GROWTH-RESPONSES OF SOME SOIL FUNGI TO SPATIALLY HETEROGENEOUS NUTRIENTS

The natural nutritional environments of most fungi are spatially non-uniform, yet the majority of studies of fungal growth take no account of this fact. An experimental system is described which permits the growth responses of eucarpic fungi to heterogeneously distributed nutrient resources to be studied. The system comprises tesselations of agar tiles of contrasting nutrient status separated by air gaps. Growth responses in such systems of Alternaria alternata, Mucor sp., Phoma foveata, Rhizoctonia solani and Trichoderma viride are described. Generally, the growth of the fungi reflected the nutrient status of the underlying substrate. There was evidence for growth in low-nutrient tiles being greater when high-nutrient tiles were included in the tessellation. Reproductive structures tended to be formed only in low nutrient tiles with Trichoderma and Rhizoctonia and only high nutrient tiles with Alternaria. Growth responses of Rhizoctonia were strongly asymmetric in nutritionally symmetric, but heterogeneous, tesselations. The consequences of the observations for fungal growth in heterogeneous environments such as soil is discussed.