[Truncated abstract] Weeds which invade native communities can have major impacts on biodiversity and ecosystem processes. However, these impacts are rarely quantified, and the mechanisms behind these impacts are rarely investigated. Asparagus asparagoides (L.) Druce (Asparagaceae; common name: bridal creeper), a plant native to southern Africa, is a significant environmental weed in southern Australia. Bridal creeper can invade both disturbed and undisturbed native ecosystems and then dominate native communities. As is the case for many environmental weeds, there has been little work conducted on the impacts of this plant. This lack of knowledge has hampered restoration efforts of invaded areas because very little is known about the potential for invaded communities to recover prior to undertaking weed management. There is a need to improve our understanding of how to manage ecosystem recovery during and after weed control. This can be achieved by (i) determining the impacts caused by the weed; (ii) assessing the condition of invaded communities; and (iii) predicting the impacts that weed management itself will have on the native communities. These three prerequisites to environmental weed control have been determined across sites invaded by bridal creeper in southern Australia. The impacts of this invasive geophyte have been determined through multi-site comparisons, weed removal experiments and controlled glasshouse and laboratory experiments. ... Without additional restoration, we will see those species that readily germinate and those that respond positively to increased soil fertility, replacing bridal creeper after control. This will be dominated by other weeds as the invaded sites have large exotic seed banks that will readily germinate. The tuberous mats of older bridal creeper plants will also leave a legacy as they will remain many years after control and still impact on vegetation, even if control has killed the plant. These impacts will be highest at sites where bridal creeper has dominated over the longer term. Environmental weeds, such as bridal creeper, that are capable of altering ecosystem functions can lead to substantial declines in biodiversity. Therefore, it was fortunate that bridal creeper became a target for biocontrol in Australia even though the impacts of the weed were not quantified when this decision was made. There are areas in southern Australia that are still free of bridal creeper or have sparse populations, and it is highly likely that this biological control programme has lead to the protection of these areas. This protection would not have been possible if other control measures were chosen over biological control, given that biocontrol agents can self-disperse and are able to give continuous control. This means that biological control of weeds in conservation areas can be very effective and is the only economically viable option for the control of widespread environmental weeds such as bridal creeper.

The wide utilization and popularity of medicinal plants in African Traditional Medicine (ATM) has been recognized and attributed to the effectiveness, affordability and accessibility of these medicinal plants. However, the extensive exploitation of medicinal plants has exacerbated the strain on the wild populations. In vitro propagation/micropropagation is an effective method which allows for mass production or multiplication of pathogen-free plants that are morphologically and genetically identical to the parent plant. In addition, the technique is contributing to the understanding of metabolic pathways and regulating the production of plant secondary products. Eucomis autumnalis (Mill.) Chitt. subspecies autumnalis (Hyacinthaceae) is a valuable medicinal species in ATM and commonly traded in the urban street markets of South Africa. Currently, the conservation status of this species has not been evaluated. However, as with most bulbous plants, the wild population is continuously under threat due to over-harvesting and habitat loss via various anthropogenic factors. Thus, in vitro propagation is a viable means of ensuring conservation of the plant species. However, mass propagation of medicinal plants should be accompanied with increased secondary metabolite production to guarantee their therapeutic efficacy. Therefore, the current study was aimed at understanding the different factors that affect the growth and secondary metabolite production in micropropagated E. autumnalis subspecies autumnalis. The influence of the type of gelling agent (gelrite versus agar) and source of initial/primary explant source (LDL = leaf explant derived from primary leaf regenerants and LDB = leaf explant derived from primary bulb regenerants) were evaluated. Gelrite-solidified medium significantly improved shoot proliferation when compared to the use of agar as a solidifying medium. In contrast, quantified phytochemicals such as flavonoids and phenolics were more enhanced in agar-supplemented media. On the basis of the explant source, shoot proliferation and secondary metabolites in regenerants from LDB were similar to those from LDL in most cases. Overall, the type of gelling agents and primary explant source individually or/and interactively significantly influenced the growth parameters as well as the production of iridoid, condensed tannin, flavonoid and phenolic content. The influence of different types of plant growth regulators (PGRs) on growth, phytochemical and antioxidant properties were evaluated. The PGRs were BA (benzyladenine); mT (meta-topolin); mTTHP [meta-topolin tetrahydropyran-2-yl or 6-(3-hydroxybenzylamino)-9-tetrahydropyran-2-ylpurine]; MemT [meta-methoxytopolin or 6-(3-methoxybenzylamino)purine]; MemTTHP [meta-methoxy 9-tetrahydropyran-2-yl topolin or 2-[6-(3-Methoxybenzylamino)-9-(tetrahydropyran-2-yl)purine] and NAA (α-naphthalene acetic acid). Five cytokinins (CKs) at 2 μM in combination with varying (0, 2.5, 5, 10, 15 μM) concentrations of NAA were tested. After 10 weeks of in vitro growth, the regenerants were acclimatized in the greenhouse for four months. Growth, phytochemical content and antioxidant activity of in vitro regenerants and ex vitro-acclimatized plants were evaluated. The highest number of shoots (approximately 9 shoots/explant) were observed with 15 μM NAA alone or with BA treatment. Acclimatized plants derived from the 15 μM NAA treatment had the highest number of roots, largest leaf area and widest bulb diameter. While applied PGRs increased the iridoids and condensed tannins in the in vitro regenerants, total phenolics and flavonoids were higher in the PGR-free treatment. In contrast to the PGR-free regenerants, 5 μM NAA and 2 μM BA treatments produced the highest antioxidant activity in the DPPH (55%) and beta-carotene (87%) test systems, respectively. A remarkable carry-over effect of the PGRs was noticeable on the phytochemical levels and antioxidant activity of the 4-month-old plants. In addition to the development of an optimized micropropagation protocol, manipulating the type and concentration of applied PGRs may serve as an alternative approach to regulate phytochemical production in Eucomis autumnalis subspecies autumnalis. The influence of smoke-water (SW), karrikinolide (KAR1) and CK analogues (PI-55 = 6-(2-hydroxy-3-methylbenzylamino)purine and INCYDE= inhibitor of cytokinin dehydrogenase or 2-chloro-6-(3-methoxyphenyl)aminopurine) individually or in combination with some selected PGRs [BA (4 μM), NAA (5 μM) and both] for in vitro propagated E. autumnalis subspecies autumnalis was evaluated. While these compounds had no significant stimulatory effect on shoot proliferation, they influenced root length at varying concentrations and when interacted with applied PGRs. The longest roots were observed in SW (1:1500), PI-55 and INCYDE (0.01 μM) treatments. There was an increase in the concentration of quantified phytochemicals (especially condensed tannins, flavonoids and phenolics) with the use of these compounds alone or when combined with PGRs. In the presence of BA, an increase in the concentration of PI-55 significantly enhanced the condensed tannin, flavonoid and phenolic contents in the regenerants. Both phenolic and flavonoid content in E. autumnalis subspecies autumnalis were significantly enhanced with 0.01 μM INCYDE. Condensed tannins was about 8-fold higher in 10-7 M KAR1 with BA and NAA treatment when compared to the control. To some varying degree, the effect of the tested compounds on the antioxidant activity of the in vitro regenerants was also noticeable. In most cases, there was no direct relationship between the level of phytochemicals and antioxidant activity recorded. The current findings indicate the array of physiological processes influenced by SW and KAR1 during micropropagation. In addition, targeting or manipulation of phytohormone metabolic pathways using CK analogues demonstrated some noteworthy effects. Perhaps, it may offer other potential practical applications in plant biotechnology and agriculture. Thus, more studies such as quantification of endogenous hormones and identification of specific phytochemicals responsible for the bioactivity in this species will provide better insights on the mechanism of action for CK analogues as well as SW and KAR1. / M. Sc. University of KwaZulu-Natal, Durban 2014.

Thesis (D. Tech. (Biomedical Technology)) -- Central University of Technology, Free State, 2014 / Medicinal plants are part of indigenous people‟s cultural heritage, thus since ancient times treatment of various diseases using medicinal plants has been part of human culture. The value of medicinal plants to mankind has been very well proven. It is estimated that 70% to 80% of people worldwide rely mainly on traditional health care systems, especially on herbal medicines (Stanley and Luz, 2003). In many societies the medicinal properties of plants were discovered mostly through trial and error, but use was also influenced by the belief systems of the people involved and often became entangled with religious and mythical practices (Mathias et al., 1996). Besides that, medicinal plants are proving to be rich resources of constituents that can be used in drug development and synthesis. Medicinal plants have been a source of a wide variety of biologically active compounds for many centuries and have been used extensively as crude material or as pure compounds for treating various disease conditions. Between 1% and 10% of plants out of an estimated 250 000 to 500 000 species of plants on earth are used by humans (Boris, 1996). 2 Plants used for medicinal purposes contribute significantly to the development of major medical drugs that are used today. Most common medicines have compounds extracted from plants as their primary active ingredients and many have provided blueprints for synthetic or partially synthesized drugs (Simpson and Ogorzaly, 2001). There has been a major resurgence of interest in traditionally used medicinal plants, with a number of international and local initiatives actively exploring the botanical resources of southern Africa with the intention to screen indigenous plants for pharmacologically active compounds (Gurib-Fakim et al., 2010; Rybicki et al., 2012). South Africa is considered a “hot spot” for biodiversity and more than 22 000 plant species occur within its boundaries. This represents 10% of the world‟s species, although the land surface of South Africa is less than 1% of the earth‟s surface (Coetzee et al., 1999). Plants have also been used by man for various purposes, among others as arrow and dart poisons for hunting, poisons for murder, hallucinogens used for ritualistic purposes, stimulants for endurance and hunger suppression, as well as medicine (Duke et al., 2008; Cragg and Newman, 2005). A derivative of the polyhydroxy diterpenoid ingenol isolated from the sap of Euphorbia peplus (known as “petty spurge” in England or “radium weed” in Australia), which is a potential chemotherapeutic agent for skin cancer, is currently under clinical development by Peplin Biotech for the topical treatment of certain skin cancers (Kedei et al., 2004; Ogbourne et al., 2004). Combretastatin A-4 phosphate, 3 a stilbene derivative from the South African bush willow, Combretum caffrum, acts as an anti-angiogenic agent causing vascular shutdowns in tumors (Newman et al., 2005; Holwell et al., 2002). Further reliance on plants for drug development is demonstrated by the use of galantamine hydrobromide, an alkaloid obtained from the plant Galanthus nivalis used traditionally in Turkey and Bulgaria for the treatment of Alzheimer‟s disease (Howes et al., 2003; Heinrich and Teoh, 2004). The plant chemicals used for the above-mentioned purposes are secondary metabolites, which are derived biosynthetically from plant primary metabolites (e.g. carbohydrates, amino acids and lipids). Secondary metabolites are organic compounds that are exclusively produced by plants and that are not directly involved in the normal growth, development and reproduction of a plant (Firn and Jones, 2003). Yet, they have many functions that are important for the plant‟s long-term health and appearance. Plants, being stationary, have to cope with a number of challenges, including engineering their own pollination and seed dispersal, local variation in the supply of the simple nutrients that they require to synthesize their food and the coexistence of herbivores and pathogens in their immediate environment. Plants have therefore evolved secondary biochemical pathways that allow them to synthesize a spectrum of organic molecules, often in response to specific environmental stimuli, such as herbivore-induced damage, pathogen attacks, or nutrient deprivation (Reymond et al., 2000; Hermsmeier et al., 2001). 4 The biosynthesis of secondary metabolites is derived from the fundamental processes of photosynthesis, glycolysis and the Krebs cycle to afford biosynthetic intermediates which, ultimately, result in the formation of secondary metabolites also known as natural products (Dewick, 2002). It is hypothesized that secondary metabolism utilizes amino acids and the acetate and shikimate pathways to produce “shunt metabolites” (intermediates) that have adopted an alternate biosynthetic route, leading to the biosynthesis of secondary metabolites (Sarker et al., 2006). Modifications in the biosynthetic pathways that produce secondary metabolites are probably due to natural causes (e.g. viruses or environmental changes) or unnatural causes (e.g. chemical or radiation processes) in an effort to adapt or provide longevity for the plant (Sarker et al., 2006). Plants‟ secondary metabolites can be classified into several groups according to their chemical classes, such alkaloids, terpenoids and phenolics (Harbone, 1984; Wink, 2003).