363 



Kouchkovsky et al 



with a platinum electrode covered by a polyethylene membrane '^K A concen- 

 tration change of ± 10"^ M O2 in -^ 2 sec could be measured. 



Experiments were usually performed with saturating white light, at 15°C, 

 and with suspensions equilibrated with air. 



Abbreviations 



DPIP : 2,6 dichlorophenol indophenol; CMU : 3-(p-chlorophenyl) - 1, 

 1-dimethylurea; FeCy : potassium ferricyanide; TMS : trismaleate buffer 

 0, 1 M + sucrose 0.4 M. 



RESULTS 



Chloroplasts Without Hill Reagents 



ou/oeoniommaHon 



Fig. 1. Photographic reproduction of a recording of oxygen con- 

 centration changes with isolated chloroplasts in the absence of 

 Hill reagents. 



Chloroplasts: 300 ug chlorophyll /ml in TMS pH 6. 6 . 

 I : light on; + : light off. "Autoconsommation" : negative 



current, measured replacing chloroplasts by buffer, a, b, c , 

 and d : see text. 



Results of a typical experiment with chloroplasts in the absence of Hill 

 reagents are shown in Fig. 1. In darkness, there is a very slow endogenous 



