Membrane overcultures of Rhizopus oligosporue were shifted from 37 to 50 degrees C for 10 h and then returned to 37 degrees C, mimicking the temporal temperature profiles which typically occur in SSF due to heat transfer limitations. Analysis with a modified two-phase growth model suggests that the temperature upshift causes a 48% decrease in the number of actively extending hyphal rips, and that the first order death rate constant of tips increases from 0.059 to 0.073 h(-1). The fungus did not im mediately recover when the temperature was returned to 37 degrees C. The model assumed that the specific growth rate constant mu(g), was not affected by the increase of temperature, although contradictory data was obtained from radial growth rate experiments.