In an electron spin resonance (ESR) survey of various liquid cultures and wood slivers innoculated with the brown-rot fungus, Postia placenta, the spin trap dimethyl-l-pyrroline N-oxide (DMPO) was used to detect the presence of the hydroxyl radical. The ESR spectra for the paramagnetic DMPO- hydroxyl radical adduct was observed in (1) nitrogen-limited, liquid cultures having 1.0% glucose or 0.1% cellobiose as the carbohydrate source and (2) fungal infected wood slivers of Douglas-fir (Pseudotsuga menziesii) and white fir (Abies concolor). The 4-line ESR signal had a 1:2:2:1 intensity ratio, 15 G line splitting, and a g-factor of 2.003. The signal was stronger and more stable in wood slivers than in liquid cultures. The effect of free radical scavengers on the DMPO-hydroxyl adduct signal is currently being studied.

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