Abstract
Plants curve their organs such as stems and petioles toward the incident light and intercept light efficiently. To regulate the light interception by respective leaves, the petiole curvature would be more effective than the stem curvature.
In our observation with Chenopodium album L., it was clarified that the petiole curvature was induced by continuous blue-light illumination from the abaxial side of the petiole, and the curvature rate tended to increase with the increase in blue-light intensity. On the other hand, the curvature increase was ceased when the adaxial side of the petiole was illuminated by blue or red light.
The blue-light receptor for the stem phototropism may be also concerned in the stimulation of the petiole curvature. In the cessation of the curvature, photosynthesis in the petiole may play an important role.
