Most land plants depend on a hidden partnership. In the thin zone of soil around roots—the rhizosphere—mycorrhizal fungi grow as threadlike hyphae that gather nutrients and pass them to plants. The filaments are extremely fine: one gram of soil can hold up to 90 meters of mycelium. Because plants feed animals, this tiny zone underpins food webs and the carbon cycle, with some research estimating that the fungi absorb the equivalent of 13 billion tons of CO2 annually.
Until now, scientists could not easily see these networks in undisturbed soil. Removing soil destroys the structure, and ordinary lab CT scans take hours, during which fungi grow and blur the image. A synchrotron, by contrast, produces about a million times the energy of a lab CT and can capture scans in minutes. Henri Braunmiller and colleagues grew tomato plants in loam and sandy soil, then used the SOLEIL synchrotron near Paris to scan intact soil cylinders. Stacking the images produced 3D reconstructions of roots, hyphae, and spores in their natural arrangement. The work appears in New Phytologist.
Justin Stewart, an ecologist at the Society for the Protection of Underground Networks and Vrije Universiteit Amsterdam, called the approach a 'major advance' because it allows researchers to examine the interface between living fungal networks and the mineral soil matrix and to study how fungal carbon moves into soil minerals. The researchers hope the method will help guide practical use of mycorrhizal fungi—for example, to improve nutrient uptake, pathogen resistance, and crop yield stability during drought. 'These networks are a tool, but you also have to understand the tool,' Braunmiller said. The source article reports a single study and notes no conflicting findings.