120 



li. L. STREHLER 



does not appear to saturate at high Ught intensity (note resemblance 

 to Emerson-Arnold time). 



h. A slowly decaying limiinescence that reaches saturation at 

 moderate incident light intensity. 



8. The time course of the luminescence induction period is dif- 

 ferent for different portions of the decay curve (6). The long-term 



180 

 Milliseconds 

 Time between Illumination and Meosurement 



360 



Fig. 1. The decay of Chlorella luminescence measured in a phosphoroscope 

 Integrated intensity constant at ca. 300 foot-candles. Temperature, 25°C. 



decay possesses a marked induction maximum whereas the fast de- 

 cay component shows a much less marked maximum and actually in- 

 creases with time of illumination. 



RELATION TO PHOTOSYNTHESIS 



1. In intact plants the intensity of luminescence is influenced by 

 the presence or absence of CO2 and by anaerobic conditions (1,9). 

 CO2 depresses luminescence, as might be expected if it removes 

 photochemically produced reductant. Prolonged exposure to anaerobic 

 conditions inhibits the luminescence (9) . 



In a parallel manner, the luminescence of chloroplasts is inhibited 

 by the addition of hydrogen acceptors such as the Hill oxidants, 

 ferricyanide, or quinone (6,9). 



2. The luminescence is also exhibited by chloroplasts and saturates 

 parallel to the Hill reaction rate as a function of incident light inten- 



