414 



George Hoch and Olga v. H. Owens 



ment". This effect is a general one, Emerson 



(8) 



found it 



in the blue-^vreen Anacystis, the diatom Navicula, and in the 



red algae Phorphyridium . Govindjee and Rabinowitch 



(9) 



showed the effect in Chlorella . The answer to this is again 

 suppression of respiration. The first light beam gives both 

 oxygen production and suppression of uptake while the second 

 yields only photosynthesis, therefore, the second beam gives 

 less net oxygen exchange when added to another beam also 

 absorbed by chlorophyll a than it did v«;hen measured by it- 

 self. This effect also makes the observed enhancement, in 

 those regions v/here it occurs, less than the true amount^-^^< 

 This is shown in Table 1. The observation of negative 

 enhancement in Chlorella is especially reassuring because 

 here, as we mentioned before, the suppression of uptake is 

 often too small for us to measure with the isotopes. 



In several experiments we have found positive values for 

 enhancement when we superimposed light beams of 680 and 705 

 mu and measured oxygen production with isotopes. However, 

 with a total of 22 different experiments we obtained an 

 average enhancement equal to 1.1, well within our experi- 

 mental error. While v.'e do not feel this disproves the pos- 

 sibility of enhancement between these wavelengths, any 

 enhancement effect must be of small magnitude. 



Influence of cyanide on enhancement . 



Table 2 shows some rather unexpected results. Although 

 our attempts to show a specific effect of cyanide on one or 

 the other wavelength have not been successful the inhibi- 

 tion does have an effect on enhancement observed with 

 isotopes. Addition of cyanide slir.htly decreases the oxygen 

 production of both beams (much less, of course, in this 



