54 



PHOTOSYNTHESIS 



inhibition of photosynthesis at high concentrations of carbon 

 dioxide was greater at higher hght intensities than at low 

 and this led him to suggest that cyanide did not affect the 

 photochemical process in photosynthesis but inhibited the 

 dark reaction (Fig. 4.7). More recently it has been shown 



/ntensi'ty of illumination 



FIG. 4.7. Rate of photosynthesis of Chlorella at different light in- 

 tensities in the presence (•) and absence (o) of cyanide. (After 

 Wassink et al.) KCN ^ 2-3 10 "^m. 



that at high intensities of illumination the inhibition of 

 photosynthesis by cyanide is greater at low concentrations 

 of carbon dioxide (Whittingham, 1952) suggesting that the 

 dark process concerned is that in which carbon dioxide is 

 concerned (Process i). Warburg originally claimed that 



I 



