1,720,990 research outputs found
Determination of the Effect of Co-cultivation on the Production and Root Exudation of Flavonoids in Four Legume Species Using LC–MS/MS Analysis
Full text linkFlavonoids play a key role in the regulation of plant−plant and plant−microbe interactions, and factors determining their release have been investigated in most of the common forage legumes. However, little is known about the response of flavonoid production and release to co-cultivation with other crop species. This study investigated alterations in the concentration of flavonoids in plant tissues and root exudates in four legumes [alfalfa (Medicago sativa L.), black medic (Medicago polymorpha L.), crimson clover (Trifolium incarnatum L.), and subterranean clover (Trifolium subterraneum L.)] co-cultivated with durum wheat [
Triticum turgidum subsp. durum (Desf.) Husn.]. For this purpose, we carried out two experiments in a greenhouse, one with glass beads as growth media for root exudate extraction and one with soil as growth media for flavonoid detection in shoot and root biomass, using LC−MS/MS analysis. This study revealed that interspecific competition with wheat negatively affected legume growth and led to a significant reduction in shoot and root biomass compared with the same legume species grown in monoculture.
In contrast, the concentration of flavonoids significantly increased both in legume biomass and in root exudates. Changes in flavonoid concentration involved daidzein, genistein, medicarpin, and formononetin, which have been found to be involved in legume nodulation and regulation of plant−plant interaction. We hypothesize that legumes responded to the co-cultivation with wheat by promoting nodulation and increasing exudation of allelopathic compounds, respectively, to compensate for the lack of
nutrients caused by the presence of wheat in the cultivation system and to reduce the competitiveness of neighboring plants. Future studies should elucidate the bioactivity of flavonoid compounds in cereal-legume co-cultivation systems and their specific role in the nodulation process and inter-specific plant interactions such as potential effects on weeds
Polyphenol contents in amaranth cultivars and their relationship with insect feeding deterrence
No full textThe role of secondary metabolites (SMs) in Amaranthus plant defense is a poorly studied field. Different cultivars of amaranth have shown varying degrees of susceptibility to insect attack in the field, and previous research has discussed the potential role of these compounds as insect phagodeterrents. In this study, we measured the content of five hydroxybenzoic acids, three hydroxycinnamic acids, and three flavonoids in 30-days-old undamaged plants, over two consecutive years. In addition, we examined the impact of SM content in the leaves of amaranth cultivars on food preference and the rate of plant tissue utilization by the generalist insect Spodoptera frugiperda. In the first year, experiments were conducted using two cultivars: A. cruentus (1) and A. mantegazzianus (1), while the second-year experiments included three cultivars of A. hypochondriacus (a total of five cultivars). Our results showed that, under identical growth conditions and in the absence of stress, flavonoid content emerged as the most consistent trait for distinguishing between cultivars, with rutin being the key variable accounting for the observed variability. In contrast, the contents of hydroxybenzoic and hydroxycinnamic acids exhibited significant variability among cultivars and between years. Additionally, we observed that high concentrations of phenolic acids in plant tissue correlated with lower rates of food utilization by S. frugiperda, without affecting preference indices. The potential defensive capabilities of these SMs for mitigating insect herbivory damage in amaranth crops are discussed in this work.Fil: Niveyro, Selene Leonor. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Pampa; ArgentinaFil: Salvo, Silvia Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Laursen, Bente. University Aarhus; DinamarcaFil: Fomsgaard, Inge S.. University Aarhus; Dinamarc
Secondary metabolites of amaranth varieties (Amaranthus spp.) and its relationship with leaf damage by chewing insects in the field
No full textIn this study, we determined the abundance of secondary metabolites present in leaves of five varieties of Amaranthus, described the community of chewing insects observed in the foliage and also quantified damage by folivore insects in the field. Three flavonoid glucosides (rutin, nicotiflorin and isoquercitin), nine phenolic compounds (coumaric, vanillic, caffeic, syringic, ferulic, sinapic, protocatechuic, salicylic and 4-hydroxybenzoic acid) and three betalains (amaranthine, iso-amaranthine and betanin) were found to be present in amaranth leaves. Flavonoids appeared in of all varieties analyzed, with rutin being the most important. Betalains occurred only in some varieties and at different proportions, and nine phenolic acids were observed in all the varieties, with the exception of sinapic acid. Significant differences in the chemical composition of the varieties were noted. A total of 17 species of chewing phytophagous insects were observed through visual counting in Amaranthus plants, with the order Coleoptera being the most important and having the highest diversity of species. The degree of herbivory differed significantly among the varieties. Multivariate regression analysis indicated that the eight analyzed compounds detected in the plants had significant linear relationships with herbivory in the field. However, to draw any conclusions relating the amount of any compound to the degree of herbivory damage is premature at this stage of the research.Fil: Niveyro, Selene Leonor. Universidad Nacional de La Pampa. Falcultad de Agronomía; ArgentinaFil: Mortensen, Anne G.. Aarhus University. Faculty of Agricultural Sciences, Department of Integrated Pest
Management Research Centre; DinamarcaFil: Fomsgaard, Inge S.. Aarhus University. Faculty of Agricultural Sciences, Department of Integrated Pest
Management Research Centre; DinamarcaFil: Salvo, Silvia Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentin
Caracterización de ácidos fenólicos y flavonoides presentes en hojas de amaranto (Amaranthus hypochondriacus L.).
Full text linkTesis (Maestría en Ciencias en Biología Molecular)"Las hojas de amaranto (Amaranthus spp) son consideradas como plantas medicinales y son utilizadas para preparar alimentos. El objetivo de éste trabajo fue obtener el perfil cualitativo y cuantitativo de ácidos fenólicos y flavonoides en hojas de dos variedades de A. hypochondriacus con diferentes colores de hojas (rojas y verdes) crecidos en diferentes condiciones de cultivo (maceta chica y grande dentro de invernadero; cultivadas en campo, cultivadas en campo pero que presentaban daño por insecto. Los ácidos fenólicos son compuestos involucrados en la respuesta al estrés biótico y abiótico por las plantas mientras que los flavonoides son compuestos con mayor frecuencia relacionados con las propiedades nutracéuticas. La cuantificación de tres flavonoides y cinco ácidos fenólicos en hojas de amaranto se determinó empleando la metodología de extracción con solventes acelerada (ASE) y la cromatografía de líquidos acoplada a espectrómetro de masas (LC/MS/MS). En las hojas de amaranto, el principal flavonoide fue la rutina, en concentraciones de 3441 hasta 9236 μg/g. La concentración de nicotiflorin fue de 523 a 1,297 μg/g, y la de la iso-quercitrina fue de 371 a 930 μg/g. Los ácidos fenólicos fueron los compuestos detectados en menor proporción en las hojas de amaranto. El ácido ferúlico se detectó únicamente en hojas rojas (0.5 μg/g) crecidas en maceta pequeña en invernadero, mientras que el ácido cumárico solo se detectó en hojas verdes (0.7 μg/g) cultivadas en maceta grande en invernadero. Los resultados indican que la producción de ciertos productos naturales en hojas de amaranto puede ser influenciada por las condiciones de cultivo.""Leaves from amaranth (Amaranthus spp.) are used as medicines and in the preparation of food. The aim of this work was to obtain the qualitative and quantitative profile of flavonoid and phenolic acid compounds in leaves of two varieties of A. hypochondriacus with different leaf colors (red and green) that were grown in different conditions (small and big pots inside greenhouse, grown in fields, grown in fields with insect damage). Phenolic acids are compounds produced in response to biotic and abiotic stresses in plants, while flavonoids are related to the nutraceutical properties of amaranth leaves. The three flavonoids and five phenolic acids in amaranth leaves were determined using accelerated solvent extraction and Liquid Chromatography/Mass Spectrometry. In amaranth leaves the main flavonoid was rutin, with concentrations from 3,441-9,236 μg/g; the concentration of nicotiflorin ranged from 1,297–523 μg/g, and for iso-quercitrin 930–371 μg/g. Phenolic acids were minor compounds in amaranth leaves: ferulic acid was only present in red leaves grown in small pots in greenhouse (0.5 μg/g) and coumaric acid was only detected in green leaves (0.7 μg/g). Our findings indicate that the production of certain natural products in amaranth leaves could be influenced by growth conditions.
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
- …
