REACTION PATTERNS TN PHOTOSYNTHESIS 



77 



At teniperatvres near 50°C. the change of absorption decreases 

 with increasing temperature (Fig. 3). At this temperature photo- 

 synthesis also decHnes. With decreasing temperature we can observe 

 by using short saturating flashes that at 515 m/x the fast increase of 

 absorption is independent of temperature (Fig. 4). But in the dark 

 time after the flash the decline of the change of absorption is a function 

 of temperature. Between 30° C. and 5°C. we measured half-times of 



c 

 .o 



5- 



o 



-Q 



C 



time ' ' 25-/0* sec 



_j A. — — ^ -• -i — -^ 



2 4 6 8 10 



lightintensity 



Fig. 2. Change of absorption of Chlorella at 515 mfi as a function of flash light 

 intensity, ij = 5 X 10~^ second, td = 0.24 second. Temperature 18 °C. The 

 abscissa (broken line) belongs to a curve that connects the maxima of the changes 

 of absorption. 



49° 50° 51° 52° 53 °C 



.o 



^ / 



9- 



o 



-Q 



CD 



C 



-C 

 o 









time I 1 35 • 10 SeC 



Fig. 3. Change of absorption of Chlorella at 515 m/j. as a function of time at 

 different temperatures around 50°C. ti = I X lO"* second, <d = 3 seconds. 



1 X 10~' second and 7 X 10"^ second (see arrows in Fig. 4). Emer- 

 son and Arnold (5) found a reaction period of similar length indirectly 

 by measurements of oxygen production in photosynthesis. This 

 reaction period of photosynthesis is perhaps identical with the lifetime 

 of the changes of absorption. 



