1,721,131 research outputs found
Improved micropropagation in Polygala myrtifolia
No full textStem segments from apical shoot tips of Polygala myrtifolia were used as primary explants to establish in vitro cultures. Axillary shoots produced on noncontaminated explants were excised and recultured in the same medium to increase the stock of shoot cultures. Equal molar concentrations of five cytokinins 2-isopentenyladenine (2iP), kinetin, zeatin, N6-benzyladenine (BA) and adenine were tested for ability to induce axillary shoot development from double node stem segments. The highest rate of axillary shoot proliferation was induced on Murashige and Skoog agar medium supplemented with 1.8 M BA. Seven indole-3-acetic acid (IAA) concentrations (2.8, 5.7, 8.6, 11.4, 14.3, 17.1 M) were tested to determine the optimum conditions for in vitro rooting of microshoots. Up to 72 % of the microshoots rooted with 14.3 M IAA. Other auxins tested, -naphthaleneacetic acid (NAA) and indole-3-butyric acid (IBA), were less effective than IAA in inducing adventitious root formation. All rooted plantlets having more than 3 roots were successfully established in soil
Auxin application and cutting length affect rooting in Cuphea hyssopifolia stem cuttings
No full textThe effect of cutting length and indole-3-buyric acid (IBA) application on adventitious root formation stem cuttings was studied in Cuphea hyssopifolia. Softwood terminal cuttings of a clone grown in Sicily were trimmed to three lengths (2, 4 or 6 cm) and inserted to a 1-cm depth in bottom heated plastic trays containing a humidified peat-vermiculite mixture 1:2 (v/v). To verify the cutting response to different auxin concentrations, cuttings were dipped to a 1.0 cm depth in a 500ppm or 1000 ppm IBA solutions for 10 seconds.
Cutting percent survival was 100%. Regardless of cutting length, the highest rooting percentage was obtained with IBA at 1000 ppm (avg. 86.7%), whereas rooting significantly declined to 73% and 81%, in absence of IBA and at 500 ppm IBA, respectively. Percentage rooting averaged over IBA treatment accounted for 93.3% and 90% in 6 and 4 cm long cutting treatments,
espectively. The lowest percentage of rooting was recorded with the 2 cm cutting treatments (59%). Cutting length and IBA application significantly interacted as percentage rooting ranged from 43% in 2 cm long cuttings rooted in absence of IBA to 100% in 4 cm long cuttings with 1000 ppm IBA. The highest number of roots was observed from cuttings exposed to IBA at 500 and 1000 ppm (19.7 and 19.6 roots per cutting, respectively). Root number significantly declined in absence of IBA (16.8 roots per cutting). Our results demonstrated that the use of 4 or 6 cm long cuttings and the application of 1000 ppm IBA for 10 seconds could induce optimal adventitious root formation in C. hyssopifolia. The application of the technique described would enhance propagation of this valuable ornamental species
Micropropagation of Ageratum houstonianum by nodal segments
No full textAgeratum houstonianum is a bedding and flowering potted plant originated from
Central America which is generally propagate by seed. In this report a preliminary in
vitro technique for propagation of A. houstonianum was investigated. In vitro
germinated seeds were used to establish aseptic shoot cultures of several clones.
Seedling stem segments bearing 3-4 nodes were placed on Murashige and Skoog (MS)
basal medium plus 20 g L-1 sucrose, 8.0 g L-1 Agar to induce axillary shoot
development. Axillary shoots were subcultured into the same medium and nodal
segments were sectioned and subcultured to increase the stock of shoot cultures.
Shoot cultures of the selected clone AG14 were used to accomplish in vitro
propagation experiments. The MS medium, augmented with different concentrations
of N-6-benzyladenine (BA) (0, 0.88, 1.78, 3.55, or 7.1 μM) either singly or in
combination with indole-3-acetic acid (IAA) at 5.7 μM, as potential medium for shoot
multiplication by single node segments was tested. The highest rate of axillary shoot
proliferation was induced on the medium supplemented with 7.1 μM BA. Explants
were divided, subcultured and continued to proliferate shoots. A proliferation rate of
5.2 shoots per single node explants every four weeks occurred. The highest number of
node per axillary shoots after 8 week culture (4.5 nodes) was obtained in the medium
with 0.88 μM BA and 5.7 μM IAA. The elongated axillary shoots could be in turn
sectioned and subcultured to form an elongated stem again. Five IAA concentrations
(0, 1.14, 2.28, 4.57, 5.71 μM) were tested to determine the optimum conditions for in
vitro rooting of microshoots. The highest number of roots per microshoots was
obtained with IAA at 2.28 μM. Ninety percent of the in vitro rooted plantlets were
successfully established in soil. This micropropagation system of A. houstonianum
based on axillary shoot development from nodal segments, followed by in vitro
rooting, might be used for rapid and efficient mass propagation of improved
selections and disease-free germplasm
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
Investigating the cryopreservation of nodal explants of Lithodora rosmarinifolia (Ten.) Johnst., a rare, endemic Mediterranean species
No full textIn this study, we investigated the possibility of using the droplet-vitrification technique for cryopreserving nodal segments of in vitro plantlets of the endangered plant species Lithodora rosmarinifolia. Among the three vitrification solutions tested, only solutions B1, containing (w/v) 50 % glycerol and 50 % sucrose, and B3, containing 40 % glycerol and 40 % sucrose, were able to induce cryotolerance in nodal explants, resulting in intermediate survival and recovery after cryopreservation. A three-step vitrification protocol, including an additional dehydration treatment with half-strength vitrification solution for 30 min before the treatment with full-strength vitrification solution, did not lead to any improvement in survival and recovery compared with the two-step protocol. The optimal protocol was the following: preculture of nodal segments in liquid medium with 0.3 M sucrose for 16 h and 0.7 M sucrose for 5 h, treatment for 20 min in loading solution containing 1.9 M glycerol + 0.5 M sucrose, dehydration with vitrification solution B1 (glycerol 50.0 %, sucrose 50.0 %, w/v) for 60 min at room temperature, rapid cooling in minute droplets of vitrification solution, and rapid rewarming by immersion of nodal segments for 20 min in unloading solution containing 1.2 M sucrose. Under these conditions, 33 % recovery of cryopreserved nodal explants was achieved. Regrowth of cryopreserved samples was rapid and direct. These results indicate that long-term storage of L. rosmarinifolia by means of cryopreservation of nodal segments is possible, thereby contributing to securing the diversity of this rare and endangered plant species
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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