383 



Max H. Hommersand 



525 mu 20 480 mu 



40 480mu 60 525inM 80 



TIME (min ) 



680 nv 



20 480itui 40 



Fig. 2. Sequence of oxygen transients 525mP< -♦ 

 480mtx -> 480nm -» 525mu (left side) and 680nijj - 480nui 

 (right side). 



different magnitude from the previous one may be generated. The 

 greatest changes in the magnitude of negative transients have 

 been observed in shifts from a wavelength where the primary pig- 

 ment system (System I of Duysens^ O is the principal light ab- 

 sorber to a wavelength where the secondary pigment system (System 

 II of Duysens) is the principal light absorber. Two such shifts 

 (525mM. -« 480miJ.; 680m|i - 480mM.) are shown in figure 2. After a 

 single aberrant transient has been produced, all succeeding 

 transients are normal for the particular wavelength. In the 

 reverse shift, from a wavelength where the pigments of System II 

 predominate to one where the pigments of System I predominate, 

 in this case from 480mli' - 525mM., or from 480mM. - 680m|J., no tempo- 

 rary change in the behavior of the transient is observed. I 

 would interpret these results as indicating that an adjustment 

 takes place, either in the relative efficiency in the utilization 

 of energy trapped by the two pigment systems for photosynthesis, 

 or in the balance between photo synthetic and respiration rates, 

 when a shift is made from one wavelength to another. This 

 adjustment is probably of such a nature as to tend to maximize 

 the quantum yield. The adjustment probably takes place rapidly 



