Extent, development and function of mycelial cord systems in soil

Abstract

Mycelial cord systems of Phallus impudicus, Phanerochaete velutina, Steccherinum fimbriatum, Stropharia aeruginosa and Tricholomopsis platyphylla, when excavated in the field, were found to be between 318 m (5. aeruginosa) and 317 m (P. velutina) in overall length. Cord systems of P. impudicus, P. velutina and T. platyphylla increased in length by 0.8, 0.95 and l.0 m respectively over 12–14 months. In all cases extension occurred via the peripheries of the systems, whilst certain more central parts disappeared. Mycelial development from colonized wood-blocks in tubes of non-sterile soil showed similar patterns to that observed in the field. However, in tubes of γ-irradiated soil mycelia were not aggregated into cords to such an extent as in non-sterile soil, and, except for T. platyphylla, had slower extension rates, although sometimes being more luxuriant. Wood-blocks colonized by Hypholoma fasciculate, S. fimbriatum, P. impudicus and P. velutina underwent significantly greater losses in dry weight in sterile soil than did blocks in non-sterile soil, except for those colonized by T. platyphylla. Cord systems of like and unlike mycelial types of P. velutina from wood blocks fused in soil, but whilst fusion of those of like mycelial type gave rise to cords of substantial diameter, fusions between different mycelial types were followed by death of the fine cords in the fused regions and avoidance of such regions thereafter. Cord formation by a coprophilous species occurred in non-sterile but not sterile conditions, and was associated with strong substratum directed growth responses.