1660 CHEMICAL PATH OF CARBON DIOXIDE REDUCTION CHAP. 36 



inactive carbonate for 0.5 to 1 hr. During this exposure time, no activity 

 entered any compounds insoluble in aqueous alcohol. 



In the carhoxylic acid field (upper right), a number of spots appeared 

 which were identified as malic, succinic, glycolic and fumaric acids. In 

 similar radiograms from dark -exposed (nonpreilluminated) cells ("respira- 

 tory C* uptake"), iso-citric, succinic, fumaric, and malic acids were found. 

 Each of these identifications was checked by "co-chromatographing" with 

 the corresponding pure acids. 



■LIPID 



SCENEDESMUS 

 I HOUR P32 



INORGANIC ^^ 



Fig. 36.15. Radiophosphorus-containing products of 1 hour photosynthesis 

 in Scenedesmus (after Benson, Calvin et al. 1951). 



The shorter the exposure, the greater was the proportion of activity 

 which stayed near the original spot (fig. 36.14). After an exposure of 15 

 sec. or 1 min., three or four dark areas could be distinguished there (fig. 

 36.14B,C), but after five-seconds exposure or less, only the uppermost of 

 them was significant (fig. 36.14A). This spot was therefore considered as 

 containing the earliest identifiable product of the fixation of carbon dioxide 

 in light. From the general position of the spots, it could be surmised that 

 the compounds in all three spots were phosphate esters; to test this hypoth- 

 esis, radiograms were made of algae which had been allowed to photo- 



