88 



Walter Bonner and Robert Hill 



cytochrome f^ oxidation in partially greened mung bean leaves are 

 shown in Figure 6. It may be seen in this figure that the dark 

 reduction of cytochrome f^ is rapid, so rapid in fact that the 

 techniques that have been used previously to observe light 

 induced optical changes in chloroplasts (2,3) and in Chlorella 

 (11) would fail in any attempt to obsei*ve specific light induced 

 changes. 



AQD.= 0.005 



Fig. 6 An illustration of the time relations involved in light 

 activated cytochrome f^ oxidation and the subsequent dark 

 reduction of cytochrome f^ in partially greened mung bean leaves. 



DISCUSSION 



The paper documents, for the first time, specific light- 

 induced optical changes in the partially greened leaf as well as 

 in fully greened leaves and in green algae. This papsr also con- 

 firms the observations of Amesz and Duysens (10) and of Olson and 

 Smillie (this symposium) relating to the light-induced cytochrome 

 f^ oxidation in Anacystis and in Euglena . The accumulated exper- 

 ience gained through comparison of the light-activated cytochrome 

 £ oxidation in partially greened leaves and in various fully 

 greened leaves has emphasized the need for considerable care in 

 investigations on fully greened leaves. Extra precautions are 

 required because of a low light requirement that can be met, 

 partially, by the measuring light. The partially greened leaf 

 has three distinct advantages, compared to the green leaf: (a) 

 better optical properties; (b) the high light intensity require- 



