71 research outputs found
Evidence of Bi-Directional Volatile-Mediated Communication between Drought-Stressed and Well-Watered Grapevines (Vitis vinifera L.)
No full textThe volatile-mediated interplay between stressed and non-stressed plants has been described in many studies involving both biotic and abiotic stresses as a one-way channel. However, very little is known about the molecular basis and mechanisms by which volatile organic compounds (VOCs) mediate plant communication between drought-stressed ‘emitter’ plants and non-stressed ‘receiver’ neighbours for the defence against impending stress challenges. Aiming to address this in grapevine, this study investigated the effect of two-way VOC exchange between stressed and non-stressed Vitis vinifera L. cv. Shiraz during drought and recovery using four treatments: isolated well-watered (WW) vines, isolated drought-stressed (DS) vines, and co-located DS ‘emitter’ and WW ‘receiver’ vines in a growth room. The results obtained from solid-phase microextraction (SPME) gas chromatography mass spectrometry (GC-MS) analysis showed a synchronised decline in α-pinene concentration in the co-located treatment vines and higher isoprene levels in the DS emitters compared to the isolated DS vines. Targeted gene expression analysis further identified the over-expression of a key gene, allene oxide synthase (AOS), in the jasmonic acid (JA) biosynthesis pathway during peak drought in the DS emitter. Transcript expression of chorismate synthase (CHORS) and α-pinene synthase (VvPNaPin1) showed similar trends in the DS emitter. The results suggest that isoprene and α-pinene may be interplant signalling molecules used by grapevine during drought. To the best of our knowledge, this is the first report of a bi-directional interaction in grapevine between the emitters and receivers under drought stress mediated by the JA and terpenoid biosynthesis pathways.Joanah Midzi, David W. Jeffery, Ute Baumann, Dimitra L. Capone, Suzy Y. Rogiers, and Vinay Paga
Theology, innovation and Society: Towards developing Dialogical Theology for African society
No full textTheology and society are inseparable due to the fact that they are both composed of that
which makes for both human and universal well-being. Indeed the two have through the ages
inspired each other in the pursuit of a better world. This paper aims to explore three
religions; African Indigenous Religion (AIR) Islam and Christianity as practised in
developing countries such as Kenya, with the intention of deducing whether or not believers
of these religions (can engage) engage in dialogue with each other for the purpose of
providing sustainable solutions for community well-being and wholeness. Theology of
dialogue is a methodology used by the author, as a means for innovation; towards creating
harmony and equilibrium in a plural and multi-religious Kenyan society and Africa in
general. Of significance for this timely theological concept in Africa are the dreams that need
achievement; the Millennium Development Goals and state visions such as the Kenya 2030
vision. In approaching the subject, the author shall endeavor to outline pre-colonial, colonial
and post-colonial religious histories in Africa. The author shall use the Midzi-Chenda
(written Mijiknda) community of Coastal Kenya as a case study population. This choice is
due to their diverse and long-lived inter-cultural and inter-religious experiences, particularly
with the Arab, Portuguese and British conquests along the East Coast of Africa. The triple
conquest experiences influenced the Midzi-Chenda community negatively and positively in all
spheres of their life-system; economic, political and religious, compelling them to embrace
foreign culture, religion and politics, all of which gradually shaped their theological
parameters. This latter experience and the contemporary post-colonial religious wave
significantly situate the theology of dialogue as a benchmark for innovation in African
society
Association between Micronutrients (Vitamin A, D, Iron) and Schistosome-Specific Cytokine Responses in Zimbabweans Exposed to Schistosoma haematobium
No full textMicronutrients play an important role in the development of effective immune responses. This study characterised a populations exposed to schistosome infections in terms of the relationship between micronutrients and immune responses. Levels of retinol binding protein (RBP; vitamin A marker), vitamin D, ferritin and soluble transferrin receptor (sTfR), and C reactive protein (CRP) were related to levels of schistosome specific cytokines (IFN-γ, IL-4/5/10) in 40 Zimbabweans (7–54 years) exposed to Schistosoma haematobium infection. 67.2% of the participants were deficient in vitamin D. RBP levels were within normal ranges but declined with age. The two indicators of iron levels suggested that although levels of stored iron were within normal levels (normal ferritin levels), levels of functional iron (sTfR levels) were reduced in 28.6% of the population. Schistosome infection alone was not associated with levels of any of the micronutrients, but altered the relationship between parasite-specific IL-4 and IL-5 and levels of ferritin and sTfR
An intensity database for earthquakes in South Africa from 1912 to 2011
No full textA database of intensity observations from instrumentally-recorded earthquakes in South Africa has been compiled as a contribution to the characterisation of seismic hazard. The database contains about 1,000 intensity data points (IDPs) that have been assigned from macroseismic observations retrieved from newspaper reports and questionnaires, and also digitised from previously published isoseismal maps. The database includes IDPs from 57 earthquakes with magnitudes in the range of Mw 2.2 to 6.4, for epicentral distances up to 1,000 km. Sixteen events have 20 or more IDPs, with half of these events having more than 80 IDPs. The database is dominated by relatively low intensity values, mostly determined from human perception of shaking rather than structural damage. However, 19 IDPs correspond to intensity values greater than VI MMI-56. Using geological maps of South Africa, the sites of 60% the IDPs were geologically classified as either ‘rock’ or ‘soil’, the uncertainty in locations precluding such a classification for the remaining data points. A few of the IDPs identified as being from soil sites appear to be strongly influenced by site effects and these were removed from the trimmed database created for exploring ground-motion levels. The trimmed database included 15 earthquakes which have a minimum of five useful IDPs, excluding those with intensity MMI=I and those based on a single observation. After removing such points, and those identified as clear ‘outliers’, a total of 436 useful IDPs were selected.Published1183-12053T. Pericolosità sismica e contributo alla definizione del rischioJCR Journalreserve
Inter-vine Signalling via Plant Volatiles
No full textWith the help of an evolved innate immune system, the sessile plants have created mechanisms to withstand the background noise of their natural environment. One of these mechanisms is the ability of plants to release volatile organic compounds (VOCs) during episodes of environmental stress and subsequently triggering defence responses that might give them some level of tolerance against the stresses. In some instances, plants will “eavesdrop” these volatile cues from their stressed neighbours to adjust their phenotypes against imminent stress. The priming effect of stress-induced VOCs on non-stressed neighbouring plants for quicker and effective defence response to post stress challenge has been demonstrated in many studies involving biotic stress, with only a few
studies being related to abiotic stress. There is an emerging knowledge of the mechanisms involved, and compelling discussions about the ecological significance of such interactions under various environmental stress conditions have been documented. To that end, this thesis begins by reviewing the significance of VOC-mediated inter-plant interactions under both biotic and abiotic stresses and highlights the potential to manipulate outcomes in agricultural systems for sustainable crop protection via enhanced defence (Chapter 1). The overarching aim of my PhD research was to investigate plant-plant volatile-mediated communication in grapevine under drought stress using physiological, transcriptome and volatilome analyses. The volatile-mediated interplay between stressed and non-stressed plants has been described in many studies
involving both biotic and abiotic stresses as a one-way channel, where the focus is mainly on how inducible VOCs from stressed ‘emitter’ plants prime their non-stressed ‘receiver’ neighbours for defence against impending stress. In Chapter 2, an investigation of VOC-mediated interactions between stressed and non-stressed V. vinifera L. cv. Shiraz during drought and recovery was carried out. Under these experimental conditions, I was interested in exploring the role played by water stress on VOC emissions, specifically α-pinene, isoprene, methyl jasmonate, methyl salicylate, and (Z)-3-hexen-1-ol, as well as how these VOCs induce drought defence responses and stomatal closure in well-watered (WW) receiver vines. A synchronised decline in α-pinene concentration in colocated drought-stressed (DS) and WW receivers, as well as a differential increase in the isoprene levels in the DS emitter compared to the isolated DS vines was observed. An over-expression of a key gene in the jasmonic acid (JA) biosynthesis pathway, allene oxide synthase (AOS) was identified in only the DS emitter during peak drought. Transcript expression of key genes involved in SA and α-pinene biosynthesis, chorismate synthase and α-pinene synthase, respectively, showed similar trends to those of AOS. The results suggested that isoprene and α-pinene may be inter-plant signalling molecules used by grapevine during drought and the study presents the first report of a bidirectional interaction between the emitters and receivers under drought stress, mediated by the JA and terpenoid biosynthesis pathways. To confirm the involvement of isoprene and α-pinene in VOC-mediated signalling in grapevine, as well as other well-known VOC biomarkers, MeJA, MeSA, methanol, and (Z)-3-hexen-1-ol, experiments were carried using sensitive leaf hydraulic and gas exchange measurements to determine the individual VOCs’ effects on stomatal
responses (Chapter 3). A modified Xyl'EM embolism meter in conjunction with a high sensitivity liquid mass flow meter was used to monitor the flow rate into single leaves detached from grapevines. Transient changes in the flow rate were observed in response to methanol and (Z)-3-hexen-1-ol volatiles. Grapevine leaves measured in
vivo showed a decline in leaf gas exchange in response to methanol, but not with (Z)-3-hexen-1-ol. The hydraulics data from this study indicated that both methanol and (Z)-3-hexen-1-ol are signalling molecules in grapevine, which were hypothesised are elicitors of plant defence responses. Following on from this study, a comprehensive genome-wide transcriptome analysis using RNAseq, together with physiological and metabolite analyses were carried out in Chapter 4 to further explore the molecular basis of intervine
signalling under drought stress. No differentially expressed genes (DEGs) were identified between WW control and co-located WW receivers at peak drought, therefore implying that the presence of the co-located DS emitter did not modulate the gene expression of the WW receiver. Contrary to what was observed in Chapter 2, VOCs collected from all the treatment vines showed no treatment effects. The gs of the receivers was also not affected by DS emitters. Overall, no evidence of VOC-mediated communication between the emitters and receivers was found, in contrast to findings from the previous study. It is likely that this difference may have been as a result of the variation in growth stages of each treatment in the previous study, where treatments were evaluated
sequentially rather than concurrently, as was the case with the current study (Chapter 4). Nevertheless, from the RNAseq data from the study, drought was shown to induce the expression of DEGs related to the biosynthesis and signalling pathways of well-known VOC biomarkers, including JA, green leaf volatiles (GLVs), and isoprenoids.
Although DEGs related to SA biosynthesis were not found, an up-regulation of SA-responsive pathogenesis-related genes and associated transcription factors were identified, suggesting that SA signalling pathway is also involved in grapevine drought defence responses. In summary, my PhD thesis has been devoted to advance the knowledge of the underlying mechanisms and signalling pathways involved in VOC-mediated inter-plant communication using grapevine as a model plant.
Although inter-vine signalling could not be concluded from the results obtained in Chapter 4, the gene information from the study identified DEGs related to VOC biosynthesis and drought defence responses, which could be explored in future plant communication studies under drought stress. Using real-time monitoring of VOC-induced
transpiration, the study was able to provide conclusive evidence of immediate grapevine responses to volatile cues. Future studies involving other putative VOC signals will benefit from this approach. Post challenge experiments following VOC exposure is also recommended for future investigations to determine the relevance of VOC-mediated priming in eliciting drought tolerance in grapevine and other plant species. The outcomes of this thesis offer opportunities for a wider application of VOCs in agricultural systems as an eco-sustainable plant protection strategy against biotic and abiotic stressors, such as using specific VOCs to enhance disease resistance and mitigate the effects of abiotic stressors on plant health.Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food & Wine, 202
The feminisation of poverty and victimhood in Dangarembga's print oeuvre: Cyclical evocations of nervous conditions, survival, and agency
No full textA dissertation submitted in partial fulfilment of the requirements for the degree of
Doctor of Philosophy (Education)Feminisation of poverty is a term that was coined by Diana Pearce in 1976 after observing an increased concentration of income poverty among women in America (Peterson, 1987). This term was applied in the analysis of Tsitsi Dangarembga’s oeuvre, mainly focusing on the victimhood, cyclical evocations of nervous conditions, survival strategies and agency that Zimbabwean women experienced and are still experiencing. This dissertation employed a qualitative desktop literary in the examination of four novels, Nervous Conditions (1988), The Book of Not (2006), This Mournable Body (2018) – which make up a trilogy spanning up to 30 years; and She No Longer Weeps (1987). The researcher employed Africana Womanism, STIWANISM, and Nego-feminism literary theories to underpin this study, from examining the complex position that African women face in the light of detrimental effects of colonisation and its impact and legacy as it integrates with traditional patriarchal structures as articulated in Dangarembga’s novels. Africana Womanism as a concept was used so as to accommodate the characteristics of the African society which are unique and different because of its cultural, political, historical and social backgrounds, as other feminisms are peculiar to their place of origin. STIWANISM understands the female struggle from the perspective of African feminism which is entirely dependent on the commitment from both sexes, and not a woman affair as emphasised by other feminisms. Nego-feminism places both genders side by side as men and women to try and negotiate their places in life and establish a harmonious co- existence, with the negative patriarchal structures melting away. The study analysed how the author used the novels to expose issues related to post- colonial conditions, gender inequalities, cultural limitations, female self- definition and struggle for survival. The study found that the women in the Shona society are presented diversely depending on the socio- cultural background. Dangarembga strategically captured a world before and after independent Zimbabwe (1980s), where her main theme were her two protagonists’ struggles to reshape women’s heterosexuality and femininity in a religiously conservative society adopted in a colonial era. The shared themes of womanhood that are depicted in all the texts are the need for a shift of women from the margins of the society to becoming priorities economically, socially, and culturally. This is the recurring theme whether the setting is in the 1980s or the 2000s, rural or urban; Shona women are still victims of the nervous conditions surrounding them
Mapping the Stress Field in Southern Africa: a Tool to Unravel the M5.5 Earthquake of 5 August 2014 near Orkney
No full textThe 5th August 2014 event with epicentre near Orkney, the strongest recorded in South Africa in 45 years, received much attention by the press and the seismological community; and the analysis of the seismic data, including those of the aftershocks, revealed some intriguing facts. Focal mechanism solutions computations provided evidence for a NW-oriented, sub-horizontal σ1 and a left-lateral, predominantly strike slip movement along a cryptic fault plane oriented NNW to N. Adding to the puzzle, the aftershock data also indicated that most of the seismogenic displacement happened below the gold-bearing reef [1]. Prompted by these results, an international effort is being planned to study in situ the slippage zone with an inclined borehole drilled from one of the adjacent mines [2]. Our companion approach aims to capture data on the tectonic stresses that acted on the southern African crust for the past 130 Ma and to model their effects on the Witwatersrand basin. For this, the more reliable stress data are computed from borehole breakouts measurements (mainly offshore exploration wells [3] and fault plane solutions from seismic events recorded by multiple stations. Less reliable are instead stress and strain release structures in mines and tunnels as they may reflect in varying degrees anthropogenic influences. Further stress data were obtained from the structural analysis of fault displacing Late Cenozoic sediments; however, the difficulty to date the last age of movement severely constrains the applications of this technique. Available observations consistently indicate a NNW - N orientation of the maximum horizontal compressive stress (σH) that prevails across most of South Africa, and in Namibia up to the Angola border. An early compilation of our data was adopted by G. Viola et al. [4] and P. Bird et al. [5] to produce kinematic models of stress and strain rate across southern Africa. In particular, Bird s best fit model (AF-SO- 013) is based on realistic rates of remote boundary conditions and generates a belt of strike slip stress (strain rate tensor, E3-E1 = ~10-17units) that extends from the Northern Natal basin, through N Natal and the eastern side of the Witwatersrand region to Central Botswana. Given the coarseness of the AF-SO- 013 model, minor changes in model input parameters would easily allow the strike slip belt to include the western sector of the Witwatersrand basin; whereas the orientation of the conjugate faults and their sense of movement already match within error those computed for the Orkney event. To conclude, the recognition of neotectonic activity in the Witwatersrand basin is consistent with other finds within 100km from Orkney, namely the undated thrust faults cutting calcrete at Bultfontein, and the proposed Late Pleistocene seismites in hot spring deposits at Florisbad [6]. The dearth of data precludes a quantitative assessment of the seismic hazard in the Orkney area, however greater insights might be obtained from more work at Bultfontein and Florisbad, and from a forensic scrutiny of the major tremors swarms in the wider Witwatersrand basins [6], starting from those between Orkney and Welkom with M >2 x the Standard Deviation of the area average. [1] Midzi, V., et al., 2015. J. Seismology 19: 741 751 [2] Ogasawara, H., et al., 2015. AGU Assembly, 14 December 2015, San Francisco: S13B-2834 [3] Logue, A., 2015. M. Sc. Thesis, University of Cape Town. [4] Viola, G., et al., 2005. Earth and Planetary Sci. Letters 231: 147 160 [5] Bird, P., et al., 2006. J. Geophys. Res. 111, B08402: 14 pp. [6] Andreoli, M.A.G., et al., 1996. Africa Geoscience Review 3: 1-16 Key words: Witwatersrand basin, Orkney, borehole breakouts, neotectonic stress, focal mechanism solution
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