Differential Responses to Environmental Conditions by Fungal Cells Sensitized by Heat Shock or UV Irradiation

Cells of the ascomycele Ophiostoma multianulatum were sensitized to the supra‐optimal temperature of 30°C either by heat shock or by UV irradiation. At this incubation temperature the death rate of the heat‐shocked cells was higher than that of the irradiated cells. This difference was increased if hydrolysed casein was added to the incubation medium. The heat‐shocked cells were also killed faster at 30°C, if nitrogen instead of air was bubbled through the cell suspension. Heat shock, in contrast to UV irradiation, strongly increased the sensitivity to a high concentration of sodium chloride.