Light Effects on Fruiting of Physarum Gyrosum

SUMMARY

Physarum gyrosum, when cultured on water agar and on oatmeal-filter paper, remained plasmodial in the dark, but after exposure to light produced sporangia. Cultures exposed to 440 ft-c of light fruited more rapidly than those exposed to lower intensities; however, 1 ft-c for 180 hr was sufficient to stimulate fruiting. Twelve hours exposure to 440 ft-c stimulated fruiting, but responses of replicates varied. Age affected the response of plasmodia to light, 12-day-old cultures responding most rapidly to the light exposure. Temperatures also affected the plasmodial response. A day-night regime temperature of 32–26.5 C induced fruiting more rapidly than 26.5-21 and 21–15.5 C. Cultures deprived of nutrients required longer light exposure for fruiting than did fed cultures. Plasmodia were colorless when developing in darkness, but they became pale yellow when exposed to light. A bright red pigmentation developed rapidly when the Plasmodium was wounded.