129 



J. L. Rosenterg and Tevfik Bigat 



c 



4 6 

 Time (Steondt) 



Fig. k. Fluorescence at 680 m^i of a bean leaf following 

 the transition from high light to low light irradiation. 

 Incident intensity in "blue-green prior to zero time^ in 

 units of 10"^ einstein/cm^-sec: A, I = 336, B, I = 250. 

 Intensity was reduced to one-eighth initial intensity at 

 zero time. A: leaf in moist air; B, leaf in COo-free 

 air , 



(107 



steps come into phase with each other. The above explanation 

 may not include all factors responsible for the transients in 

 Fig. h but does provide a basis for understanding the dif- 

 ference between the two cases studied. 



ACKNOWLEDGMENTS 



This work was supported by the Office of Naval Research, 

 Department of the Navy, under contract W.30k-kl6 with the 

 University of Pittsb\argh. We thank Dr. Mary B. Allen of the 

 Kaiser Foundation Research Institute for supplying the 

 Poirphyridium strain -used in this work. 



