58 THE SYNTHESIS OF CARBOHYDRATES 



It does not therefore follow that carbon monoxide is not formed 

 in plants. As is well known, carbon dioxide is itself an anaes- 

 thetic if present in a sufficient amount, and possibly it is more 

 potent in this respect than is carbon monoxide, for Sulander 

 found that often the streaming movements of protoplasm was 

 not affected even after several hours' exposure to the last- 

 named gas. 



According to Baeyer's hypothesis oxygen and formalde- 

 hyde are early products of the process and these may now be 

 considered. 



ORIGIN OF THE OXYGEN. 



On the thesis that there are two phases in the photo- 

 synthetic process, one a light reaction and the other a dark, 

 or chemical, reaction, the oxygen may be split off in either the 

 one or the other. Accordingly Warburg * and others tried the 

 effect of increased temperature, poisons and narcotics on 

 Chlorella under high illumination, the Blackman reaction, and 

 under low light intensity. In both conditions carbon assimila- 

 tion was inhibited by narcotics and the Blackman reaction also 

 by hydrocyanic acid, but not that in low illumination. Further, 

 the former was accelerated by a rise in temperature, the curve 

 showing a linear function of temperature between io°-30° C. ; 

 but when light was limiting, an increased temperature was 

 without effect on the photochemical reaction. The alga was 

 then grown in the dark with hydrogen peroxide added to the 

 culture solution and the rate of the evolution of oxygen, by 

 the action of the Chlorella on the peroxide, measured after 

 treatment with narcotics, poisons and varying temperatures. 

 With regard to temperature the same linear function was found 

 as in the Blackman reaction, and the action of hydrocyanic 

 acid and narcotics was the same. In view of this parallelism, 

 these authors support Willstatter's hypothesis that the oxygen 

 evolved during carbon assimilation owes its origin to the split- 

 ting of the chlorophyll peroxide combination (p. 65). 



♦Warburg: " Biochem. Zeit.," 1919, 100,, 230; 1920, 103, 188; 1926, 

 166,386. Warburg and Uyesugi : id., 1924, 146, 486. Yabusoe : id., 1924, 

 152, 498. 



