Effect of pre-exposure light on the first positive phototropic curvature in dark-grown radish seedlings

摘要

Effect of pre-exposure light on the first positive phototropic curvature in dark-grown radish seedlings(Raphanus sativus L. cv. Miyashige) was investigated. When the seedlings are pre-exposed to white-light from above, the magnitude of the first positive phototropic curvature of the hypocotyls responding to unilateral blue-light pulseirradiation was enhanced. The pre-exposure treatment to the hypocotyls only accelerated the development of the phototropic curvature. Treatment to the apex and cotyledons had no effect on the increase of the phototropic curvature. These results suggest that the pre-exposure treatment enhances the first positive phototropic curvature of the dark-grown radish seedlings, and the pre-exposure light may be perceived by the phototropic responding organ, the hypocotyl itself.