1,720,961 research outputs found
Glyphosate tolerance in maize (Zea mays L.) 1. Differential response among inbred lines.
No full textVariation in susceptibility to the safe broad-spectrum herbicide glyphosate was investigated in maize. Eleven inbred lines, grown in a growth chamber, were evaluated for their tolerance to the herbicide at 2.4 mM (0.2 kg a.i. in 400 I ha-1 of water). Following treatment with glyphosate at the three-leaf stage, significant variation in damage, expressed as visual injury ratings scored 7, 14 and 21 days after the application of the herbicide, was found. Effects on dry weight and shoot height were consistent with visual scores and the carbon-exchange rate was found to be a sensitive index of differential injury.
Biochemical characterization of 5-enol-pyruvyl-shikimate-3-phosphate (EPSP) synthase, the main target of the herbicide, ruled out the possibility that this differential susceptibility was due to variations in the sensitivity of the enzyme. On the contrary, a positive correlation was found between in vivo tolerance and EPSP synthase levels, measured at different stages during seedling growth. This result suggests that a naturally occurring difference in EPSP synthase levels in the tissues may contribute to the differential response observed in vivo in maize inbreds
ARBUSCULAR MYCORRHIZAL SYMBIOSIS PROMOTES THE TRANSCRIPTION OF ANTIOXIDANT GENES IN A WHITE POPLAR CLONE TOLERANT THE HEAVY METALS
No full textInheritance of glyphosate tolerance among maize somaclones
No full textTwo families derived from a maize somaclone previously found to tolerate the exposure to 2.4 mM (0.2 kg a.i. in 400 1 ha -1 of water) glyphosate were evaluated genetically for herbicide tolerance. The lines were self-crossed and crossed with three inbred genotypes showing significant variation in tolerance to the herbicide. Seedlings of the families this way obtained were evaluated in a growth chamber following a treatment with 2.4 mM glyphosate at the three-leaf stage. Visual injury rating, dry weight, shoot height and carbon-exchange rate were scored two weeks after the application of the herbicide. General combining ability effects were significant, suggesting that additive gene action is important in conferring tolerance to glyphosate. Tile results strengthen the possibility that additional factors, not related to the properties of the main target of herbicide action, the activity of the shikimate pathway enzyme 5-enol-pyruvyl-shikimate-3-phosphate synthase, may provide the basis f..
Glyphosate tolerance in maize (zea-mays l) .2. selection and characterization of a tolerant somaclone
No full textThe progeny of 104 regenerated maize plants were screened for tolerance to the safe broad-spectrum herbicide glyphosate during seed germination and early growth. Seven somaclones showed varying degrees of resistance to the application of the herbicide at 1.2 mM (0.1 kg a.i. in 400 1 ha(-1) of water). Plants capable of a normal growth following treatment with 2.4 mM (0.2 kg ha(-1)) glyphosate at the three leaf stage were selfed, and their progeny analyzed. A family able to tolerate the exposure to glyphosate at 2.4 mM was isolated and shown to maintain a photosynthetic rate comparable with control after the application of the herbicide.
The selfed progeny of the tolerant somaclone was characterized as to the properties of two targets of glyphosate, the shikimate pathway enzymes 5-enol-pyruvyl-shikimate-3-phosphate (EPSP) synthase and 3-deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) synthase. In vitro tests ruled out the possibility that the tolerance was due to altered forms of these enzymes. Families showed significant variability with regard to EPSP and DAHP synthase levels, measured at different stages during seedling growth; however, not even these traits were correlated with in vivo response to glyphosate. The possible role of other physiological processes in determining the increased tolerance to the herbicide is discussed
A glyphosate-resistant 5-enolpyruvilshikimate-3-phosphate synthase confers tolerance to a maize cell line
No full textAmong a few cell lines of maize (Zea mays L., cv. Black Mexican Sweet (BMS)) tested, one showed a natural, remarkable tolerance to glyphosate at concentrations as high as 10 mM. Two activities of 5-enol-pyruvyl-shikimate-3-phosphate (EPSP) synthase, the target enzyme of the herbicide, were separated in the tolerant culture by anion-exchange chromatography. One peak of activity was not significantly inhibited by glyphosate even at millimolar concentrations. While the glyphosate-sensitive isoform persisted throughout the growth cycle of the culture, the glyphosate-resistant EPSP synthase increased only after the onset of exponential growth and declined in the stationary phase. Tolerance to the herbicide was accompanied by a reduced affinity of the enzyme for the substrate phospho-enol-pyruvic acid
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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