THE BIOLOGY OF MYCORRHIZA IN <i>HELIANTHEMUM</i> MILL

Abstract

SUMMARY The mycorrhizal status of Helianthemum chamaecistus was assessed. Vegetative and reproductive tissues of mature plants were free from infection by a fungus capable of producing mycorrhizas and were normally free from any internal fungal infection. The mature gelatinous sheath of the seed was infected by a number of non‐mycorrhizal fungi of which the commonest were the saprophytes, Cladosporium herbarum and Ulocladium chartarum. The so called ‘tuberous roots’ are typical ecto‐mycorrhizal short roots. They develop following infection by a soil‐borne sclerotium‐producing fungus. Isolates of the sclerotia and roots produced typical mycorrhizal short roots in sterile cultures of both Helianthemum and Betula pubescens. This mycorrhizal associate is believed to be Cenococcum graniforme. It is concluded that cyclic infection does not occur in Helianthemum and that the mycorrhizal status of members of this genus is comparable with that of many woody species. The possible ecological significance of the mycorrhizal association is discussed.