1,720,957 research outputs found
The impact of elevated carbon dioxide on the stress tolerance of selected vegetable crops
No full textPlant responses to different stresses are highly complex and involve changes at both the cellular and physiological levels. The physiological interaction between carbon dioxide (CO2) enrichment, biotic and abiotic stressor was studied in crop plants. Metabolic acclimation through the accumulation of protective metabolites is regarded as a basic strategy for protection and survival of plants in stress environments. The aim of this study was to investigate the relations between CO2 enrichment and stress-inducing microcystins or Red clover necrotic mosaic virus (RCNMV) replication on plant growth and physiology. A preliminary study was carried out to investigate the growth and developmental response of selected leafy vegetable crops that were exposed to elevated carbon dioxide (CO2). Lettuce cvs. Great Lake and Red Fire, spinach, Swiss chard and cabbage were grown under ambient (380 ppm) and elevated (760 ppm) CO2 concentrations. Elevated CO2 was positively correlated with increased plant height, number of leaves and total leaf area except in cabbage. However, the photosynthetic pigments for lettuce, Swiss chard and cabbage decreased under elevated CO2, while the photochemical efficiency of PS II (fv/fm) remained unchanged under elevated CO2 except in cabbage and Swiss chard.
Microcystin contamination of soil is a widespread environmental problem. A large-scale experiment was conducted to study the mechanisms involved in plant adaptation to microcystin stress under increasing atmospheric CO2 levels. Selected leafy vegetable species were grown under ambient (380 ppm) and elevated (760 ppm) CO2 concentrations. Microcystins caused oxidative damage, with increased levels of protein carbonyls and lipid hydroperoxides in microcystin-treated plants. Subsequently a significant increase in antioxidant enzymes (i.e. superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase and ascorbate peroxidase) was observed. A significant increased of total ascorbate was recorded in microcystin-treated plants under elevated CO2 levels, but the percentage of oxidized ascorbate increased in microcystin-treated plants at both CO2 levels. The level of total glutathione increased rapidly in microcystin-treated plants under elevated CO2 levels and the oxidation process increased in microcystin-treated plants. Microcystin treatments drastically influenced the accumulation of polyamine compounds especially in the plants grown at ambient CO2 levels. It has been suggested that an increased ability to accumulate polyamines represents a plant defence mechanism. Results from this study provide evidence that microcystins cause oxidative stress and that exposure to microcystins through the irrigation route poses a threat to the yield and quality of leafy vegetables.
The effect of RCNMV on Top Crop beans was also investigated in this study. Following RCNMV inoculation, plants were grown at ambient (380 ppm) and elevated CO2 (760 ppm) levels. Findings suggest that, CO2 enrichment could help infected plants to survive under biotic stress (RCNMV infection). It was observed that Top Crop beans grown at elevated CO2 levels showed increased antioxidant and polyamine metabolisms, accompanied by an increased in virus resistance. The virus titre was reduced as indicated by significantly lower amounts of RCNMV coat protein in plants grown at elevated CO2. The combination of elevated CO2 and RCNMV infections promoted an increase in antioxidant metabolism in Top Crop beans. Polyamine metabolism also increased following RCNMV infection under elevated CO2. Therefore, it was suggested that the increase in antioxidant and polyamine levels in plants exposed to elevated CO2 is associated with stress tolerance to RCNMV infection.
In conclusion, results from this study show that both stressors (biotic and abiotic) have common defense mechanisms. Since H2O2 is one product of stress, the necessity for H2O2 detoxification is required for the survival of plants. The results also underline that environmental conditions can have a strong and complex modifying influence on antioxidant and polyamine metabolism. There are metabolic similarities between virus infection and toxin exposure
Improving the BRIS Soil management and practices for growing roselle (Hibiscus sabradiffa L.)
No full textBeach ridges with interspersed swales (BRIS), commonly referred to as BRIS soil or sandy soil, are extensively distributed along the eastern coast of Peninsular Malaysia. Despite the challenging nature of the lowland agricultural soil, characterised by its sandy texture and sterility, agricultural activities on BRIS soils have experienced an upward trend in recent times. The objective of this study was to conduct a literature review on the challenges and possibilities of roselle (Hibiscus sabdariffa L.) growth in the BRIS soil environment. Soil concerns can be classified into three categories: physical, chemical, and biological. The soil in BRIS is characterised by its acidic nature and low CEC values, with sand content occasionally reaching as high as 95 percent. Significant challenges associated with sandy soil conditions encompass soil water repellency (SWR), soil compaction, surface crust formation, soil erosion, low fertility, and Cation Exchange Capacity (CEC) value, as well as nutrient leaching into the groundwater, leading to pollution. The roselle plant is currently being commercially cultivated in the state of Terengganu as a substitute for tobacco in BRIS soil. This is due to the plant\u27s exceptional aeration and deep root zone. However, owing to its diminished fertility, its output is restricted. This book concentrates on the challenges related to BRIS soil and environmental concerns, including issues such as inadequate nutrient levels, weak soil structure, and excessive drainage. This review comprehensively elucidates the management strategies for sandy soil in the context of agricultural operations and evolving climatic conditions, thereby contributing to the advancement of research on the prospective cultivation of roselle
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
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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