594 



Lester Packer 



substantiated, it may be that alternate routes of energy transduc- 

 tion are possible. Thus intermediates in the dark energy transfer 

 pathvay may be generated either by photophosphory.lation or rever- 

 sal of the terminal steps by ATP. Both of these conditions lead 

 to favorable circumstances for scattering changes in both mito- 

 chondria and chloroplasts. Since these conditions also lead to 

 specific cation accumulation mechanisms in mitochondria, it seems 

 possible that an ion accumulation mechanism driven by these reac- 

 tions may also exist in photosynthetic membrane systems. This 

 hypothesis, if established, may warrant some evaluation in terms 

 of the quantum efficiency of the photosynthetic energy conversion 

 process. 



Finally, no conclusion can, at present be made, concerning the 

 exact correspondence of light- scattering changes under the condi- 

 tions described here with changes in chloroplast structure. How- 

 ever some correlation betireen scattering responses and structural 

 changes are supported by the very interesting observation made 

 independently by Itoh, Izawa and Shibata (l2) involving entirely 

 different techniques. The observation of Itoh et £l. (l2) are 

 also substantiated by recent studies made in our o^-m laboratory 

 by m.eans of rapid time recoraings of viscosity changes in chloro- 

 plast suspensions observed with a rotating viscometer (2l). The 

 nature of the physical change of which scatter5.ng and viscosity 

 changes may be a measure are currently under active investigation. 



This research was supported by the National Science Foundation. 



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