Transport and development in fungal networks
Multi-cellular organisms have evolved sophisticated systems to supply individual cells with the resources necessary for survival. Plants circulate nutrients through the xylem and phloem, mammals have cardio-vascular systems, but how do fungi translocate materials? Cord-forming fungi form extensive networks that continuously adapt to their surroundings, but what is the developmental logic of such fungal networks, and how does fungal morphology enable efficient transport? In this talk I shall address these fundamental questions, and present the concept of growth-induced mass flows. The key idea is that aqueous fluids are incompressible, so as the fluid filled vessel expand, there must be movement of fluid from the sites of water uptake to the sites of growth. We have developed a model of delivery in growing fungal networks, and found good empirical agreement between our model and experimental data gathered using radio-labeled tracers. Our results lead us to suggest that in fora ging fungi, growth-induced mass flow is sufficient to account for long distance transport, if the system is well insulated. We conclude that active transport mechanisms may only be required at the very end of the transport pathway, near the growing tips.