Nutrient Availability Regulates an Exploration-Elaboration Trade-off in Fungal Rhizomorph Networks

Rhizomorphs, specialized root-like structures in fungi, have shown potential for creating robust fungal-based materials, though the factors influencing their network formation are not well understood. In this study, researchers employed an image-based method to examine the growth patterns and organization of Armillaria gallica rhizomorphs under different nutrient conditions and light exposure.

Through time-lapse imaging, segmentation, skeleton-based network analysis, optical measurements, and Gompertz growth modeling, the researchers found that nutrient availability had a complex effect on the rhizomorphs. Moderate nutrient limitation (at 0.5 times the standard concentration) led to a rapid, coherent exploratory growth.

Conversely, intermediate enrichment (at 1.5 times the standard concentration) resulted in the largest overall network extent, with a total strand length of approximately 975 mm. The researchers observed that network extent and radial expansion were significantly different among the various nutrient levels (with a p-value of 0.0012).

When nutrient availability was further increased, the fungi maintained a significant fungal coverage without any additional network elaboration. This suggests that the fungi shifted from long-range exploration towards more localized consolidation of the network. In contrast, the presence or absence of ambient light did not produce any significant differences in the growth patterns after accounting for multiple testing corrections.

These findings indicate that there is a resource-dependent trade-off between exploration and network elaboration in fungal rhizomorphs. The study also reveals that fungal coverage and the formation of an organized network are two distinct outcomes, providing a quantitative basis for controlling self-organized biological architectures for the design of bio-derived materials.