BOUNDARIES BETWEEN SOIL COMPARTMENTS FORMED BY MICROPOROUS HYDROPHOBIC MEMBRANES (GORE-TEX(R)) CAN BE CROSSED BY VESICULAR-ARBUSCULAR MYCORRIZAL FUNGI BUT NOT BY IONS IN THE SOIL SOLUTION

Various container systems have been described in which soil regions available to hyphae only are separated from the mycorrhizal root region by 30-60 mum mesh screens to study nutrient exchange between plants and fungi in the mycorrhizal symbiosis. The screens designed up to now prevent penetration by roots but allow easy passage of fungal hyphae as well as diffusion or mass flow of water and nutrient solutions. We tested hydrophobic microporous polytetrafluorethylene (PTFE) membranes (GORE-TEX(R)) with 5 to 15 mum diameter pores in an attempt to obtain a better seal between compartments and to prevent uncontrolled nutrient transport by diffusion or mass flow. We found that these membranes completely prevented diffusion or mass flow of ions between two soil compartments but could be penetrated easily by the vesicular-arbuscular mycorrhizal fungus Glomus mosseae, as demonstrated by the rapid colonization of soybean roots (Glycine max L.) from an inoculum across the membranes.