Blue Light-Induced Phytochrome Increase in Mung Bean Hooks

An “action spectrum” between 400 and 620 nm for the radiation-induced phytochrome increase was obtained with mung bean hooks. A broad band between 410 and 480 nm was found to induce significant increases in phytochrome content. Radiation from 500 to 620 nm failed to promote any significant increase. Red irradiation immediately following far-red treatment showed no reversal. These results and an earlier finding that far-red irradiation promotes phytochrome increase suggest that the photoreceptor for the radiation-induced increase is probably not phytochrome, but could be a related pigment if the phenomenon is due to one photoreceptor. The blue light-induced increase in phytochrome content increases the possibility of the participation of phytochrome in blue light-mediated high irradiance responses of plants.