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Saprophytes in the stem of living, healthy Tsuga heterophylla (Raf.) Sarg. and their role in decay resistance of the wood Hudak, Janos

Abstract

It was demonstrated that the sound wood of two stems of living western hemlock, Tsuga heterophylla (Raf.) Sarg., was colonized by microorganisms, which were isolated by shaking samples of the wood in sterile distilled water. The microfloras inhibited the growth of Fomes annosus, (Fr.) Cke., and Poria monticola Murr. when added to one per cent malt agar. The test fungi were also inhibited on untreated surface sterilized wood incubated at one hundred per cent relative humidity at room temperature. Significant variation was observed, in the rate of inhibition between the sapwood and heartwood and between the various sections of the two stems investigated. A drier environment (higher agar concentration of malt agar media, and lower relative humidity with wood) resulted in a significant decrease in inhibition rate of F. annosus and P. monticola. Autoclaving the experimental material led to the loss of inhibition with both malt agar media and wood. Removal of the microorganisms from the shake solutions by Millipore filtration also resulted in loss of the inhibiting factor. The relatively drier environment did not effect the rate of growth of the test fungi on autoclaved wood and in malt agar containing the autoclaved portion of the shake solutions. Results of the experiment provide evidence that the microfloras inhabiting the sound wood were responsible for inhibition of F. annosus and. P. monticola. Furthermore, sufficient moisture level appeared necessary for maintaining the inhibiting power of these microorganisms.

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