M ELI IN CALVIN 



341 



ol)seived. One ot these is the generation and tlisapi)earance of the nn- 

 shaied elections which we have seen manipulated in the model sys- 

 tem. Fig. 20 sho^\•s the i)hotoi)roduction ot inishared electron pairs 

 in whole spinach chloroplasts at room temperature and at — 150°C 

 (61) . The fact that unshared i)airs of electrons can be produced by 



10 GAUSS 



T=-I50"' C 



10 GAUSS 



Fig. 20. Light signals from whole spinach chloroplasts. 



red light is in itself some indication that rather profound changes 

 are occurring in the chloroplast. These cannot be due to triplet 

 states because the interaction of the two electrons in a single triplet 

 molecule in randomly arranged chlorojilasts would broaden the signal 

 so as to make it unobservable (34) . The direct photochemical fission 

 of a chemical bond (by some sort of jjredissociation process) seems 

 entirely unlikely by a quantum supplying no more than 40 kcal of 

 energy at .most. 



