Secondary fluorescence kinetics of spinach leaves in relation to the onset of photosynthetic carbon assimilation

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.

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.

Changes in the distribution of light energy between the two photosystems in spinach leaves

Time courses of chlorophyll fluorescence at room temperature and fluorescence spectra at 77 K were measured to investigate the light-induced changes in the distribution of light energy between the two photosy stems in young spinach leaves. Illumination of the dark adapted leaves with primarily system II light induced typical fluorescence transients at room temperature. Fluorescence spectra at 77 K showed that the intensity of system II fluorescence at 77 K changed nearly in parallel with the fluorescence transients at room temperature within the range from M1 to T during illumination of the leaf.Illumination of the dark adapted leaves with light I produced an increase of system II fluorescence measured at 77 K. The characteristics of the changes induced by light I or II were different, showing that these two effects are related to different mechanisms.These results suggest that the dark state in spinach leaves is state II, that light I induces a state II to I transition, while light II induces fluorescence changes that are produced by mechanisms other than state I-state II transitions.