1372 



INDUCTION PHENOMENA 



CHAP. 33 



Franck and French (1941). The}^ found that, if a carbon dioxide-starved 

 leaf, after a period of photoxidation, was exposed to light in the presence of 



E 

 E 



LJ 

 O 



z 

 < 

 I 

 o 



UJ 



cr 



Z) 



en 



CO 

 UJ 



a: 

 a. 



20 



30 



40 



50 



60 



10 



20 



40 



50 



60 



30 

 TIME, min. 



Fig. 33.18C. Photosynthesis in the presence of sufficient CO2, (a) before and (6) after 

 photoxidation (after Franck and French 1941). Straight lines on right show increase 

 in respiration after photoxidation. Corrected for this increased respiration, the final 

 rate of photosynthesis, 7.3, is about equal to that before photoxidation, but is reached 

 only 20 minutes after admission of COa in light. 



E 

 E 



o 



Z) 



o 

 o 



Q. 



>- 



X 



o 



100 



60 



20 







-20 



-40 



■ 1000 f 



28,000 f 



I 28,OOOJ 1000 f.-c 

 I f-c,^ 



28,000 f-c 'darkness 



300 



50 100 150 200 250 



TIME OF ILLUMINATION, min. 



Fig. 33.18D. Progressive injury of cells by 28,000 foot-candles 

 of light, and recovery in darkness (D) and in 1000 foot-candles 

 {B and C) (after Myers and Burr 1940). 



carbon dioxide, 10 or 20 minutes were needed to recover its full photosyn- 

 thetic efficiency (fig. 33.18C). The exact length of the recovery period 



