Chlorophyll a fluorescence transients: a fast data acquisition system to facilitate in vivo measurements

Characteristics of primary phases in chlorophyll a fluorescence transients based on room temperature in vivo measurement with a Plant Productivity Fluorometer (Brancker Model SF-10) can be greatly facilitated by coupling the instrument to a fast data acquisition system. The SF-10 was linked to a Multitech Industrial Corporation Microprofessor Microcomputer and further modified to ensure simultaneous onset of light activation and signal capture. Circuit diagrams and program listings are given in detail.This microprocessor system is capable of capturing signal changes over a minimum period of 200 milliseconds to a maximum of 6 seconds. Accuracy of recorded data is dependent on rate of change of the input signal and the recording time period. Acquisition and storage of 5000 points from zero to 300 milliseconds ensured clear resolution of Fo, I and D when played back over 120 seconds on a chart recorder. For routine use, the primary transient can be captured over 0-2 seconds and then replayed as an accompaniment to standard slower presentation of primary plus secondary transients. Coincidence of signal amplitude for Fp on both systems can then be ascertained while retaining adequate resolution of Fo and I.