This short movie shows the phototropic response of dark-grown Arabidopsis seedlings. 60 hours after germination, blue light was provided from the left side for around 5 hours. The movies show the amount of phototropic curvature over a 5 hours period (Images were captured every 10 min and are played back at 6 frames per sec.)

In this example the seedlings were exposed to red light from above for 1 hour prior to receiving blue light from the side. The red light treatment results in an enhancement of blue-light phototropism through the action of the phytochrome photoreceptor systems. If you compare the two movies by advancing one frame at a time you should see that by the 3rd and 4th frame (30 to 40 min), the seedlings that received the red light treatment curve before the seedlings that did not receive the red light treatment.