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The study of the understory percentage vegetation covers in three savanna plant species
Abstracts
phenotypes to visitors. Single visitation experiments showed that native flowers received more pollen, and set more seeds per visit, than introduced phenotypes. This suggests that the degree of mechanical fit between the flowers and the visitors determines the effectiveness of visits. We provide strong evidence that floral divergence among plant populations occurs when populations shift from one visitor community to another functionally different visitor community. doi:10.1016/j.sajb.2015.03.099
Antimicrobial activity of some plant extracts B. Ngobenia, I.T. Madamombe-Mandunaa, S.S. Mashelea, E. Van De Wattb a Central University of Technology, Department of Health Sciences, Bloemfontein 9320, South Africa b University of the Free State, Department of Soil, Crop and Climate Sciences, South Africa This study evaluated the antimicrobial properties of methanolic extracts from Xanthocercis zambesiaca, Buxus macowanii, Scilla sp. and Polygala myrtifolia in order to assess their potential use in the development of novel antimicrobial drugs. Antimicrobial activity of the extracts at concentrations between 0.16 mg/ml and 2.5 mg/ml was tested using the broth micro-dilution and agar dilution methods against eight microbial species. Iodonitrotetrazolium chloride was used as an indicator for microbial growth in the micro-dilution method. Chloramphenicol and Amphotericin B served as positive controls. The phytochemical contents of the extracts were also determined as a preliminary indication of the bioactive compounds in the extracts. The leaves and twigs of B. macowanii were most active against all the bacterial and fungal species used. The Minimum Inhibitory Concentration (MIC) of the plant against Escherichia coli and Enterococcus faecalis was 1.2 mg/ml and on the other species it was 2.5 mg/ml using both methods. The other plant extracts did not show activity against the same microorganisms. Phytochemical analysis showed that B. macowanii has alkaloids, phenols, carbohydrates and alkaloids, whereas the other extracts showed the presence of only 1 or 2 of these phytochemicals. Buxus macowanii has potential as an antimicrobial agent. Further studies will be carried out to ascertain the bioactive principles in the plant and their mechanism of action. doi:10.1016/j.sajb.2015.03.100
Spatial changes in vegetation cover over time in a highly threatened vegetation unit, Limpopo Province C. Niemandt, M. Greve Department of Plant Science, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa One of the consequences of land use changes is that natural vegetation, and thus the habitat for native species, diminishes and becomes fragmented. Quantifying the progress and extent of fragmentation in time and space can be a useful proxy of the state of biodiversity within the remaining habitat fragments. The Woodbush Granite Grassland (WGG) is the most threatened vegetation type in Limpopo as almost 90% has been transformed. It is heavily fragmented and currently has no protection. Our objective was to quantify how land use change has altered the original extent of the WGG at both a spatial and temporal scale, and characterize the landscape structure of the WGG using different fragmentation metrics. Three series of aerial photos, from 1948, 1977 and 2008, were used to quantify changes in habitat area of seven land cover
195
types and to calculate a set of landscape metrics to measure WGG fragmentation over time. The following metrics were analysed: patch size, isolation from main patch, isolation from the nearest neighbour patch, isolation from the nearest large patch, and edge effects. General linear models were used to assess how these fragment metrics have changed over time. The cover of the different land cover types has changed significantly from 1948 to 2008, resulting in greater habitat loss and fragmentation of WGG. From 1948 to 1977 grassland cover decreased by 22%, with a further reduction of 7% between 1977 and 2008. Plantations were the main driver of this change, with their cover increasing from 33.5% in 1948 to 56% in 2008. Remaining WGG patches became more isolated between 1948 and 1977, whereas patch size decreased and edge effects increased between 1977 and 2008. Results indicate that species diversity is mainly affected by reduced patch sizes and increased edge effects and less by isolation. doi:10.1016/j.sajb.2015.03.101
The study of the understory percentage vegetation covers in three savanna plant species M. Nndwammbi, M.H. Ligavha-Mbelengwa Department of Botany, School of Life Science, University of Venda, Private Bag X5050, Thohoyandou 0950, South Africa Canopy plant species create a living environment for understory vegetation that is different from vegetation growing away from the canopy. Under the canopy understory plants are protected from grazers. Any means of disturbance of both understory and canopy plant create a change in species composition and distribution of vegetation. Species diversity under canopy differs according to overstory plant species because of the environment it creates under its canopy. On the 6th April 2013 and on the 14th December 2013 thirty five quadrats were constructed under the canopy of Burkea africana, Dichrostachys cinerea, Terminalia sericea and others were constructed away from their canopies. In each quadrat vegetation percentage covers were estimated, number of species counted, dominant species identified and heights of the tallest individuals measured. On the 20th September 2013 fire occurred at the reserve. From the results obtained before fire high average vegetation percentage covers were found away from the canopy, after fire it was high under D. cinerea, with high number of species under the canopies of B. africana and tallest individuals under T. sericea canopies both before and after fire. Disturbance indeed changes the structural makeup of the biome depending more especially on the intensity of disturbance and it also encourages invasion leading to the loss of native species. doi:10.1016/j.sajb.2015.03.102
Interactive effects of Cd and Al on physiology, anatomical changes and biosynthesis of secondary metabolites in Hypoxis hemerocallidea A. Okem, W.A. Stirk, R.A. Street, J.F. Finnie, J. Van Staden Research Centre for Plant Growth and Development, School of Life Sciences, University of KwaZulu-Natal Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa Dubbed the “miracle” medicinal plant, Hypoxis hemerocallidea is used to treat many kinds of human and veterinary diseases. The high demand for this plant species has led to a drastic detrimental pressure on the wild population due to destructive harvesting. There is a misconception that “natural” always means “safe” and that
phenotypes to visitors. Single visitation experiments showed that native flowers received more pollen, and set more seeds per visit, than introduced phenotypes. This suggests that the degree of mechanical fit between the flowers and the visitors determines the effectiveness of visits. We provide strong evidence that floral divergence among plant populations occurs when populations shift from one visitor community to another functionally different visitor community. doi:10.1016/j.sajb.2015.03.099
Antimicrobial activity of some plant extracts B. Ngobenia, I.T. Madamombe-Mandunaa, S.S. Mashelea, E. Van De Wattb a Central University of Technology, Department of Health Sciences, Bloemfontein 9320, South Africa b University of the Free State, Department of Soil, Crop and Climate Sciences, South Africa This study evaluated the antimicrobial properties of methanolic extracts from Xanthocercis zambesiaca, Buxus macowanii, Scilla sp. and Polygala myrtifolia in order to assess their potential use in the development of novel antimicrobial drugs. Antimicrobial activity of the extracts at concentrations between 0.16 mg/ml and 2.5 mg/ml was tested using the broth micro-dilution and agar dilution methods against eight microbial species. Iodonitrotetrazolium chloride was used as an indicator for microbial growth in the micro-dilution method. Chloramphenicol and Amphotericin B served as positive controls. The phytochemical contents of the extracts were also determined as a preliminary indication of the bioactive compounds in the extracts. The leaves and twigs of B. macowanii were most active against all the bacterial and fungal species used. The Minimum Inhibitory Concentration (MIC) of the plant against Escherichia coli and Enterococcus faecalis was 1.2 mg/ml and on the other species it was 2.5 mg/ml using both methods. The other plant extracts did not show activity against the same microorganisms. Phytochemical analysis showed that B. macowanii has alkaloids, phenols, carbohydrates and alkaloids, whereas the other extracts showed the presence of only 1 or 2 of these phytochemicals. Buxus macowanii has potential as an antimicrobial agent. Further studies will be carried out to ascertain the bioactive principles in the plant and their mechanism of action. doi:10.1016/j.sajb.2015.03.100
Spatial changes in vegetation cover over time in a highly threatened vegetation unit, Limpopo Province C. Niemandt, M. Greve Department of Plant Science, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa One of the consequences of land use changes is that natural vegetation, and thus the habitat for native species, diminishes and becomes fragmented. Quantifying the progress and extent of fragmentation in time and space can be a useful proxy of the state of biodiversity within the remaining habitat fragments. The Woodbush Granite Grassland (WGG) is the most threatened vegetation type in Limpopo as almost 90% has been transformed. It is heavily fragmented and currently has no protection. Our objective was to quantify how land use change has altered the original extent of the WGG at both a spatial and temporal scale, and characterize the landscape structure of the WGG using different fragmentation metrics. Three series of aerial photos, from 1948, 1977 and 2008, were used to quantify changes in habitat area of seven land cover
195
types and to calculate a set of landscape metrics to measure WGG fragmentation over time. The following metrics were analysed: patch size, isolation from main patch, isolation from the nearest neighbour patch, isolation from the nearest large patch, and edge effects. General linear models were used to assess how these fragment metrics have changed over time. The cover of the different land cover types has changed significantly from 1948 to 2008, resulting in greater habitat loss and fragmentation of WGG. From 1948 to 1977 grassland cover decreased by 22%, with a further reduction of 7% between 1977 and 2008. Plantations were the main driver of this change, with their cover increasing from 33.5% in 1948 to 56% in 2008. Remaining WGG patches became more isolated between 1948 and 1977, whereas patch size decreased and edge effects increased between 1977 and 2008. Results indicate that species diversity is mainly affected by reduced patch sizes and increased edge effects and less by isolation. doi:10.1016/j.sajb.2015.03.101
The study of the understory percentage vegetation covers in three savanna plant species M. Nndwammbi, M.H. Ligavha-Mbelengwa Department of Botany, School of Life Science, University of Venda, Private Bag X5050, Thohoyandou 0950, South Africa Canopy plant species create a living environment for understory vegetation that is different from vegetation growing away from the canopy. Under the canopy understory plants are protected from grazers. Any means of disturbance of both understory and canopy plant create a change in species composition and distribution of vegetation. Species diversity under canopy differs according to overstory plant species because of the environment it creates under its canopy. On the 6th April 2013 and on the 14th December 2013 thirty five quadrats were constructed under the canopy of Burkea africana, Dichrostachys cinerea, Terminalia sericea and others were constructed away from their canopies. In each quadrat vegetation percentage covers were estimated, number of species counted, dominant species identified and heights of the tallest individuals measured. On the 20th September 2013 fire occurred at the reserve. From the results obtained before fire high average vegetation percentage covers were found away from the canopy, after fire it was high under D. cinerea, with high number of species under the canopies of B. africana and tallest individuals under T. sericea canopies both before and after fire. Disturbance indeed changes the structural makeup of the biome depending more especially on the intensity of disturbance and it also encourages invasion leading to the loss of native species. doi:10.1016/j.sajb.2015.03.102
Interactive effects of Cd and Al on physiology, anatomical changes and biosynthesis of secondary metabolites in Hypoxis hemerocallidea A. Okem, W.A. Stirk, R.A. Street, J.F. Finnie, J. Van Staden Research Centre for Plant Growth and Development, School of Life Sciences, University of KwaZulu-Natal Pietermaritzburg, Private Bag X01, Scottsville 3209, South Africa Dubbed the “miracle” medicinal plant, Hypoxis hemerocallidea is used to treat many kinds of human and veterinary diseases. The high demand for this plant species has led to a drastic detrimental pressure on the wild population due to destructive harvesting. There is a misconception that “natural” always means “safe” and that