A measurement system to detect small plant movements

A measurement system based on a photodiode array technique is presented, together with some results from recordings of phototropic responses of Avena sativa L. (cv. Seger I) coleoptiles.
A commercial photodiode array (RL-256G) was used, controlled by a likewise commercial control board RC-301. Electronic circuits were built to connect the control board to the interface card IO-801 of an Apple IIe microcomputer. The circuits constitute a fast temporary memory, which mainly contains two shift registers and two timers. Programs, which control the measurements, have been written and are presented.
Detailed recordings of blue light induced phototropic movements are presented: resolution and other features of the equipment are discussed.