements targeted by these two regulatory mechanisms. A 150 bp sequence located upstream of the TATA box that is required for both stimulation by NO3 - and repression by N metabolites of the promoter has been identified. This sequence is able to confer these two regulations to a minimal promoter. Split-root experiments indicate that the stimulation of the chimaeric promoter by NO3 - occurs only at the local level, whereas its repression by N metabolites is mediated by a systemic signal spread to the whole plant. The activity of the cis -acting 150 bp element is also regulated by sucrose supply to the roots, suggesting a possible interaction between N and C signalling within this short region. Accordingly, multiple motifs potentially involved in regulations by N and/or C status are identified within this sequence by bioinformatic approaches. This is the first report of such a cis -acting element in higher plants. [source] Differential expression of three members of the AMT1 gene family encoding putative high-affinity NH4+ transporters in roots of Oryza sativa subspecies indicaPLANT CELL & ENVIRONMENT, Issue 6 2003A. KUMAR ABSTRACT In order to investigate the molecular basis of high-affinity ammonium absorption by roots of rice plants (Oryza sativa subspecies indica) the expression patterns of three members of the AMT1 family of genes in rice seedling roots in response to altered nitrogen provision and diurnal changes in irradiance were examined. The 13NH4+ influx and transcript levels of OsAMT1.1 in roots decreased several fold within 48 h when plants acclimated to 10 µm external NH4+ for 3 weeks were transferred to 10 mm NH4+. Likewise when plants acclimated in 10 mm NH4+ were transferred to 10 µm NH4+, there was an equally rapid up-regulation of OsAMT1.1 and 13NH4+ influx in the roots. Changes in transcript abundance of OsAMT1.2 following these treatments were approximately 50% less than in OsAMT1.1, and changes of OsAMT1.3 expression were even less. By contrast, in response to the diurnal changes of irradiance, root transcript abundance of OsAMT1.3 and 15NH4+ influx increased approximately three-fold late in the photoperiod, whereas OsAMT1.1 and OsAMT1.2 exhibited only modest changes. The present results suggest that high-affinity NH4+ influx is differentially regulated at the transcriptional level through the expression of three members of the OsAMT1 family of genes in roots of rice seedlings in response to changes of N status and daily irradiance. In general, these findings are in agreement with earlier observations in Arabidopsis and tomato. [source] Mitochondrial respiratory pathways modulate nitrate sensing and nitrogen-dependent regulation of plant architecture in Nicotiana sylvestrisTHE PLANT JOURNAL, Issue 6 2008Till K. Pellny Summary Mitochondrial electron transport pathways exert effects on carbon,nitrogen (C/N) relationships. To examine whether mitochondria,N interactions also influence plant growth and development, we explored the responses of roots and shoots to external N supply in wild-type (WT) Nicotiana sylvestris and the cytoplasmic male sterile II (CMSII) mutant, which has a N-rich phenotype. Root architecture in N. sylvestris seedlings showed classic responses to nitrate and sucrose availability. In contrast, CMSII showed an altered ,nitrate-sensing' phenotype with decreased sensitivity to C and N metabolites. The WT growth phenotype was restored in CMSII seedling roots by high nitrate plus sugars and in shoots by gibberellic acid (GA). Genome-wide cDNA-amplified fragment length polymorphism (AFLP) analysis of leaves from mature plants revealed that only a small subset of transcripts was altered in CMSII. Tissue abscisic acid content was similar in CMSII and WT roots and shoots, and growth responses to zeatin were comparable. However, the abundance of key transcripts associated with GA synthesis was modified both by the availability of N and by the CMSII mutation. The CMSII mutant maintained a much higher shoot/root ratio at low N than WT, whereas no difference was observed at high N. Shoot/root ratios were strikingly correlated with root amines/nitrate ratios, values of <1 being characteristic of high N status. We propose a model in which the amine/nitrate ratio interacts with GA signalling and respiratory pathways to regulate the partitioning of biomass between shoots and roots. [source] Effects of timing and rate of N supply on leaf nitrogen status, grape yield and juice composition from Shiraz grapevines grafted to one of three different rootstocksAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 1 2007B.P. HOLZAPFEL Abstract Yeast cells have a minimum N requirement to ferment a must through to dryness, so that grape N content (hence must N) becomes critical in meeting that prerequisite. Viticultural practices aimed at meeting that N requirement are of special relevance because interactions between rootstock and vineyard nitrogen supply strongly influence scion mineral nutrient status as well as shoot vigour, and via those processes, fruit composition. Such outcomes were investigated in a field trial involving Shiraz on three rootstocks viz. Teleki 5C, Schwarzmann and Ramsey. Five N supply regimes, varying from 0 to 80 kg/(haseason), were imposed through a drip-irrigation system during two periods (either flowering to veraison, or post-harvest to leaf-fall, or both) over three successive growing seasons. Post-harvest N supply increased scion leaf N and nitrate N concentrations at flowering for vines on Teleki 5C and Schwarzmann. By veraison, N recently applied in the flowering to veraison period elevated these indicators of N status in all vines on all rootstocks. Grape yields from vines on Teleki 5C and Schwarzmann were elevated by N supply after harvest, whereas juice soluble solids levels were lowered. Free amino acids in Shiraz juice were dominated by non-assimilable N, amounting to about 50% or more of the total free amino-N in the juice. Increasing N supply increased free amino acid concentrations in the juice of berries from vines on all rootstocks, but only vines on Schwarzmann derived any benefit from N supplied after harvest. The highest concentrations of free amino acids were measured in the berries from vines on Schwarzmann receiving 80 kg N/(ha.season). Of immediate practical relevance for N management of Shiraz grapevines on either Teleki 5C or Ramsey rootstocks, the minimum value for assimilable free amino-N concentration required to ferment a must through to dryness was not achieved if vineyard N application was limited to the post-harvest period. [source] | ||||||||||