How waves of mycorrhizal fungi build and operate fluid-flow networks for underground nutrient trade

The symbiotic exchange of nutrients between arbuscular mycorrhizal (AM) fungi and their plant hosts underlies growth of terrestrial vegetation that makes up ~85% of the Earth's biomass, and funnels several Gt of carbon into soil environments each year. Yet despite their importance for ecosystem function and carbon cycling at the planetary scale, little is known about the mechanisms that enable these fungal trade and transport behaviors. AM fungi grow as networks of hyphal filaments. Each of these hyphal tubes are open conduits for fluid flows carrying nutrients both toward and away from host roots. We have been building bespoke imaging robots to map the full network topology of growing fungal networks, as well as internal flow dynamics. I will describe some of the insights gained from these efforts so far - and highlight open questions - about how an organism that functions as a 'connective tissue' for much of life on Earth efficiently explores, moves and exchanges nutrients to support a vast underground market for biological resource trade.