1,721,015 research outputs found
Le macchine molecolari deputate alla costruzione e modificazione delle pareti delle cellule vegetali
No full textLe pareti sono uno degli elementi funzionali caratterizzanti delle cellule vegetali, dove biosintesi, assemblaggio e rimodellamento sono sotto stretto controllo genetico e ambientale. La principale macchina molecolare coinvolta è la cellulosa sintasi, la cui attività permette la polimerizzazione degli zuccheri in cellulosa e la cui interazione con il citoscheletro determina l'accrescimento e la forma definitiva delle cellule mature. Altri meccanismi enzimatici sono ad oggi sotto investigazione per comprendere meglio come avvengono la costruzione e le modificazioni di questa struttura
cellulare, che garantisce alle piante il necessario sostegno meccanico e fornisce al contempo all'uomo materie prime come la cellulosa ed il legno.The cell wall is one of the functional elements of the plant cell, where biosynthesis, assembly and remodeling are under genetic and environmental control. The main molecular machinery involved is cellulose synthase, that polymerizes sugars into cellulose and interacts with the cytoskeleton to guarantee growth and shape of the mature cell. Other enzymatic mechanisms are being elucidated, that explain how this fundamental cellular structure is built and modified. Research interest in this field is motivated by the importance of this structure both for the plant’s mechanical properties and as a source of raw materials such as cellulose and timber
Total phenolic content in brown algae from the Sicilian coast
No full textPhlorotannins are polyphenolic secondary metabolites found in almost all brown algae that function as defense against grazers, pathogens and epiphytes but are also involved in photoprotection mechanisms. These com- pounds, produced in the Golgi apparatus, are accumulated in cytoplasm, within vesicules called physodes, or bound to the cell wall. The concentration of phlorotannins differs within and between species, shows geograph- ical variations but may be also affected by abiotic or biotic factors. We present here an overview of the studies carried out on total phenolic content in brown algae collected along the north-western coast of Sicily. The aims of these studies were in particular a) to analyse total phenolic content in four Mediterranean brown algae (Cys toseira amentacea, Cystoseira compressa, Dictyopteris polypodioides and Padina pavonica), b) to follow the sea- sonal changes in total phenolic content in D. polypodioides and C. amentacea and c) to test the effects of temperature on total phenolic content of C. amentacea. Results showed signiicant differences in total phenolic content between leathery and sheet-like algae and also within each morphological group. Among the four species, the sheet-like alga D. polypodioides showed the highest concentration of phenolic compounds. Differ- ences in the seasonal pattern of total phenolic content and in the period of maximum production were observed between D. polypodioides and C. amentacea. In D. polypodioides the peak was observed during winter and autumn whereas for C. amentacea the peak was observed during spring and summer. Moreover, C. amentacea responded signiicantly to the exposition to an increase of temperature, suggesting that increasing global temperatures predicted in the coming century might have effects on the chemical defences and then on the trophic interactions of these algae. The results of these studies seem to conirm that total phenolic content in brown algae is a re- sponse to a combination of several factors. However, due to the complexity of total phenolic content responses in brown algae and the multiple roles of phlorotannins, for a better understanding of this process, it is still nec- essary to identify which types of phlorotannins are responsible for the different activities in order to clarify who does what. Therefore, studies are currently in progress in order to characterize phlorotannins in some species belonging to the Fucales and Dictyotales and to test their biological activities
Effects of foliar application of glycine betaine and chitosan on Puccinellia distans (Jacq.) Parl. subjected to salt stress
Full text linkIntroduction:Using brackish water for irrigation may expose turfgrasses to salinity stress.Employing the best treatments to maintain high-quality turfs under saline conditions is animportant requirement for turfgrass management.Methods:We tested the response of ahalophyte grass,Puccinellia distans, to irrigation with saline solutions and to foliarapplication of two osmoprotectants, such as glycine betaine (GB) or chitosan (CH). Plantswere grown in pots under controlled conditions and irrigated with 200 mM or 600 mM ofNaCl solutions. The response to salinity treatments and osmoprotectant application wasevaluated after 90 days by measuring leaffiring, leaf density, shoot length and biomass, rootlength, and shoot water potential.Results:Increasing salinity reduced shoot density, shootand root length, shoot water potential, and increased leaffiring and shoot solute potential at200 mM of NaCl. These effects were more pronounced at 600 mM of NaCl. Application ofGB greatly increased shoot growth traits at 200 mM of NaCl and also showed beneficialeffects on most traits at 600 mM. Application of CH showed positive effects only on leaffiring and leaf water potential at 600 mM.Conclusions:Our results show thatP. distanscantolerate high levels of salt stress, which can be best alleviated by GB treatmen
Usefulness of Cyperus alternifolius L. for water and soil reclamation: effect of copper, cadmium, and chromium on antioxidant systems
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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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