Abstract
The bending of a plant toward the direction of intense light is called phototropism. This directional growth response is caused by the plant growth regulating substances. In this aspect, Bruinsma-Hasegawa hypothesis (1990) stated that the gradient of growth-inhibiting substances in the illuminated side is a key factor of bending during phototropic curvature. The symbolic growth inhibitors, cis- and trans-raphanusanins have been isolated from radish hypocotyls. These compounds were dramatically accumulated on the side of blue light illumination. To understand the role of raphanusanins in phototropic curvature and the responsible genes for the growth inhibition, DD-PCR was performed between the raphanusanin applied and control hypocotyls. We could trace some candidate genes indicating a close linkage between raphanusanins and phototropic curvature. The detailed roles and functional impacts of these genes for the growth inhibition in response to phototropic stimulation will be presented.
