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Environmental stress effects on the phytochemistry and bioactivity responses of a South African medicinal bulbous plant, Tulbaghia violacea Harvey (Alliaceae)
No full textThesis (MTech (Horticulture))--Cape Peninsula University of Technology, 2018.Deteriorating living and environmental conditions have contributed to the increasing prevalence of diseases in plants and animals. In humans, accumulation of abnormally high levels of free radicals in the tissues has been implicated in many non-communicable diseases, such as diabetes, cancer, arthritis, ischemia, gastritis, obesity and asthma. Worldwide, there is recognition of need to improve plant and animal health. Tulbaghia violacea (Alliaceae) is a medicinal plant that is extensively harvested by traditional healers in the wild for its medicinal uses and if this practice continues, it may result in an unsolicited decline of the species in situ. Therefore, there is a need for cultivation of this species. Plant cultivation in a controlled environment for conservation purposes as well as the enhancement of yield and quality is gaining favour among farmers and consumers. The main aim of this study was to investigate the effects of altering the growing conditions by applying environmental stresses on the plant growth, antifungal and antioxidant activities of T. violacea, with the view of enhancing the future cultivation of this species for pharmaceutical companies, traditional healers and the horticulture industry. This study was divided into two parts, and the first part, which was further sub-divided into two separate preliminary experiments, is presented in chapter three. Simultaneous assessments of the effects of i) varied pH levels (pH 4, pH 6, pH 8) and ii) light intensity on plant growth, antioxidant-content and -capacity of extracts of T. violacea were carried out. The second part of the thesis consisted of a more detailed assessment of the above-mentioned independent variables and interactions thereof on plant growth, and antifungal activity of extracts of T. violacea. Results obtained from the first part of the study, showed that plants exposed to pH 6 showed a marked increase in plant height (from 25-37 cm) after 2 months of treatment although, generally, the variations of the different growth parameters among the pH treatments were not significant (p > 0.05). Antioxidant-contents and -capacity were not significantly different (p > 0.05) when pH treatments were compared. However, a high polyphenol content value (of 3 mg/g) occurred in leaves of plants exposed to pH 8. Overall, comparatively, there was no significant difference (p > 0.05) in antioxidant-content and -capacity when pH treatments. In the light experiment, decreasing light intensity led to the elongation of plant height. A higher mean shoot length of 34.6 cm was obtained under low light compared to normal light (26.5 cm) two months post-treatment. The results obtained in this study indicated that light had a significant affect (p < 0.05) on the vegetative growth of this species. In contrast, normal light intensity yielded higher antioxidant-content and -capacity. The polyphenol and flavanol content were fluctuating between the averages of 5.8 mg/g to 8.5 mg/g. Overall, there was a significant difference (p < 0.05) in the antioxidant-content and -capacity when low and normal light intensity treatments compared. In conclusion, both normal light intensity and at pH 8 induced better antioxidant results. In the second part of the study, chapter four, one-month old T. violacea plantlets were grown under two light intensities (low light and normal light) in a greenhouse and concurrently exposed to varying pH levels: pH 4, pH 6 and pH 8. Plants exposed to normal light received natural sunlight through the roof of the greenhouse, while low light intensity (40% reduction) was achieved using shade nets. Plants were drip irrigated with Nutrifeed fertilizer. Plant growth parameters such as height and fresh and dry weights were determined. Leaf samples were analysed for macro-and micro-nutrients contents. Antifungal tests were carried out on the plant extracts from the various treatments in an antifungal bioassay (minimum inhibitory concentration [MIC]). The experimental data collected were analysed using one and two-way analyses of variance (ANOVA), and Tukey HSD was used to separate the means at p < 0.05 level of significance. Varied effects of different pH levels (4, 6 and 8) and light intensities (low and normal) on plant height, and fresh and dry weights were recorded in the current study. A significant interactive (df, 2; F = 0.001; p < 0.001) effect between pH and light on fresh weight was observed. The results revealed that there was a significant difference (df, 2, 57; F = 12.63; p < 0.001) in dry weights with plants under normal light intensity and pH 4 treatment (8.285 ± 0.802 g) producing the highest dry weight. There was a significant interaction (df, 2; F = 6.4; p < 0.001) between pH and light intensity on plant dry weight. Extracts from plants grown under normal light intensity showed stronger antifungal activity at pH level 4, and MIC values ranged from 0.18 ± 0 to 0.375 ± 0.04 mg/ml at 6h and 1.5 ± 0 to 0.97 ± 0.18 mg/ml at 18h. In conclusion, this study demonstrated the interactive effects of pH and light intensity on the growth of T. violacea. These findings also confirmed that it is possible to enhance the cultivation of T. violacea under greenhouse conditions. Chapter 5 focused on the interactive effects of pH and watering regime on plant growth, nutrient uptake and antifungal activity of T. violacea plant extracts, grown hydroponically. The results showed that there were significant differences (p < 0.05) on plant growth parameters amongst the different watering regimes under normal light intensity. Broadly, two trends occurred in the results: firstly, more macro-nutrients were taken up by plants in the higher frequency watering intervals as opposed to higher tissue micronutrient nutrient values for plants grown under the lower light intensity conditions. The levels of N, P, K, Mg nutrient uptake differed significantly in plants (p < 0.001) among watering interval periods. On the other hand, plants simultaneously exposed to extended watering intervals of 21-day and low light intensity showed more bioactivity of the crude extracts against F. oxysporum in the MIC bioassay. Based on the current results, a combination of shorter watering interval and normal light intensity favoured plant growth and development, while plants grown under low light intensity with longer watering interval showed good bioactivity. Broadly, these results demonstrated that varying pH, light intensity, and watering regime can influence plant growth, secondary metabolite contents and antifungal activity of crude extracts of T. violacea. These findings will contribute to the current body of knowledge around cultivation of indigenous medicinal plants. The study will further benefit the conservation of medicinal plant initiatives, increased income of small-scale farmers and potentially promote indigenous knowledge by increasing the availability of South African medicinal plants
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Effects of light intensities and varying watering intervals on growth, tissue nutrient content and antifungal activity of hydroponic cultivated Tulbaghia violacea L. under greenhouse conditions
No full textOptimization of the quality and quantity of medicinal materials during cultivation could improve the value of
medicinal plants. Light intensity and water availability affect physiological processes and growth of plants. Tulbaghia violacea L. (Alliaceae) bulbs and leaves are widely used traditionally in southern Africa for treatments of many ailments. The interactive effects of light intensity and watering regime on plant growth, nutrient uptake and antifungal activity of T. violacea were evaluated in the current study. Seedlings of T. violacea were grown hydroponically under two shading levels (0% and 40%) while being exposed simultaneously to one of three watering intervals: 5-day, 14-day and 21-day. Different growth parameters (plant height, plant fresh and dry weights) and tissue nutrient contents were evaluated at the end of the experiment. The antifungal activity of acetone extracts on Fusarium oxysporum were evaluated in a microdilution bioassay. Generally, significantly higher concentrations of macronutrients were recorded in the tissue of plants exposed to shorter watering interval. The results showed that different watering frequencies and light intensities significantly (p < 0.05) influenced plant growth parameters (height, and dry and fresh weights). Moreover, there were strong interactive effects of watering frequency and light intensity on most of the plant growth parameters. Remarkably, plants that were simultaneously exposed to the extended watering interval (21-day) and low light intensity showed the best anti-F. oxysporum activity. Key findings of this study revealed that shading alleviated the negative effects of waterdeficit stress on plant growth and improved antifungal activity
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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