721 



Edgar Inselberg and J. L. Rosenberg 



the monochromator at the same Y»avelength as the transmission max- 

 imum of a given filter, while maintaining the same intensity of 

 monochromatic li^t reaching the phototube as in the absence of 

 the interference filter. 



The results presented in Table I demonstrate that most of the 

 increment in li^t intensity detected by the phototube following 

 a flash is of a wavelength range other than that of the monochro- 

 matic beam. Hence, it is evident that the negative changes ob- 

 served represent primarily fast, reversible increases in lumines- 

 cence. The difference between the total change and the change ob- 



TABLE I 

 GOOTRIBUTION OF EMISSION CHANGES TO THE NEGATIVE CHANCES OBSERVED 



IN PORPHYRIDIUM 



AA: apparent change in absorbance. A^qq: absorbance 



at 680 mp., 

 2 

 Four pictures of flash plus measuring li^t and two 



flash-only pictures were used to obtain each value. 



served with the interference filter in the path of the monochro- 

 matic li^t evidently provides a minimum estimate of the emission 

 change; the fraction of luminescence transmitted by a given fil- 

 ter (or a monochromator located between the sample and the photo- 

 tube) would still act as a negative absorption change, superim- 

 posed on a true absorption change of the same or opposite sigi. 



Next, the nature of the change at 700 mjo, was investigated in 

 Chlorella and spinach chloroplasts , in which the change was re- 

 ported by Kok (3) J as well as in aged chloroplasts with reduced 

 phenazine methosulfate (PM5) studied by Witt et al. (7). The 

 findings at 700 rn\i. (Table II) were similar to those for Porphyr- 

 idiTni at other wavelengths. 



I 



