Faculty of Science

Permanent URI for this community

https://wiredspace.wits.ac.za/handle/10539/20140
For queries regarding content of Faculty of Science please contact Salome Potgieter by email : salome.potgieter@wits.ac.za or Tel : 011 717 1961

Browse

Browsing Faculty of Science by School "Animal, Plant and Environmental Sciences"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    A Partially Articulated Cynodont Encased in a Putative Burrow Structure from the Cynognathus Subzone C
    (2015-10) Afonso, Nadia
    A sedimentary structure containing a fossilized therapsid, and bioglyphs on the surface morphology, was found during a field expedition to Cynognathus subzone-C in the Eastern Cape, South Africa. A combination of surface scanning, petrographic thin sections, bone mapping and anatomical comparison were used to determine the deposit type and taxonomic identity of the encased therapsid, and examine the implications for biostratigraphy and faunal assemblage of the Cynognathus Assemblage Zone. The deposit is hypothesized to be a portion of a cynodont burrow (burrow margin) that was constructed in fluvial sediment near a river bank. This is the first account of a burrow in subzone-C. Pattern and directionality analysis of the bioglyphs suggest that the bioglyphs are scratch marks made by the burrower during excavation. The scratch marks are mediolaterally narrow, with some exhibiting indentation marks, indicating that the tracemaker had mediolaterally narrow unguals at the distal phalanx (claws). Anomodonts and cynodonts were common burrowers during the Triassic, however comparisons of Thrinaxodon and Lystrosaurus scratch marks to the bioglyphs on this deposit suggests that the bioglyphs were likely constructed by a cynodont as anomodont unguals are laterally wider, and are unable to create mediolaterally narrow markings. The tracemaker is hypothesized to be closely related to Thrinaxodon based on scratch mark comparison. However, bioglyph published literature is limited, and therefore the tracemaker cannot be identified. The therapsid was identified as Diademodon based on cranial and dental morphology. There is limited published literature on Diademodon constructing and/or exploiting burrows, however the taphonomy suggests that the Diademodon was near the entrance or in the tunnel of burrow nearing/during death. This is the first account of Diademodon encased in a burrow.
  • Thumbnail Image
    Item
    Concurrent effects of elevated carbon dioxide and temperatures on the polyphenolics profile, in-vitro selected antioxidant and antimicrobial activities in Carpobrotus edulis (L.) leaves
    (University of the Witwatersrand, Johannesburg, 2022) Sebothoma, Lethabo; Risenga, Ida; Nuapia, Yannick; Mayonde, Samalesu
    Anthropogenic activities have led to the accumulation of carbon dioxide in the atmosphere and consequently the elevation of temperature. Carbon dioxide and temperature influence the physiological and biochemical activities in plants and thus, are important for plant survival, growth, and development. The sessile nature of plants prevents them from physically avoiding environmental factors such as high CO2 and temperatures, as a result they have developed a physiological response mechanism for protection. This mechanism involves the production of secondary metabolites, which in return have human-health benefits. How then is the production of secondary metabolites impacted by rising atmospheric CO2 concentrations and temperatures? Moreover, is the pharmaceutical efficacy of medicinal plants impacted as the atmospheric CO2 concentrations and temperature conditions rise due to climate change? This study therefore, aimed to investigate the possible modifications in the composition of polyphenolic compounds, antioxidant and antibacterial activities in Carpobrotus edulis leaves under controlled concurrent elevated atmospheric CO2 and temperatures. A total of 36 C. edulis potted plant samples, constituting 12 pots, divided into 3 pots per treatments were exposed to combined 600 ppm and 35/30°C (day/night), 600 ppm and 45/35°C (day/night), 800 ppm and 35/30°C (day/night), 800 ppm and 45/35 °C (day/night), respectively. The control samples were kept at ambient conditions of combined 400 ppm and 28/25°C (day/night). The plant samples were exposed to these conditions for up to 192 hours, and leave samples were harvested episodically every 48 hours (48, 96, 144 and 192 hours) during the exposure period. All harvested leave samples were air-dried under 40°C and crude extracts were obtained using methanol. Preliminary phytochemical screening was performed to test the presence of tannins, phenolics, flavonoids, steroids, terpenoids, 6 glycosides, and saponins. The LC-MS/MS method was used to profile the polyphenolic compounds and 2,2-diphenyl-1- picrylhydrazyl (DPPH) used to measure the antioxidant activity of the plant. The antibacterial activity of C. edulis was determined by the use of two popular bacterial strains, Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive), using the Agar well diffusion method. The preliminary phytochemical screening results showed the consistent presence of tannins, phenolics, flavonoids, steroids, terpenoids, glycosides, and saponins throughout the treatments as compared with the control, however flavonoids were not detected in the samples under combined 800 ppm and 45/35°C, 600 ppm and 35/30°C as well as 800 ppm and 35/30°C. This indicated that combined elevated CO2 and temperatures could have impacted on the production of flavonoids. The LC-MS/MS results showed the presence of 24 polyphenolic compounds in Carpobrotus edulis leaves and of those only 14 (58.83%) were present in C. edulis leaves under ambient/control conditions. Furthermore, the concurrent increment of CO2 concentrations and temperatures prompted the appearance of 10 (41.67%) more compounds. A total of 17 (70.83%) polyphenolic compounds were identified under the 600 ppm and 45/35°C treatment. The presence of these 17 compounds seemed to be influenced by the duration of exposure to these conditions. Polyphenolic compounds profiling showed the disappearance of compounds and appearance of new compounds. The disappearance of some compounds was mainly observed under extreme conditions. Antioxidant activity decreased with increasing combined CO2 concentration and temperature exposure. Antimicrobial activity showed some inhibition of S. aureus and E. coli, and the inhibition activity remained constant in all the climatic conditions. This response maybe attributed to the appearance of new polyphenolic compounds. These results suggested that C. edulis is a strong antioxidant and antimicrobial agent, owing it to the polyphenolic compounds composition. However, these properties could be negatively impacted by elevated CO2 and temperatures, thus influencing the efficacy of C. edulis. Future studies could investigate the influences of elevated CO2 and temperatures independently to assess which factor plays the biggest role in the pharmaceutical efficacy of C. edulis