The luminescence of isolated chloroplasts

Abstract

1. 1. The luminescence of isolated spinach and mustard chloroplasts has been studied under various conditions, using a quantum-counting photomultiplier at the temperature of liquid nitrogen. 2. 2. It has been found that luminescence and the Hill reaction rate, as determined by direct potentiometric measurement, saturate at nearly identical light intensities. 3. 3. Spinach chloroplasts show a temperature dependence for luminescence similar to that observed for Chlorella luminescence. Optimum activity was at ca. 36 °C. 4. 4. The influence of pH on spinach and mustard chloroplast luminescence is characterized by two optima at ca. pH 5 and ca. pH 9. It is suggested that the initial reaction may have a broad pH optimum while a succeeding reaction may have a narrower optimum. The resulting interaction of the two systems would give the pH dependence curve observed. 5. 5. The decay curves for spinach chloroplast, spinach and mustard leaf, and Chlorella luminescence are very similar, approaching zero about 5 min. after illumination. Mustard chloroplasts, on the other hand, show a low level of luminescence for as long as 35 min. after illumination. 6. 6. Spinach and mustard chloroplasts, in contrast to Chlorella, show no induction phenomenon or effect of CO 2 on the level of luminescence. 7. 7. Inhibitors previously tested on Chlorella luminescence also showed some differences in their effect on spinach chloroplast luminescence. Hydroxylamine was more strongly inhibitory to spinach luminescence than to Chlorella luminescence while dinitrophenol, cyanide, and azide were appreciably less inhibitory.