722 



Edgar Inselberg and J, L. Rosenberg 



TABLE II 

 CONTRIBUTION OF EMISSION CHANGES TO THE NEGATIVE CHANCES OBSERVED 



AT 700 in^i 



System 



^^680 



1,2 



Total 

 change 



mth 



interference 

 filter 



Minimum 

 percentage 

 accounted 

 by emission 



Chlorella 



Spinach chloroplasts 



Spinach chloroplasts aged for 

 5 days, 5 X 10"° M PMS and 

 5 X 10"^ M ascorbic acid 



-0.0055 

 -0.005U 



-0,0001 

 +0.001U 



-0.0071 -0.0008 



98 

 100 



89 



680* 



AA: apparent change in absorbance at 700 mp,. 



absorbance at 680 rap., 

 2 

 Three to four pictures of flash plus measuring li^t 



and 3-h pictures of flash only per value. 



TOiile the data presented demonstrate that interference from 

 luminescence can be considerable, it certainly does not follow 

 that emission changes interfered to the same extent in the work 

 of other investigators. The experimental conditions that were 

 suitable for observing the 703 mp, change in our apparatus dif- 

 fered in several respects from those selected by other workers. 

 For example, our flash intensities were probably of a hi^er or- 

 der of magnitude than Kok's, 



Several procedures for circiimventing the interference of Ixorai- 

 nescence were considered. Locating the monocliromator between the 

 sample and the phototube (cf. Fig. 1) would still involve the un- 

 certainty that at some wavelengths an emission change would be 

 superimposed on the absorption changes. 



The essential features of an apparatus design (Fig, 5) and a 

 procedure for resolving the contribution of emission and absorp- 

 tion changes to overall changes in li^t intensity are given be- 



low. Two identical red-sensitive phototubes, P-, and 



2* 



are lo- 



cated symmetrically vdth respect to the flashtube, so that the 

 flash-only wavefoirm will appear the same. P2, located at ri^t 



