1,720,977 research outputs found
Photosynthetical response to ozone exposure and nitrogen enrichment of C. betulus and Q. robur saplings : results of the first year of experimentation under the ECLAIRE project
No full textA manipulation experiment on ozone enrichment and increased nitrogen deposition has been performed in 2012 in Northern Italy on young trees of Quercus robur and Carpinus betulus, two of the most representative species of forest vegetation of the Po valley and the pre-alpine region. Two hundreds and twentyfour saplings of each species have been potted and placed in 12 Open-Top Chambers following a split-plot design with 3 randomized blocks and two factors: ozone concentration, the main factor, at 4 different levels (CF, AA, AA+35%, AA+70%), and nitrogen irrigation, the nested factor, at 2 different levels (tap water, tap water + 70Kg of N*ha*y-1).
Saplings growth and physiological have been monitored during the whole growing season from April to the end of September. Gas exchange measurements were performed once a month as well as photosynthetic performance of PSII and stomatal conductance measurements (3 daily cycles).
Moreover A/Ci and A/Light response curves have been made in June and September to assess the maximum carboxylation rate of RuBisCO, the maximum assimilation at non-limiting Ci concentration, photorespiration and dark respiration rates. At the end of the growing season half of the saplings have been harvested in order to estimate the total biomass production and its root/shoot partition.
Preliminary results of the first year of experimentation (ECLAIRE experiment will last two years) reveal significant positive effects of nitrogen and negative effects of ozone at photosynthetic level in both species.
Effects on growth and biomass partition were detected only for nitrogen, particularly for Q. robur, while the ozone effects were weak and scattered. The only detectable effect of ozone was a clear reduction of stomatal conductance starting from the mid-season. This fact highlights the need to include a f(O3) modifying function in the stomatal conductance models, one of which is proposed for these two species.
The interaction between the two factors shows an antagonistic effects of nitrogen and ozone on the photosynthetic parameters.
The observed incoherence among the ozone effects on photosynthetic parameters and the real plant growth rises a question about the possibility to predict ozone impacts on plant growth with a purely modellistic approach based upon photosynthesis and, once again, highlights the need to set up and support pluriannual experiments on field
Frumento duro e ozono: caratteristiche biochimiche e ultrastrutturali di due cultivar sensibili ma con diversa risposta sintomatologica
No full textColombo e Sculptur sono due cultivar moderne di grano duro molto sensibili all’ozono in termini di parametri eco-fisiologici, con inevitabili effetti negativi sulla produttività. Tuttavia, la loro risposta sintomatologica è molto diversa: Colombo, dopo alcune settimane di esposizione all’inquinante, mostra danni fogliari macroscopici, consistenti in spot clorotici spesso degeneranti in estese lesioni necrotiche, mentre Sculptur rimane quasi asintomatica per molte settimane. Nel presente lavoro si è cercato di chiarire, attraverso analisi biochimiche e microscopiche, i meccanismi alla base di questa differente risposta sintomatologica.
Allo scopo, piante delle due cultivar sono state cresciute in Open Top Chambers (OTCs) ed esposte ad aria filtrata o arricchita di ozono. Le analisi sono state effettuate su foglie a bandiera campionate in corrispondenza di due diversi stadi fenologici (pre- e post-antesi). I risultati hanno evidenziato che in Colombo il contenuto di acido ascorbico era significativamente più basso rispetto a Sculptur, in entrambi gli stadi analizzati, e che non variava con l’esposizione all’ozono. Il livello di glutatione ossidato, invece, aumentava nelle foglie di Colombo esposte all’inquinante, e le cellule attorno alla cavità sottostomatica presentavano abbondanti depositi di H2O2. Al contrario, le foglie della cultivar Sculptur esposte ad ozono non mostravano aumenti di H2O2, ma i loro stomi apparivano spesso chiusi. In Sculptur, le cellule del mesofillo apparentemente non danneggiate presentavano cloroplasti leggermente rigonfi e caratterizzati da numerosi plastoglobuli, probabilmente come conseguenza di un leggero stress ossidativo generalizzato.
Questi risultati suggeriscono che l’assenza di una sintomatologia visibile in Sculptur sia determinata da un suo maggiore contenuto di acido ascorbico nonché da un più efficiente meccanismo di chiusura stomatica. Al contrario, le lesioni clorotiche/necrotiche mostrate dalle foglie di Colombo potrebbero essere causate sia da una minore capacità di detossificazione che da una ridotta capacità di chiusura stomatica. Ciò si tradurrebbe in un severo danno localizzato a gruppi di cellule del mesofillo adiacenti alla camera sottostomatica, lasciando tuttavia una parte del tessuto fotosintetico ancora funzionale. La perdita di produzione, molto simile nelle due cultivar, sarebbe quindi dovuta in entrambi i casi a ridotta attività fotosintetica, tuttavia con meccanismi diversi: nel caso di Sculptur per chiusura degli stomi e lieve danno ai cloroplasti mentre nel caso di Colombo per riduzione della quantità di tessuto fotosinteticamente attivo
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
PHYSIOLOGICAL AND ECOLOGICAL DRIVERS AND AGRONOMICAL CONSEQUENCES OF THE OZONE-LIKE SYNDROME IN WHEAT
Full text linkTropospheric ozone (O3) is known to adversely affect the productivity of a wide range of crops including wheat. However different species, can exhibit different responses to ozone exposure. Since the Triticum genus (wheat) is one of the most cultivated and consumed cereal on the global scale and also considered an O3-sensitive crop, research on its protection against ozone damages can contribute to the improvement of its productivity and thus the worldwide food security.
The first part of this research was focused on a varietal screening experiment carried out in 2013 to assess the ozone sensitivity of 3 Italian and 2 Spanish cultivars of durum wheat (Triticum durum), applying two different levels of ozone (50% increment and 50% decrement of the ambient ozone concentration ) to plants grown in Open-Top Chambers. The durum wheat sensitivity to ozone was based on the assessment of leaf visible injuries, histochemical observations, physiological parameters, yield and yield quality analysis. Two Italian cultivars (Colombo and Sculptur) resulted more sensitive to ozone than the others, according to the physiological parameters tested and to the grain yield and quality analysis. However, they also showed different levels of leaf visible and microscopic injuries. The flag-leaves of cv Colombo resulted clearly more damaged by ozone exposure than the flag-leaves of cv Sculptur at both visible and microscopic levels.
The second part of the research tried to analyze to a deeper extent the response to ozone exposure of the two most sensitive cultivars selected from the previous experiment. A second experiment was performed in 2014 using four ozone levels: -5% and -50% of ambient ozone concentration in non-filtered and charcoal-filtered OTCs, respectively; +30 and +60% of ambient ozone concentration in ozone-enriched OTCs (OZ+ and OZ++ OTC).
In order to test the effectiveness of an antitranspirant compound in protecting durum wheat from ozone oxidative stress, a chitosan solution was weekly applied as leaf spraying during the growing season in 2014. The chitosan treatments were applied at 3 levels: tap-water (CTRL, no chitosan), 40kDa chitosan solution (CHI40) and 300kDa chitosan solution (CHI300). Both durum wheat cultivars confirmed their sensitivity to ozone as observed in the previous experiment. Grain yield losses observed in ozonated treatments were related to a decrease of stomatal conductance that is due to damages to the Rubisco and Calvin cycle. No protective effect due to chitosan treatments was observed in both cultivars. However, chitosan improved slightly the grain yield and the aboveground biomass production in plants grown in charcoal-filtered and non-filtered OTCs. Biomass data were also used for the definition of dose-effect relationships based on the ozone exposure (AOT40), the phytotoxic ozone dose (POD6) and the yield losses. The grain yield losses were plotted against AOT40 and POD6 in order to test the linear regression of these two indices. Each increase of AOT40 3000 ppb.h caused a grain yield loss of about 1.8%, while for the POD6, an increase of 1mmol O3 m-2 caused 1.3% reduction. Both AOT40 and POD6 resulted appropriated for assessment of durum wheat yield losses. However, the dose-effect relationship based on POD6 showed a better fit compared to the AOT40.
During the 2014 experiment an important part of the research regarded the ultrastructural analysis of ozone-like symptoms on flag-leaves carried out by transmission electron microscopy (TEM), and the assessment of the levels of some antioxidant molecules (ascorbate and glutathione) involved in the ozone-detoxifying process, to understand the mechanisms underlying the different ozone sensitivity of Colombo and Sculptur in terms of visible and microscopic symptoms. Results from TEM demonstrated that visible symptoms in Colombo are due to the presence of damaged stomata and plasmolyzed mesophyll cells around the sub-stomatal cavity. On other hand, no damage on stomata, mesophyll cells and chloroplasts were observed in Sculptur cultivar explaining the absence of the visible symptoms. In general Sculptur showed higher levels of ascorbate content than Colombo, suggesting a higher capacity ascorbate biosynthesis. No significant difference in ascorbate content was found between plants exposed and not exposed to elevated ozone. The total and the oxidized glutathione content increased in the Colombo cultivar grown in elevated ozone conditions indicating that plant ability to maintain glutathione in the reduced form was decreased by the ozone stress
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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