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Effects of pre-slaughter stress, sex and breed on blood stress indicators, heat shock proteins, glycolytic potential and lamb quality

  • Authors: Stempa, Thuthuzelwa
  • Date: 2019
  • Subjects: Animal welfare , Meat--Quality
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10353/15376 , vital:40402
  • Description: The main objective of this study was to determine the effects of pre-slaughter stress (transportation distance and lairage duration), sex and breed on blood stress indicators, heat shock proteins, post-mortem muscle metabolites (glycogen, glucose, glucose-6-phosphate and lactate), glycolytic potential and meat quality attributes from lambs slaughtered at a commercial abattoir. The study was conducted in a high-throughput commercial abattoir in the Buffalo City local municipality of the Eastern Cape Province, South Africa. A total of a hundred eight-month old Dorper and Merino lambs, both male and female, were used in the study. Blood samples for the analysis of glucose and lactate levels were collected using 10.0 mL disposable Becton Dickinson vacutainer tubes treated with fluoride oxalate (grey top) whereas those for determination of cortisol and heat shock protein 70 (HSPA1A) levels were collected using plasma separating vacutainer tubes (SSTTMII, gold top), and those for analysis of creatine kinase and lactate dehydrogenase were collected using 10.0 ml vacutainer tubes treated with Ethylenediaminetetraacetic acid (EDTA). Meat samples (~50 g) for the measurement of post-mortem energy metabolites (glycogen, lactate glucose-6-phosphate and glucose content) were collected from the Muscularis longimissius thoracis et lumborum (LTL) of each carcass ~30 minutes after slaughter and immediately frozen in liquid nitrogen (-196 oC) to prevent further glycolysis. Cold carcass weight (CCW), warm carcass weight (WCW) and carcass fatness (CF) was measured. Meat pH and temperature were measured at iii 45 minutes (initial pH), 6 hours and 24 hours ultimate pH (pHu) post-mortem. Meat colour coordinates [lightness (L*), redness (a*), yellowness (b*), hue angle (H*), chroma (C*)] were also measured 24 hours after slaughter. Furthermore, thawing loss (TL%), cooking loss (CL%) and warner braztler shear force (WBSF) was measured in the LTL 7 days post slaughter. Breed had a significant effect on plasma HSPA1A, plasma lactate, WCW, CCW, L*, muscle glycogen and WBSF. Sex had a significant effect on plasma HSPA1A and pHu. Pearson‘s correlations showed that meat muscle glycogen was positively correlated to glycolytic potential (P<0.001; r=0.63) and initial pH (P<0.05, r=0.20). Muscle lactate was positively correlated to muscle glucose (P<0.01, r=0.30) and glycolytic potential (P<0.001, r=0.79). A positive correlation was shown between muscle glucose and glycolytic potential (P<0.05, r=0.23). The level of LDH was affected by the distance travelled by lambs prior to slaughter. Lairage duration did not affect the levels of CK and LDH. Principal Component Analysis showed a relationship between distance travelled and CK and LDH; and that CK and LDH also influenced the quality of meat from lambs. With respect to sex and breed, the results indicate that female and Dorper were more stressed than male and Merino respectively. Muscle glycolytic potential and post-mortem metabolites have an impact on the quality of meat produced and the Merino had higher muscle glycogen levels at slaughter; hence they produced better meat quality compared to the Dorper. Moreover, no associations were seen between pHu and blood stress indicators. These results indicate that blood stress indicators at exsanguination cannot be used as useful indicators of dark cutting condition in lamb. A relationship between pHu, muscle glycogen and glycolytic potential was established and thus meat pHu can be used as a reliable indicator of tenderness in lamb.
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  • Date Issued: 2019

Muscle nanostructure, fat colour related fatty acids and Check-All-That-Apply visual profiling of South African A2 beef longissimus

  • Authors: Soji, Zimkhitha
  • Date: 2019
  • Subjects: Meat -- Quality
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: http://hdl.handle.net/10353/15264 , vital:40332
  • Description: The main objective of this study was to determine the effect of muscle nanostructure on tenderness, fat colour related fatty acids and Check-All-That-Apply visual profiling of South African A2 beef longissimus. Fifty two A-class steers (n=52) of five breeds (Bonsmara (n=19), Beef master (n=7), Hereford (n=9) and Simbra (n=17)) typically processed in different South African feedlots were studied. The animals were humanely slaughtered at an abattoir following the commercial standard procedures. Fat colour measurements (CIE b*) were taken at the P8 site on hot carcasses at the abattoir. Carcass mass (warm and cold) was recorded at the slaughter line before chilling (warm) and after chilling (cold) while pH0 and temperature were measured at 45 minutes post-mortem on the Longissimus thoracis et lumborum (LTL) muscle. Thereafter, a 20 g subsection of the LTL muscle on the left side of each carcass was sampled for muscle nanostructure analysis. At 24 hours post-slaughter, ultimate pH (pH24) was measured, further subsections of the LTL muscle (20 g) were harvested for further muscle nanostructure analysis and 2.5 kg of the LTL muscle was also harvested for analysis of tenderness, fatty acids and sensory evaluation. The muscle nanostructure (myofibril diameter (MYD), myofibril spacing (MYS), muscle fibre diameter (MFD), muscle fibre spacing (MFS) and sarcomere length (SL)) was analysed using the scanning electron microscope (SEM) while tenderness was measured using Warner Bratzler Shear Force after 45mins, 24hrs, 3 and 7 days aging period at -20 ºC refrigerator temperature. Some proximate fractions (total extractable intramuscular fat (Fat %), Fat Free Dry matter (FFDM %) and Moisture content) and fatty acid profile were measured using extracted fat and fatty acid indices (desaturase index, atherogenicity index) were calculated. Lastly a Check-All-That-Apply visual profiling method rated by an 80-member consumer panel was done to assess consumer meat preferences and perceptions of Bonsmara, Hereford and Simbra A2 fresh steaks. At 45mins post-slaughter breed affected (P<0.05) MYD and MYS, while at 24hrs breed affected MFD and MFS only. Early post-mortem pH (pH0) had no effect on the muscle nanostructure and tenderness while ultimate pH (pH24) affected MYD and MYS only. Muscle temperature at 45mins affected (P<0.05) the MYD, MFD and MFS, while 24hrs muscle temperature affected (P<0.05) MYD only. Tenderness was not related to the muscle nanostructure early post-mortem and there was no uniformity on the changes in muscle nanostructure and tenderness from early post-mortem to 24hrs against the multifaceted carcass mass, muscle pH and temperature effects. During ageing, breed affected the MYD and MYS at 45mins, while at 24hrs in addition to the myofibril structure breed also had an effect on muscle fibre bundle characteristics (MFD and MFS). The changes in MYD, MYS and MFS became constant on day 3 while variations in the MFD still progressed. There was no uniformity on the SL pattern during ageing and a very weak linear relationship between tenderness, SL, MFD and MFS was observed. Notably there was also no uniformity on how the muscle texture features; including the surface structure, fibre separation, and the mechanism of muscle contraction and relaxation; changed throughout the ageing period across and within the breeds. Moreover, breed had a significant effect on pentadecyclic acid, total saturated fatty acids (SFA) and docosahexanoic acid. Differences (P<0.05) in SFA, monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), n-6, n-3, fatty acid ratios, and desaturase index were observed among the white, creamy-white and creamy fat colour. The distribution of fatty acid classes was SFA>MUFA>PUFA in descending order of concentrations of mean values (44.19:40.06:15.75, respectively), while the n-6: n-3 ratio was 12:1. In sensory evaluation, consumers indicated how they would prefer to pay premium for meat with guaranteed muscle and fat colour, low fat content, high marbling and tenderness. Consumers observed breed differences (P<0.05) in muscle fibre separation and muscle colour. The overall liking of each attribute was more on moderate bright cherry red lean colour, moderate yellow fat, very abundant marbling and slight separation of muscle fibres. Differences on discrete liking of each attribute among consumers had an effect on the overall liking of each steak with Hereford steaks being more preferred by consumers. It was concluded that meat from beef animals within the same feeding regime has a different fatty acid composition owing to different breed synthetic pathways and feed ingredients and that meat tenderness is not affected by the muscle nanostructure early post-mortem. However, during ageing, meat tenderness is directly linked to breed related myofibril structure changes in particular the myofibril diameter, spacing between myofibrils and their interaction; while the muscle texture features, fibre diameter, spacing between muscle fibres and sarcomere length explain the non-uniformity of beef tenderness. Also the organoleptic and health related quality of meat assumed more importance among consumers in sensory evaluation. Thus meat classification systems should include more credence aspects or indicators that support credence quality of meat
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  • Date Issued: 2019

The enforceability of by-laws of district municipalities on local municipalities with specific reference to solid waste disposal

  • Authors: De Villiers, Nico Francois
  • Date: 2019
  • Subjects: South Africa -- Local Government: Municipal Systems Act, 2000 , Local government -- Law and legislation -- South Africa Refuse and refuse disposal -- Law and legislation -- South Africa Refuse and refuse disposal
  • Language: English
  • Type: Thesis , Masters , LLM
  • Identifier: http://hdl.handle.net/10948/42118 , vital:36627
  • Description: A consequence of the regionalisation of waste disposal services is that waste management services are no longer the primary responsibility of local municipalities but shared between local and district municipalities. The process of regionalising solid waste disposal and the regulation thereof presents unchartered territory in South Africa and raises several questions including whether, in regulating regional waste disposal services, a district municipality may do so through adopting by-laws and if so, whether these by-laws are enforceable on the local municipalities who benefit from the waste disposal service. The study confirmed the importance of cooperative governance and public participation in all decision making processes including the enactment of legislation. The absence of constitutional and legislative guidance on implementation processes for regionalisation and the overlapping nature of the functions and powers of the effected local and district municipalities are identified as challenges to the regionalisation process. The study concluded that district municipal by-laws may regulate the regional waste disposal function. These adopted by-laws, although not without boundaries, will be enforceable on local municipalities provided that the principles of cooperative governance and public participation were adhered to.
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  • Date Issued: 2019

The effects of collective bargaining on wages at University of Fort Hare 2007-2016

  • Authors: Olusola, Olasupo
  • Date: 2018
  • Subjects: Wages Collective bargaining -- South Africa Labor unions -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , Public Administration
  • Identifier: http://hdl.handle.net/10353/9962 , vital:35208
  • Description: Collective bargaining is essential in labour relations because of its significant role on wages thereby structuring cordial labour-management relations. The essence of labour unions in South African higher education institutions such as National Education, Health and Allied Workers’ Union (NEHAWU) with specific reference to University of Fort Hare, is to ensure the good wages and conditions of service for their members through the instrumentality of collective bargaining between the Union and University management. The end result which is the bargaining agreement may improve on staff pay and encourage more cordial labour-management relations in South African higher institutions and specifically at University of Fort Hare which is the case study. This study was motivated by claims and evidences which show that University of Fort Hare’s staff is the least paid in South African higher education sector over the years due to unsustainability status of the University in the time past. Both the organized labour union and management at the University of Fort Hare entered into agreement that led to sacrificial forfeiture of salary increase by staff over the period of unsustainability of the University to avoid it from being closed down. This state has made the staff to suffer so many imbalances in their wages compared to what is obtainable in other universities in South Africa. This lingering situation has compelled NEHAWU to consistently engage the University management in bargaining in a bid to improve the wages of their members. The study made use of mixed research method which reveals that collective bargaining has effects on wages at University of Fort Hare. 307 participating staff were randomly selected from the following ÜFH Campuses; Bisho, Alice and East London.The questionnaire measured the effects of collective bargaining on wages at the University. In-depth Interviews were conducted among the staff at UFH. It involves the University management, NEHAWU officialsand top officers from the University Human Resources Department. Statistical Package for Social Science (SPSS) was utilized to analyze data collected. Descriptive and inferential statistics was used to interpret the data. Tables and graphs; confidence interval and p-value was utilized to demonstrate the characteristics of information collected from the participants. The research questions were tested by Pearson correlation and T. Test. The reliability of different instruments that were used in this study was tested by Cronbach alpha coefficients and also computed to determine the validity of question. The study concludes that there is a significant relationship between collective bargaining and wages at UFH. Recommendations were made in favour of transparency, time bound bargaining, mutual trust, proper communication and accountability among the negotiating parties at UFH for more successful bargaining that will further improve on staff pay at the University.
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  • Date Issued: 2018

The history and historiography of the Amamfengu of the Eastern Cape, 1820-1900

  • Authors: Maxengana, Nomalungisa Sylvia
  • Date: 2018
  • Subjects: Fingo (African people) -- History Eastern Cape (South Africa) -- History
  • Language: English
  • Type: Thesis , Doctoral , PhD (History)
  • Identifier: http://hdl.handle.net/10353/17872 , vital:41624
  • Description: The name '' amaMfengu '' refers not to any specific African people, but is an umbrella term used up to the present day as a collective designation for amaHlubi, amaBhele, amaZizi and other chiefdoms and individuals who fled KwaZulu-Natal in the time of King Tshaka (1818 - 1828) and found refuge in the lands of the Xhosa King Hintsa. Despite their diverse origins, the shared historical experience of the various Mfengu groups provided them with a common identity and a common destiny. Their dire situation as refugees inclined them to mission Christianity which led, in turn, to alliance with the British Empire followed ultimately by rejection from the racist settler regime of the Cape Colony. All these traumatic events took place within a period of eighty years, and it is these eighty years which will be the focus of this dissertation
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  • Date Issued: 2018

User interface design guidelines for digital television virtual remote controls

  • Authors: Wentzel, Alicia Veronica
  • Date: 2016
  • Subjects: Remote control , User interfaces (Computer systems) , Television broadcasting , Human-computer interaction
  • Language: English
  • Type: Thesis , Masters , MCom
  • Identifier: vital:1158 , http://hdl.handle.net/10962/d1020617
  • Description: The remote control is a pivotal component in households worldwide. It helps users enjoy leisurely television (TV) viewing. The remote control has various user interfaces that people interact with. For example, the physical user interface includes the shape of the remote and the physical buttons; the logical user interface refers to how the information is laid out; and the graphical user interface refers to the colours and aesthetic features of the remote control. All of the user interfaces together with the context of use, cultural factors, social factors, and prior experiences of the user influences the ways people interact with their remote control and ultimately has an effect on their user experiences. Advances in the broadcasting sector and transformations of the TV physical remote control have compounded the simple remote control into a multifaceted, indispensable device, overcrowded with buttons. The usability and ultimately the user experience of physical remote controls (PRCs) have been affected by the overloaded functionality and small button sizes. The usability issues with current PRCs, the evolution of mobile phones into touchscreen smartphones, and the trend of global companies moving towards virtual remote controls (VRCs) have prompted this research to discover what user interface design features will contribute towards an enhanced user experience for digital TV VRCs. This research used the design science research process model (DSRP), which comprised six steps, to investigate this topic area further. A review of the domain literature pertaining to mobile user experiences (MUX) and all the encompassing factors, mobile human computer interaction (MHCI) and the physical, logical, graphical and natural user interfaces was completed, as well as a review of the literature regarding the usability issues of PRCs and VRCs. A contextual task analysis (CTA) of a single South African digital TV PRC was used to identify how users utilise PRCs to perform tasks, and the usability issues they encountered during the tasks. Brainstorming focus groups were used to understand how to represent certain user interface elements and attempted to source ideas from users about what potential functionality digital TV VRCs should contain. Together with all the other results gathered from the previous chapters amalgamated into a set of user interface design guidelines for digital TV VRCs. The proposed user interface guidelines were used to instantiate a digital TV VRC prototype that underwent usability testing in order to validate the proposed user interface design guidelines. The results of the usability testing revealed that the user interface design guidelines for digital TV VRCs were successful, with the addition of one guideline that was discovered during the usability testing.
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  • Date Issued: 2016

A comparative exploratory analysis of vigilante occurrences in two communities in Port Elizabeth (Kwazakhele and New Brighton)

  • Authors: Loqani, Anelisa
  • Date: 2015
  • Subjects: Vigilantes Crime prevention -- Citizen participation -- Social aspects -- South Africa -- Eastern Cape Crime -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Masters , M Soc Sci
  • Identifier: http://hdl.handle.net/10353/2523 , vital:27885
  • Description: The study explores and compares the incidents of vigilantism in two selected communities in Port Elizabeth. However, the word ‘vigilantism’ as utilized in the study can be explained as the group of people in a community who take the law into their own hands and punish alleged societal offenders on the spot. Vigilante activities have become a regular occurrence in many communities in Port Elizabeth and in South Africa as whole. This phenomenon as reported by several authors has destroyed many young men’s lives and ambitions. This is a paradoxical situation that violates human rights because South Africa is a country with a Constitution that prioritizes human dignity for all, and citizens that are totally free from violence of any kind. The aim of the study is to explore, analyze and compare the incidents of vigilantism in New Brighton and Kwazakhele communities in Port Elizabeth. The intention is to educate and enlighten the members of the selected communities, together with the public about vigilantism and its impact on communities.
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  • Date Issued: 2015

An analysis of the certificate of the theory of accounting knowledge and knower structures : a case study of professional knowledge

  • Authors: Mkhize, Thandeka Fortunate
  • Date: 2015
  • Subjects: Accounting -- Study and teaching (Higher) , Dropout behavior, Prediction of , Knowledge, Theory of , Knowledge and learning , Critical realism , Education -- Philosophy , Educational sociology
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:2057 , http://hdl.handle.net/10962/d1019771
  • Description: This research project explores issues around the poor throughput and high dropout rate in the Certificate of the Theory of Accounting (CTA) by focusing on Accounting knowledge as an object of study. The CTA was identified as a serious block in the steps that one needs to go through on the journey to becoming a Chartered Accountant. Having a clear understanding of Accounting knowledge can lead to finding ways that can make the subject more accessible to students from diverse backgrounds. This study contributes to understanding Accounting knowledge at the CTA level with the aim of clearly delineating its legitimate knowledge and knower structures. It answers the following two research questions: • What constitutes legitimate knowledge structures in the CTA? • What constitutes legitimate knower structures in the CTA? Academics from nine universities and representatives of the South African Institute of Chartered Accountants (SAICA) participated in this study. Data was collected through interviews, observation and document analysis. Eighteen CTA lecturers and two members of the SAICA management team were interviewed. Three universities provided documents on their practices, which included learner guides, examination papers, suggested answers, lecture notes, tutorials and other curriculum documents for each of the four CTA subjects. SAICA provided the competency framework and examinable pronouncements. A conference that was jointly hosted by SAICA and International Financial Reporting Standards (IFRS) Foundation was observed. This study used Critical Realism as its ontological underpinnings and Legitimation Code Theory (LCT) as its substantive theory. It used the Specialisation and Autonomy principles of LCT to analyse the data. Specialization establishes the ways agents and discourses within a field are constructed as special, different or unique and thus deserving of distinction and status (Maton, 2014). The principle of Autonomy is concerned with the extent to which the field is self-governing and can do things of its own free-will (Maton, 2004). The study found that the CTA has a hierarchical knowledge structure, which means that when new knowledge is created in Accounting it is integrated into existing knowledge, resulting in coherent and integrated knowledge. CTA also has a hierarchical curriculum structure. While horizontal curriculum structures evolve through the replacement of existing knowledge by new approaches and content, a hierarchical curriculum typically grows through integration and subsumption of new knowledge into pre-existing knowledge and it relies on the acquisition of knowledge developed in previous modules or levels of study.
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  • Date Issued: 2015

Gametogenesis, gonadal recrudescence, restraint and spawning patterns in Nile perch, Lates niloticus (Linnaeus, 1758)

  • Authors: Kahwa, David
  • Date: 2013
  • Subjects: Nile perch -- Victoria, Lake Gametogenesis Oogenesis Spermatogenesis Nile perch -- Spawning -- Victoria, Lake Nile perch -- Induced spawning -- Victoria, Lake Nile perch -- Reproduction -- Endocrine aspects -- Victoria, Lake Fish culture -- Victoria, Lake
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5182 , http://hdl.handle.net/10962/d1001834
  • Description: The Nile perch, Lates niloticus (Linnaeus, 1758), is a predacious freshwater fish widely distributed throughout the Afro-tropic eco-zone. The species was introduced to Lake Victoria in the early 1950s and by 1980 it had dominated the fisheries of Lake Victoria. This was followed by a dramatic decrease in the Nile perch fisheries production due to uncontrolled exploitation. The purpose of this thesis is to provide fundamental knowledge that can be applied in aquaculture and fisheries management through the study of the reproductive biology of L. niloticus. The research was aimed at the studying of the diverse aspects of the reproductive biology of L. niloticus in the Lake Victoria, Ugandan populations. This included reproductive patterns in relation to proximate environmental conditions, size at sexual maturity, gonad and gamete structure, gametogenesis and induced ovulation. The size at 50% sexual maturity for female Nile perch was 59.4 cm, which is lower than the earlier reported size of greater than 90 cm total length. Male L. niloticus matured at 57.8 cm total length in Lake Victoria. Microscopy revealed that L. niloticus from Lake Victoria had one spawning period that started in November and ended in March. Type I atresia occurred at high frequency from March to June, and type III atresia was present from July to September and between November and December. Spermatogenesis in L. niloticus is cystic and sperm development is the result of asynchronous activation of the germ cells. Type II spermatozoa are simple, uni-flagellate aquasperm with no acrosome. Oogenesis in L. niloticus differed from that of other fishes in that no cortical alveoli were present in any stage of oogenesis. Numerous oil globules were present in the primary yolk vesicle stage. This formed one centrally positioned, large oil globule in the tertiary yolk vesicle oocytes during final oocyte maturation. Clove oil was an effective sedative and an anaesthetic for the handling of L. niloticus. Induction time was more rapid at clove oil concentrations of 50 - 100 μl L⁻¹ than in fish exposed to clove oil concentrations less than 50 μl L⁻¹. Fish exposed to high concentrations exhibited significantly short induction times of less than 240 seconds. On average, fish recovered within 673 ± 58 seconds for all the concentrations used. Prolonged exposure of L. niloticus to low clove oil concentrations of 2.5 - 10 μl L⁻¹ did not change the blood plasma cortisol, glucose, and the lactate and chloride ion concentration, relative to the control treatment. Captive breeding was attempted by conducting induced spawning experiments. Only final oocyte maturation was achieved using a decapeptide Gonadotropin Releasing Hormone (Dargin, sGnRH-MET), combined with a water-soluble dopamine receptor antagonist metoclopramide. This thesis suggests a research approach that provides a basis for aquaculture of the new species by first studying reproductive biology patterns and then linking the information to gonad and gamete structure so that spawning times can be estimated. It further provides insights into aspects of the reproductive biology of the species and the effects of hormonal intervention on oocytes by showing at which stage of oocyte development hormones should be applied in L. niloticus. Clove oil can be used to sedate and anaesthetise L. niloticus broodfish to reduce the stress related to the handling of large specimens.
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  • Date Issued: 2013

Effect of alkaline pre-treatments on the synergistic enzymatic hydrolysis of sugarcane (Saccharum officinarum) bagasse by Clostridium cellulovorans XynA, ManA and ArfA

  • Authors: Beukes, Natasha
  • Date: 2011
  • Subjects: Sugarcane -- Biotechnology Lignocellulose -- Biotechnology Renewable energy sources Hydrolysis Enzymes
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:3952 , http://hdl.handle.net/10962/d1004011
  • Description: The continual increase in industrialization and global population has increased the dependency and demand on traditional fossil fuels for energy; however, there are limited amounts of fossil fuels available. The slow depletion of fossil fuels has sparked a fresh interest in renewable sources such as lignocellulose to produce a variety of biofuels, such as biogases (e.g. methane), bioethanol, biodiesel and a variety of other solvents and economically valuable by-products. Agricultural crop wastes produced in surplus are typically lignocellulosic in composition and thus partially recalcitrant to enzymatic degradation. The recalcitrant nature of plant biomass and the inability to obtain complete enzymatic hydrolysis has led to the establishment of various pre-treatment strategies. Alkaline pre-treatments increase the accessibility of the exposed surface to enzymatic hydrolysis through the removal of acetyl and uronic acid substituents on hemicellulose. Unlike the use of steam and acid pre-treatments, alkaline pre-treatments solubilize lignin and a small percentage of the hemicellulose, increasing enzyme accessibility and thus the hydrolysis of lignocellulose. The majority of Clostridium cellulovorans associated enzyme synergy studies have been devoted to an understanding of the cellulolytic and hemi-cellulolytic degradation of plant cell walls. However, little is known about the effect of various physical and chemical pre-treatments on the synergistic enzymatic degradation of plant biomass and possible depolymerization of plant cell walls. This study investigates the use of slake lime, sodium hydroxide and ammonium hydroxide to pre-treat sugarcane bagasse under mild conditions and elucidates potentially important synergistic associations between the C. cellulovorans enzymes for the enhanced degradation of lignocellulose. The primary aims of the study were addressed using of a variety of techniques. This included suitable vector constructs for the expression and purification of recombinant C. cellulovorans enzymes, identification of the effects of various pre-treatments on enzyme synergy, and identification of the resultant reducing sugars and phenolic compounds (released during the pre-treatment of the bagasse). This study also made use of physical and chemical pre-treatment methods, protein purification using affinity, high performance liquid and thin layer chromatography, mass spectrometry, sodium dodecyl sulphate and fluorophore-assisted polyacrylamide gel electrophoresis (FACE) , enzymatic degradation and synergy studies with various substrates indirectly using the 3, 4-dinitrosalicylic acid (DNS) reducing sugar assay. From this investigation, the following conclusions were made: alkaline pre-treatment successfully solublised, redistributed and removed lignin from the bagasse, increasing the digestibility of the substrates. In summary, the most effective pre-treatment employed 0.114 M ammonium hydroxide / gram bagasse at 70°C for 36 hours, followed by hydrolysis with an enzyme cocktail containing 25% ManA and 75% XynA. This increased the production of sugars approximately 13-fold. Analysis of the sugars produced by the synergistic hydrolysis of sugarcane bagasse (SCB) indicated the presence of xylose, indicating that the enzymes are potentially bifunctional under certain conditions. This study indicated that the use of mild pre-treatment conditions sufficiently removed a large portion of lignin without affecting the hemicellulose moiety of the SCB. This facilitated the potential use of the hemicellulose component for the production of valuable products (e.g. xylitol) in addition to the production of bioethanol. Thus, the potential use of additional components of holocellulose may generate an additional biotechnological benefit and allow a certain degree of flexibility in the biofuel industry, depending on consumer and industrial needs.
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  • Date Issued: 2011

Application of Baylis-Hillman methodology in the construction of complex heterocyclic targets

  • Authors: Ganto, Mlungiseleli MacDonald
  • Date: 2009
  • Subjects: Heterocyclic compounds -- Derivatives Heterocyclic chemistry
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4401 , http://hdl.handle.net/10962/d1006703
  • Description: Baylis-Hillman reactions using various aromatic aldehydes, activated alkenes and catalysts have been used to: - access an extensive range of poly-heterocyclic products;explore chemoselectivity; and optimise reaction efficiency. Chromone-3-carbaldehydes and chromone-2-carbaldehydes, prepared via Vielsmeier-Haack and Kostanecki-Robinson methodology, respectively, have been used as Baylis-Hillman substrates with four different catalysts, viz., 1,4-diazabicyclo[2.2.2]octane (DABCO), 3-hydroxyquinuclidine (3-HQ), imidazole and N’,N’,N’,N’- tetramethylpropanediamine (TMPDA), and with methyl vinyl ketone (MVK), methyl acrylate, cyclic enones (2-cyclohexen-1-one, 2-cyclopenten-1-one and chromones) as activated alkenes. Reactions of the chromone- -carbaldehydes with MVK afforded dimeric Baylis-Hillman adducts when catalyzed by DABCO but when the same reactions were repeated using 3-HQ as catalyst, the dimeric products were accompanied by tricyclic Baylis-Hillman adducts. Use of excess MVK, however, led to mixtures of the normal Baylis-Hillman adducts and the tricyclic adducts – interestingly, with the apparent absence of the dimeric products. While reactions of chromone-3-carbaldehydes with methyl acrylate afforded the normal Baylis-Hillman adducts, the chromone-2- carbaldehydes produced, instead, rearrangement products, consistent with an earlier, single observation. Reactions of 2-nitrobenzaldehydes with cyclic enones using imidazole as catalyst afforded the normal Baylis-Hillman adducts, reductive cyclisation of the 2-cyclohexen-1- one and 2-cyclopenten-1-one adducts, using acetic acid and iron powder, afforded the corresponding quinoline erivatives. Treatment of cyclic enones with pyridine-2-carbaldehydes and quinoline-2-carbaldehydes using TMPDA as catalyst generally gave the expected Baylis-Hillman adducts. However, indolizine derivatives were isolated directly from Baylis-Hillman reactions involving pyridine-2-carbaldehydes and 2-cyclohexen-1-one. The remaining Baylis-Hillman adducts were cyclized to the corresponding indolizines by treatment with acetic anhydride both under reflux and under microwave-assisted conditions, the latter approach providing remarkably rapid and efficient access to the polycyclic products. Computer modelling studies have been conducted on selected polycyclic products at the Molecular Mechanics (MM), Quantum Mechanical (QM) and Density Functional (DFT) levels. The theoretical results have been used to calculate UV, IR and NMR absorption data, which have been compared, in turn, with the experimental spectroscopic data. Use has also been made of the estreNova NMR prediction programme and, generally, good agreement has been observed between the predicted and experimental spectroscopic data.
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  • Date Issued: 2009

Neuroprotective mechanisms of nevirapine and efavirenz in a model of neurodegeneration

  • Authors: Zheve, Georgina Teurai
  • Date: 2008
  • Subjects: HIV infections -- Treatment AIDS (Disease) -- Treatment AIDS dementia complex -- Treatment Nervous system -- Degeneration -- Treatment Melatonin Neurotoxic agents Quinolinic acid
  • Language: English
  • Type: Thesis , Masters , MPharm
  • Identifier: vital:3807 , http://hdl.handle.net/10962/d1003285
  • Description: AIDS Dementia Complex (ADC) is a neurodegenerative disorder implicated in HIV-1 infection that is associated with elevated levels of the neurotoxin, quinolinic acid (QA) which causes a cascade of events to occur, leading to the production of reactive oxygen species (ROS), these being ultimately responsible for oxidative neurotoxicity. In clinical studies, Non-nucleoside reverse transcriptase inhibitors (NNRTIs), efavirenz (EFV) and nevirapine (NVP) have been shown to potentially delay the progressive degeneration of neurons, thus reducing the frequency and neurological deficits associated with ADC. Despite these neuroprotective implications, there is still no biochemical data to demonstrate the mechanisms through which these agents offer neuroprotection. The present study aims to elucidate and further characterize the possible antioxidant and neuroprotective mechanisms of NVP and EFV in vitro and in vivo, using QA-induced neurotoxicity as a model. Research has demonstrated that antioxidants and metal chelators have the ability to offer neuroprotection against free radical induced injury and may be beneficial in the prevention or treatment of neurodegeneration. Hence the antioxidant and metal binding properties of these agents were investigated respectively. Inorganic studies, including the 1, 1-diphenyl-2 picrylhydrazyl (DPPH) assay, show that these agents readily scavenge free radicals in vitro, thus postulating the antioxidant property of these agents. The enhancement of superoxide radical generation and iron mediated Fenton reaction by QA is related to lipid peroxidation in biological systems, the extent of which was assayed using the nitroblue tetrazolium and thiobarbituric acid method respectively. Both agents significantly curtail QA-induced lipid peroxidation and potentially scavenge superoxide anions generated by cyanide in vitro. Furthermore, in vivo results demonstrate the ability of NVP and EFV to protect hippocampal neurons against lipid peroxidation induced by QA and superoxide radicals generated as a consequence thereof. The alleviation of QA-induced oxidative stress in vitro possibly occurs through the binding of iron (II) and / or iron (III), and this argument is further strengthened by the ability of EFV and not NVP to reduce iron (II)-induced lipid peroxidation in vitro directly. In addition the ferrozine and electrochemistry assay were used to measure the extent of iron (II) Fe[superscript 2+] and iron (III) Fe[superscript 3+] chelation activity. Both assays demonstrate that these agents bind iron (II) and iron (III), and prevent redox recycling of iron and subsequent complexation of Fe[superscript 2+] with QA which enhances neuronal damage. Both NNRTIs inhibit the endogenous biosynthesis of QA by inhibiting liver tryptophan 2, 3-dioxygenase activity in vivo and subsequently increasing hippocampal serotonin levels. Furthermore, these agents reduce the turnover of hippocampal serotonin to 5-hydroxyindole acetic acid. NVP and not EFV increase 5-hydroxyindole acetic acid and norepinephrine levels in the hippocampus. The results of the pineal indole metabolism study show that NVP increases the synthesis of melatonin, but decreases N-acetylserotonin, 5-hydroxyindole acetic acid and 5-hydroxytryptophol levels. Furthermore, it shows that EFV decreases 5-hydroxyindole acetic acid and melatonin synthesis. Behavioural studies using a Morris water maze show that the post-treatment of rats with NVP and EFV significantly improves QA-induced spatial memory deficits in the hippocampus. This study therefore provides novel information regarding the neuroprotective mechanisms of NVP and EFV. These findings strengthen the argument that these NNRTIs not only have antiviral effects but possess potential neuroprotective properties, which may contribute to the effectiveness of these drugs in the treatment of ADC.
  • Full Text:
  • Date Issued: 2008

How the internet supports the consumer decision process: the case study of McCarthy Call-a-Car

  • Authors: Limbada, Suhayl
  • Date: 2006
  • Subjects: McCarthy Call-a Car , Automobile dealers -- South Africa , Automobile industry and trade , Internet marketing , Consumer behavior , Customer services , Consumer satisfaction
  • Language: English
  • Type: Thesis , Masters , MCom
  • Identifier: vital:1171 , http://hdl.handle.net/10962/d1002787 , McCarthy Call-a Car , Automobile dealers -- South Africa , Automobile industry and trade , Internet marketing , Consumer behavior , Customer services , Consumer satisfaction
  • Description: This thesis aims to provide a better understanding of the ways in which the Internet supports the consumer decision process of potential customers in an online car retail environment. The thesis is mainly focused on how this can be done in South Africa. A case study approach was adopted in investigating the case of McCarthy Call-a-Car. Interviews were carried out with McCarthy Call-a-Car employees and documents and the Call-a-Car website, were analysed. It was revealed that Call-a-Car focuses on using the Internet to support customers in the pre-purchase phase only. The purchase and post-purchase phases are carried out offline at its dealership network and Club McCarthy respectively. The findings showed that Call-a-Car views the Internet as a marketing tool that provides convenience to customers searching for product information in the pre-purchase phase. The interviews revealed that due to Call-a-Car's strategy, as well as practical problems of selling online, the customer will still have to visit a dealership to conclude a purchase and for post-purchase support. From this research it appears that there are three main issues arising out of Call-a-Car's usage of the Internet in the customer buying process: firstly, the research revealed that instead of cutting out the middle-man, the Internet has created new types of intermediaries called "cybermediaries" and that Call-a-Car is one such intermediary. Secondly, it was revealed that trust is crucial in the online environment and that Call-a-Car builds trust through branding. Thirdly, the Internet has not affected prices online, despite theoretical estimations that the Internet would induce lower prices. The main recommendations for future research are empirical studies to investigate if the cybermediary model is unique to the car industry and whether this business model could be applied to other look and feel industries such as real estate. Future studies could also investigate the mechanics of trust-building and brand-building in the online environment and finally, studies from the customer perspective considering what Internet tools the customer would like to see online to support them during their buying decision process.
  • Full Text:
  • Date Issued: 2006

The role of a principal in an academically successful farm school: a case study

  • Authors: Nongauza, Anthony Davidson Mbulelo
  • Date: 2005
  • Subjects: School principals -- South Africa -- Case studies School management and organization -- South Africa -- Case studies Rural schools -- South Africa -- Case studies Education, Rural -- South Africa -- Case studies School supervision, Rural -- South Africa -- Case studies Rural schools -- South Africa -- Administration of -- Case studies
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:1747 , http://hdl.handle.net/10962/d1003631
  • Description: This study looks at the various actions by the principal of a farm school in running an academically successful school. The study exposes the difficulties faced by farm schools and looks at how the principal confronts these difficulties and turn some of these into success stories. In trying to understand the role of the principal this study uses school effectiveness literature as a source and reference in an attempt to understand the actions adopted by the principal to make this farm school successful. The study uses the interpretive orientation as the methodology for investigating the principal’s role. This is in line with my attempt at explaining the perceptions, views and experiences of the people who are working closely with the principal. I have done this by employing semi-structured interviews and participant observation. The information gathered from the respondents helped in the development of the role of the principal which in this case, is the expressed views of the respondents. The investigation is conducted as a case study and the handling of the information provided by the respondents is in line with case study methods. The study has revealed that actions of the leader have an influence on the organizational success. The way in which the leader of Rocklands farm School conducts herself and the vision she shares with the people within the organization go a long way towards the improvement of organizational structures and their functioning. In this case the principal has been noted as particularly transformational, charismatic, instructional and transactional in her approaches to school administration and that her dedication to the cause of learners from disadvantaged background is reflected in her sacrificial actions. The study has also found that the principal is considered to be fairly autocratic in her leadership, which is a departure from current leadership thinking. The study has also shown that socio-economic disadvantages do not necessarily inhibit the school from performing beyond expectation. With good guidance from the leader and trust among staff members the farm school has been able to overcome some socio-economic pressures to emerge successful in the academic field. The fact that the principal of this school is a woman has not changed the overall findings that leadership qualities for successful schooling are universal and do not necessarily depend on the gender of the leader. This study suggests that leaders have a potential to turn poor situations in schools around and that leaders should as a matter of course ensure that they understand the organizational dynamics within their schools. They should be in the forefront as agents of change being mindful that those within the school understand and share the vision the leader has. The study also suggests that the human element in the educational processes in schools is of critical importance than the conditions in which schools find themselves.
  • Full Text:
  • Date Issued: 2005

Aspects of the new repurchase system of monetary control in South Africa

  • Authors: Springfield, Samantha Claire
  • Date: 2001
  • Subjects: Monetary policy -- South Africa Credit control -- South Africa
  • Language: English
  • Type: Thesis , Masters , MEcon
  • Identifier: vital:940 , http://hdl.handle.net/10962/d1002673
  • Description: The main objective of monetary policy is to protect the value of the currency, and in so doing, achieve the objectives of maximum economic growth, development, and the creation of employment opportunities. As from 1985, under the advice of the De Kock Commission, the South African Reserve Bank (SARB), implemented the classical cash reserve system of monetary control. Under this system, the SARB was willing to refinance the money market shortage fully, automatically, and on certain predetermined terms, conditions and costs. However, since the new political dispensation in 1994, South Africa’s financial markets have become more globalized, liberalised, and integrated. Thus, the classical cash reserve system had lost its usefulness, and was no longer effective. As from March 1998, the SARB implemented the new repurchase system of monetary control. In implementing the repurchase system of monetary control, South Africa was adopting a more eclectic approach. This system is aimed at making monetary policy more effective and more flexible in a financial environment filled with complexities. This study finds that the repurchase system has thus far been successful in meeting its objectives. Interest rates are more flexible and sensitive to developments in the domestic and external environment, the signalling mechanism of the SARB has proved to be successful, accommodation and interest rates are closely related and the interbank market has become more developed. Therefore, the repurchase system appears to be more efficient than the previous system of monetary control in South Africa.
  • Full Text:
  • Date Issued: 2001

Using virtual reality to monitor and control an industrial robot via the Internet

  • Authors: Vermeulen, Heinrich
  • Date: 2001
  • Subjects: Virtual reality , Robotics -- Computer programs
  • Language: English
  • Type: Thesis , Masters , MTech (Engineering)
  • Identifier: vital:10820 , http://hdl.handle.net/10948/74 , Virtual reality , Robotics -- Computer programs
  • Description: Manufacturing processes may be modeled in various ways, including 3D modeling. There is a need to visualise, control and monitor manufacturing processes remotely via the Internet. Virtual Reality (VR) can be described as the science of integrating man with information. It is based on three distinct environments: three-dimensional, interactive and computer-generated. VR has come to the Internet in the form of VR modeling. The evolution of Web technologies in recent years has enabled the use of VR modeling for visualisation of manufacturing processes. The VR modeling language (VRML), which has become the standard for transmitting 3D virtual worlds across the Internet, can be used to control and monitor manufacturing processes visually. A 3D model of a manufacturing process, specifically an industrial robot arm, was created for this project. This model was successfully linked to the industrial robot that it represents in order to control and monitor the robot’s actions remotely via the Internet using Web technologies. This dissertation proves the viablity of using Virtual Reality to effectively visualise, monitor and control an industrial robot via the Internet. It also describes the methodology that was followed in modeling the industrial robot arm in VRML as well as linking the model to the real world application.
  • Full Text:
  • Date Issued: 2001

An investigation of the structure of the Southern Hemisphere radio-meteor streams

  • Authors: Roux, David Gerhardus
  • Date: 1988
  • Subjects: Radio meteorology -- Southern Hemisphere , Solar system
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5448 , http://hdl.handle.net/10962/d1004587 , Radio meteorology -- Southern Hemisphere , Solar system
  • Description: Our current knowledge of the Solar System, with a particular emphasis on the systems of interplanetary objects, is reviewed, and the theory of meteors and the reflection of radio waves from meteoric ionization is then discussed. A description of the meteor radar is given and a method of calibrating the antenna beam is developed. The main project comprises two parts: (a) A general survey of the radar echorate for 20 major and minor meteor streams and the sporadic meteor background, conducted from Grahamstown over the period 1986 April to 1988 January, is described. Definite shower activity was observed for all of the major and some of the minor showers. (b) Based on a scheme proposed by previous workers (Morton & Jones), a method of recovering meteor radiant distributions from the distribution of echo directions is developed. We devise a technique of compensating for possible distortions of the resulting radiant maps, which may arise due to the arisotropic antenna beam. This involves a system of echo-weighting. Radiant maps which showed considerably less distortion than those of the above workers were obtained without the weighting procedure. It is concluded that, although the method in its present form introduces spurious features into the maps, the principle is sound and should eventually be refined to produce the desired compensation
  • Full Text:
  • Date Issued: 1988

Studies on the biology of the economic marine red alga Gelidium pristoides (Turner) Kuetzing (Gelidiales : Rhodophyta)

  • Authors: Carter, Alan Robert
  • Date: 1987
  • Subjects: Red algae Marine algae
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4240 , http://hdl.handle.net/10962/d1004774
  • Description: Various aspects of the biology of the intertidal agarophyte, Gelidium pristoides, were investigated, with the aim of providing information that would assist in formulating a management policy for this economic seaweed resource. G.pristoides occurs as tufts comprising as many as 40 individual plants, representing all three conspicuous life history stages, that are linked by the intertwining of their basal creeping axes. Individual plants consist of a system of branched creeping axes, which is largely responsible for colonizing surrounding substrata, from which one or more erect flattened fronds arise. These erect fronds may reach a height of 15 cm, and are irregularly bipinnately branched. Internal vegetative anatomy is generally typical of the genus. Morphological variation in mature plants is limited to increased plant height and branch density during the summer season. A dorso-ventrally flattened creeping habit was seen during early recruitment on flat rock surfaces and limpet shells within grazer exclusion plots, which developed into typical erect plants. Although there is a close taxonomic affinity between G.pristoides and the low-growing Gelidium turf, which occurs on wave-cut platforms in the eastern Cape (both produce bispores), the turf appears to represent a genetically divergent ecotype of the typical G.pristoides habit. In the light of present observations, it is suggested that the recent inclusion of G.pristoides in the new Onikusa genus should be questioned. Reproduction in G.pristoides is typical of the genus, except for the production of bispores, instead of tetraspores, in the sporophyte generation. The smaller nuclei in the binucleate bispores, in comparison to carpospores, suggested they are the product of normal meiosis (meiospores). This was confi rmed by chromosome counts of germl i ngs deri ved from bispores (n = 13-17) and carpospores (2n = 28-33). Throughout the geographical range of the seaweed, the bisporophyte generation is dominant over the combined male and female gametophyte generati on by a ratio of about 3 : 1. This imbalance may be due to bispores. G.pristoides a greater germination success of carpospores over plants are fertile throughout the year, while at Port Alfred there is no apparent seasonality in spore release. Growth of carpospore and bispore germlings is similar under various temperature treatments in culture. Optimum temperatures for growth were from 15-23°C, which corresponds with the sea temperatures experienced within the geographical range of the species . At Port Alfred, growth (linear frond elongation) and standing crop levels were maximal during summer . Ory weight levels were significantly inversely related to both growth and ash levels. Agar contents (% of dry weight) were generally greater in summer (48% ) than in winter (30%), and were inversely correlated with thallus nitrogen levels. Agar contents of distal plant halves were higher (8-15%) than in proximal halves. Regrowth of G.pristoides to original biomass or standing crop levels after harvesting, is similar for plucking and shearing at different times of the year. Regrowth is more rapid after spring and summer harvests (2-3 months) than after winter harvests (4-5 months). During the summer season, harvesting at monthly intervals showed significantly greater total yields, and production rates (e.g . 3.13 g. dry wt. / m2 / day for plucking) than under 3-monthly intervals (1.42 g. dry wt. / m2 / day for plucking). In contrast, average yields per harvest were Significantly greater when recovery period was longer (e.g. 3 months). Quadrats that were completely denuded failed to recover after a year, while regrowth was also retarded with increased elevation on the shore. Agar contents did not differ Significantly between plucked (38%) and sheared (42%) plant material. G.pristoides is distributed from about 0 . 2-0.75 m above MLWS, with a reduction in stature and frequency corresponding to increased elevation on the shore. Frond elongation rates, germling survival and recruitment within grazer-exclusion plots, is retarded with increased elevation level. Plants transplanted above the normal vertical range of the seaweed became severely bleached and died, while plants transplanted below the normal range of the seaweed (sub littoral fringe) senesced due to overgrowth by the epiphytic encrusting coralline, Polyporolithon patena (Hook . et Harv . ) Mason . G.pristoides recrui t ment in the sublittoral fri nge was enhanced with the exclusion of grazers . However, successful recruits were displaced due to smothering by articulated corallines (e.g. Corallina sp. and Jania sp. ) . G.pristoides is largely restricted to cracks and crevices in the rock, and also occurs on a large proportion of the available shells of the limpet Patella oculus Born., and to a lesser extent, shells of the barnacle Tetraclita serrata. G.pristoides recruitment was significantly enhanced by the exclusion of grazers (using toxic antifouling paint barriers). G.pristoides recruitment within the exclusion plots was significantly greater on artificially attached limpet shells (almost 100% cover) than on rock surfaces (20-30% cover), which occurred largely within cracks and crevies in the rocky substratum. ly attached to limpet G.pristoides plants are significantly more strongand barnacle shells than to rock and epilithic encrusting corallines (Lithothamnion sp.). Removal of G.pristoides from limpet shells revealed pits of a uniform size in the surface of the shells, into which the rhizoidal attachment organs of the seaweed penetrate. It is concluded that the horizontal distribution of G.pristoides is largely controlled by grazers (and "escapes" from grazing) and resistance to dislodgement by wave action. Based on present results, and considering some of the socio-economic factors associated with the Gelidium industry in South Africa, suggestions are made concerning the management and long-term maintenance of G.pristoides resources in the eastern Cape.
  • Full Text:
  • Date Issued: 1987

Studies on the biology of the economic marine red alga Gelidium pristoides (Turner) Kuetzing (Gelidiales : Rhodophyta)

  • Authors: Carter, Alan Robert
  • Date: 1987
  • Subjects: Red algae Marine algae
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4239 , http://hdl.handle.net/10962/d1004774
  • Description: Various aspects of the biology of the intertidal agarophyte, Gelidium pristoides, were investigated, with the aim of providing information that would assist in formulating a management policy for this economic seaweed resource. G.pristoides occurs as tufts comprising as many as 40 individual plants, representing all three conspicuous life history stages, that are linked by the intertwining of their basal creeping axes. Individual plants consist of a system of branched creeping axes, which is largely responsible for colonizing surrounding substrata, from which one or more erect flattened fronds arise. These erect fronds may reach a height of 15 cm, and are irregularly bipinnately branched. Internal vegetative anatomy is generally typical of the genus. Morphological variation in mature plants is limited to increased plant height and branch density during the summer season. A dorso-ventrally flattened creeping habit was seen during early recruitment on flat rock surfaces and limpet shells within grazer exclusion plots, which developed into typical erect plants. Although there is a close taxonomic affinity between G.pristoides and the low-growing Gelidium turf, which occurs on wave-cut platforms in the eastern Cape (both produce bispores), the turf appears to represent a genetically divergent ecotype of the typical G.pristoides habit. In the light of present observations, it is suggested that the recent inclusion of G.pristoides in the new Onikusa genus should be questioned. Reproduction in G.pristoides is typical of the genus, except for the production of bispores, instead of tetraspores, in the sporophyte generation. The smaller nuclei in the binucleate bispores, in comparison to carpospores, suggested they are the product of normal meiosis (meiospores). This was confi rmed by chromosome counts of germl i ngs deri ved from bispores (n = 13-17) and carpospores (2n = 28-33). Throughout the geographical range of the seaweed, the bisporophyte generation is dominant over the combined male and female gametophyte generati on by a ratio of about 3 : 1. This imbalance may be due to bispores. G.pristoides a greater germination success of carpospores over plants are fertile throughout the year, while at Port Alfred there is no apparent seasonality in spore release. Growth of carpospore and bispore germlings is similar under various temperature treatments in culture. Optimum temperatures for growth were from 15-23°C, which corresponds with the sea temperatures experienced within the geographical range of the species . At Port Alfred, growth (linear frond elongation) and standing crop levels were maximal during summer . Ory weight levels were significantly inversely related to both growth and ash levels. Agar contents (% of dry weight) were generally greater in summer (48% ) than in winter (30%), and were inversely correlated with thallus nitrogen levels. Agar contents of distal plant halves were higher (8-15%) than in proximal halves. Regrowth of G.pristoides to original biomass or standing crop levels after harvesting, is similar for plucking and shearing at different times of the year. Regrowth is more rapid after spring and summer harvests (2-3 months) than after winter harvests (4-5 months). During the summer season, harvesting at monthly intervals showed significantly greater total yields, and production rates (e.g . 3.13 g. dry wt. / m2 / day for plucking) than under 3-monthly intervals (1.42 g. dry wt. / m2 / day for plucking). In contrast, average yields per harvest were Significantly greater when recovery period was longer (e.g. 3 months). Quadrats that were completely denuded failed to recover after a year, while regrowth was also retarded with increased elevation on the shore. Agar contents did not differ Significantly between plucked (38%) and sheared (42%) plant material. G.pristoides is distributed from about 0 . 2-0.75 m above MLWS, with a reduction in stature and frequency corresponding to increased elevation on the shore. Frond elongation rates, germling survival and recruitment within grazer-exclusion plots, is retarded with increased elevation level. Plants transplanted above the normal vertical range of the seaweed became severely bleached and died, while plants transplanted below the normal range of the seaweed (sub littoral fringe) senesced due to overgrowth by the epiphytic encrusting coralline, Polyporolithon patena (Hook . et Harv . ) Mason . G.pristoides recrui t ment in the sublittoral fri nge was enhanced with the exclusion of grazers . However, successful recruits were displaced due to smothering by articulated corallines (e.g. Corallina sp. and Jania sp. ) . G.pristoides is largely restricted to cracks and crevices in the rock, and also occurs on a large proportion of the available shells of the limpet Patella oculus Born., and to a lesser extent, shells of the barnacle Tetraclita serrata. G.pristoides recruitment was significantly enhanced by the exclusion of grazers (using toxic antifouling paint barriers). G.pristoides recruitment within the exclusion plots was significantly greater on artificially attached limpet shells (almost 100% cover) than on rock surfaces (20-30% cover), which occurred largely within cracks and crevies in the rocky substratum. ly attached to limpet G.pristoides plants are significantly more strongand barnacle shells than to rock and epilithic encrusting corallines (Lithothamnion sp.). Removal of G.pristoides from limpet shells revealed pits of a uniform size in the surface of the shells, into which the rhizoidal attachment organs of the seaweed penetrate. It is concluded that the horizontal distribution of G.pristoides is largely controlled by grazers (and "escapes" from grazing) and resistance to dislodgement by wave action. Based on present results, and considering some of the socio-economic factors associated with the Gelidium industry in South Africa, suggestions are made concerning the management and long-term maintenance of G.pristoides resources in the eastern Cape.
  • Full Text:
  • Date Issued: 1987

History field trips in and around East London as related to the standard eight Cape history syllabus

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