THERMOLUMINESCENCE AND TEMPERATURE EFFECTS ON DELAYED LIGHT EMISSION (CORRECTED FOR CHANGES IN QUANTUM YIELD OF FLUORESCENCE) IN DCMU‐TREATED ALGAE*

<jats:p><jats:bold>Abstract—</jats:bold> <jats:list list-type="explicit-label"> <jats:list-item><jats:p>The simultaneous measurements of delayed light emission (DLE) and chlorophyll (Chl) fluorescence yield in DCMU§ treated <jats:italic>Chlorella</jats:italic> 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 <jats:italic>Synechococcus</jats:italic> in the temperature range of 0 to 75°C.</jats:p></jats:list-item> <jats:list-item><jats:p>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 <jats:italic>J</jats:italic><jats:sup>‐1/2</jats:sup> (where <jats:italic>J</jats:italic> 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.</jats:p></jats:list-item> <jats:list-item><jats:p>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.</jats:p></jats:list-item> <jats:list-item><jats:p>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 (Δ<jats:italic>T</jats:italic>), 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.</jats:p></jats:list-item> <jats:list-item><jats:p>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.</jats:p></jats:list-item> <jats:list-item><jats:p>It is suggested that, in addition to the back reaction of <jats:italic>Z</jats:italic><jats:sup>+</jats:sup> (the primary oxidized photoproduct of system II) with <jats:italic>Q</jats:italic><jats:sup>‐</jats:sup> (the primary reduced photoproduct of system II), a reducing entity, beyond the sites of DCMU and antimycin <jats:italic>a</jats:italic> action, is somehow involved in the production of slow DLE.</jats:p></jats:list-item> </jats:list> </jats:p>