Cultivar‐dependent increases in mycorrhizal nutrient acquisition by barley in response to elevated CO2

Societal Impact Statement Modern agriculture is under pressure to meet yield targets while reducing reliance on finite resources to improve sustainability. Climate change represents an additional challenge—elevated atmospheric CO2 concentrations may increase plant growth and boost yield, but the nutritional value of crops grown at elevated CO2 is often reduced. Arbuscular mycorrhizal fungi (AMF) can improve plant nutrition, although how this symbiosis will be affected by climate change is unclear. Here, we demonstrate mycorrhizal contribution to nitrogen and phosphorus nutrition in barley under current and future CO2 concentrations. In one cultivar, AMF substantially increased phosphorus uptake at elevated CO2 and prevented phosphorus dilution, suggesting the symbiosis may become more important for crop nutrient uptake in the future. Summary Globally important cereals such as barley (Hordeum vulgare L.) often engage in symbiosis with arbuscular mycorrhizal fungi (AMF). The impact of elevated atmospheric CO2 on nutrient exchange between these symbionts remains unknown. In controlled environment experiments, we used isotope tracers (15N, 33P, 14C) to quantify nutrient fluxes between two barley cultivars (Moonshine and Riviera) and their associated AMF at ambient (440 ppm) and elevated (800 ppm) CO2. Elevated CO2 reduced shoot N concentration in Moonshine, and shoot N and P concentration in Riviera. Elevated CO2 substantially increased mycorrhizal 33P acquisition in Moonshine. Mycorrhizal contribution to P uptake in Moonshine may have prevented dilution of tissue P concentration at elevated CO2. In Riviera, AMF did not improve 33P acquisition. Both cultivars received 15N from their AMF symbionts, and this acquisition was not influenced by CO2 concentration, although Moonshine received more 15N than Riviera. Our results suggest that AMF may provide substantial contributions to barley nutrition at current and projected future CO2 concentrations. This is especially noteworthy for barley, which is generally considered to have low mycorrhizal receptivity. AMF may help alleviate or avoid nutrient dilution normally observed at elevated CO2. Variation between cultivars indicates that mycorrhizal contribution to cereal nutrition could be improved through selective breeding practices

Arbuscular Mycorrhizal Fungi and Plant Chemical Defence : Effects of Colonisation on Aboveground and Belowground Metabolomes

Arbuscular mycorrhizal fungal (AMF) colonisation of plant roots is one of the most ancient and widespread interactions in ecology, yet the systemic consequences for plant secondary chemistry remain unclear. We performed the first metabolomic investigation into the impact of AMF colonisation by Rhizophagus irregularis on the chemical defences, spanning above- and below-ground tissues, in its host-plant ragwort (Senecio jacobaea). We used a non-targeted metabolomics approach to profile, and where possible identify, compounds induced by AMF colonisation in both roots and shoots. Metabolomics analyses revealed that 33 compounds were significantly increased in the root tissue of AMF colonised plants, including seven blumenols, plant-derived compounds known to be associated with AMF colonisation. One of these was a novel structure conjugated with a malonyl-sugar and uronic acid moiety, hitherto an unreported combination. Such structural modifications of blumenols could be significant for their previously reported functional roles associated with the establishment and maintenance of AM colonisation. Pyrrolizidine alkaloids (PAs), key anti-herbivore defence compounds in ragwort, dominated the metabolomic profiles of root and shoot extracts. Analyses of the metabolomic profiles revealed an increase in four PAs in roots (but not shoots) of AMF colonised plants, with the potential to protect colonised plants from below-ground organisms

Development Discourse and Practice: Alternatives and New Directions from Postcolonial Perspectives

Development and aid programs, such as those aimed at promoting economic growth and prosperity in ‘Third World’ nations and transition economies, often arise out of Western and neo-liberal policy ideologies and practices. These programs may, in some cases, provide useful guidelines for restructuring institutional structures and governance mechanisms in nations that have long struggled with poverty, economic instability, health crises, and social and political turmoil. However, a growing number of critical voices are raising concerns over the guiding assumptions and inclusiveness of these policies and programs in their aims to promote economic development and social well-being in non-Western nations. We join these critical perspectives by way of postcolonial frameworks to highlight some of the problematic assumptions and oversights of development programs, while offering new alternatives and directions. By doing so, we contribute to organizational theorizing in a global context, as postcolonial insights provide much needed engagement with international aid policies and programs, as well as development organizations and institutions. To accomplish this, we offer a historical perspective on development, present a critique of the policies and practices guiding many aid programs, and conclude with suggestions emanating from postcoloniality

Carbon for nutrient exchange between Lycopodiella inundata and Mucoromycotina fine root endophytes is unresponsive to high atmospheric CO2.

Non-vascular plants associating with arbuscular mycorrhizal (AMF) and Mucoromycotina ‘fine root endophyte’ (MFRE) fungi derive greater benefits from their fungal associates under higher atmospheric [CO2] (a[CO2]) than ambient; however, nothing is known about how changes in a[CO2] affect MFRE function in vascular plants. We measured movement of phosphorus (P), nitrogen (N) and carbon (C) between the lycophyte Lycopodiella inundata and Mucoromycotina fine root endophyte fungi using 33P-orthophosphate, 15 N-ammonium chloride and 14CO2 isotope tracers under ambient and elevated a[CO2] concentrations of 440 and 800 ppm, respectively. Transfers of 33P and 15 N from MFRE to plants were unaffected by changes in a[CO2]. There was a slight increase in C transfer from plants to MFRE under elevated a[CO2]. Our results demonstrate that the exchange of C-for-nutrients between a vascular plant and Mucoromycotina FRE is largely unaffected by changes in a[CO2]. Unravelling the role of MFRE in host plant nutrition and potential C-for-N trade changes between symbionts under different abiotic conditions is imperative to further our understanding of the past, present and future roles of plant-fungal symbioses in ecosystems