Growth-induced mass flows in fungal networks

TL;DR

This study demonstrates that growth-induced mass flows in fungal networks, driven by fluid incompressibility, are crucial for their adaptive transport efficiency, with flows predicting growth patterns and network responses.

Contribution

It introduces a model linking growth, fluid flow, and network adaptation in fungi, highlighting the role of mass flow in network development and function.

Findings

Predicted flow speeds match experimental data.

Fast or large flows correlate with cord growth.

Fluid incompressibility enables rapid network responses.

Abstract

Cord-forming fungi form extensive networks that continuously adapt to maintain an efficient transport system. As osmotically driven water uptake is often distal from the tips, and aqueous fluids are incompressible, we propose that growth induces mass flows across the mycelium, whether or not there are intrahyphal concentration gradients. We imaged the temporal evolution of networks formed by Phanerochaete velutina, and at each stage calculated the unique set of currents that account for the observed changes in cord volume, while minimising the work required to overcome viscous drag. Predicted speeds were in reasonable agreement with experimental data, and the pressure gradients needed to produce these flows are small. Furthermore, cords that were predicted to carry fast-moving or large currents were significantly more likely to increase in size than cords with slow-moving or small currents. The incompressibility of the fluids within fungi means there is a rapid global response to local fluid movements. Hence velocity of fluid flow is a local signal that conveys quasi-global information about the role of a cord within the mycelium. We suggest that fluid incompressibility and the coupling of growth and mass flow are critical physical features that enable the development of efficient, adaptive, biological transport networks.