Temperature-sensitivity of light inhibition of uredospore germination in melampsora medusae

Abstract

The germination of uredospores of Melampsora medusae, deposited on cover glasses and incubated in sealed humidity chambers (ca. 100%) at 15 and 25 C in darkness and at five levels of increasing light intensity (range 100-500 μE m^-2 s^-1), was recorded at 12 and 24 h. At both temperatures, germination (per cent) decreased with increasing light intensity, being a maximum in continuous darkness and zero at 25 C coupled with light intensities of 400 and 500 μE m^-2 s^-1. The latter inhibition of germination was reversible and normal germination occurred when these uredospores were subsequently incubated in the dark. The inhibitory effect of comparable light intensities was temperature sensitive being more pronounced at 25 than at 15 C.