Climatic drivers of silicon accumulation in a model grass operate in low- but not high-silicon soils

Grasses are hyper-accumulators of silicon (Si), which is known to alleviate diverse environmental stresses, prompting speculation that Si accumulation evolved in response to unfavourable climatic conditions, including seasonally arid environments. We conducted a common garden experiment using 57 accessions of the model grass Brachypodium distachyon, sourced from different Mediterranean locations, to test relationships between Si accumulation and 19 bioclimatic variables. Plants were grown in soil with either low or high (Si supplemented) levels of bioavailable Si. Si accumulation was negatively correlated with temperature variables (annual mean diurnal temperature range, temperature seasonality, annual temperature range) and precipitation seasonality. Si accumulation was positively correlated with precipitation variables (annual precipitation, precipitation of the driest month and quarter, and precipitation of the warmest quarter). These relationships, however, were only observed in low-Si soils and not in Si-supplemented soils. Our hypothesis that accessions of B. distachyon from seasonally arid conditions have higher Si accumulation was not supported. On the contrary, higher temperatures and lower precipitation regimes were associated with lower Si accumulation. These relationships were decoupled in high-Si soils. These exploratory results suggest that geographical origin and prevailing climatic conditions may play a role in predicting patterns of Si accumulation in grasses

Drought adversely affects tuber development and nutritional quality of the staple crop cassava (Manihot esculenta Crantz)

Cassava (Manihot esculenta Crantz) is the staple food source for over 850 million people worldwide. Cassava contains cyanogenic glucosides and can be toxic to humans, causing paralysing diseases such as konzo, and even death if not properly processed. Konzo epidemics are often associated with times of drought. This may be due to a greater reliance on cassava as it is drought tolerant, but it may also be due to an increase in cyanogenic glucosides. Episodic droughts are forecast to become more common in many cassava-growing regions. We therefore sought to quantify the effect of water-stress on both yield and cyanogenic glucoside concentration (CNc) in the developing tubers of cassava. Five-month-old plants were grown in a glasshouse and either well watered or droughted for 28 days. A subset of droughted plants was re-watered half way through the experiment. Droughted plants had 45% fewer leaves and lower tuber yield, by 83%, compared with well-watered plants. CNc was 2.9-fold higher in the young leaves of droughted plants, whereas CNc in tubers from droughted plants was 4-fold greater than in tubers from well-watered plants. Re-watered plants had a similar biomass to control plants, and lower CNc than droughted plants. These findings highlight the important link between food quality and episodic drought.Rebecca Vandegeer, Rebecca E. Miller, Melissa Bain, Roslyn M. Gleadow and Timothy R. Cavagnar

Antioxidant defence systems and symptom expression of wheat infected with Barley yellow dwarf virus and grown under elevated CO2

© 2016 Dr. Rebecca Kate VandegeerBarley yellow dwarf virus (BYDV) is regarded as the most significant viral pathogen of wheat worldwide. Symptoms produced during viral infection may have an interactive effect with environmental conditions expected under future anthropogenic climate change, including the rising atmospheric CO2 concentration. In particular, antioxidant defence systems – including the key non-enzymatic antioxidants ascorbate and glutathione – play an important role in regulating potentially harmful reactive oxygen species (ROS) produced during plant-virus interactions. However, the role of ascorbate and glutathione during systemic virus infection and growth under elevated CO2 (eCO2) is not well understood. This thesis investigated BYDV infection of three Australian wheat cultivars: the BYDV-susceptible spring wheat ‘Yitpi’, the susceptible winter wheat ‘Revenue’ and the resistant winter wheat ‘Manning’. In addition, the system was investigated under eCO2 to determine any interactions with infection on symptom expression and antioxidant defence capacity. Studies were performed within controlled environment chambers and the field at the Australian Grains Free Air CO2 Enrichment (AGFACE) facility located in the semi-arid grain-growing region of Horsham, Victoria, Australia. The response of plants to virus infection and eCO2 was assessed by measurement of the total concentration and redox state of ascorbate and glutathione. In addition, symptom expression was measured including growth, photosynthesis, stomatal conductance, leaf chlorophyll and nitrogen, and disease incidence and severity. BYDV infection was associated with an imbalance in antioxidative metabolism, which is an indicator of oxidative stress. Greater ROS turnover is the likely cause of the observed decrease in total ascorbate and glutathione and increase in the oxidised fraction of ascorbate after infection. In particular, a decrease in total ascorbate was the most consistent response to infection by all cultivars grown in both chambers and the field. The present research demonstrates that the observed imbalance in non-enzymatic antioxidant metabolism can be used as a marker for oxidative stress during systemic BYDV infection of wheat. The antioxidant response of both the BYDV-susceptible and resistant winter wheat cultivars was similar. Oxidative stress was not influenced by the putatively different virus concentration between these cultivars, but simply by virus infection alone. Infection was also associated with decreased biomass and height in both these cultivars and in both chamber and field studies, which indicates a sensitivity of the resistant cultivar to infection regardless of a putatively lower virus concentration. Despite few interactive effects between virus and eCO2 treatments on symptom expression, eCO2 altered the expression of yellowing disease symptoms in virus-infected plants, although not consistently between cultivars and environmental growing conditions. In addition, although there were significant changes to antioxidants in plants grown under eCO2, results were not consistent between studies. Research into this topic increases our understanding of how plants respond to virus infection and oxidative stress, and how plant-virus interactions may change under future eCO2. With the findings presented in this thesis, I have furthered the knowledge of this area by elucidating the response of ascorbate and glutathione during systemic wheat-BYDV interactions, and reinforced the potential use of these metabolites as markers of oxidative stress

The finality of Christ and the religious alternative

This article shows how the modern category of religion largely shapes the horizon of many contemporary theological appropriations of the finality of Christ, and how the influence of this category creates serious problems. Though affirming Christ’s finality often seems to pose theological difficulties in religiously pluralistic contexts, I argue that it is not at all a matter of exclusion or denigration of other religions. Quite the opposite: the doctrine at heart expresses the Christian community’s hope for universal fellowship

Theology and genealogies of religious studies

In its relatively short life, the discipline of religious studies has issued several challenges to theology. The currency of genealogical strategies in the study of religion changes the nature of the disciplinary contest because these strategies challenge both disciplines to account for their normative dimensions. In this article, I show how different scholars and theologians typically negotiate the relationship between theology and genealogies of religion by closing off historicist inquiries in directions that either reduce or preserve the analytic value of the discourses of religion. These two options (either/or) cross disciplinary boundaries and relativize matters of belief and unbelief. Drawing on Robert Orsi’s work, I argue for a third option, which opens the study of religion and theology to competing presences, and distinguishes, as Bruno Latour does, the procedures of multiplying networks of actors from composing a common world. This third option suggests a freer, more collaborative vision of academic life

Sanctifying Grace in a "Methodical Theology"

Bernard Lonergan claimed that his description of religious experience as “being in love unrestrictedly” differs merely notionally from the Scholastic idea of “sanctifying grace.” However, he did not offer the detailed explanation needed to establish the continuity between his development and the medieval category of “sanctifying grace.” His account of religious experience, therefore, remains ambiguous. Consequently, notable Lonergan scholars have explained the meaning of religious experience differently for a methodical theology. After discussing their explanations, the author offers his own account of “unrestricted being in love” according to the critical directives of the Scholastic categories. </jats:p

Method, meaning, and the theologies of religions

The theologies of religions respond to important questions about the meaning of Christian faith in a religiously pluralistic world, but the debates among their various positions are often criticized for militating against actual engagement with the world’s religions. Most often these theologies presume the need for a framework that relates Christianity to the religions. This article uses the work of Bernard Lonergan to propose foundations for a theology of religions that undercuts the imposition of conceptualist frameworks, attends to the yet unfolding histories of Christianity and the religions, and grounds Christian doctrine in the context of pluralism

The Unity of Salvation: Divine Missions, the Church, and World Religions

The author addresses the doctrinal affirmations of the universality of God’s salvific will and the necessity of the church for salvation. Jacques Dupuis and Gavin D’Costa propose distinct ways of reconciling them; comparing their proposals illustrates the challenge that contemporary Catholic theology faces in its current context of religious pluralism. The author appeals to Bernard Lonergan’s work to suggest an alternative that both anticipates the presence of God outside the church and simultaneously affirms the necessity of the church for the salvation of all

The Finality of Christ and the Religious Alternative

This article shows how the modern category of religion largely shapes the horizon of many contemporary theological appropriations of the finality of Christ, and how the influence of this category creates serious problems. Though affirming Christ’s finality often seems to pose theological difficulties in religiously pluralistic contexts, I argue that it is not at all a matter of exclusion or denigration of other religions. Quite the opposite: the doctrine at heart expresses the Christian community’s hope for universal fellowship