1,720,956 research outputs found
Efecto de la inoculación de Hongos Formadores de Micorrizas Arbusculares (HFMA) sobre un sistema suelo-planta de cacao en suelos contaminados con cadmio en etapa de vivero
Get PDFilustraciones, fotografías, gráficas, tablasLa presente investigación estudia la dinámica del cadmio (Cd) en el trópico ácido en presencia de hongos formadores de micorrizas arbusculares (HFMA) cuando se tienen suelos con concentraciones del metal, destinados para cultivo de cacao. Para lograr este objetivo se examina la distribución del Cd en las fracciones del suelo y en los diferentes órganos de la planta. Se concluye que, principalmente, a altas concentraciones del metal en el suelo, cuando la fuente del mismo es antrópica, el hongo puede modificar la dinámica del mismo, su disponibilidad en el tiempo. Adicionalmente, por medio del análisis de parámetros fisiológicos y de producción de biomasa sobre las plantas se encuentra que dependiendo del nivel de cadmio y para las concentraciones más altas del metal, el hongo tiene un efecto benéfico sobre el funcionamiento del aparato fotosintético, permitiendo a las plantas una ventaja sobre las plantas no inoculadas contra los efectos tóxicos del metal pesado. Se estudió adicionalmente la capacidad de absorción, translocación y fitoextracción de las plantas inoculadas comparadas con las no inoculadas, de lo que se concluye que para concentraciones altas de cadmio en el suelo la Eficiencia de Absorción (E abs) es mayor en plantas inoculadas, al igual que la Eficiencia de translocación (E transl) del metal, mientras que la Eficiencia de la fitoextracción (E fitoext) tiende a disminuir. (Texto tomado de la fuente).This research studies the dynamics of cadmium in a tropical acidic soil when it is contaminated with different metal concentration and in the presence of Arbuscular Mycorrhizal fungi (AMF), in cocoa cropping. In order to achieve this goal we´ve looked for cadmium distribution in different soils fractions and in different plant organs, concluding that, at high soil cadmium concentration, when the origin of cadmium contamination is antropogenic, the AMF can modify the metal dynamics, changing its bioavailability along. Aditionally, the physiological parameters and biomass plants production depended on the cadmium level. For the higher soil cadmium concentrations, the AMF exerted a beneficial effects, on the photosynthetic apparatus performance, giving inoculated plants an advantage over the non-inoculated plants against the toxic heavy metal´s effects. The uptake, translocation and fitoextraction plant´s ability was calculated for inoculated plants compared to non-inoculated plants. We concluded that at high soil cadmium concentration, the E uptake is better in inoculated plants, the same was observed for E translocation, while an opposite effect was observed for E fitoextraction.MaestríaMagíster en Ciencias AgrariasSuelos y aguasCiencias Agronómica
Efecto de la simbiosis de Rhizophagus irregularis con plántulas de cacao (Theobroma cacao L.) en el tizón de plántulas (Phytophthora palmivora (Butler)
Get PDFilustraciones, fotografías, gráficas, tablasEl presente trabajo de investigación se propuso evaluar el efecto de la simbiosis del hongo formador de micorrizas arbúsculares (HFMA) Rhizophagus irregularis con plántulas de cacao (Theobroma cacao L.), sobre el “tizón de plántulas” (Phytophthora palmivora (Butler)) en condiciones de Yopal (Casanare), Colombia. La metodología empleada incluyó una caracterización previa de los HFMA locales presentes en la rizósfera de plantas adultas de cacao, donde se encontraron seis géneros representativos de HFMA, siendo Rhizophagus abundante entre ellos (Capítulo I). Adicionalmente, se realizó un análisis preliminar en la misma plantación sobre el comportamiento de la enfermedad “pudrición negra del fruto” (PNF), causada por Phytophthora spp., en el contexto de enfermedades co-ocurrentes. Esto para tener aproximaciones sobre la funcionalidad del mejoramiento genético en la dinámica de Phytophthora spp. en la zona de estudio (Capítulo II). A nivel de vivero, se evaluó el efecto de la simbiosis de Rhizophagus irregularis con plántulas de cacao sobre la intensidad de la enfermedad “tizón de plántulas” (P. palmivora). Este análisis se compuso por dos experimentos principales, el primero se refiere a la prueba de inoculación del oomycete en las plántulas para garantizar el proceso de infección. El segundo experimento, estuvo dirigido al efecto que causa el establecimiento de la simbiosis de Rhizophagus irregularis con las plántulas sobre la incidencia y severidad de la enfermedad bajo análisis. La mayor intensidad de la enfermedad se logró con la infección de zoosporas de P. palmivora en hojas y la simbiosis con R. irregularis redujo significativamente el “tizón de plántulas” de cacao (Capítulo III). Adicionalmente, se hizo un seguimiento a la dinámica de dos variables respuesta indicadoras de resistencia a enfermedades, con el fin de tener una aproximación a la resistencia sistémica inducida (ISR). Para esto, se realizó el monitoreo de la actividad guayacol peroxidasa (GPX) y de deposición de calosa en los tejidos de plántulas de cacao, dónde se obtuvo mayor actividad de estas dos variables bajo el efecto de la simbiosis (Capítulo IV). Finalmente, se presenta un análisis integrado sobre la dinámica de colonización (%) de R. irregularis en las raíces de plántulas de cacao y el seguimiento a variables de crecimiento vegetal. (Texto tomado de la fuente).This research was aimed to evaluate the effect of the symbiosis of the arbuscular mycorrhizal fungi (AMF) Rhizophagus irregularis with cocoa seedlings (Theobroma cacao L.) on the "seedling wilt" (Phytophthora palmivora) at Yopal (Casanare), Colombia conditions. The methodology involved included a previous characterization of AMF local present in the rhizosphere of cocoa plants where six representative genera of AMF were found, being Rhizophagus abundant among them (Chapter I). A preliminary analysis was carried out in the same plantation on the disease behavior "black pod rot”, caused by Phytophthora spp., in the context of co-occurring diseases. This to have approximations on the functionality of the genetic improvement in the dynamics of Phytophthora spp. in the study area (Chapter II). At nursery stage, effect of the symbiosis of the AMF fungus Rhizophagus irregularis with cocoa seedlings on the intensity of the "seedling wilt" disease (P. palmivora) was evaluated. This analysis was composed by two main experiments, the first one refers to the test of oomycete inoculation in cocoa seedlings to guarantee the infection process. The second experiment was directed to the effect that causes the establishment of the symbiosis of R. irregularis with cocoa seedlings on the incidence and severity of the disease under analysis. The highest intensity of the disease was achieved with the infection of zoospores of P. palmivora in leaves and the symbiosis with R. irregularis significantly reduced the “cocoa seedling blight" (Chapter III). The dynamics of two response indicator variables of disease resistance were monitored, in order to have an approximation to induced systemic resistance (ISR). Thus, the analysis of the guayacol peroxidase (GPX) activity and callose deposition in cacao seedlings inoculated with R. irregularis was performed, where greater activity of these two variables was obtained under the effect of symbiosis (Chapter IV). Finally, an integrated analysis on the dynamics of colonization (%) of R. irregularis in the roots of cocoa seedlings and the follow-up to plant growth variables is presented.Incluye anexosMaestríaMagíster en Ciencias AgrariasFitopatologíaCiencias Agronómica
Funcionalidad de la interacción simbiótica entre variedades de yuca y genotipos de Rhizophagus irregularis en la Orinoquía Colombiana
Get PDFEn este trabajo se encontró que la inoculación con un aislado de Rhizophagus irregularis producido in vitro aumentó significativamente las producciones y la eficiencia en la aplicación de fertilizantes fosfatados en un cultivo de la variedad de yuca MCOL2737 sembrado en Yopal (Casanare). Luego, un experimento en campo fue establecido para evaluar el efecto de líneas genéticamente diferentes de esta especie de hongo en la producción, calidad y colonización de raíces y en el crecimiento y supervivencia de las plantas de tres variedades diferentes de yuca (MCOL2737, CM4574 y CM6438). Este experimento fue establecido en Yopal en dos años consecutivos. La producción, calidad y colonización de las raíces y el crecimiento de las plantas fueron diferentes según la línea inoculada y, las respuestas inducidas por cada línea genética dependieron de la variedad de yuca. Además, los efectos generados en la producción por las líneas fúngicas fueron reproducibles en las dos repeticiones de los experimentos. Algunas de estas líneas, producidas en el laboratorio a partir del cultivo in vitro de una espora tomada de líneas iniciales, produjeron efectos diferentes que los de sus parentales. El experimento también se estableció en Santana, donde el clima y el suelo son diferentes a los de Yopal. Se concluyó que: 1) La diversidad funcional causada por la variabilidad genética de R. irregularis fue suficiente para ser detectada en campo en Yopal; 2) Algunas líneas de R. irregularis obtenidas en el laboratorio en cultivos in vitro, generaron efectos diferentes a los de sus parentales, en la producción y la calidad de la yuca en Yopal; 3) El efecto de esas líneas dependió de la variedad de yuca sembrada y del ambiente donde ocurrió la interacción. Con este trabajo se demostró que la selección de líneas genéticas de R. irregularis puede ser utilizada para obtener líneas fúngicas que produzcan un efecto deseado en un determinado cultivo como el de la yuca y en un ambiente particular como el que ofrece YopalAbstract. In this work, it was found that the in vitro mass-produced Rhizophagus irregularis significantly increased the root production and the phosphate fertilizers efficiency in a commercial crop with MCOL2737 cassava variety located in Yopal (Eastern Plains of Colombia). Then, a field experiment was established to study if R. irregularis genetic lines lead to differences on root production, quality and colonization and on plant growth and survival for three cassava varieties (MCOL2737, CM4574 and CM6438). This experiment was established in Yopal in two different years. Root production, quality and colonization and plant growth varied according to the inoculated AMF line and, the responses induced by each fungal line were also different between cassava varieties. Further, fungal lines effects on root production were reproducible in the two years. Some fungal lines were obtained in the lab by culturing one AMF spore isolated from initial AMF lines, and some of them, did not produce the same effect than their parental lines in cassava plants. The same experiment was also established in Santana, where the climate and soil are different than in Yopal. We conclude that: 1) Functional diversity within R. irregularis was enough to be detected in field conditions in Yopal; 2) Inoculation with R. irregularis lines obtained from culturing in the lab altered production and quality cassava crops in Yopal in a different way than their parental lines; 3) AMF lines effect depended on the cassava variety and the environment. We demonstrated that selection of R. irregularis genetic lines produced in vitro could be used to find lines that have a desired effect on a given crop such as cassava in a particular environment like Yopal.Doctorad
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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