736 



John D. Spikes and Dennis C. Hall 



ability vith average dark activity was selected for more detailed 

 studies. Photochemical inactivation with Rose bengal followed 

 the classical photodynamic pattern in that systems illiiminated 

 under flowing tank nitrogen showed only slight loss of Hill 

 reaction and photosynthetic activities^ while systems illuminated 

 in the same way in air showed a rapid loss of activity. Inacti- 

 vation was apparently not produced to any great extent by stable 

 toxic photoproductS; since samples of Rose bengal which had been 

 illuminated in air were no more inhibitory in the dark than 

 unillurainated dye. 



The dark and light inactivation of Chlorella in the presence 

 of Rose bengal was investigated as a function of various combi- 

 nations of dye concentration, duration of dark treatment with 

 the dye, and duration of illumination in the presence of the dye. 

 Treatment with dye in the dark inhibited photosynthetic activity; 

 inhibition increased \^^ith the duration of treatment. Hill 

 reaction activity was relatively insensitive to dark treatment. 

 Inhibition of both activities increased progressively with dur- 

 ation of illumination in the presence of dye. Loss of activity 

 in the light was not strictly first-order. Inactivation, in 

 general, increased with increasing dye concentration. A typical 

 set of data illustrating the effects of Rose bengal concentration 

 on both dark and light inactivation is shown in Table I. 



Table I - Effect of Rose bengal concentration 

 on the photodynamic and dark inactivation of 

 Chlorella photosynthesis and quinone Hill reaction. 

 The algae were treated in the dark with dye in the 

 concentrations given for 60 rain., and then illumi- 

 nated for 15 min. at i|,000 foot-candles in the case 

 of the light experiments. 



