RESPONSE OF MAPLE SAPWOOD TO INJURY AND INFECTION

In sapwood challenge experiments in Acer rubrum, columns of discoloura tion initiated by wounding and inoculation with pioneer fungi (Cephalo sporium sp., Phialophora sp.) were similar in size to untreated wounds . Inoculation with decay fungi (Pleurotus ostreatus, Trametes versicol or) produced larger columns of wound-initiated discolouration. The rem oval of bark around a bore wound caused a significantly larger column to form compared to the sum of the columns initiated by separate wound s. Stage-I discoloured wood, nor associated with obviously rotted wood , had concentrations of mobile cations and soluble phenols similar to sapwood. Stage-II discoloured wood, spatially associated with rotted w ood, was frequently bounded by a chemically distinct boundary la;er an d the discoloured wood contained significantly greater concentrations of mobile cations and soluble phenols than stage-I discoloured wood.