The National Science Foundation introduced the term "biocomplexity" to refer to phenomena that result from dynamic interactions within organisms and between organisms and the physical environment. Recognition of biocomplexity is helpful in selecting observations and designing experiments that encourage understanding of interactions in complex environmental systems and integration across temporal, spatial and conceptual boundaries. Plant roots and fungi interact to form three-dimensional structures with varying degrees of temporal and spatial stability in a substrate that exhibits temporal variation and spatial heterogeneity. Studies on mycorrhizal symbioses are expanding to include developmental and structural approaches. These include the genetic signaling dialog between roots and hyphae in development of mycorrhizae; the nature of the interface between plant cells and fungi; observation of multiple infections, including ecto- and endomycorrhizae, with diverse abilities to take up phosphate; and common mycorrhizal networks in which one fungus links multiple plants. This symposium will explore the mechanistic and functional complexity of mycorrhizae.

Key words: biocomplexity, fungi, mycorrhizae, roots, symbiosis