RECENT RESULTS AT WAGENINGEN 



355 



period could also be varied within a wide range (from 10 ~' second 

 upwards) . 



Four types of experimentation were carried out for revealing the 

 kinetics of photosynthesis : 



1). Careful determinations of the intensity vs. assimilation curve 

 in continuous light. 



2). The "classical" flashing-light experiment: alternating brief 

 flashes with dark periods of variable length. This was done for flash 

 times ranging from 10"^ to 10~^ second. 



20 30 



darkt'ime — »• m. sec 



Fig. 2. Maximum flash j'ield as a function of dark time between flashes meas- 

 ured at two temperatures with Chlorella cells suspended in bufi"er mixture. In the 

 right-hand drawing the time scale is expanded tenfold. Dashed slopes represent 

 the saturation rate in continuous light. Dotted line indicates a first-order time 

 course calculated for the observed maximum flash j-ield and initial slope at 30°C. 

 Here tf = 0.5 m sec. After Kok (3a). 



3). Determinations of the intensity-rate curves in flashing light 

 procedures similar to those followed in the experiments described in 



4). Flashing-light experiments, in which equal (long) dark times 

 were alternated with flashes of variable length (10~*— 1 second). 



Important plots are that of the maximum flash yield (R/m) as a 

 function of dark time (to) (measured with very brief, saturating flashes 

 (I-»- CO , tf-^O)) {cf. Fig. 2) and that of the maximum flash yield (Rfm) as 

 dependent oi jiashtime (tf) measured with long dark periods (/-*«> . 



^,^a.)(cf.Fig.3). 



