Thesis (M.Sc) (Agriculture) --University of Limpopo,2009. / The study was conducted to determine the effect of dietary energy level and tanniniferous Acacia karroo leaf meal level of supplementation at finisher stage on performance and carcass characteristics of male and female Ross 308 broiler chickens. Three hundred and sixty, 21-day old male and female broiler chickens were assigned to twelve treatments with three replications of ten birds in a 2 (sex) x 3 (dietary energy level) x 3 (tanniniferous Acacia karroo leaf meal level) factorial, complete randomized design. Supplementation with Acacia karroo leaf meal had no effect on diet intake, digestibility and live weight of broiler chickens. However, supplementation with 9 and 12 g of Acacia karroo leaf meal per kg DM feed reduced fat pad weights in male broiler chickens by 26 and 29 percentage points, respectively. Similarly, supplementation with 9 and 12 g of Acacia karroo leaf meal per kg DM feed reduced fat pad weights in female chickens by 26 percentage points. These reductions were achieved without any significant reduction in feed intake and digestibility. However, the physiological explanation for this effect is not clear and it, thus, merits further investigation. / National Research Foundation.

The principle aim of this work was to ascertain the relative importance of water and nutrient supply in determining the success of deciduous and evergreen plant forms on two main substrate types in the Worcester-Robertson valley, situated in the Succulent Karoo Biome. The substrate types selected for study represent soils of zoogenic soil mounds (locally termed "heuweltjies", and often referred to in the literature as "Mirna-like" mounds), and soils immediately adjacent to and surrounding the soil mounds. The distribution of deciduous and evergreen plant forms in the Worcester-Robertson valley was analys~d relative to the selected substrate types. Foliar elemental concentrations of four selected species growing on both substrates at five separate sites within the valley were determined. Also, the patterns of seasonal water stress exhibited by three deciduous and five evergreen non-succulent woody perennials growing in both substrates were investigated on high radiation (equator-facing) and low radiation (pole-facing) slopes at one intensive study site, the Worcester Veld Reserve.

Newspaper article: "Bold man saves tree”

Newspaper article: "Old tree chopped by age and insects. Age and insects have put and end to one of Maritzburg's national monuments. An acacia mimosa tree that stood in the centre lawn of the Parkside home of the Administrator of Natal since about 1800, has been chopped down for safety reasons. The stately old tree was National Monument and the plaque on the stump reads: Monuments Commission. Around this tree, Commandant A. W. J. Pretorius, member of the Volksraad and the Burgers of the Republic Natalia decided by a majority on July 5, 1842, to accept British rule.”

Caption "Enormous thorns on type of A. Karoo found in Fish River Bush near Grahamstown. 1958.”

The biology and ecology of an indigenous, non-pest insect on an indigenous host plant were investigated. The study includes a taxonomic description of this new species, an account of its general biology, monitoring of the seasonal fluctuations in numbers of the psyllid and its hymenopterous parasitoids, and a study of various aspects of the host plant, including nitrogen levels, water stress, leaf hardness, and the effect of cutting, in relation to spatial and temporal differences in insect population numbers. Natural enemies, inter- and intra-specific competition had very little determining influence on the population numbers of the psyllid. Temperature and humidity had little direct effect, but may have influenced the population dynamics via its effects on the host plant. Seasonal patterns in psyllid numbers followed fluctuations in nitrogen levels; statistically valid correlations were obtained between leaf nitrogen and psyllid numbers on individual trees at various times. These findings were supported by the results of preliminary laboratory experiments employing different fertilizer treatments. No effect of water stress or leaf hardness was clearly discerned. Cutting of trees altered the characteristics of the subsequent regenerative growth so as to allow massive psyllid infestations to develop, thus showing the tremendous importance of the host plant in determining population levels in this insect. Preliminary investigations of the nature and mechanism of this effect were conducted, and its significance is discussed. The relevance of these findings to modern concepts of regulation in insect populations and to principles of pest management is discussed.

>Magister Scientiae - MSc / Invasive alien plants (IAPs) are often reported to use more water than indigenous plants. Inaddition, IAPs have an ability to adapt to harsh environmental conditions and they tend to spread at rapid rates, thereby threatening the country’s water resources, agricultural land, and biodiversity. Much of South Africa is expected to get drier in future due to climate change and the new climatic conditions are also predicted to accelerate the rate at which alien plants will spread. Approximately 10 million hectares are currently estimated to have been invaded by alien plants in South Africa, with an estimated average annual rate of spread of more than 5%. The first objective of this study was to compare the water use by deep rooted tree species which include invasive alien Prosopis (sp) trees and the co-occurring indigenous A. karroo. These trees are growing in a flood plain of a groundwater dependent catchment in the Northern Cape Province. Both species are dependent on groundwater and thus compete with local communities for this resource. The second objective was to determine the sources of water that the trees were using in order to understand the impacts of each species on groundwater resources. Transpiration was measured using the heat ratio method of the heat pulse velocity sap flow technique while the volumetric soil water content was monitored at several depths down the soil profile using automated capacitance soil water content probes. Weather data was collected using an automatic weather station. Stable isotopes of oxygen and hydrogen from plant, soil and groundwater samples were analysed to determine the sources of water used by the trees. Average tree density was approximately 613 stems per hectare for Prosopis compared to about 100 stems per hectare for A. karroo. Comparative measurements of water use shows that the annual stand level transpiration from Prosopis invasions was approximately 353 mm/year while that from A. karroo was only about 137 mm/year. Differences in stand transpiration were a result of the higher plant density for Prosopis than A. karroo. There were no significant differences in the transpiration rates of the two species for trees with a similar transpiring leaf area. Application of a two compartment linear mixing model for the oxygen isotope ratio during the peak transpiration period in summer showedthat Prosopis derived 23% of its water from the unsaturated zone and 77% from the saturated zone. A. karroo on the other hand derived 53% of its water from the unsaturated zone and47% from the saturated zone. Diurnal fluctuations in groundwater levels were strongly related to the transpiration dynamics of both species. This supports the observation that these deep rooted trees have substantial impacts on groundwater at the study site. Root sap flow patterns of Prosopis showed evidence of hydraulic redistribution wherein the groundwater abstracted by the tap roots was deposited in the shallow soil layers by lateral roots. However, the root sap flow patterns of A. karroo growing adjacent to the Prosopis did not show this phenomenon.

Thirteen South African medicinal plants which are used traditionally to treat symptoms associated with Listeria monocytogenes infections, were screened for activity against the pathogen. Different plant parts were extracted separately with ethyl acetate or chloroform. All the extracts were first screened against the bacteria using the disc diffusion method. Zones of inhibition observed in the presence of the chloroform extracts of Eucomis autumnalis, ethyl acetate extracts of Acacia karroo and Plectranthus ecklonii (50 mg/ml) were 12 mm, 14 mm and 15 mm respectively. Active extracts were further tested against the bacteria for minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) using the microtitre dilution method. Ethyl acetate extracts of A. karroo exhibited MIC of 3.1 mg/ml and MBC of 6.25 mg/ml. Ethyl acetate extracts of P. ecklonii showed MIC of 0.5 mg/ml and MBC of 1.0 mg/ml. Five samples namely A. karroo (ethyl acetate extract), P ecklonii (ethyl acetate extract), Senecio inonartus (ethyl acetate extract), S. inonartus (chloroform extract) and Aloe arborescens (ethyl acetate extract) showed good MIC against L. monocytogenes and a MBC range from 1.0 to 12.5 mg/ml. The two plants, A. karroo and P. ecklonii were further selected for the isolation of the active compound(s). Column chromatographic purification of ethyl acetate extracts of the leaves of A. karroo led to the isolation of three known pure compounds namely â-sitosterol, epigallocatechin and epicatechin. The MICs of the â-sitosterol and epigallocatechin that were isolated from A. karrroo were found to be 31.25 µg/ml and 62.5 µg/ml respectively against L. monocytogenes. The confocal scanning laser microscopy (CSLM) showed that the biomass of the listerial biofilms were reduced when the isolated compounds were added and slightly reduced when the crude extract was added. The aggregation of cells which were exposed to â-sitosterol and epigallocatechin was reduced from 25 µm as observed in untreated cells to < 10 µm in length. Therefore as one of the local South African plants identified in the present study, the pure compounds isolated from A. karroo, could be used as a potential natural alternative for eliminating L. monocytogenes biofilms from food processing surfaces. This could help in combating the problem of food contamination and food poisoning caused by the pathogen. It could also help in preparing antibiofilm agents that are cost effective and easily accessible to the public. A. karroo should be further be explored in this regard. The present study reports for the first time the isolation of the three compounds, â-sitosterol, and epicatechin and epigallocatechin from A. karroo. Bioassay-guided fractionation of the P. ecklonii ethyl acetate extract led to the isolation of two known compounds, parvifloron D and parvifloron F. Parvifloron D and F exhibited a minimum inhibitory concentration (MIC) of 15.6 and 31.25 µg/ml respectively against L. monocytogenes. The MICs of parvifloron D and F against a drug-sensitive strain of Mycobacterium tuberculosis were found to be 190 and 95 µg/ml respectively. The ethyl acetate extract of P. ecklonii and its isolated compounds were tested for their activity on tyrosinase inhibition. The concentration of plant extract at which half the tyrosinase activity was inhibited (IC50) was found to be 61.73 ± 2.69 µg/ml. The antibacterial activity of the extract of P. ecklonii and its isolated compounds correlates with the traditional use of the plant for various ailments such as stomach-aches, diarrhoea and skin diseases. This is the first report on the bioactivity of an extract of P. ecklonii and its two compounds. The antibacterial activity of the extracts of A. karroo, P. ecklonii and their isolated compounds correlates with the traditional use of these plants for symptoms associated with listeriosis. / Thesis (PhD)--University of Pretoria, 2011. / Plant Science / unrestricted

Urban open spaces are of strategic importance to the quality of life of our increasingly urbanized society. Trees and related vegetation are planted and managed within the communities and cities to create or add value to the busy lives of the city dwellers. Trees in towns and cities form an important part of complex urban ecosystems and provide significant ecosystem services and benefits for urban dwellers, for example: reducing particulate pollution, carbon sequestration, decreasing air temperature, decreasing water runoff, aesthetic value and an increase in human health. Trees are solarpowered technology that can help restore balance to dysfunctional urban ecosystems. Trees form strands in the urban fabric that connect people to nature and to each other. The urban environment puts tremendous strain on trees by trenching, limited space for root growth and emission of pollutants into the atmosphere, water and soil. The problem is that the real impact of the urban environment on the trees within our community is unknown. The aim of this investigation was to assess the overall anthropogenic and environmental impacts on urban trees by measuring the tree vitality of Acacia karroo using chlorophyll fluorescence kinetics (JIP-test) and the leaf water potential using a pressure chamber. Tree vitality was quantified as the chlorophyll fluorescence-based performance index (PIABS)T. ree vitality measurements were also correlated with soil physical and chemical data. In the comparative study, an urbanization gradient approach was followed in which results of trees in rural areas were regarded as controls. The gradient approach is used worldwide and provides a background for questions of ecological structure and function. The urbanization gradient was quantified using the V-I-S model, based on % cover of vegetation, impervious surface and soil. Additionally, a model to determine the monetary value of trees in urban environments (SATAM) was tested. All this information could eventually contribute to develop an urban tree management program for Potchefstroom. It was evident from the current study that urbanization has a negative impact on tree vitality. The leaf water potential of a tree was, however, not necessarily negatively impacted upon. Although trees in urban environments did not always have a high vitality (PIABS)t, hey still played a major role in the urban environment. According to the tree appraisal method (SATAM), some of these trees have a value of R60 000. / Thesis (M. Environmental Science (Ecological Remediation and Sustainable Utilisation))--North-West University, Potchefstroom Campus, 2007.

Thesis (M. Environmental Science (Ecological Remediation and Sustainable Utilisation))--North-West University, Potchefstroom Campus, 2007.