1,720,972 research outputs found
Energy conversion processes and related gene expression in a sunflower mutant with altered salicylic acid metabolism
Full text linkSalicylic acid (SA) is involved in several responses associated with plant development and defence against biotic and abiotic stress, but its role on photosynthetic regulation is still under debate. This work investigated energy conversion processes and related gene expression in the brachytic mutant of sunflower lingering hope (linho). This mutant was characterized by a higher ratio between the free SA form and its conjugate form SA O-β-D-glucoside (SAG) compared to wild type (WT), without significant changes in the endogenous level of abscisic acid and hydrogen peroxide. The mutant showed an inhibition of photosynthesis due to a combination of both stomatal and non-stomatal limitations, although the latter seemed to play a major role. The reduced carboxylation efficiency was associated with a down-regulation of the gene expression for both the large and small subunits of Rubisco and the Rubisco activase enzyme. Moreover, linho showed an alteration of photosystem II (PSII) functionality, with reduced PSII photochemistry, increased PSII excitation pressure and decreased thermal energy dissipation of excessive light energy. These responses were associated with a lower photosynthetic pigments concentration and a reduced expression of genes encoding for light-harvesting chlorophyll a/b binding proteins (i.e. HaLhcA), chlorophyll binding subunits of PSII proteins (i.e. HaPsbS and HaPsbX), phytoene synthase enzyme and a different expression level for genes related to PSII repair cycle, such as HaPsbA and HaPsbD. The concomitant stimulation of respiratory metabolism, suggests that linho activated a coordinate modulation of chloroplast and mitochondria activities to compensate the energy imbalance and regulate energy conversion processes
Genetic and physiological characterization of a new brachytic sunflower mutant, lingering hope (linho).
No full textDwarf mutants in plants are crucial to elucidate regulatory mechanisms for plant growth and development. A new dwarf mutant named lingering hope (linho) was isolated from sunflower (Helianthus annuus). With the aim to characterize this new brachytic mutant, we performed genetic analysis and several morphometric data were collected. The hormonal profile and the photosynthetic performance were also investigated in this mutant. The brachytic trait is controlled by a recessive nuclear gene. The reduction of plant height is not due to the production of fewer phytomers but the phenotype depends on shorter internodes especially during reproductive stage.
The mutant and wild type (WT) phenotype is normal from the cotyledonary stage to the first two pairs of leaves. However, after this vegetative stage, linho leaves show an altered ratio length/width of the blade, delayed greening phenomena and chlorosis in proximal area of the lamina; moreover, asymmetric shape and epinasty have been frequently observed. The linho mutant has defects in inflorescence development because blossoming is not regular. In several organs of linho and WT we analyzed endogenous hormonal level of abscisic acid, jasmonic acid, indoleacetic acid, salicylic
acid (SA) and gibberellins. Results demonstrate that the brachytic trait is not associated to a specific hormonal reduction but the endogenous SA content in some organs (i.e. young leaves in reproductive stage) of the mutant is very high. SA plays key role in plant response to abiotic and biotic stresses although SA effects on plant growth and development are very complex and not still well understood. To evaluate the photosynthetic performance and the light energy dissipation mechanisms, gas exchange and fluorescence measurements were determined in linho and WT
plants. The CO 2 assimilation rate significantly decreased in linho, due to the effects of both stomatal and non-stomatal constraints. In addition, the reduction of both photochemical efficiency of photosystem II and non-photochemical quenching at saturating light intensity indicated a lower capacity of linho to dissipate the absorbed light energy, associated with a reduced content of chlorophylls and carotenoids. These results suggest that the linho mutant could be useful to investigate the role of SA during plant growth and developmen
Azospirillum baldaniorum Sp245 Induces Physiological Responses to Alleviate the Adverse Effects of Drought Stress in Purple Basil
Full text linkAzospirillum spp. are plant growth-promoting rhizobacteria (PGPR) that exert beneficial effects on plant growth and yield of agronomically important plant species. The aim of this study was to investigate the effects of a root treatment with Azospirillum baldaniorum Sp245 on hormones in xylem sap and physiological performance in purple basil (Ocimum basilicum L. cv. Red Rubin) plants grown under well-watered conditions and after removing water. Treatments with A. baldaniorum Sp245 included inoculation with viable cells (1 center dot 10(7) CFU mL(-1)) and addition of two doses of filtered culture supernatants (non-diluted 1 center dot 10(8) CFU mL(-1), and diluted 1:1). Photosynthetic activity, endogenous level of hormones in xylem sap (salicylic acid, jasmonic acid, and abscisic acid), leaf pigments, leaf water potential, water-use efficiency (WUE), and drought tolerance were determined. Fluorescence and gas exchange parameters, as well as leaf water potential, showed that the highest dose of filtered culture supernatant improved both photosynthetic performance and leaf water status during water removal, associated with an increase in total pigments. Moreover, gas exchange analysis and carbon isotope discrimination found this bacterial treatment to be the most effective in inducing an increase of intrinsic and instantaneous WUE during water stress. We hypothesize that the benefits of bacterial treatments based on A. baldaniorum Sp245 are strongly correlated with the synthesis of phytohormones and the induction of plant-stress tolerance in purple basil
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
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