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Made available in DSpace on 2014-10-09T12:32:52Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:08:59Z (GMT). No. of bitstreams: 1 12889.pdf: 3125642 bytes, checksum: b56aa69cfba2da94049299248d6af43e (MD5) / Tese (Doutoramento) / IEA/T / University of London - Dept. of Chemistry

Made available in DSpace on 2014-10-09T12:32:52Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:08:59Z (GMT). No. of bitstreams: 1 12889.pdf: 3125642 bytes, checksum: b56aa69cfba2da94049299248d6af43e (MD5) / Tese (Doutoramento) / IEA/T / University of London - Dept. of Chemistry

Among ornamental plants, roses (Rosa L.) are considered the most economically important, being among the most popular garden shrubs, as well as the favorite cut flowers sold by florists. In the past roses have been classified as fairly salt-sensitive, however, recent nutrition studies suggest that they may actually tolerate moderate to relatively high salinities. The general objective of this research was to reassess the limits of tolerance to salinity of roses and the influence of the rootstock used, to determine the ameliorative properties of supplemental Ca2+ on the response to salt stress, and to establish the influence of Na+- and Cl--counter ions on the detrimental effects caused by these salinizing elements. The NaCl or NaCl-CaCl2-salinity tolerance limit for greenhouse roses, although greatly influenced by the rootstock, was between 12 and 15 mmol.L-1. Plants grafted on ?Manetti? sustained their productivity/quality characteristics for longer time periods, tolerated greater salinity concentrations, and accumulated less Cl- and Na+ in leaves of flowering shoots than those grafted on ?Natal Briar?, confirming the greater ability of the former rootstock to tolerate salt stress. Supplementing the saline solution with 0-10 mmol.L-1 Ca2+ (as CaSO4) did not alleviate the harmful effects caused by NaCl-salt stress (12 mmol.L-1) on the productivity and quality responses of roses. The detrimental effects caused by Na- and Cl-based salinity were greatly influenced by the composition of the salt mixtures (i.e. their counter ions). Sodium sulfate and CaCl2 were the least harmful salts; NaCl had intermediate effects, while NaNO3 and KCl were the most deleterious. Among the most distinguishable effects caused by the more toxic Na+ and Cl- counter ions were lower osmotic potential (piSS) and greater electrical conductivity (ECSS) of the salinized solutions, markedly increased uptake and/or transport of either Na+ or Cl- to the flowering shoot leaves, and altered uptake and/or transport of other mineral nutrients. Computations of the saline solutions? chemical speciation revealed that salts containing divalent ions had lower ionization and exhibited greater ion associations compared to monovalent ion salts, rendering a lower number in free ions/molecules in solution which caused greater SS and lower ECSS in those solutions.

published_or_final_version / Ecology and Biodiversity / Master / Master of Philosophy

dissertation submitted to the faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2015. / Global environmental change due to anthropogenic activity results in alterations to the Earth’s biogeochemical cycles. This study focused on nitrogen and sulphur deposition, which results in the acidification of ecosystems. Alterations to these processes will have an effect on the diversity and ecophysiology of the vegetation; moreover, little is known about the long-term impacts on the vegetation structure and composition. Increased development, mining and industrialization, within the Waterberg area, particularly with the construction of the Medupi power station, have resulted in this area coming under study. The impacts of additional air pollution to the vegetation in this area are currently unknown. The aim of this research was to determine whether increased ambient levels of atmospheric nitrogen and sulphur, resulting from the power stations, will impact the structure, functional type and the composition of the vegetation, and the resultant impacts on vegetation structure and growth as a result of the added nitrogen and sulphur to the system and increased acidity. A baseline of quantitative data was needed in order for future comparisons to be made to assess whether biodiversity is changing and at what rate. One part of the study involved the collection of baseline vegetation data along a pre-determined transect in the Waterberg area. A transect was identified which could serve as a vehicle for monitoring changes over time, with areas downwind of the Matimba and Medupi power stations assumed to be more impacted than areas upwind. The two downwind sites and the two sites closest to the power stations were found to have the highest beta diversities, with the two downwind sites having a value of 0.60 and the downwind Landelani site and upwind Withoutpan site having a value of 0.53. The high species variation between these sites may already be an indication of pollution impacts within the area. The downwind site closest to the power stations, Landelani, is particularly vulnerable as it has a high Shannon diversity index, with a value of 2.84, and high tree biomass, 46.64 tonnes/ha, with low tree density, 625 trees per hectare. iii Functional groups are assumed to react similarly under changing environmental conditions. The second part of this research focussed on photosynthetic pathways, by using two C3 woody species and two C4 grasses. The experiment was conducted in the greenhouse at the University of the Witwatersrand and showed that both tree and both grass species selected were sensitive to sulphur additions to varying degrees. Additionally Acacia sieberiana was found to be sensitive to nitrogen addition, however Combretum erythrophyllum responded to nitrogen when it was added alone. A positive response to nitrogen was seen in both grass species; however the positive response was negated by the addition of any sulphur in Eragrostis curvula. In Panicum maximum the positive response in growth to nitrogen addition exceeded any negative effects from the sulphur addition. The results of plant growth to increasing soil acidity were different between functional groups and within functional groups. A relationship between the increase in the average above and below ground mass was found to exist with a decrease in soil acidity in Acacia sieberiana (R2 = 0.45). A relationship between an increase in the average above and below ground mass with a decrease in soil acidity in Eragrostis curvula was also seen (R2 = 0.31). Changes to the structure and composition of vegetation in this area will impact land use and the management thereof, impacting land users and owners ability to generate an income and therefore their livelihoods. Changes to vegetation structure and composition will also have a greater overall effect by impacting ecosystem functioning and resilience to future disturbances.

Thesis (MSc. (Microbiology)) -- University of Limpopo, 2017 / This study was aimed at isolating and evaluating the antibacterial, antioxidant and cytotoxic effects of active compounds from selected medicinal plant species. The biological activities and cytotoxic effects of Commelina africana, Dombeya rotundifolia, Elephantorrhiza elephantina and Schkuhria pinnata were investigated based on their traditional uses. The plants were extracted with different solvents of varying polarities. Methanol was the best extractant with the highest yield. The presence of different phytoconstituents was screened using standard methods; this revealed the presence of terpenoids, flavonoids, tannins, and saponins. Meanwhile, the phytochemicals were screened on TLC, where different colours observed indicated the presence of different compounds. The total phenolic, tannin and flavonoid content were estimated using spectrophotometric methods. D. rotundifolia had the highest amounts of phenol, tannin and flavonoid content, while S. pinnata had the least. The antibacterial and antioxidant screening employed both qualitative and quantitative assays. Although not separated, this study demonstrated the antioxidant potential of D. rotundifolia extracts developed in BEA and CEF. D. rotundifolia also demonstrated the highest free radical scavenging and reducing power antioxidant potential. These activities could be attributed to the high phenolic, tannin and flavonoid content observed. All the selected plants had antibacterial potential against E. coli and P. aeruginosa. Only S. pinnata extracts were active against E. faecalis and S. aureus. The MIC values of the plants and ampicillin ranged from 0.02 to 2.50 mg/mL and 0.02 to 0.08 mg/mL, respectively. The plants were combined to determine any interaction effects in exhibiting antibacterial activity. Among all the possible combinations, combinations with S. pinnata had improved antibacterial activity. The effects of D. rotundifolia and S. pinnata extracts on the inhibition of the production of reactive oxygen species on LPS-induced RAW 264.7 macrophages was determined using the DCFHD-A assay. Both plants demonstrated anti-inflammatory potential by inhibiting the production of ROS in a dose-dependent manner. Cell viability assays revealed that S. pinnata had cytotoxic effects on African green monkey kidney (Vero) cells with the lowest LC50 (25 µg/mL). Bioassay guided fractionation and nuclear magnetic resonance spectroscopy of dichloromethane extracts of S. pinnata on column chromatography afforded isolation and characterisation of three sesquiterpene lactones. These were identified as 6-(2, 3- xxvi dihydroangeloylory)-6α-hydroxyinuviscolide, heliangolide and eucannabiolide. All three compounds had antibacterial, anti-inflammatory and cytotoxic effects. The compounds may serve as leads for synthesis of less toxic therapeutic antibacterial and anti-inflammatory drugs in the pharmaceutical industry. / National Research Foundation (NRF)

In a Monte Carlo analysis of meta-analytic data, Type I and Type II error rates were compared for four homogeneity tests. The study controlled for violations of normality and homogeneity of variance. This study was modeled after Harwell (1997) and Kromrey and Hogarty's (1998) experimental design. Specifically, it entailed a 2x3x3x3x3x3x2 factorial design. The study also controlled for between-studies variance, as suggested by Hedges and Vevea's (1998) study. As with similar studies, this randomized factorial design was comprised of 5000 iterations for each of the following 7 independent variables: (1) number of studies within the meta-analysis (10 and 30); (2) primary study sample size (10, 40, 200); (3) score distribution skewness and kurtosis (0/0; 1/3; 2/6);(4) equal or random (around typical sample sizes, 1:1; 4:6; and 6:4) within-group sample sizes;(5) equal or unequal group variances (1:1; 2:1; and 4:1);(6)between-studies variance, tau-squared(0, .33, and 1); and (7)between-class effect size differences, delta(0 and .8). The study incorporated 1,458 experimental conditions. Simulated data from each sample were analyzed using each of four significance test statistics including: a)the fixed-effects Q test of homogeneity; b)the random-effects modification of the Q test; c) the conditionally-random procedure; and d)permuted Qbetween. The results of this dissertation will inform researchers regarding the relative effectiveness of these statistical approaches, based on Type I and Type II error rates. This dissertation extends previous investigations of the Q test of homogneity. Specifically, permuted Q provided the greatest frequency of effectiveness across extreme conditions of increasing heterogeneity of effects, unequal group variances and nonnormality. Small numbers of studies and increasing heterogeneity of effects presented the greatest challenges to power for all of the tests under investigation.

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The main idea of this thesis is studying the importance of the carry-over effects and interaction effects in statistical models. To investigate it, a hand-milking experiment in Burkina Faso was studied. In many no electricity access countries, such as Burkina Faso, the amount of milk and milk compositions are still highly  relying on hand-milking techniques and milkers. Moreover, the time effects also plays a important role in stockbreeding system. Therefore, falling all effects, carry-over effects and interaction effects into a linear mixed effects model, it is concluded that the carry-over effects of milker and hand-milking techniques cannot be neglected, and the interaction effects among hand-milking techniques, different milkers, days and periods can be substantial.