Graphical and numerical analysis of thermoluminescence and fluorescence F0 emission in photosynthetic material

A set-up for recording thermoluminescence emission together with the constant F₀ fluorescence yield is described briefly. It is driven by a microcomputer through plugged-in cards.Practical aspects of the simulation of TL bands and of decomposition of complex TL signals are examined. A reproducible and linear temperature gradient and the use of photon counting for luminescence detection are important features for further analyzing the recorded signal. The simulation procedure used is a step-by-step calculation of the number of charge recombinations, which is then substracted from the number of remaining charge pairs able to produce luminescence. This procedure consists first of a graphical fitting, followed by a numerical minimization, with a maximum of five simulated components. The quality of the simulation is evaluated by the sum of squares of differences (signal-simulation), related to the signal area. Equivalent decomposition patterns may be found for the same recording and additional information is needed for interpretation of TL data. Averaging signals is feasible, provided that maximum temperatures Tm of averaged bands are sufficiently similar (±3°C). Simultaneous measurement of the antenna fluorescence yield F₀, using an ultra-weak pulsed blue LED, gives an estimate of the luminescence yield. This has to be taken into account in the analysis of the Q band and of high temperature (>40°C) bands.The simulation parameters appear to be dependent on plant growth conditions. Quantitative analysis of thermoluminescence emission could be useful in the study of the effects of climatic factors on the photosynthetic apparatus in plants.Abbreviations PS-II Photosystem II - TL thermoluminescence - F₀ constant fluorescence emission, under ultra-low light intensity - Q_A and Q_B respectively, primary and secondary electron acceptors of Photosystem II - S₂ and S₃ respectively, the two and three positively charged states of the oxygen evolving system - SSD sum of squares of differences between the signal and a simulation (fitting) or between the signal and a smoothed curve (noise)