S«M Chord LMf 77*K 

 555-540m^ 



680 m^ T 



°l690m,. log I./I. 0.001 



On / ^ 



73 



^'\ On 



,/ \' / 670m^ 



4.IO"*Mc' V' 0"660m^ 



t -^^ ,°" 



MaoMring Light On t ^ 1 



555— 540 m^ ^bm^ ^. 



Measuring Light 



FIGURS 5. 



FIGUEE 6. 



F igure ^ . Illustrating the effect of light of various vravelen^ths in the red 

 region upon the rate of cytoclirome f oxidation in the S\7iss chard leaf at 

 77° K. Tine proceeds from left to right. Measuring light slits set at 1 mu 

 cause little tneasurahle oxidation, Hov/ever, illumination with 680 n+i givt-o 

 rise to a rate of ij- x lO"'^ per second per leaf thickness {O.h mm). The 

 tines at which the illumination is changed to various other wavelengths is 

 indicated on the diagr-aa. Eiwerinent 63-I5. 



Figur e 6. A plot of the effect of red illumination upon the rate of cyto- 

 chroriT oxidation for a a^iss chard leaf at 77° K. The points are taken from 

 the initial velocity" of a nuraber of similar Swiss chard leaves. The rates 

 of absorhancy change are per leaf thickness (0.4 mm). The diagram also in- 

 dicates the rate obtained lith measuring light only. The data are corrected 

 for the small change of energy distriT^ution of the monochromatic light over 

 the spectral interval. Ecperiment 63. 



Swiss Chard Leaf TT'K 

 "'^ 555-540m/i 



1.0x10 -sec' V'^ ! 



t' 



Actinic 



Light On 



t 436m/i ;s: 



Measuring 

 Light On 



t 

 Off 



log I./I= 0.001 



T 



).00 



1 



-50sec- 



7O -,r 



Figure 7. Activation of cj'tochxome f oxidation in &7iss chard leaf at 77 K 

 with J4-36 mti actinic light obtained from a medium pressure mercury arc (see 

 Fig. 6) . Tlie convention used in recording is similar to that in previous ex- 

 periments. Experiment 6I-IO. 



