1392 



INDUCTION PHENOMENA 



CHAP. 33 



different species, or of shorter dark intervals. (All curves in figure 33.34 

 were obtained after 1 hour dark rest, the decay of fluorescence in 80% CO2 

 being very slow. Earlier repetition might have given a result much more 

 like that shown in figure 33.35.) 



o 



UJ 



o 



UJ 



o 



C02 



-d- 80% 





Q- 20% 



5% 

 »• None 

 A- 5% 



TIME, min. 



Fig. 33.34. Effect of excess carbon dioxide on decay of fluorescence 

 outburst in Hydrangea (after Fianck, French and Puck 1941). 4 min. 

 exposure after 1 hour dark. / = 1.7 X 10* erg/cm.^ sec; Hg lines 436, 

 492, 546 niju. ( O ) Control after the series, with no CO2. 



TIME, sec. 



Fig. 33.35. Effect of excess carbon dioxide on fluore.scence time curve of Ulva 

 laduca at 20° C. (after Kautsky and Franck 1943). / = 40 m. c. (equivalent). 



The influence of carbon dioxide concentration in the range where it 

 represents a strong "limiting factor" in photosynthesis (i. e., below ap- 

 proximately 0.1%) is not shown clearly by figures 33.34 and 33.35. Ac- 



