Phytochrome transformation in lettuce seed irradiated at various temperatures

Phototransformation of phytochrome in lettuce seeds (Lactuca sativa L. var. Grand Rapids) was examined by testing germination responses of seeds irradiated at various temperatures. Temperature variations from 0 to 50 C had no influence on the germination of partially hydrated seeds (about 15% water content) irradiated with either red or far red light prior to imbibition. At -15 C far red light more effectively retarded germination than red light promoted it. No effective phototransformation was detected at -79 C or -196 C.