SPECTRAL DEPENDENCE OF SOME UV‐B AND UV‐C RESPONSES OF Tetrahymena pyriformis IRRADIATED WITH DYE LASER GENERATED UV

We have generated UV‐B and UV‐C radiations using a flashlamp driven tunable dye laser combined with frequency doubling crystals. Using this novel UV source, we have investigated lethality and its modification by growth phase, photoreactivation and caffeine in Tetrahymena pyriformis at 254 nm and from 260–315 nm in 5 nm steps. From the observed responses we have constructed action spectra for lethality, with or without caffeine (a repair inhibitor) and under conditions of photoreactivation. We have also estimated quantum efficiencies for these responses. Our observations suggest that complex changes in response occur at several wavelengths over the UV‐C and UV‐B regions.