BOLETINELLUS-MERULIOIDES ALTERS ROOT MORPHOLOGY OF PINUS-DENSIFLORA WITHOUT MYCORRHIZAL FORMATION

A stimulatory effect of Boletinellus merulioides on the roots of Pinus densiflora was evaluated using pure culture synthesis. Seedlings of P. densiflora were inoculated with cultures of B. merulioides at high and low glucose levels. After 180 days, shoot weight was not enhanced over controls by inoculation with the fungus, but root weight was significantly increased and roots were highly branched. Short roots were dichotomously branched, lacked root hairs, and had an internal morphology similar to that of ectomycorrhizal rootlets. A loose weft of fungal hyphae surrounded the short roots, but did not penetrate the epidermis. Higher glucose levels further increased root weight and branching. Filtrates from liquid-grown cultures of B. merulioides and Pisolithus tinctorius were compared using high performance liquid chromatography. Both fungi produced measurable quantities of indole-3-acetic acid, the in-vitro production of which was enhanced by higher glucose levels.