NEW FLASHING LIGHT EXPERIMENTS 



1469 



tion at the bottom of the suspension vessel was 120 kliix. By varying 

 flash duration and lamp voltage, flash energies from 10 to 1000 lux sec. 

 could be obtained. (According to p. 838, this should mean from 1.4 X 

 10^^ to 1.4 X 10'^ incident quanta per cm.^ per flash, or from one absorption 

 act per about 500, to one absorption act per about 5, chlorophyll molecules; 

 these estimates could be too high because the copper sulfate filter must 

 have affected the spectral composition and thus also the average absorption 

 of the light reaching the suspension.) 



- 2 

 o '■ 



e 



1 = 21 lux sec. 



0.6 - 



0.4 - 



0.2 



02 



0.4 



15° 8 7° P= 0.5 X 10" 



0.05 



15 



0.1 

 'rf, sec. 

 Fig. 34.23. Oxygen jdeld per flash as function of dark intervals in Chlorella eilipsoidea 

 for subsaturating flash energy (after Tamiya and Chiba 1949). 



The yield was measured manometrically in carbonate buffer No. 9, in 

 10 minute runs, with dark intervals from 0.015 to 0.60 sec, at 7°, 15° and 

 25° C. A suspension of 4 mg. algae covered an area of about 20 cm.'^ 

 (about 10 ~* mole chlorophyll per cm.'^, indicating a probable absorption of 

 <50% of incident Hght). 



The results differed from earlier data in three significant ways. 



(1) As shown in figure 34.21, the yield per flash increased with the dura- 

 tion of dark intervals up to 0.2 sec. at 25° C, 0.3 sec. at 15° C. and about 

 0.5 sec. at 7° C. (for saturating flashes) — ten times longer than in table 

 39.11. 



(2) The absolute maximum flash yield at 25° C. was 7.3 X 10 ~* mole 

 oxygen per gram dry weight ; with a chlorophyll concentration of about 5% 

 this is equivalent to one molecule oxygen per 700 molecules chlorophyll — 

 about three times the maximum flash yield observed in the earlier experi- 



