Kinetics of upward bending response of gravistimulated snapdragon shoots.
Discussion

'Simulated time-lapse photography'

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For the first time, the bending of a snapdragon shoot was captured on 'film' using 'Simulated time-lapse' photography. By using the computer to overlay the images, one can get a view of the complex upward movement. In this experiment, so called, 'overshoot' and migration of the bending zone along the shoot were clearly demonstrated.

Some recommendations can be made with respect to measuring the gravitropic response of plant shoots. Although an APT in combination with a strip chart recorder is in theory the system of choice for measuring the response accurate and over a long period of time, a few remarks can be made. The Gould transducer is probably not sensitive enough to record the upward bending of snapdragon shoots accurately. Other disadvantages are that only one shoot at a time can be monitored and that the bending angle is restricted to a maximum angle of 30^o (see box 1). Gould instrument systems also offers more sophisticated transducers which only need a displacement of 60 microns for full scale deflection. However these transducers, designed for medicel systems, are very costly (up to $6,000). Another system which can be helpful in determining the gravitropic responses of several shoots at the same time, is the use of a digital camera and a computer. If pictures are automatically taken at regular intervals, the angle can be measured with image processing software like Adobe Photoshop^TM. The price of these cameras is much lower than that of an advanced APT and it can provide a better insight in the whole gravitropic curvature. However a system like this could be less accurate in recording the initial bending response.