Phytochrome-mediated flavone glycoside synthesis in cell suspension cultures of Petroselinum hortense after preirradiation with ultraviolet light

Summary Ultraviolet light was demonstrated to stimulate flavone glycoside synthesis in Petroselinum cell suspension cultures. The data presented suggest the involvement of phytochrome in this response: Flavone glycoside formation resulting from 1 h of ultraviolet irradiation was increased by subsequent continuous far-red light irradiation. However, the ultraviolet effect was reduced by a subsequent irradiation with 10 min of far-red. This far-red effect was fully reversed by a sub-sequent irradiation with 10 min of red. Red and far-red irradiations were ineffective without ultraviolet preirradiation. It is concluded that in this system ultraviolet irradiation is required in order to change the cells in such a way as to allow a physiological effectiveness of the phytochrome system.