A re-evaluation of plastochron index determination in peas - a case for using leaflet length
- Ade-Ademilua, Omobolanle Elizabeth, Botha, Christiaan E J
- Authors: Ade-Ademilua, Omobolanle Elizabeth , Botha, Christiaan E J
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6491 , http://hdl.handle.net/10962/d1004472
- Description: The plastochron index (PI) is a measure of plant growth reports our findings on PI using the average length of and can be used to determine growth rate, based upon the first pair of leaflets on each node. Early leaflet appearance of successive leaves on the axis of the growth in peas occurs exponentially and the early plant. PI should under ideal growth conditions be a stages of growth of successive pairs of leaflets occur at regular event and should be predictable with a relatively the same relative growth rate. Given that growth of small error of a few hours. PI has been variously leaflets during early development can be measured calculated in peas, and each method reported has had successfully, we propose the use of leaflet growth as a with it a number of problems that do not allow for measure of the plastochron index in peas. Our results reasonable prediction of PI. Internode length varies suggest that plant age is best expressed using the greatly and is dependent upon the variety, which may be plastochron index, which is a measure of the time short- or long-stemmed; thus this parameter is not ideal interval between the initiations of successive events — for determining growth rate or plant age. This paper in the case of peas, of successive pairs of leaflets.
- Full Text:
- Date Issued: 2005
- Authors: Ade-Ademilua, Omobolanle Elizabeth , Botha, Christiaan E J
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6491 , http://hdl.handle.net/10962/d1004472
- Description: The plastochron index (PI) is a measure of plant growth reports our findings on PI using the average length of and can be used to determine growth rate, based upon the first pair of leaflets on each node. Early leaflet appearance of successive leaves on the axis of the growth in peas occurs exponentially and the early plant. PI should under ideal growth conditions be a stages of growth of successive pairs of leaflets occur at regular event and should be predictable with a relatively the same relative growth rate. Given that growth of small error of a few hours. PI has been variously leaflets during early development can be measured calculated in peas, and each method reported has had successfully, we propose the use of leaflet growth as a with it a number of problems that do not allow for measure of the plastochron index in peas. Our results reasonable prediction of PI. Internode length varies suggest that plant age is best expressed using the greatly and is dependent upon the variety, which may be plastochron index, which is a measure of the time short- or long-stemmed; thus this parameter is not ideal interval between the initiations of successive events — for determining growth rate or plant age. This paper in the case of peas, of successive pairs of leaflets.
- Full Text:
- Date Issued: 2005
A decision-making framework for restoring riparian zones degraded by invasive alien plants in South Africa
- Holmes, P M, Richardson, D M, Esler, K J, Witkowski, Ed T F, Fourie, S
- Authors: Holmes, P M , Richardson, D M , Esler, K J , Witkowski, Ed T F , Fourie, S
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6635 , http://hdl.handle.net/10962/d1006859
- Description: Riparian habitats in many parts of South Africa are severely degraded by invasive alien plants, especially trees. These invasions reduce water yields from catchments and affect riverine functioning and biodiversity. Initiatives are under way countrywide to clear alien plants from watercourses and surrounding catchments. Current understanding of key processes that regulate riparian functioning and define options for restoration is rudimentary. We review the impacts of riparian invasions and identify factors limiting the recovery of natural vegetation following alien clearance. We propose a framework of strategic interventions for optimizing restoration success. The framework identifies abiotic and biotic barriers to restoration at the scales of catchments and local reaches. In highly transformed catchments, interventions at the reach scale may fail if important barriers at the catchment scale are not addressed. The extent to which propagule supply and microsite conditions inhibit vegetation recovery is unknown. We also know little of the relative importance of dispersing vegetative propagules, dispersing seeds and soil-stored seed banks in vegetation dynamics, particularly after severe disturbances such as dense invasion by alien plants. The importance of geomorphological and hydrological factors in mediating recovery of riparian vegetation has not been adequately explored for all climatic areas in South Africa. More research is needed to determine the influence of different alien species and clearing treatments on the recovery of riparian vegetation. The literature strongly suggests that in highly alien-transformed catchments, the re-introduction of riparian species is required to promote recovery and suppress re-invasion. However, such interventions are unlikely to be widely implemented unless the cost: benefit ratios are favourable.
- Full Text:
- Date Issued: 2005
- Authors: Holmes, P M , Richardson, D M , Esler, K J , Witkowski, Ed T F , Fourie, S
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6635 , http://hdl.handle.net/10962/d1006859
- Description: Riparian habitats in many parts of South Africa are severely degraded by invasive alien plants, especially trees. These invasions reduce water yields from catchments and affect riverine functioning and biodiversity. Initiatives are under way countrywide to clear alien plants from watercourses and surrounding catchments. Current understanding of key processes that regulate riparian functioning and define options for restoration is rudimentary. We review the impacts of riparian invasions and identify factors limiting the recovery of natural vegetation following alien clearance. We propose a framework of strategic interventions for optimizing restoration success. The framework identifies abiotic and biotic barriers to restoration at the scales of catchments and local reaches. In highly transformed catchments, interventions at the reach scale may fail if important barriers at the catchment scale are not addressed. The extent to which propagule supply and microsite conditions inhibit vegetation recovery is unknown. We also know little of the relative importance of dispersing vegetative propagules, dispersing seeds and soil-stored seed banks in vegetation dynamics, particularly after severe disturbances such as dense invasion by alien plants. The importance of geomorphological and hydrological factors in mediating recovery of riparian vegetation has not been adequately explored for all climatic areas in South Africa. More research is needed to determine the influence of different alien species and clearing treatments on the recovery of riparian vegetation. The literature strongly suggests that in highly alien-transformed catchments, the re-introduction of riparian species is required to promote recovery and suppress re-invasion. However, such interventions are unlikely to be widely implemented unless the cost: benefit ratios are favourable.
- Full Text:
- Date Issued: 2005
Trauma, resilience and vulnerability to PTSD : a review and clinical case analysis
- Edwards, David J A, Sakasa, P, Van Wyk, G
- Authors: Edwards, David J A , Sakasa, P , Van Wyk, G
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6230 , http://hdl.handle.net/10962/d1007780
- Description: This article begins with two case examples of a girl and an adolescent who were raped and developed chronic PTSD. These are used as a basis for understanding the role of a range of factors that are associated with resilience and vulnerability in the face of traumatic events. A literature review examines the proportion of individuals who develop PTSD following trauma and the factors associated with vulnerability and resilience. These include gender, developmental factors, social support and personality factors. Psychological factors associated with maintenance of chronic PTSD are also briefly reviewed. This material is used as a basis for reconsidering the case examples. Each case is formulated within a framework based on sources of vulnerability and qualities of resilience. Approaches to intervention are suggested that could address the range of factors making the individuals vulnerable to chronic psychological problems and support resiliency and recovery.
- Full Text:
- Date Issued: 2005
- Authors: Edwards, David J A , Sakasa, P , Van Wyk, G
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6230 , http://hdl.handle.net/10962/d1007780
- Description: This article begins with two case examples of a girl and an adolescent who were raped and developed chronic PTSD. These are used as a basis for understanding the role of a range of factors that are associated with resilience and vulnerability in the face of traumatic events. A literature review examines the proportion of individuals who develop PTSD following trauma and the factors associated with vulnerability and resilience. These include gender, developmental factors, social support and personality factors. Psychological factors associated with maintenance of chronic PTSD are also briefly reviewed. This material is used as a basis for reconsidering the case examples. Each case is formulated within a framework based on sources of vulnerability and qualities of resilience. Approaches to intervention are suggested that could address the range of factors making the individuals vulnerable to chronic psychological problems and support resiliency and recovery.
- Full Text:
- Date Issued: 2005
Treating PTSD in South African contexts : a theoretical framework and a model for developing evidence-based practice
- Authors: Edwards, David J A
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6231 , http://hdl.handle.net/10962/d1007781
- Description: Several psychological factors contribute to the development and maintenance of post-traumatic stress disorder (PTSD) because they interfere with the emotional processing of the traumatic event. These include problematic and painful emotions such as anxiety, shame, guilt and grief, distorted or dysfunctional cognitions, and cognitive, emotional, and behavioural avoidance mechanisms. Analysis of these maintaining factors provides the basis for current approaches to treatment which support traumatised individuals in facing emotional pain, working to resolve shame, grief and guilt, and expanding existing schemas to accommodate the traumatic event(s). Randomised controlled trials (RCTs) are reviewed in which the efficacy of some of these treatments have been evaluated. While many South African practitioners are familiar with current evidence-based approaches and are skilled at adapting them to local cultural and contextual conditions, a great deal still needs to be done to build a sound research base for local practice in the treatment of PTSD and disseminating that research to practitioners in the field. It is recommended that a case-based evaluation strategy be used to complement the findings of international RCT studies in order to build a foundation of locally contextualised and applicable scientific knowledge.
- Full Text:
- Date Issued: 2005
- Authors: Edwards, David J A
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6231 , http://hdl.handle.net/10962/d1007781
- Description: Several psychological factors contribute to the development and maintenance of post-traumatic stress disorder (PTSD) because they interfere with the emotional processing of the traumatic event. These include problematic and painful emotions such as anxiety, shame, guilt and grief, distorted or dysfunctional cognitions, and cognitive, emotional, and behavioural avoidance mechanisms. Analysis of these maintaining factors provides the basis for current approaches to treatment which support traumatised individuals in facing emotional pain, working to resolve shame, grief and guilt, and expanding existing schemas to accommodate the traumatic event(s). Randomised controlled trials (RCTs) are reviewed in which the efficacy of some of these treatments have been evaluated. While many South African practitioners are familiar with current evidence-based approaches and are skilled at adapting them to local cultural and contextual conditions, a great deal still needs to be done to build a sound research base for local practice in the treatment of PTSD and disseminating that research to practitioners in the field. It is recommended that a case-based evaluation strategy be used to complement the findings of international RCT studies in order to build a foundation of locally contextualised and applicable scientific knowledge.
- Full Text:
- Date Issued: 2005
Interacting effects of wave exposure, tidal height and substratum on spatial variation in densities of mussel Perna perna plantigrades
- McQuaid, Christopher D, Lindsay, Justin R
- Authors: McQuaid, Christopher D , Lindsay, Justin R
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6879 , http://hdl.handle.net/10962/d1011635
- Description: A fine time-scale study was undertaken on the effects of wave exposure, tidal height and substratum type on mussel recruit densities on the south coast of South Africa. Prior to sampling, an exposed and a sheltered shore were identified at each of 2 sites (Diaz Cross and High Rocks) 7 km apart. Each shore was divided into 3 shore levels (termed zones) within which 3 substrata (adult mussels, coralline and non-coralline macroalgae) were sampled. Destructive sampling of early (<1 mm) and late (1 to 5 mm) plantigrades was performed daily over 30 d during a period of comparatively high recruitment. Recruitment was synchronised among substrata within zones, but not among zones or between sites. This suggests that larvae will settle on all substrata within a zone, but will prefer some substrata over others. They will not, however, search among zones for favoured substrata. Densities of early (but not late) plantigrades were consistently greater at Diaz Cross than High Rocks, indicating important differences in post-settlement mortality between sites. At both sites, densities of both recruit classes were greater on the low and mid shore than on the high shore. Generally (18 out of 20 comparisons), plantigrade densities within each zone were greater on algae than on adult mussels. Approximately 45% of all recruits collected were found on the foliose coralline alga Corallina, 37% on adult mussels and 18% on the rhodophyte Gelidium pristoides. Without secondary relocation from macroalgae to adult mussel beds, juveniles recruiting onto algae are likely to be lost. On low shore algae, densities of both early and late plantigrades were greater for exposed shores. Densities of plantigrades on the mussel bed and on algae on the mid and high shore were not correlated with exposure. Thus, site, substratum and zone all had significant and interacting effects on the density of recruits on both exposed and sheltered shores. The effect of wave exposure on recruitment, at least on the low shore, suggests that spatial subsidies not only in the form of food supply, but also in the form of larval transport, have a role in structuring mussel populations.
- Full Text:
- Date Issued: 2005
- Authors: McQuaid, Christopher D , Lindsay, Justin R
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6879 , http://hdl.handle.net/10962/d1011635
- Description: A fine time-scale study was undertaken on the effects of wave exposure, tidal height and substratum type on mussel recruit densities on the south coast of South Africa. Prior to sampling, an exposed and a sheltered shore were identified at each of 2 sites (Diaz Cross and High Rocks) 7 km apart. Each shore was divided into 3 shore levels (termed zones) within which 3 substrata (adult mussels, coralline and non-coralline macroalgae) were sampled. Destructive sampling of early (<1 mm) and late (1 to 5 mm) plantigrades was performed daily over 30 d during a period of comparatively high recruitment. Recruitment was synchronised among substrata within zones, but not among zones or between sites. This suggests that larvae will settle on all substrata within a zone, but will prefer some substrata over others. They will not, however, search among zones for favoured substrata. Densities of early (but not late) plantigrades were consistently greater at Diaz Cross than High Rocks, indicating important differences in post-settlement mortality between sites. At both sites, densities of both recruit classes were greater on the low and mid shore than on the high shore. Generally (18 out of 20 comparisons), plantigrade densities within each zone were greater on algae than on adult mussels. Approximately 45% of all recruits collected were found on the foliose coralline alga Corallina, 37% on adult mussels and 18% on the rhodophyte Gelidium pristoides. Without secondary relocation from macroalgae to adult mussel beds, juveniles recruiting onto algae are likely to be lost. On low shore algae, densities of both early and late plantigrades were greater for exposed shores. Densities of plantigrades on the mussel bed and on algae on the mid and high shore were not correlated with exposure. Thus, site, substratum and zone all had significant and interacting effects on the density of recruits on both exposed and sheltered shores. The effect of wave exposure on recruitment, at least on the low shore, suggests that spatial subsidies not only in the form of food supply, but also in the form of larval transport, have a role in structuring mussel populations.
- Full Text:
- Date Issued: 2005
Abundance and commercialization of Phoenix Reclinata in the King Williamstown area, South Africa
- Gyan, C A, Shackleton, Charlie M
- Authors: Gyan, C A , Shackleton, Charlie M
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6634 , http://hdl.handle.net/10962/d1006829
- Description: In the Eastern Cape of South Africa the fronds of the wild palm Phoenix reclinata are harvested by rural women and manufactured into hand brushes, which are sold in urban centres. This paper reports on the abundance of P. reclinata palms, the profile of the harvesters, and the economic returns from trading in palm brushes as a case study of locally driven non-timber forest product commercialization. The palm resource was in a reasonable state with most clumps being lightly (36%) or moderately (43%) harvested, with many others uncut due to physical or culturally defined refugia. Tall trees within a clump were uncut because the fronds were too high. The estimated production of fronds was less than 25 per cent of the local demand. Consequently, harvesters were seeking alternative areas and species. Mean gross monthly income was R475 (USD45) which was an important cash contribution. Net income was 75 per cent of this. Income earned per seller was influenced by factors such as age, education, hours in the trade, and whether any household member received an old-age pension from the State. Older and less educated sellers had been trading longer than younger or more educated vendors.
- Full Text:
- Date Issued: 2005
- Authors: Gyan, C A , Shackleton, Charlie M
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6634 , http://hdl.handle.net/10962/d1006829
- Description: In the Eastern Cape of South Africa the fronds of the wild palm Phoenix reclinata are harvested by rural women and manufactured into hand brushes, which are sold in urban centres. This paper reports on the abundance of P. reclinata palms, the profile of the harvesters, and the economic returns from trading in palm brushes as a case study of locally driven non-timber forest product commercialization. The palm resource was in a reasonable state with most clumps being lightly (36%) or moderately (43%) harvested, with many others uncut due to physical or culturally defined refugia. Tall trees within a clump were uncut because the fronds were too high. The estimated production of fronds was less than 25 per cent of the local demand. Consequently, harvesters were seeking alternative areas and species. Mean gross monthly income was R475 (USD45) which was an important cash contribution. Net income was 75 per cent of this. Income earned per seller was influenced by factors such as age, education, hours in the trade, and whether any household member received an old-age pension from the State. Older and less educated sellers had been trading longer than younger or more educated vendors.
- Full Text:
- Date Issued: 2005
Current trends in research focused on pushing and pulling : research article
- Authors: Todd, Andrew I
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6744 , http://hdl.handle.net/10962/d1009313
- Description: The purpose of this review paper is to provide a synopsis of the findings of papers on pushing and pulling; and to identify areas of contention which require further in depth analysis. It is evident from reviewing the published papers on pushing and pulling that there is a lack of consensus as to which one of these two actions has the greatest force production. The main problem is probably the lack of standardized methodology in push-pull research. Furthermore, even when similar methodologies have been used the description of postures adopted during testing by the subjects varies greatly from paper to paper. The various studies have employed different postures and also imposed different restrictions on the postures adopted during experimentation, making comparisons between findings difficult. Much emphasis has been placed on the evaluation of static pushing and pulling tasks, and there is a clear need for further research into dynamic pushing and pulling. Additionally to date the focus of much of this research has been on the biomechanical stresses placed on the body with little attention being given to the physiological cost of pushing and pulling.
- Full Text:
- Date Issued: 2005
- Authors: Todd, Andrew I
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6744 , http://hdl.handle.net/10962/d1009313
- Description: The purpose of this review paper is to provide a synopsis of the findings of papers on pushing and pulling; and to identify areas of contention which require further in depth analysis. It is evident from reviewing the published papers on pushing and pulling that there is a lack of consensus as to which one of these two actions has the greatest force production. The main problem is probably the lack of standardized methodology in push-pull research. Furthermore, even when similar methodologies have been used the description of postures adopted during testing by the subjects varies greatly from paper to paper. The various studies have employed different postures and also imposed different restrictions on the postures adopted during experimentation, making comparisons between findings difficult. Much emphasis has been placed on the evaluation of static pushing and pulling tasks, and there is a clear need for further research into dynamic pushing and pulling. Additionally to date the focus of much of this research has been on the biomechanical stresses placed on the body with little attention being given to the physiological cost of pushing and pulling.
- Full Text:
- Date Issued: 2005
Trauma, imagery and the therapeutic relationship : Langu's story
- Karpelowsky, Belinda J, Edwards, David J A
- Authors: Karpelowsky, Belinda J , Edwards, David J A
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6268 , http://hdl.handle.net/10962/d1008267
- Description: This paper, a phenomenological case study, describes the psychotherapy of Langu (pseudonym), a 21-year-old student, who presented with Acute Stress Disorder following a series of motor accidents that affected him and his family. Langu's most distressing experience was having to identify his brother's mutilated and severely burned body. Because of the intensity of the intrusive re-experiencing of traumatic imagery and the degree of dissociative numbing, Langu participated in four intensive guided imagery sessions, which involved reliving the incident, and imaginal dialogues with his dead brother. Session records and supervision notes from the therapy process that unfolded over 22 sessions served as the basis for a thematically selective case narrative. Additional material was obtained from several research interviews with Langu over the following months. The narrative highlights the impact of the imagery work as well as relational aspects of the therapy. The case narrative provides a source for examining many aspects of the psychological impact of trauma and the path to healing, as well as the dilemmas and challenges faced by therapists working with traumatised individuals.
- Full Text:
- Date Issued: 2005
- Authors: Karpelowsky, Belinda J , Edwards, David J A
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6268 , http://hdl.handle.net/10962/d1008267
- Description: This paper, a phenomenological case study, describes the psychotherapy of Langu (pseudonym), a 21-year-old student, who presented with Acute Stress Disorder following a series of motor accidents that affected him and his family. Langu's most distressing experience was having to identify his brother's mutilated and severely burned body. Because of the intensity of the intrusive re-experiencing of traumatic imagery and the degree of dissociative numbing, Langu participated in four intensive guided imagery sessions, which involved reliving the incident, and imaginal dialogues with his dead brother. Session records and supervision notes from the therapy process that unfolded over 22 sessions served as the basis for a thematically selective case narrative. Additional material was obtained from several research interviews with Langu over the following months. The narrative highlights the impact of the imagery work as well as relational aspects of the therapy. The case narrative provides a source for examining many aspects of the psychological impact of trauma and the path to healing, as well as the dilemmas and challenges faced by therapists working with traumatised individuals.
- Full Text:
- Date Issued: 2005
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