Effects of cold periods on the stimulus-response system of Phycomyces

The sporangiophores of Phycomyces do not exhibit phototropic responses when growth is arrested reversibly by cooling to 1 degrees C. Unilateral UV stimuli (254 nm) applied during cold periods are stored for at least 2 hr and produce tropic responses away from the light after warm-up. During the cold period dark adaptation proceeds at a rate which decreases with the temperature.