Physiological Studies on Pea Tendrils—x. Characterization of the Light Activation Effect on Contact Coiling as a Blue Light Trigger*

Tendrils of the Alaska pea lose their capacity to coil in response to a mechanical stimulus between 24 and 48 h after being placed in the dark. Light is thereafter necessary for the motor response to proceed once the mechanical stimulus has becn sensed by dark‐adapted tendrils. An action spectrum for this light activation effect showed that the most effective region of the visible spectrum was a narrow band in the blue region. Tendrils excised from their petiole and leaflets coiled more than any other preparation used. A linear relationship was found between the duration of post‐stimulated white light treatment and the amount of coiling.