(117aw) Quantifying Carbon Sequestered from Symbiotic Plant-Microbe Interactions for Sustainable Agriculture

Plants engage in symbiosis with arbuscular mycorrhizal fungi (AMF) to exchange plant-derived carbon for essential plant inorganic nutrients, such as nitrogen and phosphorus. This symbiosis may improve plant tolerance to abiotic and biotic stresses and sequester carbon in the form of root and microbial biomass. The carbon cost of this nutrient exchange and the partitioning of plant-derived carbon to fungal storage organs likely depends on the AMF species or strain. A better understanding of the fate of carbon within various plant-AMF systems will enable the optimization of AMF consortia for carbon sequestration and plant growth. However, quantification of AMF effects on plant carbon allocation is limited, and most methods require destructive sampling. Here, we combine X-ray computed tomography (XCT) and positron emission tomography (PET) to observe and quantify in situ the flow of 11-carbon from leaves to roots to hyphae. Preliminary results in a maize-Rhizophagus irregularis system suggest that R. irregularis induces an increase in carbon allocation to the maize root system compared to uninoculated controls. Co-registered XCT and PET images suggest the increase in carbon correlates with increased lateral root growth near the inoculation site. While the increased number of lateral roots account for some of the ¹¹C signal increase, the remaining carbon is likely allocated to AMF. Our in situ method for quantifying carbon allocation has deepened our understanding of maize-AMF symbiosis and will enable future studies on the impact of plant and fungal genetics on carbon allocation in plant-AMF symbioses.