GROWTH STIMULATION OF FOREST TREE SEEDLINGS BY THE ACTIVITY OF FREE-LIVING MYCORRHIZAL MYCELIA

Abstract

Observations by the late Dr. M. C. Rayner on a field experiment and the results of subsequent pot-culture experiments demonstrate that the soil activity of mycorrhizal fungi can improve the development of forest tree seedlings ( Picea, Pinus, Betula ) before actual mycorrhizal infection takes place. Further experiments show that ectotrophic mycelia are capable of stimulating endotrophic tree species ( Fraxinus excelsior, Cbamæcyparis lawsoniana, Robinia pseudacacia ), i.e. that these ectotrophic mycorrhiza-formers bring about growth stimulation of the plant although no infection is formed at a later stage. It is suggested provisionally that at least some ectotrophic mycelia, Boletus scaber and Rbizopogon luteolus , may influence seedling growth by attacking soil organic matter and liberating ‘nutrients’ from which the higher plant benefits.