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Le Collezioni Briologiche dell'Erbario di Roma (RO). - Stato delle conoscenze.
No full textThe Collections of Bryophytes in the Herbarium of Rome (RO). The present status of Knowledge.
The section of Bryophytes of the Herbarium of Rome (RO) is described. It consists of two Collections, belonging to Erbario generale and Erbario Cesati, respectively, with a total number of 35000 specimens. The manual and computerized filing are in progress
Exogenous calcium enhances the formation of vegetative buds, flowers and roots in tobacco pith explants cultured in the absence of exogenous hormones
No full textPith explants excised from the apical stem internodes of vegetative, flowering, and fruiting tobacco plants were cultured on hormone-free medium in the presence or absence of CaCl2 ( 3 mM). The aim was to determine the role of exogenous calcium (Ca2+), applied at the concentration normally present in the Murashige and Skoog ( 1962) medium, in organ formation obtainable in the absence of the exogenous hormonal input. Exclusive formation of vegetative buds was obtained from explants excised from vegetative plants ( pure vegetative programme); vegetative buds and flowers ( and occasionally roots) on the same sample were obtained from explants from flowering plants ( mixed flowering programme); whereas roots, very occasionally associated with vegetative buds and flowers on the same sample, were obtained from explants from fruiting plants ( mixed rooting programme). Histological analysis showed that the organs always exhibited indirect regeneration. Exogenous Ca2+ promoted the formation of meristemoids and the first phases of their growth into organs, but did not change the realization of the organogenic programme and did not affect callogenesis. Instead, the influence of exogenous Ca2+ changed with the programme, when considering the last phases of organ growth (i.e., macroscopic development and elongation), and the appearance of morphological anomalies in the organs
The protein of rolB gene enhances shoot formation in tobacco leaf explants and thin cell layers from plants in different physiological stages
No full textThe objective was to determine whether the protein of rolB affects shoot formation and whether this potential relationship depends on the developmental stages of the plant and/or on the culture conditions. Thin cell layers (TCL) and leaf explants were excised from tobacco plants in the vegetative and flowering stages and cultured under various hormonal conditions. In TCLs of vegetative-stage plants, the expression of rolB enhanced the formation of the shoot buds under hormone-free conditions and with specific concentrations of auxin and/or cytokinin, Histological examination showed that the induction of the shoot meristemoids was particularly enhanced by rolB protein and that meristemoid growth was accelerated. In leaf explants from vegetative-stage plants, the expression of rolB increased the formation of shoot buds in the presence of 1 mu M IAA plus 1 or 10 mu M cytokinin, With BA alone, at a 0,1 mu M concentration, shoot formation occurred in the transgenic explants only, whereas with concentrations ranging from 0.5 to in mu M, it was higher in these explants than in controls. RolB protein enhanced the formation of shoot buds in TCLs from flowering plants under all hormonal conditions. In the presence of 1 mu M IAA and kinetin, the protein also increased the flowering response. In leaf explants from flowering plants, the expression of rolB increased the number of shoot buds in the presence of 1 mu M IAA with 10 mu M BA, In conclusion, rolB protein promotes shoot formation; it seems to have a positive interaction with cytokinin and an effect on the induction of the meristematic condition
The role of hormones on morphogenesis of thin layer explants from normal and transgenic tobacco plants
No full textThe organogenic potential of thin layer stem explants of non‐reproductive tobacco plants was tested on a hormone‐free medium and under various hormonal conditions. A comparison was made between thin layers excised from normal and transgenic plants at the same developmental stage. The transgenic plants were transformed by insertion of TR‐ and TL‐DNA from Agrobacterium rhizogenes 1855 root‐inducing plasmid. The aim was to identify hormonal conditions capable of stimulating the expression of the flowering competence present in the differentiated stem tissues at the induced stage before any visible sign of transition to reproductive development. Flower neoformation, observed at the end of the culture period (day 25), occurred on untransformed thin layers only with kinetin treatment. Explants from transgenic plants showed flower bud regeneration on hormone‐free medium, indoleacetic acid alone (1 μM), kinetin alone (1 μM), and most abundantly on indoleacetic acid plus kinetin (1 μM each). No flower formation was observed on indolebutyric acid plus kinetin (10 μM and 0.1 μM, respectively) in both normal and transgenic explants. The latter treatment enhanced rooting instead, above all in the transgenic explants. On hormone‐free medium vegetative bud formation was well expressed both by untransformed and transgenic explants, and enhanced by the combined, equimolar concentrations of indoleacetic acid and kinetin. The results show that cytokinin allows flowering in florally determined stem explants from normal plants. In the transgenic explants, the flowering response increases when indoleacetic acid is added to cytokinin, thus suggesting a role for auxin in enhancing the expression of the florally determined state in thin cell layers of non‐reproductive plants
Rhizogenesis from tobacco thin layers: effects of various inhibitors of polyamine biosynthesis.
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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
Il metilgiasmonato riduce la cauologenesi in strati sottili di Nicotiana tabacum deregolando la divisione e l'espansione cellulare e inducendo modificazioni di parete
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