1,720,962 research outputs found
An overview of the plant response to pathogen attack: chitosan as a general elicitor of induced resistance in plants.
No full textPlant disease resistance is the ability of a plant to prevent or restrict pathogen growth and multiplication. All plants, whether they are resistant or susceptible, respond to pathogen attack by the induction of coordinate signalling system, which required the accumulation of different gene products. In plant immunity general elicitors, including chitin/chitosan oligomers are able to induce host defence response by binding to specific molecule
Effect of chitosan seed treatment as elicitor of resistance to Fusarium graminearum in wheat.
No full textThe potential ability of chitosan seed treatment to induce resistance in plants of durum wheat (Triticum durum) against the seed borne fungal pathogen Fusarium graminearum, one of the main causal agents of root and foot rot in wheat, was evaluated. The chitosan seed treatment efficacy was evaluated by biochemical analyses, comparing: seed treated, seed treated and inoculated with the fungus, seed not treated and inoculated, seeds not treated and not inoculated. The enzymatic activities of some enzymes involved in defense mechanisms were analysed: guaiacol peroxidase (POD), ascorbate peroxidase (APX), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL), as well as the phenol content. Seed treatment induced changes in the enzymatic activities and increased phenol production. Greenhouse trials were performed with inoculated soil and the disease incidence on the plants was significantly reduced by chitosan seed treatment. Finally, field trials were conducted with inoculated seeds and then treated with chitosan. The chitosan seed treatment induced a decrease in disease severity and enhanced quantitative yield parameters, suggesting the possibility of the use of chitosan as a seed treatment in crop protection in order to improve the plant defense response
Chitosan in Agriculture: A New Challenge for Managing Plant Disease
No full textIn recent years, environmental friendly measures have been developed for managing crop diseases as alternative to chemical pesticides, including the use of natural compounds such as chitosan. In this chapter, the common uses of this natural product in agriculture and the potential uses in plant disease control are reviewed. The last advanced researches as seed coating, plant resistance elicitation and soil amendment applications are also described. Chitosan is a deacetylated derivative of chitin, that is naturally present in the fungal cell wall and in crustacean shells from which it can be easily extracted. Chitosan have been reported to possess antifungal and antibacterial activity and it showed to be effective against seed-borne pathogens when applied as seed treatment. It can form physical barriers (film) around the seed surface and it can vehicular other antimicrobial compounds that could be added to the seed treatments. Chitosan behaves as a resistance elicitor inducing both local and systemic plant defense responses even when applied to the seeds. The chitosan used as soil amendment was shown to give many benefits to different plant species by reducing the pathogen attack and infection. Concluding, the chitosan is an active molecule that finds many possibilities for application in agriculture, including plant disease control
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
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