| Abstract: | Abstract— - 1 The simultaneous measurements of delayed light emission (DLE) and chlorophyll (Chl) fluorescence yield in DCMU§ treated Chlorella were made in the time range of 1 to 10 sec at various temperatures from 0 to 50°C. Similar measurements were made for DCMU treated thermophilic strain of Synechococcus in the temperature range of 0 to 75°C.
- 2 Using the basic assumption that DLE is produced by the back reaction of primary photoproducts of system II, and that two such reactions are required for it, a linear relationship between J-1/2 (where J is energy per unit time available for DLE) and time after illumination was derived. This second-order relationship was confirmed experimentally at several temperatures (2°, 5°, 10° and 15°C). From these analyses, reaction rate decay constants, at specific temperatures, were calculated.
- 3 An Arrhenius plot was made for these calculated rate constants. Its slope (8–10 kcal/mole) agreed well with previous reports; however, it had a region of zero slope which occurred at the physiological temperature of the organisms used.
- 4 Thermoluminescence or temperature jump delayed light emission (TDLE) was measured using various temperature conditions and it was found that not only the magnitude of the temperature jump (ΔT), but the initial and final temperatures of the sample were important. For example, a temperature jump of 8°C from 2 to 10°C gave much higher TDLE than from 12 to 20°C.
- 5 Many properties e.g., magnitude, temperature dependence and time independence of TDLE could be explained by the DLE decay data (corrected for changes in fluorescence yield) and the kinetic analysis.
- 6 It is suggested that, in addition to the back reaction of Z+ (the primary oxidized photoproduct of system II) with Q- (the primary reduced photoproduct of system II), a reducing entity, beyond the sites of DCMU and antimycin a action, is somehow involved in the production of slow DLE.
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