1440 



PHOTOSYNTHESIS IN INTERMITTENT LIGHT 



CHAP. 34 



t = 60 seconds; it increases gradually when t declines to }qo second, or 

 increases from 60 seconds to infinity. (The yields obtained at ^ = 120 

 and 300 seconds, not shown in figure 34.3, were intermediate between 

 those obtained at 60 seconds and in continuous light.) 



15 20 60150 600 3600 

 TIME, sec. 



0.7 



I I I 



J L 



60 150 600 3600 

 TIME, sec. 



1.7 



1.6 



1.5 



1.4 



1.3 



1.2 



I.I 



Hormidium flaccidum, 

 20.5° C, 1500 lux, 

 short intervals 



_L. 



_L 



1.05 



1.00 



095 



0.90 



Stichococcus bacillans, 

 2II°C., 1500 lux, long mtervols 



(d) 



_L 



_L 



600 



3600 12600 

 TIME, sec. 



Fig. 34.4. Intermittency factors for two species 

 of algae for equal dark and light periods (after 

 Aufdemgarten 1939). 



0.0085 0.06 0.2 Q5 5 

 TIME, sec. 



Factor ijt is determined in figure 34.3 by the ratio of the slope of the line 

 representing the average consumption of carbon dioxide in intermittent 

 light, and the slope of the corresponding line for continuous light, in is < 

 0.5 (iiB < 1) for / = 60 and 15 seconds, and > 0.5 (ite > 1) for the smaller 

 values of t. At t = I^q second, ijt almost reaches unity {{k — 0.93, 

 iip = 1.86). 



The findings of Warburg et al. (1951) that the gas exchange in alternating light, t = 

 1-3 min., results from a photosynthesis enhanced up to 3 times and respiration enhanced 

 up to 10 times (compared to steady conditions), and the failure of Brown (1953) and 

 of Whittingham (1954) to confirm them will be discussed in chapter 37D. 



