1,721,007 research outputs found
Growth form rather than phylogenetic relationship predicts broad volatile emission patterns in the Brassicaceae
No full textVolatile organic compounds (VOCs) released from plants are known to mediate indirect defense against herbivores and trigger intra- and interplant signaling. While systemic defense response can be mediated both via volatile and vascular signals, it is not clear whether common ancestry and/or plant growth forms influence the choice of either mode in planta. We hypothesize that larger woody plants with a complex anatomy should rely more on volatile-mediated signaling, apparently to circumvent vascular restrictions that slow down the communication over a large distance. On the other hand, in smaller herbaceous plants faster systemic response can be achieved via vascular signaling. To investigate whether plant VOCs emission is related to plant phylogeny or growth form, we studied the composition of herbivory-induced plant volatiles in 13 Brassicaceae species representing all four evolutionary lineages, because this family is characterized by both a well-resolved phylogeny and highly diverse growth forms. Our results revealed that woody species consistently emitted a more complex blend of volatiles than herbaceous species. However, phylogenetic relatedness of the species did not explain the observed volatile emission patterns. This emphasizes the influence of growth form, rather than phylogenetic relationships on the variation in plant volatile emissions. Our findings suggest that woody, perennial plant species emit diverse VOCs, likely because these compounds comprise a more efficient mode of defense response in these large, anatomically complex plants
Isotope labeling reveals contribution of newly fixed carbon to carbon storage and monoterpenes production under water deficit and carbon limitation
No full textSecondary metabolites play important roles in plant responses to environmental stress but may also represent a large carbon (C) cost, resulting in trade-offs with other C sinks like growth and storage. However, it remains uncertain how such trade-offs may vary with changes in resource availability including water and CO2 availability. We conducted a glasshouse experiment with peppermint (Mentha x piperita L.) exposed to four treatments: control (sufficient irrigation and near-ambient CO2), water deficit (50% irrigation and near-ambient CO2), CO2 limitation (sufficient irrigation and below-ambient CO2) and the combination of water and CO2 deficits. Continuous 13CO2 labelling was used to trace allocation of newly-assimilated C. Concentrations of soluble sugars significantly increased under water deficit but decreased along with aboveground biomass under low CO2, while monoterpene concentrations remained relatively constant, independent of treatments. Under water deficit, there were no differences in allocation of new vs old C to monoterpenes production, structural growth and storage; plants grown under low CO2 even invested proportionally more newly-assimilated C for monoterpenes production, suggesting a preferential allocation to defense at the expense of growth. We concluded that C allocation to monoterpenes is actively regulated in coordination with growth and storage under water and C stresses, consistent with an optimal defense strategy to protect young tissues
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
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