ACTION SPECTRA FOR SUPEROXIDE GENERATION AND UV AND VISIBLE LIGHT PHOTOAVOIDANCE IN PLASMODIA OF Physarum polycephalum

Abstract— The initial photochemical process leading to photoavoidance by plasmodia of an albino strain of Physarum Plasmodium was studied. Superoxide (O), detected as superoxide dismutase (SOD)-inhibitable electron spin resonance (ESR) signal of a spin trap (tBN), was formed upon irradiation. The amount of O formed increased linearl) with log fluence rate above the threshold. The photoavoidance to radiation at wavelengths between200–800 nm also showed the similar linear relationship in log fluence rate-response curves. Thresholds for photoavoidance and O generation agreed with each other and the action spectra showed peaks at about 260, 370, and 460 nm. Thus, active oxygen generated by photosensitization seems to trigger the UV and blue light photoavoidance.