Effects of Supraoptimal Temperatures on Merulius lacrymans

The growth rate of Merulius lacrymans (Jacq.) Fr. decreases very rapidly at temperatures above optimum (about 22°C). No growth occurred above 28°C. The thermal death‐time of the fungus at different temperatures above maximum was determined. At 37.5°C the thermal death‐time is 4 hours. At this temperature, the respiration is not directly affected, since an appreciable respiration occurred even after 6 hours. On the basis of 14C‐experiments and analysis of UV‐absorbing material excreted from the mycelium at supraoptimal temperatures, it is suggested that the detrimental effects of supraoptimal temperatures on this fungus include a degradation of the nucleic acids and a subsequent leakage of the nucleotides out of the cells.